beta-endorphin and Inflammation

β-Endorphins are peptides that exert a wide variety of effects throughout the body. Produced through the cleavage pro-opiomelanocortin (POMC), β-endorphins are the primarily agonist of mu opioid receptors, which can be found throughout the body, brain, and cells of the immune system that regulate a diverse set of systems. As an agonist of the body's opioid receptors, β-endorphins are most noted for their potent analgesic effects, but they also have their involvement in reward-centric and homeostasis-restoring behaviors, among other effects. These effects have implicated the peptide in psychiatric and neurodegenerative disorders, making it a research target of interest. This review briefly summarizes the basics of endorphin function, goes over the behaviors and regulatory pathways it governs, and examines the variability of β-endorphin levels observed between normal and disease/disorder affected individuals.

Topics: Animals; Behavior; Behavior, Animal; beta-Endorphin; Brain; Energy Metabolism; Humans; Inflammation; Stress, Physiological

It is well established that cholecystokinin (CCK) reduces the antinociceptive effect of opioids. The level of CCK and CCK receptors, as well as CKK release, exhibits considerable plasticity after nerve injury and inflammation, conditions known to be associated with chronic pain. Such altered CCK release coupled in some situation with changes in CCK receptor levels may underlie the clinical phenomenon of varying opioid sensitivity in different clinical pain conditions. In particular, neuropathic pain after injury to the peripheral and central nervous system does not respond well to opioids, which is likely to be caused by increased activity in the endogenous CCK system. CCK receptor antagonists may thus be useful as analgesics in combination with opioids to treat neuropathic pain.

Topics: Analgesia; Animals; beta-Endorphin; Cholecystokinin; Chronic Disease; Humans; Inflammation; Morphine; Pain; Rats; Receptors, Cholecystokinin; Spinal Cord Injuries

Topics: Animals; Antibodies; beta-Endorphin; Disease Models, Animal; Endorphins; Immunity, Cellular; Inflammation; Naloxone; Neuroimmunomodulation; Neurons, Afferent; Pain; Pain Threshold; Rats; Receptors, Opioid

The purpose of this exploratory study was to examine the effects of Tai Chi on blood levels of beta endorphin (β-endorphin) and inflammatory markers in older adults with chronic pain. Forty community-dwelling older adults with chronic pain were randomized to Tai Chi or light physical exercise, and each offered twice weekly for 12 weeks. Following the 12-week intervention, neither Tai Chi nor light physical exercise changed levels of β-endorphin and inflammatory markers. However, in older adults who completed 70% or more classes, Tai Chi significantly lowered levels of β-endorphin (p < 0.05), whereas light physical exercise did not change levels of β-endorphin. The results suggest that Tai Chi may reduce levels of β-endorphin in older adults with chronic pain. Future studies are needed to better understand the role of the opioid analgesic system and immune system in regulating pain with aging and the long-term effects of Tai Chi on pain-related biomarkers.

Topics: Aged; Aged, 80 and over; beta-Endorphin; Biomarkers; Chronic Pain; Exercise; Female; Humans; Independent Living; Inflammation; Male; Tai Ji

Previously it was shown that a brief yoga-based lifestyle intervention was efficacious in reducing oxidative stress and risk of chronic diseases even in a short duration. The objective of this study was to assess the efficacy of this intervention in reducing stress and inflammation in patients with chronic inflammatory diseases.. This study reports preliminary results from a nonrandomized prospective ongoing study with pre-post design.. The study was conducted at the Integral Health Clinic, an outpatient facility conducting these yoga-based lifestyle intervention programs for prevention and management of chronic diseases.. Patients with chronic inflammatory diseases and overweight/obese subjects were included while physically challenged, and those on other interventions were excluded from the study.. A pretested intervention program included asanas (postures), pranayama (breathing exercises), stress management, group discussions, lectures, and individualized advice.. There was a reduction in stress (plasma cortisol and β-endorphin) and inflammation (interleukin [IL]-6 and tumor necrosis factor [TNF]-α) at day 0 versus day 10.. Eighty-six (86) patients (44 female, 42 male, 40.07 ± 13.91 years) attended this program. Overall, the mean level of cortisol decreased from baseline to day 10 (149.95 ± 46.07, 129.07 ± 33.30 ng/mL; p=0.001) while β-endorphins increased from baseline to day 10 (3.53 ± 0.88, 4.06 ± 0.79 ng/mL; p=0.024). Also, there was reduction from baseline to day 10 in mean levels of IL-6 (2.16 ± 0.42, 1.94 ± 0.10 pg/mL, p=0.036) and TNF-α (2.85 ± 0.59, 1.95 ± 0.32 pg/mL, p=0.002).. This brief yoga-based lifestyle intervention reduced the markers of stress and inflammation as early as 10 days in patients with chronic diseases; however, complete results of this study will confirm whether this program has utility as complementary and alternative therapy.

Topics: Adult; beta-Endorphin; Breathing Exercises; Chronic Disease; Counseling; Female; Group Processes; Health Education; Humans; Hydrocortisone; Inflammation; Interleukin-6; Life Style; Male; Meditation; Middle Aged; Obesity; Relaxation Therapy; Stress, Psychological; Treatment Outcome; Tumor Necrosis Factor-alpha; Yoga

Asthma, a chronic respiratory disease is characterized by airway inflammation, remodelling, airflow limitation and hyperresponsiveness. At present, it is considered as an umbrella diagnosis consisting several variable clinical presentations (phenotypes) and distinct pathophysiological mechanisms (endotypes). Recent evidence suggests that oxidative stress participates in airway inflammation and remodelling in chronic asthma. Opioids resembled by group of regulatory peptides have proven to act as an immunomodulator. β-Endorphin a natural and potent endogenous morphine produced in the anterior pituitary gland play role in pain modulation. Therapeutic strategy of many opioids including β-Endorphin as an anti‑inflammatory and antioxidative agent has not been yet explored despite its promising analgesic effects. This is the first study to reveal the role of β-Endorphin in regulating airway inflammation, cellular apoptosis, and oxidative stress via Nrf-2 in an experimental asthmatic model. Asthma was generated in balb/c mice by sensitizing with 1% Toulene Diisocyanate on day 0, 7, 14 and 21 and challenging with 2.5% Toulene Diisocyanate from day 22 to 51 (on every alternate day) through intranasal route. β-Endorphin (5 µg/kg) was administered through the nasal route 1 h prior to sensitization and challenge. The effect of β-Endorphin on pulmonary inflammation and redox status along with parameters of oxidative stress were evaluated. We found that pre-treatment of β-Endorphin significantly reduced inflammatory infiltration in lung tissue and cell counts in bronchoalveolar lavage fluid. Also, pre-treatment of β-Endorphin reduced reactive oxygen species, Myeloperoxidase, Nitric Oxide, Protein and protein carbonylation, Glutathione Reductase, Malondialdehyde, IFN-γ, and TNF-α. Reversely, β-Endorphin significantly increased Superoxide dismutase, Catalase, glutathione, Glutathione-S-Transferase, and activation of NF-E2-related factor 2 (Nrf-2) via Kelch-like ECH-associated protein 1 (Keap1), independent pathway in the lung restoring architectural alveolar and bronchial changes. The present findings reveal the therapeutic potency of β-END in regulating asthma by Keap-1 independent regulation of Nrf-2 activity. The present findings reveal the therapeutic potency of β-Endorphin in regulating asthma.

Topics: Analgesics, Opioid; Animals; Apoptosis; Asthma; beta-Endorphin; Bronchoalveolar Lavage Fluid; Disease Models, Animal; Glutathione; Inflammation; Kelch-Like ECH-Associated Protein 1; Mice; Mice, Inbred BALB C; NF-E2-Related Factor 2; Oxidative Stress

Postpartum uterine infections are common reproductive diseases in postpartum cows. Evidence has shown that plasma β-endorphins increase during bovine uterine inflammation. However, the effect of β-endorphins on the inflammatory response in bovine endometrium has not been clarified. The aim of this study was to investigate the effect of β-endorphins on the inflammatory response of bovine endometrial epithelial and stromal cells, and to explore the possible mechanism. The cells were treated with E. coli lipopolysaccharide (LPS) to simulate inflammation, which was characterized by the significant activation of NF-κB signaling pathway and the increased gene expression of the downstream proinflammatory cytokines (approximately 1.2- to 15-fold increase, P < 0.05). By using Western blot and qPCR techniques, we found that β-endorphins inhibited the key protein expression of NF-κB pathway, and the gene expressions of TNF, IL1B, IL6, CXCL8, nitric oxide synthase 2, and prostaglandin-endoperoxide synthase 2 (P < 0.05). The co-treatment of β-endorphins and opioid antagonists showed that the anti-inflammatory effect of β-endorphins could be blocked (P < 0.05) by non-selective opioid antagonist naloxone or δ opioid receptor antagonist ICI 154129, but not the μ opioid receptor antagonist CTAP (P > 0.05). In conclusion, β-endorphins may inhibit the inflammatory response of bovine endometrial epithelial and stromal cells through δ opioid receptor.

Topics: Animal Husbandry; Animals; beta-Endorphin; Cattle; Cells, Cultured; Endometritis; Endometrium; Enkephalin, Leucine; Epithelial Cells; Escherichia coli; Female; Inflammation; Lipopolysaccharides; Naloxone; Narcotic Antagonists; NF-kappa B; Primary Cell Culture; Puerperal Infection; Receptors, Opioid, delta; Signal Transduction

Background Nowadays, yoga is endorsed and advised routinely to stay fit and healthy, as well as control many chronic diseases including diabetes type 2, hypertension, coronary artery diseases, etc. Now, our assumption is that those who do regular yoga have different persona than who do not do yoga regularly. We planned to test our hypothesis scientifically, and therefore baseline physiological characteristics with stress and inflammation levels in long-term and short-term meditators and healthy novice controls were analyzed. Methods In this retrospective analysis, 97 male participants were included for their Baseline analysis. Fifteen apparently healthy subjects practicing preksha meditation (since >5 years, at least 5 days a week) were included as long-term meditators (LTMs); 58 subjects who attended one of our short-term yoga-based lifestyle intervention programs for 2 weeks were included as short-term meditators (STMs); 24 male novice subjects, who did not participate in any yogic intervention, were included as healthy controls. Here, we analyzed the Baseline plasma levels of stress and inflammatory markers, cortisol, β-endorphin, interleukin (IL)-6 and tumor necrosis factor (TNF)-α in long-term meditators vs. short-term meditators vs. healthy controls. Outcome measures The study parameters body mass index (BMI), systolic blood pressure (SBP), diastolic blood pressure (DBP), plasma levels of stress and immune markers, cortisol, β-endorphin (β-Ed), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), were assessed in all the three groups at baseline. Results Significant (p<0.05) differences were observed at baseline for plasma levels of stress and inflammatory markers as well as body mass index and systolic blood pressure among LTM vs. STM vs. healthy controls. Conclusions Our observations suggest that the subjects who do regular yoga-meditation practice have better stress & inflammation status than comparable age matched healthy controls.

Topics: Adult; Aged; beta-Endorphin; Biomarkers; Blood Pressure; Body Mass Index; Humans; Hydrocortisone; Inflammation; Interleukin-6; Male; Meditation; Middle Aged; Retrospective Studies; Stress, Psychological; Tumor Necrosis Factor-alpha

Endogenous β-endorphin is delivered exclusively from the pituitary gland in various stressful conditions and plays an essential role in the nervous system. Recently, a few studies demonstrated peripheral endogenous opioid secretion from immune cells at inflammatory sites. Here, we investigated the expression of β-endorphin, the most powerful endogenous opioid peptide, in peripheral tissues in response to systemic administration of lipopolysaccharide in mice.. Male C57BL/6N mice received intravenously administered lipopolysaccharide to induce an endotoxic shock-like condition. mRNA for proopiomelanocortin, a precursor of β-endorphin, was quantified in peripheral blood cells, liver and spleen. β-endorphin peptide was measured in the liver and spleen.. Expression of proopiomelanocortin mRNA was detected in peripheral tissues after systemic administration of lipopolysaccharide. Lipopolysaccharide also induced β-endorphin expression in the liver and spleen.. Expression of proopiomelanocortin mRNA and β-endorphin was detected in peripheral tissues after systemic administration of lipopolysaccharide. These results provide new evidence that peripheral endogenous opioids can be produced not only as a result of local inflammation but also by severe systemic stress such as endotoxic shock. Further study is required to clarify the role of peripheral β-endorphin during endotoxic shock.

Topics: Animals; beta-Endorphin; Blood Cells; Disease Models, Animal; Gene Expression; Inflammation; Lipopolysaccharides; Liver; Male; Mice; Mice, Inbred C57BL; Pro-Opiomelanocortin; Shock, Septic; Spleen; Tissue Distribution

Analgesia with opioids such as morphine is an effective clinical strategy for the treatment of cancer pain and chronic inflammatory pain. However, long-term use of morphine can cause morphine tolerance (MT), which limits the clinical application of opioids. Polysaccharopeptide from Trametes versicolor (TPSP) is a biologically active macromolecule that exerts anti-tumor, immune-enhancing and pain-relieving effects. In order to address the clinical problem of MT, herein, we investigated the inhibitory effect and mechanism of TPSP in rats with inflammatory pain-morphine tolerance. A chronic inflammatory osteoarthritis pain-morphine tolerance model was simulated by injection of complete Freund's adjuvant (CFA) through the ankle joint cavity and continuous intrathecal administration of morphine. Different doses of TPSP (50 μg/kg, 100 μg/kg and 200 μg/kg) were intrathecally administered for consecutive 3 weeks. Our results indicate that TPSP can significantly inhibit the development of morphine dependence and acute withdrawal in rats, alleviate the decrease of paw withdrawal mechanical threshold and heat stimulation retraction latency. In addition, mechanistically at the molecular level, these effects are elicited via up-regulation of the cannabinoid type 2 receptor, up-regulating the level of β-endorphin, and reducing the levels of IL-1, NO and PGE

Topics: Animals; Behavior, Animal; beta-Endorphin; Dinoprostone; Down-Regulation; Inflammation; Interleukin-1; Male; Morphine; Nitric Oxide; Osteoarthritis; Pain; PC12 Cells; Proteoglycans; Rats; Rats, Sprague-Dawley; Receptor, Cannabinoid, CB2; Recombinant Proteins; Trametes

Therapeutic effects of Dead Sea (DS) minerals are well established, and their unique combination is analysed and reported. DS water (DSW) is a key source for DS minerals, and various studies report the capability of DSW to alleviate symptoms of different skin disorders and to contribute to skin maintenance. However, the biological mechanisms beyond reported effects are not fully understood yet.. To elucidate the effect of topically applied DSW via the expression of different skin biomarkers related to barrier function, homeostasis, inflammation and irritation.. In vitro skin equivalents and ex vivo human skin organ culture were used to assess the biological effects of DSW. Epidermal barrier protein expression and DSW ions transdermal penetration were analysed on skin equivalents. β-endorphin secretion was tested on human skin organ culture. The capability of DSW to protect against skin inflammation and irritation was tested on ex vivo human skin organ culture by lipopolysaccharides and sodium dodecyl sulphate addition, respectively.. Topical application of DSW encouraged the expression of the barrier-related proteins: filaggrin, involucrin and transglutaminase, while transdermal penetration of calcium ions was not detected. Additionally, DSW application had increased skin secretion of β-endorphin and attenuated the expression of inflammatory and irritation-related cytokines.. This study reports new findings of DSW effects on skin. Signalling pathway activation is proposed as a key step that may result in a vast range of proven biological activities following skin exposure to DS minerals, and specifically DSW.

Topics: beta-Endorphin; Biomarkers; Calcium; Cytokines; Epidermis; Filaggrin Proteins; Homeostasis; Humans; Inflammation; Ions; Lipopolysaccharides; Microscopy, Fluorescence; Minerals; Organ Culture Techniques; Seawater; Skin; Skin Diseases; Sodium Dodecyl Sulfate

Immune cell-derived beta-endorphin (END) and other opioid peptides elicit potent and clinically relevant inhibition of pain (analgesia) in inflamed tissue by activation of peripheral opioid receptors. Pro-opiomelanocortin (POMC) is the polypeptide precursor of END and is processed by prohormone convertases (PCs). This study aims to decipher the processing of POMC in lymphocyte subsets in a rat model of unilateral painful hindpaw inflammation. Lymphocytes, isolated from popliteal lymph nodes, were separated into B-cells, T-cells, T-helper cells and cytotoxic T-cells using magnetic cell sorting, and were examined by polymerase chain reaction, immunofluorescence and radioimmunoassay. At 2 h of inflammation, POMC exon 2-3 mRNA was mostly expressed in B- but not in T-cells. Prohormone convertase 1 (PC1) mRNA and protein were upregulated in B-cells and T-helper cells. Prohormone convertase 2 (PC2) was expressed in T- and B-cells, both in inflamed and non-inflamed lymph nodes. END was expressed in B- but not in T-cells. We conclude that POMC, its processing enzymes and END are predominantly expressed in B-lymphocytes at 2 h of paw inflammation.

Topics: Animals; B-Lymphocytes; beta-Endorphin; Gene Expression; Inflammation; Male; Pain; Pro-Opiomelanocortin; Proprotein Convertase 1; Proprotein Convertase 2; Rats; Rats, Wistar; RNA, Messenger; Serine Endopeptidases

This study was designed to investigate the contribution of prostaglandins to the maintenance of inflammatory pain. Inflammation was induced by intraplantar (i.pl.) injection of carrageenan in right hindpaw in rats. Indomethacin (non-selective COX inhibitor) was administered i.pl. 1 h after the carrageenan injection, and paw withdrawal latency (PWL) responding to noxious heat was measured. β-endorphin (β-END) and μ-opioid receptor (MOR) expressed in the inflamed site were examined by using immunocytochemistry, ELISA and RT-PCR techniques. The results showed that indomethacin dose-dependently increased PWL to the levels that were above the baseline on the day 2 and 3, referred to as hypoalgesia. The hypoalgesia was abolished by a local injection of the non-selective opioid receptor inhibitor naloxone methiodide. The number of β-END-positive cells, the content of β-END and the expression of MOR mRNA in the inflammatory site of inflammation model rats were all significantly increased by indomethacin. These results reveal a novel mechanism of prostaglandins for the inhibition of inflammation-induced endogenous opioid activity. This study provides further evidence that inhibition of prostaglandins in inflamed site could be a promising therapy for inflammatory pain.

Topics: Analgesics, Opioid; Animals; beta-Endorphin; Carrageenan; Indomethacin; Inflammation; Naloxone; Pain; Prostaglandins; Rats; Receptors, Opioid

Obesity is the result of a long-term positive energy balance in which caloric intake overrides energy expenditure. This anabolic state results from the defective activity of hypothalamic neurons involved in the sensing and response to adiposity. However, it is currently unknown what the earliest obesity-linked hypothalamic defect is and how it orchestrates the energy imbalance present in obesity. Using an outbred model of diet-induced obesity we show that defective regulation of hypothalamic POMC is the earliest marker distinguishing obesity-prone from obesity-resistant mice. The early inhibition of hypothalamic POMC was sufficient to transform obesity-resistant in obesity-prone mice. In addition, the post-prandial change in the blood level of β-endorphin, a POMC-derived peptide, correlates with body mass gain in rodents and humans. Taken together, these results suggest that defective regulation of POMC expression, which leads to a change of β-endorphin levels, is the earliest hypothalamic defect leading to obesity.

Topics: Adolescent; Adult; Animals; beta-Endorphin; Diet; Dietary Fats; Energy Intake; Humans; Hypothalamus; Inflammation; Male; Mice; Mice, Obese; Obesity; Pro-Opiomelanocortin; Rats; Rats, Wistar; Young Adult

This study quantified the expression of substance P (SP), calcitonin gene-related peptide (CGRP), β-endorphins (β-End), and methionine-enkephalin (Met-Enk) in human dental pulp following orthodontic intrusion.. Eight patients were selected according to preestablished inclusion criteria. From each patient, two premolars (indicated for extraction due to orthodontic reasons) were randomly assigned to two different groups: the asymptomatic inflammation group (EXPg), which would undergo controlled intrusive force for seven days, and the control group (CTRg), which was used to determine the basal levels of each substance. Once extracted, dental pulp tissue was prepared to determine the expression levels of both neuropeptides and endogenous opioids by radioimmunoassay (RIA).. All samples from the CTRg exhibited basal levels of both neuropeptides and endogenous opioids. By day seven, all patients were asymptomatic, even when all orthodontic-intrusive devices were still active. In the EXPg, the SP and CGRP exhibited statistically significant different levels. Although none of the endogenous opioids showed statistically significant differences, they all expressed increasing trends in the EXPg.. SP and CGRP were identified in dental pulp after seven days of controlled orthodontic intrusion movement, even in the absence of pain.

Topics: Adolescent; Analgesics, Opioid; beta-Endorphin; Calcitonin Gene-Related Peptide; Child; Dental Pulp; Enkephalins; Female; Humans; Inflammation; Male; Methionine; Molar; Neuropeptides; Orthodontics; Pain; Pilot Projects; Radioimmunoassay; Substance P

Less than 60% of infants undergoing invasive procedures in the neonatal intensive care unit receive analgesic therapy. These infants show long-term decreases in pain sensitivity and cortisol reactivity. In rats, we have previously shown that inflammatory pain experienced on the day of birth significantly decreases adult somatosensory thresholds and responses to anxiety- and stress-provoking stimuli. These long-term changes in pain and stress responsiveness are accompanied by two-fold increases in central met-enkephalin and β-endorphin expression. However, the time course over which these changes in central opioid peptide expression occur, relative to the time of injury, are not known. The present studies were conducted to determine whether the observed changes in adult opioid peptide expression were present within the first postnatal week following injury. The impact of neonatal inflammation on plasma corticosterone, a marker for stress reactivity, was also determined. Brain, spinal cord, and trunk blood were harvested at 24 h, 48 h, and 7 d following intraplantar administration of the inflammatory agent carrageenan on the day of birth. Radioimmunoassay was used to determine plasma corticosterone and met-enkephalin and β-endorphin levels within the forebrain, cortex, midbrain, and spinal cord. Within 24 h of injury, met-enkephalin levels were significantly increased in the midbrain, but decreased in the spinal cord and cortex; forebrain β-endorphin levels were significantly increased as a result of early life pain. Corticosterone levels were also significantly increased. At 7 d post-injury, opioid peptides remained elevated relative to controls, suggesting a time point by which injury-induced changes become programmed and permanent.

Topics: Animals; Animals, Newborn; beta-Endorphin; Biomarkers; Brain Chemistry; Carrageenan; Corticosterone; Enkephalin, Methionine; Female; Inflammation; Pain; Pregnancy; Rats; Rats, Sprague-Dawley; Spinal Cord; Stress, Psychological

Leukocytes containing opioid peptides locally control inflammatory pain. In the early phase of complete Freund's adjuvant (CFA)-induced hind paw inflammation, formyl peptides (derived e.g. from Mycobacterium butyricum) trigger the release of opioid peptides from neutrophils contributing to tonic basal antinociception. In the later phase we hypothesized that toll-like-receptor-(TLR)-4 activation of monocytes/macrophages triggers opioid peptide release and thereby stimulates peripheral opioid-dependent antinociception.. In Wistar rats with CFA hind paw inflammation in the later inflammatory phase (48-96 h) systemic leukocyte depletion by cyclophosphamide (CTX) or locally injected naloxone (NLX) further decreased mechanical and thermal nociceptive thresholds. In vitro β-endorphin (β-END) content increased during human monocyte differentiation as well as in anti-inflammatory CD14+CD16- or non-classical M2 macrophages. Monocytes expressing TLR4 dose-dependently released β-END after stimulation with lipopolysaccharide (LPS) dependent on intracellular calcium. Despite TLR4 expression proinflammatory M1 and anti-inflammatory M2 macrophages only secreted opioid peptides in response to ionomycin, a calcium ionophore. Intraplantar injection of LPS as a TLR4 agonist into the inflamed paw elicited an immediate opioid- and dose-dependent antinociception, which was blocked by TAK-242, a small-molecule inhibitor of TLR4, or by peripheral applied NLX. In the later phase LPS lowered mechanical and thermal nociceptive thresholds. Furthermore, local peripheral TLR4 blockade worsened thermal and mechanical nociceptive pain thresholds in CFA inflammation.. Endogenous opioids from monocytes/macrophages mediate endogenous antinociception in the late phase of inflammation. Peripheral TLR4 stimulation acts as a transient counter-regulatory mechanism for inflammatory pain in vivo, and increases the release of opioid peptides from monocytes in vitro. TLR4 antagonists as new treatments for sepsis and neuropathic pain might unexpectedly transiently enhance pain by impairing peripheral opioid analgesia.

Topics: Analgesia; Animals; beta-Endorphin; Calcium; Cell Differentiation; Freund's Adjuvant; Humans; Hyperalgesia; Inflammation; Lipopolysaccharide Receptors; Lipopolysaccharides; Macrophages; Male; Monocytes; Nociception; Opioid Peptides; Rats; Rats, Wistar; Receptors, IgG; Receptors, Opioid; Toll-Like Receptor 2; Toll-Like Receptor 4

A large body of evidence now exists for the immune cell expression, production, and the release of beta-endorphin (BE 1-31) within inflamed tissue. The inflammatory milieu is characterised by increased acidity, temperature and metabolic activity. Within these harsh conditions BE 1-31 is even more susceptible to increased enzymatic degradation over that of plasma or other non-injured tissue. To elucidate the biotransformation pathways of BE 1-31 and provide an insight to the impact of inflamed tissue environments, BE 1-31 and three of its major N-terminal fragments (BE 1-11, BE 1-13 and BE 1-17) were incubated in inflamed tissue homogenates at pH 5.5 for 2 hrs. In addition, the potency of BE 1-31 and five main N--terminal fragments (BE 1-9, BE 1-11, BE 1-13, BE 1-17, BE 1-20) was assessed at mu-opioid receptors (MOR), delta-opioid receptors (DOR), and kappa-opioid receptors (KOR). Opioid receptor potency was investigated by examining the modulation of forskolin induced cAMP accumulation. The majority of the N-terminal fragment of BE 1-31 had similar efficacy to BE 1-31 at MOR. The shortest of the major N-terminal fragments (BE 1-9), had partial agonist activity at MOR but possessed the highest potency of all tested peptides at DOR. There was limited effect for BE 1-31 and the biotransformed peptides at KOR. Major N-terminal fragments produced within inflamed tissue have increased presence within inflamed tissue over that of the parent molecule BE 1-31 and may therefore contribute to BE 1-31 efficacy within disease states that involve inflammation.

Topics: Animals; beta-Endorphin; Cell Line; Colforsin; Cyclic AMP; Disease Models, Animal; Gene Expression; Humans; Hydrogen-Ion Concentration; Inflammation; Male; Metabolic Networks and Pathways; Peptides; Rats; Receptors, Opioid; Receptors, Opioid, kappa

Interleukin-17 (IL-17) is involved in a wide range of inflammatory disorders and in recruitment of inflammatory cells to injury sites. A recent study of IL-17 knock-out mice revealed that IL-17 contributes to neuroinflammation and neuropathic pain after peripheral nerve injury. Surprisingly, little is known of micro-environment modulation by IL-17 in injured sites and in pathologically related neuroinflammation and chronic neuropathic pain. Therefore, we investigated nociceptive sensitization, immune cell infiltration, myeloperoxidase (MPO) activity, and expression of multiple cytokines and opioid peptides in damaged nerves of wild-type (IL-17(+/+)) and IL-17 knock-out (IL-17(-/-)) mice after partial sciatic nerve ligation. Our results demonstrated that the IL-17(-/-) mice had less behavioral hypersensitivity after partial sciatic nerve ligation, and inflammatory cell infiltration and pro-inflammatory cytokine (tumor necrosis factor-α, IL-6, and interferon-γ) levels in damaged nerves were significantly decreased, with the levels of anti-inflammatory cytokines IL-10 and IL-13, and expressions of enkephalin, β-endorphin, and dynorphin were also decreased compared to those in wild-type control mice. In conclusion, we provided evidence that IL-17 modulates the micro-environment at the level of the peripheral injured nerve site and regulates progression of behavioral hypersensitivity in a murine chronic neuropathic pain model. The attenuated behavioral hypersensitivity in IL-17(-/-) mice could be a result of decreased inflammatory cell infiltration to the injured site, resulting in modulation of the pro- and anti-inflammatory cytokine milieu within the injured nerve. Therefore, IL-17 may be a critical component for neuropathic pain pathogenesis and a novel target for therapeutic intervention for this and other chronic pain states.

Topics: Animals; Behavior, Animal; beta-Endorphin; Central Nervous System Sensitization; Cytokines; Disease Models, Animal; Dynorphins; Enkephalins; Hyperalgesia; Inflammation; Interleukin-10; Interleukin-13; Interleukin-17; Interleukin-1beta; Interleukin-2; Interleukin-6; Macrophages; Mice; Mice, Inbred C57BL; Mice, Knockout; Neuralgia; Neutrophils; Nociception; Peripheral Nerve Injuries; Peroxidase; Sciatic Nerve; T-Lymphocytes; Tumor Necrosis Factor-alpha

Beta endorphin (β-END) is recognised as one of the most significant endogenous neuropeptides, responsible for a wide range of biological activities in the body. However, within the body β-END is exposed to hydrolysis by a variety of enzymes. In this study, we investigated the metabolism and fragmentation pattern of β-END in rat inflamed tissue, in rat serum and in trypsin solution. β-END (1-31)-rat was incubated at 37 °C in each matrix for different incubation times. The resultant fragments were separated using a C4 column and detected by mass spectrometry using total ion current mode. Structural information for the fragments was elucidated using tandem mass spectrometry. Incubation of β-END (1-31)-rat in trypsin solution and in rat serum resulted in 8 and 13 fragments, respectively. Incubation in inflamed rat paw tissue resulted in 22 fragments at pH 7.4 and 26 fragments at pH 5.5. Some of these fragments were common to both pH values. The degradation of β-END (1-31)-rat in inflamed tissue at pH 5.5 was faster than that at pH 7.4. Secondary fragmentation of some larger primary fragments was also observed in this study.

Topics: Animals; beta-Endorphin; Chromatography, High Pressure Liquid; Inflammation; Rats; Tandem Mass Spectrometry; Trypsin

The aim of the present study was to investigate the mechanisms underlying the endogenous control of nociception at a peripheral level during inflammation. Using a pharmacological approach and the rat paw pressure test, we assessed the effect of an intraplantar injection of naloxone, an opioid receptor antagonist, and bestatin, an aminopeptidase inhibitor, on hyperalgesia induced by carrageenan, which mimics an inflammatory process, or prostaglandin E(2) (PGE(2)), which directly sensitizes nociceptors. Naloxone induced a significant and dose-dependent (25, 50 or 100 μg) increase in carrageenan-induced hyperalgesia, but not PGE(2)-induced hyperalgesia. Bestatin (400 μg/paw) significantly counteracted carrageenan-induced hyperalgesia, inducing an increase in the nociceptive threshold compared to control, but it did not modify hyperalgesia induced by PGE(2) injection into the rat paw. Positive β-endorphin immunoreactivity was increased in paw inflammation induced by carrageenan in comparison with the control group. However, PGE(2) did not significantly alter the immunostained area. These results provide evidence for activation of the endogenous opioidergic system during inflammation and indicate that this system regulates hyperalgesia through a negative feedback mechanism, modulating it at a peripheral level.

Topics: Animals; beta-Endorphin; Carrageenan; Dinoprostone; Dose-Response Relationship, Drug; Hyperalgesia; Inflammation; Leucine; Male; Naloxone; Narcotic Antagonists; Opioid Peptides; Pain Threshold; Protease Inhibitors; Rats; Rats, Wistar

Postoperative pain management is a critical aspect of patient care. The inflammatory state of the post-sternotomy surgical wound sensitizes nerve endings, causing pain. Unrelieved or improperly managed pain compromises wound healing. Peripheral opioid receptors play a major role in analgesia, particularly under inflammatory conditions where both opioid receptor expression and efficacy are increased. Leukocytic opioid peptides include β-endorphin (END), met-enkephalin (ENK), and dynorphin-A (DYN), with END and ENK being predominant.. This work represents the first study of inflammatory cells collected from post-sternotomy wounds of patients undergoing cardiac surgery including coronary artery bypass grafting (CABG). Wound fluid (WF) and cells were collected from sternal wounds using a JP Blake drain at 24, 48, and 72 hours post sternum closure. Anti-CD15 staining and flow cytometry revealed that polymorphonuclear neutrophils (PMN) are the predominant cells present in wound fluid collected post-surgery. Compared to peripheral blood (PB) derived PMN, significant increases in CD177+/CD66b+ PMN were observed suggesting activation of wound-site PMN. Such activation was associated with higher levels of opioid peptide expression in PMN derived from WF. Indeed, increased level of opioid peptides in sternal wound environment was noted 72 h post-surgery. We demonstrate that WF contains factors that can significantly induce POMC transcription in human PMNs. IL-10 and IL-4 were abundant in WF and both cytokines significantly induced POMC gene expression suggesting that WF factors such as IL-10 and IL-4 contribute towards increased opioid peptide expression in wound-site PMN.. This approach provided a unique opportunity to study the cross-talk between inflammation and opioid peptides in PMN at a sternotomy wound-site. Wound-site PMN exhibited induction of END and ENK. In addition, sternal wound fluid significantly induced END expression in PMN. Taken together, these data constitute first clinical evidence that human wound-site PMNs are direct contributors of opioids at the sternal wound-site.

Topics: Aged; beta-Endorphin; Dynorphins; Enkephalin, Methionine; Female; Flow Cytometry; Gene Expression Regulation; Humans; Inflammation; Interleukin-10; Interleukin-4; Male; Middle Aged; Neutrophils; Pain Management; Postoperative Period; Sternotomy; Wound Healing

We have recently reported that treatment with the 5-HT(2A) receptor antagonist ketanserin in the inflamed paw raises the nociceptive threshold above normal level (hypoalgesia) and this response is naloxone-reversible. The present study aimed to investigate neurochemical changes at the site of inflammation and in dorsal root ganglia (DRG) and the spinal cord following the blockade of 5-HT(2A) receptors. Intraplantar injection of ketanserin (20 μg) inhibited carrageenan-induced increase in CGRP immunoreactivity-positive neurons in DRG. On the other hand, administration of ketanserin (20 μg) and 5-HT (10 μg), but not vehicle, enhanced and inhibited recruitment of β-endorphin-expressing immune cells, respectively, in subcutaneous loci of inflamed hindpaw. Moreover, the treatment with ketanserin increased the number of endomorphine-containing cells in the inflamed paw and μ-opioid receptor-expressing neurons in DRG at L4-5 but reduced the expression of endomorphine in superficial layers of the lumbar spinal cord. The present study provided evidence at the cellular level showing that the blockade of 5-HT(2A) receptors inhibited inflammation-associated increase in pronociceptive mediator, and that the pronociceptive property of 5-HT is mediated by the suppression of inflammation-activated opioid mechanism. Therefore, targeting the 5-HT(2A) receptors in the site of inflammation may be a promising approach to inhibit inflammatory pain.

Topics: Animals; beta-Endorphin; Calcitonin Gene-Related Peptide; Carrageenan; Ganglia, Spinal; Inflammation; Ketanserin; Male; Pain; Rats; Rats, Sprague-Dawley; Receptor, Serotonin, 5-HT2A; Receptors, Opioid, mu; Serotonin; Serotonin 5-HT2 Receptor Antagonists; Spinal Cord

We have evaluated the possible underlying mechanisms of immobilization stress-induced analgesia (SIA) by behavioral cross-tolerance studies and molecular studies. In the behavioral studies, the cross-tolerance between single or repeated immobilization SIA and the antinociceptive effects of β-endorphin, morphine, 5-hydroxytryptamine (5-HT), or WIN55,212-2 were assessed. Both single and repeated (×7) immobilization stress significantly attenuated the β-endorphin and 5-hydroxytryptamine-induced antinociception in the 2nd phase of formalin response, respectively. However, these cross-tolerances disappeared in prolonged repetition of the stress (×14). Neither single nor repeated (×7 and ×14) immobilization stress affected the antinociceptive effect of morphine or WIN55,212-2 at all. We also found that immobilization stress activated hypothalamic proopiomelanocortin (POMC) gene and β-endorphin expression. Since, it has potent inhibitory activity on the noxious stimuli-induced POMC expression, immobilization stress seemed to dissipate the POMC gene expression process. Meanwhile, we did not find any changes in the opioid receptors' (mu-, delta- and kappa-receptor) and the cannabinoid receptors' (CB1 and CB2) expressions in the midbrain regions elicited by single or repeated stress. These results suggested that a single immobilization stress activates the descending pain modulatory system, which is mainly mediated through endorphinergic and serotonergic activation. Moreover, the tolerance of SIA induced by repeated stresses may be due to the prolonged activation of these systems induced by repeated immobilization.

Topics: Analgesics; Animals; Benzoxazines; beta-Endorphin; Disease Models, Animal; Inflammation; Infusions, Intraventricular; Male; Mice; Mice, Inbred ICR; Morphine; Morpholines; Naphthalenes; Pain; Receptors, Cannabinoid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Restraint, Physical; Serotonin; Stress, Physiological; Stress, Psychological

Electroacupuncture (EA) can produce analgesia by increasing the β-endorphin level and activation of peripheral μ-opioid receptors in inflamed tissues. Endogenous cannabinoids and peripheral cannabinoid CB2 receptors (CB2Rs) are also involved in the antinociceptive effect of EA on inflammatory pain. However, little is known about how peripheral CB2Rs interact with the endogenous opioid system at the inflammatory site and how this interaction contributes to the antinociceptive effect of EA on inflammatory pain. In this study, we determined the role of peripheral CB2Rs in the effects of EA on the expression of β-endorphin in inflamed skin tissues and inflammatory pain.. Inflammatory pain was induced by injection of complete Freund's adjuvant into the left hindpaw of rats. Thermal hyperalgesia was tested with a radiant heat stimulus, and mechanical allodynia was quantified using von Frey filaments. The mRNA level of POMC and protein level of β-endorphin were quantified by real-time PCR and Western blotting, respectively. The β-endorphin-containing keratinocytes and immune cells in the inflamed skin tissues were detected by double-immunofluorescence labeling. The CB2R agonist AM1241 or EA significantly reduced thermal hyperalgesia and mechanical allodynia, whereas the selective μ-opioid receptor antagonist β-funaltrexamine significantly attenuated the antinociceptive effect produced by them. AM1241 or EA significantly increased the mRNA level of POMC and the protein level of β-endorphin in inflamed skin tissues, and these effects were significantly attenuated by pretreatment with the CB2R antagonist AM630. AM1241 or EA also significantly increased the percentage of β-endorphin-immunoreactive keratinocytes, macrophages, and T-lymphocytes in inflamed skin tissues, and these effects were blocked by AM630.. EA and CB2R stimulation reduce inflammatory pain through activation of μ-opioid receptors. EA increases endogenous opioid expression in keratinocytes and infiltrating immune cells at the inflammatory site through CB2R activation.

Topics: Animals; beta-Endorphin; Electroacupuncture; Hyperalgesia; Inflammation; Keratinocytes; Male; Pro-Opiomelanocortin; Rats; Rats, Sprague-Dawley; Real-Time Polymerase Chain Reaction; Receptor, Cannabinoid, CB2; Skin; Up-Regulation

Inflammatory pain can be controlled by intraplantar opioid injection or by secretion of endogenous opioid peptides from leukocytes in inflamed rat paws. Antinociception requires binding of opioid peptides to opioid receptors on peripheral sensory nerve terminals. In the absence of inflammation, hydrophilic opioid peptides do not penetrate the perineurial barrier and, thus, do not elicit antinociception. This study was designed to examine the conditions under which endogenous, neutrophil-derived hydrophilic opioid peptides (i.e. Met-Enkephalin and beta-endorphin) can raise nociceptive thresholds in noninflamed tissue in rats. Intraplantar injection of the chemokine CXCL2/3 (macrophage inflammatory protein-2) induced selective neutrophil recruitment without overt signs of inflammation or changes in mechanical nociceptive thresholds (paw pressure threshold). Following intraplantar injection of hypertonic saline, the perineurial barrier was permeable for hours and intraplantar injection of opioid peptides increased mechanical nociceptive thresholds. While formyl-Met-Leu-Phe (fMLP) triggered opioid peptide release from neutrophils in vitro, nociceptive thresholds were unchanged in vivo. In vitro, hypertonicity interfered with fMLP-induced p38 mitogen activated kinase (MAPK) phosphorylation and opioid peptide release from neutrophils. These inhibitory effects were fully reversible by washout. In vivo, return to normotonicity occurred within 30min while the perineurium remained permeable for hours. Under these conditions, fMLP triggered MAPK phosphorylation and induced opioid peptide-mediated increases in nociceptive thresholds in the noninflamed paw. Taken together, antinociception mediated by endogenous opioids in noninflamed tissue has two important requirements: (i) opening of the perineurial barrier for opioid peptide access and (ii) opioid peptide release from neutrophils involving p38 MAPK.

Topics: Analgesia; Analgesics, Opioid; Analysis of Variance; Animals; Apoptosis; beta-Endorphin; Blotting, Western; Cell Count; Drug Administration Schedule; Enkephalin, Methionine; Flow Cytometry; Imidazoles; Immunohistochemistry; Inflammation; Male; N-Formylmethionine Leucyl-Phenylalanine; Necrosis; Neutrophils; Opioid Peptides; p38 Mitogen-Activated Protein Kinases; Pain Threshold; Peripheral Nerves; Phosphorylation; Pyridines; Radioimmunoassay; Rats; Rats, Wistar; Saline Solution, Hypertonic

Leukocytes infiltrating inflamed tissue produce and release opioid peptides such as beta-endorphin, which activate opioid receptors on peripheral terminals of sensory nerves resulting in analgesia. Gene therapy is an attractive strategy to enhance continuous production of endogenous opioids. However, classical viral and plasmid vectors for gene delivery are hampered by immunogenicity, recombination, oncogene activation, anti-bacterial antibody production or changes in physiological gene expression. Non-viral, non-plasmid minimalistic, immunologically defined gene expression (MIDGE) vectors may overcome these problems as they carry only elements needed for gene transfer. Here, we investigated the effects of a nuclear localization sequence (NLS)-coupled MIDGE encoding the beta-endorphin precursor proopiomelanocortin (POMC) on complete Freund's adjuvant-induced inflammatory pain in rats.. POMC-MIDGE-NLS injected into inflamed paws appeared to be taken up by leukocytes resulting in higher concentrations of beta-endorphin in these cells. POMC-MIDGE-NLS treatment reversed enhanced mechanical sensitivity compared with control MIDGE-NLS. However, both effects were moderate, not always statistically significant or directly correlated with each other. Also, the anti-hyperalgesic actions could not be increased by enhancing beta-endorphin secretion or by modifying POMC-MIDGE-NLS to code for multiple copies of beta-endorphin.. Although MIDGE vectors circumvent side-effects associated with classical viral and plasmid vectors, the current POMC-MIDGE-NLS did not result in reliable analgesic effectiveness in our pain model. This was possibly associated with insufficient and variable efficacy in transfection and/or beta-endorphin production. Our data point at the importance of the reproducibility of gene therapy strategies for the control of chronic pain.

Topics: Animals; beta-Endorphin; Flow Cytometry; Genetic Vectors; Immunohistochemistry; Inflammation; Male; Mice; Models, Biological; Pain Management; Pro-Opiomelanocortin; Radioimmunoassay; Rats; Rats, Wistar

Low-level laser therapy (LLLT) has been reported to relieve pain, free of side effects. However, the mechanisms underlying LLLT are not well understood. Recent studies have also demonstrated that opioid-containing immune cells migrate to inflamed sites and release beta-endorphins to inhibit pain as a mode of peripheral endogenous opioid analgesia. We investigated whether pre-irradiation of blood by LLLT enhances peripheral endogenous opioid analgesia.. The effect of LLLT pretreatment of blood on peripheral endogenous opioid analgesia was evaluated in a rat model of inflammation. Additionally, the effect of LLLT on opioid production was also investigated in vitro in rat blood cells. The expression of the beta-endorphin precursors, proopiomelanocortin and corticotrophin releasing factor, were investigated by reverse transcription polymerase chain reaction.. LLLT pretreatment produced an analgesic effect in inflamed peripheral tissue, which was transiently antagonized by naloxone. Correspondingly, beta-endorphin precursor mRNA expression increased with LLLT, both in vivo and in vitro.. These findings suggest that that LLLT pretreatment of blood induces analgesia in rats by enhancing peripheral endogenous opioid production, in addition to previously reported mechanisms.

Topics: Adjuvants, Immunologic; Aluminum; Analgesics, Opioid; Animals; Arsenicals; beta-Endorphin; Blood; Gallium; Immunohistochemistry; Inflammation; Lasers; Male; Models, Biological; Pain; Rats; Rats, Sprague-Dawley

Although opioids are highly effective analgesics, they are also known to induce cellular adaptations resulting in tolerance. Experimental studies are often performed in the absence of painful tissue injury, which precludes extrapolation to the clinical situation. Here we show that rats with chronic morphine treatment do not develop signs of tolerance at peripheral mu-opioid receptors (micro-receptors) in the presence of painful CFA-induced paw inflammation. In sensory neurons of these animals, internalization of mu-receptors was significantly increased and G protein coupling of mu-receptors as well as inhibition of cAMP accumulation were preserved. Opioid receptor trafficking and signaling were reduced, and tolerance was restored when endogenous opioid peptides in inflamed tissue were removed by antibodies or by depleting opioid-producing granulocytes, monocytes, and lymphocytes with cyclophosphamide (CTX). Our data indicate that the continuous availability of endogenous opioids in inflamed tissue increases recycling and preserves signaling of mu-receptors in sensory neurons, thereby counteracting the development of peripheral opioid tolerance. These findings infer that the use of peripherally acting opioids for the prolonged treatment of inflammatory pain associated with diseases such as chronic arthritis, inflammatory neuropathy, or cancer, is not necessarily accompanied by opioid tolerance.

Topics: Animals; beta-Endorphin; Cells, Cultured; Cyclophosphamide; Drug Tolerance; Fentanyl; Guanosine 5'-O-(3-Thiotriphosphate); Inflammation; Male; Morphine; Neurons, Afferent; Pain; Rats; Rats, Wistar; Receptors, Opioid, mu

Proopiomelanocortin (POMC)-derived beta-endorphin1-31 (END) released from immune cells inhibits inflammatory pain. We examined the expression of END and POMC mRNA encoding the signal sequence required for entry of the nascent polypeptide into the regulated secretory pathway in lymphocytes of rats with inflamed hindpaws. Within 12 h of inflammation, END increased in popliteal lymph nodes and at 96 h the intraplantar neutralization of END exacerbated pain. Lymphocytes expressed POMC, END, and full-length POMC mRNA. Semi-nested PCR revealed 8-fold increased exon 2-3 spanning POMC mRNA. Thus, painful inflammation enhances signal sequence-encoding lymphocytic POMC mRNA needed for regulated secretion of functionally active END.

Topics: Animals; beta-Endorphin; Flow Cytometry; Freund's Adjuvant; Gene Expression Regulation; Inflammation; Lymphocytes; Male; Pain; Pro-Opiomelanocortin; Protein Sorting Signals; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Time Factors

Analgesic effects of delta opioid receptor (DOR) -selective agonists are enhanced during persistent inflammation and arthritis. Although the underlying mechanisms are still unknown, membrane density of DOR was shown to be increased 72 h after induction of inflammation, an effect abolished in mu opioid receptor (MOR) -knockout (KO) mice [Morinville A, Cahill CM, Kieffer B, Collier B, Beaudet A (2004b) Mu-opioid receptor knockout prevents changes in delta-opioid receptor trafficking induced by chronic inflammatory pain. Pain 109:266-273]. In this study, we demonstrated a crucial role of MOR in DOR-mediated antihyperalgesia. Intrathecal administration of the DOR selective agonist deltorphin II failed to induce antihyperalgesic effects in MOR-KO mice, whereas it dose-dependently reversed thermal hyperalgesia in wild-type mice. The antihyperalgesic effects of deltorphin II were blocked by naltrindole but not d-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH(2) (CTOP) suggesting that this agonist was mainly acting through DOR. SNC80-induced antihyperalgesic effects in MOR-KO mice were also attenuated as compared with littermate controls. In contrast, kappa opioid receptor knockout did not affect deltorphin II-induced antihyperalgesia. As evaluated using mice lacking endogenous opioid peptides, the regulation of DOR's effects was also independent of beta-endorphin, enkephalins, or dynorphin opioids known to be released during persistent inflammation. We therefore conclude that DOR-mediated antihyperalgesia is dependent on MOR expression but that activation of MOR by endogenous opioids is probably not required.

Topics: Animals; beta-Endorphin; Dose-Response Relationship, Drug; Dynorphins; Enkephalins; Freund's Adjuvant; Hyperalgesia; Inflammation; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Motor Activity; Naltrexone; Narcotic Antagonists; Oligopeptides; Pain Measurement; Protein Precursors; Reaction Time; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Somatostatin

During inflammation, immune cells migrate into inflamed tissue and release opioid peptides that activate opioid receptors on peripheral sensory neurons to reduce pain. A characteristic of the inflamed environment in which these opioids act is acidic pH. Activation of opioid receptors leads to a decrease in the calcium component of neuronal action potentials. We investigated the hypothesis that inhibitory effects of opioids on intracellular calcium transients in dorsal root ganglion neuronal cultures are potentiated at acidic extracellular pH. Intracellular calcium responses to stimulation with capsaicin were measured in untreated neurons or after preincubation with beta-endorphin or morphine. beta-Endorphin significantly inhibited calcium responses to 300 nmol/L capsaicin at the lowest experimental extracellular pH (6.1, 6.5, and 7.2), whereas morphine inhibited capsaicin (300 nmol/L) responses significantly at pH 6.1 with a trend of inhibition at pH 6.5. The effect of pH on morphine inhibition of K+ -evoked calcium responses was also assessed. Morphine inhibition of calcium responses was significantly enhanced at pH 6.8 compared with pH 7.2 and pH 7.6. The inhibitory effects were reversed by naloxone, an opioid receptor antagonist. In conclusion, low extracellular pH potentiated beta-endorphin and morphine inhibition of calcium transients and might contribute to improved opioid efficacy during inflammation.. The results of the current study suggest that acidic pH might contribute to increased opioid efficacy in inflamed tissue. This highlights the therapeutic potential of endogenous opioid analgesia, whereby opioid peptides are delivered locally in inflamed tissues, as well as the use of locally applied opioids in inflammatory conditions.

Topics: Analgesics, Opioid; Animals; beta-Endorphin; Calcium Signaling; Capsaicin; Cells, Cultured; Drug Interactions; Extracellular Fluid; Ganglia, Spinal; Hydrogen-Ion Concentration; Inflammation; Intracellular Fluid; Male; Morphine; Narcotic Antagonists; Neural Inhibition; Neurons, Afferent; Potassium; Rats; Rats, Wistar; Receptors, Opioid

It has been shown that inflammation of rat paws elicits accumulation of opioid peptide beta-endorphin-containing immune cells in the inflamed subcutaneous tissue, contributing to immunocyte-produced pain suppression. However, the possible mechanisms involved in the pharmacological application of beta-endorphin in rat paw inflammation have not been investigated. The present study was set up to explore the effects of intraplantar injection of beta-endorphin on Concanavalin A-induced paw edema in two inbred rat strains, Albino Oxford (AO) and Dark Agouti (DA). Both high dose-induced suppression and low dose-induced potentiation of edema development in AO and DA rats, respectively, were blocked with antagonists specific for delta (naltrindole) and kappa (nor-binaltorphimine) opioid receptors. beta-endorphin in vitro decreased phagocytosis and increased nitric oxide (NO) production in air pouch granulocytes obtained from AO rats. However, in cells from DA rat strain beta-endorphin modulated both phagocytosis and NO production in a concentration-dependent manner. It could be concluded that the strain-dependent opposing effects of beta-endorphin on paw inflammation are mediated through delta and kappa opioid receptors and probably involve changes in the production of reactive oxygen species by inflammatory cells. Our results point to the importance of genotype for pharmacological manipulations and the development of inflammation.

Topics: Animals; beta-Endorphin; Concanavalin A; Dose-Response Relationship, Drug; Edema; Female; Granulocytes; Hindlimb; Inflammation; Male; Naltrexone; Narcotic Antagonists; Neurotransmitter Agents; Nitric Oxide; Phagocytosis; Rats; Rats, Inbred Strains; Receptors, Opioid, delta; Receptors, Opioid, kappa; Species Specificity

The aim of this study was to examine the effects of plasmapheresis on serum beta-endorphin (BE) levels.. The serum BE levels of 12 patients with various autoimmune or hematological disorders were monitored during plasmapheresis therapy.. BE levels increased after the initial session in 8 of 12 patients; in the remaining 4 patients no change (n = 2) or a decline (n = 2) in BE levels was found. However, no further changes were observed during subsequent therapy. During the last session, an elevation in the BE level was detected in 5 patients, with no change in 1 and a decrease in BE level in another 5 patients.. Our findings suggest that although plasmapheresis results in an elevation in serum BE levels initially, this change does not persist during subsequent sessions.

Topics: Adult; Aged; beta-Endorphin; Female; Hematologic Diseases; Humans; Inflammation; Male; Middle Aged; Plasmapheresis

This study aimed to investigate how local pain relief is mediated by laser therapy and how dose affects the relationship.. Inflammation was induced in the hind-paws of Wistar rats. Two groups of rats received 780-nm laser therapy (Spectra-Medics Pty Ltd.) at one of two doses (2.5 and 1 J/cm(2)). One group acted as a control. Scores of nociceptive threshold were recorded using paw pressure and paw thermal threshold measures.. A dose of 1 J/cm(2) had no statistically significant effect on antinociceptive responses. A dose of 2.5 J/cm(2) demonstrated a statistically significant effect on paw pressure threshold ( p < 0.029) compared to controls. There was no difference in paw thermal threshold responses and paw volumes at either dose. Immunohistochemistry in control animals demonstrated normal beta-endorphin containing lymphocytes in control inflamed paws but no beta-endorphin containing lymphocytes in rats that received laser at 2.5 J/cm(2).. The results confirm previous findings that the effect of laser therapy is dose-related. The mechanism of effect may occur via a differentiated pressure-sensitive neural pathway rather than a thermal-sensitive neural pathway. The significance of the immunohistochemistry findings remains unknown.

Topics: Animals; beta-Endorphin; Hindlimb; Inflammation; Low-Level Light Therapy; Lymphocytes; Male; Pain; Pain Threshold; Radiotherapy Dosage; Rats; Rats, Wistar

The opioid peptide beta-endorphin (END) as well as mRNA for its precursor proopiomelanocortin (POMC) are found not only in the pituitary gland, but also within various types of immune cells infiltrating inflamed sc tissue. During stressful stimuli END is released and interacts with peripheral opioid receptors to inhibit pain. However, the subcellular pathways of POMC processing and END release have not yet been delineated in inflammatory cells. The aim of the present study was to examine the presence of POMC, carboxypeptidase E, the prohormone convertases 1 (PC1), and 2 (PC2), PC2-binding protein 7B2, and the release of END from inflammatory cells in rats. Using immunohistochemistry we detected END and POMC alone or colocalized with PC1, PC2, carboxypeptidase E, and 7B2 in macrophages/monocytes, granulocytes, and lymphocytes of the blood and within inflamed sc paw tissue. Immunoelectron microscopy revealed that END is localized within secretory granules packed in membranous structures in macrophages, monocytes, granulocytes, and lymphocytes. Finally, END is released by noradrenaline from immune cells in vitro. Taken together, our results indicate that immune cells express the entire machinery required for POMC processing into functionally active peptides such as END and are able to release these peptides from secretory granules.

Topics: Animals; beta-Endorphin; Carboxypeptidase H; Extremities; Immunohistochemistry; In Vitro Techniques; Inflammation; Leukocytes; Male; Microscopy, Immunoelectron; Norepinephrine; Pain; Pro-Opiomelanocortin; Proprotein Convertase 1; Proprotein Convertase 2; Rats; Rats, Wistar; Secretory Vesicles; Sympathomimetics

The functional integrity of the immune system is essential for peripheral antinociception. Previous studies have demonstrated that immune cells elicit potent antinociception in inflamed tissues and that corticotropin-releasing factor-induced antinociception is significantly inhibited in animals that have undergone cyclosporin A (CsA)-induced immunosuppression. In this study, we examined the effect of a single bolus of CsA on inflammatory nociception. CsA-treated rats had substantially increased nociception compared with nonimmunosuppressed rats, consistent with a reduction in circulating and infiltrating lymphocytes. Furthermore, CsA-treated rats had inhibition of corticotropin-releasing factor-induced immune-derived antinociception, which was dose-dependently reversed by IV injection of concanavalin A-activated donor lymphocytes (1.0-7.0 x 10(6) cells/0.1 mL). In conclusion, our findings provided further evidence that opioid-containing immune cells are essential for peripheral analgesia. It is evident from these findings that control of inflammatory pain relies heavily on a functioning immune system.. The immune system not only contributes to inflammation, but also provides localized analgesia. A depleted immune system results in a reduction of immune-derived analgesia and a potentiation of inflammatory pain. Donor activated lymphocytes reverse these effects, highlighting the importance of a functional immune system in inflammatory pain.

Topics: Analgesia; Animals; beta-Endorphin; CD4 Lymphocyte Count; Concanavalin A; Cyclosporine; Dose-Response Relationship, Drug; Fluorescent Antibody Technique; Foot; Freund's Adjuvant; Immunosuppressive Agents; Inflammation; Lymphocyte Activation; Lymphocytes; Male; Pain Threshold; Radioimmunoassay; Rats; Rats, Wistar

Endogenous inhibition of inflammatory pain is mediated by leukocytes that secrete opioid peptides upon exposure to stress (cold water swim stress, CWS) or after local injection of corticotropin releasing factor (CRF). Since in early inflammation few opioid-containing leukocytes are detected and since peripheral opioid-mediated antinociception is low we examined whether antinociception could be augmented by increased recruitment of opioid-containing polymorphonuclear cells (PMN). Rats were intraplantarly (i.pl.) injected with Freund's complete adjuvant (FCA) and with the PMN-recruiting chemokine macrophage inflammatory protein-2 (MIP-2, 1-10 microg; control: saline) for 2 h. Intraplantar leukocytes were quantified by flow cytometry. Paw pressure threshold (PPT) was determined before and after exposure to CWS, i.pl. injection of CRF and opioid peptides. Opioid receptors (OR) were measured by binding studies in dorsal root ganglia (DRG) and by immunohistochemistry in the paw. Our studies showed that (i) MIP-2 injection dose-dependently augmented recruitment of PMN and opioid-containing leukocytes (5-fold increase in cells/paw, P < 0.05), (ii) PPT was not different between groups at baseline and after CWS or CRF (maximum MPE: 20+/-2.3-29+/-7.2%, P < 0.05), (iii) injection of opioid peptides dose-dependently increased the PPT (P < 0.05, maximum MPE: and 18+/-2.6-21+/-3.6%), (iv) MOR (micro OR, MOP) binding sites in the ipsilateral DRG were unchanged (24+/-2-22+/-1.2 fmol/mg protein, P < 0.05, ANOVA) and (v) the number of MOR and DOR (delta OR, DOP) stained nerve fibers in peripheral tissue were unaltered (both P > 0.05, t-test). In summary, antinociception during early inflammation is apparently not limited by the number of opioid-containing leukocytes but by OR availability.

Topics: Animals; beta-Endorphin; Chemokine CXCL2; Chemotaxis; Enkephalin, Methionine; Flow Cytometry; Freund's Adjuvant; Ganglia, Spinal; Inflammation; Leukocytes; Male; Monokines; Nerve Endings; Nociceptors; Rats; Rats, Wistar; Receptors, Opioid, delta; Receptors, Opioid, mu

Stress induces analgesia by mechanisms within and outside the brain. Here we show that the sympathetic nervous system is an essential trigger of intrinsic opioid analgesia within peripheral injured tissue. Noradrenaline, injected directly into inflamed hind paws of male Wistar rats, produced dose-dependent antinociception, reversible by alpha(1)-, alpha(2)- and beta(2)-antagonists. alpha(1)-, alpha(2)- and beta(2)-adrenergic receptors were demonstrated on beta-endorphin-containing immune cells and noradrenaline induced adrenergic receptor-specific release of beta-endorphin from immune cell suspensions. This antinociceptive effect of noradrenaline was reversed by micro - and delta-opioid antagonists as well as by anti-beta-endorphin. Stress-induced peripheral analgesia was abolished by chemical sympathectomy and by adrenergic antagonists. These findings indicate that sympathetic neuron-derived noradrenaline stimulates adrenergic receptors on inflammatory cells to release beta-endorphin, which induces analgesia via activation of peripheral opioid receptors.

Topics: Adrenergic alpha-Antagonists; Adrenergic beta-Antagonists; Analgesia; Analysis of Variance; Animals; Behavior, Animal; beta-Endorphin; Cell Count; Dose-Response Relationship, Drug; Drug Interactions; Freund's Adjuvant; Immunohistochemistry; Inflammation; Male; Narcotic Antagonists; Narcotics; Norepinephrine; Pain Measurement; Radioimmunoassay; Rats; Rats, Wistar; Receptors, Adrenergic, alpha-1; Receptors, Adrenergic, beta-2; Sensory Thresholds; Stress, Physiological; Swimming; Sympathetic Nervous System; Sympathomimetics; Time Factors; Tyrosine 3-Monooxygenase

Peripheral tissue injury causes a migration of opioid peptide-containing immune cells to the inflamed site. The subsequent release and action of these peptides on opioid receptors localized on peripheral sensory nerve terminals causes endogenous analgesia. The spinal application of opioid drugs blocks the transmission of nociceptive information from peripheral injury. This study investigates the influence of exogenous spinal opioid analgesia on peripheral endogenous opioid analgesia.. Six and forty-eight hours after initiation of continuous intrathecal morphine infusion and administration of Freund's complete adjuvant into the hind paw of rats, antinociceptive and antiinflammatory effects were measured by paw pressure threshold, paw volume, and paw temperature, respectively. Inflammation and quantity of opioid-containing cells were evaluated by immunocytochemistry and flow cytometry. Cold water swim stress-induced endogenous analgesia was examined 24 h after discontinuation of intrathecal morphine administration.. Intrathecal morphine (10 micro g/h) resulted in a significant and stable increase of paw pressure threshold ( P< 0.05) without changing inflammation, as evaluated by paw volume, paw temperature, and flow cytometry ( P> 0.05). At 48 but not at 6 h after Freund's complete adjuvant, the number of beta-endorphin-containing cells and cold water swim-induced antinociception were significantly reduced in intrathecal morphine-treated rats compared with those treated with intrathecal vehicle ( P< 0.05).. These findings suggest an interplay of central and peripheral mechanisms of pain control. An effective central inhibition of pain apparently signals a reduced need for recruitment of opioid-containing immune cells to injured sites.

Topics: Analgesics, Opioid; Animals; beta-Endorphin; Central Nervous System; Endorphins; Enkephalin, Methionine; Flow Cytometry; Foot; Immunohistochemistry; Inflammation; Injections, Spinal; Male; Morphine; Neurons, Afferent; Pain Threshold; Peripheral Nerves; Psychomotor Performance; Rats; Rats, Wistar

Although exogenous administration of beta-endorphin to the arcuate nucleus of hypothalamus (ARC) had been shown to produce antinociception, the role of endogenous beta-endorphin of the ARC in nociceptive processing has not been studied directly. The aim of the present study was to investigate the effect of endogenous beta-endorphin in the ARC on nociception in rats with carrageenan-induced inflammation. The hindpaw withdrawal latency (HWL) to noxious thermal and mechanical stimulation was assessed by the hot-plate test and the Randall Selitto Test. Intra-ARC injection of naloxone had no significant influence on the HWL to thermal and mechanical stimulation in intact rats. The HWL decreased significantly after intra-ARC injection of 1 or 10 microg of naloxone in rats with inflammation, but not with 0.1 microg of naloxone. Furthermore, intra-ARC administration of the selective mu-opioid receptor antagonist beta-funaltrexamine (beta-FNA) decreased the nociceptive response latencies to both stimulation in a dose-dependent manner in rats with inflammation, while intra-ARC administration of the selective delta-opioid receptor antagonist naltrindole or the selective kappa-opioid receptor antagonist nor-binaltorphimine (nor-BNI) showed no influences on the nociceptive response latency. The antiserum against beta-endorphin, administered to the ARC, also dose-dependently reduced the HWL in rats with inflammation. The results indicate that endogenous beta-endorphin in the ARC plays an important role in the endogenous antinociceptive system in rats with inflammation, and that its effect is predominantly mediated by the mu-opioid receptor.

Topics: Analgesics; Animals; Arcuate Nucleus of Hypothalamus; beta-Endorphin; Immune Sera; Inflammation; Male; Narcotic Antagonists; Rats; Rats, Wistar; Receptors, Opioid, mu

In painful inflammation, exogenous as well as endogenous corticotropin-releasing hormone (CRH) can release opioid peptides (mainly beta-endorphin) from various types of immune cells and produce antinociception by activating opioid receptors on peripheral sensory nerve endings. CRH mediates its central effects through two high-affinity membrane receptors, the CRH receptor subtypes 1 and 2. It is unclear at present whether the peripheral antinociceptive effects of CRH are mediated through CRH receptor 1 (CRH R1) or CRH receptor 2 (CRH R2). Employing a double-immunocytochemical technique, this study investigated in Wistar rats with Freund's complete adjuvant-induced hind paw inflammation whether immune cells within blood and inflamed subcutaneous tissue express CRH R1 and/or CRH R2 together with the opioid peptide beta-endorphin (END). Additionally, we examined using selective CRH R1 and CRH R2 antagonists whether peripheral CRH-induced antinociception is mediated by the respective CRH receptor subtypes. We found a high degree of co-expression of END together with both CRH R1 and CRH R2 in macrophage/monocytes, granulocytes and lymphocytes within blood and inflamed subcutaneous tissue. Also we observed a high degree of co-localization of CRH R1 and CRH R2 receptors on circulating and resident immune cells. Both the selective CRH R1 antagonist CP-154,526 and the selective CRH R2 antagonist astressin 2B significantly attenuated peripheral antinociceptive effects of CRH indicating the involvement of both CRH receptor subtypes. Taken together, these findings suggest that in inflammatory pain CRH-induced peripheral antinociception is mediated via both CRH R1 and CRH R2 located on END containing immune cells within inflamed sites.

Topics: Animals; beta-Endorphin; Corticotropin-Releasing Hormone; Dose-Response Relationship, Drug; Freund's Adjuvant; Inflammation; Male; Opioid Peptides; Pain; Rats; Rats, Wistar; Receptors, Corticotropin-Releasing Hormone

The literature indicates that beta-endorphin can be found in the mononuclear cells of peripheral blood. In the present experiments the endorphin content of granulocytes was studied, compared to lymphocytes as reference cells. Granulocytes as well, as lymphocytes contain endorphin. The granulocytes' endorphin content is much higher. Both lymphocytes and granulocytes are also able to take up endorphin from the milieu.

Topics: Animals; beta-Endorphin; Cell Count; Flow Cytometry; Fluorescent Antibody Technique; Granulocytes; Inflammation; Lymphocytes; Male; Pain; Rats; Rats, Wistar

Pain can be effectively controlled by endogenous mechanisms based on neuroimmune interactions. In inflamed tissue immune cell-derived opioid peptides activate opioid receptors on peripheral sensory nerves leading to potent analgesia. This is brought about by a release of opioids from inflammatory cells after stimulation by stress or corticotropin-releasing hormone (CRH). Immunocytes migrate from the circulation to inflamed tissue in multiple steps, including their rolling, adhesion, and transmigration through the vessel wall. This is orchestrated by adhesion molecules on leukocytes and vascular endothelium. Intercellular adhesion molecule-1 [ICAM-1 (or CD54)] is expressed by endothelium and mediates adhesion and extravasation of leukocytes. The goal of this study was to show that ICAM-1 regulates the homing of opioid-producing cells and the subsequent generation of analgesia within sites of painful inflammation. This was accomplished using immunofluorescence, flow cytometry, and behavioral (paw pressure) testing. We found that ICAM-1 is upregulated on the vascular endothelium, simultaneously with an enhanced immigration of opioid-containing immune cells into inflamed paw tissue. The intravenous administration of a monoclonal antibody against ICAM-1 markedly decreased the migration of opioid-containing leukocytes and of granulocytes, monocytes-macrophages, and T cells to the inflamed tissue. At the same time, circulating immunocytes increased in numbers, and macroscopic inflammation (hyperalgesia, paw volume, and paw temperature) remained primarily unchanged. Most importantly, peripheral opioid analgesia elicited either by cold water swim stress or by intraplantar administration of CRH was dramatically reduced. Together, these findings indicate that ICAM-1 expressed on vascular endothelium recruits immunocytes containing opioids to promote the local control of inflammatory pain.

Topics: Analgesia; Animals; Antibodies; beta-Endorphin; Cell Adhesion; Cell Movement; Forelimb; Inflammation; Intercellular Adhesion Molecule-1; Leukocytes; Male; Models, Immunological; Neuroimmunomodulation; Pain; Rats; Rats, Wistar; Up-Regulation

Immunocyte-derived beta-endorphin can activate peripheral opioid receptors on sensory neurons to inhibit pain within inflamed tissue. This study examined mu-opioid receptors (MOR) on sensory nerves and beta-endorphin (END) in activated/memory CD4(+) cells (the predominant population homing to inflamed tissue). We found an upregulation of MOR in dorsal root ganglia, an increased axonal transport of MOR in the sciatic nerve and an accumulation of MOR in peripheral nerve terminals in Freund's adjuvant-induced hindpaw inflammation. A large number of CD4(+) cells containing beta-endorphin, but very few naive cells (CD45RC(+)), were observed in inflamed tissue, suggesting that this opioid is mainly present in activated/memory cells (CD4(+)/CD45RC(-)). Taken together, our results indicate an enhanced transport of both MOR and of the endogenous ligand beta-endorphin to injured tissue. This unique simultaneous upregulation of both receptors and ligands may serve to prevent excessive and/or chronic inflammatory pain.

Topics: Animals; Axonal Transport; beta-Endorphin; Blotting, Western; CD4-Positive T-Lymphocytes; Disease Models, Animal; Freund's Adjuvant; Ganglia, Spinal; Hindlimb; Immunologic Memory; Inflammation; Ligation; Male; Neurons, Afferent; Rats; Rats, Wistar; Receptors, Opioid, mu; Sciatic Nerve; Skin

Previous studies have shown that the same stressor, depending on intensity, controllability, or duration, can have different effects on the immune system. The purpose of this study was to determine the effect of 10- and 20-min rotation on natural killer (NK) cell activity and also to establish if changes in body temperature, proinflammatory cytokine (IL-1beta, IL-6, and TNF-alpha) levels, and proopiomelanocortin (POMC)-derived peptide (ACTH and beta-endorphin) levels parallel the changes in NK cell activity in mice. We found that 10-min rotation significantly increased NK cell activity as compared to both the control (home cage) group and the 20-min-rotation group, while NK cell activity in the 20-min group was not significantly changed compared to the control group. Both 10 and 20 min of rotational stress decreased body temperature and induced significant changes in the proinflammatory cytokine and POMC-derived peptide levels as compared to the control group. The pattern of proinflammatory cytokine expression was quite different between the 10- and 20-min rotation groups. All three proinflammatory cytokines were expressed sequentially (at 0 h after rotation TNF-alpha, at 6 h IL-1beta and IL-6, and at 24 h IL-6) in the 10-min rotation group, while the 20-min rotation group had a small increase in IL-1beta (6.7 +/- 1.8 pg/ml) at 0 h and increased levels of IL-6 at 6 and 24 h. There was a dissociation of ACTH and beta-endorphin expression in both groups resulting in significantly more beta-endorphin (p < 0.05) in the 10-min group at 6 h and significantly more ACTH (p < 0.04) in the 20-min group at 6 h. IL-1beta and beta-endorphin have both been shown to have a direct stimulatory effect on NK cell activity. Therefore, we suspect that the significant increase in both IL-1beta and beta-endorphin at 6 h in the 10-min-rotation group may be involved in the increased NK cell activity observed at 24 h in the 10-min-rotation group.

Topics: Adrenocorticotropic Hormone; Animals; beta-Endorphin; Cytotoxicity, Immunologic; Female; Hypothermia; Inflammation; Interleukin-1; Interleukin-6; Killer Cells, Natural; Mice; Mice, Inbred BALB C; Neuroimmunomodulation; Rotation; Stress, Physiological; Tumor Necrosis Factor-alpha

Inflammatory pain can be effectively controlled by an interaction of opioid receptors on peripheral sensory nerve terminals with opioid peptides released from immune cells upon stressful stimulation. To define the source of opioid peptide production, we sought to identify and quantify populations of opioid-containing cells during the course of Freund's complete adjuvant-induced hind paw inflammation in the rat. In parallel, we examined the development of stress-induced local analgesia in the paw.. At 2, 6, and 96 h after Freund's complete adjuvant inoculation, cells were characterized by flow cytometry using a monoclonal pan-opioid antibody (3E7) and antibodies against cell surface antigens and by immunohistochemistry using a polyclonal antibody to beta-endorphin. After magnetic cell sorting, the beta-endorphin content was quantified by radioimmunoassay. Pain responses before and after cold water swim stress were evaluated by paw pressure thresholds.. In early inflammation, 66% of opioid peptide-producing (3E7+) leukocytes were HIS48+ granulocytes. In contrast, at later stages (96 h), the majority of 3E7+ immune cells were ED1+ monocytes or macrophages (73%). During the 4 days after Freund's complete adjuvant inoculation, the number of 3E7+ cells increased 5.6-fold (P < 0.001, Kruskal-Wallis test) and the beta-endorphin content in the paw multiplied 3.9-fold (P < 0.05, Kruskal-Wallis test). In parallel, cold water swim stress-induced analgesia increased by 160% (P < 0.01, analysis of variance).. The degree of endogenous pain inhibition is proportional to the number of opioid peptide-producing cells, and distinct leukocyte lineages contribute to this function at different stages of inflammation. These mechanisms may be important for understanding pain in immunosuppressed states such as cancer, diabetes, or AIDS and for the design of novel therapeutic strategies in inflammatory diseases.

Topics: Analgesia; Animals; Antibodies, Monoclonal; beta-Endorphin; Fluorescent Dyes; Hematopoietic Stem Cells; Immunohistochemistry; Immunomagnetic Separation; Inflammation; Leukocyte Common Antigens; Leukocytes; Lymphocytes; Male; Opioid Peptides; Pain; Pain Measurement; Radioimmunoassay; Rats; Rats, Wistar

LPS administration and hemorrhage are frequently used models for the in vivo study of the stress response. Both challenges stimulate cytokine production as well as activate opiate and neuro-endocrine pathways; which in turn modulate the inflammatory process. Differences in the magnitude and tissue specificity of the proinflammatory cytokine and neuro-hormonal responses to these stressors are not well established. We contrasted the tissue specificity and magnitude of the increase in circulating and tissue cytokine (TNF-alpha, IL-1alpha and IL-1beta) content in response to either fixed-pressure hemorrhage (approximately 40 mm Hg) followed by fluid resuscitation (HEM) or lipopolysaccharide (LPS; 100 microg/100 g BW) administration. LPS and HEM elevated circulating levels of TNF-alpha, while neither stress altered circulating IL-1-alpha and IL-beta. LPS-induced increases in TNF-alpha content were greater than those elicited by HEM in all tissues studied except for the lung, where both stressors produced similar increases. Tissue (lung, spleen and heart) content of IL-1alpha was increased by HEM but was not affected by LPS. Tissue (lung, spleen, and heart) content of IL-1beta was increased by LPS but was not affected by HEM. HEM produced greater increases than LPS in epinephrine (16- vs. 4-fold) and norepinephrine (4-fold vs. 60%) levels and similar elevations in beta-endorphin. LPS produced greater elevation in corticosterone levels (2-fold) than HEM (50%). These results suggest differential tissue cytokine modulation to HEM and LPS, both with respect to target tissue and cytokine type. The hormonal milieu to HEM is characterized by marked catecholaminergic and moderate glucocorticoid while that of LPS is characterized by marked glucocorticoid with moderate catecholaminergic influence.

Topics: Animals; beta-Endorphin; Blood Pressure; Catecholamines; Corticosterone; Disease Models, Animal; Epinephrine; Hemorrhage; Inflammation; Interleukin-1; Lipopolysaccharides; Male; Narcotics; Norepinephrine; Rats; Rats, Sprague-Dawley; Resuscitation; Stress, Physiological; Time Factors; Tumor Necrosis Factor-alpha

The present study investigated the perioperative course of cytokine release and hypothalamic-pituitary-adrenal (HPA) axis activation in relation to the duration of the inflammatory response in cardiac surgery patients. Twelve male patients scheduled for elective coronary artery bypass grafting surgery with cardiopulmonary bypass and general anaesthesia were divided into two study groups: group 1 (n=6) underwent surgery at 13.00 h+/-30 min, group 2 (n=6) at 08.30 h+/-50 min. Blood samples were collected preoperatively and up to the first postoperative day. Postoperatively, on the day of surgery, serum concentrations of the proinflammatory cytokines interleukin (IL)-6, IL-1beta and tumour necrosis factor (TNF)-alpha were not significantly different between the two groups, while blood concentrations of cortisol, adrenocorticotrophic hormone (ACTH) and beta-endorphin in group 2 patients were significantly higher than in group 1 patients. Postoperatively, on the day of surgery, ACTH and cortisol concentrations in group 1 patients were positively correlated to the blood concentrations of IL-1beta, IL-6 and TNF-alpha. By contrast, group 2 patients showed no significant relationship between cytokine release and activation of HPA axis at this time. Our results suggest that in patients undergoing cardiac surgery, the cytokine response is initiated before the HPA axis is fully activated. In the early postoperative period, cytokines appear to be involved in the activation of the HPA axis, while in the later postoperative period, high cortisol concentrations may inhibit the release of IL-6.

Topics: Adrenocorticotropic Hormone; Aged; beta-Endorphin; Cardiac Surgical Procedures; Cytokines; Endocrine Glands; Humans; Hydrocortisone; Immune System; Inflammation; Inflammation Mediators; Male; Middle Aged; Time Factors

Opioid-containing immunocytes migrate to inflamed sites where they release beta-endorphin which activates peripheral opioid receptors and produces analgesia. The immigration of immunocytes to sites of inflammation is mediated by adhesion molecules. In this study, the expression of L-, P-, E-selectin and platelet-endothelial adhesion molecule-1 (PECAM-1) in relation to beta-endorphin expression was analyzed by immunohistochemistry in inflamed tissues. The proportion of immunocytes expressing L-selectin was increased in inflamed lymph nodes and subcutaneous paw tissue. P-selectin and PECAM-1 were constitutively expressed on endothelia of noninflamed lymph nodes and subcutaneous tissue and were upregulated in inflammation. beta-endorphin positive cells expressed L-selectin in lymph nodes and subcutaneous tissue. Upregulation of P-selectin and PECAM-1 and the co-localization of L-selectin and beta-endorphin in immunocytes suggest an important role of these adhesion molecules for the recruitment of immunocytes containing beta-endorphin to sites of painful inflammation.

Topics: Animals; beta-Endorphin; Cell Adhesion Molecules; Chemotaxis, Leukocyte; Disease Models, Animal; E-Selectin; Freund's Adjuvant; Hindlimb; Immunohistochemistry; Inflammation; L-Selectin; Lymph Nodes; Male; P-Selectin; Pain; Platelet Endothelial Cell Adhesion Molecule-1; Rats; Rats, Wistar; Skin; Up-Regulation

The aim of the present study was to investigate the effect of somatostatin administration in arthritic rats. Inflammation was induced by daily interplantar injection of 100 microl of Freund's complete adjuvant into the left hind paw of the rat. Arthritis developed 20 days following the first injection and was stable in the inoculate paw. Arthritic rats were treated interplantarly with somatostatin (5 or 10 microg) or with indomethacin (100 microg) daily for 14 days. Inflammatory response was studied at 12 h, 7 and 14 days following drug administration. The effect of somatostatin was determined by local (into popliteal lymph nodes) and systemic production of beta-endorphin. Our results showed that somatostatin treatment significantly increased beta-endorphin levels in the blood and lymphocytes from popliteal lymph nodes. Greater efficiency was seen when 5 microg instead of 10 microg of somatostatin was used. A significant decrease of absolute leukocytosis was observed at the 14th day following somatostatin administration. Moreover, a significant reduction of plasmatic beta-globulins at 12 h and the 7th day and of plasmatic alpha2-globulins at the 14th day was observed after the beginning of somatostatin treatment.

Topics: Alpha-Globulins; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arthritis; beta-Endorphin; Beta-Globulins; Chronic Disease; gamma-Globulins; Indomethacin; Inflammation; Male; Pain; Rats; Rats, Wistar; Somatostatin

Very suggestive evidence for possible role of beta-endorphin (BE) in immune activity has been continuously accumulated in the literature in spite of contradictory results about the involvement of the opiate system in immunological response. The reversed passive Arthus reaction (RPAR) was performed in the dorsal area of the guinea pig skin and immunohistochemical PAP method was applied for visualisation of BE. The positive BE immunoreactivity was observed in sebaceous gland cells (SGC) , mainly localized in the middle layer of the glands, both in the normal and experimental skin. The maximal intensity of immunoreactivity to BE in SGC during RPAR was stronger than normal. In control skin, 50% of SGC revealed positive immunoreactivity comparing to 60-66% in the late phase of RPAR. Sebaceous glands (SGs) probably take part in local homeostasis in the skin, also during immune inflammation.

Topics: Animals; Arthus Reaction; beta-Endorphin; Guinea Pigs; Immunohistochemistry; Inflammation; Male; Sebaceous Glands; Skin

Topics: Animals; beta-Endorphin; Corticotropin-Releasing Hormone; Inflammation; Pain; Rats; Stress, Psychological; T-Lymphocytes

Topics: Analgesia; Animals; beta-Endorphin; Cell Movement; Drug Design; Humans; Immune System; Inflammation; Nociceptors; Pain; Selectins

Opioid-containing immune cells migrate preferentially to inflamed sites, where they release beta-endorphin which activates peripheral opioid receptors to inhibit pain. Immunocyte recruitment is a multistep, sequential engagement of various adhesion molecules located on immune cells and vascular endothelium. Selectins mediate the initial phase of immunoctye extravasation into inflamed sites. Here we show that anti-selectin treatment abolishes peripheral opioid analgesia elicited either endogenously (by stress) or by corticotropin-releasing factor. This results from a blockade of the infiltration of immunocytes containing beta-endorphin and the consequent decrease of the beta-endorphin content in the inflamed tissue. These findings indicate that the immune system uses mechanisms of cell migration not only to fight pathogens but also to control pain in injured tissue. Thus, pain is exacerbated by measures inhibiting the immigration of opioid-producing cells or, conversely, analgesia might be conveyed by adhesive interactions that recruit those cells to injured tissue.

Topics: Analgesia; Animals; beta-Endorphin; Cell Movement; Corticotropin-Releasing Hormone; Drug Design; Immune System; Inflammation; Male; Nociceptors; Pain; Polysaccharides; Radioimmunoassay; Rats; Rats, Wistar; Selectins; Sulfuric Acid Esters

Localized inflammation of a rat's hindpaw elicits an accumulation of beta-endorphin-(END) containing immune cells. We investigated the production, release, and antinociceptive effects of lymphocyte-derived END in relation to cell trafficking. In normal animals, END and proopiomelanocortin mRNA were less abundant in circulating lymphocytes than in those residing in lymph nodes (LN), suggesting that a finite cell population produces END and homes to LN. Inflammation increased proopiomelanocortin mRNA in cells from noninflamed and inflamed LN. However, END content was increased only in inflamed paw tissue and noninflamed LN-immune cells. Accordingly, corticotropin-releasing factor and IL-1beta released significantly more END from noninflamed than from inflamed LN-immune cells. This secretion was receptor specific, calcium dependent, and mimicked by potassium, consistent with vesicular release. Finally, both agents, injected into the inflamed paw, induced analgesia which was blocked by the co-administration of antiserum against END. Together, these findings suggest that END-producing lymphocytes home to inflamed tissue where they secrete END to reduce pain. Afterwards they migrate to the regional LN, depleted of the peptide. Consistent with this notion, immunofluorescence studies of cell suspensions revealed that END is contained predominantly within memory-type T cells. Thus, the immune system is important for the control of inflammatory pain. This has implications for the understanding of pain in immunosuppressed conditions like cancer or AIDS.

Topics: Analysis of Variance; Animals; beta-Endorphin; Corticotropin-Releasing Hormone; Freund's Adjuvant; Hindlimb; Humans; Inflammation; Interleukin-1; Lymph Nodes; Male; Pain; Pro-Opiomelanocortin; Rats; Rats, Wistar; Regression Analysis; RNA, Messenger; T-Lymphocytes; Time Factors; Transcription, Genetic

Topics: Animals; beta-Endorphin; Immunohistochemistry; Inflammation; Pain; Pro-Opiomelanocortin; Radioimmunoassay; Rats; RNA, Messenger; T-Lymphocytes

The aim of the present study was to investigate the effect of somatostatin administration on experimentally induced inflammation in rats. Inflammation was induced by the intraplantar injection of carrageenan (50 microL) into the hind paw of the rat. Animals were treated intraplantarly with somatostatin in a volume of 50 microL at different doses (2.5, 25, and 250 ng, 10 microg). The inflammatory response was studied 120, 180, and 240 min after drug administration. The antinociceptive effect of somatostatin was determined by using the Randall and Selitto test and by local production of beta-endorphin from lymphocytes obtained from popliteal lymph nodes. Data show that small doses of somatostatin were the most effective in reducing hyperalgesia. Moreover, our results show that somatostatin treatment significantly increased beta-endorphin in lymphocytes from popliteal lymph nodes. The secretion of opioid peptides, which enhance analgesia, could be stimulated by locally administered somatostatin.. Acute pain because of intraplantar inflammation induced in rats by carrageenan injection was significantly reduced by small-dose, local administration of somatostatin, which possibly favors beta-endorphin release as a mechanism. These results may have implications regarding treatment of pain conditions associated with an inflammatory response.

Topics: Animals; beta-Endorphin; Carrageenan; Dose-Response Relationship, Drug; Hormone Antagonists; Hyperalgesia; Inflammation; Lymph Nodes; Lymphocytes; Male; Nociceptors; Rats; Rats, Wistar; Somatostatin

We sought to evaluate the antiinflammatory effects of synthetic human beta-endorphin (SHB) when injected into the canine knee joint. Sixteen healthy dogs, aged 1-2 yr, were selected. SHB was injected pre- and postinjury into each knee. The sample size was n = 32 after a randomized factorial arrangement; 2 x 4 with four cases per treatment being performed. Factors considered were: Factor A with two levels: A1 = Preinjury and A2 = Postinjury; Factor B (SHB dose) with four levels: B1 = Control, B2 = 250 micrograms, B3 = 500 micrograms, B4 = 1000 micrograms. The control group received 0.9% NaCl solution. Anesthesia was induced with intravenous thiopental, 14 mg/kg, and acepromazine, 0.5 mg/kg. Injury was produced with an intraarticular injection of 4 mL HCl 0.5 M, which was left in situ for 20 min. Inflammation was measured using the 610 nm absorbency of Evans blue extravasate in biopsy specimens. Histopathologic studies were performed on each knee. We found that beta-endorphin has a clear, dose-related, antiinflammatory effect, reducing the tissue extravasation of Evans blue and its absorbency, especially with large doses. This finding was consistent with the histopathologic observations. We conclude that SHB has an antiinflammatory effect. It is still not clear which mechanisms inhibit polymorphonuclear cell adhesion to vascular endothelium or cell and plasmatic protein extravasation.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; beta-Endorphin; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Humans; Inflammation; Injections, Intra-Articular; Knee Injuries; Knee Joint

This study investigates the role of the opiod receptors and of the opioid peptide beta-endorphin in the development of yeast-induced inflammation in the rat paw. Pretreatment with the opioid receptor antagonist naltrexone (10 mg/kg i.p.) exacerbates the paw edema, while morphine pretreatment (5 and 10 mg/kg) reduces it. In addition, the intravenous injection of a specific anti-beta-endorphin antibody aggravates the yeast-induced inflammation. On the contrary, both the kappa-opioid receptor antagonist MR 1452 (2.5, 5 and 10 mg/kg i.p.) and the delta-opioid receptor antagonist ICI 174-864 (2.5, 5 and 10 mg/kg i.p.) do not interfere with the inflammatory process. After intraplantar injection, naltrexone, morphine and the anti-beta-endorphin antibody do not interfere with the yeast-induced inflammatory edema. Our data suggest that beta-endorphin exerts an inhibitory regulation on the inflammatory responses through the activation of mu-opioid receptors probably located on immune cells, rather than in the paw.

Topics: Animals; Antibodies; Benzomorphans; beta-Endorphin; Edema; Enkephalin, Leucine; Foot; Inflammation; Male; Morphine; Naltrexone; Narcotic Antagonists; Rats; Rats, Sprague-Dawley; Receptors, Opioid; Yeasts

Human semen contains large amounts of opioid peptides and cytokines. We have measured the concentrations of interleukin (IL)-6 in 140 semen samples and of beta-endorphin in 77 semen samples. The median concentration of beta-endorphin in seminal plasma from normozoospermic men (n = 23) was 154.7 pg/ml (10th-90th percentiles, 42.0-774.6), and there was no significant difference in the beta-endorphin concentration among normozoospermic, oligozoospermic (n = 28), asthenozoospermic (n = 15), azoospermic (n = 4) and post-vasectomy (n = 7) samples. There was no correlation between beta-endorphin concentration and sperm characteristics, nor with blood hormones. beta-Endorphin concentration was lower in cases with immunological infertility, as revealed by a positive direct mixed antiglobulin reaction test (n = 12) (P < 0.01), than in matched controls. The median concentration of IL-6 in samples with normal sperm concentration, motility and morphology with or without white blood cells (n = 39) was 26.1 pg/ml (10th-90th percentiles, 7.3-172.3), and there was no significant difference in the IL-6 concentration among normozoospermic, oligozoospermic (n = 46), asthenozoospermic (n = 32), azoospermic (n = 13) and post-vasectomy (n = 10) samples. The IL-6 concentration was significantly higher in cases of varicocele (n = 22) without white blood cells in semen (P < 0.001) than in matched controls without varicocele (n = 23). In addition, the IL-6 concentration was elevated (P < 0.0001) in cases with accessory sex gland inflammation (n = 40). IL-6 concentration was positively correlated with white blood cells in semen (n = 60, r = 0.59, P < 0.0001), but there was no correlation with beta-endorphin concentration. The IL-6 concentration chosen to differentiate between cases with and without accessory gland inflammation was 45.3 pg/ml, with a specificity of 80.6% and a sensitivity of 92.5%. It is concluded that beta-endorphin in seminal plasma plays an immune suppressive role, and that increased IL-6 concentration may be related to testicular dysfunction in cases with varicocele. Furthermore, IL-6 is an accurate marker of accessory sex gland inflammation.

Topics: beta-Endorphin; Case-Control Studies; Genital Diseases, Male; Humans; Infertility, Male; Inflammation; Interleukin-6; Leukocyte Count; Male; Oligospermia; Semen; Varicocele; Vasectomy

The acute effect of the non-tricyclic, pro-serotoninergic, antidepressant drug fluoxetine on inflammatory edema was evaluated in the rat. Fluoxetine significantly and dose dependently reduced the swelling induced by the injection of 10% brewer's yeast suspension in the hindpaw. Both adrenalectomy and hypophysectomy prevented the effect of fluoxetine. In contrast pretreatment with the corticotropin-releasing hormone antagonist alpha-helical CRH-(9-41) did not interfere with the anti-inflammatory action of fluoxetine. Moreover, the drug induced a significant increase of corticosterone plasma concentrations in vivo, whereas, in vitro, it did not stimulate beta-endorphin release from anterior pituitary cells. Our data suggest that fluoxetine exerts a potent anti-inflammatory action by inducing pituitary-adrenocortical activation via serotonin.

Topics: Adrenalectomy; Animals; beta-Endorphin; Corticosterone; Dose-Response Relationship, Drug; Edema; Fluoxetine; Hypophysectomy; Hypothalamo-Hypophyseal System; Inflammation; Male; Pituitary-Adrenal System; Rats; Rats, Sprague-Dawley

To study the effects of the cytokine and neuroendocrine hormone beta-endorphin on the transendothelial migration of neutrophils, bovine pulmonary artery endothelial cells were grown to confluence on PVP-free polycarbonate filters coated with gelatin. Pretreatment of endothelial cell cultures with 1 to 10 mumol/liter of beta-endorphin for 60 min resulted in significantly stimulated migration of subsequently added neutrophils across the endothelial monolayer. The number of neutrophils that migrated across beta-endorphin-treated endothelial cells was similar to the number that traversed untreated monolayers in response to gradients of formylpeptide. Consistently, an additive effect was seen when migration was induced by both beta-endorphin pretreatment of the endothelial cells and a formylpeptide chemotactic gradient. When used at optimal concentration, beta-endorphin was equally effective in stimulating neutrophil migration as was tumor necrosis factor-alpha. In the absence of formylpeptide the effect of apical surface exposure of endothelial cells to beta-endorphin versus basal surface exposure was comparable. Stimulation of neutrophil transendothelial migration in this system appeared to be specific and mediated by opiate receptors, since excess concentration of naloxone completely abolished the effect of beta-endorphin but not of tumor necrosis factor-alpha. These results suggest that beta-endorphin, released during stress, may act upon the endothelium to promote emigration of neutrophils from the vasculature.

Topics: Animals; beta-Endorphin; Cattle; Cells, Cultured; Chemotaxis, Leukocyte; Endothelium, Vascular; Humans; Inflammation; N-Formylmethionine Leucyl-Phenylalanine; Naloxone; Neutrophils; Pulmonary Artery; Receptors, Opioid; Stimulation, Chemical; Tumor Necrosis Factor-alpha

Local analgesic effects of exogenous opioid agonists are particularly prominent in painful inflammatory conditions and are mediated by opioid receptors on peripheral sensory nerves. The endogenous ligands of these receptors, opioid peptides, have been demonstrated in resident immune cells within inflamed tissue of animals and humans. Here we examine in vivo and in vitro whether interleukin 1 beta (IL-1) or corticotropin-releasing factor (CRF) is capable of releasing these endogenous opioids and inhibiting pain. When injected into inflamed rat paws (but not intravenously), IL-1 and CRF produce antinociception, which is reversible by IL-1 receptor antagonist and alpha-helical CRF, respectively, and by the immunosuppressant cyclosporine A. In vivo administration of antibodies against opioid peptides indicates that the effects of IL-1 and CRF are mediated by beta-endorphin and, in addition, by dynorphin A and [Met]enkephalin, respectively. Correspondingly, IL-1 effects are inhibited by mu-, delta-, and kappa-opioid antagonists, whereas CRF effects are attenuated by all except a kappa-antagonist. Finally, IL-1 and CRF produce acute release of immunoreactive beta-endorphin in cell suspensions freshly prepared from inflamed lymph nodes. This effect is reversible by IL-1 receptor antagonist and alpha-helical CRF, respectively. These findings suggest that IL-1 and CRF activate their receptors on immune cells to release opioids that subsequently occupy multiple opioid receptors on sensory nerves and result in antinociception. beta-Endorphin, mu- and delta-opioid receptors play a major role, but IL-1 and CRF appear to differentially release additional opioid peptides.

Topics: Analysis of Variance; Animals; Antibodies; beta-Endorphin; Corticotropin-Releasing Hormone; Cyclosporine; Dose-Response Relationship, Drug; Dynorphins; Endorphins; Enkephalin, Leucine; Enkephalin, Methionine; Humans; Inflammation; Injections; Interleukin-1; Male; Naloxone; Pain; Rats; Rats, Wistar; Recombinant Proteins; Regression Analysis; Somatostatin

We have developed a method to generate immortalized phagocytic and dendritic cell clones from various mouse tissues such as spleen, thymus, brain and bone marrow. The clones were phenotypically characterized and shown to retain the ability to respond to immune or inflammatory signals, e.g., IFN-gamma. Functional cytokine activity and nitric oxide production were maintained in activated macrophages, microglial and dendritic cell clones. Immune functions, such as antigen presentation was exhibited by all clones whereas tissue-specific properties such as the ability to respond to corticotropin-releasing hormone and produce beta-endorphin was shown in microglial cell clones but not in macrophage cell clones, indicating that heterogeneity of cells of the mononuclear-phagocytic lineage can be maintained in vitro after the immortalization procedure. Moreover, the continuous proliferation of the clones could be inhibited by various stimuli and further differentiation of the cells could be achieved in vitro.

Topics: Animals; Antigen-Presenting Cells; beta-Endorphin; Cell Differentiation; Cell Division; Cell Transformation, Viral; Clone Cells; Dendritic Cells; Immunophenotyping; Inflammation; Interferon-gamma; Mice; Mice, Inbred Strains; Nitric Oxide; Phagocytes; Retroviridae; Tumor Necrosis Factor-alpha

The effect of inflammation, induced by unilateral intraplantar injection of Freund's adjuvant, on opioid receptors transported in the sciatic nerve and on opioid receptors present in the paw of the rat was studied by means of in vitro receptor autoradiography using [125I]beta-endorphin (human) as ligand. In the absence of inflammation, human beta-endorphin binding sites accumulated proximally and distally to a ligature placed on the sciatic nerve in a time-dependent manner, indicating bidirectional axonal transport. Some human beta-endorphin binding was also visible in non-inflamed paw tissue. Inflammation of the paw tissue massively increased human beta-endorphin binding on both sides of the sciatic nerve ligature and in the ipsilateral paw tissue. In inflamed paw tissue, beta-endorphin binding accumulated in the cutaneous nerve fibers as well as in the immune cells infiltrating the surrounding tissue. In the sciatic nerve and paw tissue, beta-endorphin binding was displaced by (D-Ala2, N-methyl-Phe4, Gly-ol5)enkephalin and (D-Pen2, D-Pen5)enkephalin, selective mu- and delta-opioid receptor agonists, respectively, and by the universal opioid antagonist naloxone, but not by U-50,488H, a k-selective receptor agonist. Taken together, these data provide neuroanatomical evidence for local inflammation-induced enhanced axonal transport of opioid receptors in rat sciatic nerve and accumulation in paw tissue.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Axonal Transport; beta-Endorphin; Biological Transport; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Enkephalins; Foot; Freund's Adjuvant; Inflammation; Ligation; Male; Naloxone; Nerve Tissue Proteins; Pyrrolidines; Rats; Rats, Wistar; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, mu; Sciatic Nerve

It has been shown previously that opioids induce antinociceptive effects at peripheral sites in the presence of inflammatory processes. Besides being elicited by local injection of opioids, such effects can also be obtained by activation of intrinsic opioid mechanisms, e.g. following stress. In the present study the possible role of cytokines in this mechanism was investigated. Unilateral inflammation of the hindpaw of rats was induced by local injection of Freund's complete adjuvant. Intraplantar injection of tumor necrosis factor alpha (TNF alpha) or interleukin-6 induced a dose-dependent increase in the threshold in the paw pressure test in the inflamed but not in the non-inflamed paw. This increase was prevented by local injection of naloxone and the mu-opioid receptor specific antagonist CTOP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2) as well as by 3-E7, an universal opioid peptide antibody. In rats pretreated with cyclosporin A to suppress the immune system, the antinociceptive effect of TNF alpha was completely inhibited. In concert with previous studies these data indicate that the tested cytokines release opioid peptides (e.g. beta-endorphin and/or enkephalins) from immune cells of the inflamed tissue which act on opioid receptors present on sensory nerve terminals, resulting in antinociception.

Topics: Amino Acid Sequence; Animals; beta-Endorphin; Cyclosporine; Cytokines; Inflammation; Interleukin-6; Male; Molecular Sequence Data; Narcotic Antagonists; Pain; Peripheral Nervous System; Rats; Rats, Wistar; Receptors, Opioid; Tumor Necrosis Factor-alpha

Our previous studies indicate that endogenous opioids (primarily beta-endorphin) released during stressful stimuli can interact with peripheral opioid receptors to inhibit nociception in inflamed tissue of rats. This study sought to localize opioid precursor mRNAs and opioid peptides deriving therefrom in inflamed tissue, identify opioid containing cells and demonstrate their functional significance in the inhibition of nociception. In rats with Freund's adjuvant-induced unilateral hindpaw inflammation we show that: (i) pro-opiomelanocortin and proenkephalin-mRNAs (but not prodynorphin mRNA) are abundant in cells of inflamed, but absent in non-inflamed tissue; (ii) numerous cells infiltrating the inflamed subcutaneous tissue are stained intensely with beta-endorphin and [Met]enkephalin (but only few scattered cells with dynorphin) antibodies; (iii) beta-endorphin is present in T- and B-lymphocytes, monocytes and macrophages; and (iv) whole-body irradiation suppresses stress-induced antinociception in the inflamed paw. Taken together, these data suggest that endogenous opioid peptides are synthesized and processed within various types of immune cells at the site of inflammation. Immunosuppression abolishes the intrinsic antinociception in inflammatory tissue confirming the functional significance of these cells.

Topics: Analysis of Variance; Animals; beta-Endorphin; Calcitonin Gene-Related Peptide; Endorphins; Freund's Adjuvant; Gene Expression; Hindlimb; Inflammation; Male; Nerve Fibers; Nucleic Acid Hybridization; Oligonucleotide Probes; Pain; Pain Measurement; Rats; Rats, Inbred Strains; RNA, Messenger; T-Lymphocytes; Whole-Body Irradiation

Besides the neurophysiological component of pain, subject of a previous article, biochemical components exist. Humorals, released in case of tissue damage and inflammation, cause among others vasodilatation, increased permeability of the blood vessels, itching and pain. Other endogenous biochemical products, among which endorphin beta, lessen the pain. It is also possible to further diminish the noxious (painful) action of the biochemical products with anti-biochemical medication.

Topics: beta-Endorphin; Capillary Permeability; Humans; Inflammation; Neurotransmitter Agents; Pain

The influence of prolonged pain upon hypothalamic opioid peptide release in vitro was examined in rats subjected to Freund's adjuvant (FA)-induced unilateral inflammation of the hindlimb. Basal release of enkephalin (ENK) but not beta-endorphin (END) or dynorphin (DYN) was increased 10 days following FA treatment. Superfusion of corticotropin-releasing factor (CRF; 10(-8) M) stimulated the release of opioid peptides in control hypothalami. CRF, however, failed to modify beta-END and DYN release in hypothalami of FA-treated rats, whereas ENK release was markedly reduced. In contrast, KCl-stimulated opioid peptide release did not differ between FA and control hypothalami. These data demonstrate that prolonged inflammatory pain alters the responsiveness of hypothalamic opioid systems to CRF. It is suggested that this effect is mediated at the level of the CRF neuron or its receptor.

Topics: Animals; Arthritis, Experimental; Behavior, Animal; beta-Endorphin; Corticotropin-Releasing Hormone; Dynorphins; Electroshock; Endorphins; Enkephalin, Methionine; Hypothalamus; In Vitro Techniques; Inflammation; Male; Pain; Potassium Chloride; Radioimmunoassay; Rats; Rats, Inbred Strains; Restraint, Physical; Stress, Psychological

Exogenous opioids can produce localized opioid receptor-mediated antinociception in peripheral inflamed tissue. Previous studies show that activation of endogenous opioids by a cold water swim in rats with hind paw inflammation results in a similar local antinociceptive effect but suggest that pituitary-adrenal opioid pools are not directly involved in producing this effect. Here we show increased amounts of opioid peptides in immune cells infiltrating the inflamed tissue. Furthermore, we demonstrate immunoreactive opioid receptors on peripheral terminals of sensory neurons. The local administration of antibodies against opioid peptides or receptors or systemic pretreatment with the immunosuppressant cyclosporine blocks cold water swim-induced antinociception. These findings suggest that antinociception in inflammation can be brought about by endogenous opioids from immune cells interacting with opioid receptors on peripheral sensory nerves.

Topics: Animals; Antibodies, Monoclonal; beta-Endorphin; Dynorphins; Enkephalin, Methionine; Freund's Adjuvant; Immunoenzyme Techniques; Inflammation; Male; Neurons, Afferent; Pain; Physical Exertion; Radioimmunoassay; Rats; Rats, Inbred Strains; Receptors, Opioid; Reference Values; Skin

This study examined antinociception induced through the activation of local opioid receptors in inflammation by endogenous opioids. Rats developed a unilateral localized inflammation upon injection of Freund's adjuvant into one hindpaw. Four to 6 d later they were subjected to cold water swim (CWS), an environmental stimulus known to activate intrinsic opioid systems. Following CWS (1 min) the animals' withdrawal threshold to noxious pressure applied onto the paws increased significantly more on the inflamed paw than on the noninflamed paw. This unilateral antinociceptive effect in inflamed paws was dose-dependently and stereospecifically reversible by intraplantar (i.pl.) but not systemic (i.v. or s.c.) administration of the opioid antagonist naloxone (18 micrograms). This suggested that CWS-induced antinociception in inflamed tissue was brought about by the activation of local opioid receptors. Antiinflammatory or vasoconstrictive events, as measured by paw volume and temperature, did not contribute to this unilateral antinociception. Receptor-selective antagonists indicated the involvement of mu- and delta- but not kappa-receptors. Intravenous application of a universal antibody to endogenous opioid peptides (3-E7) and a specific antibody to beta-endorphin, but not antisera against metenkephalin or dynorphin, abolished the CWS effect. Finally, the i.pl. injection of synthetic beta-endorphin (1-31) produced an antinociceptive effect in inflamed paws which was reversible by i.pl. naloxone and selective mu- and delta-receptor antagonists. These findings suggest that antinociception in inflamed tissue can be induced through the activation of local opioid receptors by endogenous beta-endorphin released during CWS.

Topics: Animals; beta-Endorphin; Biomechanical Phenomena; Cold Temperature; Dose-Response Relationship, Drug; Foot; Inflammation; Male; Narcotic Antagonists; Nociceptors; Pressure; Rats; Rats, Inbred Strains; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, mu; Sensory Thresholds; Swimming

In response to stressors involving tissue injury, pituitary corticotroph secretion of immunoreactive beta-endorphin (iB-END) could be either due to release of hypothalamic factors such as corticotropin-releasing factor (CRF) or to release of a tissue factor from the periphery. In the present experiments, we investigated whether inflamed tissue releases a factor which evokes pituitary secretion of iB-END. In an initial experiment, rats with an inflamed hindpaw due to carrageenan injection had significantly greater levels of circulating iB-END as compared to rats with saline-injected paws. Removal of afferent input, by hindlimb denervation, failed to block the carrageenan-induced increase in iB-END levels. Subcutaneous perfusates were then collected from inflamed and control hindlimbs and applied to rat anterior pituitary cell cultures. Pituitary release of iB-END due to administration of perfusate from inflamed paws was significantly greater than iB-END release due to perfusate from saline-injected paws or to basal release. The releasing activity in the perfusates was blocked in calcium-free medium and was not due to a direct action of carrageenan, bradykinin, substance P or calcitonin gene-related peptide. The results indicate that inflamed tissue releases a CRF-like factor which stimulates iB-END release both in the denervated rat and cultured pituitary cells.

Topics: Animals; beta-Endorphin; Calcium; Carrageenan; Chromatography, High Pressure Liquid; Corticotropin-Releasing Hormone; Denervation; Hindlimb; Inflammation; Male; Radioimmunoassay; Rats; Rats, Inbred Strains

The role of mast cell histamine in body reactivity of rats under experimental stressful conditions was studied. Animals submitted to chronic anaphylactoid reactions (by injecting compound 48/80 at the dose of 1 mg/kg, i.p., twice daily, for five days), when exposed to cold-restraint stress, exhibited a fully evident inflammatory response in the carrageenin-oedema test, whereas saline-treated rats, under the same experimental conditions, showed reduced paw oedema. Interestingly, a single injection of compound 48/80 increased the pituitary content of Beta-endorphin(ir), but chronic administration failed to produce this effect suggesting that some adaptation of the organism to repeated anaphylactoid reactions may occur. These results support the hypothesis of correlations between pituitary Beta-endorphin and mast cell histamine in the reactivity of the organism to stressful stimuli.

Topics: Animals; beta-Endorphin; Histamine; Inflammation; Male; Mast Cells; p-Methoxy-N-methylphenethylamine; Pituitary Gland; Rats; Rats, Inbred Strains; Stress, Physiological

Effects of hormonal peptides on inflammation were investigated in normal rats receiving injections of urate crystals into the hindpaw. Beta endorphin, somatostatin and alpha melanocyte stimulating hormone injected along with urate crystals produced diminished swelling. Neurotensin and substance P produced increased swelling. Intramuscular calcitonin inhibited inflammation. In rats made deficient in essential fatty acids, thereby becoming deficient in prostaglandins, beta endorphin nullified the proinflammogenic activity of prostaglandin E2. A hypothesis is proposed that modification of inflammation by neuropeptides is part of the continuum of inflammation-regeneration, a generalized host defense mechanism against noxious stimuli.

Topics: Animals; beta-Endorphin; Calcitonin; Dinoprostone; Endorphins; Fatty Acids, Essential; Inflammation; Male; Melanocyte-Stimulating Hormones; Neurotensin; Peptides; Prostaglandins E; Rats; Rats, Inbred Strains; Somatostatin; Substance P; Uric Acid