endothelin-1 and Pain

The endogenous peptide endothelin-1 (ET-1), originally identified as a potent vasoconstrictor, plays a role in a number of painful conditions. In this review article we discuss the mechanisms that are essential for local sensitization by subcutaneously administered ET-1, and report evidence of ET-1's ability to sensitize distant regions of the body, through the central nervous system and, likely, coupling through the spinal cord. In addition, we will review the latest information on the role of ET-1 in cancerous and non-cancerous conditions. Cancer pain has indeed been shown to be attenuated by antagonists of endothelin receptors, and ET-1 is known to be secreted by cancer cells of many different histologic types. Furthermore, a growing body of evidence links increased expression and secretion of ET-1 to the occurrence of non-cancer related pain syndromes, such as inflammatory and neuropathic pain syndromes.

Topics: Animals; Central Nervous System; Disease Models, Animal; Endothelin Receptor Antagonists; Endothelin-1; Humans; Inflammation Mediators; Neoplasms; Nociceptors; Pain; Receptors, Endothelin; Receptors, G-Protein-Coupled; Sensory Receptor Cells

Pain in patients with metastatic cancer contributes to increased suffering in those already burdened by their advancing illness. The causes of this pain are unknown, but are likely to involve the action of tumour-associated mediators and their receptors. In recent years, several chemical mediators have increasingly come to the forefront in the pathophysiology of cancer pain. One such mediator, endothelin-1 (ET-1), is a peptide of 21 amino acids that was initially shown to be a potent vasoconstrictor. Extensive research has revealed that members of the ET family are indeed produced by several epithelial cancerous tumours, in which they act as autocrine and/or paracrine growth factors. Several preclinical and clinical studies of various malignancies have suggested that the ET axis may represent an interesting contributor to tumour progression. In addition, evidence is accumulating to suggest that ET-1 may contribute to pain states both in humans and in other animals. ET-1 both stimulates nociceptors and sensitises them to painful stimuli. Selective stimulation of ET receptors has been implicated as a cause of inflammatory, neuropathic and tumoural pain. ET-1-induced pain-related behaviour seems to be mediated either solely by one receptor type or via both endothelin-A receptors (ETAR) and endothelin-B receptors (ETBR). Whereas stimulation of ETAR on nociceptors always elicits a pain response, stimulation of ETBR may cause analgesia or elicit a pain response, depending on the conditions. The administration of ETAR antagonists in the receptive fields of these nociceptors has been shown to ameliorate pain-related behaviours in animals, as well as in some patients with advanced metastatic prostate cancer. The identification of tumour-associated mediators that might directly or indirectly cause pain in patients with metastatic disease, such as ET-1, should lead to improved, targeted analgesia for patients with advanced cancer. In this review, we will describe the current status of the role of ET-1 in different types of painful syndromes, with special emphasis on its role in the pathophysiology of cancer pain. Finally, potential new treatment options that are based on the role of the ET axis in the pathophysiology of cancer are elaborated.

Topics: Animals; Endothelin-1; Humans; Hyperalgesia; Pain; Pain Management; Receptors, Endothelin

Recent findings by Khodorova et al. demonstrate that the vasoconstrictor endothelin-1 plays an important role in certain nociceptive behaviors in an animal model of pain, through activation of sensory neurons. Endothelin-1 might also have the unexpected capacity to release an opioid from surrounding keratinocytes and thereby inhibit the pain response. Such results suggest that, in the periphery, there are important interactions between sensory nerve terminals and surrounding cells, and that glia and keratinocytes could modulate the perception of environmental stimuli to a greater extent than previously considered.

Topics: Analgesia; Animals; Behavior, Animal; Disease Models, Animal; Endothelin-1; Keratinocytes; Narcotics; Pain; Receptors, Endothelin; Sensory Receptor Cells

Alterations in bone architecture and mineral metabolism are common complications of malignancy. Cancers such as breast, prostate, and lung can affect the skeleton either indirectly through the elaboration of factors that act to disrupt normal calcium homeostasis at the level of the kidney and bone; or directly via secondary spread of tumor to bone. Although the pathophysiology of these skeletal complications is diverse, it is clear that the osteoclast and osteoblast are not just bystanders but are active participants in the development and progression of hypercalcemia and bone metastasis. Our understanding of the molecular mechanisms of metastasis leading to tumor cell escape, homing, adhesion, and secondary growth in a hospitable environment are evolving. Treatment modalities aimed at not only reducing tumor burden but altering the skeletal response to tumor have shown benefit. Newer generation bisphosphonates are quite effective in controlling hypercalcemia of malignancy and have been shown to delay progression of skeletal metastases. Clearly, cancer-associated bone morbidity remains a major public health problem. To improve therapy and prevention it is important to understand the pathophysiology of the effects of cancer on bone. This review will detail scientific advances regarding this area.

Topics: Animals; Atrasentan; Bone Neoplasms; Cell Adhesion Molecules; Cytokines; Diphosphonates; Endothelin-1; Female; Gene Expression Regulation, Neoplastic; Humans; Hypercalcemia; Immunotherapy; Intercellular Signaling Peptides and Proteins; Male; Mice; Mice, Nude; Neoplasm Proteins; Osteoblasts; Osteolysis; Pain; Pain Management; Pyrrolidines; Xenograft Model Antitumor Assays

Topics: Endothelin-1; Humans; Male; Pain; Prostate; Prostatic Neoplasms; Receptors, Endothelin; Tumor Cells, Cultured

Although pain is a frequent feature in patients with cancer, its etiology is still poorly understood. In recent years, endothelin-1 (ET-1) has become a major target molecule in the etiology of cancer pain. In this randomised, double-blind study the effects of intradermal injection of ET-1 on spontaneous pain, temperature perception and sensation of punctate stimulation were evaluated. Thirty-five subjects were randomised to receive either placebo or one of four concentrations of ET-1 (ranging from 10(-10) to 10(-6)M). Besides assessment of spontaneous pain, three neurosensory testings were performed: (1) cold and warm sensation, (2) cold and heat pain, and (3) punctate stimulation using a von Frey monofilament. ET-1 produced a dose-dependent flare zone that was absent after placebo injection. Subjects reported a short-lasting spontaneous pain upon administration of the highest concentrations of ET-1. Injection of ET-1 induced a long-lasting and dose-dependent punctate hyperalgesia in an area around the injection site (secondary hyperalgesia). Thermal testing revealed a short period of hypoesthesia to non-noxious warm and cold stimuli after some doses of ET-1. In addition to the mechanical hyperalgesia, intradermal injection of ET-1 almost instantaneously induced a state of cold hyperalgesia outlasting the study period (120 min). No development of heat hyperalgesia was observed. The observed psychophysical characteristics of this new model of ET-1 induced nociception indicate its potential as a human experimental model for cancer pain.

Topics: Adult; Behavior; Biophysics; Dose-Response Relationship, Drug; Double-Blind Method; Endothelin-1; Humans; Hyperalgesia; Injections, Intradermal; Male; Models, Neurological; Neoplasms; Nociceptors; Pain; Receptor, Endothelin A; Sensory Receptor Cells; Thermosensing

Topics: Atrasentan; Disease Progression; Double-Blind Method; Endothelin-1; Humans; Male; Neoplasm Metastasis; Pain; Prostate-Specific Antigen; Prostatic Neoplasms; Pyrrolidines; Quality of Life; Survival Analysis; Treatment Outcome

Single intradermal injections of nerve growth factor (NGF) evoke prolonged but temporally distinct sensitization patterns to somatosensory stimuli. Focal administration of the non-histaminergic pruritogen cowhage but not histamine resulted in elevated itch at day 21 after NGF administration. Here, we injected bovine adrenal medulla peptide 8-22 (BAM8-22), β-alanine (β-ALA) and endothelin-1 (ET-1) into NGF-treated skin of 11 healthy volunteers and investigated the corresponding itch/pain and flare reactions. β-ALA was the weakest pruritogen, while BAM8-22 and ET-1 were equally potent as histamine. NGF did not sensitize itch or flare reactions induced by any compound, but injection and evoked pain were increased at day 21 and 49. The involvement of histamine H1 receptors in itch was explored in eight subjects after oral cetirizine. ET-1-induced itch and flare were significantly reduced. BAM8-22 and β-ALA itch were not affected, but flare responses after BAM8-22 reduced by 50%. The results indicate that a single NGF injection does not sensitize for experimentally induced itch but increases pain upon pruritogen injection. In healthy humans, pruritic and algetic processing appear differentially regulated by NGF. However, in patients suffering chronic itch, prolonged elevation of NGF-levels under inflammatory conditions may contribute to elevated itch.

Topics: Adult; Animals; beta-Alanine; Cattle; Endothelin-1; Female; Humans; Male; Nerve Growth Factor; Pain; Peptide Fragments; Pruritus; Skin

Endothelin-1 (ET-1) is one of the probable inflammatory factors stimulating cartilage degradation in osteoarthritis (OA) pathogenesis.. To assess ET-1 level in OA and its correlation with radiographic findings, cartilage morphology and clinical parameters.. One hundred and thirty-nine subjects (89 OA, 50 controls) were included in this cross-sectional study. Both knee and hand joints of the participants were examined using plain radiography and ultrasound imaging by which distal femoral cartilage thickness/grading and second metacarpophalangeal cartilage thickness were assessed. Subjects were evaluated for pain and functional status using visual analogue scale, Western Ontario and McMaster Universities Arthritis Index and Duruöz Hand Index.. Serum ET-1 levels were higher in the OA group than the control group. Serum ET-1 levels were not correlated with cartilage thickness in patients with OA. Serum ET-1 levels were not correlated with either pain or other clinical parameters in the knee OA group and in the hand OA group.. This is the first study evaluating the relationship between serum ET-1 levels and cartilage morphology and clinical parameters, which did not show any conclusive result. Future studies, overcoming the limitations of this study, might provide a better understanding of the role of ET-1 in the pathogenesis of OA.

Topics: Biomarkers; Case-Control Studies; Cross-Sectional Studies; Endothelin-1; Female; Hand Joints; Humans; Knee Joint; Middle Aged; Osteoarthritis, Knee; Pain; Pain Measurement; Radiography; Severity of Illness Index; Ultrasonography

Endometriosis is a gynaecological disease exhibiting severe pelvic pain, but the mechanism of pain production remains unknown. Bradykinin (BK) is known as an inflammatory mediator, and shows elevated levels in inflammatory diseases such as rheumatoid arthritis. In the present study, we evaluated whether BK is involved in endometriosis-related pain.. Endometriotic lesions were used for immunohistochemistry. Primary cultures of endometriotic stromal cells (ESC) were stimulated with IL-1β and/or BK. Quantitative RT-PCR was used to evaluate the mRNA expressions of BK receptors (BKR) and endothelin-1 in ESC. The concentration of endothelin-1 in cystic fluid of endometrioma or non-endometrioma was measured with ELISA. The conditioned medium of ESC stimulated with IL-1β and/or BK was injected intraplantarly in mice, and evaluated whether pain-related licking behaviour was elicited.. The expressions of BK and BKR in endometriotic lesions were observed by immunohistochemistry. In vitro experiments showed that IL-1β induced BKR-B1 and B2 on ESC. Activation of these receptors by BK significantly induced endothelin-1 expression in ESC, which was negated completely by HOE-140, a BKR-B2 antagonist. The cystic fluid of endometrioma contained higher amount of endothelin-1 compared to non-endometrioma. Intraplantar injection of the conditioned medium of ESC treated with IL-1β and BK significantly induced licking behaviour, which was suppressed with BQ-123, an endothelin type-A receptor antagonist.. The present study demonstrated the presence and the function of the BK axis in endometriosis, and established a potential new therapy target for endometriosis-related pain.. The present study demonstrated (1) the presence and the function of the BK system in endometriosis, (2) activation of BKR induced endothelin-1 in endometriotic lesion and (3) blocking endothelin-1 was effective to decrease pain.

Topics: Animals; Behavior, Animal; Bradykinin; Bradykinin B2 Receptor Antagonists; Case-Control Studies; Cells, Cultured; Culture Media, Conditioned; Cyst Fluid; Endometriosis; Endothelin-1; Female; Humans; Interleukin-1beta; Mice; Ovarian Diseases; Pain; Peritoneal Diseases; Receptors, Bradykinin; RNA, Messenger; Stromal Cells

Oral ulcer is the most common oral disease and leads to pain during meals and speaking, reducing the quality of life of patients. Recent evidence using animal models suggests that oral ulcers induce cyclooxygenase-dependent spontaneous pain and cyclooxygenase-independent mechanical allodynia. Endothelin-1 is upregulated in oral mucosal inflammation, although it has not been shown to induce pain in oral ulcers. In the present study, we investigated the involvement of endothelin-1 signaling with oral ulcer-induced pain using our proprietary assay system in conscious rats. Endothelin-1 was significantly upregulated in oral ulcers experimentally induced by topical acetic acid treatment, while endothelin-1 production was suppressed by antibacterial pretreatment. Spontaneous nociceptive behavior in oral ulcer model rats was inhibited by swab applications of BQ-788 (ET

Topics: Acetanilides; Anilides; Animals; Bridged Bicyclo Compounds; Caproates; Cinnamates; Disease Models, Animal; Endothelin-1; Male; Oligopeptides; Oral Ulcer; Pain; Peptides, Cyclic; Piperidines; Purines; Rats; Rats, Wistar; Signal Transduction; Sulfonamides; TRPV Cation Channels

Sickle cell disease is associated with acute painful episodes and chronic intractable pain. Endothelin-1, a known pain inducer, is elevated in the blood plasma of both sickle cell patients and mouse models of sickle cell disease. We show here that the levels of endothelin-1 and its endothelin type A receptor are increased in the dorsal root ganglia of a mouse model of sickle cell disease. Pharmacologic inhibition or neuron-specific knockdown of endothelin type A receptors in primary sensory neurons of dorsal root ganglia alleviated basal and post-hypoxia evoked pain hypersensitivities in sickle cell mice. Mechanistically, endothelin type A receptors contribute to sickle cell disease-associated pain likely through the activation of NF-κB-induced Nav1.8 channel upregulation in primary sensory neurons of sickle cell mice. Our findings suggest that endothelin type A receptor is a potential target for the management of sickle cell disease-associated pain, although this expectation needs to be further verified in clinical settings.

Topics: Anemia, Sickle Cell; Animals; Biomarkers; Disease Models, Animal; Disease Susceptibility; Endothelin-1; Ganglia, Spinal; Hyperalgesia; Male; Mice; Mice, Knockout; Mice, Transgenic; Pain; Posterior Horn Cells; Receptor, Endothelin A

Endothelin-1 (ET-1) and Nerve Growth Factor (NGF) are proteins, released from cancer-ridden tissues, which cause spontaneous pain and hypersensitivity to noxious stimuli. Here we examined the electrophysiological and behavioral effects of these two agents for evidence of their interactions. Individual small-medium cultured DRG sensory neurons responded to both ET-1 (50 nM, n=6) and NGF (100 ng/ml, n=4), with increased numbers of action potentials and decreased slow K(+) currents; pre-exposure to ET-1 potentiated NGF´s actions, but not vice versa. Behaviorally, single intraplantar (i.pl.) injection of low doses of ET-1 (20 pmol) or NGF (100 ng), did not increase hindpaw tactile or thermal sensitivity, but their simultaneous injections sensitized the paw to both modalities. Daily i.pl. injections of low ET-1 doses in male rats caused tactile sensitization after 21 days, and enabled further tactile and thermal sensitization from low dose NGF, in ipsilateral and contralateral hindpaws. Single injections of 100 ng NGF, without changing the paw's tactile sensitivity by itself, acutely sensitized the ipsilateral paw to subsequent injections of low ET-1. The sensitization from repeated low ET-1 dosing and the cross-sensitization between NGF and ET-1 were both significantly greater in female than in male rats. These findings reveal a synergistic interaction between cutaneously administered low doses of NGF and ET-1, which could contribute to cancer-related pain.

Topics: Animals; Endothelin-1; Female; Injections, Subcutaneous; Male; Nerve Growth Factor; Pain; Pain Measurement; Physical Stimulation; Protein Binding; Rats; Rats, Sprague-Dawley; Touch

Children with sickle cell disease (SCD) have painful vaso-occlusive episodes (VOEs), which often reoccur across the individual's lifespan. Vaso-constrictive and vaso-dilatory molecules have been hypothesized to play a role in VOEs. Endothelin-1 (ET-1) is a potent vasoconstrictor that is released during VOEs and is correlated with pain history. Apelin is a vaso-dilatory peptide that also has a modulatory role in pain processing. We hypothesize that the ratio between vaso-dilatory and vaso-constrictive tone in children with SCD may be a marker of pain sensitization and vaso-occlusion. Plasma endothelin and apelin levels were measured in 47 children with SCD. Procedural pain and baseline pain were assessed via child- and caregiver-reports and observational distress. Pain history was assessed using retrospective chart review. Plasma apelin was related to age, with decreased levels in older children. The ratio between apelin and ET-1 was negatively correlated to observational baseline pain. The ratio between apelin and Big ET was negatively correlated to caregiver ratings of baseline pain and positively correlated to history of VOEs, which is possibly due to hydroxyurea treatment. These results suggest that an imbalance in the apelin and endothelin systems may contribute to an increasing number of VOEs and baseline pain in children with SCD.

Topics: Adolescent; Age Factors; Anemia, Sickle Cell; Antisickling Agents; Apelin; Biomarkers; Child; Child, Preschool; Endothelin-1; Female; Gene Expression Regulation; Humans; Hydroxyurea; Intercellular Signaling Peptides and Proteins; Male; Pain; Pain Measurement; Signal Transduction; Vasoconstriction; Vasodilation

Canine osteosarcoma (OS) is associated with localized pain as a result of tissue injury from tumor infiltration and peritumoral inflammation. Malignant bone pain is caused by stimulation of peripheral pain receptors, termed nociceptors, which reside in the localized tumor microenvironment, including the periosteal and intramedullary bone cavities. Several nociceptive ligands have been determined to participate directly or indirectly in generating bone pain associated with diverse skeletal abnormalities.. Canine OS cells actively produce nociceptive ligands with the capacity to directly or indirectly activate peripheral pain receptors residing in the bone tumor microenvironment.. Ten dogs with appendicular OS.. Expression of nerve growth factor, endothelin-1, and microsomal prostaglandin E synthase-1 was characterized in OS cell lines and naturally occurring OS samples. In 10 dogs with OS, circulating concentrations of nociceptive ligands were quantified and correlated with subjective pain scores and tumor volume in patients treated with standardized palliative therapies.. Canine OS cells express and secrete nerve growth factor, endothelin-1, and prostaglandin E2. Naturally occurring OS samples uniformly express nociceptive ligands. In a subset of OS-bearing dogs, circulating nociceptive ligand concentrations were detectable but failed to correlate with pain status. Localized foci of nerve terminal proliferation were identified in a minority of primary bone tumor samples.. Canine OS cells express nociceptive ligands, potentially permitting active participation of OS cells in the generation of malignant bone pain. Specific inhibitors of nociceptive ligand signaling pathways might improve pain control in dogs with OS.

Topics: Animals; Cell Line, Tumor; Dog Diseases; Dogs; Endothelin-1; Gene Expression Regulation, Neoplastic; Humans; Intramolecular Oxidoreductases; Ligands; Mice; Nerve Growth Factor; Nociceptors; Osteosarcoma; Pain; Prostaglandin-E Synthases; Rats

We evaluated the role of a mechanically-gated ion channel, Piezo2, in mechanical stimulation-induced enhancement of hyperalgesia produced by the pronociceptive vasoactive mediator endothelin-1, an innocuous mechanical stimulus-induced enhancement of hyperalgesia that is vascular endothelial cell dependent. We also evaluated its role in a preclinical model of a vascular endothelial cell dependent painful peripheral neuropathy.. The local administration of oligodeoxynucleotides antisense to Piezo2 mRNA, at the site of nociceptive testing in the rat's hind paw, but not intrathecally at the central terminal of the nociceptor, prevented innocuous stimulus-induced enhancement of hyperalgesia produced by endothelin-1 (100 ng). The mechanical hyperalgesia induced by oxaliplatin (2 mg/kg. i.v.), which was inhibited by impairing endothelial cell function, was similarly attenuated by local injection of the Piezo2 antisense. Polymerase chain reaction analysis demonstrated for the first time the presence of Piezo2 mRNA in endothelial cells.. These results support the hypothesis that Piezo2 is a mechano-transducer in the endothelial cell where it contributes to stimulus-dependent hyperalgesia, and a model of chemotherapy-induced painful peripheral neuropathy.

Topics: Animals; Antineoplastic Agents; Endothelial Cells; Endothelin-1; Gene Expression Profiling; Gene Expression Regulation; Hyperalgesia; Ion Channels; Male; Models, Animal; Oligonucleotides, Antisense; Organoplatinum Compounds; Oxaliplatin; Pain; Peripheral Nervous System Diseases; Rats; Rats, Sprague-Dawley; Touch

At our body surface, the epidermis absorbs UV radiation. UV overexposure leads to sunburn with tissue injury and pain. To understand how, we focus on TRPV4, a nonselective cation channel highly expressed in epithelial skin cells and known to function in sensory transduction, a property shared with other transient receptor potential channels. We show that following UVB exposure mice with induced Trpv4 deletions, specifically in keratinocytes, are less sensitive to noxious thermal and mechanical stimuli than control animals. Exploring the mechanism, we find that epidermal TRPV4 orchestrates UVB-evoked skin tissue damage and increased expression of the proalgesic/algogenic mediator endothelin-1. In culture, UVB causes a direct, TRPV4-dependent Ca(2+) response in keratinocytes. In mice, topical treatment with a TRPV4-selective inhibitor decreases UVB-evoked pain behavior, epidermal tissue damage, and endothelin-1 expression. In humans, sunburn enhances epidermal expression of TRPV4 and endothelin-1, underscoring the potential of keratinocyte-derived TRPV4 as a therapeutic target for UVB-induced sunburn, in particular pain.

Topics: Analysis of Variance; Animals; Cells, Cultured; Endothelin-1; Epithelial Cells; Immunohistochemistry; Mice; Mice, Transgenic; Microscopy, Electron; Pain; Signal Transduction; Skin; Sunburn; TRPV Cation Channels; Ultraviolet Rays

Endothelin-1 (ET-1) is an endogenously expressed potent peptide vasoconstrictor. There is growing evidence that ET-1 plays a role in the pain signaling system and triggers overt nociception in humans. The underlying neuronal pathways are still a matter of great debate. In the present study, we applied an intradermal ET-1 sensitization model to induce mechanical hyperalgesia in healthy subjects. Functional magnetic resonance imaging (fMRI) was used to tease out the cortical regions associated with the processing of ET-1-induced punctate hyperalgesia, as compared to a nonnoxious mechanical stimulation of the contralateral arm. Von Frey hair testing revealed the presence of increased responsiveness to punctate stimulation in all subjects. Activational patterns between nonpainful control stimulation and hyperalgesic stimulation were compared. Two major observations were made: (1) all cortical areas that showed activation during the control stimulation were also present during hyperalgesic stimulation, but in addition, some areas showed bilateral activation only during hyperalgesic stimulation, and (2) some brain areas showed significantly higher signal changes during hyperalgesic stimulation. Our findings suggest that injection of ET-1 leads to a state of punctate hyperalgesia, which in turn causes the activation of multiple brain regions. This indicates that ET-1 activates an extended neuronal pathway.

Topics: Adult; Cerebral Cortex; Endothelin-1; Female; Humans; Hyperalgesia; Magnetic Resonance Imaging; Male; Neurons; Nociception; Pain; Radiography; Signal Transduction; Spinal Nerves

IL-33 signals through ST2 receptors and induces adaptive and innate inflammation. IL-33/ST2 is involved in adaptive inflammation-induced pain. Here, we have investigated the contribution of IL-33/ST2-triggered mechanisms to carrageenin-induced innate inflammation.. Carrageenin- and IL-33-induced inflammatory responses were assessed in BALB/c- (WT) and ST2-deficient ((-/-) ) mice as follows: oedema (plethysmometer), myeloperoxidase activity (colorimetric assay), mechanical hyperalgesia (electronic version of von Frey filaments), cytokine levels (ELISA), PGE2 (RIA), mRNA expression (quantitative PCR), drug treatments targeting leukocyte recruitment (fucoidin), TNF-α (infliximab), CXCL1 (antibody to CXCL1), IL-1 (IL-1ra), endothelin ETA (clazosentan) and ETB (BQ788) receptors and COX (indomethacin).. Carrageenin injection increased ST2 and IL-33 mRNA expression and IL-33 production in paw skin samples. Carrageenin-induced paw oedema, hyperalgesia and myeloperoxidase activity were reduced in ST2(-/-) compared with WT mice, effects mimicked by IL-33 injection in the paw. Furthermore, IL-33-induced hyperalgesia was reduced by fucoidin suggesting a role for recruited leukocytes in its hyperalgesic effect. IL-33-induced hyperalgesia in naïve mice was reduced by treatments targeting TNF, CXCL1, IL-1, endothelin receptors and COX while carrageenin-induced ST2-dependent TNF-α, CXCL1, IL-1β, IL-10 and PGE2 production and preproET-1 mRNA expression. Combining IL-33 and carrageenin at doses that were ineffective as single treatment induced significant hyperalgesia, oedema, myeloperoxidase activity and cytokine production in a ST2-dependent manner.. IL-33/ST2 signalling triggers the production of inflammatory mediators contributing to carrageenin-induced inflammation. These data reinforces the importance of IL-33/ST2 signalling as a target in innate inflammation and inflammatory pain.

Topics: Animals; Carrageenan; Cytokines; Dinoprostone; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin-1; Female; Inflammation; Inflammation Mediators; Interleukin-1 Receptor-Like 1 Protein; Interleukin-33; Interleukins; Male; Mice; Mice, Inbred BALB C; Mice, Knockout; Pain; Receptors, Interleukin; RNA, Messenger; Signal Transduction

To date, suggestions that endothelin-1 (ET-1) causes nociception and pruritus are based on results in preclinical models in which responses to pruritic and nociceptive stimuli cannot be distinguished. This study reexamines these sensory effects of ET-1 in the new mouse cheek model, in which pruritogens and algogens evoke distinct behavioral responses.. Mice received intradermal (i.d.) injections of test substances into the left cheek and bouts of hind limb scratches or forepaw wipes, directed to the injection site, were considered indicative of pruritus and nociception, respectively.. Histamine and capsaicin selectively evoked scratching and wipes, respectively, whereas ET-1 (3-60 pmol) promoted dose-dependent bouts of both behaviors. While scratching and wipe responses to ET-1 (30 pmol) were potentiated by BQ-788 (an ET(B) receptor antagonist) and reduced by co-injection of BQ-788 plus BQ-123 (an ET(A) receptor antagonist), BQ-123 alone inhibited scratching responses only. CTOP (μ-opioid receptor selective antagonist) only augmented scratching responses to ET-1, whereas DAMGO (μ-opioid receptor selective agonist) reduced both behaviors. Loratadine (histamine H(1) receptor antagonist) marginally reduced scratching, but markedly suppressed wipes.. These results demonstrate that ET-1 evokes pruritic and nociceptive behaviors in the mouse cheek model. Both responses to ET-1 appear to be mediated via ET(A) receptors and subjected to limitation by simultaneous ET(B) receptor activation. Local endogenous opioids acting on μ-opioid receptors selectively modulate the pruritic response to ET-1, whereas histamine, possibly derived from mast cells and acting on H(1) receptors, contributes importantly to the nociceptive effect of ET-1 in this model.

Topics: Animals; Behavior, Animal; Capsaicin; Cheek; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Histamine; Injections, Intradermal; Male; Mice; Pain; Pruritus; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Histamine H1; Receptors, Opioid, mu

The impact of pain early in life is a salient issue for sickle cell disease (SCD), a genetic condition characterized by painful vaso-occlusive episodes (VOEs) that can begin in the first year of life and persist into adulthood. This study examined the effects of age and pain history (age of onset and frequency of recent VOEs) on acute procedural pain in children with SCD. Endothelin-1, a vaso-active peptide released during VOEs and acute tissue injury, and its precursor, Big Endothelin, were explored as markers of pain sensitization and vaso-occlusion. Sixty-one children with SCD (ages 2 to 18) underwent venipuncture at routine health visits. Procedural pain was assessed via child and caregiver reports and observational distress. Pain history was assessed using retrospective chart review. Three primary results were found: 1) younger age was associated with greater procedural pain across pain outcomes; 2) higher frequency of VOEs was associated with greater procedural pain based on observational distress (regardless of age); and 3) age was found to moderate the relationship between VOEs and procedural pain for child-reported pain and observational distress for children 5 years of age and older. Associations between the endothelin variables and pain prior to venipuncture were also observed.. For children with SCD, the child's age and recent pain history should be considered in procedural pain management. The endothelin system may be involved in preprocedure pain, but additional research is needed to understand the role of endothelins in pain sensitization.

Topics: Adolescent; Age Factors; Anemia, Sickle Cell; Child; Child, Preschool; Endothelin-1; Female; Humans; Infant; Male; Pain; Pain Management; Pain Measurement; Pain Perception; Phlebotomy; Surveys and Questionnaires

Endothelin-1 (ET-1) has been suggested to be involved in different types of pain due to its neuromodulatory nature. However, its role in inflammatory pain processing, specifically the origin-specific effect, has not yet been clearly defined. Therefore, the aim of this study is to determine the role of cell-type specific ET-1 induction in the modulation of inflammatory pain processing.. The current study assesses the effects of ET-1 over-expression specifically targeted to astrocytes (GET-1) or endothelial cells (TET-1) on the expression of pain-like behaviors induced by a model of inflammatory pain, consisting of a formalin injection into the hind paw.. The baseline sensitivity thresholds of GET-1 and TET-1 mice to the response elicited by tactile and radiant heat stimulation were similar to those observed in age-matched non-transgenic (NTg) controls. Relative to the NTg controls, GET-1 mice displayed a marked decrease in pain-like behavioral responses during the second phase of formalin-induced pain (i.e., 15-20 min after injection), whereas the responses elicited in TET-1 mice were unaltered. The levels of mRNA encoding adrenomedullin, calcitonin gene-related peptide and calcitonin-like receptor were elevated in the spinal cord of saline-injected GET-1 mice compared to those of NTg mice.. The current results support a suppressor role for astrocyte-derived ET-1 in inflammatory pain and suggest that the study of GET-1 mice might provide mechanistic insights for improving the treatment of inflammatory pain.

Topics: Adrenomedullin; Animals; Astrocytes; Behavior, Animal; Calcitonin Gene-Related Peptide; Calcitonin Receptor-Like Protein; Disease Models, Animal; Endothelial Cells; Endothelin-1; Formaldehyde; Gene Expression Regulation; Inflammation; Mice; Mice, Inbred C57BL; Mice, Transgenic; Pain; RNA, Messenger; Spinal Cord

Subcutaneous injection of the peptide endothelin-1 (ET-1) into the rat's footpad is known to cause rapid, transient ipsilateral mechanical and thermal sensitization and nocifensive hind paw flinching. Here we report that local injection of ET-1 (2 nmoles) into one hind paw slowly sensitizes the contralateral paw to chemical and mechanical stimulation. There was a 1.5-2-fold increase in the hind paw flinching response, over that from the first injection, to a second injection of the same dose of ET-1 delivered 24 h later into the contralateral paw. A similar increase in the number of flinches during the second phase of the response to formalin also occurred in the contralateral paw 24 h after ET-1. The contralateral paw withdrawal threshold to von Frey hairs was lowered by approximately 55% at 24 h after ipsilateral ET-1 injection. ET-1 injected s.c. at a segmentally unrelated location, the nuchal midline, caused no sensitization of the paws, obviating a systemic route of action. Local anesthetic block of the ipsilateral sciatic nerve during the period of initial response to ipsilateral ET-1 prevented contralateral sensitization, indicating the importance of local afferent transmission, although ipsilateral desensitization was not changed. These findings suggest that peripheral ET-1 actions lead to central sensitization that alters responses to selected stimuli.

Topics: Anesthetics, Local; Animals; Brain; Endothelin-1; Foot; Formaldehyde; Functional Laterality; Hindlimb; Male; Neurons, Afferent; Pain; Pain Measurement; Pain Threshold; Peripheral Nerves; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Spinal Cord; Synaptic Transmission; Time Factors

The peptide endothelin-1 (ET1), which was originally identified as a vasoconstrictor, has emerged as a critical regulator of a number of painful conditions, including inflammatory pain and tumor-associated pain. There is considerable pharmacological evidence supporting a role for endothelin A receptors (ET(A)) in mediating ET1-induced pro-algesic functions. ET(A) receptors are expressed in small-diameter nociceptive neurons, but also found in a variety of other cell types in peripheral tissues, including immune cells, keratinocytes, endothelial cells, which have the potential to modulate nociception. To elucidate the functional contribution of ET(A) receptors expressed in sensory neurons towards the functions of the ET1 axis in pathological pain states, we undertook a conditional gene deletion approach to selectively deplete expression of ET(A) in sensory nerves, preserving expression in non-neural peripheral tissues; the expression of ET(B) remained unchanged. Behavioural and pharmacological experiments showed that only late nociceptive hypersensitivity caused by ET1 is abrogated upon a loss of ET(A) receptors on nociceptors and further suggest that ET1-induced early nociceptive hypersensitivity involves activation of ET(A) as well as ET(B) receptors in non-neural peripheral cells. Furthermore, in the context of alleviation of cancer pain and chronic inflammatory pain by ET(A) receptor antagonists, we observed in corresponding mouse models that the contribution of ET(A) receptors expressed in nociceptors is most significant. These results help understand the role of ET(A) receptors in complex biological processes and peripheral cell-cell interactions involved in inflammatory and tumor-associated pain.

Topics: Analysis of Variance; Animals; Carcinoma; Disease Models, Animal; Endothelin A Receptor Antagonists; Endothelin-1; Ganglia, Spinal; Hyperalgesia; Lung Neoplasms; Mice; Mice, Inbred C57BL; Mice, Transgenic; NAV1.8 Voltage-Gated Sodium Channel; Nociceptors; Pain; Pain Measurement; Peptides, Cyclic; Receptor, Endothelin A; RNA, Messenger; Sensory Receptor Cells; Sodium Channels; Time Factors; Tubulin

Transient receptor potential ankyrin subfamily member 1 (TRPA1) is a nonselective cation channel known as a noxious cold-activated ion channel. Recent findings implicated its involvement in acute and chronic cold nociception processes. Here, we investigated whether TRPA1 is involved in endothelin-1 (ET-1)-induced spontaneous pain-like behavior in C57BL/6J mice. We found that TRPA1 antagonists, HC-030031 and AP18, significantly reduced the pain-like behavior caused by ET-1. AP18 also significantly reduced the pain caused by cinnamaldehyde, an agonist of TRPA-1. However, AP18 did not alleviate the pain caused by capsaicin. The pain-like behavior caused by ET-1 was inhibited by phospholipase C inhibitor, but not by protein kinase C inhibitor. Low dose of ET-1 could potentiate cinnamaldehyde-induced nociception. Our results suggested that TRPA1 is involved in ET-1-induced spontaneous pain-like behavior in mice.

Topics: Acrolein; Animals; Behavior, Animal; Endothelin-1; Enzyme Inhibitors; Irritants; Male; Mice; Mice, Inbred C57BL; Pain; Transient Receptor Potential Channels; TRPA1 Cation Channel

Endothelin-1 (ET-1) produced by various cancers is known to be responsible for inducing pain. While ET-1 binding to ETAR on peripheral nerves clearly mediates nociception, effects from binding to ETBR are less clear. The present study assessed the effects of ETBR activation and the role of endogenous opioid analgesia in carcinoma pain using an orthotopic cancer pain mouse model. mRNA expression analysis showed that ET-1 was nearly doubled while ETBR was significantly down-regulated in a human oral SCC cell line compared to normal oral keratinocytes (NOK). Squamous cell carcinoma (SCC) cell culture treated with an ETBR agonist (10(-4)M, 10(-5)M, and 10(-6) M BQ-3020) significantly increased the production of beta-endorphin without any effects on leu-enkephalin or dynorphin. Cancer inoculated in the hind paw of athymic mice with SCC induced significant pain, as indicated by reduction of paw withdrawal thresholds in response to mechanical stimulation, compared to sham-injected and NOK-injected groups. Intratumor administration of 3mg/kg BQ-3020 attenuated cancer pain by approximately 50% up to 3h post-injection compared to PBS-vehicle and contralateral injection, while intratumor ETBR antagonist BQ-788 treatment (100 and 300microg/kg and 3mg/kg) had no effects. Local naloxone methiodide (500microg/kg) or selective mu-opioid receptor antagonist (CTOP, 500microg/kg) injection reversed ETBR agonist-induced antinociception in cancer animals. We propose that these results demonstrate that peripheral ETBR agonism attenuates carcinoma pain by modulating beta-endorphins released from the SCC to act on peripheral opioid receptors found in the cancer microenvironment.

Topics: Animals; beta-Endorphin; Cell Line, Tumor; Disease Models, Animal; Down-Regulation; Endothelin-1; Endothelins; Humans; Mice; Mice, Nude; Narcotic Antagonists; Neoplasm Transplantation; Neoplasms; Nociceptors; Oligopeptides; Opioid Peptides; Pain; Peptide Fragments; Piperidines; Receptor, Endothelin B; Receptors, Opioid; Sensory Receptor Cells; Up-Regulation

A profound tachyphylaxis of the acute nocifensive flinching (pain) response to subcutaneous injection of endothelin-1 (ET-1) into the hind paw footpad is shown by the reduced response to a second injection. Flinching from the second injection was 20% +/- 5%, 57% +/- 18%, 79% +/- 35%, and 100% +/- 17% of that from the first injection (both 200 micromol/L, 2 nmol) at respective intervals of 24, 30, 48, and 72 h. Inhibition of afferent impulses by local anesthesia of the sciatic nerve, reducing initial flinching to 6%-13% of control, did not affect the tachyphylaxis for the second injection at 24 h. There was no cross-desensitization between formalin and ET-1 injected sequentially into the same paw. Suppression of descending inhibitory effects from endogenous opiates by naloxone (5-8 mg/kg, i.p.), given 30 min before the second ET-1 injection, did not prevent tachyphylaxis. Diffuse effects caused by an initial subcutaneous ET-1 injection into the tail or forepaw resulted in sensitization of the response to ET-1 in the hind paw, rather than tachyphylaxis. In contrast, selective inhibition of local ETA receptors during the initial administration of ET-1, by the antagonist BQ-123 (3.2 mmol/L), reduced tachyphylaxis of nocifensive flinching. Therefore, prolonged pain tachyphylaxis is not due to reduced responsiveness of the CNS, but rather depends on the functional sensitivity or availability of peripheral ET(A) receptors.

Topics: Anesthetics; Animals; Central Nervous System; Endothelin A Receptor Antagonists; Endothelin-1; Foot; Formaldehyde; Hindlimb; Hyperalgesia; Male; Naloxone; Pain; Pain Measurement; Peptides, Cyclic; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Tachyphylaxis; Time Factors; Touch

The complex regional pain syndrome (CRPS) is characterized by enhanced neurogenic inflammation, mediated by neuropeptides. Neutral endopeptidase (NEP) is a key enzyme in neuropeptide catabolism. We used NEP knock out (ko) mice to investigate whether NEP deficiency leads to increased pain behavior and signs of neurogenic inflammation after soft tissue trauma with and without nerve injury. After chronic constriction injury (CCI) of the right sciatic nerve, NEP ko mice were more sensitive to heat, to mechanical stimuli, and to cold than wild type mice. Tissue injury without nerve injury produced no differences between genotypes. After CCI, NEP ko mice showed increased hind paw edema but lower skin temperatures than wild type mice. Substance P (SP) and endothelin 1 (ET 1) determined by enzyme immuno assay (EIA) were increased in sciatic nerves from NEP ko mice after CCI. Tissue CGRP content did not differ between the genotypes. The results provide evidence that pain behavior and neurogenic inflammation are enhanced in NEP ko mice after nerve injury. These findings resemble human 'cold' CRPS and suggest that ET 1 plays an important role in the pathogenesis of CRPS with nerve injury.

Topics: Animals; Cold Temperature; Edema; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Hindlimb; Hot Temperature; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Skeletal; Neprilysin; Neurogenic Inflammation; Pain; Pain Measurement; Physical Stimulation; Sciatic Nerve; Skin; Skin Temperature; Substance P

Endothelin (ET)-1 is a chemical mediator released by the body at sites of injury and disease and is involved in various painful states. This study examined whether ET-1 exposure in the neonatal period alters subsequent ET-1 induced nociception and expression of the ET(B) receptor. ET-1 or saline was administered to postnatal day 7 rats. On postnatal day 11, ET-1 or saline was administered; a first exposure to ET-1 for one group, and a second exposure to ET-1 for another group. A statistically significant increase in ET-1 induced paw flinching was observed in postnatal day 11 male rats exposed to ET-1 for the second time as compared to male rats exposed to ET-1 for the first time. In contrast, a statistically significant decrease in ET-1 induced paw flinching was observed in postnatal day 11 female rats exposed to ET-1 for the second time as compared to female rats exposed to ET-1 for the first time. Furthermore, in males a positive correlation was found between ET-1 induced paw flinching on postnatal day 7 versus 11. In contrast, in females a negative correlation was found between ET-1 induced paw flinching on postnatal day 7 versus 11. Changes in behavioral sensitivity to ET-1 were accompanied by sex-specific ET-1 induced changes in expression of the ET(B) receptor on postnatal day 11 in the plantar hind paw with a statistically significant decrease and increase in ET(B) receptor expression in males and females, respectively. These findings suggest that ET-1 exposure in the neonatal period sex-specifically alters expression of the ET(B) receptor and behavioral sensitivity to ET-1 whereby males show sensitization and females show de-sensitization.

Topics: Aging; Animals; Animals, Newborn; Behavior, Animal; Brain; Drug Tolerance; Endothelin-1; Female; Male; Pain; Pain Measurement; Pain Threshold; Rats; Rats, Sprague-Dawley; Reaction Time; Receptor, Endothelin B; Sex Characteristics

Although local administration of endothelin-1 (ET-1) is known to evoke spontaneous pain, the mechanism of ET-1-induced pain has not been elucidated. We investigated the involvement of protein kinase C (PKC) and transient receptor potential vanilloid subfamily 1 (TRPV1) in ET-1-induced pain-like behavior. Intraplantar ET-1 evoked pain-like behaviors, including licking, flinching, and biting, in a dose-dependent manner in wild-type mice. ET-1-induced pain-like behavior was attenuated by an endothelin type A receptor antagonist but not by PKC inhibitors and was also attenuated in TRPV1-deficient (KO) mice. In addition, we found a significant reduction of spinal Fos expression caused by the same dose of ET-1 in KO mice compared with that in wild-type mice. This study showed that endothelin type A receptor and TRPV1 are involved in ET-1-induced pain-like behaviors but failed to reveal the contribution of PKC.

Topics: Animals; Behavior, Animal; Biomarkers; Dose-Response Relationship, Drug; Down-Regulation; Endothelin A Receptor Antagonists; Endothelin-1; Enzyme Inhibitors; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Nociceptors; Pain; Pain Measurement; Pain Threshold; Posterior Horn Cells; Protein Kinase C; Proto-Oncogene Proteins c-fos; Receptor, Endothelin A; Sensory Receptor Cells; TRPV Cation Channels

Evidence on the relative roles of endothelin ET(A) and ET(B) receptors in mediating the nociceptive and hyperalgesic actions of endothelin-1 is still fragmented and conflicting, due to variations between species and/or models. This study assesses the participation of ET(A) and ET(B) receptors on the nociceptive behavior and hyperalgesia to chemical (formalin), mechanical and thermal stimuli evoked by endothelin-1 injected into the rat hind-paw. Intraplantar (i.pl.) injection of endothelin-1 (1-30 pmol, 50 microl) induced dose-dependent nociceptive behaviors over the first hour. Endothelin-1 (3-30 pmol) also potentiated both phases of nociception induced by a subsequent ipsilateral i.pl. injection of formalin (0.5%, 50 microl). Endothelin-1, at 10 pmol, increased responses of the first phase (0-10 min) by 97% and of the second phase (15-60 min) by 120%, and similar degrees of potentiation were observed following 30 pmol of the peptide. Endothelin-1 (1-30 pmol) caused slowly developing long-lasting thermal and mechanical hyperalgesia with maximum effects at 10 and 30 pmol, respectively, reaching significance at 2-3h and remaining elevated for up to at least 8h after injection. Treatment with the selective ET(A) and ET(B) peptidic antagonists BQ-123 and BQ-788 (i.pl., both at 10 nmol, 3.5h after ET-1 injection) or with the non-peptidic antagonists atrasentan and A-192621 systemically (i.v., 10 and 20mg/kg, respectively) each caused significant reductions in endothelin-1-induced nociception, as well as chemical, thermal and mechanical hyperalgesia. Thus, the nociceptive and hyperalgesic effects induced by i.pl. endothelin-1 seem to be mediated by both ET(A) and ET(B) receptors.

Topics: Animals; Dose-Response Relationship, Drug; Endothelin-1; Formaldehyde; Hindlimb; Hyperalgesia; Male; Pain; Rats; Rats, Wistar; Receptor, Endothelin A; Receptor, Endothelin B

Subcutaneous injection of endothelin-1 (ET-1) into the glabrous skin of the rat's hind paw is known to produce impulses in nociceptors and acute nocifensive behavioral responses, such as hind paw flinching, and to sensitize the skin to mechanical and thermal stimulation. In this report, we show that in contrast to the responses in glabrous skin, ET-1 injected subcutaneously into rat hairy skin causes transient antinociception. Concentrations of 1 to 50 microM ET-1 (in 0.05 mL) depress the local nocifensive response to noxious tactile probing at the injection site with von Frey filaments for 30 to 180 minutes; distant injections have no effect at this site, showing that the response is local. Selective inhibition of ET(A) but not of ET(B) receptors inhibits this antinociception, as does coinjection with nimodipine (40 muM), a blocker of L-type Ca(2+) channels. Local subcutaneous injection of epinephrine (45 microM) also causes antinociception through alpha-1 adrenoreceptors, but such receptors are not involved in the ET-1-induced effect. Both epinephrine and ET-1, at antinociceptive concentrations, reduce blood flow in the skin; the effect from ET-1 is largely prevented by subcutaneous nimodipine. These data suggest that ET-1-induced antinociception in the hairy skin of the rat involves cutaneous vasoconstriction, presumably through neural ischemia, resulting in conduction block.. The pain-inducing effects of ET-1 have been well documented in glabrous skin of the rat, a frequently used test site. The opposite behavioral effect, antinociception, occurs from ET-1 in hairy skin and is correlated with a reduction in blood flow. Vasoactive effects are important in assessing mechanisms of peripherally acting agents.

Topics: Adrenergic alpha-Agonists; Analgesics, Non-Narcotic; Animals; Calcium Channel Blockers; Calcium Channels, L-Type; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Epinephrine; Hair; Male; Narcotic Antagonists; Nimodipine; Pain; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Opioid; Regional Blood Flow; Skin; Tachyphylaxis

Intraplantar injection of endothelin-1 (ET-1) (1.5-10 muM) in the rat produces mechanical allodynia. Here we identify the receptor subtypes for ET-1, glutamate and CGRP critical to such allodynia. Antagonism of ET(A) or ET(B) receptors alone, by BQ123 or BQ788, respectively, only partially suppressed allodynia; the combined antagonists prevented allodynia, showing the involvement of both receptor subtypes. Co-injection of NMDA receptor antagonists, (+)MK-801 or D-AP5, with ET-1 also prevented allodynia. In contrast, co-injection of the CGRP1 antagonist CGRP(8-37) attenuated only the later phase of allodynia (>30 min). A mechanistic basis for these effects is shown by ET-1's ability to enhance basal release from cultured sensory neurons of glutamate and CGRP (2.4-fold and 5.7-fold, respectively, for 10 nM ET-1). ET(A) blockade reduced ET-1's enhancement of basal CGRP release by approximately 80%, but basal glutamate release by only approximately 30%. ET-1 also enhanced the capsaicin-stimulated release of CGRP (up to 2-fold for 0.3 nM ET-1), but did not change capsaicin-stimulated glutamate release. Release stimulated by elevated K+ was not altered by ET(A) blockade, nor did blockade of ET(B) reduce any type of release. Thus, ET-1 may induce release of glutamate and CGRP from nerve terminals innervating skin, thereby sensitizing primary afferents, accounting for ET-1-dependent tactile allodynia.. The endogenous endothelin peptides participate in a remarkable variety of pain-related processes. The present results provide evidence for the participation of ionotropic glutamatergic receptors and CGRP receptors in the hyperalgesic responses to exogenous ET-1 and suggest clinically relevant targets for further study of elevated pain caused by release of endogenous ET-1.

Topics: Animals; Calcitonin Gene-Related Peptide; Calcitonin Gene-Related Peptide Receptor Antagonists; Cells, Cultured; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Ganglia, Spinal; Glutamic Acid; Male; Pain; Pain Measurement; Pain Threshold; Physical Stimulation; Potassium; Rats; Rats, Sprague-Dawley; Receptors, Calcitonin Gene-Related Peptide; Receptors, N-Methyl-D-Aspartate; Sensory Receptor Cells; Time Factors

The mechanisms that generate itch are poorly understood at both the molecular and cellular levels despite its clinical importance. To explore the peripheral neuronal mechanisms underlying itch, we assessed the behavioral responses (scratching) produced by s.c. injection of various pruritogens in PLCbeta3- or TRPV1-deficient mice. We provide evidence that at least 3 different molecular pathways contribute to the transduction of itch responses to different pruritogens: 1) histamine requires the function of both PLCbeta3 and the TRPV1 channel; 2) serotonin, or a selective agonist, alpha-methyl-serotonin (alpha-Me-5-HT), requires the presence of PLCbeta3 but not TRPV1, and 3) endothelin-1 (ET-1) does not require either PLCbeta3 or TRPV1. To determine whether the activity of these molecules is represented in a particular subpopulation of sensory neurons, we examined the behavioral consequences of selectively eliminating 2 nonoverlapping subsets of nociceptors. The genetic ablation of MrgprD(+) neurons that represent approximately 90% of cutaneous nonpeptidergic neurons did not affect the scratching responses to a number of pruritogens. In contrast, chemical ablation of the central branch of TRPV1(+) nociceptors led to a significant behavioral deficit for pruritogens, including alpha-Me-5-HT and ET-1, that is, the TRPV1-expressing nociceptor was required, whether or not TRPV1 itself was essential. Thus, TRPV1 neurons are equipped with multiple signaling mechanisms that respond to different pruritogens. Some of these require TRPV1 function; others use alternate signal transduction pathways.

Topics: Animals; Behavior, Animal; Endothelin-1; Injections; Mice; Mice, Inbred C57BL; Models, Biological; Mutation; Neurons, Afferent; Nociceptors; Pain; Phospholipase C beta; Physical Stimulation; Posterior Horn Cells; Proto-Oncogene Proteins c-fos; Pruritus; Serotonin; Temperature; TRPV Cation Channels

In this study, we investigated the role of the peripheral endothelin-1 (ET-1) concentration in a cancer pain model. To test the hypothesis that the concentration of ET-1 in the tumor microenvironment is important in determining the level of cancer pain we used two cancer pain mouse models that differed significantly in production of ET-1. The two mouse cancer models were produced by injection of cells derived from a human oral squamous cell carcinoma (SCC) and melanoma into the hind paw of female mice. Pain, as indicated by reduction in withdrawal thresholds in response to mechanical stimulation, was significantly greater in the SCC group than the melanoma group. The peripheral concentration of ET-1 within the cancer microenvironment was significantly greater in the SCC group. Intra-tumor expression of both ET-1 mRNA and ET-1 protein were significantly higher in the SCC model compared to the melanoma model. ET receptor antagonism was effective as an analgesic for cancer pain in the SCC model only. To address the potential confounding factor of tumor volume we evaluated the contribution of tumor volume to cancer pain in the two models. The mean volumes of the tumors in the melanoma group were significantly greater than the tumors in the SCC group. In both groups, the pain level correlated with tumor volume, but the correlation was stronger in the melanoma group. We conclude that ET-1 concentration is a determinant of the level of pain in a cancer pain mouse model and it is a more important factor than tumor volume in producing cancer pain. These results suggest that future treatment regimens for cancer pain directed at ET-1 receptor antagonism show promise and may be tumor type specific.

Topics: Animals; Carcinoma, Squamous Cell; Cell Line, Tumor; Endothelin A Receptor Antagonists; Endothelin-1; Female; Hyperalgesia; Melanoma, Experimental; Mice; Mice, Nude; Mouth Neoplasms; Neoplasm Proteins; Organ Specificity; Pain; Pain Measurement; Peptides, Cyclic; Receptor, Endothelin A; RNA, Messenger; RNA, Neoplasm; Transplantation, Heterologous; Tumor Burden

IL-33, a new member of the IL-1 family, signals through its receptor ST2 and induces T helper 2 (Th2) cytokine synthesis and mediates inflammatory response. We have investigated the role of IL-33 in antigen-induced hypernociception. Recombinant IL-33 induced cutaneous and articular mechanical hypernociception in a time- and dose-dependent manner. The hypernociception was inhibited by soluble (s) ST2 (a decoy receptor of IL-33), IL-1 receptor antagonist (IL-1ra), bosentan [a dual endothelin (ET)(A)/ET(B) receptor antagonist], clazosentan (an ET(A) receptor antagonist), or indomethacin (a cyclooxygenase inhibitor). IL-33 induced hypernociception in IL-18(-/-) mice but not in TNFR1(-/-) or IFNgamma(-/-) mice. The IL-33-induced hypernociception was not affected by blocking IL-15 or sympathetic amines (guanethidine). Furthermore, methylated BSA (mBSA)-induced cutaneous and articular mechanical hypernociception depended on TNFR1 and IFNgamma and was blocked by sST2, IL-1ra, bosentan, clazosentan, and indomethacin. mBSA also induced significant IL-33 and ST2 mRNA expression. Importantly, we showed that mBSA induced hypernociception via the IL-33 --> TNFalpha --> IL-1beta --> IFNgamma --> ET-1 --> PGE(2) signaling cascade. These results therefore demonstrate that IL-33 is a key mediator of immune inflammatory hypernociception normally associated with a Th1 type of response, revealing a hitherto unrecognized function of IL-33 in a key immune pharmacological pathway that may be amenable to therapeutic intervention.

Topics: Aflatoxin B1; Animals; Antigens; Dinoprostone; Endothelin-1; Female; Gene Expression Regulation; Interleukins; Male; Methylation; Mice; Mice, Knockout; Pain; RNA, Messenger; Serum Albumin; Skin

We investigated whether endothelin (ET) would be involved in skin cancer pain in mice. Orthotopic inoculation of B16-BL6 melanoma cells into the plantar region of the hind paw produced marked mechanical allodynia in C57BL/6 mice. Intraplantar injections of the ET(A)-receptor antagonist BQ-123 (0.3 - 3 nmol/site), but not the ET(B)-receptor antagonist BQ-788 (1 and 3 nmol/site), inhibited mechanical allodynia in mice with grown melanoma. In naive mice, an intraplantar injection of tumor extract (1 and 3 mg/site), which was prepared from the grown melanoma in the paw, produced mechanical allodynia, which was inhibited by BQ-123 and BQ-788 at doses of 3 and 10 nmol/site. An intraplantar injection of ET-1 (1 and 10 pmol/site) elicited licking behavior, which was increased in the melanoma-bearing hind paw. BQ-123 (3 and 10 nmol/site) inhibited licking induced by ET-1 (10 pmol/site). The level of mRNA of ET(A), but not ET(B), receptor, was significantly increased in the dorsal root ganglia on the inoculated side. Cultured B16-BL6 cells contained ET, and the melanoma mass increased the concentration of ET as it grew bigger. These results suggest that ET-1 and ET(A) receptor are at least partly involved in the induction of pain induced by melanoma cell inoculation.

Topics: Animals; Behavior, Animal; Cell Line, Tumor; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Ganglia, Spinal; Male; Melanoma, Experimental; Mice; Mice, Inbred C57BL; Neoplasm Transplantation; Oligopeptides; Pain; Peptides, Cyclic; Piperidines; Receptor, Endothelin A; Receptor, Endothelin B; RNA, Messenger

Whilst not strictly a neuropathic injury, cancer-induced bone pain (CIBP) is a unique state with features of neuropathy and inflammation. Recent work has demonstrated that osteoclasts damage peripheral nerves (peptidergic C fibres and SNS) within trabeculated bone leading to deafferentation. In addition, glia cell activation and neuronal hyperexcitability within the dorsal horn, are all similar to a neuropathy. Gabapentin and carbamazepine (both anti-convulsants that modulate neuropathy) are effective at attenuating dorsal horn neuronal excitability and normalizing pain-like behaviours in a rat model of CIBP. However alterations in neuroreceptors in the dorsal horn do not mimic neuropathy, rather only dynorphin is upregulated, glia cells are active and hypertrophic and c-fos expression is increased post-noxious behavioural stimulus. CIBP perhaps illustrates best the complexity of cancer pains. Rarely are they purely neuropathic, inflammatory, ischaemic or visceral but rather a combination. Management is multimodal with radiotherapy, analgesics (opioids, NSAIDs), bisphosphonates, radioisotopes and tumouricidal therapies. The difficulty with opioids relates to efficacy on spontaneous pain at rest and movement-related pain. Potential adjuvants to standard analgesic therapies for CIBP are being explored in clinical trials and include inhibitors of glutamate release.

Topics: Analgesics; Anti-Inflammatory Agents, Non-Steroidal; Bone Density Conservation Agents; Bone Diseases; Bone Neoplasms; Diphosphonates; Drug Administration Routes; Endothelin-1; Humans; Lidocaine; N-Methylaspartate; Osteoprotegerin; Pain; Receptors, Vitronectin

Some children report significant pain with peripheral intravenous catheter (IV) insertion, despite the appropriate use of topical lidocaine anesthetics. This analysis of data from an existing study identified factors related to variation in topical anesthetic effectiveness used for IV insertion. The children (n = 218) in this investigation were 4 to 10 years old and undergoing a scheduled IV insertion. Inclusion criteria were (1) topical anesthetic was used according to manufacturer's recommendations, (2) DNA material was available, and (3) child completed a self-report measure of pain intensity (Oucher scale). Low pain phenotype was defined as a pain intensity score of 0 to 3, and high pain phenotype was an intensity score of 4 to 10. Potential predictor variables included child age, gender, number of previous painful procedures, state and trait anxiety, temperament characteristics, and alleles in 3 candidate genes in a pain pathway influenced by topical anesthetics (endothelin-1 [EDN1], endothelin receptor A [EDNRA], endothelin receptor B [EDNRB]). All subjects were genotyped for a single-nucleotide polymorphism in each gene. Children in the high pain group (n = 89) were significantly younger (P < .0001), more active (P = .0029), scored higher for trait (P = .0009) and state anxiety (P = .0312), and had the EDNRA TT genotype (high pain group, TT 67.35%; low pain group, TT 39.47%; P = .026).. The identification of factors that influence peripheral pain sensation aids in selecting the most appropriate pharmacologic and nonpharmacologic interventions. Until genotyping is available at a clinically prescriptive level, other predictors (eg, age and activity level) can be used to tailor pain-relieving strategies for children undergoing needle sticks.

Topics: Administration, Topical; Age Factors; Anesthetics, Local; Anxiety; Catheterization, Peripheral; Child; Child, Preschool; Drug Resistance; Endothelin-1; Female; Gene Frequency; Genotype; Humans; Lidocaine; Lidocaine, Prilocaine Drug Combination; Male; Pain; Pain Threshold; Phenotype; Predictive Value of Tests; Prilocaine; Receptor, Endothelin A; Receptor, Endothelin B; Regression Analysis; Sex Factors; Temperament

Endothelin-1 (ET-1) is a chemical mediator released by the body at sites of injury and disease. This study tests the hypothesis that ET-1-induced nociception changes with age and sex. Intraplantar ET-1 (1.1 and 3.3 nmol) produced age-specific paw flinching and licking (postnatal day 7 > 21 > 60). The onset and duration of the nociceptive responses was dependent on age. Postnatal day (P) 21 and 60 rats displayed an immediate onset of behavior that subsided with time, whereas the P7 rats had a delayed behavioral response that onset at 20 minutes after ET-1 administration and continued beyond the 75 minute observation period. P7 males showed greater paw flinching compared with females. In addition to spontaneous nociceptive behaviors, ET-1 produced mechanical allodynia in all ages. As with spontaneous nociception, ET-1-induced mechanical allodynia was of a longer duration in the younger aged rats compared with adult rats. These findings show that ET-1 produces both spontaneous nociceptive behaviors and evoked mechanical allodynia in both young and adult rats but that the temporal profile and the size of the responses are age- and sex-dependent. These findings are the first description of age- and sex-specific ET-1-induced nociception.. Endothelin-1 is a vasoactive peptide released into the systemic circulation after stress and cold pain as well as locally in tissue after injury and disease. These findings suggest greater pain to stimuli that release endogenous endothelin in younger versus older organisms. This developmental approach to studying ET-1-induced pain further illustrates the need for understanding pain mechanisms as a function of the development of the organism so as to better treat pain across the life span.

Topics: Aging; Analysis of Variance; Animals; Animals, Newborn; Dose-Response Relationship, Drug; Endothelin-1; Female; Male; Pain; Pain Measurement; Rats; Rats, Sprague-Dawley; Reaction Time; Sensory Thresholds; Sex Characteristics; Time Factors

Trigeminal neuropathic pain, which is associated with marked orofacial mechanical allodynia, is frequently refractory to currently available drugs. Because endothelins (ETs) can contribute to nociceptive changes in animal models of inflammatory, cancer, and diabetic neuropathic pain, the present study evaluated the influence of ET(A) and ET(B) receptor antagonists on orofacial mechanical allodynia in a rat model of trigeminal neuropathic pain. Unilateral constriction (C) of the infraorbital nerve (ION) caused pronounced and sustained bilateral mechanical allodynia, evaluated by application of von Frey hairs to the vibrissal pad. Mechanical allodynia on postoperative days 12-15 after nerve injury was abolished for up to 90 mins by subcutaneous administration of 2.5 mg/kg morphine, but was fully refractory to intravenous (iv) administration of 10 mg/kg of the dual ET(A) plus ET(B) or selective ET(A) receptor antagonists, bosentan and atrasentan, respectively. In sharp contrast, iv administration of 20 mg/kg of the selective ET(B) receptor antagonist, A-192621, caused a net 61 +/- 15% reduction of mechanical threshold, lasting 2 hrs. Co-injection of atrasentan plus A-192621 did not modify ION injury-induced mechanical allodynia. Injection of 10 pmol ET-1 into the upper lip of naive rats caused ipsilateral mechanical allodynia lasting up to 5 hrs. Thus, ET(B) receptor-mediated mechanisms contribute to orofacial mechanical allodynia induced by CION injury, but, some-how, functional ET(A) receptors are required for expression of the antiallodynic effect of ET(B) receptor blockade.

Topics: Animals; Atrasentan; Bosentan; Drug Therapy, Combination; Endothelin B Receptor Antagonists; Endothelin-1; Male; Pain; Pain Threshold; Pyrrolidines; Pyrrolidinones; Rats; Rats, Wistar; Sulfonamides; Time Factors; Trigeminal Neuralgia

Subcutaneous endothelin-1 (ET-1; 200 microM, 2 nmoles/paw) injected into the rat hind paw, has been shown to cause robust hind paw flinching (HPF) and paw licking, and to induce impulses selectively in primary nociceptors. Here we report that a much lower [ET-1] sensitizes the paw to a nocifensive withdrawal response to tactile stimulation (by von Frey hairs, VFH), a sensitization that involves local TRPV1 receptors. Injection of 10 microM ET-1 (0.1 nmole/paw) causes only marginal HPF but rapidly (20 mins after injection) lowers the force threshold for paw withdrawal (PWT) to VFH, to approximately 30% of pre-injection baseline. Such tactile allodynia persists for 3 hrs. In rats pre-injected with the TRPV1-antagonists capsazepine (CPZ; 1.33 mM) or 5'-iodoresiniferatoxin (I-RTX; 0.13 microM), 15 min before ET-1, a fast initial drop in PWT, as with ET-1 alone, occurs (to 40% or to 19% of baseline, respectively), but this earliest reduction then regresses back to the pre-injection PWT value more rapidly than with ET-1 alone. The recovery of allodynia from the maximum value is about two times faster for ET-1+CPZ and about 4 times faster for ET-1+ I-RTX, compared with that from ET-1 +vehicle (t(1/2) = 130, 60, and 250 mins, respectively). In contrast, spontaneous pain indicated by overt HPF from ET-1 is not attenuated by TRPV1 antagonists. Tactile allodynia is similarly abbreviated by antagonists of both ET(A) (BQ-123, 32 nmoles/paw) and ET(B) (BQ-788, 30 nmoles/paw) receptors, whereas HPF is abolished by this ET(A) antagonist but enhanced by the ET(B) antagonist. We conclude that low ET-1 causes tactile allodynia, which is characterized by a different time-course and pharmacology than ET-1-induced nociception, and that local TRPV1 receptors are involved in the maintenance of this ET-1-induced allodynia but not in the overt algesic action of ET-1.

Topics: Animals; Behavior, Animal; Capsaicin; Diterpenes; Dose-Response Relationship, Drug; Endothelin-1; Injections, Subcutaneous; Male; Nociceptors; Pain; Rats; Rats, Sprague-Dawley; Reaction Time; Receptor, Endothelin A; Touch; TRPV Cation Channels

The association of endothelin 1 (ET-1) and endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphisms (G5665T and T8002C, VNTR and T-786C respectively) with the occurrence of acute chest syndrome and painful vaso-occlusive crises was evaluated in homozygous SS children. This retrospective study reveals that ET-1 T8002 and ecNOS C-786 alleles are associated with, respectively, an increased and a decreased risk of acute chest syndrome.

Topics: Adolescent; Anemia, Sickle Cell; Chest Pain; Child; Endothelin-1; Female; Genetic Predisposition to Disease; Humans; Male; Nitric Oxide Synthase Type III; Pain; Polymorphism, Genetic; Vascular Diseases

Endothelin-1 (ET-1) exists in endothelial cells as well as a variety of other cell types. The presence of ET-1 and its receptors in neurons suggests its possible role as a neurotransmitter and/or neuromodulator. Studies utilizing exogenous ET-1 have suggested that ET-1 affects pain transmission. This study was designed to examine the possible role(s) of neuronal ET-1 in pain processing. We produced neuron-specific ET-1 knockout mice using the Cre/loxP system with a synapsin I promoter and examined the effects produced by the lack of neuronal ET-1 on pain behavior using common pain models and a model of stress-induced analgesia. In acute nociceptive pain models, paw withdrawal thresholds to radiant heat and mechanical stimuli applied with von Frey hairs were significantly lower in the knockout mice compared with control. This indicated that the absence of neuronal ET-1 leads to greater sensitivity to acute nociceptive stimuli. After inflammation was produced by intraplantar injection of carrageenan, there was a significantly greater degree of thermal hyperalgesia and mechanical allodynia in the knockout mice even after the difference in baseline values was compensated. Furthermore, in a neuropathic pain model produced by spinal nerve ligation, there was also a greater degree of mechanical allodynia in the knockout mice. Finally, in a swim-stress model, the magnitude of stress-induced analgesia was less in the knockout mice, indicating the involvement of neuronal ET-1 in stress-induced analgesia. The results suggest that there is a basal release of ET-1 from neurons that affect baseline pain thresholds as well as an additional release during persistent pain states that acts to suppress the pain. The involvement of neuronal ET-1 in stress-induced analgesia further suggests its role in endogenous pain inhibitory systems. To confirm that ET-1 is released in persistent pain states and to determine which part of the CNS is involved, we measured the concentrations of ET-1 before and after inducing peripheral inflammation in different parts of the CNS involved in endogenous pain inhibitory systems in normal mice. We found that ET-1 was increased in the hypothalamus while no significant increase was observed in the midbrain, medulla and spinal cord. The results of the present study suggest that neuronal ET-1 is involved in endogenous pain inhibitory control likely via pathways through the hypothalamus.

Topics: Acute Disease; Animals; Disease Models, Animal; Endothelin-1; Hyperalgesia; Hypothalamus; Mice; Mice, Knockout; Neural Inhibition; Neural Pathways; Neurons; Pain; Pain Measurement; Pain Threshold; Pain, Intractable; Peripheral Nervous System Diseases; Physical Stimulation; Promoter Regions, Genetic; Reaction Time; Stress, Physiological; Synapsins

The purpose of this study was to explore the role of endothelin in neuropathic pain. Endothelins (ET) are a family (ET-1, ET-2, ET-3) of ubiquitously expressed peptides involved in control of vascular tone. Injected ET-1 causes intense pain via activation of ETA receptors, modulated by analgesic signals initiated by ETB receptor activation. Using a rat model of chronic constriction injury of the sciatic nerve, we found that pharmacologic ETA receptor antagonism acutely and significantly reduced thermal and mechanical hyperalgesic responses 5 days after injury. Furthermore, ET-1 and the ETA receptor are locally upregulated at the site of chronic constriction injury at both the message and the protein levels, suggesting that ET-1 may be involved in establishing pain after the injury. These data point to ET-1 as an important mediator of pain in general and suggest that ETA antagonism deserves study as a potential novel therapy for neuropathic pain.

Topics: Animals; Constriction, Pathologic; Endothelin A Receptor Antagonists; Endothelin-1; Male; Pain; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Sciatic Neuropathy

In some diseases in which endothelin-1 production increases, e.g. prostate cancer, endothelin-1 is considered to be involved in the generation of pain. In the present study, we investigated the effects of a selective endothelin ET(A) receptor antagonist, (E)-N-[6-methoxy-5-(2-methoxyphenoxy)[2,2'-bipyrimidin]-4-yl]-2-phenylethenesulfonamide monopotassium salt (YM598), on the nociception potentiated by endothelin-1 in a cancer inoculation-induced pain model in mice, induced by inoculation of the androgen-independent human prostate cancer cell line PPC-1 into the hind paws of severe combined immunodeficiency (SCID) mice. No pain responses were observed in the sham-operated mice, whereas monophasic pain responses were observed in the PPC-1-inoculated mice. Endothelin-1 (1 to 10 pmol/paw) but not sarafotoxin S6c potentiated the pain response in prostate cancer-inoculated mice. Both YM598 and atrasentan (0.3 to 3 mg/kg, p.o.) significantly inhibited the endothelin-1 (10 pmol/paw)-induced potentiation of nociception in a dose-dependent manner. These results suggest that selective endothelin ET(A) receptor antagonists might relieve pain in patients with various diseases in which endothelin-1 production is increased, e.g. prostate cancer.

Topics: Analgesics, Non-Narcotic; Animals; Atrasentan; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin-1; Hindlimb; Male; Mice; Mice, SCID; Pain; Prostatic Neoplasms; Pyrimidines; Pyrrolidines; Sulfonamides; Time Factors; Viper Venoms

Tumors including sarcomas and breast, prostate, and lung carcinomas frequently grow in or metastasize to the skeleton where they can induce significant bone remodeling and cancer pain. To define products that are released from tumors that are involved in the generation and maintenance of bone cancer pain, we focus here on endothelin-1 (ET-1) and endothelin receptors as several tumors including human prostate and breast have been shown to express high levels of ETs and the application of ETs to peripheral nerves can induce pain. Here we show that in a murine osteolytic 2472 sarcoma model of bone cancer pain, the 2472 sarcoma cells express high levels of ET-1, but express low or undetectable levels of endothelin A (ETAR) or B (ETBR) receptors whereas a subpopulation of sensory neurons express the ETAR and non-myelinating Schwann cells express the ETBR. Acute (10 mg/kg, i.p.) or chronic (10 mg/kg/day, p.o.) administration of the ETAR selective antagonist ABT-627 significantly attenuated ongoing and movement-evoked bone cancer pain and chronic administration of ABT-627 reduced several neurochemical indices of peripheral and central sensitization without influencing tumor growth or bone destruction. In contrast, acute treatment (30 mg/kg, i.p.) with the ETBR selective antagonist, A-192621 increased several measures of ongoing and movement evoked pain. As tumor expression and release of ET-1 has been shown to be regulated by the local environment, location specific expression and release of ET-1 by tumor cells may provide insight into the mechanisms that underlie the heterogeneity of bone cancer pain that is frequently observed in humans with multiple skeletal metastases.

Topics: Analysis of Variance; Animals; Atrasentan; Behavior, Animal; Bone Neoplasms; Calcitonin Gene-Related Peptide; Disease Models, Animal; Dynorphins; Endothelin Receptor Antagonists; Endothelin-1; Ganglia, Spinal; Gene Expression Regulation, Neoplastic; Glial Fibrillary Acidic Protein; Immunohistochemistry; Male; Mice; Mice, Inbred Strains; Pain; Pain Measurement; Pyrrolidines; Receptors, Endothelin; Sarcoma; Sciatic Nerve; Time Factors

Endothelin-1 (ET-1) applied to the sciatic nerve or injected into the plantar hindpaw of rats induces pain behavior (ipsilateral hindpaw flinching) and selective excitation of nociceptors by activation of endothelin-A (ET(A)) receptors. To determine the pharmacological profile of the sensory fibers that mediate this pain behavior, we administered lidocaine (LID, a non-selective conduction blocker) or tetrodotoxin (TTX) prior to ET-1. LID (1 or 2%, 0.1 ml) was injected percutaneously into the sciatic notch, or TTX (10 microM, 4 microl) was injected into the sciatic nerve prior to the more distal application of ET-1 (400 microM, 40 microl) onto the sciatic nerve or subcutaneously into the plantar hindpaw (400 microM, 10 microl). LID inhibited ET-1-induced flinching in a dose-dependent manner; the mean total number of flinches was reduced by 39% for 1% LID and by 87% for 2% LID. In contrast, TTX failed to inhibit flinching behavior induced by sciatic nerve application of ET-1 despite a similar magnitude of motor and sensory blockade as that observed with 2% LID. Partial blockade of flinching behavior by intraneural TTX (mean total flinches were reduced by 51%) was observed after subcutaneous injection of ET-1. Unexpectedly, ET-1 prolonged the actions of 1% LID and, even when applied alone, produced clear signs of motor and sensory conduction block. These results are evidence that ET-1-induced pain is transmitted to the central nervous system via sensory fibers using tetrodotoxin-resistant sodium channels, and that ET-1 has analgesic actions that exist despite the activation of local pain pathways.

Topics: Animals; Dose-Response Relationship, Drug; Endothelin-1; Male; Neurons, Afferent; Pain; Pain Measurement; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Tetrodotoxin

The participation of the endothelin system on nociception and priming induced by carrageenan in the knee-joint was investigated. Intra-articular (i.a.) carrageenan (300 microg) caused long-lasting nociceptive effects (i.e., increases in paw elevation time [PET]), which were potentiated by endothelin-1 (dual endothelin ETA/ETB receptor agonist) and inhibited by sarafotoxin S6c (endothelin ETB receptor agonist; both at 30 pmol, i.a., 24 h beforehand). Priming the naive joint with carrageenan augmented nociceptive responses to a second carrageenan challenge, 72 h later. Carrageenan-induced priming, but not nociception, was potentiated by local BQ-788 (10 nmol, i.a., 15 min before priming; endothelin ETB receptor antagonist; N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D-1-methoxycarbonyl-tryptophanil-D-norleucine), but BQ-123 (endothelin ETA receptor antagonist; cyclo [D-Asp-Pro-D-Val-Leu]) was ineffective. Sarafotoxin S6c markedly suppressed carrageenan-induced priming to nociception triggered by carrageenan, endothelin-1 or sarafotoxin S6c, and BQ-788 prevented this action. Thus, selective endothelin ETB receptor agonists inhibit carrageenan-induced nociception and priming in the naive joint. This priming effect of carrageenan to nociception evoked by subsequent inflammatory insults is limited by an endothelin ETB receptor-operated mechanism.

Topics: Animals; Carrageenan; Endothelin B Receptor Antagonists; Endothelin-1; Joint Capsule; Knee Joint; Male; Pain; Pain Measurement; Peptides, Cyclic; Rats; Rats, Wistar; Receptor, Endothelin B

Endothelin-1 (ET-1) in the central nervous system has been suggested to produce suppressive effects on pain transmission. We investigated the manner by which ET-1 exerts this action. ET-1 administered intracerebroventricularly produced a dose-dependent antinociceptive effect in a thermal pain test that utilized a spinal reflex to determine nociceptive thresholds. This suggested that the antinociceptive effect of ET-1 involved a descending pain inhibitory system. The antinociceptive effect was blocked by an ETA receptor antagonist but not by an ETB receptor antagonist, indicating that the action was mediated through the ETA receptor. Antagonists of opioid receptors, serotonin receptors, alpha-2 adrenergic receptors, oxytocin receptors, and dopamine receptors did not block the antinociceptive effect of ET-1. Thus, major descending inhibitory systems were probably not involved. The antinociceptive effect was blocked by intracerebroventricular administration of an alpha-1 adrenergic receptor antagonist. This indicated that the antinociceptive effect involved the activation of a supraspinal noradrenergic pathway, which in turn may activate a still unknown descending pain inhibitory system.

Topics: Adrenergic alpha-1 Receptor Antagonists; Adrenergic alpha-Antagonists; Analgesics, Non-Narcotic; Animals; Brain; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin-1; Injections, Intraventricular; Male; Mice; Mice, Inbred C57BL; Neural Inhibition; Neural Pathways; Oligopeptides; Pain; Pain Measurement; Pain Threshold; Peptides, Cyclic; Piperidines; Prazosin; Reaction Time; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Adrenergic, alpha-1; Yohimbine

In some diseases in which endothelin-1 (ET-1) production increases (e.g. prostate cancer), ET-1 is considered to be involved in the generation of pain. In the present study, we investigated the effects of a selective endothelin-A receptor antagonist, YM598, on the nociception potentiated by ET-1 in formalin-induced and cancer inoculation-induced pain models in mice. The formalin-induced pain model was prepared by intraplantar injection of 0.7% formalin into the hind paws of ICR mice, and the cancer pain model was prepared by inoculation of the human prostate cancer cell line PPC-1 into the hind paws of severe combined immunodeficiency mice. Formalin caused a biphasic pain response and paw edema in the mouse hind paw. ET-1 (10 pmol/paw) potentiated these responses, and single oral administration of YM598 (0.3-3 mg/kg) significantly inhibited this ET-1-induced potentiation of nociception and paw edema. ET-1 (10 pmol/paw) also potentiated the pain response in prostate cancer-inoculated mice. Both YM598 and atrasentan (0.3-3 mg/kg) significantly inhibited the ET-1-induced potentiation of nociception. These results suggest that selective endothelin-A receptor antagonists relieve pain in patients with various diseases in which ET-1 production increases (e.g. prostate cancer).

Topics: Administration, Oral; Analgesics, Non-Narcotic; Animals; Behavior, Animal; Cell Line, Tumor; Disease Models, Animal; Dose-Response Relationship, Drug; Endothelin A Receptor Antagonists; Endothelin-1; Formaldehyde; Humans; Male; Mice; Mice, Inbred ICR; Mice, SCID; Pain; Pain Measurement; Prostatic Neoplasms; Pyrimidines; Receptor, Endothelin A; Sulfonamides; Time Factors

Endothelin-1 (ET-1) is a newly described pain mediator that is involved in the pathogenesis of pain states ranging from trauma to cancer. ET-1 is synthesized by keratinocytes in normal skin and is locally released after cutaneous injury. While it is able to trigger pain through its actions on endothelin-A (ET(A)) receptors of local nociceptors, it can coincidentally produce analgesia through endothelin-B (ET(B)) receptors. Here we map a new endogenous analgesic circuit, in which ET(B) receptor activation induces the release of beta-endorphin from keratinocytes and the activation of G-protein-coupled inwardly rectifying potassium channels (GIRKs, also named Kir-3) linked to opioid receptors on nociceptors. These results indicate the existence of an intrinsic feedback mechanism to control peripheral pain in skin, and establish keratinocytes as an ET(B) receptor-operated opioid pool.

Topics: Analgesia; Animals; beta-Endorphin; Cells, Cultured; Endothelin-1; G Protein-Coupled Inwardly-Rectifying Potassium Channels; Humans; Keratinocytes; Male; Pain; Pain Measurement; Potassium Channels; Potassium Channels, Inwardly Rectifying; Rats; Rats, Sprague-Dawley; Receptor, Endothelin B; Receptors, Endothelin; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Signal Transduction; Skin

Endothelin-1 (ET-1) causes pain through activation of nociceptors, by either direct depolarization or increased excitability. Here we examined the effect of ET-1 on nociceptor-associated tetrodotoxin-resistant (TTX-R) sodium currents using whole-cell voltage clamp of acutely dissociated rat dorsal root ganglion (DRG) neurons. DRG neurons that responded had enhanced activation gating when exposed to 10 nm ET-1, as determined by significant shifts in their average activation midpoint potentials (DeltaE(0.5) = -8.0 +/- 0.5 mV) when compared with control (DeltaE(0.5) = -2.2 +/- 0.4 mV; n = 6) and ET-1 unresponsive cells (DeltaE(0.5) = -3.2 +/- 0.2 mV). ET-1 also modified the availability of TTX-R channels, as determined by negative shifts in the average midpoint potential for inactivation of ET-1 responsive cells when compared with controls. These actions of ET-1 occurred predominantly in cells with more slowly inactivating TTX-R currents. Both time-to-peak current and inactivation time constants were shortened by ET-1 in responsive cells. Previous exposure of cells to the endothelin-A (ET(A)) receptor antagonist BQ-123 (1 microm) prevented ET-1-induced shifts in TTX-R activation. In contrast to changes in TTX-R, ET-1 did not modify tetrodotoxin-sensitive currents recorded from DRG neurons. These results demonstrate that the algogenic peptide ET-1 induces ET(A) receptor-mediated, hyperpolarizing shifts in the voltage-dependent activation of TTX-R Na+ channels, a potential mechanism for selective excitation by ET-1 of nociceptors that we observed in vivo.

Topics: Animals; Cell Separation; Cells, Cultured; Endothelin-1; Ganglia, Spinal; Ion Channel Gating; Kinetics; Male; Membrane Potentials; Neurons, Afferent; Nociceptors; Pain; Patch-Clamp Techniques; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Endothelin; Sodium; Sodium Channels; Tetrodotoxin

We showed previously that subcutaneous injection of the injury-associated peptide mediator endothelin-1 (ET-1) into the rat plantar hindpaw produces pain behavior and selective excitation of nociceptors, both through activation of ET(A) receptors likely on nociceptive terminals. The potential role of ET(B) receptor activation in these actions of ET-1-has not been examined. Therefore, in these experiments, we studied the effect of blocking or activating ET(B) receptors on ET-1-induced hindpaw flinching and excitation of nociceptors in rats. An ET(B) receptor-selective antagonist, BQ-788 (3 mm), coinjected with ET-1 (200 microm) reduced the time-to-peak of flinching and significantly enhanced the average maximal flinch frequency (MFF). In contrast, coinjection of an ET(B) receptor selective agonist, IRL-1620 (100 or 200 microm), with ET-1 reduced the average MFF and the average total number of flinches. Interestingly, this unexpected inhibitory effect of IRL-1620 was prevented by the nonselective opioid receptor antagonist naloxone (2.75 mm). To confirm these inhibitory actions, we studied the effects of IRL-1620 on ET-1-induced spike responses in single, physiologically characterized nociceptive C-fibers. IRL-1620 suppressed spike responses to ET-1 in all (n = 12) C-units, with mean and maximum response frequencies of 0.08 +/- 0.02 and 1.5 +/- 0.4 impulses/sec versus 0.32 +/- 0.07 and 4.17 +/- 0.17 impulses/sec for ET-1 alone. In additional support of the behavioral results, coinjection of naloxone (2.75 mm) completely prevented this inhibitory action of IRL-1620. These results establish that ET(B) receptor activation inhibits ET-1-induced pain behavior and nociception in a naloxone-sensitive manner and point to a previously unrecognized dual modulation of acute nociceptive signaling by ET(A) and ET(B) receptors in cutaneous tissues.

Topics: Action Potentials; Animals; Behavior, Animal; Dose-Response Relationship, Drug; Drug Antagonism; Drug Synergism; Endothelin Receptor Antagonists; Endothelin-1; Endothelins; Hindlimb; Injections, Subcutaneous; Male; Naloxone; Nerve Fibers; Nociceptors; Oligopeptides; Pain; Pain Measurement; Peptide Fragments; Piperidines; Rats; Rats, Sprague-Dawley; Reaction Time; Receptor, Endothelin B; Receptors, Endothelin

To compare plasma endothelin (ET)- like immunoreactivity between healthy horses and those with naturally acquired gastrointestinal tract disorders.. 29 healthy horses and 142 horses with gastrointestinal tract disorders.. Blood samples were collected from healthy horses and from horses with gastrointestinal tract disorders prior to treatment. Magnitude and duration of abnormal clinical signs were recorded, and clinical variables were assessed via thorough physical examinations. Plasma concentrations of ET-like immunoreactivity were measured by use of a radioimmunoassay for human endothelin-1, and CBC and plasma biochemical analyses were performed.. Plasma ET-like immunoreactivity concentration was significantly increased in horses with gastrointestinal tract disorders, compared with healthy horses. Median plasma concentration of ET-like immunoreactivity was 1.80 pg/ml (range, 1.09 to 3.2 pg/ml) in healthy horses. Plasma ET-like immunoreactivity was greatest in horses with strangulating large-intestinal obstruction (median, 10.02 pg/ml; range, 3.8 to 22.62 pg/ml), peritonitis (9.19 pg/ml; 789 to 25.83 pg/ml), and enterocolitis (8.89 pg/mI; 6.30 to 18.36 pg/ml). Concentration of ET-like immunoreactivity was significantly associated with survival, PCV, and duration of signs of pain. However, correlations for associations with PCV and duration of pain were low.. Horses with gastrointestinal tract disorders have increased plasma concentrations of ET-like immunoreactivity, compared with healthy horses. The greatest values were detected in horses with large-intestinal strangulating obstructions, peritonitis, and enterocolitis. This suggests a potential involvement of ET in the pathogenesis of certain gastrointestinal tract disorders in horses.

Topics: Animals; Endothelin-1; Gastrointestinal Diseases; Hematocrit; Horse Diseases; Horses; Logistic Models; Pain; Radioimmunoassay; Survival Analysis

Neurobehavioral and neurophysiological actions of the peptide endothelin-1 (ET-1) were investigated after subcutaneous plantar hindpaw injections in adult male Sprague Dawley rats. Hindpaw flinching developed within minutes after ET-1 (8-16 nmol) injection, peaked at 30 min, lasted for 60 min, and was strongly inhibited by the endothelin-A (ET(A)) receptor antagonist, BQ-123 (3.2 m). In separate experiments, impulse activity of single, physiologically characterized sensory C-, Adelta-, and Abeta-fibers was recorded from the sciatic nerve in anesthetized rats after subcutaneous injections of endothelin-1 (1-20 nmol), alone or together with BQ-123 (3.2 m), into the plantar hindpaw receptive fields of these units. All nociceptive C-fibers (31 of 33 C-fibers studied) were excited by ET-1 (1-20 nmol) in a dose-dependent manner. For doses of 16-20 nmol, the mean latency for afferent activation after injection of ET-1 was 3.16 +/- 0.31 min, and the mean and maximum response frequency were 2.02 +/- 0.48 impulses (imp)/sec and 14.0 +/- 3.2 imp/sec, respectively. All 10 nociceptive Adelta-fibers (of 12 Adelta-fibers studied) also responded to 1-20 nmol of ET-1 in a dose-dependent manner with a mean latency of 3.5 +/- 0.12 min and mean response frequency of 3.3 +/- 2.3 imp/sec. In contrast, most Abeta-fibers (9 of 12) did not respond to ET-1. BQ-123, when coinjected with ET-1, blocked ET-1-induced activation in all C- and Adelta-fibers tested. These data demonstrate that subcutaneous administration of ET-1 to the rat plantar hindpaw produces pain-like behavior and selective excitation of nociceptive fibers through activation of ET(A) receptors.

Topics: Action Potentials; Animals; Behavior, Animal; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Hindlimb; Injections, Subcutaneous; Male; Nerve Fibers; Nerve Fibers, Myelinated; Neurons, Afferent; Nociceptors; Pain; Pain Measurement; Peptides, Cyclic; Rats; Rats, Sprague-Dawley; Reaction Time; Receptor, Endothelin A; Sciatic Nerve

The aim of this study was to determine the response of inflammatory and vasoactive mediators to 3 consecutive days of exercise in African-American women with and without sickle cell anemia (SCA). Circulating inflammatory mediators [C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor alpha (TNFalpha)] were measured before, and vasoactive mediators [endothelin-1 (ET-1), nitric oxide metabolites (NOx)] before and after each exercise bout in ten subjects with SCA and ten controls. Exercise did not affect ET-1, IL-6 or CRP concentrations (p >.05). TNFalpha was higher in SCA than controls (p < or = .0005) at all times; however, the response pattern was similar for the groups: no change from day 1 to day 2, but a decrease from day 2 to day 3 (p < or = .05). NOx increased significantly after exercise (p < or = .0001) but returned to baseline by 24 h afterward. On the 3rd day, NOx increased after exercise in SCA but not in the controls (p < or = .05). In conclusion, exercise did not cause a harmful inflammatory response in these individuals with SCA. However, NOx increased after exercise on all 3 days in SCA but appeared attenuated after 2 days in controls.

Topics: Adult; Anemia, Sickle Cell; Biomarkers; C-Reactive Protein; Endothelin-1; Enzyme-Linked Immunosorbent Assay; Exercise; Female; Fluorescence Polarization; Heart Rate; Hematocrit; Hemoglobins; Humans; Immunoassay; Interleukin-6; Nitric Oxide; Pain; Time Factors; Tumor Necrosis Factor-alpha

This paper describes a model of tumor-induced bone destruction and hyperalgesia produced by implantation of fibrosarcoma cells into the mouse calcaneus bone. Histological examination indicates that tumor cells adhere to the bone edge as early as post-implantation day (PID) 3, but osteolysis does not begin until PID 6, correlating with the development of hyperalgesia. C3H/He mice exhibit a reproducible hyperalgesia to mechanical and cold stimuli between PID 6 and 16. These behaviors are present but significantly reduced with subcutaneous implantation that does not involve bone. Systemic administration of morphine (ED(50) 9.0 mg/kg) dose-dependently attenuated the mechanical hyperalgesia. In contrast, bone destruction and hypersensitivity were not evident in mice implanted with melanoma tumors or a paraffin mass of similar size. A novel microperfusion technique was used to identify elevated levels of the putative algogen endothelin (ET) in perfusates collected from the tumor sites of hyperalgesic mice between PID 7 and 12. Increased ET was evident in microperfusates from fibrosarcoma tumor-implanted mice but not from melanoma tumor-implanted mice, which are not hyperalgesic. Intraplantar injection of ET-1 in naive and, to a greater extent, fibrosarcoma tumor-bearing mice produced spontaneous pain behaviors, suggesting that ET-1 activates primary afferent fibers. Intraplantar but not systemic injection of the ET-A receptor antagonist BQ-123 partially blocked tumor-associated mechanical hyperalgesia, indicating that ET-1 contributes to tumor-induced nociception. This model provides a unique approach for quantifying the behavioral, biochemical, and electrophysiological consequences of tumor-nerve interactions.

Topics: Animals; Behavior, Animal; Calcaneus; Crosses, Genetic; Disease Models, Animal; Endothelin-1; Fibrosarcoma; Hindlimb; Hyperalgesia; Melanoma, Experimental; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Neoplasm Transplantation; Neoplasms, Experimental; Pain; Pain Measurement; Peripheral Nerves; Physical Stimulation; Tumor Cells, Cultured

Endothelin-1 (ET-1) induces endothelin-A (ETA) receptor-mediated pain and selective excitation of nociceptors. Here we studied ET-1-induced changes in intracellular calcium (Ca2+in) in Fura-2 loaded mouse neuroblastoma-rat dorsal root ganglion hybrid cells (ND7/104). ET-1 (1-400 nM) induced concentration-dependent, transient increases in Ca2+in, probably of intracellular source. Responses to repeated application declined with increasing ET-1 concentration, implying receptor desensitization. Treatment of cells with the selective ETA receptor antagonist, BQ-123, produced a dose-dependent inhibition of the response that was 20% of ET-1 alone (IC50 = 20 nM, KI = 7 nM). No inhibition of the calcium response was observed with the selective ETB antagonist, BQ-788 (10-1000 nM). These results demonstrate that ET-1 induces dose- and ETA receptor-dependent release of Ca2+in in nociceptor-like neurons, and permit further examination of the pathways that underlie ET-1-induced pain signaling.

Topics: Animals; Antihypertensive Agents; Calcium; Calcium Channels; Calcium Signaling; Cell Line, Transformed; Dose-Response Relationship, Drug; Endothelin Receptor Antagonists; Endothelin-1; Fluorescent Dyes; Fluorometry; Fura-2; Ganglia, Spinal; Intracellular Fluid; Mice; Models, Biological; Neuroblastoma; Neurons, Afferent; Nociceptors; Oligopeptides; Pain; Peptides, Cyclic; Piperidines; Rats; Receptor, Endothelin A; Receptors, Endothelin

We examined whether endothelin-1 (ET-1), a potent vasoconstrictive peptide secreted in high concentration by metastatic prostate cancer cells, produces endothelin receptor-dependent pain behavior when applied to rat sciatic nerve. ET-1 (200-800 microM) applied to the epineurial surface of rat sciatic nerve produced reliable, robust, unilateral hindpaw flinching lasting 60 min. Pre-emptive systemic morphine completely blocked this effect in a naloxone-reversible manner, suggesting that this behavior was pain-related. Equipotent doses of epineurially applied epinephrine had no effect, suggesting that ET-1 effects are on tissue sites other than sciatic nerve microvessels. Prior and co-administration of BQ-123, an endothelin-A (ET(A)) receptor antagonist, also blocked ET-1-induced hindpaw flinching establishing that pain behavior induced by ET-1 application to rat sciatic nerve is ET(A) receptor mediated.

Topics: Acute Disease; Administration, Topical; Adrenergic alpha-Agonists; Analgesics, Opioid; Animals; Behavior, Animal; Drug Interactions; Endothelin-1; Epinephrine; Male; Microcirculation; Morphine; Naloxone; Narcotic Antagonists; Pain; Rats; Rats, Sprague-Dawley; Receptor, Endothelin A; Receptors, Endothelin; Sciatic Nerve

The relative contributions of microvascular inflammation and vasomotor dysregulation to the development of acute vaso-occlusive crisis in sickle cell disease have been intensely studied. The present observational study was designed to examine the levels of circulating proinflammatory cytokines, anti-inflammatory cytokines, and vasoactive mediators during and after acute painful crisis. In symptomatic sickle cell patients, plasma levels of endothelin-1 and prostaglandin E2 were elevated during crises compared with healthy African-American controls. These levels had decreased, but not normalized, when patients were seen 1 to 3 weeks after discharge from hospital. Other mediators (tumor necrosis factor alpha [TNFalpha], interleukin-1beta [IL-1beta], IL-6, IL-8, and IL-10) were neither elevated in asymptomatic sickle cell disease nor in acute vaso-occlusive crisis. As a potent long-acting mediator of vasoconstriction and inflammation, endothelin-1 may play a key role in the cycle of ischemia and inflammation that initiates and sustains pain of crisis. The downregulatory effects of prostaglandin E2 on immune cell function may contribute to the increased susceptibility to infection observed in patients with sickle cell disease.

Topics: Acute Disease; Adult; Anemia, Sickle Cell; Cell Adhesion Molecules; Cytokines; Dinoprostone; Endothelin-1; Humans; Ischemia; Microcirculation; Middle Aged; Monocytes; Pain; Vascular Diseases; Vasculitis; Vasoconstriction