losartan-potassium and Neuralgia

Schwann cells provide trophic support and in some cases, insulation to axons. After injury, Schwann cells undergo phenotypic modulation, acquiring the capacity to proliferate, migrate, and secrete soluble mediators that control Wallerian degeneration and regeneration. Amongst the soluble mediators are pro-inflammatory cytokines that function as chemoattractants but also may sensitize nociceptors. At the same time, Schwann cells produce factors that counterbalance the pro-inflammatory cytokines, including, for example, interleukin-10 and erythropoietin (Epo). Epo and its receptor, EpoR, are up-regulated in Schwann cells after peripheral nerve injury. EpoR-dependent cell signaling may limit production of TNF-alpha by Schwann cells within the first five days after injury. In addition, EpoR-dependent cell signaling may reduce axonal degeneration and facilitate recovery from chronic pain states. Other novel factors that regulate Schwann cell phenotype in nerve injury have been recently identified, including the low-density lipoprotein receptor related protein (LRP-1). Our recent studies indicate that LRP-1 may be essential for Schwann cell survival after peripheral nerve injury. To analyze the function of specific Schwann cell gene products in nerve injury and sensory function, conditional gene deletion and expression experiments in mice have been executed using promoters that are selectively activated in myelinating or non-myelinating Schwann cells. Blocking ErbB receptor-initiated cell-signaling in either myelinating or non-myelinating Schwann cells results in unique sensory dysfunctions. Data obtained in gene-targeted animals suggest that sensory alterations can result from changes in Schwann cell physiology without profound myelin degeneration or axonopathy. Aberrations in Schwann cell biology may lie at the foundation of neuropathic pain and represent an exciting target for therapeutic intervention.

Topics: Animals; Cytokines; Erythropoietin; Humans; Nerve Fibers, Myelinated; Neuralgia; Peripheral Nervous System; Peripheral Nervous System Diseases; Receptors, Erythropoietin; Schwann Cells

Neuropathic pain is a refractory disease with limited treatment options due to its complex mechanisms. Whereas erythropoietin-producing hepatocyte A1 (EphA1) mediates the production of inflammatory factors that are important in the progression of neurological diseases, its role and molecular mechanisms in neuropathic pain remain unclear. In the present study, we established a mouse model of chronic constriction injury (CCI). EphA1 expression was observed to be progressively upregulated at the mRNA and protein levels with the progression of the disease. Subsequently, knockdown of EphA1 expression levels using adenovirus short hairpin RNA (AAV-shEphA1) revealed an increase in mechanical stimulation withdrawal threshold (PWT) and withdrawal latency (PWL) when EphA1 expression was decreased, accompanied by improved dorsal root ganglion injury, increased leukocytosis, decreased microglia, and decreased levels of pro-inflammatory factors. For the underlying mechanism, it was found that EphA1 regulates the activity of the RhoA/ROCK2 pathway by modulating the level of CXCR4. Inhibition of CXCR4 and RhoA/ROCK2 could effectively alleviate the promoting effect of EphA1 upregulation on neuropathic pain. In conclusion, our study suggests that depletion of EphA1 ameliorates neuropathic pain by modulating the CXCR4/RhoA/ROCK2 signaling pathway, and targeting EphA1 may be a potential clinical treatment for neuropathic pain.

Topics: Animals; Erythropoietin; Mice; Microglia; Neuralgia; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; Signal Transduction

Neuroprotective effects of erythropoietin (EPO) on peripheral nerve injury remain uncertain. This study investigated the efficacy of EPO in attenuating median nerve chronic constriction injury (CCI)-induced neuropathy. Animals received an intraneural injection of EPO at doses of 1,000, 3,000, or 5,000 units/kg 15 min before median nerve CCI. Afterwards, the behavioral and electrophysiological tests were conducted. Immunohistochemistry and immunoblotting were used for qualitative and quantitative analysis of microglial and mitogen-activated protein kinases (MAPKs), including p38, JNK, and ERK, activation. Enzyme-linked immunosorbent assay and microdialysis were applied to measure pro-inflammatory cytokine and glutamate responses, respectively. EPO pre-treatment dose-dependently ameliorated neuropathic pain behavior, decreased microglial and MAPKs activation, and diminished the release of pro-inflammatory cytokines and glutamate in the ipsilateral cuneate nucleus after CCI. Moreover, EPO pre-treatment preserved myelination of the injured median nerve on morphological investigation and suppressed injury-induced discharges. We also observed that EPO receptor (EPOR) expression was up-regulated in the injured nerve after CCI. Double immunofluorescence showed that EPOR was localized to Schwann cells. Furthermore, siRNA-mediated knockdown of EPOR expression eliminated the therapeutic effects of EPO on attenuating the microglial and MAPKs activation, pro-inflammatory cytokine responses, injury discharges, and neuropathic pain behavior in CCI rats. In conclusion, binding of EPO to its receptors on Schwann cells maintains myelin integrity and blocks ectopic discharges in the injured median nerve, that in the end contribute to attenuation of neuropathic pain via reducing glutamate release from primary afferents and inhibiting activation of microglial MAPKs and production of pro-inflammatory cytokines.

Topics: Action Potentials; Animals; Cytokines; Disease Models, Animal; Erythropoietin; Gene Expression Regulation; Hyperalgesia; Male; Median Nerve; Microglia; Mitogen-Activated Protein Kinase Kinases; Neuralgia; Pain Threshold; Peripheral Nervous System Diseases; Phosphorylation; Polyradiculoneuropathy; Rats; Rats, Sprague-Dawley; Receptors, Erythropoietin; RNA, Small Interfering; Schwann Cells; Signal Transduction

Vascular endothelial growth factor (VEGF) is an angiogenic cytokine that stimulates the differentiation and function of vascular endothelial cells. VEGF has been implicated in improving nervous system function after injury. However, uncontrolled overexpression of VEGF increases the risk of tumor formation at the site of gene delivery. For this reason, VEGF expression needs to be strictly controlled. The goal of the present study was to understand the effects of hypoxia-induced gene expression system to control VEGF gene expression in neural stem cells (NSCs) on the regeneration of neural tissue after sciatic nerve injury. In this study, we used the erythropoietin (Epo) enhancer-SV40 promoter system (EpoSV-VEGF-NSCs) for hypoxia-specific VEGF expression. We used three types of NSCs: DsRed-NSCs as controls, SV-VEGF-NSCs as uncontrolled VEGF overexpressing NSCs, and EpoSV-VEGF-NSCs. For comparison of VEGF expression at normoxia and hypoxia, we measured the amount of VEGF secreted. VEGF expression decreased at normoxia and increased at hypoxia for EpoSV-VEGF-NSCs; thus, EpoSV-VEGF-NSCs controlled VEGF expression, dependent upon oxygenation condition. To demonstrate the therapeutic effect of EpoSV-VEGF-NSCs, we transplanted each cell line in a neuropathic pain sciatic nerve injury rat model. The transplanted EpoSV-VEGF-NSCs improved sciatic nerve functional index (SFI), mechanical allodynia, and re-myelination similar to the SV-VEGF-NSCs. Additionally, the number of blood vessels increased to a level similar to that of the SV-VEGF-NSCs. However, we did not observe tumor generation in the EpoSV-VEGF-NSC animals that were unlikely to have tumor formation in the SV-VEGF-NSCs. From our results, we determined that EpoSV-VEGF-NSCs safely regulate VEGF gene expression which is dependent upon oxygenation status. In addition, we found that they are therapeutically appropriate for treating sciatic nerve injury.

Topics: Animals; Cell Hypoxia; Cell Line; Erythropoietin; Gene Expression Regulation; Gene Transfer Techniques; Male; Mice; Neural Stem Cells; Neuralgia; Plasmids; Promoter Regions, Genetic; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Up-Regulation; Vascular Endothelial Growth Factor A

Neuropathic pain is a difficult to treat disorder arising from central or peripheral nervous system lesions. The etiology of neuropathic pain consists of several overlapping pathways converging into an exaggerated pain state with symptoms such as allodynia and hyperalgesia. One of these pathways involves activation of spinal cord microglia and astrocytes, which drive and maintain the inflammatory response following the lesion. These cells are a potential target for drugs for neuropathic pain relief. In this current study, we investigated the dose-effect relationship of the tissue protective peptide ARA 290, derived from the tertiary structure of erythropoietin, on allodynia and concurrent spinal cord microglia and astrocytes.. Following a spared nerve injury in rats, vehicle or ARA290 (administered in either one of 4 doses: 3, 10, 30 and 60 μg/kg) was administered on days 1, 3, 6, 8 and 10. ARA290 exerted a dose-response effect by significantly reducing mechanical allodynia up to 20 weeks when compared to vehicle. The reduction of cold allodynia was significant up to 20 weeks for the doses 3, 10, 30 and 60 μg/kg when compared to vehicle. The effect 10 and 30 μg/kg ARA290 and vehicle on the microglia response (iba-1-immunoreactivity, iba-1-IR) and astrocyte reaction (GFAP-immunoreactivity, GFAP-IR) was investigated in animals surviving 2 (group 1) or 20 (group 2) weeks following lesion or sham surgery. In group 1, significant microglia reactivity was observed in the L5 segment of the spinal cord of animals treated with vehicle when compared to sham operated, while animals treated with 10 or 30 μg/kg did not show a increase. In group 2, a more widespread and increased microglia reactivity was observed for animals treated with 0 and 10 μg/kg when compared to sham operated animals, indicated by involvement of more spinal cord segments and higher iba-1-IR. Animals treated with 30 μg/kg did not show increased microglia reactivity. No difference in astrocyte reaction was observed.. The erythropoietin-analogue ARA290 dose-dependently reduced allodynia coupled to suppression of the spinal microglia response, suggestive of a mechanistic link between ARA290-induced suppression of central inflammation and relief of neuropathic pain symptoms.

Topics: Animals; Calcium-Binding Proteins; Dose-Response Relationship, Drug; Erythropoietin; Female; Glial Fibrillary Acidic Protein; Hyperalgesia; Microfilament Proteins; Microglia; Neuralgia; Oligopeptides; Posterior Horn Cells; Protein Structure, Tertiary; Rats; Rats, Sprague-Dawley; Sciatic Nerve; Spinal Cord; Time Factors

Studies on the neuritis model suggest that in many patients with neuropathic pain, symptoms may be due to nerve inflammation rather than frank nerve injury. Treatments for these patients are often ineffective. The neuroprotective and hematopoietic agent erythropoietin (EPO) has been shown to reverse pain behaviors in nerve injury models and therefore may be of therapeutic benefit. However, EPO can cause thrombosis. ARA290 is an analog of EPO that has the neuroprotective activities of EPO without stimulating hematopoiesis. The present study has examined the effects of ARA290 on pain behavior in the neuritis model. Following neuritis induction, 30 or 120 μg/kg ARA290 or saline vehicle was injected intraperitoneally into rats daily from day 1 post surgery. Animals were assessed for mechanical allodynia and heat hyperalgesia. Levels of the cytokine tumor necrosis factor-α (TNF-α) and chemokine (CC motif) ligand 2 (CCL2) mRNA were also assessed using polymerase chain reaction. Vehicle-treated neuritis animals (n=20) developed signs of mechanical allodynia and heat hyperalgesia that reached a maximum on day 4 and 3 of testing, respectively. Treatment with either 30 (n=11) or 120 μg/kg ARA290 (n=9) prevented the development of mechanical allodynia. However, ARA290 did not significantly affect heat hyperalgesia. There was no significant difference between the effects of each drug dose (p<0.05, unpaired t test comparing area under the curve for mechanical allodynia). The levels of CCL2 and TNF-α mRNA in the nerve and Gelfoam were not significantly different following 120 μg/kg ARA290 treatment (n=3-7) compared to vehicle-treated animals (n=3-7; p=0.24; unpaired t tests). In summary, ARA290 may be beneficial in the treatment of neuropathic pain symptoms where signs of nerve injury are absent on clinical assessment. The mechanisms of action do not appear to involve the inhibition of TNF-α or CCL2 production.

Topics: Animals; Chemokine CCL2; Disease Models, Animal; Erythropoietin; Hyperalgesia; Male; Neuralgia; Neuritis; Neuroprotective Agents; Oligopeptides; Rats; Rats, Sprague-Dawley; RNA, Messenger; Sciatic Nerve; Tumor Necrosis Factor-alpha

Exogenous erythropoietin inhibits development of allodynia in experimental painful neuropathy because of its antiinflammatory and neuroprotective properties at spinal, supraspinal, and possibly peripheral sites. The authors assess the effect of a nonhematopoietic erythropoietin analog, ARA290, on tactile and cold allodynia in a model of neuropathic pain (spared nerve injury) in rats and mice lacking the β-common receptor (βcR mice), a component of the receptor complex mediating tissue protection.. Twenty-four hours after peripheral nerve injury, rats and mice were injected with ARA290 or vehicle (five 30-μg/kg intraperitoneal injections at 2-day intervals, followed by once/week, n = 8/group). In a separate group of eight rats, ARA290 treatment was restricted to five doses during the initial 2 weeks after surgery.. In rats, irrespective of treatment paradigm, ARA290 produced effective, long-term (as long as 15 weeks) relief of tactile and cold allodynia (P < 0.001 vs. vehicle-treated animals). ARA290 was effective in wild-type mice, producing significant relief of allodynia. In contrast, in βcR mice no effect of ARA290 was observed.. ARA290 produces long-term relief of allodynia because of activation of the β-common receptor. It is argued that relief of neuropathic pain attributable to ARA290 treatment is related to its antiinflammatory properties, possibly within the central nervous system. Because ARA290, in contrast to erythropoietin, is devoid of hematopoietic and cardiovascular side effects, ARA290 is a promising new drug in the prevention of peripheral nerve injury-induced neuropathic pain in humans.

Topics: Animals; Erythropoietin; Female; Hyperalgesia; Mice; Mice, Knockout; Neuralgia; Peptides; Protein Structure, Tertiary; Rats; Rats, Sprague-Dawley; Receptors, Erythropoietin

Neuropathic pain is a complex syndrome resulting from damage to the peripheral nervous system. Central neuroimmune activation contributes to the generation and maintenance of chronic pain after nerve injury. The current study determined the effects of recombinant human erythropoietin (rhEPO) on behavioral hyperalgesia and neuroimmune activation in a rat model of neuropathic pain induced by L5 spinal nerve transection. Animals were randomly assigned into 3 groups: sham-operation with saline; L5 spinal nerve transection with rhEPO (5000 units/kg); or L5 transection with saline. The rhEPO or saline was given ip on the day before surgery and continued daily to day 7 post-transection. The paw pressure threshold and paw withdrawal latencies were measured before surgery and on days 1, 3, and 7 post-operation. Glial activation markers such as macrophage antigen complex-1 (Mac-1, OX-42) and glial fibrillary acidic protein (GFAP), production of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-10, as well as nuclear factor-kappa B (NF-kappaB) activation were determined in the lumbar spinal cord. Administration of rhEPO resulted in attenuation of mechanical and thermal hyperalgesia. Furthermore, rhEPO markedly inhibited neuroimmune activation characterized by glial activation, production of proinflammatory cytokines like TNF-alpha, IL-1beta, and NF-kappaB activation, but rhEPO enhanced the level of IL-10. These results support the significance of neuroinflammation and neuroimmune activation in the initiation and persistence of behavioral pain responses. The data indicate that rhEPO attenuates behavioral hyperalgesia and neuroimmune activation in neuropathic pain induced by L5 nerve transection.

Topics: Animals; Behavior, Animal; Biomarkers; Cytokines; Erythropoietin; Glial Fibrillary Acidic Protein; Humans; Hyperalgesia; Inflammation Mediators; Male; Neuralgia; Neuroglia; Neuroimmunomodulation; NF-kappa B; Pain Measurement; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Spinal Cord; Spinal Nerves; Temperature

The effect of recombinant human erythropoietin (rhEPO) on neuropathic pain remains unclear. This study aimed to determine the effects of preemptive administration of rhEPO on the behavioural changes and neuroinflammatory responses in a rat model of neuropathic pain.. Fifty rats were randomly allocated into five groups, sham-operation treated with saline and L5 spinal nerve transection treated with different doses of rhEPO (0 [saline], 1000, 3000, or 5000 U x kg(-1), respectively). The rats were intraperitoneally treated from 1 day before surgery to post-surgery day 7. The mechanical (paw pressure thresholds, PPT) and thermal thresholds (paw withdrawal latencies, PWL) were measured on post-surgery days 1, 3, and 7. The contralateral brain was obtained on post-surgery day 7 to determine the expressions of tumour necrosis factor (TNF-alpha), interleukin (IL)-1beta, IL-6, L-10, and nuclear factor-kappa B (NF-kappaB) activity.. There were significant decreases in PPT and PWL after L5 spinal nerve transection (P < 0.001). Compared with the saline group, the rhEPO 3000 and 5000 U x kg(-1) groups resulted in significant increases in PPT and PWL (P < 0.001) and reduced the cerebral expressions of TNF-alpha, IL-1beta, IL-6, and NF-kappaB activity associated with the increase in IL-10 (rhEPO3000 group, P < 0.05, and rhEPO5000 group, P < 0.001, respectively). Administration of rhEPO 1000 U x kg(-1) had no significant effects on these variables.. Preemptive rhEPO dose-dependently attenuated the mechanical and thermal hyperalgesia in L5 spinal nerve transection rats, which correlated with the decreased cerebral expressions of TNF-alpha, IL-1beta, and IL-6 via downregulating NF-kappaB activity and the increased expression of IL-10.

Topics: Animals; Cytokines; Disease Models, Animal; Dose-Response Relationship, Drug; Erythropoietin; Gene Expression; Interleukin-10; Interleukin-1beta; Interleukin-6; Male; Neuralgia; NF-kappa B; Pain Measurement; Pain Threshold; Random Allocation; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Tumor Necrosis Factor-alpha