hc-030031 and Neuralgia

Central neuropathic pain is a common untreated symptom in progressive multiple sclerosis (PMS) and is associated with poor quality of life and interference with patients' daily activities. The neuroinflammation process and mitochondrial dysfunction in the PMS lesions generate reactive species. The transient potential receptor ankyrin 1 (TRPA1) has been identified as one of the major mechanisms that contribute to neuropathic pain signaling and can be activated by reactive compounds. Thus, the goal of our study was to evaluate the role of spinal TRPA1 in the central neuropathic pain observed in a PMS model in mice. We used C57BL/6 female mice (20-30 g), and the PMS model was induced by the experimental autoimmune encephalomyelitis (EAE) using mouse myelin oligodendrocyte glycoprotein (MOG

Topics: Acetanilides; Acetophenones; Analgesics; Animals; Antipyrine; Dipyrone; Encephalomyelitis, Autoimmune, Experimental; Female; Hyperalgesia; Mice; Mice, Inbred C57BL; Myelin-Oligodendrocyte Glycoprotein; NADPH Oxidases; Nerve Tissue Proteins; Neuralgia; Nociception; Oligonucleotides, Antisense; Oxidative Stress; Oximes; Peptide Fragments; Pregabalin; Purines; Spinal Cord; Thioctic Acid; TRPA1 Cation Channel; Up-Regulation

Bortezomib (BTZ) is used as a chemotherapeutic agent for the treatment of multiple myeloma. Nevertheless, one of the significant limiting complications of BTZ is painful peripheral neuropathy during BTZ therapy. Thus, in this study we examined signaling pathways of interleukin-6 (IL-6) and transient receptor potential ankyrin 1 (TRPA1) in the sensory nerves responsible for neuropathic pain induced by BTZ and further determined if influencing the pathways can improve neuropathic pain. ELISA and western blot analysis were used to examine the levels of IL-6, and IL-6 receptor (IL-6R), TRPA1 and p38-MAPK and JNK signal in the lumbar dorsal root ganglion. Behavioral test was performed to determine mechanical and cold sensitivity in a rat model. Our results showed that systemic injection of BTZ increased mechanical pain and cold sensitivity as compared with control animals. Data also showed that protein expression of TRPA1 and IL-6R was upregulated in the dorsal root ganglion of BTZ rats and blocking TRPA1 attenuated mechanical and cold sensitivity in control rats and BTZ rats. Notably, the inhibitory effect of blocking TRPA1 was smaller in BTZ rats than that in control rats. In addition, a blockade of IL-6 signal attenuated intracellular p38-MAPK and JNK in the sensory neuron. This also decreased TRPA1 expression and alleviated mechanical hyperalgesia and cold hypersensitivity in BTZ rats. In conclusion, we revealed specific signaling pathways leading to neuropathic pain induced by chemotherapeutic BTZ, including IL-6-TRPA1, suggesting that blocking these signals is beneficial to alleviate neuropathic pain during BTZ intervention.

Topics: Acetanilides; Analgesics; Animals; Bortezomib; Disease Models, Animal; Ganglia, Spinal; Interleukin-6; JNK Mitogen-Activated Protein Kinases; Male; Neuralgia; p38 Mitogen-Activated Protein Kinases; Pain Threshold; Phosphorylation; Proteasome Inhibitors; Purines; Pyrazines; Quinoxalines; Rats, Sprague-Dawley; Receptors, Interleukin-6; Sensory Receptor Cells; Signal Transduction; TRPA1 Cation Channel

Spinal cord injury (SCI) is an extremely serious type of physical trauma observed in clinics. Especially, neuropathic pain resulting from SCI has a lasting and significant impact on most aspects of daily life. Thus, a better understanding of the molecular pathways responsible for the cause of neuropathic pain observed in SCI is important to develop effectively therapeutic agents and treatment strategies. Proteinase-activated receptors (PARs) are a family member of G-protein-coupled receptors and are activated by a proteolytic mechanism. One of its subtypes PAR2 has been reported to be engaged in mechanical and thermal hyperalgesia. Thus, in this study we specifically examined the underlying mechanisms responsible for SCI evoked-neuropathic pain in a rat model. Overall, we demonstrated that SCI increases PAR2 and its downstream pathways TRPV1 and TRPA1 expression in the superficial dorsal horn of the spinal cord. Also, we showed that blocking spinal PAR2 by intrathecal injection of FSLLRY-NH2 significantly inhibits neuropathic pain responses induced by mechanical and thermal stimulation whereas FSLLRY-NH2 decreases the protein expression of TRPV1 and TRPA1 as well as the levels of substance P and calcitonin gene-related peptide. Results of this study have important implications, i.e. targeting one or more of these signaling molecules involved in activation of PAR2 and TRPV1/TRPA1 evoked by SCI may present new opportunities for treatment and management of neuropathic pain often observed in patients with SCI.

Topics: Acetanilides; Anilides; Animals; Cinnamates; Injections, Spinal; Male; Neuralgia; Oligopeptides; Purines; Rats; Rats, Wistar; Receptor, PAR-2; Spinal Cord Injuries

Despite intense investigation, the mechanisms of the different forms of trigeminal neuropathic pain remain substantially unidentified. The transient receptor potential ankyrin 1 channel (encoded by TRPA1) has been reported to contribute to allodynia or hyperalgesia in some neuropathic pain models, including those produced by sciatic nerve constriction. However, the role of TRPA1 and the processes that cause trigeminal pain-like behaviours from nerve insult are poorly understood. The role of TRPA1, monocytes and macrophages, and oxidative stress in pain-like behaviour evoked by the constriction of the infraorbital nerve in mice were explored. C57BL/6 and wild-type (Trpa1(+/+)) mice that underwent constriction of the infraorbital nerve exhibited prolonged (20 days) non-evoked nociceptive behaviour and mechanical, cold and chemical hypersensitivity in comparison to sham-operated mice (P < 0.05-P < 0.001). Both genetic deletion of Trpa1 (Trpa1(-/-)) and pharmacological blockade (HC-030031 and A-967079) abrogated pain-like behaviours (both P < 0.001), which were abated by the antioxidant, α-lipoic acid, and the nicotinamide adenine dinucleotide phosphate oxidase inhibitor, apocynin (both P < 0.001). Nociception and hypersensitivity evoked by constriction of the infraorbital nerve was associated with intra- and perineural monocytic and macrophagic invasion and increased levels of oxidative stress by-products (hydrogen peroxide and 4-hydroxynonenal). Attenuation of monocyte/macrophage increase by systemic treatment with an antibody against the monocyte chemoattractant chemokine (C-C motif) ligand 2 (CCL2) or the macrophage-depleting agent, clodronate (both P < 0.05), was associated with reduced hydrogen peroxide and 4-hydroxynonenal perineural levels and pain-like behaviours (all P < 0.01), which were abated by perineural administration of HC-030031, α-lipoic acid or the anti-CCL2 antibody (all P < 0.001). The present findings propose that, in the constriction of the infraorbital nerve model of trigeminal neuropathic pain, pain-like behaviours are entirely mediated by the TRPA1 channel, targeted by increased oxidative stress by-products released from monocytes and macrophages clumping at the site of nerve injury.

Topics: Acetanilides; Acetophenones; Animals; Chemokine CCL2; Clodronic Acid; Hyperalgesia; Macrophages; Male; Mice; Mice, Knockout; Monocytes; Neuralgia; Oxidative Stress; Oximes; Purines; Thioctic Acid; Transient Receptor Potential Channels; TRPA1 Cation Channel

Sympathetic fibres maintain some forms of neuropathic pain, but the underlying mechanisms are poorly understood. Therefore, this study investigated the possible involvement of transient receptor potential ankyrin 1 (TRPA1) and the role of the sympathetic nervous system (involved in sympathetically maintained neuropathic pain) in a model of neuropathic pain induced by sciatic nerve chronic constriction injury (CCI) in mice. Systemic injection of the selective TRPA1 antagonist HC-030031 reversed the mechanical and cold allodynia that was induced by sciatic nerve chronic constriction injury (CCI). Nerve injury also sensitised mice to nociception, which was induced by the intraplantar injection of a low dose of the TRPA1 agonist allyl isothiocyanate without changing TRPA1 immunoreactivity in the injected paw. Furthermore, chemical sympathectomy produced by guanethidine largely prevented CCI-induced mechanical and cold allodynia. CCI also induced a norepinephrine-triggered nociception that was inhibited by an α-adrenoceptor antagonist, norepinephrine transporter block and monoamine oxidase inhibition. Finally, the peripheral injection of HC-030031 also largely reduced CCI-induced norepinephrine nociception and mechanical or cold allodynia. Taken together, the present findings reveal a critical role of TRPA1 in mechanical and cold hypersensitivity and norepinephrine hypersensitivity following nerve injury. Finally, our results suggest that TRPA1 antagonism may be useful to treat patients who present sympathetically maintained neuropathic pain.

Topics: Acetanilides; Analgesics; Animals; Constriction; Disease Models, Animal; Hyperalgesia; Male; Mice; Neuralgia; Nociception; Purines; Sciatic Nerve; Sympathetic Nervous System; Transient Receptor Potential Channels; TRPA1 Cation Channel

The aim of this research was to assess the antinociceptive activity of the transient receptor potential (TRP) channel TRPV1, TRPM8, and TRPA1 antagonists in neurogenic, tonic, and neuropathic pain models in mice. For this purpose, TRP channel antagonists were administered into the dorsal surface of a hind paw 15 min before capsaicin, allyl isothiocyanate (AITC), or formalin. Their antiallodynic and antihyperalgesic efficacies after intraperitoneal administration were also assessed in a paclitaxel-induced neuropathic pain model. Motor coordination of paclitaxel-treated mice that received these TRP channel antagonists was investigated using the rotarod test. TRPV1 antagonists, capsazepine and SB-366791, attenuated capsaicin-induced nociceptive reaction in a concentration-dependent manner. At 8 µg/20 µl, this effect was 51% (P<0.001) for capsazepine and 37% (P<0.05) for SB-366791. A TRPA1 antagonist, A-967079, reduced pain reaction by 48% (P<0.05) in the AITC test and by 54% (P<0.001) in the early phase of the formalin test. The test compounds had no influence on the late phase of the formalin test. In paclitaxel-treated mice, they did not attenuate heat hyperalgesia but N-(3-aminopropyl)-2-{[(3-methylphenyl)methyl]oxy}-N-(2-thienylmethyl) benzamide hydrochloride salt (AMTB), a TRPM8 antagonist, reduced cold hyperalgesia and tactile allodynia by 31% (P<0.05) and 51% (P<0.01), respectively. HC-030031, a TRPA1 channel antagonist, attenuated tactile allodynia in the von Frey test (62%; P<0.001). In conclusion, distinct members of TRP channel family are involved in different pain models in mice. Antagonists of TRP channels attenuate nocifensive responses of neurogenic, tonic, and neuropathic pain, but their efficacies strongly depend on the pain model used.

Topics: Acetanilides; Analgesics; Animals; Benzamides; Capsaicin; Cold Temperature; Disease Models, Animal; Formaldehyde; Hyperalgesia; Isothiocyanates; Male; Mice; Neuralgia; Oximes; Paclitaxel; Pain Measurement; Purines; Thiophenes; Touch; Transient Receptor Potential Channels; TRPA1 Cation Channel; TRPM Cation Channels; TRPV Cation Channels

The fact that transient receptor potential ankyrin 1 (TRPA1) on the peripheral terminals could attenuate hyperalgesia is widely accepted, but the effect of spinal TRPA1 in the modulation of hyperalgesia has not been fully demonstrated. In the present study, we investigated the effect of intrathecal (i.t.) administration TRPA1 antagonists on chronic pain and expression of TRPA1 and phosphorylation N-methyl-D-aspartate receptor 2B subunit (p-NR2B) in the spinal cord with chronic compression of the dorsal root ganglia (CCD) in rats.. The study was conducted in 2 parts. Part 1: Sixteen rats were divided into 2 groups (n = 8 each): a sham group and CCD group. Paw withdrawal mechanical thresholds (PWMT) were measured at baseline and 1, 3, 7, 10, 14, and 21 days after CCD. Sixteen other rats were used to evaluate expression of TRPA1 and p-NR2B in spinal cord on the seventh and 14th days after CCD; Western blotting was used to evaluate expression levels (n = 4 each). Part 2: 40 rats were divided into 5 groups (n = 8 each): CCD group, CCD + Vehicle group, CCD + HC-030031(10 μg, i.t.) group, CCD + HC-030031(25 μg, i.t.) group, and CCD + HC-030031(50 μg, i.t.) group. PWMTs were measured at baseline and 0.5, 1, 2, 4, and 6 hours after i.t. HC-030031 on the third, seventh, 10th, and 14th days after CCD. Another 48 rats were used to evaluate expression of TRPA1 and p-NR2B in spinal cord 2 hours after injection on the seventh and 14th days after CCD in groups CCD, CCD + Vehicle, and CCD+ HC-030031(50 μg, i.t.) using Western blotting (n = 4 each).. Compared with the sham group, PWMT was significantly decreased, and protein expression of TRPA1 and p-NR2B were upregulated, in spinal cord on the seventh and 14th days after CCD operation. TRPA1 antagonists (HC-030031, 50 μg, i.t.) increased the PWMT after CCD and downregulated the protein level of TRPA1 and p-NR2B in spinal cord at 2 hours after the injection on the seventh and 14th days after CCD.. These data demonstrated that the i.t. administration of TRPA1 antagonists could attenuate neuropathic pain in CCD rats, and this effect could be partially reduced by p-NR2B receptor expression in spinal cord.

Topics: Acetanilides; Animals; Disease Models, Animal; Hyperalgesia; Injections, Spinal; Male; Neuralgia; Purines; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; TRPA1 Cation Channel; TRPC Cation Channels

Transient receptor potential ankyrin 1 (TRPA1) channel antagonists have suppressed mechanical hypersensitivity in peripheral neuropathy, while their effect on ongoing neuropathic pain is not yet known. Here, we assessed whether blocking the TRPA1 channel induces place-preference, an index for the relief of ongoing pain, in two experimental rat models of peripheral neuropathy. Diabetic neuropathy was induced by streptozotocin and spared nerve injury (SNI) model of neuropathy by ligation of two sciatic nerve branches. Conditioned place-preference (CPP) paradigm involved pairing of the drug treatment with one of the chambers of a CPP device once or four times, and the time spent in each chamber was recorded after conditioning sessions to reveal place-preference. The mechanical antihypersensitivity effect was assessed by the monofilament test immediately after the conditioning sessions. Intraperitoneally (30mg/kg; diabetic and SNI model) or intrathecally (10μg; diabetic model) administered Chembridge-5861528 (CHEM) was used as a selective TRPA1 channel antagonist. In diabetic and SNI models of neuropathy, CHEM failed to induce CPP at a dose that significantly attenuated mechanical hypersensitivity, independent of the route of drug administration or number of successive conditioning sessions. Intrathecal clonidine (an α2-adrenoceptor agonist; 10μg), in contrast, induced CPP in SNI but not control animals. The results indicate that ongoing pain, as revealed by CPP, is less sensitive to treatment by the TRPA1 channel antagonist than mechanical hypersensitivity in peripheral neuropathy.

Topics: Acetanilides; Adrenergic alpha-2 Receptor Agonists; Animals; Clonidine; Conditioning, Psychological; Diabetic Neuropathies; Disease Models, Animal; Hyperalgesia; Male; Neuralgia; Peripheral Nervous System Diseases; Purines; Rats; Rats, Wistar; TRPA1 Cation Channel; TRPC Cation Channels

Safe and effective treatment for chronic inflammatory and neuropathic pain remains a key unmet medical need for many patients. The recent discovery and description of the transient receptor potential family of receptors including TRPV1 and TRPA1 has provided a number of potential new therapeutic targets for treating chronic pain. Recent reports have suggested that TRPA1 may play an important role in acute formalin and CFA induced pain. The current study was designed to further explore the therapeutic potential of pharmacological TRPA1 antagonism to treat inflammatory and neuropathic pain.. The in vitro potencies of HC-030031 versus cinnamaldehyde or allyl isothiocyanate (AITC or Mustard oil)-induced TRPA1 activation were 4.9 +/- 0.1 and 7.5 +/- 0.2 microM respectively (IC50). These findings were similar to the previously reported IC50 of 6.2 microM against AITC activation of TRPA1 1. In the rat, oral administration of HC-030031 reduced AITC-induced nocifensive behaviors at a dose of 100 mg/kg. Moreover, oral HC-030031 (100 mg/kg) significantly reversed mechanical hypersensitivity in the more chronic models of Complete Freunds Adjuvant (CFA)-induced inflammatory pain and the spinal nerve ligation model of neuropathic pain.. Using oral administration of the selective TRPA1 antagonist HC-030031, our results demonstrated that TRPA1 plays an important role in the mechanisms responsible for mechanical hypersensitivity observed in inflammatory and neuropathic pain models. These findings suggested that TRPA1 antagonism may be a suitable new approach for the development of a potent and selective therapeutic agent to treat both inflammatory and neuropathic pain.

Topics: Acetanilides; Analgesics; Animals; Ankyrins; Calcium Channels; Cell Line; Disease Models, Animal; Humans; Inflammation; Male; Nerve Tissue Proteins; Neuralgia; Pain; Purines; Rats; Rats, Sprague-Dawley; Transient Receptor Potential Channels; TRPA1 Cation Channel; TRPC Cation Channels