Modulation of TRPV1 function by Citrus reticulata (tangerine) fruit extract for the treatment of sensitive skin.

BACKGROUND: Sensitive skin (SS) is a clinical syndrome defined by the occurrence of unpleasant sensations (such as stinging, burning, pain, pruritus, and tingling) in response to stimuli that normally should not provoke them. According to growing evidence, transient receptor potential vanilloid subtype 1 (TRPV1) has elevated expression in individuals with SS and is linked with the severity of SS symptoms. However, its pathogenesis is still unknown. OBJECTIVE: Herein, Citrus reticulata (Tangerine) fruit extract (CR) was obtained and examined for its effect on SS with a focus on TRPV1 stimulation and expression. METHODS: A recombinant hTRPV1 over-expression cell line (HaCaT-TRPV1-OE cell) was constructed to screen substances and extracts from several plants. Intracellular calcium mobilization was monitored by Flexstation 3 and a fluorescence microscope using Fluo 8 AM fluorophore. Next, immunofluorescence was used to detect the TRPV1 expression under different stimulants treated for 24 h. To investigate the relief and increased tolerance of CR to lactic acid-induced skin discomfort, clinical tests were carried out on the nasolabial folds or cheek areas. RESULTS: According to the obtained results, compared to HaCaT cells, HaCaT-TRPV1-OE cells showed a higher expression of TRPV1. Neuronal hyperresponsiveness in SS triggered by capsaicin (CAP), lactic acid, phenoxyethanol or nicotinamide may be through activation of TRPV1 and increased TRPV1 expression. CAP activates TRPV1 in HaCaT-TRPV1-OE cells, and more than 100 plants or chemicals were tested for their inhibitory effects before being screened for CR. CR (1%-4%) inhibited TRPV1 activation induced by CAP or phenoxyethanol or nicotinamide. Meanwhile, CR (0.25%) suppressed TRPV1 protein expression induced by phenoxyethanol or lactic acid. In vivo results showed that CR not only instantly relieved lactic acid-induced skin discomfort under 5 min but also enhanced skin tolerance to lactic acid after 7 days of continuous use. CONCLUSIONS: Topical application of CR showed an instant and long-lasting improvement in SS by modulating the activation and expression of TRPV1. Moreover, it has been suggested that CR might act as a TRPV1 inhibitor to reduce skin irritation or sensitivity.

Magnolol and honokiol target TRPC4 to regulate extracellular calcium influx and relax intestinal smooth muscle.

ETHNOPHARMACOLOGICAL RELEVANCE: Magnolia officinalis Cortex (M. officinalis) is a classical traditional Chinese medicine (TCM) widely used to treat digestive system diseases. It effectively regulates gastrointestinal motility to improve abdominal pain, abdominal distension and other symptoms. Magnolol (MAG) and honokiol (HON) are the main pharmacodynamic components responsible for the gastrointestinal activity of M. officinalis. AIM OF THE STUDY: The transient receptor potential (TRP) family is highly expressed in the gastrointestinal tract and participates in the regulation of gastrointestinal motility, visceral hypersensitivity, visceral secretion and other physiological activities. In this study, the calcium-lowering mechanisms of MAG and HON contributing to the smooth muscle relaxation associated with TRP are discussed. MATERIALS AND METHODS: The relaxation smooth muscle effects of MAG and HON were tested by the isolated intestine tone tests. A synthetic MAG probe (MAG-P) was used to target fishing for their possible target. The distribution of MAG on the smooth muscle was identified by a molecular tracer based on chemical biology. Ca2+ imaging and dual-luciferase reporter assays were used to determine the effects on the target proteins. Finally, the calcium-mediating effects of MAG and HON on smooth muscle cells and TRPC4-knockdown cells were compared to verify the potential mechanism. RESULTS: After confirming the smooth muscle relaxation in the small intestine induced by MAG and HON, the relaxation effect was identified mainly due to the downregulation of intracellular calcium by controlling external calcium influx. Although MAG and HON inhibited both TRPV4 and TRPC4 channels to reduce calcium levels, the inhibitory effect on TRPC4 channels is an important mechanism of their smooth muscle relaxation effect, since TRPC4 is widely expressed in the small intestinal smooth muscle cells. CONCLUSIONS: The inhibition of MAG and HON on TRPC4 channels contributes to the relaxation of intestinal smooth muscle.

Effect of Shixiao San on inflammatory factors and pain in rats with endometriosis.

ETHNOPHARMACOLOGICAL RELEVANCE: In the practice of traditional Chinese medicine, endometriosis is believed to be caused by blood stasis and is characterised by dysmenorrhea, which is difficult to control. Shixiao San (SXS) has a long history of use in the treatment of gynaecological diseases. The prescriptions composed of SXS include Typhae Pollen and Faeces Trogopterori, both of which have anti-inflammatory activity. In addition, Typhae Pollen can be used to treat many kinds of blood stasis diseases. AIM OF THE STUDY: The purpose of the present study was to investigate the effect of SXS on pain relief in rats with endometriosis and to preliminarily explore its mechanism of action in alleviating pain. MATERIAL AND METHODS: Ten rats received sham operation as the Sham group, and 30 endometriosis model rats were randomly divided into three groups: the Model, Shixiao San-Low (SXS-L), and Shixiao San-High (SXS-H) groups. The rats were administered the appropriate treatment via intragastric gavage for 4 weeks. The thermal radiation pain and mechanical pain thresholds of the rats were measured every 7 days after treatment. Finally, the distribution density of nerve fibres in endometrial tissue, the inflammatory infiltration of the dorsal root ganglion (DRG), the expression of TRPV1 in the DRG, and the expression of IL-1ß, TNF-α, and IL-6 in ectopic tissue were measured. RESULTS: After SXS treatment, the growth of ectopic tissue in rats with endometriosis was significantly suppressed, their thermal radiation pain and mechanical pain thresholds increased, the density of nerve fibres and the expression of inflammatory factors in ectopic tissues reduced, and inflammatory cells infiltration in the DRG of the animals alleviated. Meanwhile, the expression of TRPV1 in the DRG was downregulated in rats with endometriosis. CONCLUSIONS: SXS could possibly inhibit the development of endometriosis and relieve pain in patients with endometriosis by reducing inflammatory responses in ectopic tissue and the DRG.

L-carnitine suppresses transient receptor potential vanilloid type 1 activity and myofibroblast transdifferentiation in human corneal keratocytes.

Corneal stromal wound healing is a well-balanced process promoted by overlapping phases including keratocyte proliferation, inflammatory-related events, and tissue remodeling. L-carnitine as a natural antioxidant has shown potential to reduce stromal fibrosis, yet the underlying pathway is still unknown. Since transient receptor potential vanilloid 1 (TRPV1) is a potential drug target for improving the outcome of inflammatory/fibrogenic wound healing, we investigated if L-carnitine can mediate inhibition of the fibrotic response through suppression of TRPV1 activation in human corneal keratocytes (HCK). We determined TRPV1-induced intracellular calcium transients using fluorescence calcium imaging, channel currents by planar patch-clamping, and cell migration by scratch assay for wound healing. The potential L-carnitine effect on TRPV1-induced myofibroblast transdifferentiation was evaluated by immunocytochemical detection of alpha smooth muscle actin. RT-PCR analysis confirmed TRPV1 mRNA expression in HCK. L-carnitine (1 mmol/l) inhibited either capsaicin (CAP) (10 µmol/l), hypertonic stress (450 mOsmol/l), or thermal increase (>43 °C) induced Ca2+ transients and corresponding increases in TRPV1-induced inward and outward whole-cell currents. This was accompanied by suppression of injury-induced increases in myofibroblast transdifferentiation and cell migration. In conclusion, L-carnitine contributes to inhibit stromal scarring through suppressing an injury-induced intrinsic TRPV1 activity that is linked with induction of myofibroblast transdifferentiation in HCK cells.

Neuroprotective Effect of Nypa fruticans Wurmb by Suppressing TRPV1 Following Sciatic Nerve Crush Injury in a Rat.

Peripheral nerve injury can result in severe functional impairment and decreased quality of life due to loss of sensory and motor function. Nypa fruticans wurmb (NF) has been used in diverse folk remedies in East Asia. We have previously shown that Nypa fruticans wurmb extract has antinociceptive and anti-inflammatory effects by suppressing TRPV1 in the sciatic nerve injury. The present study investigated the effects of NF on the control of TRPV1 in relation to neuroprotective effects of a sciatic nerve crush injury. To evaluate the neuroprotective effects, an animal behavior test and a physiological function test were performed. Functional recovery and nerve recovery were improved in the NF and NF + SB (SB366791; TRPV1 antagonist) treated group. In the histomorphology evaluation, the neuronal regenerative effect of NF on the injured sciatic nerve was confirmed via hematoxylin and eosin (H&E) staining. In this study, the NF and NF + SB treated group showed neuroprotective and functional recovery effects from the sciatic nerve crush injury. Furthermore, the expression of NF-κB and iNOS showed a significantly suppressive effect on NF (p < 0.01), SB (p < 0.01), and NF + SB (p < 0.01) treated group at the 7th and 14th day compared to the vehicle group. This study confirmed the neuroprotective effects of NF on suppressing TRPV1 in a sciatic nerve crush injury. The findings of this study establish the effect of NF as a neurotherapeutic agent to protect the peripheral nerve after a sciatic nerve crush injury.

Desensitization of transient receptor potential vanilloid type-1 (TRPV1) channel as promising therapy of irritable bowel syndrome: characterization of the action of palvanil in the mouse gastrointestinal tract.

TRPV1 are involved in the control of the gastrointestinal (GI) functions and pain sensation. Their activation induces pain but it is followed by desensitization, which in turn causes analgesia. The studies from the last two decades indicate that TRPV1 are involved in visceral hypersensitivity in the GI tract and pathogenesis of irritable bowel syndrome (IBS). Therefore, the aim of this study is to assess the action of fast desensitizing agonist of TRPV1, palvanil (N-palmitoyl-vanillamine), in the murine GI tract and on nociception to evaluate its potential application in the therapy of IBS. The effect of palvanil on smooth muscle contractility was evaluated using organ baths. The impact of palvanil on intestinal secretion was assessed in Ussing chambers. In vivo, the action of palvanil (0.1-1 mg/kg) was assessed in whole GI transit, fecal pellet output, and colonic bead expulsion tests. The antinociceptive potency of palvanil was tested in the mustard oil-induced pain test. Palvanil inhibited colonic contractions (evoked by electrical field stimulation, EFS) and decreased the ion transport in the colon stimulated with forskolin. It did not affect secretion in experiments with veratridine. In vivo, palvanil prolonged whole GI transit at all doses tested. At the lower dose tested, it accelerated colonic motility during first 60 min following injection. By contrast, at the dose of 1 mg/kg, colonic motility was inhibited. Palvanil induced antinociceptive action at all tested doses in mustard oil-induced pain test. TRPV1 fast-desensitizing compounds, i.e., palvanil, may be promising agents in the therapy of IBS since it modulates intestinal motility and reduces visceral pain.

Antinociceptive and Anti-Inflammatory Effects of Nypa fruticans Wurmb by Suppressing TRPV1 in the Sciatic Neuropathies.

Neuropathic pain is generally characterized by sensory abnormalities such as sensory disorders, hyperalgesia, and allodynia. Recent studies have reported that TRPV1 activation is essential for establishing of inflammation in the neuropathy pain models, showing that the expression of this receptor is increased, and contributing to enhanced thermal sensitivity. Nypa fruticans Wurmb (NF), which was used as a folk remedy, is a plant that is gaining attention due to its various effects. In this study, we investigated the antinociceptive and anti-inflammatory effects of NFE (Nypa fruticans Wurmb extracts) by controlling the neurological function of TRPV1. In sciatic crush injury rat models, a significant level of antinociceptive effect was observed in the thermal hyperalgesia test in which NF extracts (NFE 500 mg/kg) were orally administered, daily. Protein quantification of the sciatic nerve and the of the L4-L6 spinal cord showed a decrease of the TRPV1 expression, the inflammatory expression factor, COX2, and proinflammatory factors in the NFE treated groups. Our results indicate that NFE affects antinociceptive and anti-inflammatory by controlling TRPV1 in sciatic neuropathic pain models.

Eugenol Reduces LDL Cholesterol and Hepatic Steatosis in Hypercholesterolemic Rats by Modulating TRPV1 Receptor.

Eugenol, a component of essential oils of medicinal and food plants, has a hypolipidemic effect in experimental animals although its mechanism of action is still unclear. This study aims to explore the mechanism of the hypolipidemic effect of eugenol in rats fed a high cholesterol and fat diet (HCFD). Eugenol significantly reduced total cholesterol (TC), low-density lipoproteins (LDL), atherogenic index (AI) but not high-density lipoproteins (HDL) or triglycerides (TG). Eugenol also decreased steatosis and hepatic inflammation in liver sections, decreased hepatomegaly, and the hepatic marker enzymes alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activity and increased the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activity in hypercholesterolemic rats. Eugenol did not inhibit hepatic 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase but caused down-regulation of transient receptor potential vanilloid (TRPV1) channels in the liver. Docking simulation using fast, rigid exhaustive docking (FRED) software indicated a tail-up/head-down interaction of eugenol with TRPV1 channel. Data indicate that eugenol does not inhibit HMG-CoA reductase but rather induces its action by interaction with TRPV1 channels.

Chronic pain models amplify transient receptor potential vanilloid 1 (TRPV1) receptor responses in adult rat spinal dorsal horn.

Persistent pain is associated with negative affect originating from hypersensitivity and/or allodynia. The spinal cord is a key area for nociception as well as chronic pain processing. Specifically, the dorsal horn neurons in lamina II (substantia gelatinosa: SG) receive nociceptive inputs from primary afferents such as C fibers and/or Aδ fibers. Transient receptor potential vanilloid 1 (TRPV1) is a major receptor to sense heat as well as nociception. TRPV1 are expressed in the periphery and the central axon terminals of C fibers and/or Aδ fibers in the spinal cord. Activating TRPV1 enhances the release of glutamate in the spinal cord from naïve rodents. Here, we studied whether or not chronic pain could alter the response of TRPV1 channels to exogenous, capsaicin through study of synaptic transmission and neural activity in rat SG neurons. Using in vitro whole-cell patch-clamp recording, we found that bath application of capsaicin facilitated both the frequency and amplitude of miniature and spontaneous excitatory postsynaptic currents beyond a nerve injury and a complete Freund's adjuvant injection observed in the naïve group. Strikingly, capsaicin produced larger amplitudes of inward currents in pain models than compared to the naïve group. By contrast, the proportions of neurons that show capsaicin-induced inward currents were similar among naïve and pain groups. Importantly, the capsaicin-induced inward currents were conducted by TRPV1 and required calcium influx that was independent of voltage-gated calcium channels. Our study provides fundamental evidence that chronic inflammation and neuropathic pain models amplify the release of glutamate through the activation of TRPV1 in central axon terminals, and that facilitation of TRPV1 function in rat spinal SG neurons may contribute to enhanced capsaicin-induced inward currents.

Ba-Wei-Die-Huang-Wan (Hachimi-jio-gan) can ameliorate ketamine-induced cystitis by modulating neuroreceptors, inflammatory mediators, and fibrogenesis in a rat model.

AIM: We investigated the effects of Ba-Wei-Die-Huang-Wan (BWDHW) on ketamine-induced cystitis (KIC) in a rat model. METHODS: Female Sprague-Dawley rats were distributed into three groups: control (saline), ketamine (25 mg/kg/day for 28 days), or ketamine (25 mg/kg/day for 28 days) plus BWDHW (90 mg/kg/day, started from day 14). Functional magnetic resonance imaging (fMRI), metabolic cage study, and cystometry were evaluated. Bladder histology was evaluated. Western blots of the bladder proteins were carried out. RESULTS: Compared with controls, ketamine-treated rats showed stronger fMRI intensity in the periaqueductal gray area and bladder overactivity in the bladder functional study, but the ketamine/BWDHW-treated rats did not. Furthermore, ketamine breached the uroplakin III membrane at the apical surface of the urothelium, enhanced substance P spread over the urothelium, induced suburothelial hemorrhage and monocyte/macrophage infiltration, and caused interstitial fibrosis deposition. By contrast, the BWDHW-treated rats exhibited less substance P spread, lower suburothelial monocyte/macrophage infiltration, and lower interstitial fibrosis deposition. The ketamine group showed significant overexpression of neuroreceptors in the bladder mucosa (the transient receptor potential vanilloid 1 and M2 - and M3 -muscarinic receptors) and detrusor (M2 - and M3 -muscarinic receptors); inflammatory mediators in the detrusor (interleukin-1ß [IL-1ß], IL-6, tumor necrosis factor-α, nuclear factor-κB, cyclooxygenase-2, and intercellular adhesion molecule-1); and fibrogenesis molecules in the detrusor (transforming growth factor-ß1, collagen I, collagen III, and fibronectin). However, no significant changes were noted between the ketamine/BWDHW and control groups. CONCLUSION: BWDHW could exert therapeutic effects by inhibiting the upregulation of neuroreceptors, modulating inflammatory mediators, suppressing fibrogenesis, and ameliorating bladder overactivity in rats with KIC.

[Effects of estrogen and remifemin on neuronal nitric oxide synthase and transient receptor potential vanilloid 1 in submandibular gland of ovariectomized rats].

Objective: To investigate the effects of estrogen and remifemin on the expression of neuronal nitric oxide synthase (nNOS), transient receptor potential vanilloid 1 (TRPV1), muscarinic acetylcholine receptor, member 1 and 3 (M1 and M3 receptor) and acetylcholinesterase (AChE) in the submandibular gland of rats. Methods: Forty SD female adult rats were divided into SHAM group (sham operation), OVX group (ovarian removal), OVX+E group (ovarian removal + estrogen treatment) and OVX+ICR group (ovarian removal + remifemin treatment), 10 per group. The rats were recovered for 2 weeks after operation. The SHAM group and the OVX group were treated with distilled water, the OVX+E group and the OVX+ICR group were treated with ß-estradiol and remifemin respectively. After 4 weeks, the location and expression of nNOS, TRPV1, M1 and M3 receptors in the submandibular gland were evaluated by immunohistochemistry. The changes of AChE expression in rat submandibular gland were observed by AChE staining. Results: Compared with SHAM group (0.23±0.02, 0.28±0.01, 0.25±0.03, 0.19±0.03), the expression of nNOS, TRPV1, M1 and M3 receptors in OVX group (0.16±0.01, 0.21±0.01, 0.15±0.02, 0.09±0.02) were significantly lower (P<0.05); there were no significant difference between OVX+E group (0.23±0.01, 0.28±0.02, 0.23±0.03, 0.19±0.01) and SHAM group (P>0.05). But compared with OVX group, the expression of nNOS, TRPV1 and M3 receptors in OVX+ICR group were no significantly changed (P>0.05), and only M1 receptor expression (0.22±0.03) was significantly increased (P<0.05). The expression of AChE in OVX group (0.14±0.01) was significantly higher than that in SHAM group (0.10±0.01) (P<0.05). The expression of AChE in OVX+E group (0.15±0.01) was significantly higher than that in SHAM group (P<0.05). The expression of AChE in OVX+ICR group (0.09±0.01) was not significantly different from that in SHAM group (P>0.05). Conclusions: Estrogen can significantly increase the expression of nNOS and TRPV1 in the submandibular gland of rats, suggesting that estrogen may regulate the salivary secretion function of the submandibular gland through nNOS and TRPV1. The mechanism of remifemin is different from that of estrogen, and remifemin does not play a regulatory role by nNOS and TRPV1.

Involvement of Substance P in the Analgesic Effect of Low-Level Laser Therapy in a Mouse Model of Chronic Widespread Muscle Pain.

BACKGROUND: Low-level laser therapy (LLLT) is widely used in pain control in the field of physical medicine and rehabilitation and is effective for fibromyalgia pain. However, its analgesic mechanism remains unknown. A possible mechanism for the effect of LLLT on fibromyalgia pain is via the antinociceptive signaling of substance P in muscle nociceptors, although the neuropeptide has been known as a neurotransmitter to facilitate pain signals in the spinal cord. OBJECTIVE: To establish an animal model of LLLT in chronic muscle pain and to determine the role of substance P in LLLT analgesia. METHODS: We employed the acid-induced chronic muscle pain model, a fibromyalgia model proposed and developed by Sluka et al., and determined the optimal LLLT dosage. RESULTS: LLLT with 685 nm at 8 J/cm2 was effective to reduce mechanical hyperalgesia in the chronic muscle pain model. The analgesic effect was abolished by pretreatment of NK1 receptor antagonist RP-67580. Likewise, LLLT showed no analgesic effect on Tac1-/- mice, in which the gene encoding substance P was deleted. Besides, pretreatment with the TRPV1 receptor antagonist capsazepine, but not the ASIC3 antagonist APETx2, blocked the LLLT analgesic effect. CONCLUSIONS: LLLT analgesia is mediated by the antinociceptive signaling of intramuscular substance P and is associated with TRPV1 activation in a mouse model of fibromyalgia or chronic muscle pain. The study results could provide new insight regarding the effect of LLLT in other types of chronic pain.

The role of transient receptor potential vanilloid receptor 1 and peroxisome proliferator-activated receptors-α in mediating the antinociceptive effects of palmitoylethanolamine in rats.

Palmitoylethanolamine (PEA) is a ligand at peroxisome proliferator-activated receptors-α (PPARα), a nuclear receptor that has anti-inflammatory effects. Herein, complete Freund's adjuvant (CFA)-induced inflammatory pain model in rats and in-vitro calcium imaging studies were used to evaluate the mechanisms that underlie the antinociceptive effects of PEA, including modulating the activity of the transient receptor potential vanilloid receptor 1, which is a key receptor involved in the development of inflammatory pain. Adult male Sprague-Dawley rats (180-250 g) received subcutaneous injections of CFA (0.1 ml) into the plantar surface of the left hind paw. Von Frey filaments were used to determine the paw withdrawal threshold. PEA (50 µg), WY14643 (50 µg, a selective PPARα agonist) were injected into the plantar surface of the left hind paw at day 7 after CFA injection, and behavioral tests were repeated 6 h after drug administration. Rats were killed and dorsal root ganglia neurons were dissected and prepared for calcium imaging. Neurons were loaded with the calcium-sensitive ratiometric dye Fura-2AM. Changes in [Ca]i were measured as ratios of peak florescence at excitation wavelengths of 340 and 380 nm and expressed as a percentage of the KCl (60 mM) response. Both PEA and WY14643 significantly restored the paw withdrawal threshold in a PPARα-dependent fashion (P<0.01). Capsaicin of 15 nM produced 63.9±13.4% of KCl response. Preincubation of dorsal root ganglia neurons with PEA 6 h before stimulation with capsaicin, significantly reduce capsaicin-evoked calcium responses (42.9±6.4% of KCl response, n=54, P<0.001). In conclusion, modulating transient receptor potential vanilloid receptor 1 activity could provide the mechanism that underlies PEA antinociceptive effects observed in vivo.

KChIP3 N-Terminal 31-50 Fragment Mediates Its Association with TRPV1 and Alleviates Inflammatory Hyperalgesia in Rats.

Potassium voltage-gated channel interacting protein 3 (KChIP3), also termed downstream regulatory element antagonist modulator (DREAM) and calsenilin, is a multifunctional protein belonging to the neuronal calcium sensor (NCS) family. Recent studies revealed the expression of KChIP3 in dorsal root ganglion (DRG) neurons, suggesting the potential role of KChIP3 in peripheral sensory processing. Herein, we show that KChIP3 colocalizes with transient receptor potential ion channel V1 (TRPV1), a critical molecule involved in peripheral sensitization during inflammatory pain. Furthermore, the N-terminal 31-50 fragment of KChIP3 is capable of binding both the intracellular N and C termini of TRPV1, which substantially decreases the surface localization of TRPV1 and the subsequent Ca2+ influx through the channel. Importantly, intrathecal administration of the transmembrane peptide transactivator of transcription (TAT)-31-50 remarkably reduces Ca2+ influx via TRPV1 in DRG neurons and alleviates thermal hyperalgesia and gait alterations in a complete Freund's adjuvant-induced inflammatory pain model in male rats. Moreover, intraplantar injection of TAT-31-50 attenuated the capsaicin-evoked spontaneous pain behavior and thermal hyperalgesia, which further strengthened the regulatory role of TAT-31-50 on TRPV1 channel. In addition, TAT-31-50 could also alleviate inflammatory thermal hyperalgesia in kcnip3-/- rats generated in our study, suggesting that the analgesic effect mediated by TAT-31-50 is independent of endogenous KChIP3. Our study reveals a novel peripheral mechanism for the analgesic function of KChIP3 and provides a potential analgesic agent, TAT-31-50, for the treatment of inflammatory pain.SIGNIFICANCE STATEMENT Inflammatory pain arising from inflamed or injured tissues significantly compromises the quality of life in patients. This study aims to elucidate the role of peripheral potassium channel interacting protein 3 (KChIP3) in inflammatory pain. Direct interaction of the KChIP3 N-terminal 31-50 fragment with transient receptor potential ion channel V1 (TRPV1) was demonstrated. The KChIP3-TRPV1 interaction reduces the surface localization of TRPV1 and thus alleviates heat hyperalgesia and gait alterations induced by peripheral inflammation. Furthermore, the transmembrane transactivator of transcription (TAT)-31-50 peptide showed analgesic effects on inflammatory hyperalgesia independently of endogenous KChIP3. This work reveals a novel mechanism of peripheral KChIP3 in inflammatory hyperalgesia that is distinct from its classical role as a transcriptional repressor in pain modulation.

Effects of curcumin and curcumin analogues on TRP channels.

A series of 33 curcumin analogues was synthesized and tested on TRPA1, TRPM8, and TRPV1 channels. Twenty of them acted as good modulators of TRPA1 channels. None was able to significantly activate TRPM8 channels, while curcumin itself and six curcuminoids belonging to the 1,3-dicarbonyl and acyclic series behaved as 'true' antagonists with IC50 values<5µM. Only few curcuminoids were able to modulate TRPV1 channels with EC50 and IC50 values ranging from 3.4 and 6.0µM.

[Approaching new pharmacotherapy options in pain treatment]. / A gyógyszeres fájdalomcsillapítás közelgõ új lehetõségei.

The evolution of medicine is noticeable in most therapeutic areas, the worse the current therapeutic result, the more quick the improvement. This is especially true in such areas that require substantial social resources, namely oncology, diabetology and CNS diseases. Pain is not a disease, it is a symptom. Pain is one of the most important components of human suffering thus it deserves special attention. In recent years new formulations of old medicines were introduced rather than new medicines. Maybe ziconitide is the last pain killer with new mechanism of action which was approved by FDA in 2004. However, the new information and techniques are also appearing in the field of analgesia. Nowadays one can talk about genetic/epigenetic targets, RNA therapies, voltage-gated calcium channels, new pain receptors (TRPV1, TRPV4, NMDA, Nav receptors) regarding pain treatment, indicating that the practice of the pharmacotherapy of pain will change fundamentally in the immediate future. This paper is intended to give a short summary of these new options.

Analgesic effect of coumarins from Radix angelicae pubescentis is mediated by inflammatory factors and TRPV1 in a spared nerve injury model of neuropathic pain.

ETHNOPHARMACOLOGICAL RELEVANCE: Coumarins from Radix angelicae pubescentis (CRAP) are a major active component that are isolated from dried roots of Angelica biserrata Yuan et Shan, which has been used clinically to cure headaches for a long period of time, and it is an effective treatment for pain. The aim of the present study was to investigate the analgesic effect of CRAP on a spared nerve injury (SNI) model of neuropathy. MATERIALS AND METHODS: Antinociceptive effects of CRAP were assessed in Sprague-Dawley male rats using a spared nerve injury model of neuropathic pain. Inflammatory factors were determined by Enzyme-linked immunosorbent assay (ELISA). Transient receptor potential cation channel 1 (TRPV1) and Phosphorylated extracellular regulated protein kinases (pERK) were detected by Immunofluorescence and Western blotting, respectively. RESULTS: The high performance liquid chromatography (HPLC) analysis showed the presence of osthole and columbianadin in Radix angelicae pubescentis. CRAP induced the dose-dependent effect of on attenuating the development of mechanical hypersensitivity. Molecular profiling revealed that CRAP reduced the levels of pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and interleukin-6 (IL-6) and significantly attenuated the expression of TRPV1 and pERK in damaged DRG neurons. CONCLUSION: This results demonstrate that CRAP possess remarkable antinociceptive activities which may be due to osthole and columbianadin at least in part, supporting the folkloric usage of the plant to treat various pain diseases.

Partial Activation and Inhibition of TRPV1 Channels by Evodiamine and Rutaecarpine, Two Major Components of the Fruits of Evodia rutaecarpa.

Evodiamine (1) and rutaecarpine (2) are the two major components of Evodia rutaecarpa, which has long been used in traditional medicine for the treatment of many diseases. Using transient receptor potential vanilloid 1 (TRPV1)-expressing HEK293 cells and patch-clamp recording, the inhibitory actions of 1 and 2 against TRPV1 channels were investigated. The effects of these compounds against capsaicin- or proton-activated TRPV1 activities were evaluated. The results showed that, although 1 and 2 can activate TRPV1, the maximum response was 3.5- or 9-fold lower than that of capsaicin, respectively, suggesting partial agonism. In comparison to capsaicin, coadministration of 1 and capsaicin increased the half-maximal effective concentration (EC50) of capsaicin-activated TRPV1 currents as shown by a right shift in the dose-response curve, whereas coadministration of 1 with protons failed to inhibit the proton-induced current. Moreover, preadministration of 1, but not 2, inhibited both capsaicin- and proton-induced TRPV1 currents, which might involve channel desensitization. Taken together, 1 and 2 may share the same binding site with capsaicin and act as partial agonists (antagonists) of TRPV1. Evodiamine (1), but not rutaecarpine (2), can desensitize or competitively inhibit the activity of TRPV1.

Hyaluronan modulates TRPV1 channel opening, reducing peripheral nociceptor activity and pain.

Hyaluronan (HA) is present in the extracellular matrix of all body tissues, including synovial fluid in joints, in which it behaves as a filter that buffers transmission of mechanical forces to nociceptor nerve endings thereby reducing pain. Using recombinant systems, mouse-cultured dorsal root ganglia (DRG) neurons and in vivo experiments, we found that HA also modulates polymodal transient receptor potential vanilloid subtype 1 (TRPV1) channels. HA diminishes heat, pH and capsaicin (CAP) responses, thus reducing the opening probability of the channel by stabilizing its closed state. Accordingly, in DRG neurons, HA decreases TRPV1-mediated impulse firing and channel sensitization by bradykinin. Moreover, subcutaneous HA injection in mice reduces heat and capsaicin nocifensive responses, whereas the intra-articular injection of HA in rats decreases capsaicin joint nociceptor fibres discharge. Collectively, these results indicate that extracellular HA reduces the excitability of the ubiquitous TRPV1 channel, thereby lowering impulse activity in the peripheral nociceptor endings underlying pain.

N-acetyl cysteine reduces oxidative toxicity, apoptosis, and calcium entry through TRPV1 channels in the neutrophils of patients with polycystic ovary syndrome.

Polycystic ovary syndrome (PCOS) is a common inflammatory and oxidant disease with an uncertain pathogenesis. N-acetyl cysteine (NAC) decreases oxidative stress, intracellular free calcium ion [Ca(2+)]i, and apoptosis levels in human neutrophil. We aimed to investigate the effects of NAC on apoptosis, oxidative stress, and Ca(2+) entry through transient receptor potential vanilloid 1 (TRPV1) and TRP melastatin 2 (TRPM2) channels in neutrophils from patients with PCOS. Neutrophils isolated from PCOS group were investigated in three settings: (1) after incubation with TRPV1 channel blocker capsazepine or TRPM2 channel blocker 2-aminoethyl diphenylborinate (2-APB), (2) after supplementation with NAC (for 6 weeks), and (3) with combination (capsazepine + 2-APB + NAC) exposure. The neutrophils in TRPM2 and TRPV1 experiments were stimulated by N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMLP; 1 µM) and capsaicin (10 µM) as concentration agonists, respectively. Neutrophil lipid peroxidation and capsaicin-induced increase in [Ca(2+)]i concentrations were reduced by capsazepine and NAC treatments. However, the [Ca(2+)]i concentration did not change by fMLP stimulation. Neutrophil lipid peroxidation, apoptosis, caspase-3, caspase-9, cytosolic reactive oxygen species production, and mitochondrial membrane depolarization values were decreased by NAC treatment although neutrophil glutathione peroxidase and reduced glutathione levels were increased by the NAC treatment. Serum lipid peroxidation, luteinizing hormone, testosterone, insulin, interleukin-1 beta, and homocysteine levels were decreased by NAC treatment although serum vitamin A, beta-carotene, vitamin E, and total antioxidant status were increased by the NAC treatment. In conclusion, NAC reduced oxidative stress, apoptosis, cytokine levels, and Ca(2+) entry through TRPV1 channel, which provide supportive evidence that oxidative stress and TRPV1 channel plays a key role in etiology of PCOS.