Transient Potential Vanilloid Research Articles

Small caliber arterial endothelial cells calcium signals elicited by PAR2 are preserved from endothelial dysfunction.

Endothelial cell (EC)-dependent vasodilation by proteinase-activated receptor 2 (PAR2) is preserved in small caliber arteries in disease states where vasodilation by muscarinic receptors is decreased. In this study, we identified and characterized the PAR2-mediated intracellular calcium (Ca2+)-release mechanisms in EC from small caliber arteries in healthy and diseased states. Mesenteric arterial EC were isolated from PAR2 wild-type (WT) and null mice, after saline (controls) or angiotensin II (AngII) infusion, for imaging intracellular calcium and characterizing the calcium-release system by immunofluorescence. EC Ca2+ signals comprised two forms of Ca2+-release events that had distinct spatial-temporal properties and occurred near either the plasmalemma (peripheral) or center of EC. In healthy EC, PAR2-dependent increases in the densities and firing rates of both forms of Ca2+-release were abolished by inositol 1,4,5- trisphosphate receptor (IP3R) inhibitor, but partially reduced by transient potential vanilloid channels inhibitor ruthenium red (RR). Acetylcholine (ACh)-induced less overall Ca2+-release than PAR2 activation, but enhanced selectively the incidence of central events. PAR2-dependent Ca2+-activity, inhibitors sensitivities, IP3R, small- and intermediate-conductance Ca2+-activated potassium channels expressions were unchanged in EC from AngII WT. However, the same cells exhibited decreases in ACh-induced Ca2+-release, RR sensitivity, and endothelial nitric oxide synthase expression, indicating AngII-induced dysfunction was differentiated by receptor, Ca2+-release, and downstream targets of EC activation. We conclude that PAR2 and muscarinic receptors selectively elicit two elementary Ca2+ signals in single EC. PAR2-selective IP3R-dependent peripheral Ca2+-release mechanisms are identical between healthy and diseased states. Further study of PAR2-selective Ca2+-release for eliciting pathological and/or normal EC functions is warranted.

β-arrestin-2-biased agonism of delta opioid receptors sensitizes transient receptor potential vanilloid type 1 (TRPV1) in primary sensory neurons.

Despite advances in understanding the signaling mechanisms involved in the development and maintenance of chronic pain, the pharmacologic treatment of chronic pain has seen little advancement. Agonists at the mu opioid receptor (MOPr) continue to be vital in the treatment of many forms of chronic pain, but side-effects limit their clinical utility and range from relatively mild, such as constipation, to major, such as addiction and dependence. Additionally, chronic activation of MOPr results in pain hypersensitivity known as opioid-induced hyperalgesia (OIH), and we have shown recently that recruitment of β-arrestin2 to MOPr, away from transient potential vanilloid eceptor type 1 (TRPV1) in primary sensory neurons contributes to this phenomenon. The delta opioid receptor (DOPr) has become a promising target for the treatment of chronic pain, but little is known about the effects of chronic activation of DOPr on nociceptor sensitivity and OIH. Here we report that chronic activation of DOPr by the DOPr-selective agonist, SNC80, results in the sensitization of TRPV1 and behavioral signs of OIH via β-arrestin2 recruitment to DOPr and away from TRPV1. Conversely, chronic treatment with ARM390, a DOPr-selective agonist that does not recruit β-arrestin2, neither sensitized TRPV1 nor produced OIH. Interestingly, the effect of SNC80 to sensitize TRPV1 is species-dependent, as rats developed OIH but mice did not. Taken together, the reported data identify a novel side-effect of chronic administration of β-arrestin2-biased DOPr agonists and highlight the importance of potential species-specific effects of DOPr agonists.

Different TRPV1‐mediated brain responses to intragastric infusion of capsaicin and capsiate

Capsaicin and capsiate, which is an analogue of capsaicin, are agonists of capsaicin-binding transient potential vanilloid 1 (TRPV1) receptors. However, their physiological effects are different. Capsaicin induces thermogenesis and nociception, while the different kinetics of capsiate result in thermogenesis without nociception in the oral cavity. In the present study, using functional magnetic resonance imaging, we compared the brain activation after intragastric infusion of non-nociceptive levels of capsaicin and capsiate in wild-type and TRPV1-knockout (KO) mice. Capsaicin activated several brain regions, such as the periaqueductal grey (PAG), thalamic nuclei and hypothalamus, including the medial preoptic area (mPOA) and ventromedial hypothalamus (VMH). Most of these areas were not activated in TRPV1-KO mice. Capsiate activated several regions, including the thalamic nuclei, mPOA and VMH but not PAG in wild-type mice. Most of the activated areas were not activated by intragastric capsiate infusion in TRPV1-KO mice. These results demonstrate that TRPV1 is critical for the induction of activation in the hypothalamus by capsaicin and capsiate, and these distinct brain activations could help to explain the individual physiological reactions of capsaicin and capsiate.

Far-infrared radiation acutely increases nitric oxide production by increasing Ca2+ mobilization and Ca2+/calmodulin-dependent protein kinase II-mediated phosphorylation of endothelial nitric oxide synthase at serine 1179

Repeated thermal therapy manifested by far-infrared (FIR) radiation improves vascular function in both patients and mouse model with coronary heart disease, but its underlying mechanism is not fully understood. Using FIR as a thermal therapy agent, we investigate the molecular mechanism of its effect on endothelial nitric oxide synthase (eNOS) activity and NO production. FIR increased the phosphorylation of eNOS at serine 1179 (eNOS-Ser1179) in a time-dependent manner (up to 40min of FIR radiation) in bovine aortic endothelial cells (BAEC) without alterations in eNOS expression. This increase was accompanied by increases in NO production and intracellular Ca2+ levels. Treatment with KN-93, a selective inhibitor of Ca2+/calmodulin-dependent protein kinase II (CaMKII) and H-89, a protein kinase A inhibitor, inhibited FIR radiation-stimulated eNOS-Ser1179 phosphorylation. FIR radiation itself also increased the temperature of culture medium. As transient receptors potential vanilloid (TRPV) ion channels are known to be temperature-sensitive calcium channels, we explore whether TRPV channels mediate these observed effects. Reverse transcription-PCR assay revealed two TRPV isoforms in BAEC, TRPV2 and TRPV4. Although ruthenium red, a pan-TRPV inhibitor, completely reversed the observed effect of FIR radiation, a partial attenuation (∼20%) was found in cells treated with Tranilast, TRPV2 inhibitor. However, ectopic expression of siRNA of TRPV2 showed no significant alteration in FIR radiation-stimulated eNOS-Ser1179 phosphorylation. This study suggests that FIR radiation increases NO production via increasing CaMKII-mediated eNOS-Ser1179 phosphorylation but TRPV channels may not be involved in this pathway. Our results may provide the molecular mechanism by which FIR radiation improves endothelial function.

Role of TRPV1 receptors on panic-like behaviors mediated by the dorsolateral periaqueductal gray in rats

The transient receptors potential vanilloid type 1 channels (TRPV1) are expressed in several brain regions related to defensive behaviors, including the dorsolateral periaqueductal gray (dlPAG). The endocannabinoid anandamide, in addition to its agonist activity at cannabinoid type 1 (CB1), is also proposed as an endogenous agonist of these receptors, through which it could facilitate anxiety-like responses. The aim of this work was to test the hypothesis that TRPV1 in the dlPAG of rats would mediate panic-like responses in two models, namely the escape responses induced by chemical stimulation of this structure or by exposure to the elevated T-Maze (ETM). Antagonism of TRPV1 with capsazepine injected into the dlPAG reduced the defense response induced by local NMDA-injection, suggesting an anti-aversive effect. In the ETM, capsazepine inhibited escape response, suggesting a panicolytic-like effect. Interestingly, this effect was prevented by a CB1 antagonist (AM251). The present study showed that antagonism of TRPV1 in the dlPAG induces panicolytic-like effects, which can be prevented by a CB1 antagonist. Therefore, these antiaversive effects of TRPV1 blockade may ultimately occur due to a predominant action of anandamide through CB1 receptors.

Colonic inflammation up‐regulates voltage‐gated sodium channels in bladder sensory neurons via activation of peripheral transient potential vanilloid 1 receptors

Primary sensory neurons express several types of ion channels including transient receptor potential vanilloid 1 (TRPV1) and voltage-gated Na(+) channels. Our previous studies showed an increased excitability of bladder primary sensory and spinal neurons triggered by inflammation in the distal colon as a result of pelvic organ cross-sensitization. The goal of this work was to determine the effects of TRPV1 receptor activation by potent agonists and/or colonic inflammation on voltage-gated Na(+) channels expressed in bladder sensory neurons. Sprague-Dawley rats were treated with intracolonic saline (control), resiniferatoxin (RTX, 10(-7 ) mol L(-1)), TNBS (colonic irritant) or double treatment (RTX followed by TNBS). TNBS-induced colitis increased the amplitude of total Na(+) current by two-fold and of tetrodotoxin resistant (TTX-R) Na(+) current by 78% (P ≤ 0.05 to control) in lumbosacral bladder neurons during acute phase (3 days post-TNBS). Instillation of RTX in the distal colon caused an enhancement in the amplitude of total Na(+) current at -20 mV from -112.1 ± 18.7 pA/pF (control) to -183.6 ± 27.8 pA/pF (3 days post-RTX, P ≤ 0.05) without changes in TTX resistant component. The amplitude of net Na(+) current was also increased by 119% at day 3 in the group with double treatment (RTX followed by TNBS, P ≤ 0.05 to control) which was significantly higher than in either group with a single treatment. These results provide evidence that colonic inflammation activates TRPV1 receptors at the peripheral sensory terminals leading to an up-regulation of voltage gated Na(+) channels on the cell soma of bladder sensory neurons. This mechanism may underlie the occurrence of peripheral cross-sensitization in the pelvis and functional chronic pelvic pain.

Vasorelaxation to capsaicin and its effects on calcium influx in arteries

Capsaicin, an activator of the transient potential vanilloid receptor type 1 (TRPV1), is a commonly used pharmacological tool for desensitising sensory nerves. Capsaicin can induce vasorelaxation of isolated blood vessels by activating perivascular TRPV1 receptors, causing the release of vasoactive neuropeptides. This study attempted to characterise the vascular effects of capsaicin in the rat isolated aorta and porcine coronary arteries. Capsaicin elicited concentration-dependent vasorelaxation of both rat aortae and porcine coronary arteries. Capsaicin-induced vasorelaxation of rat aorta was unaffected by a chronic pre-treatment of vessels with capsaicin. Moreover, relaxation was insensitive to the presence of capsazepine, a competitive TRPV1 antagonist, in both the rat aorta and porcine coronary artery. It was hypothesised that capsaicin may be inhibiting calcium influx into smooth muscle cells. Indeed, in vessels incubated in a Ca2+-free high-k+ buffer, the presence of 30μM capsaicin significantly inhibited the contractile response to the re-introduction of Ca2+. In porcine coronary arteries 100μM capsaicin completely abolished the contractile response to the re-introduction of Ca2+. In addition, capsaicin also abolished the concentration-dependent contraction of porcine coronary arteries induced by the L-type calcium activator Bay-K 8644. Therefore, we suggest that capsaicin causes vascular responses in arteries through the inhibition of L-type Ca2+ channels. In summary, we have identified a potential mechanism underlying TRPV1-independent capsaicin-induced vasorelaxation. Our results also question the use of chronic capsaicin pre-treatment in experimental pharmacology in order to elucidate the role of sensory nerves in vascular responses.

反向药理学和基于传统药物的现代镇痛药的研发

疼痛是许多急慢性疾患中皆可出现的症状，它是危及人类健康及防碍正常生活的主要问题之一。为了抗御疼痛，人类一直在孜孜不倦地寻求镇痛药物。目前临床上使用最多的镇痛药是以吗啡为代表的阿片生物碱类及其合成代用品(或称阿片类药物——opioids)和非甾体抗炎药(Nonsteroidal Antiinflammatory Drugs，NSAIDs)，它们都有较为严重的毒、副作用。一些致痛因子和炎性介质，如5-HT，ATP，BK，His，PGE2，SP等，其相应的受体阻断剂的应用对于镇痛虽有一定效应，但由于此等受体分布广泛，故选择性作用部位不强而且副作用也较多。因此关注的焦点主要集中在探索表达于中、小直径的初级感觉神经元的河豚毒素不敏感型(tetrodotoxin-resistant，TTX-R)钠通道和瞬时感受器电位香草酸受体1(transient potential vanilloid receptor1，TRPV1)。遗憾的是多年来在这方面并无突破性进展。以植物为本的各民族传统药物是当今国际药品市场的潜在丰富来源。遵循“反向药理学”的研究模式，形成先导物发现可践行的方法学，结合先进的科学技术和方法，从长期临床应用证实具有较显著镇痛功效和较少毒、副作用的传统药物中提取、分离多种单体化学成分，对其进行系统的药理研究，开发出化学结构和镇痛机理明确、安全性高的新型镇痛药物，将是镇痛药研发中具有较高效率的新途径。在我们的研究中，发现了两种对TTX-R钠通道和TRPV1均具有调制作用的民族药物——龙血竭和野木瓜。这两种药物在临床上都有较好的镇痛疗效，并且无成瘾性方面的记录。我们还确定了龙血竭调制TTX-R钠通道和TRPV1的药效物质基础是其化学成分剑叶龙血素A、剑叶龙血素B和龙血素B的组合。 Pain is a major symptom in many medical conditions, and can significantly interfere with a person’s quality of life and general function. To relieve pain, people are unwearied to look for the analgesic drugs. Nowadays, the most popular analgesics in clinic practice are opioids and non-steroidal anti-inflammatory drugs (NSAIDs), both of which have some adverse reactions. Although the antagonists of some painful factor such as 5-HT, ATP, BK, His, PGE2 and SP receptors can relieve pain to some extent, they have some unpleasant side-effects and low selectivity for analgesic sites due to the wide distribution of them. Therefore, the focus of the research was concentrated on tetrodotoxin-resis- tant (TTX-R) sodium channel and transient potential vanilloid receptor 1(TRPV1) distributed in small-to-medium-sized primary sensory neurons. However, little breakthrough has been made for the past many years. The plentiful plant-derived national traditional medicine are potential resource of international pharmaceutical market nowadays. Based on the research framework of reverse pharmacology, combined with advanced science technique and methods, shaping into feasible methodology of discovering lead compounds, a new approach of developing analgesics is to ex- tract and separate various monomers from traditional medicine which have been confirmed significant efficacy and low side effect in clinic practice for a long period. The monomers will then be investigated systematically and developed into new analgesics with identified chemicial construction, clear-cut mechanism and high security. Our study discovered that two ethnodrugs, Dragon’s Blood Resin and Stauntonia chinensis DC., could interfere with pain messages and modulate TTX-R sodium and TPVR1 channels. They could produce excellent analgesic therapy in clinic without drug addiction. Moreover, the material basis for the modulation on TTX-R sodium channel and TPVR1 of Dragon’s Blood Resin was successfully validated to be the effective combination of cochinchinenin A, cochinchinenin B and loureirin B.

Endocannabinoids Modulate Human Epidermal Keratinocyte Proliferation and Survival via the Sequential Engagement of Cannabinoid Receptor-1 and Transient Receptor Potential Vanilloid-1

We have recently shown that lipid mediators of the emerging endocannabinoid system (ECS) are key players of growth control of the human pilosebaceous unit. In this study, we asked whether the prototypic endocannabinoid anandamide (N-arachidonoylethanolamine, AEA) has a role in growth and survival of epidermal keratinocytes (KCs). Using human cultured KCs and skin organ-culture models, and by employing combined pharmacological and molecular approaches, we provide early evidence that AEA markedly suppresses KC proliferation and induces cell death, both in vitro and in situ. Moreover, we present that these cellular actions are mediated by a most probably constitutively active signaling mechanism that involves the activation of the metabotropic cannabinoid receptor CB(1) and a sequential engagement of the "ionotropic cannabinoid receptor" transient receptor potential vanilloid-1 (TRPV1). Finally, we demonstrate that the cellular effects of AEA are most probably due to a Ca(2+) influx via the non-selective, highly Ca(2+)-permeable ion channel TRPV1, and the concomitant elevation of intracellular Ca(2+) concentration. The data reported here may encourage one to explore whether the targeted manipulation of the above signaling pathway of the cutaneous ECS could become a useful adjunct treatment strategy for hyperproliferative human dermatoses such as psoriasis or KC-derived skin tumors.

Mechanisms underlying the protective effect of eugenol in rats with acute doxorubicin cardiotoxicity

The protective effect of eugenol and its possible mechanisms were investigated in rats with acute doxorubicin cardiotoxicity. Cardiac toxicity was induced by a single intraperitoneal injection of doxorubicin (20 mg/kg). Eugenol treatment (5 mg/kg/day, orally) was started 2 days before doxorubicin administration and continued for five consecutive days. Eugenol significantly reduced the elevated serum creatine kinase and lactate dehydrogenase levels, and restored the electrocardiographic disturbances resulted from doxorubicin administration. Also, eugenol reversed doxorubicin-induced deficits in the antioxidant defense mechanisms, decreased lipid peroxidation and attenuated the elevations in cytosolic Ca(2+) and nitric oxide levels in cardiac tissue. In addition, doxorubicin-induced cardiac tissue damage observed by histopathological examination was markedly ameliorated with eugenol. Immunohistochemical analysis revealed that eugenol prevented the doxorubicin-induced activation of caspase-3 in cardiomyocytes. The cardioprotective effect afforded by eugenol was not significantly inhibited by prior administration of capsazepine, the transient potential vanilloid receptor-1 antagonist. It was concluded that eugenol, through its antioxidant activity and its ability to reduce cardiac Ca(2+) accumulation and nitric oxide levels, is a potential candidate to protect against acute doxorubicin cardiotoxicity, a major and dose-limiting clinical problem.

Eriodictyol: A flavonoid antagonist of the TRPV1 receptor with antioxidant activity

The transient potential vanilloid 1 receptor (TRPV1) is a calcium-permeable channel responsible for the transduction and modulation of acute and chronic pain signaling. As such, this receptor is a potential target for the treatment of a number of pain disorders. However, AMG517, a TRPV1 antagonist, presents several clinical limitations that include the induction of severe hyperthermia. The aim of this study was to investigate the possible interaction of the flavonoid eriodictyol with the TRPV1 receptor and to determine its putative antinociceptive and hyperthermic effects. Eriodictyol was able to displace [3H]-resiniferatoxin binding (IC50=47; 21–119nM) and to inhibit calcium influx mediated by capsaicin (IC50=44; 16–125nM), suggesting that eriodictyol acts as a TRPV1 antagonist. Moreover, eriodictyol induced antinociception in the intraplantar capsaicin test, with maximal inhibition of 49±10 and 64±4% for oral (ID50=2.3; 1.1–5.7mg/kg) and intrathecal (ID50=2.2; 1.7–2.9nmol/site) administration, respectively. Eriodictyol did not induce any change in body temperature or locomotor activity. Orally administered eriodictyol (4.5mg/kg) prevented the nociception induced by intrathecal injections of capsaicin, as well as the non-protein thiol loss and 3-nitrotyrosine (3-NT) formation induced by capsaicin in spinal cord. Eriodictyol also reduced the thermal hyperalgesia and mechanical allodynia elicited by complete Freund's adjuvant (CFA) paw injection. In conclusion, eriodictyol acts as an antagonist of the TRPV1 receptor and as an antioxidant; it induces antinociception without some of the side effects and limitations such as hyperthermia that are expected for TRPV1 antagonists.

Intracellular Ca2+ responses and cell volume regulation upon cholinergic and purinergic stimulation in an immortalized salivary cell line

The water channel aquaporin 5 (AQP5) seems to play a key role in salivary fluid secretion and appears to be critical in the cell volume regulation of acinar cells. Recently, the cation channel transient potential vanilloid receptor 4 (TRPV4) was shown to be functionally connected to AQP5 and also to cell volume regulation in salivary glands. We used the Simian virus 40 (SV40) immortalized cell line SMG C10 from the rat submandibular salivary gland to investigate the effect of ATP and the neurotransmitter analogue carbachol on Ca(2+) signalling and cell volume regulation, as well as the involvement of TRPV4 in the responses. We used fura-2-AM imaging, cell volume measurements, and western blotting. Both carbachol and ATP increased the concentration of intracellular Ca(2+), but no volume changes could be measured. Inhibition of TRPV4 with ruthenium red impaired both ATP- and carbachol-stimulated Ca(2+) signals. Peak Ca(2+) signalling during hyposmotic exposure was significantly decreased following inhibition of TRPV4, while the cells' ability to volume regulate appeared to be unaffected. These results show that in the SMG C10 cells, simulation of nervous stimulation did not induce cell swelling, although the cells had intact volume regulatory mechanisms. Furthermore, even though Ca(2+) signals were not needed for this volume regulation, TRPV4 seems to play a role during ATP and carbachol stimulation.

Assessment of the Biological Similarity of Three Capsaicin Analogs (Capsinoids) Found in Non-Pungent Chili Pepper (CH-19 Sweet) Fruits

CH-19 Sweet is a newly found chili pepper breed bearing much less pungent fruits. Because CH-19 Sweet fruits were found to contain three analogs (capsinoids) of capsaicin, a major component of pungency of hot peppers (the analogs are capsiate or CST, dihydrocapsiate or DCT, and nordihydrocapsiate or NDCT), we assessed in this study the bio-potencies of these three capsinoids by comparing them with capsaicin. The three capsinoids bound to transient potential vanilloid 1 (TRPV1) receptors expressed in cultured cells and activated Ca(2+) influx in a concentration-dependent manner with similar magnitudes. In contrast to capsaicin, capsinoids at the same concentration induced virtually no nociceptive responses when applied to the eyes or the oral cavities of mice. Intravenous administration of capsaicin or 20-fold increased doses of each capsinoid to rats induced significant increases in plasma catecholamine levels. Orally administered, each capsinoid enhanced oxygen consumption in mice. Based on the present results, capsaicin and these three capsinoids should have similar bio-potency, though capsinoids do not generate pungency or sensory irritation.

Vasorelaxation Caused by Cannabinoids: Mechanisms in Different Vascular Beds

Cannabinoids (natural, endogenous and synthetic compounds) produce vasorelaxation in resistance and conduit arteries. Several putative mechanisms have been proposed to explain this effect of cannabinoids. The aim of the present review is to discuss the different mechanisms involved in the vasorelaxant effect of endogenous and synthetic cannabinoids in resistance and conduit arteries. Research on the vascular effects of cannabinoids suggests that the magnitude of the vasorelaxation and the mechanisms involved are not identical in all vascular beds with one or two mechanisms predominating. Either extracellular or intracellular mechanisms are involved. With regard to the former, the stimulation of cannabinoid CB1, CB2 or nonCB1/nonCB2 cannabinoid receptors and the stimulation of vanilloid receptors, transient potential vanilloid receptors, on perivascular nerve endings with the subsequent release of the vasodilator neurotransmitter calcitonin gene-related peptide have been described. With regard to the latter, the main mechanisms implicated include nitric oxide release, metabolism to vasoactive arachidonic metabolites or prostanoid analogues, or endothelium derived hyperpolarising factor release. The knowledge of these mechanisms is crucial to identify new therapeutic targets and to understand the consequences in different vascular beds.

Characterization of the vasorelaxant mechanisms of the endocannabinoid anandamide in rat aorta

Studies in isolated preparations of vascular tissue (mainly resistance vessels) provide evidence that anandamide exerts vasorelaxation. The aim of the present work was to further characterize the mechanisms involved in the vascular response induced by anandamide in a conduit vessel, rat aorta. Isometric tension changes in response to a cumulative concentration-response curve of anandamide (1 nM-100 micro M) were recorded in aortic rings from male Wistar rats. The involvement of a number of factors in this relaxation was investigated including endothelium-derived vasorelaxant products, cannabinoid and vanilloid receptors (transient potential vanilloid receptor-1 (TRPV1)), release of calcitonin gene-related peptide (CGRP), anandamide metabolism and the membrane transporter for anandamide. Anandamide caused a significant concentration-dependent vasorelaxation in rat aorta. This vasorelaxation was significantly inhibited by Pertussis toxin, by a non-CB1/non-CB2 cannabinoid receptor antagonist, by endothelial denudation, by inhibition of nitric oxide synthesis or inhibition of prostanoid synthesis via cyclooxygenase-2 (COX-2), by blockade of prostaglandin receptors EP4 and by a fatty acid amino hydrolase inhibitor. Antagonists for CB1, CB2, TRPV1 or CGRP receptors, an inhibitor of the release of endothelium-derived hyperpolarizing factor, and an inhibitor of anandamide transport did not modify the vascular response to anandamide. Our results demonstrate, for the first time, the involvement of the non-CB1/non-CB2 cannabinoid receptor and an anandamide-arachidonic acid-COX-2 derived metabolite (which acts on EP4 receptors) in the endothelial vasorelaxation caused by anandamide in rat aorta.

The transient receptor potential vanilloid 1 (TRPV1) receptor protects against the onset of sepsis after endotoxin

Transient potential vanilloid 1 (TRPV1) receptor is an ion channel receptor primarily localized on sensory nerves and activated by specific stimuli to initiate and amplify pain and inflammation, as typified by murine models of scald and arthritis. Little is known of the role of TRPV1 in sepsis, an infective disease associated with inflammation. Through use of a sublethal murine model of lipopolysaccharide-induced peritoneal sepsis, we provide novel evidence that genetic deletion of TRPV1 leads to an enhanced onset of various pathological components of systemic endotoxemia. Paired studies of TRPV1 knockout (KO) and wild-type mice demonstrate significantly enhanced hypotension (56+/-2% vs. 38+/-6% decrease in blood pressure, n=12), hypothermia (13+/-3% vs. 7+/-1% decrease in core temperature, n=6), and peritoneal exudate mediator levels (TNF-alpha, 0.78+/-0.2 vs. 0.38+/-0.1 ng/ml; nitrite, for NO, 35+/-10 vs. 15+/-3 microM; n=8) in TRPV1 KO mice, indicating loss of protective effect. Findings correlated with liver edema and raised plasma levels of aspartate aminotransferase in TRPV1 KO mice. These data suggest that TRPV1 may play an important regulatory role in sepsis independent of the major sensory neuropeptide substance P. The findings are relevant to developing strategies that increase the beneficial, and reduce the harmful, components of sepsis to prevent and treat this often fatal condition.

A potential role for the vanilloid receptor TRPV1 in the therapeutic effect of curcumin in dinitrobenzene sulphonic acid‐induced colitis in mice

A protective role of the transient potential vanilloid receptor 1 (TRPV1) in intestinal inflammation induced by dinitrobenzene sulphonic acid (DNBS) has been recently demonstrated. Curcumin, the major active component of turmeric, is also able to prevent and ameliorate the severity of the damage in DNBS-induced colitis. We evaluated the possibility that curcumin (45 mg kg(-1) day p.o. for 2 days before and 5 days after the induction of colitis) was able to reduce DNBS-induced colitis in mice, by acting as a TRPV1 agonist. Macroscopic damage score, histological damage score and colonic myeloperoxidase (MPO) activity were significantly lower (by 71%, 65% and 73%, respectively; P < 0.01), in animals treated with curcumin compared with untreated animals. Capsazepine (30 mg kg(-1), i.p.), a TRPV1 receptor antagonist, completely abolished the protective effects of curcumin. To extend these data in vitro, Xenopus oocytes expressing rat TRPV1 were examined. Capsaicin-evoked currents (3.3 micromol L(-1)) disappeared subsequent either to removal of the agonist or subsequent to the addition of capsazepine. However, curcumin (30 micromol L(-1)) was ineffective both as regard direct modification of cell membrane currents and as regard interference with capsaicin-mediated effects. As sensitization of the TRPV1 receptor by mediators of inflammation in damaged tissues has been shown previously, our results suggest that in inflamed, but not in normal tissue, curcumin can interact with the TRPV1 receptor to mediate its protective action in DNBS-induced colitis.

P.4.b.004 Stimulation of the lateral habenula inhibits a panic-like behaviour by activation of serotonin-1A receptors in the rat dorsal periaqueductal gray

The transient receptors potential vanilloid type 1 channels (TRPV1) are expressed in several brain regions related to defensive behaviors, including the dorsolateral periaqueductal gray (dlPAG). The endocannabinoid anandamide, in addition to its agonist activity at cannabinoid type 1 (CB1), is also proposed as an endogenous agonist of these receptors, through which it could facilitate anxiety-like responses. The aim of this work was to test the hypothesis that TRPV1 in the dlPAG of rats would mediate panic-like responses in two models, namely the escape responses induced by chemical stimulation of this structure or by exposure to the elevated T-Maze (ETM). Antagonism of TRPV1 with capsazepine injected into the dlPAG reduced the defense response induced by local NMDA-injection, suggesting an anti-aversive effect. In the ETM, capsazepine inhibited escape response, suggesting a panicolytic-like effect. Interestingly, this effect was prevented by a CB1 antagonist (AM251). The present study showed that antagonism of TRPV1 in the dlPAG induces panicolytic-like effects, which can be prevented by a CB1 antagonist. Therefore, these antiaversive effects of TRPV1 blockade may ultimately occur due to a predominant action of anandamide through CB1 receptors.