Activation Of TRPV1 Receptors Research Articles

Dexamethasone Rapidly Increases GABA Release in the Dorsal Motor Nucleus of the Vagus via Retrograde Messenger-Mediated Enhancement of TRPV1 Activity

Glucocorticoids influence vagal parasympathetic output to the viscera via mechanisms that include modulation of neural circuitry in the dorsal vagal complex, a principal autonomic regulatory center. Glucocorticoids can modulate synaptic neurotransmitter release elsewhere in the brain by inducing release of retrograde signalling molecules. We tested the hypothesis that the glucocorticoid agonist dexamethasone (DEX) modulates GABA release in the rat dorsal motor nucleus of the vagus (DMV). Whole-cell patch-clamp recordings revealed that DEX (1-10 µM) rapidly (i.e. within three minutes) increased the frequency of tetrodotoxin-resistant, miniature IPSCs (mIPSCs) in 67% of DMV neurons recorded in acutely prepared slices. Glutamate-mediated mEPSCs were also enhanced by DEX (10 µM), and blockade of ionotropic glutamate receptors reduced the DEX effect on mIPSC frequency. Antagonists of type I or II corticosteroid receptors blocked the effect of DEX on mIPSCs. The effect was mimicked by application of the membrane-impermeant BSA-conjugated DEX, and intracellular blockade of G protein function with GDP βS in the recorded cell prevented the effect of DEX. The enhancement of GABA release was blocked by the TRPV1 antagonists, 5’-iodoresiniferatoxin or capsazepine, but was not altered by the cannabinoid type 1 receptor antagonist AM251. The DEX effect was prevented by blocking fatty acid amide hydrolysis or by inhibiting anandamide transport, implicating involvement of the endocannabinoid system in the response. These findings indicate that DEX induces an enhancement of GABA release in the DMV, which is mediated by activation of TRPV1 receptors on afferent terminals. The effect is likely induced by anandamide or other ‘endovanilloid’, suggesting activation of a local retrograde signal originating from DMV neurons to enhance synaptic inhibition locally in response to glucocorticoids.

Nerve growth factor enhances cough via a central mechanism of action

The mechanisms involved in enhanced cough induced by central and inhaled NGF in guinea pigs were investigated. Cough and airway function were assessed by plethysmography following inhaled or intracerebroventricular (i.c.v.) NGF treatment. Expression of TrkA and/or TRPV1 was determined in bronchi and/or brainstem by real-time PCR and immunoblotting. I.c.v. and inhaled NGF enhanced citric acid induced-cough and airway obstruction. Pretreatment (i.c.v.) with antagonists of TrkA (K252a) or TRPV1 (IRTX) significantly reduced both the NGF (i.c.v.) enhanced cough and airway obstruction whereas the NK1 antagonist (FK888) inhibited only cough. The H1 antagonist (cetirizine) did not affect either. Inhaled NGF increased phosphorylation of TrkA receptors in the bronchi but not the brainstem at 0.5h post-treatment. TrkA mRNA was elevated at 0.5h in the bronchi and at 24h in the brainstem while TRPV1 mRNA was elevated from 0.5h to 24h in brainstem and at 24h in the bronchi. Pretreatment (i.c.v.) with IRTX, but not K252a, significantly inhibited the inhaled NGF-enhanced cough. Central NGF administration enhances cough and airway obstruction by mechanisms dependent on central activation of TrkA, TRPV1 and NK1 receptors while inhaled NGF enhances cough via a mechanism dependent on central TRPV1 and not TrkA receptors. These data show that NGF, in addition to its effects on the airways, has an important central mechanism of action in the enhancement of cough. Therefore, therapeutic strategies targeting NGF signaling in both the airways and CNS may be more effective in the management of cough.

No relevant modulation of TRPV1-mediated trigeminal pain by intranasal carbon dioxide in healthy humans

BackgroundNasal insufflation of CO2 has been shown to exert antinociceptive respectively antihyperalgesic effects in animal pain models using topical capsaicin with activation of TRPV1-receptor positive nociceptive neurons. Clinical benefit from CO2 inhalation in patients with craniofacial pain caused by a putative activation of TRPV1 receptor positive trigeminal neurons has also been reported. These effects are probably mediated via an activation of TRPV1 receptor - positive neurons in the nasal mucosa with subsequent central inhibitory effects (such as conditioned pain modulation). In this study, we aimed to examine the effects of intranasal CO2 on a human model of craniofacial pain elicited by nasal application of capsaicin.MethodsIn a first experiment, 48 healthy volunteers without previous craniofacial pain received intranasal capsaicin to provoke trigeminal pain elicited by activation of TRVP1 positive nociceptive neurons. Then, CO2 or air was insufflated alternatingly into the nasal cavity at a flow rate of 1 l/min for 60 sec each. In the subsequent experiment, all participants were randomized into 2 groups of 24 each and received either continuous nasal insufflation of CO2 or placebo for 18:40 min after nociceptive stimulation with intranasal capsaicin. In both experiments, pain was rated on a numerical rating scale every 60 sec.ResultsContrary to previous animal studies, the effects of CO2 on experimental trigeminal pain were only marginal. In the first experiment, CO2 reduced pain ratings only minimally by 5.3% compared to air if given alternatingly with significant results for the main factor GROUP (F1,47 = 4.438; p = 0.041) and the interaction term TIME*GROUP (F2.6,121.2 = 3.3; p = 0.029) in the repeated-measures ANOVA. However, these effects were abrogated after continuous insufflation of CO2 or placebo with no significant changes for the main factors or the interaction term.ConclusionsAlthough mild modulatory effects of low-flow intranasal CO2 could be seen in this human model of TRPV-1 mediated activation of nociceptive trigeminal neurons, utility is limited as observed changes in pain ratings are clinically non-significant.

Lack of interaction of co‐existing TRPV1 and CB1 receptors indicates differential control of separate basal and synchronous glutamate release mechanisms in the solitary tract nucleus

Cannabinoid receptor agonists structurally parallel TRPV1 agonists. Both endocannabinoids and endovanilloids resemble membrane derived phospholipids. In spinal dorsal horn, TRPV1 and CB1 co‐localize. Can single compounds crossover to activate both receptors? Can activation of one receptor influence function of the other? Support for both CB1/TRPV1 interactions exists. Here we examined CB1 and TRPV1 receptor activation in synaptic transmission by solitary tract afferents (ST) in horizontal slices of the solitary tract nucleus (NTS). The CB1 selective compound ACEA (10 μM) depressed excitatory postsynaptic current amplitude (ST‐EPSCs) in 78% of ST afferents (TRPV1+, capsaicin sensitive, −38 ± 7% n=14 vs. TRPV1‐ −37 ± 10%, n= 7) but CB1‐ afferents were uncommon. In addition, CB1 activation increased synaptic failures only in TRPV1+. ACEA did not alter spontaneous EPSCs frequency or amplitude. WIN 55,212–2 (10 μM) had identical actions. ACEA actions were blocked by CB1 antagonist AM251 (10 μM). CB1 activation or block failed to alter temperature driven changes in basal or spontaneous EPSCs that depend on TRPV1. The results indicate widespread presynaptic CB1 and suggest that CB1 selectively targets action potential dependent glutamate release likely by inhibiting voltage dependent calcium channels (decreasing release probability) and action currents that depolarize terminals (synaptic failures).

Role of TRPA1 and TRPV1 in the ROS-dependent sensory irritation of superior laryngeal capsaicin-sensitive afferents by cigarette smoke in anesthetized rats

BackgroundLaryngeal exposure to cigarette smoke (CS) evokes sensory irritation, but the mechanisms are largely unclear. The TRPA1 and TRPV1 receptors are two types of Ca2+-permeant channels located at the terminals of airway capsaicin-sensitive afferents. We investigated the mechanisms underlying the airway reflex evoked by laryngeal CS exposure in anesthetized rats. MethodsCS (7 ml) was delivered into a functionally isolated larynx, while the animals (n = 201) breathed spontaneously. Respiratory parameters were measured. All use of pharmacological agents involved pretreatment by laryngeal application. ResultsLaryngeal CS exposure immediately evoked a concentration-dependant apneic response that was unrelated to the nicotine content of the CS. This inhibition of breathing was abolished by bilateral sectioning of the superior laryngeal nerves (SLNs) or by perineural capsaicin treatment of the SLNs (selective blocking of capsaicin-sensitive afferent neural conduction), suggesting the involvement of superior laryngeal capsaicin-sensitive afferents in the reflex. The reflex apnea was significantly attenuated by N-acetyl-l-cysteine (antioxidant), EGTA (extracellular Ca2+ chelator) and BAPTA-AM (intracellular Ca2+ chelator), indicating the importance of reactive oxygen species (ROS) and Ca2+. This reflex apnea was also partially reduced by HC030031 (TRPA1 receptor antagonist) and capsazepine (TRPV1 receptor antagonist), and was nearly abolished by a combination of these two antagonists, suggesting a central role for the TRPA1 and TRPV1 receptors. Furthermore, the reflex apnea was attenuated by indomethacin (cyclooxygenase inhibitor); however, the attenuation by indomethacin was not increased by pretreatment with HC030031 or capsazepine, indicating that TRPA1 and TRPV1 receptor functionality is, at least in part, linked to cyclooxygenase metabolites. ConclusionsThe reflex apnea evoked by laryngeal CS requires activation of both TRPA1 and TRPV1 receptors, which are likely to be located at the terminals of superior laryngeal capsaicin-sensitive afferents. Laryngeal sensory irritation by CS seems to depend on the actions of ROS and cyclooxygenase metabolites on these two types of receptors.

P152 The Impact of a Selective oral TRPV1 Antagonist in Patients with Chronic Cough

BackgroundIncreased expression of TRPV1 receptors in the airways of chronic cough patients and heightened cough responses to inhaled capsaicin are suggestive of a role for TRPV1 receptors in chronic cough....

Colonic mucosal mediators from patients with irritable bowel syndrome excite enteric cholinergic motor neurons

Mediators released in the mucosal milieu have been suggested to be involved in visceral hypersensitivity and abdominal pain in patients with irritable bowel syndrome (IBS). However, their impact on myenteric neurons remains unsettled. Mucosal biopsies were obtained from the descending colon of patients with IBS and controls. Mucosal mast cells were identified immunohistochemically. The impact of spontaneously released mucosal mediators on guinea pig electrically stimulated longitudinal muscle myenteric plexus (LMMP) preparations was assessed in vitro by means of selective receptor antagonists and inhibitors. Patients with IBS showed an increased mast cell count compared with controls. Application of mucosal mediators of IBS to LMMPs potentiated cholinergic twitch contractions, an effect directly correlated with mast cell counts. Enhanced contractions were inhibited by 50.3% with the prostaglandin D2 antagonist BW A868C, by 31.3% and 39% with the TRPV1 antagonists capsazepine and HC-030031, respectively, and by 60.5% with purinergic P2X antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid. Conversely, the serotonin1-4, histamine1-3, tachykinin1-3 receptor blockade, and serine protease inhibition had no significant effect. Colonic mucosal mediators from patients with IBS excite myenteric cholinergic motor neurons. These effects were correlated with mast cell counts and mediated by activation of prostanoid receptors, TRPV1, and P2X receptors. These results support the role of mucosal inflammatory mediators and mast cell activation in altered motor function of IBS.

Inhibition of airway hyper‐responsiveness by TRPV1 antagonists (SB‐705498 and PF‐04065463) in the unanaesthetized, ovalbumin‐sensitized guinea pig

BACKGROUND AND PURPOSE Airway sensory nerves play a key role in respiratory cough, dyspnoea, airway hyper-responsiveness (AHR), all fundamental features of airway diseases [asthma and chronic obstructive pulmonary disease (COPD)]. Vagally mediated airway reflexes such as cough, bronchoconstriction and chest tightness originate from stimulation of airway sensory nerve endings. The transient receptor potential vanilloid 1 receptor (TRPV1) is present on peripheral terminals of airway sensory nerves and modulation of its activity represents a potential target for the pharmacological therapy of AHR in airway disease. EXPERIMENTAL APPROACH As guinea pig models can provide some of the essential features of asthma, including AHR, we have established the model with some classical pharmacological agents and examined the effect of the TRPV1 antagonists, SB-705498 and PF-04065463 on AHR to histamine evoked by ovalbumin (OA) in unanaesthetized sensitized guinea pigs restrained in a double chamber plethysmograph. Specific airway conductance (sGaw) derived from the airflow was calculated as a percentage of change from baseline. KEY RESULTS Cetirizine and salbutamol significantly inhibited OA-evoked bronchoconstriction [sGaw area under the curve (AUC): 70 and 78%, respectively]. Atropine, SB-705498 and PF-04065463 significantly inhibited OA-evoked AHR to histamine in unanaesthetized, OA-sensitized guinea pigs (sGaw AUC: 94%, 57% and 73%, respectively). Furthermore, this effect was not related to antagonism of histamine's activity. CONCLUSION AND IMPLICATIONS These data suggest that TRPV1 receptors located on airway sensory nerves are important in the development of AHR and that modulation of TRPV1-receptor activity represents a potential target for the pharmacological therapy of AHR in airway disease.

Complex regulation of capsaicin on intracellular second messengers by calcium dependent and independent mechanisms in primary sensory neurons

Intracellular second messengers play an important role in capsaicin- and analogous-induced sensitization and desensitization in pain. Fluorescence Ca2+ imaging, enzyme immunoassay and PKC assay kit were used to determine a novel mechanism of different Ca2+ dependency in the signal transduction of capsaicin-induced desensitization. On the average, capsaicin increased cAMP, cGMP concentration and SP release in bell-shaped concentration-dependent manner, with the maximal responses at concentrations around 1μM, suggesting acute desensitization of TRPV1 receptor activation. Capsaicin-induced intracellular Ca2+ concentration ([Ca2+]i) increase depended on extracellular Ca2+ influx as an initial trigger. The Ca2+ influx by capsaicin increased PKC activation and SP release. These increases were completely abolished in Ca2+-free solution, suggesting that the modulation of capsaicin on PKC and SP are Ca2+-dependent. Interestingly, the maximal cAMP increase by TRPV1 activation was not blocked Ca2+ removal, suggesting at least in part a Ca2+-independent pathway is involved. Further study showed that cAMP increase was totally abolished by G-protein and adenylate cyclase (AC) antagonist, suggesting a G-protein-dependent pathway in cAMP increase. However, SP release was blocked by inhibiting PKC, but not G-protein or AC, suggesting a G-protein independent pathway in SP release. These results suggest that both Ca2+-dependent and independent mechanisms are involved in the regulation of capsaicin on second messengers systems, which could be a novel mechanism underlying distinct desensitization of capsaicin and might provide additional opportunities in the development of effective analgesics in pain treatment.

Spinal 12-lipoxygenase-derived hepoxilin A3contributes to inflammatory hyperalgesia via activation of TRPV1 and TRPA1 receptors

Peripheral inflammation initiates changes in spinal nociceptive processing leading to hyperalgesia. Previously, we demonstrated that among 102 lipid species detected by LC-MS/MS analysis in rat spinal cord, the most notable increases that occur after intraplantar carrageenan are metabolites of 12-lipoxygenases (12-LOX), particularly hepoxilins (HXA(3) and HXB(3)). Thus, we examined involvement of spinal LOX enzymes in inflammatory hyperalgesia. In the current work, we found that intrathecal (IT) delivery of the LOX inhibitor nordihydroguaiaretic acid prevented the carrageenan-evoked increase in spinal HXB(3) at doses that attenuated the associated hyperalgesia. Furthermore, IT delivery of inhibitors targeting 12-LOX (CDC, Baicalein), but not 5-LOX (Zileuton) dose-dependently attenuated tactile allodynia. Similarly, IT delivery of 12-LOX metabolites of arachidonic acid 12(S)-HpETE, 12(S)-HETE, HXA(3), or HXB(3) evoked profound, persistent tactile allodynia, but 12(S)-HpETE and HXA(3) produced relatively modest, transient heat hyperalgesia. The pronociceptive effect of HXA(3) correlated with enhanced release of Substance P from primary sensory afferents. Importantly, HXA(3) triggered sustained mobilization of calcium in cells stably overexpressing TRPV1 or TRPA1 receptors and in acutely dissociated rodent sensory neurons. Constitutive deletion or antagonists of TRPV1 (AMG9810) or TRPA1 (HC030031) attenuated this action. Furthermore, pretreatment with antihyperalgesic doses of AMG9810 or HC030031 reduced spinal HXA(3)-evoked allodynia. These data indicate that spinal HXA(3) is increased by peripheral inflammation and promotes initiation of facilitated nociceptive processing through direct activation of TRPV1 and TRPA1 at central terminals.

Enhanced vasorelaxant effects of the endocannabinoid-like mediator, oleamide, in hypertension

Oleamide is an endocannabinoid-like, fatty acid amide with structural similarities to anandamide. The cardiovascular effects of anandamide are enhanced in hypertension and we have now examined how hypertension affects responses to oleamide. Vasorelaxant responses to oleamide were significantly (P<0.001) enhanced in aortic rings from spontaneously hypertensive rats (SHRs), such that the maximal relaxation to oleamide was 40.3±3.5%, compared to 15.7±3.9% in normotensive Wistar Kyoto (WKY) controls. The augmented responses to oleamide in SHR arteries were unaffected by either inhibition of nitric oxide synthase (300μM l-NAME) or fatty acid amide hydrolase (1μM URB597) and independent of cannabinoid CB1 receptors or the endothelium. The enhanced responses to oleamide were opposed by pre-treatment with capsaicin (such that Rmax was reduced to 9.8±1.5%) and this occurred independently of TRPV1 receptor and sensory nerve activity, as the TRPV1 antagonist capsazepine (1–5μM) and the cation channel inhibitor ruthenium red (10μM) had no effect on the responses to oleamide. However, inhibition of cyclooxygenase (10μM indomethacin) enhanced the responses in the WKY aortae, such that the responses were comparable to those in the SHR. The results suggest that the cyclooxygenase pathway has a role in modulating vasorelaxation caused by oleamide in normotensive aortae and that this is lost in hypertension, possibly as an adaptation to the increase in blood pressure.

Differential role of CB1 and TRPV1 receptors on anandamide modulation of defensive responses induced by nitric oxide in the dorsolateral periaqueductal gray

CB1, TRPV1 and NO can regulate glutamate release and modify defensive behaviors in regions related to defensive behavior such as the dorsolateral periaqueductal gray (dlPAG). A possible interaction between the endocannabinoid and nitrergic systems in this area, however, has not been investigated yet. The objective of the present work was to verify if activation of CB1 or TRPV1 receptors could interfere in the flight responses induced in rats by the injection of SIN-1, an NO donor, into the dlPAG. The results showed that local administration of a low dose (5 pmol) of anandamide (AEA) attenuated the flight responses, measured by the total distance moved and maximum speed in an open arena, induced by intra-dlPAG microinjection of SIN-1 (150 nmol). URB597 (0.1 nmol), an inhibitor of anandamide metabolism, produced similar effects. When animals were locally treated with the CB1 receptor antagonist AM251 the effective AEA dose (5 pmol) increased, rather than decreased, the flight reactions induced by SIN1-1. Higher (50–200 nmol) doses of AEA were ineffective and even tended to potentiate the SIN-1 effect. The TRPV1 antagonist capsazepine (CPZ, 30 nmol) prevented SIN-1 effects and attenuated the potentiation of its effect by the higher (200 nmol) AEA dose. The results indicate that AEA can modulate in a dual way the pro-aversive effects of NO in the dlPAG by activating CB1 or TRPV1 receptors.

Acute myocardial ischemia enhances the vanilloid TRPV1 and serotonin 5-HT3 receptor-mediated Bezold-Jarisch reflex in rats

AbstractThe Bezold-Jarisch reflex is characterized by a sudden bradycardia associated with hypotension induced by the activation of the vanilloid TRPV1 and serotonin 5-HT3 receptors. This reflex is associated with several health conditions, including myocardial infarction. The aim of the present study was to elucidate the influence of acute experimental myocardial ischemia on the reflex bradycardia induced by anandamide and phenylbiguanide, agonists of the TRPV1 and 5-HT3 receptors, respectively.In urethane-anesthetized rats, the rapid iv injection of anandamide (0.6µmol/kg) or phenylbiguanide (0.03µmol/kg) decreased heart rate (HR) by about 7–10% of the basal values. Myocardial ischemia (MI) was induced by ligation of the left anterior coronary artery. The agonists were injected 5min before MI (S1) and 10, 20 and 30min thereafter (S2–S4).MI potentiated the anandamide-induced reflex bradycardia by approximately 105% at S2 and 70% at S3 but had no effect at S4. This amplificatory effect of MI was virtually abolished by the TRPV1 receptor antagonist capsazepine (1µmol/kg) and was not modified by the cannabinoid CB1 receptor antagonist rimonabant (0.1µmol/kg). MI also amplified the reflex bradycardia elicited by phenylbiguanide by approximately 110, 60 and 90% (S2, S3 and S4, respectively), and this effect was sensitive to the 5-HT3 receptor antagonist ondansetron (3µmol/kg).In conclusion, our results suggest that acute myocardial ischemia augments the Bezold-Jarisch reflex induced via activation of TRPV1 and 5-HT3 receptors located on sensory vagal nerves in the heart.

Role of TRPV1 in nociception and edema induced by monosodium urate crystals in rats

Gout is characterized by the deposition of monosodium urate (MSU) crystals. Despite being one of the most painful forms of arthritis, gout and the mechanisms responsible for its acute attacks are poorly understood. In the present study, we found that MSU caused dose-related nociception (ED50 [ie, the necessary dose of MSU to elicit 50% of the response relative to the control value]=0.04 [95% confidence interval 0.01–0.11]mg/paw) and edema (ED50=0.08 [95% confidence interval 0.04–0.16]mg/paw) when injected into the hind paw of rats. Treatment with the selective TRPV1 receptor (also known as capsaicin receptor and vanilloid receptor-1) antagonists SB366791 or AMG9810 largely prevented nociceptive and edematogenic responses to MSU. Moreover, the desensitization of capsaicin-sensitive afferent fibers as well as pretreatment with the tachykinin NK1 receptor antagonist RP 67580 also significantly prevented MSU-induced nociception and edema. Once MSU was found to induce mast cell stimulation, we investigated the participation of these cells on MSU effects. Prior degranulation of mast cells by repeated treatment with the compound 48/80 decreased MSU-induced nociception and edema or histamine and serotonin levels in the injected tissue. Moreover, pretreatment with the mast cell membrane stabilizer cromolyn effectively prevented nociceptive and edematogenic responses to MSU. MSU induced a release of histamine, serotonin, and tryptase in the injected tissue, confirming mast cell degranulation. Furthermore, the antagonism of histaminergic H1 and serotoninergic receptors decreased the edema, but not the nociception of MSU. Finally, the prevention of the tryptase activity was capable of largely reducing both MSU-induced nociception and edema. Collectively, the present findings demonstrate that MSU produces nociceptive and edematogenic responses mediated by TRPV1 receptor activation and mast cell degranulation.Monosodium urate crystals produce nociceptive and edematogenic response mediated by TRPV1 receptor activation and mast cell degranulation.

Role of Myeloid-Derived Suppressor Cells in Amelioration of Experimental Autoimmune Hepatitis Following Activation of TRPV1 Receptors by Cannabidiol

BackgroundMyeloid-derived suppressor cells (MDSCs) are getting increased attention as one of the main regulatory cells of the immune system. They are induced at sites of inflammation and can potently suppress T cell functions. In the current study, we demonstrate how activation of TRPV1 vanilloid receptors can trigger MDSCs, which in turn, can inhibit inflammation and hepatitis.Methodology/Principal FindingsPolyclonal activation of T cells, following injection of concanavalin A (ConA), in C57BL/6 mice caused acute hepatitis, characterized by significant increase in aspartate transaminase (AST), induction of inflammatory cytokines, and infiltration of mononuclear cells in the liver, leading to severe liver injury. Administration of cannabidiol (CBD), a natural non-psychoactive cannabinoid, after ConA challenge, inhibited hepatitis in a dose-dependent manner, along with all of the associated inflammation markers. Phenotypic analysis of liver infiltrating cells showed that CBD-mediated suppression of hepatitis was associated with increased induction of arginase-expressing CD11b+Gr-1+ MDSCs. Purified CBD-induced MDSCs could effectively suppress T cell proliferation in vitro in arginase-dependent manner. Furthermore, adoptive transfer of purified MDSCs into naïve mice conferred significant protection from ConA-induced hepatitis. CBD failed to induce MDSCs and suppress hepatitis in the livers of vanilloid receptor-deficient mice (TRPV1−/−) thereby suggesting that CBD primarily acted via this receptor to induce MDSCs and suppress hepatitis. While MDSCs induced by CBD in liver consisted of granulocytic and monocytic subsets at a ratio of ∼2∶1, the monocytic MDSCs were more immunosuppressive compared to granulocytic MDSCs. The ability of CBD to induce MDSCs and suppress hepatitis was also demonstrable in Staphylococcal enterotoxin B-induced liver injury.Conclusions/SignificanceThis study demonstrates for the first time that MDSCs play a critical role in attenuating acute inflammation in the liver, and that agents such as CBD, which trigger MDSCs through activation of TRPV1 vanilloid receptors may constitute a novel therapeutic modality to treat inflammatory diseases.

Anandamide Capacitates Bull Spermatozoa through CB1 and TRPV1 Activation

Anandamide (AEA), a major endocannabinoid, binds to cannabinoid and vanilloid receptors (CB1, CB2 and TRPV1) and affects many reproductive functions. Nanomolar levels of anandamide are found in reproductive fluids including mid-cycle oviductal fluid. Previously, we found that R(+)-methanandamide, an anandamide analogue, induces sperm releasing from bovine oviductal epithelium and the CB1 antagonist, SR141716A, reversed this effect. Since sperm detachment may be due to surface remodeling brought about by capacitation, the aim of this paper was to investigate whether anandamide at physiological concentrations could act as a capacitating agent in bull spermatozoa. We demonstrated that at nanomolar concentrations R(+)-methanandamide or anandamide induced bull sperm capacitation, whereas SR141716A and capsazepine (a TRPV1 antagonist) inhibited this induction. Previous studies indicate that mammalian spermatozoa possess the enzymatic machinery to produce and degrade their own AEA via the actions of the AEA-synthesizing phospholipase D and the fatty acid amide hydrolase (FAAH) respectively. Our results indicated that, URB597, a potent inhibitor of the FAAH, produced effects on bovine sperm capacitation similar to those elicited by exogenous AEA suggesting that this process is normally regulated by an endogenous tone. We also investigated whether anandamide is involved in bovine heparin-capacitated spermatozoa, since heparin is a known capacitating agent of bovine sperm. When the spermatozoa were incubated in the presence of R(+)-methanandamide and heparin, the percentage of capacitated spermatozoa was similar to that in the presence of R(+)-methanandamide alone. The pre-incubation with CB1 or TRPV1 antagonists inhibited heparin-induced sperm capacitation; moreover the activity of FAAH was 30% lower in heparin-capacitated spermatozoa as compared to control conditions. This suggests that heparin may increase endogenous anandamide levels. Our findings indicate that anandamide induces sperm capacitation through the activation of CB1 and TRPV1 receptors and could be involved in the same molecular pathway as heparin in bovines.

302: Impact of topical capsaicin on labor in a novel mouse model

Capsaicin activates and then desensitizes TRPV1 receptors expressed in the uterus and cervix of humans and rodents, thus reducing pain transmission through TRPV1 expressing fibers. As such, capsaicin may provide labor analgesia. Secondarily, activation of TRPV1 receptors causes the release of neuropeptides that enhance cervical ripening by orchestrating a local inflammatory response. Hence, capsaicin may also enhance cervical ripening. The objective of this study was to examine whether a single intravaginal application of capsaicin in mice diminishes labor pain and shortens the time from labor induction to delivery.

A new partnership

Activation of central TRPV1 receptors by anandamide mediates long-term depression in the hippocampus and nucleus accumbens.

Modulation of single-channel properties of TRPV1 by phosphorylation

Activation of TRPV1, the heat and capsaicin receptor, is known to be promoted by phosphorylation, but the molecular details are unclear. In the present study we recorded from single TRPV1 ion channels using the cell-attached patch clamp technique. The influence of capsaicin concentration on the time constants of open and closed states demonstrates the existence of at least four closed and three open states, and shows that channel opening can occur from partially liganded states. Activation of protein kinase C (PKC) promotes channel opening in some channels but not others, consistent with some channels being inaccessible to the kinase. The changes in open and closed state time constants following activation of PKC are equivalent to an increased affinity of capsaicin binding, but other arguments suggest that channel opening must be potentiated by downstream changes in channel activation rather than by a direct action of phosphorylation on the capsaicin binding site. Mutation of functionally important PKC phosphorylation sites on TRPV1, or application of staurosporine, a broad-spectrum kinase inhibitor, completely inhibited the effect of PKC in enhancing channel open time. Staurosporine also inhibited channel activity in the absence of overt PKC activation, showing that TRPV1 is partially phosphorylated at rest. This study elucidates the mechanism by which phosphorylation by PKC potentiates the activation of single TRPV1 ion channels.

1002 ACUTE INFLAMMATION IN THE PELVIS MODULATES THE EXCITABILITY OF BLADDER EXTRINSIC SENSORY NEURONS VIA ACTIVATION OF VOLTAGE GATED SODIUM CHANNELS AND NON-SELECTIVE CATION CHANNELS

You have accessJournal of UrologyUrodynamics/Incontinence/Female Urology: Neurogenic Voiding Dysfunction1 Apr 20101002 ACUTE INFLAMMATION IN THE PELVIS MODULATES THE EXCITABILITY OF BLADDER EXTRINSIC SENSORY NEURONS VIA ACTIVATION OF VOLTAGE GATED SODIUM CHANNELS AND NON-SELECTIVE CATION CHANNELS Qi Lei, Xiao-Qing Pan, Alan Wein, and Anna Malykhina Qi LeiQi Lei More articles by this author , Xiao-Qing PanXiao-Qing Pan More articles by this author , Alan WeinAlan Wein More articles by this author , and Anna MalykhinaAnna Malykhina More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.2016AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Chronic pelvic pain is a symptom of many functional pelvic disorders and develops as a result of cross-sensitization in the pelvis. Our recent studies demonstrated increased excitability of convergent dorsal root ganglion neurons receiving input from the distal colon and urinary bladder. The objective of this study was to clarify the mechanisms modulating the expression of voltage gated sodium (Na+) channels in bladder sensory neurons after acute inflammation in the pelvis. METHODS Sprague-Dawley male rats underwent survival surgeries for retrograde labeling of sensory neurons using Fast Blue (1.5 % w/v in water, 20-22 μl). Na+ channels were recorded in lumbosacral (L6-S2) dorsal root ganglia (DRG) neurons isolated from 4 groups of animals: control, resiniferatoxin (RTX) instillation in the colon, trinitrobenzene sulfonic acid (TNBS) induced experimental colitis and double treatment (RTX+TNBS). Animals were sacrificed 3 days after the last treatment. RESULTS Acute colonic inflammation increased the peak amplitude of total Na+ current in bladder DRG neurons by 2-fold at -30 mV (-102.7±41.0 pA/pF in control group vs -229.3±18.1 pA/pF in experimental group, p≤0.05). Activation of TRPV1 receptors in the colon had similar effects on the amplitude of total Na+ current in bladder neurons as in the colitis group. However, colonic application of RTX followed by TNBS-induced colitis significantly enhanced Na+ current in bladder DRG neurons from -102.7±41.0 pA/pF to – 364.6±60.1 pA/pF (n=12, p≤0.05). Acute colitis did not change voltage dependence of steady-state activation nor inactivation in bladder sensory neurons. However, these parameters were affected by RTX treatment. Thus, V1/2 of activation curve of total Na+ current after RTX application had a leftward shift from -27.80±4.78 mV in the control group to -42.20±1.75 mV in RTX group (n=10, p≤0.05) whereas inactivation curve was shifted from -37.75±3.64 mV to -42.94±5.80 mV. Pretreatment with RTX followed by experimental colitis did not modulate the activation kinetics of Na+ current in bladder DRG neurons but caused a leftward shift in inactivation curve from -37.75±3.64 mV to -47.62±1.5 mV (n=11, p≤0.05). CONCLUSIONS Our data provide evidence that acute experimental colitis can modify the expression of Na+ channels in bladder extrinsic sensory neurons via TRPV1 signaling pathways. This data can provide a basis for the development of new therapeutic protocols to treat chronic pelvic pain of genitourinary origin. Glenolden, PA© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e389-e390 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Qi Lei More articles by this author Xiao-Qing Pan More articles by this author Alan Wein More articles by this author Anna Malykhina More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...