Mechanisms involved in potentiation of transient receptor potential vanilloid 1 responses by ethanol

The transient receptor potential vanilloid 1 or TRPV1 is a calcium‐permeable ion channel that is activated by capsaicin, the active component of hot chilli peppers, and is involved in the development of inflammatory and neuropathic hyperalgesias. Ethanol can sensitise TRPV1‐mediated responses, but the pathways contributing to the potentiation of TRPV1 by ethanol have not been clearly defined. Since the μ opioid receptor (MOP) agonist morphine can inhibit TRPV1 responses potentiated by cAMP‐dependent protein kinase A (PKA), and ethanol‐mediated modulation of other ion channels involves activation of PKA, we aimed to assess the contribution of MOP‐sensitive pathways to the potentiation of TRPV1‐mediated capsaicin responses by ethanol. Calcium responses elicited by the TRPV1 agonist capsaicin were potentiated by treatment with ethanol, but morphine was not able to inhibit ethanol‐sensitised capsaicin responses. Indeed, cAMP‐dependent PKA did not appear to contribute to potentiation of TRPV1 responses by ethanol, as the PKA inhibitor Rp‐cAMPS did not inhibit ethanol‐potentiated capsaicin responses. Similarly, treatment with specific PKC and PI3K inhibitors did not affect capsaicin responses in the presence of ethanol. However, treatment with wortmannin at concentrations reported to cause PIP2 depletion limited the ability of ethanol to sensitise TRPV1‐mediated capsaicin responses. Among other plausible mechanisms, such as non‐specific inhibition of kinases including mTOR, DNA‐PK, MLCK, MAPK and polo‐like kinases, this suggests that ethanol may affect the PIP2‐TRPV1 interaction. This was confirmed by inhibition of ethanol‐potentiation by the PLC inhibitor U73122. The results presented here suggest that morphine may be of limited use in inhibiting nociceptive TRPV1 responses that have been sensitised by exposure to ethanol.     

Novel expression of vanilloid receptor 1 on capsaicin-insensitive fibers accounts for the analgesic effect of capsaicin cream in neuropathic pain

Here, we investigated the mechanism of the antihyperalgesic effect of capsaicin cream in the nerve injury-induced neuropathic pain model in mice. In naive mice, application of capsaicin cream onto footpad caused no significant changes in the thermal latency in contrast to the severe thermal hyperalgesia induced by a capsaicin ointment. On the other hand, application of the cream 3 h before test concentration dependently reversed both thermal and mechanical hyperalgesia observed after partial sciatic nerve injury in mice. In algogenic-induced nociceptive flexion (ANF) test, application of 0.1% capsaicin cream in naive mice blocked intraplantar (i.pl.) nociceptin- and ATP-induced flexion responses, whereas prostaglandin I(2) (PGI(2)) agonist-induced responses were unaffected. After nerve injury PGI(2) agonist-induced flexion responses were hypersensitized, and capsaicin cream concentration dependently blocked these hyperalgesic responses. Intraplantar injection of capsaicin solution in ANF test also produced potent flexion responses in naive mice that were lost after neonatal capsaicin-treatment. Partial sciatic nerve injury in neonatal capsaicin-treated mice caused reappearance of i.pl. capsaicin-induced flexion responses, suggesting novel expression of capsaicin receptors due to injury. The PGI(2) agonist-induced responses were also hypersensitized in such injured mice. Capsaicin cream completely reversed both i.pl. capsaicin- or i.pl. PGI(2) agonist-induced hyperalgesia in neonatal capsaicin-treated injured mice. Finally, novel expression of VR1 receptors on neonatal capsaicin-insensitive neurons after nerve injury was confirmed by immunohistochemistry. The newly expressed VR1 receptors after nerve injury were mainly confined to A-fibers. Together, our results suggest that novel expression of capsaicin receptors in neuropathic condition contributes to the analgesic effects of the capsaicin cream.     

Effect of paclitaxel on transient receptor potential vanilloid 1 in rat dorsal root ganglion

Peripheral neuropathy is a common adverse effect of paclitaxel treatment. To analyze the contribution of transient receptor potential vanilloid 1 (TRPV1) in the development of paclitaxel-induced thermal hyperalgesia, TRPV1 expression in the rat dorsal root ganglion (DRG) was analyzed after paclitaxel treatment. Behavioral assessment using the tail-flick test showed that intraperitoneal administration of 2 and 4 mg/kg paclitaxel induced thermal hyperalgesia after days 7, 14, and 21. Paclitaxel-induced thermal hyperalgesia after day 14 was significantly inhibited by the TRP antagonist ruthenium red (3 mg/kg, s.c.) and the TRPV1 antagonist capsazepine (30 mg/kg, s.c.). Paclitaxel (2 and 4 mg/kg) treatment increased the expression of TRPV1 mRNA and protein in DRG neurons. Immunohistochemistry showed that paclitaxel (4 mg/kg) treatment increased TRPV1 protein expression in small and medium DRG neurons 14 days after treatment. Antibody double labeling revealed that isolectin B4-positive small DRG neurons co-expressed TRPV1. TRPV1 immunostaining was up-regulated in paw skin day 14 after paclitaxel treatment. Moreover, in situ hybridization histochemistry revealed that most of the TRPV1 mRNA-labeled neurons in the DRG were small or medium in size. These results suggest that paclitaxel treatment increases TRPV1 expression in DRG neurons and may contribute to functional peripheral neuropathic pain.     

Somatostatin modulates the transient receptor potential vanilloid 1 (TRPV1) ion channel

Activation of peripheral somatostatin receptors (SSTRs) inhibits sensitization of nociceptors, thus having a short term or phasic effect [Pain 90 (2001) 233] as well as maintaining a tonic inhibitory control over nociceptors [J Neurosci 21 (2001) 4042]. The present study provides several lines of evidence that an important mechanism underlying SSTR modulation of nociceptors is regulation of the transient receptor potential vanilloid 1 ion channel (TRPV1, formerly the VR1 receptor). Double labeling of L5 dorsal root ganglion cells demonstrates that 60% of SSTR2a-labeled cells are positive for TRPV1. Conversely, 33% of TRPV1-labeled cells are positive for SSTR2a. In vivo behavioral studies demonstrate that intraplantar injection of 20.0 but not 2.0 μM octreotide (OCT, SSTR agonist) significantly reduces capsaicin (CAP, a ligand for TRPV1) -induced flinching and lifting/licking behaviors. This occurs through local activation of SSTRs in the injected hindpaw and is reversed following co-application of the SSTR antagonist cyclo-somatostatin (c-SOM). In vitro studies using a skin-nerve preparation demonstrate that activation of peripheral SSTRs on nociceptors with 20.0 μM OCT significantly reduces CAP-induced activity and can prevent CAP-induced desensitization. Furthermore, blockade of peripheral SSTRs with c-SOM dramatically enhances CAP-induced behaviors and nociceptor activity, demonstrating SSTR-induced tonic inhibitory modulation of TRPV1. Finally, TRPV1 does not appear to be under tonic opioid receptor control since the opioid antagonist naloxone does not change CAP-induced excitation and does not effect OCT-induced inhibition of CAP responses. These data strongly suggest that SSTRs modulate nociceptors through phasic and tonic regulation of peripheral TRPV1 receptors.     

Opioid withdrawal increases transient receptor potential vanilloid 1 activity in a protein kinase A-dependent manner

Hyperalgesia is a cardinal symptom of opioid withdrawal. The transient receptor potential vanilloid 1 (TRPV1) is a ligand-gated ion channel expressed on sensory neurons responding to noxious heat, protons, and chemical stimuli such as capsaicin. TRPV1 can be inhibited via μ-opioid receptor (MOR)-mediated reduced activity of adenylyl cyclases (ACs) and decreased cyclic adenosine monophosphate (cAMP) levels. In contrast, opioid withdrawal following chronic activation of MOR uncovers AC superactivation and subsequent increases in cAMP and protein kinase A (PKA) activity. Here we investigated (1) whether an increase in cAMP during opioid withdrawal increases the activity of TRPV1 and (2) how opioid withdrawal modulates capsaicin-induced nocifensive behavior in rats. We applied whole-cell patch clamp, microfluorimetry, cAMP assays, radioligand binding, site-directed mutagenesis, and behavioral experiments. Opioid withdrawal significantly increased cAMP levels and capsaicin-induced TRPV1 activity in both transfected human embryonic kidney 293 cells and dissociated dorsal root ganglion (DRG) neurons. Inhibition of AC and PKA, as well as mutations of the PKA phosphorylation sites threonine 144 and serine 774, prevented the enhanced TRPV1 activity. Finally, capsaicin-induced nocifensive behavior was increased during opioid withdrawal in vivo. In summary, our results demonstrate an increased activity of TRPV1 in DRG neurons as a new mechanism contributing to opioid withdrawal-induced hyperalgesia.     

Endocannabinoid regulates blood pressure via activation of the transient receptor potential vanilloid type 1 in Wistar rats fed a high-salt diet

This study was designed to examine the role of the endocannabinoids in blood pressure regulation during high sodium (HS) intake. HS (4% Na+ by weight) intake for 3 weeks increased baseline mean arterial pressure (MAP, mm Hg) compared with normal sodium (NS, 0.4% Na+ by weight)-treated male Wistar rats. Capsazepine (3 mg/kg), a selective transient receptor potential vanilloid type 1 (TRPV1) antagonist, caused a greater increase in MAP (mm Hg) in HS-treated compared with NS-treated rats (13+/-3 versus 4+/-2, p<0.05), whereas calcitonin gene-related peptide (CGRP) dose-dependently decreased MAP in both HS- and NS-treated rats with a more profound effect in the former. HS increased plasma anandamide levels analyzed by liquid chromatography/electrospray tandem mass spectrometry (NS, 2.40+/-0.31 versus HS, 4.05+/-0.47 pmol/ml, p<0.05) and plasma CGRP levels determined by radioimmunoassay (NS, 36.6+/-3.8 versus HS, 55.7+/-6.4 pg/ml, p<0.05). Methanandamide, a metabolically stable analog of anandamide, caused a greater CGRP release in mesenteric arteries isolated from HS-treated compared with NS-treated rats. Western blot showed that expression of receptor activity-modifying protein 1, a subunit of the CGRP receptor, in mesenteric arteries was greater in HS-treated compared with NS-treated rats. These results show that HS intake increases production of anandamide, which may serve as an endovanilloid to activate TRPV1, leading to release of CGRP to blunt salt-induced increases in blood pressure. These data support the notion that TRPV1 may act as a molecular target for salt-induced elevation of endovanilloid compounds to regulate blood pressure.     

Design and characterization of a noncompetitive antagonist of the transient receptor potential vanilloid subunit 1 channel with in vivo analgesic and anti-inflammatory activity.

Vanilloid receptor subunit 1 (TRPV1) is an integrator of physical and chemical stimuli in the peripheral nervous system. This receptor plays a key role in the pathophysiology of inflammatory pain. Thus, the identification of receptor antagonists with analgesic and anti-inflammatory activity in vivo is an important goal of current neuropharmacology. Here, we report that [L-arginyl]-[N-[2,4-dichlorophenethyl]glycyl]-N-(2,4-dichlorophenethyl) glycinamide (H-Arg-15-15C) is a channel blocker that abrogates capsaicin and pH-evoked TRPV1 channel activity with submicromolar activity. Compound H-Arg-15-15C preferentially inhibits TRPV1, showing marginal block of other neuronal receptors. Compound H-Arg-15-15C acts as a noncompetitive capsaicin antagonist with modest voltage-dependent blockade activity. The compound inhibited capsaicin-evoked nerve activity in afferent fibers without affecting mechanically activated activity. Notably, administration of compound H-Arg-15-15C prevented the irritant activity of a local administration of capsaicin and formalin and reversed the thermal hyperalgesia evoked by injection of complete Freund's adjuvant. Furthermore, it attenuated carrageenan-induced paw inflammation. Compound H-Arg-15-15C specifically decreased inflammatory conditions without affecting normal nociception. Taken together, these findings demonstrate that compound H-Arg-15-15C is a channel blocker of TRPV1 with analgesic and anti-inflammatory activity in vivo at clinically useful doses and substantiate the tenet that TRPV1 plays an important role in the etiology of chronic inflammatory pain. PERSPECTIVE: This study reports the design of a potent TRPV1 noncompetitive antagonist that exhibits anti-inflammatory and analgesic activity in preclinical models of acute and chronic pain. This compound is a lead for analgesic drug development.     

α-氨基-3-羟基-5-甲基-4-异恶唑丙酸受体拮抗剂对神经病理性痛大鼠海马长时程增强的影响

目的探讨α-氨基-3-羟基-5-甲基-4-异恶唑丙酸(AMPA)受体拮抗剂对神经病理性痛大鼠海马突触长时程增强(LTP)的影响。方法成年雄性Wistar大鼠18只,随机均分为3组(n=6):神经病理性痛模型组(NP组)、CNQX 1组(C1组)、CNQX 2组(C2组)。采用结扎L4~5左侧脊神经的方法制备大鼠神经病理性痛模型。于模型制备后7、14和21 d观察大鼠痛行为学及足部形态;于模型制备前、制备后7、14和21 d时测定痛阈;于最后一次痛阈测定结束后3 d记录海马CA1区兴奋性突触后电位(EPSP),以高频刺激(HFS)诱发LTP。C1组于HFS前20 min经侧脑室输注CNQX(AMPA受体特异性拮抗剂)1μl(1.0μg),C2组于HFS后60 min给药,剂量同C1组。组间比较采用单因素方差分析,不同时间点痛阈的比较采用重复测量方差分析。结果与基础值比较,模型制备后3组各时点痛阈降低(P<0.05);与NP组相比,C1组21 min后、C2组61 min后LTP程度减弱(P<0.05);与C1组相比,C2组21~60 min LTP程度增强(P<0.05)。结论 AMPA受体拮抗剂CNQX不干扰神经病理性痛大鼠海马CA1区突触LTP的诱导,但可阻滞其维持。     

Hypoxia-induced sensitization of transient receptor potential vanilloid 1 involves activation of hypoxia-inducible factor-1 alpha and PKC

The capsaicin receptor, transient receptor potential vanilloid 1 (TRPV1), acts as a polymodal detector of pain-producing chemical and physical stimuli in sensory neurons. Hyperglycemia and hypoxia are two main phenomena in diabetes associated with several complications. Although many studies on streptozotocin-induced diabetic rats indicate that early diabetic neuropathy is associated with potentiation of TRPV1 activity in dorsal root ganglion neurons, its underlying mechanism and distinctive roles of hyperglycemia and hypoxia have not been completely clarified. Here, we show that hypoxic and high glucose conditions (overnight exposure) potentiate the TRPV1 activity without affecting TRPV1 expression in both native rat sensory neurons and human embryonic kidney-derived 293 cells expressing rat or human TRPV1. Surprisingly, hypoxia was found to be a more effective determinant than high glucose, and hypoxia-inducible factor-1 alpha (HIF-1α) seemed to be involved. In addition, high glucose enhanced TRPV1 sensitization only when high glucose existed together with hypoxia. The potentiation of TRPV1 was caused by its phosphorylation of the serine residues, and translocation of protein kinase C (PKC)ε was clearly observed in the cells exposed to the hypoxic conditions in both cell types, which was inhibited by 2-methoxyestradiol, a HIF-1α inhibitor. These data suggest that hypoxia is a new sensitization mechanism for TRPV1, which might be relevant to diabetes-related complications, and also for other diseases that are associated with acute hypoxia.     

Hydrogen peroxide is a novel mediator of inflammatory hyperalgesia,acting via transient receptor potential vanilloid 1-dependent and independent mechanisms

Inflammatory diseases associated with pain are often difficult to treat in the clinic due to insufficient understanding of the nociceptive pathways involved. Recently, there has been considerable interest in the role of reactive oxygen species (ROS) in inflammatory disease, but little is known of the role of hydrogen peroxide (H₂O₂) in hyperalgesia. In the present study, intraplantar injection of H₂O₂-induced a significant dose- and time-dependent mechanical and thermal hyperalgesia in the mouse hind paw, with increased c-fos activity observed in the dorsal horn of the spinal cord. H₂O₂ also induced significant nociceptive behavior such as increased paw licking and decreased body liftings. H₂O₂ levels were significantly raised in the carrageenan-induced hind paw inflammation model, showing that this ROS is produced endogenously in a model of inflammation. Moreover, superoxide dismutase and catalase significantly reduced carrageenan-induced mechanical and thermal hyperalgesia, providing evidence of a functionally significant endogenous role. Thermal, but not mechanical, hyperalgesia in response to H₂O₂ (i.pl.) was longer lasting in TRPV1 wild type mice compared to TRPV1 knockouts. It is unlikely that downstream lipid peroxidation was increased by H₂O₂. In conclusion, we demonstrate a notable effect of H₂O₂ in mediating inflammatory hyperalgesia, thus highlighting H₂O₂ removal as a novel therapeutic target for anti-hyperalgesic drugs in the clinic.     

Involvement of transient receptor potential vanilloid 1 receptors in protease-activated receptor-2-induced joint inflammation and nociception

Protease-activated receptor-2 (PAR-2) is a G-protein-coupled receptor activated through proteolytic cleavage. It is localized on epithelial, endothelial and inflammatory cells, as well as on transient receptor potential vanilloid 1 (TRPV1) receptor-expressing neurones. It plays an important role in inflammatory/nociceptive processes. Since there are few reports concerning PAR-2 function in joints, the effects of intraarticular PAR-2 activation on joint pain and inflammation were studied. Secondary hyperalgesia/allodynia, spontaneous weight distribution, swelling and inflammatory cytokine production were measured and the involvement of TRPV1 ion channels was investigated in rats and mice. Injection of the PAR-2 receptor agonist SLIGRL-NH₂ into the knee decreased touch sensitivity and weight bearing of the ipsilateral hindlimb in both species. Secondary mechanical allodynia/hyperalgesia and impaired weight distribution were significantly reduced by the TRPV1 antagonist SB366791 in rats and by the genetic deletion of this receptor in mice. PAR-2 activation did not cause significant joint swelling, but increased IL-1β concentration which was not influenced by the lack of the TRPV1 channel. For comparison, intraplantar SLIGRL-NH₂ evoked similar primary mechanical hyperalgesia and impaired weight distribution in both WT and TRPV1 deficient mice, but oedema was smaller in the knockouts. The inactive peptide, LRGILS-NH₂, injected into either site did not induce any inflammatory or nociceptive changes. These data provide evidence for a significant role of TRPV1 receptors in secondary mechanical hyperalgesia/allodynia and spontaneous pain induced by PAR-2 receptor activation in the knee joint. Although intraplantar PAR-2 activation-induced oedema is also TRPV1 receptor-mediated, primary mechanical hyperalgesia, impaired weight distribution and IL-1β production are independent of this channel.     

Increased expression of vanilloid receptor 1 on myelinated primary afferent neurons contributes to the antihyperalgesic effect of capsaicin cream in diabetic neuropathic pain in mice

Topical capsaicin is believed to alleviate pain by desensitizing the vanilloid receptor 1 (VR1) at the peripheral nerve endings. Here, we report that an up-regulation of VR1 expression on myelinated fibers contributes to the antihyperalgesic effect of capsaicin cream in streptozotocin (STZ)-induced diabetic neuropathic pain. Intravenous injection of STZ (200 mg/kg) in mice caused rapid onset of diabetes within 24 h. Thermal and mechanical hyperalgesia developed by 3 days after STZ injection and persisted at all time points tested until 28 days. There was also hyperalgesic response to intraplantar (i.pl.) prostaglandin I2 (PGI2) agonist-induced nociception in such mice. Application of capsaicin cream dose dependently reversed the thermal, mechanical, and PGI2 agonist-induced hyperalgesia observed in the diabetic mice. The i.pl. injection of capsaicin solution (0.4 microg/20 microl) produced nociceptive biting-licking responses in control mice, and these responses were significantly increased in STZ-induced diabetic mice. After neonatal capsaicin-treatment, which destroys most unmyelinated C-fibers, the i.pl. capsaicin-induced biting-licking responses were almost abolished. However, in neonatal capsaicin-treated diabetic mice, the i.pl. capsaicin-induced biting-licking responses reappeared. The i.pl. capsaicin-induced biting-licking responses were blocked by the competitive VR1 antagonist capsazepine. All these results suggest an increase in capsaicin receptor on myelinated fibers due to diabetes. Finally, we confirmed the up-regulation of VR1 expression on myelinated primary afferent neurons of diabetic mice by immunohistochemistry. Together, our results suggest that increased expression of VR1 on myelinated fibers might contribute to the antihyperalgesic effect of topical capsaicin in diabetic neuropathic pain.     

A polyclonal antibody to the prepore loop of transient receptor potential vanilloid type 1 blocks channel activation

Transient receptor potential vanilloid type 1 (TRPV1) can be activated by multiple chemical and physical stimuli such as capsaicin, anandamide, protons, and heat. Capsaicin interacts with the binding pocket constituted by transmembrane regions 3 and 4, whereas protons act through residues in the prepore loop of TRPV1. Here, we report on characterization of polyclonal and monoclonal antibodies to the prepore loop of TRPV1. A rabbit anti-rat TRPV1 polyclonal antibody (Ab-156H) acted as a full antagonist of proton activation (IC(50) values for pH 5 and 5.5 were 364.68 +/- 29.78 and 28.31 +/- 6.30 nM, respectively) and as a partial antagonist of capsaicin, heat, and pH 6 potentiated chemical ligand (anandamide and capsaicin) activation (50-79% inhibition). Ab-156H antagonism of TRPV1 is not affected by the conformation of the capsaicin-binding pocket because it is equally potent at wild-type (capsaicin-sensitive) rat TRPV1 and its T550I mutant (capsaicin-insensitive). With the goal of generating monoclonal antagonist antibodies to the prepore region of human TRPV1, we used a recently developed rabbit immunization protocol. Although rabbit polyclonal antiserum blocked human TRPV1 activation, rabbit monoclonal antibodies (identified on the basis of selective binding to Chinese hamster ovary cells expressing human TRPV1) did not block activation by either capsaicin or protons. Thus, rabbit polyclonal antibodies against rat and human TRPV1 prepore region seem to partially lock or stabilize the channel in the closed state, whereas rabbit anti-human TRPV1 monoclonal antibodies bind to the prepore region but do not lock or stabilize the channel conformation.     

5-Iodoresiniferatoxin evokes hypothermia in mice and is a partial transient receptor potential vanilloid 1 agonist in vitro

Transient receptor potential vanilloid 1 (TRPV1) is a capsaicin- and heat-gated ion channel required for normal in vivo responses to these painful stimuli. However, growing evidence suggests that TRPV1 also participates in thermoregulation. Therefore, we examined the effects of a selective TRPV1 antagonist, 5-iodoresiniferatoxin (I-RTX), on mouse body temperature. Surprisingly, s.c. administration of I-RTX (0.1-1 micromol/kg) evoked a hypothermic response similar to that evoked by capsaicin (9.8 micromol/kg) in naive wild-type mice, but not in mice pretreated with resiniferatoxin, a potent TRPV1 agonist, or in naive TRPV1-null mice. In response to I-RTX in vitro, HEK293 cells expressing rat TRPV1 exhibited increases in intracellular Ca(2+) (biphasic, EC(50) = 56.7 nM and 9.9 microM) that depended on Ca(2+) influx and outwardly rectifying, capsazepine-sensitive currents that were smaller than those evoked by 1 microM capsaicin. Thus, I-RTX induces TRPV1-dependent hypothermia in vivo and is a partial TRPV1 agonist in vitro.     

Role of transient receptor potential vanilloid 1 receptors in adjuvant-induced chronic arthritis: in vivo study using gene-deficient mice

The transient receptor potential vanilloid 1 (TRPV1) receptor is a nonselective cation channel localized on a subset of primary sensory neurons and can be activated by a wide range of stimuli. The present study investigated the role of this receptor in chronic arthritis evoked by complete Freund's adjuvant (CFA) using TRPV1 receptor gene-deleted (TRPV1-/-) mice and wild-type counterparts (TRPV1+/+). In TRPV1+/+ mice, CFA injected intraplantarly into the left hindpaw and the root of the tail induced swelling of the injected and contralateral paws up to 130 and 28%, respectively, measured by plethysmometry throughout 18 days. Mechanonociceptive threshold measured with dynamic plantar aesthesiometry was decreased by 50 and 18% on the injected and contralateral paws, respectively. Histological examination and scoring of the tibiotarsal joints revealed marked arthritic changes in wild-type mice. In TRPV1-/- animals edema, histological score and mechanical allodynia were significantly smaller. Daily treatment with the lipoxygenase inhibitor nordihydroguaretic acid (NDGA), the cyclooxygenase inhibitor indomethacin, the bradykinin B2 receptor antagonist HOE-140 [D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thyenyl)-L-alanyl-L-seryl-D-1,2,2,4-tetrahydro-3-isoquinolinecarbonyl-L-(2a,3b,7ab)-octahydro-1H-indole-2-carbonyl-L-arginine], or the B1 receptor antagonist desArgHOE-140 [D-arginyl-L-arginyl-L-prolyl-trans-4-hydroxy-L-prolylglycyl-3-(2-thyenyl)-L-alanyl-L-seryl-D-1,2,2,4-tetrahydro-3-isoquinolinecarbonyl-L-(2a,3b,7ab)-octahydro-1H-indole-2-carbonyl] was performed to reveal what mediators might activate TRPV1. NDGA significantly inhibited edema, hyperalgesia, and arthritis score in TRPV1+/+, but not in TRPV1-/- mice. The effect of indomethacin was markedly smaller in knockouts. In TRPV1+/+ animals, HOE-140, but not desArgHOE-140, inhibited arthritis, whereas in TRPV1-/- mice, HOE-140 produced limited effect. Thus, whereas bradykinin and lipoxygenase products seem to act exclusively via TRPV1 activation, prostanoids do not, or at least only partially, to enhance murine experimental arthritis and related hyperalgesia.     

瞬时感受器电位离子通道香草素受体4下游信号分子的确定及其对大鼠背根神经节慢性压迫后痛觉过敏的作用

目的:探讨大鼠背根神经节慢性压迫CCD后瞬时感受器电位离子通道香草素受体4(TRPV4)下游信号分子及其在痛觉过敏中的机制。方法:鞘内分别注射TRPV4拮抗剂钌红(RR)、TRPV4反义寡脱氧核苷酸(ASODN)和一氧化氮合成酶(NOS)抑制剂L-NAME,检测CCD大鼠背根神经节DRG内一氧化氮(NO)代谢产物亚硝酸盐(nitrite)含量变化,并观测热刺激缩爪反应潜伏期(PWL)的变化。结果:鞘内分别注射RR、TRPV4 AS ODN和L-NAME后,均能够显著降低CCD大鼠DRG内亚硝酸盐含量(P<0.05),CCD大鼠的热痛敏行为也能够显著改善(P<0.05)。结论:TRPV4及其下游信号分子NO参与介导CCD大鼠的热痛觉过敏。     

骨髓间充质干细胞成骨分化过程中瞬时性受体电位香草精受体5的表达：

背景：目前,钙离子通道的研究仪限r肾脏、小肠、光滑卯母细胞中瞬时性受体电位香草精受体5所表现出来的电生理特性。目的：观察新掣钙离子通道瞬时性受体电位香草精受体5在大鼠骨髓间充质干细胞来源的成骨细胞中的表达及意义。方法：分离、提取、培养大鼠骨髓问充质干细胞,诱导大鼠骨髓间充质干细胞向成骨细胞分化,用免疫组织化学法检测大鼠骨髓问充质干细胞诱导分化的成骨细胞中瞬时性受体电位香草精受体5的表达。结果与结论：实验成功将体外培养大鼠骨髓间充质干细胞诱导培养为成骨细胞。碱性磷酸酶染色和茜素红染色检测结果显示,诱导分化的成骨细胞中胞浆中可见紫黑色和红色的矿化结节。免疫组织化学染色结果显示,诱导的成竹细胞中瞬时性受体电位香革精受体5呈强阳性表达。结果证实,大鼠骨髓间充质千细胞来源的成骨细胞中存在瞬时性受体电位香草精受体5钙离子通道,此通道可能成为调节成骨细胞增殖和分化的候选通道。