15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and capsazepine

We have previously shown transient receptor potential vanilloid subtype 1 (TRPV1) channel-dependent coronary function is compromised in pigs with metabolic syndrome (MetS). However, the mechanisms through which TRPV1 channels couple coronary blood flow to metabolism are not fully understood. We employed mice lacking TRPV1 [TRPV1((-/-))], db/db diabetic, and control C57BKS/J mice to determine the extent to which TRPV1 channels modulate coronary function and contribute to vascular dysfunction in diabetic cardiomyopathy. Animals were subjected to in vivo infusion of the TRPV1 agonist capsaicin to examine the hemodynamic actions of TRPV1 activation. Capsaicin (1-100 μg·kg(-1)·min(-1)) dose dependently increased coronary blood flow in control mice, which was inhibited by the TRPV1 antagonist capsazepine or the nitric oxide synthase (NOS) inhibitor N-nitro-l-arginine methyl ester (L-NAME). In addition, the capsaicin-mediated increase in blood flow was attenuated in db/db mice. TRPV1((-/-)) mice exhibited no changes in coronary blood flow in response to capsaicin. Vasoreactivity studies in isolated pressurized mouse coronary microvessels revealed a capsaicin-dependent relaxation that was inhibited by the TRPV1 inhibitor SB366791 l-NAME and to the large conductance calcium-sensitive potassium channel (BK) inhibitors iberiotoxin and Penetrim A. Similar to in vivo responses, capsaicin-mediated relaxation was impaired in db/db mice compared with controls. Changes in pH (pH 7.4-6.0) relaxed coronary vessels contracted to the thromboxane mimetic U46619 in all three groups of mice; however, pH-mediated relaxation was blunted in vessels obtained from TRPV1((-/-)) and db/db mice compared with controls. Western blot analysis revealed decreased myocardial TRPV1 protein expression in db/db mice compared with controls. Our data reveal TRPV1 channels mediate coupling of myocardial blood flow to cardiac metabolism via a nitric oxide-dependent, BK channel-dependent pathway that is corrupted in diabetes.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Anilides; Animals; Capsaicin; Cinnamates; Coronary Vessels; Diabetes Mellitus, Type 2; Diabetic Cardiomyopathies; Enzyme Inhibitors; Large-Conductance Calcium-Activated Potassium Channels; Male; Mice; Mice, Inbred C57BL; Microvessels; NG-Nitroarginine Methyl Ester; Nitric Oxide; Peptides; TRPV Cation Channels; Vasoconstrictor Agents; Vasodilation

Endocannabinoids exhibit vasodilatory properties and reduce blood pressure in vivo. However, the influence and mechanism of action of the prominent endocannabinoid, anandamide (AEA), in pulmonary arteries are not known. The present study determined the vascular response to AEA in isolated rat pulmonary arteries. AEA relaxed rat pulmonary arteries that were pre-constricted with U-46619. This relaxation was reduced by the following conditions:removal of the endothelium; in KCl pre-constricted preparations; in the presence of the potassium channel (K(Ca)) blockers, tetraethylammonium and the combination of charybdotoxin and apamin, and the prostacyclin receptor antagonist, RO1138452. Inhibitors of cyclooxygenase (indomethacin), nitric oxide (NO) synthase (N(G)-nitro-l-arginine methyl ester) and fatty acid amide hydrolase (URB597) alone or in combination diminished AEA-induced relaxation in endothelium-intact vessels. The remaining experiments were performed in the presence of URB597 to eliminate the influence of AEA metabolites. Antagonists of the endothelial cannabinoid receptor (CB(x)), O-1918 and cannabidiol, attenuated the AEA-induced response. Antagonists of CB(1), CB(2) and TRPV1 receptors, AM251, AM630 and capsazepine, respectively, did not modify the AEA-induced response. A reference activator of CB(x) receptors, abnormal cannabidiol, mimicked the receptor-mediated AEA effects. The present study demonstrated that AEA relaxed rat pulmonary arteries in an endothelium-dependent fashion via the activation of the O-1918-sensitive CB(x) receptor and/or prostacyclin-like vasoactive products of AEA. One or both of these mechanisms may involve K(Ca) or the NO pathway.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Amidohydrolases; Animals; Anisoles; Apamin; Arachidonic Acids; Benzamides; Benzyl Compounds; Cannabinoid Receptor Antagonists; Capsaicin; Carbamates; Charybdotoxin; Cyclohexanes; Endocannabinoids; Endothelium, Vascular; Imidazoles; Indoles; Indomethacin; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Piperidines; Polyunsaturated Alkamides; Potassium Channel Blockers; Potassium Chloride; Prostaglandin-Endoperoxide Synthases; Pulmonary Artery; Pyrazoles; Rats; Rats, Wistar; Receptors, Cannabinoid; Receptors, Epoprostenol; Tetraethylammonium; TRPV Cation Channels; Vasodilation

Capsaicin, a pungent constituent from red chilli peppers, activates sensory nerve fibres via transient receptor potential vanilloid receptors type 1 (TRPV1) to release neuropeptides like calcitonin gene-related peptide (CGRP) and substance P. Capsaicin-sensitive nerves are widely distributed in human and porcine vasculature. In this study, we examined the mechanism of capsaicin-induced relaxations, with special emphasis on the role of CGRP, using various pharmacological tools. Segments of human and porcine proximal and distal coronary arteries, as well as cranial arteries, were mounted in organ baths. Concentration response curves to capsaicin were constructed in the absence or presence of the CGRP receptor antagonist olcegepant (BIBN4096BS, 1 microM), the neurokinin NK1 receptor antagonist L-733060 (0.5 microM), the voltage-sensitive calcium channel blocker ruthenium red (100 microM), the TRPV1 receptor antagonist capsazepine (5 microM), the nitric oxide synthetase inhibitor Nomega-nitro-L-arginine methyl ester HCl (L-NAME; 100 microM), the gap junction blocker 18alpha-glycyrrhetinic acid (10 microM), as well as the RhoA kinase inhibitor Y-27632 (1 microM). Further, we also used the K+ channel inhibitors 4-aminopyridine (1 mM), charybdotoxin (0.5 microM) + apamin (0.1 microM) and iberiotoxin (0.5 microM) + apamin (0.1 microM). The role of the endothelium was assessed by endothelial denudation in distal coronary artery segments. In distal coronary artery segments, we also measured levels of cyclic adenosine monophosphate (cAMP) after exposure to capsaicin, and in human segments, we also assessed the amount of CGRP released in the organ bath fluid after exposure to capsaicin. Capsaicin evoked concentration-dependent relaxant responses in precontracted arteries, but none of the above-mentioned inhibitors did affect these relaxations. There was no increase in the cAMP levels after exposure to capsaicin, unlike after (exogenously administered) alpha-CGRP. Interestingly, there were significant increases in CGRP levels after exposure to vehicle (ethanol) as well as capsaicin, although this did not induce relaxant responses. In conclusion, the capsaicin-induced relaxations of the human and porcine distal coronary arteries are not mediated by CGRP, NK1, NO, vanilloid receptors, voltage-sensitive calcium channels, K+ channels or cAMP-mediated mechanisms. Therefore, these relaxant responses to capsaicin are likely to be attributed to a non-specific, CGRP-independen

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Adolescent; Adult; Aged; Analgesics, Non-Narcotic; Animals; Arteries; Calcitonin Gene-Related Peptide; Capsaicin; Coronary Vessels; Cyclic AMP; Dipeptides; Dose-Response Relationship, Drug; Female; Humans; In Vitro Techniques; Male; Middle Aged; NG-Nitroarginine Methyl Ester; Piperazines; Piperidines; Potassium Channel Blockers; Potassium Chloride; Protein Kinase Inhibitors; Quinazolines; Swine; Vasodilation

Myogenic constriction describes the innate ability of resistance arteries to constrict in response to elevations in intraluminal pressure and is a fundamental determinant of peripheral resistance and, hence, organ perfusion and systemic blood pressure. However, the receptor/cell-type that senses changes in pressure on the blood vessel wall and the pathway that couples this to constriction of vascular smooth muscle remain unclear. In this study, we show that elevation of intraluminal transmural pressure of mesenteric small arteries in vitro results in a myogenic response that is profoundly suppressed following ablation of sensory C-fiber activity (using in vitro capsaicin desensitization resulted in 72.8+/-10.3% inhibition, n=8; P<0.05). Activation of C-fiber nerve endings by pressure was attributable to stimulation of neuronal vanilloid receptor, TRPV1, because blockers of this channel, capsazepine (71.9+/-11.1% inhibition, n=9; P<0.001) and ruthenium red (46.1+/-11.7% inhibition, n=4; P<0.05), suppressed the myogenic constriction. In addition, this C-fiber dependency is likely related to neuropeptide substance P release and activity because blockade of tachykinin NK1 receptors (66.3+/-13.7% inhibition, n=6; P<0.001), and not NK2 receptors (n=4, NS), almost abolished the myogenic response. Previous studies support a role for 20-hydroxyeicosatetraenoic acid (20-HETE) in myogenic constriction responses; herein, we show that 20-HETE-induced constriction of mesenteric resistance arteries is blocked by capsazepine. Together, these results suggest that elevation of intraluminal pressure is associated with generation of 20-HETE that, in turn, activates TRPV1 on C-fiber nerve endings resulting in depolarization of nerves and consequent vasoactive neuropeptide release. These findings identify a novel mechanism contributing to Bayliss' myogenic constriction and highlights an alternative pathway that may be targeted in the therapeutics of vascular disease, such as hypertension, where enhanced myogenic constriction plays a role in the pathogenesis.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Capsaicin; Cation Transport Proteins; CHO Cells; Cricetinae; Endothelium, Vascular; Gadolinium; Ganglia, Sympathetic; Guanethidine; Hydroxyeicosatetraenoic Acids; Ion Channels; Male; Mesenteric Arteries; Mice; Mice, Knockout; Models, Cardiovascular; Models, Neurological; Nerve Fibers, Unmyelinated; Nociceptors; Peptides, Cyclic; Piperidines; Pressure; Quinuclidines; Rats; Rats, Sprague-Dawley; Receptors, Neurokinin-1; Ruthenium Red; Sodium Channel Blockers; Splanchnic Circulation; Stress, Mechanical; Sympathectomy, Chemical; Tetrodotoxin; TRPV Cation Channels; Vascular Resistance; Vasoconstriction

1. The effects of the endocannabinoid, anandamide, and its metabolically stable analogue, methanandamide, on induced tone were examined in sheep coronary artery rings in vitro. 2. In endothelium-intact rings precontracted to the thromboxane A(2) mimetic, U46619, anandamide (0.01 - 30 microM) induced slowly developing concentration-dependent relaxations (pEC(50) [negative log of EC(50)]=6.1+/-0.1; R(max) [maximum response]=81+/-4%). Endothelium denudation caused a 10 fold rightward shift of the anandamide concentration-relaxation curve without modifying R(max). Methanandamide was without effect on U46619-induced tone. 3. The anandamide-induced relaxation was unaffected by the cannabinoid receptor antagonist, SR 141716A (3 microM), the vanilloid receptor antagonist, capsazepine (3 and 10 microM) or the nitric oxide synthase inhibitor, L-NAME (100 microM). 4. The cyclo-oxygenase inhibitor, indomethacin (3 and 10 microM) and the anandamide amidohydrolase inhibitor, PMSF (70 and 200 microM), markedly attenuated the anandamide response. The anandamide transport inhibitor, AM 404 (10 and 30 microM), shifted the anandamide concentration-response curve to the right. 5. Precontraction of endothelium-intact rings with 25 mM KCl attenuated the anandamide-induced relaxations (R(max)=7+/-7%), as did K(+) channel blockade with tetraethylammonium (TEA; 3 microM) or iberiotoxin (100 nM). Blockade of small conductance, Ca(2+)-activated K(+) channels, delayed rectifier K(+) channels, K(ATP) channels or inward rectifier K(+) channels was without effect. 6. These data suggest that the relaxant effects of anandamide in sheep coronary arteries are mediated in part via the endothelium and result from the cellular uptake and conversion of anandamide to a vasodilatory prostanoid. This, in turn, causes vasorelaxation, in part, by opening potassium channels.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 4-Aminopyridine; Animals; Apamin; Arachidonic Acid; Arachidonic Acids; Barium; Calcium Channel Blockers; Cannabinoid Receptor Modulators; Cannabinoids; Capsaicin; Coronary Vessels; Cytochrome P-450 Enzyme Inhibitors; Dose-Response Relationship, Drug; Endocannabinoids; Endothelium, Vascular; Enzyme Inhibitors; Fatty Acids, Unsaturated; Glyburide; In Vitro Techniques; Indomethacin; Miconazole; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Peptides; Phenylmethylsulfonyl Fluoride; Piperidines; Polyunsaturated Alkamides; Potassium; Potassium Channel Blockers; Potassium Channels; Pyrazoles; Receptors, Drug; Rimonabant; Sheep; Tetraethylammonium; Vasoconstrictor Agents; Vasodilation