capsazepine and 20-hydroxy-5-8-11-14-eicosatetraenoic-acid

Transient receptor potential vanilloid 1 (TRPV1) -positive sensory nerves are widely distributed in the kidney, suggesting that TRPV1-mediated action may participate in the regulation of renal function under pathophysiological conditions. Stimulation of TRPV1 channels protects against ischemia/reperfusion (I/R)-induced acute kidney injury (AKI). However, it is unknown whether inhibition of these channels is detrimental in AKI or not. We tested the role of TRPV1 channels in I/R-induced AKI by modulating these channels with capsaicin (TRPV1 agonist), capsazepine (TRPV1 antagonist) and using Trpv1-/- mice.. Anesthetized C57BL/6 mice were subjected to 25 min of renal ischemia and 24 hrs of reperfusion. Mice were pretreated with capsaicin (0.3 mg/kg body weight) or capsazepine (50 mg/kg body weight). Capsaicin ameliorated the outcome of AKI, as measured by serum creatinine levels, tubular damage,neutrophil gelatinase-associated lipocalin (NGAL) abundance and Ly-6B.2 positive polymorphonuclear inflammatory cells in injured kidneys. Neither capsazepine nor deficiency of TRPV1 did deteriorate renal function or histology after AKI. Measurements of endovanilloids in kidney tissue indicate that 20-hydroxyeicosatetraeonic acid (20-HETE) or epoxyeicosatrienoic acids (EETs) are unlikely involved in the beneficial effects of capsaicin on I/R-induced AKI.. Activation of TRPV1 channels ameliorates I/R-induced AKI, but inhibition of these channels does not affect the outcome of AKI. Our results may have clinical implications for long-term safety of renal denervation to treat resistant hypertension in man, with respect to the function of primary sensory nerves in the response of the kidney to ischemic stimuli.

Topics: Animals; Capsaicin; Eicosanoids; Hydroxyeicosatetraenoic Acids; Kidney; Mice; Mice, Inbred C57BL; Reperfusion Injury; TRPV Cation Channels

The aim of this study was to delineate the mode of action of 20-hydroxy-eicosatetraenoic acid (20-HETE) in airway smooth muscle (ASM) cells. ASM metabolizes arachidonic acid by various enzymatic pathways, including the cytochrome P-450 (CYP-450) omega-hydroxylase, which leads to the production of 20-HETE, a bronchoconstrictive eicosanoid. The present study demonstrated that 20-HETE induced concentration-dependent tonic responses in ASM, whereas transient responses were recorded in Ca2+-free solution, suggesting an intracellular Ca2+ release process. 20-HETE inotropic responses were abolished by 36 microM 2-aminoethoxydiphenyl borate or 1 microM thapsigargin but were insensitive to 10 microM ryanodine, indicating that inositol triphosphate receptors likely control the release of intracellular Ca2+. Sustained tension, which required Ca2+ entry, was partially blocked by 1 microM nifedipine (an L-type) and 100 microM Gd3+ (a nonselective cationic channel blocker). Moreover, in the absence of selective 20-HETE receptor antagonists, 20-HETE tonic responses were inhibited in a concentration-dependent manner (0.1-10 microM) by capsazepine, a well-characterized vanilloid receptor antagonist. Capsazepine was also observed to reverse cumulative responses to 20-HETE and capsaicin, a TRPV1 agonist. In addition, capsazepine pretreatment largely modified the sustained inotropic responses to 20-HETE, suggesting that 20-HETE cross-reacted with TRPV1 receptors with a low affinity (microM) or that its specific receptor was inhibited by the vanilloid antagonist. Data obtained using RHC-80267, ONO-RS-082, and eicosatetraynoic acid, respective inhibitors of diacylglycerol-lipase, phospholipase A2, and CYP-450 omega-hydroxylase, reveal that intracellular arachidonic acid production and its 20-HETE metabolite may be responsible for the activation of nonselective cationic channels and tonic responses.

Topics: 5,8,11,14-Eicosatetraynoic Acid; Animals; Bronchi; Calcium; Calcium Channels; Capsaicin; Cyclohexanones; Cytochrome P-450 CYP4A; Female; Guinea Pigs; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Intracellular Membranes; Lipoprotein Lipase; Male; Muscle Contraction; Muscle, Smooth; Protease Inhibitors; Receptors, Drug; Time Factors; Trachea

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