Capsazepine, a vanilloid antagonist, abolishes tonic responses induced by 20-HETE on guinea pig airway smooth muscle.
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.
Rousseau
E
E
Department of Physiology and Biophysics, Facluty of Medicine, Université de Sherbrooke, Sherbrooke, Quebec, Canada. Eric.Rousseau@USherbrooke.ca
Cloutier
Martin
M
Morin
Caroline
C
Proteau
Sonia
S
D015117:5,8,11,14-Eicosatetraynoic Acid / Q000494:pharmacology; D000818:Animals; D001980:Bronchi / Q000187:drug effects* / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D002211:Capsaicin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D003512:Cyclohexanones; D042926:Cytochrome P-450 CYP4A / Q000037:antagonists & inhibitors; D005260:Female; D006168:Guinea Pigs; D006893:Hydroxyeicosatetraenoic Acids / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D008071:Lipoprotein Lipase / Q000037:antagonists & inhibitors; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D011955:Receptors, Drug / Q000037:antagonists & inhibitors*; D013997:Time Factors; D014132:Trachea / Q000187:drug effects* / Q000378:metabolism
D015220:Calcium Channels; D003512:Cyclohexanones; D006893:Hydroxyeicosatetraenoic Acids; D011480:Protease Inhibitors; D011955:Receptors, Drug; D015117:5,8,11,14-Eicosatetraynoic Acid; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; C036535:1,6-bis(cyclohexyloximinocarbonyl)hexane; D042926:Cytochrome P-450 CYP4A; D008071:Lipoprotein Lipase; C071423:capsazepine; D002211:Capsaicin; D002118:Calcium