Effects of superoxide on signaling pathways in smooth muscle cells from rats.
The effects of hypoxanthine and xanthine oxidase-induced superoxide anion were evaluated on various signal transduction pathways in aortic smooth muscle cells (SMCs) from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Superoxide increased inositol 1,4,5-tris-phosphate (IP(3)) formation in a concentration- and time-dependent manner in both strains but more markedly in SMCs from SHR. Various antioxidants significantly decreased the superoxide-induced IP(3) formation in both strains. In addition, tyrosine kinase inhibitors, genistein and tyrphostin A25, inhibited the superoxide-induced IP(3) formation more markedly in SHR than in WKY. Moreover, superoxide decreased the basal level of cGMP to a greater extent in SHR and also suppressed the rise in cGMP induced by S-nitroso-N-acetylpenicillamine. In addition, the superoxide-induced increase in IP(3) formation was significantly inhibited by guanylyl cyclase stimulator S-nitroso-N-acetylpenicillamine but was potentiated by ODQ (a guanylyl cyclase inhibitor, 1H-[1,2,4]oxadiazolo[4, 3-a]quinoxalin-1-one) and KT5823 (a cGMP-dependent protein kinase inhibitor), with a greater effect in SHR. Finally, the superoxide-enhanced IP(3) formation was not accompanied by simultaneous changes in cAMP levels, and inhibition of the adenylyl cyclase pathway did not modify the superoxide-induced IP(3) formation. Our results thus demonstrate a stimulatory effect of superoxide on IP(3) formation, mediated by the tyrosine kinase-coupled phospholipase C(gamma) activity, and an inhibitory effect of superoxide on cGMP formation in vascular SMCs. The increased reactivity of the phospholipase C pathway and the decreased cross inhibition of the IP(3) pathway by cGMP in the presence of superoxide may underlie the altered functions of vascular SMCs in SHR.
Wu
L
L
Groupe de Recherche sur le Système Nerveux Autonome, Faculty of Medicine, Université de Montréal, Montreal, Quebec, Canada.
de Champlain
J
J
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001011:Aorta; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000503:physiopathology*; D019271:Hypoxanthine / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013481:Superoxides / Q000378:metabolism* / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000378:metabolism
D000975:Antioxidants; D004791:Enzyme Inhibitors; C110881:S-nitro-N-acetylpenicillamine; D013481:Superoxides; D019271:Hypoxanthine; D015544:Inositol 1,4,5-Trisphosphate; D000242:Cyclic AMP; D014969:Xanthine Oxidase; D011505:Protein-Tyrosine Kinases; D010396:Penicillamine; D006152:Cyclic GMP