Autocrine Action of NAD(P)H Oxidase‐Derived Extracellular Superoxide in Coronary Arterial Myocytes

Abstract

Our recent studies have indicated that there is an autocrine/paracrine pattern of superoxide production through NAD(P)H oxidase in coronary arterial myocytes (CAMs). The present study determined whether extracellular O2·− could serve as an autocrine factor to activate intracellular Ca2+ signaling pathway and explored related underlying mechanisms. Using a newly established dual fluorescence microscopic imaging technique, We found that M1-receptor agonist oxotremorine (Oxo) simultaneously increased the extracellular O2·− production and [Ca2+]i,, which were significantly attenuated by addition of superoxide dismutase (SOD) and catalase into the bath solution. NAD(P)H oxidase inhibitor, apocynin also inhibited this response of CAMs to Oxo. When ADP-ribosyl cyclase inhibitor - nicotinamide, RyR/Ca2+release channel antagonists - ryanodine or cADPR antagonist - 8-Br-cADPR was added into the bath solution, Oxo-induced increase in [Ca2+]i was abolished, while extracellular O2·− production remained. Furthermore, introduction of cADPR into CAMs by ultrasound microbubbles increased [Ca2+]i,,but it had no effect on extracellular O2·− production. These results provide direct evidence that extracellular O2·− derived from NAD(P)H oxidase contributes to Ca2+activation of CAMs through its autocrine action on cADPR signaling pathway (Supported by NIH grants HL057244 and HL075316).