NAD(P)H oxidase-dependent intracellular and extracellular O2•− production in coronary arterial myocytes from CD38 knockout mice

Abstract Activation of NAD(P)H oxidase has been reported to produce superoxide (O 2 •− ) extracellularly as an autocrine/paracrine regulator or intracellularly as a signaling messenger in a variety of mammalian cells. However, it remains unknown how the activity of NAD(P)H oxidase is regulated in arterial myocytes. Recently, CD38-associated ADP-ribosylcyclase has been reported to use an NAD(P)H oxidase product, NAD + or NADP + , to produce cyclic ADP-ribose (cADPR) or nicotinic acid adenine dinucleotide phosphate, which mediates intracellular Ca 2 + signaling. This study was designed to test a hypothesis that the CD38/cADPR pathway as a downstream event exerts feedback regulatory action on the NAD(P)H oxidase activity in production of extra- or intracellular O 2 •− in mouse coronary arterial myocytes (CAMs). By fluorescence microscopic imaging, we simultaneously monitored extra- and intracellular O 2 •− production in wild-type (CD38 +/+ ) and CD38 knockout (CD38 −/− ) CAMs in response to oxotremorine (OXO), a muscarinic type 1 receptor agonist. It was found that CD38 deficiency prevented OXO-induced intracellular but not extracellular O 2 •− production in CAMs. Consistently, the OXO-induced intracellular O 2 •− production was markedly inhibited by CD38 shRNA or the CD38 inhibitor nicotinamide in CD38 +/+ CAMs. Further, Nox4 siRNA inhibited OXO-induced intracellular but not extracellular O 2 •− production, whereas Nox1 siRNA attenuated both intracellular and extracellular O 2 •− production in CD38 +/+ CAMs. Direct delivery of exogenous cADPR into CAMs markedly elevated intracellular Ca 2 + and O 2 •− production in CD38 −/− CAMs. Functionally, CD38 deficiency or Nox1 siRNA and Nox4 siRNA prevented OXO-induced contraction in isolated perfused coronary arteries in CD38 WT mice. These results provide direct evidence that the CD38/cADPR pathway is an important controller of Nox4-mediated intracellular O 2 •− production and that CD38-dependent intracellular O 2 •− production is augmented in an autocrine manner by CD38-independent Nox1-derived extracellular O 2 •− production in CAMs.