Enhanced production and action of cyclic ADP–ribose during oxidative stress in small bovine coronary arterial smooth muscle

Abstract

Recent studies in our lab and by others have indicated that cyclic ADP–ribose (cADPR) as a novel second messenger is importantly involved in vasomotor response in various vascular beds. However, the mechanism regulating cADPR production and actions remains poorly understood. The present study determined whether changes in redox status influence the production and action of cADPR in coronary arterial smooth muscle cells (CASMCs) and thereby alters vascular tone in these arteries. HPLC analyses demonstrated that xanthine (X, 40 μM)/xanthine oxidase (XO, 0.1 U/ml), a superoxide-generating system, increased the ADP–ribosyl cyclase activity by 59% in freshly isolated bovine CASMCs. However, hydrogen peroxide (H 2O 2, 1–100 μM) had no significant effect on ADP–ribosyl cyclase activity. In these CASMCs, X/XO produced a rapid increase in [Ca 2+] i (Δ[Ca 2+] i = 201 nM), which was significantly attenuated by a cADPR antagonist, 8-Br-cADPR. Both inhibition of cADPR production by nicotinamide (Nicot) and blockade of Ca 2+-induced Ca 2+ release (CICR) by tetracaine (TC) and ryanodine (Rya) significantly reduced X/XO-induced rapid Ca 2+ responses. In isolated, perfused, and pressurized small bovine coronary arteries, X at 2.5–80 μM with a fixed XO level produced a concentration-dependent vasoconstriction with a maximal decrease in arterial diameter of 45%. This X/XO-induced vasoconstriction was significantly attenuated by 8-Br-cADPR, Nicot, TC, or Rya. We conclude that superoxide activates cADPR production, and thereby mobilizes intracellular Ca 2+ from the SR and produces vasoconstriction in coronary arteries.