Role of NADPH oxidase in A3 adenosine receptor‐mediated contraction using knockout mouse aorta

Abstract

Earlier we have reported that A3 adenosine receptor (A3AR) mediated endothelial‐contraction is via COX‐1 pathway in mouse aorta (Ansari et al Am J Physiol Heart Circ Physiol. 2007, 293:H3448‐55). In this study, we investigated signaling pathways coupled to A3AR activation using, Cl‐IBMECA in A3KO mouse aorta with apocynin (NADPH oxidase inhibitor) and PD98059 (p42/p44 MAP kinase inhibitor). We found that; a) treatment of aortic rings with Cl‐IBMECA resulted in NADPH oxidase subunits (gp91 & p47 phox) activation, p42/p44 MAP kinase phosphorylation and contraction, and b) preincubation of tissues with apocynin, PEG‐superoxide dismutase+PEG‐catalase and PD98059 inhibited A3AR‐induced aortic contraction significantly (p<.05). Cl‐IBMECA increased the ROS generation by 150±15% over control in WT which was inhibited by apocynin. In WT tissues, gp91 and p47 phox expressions were increased by 163±45% and 183±36%, respectively over control by Cl‐IBMECA which was blocked by apocynin. Cl‐IBMECA also increased p42/p44 MAP kinase phosphorylation by 116±42% over control and it was inhibited by PD98059 in WT. We conclude that Cl‐IBMECA leads to NADPH oxidase activation, ROS generation, p42/p44 MAP kinase phosphorylation which may play a role in A3AR‐mediated aortic contraction. Supported by HL‐027339, HL094447 and HL07180.