Impact Of Cigarette Smoke On No Bioavailability In Endothelial Cells: Role Of Vascular NADPH Oxidase
Presented at 78TH EUROPEAN ATHEROSCLEROSIS SOCIETY CONGRESS
* This author is not affiliated with PMI.
Cigarette smoking has been shown to cause endothelial dysfunction, one of the earliest steps in the development of atherosclerosis, that is characterized by a reduced synthesis and/or enhanced inactivation of vasoprotective nitric oxide (NO) produced by endothelial NO synthase (eNOS). To better understand the mechanisms involved, we investigated human umbilical vein endothelial cells (HUVECs) treated with cigarette smoke (CS) bubbled through phosphate buffered saline for no levels, by determining nitrite (NO2-), and for NO bioavailability, by measuring the activity of arginase1, a co-competitor of eNOS for arginine. In addition, superoxide (O2-) and 3-nitrotyrosine were determined to estimate the potential formation of peroxynitrite. Treatment with CS resulted in (i) reduced levels of NO2-, (ii) increased levels of O2- and 3-nitrotyrosine, and (iii) enhanced arginase 1 activity. Treatment with the NADPH oxidase inhibitor apocynin and the xanthine oxidase inhibitor allopurinol diminished the increase of O2- production. Moreover, in ex vivo experiments, both inhibitors prevented the CS-dependent impairment of vasorelaxation of rat aortic rings treated with acetylcholine. From this, we conclude that CS activates NADPH oxidase and xanthine oxidase, resulting in enhanced production of O2-, which consumes NO to form peroxynitrite. Furthermore, we speculate that the CS-induced arginase activity results in diminished l-arginine availability to eNOS. Both mechanisms may contribute to a decreased bioavailabilty of vasoprotective NO and thereby may be involved in the CS-induced development of atherosclerosis.