Poster abstracts

Poster number 1 submitted by Tamer Abdelghany

Chronic Cigarette Smoke Exposure Impairs Vascular Endothelial Function through Leukocyte Infiltration and Alterations in Endothelial NO Synthase

Tamer M. Abdelghany (Internal Medicine), Mohamed A. El-Mahdy PhD. (Internal Medicine), Craig Hemann (Internal Medicine), Saradhadevi Varadharaj PhD. (Internal Medicine), Ahmed Esmat (Internal Medicine), Gamal A. El-Sherbiny PhD. (Internal Medicine)

Abstract:
A strong association between cigarette smoke exposure (CSE) and vascular endothelial dysfunction (VED) has been established; however, the precise mechanisms warrant more investigation. The aim of this study is to investigate the mechanism of CSE-induced VED. C57BL/6 male mice were exposed for periods of up to 48 weeks to cigarette smoke generated from 3R4F reference research cigarettes using the Teague TE-10 smoking machine. CSE impaired acetylcholine (Ach)-induced endothelial-dependent relaxation of thoracic aorta segments and triggered persistent hypertension. A significant shift to the right and downward in the Ach-concentration endothelial-dependent relaxation response curve was observed in CSE mice. Mean arterial blood pressure (BP) of CSE-mice significantly increased at 32 weeks of exposure, reaching 121.5±5.7 mmHg compared to 99.3 ± 4.5 mmHg in controls. This difference in BP was further increased at 48 weeks of exposure, reaching to 135.3±5.2 mmHg compared 102± 6.3 mmHg in controls. H&E stained aortic sections showed evidence of Macrophage infiltration in CSE-mice. NAD(P)H oxidase subunits p22phox and gp91phox expression increased in aortas of CSE-mice, as early as 16 weeks of CSE, with concomitant superoxide production. Tetrahydrobiopterin (BH4) was depleted in SHS-exposed mice but not in non-exposed controls resulting in endothelial NO synthase (eNOS) uncoupling. SHS-exposed mice showed a 3- and 4-fold decrease of BH4 level at 32 and 48 weeks of SHSE, respectively. Western blotting and immunohistochemistry showed a decrease in eNOS expression in aortas from SHS-exposed mice compared to controls. A time dependent decrease in phosphorylation of eNOS and Akt was also observed in response to SHSE. Our data suggest that SHSE induces leukocyte infiltration that triggered NAD(P)H oxidase overexpresion and ROS generation which led to depletion of BH4 and eNOS uncoupling, resulting in VED and hypertension. Overall, our study provides important insights toward understanding contributions of SHSE to the genesis of cardiovascular disease.

Keywords: Cigarette smoking, Endothelial dysfunction, Reactive OxygenSpecies