Abstract 1432: Nitric Oxide Bioavailability is Lower in Endothelium of Healthy Mexican American Donors as Compared to Non-Hispanic White Donors: Effect of Nebivolol

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Background: Epidemiologic studies indicate that Mexican Americans (MA) have a higher prevalence of CV risk factors and disease as compared with non-Hispanic whites (NHW). This increase in CV risk may be due, in part, to differences in endothelial function. In this study, we measured endothelial function in cells from normotensive, age-matched MA and NHW donors, as well as the effects of treatment with nebivolol, a new β 1 -selective blocker with vasodilating properties. Methods: Endothelial nitric oxide (NO) and peroxynitrite (ONOO − ) release in human umbilical vein endothelial cells (HUVECs) from age-matched MA and NHW donors were measured simultaneously using a nanosensor array. The effects of nebivolol on NO and ONOO − release were evaluated following pretreatment (24 h) with a calcium ionophore (CaI) as a receptor-independent stimulus. Endothelial NO synthase (eNOS) levels were measured by Western blot analysis, and drug-membrane interactions were determined by small angle x-ray diffraction approaches. Results: NO bioavailability in endothelial cells of MA donors was 30% lower than that of cells from NHW donors (383 ± 10 nM versus 543 ± 8 nM, n=6) following stimulation with CaI (1.0 μM). Pretreatment with nebivolol (1.0 μM) eliminated these interracial differences and enhanced NO release disproportionately in MA cells (57%) versus NHW cells (20%). Nebivolol also reduced ONOO − levels in MA endothelium by 75% (746 ± 12 nM to 195 ± 10 nM) and by 50% in NHW cells (416 ± 7 nM to 191 ± 13 nM). The ratio of NO to ONOO − , an indicator of eNOS coupling, increased more than 5-fold in MA cells following nebivolol treatment. In addition, eNOS levels were 40% lower in MA endothelium compared to NHW, but increased 2-fold with nebivolol treatment. These effects were not observed with atenolol, a hydrophilic β 1 -selective antagonist. Conclusion: We observed differences between Mexican Americans and non-Hispanic whites in endothelial NO bioavailability and nitroxidative stress–factors that may contribute to increased CV risk. Treatment with nebivolol, but not atenolol, enhanced both the expression and coupling efficiency of eNOS in Mexican American endothelium.