Mitochondrial respiration and redox protein expression in peripheral blood mononuclear cells from Non‐Hispanic Black and White Males

Abstract

Background Non-Hispanic Black (NHB) adults exhibit a higher prevalence of cardiovascular disease (CVD) compared to Non-Hispanic White (NHW) adults. Vascular oxidative stress may be one contributing factor in these racial disparities. Peripheral blood mononuclear cells (PBMCs) are primary contributors to systemic oxidative stress and there are documented racial disparities in the PBMC-derived reactive oxygen species (ROS) production. However, it is unclear if the racial differences in PBMC-derived ROS is associated with alterations in mitochondrial function. Therefore, the purpose of this study was to investigate potential racial differences in cellular metabolism and redox protein expression in PBMCs from NHW and NHB adults. Methods Commercial PBMCs (n=10 cell lines; 5 NHW & 5 NHB males) were cultured 14-18 hours prior to cell respiration and protein harvest. Basal and maximal respiration were measured using a Clark electrode (Oxytherm, Hanstech) and then calculated coupling efficiency and leak respiration. Western blotting was used to measure protein expression for the antioxidant proteins: superoxide dismutase (SOD) isoforms 1 and 2, as well as the acetylated (i.e., inactivated) SOD2 (AcSOD2) and the NAD-dependent deacetylase sirtuin-3 (Sirt3). The pro-oxidant complex NADPH oxidase subunits p47phox and gp91phox were also assessed. Welch unpaired t-tests were used to assess the racial differences in respiration measures and independent t-tests were used for protein expression. Results For the respiration measures, NHW had significantly higher levels of basal respiration (Fig. 1A, p=0.048) and leak respiration (Fig. 1D, p=0.016), while having a lower coupling efficiency (Fig. 1C, p=0.003). There was no difference in maximal respiration (Fig. 1B, p=0.188). No baseline racial differences were found in PBMC expression for the redox regulating proteins: SOD1 (Fig. 2A, p=0.42), SOD2 (Fig. 2B, p=0.40), AcSOD2 (Fig. 2C, p=0.45), Sirt3 (Fig. 2D, p=0.45), p47phox (Fig 3A, p=0.23), or gp91phox (Fig. 3B, p=0.86). Conclusion The lower coupling efficiency and higher leak respiration in PBMCs from NHW may be beneficial in decreasing ROS production and overall oxidative damage. While we found no racial differences in the redox regulating proteins, additional data are needed, particularly in PBMCs from female participants.