Although it is well known that systemic oxidative stress increases with age, the sources and mechanisms contributing to aging induced increase in oxidative stress remain unclear. Recent findings in animals indicate that peripheral blood mononuclear cells (PBMCs) are a major source of systemic oxidative stress via stimulation of the angiotensin II type 1 receptor (AT1R)‐NADPH oxidase pathway. Thus, to better understand this pathway and its potential contribution to increased oxidative stress with age, PBMCs were isolated from whole blood in healthy recreationally active older (61 ± 2 years, n=5) and younger men (25 ± 2 years, n=7). Intracellular superoxide production was measured using dihydroethidium fluorescence and NADPH oxidase subunits (gp91phox, p22phox, and p67phox) and superoxide dismutase 1 and 2 (SOD1 and SOD2) mRNA expression was measured using real time RT‐PCR. Interestingly, intracellular superoxide production was similar between groups (2 ± 0.4 older vs. 2 ± 0.3 young, Relative Fluorescence Units; P>;0.05). Likewise, gp91phox and p22phox were not different between groups, whereas p67phox was actually significantly lower in older subjects. Aging did not influence SOD2 mRNA expression, while SOD1 expression was lower in older subjects. These preliminary findings suggest that PBMCs may not be a primary source of systemic oxidative stress in healthy older individuals.Supported by NIH Grant R01 HL093167
Previous work suggests that elevations in oxidative stress are associated with cardiovascular disease. Although it is well known that oxidative stress increases with age, whether this occurs differently in men and women remains unclear. Likewise, recent work indicating that mRNA expression for NADPH oxidase is greater in peripheral blood mononuclear cells (PBMCs) of older subjects did not differentiate sex effects. Therefore, we measured plasma and intracellular levels of superoxide (O2●‐), along with PBMC expression of NADPH oxidase subunits in 12 healthy older post‐menopausal women and 10 age‐matched older men. Older men demonstrated greater plasma O2●‐ levels (lucigenin chemiluminescence; men 202.73 ± 9.28 vs. women 171.67 ± 7.72, Relative Light Units; P<0.05) as well as intracellular O2●‐ in PBMCs (dihydroethidium fluorescence; men 1.94 ± 0.20 vs. women 0.96 ± 0.14, Relative Fluorescence Units; P<0.05) compared to older women. Similarly, western blot analysis demonstrated that older men exhibit greater NADPH oxidase subunit protein expression for gp91phox, p22phox, and p47phox in PBMCs (e.g., gp91phox; men 1.48 ± 0.38 vs. women 0.31 ± 0.07; P<0.05) and p67phox tended to be higher (P=0.14). These preliminary findings suggest that systemic O2●‐ levels are greater in older men compared to older women and PBMC‐derived O2●‐ production via NADPH oxidase is a likely contributing source.
Grant Funding Source: Supported by NIH R01 HL093167
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