Abstract 612: ACE2-Independent Sex Differences In Oxidative Stress

Abstract

Many of the pathophysiological effects of angiotensin II (Ang II) are attributed to its stimulation of NADPH oxidases and the consequent production of reactive oxygen species. Female sex has generally lower cardiovascular morbidity and is also less susceptible to kidney injury than males. The basis of these phenomena is not well understood but it is possible that sex-differential regulation of oxidative stress through activation of the RAS and its key effector, Ang II, plays an important contributor role. Here we hypothesized that Ang II levels are higher in male mice and that this is associated with sex-differences in kidney levels of ACE2, an Ang II-degrading enzyme abundantly expressed in the kidney. Parameters of oxidative stress such as, NADPH oxidase activity and malondialdehyde levels (MDA) were measured in kidneys from female and age-matched male C57BL6 mice. At 40 weeks of age, NADPH oxidase activity (p<0.01) and MDA levels (p<0.05) were significantly lower in female than in male mice. Female mice had lower kidney levels of the pro-oxidant peptide, Ang II (0.94±0.19 vs. 1.66±0.17 fmol/mg total protein, p<0.05, respectively). The difference in kidney Ang II levels between females and males was also observed in the face of complete ACE2 genetic deficiency (1.08±0.16 vs 1.97±0.25 fmol/mg total protein, p<0.05, respectively). Consistent with kidney Ang II levels, urinary Ang II levels measured in urines from female WT mice were also significantly lower than in male WT mice (23.6±2.2 vs. 47.9±8.8 pg/mg creatinine, p<0.05) despite significantly higher levels of urinary ACE2 activity in male mice as compared to female mice (7.0±0.5 vs. 3.6±0.3, p<0.01, respectively). Female mice have lower basal levels of kidney oxidative stress than males and exhibit lower levels of kidney and urinary Ang II. The mechanism involved in sex differences in the levels of kidney and urine Ang II does not appear to depend on ACE2.