Gender differences in age-related endothelial function in the murine aorta

We investigated differences in aortic endothelial function among young (5 months) and old (20 months) male or female mice. Aortas isolated from male-old mice exhibited: (a) impaired relaxation to both acetylcholine (ACh) (P < 0.01 vs. male-young or female-old) and A23187 (P < 0.01 vs. male-young; P < 0.001 vs. female-old), but unimpaired relaxation to sodium nitroprusside, and (b) increased superoxide generation (indicated by NBT reduction) (P < 0.001 vs. male-young; P < 0.01 vs. female-old) and increased 3-nitrotyrosine expression (marker for ONOO−) (P < 0.01 vs. male-young or female-old). The protein expression of gp91phox, an NAD(P)H oxidase subunit, was upregulated in aortas from old mice (vs. young ones of the same gender) (males P < 0.01; females P < 0.05). The plasma adiponectin level (P < 0.001) and the aortic Cu/Zn-SOD and EC-SOD protein expressions (each, P < 0.01) were increased in females (vs. age-matched males). Aortic total SOD activities were lower in male-old than in either male-young (P < 0.01) or female-old (P < 0.001) mice. In aortas from male-young, female-young, and female-old mice, NADH [NAD(P)H oxidase substrate] and diethyldithiocarbamate (DDC; a SOD inhibitor) (whether applied alone or together) reduced ACh-induced endothelium-dependent relaxation (P < 0.01 or P < 0.001) and increased ACh-induced superoxide generation (P < 0.05 or P < 0.001). Tempol (a SOD mimetic) enhanced ACh-induced relaxation (P < 0.05) and reduced ACh-induced superoxide generation (P < 0.01) only in male-old aortas. These results suggest: (i) the impaired endothelium-dependent aortic relaxation in male-old mice is due to enhanced superoxide production via NADPH oxidase, and (ii) the relative preservation of endothelial function in female-old aortas may be due to enhanced superoxide scavenging (via increases in Cu/Zn-SOD and EC-SOD proteins and total SOD activity).