Age-related changes in renal expression of oxidant and antioxidant enzymes and oxidative stress markers in male SHR and WKY rats

Oxidative stress has been hypothesized to play a role in aging and age-related disorders, such as hypertension. This study compared levels of oxidative stress and renal expression of oxidant and antioxidant enzymes in male normotensive Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR) at different ages (3 and 12 months). In the renal cortex of 3-month old SHR increases in hydrogen peroxide (H2O2) were accompanied by augmented expression of NADPH oxidase subunit Nox4 and decreased expression of antioxidant enzymes SOD1 and SOD3. A further increase in renal H2O2 production and urinary TBARS was observed in 12-month old WKY and SHR as compared with 3-month old rats. Similarly, expressions of NADPH oxidase subunit p22phox, SOD2 and SOD3 were markedly elevated with age in both strains. When compared with age-matched WKY, catalase expression was increased in 3-month old SHR, but unchanged in 12-month old SHR. Body weight increased with aging in both rat strains, but this increase was more pronounced in WKY. In conclusion, renal oxidative stress in 12-month old SHR is an exaggeration of the process already observed in the 3-month old SHR, whereas the occurrence of obesity in 12-month old normotensive rats may partially be responsible for the age-related increase in oxidative stress.

Research Highlights
► Young SHR show mild oxidative stress levels.
► Both aged WKY and SHR display high levels of oxidative stress.
► Expression of some oxidant and antioxidant enzymes is upregulated in old rats.
► Normotensive WKY become obese with aging.