Raspberry Increases Expression of Antioxidant Enzymes in the Kidney of Angiotensin II-Treated Rats

Abstract

Abstract Objectives To examine whether dietary supplementation with raspberries attenuates angiotensin (Ang) II-induced oxidative stress in the kidneys of rats. Methods Eight-week-old male Sprague-Dawley rats were fed an AIN-93M diet (control and Ang II groups) or AIN-93M diet supplemented with 10% w/w freeze-dried raspberry (RB + Ang II) for seven weeks. At week 4, rats were implanted with subcutaneous osmotic minipumps that delivered 0.9% saline (control) or Ang II (270 ng/kg body weight/day) for an additional three weeks. Protein expression of antioxidant enzymes, such as glutathione peroxidase 1 (GP × 1) and NADPH quinone dehydrogenase 1 (NQO1), as well as ERK1/2 phosphorylation were assessed by western blot in the kidneys. Results were analyzed using one-way ANOVA followed by Tukey-Kramer post hoc test. Data were normalized to control and are expressed as mean ± standard deviation. Results The expression of the antioxidant enzyme GP × 1 was significantly increased with raspberry supplementation (1.33 ± 0.24-fold, n = 9) in comparison to control (1.00 ± 0.18-fold, n = 9, P = 0.009) and Ang II alone (0.93 ± 0.24-fold, n = 9, P = 0.002). The expression of the antioxidant enzyme NQO1 was significantly increased with raspberry supplementation (2.10 ± 0.74-fold, n = 9) in comparison to control (1.00 ± 0.44-fold, n = 9, P = 0.0002) and Ang II alone (0.74 ± 0.16-fold, n = 9, P < 0.0001). Although not significantly, Ang II induced an increase in ERK1/2 phosphorylation in comparison to control (1.66 ± 0.45 vs 1.00 ± 0.88-fold, n = 5, P = 0.22). Nonetheless, raspberry supplementation (0.62 ± 0.22-fold, n = 5, P = 0.02) was able to attenuate ERK1/2 phosphorylation in comparison to Ang II alone. Conclusions Our findings indicate that supplementation with raspberry has the potential to significantly increase the expression of antioxidant enzymes in a model of Ang II-induced oxidative stress. Future work will focus on elucidating the mechanism through which raspberries elicit their action in the kidneys. Funding Sources This work was supported by the Agriculture and Food Research Initiative (grant no. 2019–67,017-29,257/project accession no. 1,018,642) from the USDA National Institute of Food and Agriculture.