Astaxanthin ameliorates ferric nitrilotriacetate-induced renal oxidative injury in rats

Abstract

Daily intake of vegetables can reduce the risk of cancer and lifestyle-related diseases. However, supplementary intake of β-carotene alone has been reported to increase the risk of lung cancer in male cigarette smokers and people who were exposed to asbestos. The mechanism of the antioxidative properties of carotenoids in vivo, especially under oxidative stress conditions, still remains unclear. To investigate the antioxidant properties of dietary compounds, we examined the effects of chemically modified astaxanthin (Ax-C-8) using a rat model of ferric nitrilotriacetate (Fe-NTA)-induced renal oxidative injury. Ax-C-8 demonstrated lethally toxic effects on the rats in a dose-dependent manner. Following supplementation with Ax-C-8 (0.02%, w/w) for 30 days, the rats were euthanized 1, 4 and 24 h after injection of Fe-NTA. After 4 h, Ax-C-8 pretreatment suppressed the elevation of creatinine and blood urea nitrogen and protected the rats from renal tubular necrosis and the formation of 4-hydroxy-2-nonenal-modified proteins. After 24 h, pretreatment with Ax-C-8 maintained the renal antioxidant enzyme levels and renal tubules. Here, we demonstrate the antioxidant effects of Ax-C-8 against Fe-NTA-induced oxidative injury in rats receiving a regular diet. These data suggest that dietary intake of astaxanthin may be useful for the prevention of renal tubular oxidative damage.

Keywords: astaxanthin; ferric nitrilotriacetate; oxidative stress; vitamin E.

Fig. 1

Treatment with astaxanthin C-8 (Ax-C-8) maintained renal function and antioxidant enzyme levels after ferric nitrilotriacetate (Fe-NTA)-induced oxidative injury. (A) Serum creatinine: Fe-NTA 4 h and 24 h, (B) serum BUN: Fe-NTA 4 h and 24 h. Protective effects of Ax-C-8 were observed, especially in the Fe-NTA 24 h group. (C) GSH peroxidase, (D) GSH reducase, (E) catalase. Attenuation of Fe-NTA-induced renal oxidative damage was observed in the Ax-C-8-treated group (ANOVA, p<0.0001, for a–e; ^#p<0.05 vs vehicle; *p<0.05; **p<0.01 vs vehicle + Fe-NTA and ***p<0.001 vs vehicle + Fe-NTA).

Fig. 2

Astaxanthin C-8 (Ax-C-8) suppressed renal tubular necrosis and the formation of 4-hydroxy-2-nonenal (HNE)-modified proteins after Fe-NTA-induced oxidative injury in regular diet. Representative images are shown. (A) H&E staining of the vehicle, vehicle + Fe-NTA 4 h and Ax-C-8 + Fe-NTA 4 h groups. Many necrotic tubules were observed in the vehicle + Fe-NTA group, and Ax-C-8 suppressed the formation of necrotic tubules. (B) Immunohistochemical staining of HNE in the vehicle, vehicle + Fe-NTA 4 h and Ax-C-8 + Fe-NTA 4 h groups. HNE immunostaining revealed the accumulation of oxidatively modified proteins. Whereas no HNE-positive tubules were observed in the vehicle group, many tubules were positive (indicated by arrow head) in the Fe-NTA group. The levels of positive tubules were obviously decreased in the Ax-C-8 treated rats. (C) H&E staining of the vehicle, vehicle + Fe-NTA 24 h and Ax-C-8 + Fe-NTA 24 h groups. Fe-NTA destroyed the proximal tubules. However, pretreatment with Ax-C-8 protected against oxidative injury (bar, 50 µm).

Fig. 3

Astaxanthin C-8 (Ax-C-8) accelerated lethal injury mediated by Fe-NTA in Vitamin E (VE)-deficient conditions. (A) Survival curve of rats that received pretreatment with different concentrations of Ax-C-8 and a VE-deficient diet. Fe-NTA induced death in an Ax-C-8 dose-dependent manner (^#p<0.05 vs vehicle; *p<0.05 vs vehicle + Fe-NTA for the log-rank test). (B) The body weights were decreased with repeated injections of Fe-NTA. Significant differences in body weights were not observed between the vehicle + Fe-NTA and Ax-C-8 + Fe-NTA groups. Fe-NTA induced massive diarrhea in the rats that were pretreated with Ax-C-8. (C) Microscopic examinations revealed intra-pleural and submucosal calcifications in the digestive tracts (bar, 50 µm).