*2.5. Astaxanthin Exhibited Enhancing Effects on Antioxidant Enzyme Activities in LPS-Induced DCs and LPS-Challenged Mice*

The cells are equipped with a variety of antioxidants, such as glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD), which served to counterbalance the effect of oxidants [28]. Therefore, we evaluated the effects of astaxanthin on the activities of antioxidative enzymes (GPx, CAT, and SOD) in LPS-induced DCs. As shown in Figure 6A–C, LPS destroyed the antioxidant system of DCs through decreases in GPx, CAT, and SOD activity. Surprisingly, astaxanthin possessed the ability to increase the activities of these antioxidative enzymes in a dose-dependent manner. Meanwhile, the activities of serum GPx, CAT, and SOD were also detected in LPS-challenged mice. As expected, the administration of astaxanthin remarkably upregulated the serum GPx, CAT, and SOD activities in LPS-challenged mice (Figure 6D–F). Collectively, these results indicated that astaxanthin strongly elevated the activities of the antioxidant enzymes in LPS-induced DCs and LPS-challenged mice.

**Figure 6.** Astaxanthin enhanced the activities of antioxidant enzymes in LPS-induced DCs and LPSchallenged mice. (**A**–**C**) DCs were incubated with the indicated concentrations of astaxanthin and LPS (100 ng/mL) for 24 h. (**D**–**F**) C57BL/6 mice were orally given astaxanthin before LPS injection. Serum was sampled at 4 h after LPS injection. The levels of GPx, CAT, and SOD in the lysate of DCs or serum were measured as described in the Materials and Methods section. Results are from one representative experiment of three performed. Data are presented as means ± SD. The comparisons were performed with analysis of variance (ANOVA) (multiple groups). Different lowercase letters indicate significant differences between groups (*p* < 0.05).
