Astaxanthin Provides Antioxidant Protection in LPS-Induced Dendritic Cells for Inflammatory Control.

Astaxanthin, originating from marine organisms, is a natural bioactive compound with powerful antioxidant activity. Here, we evaluated the antioxidant ability of astaxanthin on dendritic cells (DCs), a key target of immune regulation, for inflammatory control in a sepsis model. Our results showed that astaxanthin suppressed nitric oxide (NO) production, reactive oxygen species (ROS) production, and lipid peroxidation activities in LPS-induced DCs and LPS-challenged mice. Moreover, the reduced glutathione (GSH) levels and the GSH/GSSG ratio were increased, suggesting that astaxanthin elevated the level of cellular reductive status. Meanwhile, the activities of antioxidant enzymes, including glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD), were significantly upregulated. Astaxanthin also inhibited the LPS-induced secretions of IL-1ß, IL-17, and TGF-ß cytokines. Finally, we found that the expressions of heme oxygenase 1 (HO-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) were significantly upregulated by astaxanthin in LPS-induced DCs, suggesting that the HO-1/Nrf2 pathway plays a significant role in the suppression of oxidative stress. These results suggested that astaxanthin possesses strong antioxidant characteristics in DC-related inflammatory responses, which is expected to have potential as a method of sepsis treatment.

Astaxanthin Protects Dendritic Cells from Lipopolysaccharide-Induced Immune Dysfunction.

Astaxanthin, originating from seafood, is a naturally occurring red carotenoid pigment. Previous studies have focused on its antioxidant properties; however, whether astaxanthin possesses a desired anti-inflammatory characteristic to regulate the dendritic cells (DCs) for sepsis therapy remains unknown. Here, we explored the effects of astaxanthin on the immune functions of murine DCs. Our results showed that astaxanthin reduced the expressions of LPS-induced inflammatory cytokines (TNF-α, IL-6, and IL-10) and phenotypic markers (MHCII, CD40, CD80, and CD86) by DCs. Moreover, astaxanthin promoted the endocytosis levels in LPS-treated DCs, and hindered the LPS-induced migration of DCs via downregulating CCR7 expression, and then abrogated allogeneic T cell proliferation. Furthermore, we found that astaxanthin inhibited the immune dysfunction of DCs induced by LPS via the activation of the HO-1/Nrf2 axis. Finally, astaxanthin with oral administration remarkably enhanced the survival rate of LPS-challenged mice. These data showed a new approach of astaxanthin for potential sepsis treatment through avoiding the immune dysfunction of DCs.

Astaxanthin Inhibits p70 S6 Kinase 1 Activity to Sensitize Insulin Signaling.

Astaxanthin (AST) is a carotenoid with therapeutic values on hyperglycemia and diabetic complications. The mechanisms of action of AST remain incompletely understood. p70 S6 kinase 1 (S6K1) is a serine/threonine kinase that phosphorylates insulin receptor substrate 1 (IRS-1)S1101 and desensitizes the insulin receptor (IR). Our present study aims to determine if AST improves glucose metabolisms by targeting S6K1. Western blot analysis revealed that AST inhibited the phosphorylation of two S6K1 substrates, S6S235/236 and IRS-1S1101, but enhanced the phosphorylation of AKTT308, AKTS473, and S6K1T389 by feedback activation of the phosphatidylinositol-3 (PI-3) kinase in 3T3-L1 adipocytes and L6 myotubes. In vitro kinase assays revealed that AST inhibited S6K1 activity with an IC50 value of approximately 13.8 µM. AST increased insulin-induced IR tyrosine phosphorylation and IRS-1 binding to the p85 subunit of PI-3 kinase. Confocal microscopy revealed that AST increased the translocation of the glucose transporter 4 (GLUT4) to the plasma membrane in L6 cells. Glucose uptake assays using a fluorescent dye, 2-NBDG (2-N-(Nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose), revealed that AST increased glucose uptake in 3T3-L1 adipocytes and L6 myotubes under insulin resistance conditions. Our study identifies S6K1 as a previously unrecognized molecular target of AST and provides novel insights into the mechanisms of action of AST on IR sensitization.