Increasing evidence indicates that environmental tobacco smoke (ETS) impairs cognitive function and induces oxidative stress in the brain. Recently, astaxanthin (ATX), a marine bioactive compound, has been reported to ameliorate cognitive deficits. However, the underlying pathogenesis remains unclear. In this study, ATX administration (40 mg/kg and 80 mg/kg, oral gavage) and cigarette smoking were carried out once a day for 10 weeks to investigate whether the p38 MAPK is involved in cognitive function in response to ATX treatment in the cortex and hippocampus of ETS mice. Results indicated that ATX administration improved spatial learning and memory of ETS mice (p < 0.05 or p < 0.01). Furthermore, exposure to ATX prevented the increases in the protein levels of the p38mitogen-activated protein kinase (p38 MAPK; p < 0.05 or p < 0.01) and nuclear factor-kappa B (NF-κB p65; p < 0.05 or p < 0.01), reversed the decreases in the mRNA and protein levels of synapsin I (SYN) and postsynaptic density protein 95 (PSD-95) (all p < 0.05 or p < 0.01). Moreover, ATX significantly down-regulated the increased levels of pro-inflammatory cytokines including interleukin-6 (IL-6) and tumor necrosis factor (TNF-α) (all p < 0.05 or p < 0.01). Meanwhile, the increased level of malondialdehyde (MDA) and the decreased activities of superoxide dismutase (SOD), glutathione (GSH), and catalase (CAT) were suppressed after exposure to ATX (all p < 0.05 or p < 0.01). Also, the results of the molecular docking study of ATX into the p38 MAPK binding site revealed that its mechanism was possibly similar to that of PH797804, a p38 MAPK inhibitor. Therefore, our results indicated that the ATX might be a critical agent in protecting the brain against neuroinflammation, synaptic plasticity impairment, and oxidative stress in the cortex and hippocampus of ETS mice.
Keywords: antioxidant inflammatory; astaxanthin; cigarette smoke exposure; p38 MAPK; synaptic-associated plasticity.