Shikonin ameliorates D-galactose-induced oxidative stress and cognitive impairment in mice via the MAPK and nuclear factor-κB signaling pathway.

Oxidative stress acts as the major causative factor for various age-associated neurodegenerative diseases, triggering cognitive and memory impairments. In the present study, the underlying neuroprotective mechanism governing how shikonin acts against D-galactose (D-gal)-induced memory impairment, neuroinflammation and neuron damage was examined. The results revealed that chronic administration of D-gal [150 mg/kg intraperitoneally (i.p.)] in mice caused cognitive and memory impairments, as determined by Morris water-maze test. Shikonin treatment, however, alleviated D-gal-induced memory impairment and reversed the D-gal-induced neural damage and apoptosis. Furthermore, western blotting and the results of morphological analysis revealed that shikonin treatments markedly reduced D-gal induced neuroinflammation through inhibition of astrocytosis as determined by glial fibrillary acidic protein (GFAP) detection, and downregulating other inflammatory mediators, including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6. Moreover, shikonin treatment led to inhibition of the activation of nuclear factor-κB (NF-κB) and the phosphorylation of mitogen-activated protein kinases (MAPKs), preventing neurodegeneration. Hence, taken together, the results of the present study suggested that shikonin attenuated D-gal-induced memory impairment, neuroinflammation and neurodegeneration, possibly via the NF-κB/mitogen-activated protein kinase (MAPK) pathway. Our data suggest that shikonin could be a promising, endogenous and compatible antioxidant candidate for age-associated neurodegenerative diseases, including Alzheimer's disease.