TLR4 and memory impairment: Gypenoside can alleviate LPS-induced neuroinflammation and memory impairment in rats by decreasing the levels of proinflammatory mediators as well as suppressing levels of inducible nitric oxide synthase (iNOS), toll-like receptor 4 (TLR4) and inhibition of brain-derived neurotrophic factor (BDNF) mRNA (Lee et al., 2018).