TLR4 and major depressive disorder: Menze et al. analyzed the mechanism of simvastatin (SIM) in neuroprotection and depression-like behavior resistance and revealed that SIM can also inhibit the expression of P2X7R, TLR2 and TLR4 in the hippocampus of ovariectomized rats and block the activation of the NLRP3 inflammasome, thus decreasing the levels of the proinflammatory cytokines IL-1β and IL-18 and reducing the expression of ionized calcium-binding adapter molecule 1 (IBA1) and the activation of microglia.