PTGS2 and major depressive disorder: Natural drug substances can improve the levels of oxidative stress and neuroinflammation in depression, Muhammad et al. (41) used carvacrol to treat rats with depressive-like behavior induced by LPS, and significant neuronal alterations as well as elevated levels of inflammatory cytokines, such as TNF-α, COX-2 and c-Jun N-terminal kinase (p JNK).