TLR4 and major depressive disorder: Another study has also demonstrated that the inflammatory process driven by TLR4/myeloid differentiation factor88 (MyD88)/nuclear factor kappa-B (NF-κB) signaling pathway plays a critical role in the chronic unpredictable mild stress (CUMS)-induced depression-like behavior, including the significant decrease in preference for a sucrose solution or in total moving distance [28].