Toll-like receptor 4–Nuclear factor kappa B signaling pathway (TLR4–NF-κB)

The Toll-like receptor 4–Nuclear factor kappa B (TLR4–NF-κB) signaling pathway is a fundamental axis of the innate immune system, particularly prominent in intestinal epithelial cells and various immune cells like macrophages (UniProt P33527). TLR4 serves as a pattern recognition receptor that identifies lipopolysaccharide (LPS) from Gram-negative bacteria and endogenous danger signals known as damage-associated molecular patterns (DAMPs). Upon ligand binding, TLR4 initiates a downstream cascade involving adapter proteins such as MyD88, which ultimately activates the IκB kinase (IKK) complex. This leads to the phosphorylation and degradation of IκB, allowing the transcription factor NF-κB to translocate into the nucleus and drive the expression of pro-inflammatory cytokines like TNF-alpha and IL-6 (StatPearls). In the context of the intestine, overactivation of this pathway is a hallmark of chronic inflammatory diseases, including Crohn's disease and ulcerative colitis, where it contributes to mucosal damage and barrier dysfunction (PMID: 31434157). Consequently, this pathway is a major focus for therapeutic intervention, with drugs like Resatorvid and Eritoran designed to inhibit TLR4, while others target NF-κB activation to resolve inflammation (PubChem). However, therapeutic targeting is challenged by the need to maintain sufficient immune surveillance to prevent opportunistic infections (NIH).

Other names

TLR4-NF-kappaB axisTLR4/NF-kB pathwayLPS-induced TLR4-NF-kappaB signalingTLR4-mediated NF-kappaB activation

TLR4 activation by ligands like LPS triggers a signaling cascade via MyD88 or TRIF, leading to IKK complex activation, IκB degradation, and subsequent NF-κB nuclear translocation to induce pro-inflammatory gene transcription.