Toll-like receptor 4 (TLR4)–Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)–Activator protein 1 (AP-1) inflammatory signaling axis (TLR4–NF-κB–AP-1 axis)

The Toll-like receptor 4–Nuclear factor kappa-light-chain-enhancer of activated B cells–Activator protein 1 (TLR4–NF-κB–AP-1) inflammatory signaling axis is a fundamental pathway of the innate immune system responsible for detecting and responding to microbial pathogens and cellular damage (UniProt P33765). Upon activation by ligands such as lipopolysaccharide (LPS) or damage-associated molecular patterns (DAMPs), TLR4 initiates a complex intracellular signaling cascade, primarily through the MyD88-dependent and TRIF-dependent pathways (PubMed: 31434158). This process leads to the activation and nuclear translocation of the transcription factors NF-κB and AP-1, which coordinate the expression of various pro-inflammatory cytokines, chemokines, and enzymes (PubMed: 28673522). Chronic or excessive activation of this axis is a hallmark of numerous inflammatory and autoimmune diseases, as well as sepsis, cardiovascular disorders, and certain malignancies (PubMed: 30107265). Consequently, this axis is a major focus for therapeutic intervention, with drugs designed to inhibit specific components like the TLR4 receptor or the downstream transcriptional activity to mitigate pathological inflammation (PubChem CID 11481805). However, therapeutic targeting must balance the reduction of harmful inflammation with the preservation of essential host defense mechanisms (PubMed: 25848734).

Other names

TLR4/NF-κB/AP-1 signaling pathwayTLR4-mediated inflammatory cascadeMyD88-dependent TLR4 signaling axisLPS-induced TLR4-NF-kappaB-AP-1 pathway

Inhibition of the signaling cascade by blocking TLR4 ligand binding, preventing the phosphorylation and degradation of IκB to inhibit NF-κB nuclear translocation, or antagonizing AP-1 DNA-binding activity to suppress the transcription of pro-inflammatory genes.