Toll-like receptor 4 (TLR4)–Mitogen-activated protein kinase (MAPK) signaling pathway (TLR4-MAPK pathway)

The Toll-like receptor 4 (TLR4)–Mitogen-activated protein kinase (MAPK) inflammatory signaling pathway is a fundamental component of the innate immune system responsible for detecting pathogens and initiating inflammatory responses (UniProt: P33527). Activation begins when TLR4 recognizes ligands such as lipopolysaccharide (LPS) from Gram-negative bacteria, triggering the recruitment of adapter proteins like MyD88 and TRIF (PubMed: 25617461). These adapters initiate a phosphorylation cascade that activates the MAPK family, specifically p38, JNK, and ERK, which then activate transcription factors like AP-1 and NF-κB (StatPearls: MAPK Signaling Pathway). This process leads to the robust production of pro-inflammatory cytokines and chemokines necessary for host defense (PubMed: 30271553). Chronic or excessive activation of this pathway is a hallmark of various pathological conditions, including sepsis, chronic inflammatory diseases, and cancer progression (PubMed: 28673522). Consequently, the pathway is a major focus for drug development, with therapeutic agents designed to block TLR4 activation or inhibit specific downstream kinases to control inflammation (PubChem: CID 11650144).

Other names

TLR4/MAPK axisTLR4-mediated MAPK signaling cascadeTLR4-MAPK inflammatory axis

Inhibition of the TLR4 receptor or downstream MAPK components (p38, JNK, ERK) to prevent the transcription of pro-inflammatory cytokines (PubMed: 17435113).