Toll-like receptor 4 signaling axis (TLR4/MyD88/NF-κB axis)

The Toll-like receptor 4 (TLR4) signaling axis is a central component of the innate immune system, primarily recognized for its role in detecting lipopolysaccharide (LPS) from Gram-negative bacteria [UniProt: P33729]. Upon activation, TLR4 recruits the adapter protein Myeloid differentiation primary response protein MyD88, which triggers a signaling cascade that activates the Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor [PubMed: 20935639]. This process leads to the production and release of key pro-inflammatory cytokines, including Tumor necrosis factor alpha (TNF-α), Interleukin-6 (IL-6), and Interleukin-1 beta (IL-1β) [PubMed: 23999230]. This pathway is critically involved in the pathogenesis of sepsis, chronic inflammatory diseases, and autoimmune disorders, making it a significant target for therapeutic intervention [PubMed: 23510120]. Drugs such as the antagonist Eritoran have been developed to mitigate the cytokine storm in sepsis, while TLR4 agonists like Monophosphoryl lipid A (MPLA) are used as vaccine adjuvants to enhance immune memory [PubMed: 21812916]. Additionally, the pathway's involvement in neuropathic pain and opioid signaling has led to the investigation of TLR4 modulation by drugs like Naloxone [PubMed: 22891131].

Other names

TLR4-MyD88-NF-kappaB signaling pathwayLPS-induced inflammatory cascadeToll-like receptor 4 signaling axisTLR4/MyD88/NF-kappaB/Cytokine axis

TLR4 antagonists like Eritoran and Resatorvid bind to the TLR4/MD-2 complex or the intracellular domain of TLR4, respectively, to prevent receptor dimerization and the subsequent recruitment of the MyD88 adapter protein, thereby inhibiting the NF-κB-mediated production of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β [PubMed: 23510120, 19710304]. Conversely, TLR4 agonists like Monophosphoryl lipid A (MPLA) mimic bacterial components to activate this pathway, serving as adjuvants to strengthen vaccine-induced immunity [PubMed: 21812916].