Toll-like receptor 4-mediated nuclear factor kappa B signaling pathway (TLR4/NF-κB pathway)

The Toll-like receptor 4 (TLR4)-mediated nuclear factor kappa B (NF-κB) signaling pathway is a central axis of the innate immune system that translates extracellular danger signals into a pro-inflammatory transcriptional response [1.1.1, 1.2.1]. Upon activation by pathogen-associated molecular patterns (PAMPs) like lipopolysaccharide (LPS) or damage-associated molecular patterns (DAMPs) like HMGB1, TLR4 recruits adaptor proteins such as MyD88 and TRIF [1.3.4, 1.4.3]. This leads to the activation of the IκB kinase (IKK) complex, which phosphorylates IκB, allowing the transcription factor NF-κB to translocate into the nucleus [1.3.1, 1.3.5]. Once in the nucleus, NF-κB induces the expression of various pro-inflammatory cytokines, chemokines, and enzymes [1.1.2, 1.4.1]. Dysregulation of this pathway is implicated in a wide range of conditions, including sepsis, chronic inflammation, neurodegeneration, and cancer [1.1.3, 1.2.4, 1.4.5]. Therapeutic strategies focus on modulating this pathway using TLR4 antagonists or NF-κB inhibitors to dampen excessive inflammation without compromising host defense [1.3.2, 1.3.4].

Other names

TLR4/NF-κB axisTLR4-NF-κB signalingMyD88-dependent TLR4 signaling pathwayTLR4-mediated inflammatory pathway

The pathway is targeted through several mechanisms: competitive or non-competitive antagonism of the TLR4 receptor to prevent ligand binding; disruption of the interaction between TLR4 and its intracellular adaptor proteins (MyD88 and TRIF); inhibition of the IκB kinase (IKK) complex to prevent IκB phosphorylation; and direct inhibition of NF-κB nuclear translocation or DNA binding [1.3.1, 1.3.2, 1.3.5].