Lipopolysaccharide(LPS) has an important function in bacteria-invading cells. Toll-like receptor(TLR) 2 can recognize LPS by forming a heterodimer with TLR1 or TLR6, which then activates cellular immune response by the myeloid differentiation factor(MyD88)-dependent pathway. The death domain of MyD88 raises downstream signaling molecules, such as interleukin(IL)-1 and IL-4 receptor-associated kinase, tumor necrosis factor receptor-associated factor 6, transforming growth factor β1 that activates nuclear factor(NF)-κB, and P38 mitogen-activated protein kinase and activator protein(AP) 1, which lead to the production of pro-inflammatory cytokines. MyD88-independent pathway reportedlyactivates the transcription factor interferon regulatory factor 3 and AP1, and can induce the generation of interferon 1 by activating NF-κB, tumor necrosis factor receptor-associated factor 3, and interleukin-1 receptor-1. CD14 and MyD2 are required for LPS binding to TLR4. Preventing CD14/MyD2-mediated binding of LPS to TLR4 could block inflammatory response at the outset. TLR2 and TLR4 are crucial in LPS-induced inflammation. Inhibiting the expression of TLR2 and TLR4 will be an effective and direct way to control the inflammation. A better understanding of the regulation of TLR2 and TLR4 signaling pathways will provide further support to their potential therapeutic application to periodontitis, inflammatory bowel disease, cardiovascular disease, and autoimmune diseases.
