The Effect Of Dexamethasone On LPS-inducedTLR4/CD14/MD-2Complex In RAW264.7 Macrophage Cells

Text:Objectives In this study we aimed to examine the effect of dexamethasone (DEX) on LPS-induced TLR4/CD14/MD-2 complex andNF-KB signalingpathwayin RAW264.7 macrophage cells. Methods RAW264.7macrophage cells wereunstimulated or stimulated with LPS and pretreated with DEX, for 1-24h. TLR4. CD14 and MD-2 levels were measured by Real time-PCR.Expression of intracellular NF-kB protein was determined by Western blot. Production of inflammatory cytokine(TNF-α、IL-1 and IL-6) and chemotactic factors(IL-8 and MIP-1) were measured by ELISA. Result①The levels of TLR4, CD14 and MD-2increased after stimulation with LPS in 24h.② DEX significantly suppressed the TLR4、CD 14 and MD-21evels in a dose dependent manner, and the suppression of CD 14 and MD-2 levels were deeper then TLR4 level.③ Pretreated with DEX significantly suppressed the increase in TLR4^ CD 14 and MD-2 levels induced by LPS, but the suppression of TLR4 level were deeper then CD14 and MD-2 levels.④Pretreated with 100ng/μl DEX for 1-24h downregulated the TLR4, CD 14 and MD-2 levels induced by LPS, that nadir point at 14h.200ng/μl DEX showed the same results.⑤ DEX inhibited the expression of intracellular NF-kB protein induced by LPSin a dose dependent manner.⑥The production of inflammatory cytokine(TNF-α、IL-1 and IL-6) and chemotactic factors(IL-8 and MIP-1)were decreased by DEX in a dose dependent manner. Conclusions It is concluded that LPS-activated TLR4 is the target of negative regulation byDEX in the TLR4/CD14/MD-2 complex and NF-kB signaling pathways in RAW264.7. It is indicated that glucocorticoids may play an important role in weakening immune recognition of pathogens as well as downstream immuneresponse.