Role of liver X receptors alpha agonist on expressions of LPS-induced inflammatory response associated factor IRAK-4 and NF-kappaB in Kupffer cells

Abstract

Objective To explore the role of activated liver X receptor α (LXRα) on the expressions of interleukin-1 receptor associated kinase-4 (IRAK-4) and NF-kappaB (NF-κB) in the inflammatory response which induced by LPS in the Kupffer cells and to investigate the possible mechanisms of LXRα negative regulation of inflammatory response. Methods The Kupffer cells were isolated from male Kunming mice by collagen perfusion in situ. And these cells were divided into 4 groups: normal control group, LPS treatment group, LXRα agonist T0901317 treatment group, LPS and T0901317 combined treatment group. The LPS treatment group were treated with a final concentration of 1 μg/ml LPS in RPMI 1640 and cultured for 6 h, the T0901317 treatment group were treated with a final concentration of 5 μg/ml in RPMI 1640 and cultured for 24 h, and the combined treatment group received pre-culture for 24 h with a final concentration of 1 μg/ml T0901317 in RPMI 1640 and then cultured for 6 h with a final concentration of 5 μg/ml LPS in RPMI 1640. All groups were cultured for 30 h. The expression of LXRα, IRAK-4 and NF-κB at mRNA and protein levels were detected by real-time PCR and Western blotting, and the TNF-α and IL-1β levels were detected by ELISA. Results The levels of LXRα mRNA and protein were highest in T0901317 group, and lowest in LPS group ( P<0.05). The level of IRAK4 and NF-κB mRNAs and proteins were evidently lower in the Combined-treated group than in LPS group ( P<0.05). And the level of TNF-α and IL-1 were observed highest in LPS group ( P<0.05), but no difference among the Control group, T0901317 group and Combined-treated group ( P>0.05). Conclusion These date suggest that the LXR agonists can effectively up-regulate the expressions of LXRα mRNA and protein and inhibit the inflammatory response. This may be via down-regulating the expressions of IRAK4 and NF-κB at mRNA and protein levels.