Rapamycin inhibits HMGB1 expression and releases in RAW264.7 cells induced by lipopolysaccharides in vitro

AIM: To observe the mechanism that rapamycin (RPM) affects HMGB1 expression and release in RAW264.7 cells induced by lipopolysaccharides (LPS).METHODS: RAW264.7 cells were cultured in six wells plate and divided into five groups: control group, 250 μg/L LPS treatment group, 100 μg/L RPM treatment group, 50 μg/L rTNF-α treatment group and 100 μg/L TNF-α antibody treatment group. After 4 h treatment, the TNF-α level in the culture media was evaluated by ELISA assay. After 24 h, the expression of HMGB1 mRNA was measured by RT-PCR, and HMGB1 protein level in the culture media was determined by Western blotting analysis.RESULTS: TNF-α level in the culture media of RAW264.7 cells has no significant difference between RPM treatment group and control group (P>0.05). Both HMGB1 mRNA expression and HMGB1 protein level were remarkably higher in LPS treatment group than that in control group (P<0.05). RPM attenuated LPS-induced HMGB1 mRNA and HMGB1 accumulation. Compared with that in RPM treatment group, HMGB1 accumulation was increased in rTNF-α treatment group, and had no significant difference in TNF-α antibody treatment group (P>0.05).CONCLUSION: RPM inhibits HMGB1 expression not only by directly suppressing STAT3 activation, but also by indirectly reducing TNF-α level.