Melatonin Inhibits LPS-induced HMGB1 Expression In HT-29 Cells

Objective: To observe the effect of melatonin on the expression of high mobility group protein 1(HMGB1)in human colonic carcinoma epithelial cell HT29 induced by lipopolysaccharide(LPS).Methods: HT29 cells were serviced in this study and were divided into 5groups: blank control(group CT),LPS control,LPS+62.5u M melatonin,LPS+125u M melatonin,and LPS+250u M melatonin.The HMGB1 m RNA expression was detected by q RT-PCR,the content of HMGB1 protient in the culture supernatant was detected by ELISA,and the distribution of HMGB1 inside and outside the nucleus was detected by Immunofluorescence.Results: Compared with that in control cells(group CT),the HMGB1 m RNA level in the cells induced with LPS(group LPS,treated with LPS of 1mg/ml,2.5mg/ml and 5mg/ml,respectively)were increased significantly(p<0.05),while the levels in group LPS+MT62.5(u M),group LPS+MT125(u M)and group LPS+MT250(u M)were decreased,and the level in group LPS+MT250was significantly lower than in the another two groups(p<0.05).The contents of HMGB1 proteint in group LPS(concentration of 1mg/ml,2.5mg /ml and5mg/ml,respectively)were higher than in group CT(P<0.05).The HMGB1 contents in group LPS+MT62.5,group LPS+MT125 and group LPS+MT250were lower than in group LPS(P<0.05).Melatonin inhibited HMGB1 secretion with a dose-dependent way in HT29 cells induced by LPS.Immunofluorescence staining showed that HMGB1 mainly distributed in the nucleus in HT-29 cells(group CT).After intervention of LPS(2.5 mg/ml)for24 h and 48 h respectively the HMGB1 fluorescence in cytoplasm increased significantly.And after co-administration with different dose of LPS(in group LPS + MT62.5,group LPS + MT125,and group LPS + MT250)the cytoplasm HMGB1 fluorescence levels were declined with the increase of melatonin concentrations(P < 0.05).Conclusion: Melatonin could inhibit the transcription of HMGB1 m RNA and the nucleo-cytoplasmic transfer of HMGB1 in HT-29 cells induced with LPS.