Objective To observe the serum levels of high mobility group box-1 protein (HMGB1)in patients with acute cholangitis (AC) and to investigate contributions of HMGB1 in AC.Methods Serum HMGB1 concentrations were determined by an enzyme-linked immunosorbent assay in 30 patients with AC of severe type (ACST) and 42 patients with mild acute cholangitis at the time of admission (within 72 h after the onset).A total of 50 healthy subjects were recruited as the control group.Fluorescent quantitative PCR (FQPCR) was used to detect the HMGB1 mRNA expression and the relationship between serum HMGB1 levels and clinical factors was analyzed.Results The serum HMGB1 levels in healthy control group,mild group and ACST group were (1.82 ± 0.64) μg/L,(10.46 ± 3.75) μg/L,(18.89 ± 6.86) μg/L,respectively.The mean value of serum HMGB1 level in mild group was significantly higher than that in control group,while significantly lower than that in ACST group (P ＜ 0.05).Compared to the control group,the HMGB1 mRNA level in patients of AC increased significantly and the level of ACST group was higher than that of mild group.The serum HMGB1 levels of patients with positive bile or/and blood cultures were higher than that of negative.After emergency endoscopic nasal biliary drainage,the serum HMGB1 levels of patients significantly decreased compared to preoperational (P ＜ 0.05).The HMGB1 levels were significantly positively correlated with white cell counts,C-reactive protein (CRP),total serum bilirubin,direct bilirubin and alkaline phosphatase (ALP).By logistic regression analysis,serum HMGB1 levels had correlation with severity of disease.Conclusion Serum HMGB1 levels significantly increased in patients with AC and the serum concentrations of ACST group were higher than those of mild group.Serum HMGB1 level has a correlation with sepsis.ENBD could lower its serum levels.Serum HMGB1 has predictive value to severity of disease.