Salivary and serum levels of high mobility group box protein 1 in periodontitis: a cross- sectional observational study

Background High mobility group box protein 1 (HMGB1) is a damage-associated molecular pattern showing pro-inflammatory functions in chronic inflammatory diseases. HMGB1 expression is strongly associated with other inflammatory markers leading to extended inflammatory milieu; therefore HMGB1 could have a crucial undetermined role in the development and progression of periodontitis. This study aimed to evaluate HMGB1 levels and their associations with tumor necrosis factor alpha (TNFα), transforming growth factor beta (TGFβ) and interleukin- 1β (IL-1β) in the saliva and serum of the periodontitis patients. Methods The study was enrolled on sixty-six systematically healthy nonsmoker subjects. Whole-mouth clinical periodontal measurements were recorded, and participants were equally divided into three groups: 1) Control, 2) Stage I-II Periodontitis, and 3) Stage III-IV Periodontitis. HMGB1, TNFα, IL-1β and TGFβ concentrations were analyzed by enzyme-linked immunosorbent assay (ELISA). Data was analyzed with IBM SPSS Statistics version 20. One-way analysis of variance (ANOVA) was used to compare continuous variables, and Tukey test was used for post-hoc comparisons. Pearson’s correlation coefficient was used to assess the relationship between two quantitative variables. Results Clinical periodontal parameters showed a significant increase in both periodontitis groups compared to the control group (p < 0.05). Periodontitis groups had significantly higher salivary-HMGB1 levels than the control group (p < 0.0001); stage III-IV periodontitis group had significantly higher serum-HMGB1 levels than control (p = 0.022) and stage I-II periodontitis (p < 0.001) groups. TNFα and TGFβ levels in the saliva of both periodontitis groups were significantly more than the control group (p < 0.05, p < 0.001, respectively). Serum-IL-1β level in stage III-IV periodontitis group was significantly more than stage I-II periodontitis and control groups (p < 0.0001). There were positive correlations with serum-HMGB1 and -IL-1β levels in both periodontitis groups (p < 0.05 in stage I-II, p≤0.001 in stage III-IV). In the stage I-II periodontitis group, a positive correlation was observed between salivary-HMGB1 and -TNFα levels (p≤0.001). Conclusion HMGB1 levels increase in saliva and serum as periodontal disease worsens, suggesting enhanced HMGB1 expression was involved in the pathogenetic shifts in the disease process at local and systemic levels.