Proteomic Profiling and Differential Messenger RNA Expression Correlate HSP27 and Serpin Family B Member 1 to Apical Periodontitis Outcomes

Introduction: Understanding protein expression profiles of apical periodontitis may contribute to the discovery of novel diagnostic or therapeutic molecular targets.

Methods: Periapical tissue samples (n = 5) of patients with lesions characterized as nonhealing were submitted for proteomic analysis. Two differentially expressed proteins (heat shock protein 27 [HSP27] and serpin family B member 1 [SERPINB1]) were selected for characterization, localization by immunofluorescence, and association with known biomarkers of acute inflammatory response in human apical periodontitis (n = 110) and healthy periodontal ligaments (n = 26). Apical periodontitis samples were categorized as stable/inactive (n = 70) or progressive/active (n = 40) based on the ratio of expression of receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin (OPG). Next, the expression of HSP27, SERPINB1, C-X-C motif Chemokine Receptor 1 (CXCR1), matrix metalloproteinase 8 (MMP8), myeloperoxidase (MPO), and cathepsin G (CTSG) messenger RNA was evaluated using real-time polymerase chain reaction. Data analysis was performed using the Shapiro-Wilk test, analysis of variance, and the Pearson test. P values <.05 were considered statistically significant.

Results: Proteomic analysis revealed 48 proteins as differentially expressed in apical periodontitis compared with a healthy periodontium, with 30 of these proteins found to be expressed in all 4 lesions. The expression of HSP27 and SERPINB1 was ∼2-fold higher in apical periodontitis. Next, an increased expression of HSP27 was detected in epithelial cells, whereas SERPINB1 expression was noted in neutrophils and epithelial cells. HSP27 and SERPINB1 transcripts were highly expressed in stable/inactive lesions (P < .05). Significant negative correlations were found between the expression of HSP27 and SERPINB1 with biomarkers of acute inflammation including CXCR1, MPO, and CTSG.

Conclusions: Our data suggest HSP27 and SERPINB1 as potential regulators of the inflammatory response in apical periodontitis. Additional functional studies should be performed to further characterize the role of these molecules during the development/progression of apical periodontitis.