BACKGROUND Extracellular
histones have recently been suggested as critical mediators in many inflammatory diseases. However, the role of extracellular
histones in tuberculous
pleural effusion (TPE) is unclear. The goal of this study was to explore the potential involvement of extracellular
histones in patients with TPE. MATERIAL AND METHODS Samples of
pleural effusion and peripheral blood were obtained from 58 patients with
tuberculosis. Extracellular
histones were determined in both TPE and serum samples. Moreover, the
biomarkers for cellular damage, inflammatory cell activation, and systemic
inflammation including
lactate dehydrogenase (LDH),
myeloperoxidase (MPO), S100A8/A9, as well as multiple inflammatory
cytokines were measured. RESULTS Extracellular
histone levels were significantly elevated in TPE (4.762 mg/mL [3.336, 7.307]) and serum samples (1.502 mg/mL [1.084, 2.478]) from
tuberculosis patients as compared with the serum (0.585 mg/mL [0.285, 0.949]) from healthy controls. Notably, extracellular
histones in TPE were also much higher than in serum of patients (P=0.002). LDH, MPO, and S100A8/A9 levels were all increased in TPE, along with a remarkable elevation of various
cytokines. A correlation analysis showed that extracellular
histones were positively associated with LDH, MPO, and S100A8/A9, and a panel of inflammatory
cytokines in TPE. CONCLUSIONS These results suggest that high concentrations of extracellular
histones are markedly present in TPE, which may play an inflammatory role towards the progression of
tuberculosis.