Objective: To investigate the plasma level of extracellular histones in patients with silicosis, and to explore the role of extracellular histones in the pathogenesis of pulmonary fibrosis in silicosis.
Methods: Sixty-two patients with silicosis were enrolled as the silicosis group, consisting of 23 patients with stage I silicosis, 25 with stage II silicosis, and 14 with stage III silicosis; sixty workers who had a history of occupational exposure to silica dust for more than 2 years and had not been diagnosed with silicosis were enrolled as the silica dust exposure group; sixty-five healthy workers without a history of occupational exposure to dust were enrolled as healthy controls. Enzyme-linked immunosorbent assay was applied to measure the plasma levels of plasma extracellular histone (H4) and transforming growth factor-β(TGF-β).
Results: Compared with healthy controls [(0.82±0.67) μg/ml], the silica dust exposure group[(4.14±2.85) μg/ml] and silicosis group[(9.50±5.04) μg/ml] had significant increases in plasma level of H4 (P<0.01). The plasma level of H4 was significantly correlated with the stage of silicosis(r=0.8955, P=0.0388). The silicosis group had a significantly higher plasma level of TGF-β than the silica dust exposure group and healthy controls(P <0.05). In the patients with silicosis, the plasma level of H4 was significantly correlated with that of TGF-β(r=0.5375, P<0.01).
Conclusion: The plasma level of extracellular histones increases significantly in the pathogenesis of silicosis, and extracellular histones may play an important role in the progression of fibrosis in silicosis.