Fig. 3

Osteopontin binds to extracellular histones present in BALF of patients with acute respiratory distress syndrome (ARDS) and individuals with lung injury. a Levels of OPN in the BALF of ARDS patients (n = 21) and healthy control (n = 14) were assessed by ELISA. OPN levels were significantly elevated in ARDS patients. ****P = < 0.001. b Levels of histone–OPN complexes in BALF of ARDS patients (n = 21) and healthy control (n = 12) BALF. ****P = < 0.001. c Western blot analysis of BALF samples detected histone H3 after exposure of humans to swine dust. Healthy individuals (six men and two women) were exposed to swine dust for 3 h on a swine farm, and BALF was retrieved before and 24 h after the exposure. Four out of eight individuals had increased amounts of extracellular histones H3 in BALF after exposure to the swine dust. d The OPN levels in BALF were also elevated in individuals after exposure to swine dust. n = 8; *P = 0.038. e Levels of histone–OPN complexes in the BALF were significantly increased after exposure to swine dust. n = 8;**P = 0.0188. f The LDH levels in BALF were determined to assess lung damage, and were significantly higher after exposure to swine dust. Similarly, the levels of albumin were also significantly elevated, indicating increased pulmonary vascular permeability after exposure to swine dust. n = 8; *P = 0.015, **P = 0.003. g IHC showing OPN and histone (H4) co-localization in the small airways in lung sections from (a) healthy individuals, (b) COPD patients, and (c) CF patients. Histone H4 is visualized by a brown peroxidase reaction while OPN appears in green. Scale bar = 100 μm