Effect of histone H4 on polarization of alveolar macrophages in mice with acute respiratory distress syndrome / 中国职业医学

ABSTRACT

Objective To investigate the role of histone H4 in the polarization of alveolar macrophages (AM) in lipopolysaccharide (LPS)-induced acute respiratory distress syndrome (ARDS) in mice. Methods i) The specific pathogen free male C57BL/6 mice were randomly divided into control group and 2, 4, 6 and 8 mg/kg LPS groups, with six mice in each group. The mice in the LPS groups were intratracheally administered LPS according to their respective doses, while the mice in the control group received an equivalent volume of 0.9% saline. After 12 hours, the arterial blood gas was analyzed, and the pulmonary edema and histopathological changes in lung tissues of mice in each group were observed. The level of histone H4 in bronchoalveolar lavage fluid (BALF) of mice was detected using enzyme-linked immunosorbent assay , and mice AMs of the five group were isolated using adherent method. ii) AMs from normal mice were isolated using adherent method and randomly divided into control group, histone H4 injury group, BALF injury group and anti-histone H4 antibody (anti-H4) intervention group. In the histone H4 injury group, AMs were treated with histone H4 at a final concentration of 20 mg/L. In the BALF injury group and anti-H4 intervention group, AMs were treated with 200 μL BALF supernatant from mice intratracheally administered 6 mg/kg body weight LPS, with the latter group treated with 25 mg/L anti-H4 antibody. The control group AMs were treated with phosphate-buffered saline. iii) After 12 hours of stimulation, the cells were collected, and the relative expression of tumor necrosis factor-α (Tnfa), interleukin-1β (Il1b), differentiation antigen 206 (Cd206) and arginase 1 (Arg1) in AMs was detected using real-time quantitative polymerase chain reaction. Results i) Compared with the control group, mice in all four LPS groups exhibited rapid breathing, inflammatory reaction and lung edema in lung tissues, which were aggravated in a dose-dependent manner. The ratio of partial pressure of arterial oxygen to fraction of inspired oxygen in mice decreased with the increase of LPS dose (P<0.05). The wet/dry weight ratio of lung, the level of histone H4 in BALF and the relative expression of Tnfa and Il1b mRNA in AMs increased with the increase of LPS dose (all P<0.05). The mice in the 6 and 8 mg/kg LPS groups developed ARDS. The level of histone H4 in BALF and the relative expression of Tnfa and Il1b mRNA in AMs of mice in 6 and 8 mg/kg LPS groups were higher than those in the other three groups (all P<0.05). ii) The relative expression of Tnfa and Il1b mRNA increased (both P<0.05), and the relative expression of Cd206 and Arg1 mRNA decreased (both P<0.05) in AMs of histone H4 injury group and BALF injury group compared with the control group. Compared with BALF injury group, the relative mRNA expression of Tnfa and Il1b in AMs of anti-H4 intervention group decreased (both P<0.05), while the relative expression of Arg1 mRNA increased (P<0.05). Conclusion LPS can induce a dose-dependent increase in histone H4 levels in BALF in mice. Histone H4 drives the development of ARDS by activating AMs to M1 polarization. Antagonizing histone H4 to interfere with AM polarization to M1 could be a target for the treatment of ARDS.