Bone marrow derived M2 macrophages protected against lipopolysaccharide-induced acute lung injury through inhibiting oxidative stress and inflammation by modulating neutrophils and T lymphocytes responses.

Acute lung injury (ALI) is characterized by aggravated inflammatory responses and the subsequent alveolar-capillary injury for which there are no specific therapies available currently. The present study was designed to investigate the protective roles of bone marrow derived M2 macrophages (M2 BMDMs) in lipopolysaccharide (LPS) induced ALI. M2 BMDMs were obtained from bone marrow cells stimulated with M-CSF and IL-4. Mice received M2 BMDMs intratracheally 3 h after LPS administration. Histology and wet/dry (W/D) weight ratio, activated immune cells and total protein were detected. Cytokines production were measured in vivo and vitro study. The effects of PD-L1 blockade on M2 BMDMs were calculated. The results showed that M2 BMDMs administration reduced the infiltration of neutrophils, inhibited the oxidative stress, while increased the counts of CD3+T lymphocytes as well as CD4+CD25+ regulatory T lymphocytes. Further, M2 BMDMs suppressed the TNF-α, IL-1β and IL-6 production, while increased the IL-10 production. Blockade of PD-L1/PD-1 pathway reversed cytokines production of M2 BMDMs in the BALF. These findings indicated that M2 BMDMs might be a promising therapeutic strategy for LPS-induced ALI through inhibiting oxidative stress and inflammation by modulating neutrophils and T lymphocytes responses.