1,25(OH)₂D₃ protected against LPS-induced acute lung injury through modulation of gut microbiota

This study investigated whether gut and lung microbiota mediated the effects of 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] against acute lung injury (ALI). We evaluated the impact of various 1,25(OH)₂D₃ doses on lipopolysaccharide (LPS)-induced ALI and characterized microbial changes in both intestinal and pulmonary communities. Correlation between lung and gut microbiota was assessed. To further explore the role of intestinal flora, a depletion model was established using antibiotics (ABX). Our results indicated that 1,25(OH)₂D₃ alleviated LPS-induced ALI, as evidenced by reduced pathological damage, downregulated expression of proinflammatory cytokines (IL-1β, IL-6, TNF-α), increased levels of anti-inflammatory cytokine (IL-10), and suppressed TLR4/NF-κB and JNK pathways. LPS reduced α diversity and altered β diversity and composition of intestinal microbes, which were partially reversed by 1,25(OH)₂D₃ intervention. Notably, 1,25(OH)₂D₃ enhanced gut microbiota diversity and elevated the relative abundance of Muribaculaceae and Lachnospiraceae genus. Importantly, depletion of gut flora with ABX eliminated the anti-inflammatory effects of 1,25(OH)₂D₃, including its inhibition of LPS-induced cytokine expressions and pathway activation. Although LPS did not significantly affect the diversity of lung microbiota, it seemed to change its composition and induced a significant correlation between intestinal and pulmonary microbial communities, which was attenuated by 1,25(OH)₂D₃. In conclusion, our findings suggested that the protective effects of 1,25(OH)₂D₃ against LPS-induced ALI might be partially mediated by gut microbiota, highlighting a potential mechanism for vitamin D's immunomodulatory activity in inflammatory lung disease.