Thrombospondin-1 modulation by Bifidobacterium spp. mitigates lung damage in an acute lung injury mouse model

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a life-threatening condition characterized by lung inflammation and damage. Mechanical ventilation can exacerbate this condition. The gut microbiome, known to impact health, might have implications for ALI/ARDS outcomes. This study aimed to investigate the effects of probiotics in a murine ALI model. Using a two-hit approach combining lipopolysaccharide-induced inflammation and mechanical ventilation-induced injury, a severe lung injury model was established in mice. Probiotics containing Bifidobacterium spp. were administered due to their known interactions with immune cells and immune pathway modulation. The effects of probiotic administration on lung inflammation severity were evalu ated through biochemical, and histological analyses of lung tissue, and single-cell RNA sequencing analysis. Probiotic administration increased Bifidobacterium spp. composition in the gut microbiota and mitigated lung damage and inflammation. Single-cell RNA sequencing revealed the stimulation of Anxa1high macrophages, possibly promoting anti-inflammatory responses. Probiotics containing diets were prepared as follows: Bifidus-diets were prepared by spraying 3 times of mixed fluid including 1g of Bifidus and 25mL of phosphate buffer saline (PBS, pH 7.2) with a dedicated sprayer, and kept in the refrigerator at 4℃ for 1 day. Then fresh diets were given to mice. The diets were changed every 2 days.