Intranasal administration of Lactobacillus johnsonii attenuates hyperoxia-induced lung injury by modulating gut microbiota in neonatal mice

Background: Supplemental oxygen impairs lung development in newborn infants with respiratory distress. Lactobacillus johnsonii supplementation attenuates respiratory viral infection in mice and exhibits anti-inflammatory effects. This study investigated the protective effects of intranasal administration of L. johnsonii on lung development in hyperoxia-exposed neonatal mice. Methods: Neonatal C57BL/6N mice were reared in either room air (RA) or hyperoxia condition (85% O2). From postnatal days 0 to 6, they were administered intranasal 10 μL L. johnsonii at a dose of 1 × 105 colony-forming units. Control mice received an equal volume of normal saline (NS). We evaluated the following four study groups: RA + NS, RA + probiotic, O2 + NS, and O2 + probiotic. On postnatal day 7, lung and intestinal microbiota were sampled from the left lung and lower gastrointestinal tract, respectively. The right lung of each mouse was harvested for Western blot, cytokine, and histology analyses. Results: The O2 + NS group exhibited significantly lower body weight and vascular density and significantly higher mean linear intercept (MLI) and lung cytokine levels compared with the RA + NS and RA + probiotic groups. At the genus level of the gut microbiota, the O2 + NS group exhibited significantly higher Staphylococcus and Enterobacter abundance and significantly lower Lactobacillus abundance compared with the RA + NS and RA + probiotic groups. Intranasal L. johnsonii treatment increased the vascular density, decreased the MLI and cytokine levels, and restored the gut microbiota in hyperoxia-exposed neonatal mice. Conclusions: Intranasal administration of L. johnsonii protects against hyperoxia-induced lung injury and modulates the gut microbiota.