Effects of fine particulate matter on cognitive function and gut microbiota in adult male mice

Objective To study the effects of fine particulate matter(PM_(2.5))exposure to cognitive function and intestinal flora abundance and diversity in adult male mice. Methods The SPF grade male C57 BL/6 J mice with 8 weeks old were randomly divided into control group(NS group), PM_(2.5) exposure group(PM_(2.5) group), probiotic group(VSL#3 group) and PM_(2.5) + VSL#3 group(PMV group), with 8 mice in each group. The PM_(2.5) group and PMV group mice were exposed to PM_(2.5) using animal exposure system equipped with real-time PM_(2.5) concentration, and concentrated 6 times the outdoor PM_(2.5) concentration, 8 h every day, 5 d every week for 4 weeks. The VSL#3 group and PMV group mice were given VSL#3, 0.5 mL, 2×10~9 CFU/mL. After four weeks of exposure, feces from mice were collected for 16 s rRNA high-throughput sequencing, and the cognitive function was evaluated using Morris water maze and object recognition experiments. Results The escape latency of PM_(2.5) group in four-day training [(54.99±6.77) s, (41.21±9.98) s, (36.27±13.11) s, (30.01±14.80) s] were higher than that of NS group [(32.19±4.59) s, (20.50±6.77) s, (19.93±7.30) s, (16.94±9.91) s], and the difference were statistically significant(Pl0.05). The escape latency of PMV group on the first and second day of training [(39.02±6.23) s, (28.83±9.53) s] were lower than that of PM_(2.5) group(Pl0.05). The target quadrant residence time of mice in PM_(2.5) group [(18.30± 8.88) s] was lower than that in NS group and PMV group [(30.53±9.10) s, (30.00±10.61) s]. Compared with NS group(6.09±0.40), the shannon index of PM_(2.5) group and PMV group(5.05±0.65 and 5.46±0.52) were significantly reduced(Pl0.05). The target quadrant time was positively correlated with the relative abundance of Actinomyces(r=0.576, Pl0.05), and the recognition index was positively correlated with the relative abundance of Firmicutes(r=0.612, Pl0.05). Conclusion PM_(2.5) could lead to cognitive dysfunction in mice, which is related to diversity and abundance of the intestinal flora. Probiotic can improve cognitive function.