Sex-dependent differences in the gut microbiota following chronic nasal inflammation in adult mice.

A growing body of evidence suggests a relationship between olfactory dysfunction and the pathogenesis of mental disorders. Our previous studies indicated that chronic nasal inflammation caused loss of olfactory sensory neurons and gross atrophy of the olfactory bulb, which may lead to olfactory dysfunction. Simultaneously, increasing numbers of reports have elucidated the importance of gut microbiota to maintain brain function and that dysbiosis may be associated with neuropsychiatric disorders. Here we examined whether chronic nasal inflammation perturbed gut microbiota and whether there were sex differences in this pattern. Eight-week-old C57BL/6 mice repeatedly received bilateral nasal administration of lipopolysaccharide (LPS) 3 times/week to cause chronic nasal inflammation or saline as a control. At 9 weeks, cecal feces were used for 16S metagenomic analysis and whole blood and fresh tissue of spleen were used for ELISA analyses. Microbiome analysis demonstrated a remarkable change of the gut microbiota in male mice with chronic nasal inflammation which was different from that in female mice. In both mice, systemic inflammation did not occur. This has shown for the first time that chronic nasal inflammation correlates with sex-dependent changes in the gut microbiota. The detailed mechanism and potential alteration to brain functions await further studies.