Decreased Colonic Guanylin/Uroguanylin Expression and Dried Stool Property in Mice With Social Defeat Stress

Pathogenic effects of Streptococcus oralis intestinal colonization on bladder health in mice

Streptococcus oralis, a commensal oral Streptococcus, is known as an early colonizer of the tooth surface and causes opportunistic infections, such as bacterial endocarditis. However, its pathogenicity remains unclear. This study aimed to investigate the pathogenicity of S. oralis in vivo using a mouse model. To establish S. oralis-colonized mice, germ-free mice were orally infected with S. oralis. After colonization was confirmed, these infected mice were bred, and their offspring were used as S. oralis-colonized mice. S. oralis was detected only in the intestine of these mice, which exhibited soft stools but no significant inflammation in the examined tissues. Interestingly, S. oralis-colonized mice showed higher urination frequency. Bladder tissue analysis in S. oralis-colonized mice revealed atrophy, edema, fibrosis, and epithelial denudation. RNA sequencing analysis of the bladder in S. oralis-colonized mice indicated higher expression of genes related to chronic inflammation and extracellular matrix organization, and lower expression of genes related to anti-oxidative stress. In this study, we revealed that the commensal bacterium S. oralis induces chronic inflammation and fibrosis in the bladder of mice by intestinal colonization. Hence, our findings indicate that S. oralis has the potential to affect distal tissue beyond the oral cavity, potentially possessing a pathogenic factor involved in non-bacterial cystitis. This study highlights the potential impact of S. oralis on the urinary system of mice.

Early Life Social Stress Causes Sex- and Region-Dependent Dopaminergic Changes that Are Prevented by Minocycline

Early life stress (ELS) is known to modify trajectories of brain dopaminergic development, but the mechanisms underlying have not been determined. ELS perturbs immune system and microglia reactivity, and inflammation and microglia influence dopaminergic transmission and development. Whether microglia mediate the effects of ELS on dopamine (DA) system development is still unknown. We explored the effects of repeated early social stress on development of the dopaminergic system in male and female mice through histological, electrophysiological, and transcriptomic analyses. Furthermore, we tested whether these effects could be mediated by ELS-induced altered microglia/immune activity through a pharmacological approach. We found that social stress in early life altered DA neurons morphology, reduced dopamine transporter (DAT) and tyrosine hydroxylase expression, and lowered DAT-mediated currents in the ventral tegmental area but not substantia nigra of male mice only. Notably, stress-induced DA alterations were prevented by minocycline, an inhibitor of microglia activation. Transcriptome analysis in the developing male ventral tegmental area revealed that ELS caused downregulation of dopaminergic transmission and alteration in hormonal and peptide signaling pathways. Results from this study offer new insight into the mechanisms of stress response and altered brain dopaminergic maturation after ELS, providing evidence of neuroimmune interaction, sex differences, and regional specificity.