Accumulating evidence has revealed an association between
depression
and disordered intestinal microecology. The discovery of psychobiotics
has provided a promising perspective for studying the treatment of
psychiatric disorders. Here, we aimed to investigate the antidepressant
abilities of Lactocaseibacillus rhamnosus zz-1 (LRzz-1) and elucidate the underlying mechanisms. The viable
bacteria (2 × 109 CFU/day) were orally supplemented
to depressed C57BL/6 mice induced by chronic unpredictable mild stress
(CUMS), and the behavioral, neurophysiological, and intestinal microbial
effects were assessed, with fluoxetine used as a positive control.
The treatment with LRzz-1 effectively mitigated the depression-like
behavioral disorders of depressed mice and reduced the expression
of inflammatory cytokine mRNA (IL-1β, IL-6, and TNF-α)
in the hippocampus. In addition, LRzz-1 treatment also improved tryptophan
metabolic disorder in the mouse hippocampus, as well as its peripheral
circulation. These benefits are associated with the mediation of microbiome–gut–brain
bidirectional communication. CUMS-induced depression impaired the
intestinal barrier integrity and microbial homeostasis in mice, neither
of which was restored by fluoxetine. LRzz-1 prevented intestinal leakage
and significantly ameliorated epithelial barrier permeability by up-regulating
tight-junction proteins (including ZO-1, occludin, and claudin-1).
In particular, LRzz-1 improved the microecological balance by normalizing
the threatened bacteria (e.g., Bacteroides and Desulfovibrio), exerting beneficial regulation (e.g., Ruminiclostridium 6 and Alispites), and
modifying short-chain fatty acid metabolism. In summary, LRzz-1 showed
considerable antidepressant-like effects and exhibited more comprehensive
intestinal microecological regulation than other drugs, which offers
novel insights that can facilitate the development of depression therapeutic
strategies.