GABA-producing Lactococcus lactis alleviates gut dysfunction and neurobehavioral abnormalities associated with...

Aim: This study aimed to screen Lactococcus lactis strains with varying gamma-aminobutyric acid (GABA) production and evaluate their effects on intestinal dysfunction and neurobehavioral abnormalities in an irritable bowel syndrome (IBS) mouse model, with a focus on GABAergic signaling and dose-dependent mechanisms. Methods: Three Lactococcus lactis strains were selected based on GABA yield and genetic analysis. IBS was induced in mice via Citrobacter rodentium infection and water avoidance stress. Intestinal integrity, inflammation, histopathology, and behavior were assessed. GABA levels in the colon and serum were measured by liquid chromatography-mass spectrometry (LC-MS). GABA receptor subunit expression in the colon, hippocampus, and amygdala was analyzed via quantitative real-time polymerase chain reaction and Western blotting. Results: GABA-producing strains alleviated intestinal dysfunction in IBS mice by reducing IL-6 gene expression and iNOS activity, upregulating CLDN2, and improving tissue integrity. Anxiety-like behaviors and cognitive deficits were also attenuated. Colonic GABA levels, GABRA13 mRNA, and GABRA3 protein expression increased in a dose-dependent manner, whereas TRPV1 mRNA and TRPV1 protein levels were downregulated. Serum GABA remained unchanged. In the central nervous system, the expression of hippocampal GABA_A and GABA_B receptors was elevated, with both GABRA13 mRNA and GABRA3 protein levels positively correlating with colonic GABA concentrations. GABRA15 expression was upregulated in the amygdala. Conclusion: GABA-producing Lactococcus lactis effectively alleviates IBS-related intestinal dysfunction and neurobehavioral abnormalities by coordinately modulating GABAergic signaling in both the gut and the central nervous system, exhibiting a clear dose-dependent effect across multiple key phenotypes.