Lactobacillus rhamnosus GG and Lactobacillus paracasei IMPC2.1 Mitigate LPS-Induced Epithelial Barrier Dysfunction: A Focus on Autophagy Regulation

The intestinal epithelial barrier is critical for maintaining gut homeostasis, yet its integrity can be compromised by inflammation and microbial dysbiosis. Here, we demonstrate that Lactobacillus rhamnosus GG (LGG) and Lactobacillus paracasei IMPC2.1 (L. paracasei) show their effectiveness in enhancing epithelial barrier function and modulating autophagy, counteract the epithelial barrier dysfunction, induced by Lipopolysaccharide (LPS), in Caco-2 cells by modulating tight junction (TJ) protein expression through regulation of inflammation and apoptosis. LPS exposure significantly reduced transepithelial electrical resistance (TEER) and increased paracellular permeability, effects that were partially reversed by both probiotic strains. Western blot analysis revealed that LPS downregulated ZO-1, Occludin, and p-mTOR, while upregulating autophagy markers LC3-II and Beclin1, without affecting p62 levels. The latter finding indicated an impairment of autophagy flux, confirmed by immunofluorescence experiments. Co-treatment with LGG or L. paracasei restored TJ protein expression and alleviated the LPS-induced impairment of autophagic flux. Both probiotics suppressed LPS-induced cyclooxygenase-2 (Cox-2) and Bax upregulation, suggesting anti-inflammatory and anti-apoptotic effects. In the complex interplay between inflammation, autophagy, and apoptosis, these findings highlight a key regulatory mechanism in probiotic-mediated epithelial protection, underscoring the therapeutic potential of LGG and L. paracasei in mitigating gut barrier dysfunction.