Lactobacillus rhamnosus GR-1 alleviates Escherichia coli-triggered bovine endometrial epithelial cells damage via the reactive oxygen species-mitochondrial pathway

Objective: The objective of this study was to evaluate the function of the reactive oxygen species (ROS)-mitochondrial pathway in attenuating <i>Escherichia coli</i> (<i>E. coli</i>) induced apoptosis in bovine endometrial epithelial cells (BENDs) by <i>Lactobacillus rhamnosus</i> (<i>L. rhamnosus</i>) GR-1.Methods: The BENDs were exposed to preincubation with and without <i>L. rhamnosus</i> GR-1 for 3 hours (h) and they were later subject to <i>E. coli</i> for 6 h. The release of lactate dehydrogenase (LDH), the expression of oxidative factors, adhesion and invasion of <i>E. coli</i>, the expression of mitochondrial membrane potential (MMP), apoptotic rate and apoptosis-associated protein expression were observed. Then, ROS expression, MMP level and cell rate apoptosis rate were further detected after the intervention of antioxidant n-acetyl-l-cysteine (NAC).Results: <i>L. rhamnosus</i> GR-1 was capable of obviously alleviating the content of LDH, ROS expression, <i>E. coli</i> adhesion and invasion, the apoptotic rate and MDA concentrations in BENDs induced by <i>E. coli</i> (p<0.01). In addition, <i>L. rhamnosus</i> GR-1 could notably promote the levels of antioxidant factors (SOD, GSH, T-AOC) (p<0.01), inhibit the depolarization of MMP (p<0.01), and levels of apoptosis-related factors (<i>Bax</i>, <i>Caspase-3</i> and <i>Cyt-c</i>), and promote anti-apoptosis factor (<i>Bcl-2</i>) (p<0.01). Moreover, after the intervention of antioxidant NAC, ROS expression, MMP depolarization, and apoptotic rate induced by <i>E. coli</i> in BENDs were decreased (p<0.01).Conclusion: In <i>E. coli</i>-induced apoptosis in BENDs, therapeutic strategies aimed at down-regulating ROS and MDA and up-regulating antioxidant factors may maintain mitochondrial function and provide theoretical support for the use of probiotics in bovine endometritis.