Lacticaseibacillus rhamnosus GR-1 attenuates Escherichia coli -induced endometritis in mice, accompanied by modulation of uterine microbiota and metabolite profiles

Objective Endometritis in dairy cows is a highly prevalent infectious disease in cattle farming, which can cause persistent inflammatory responses in the uterus. This study aimed to evaluate the therapeutic efficacy of Lacticaseibacillus rhamnosus ( L. rhamnosus ) GR-1 against Escherichia coli ( E. coli )-induced endometritis in mice and investigate its regulatory effects on uterine microbiota and metabolites. Methods A total of 36 female BALB/c mice aged 7-8 weeks were randomly divided into 4 groups: CONT group, ECOL group (1.0×10 8 CFU/mL E. coli ), AMP group (0.1 mg/kg ampicillin), and GR-1 group (1.0×10 9 CFU/mL L. rhamnosus GR-1). Uterine morphological characteristics were observed, and the expression of uterine inflammatory cytokines, oxidative apoptosis-related genes and proteins, as well as related reproductive indices were detected. 16S rRNA sequencing and metabolomic sequencing were performed to evaluate the profiles of uterine microbiota and metabolites. Results L. rhamnosus GR-1 effectively alleviated E. coli -induced uterine edema and inflammatory infiltration, and modulated the levels of inflammatory factors (MPO, IL-6, IL-1β, TNF-α, IL-10 and MDA) in the uterus. Meanwhile, this strain elevated the levels of antioxidant factors (GSH-Px and SOD), inhibited the expression of the oxidative apoptosis-related factors Keap1, Bax and caspase-3, and upregulated that of Nrf2, HO-1, NQO1 and Bcl-2. Furthermore, treatment with L. rhamnosus GR-1 increased the abundance of beneficial uterine microbiota, promoted the accumulation of L-isoleucyl-L-proline and N-acetylcysteine, and ameliorated the pregnancy status of mice. Conclusion L. rhamnosus GR-1 enhanced uterine anti-inflammatory and antioxidant stress capacity to alleviate E. coli -induced endometritis in mice. It modulated uterine microbiota and metabolites, and also improved the reproductive capacity of mice. Thus it may provide a potential antibiotic alternative for the treatment of dairy cow endometritis.