Background MMP8 inhibitors may serve as potential therapeutic targets for sepsis. Currently, there are limited domestic studies investigating the effects of MMP8 inhibitors on the treatment of sepsis and their impact on the gut microbiome of mice.

Objective To investigate the compositional characteristics of the gut microbiome in septic mice, identify differential microbiome, and evaluate the impact of MMP8 inhibitors on the gut microbiome of these septic mice.

Methods Twenty 6-week-old SPF grade C57BL/6J mice were randomly assigned to model group, treatment group, sham operation group, and control group, with five mice in each group. The treatment and model groups underwent laparotomy to expose the cecum, followed by mid-point ligation and puncture for establishing the sepsis model. Mice in the sham operation group underwent the same abdominal procedure, but the cecum was not ligated or punctured, and the cavity was closed afterward. Twenty-four hours prior to modeling, the treatment and sham operation groups received intraperitoneal injections of 0.3 mg/kg MMP8 inhibitor every 12 hours, while the control and model groups were administered an equal volume of PBS buffer. All mice were sacrificed at 24 hours after surgery, and the colon contents from each group were collected for sequencing of the V3-V4 region of the 16S rRNA gene. Subsequently, the α and β-diversity, as well as the gut microbiome composition of each group, were analyzed to assess changes in differential microbiome composition and diversity.

Results Compared with the model group, the number of ASVs (P=0.029), Observed species index (P=0.029), Chao1 index (P=0.028), and Shannon index (P=0.016) in the treatment group after treatment were significantly increased. PCA (P=0.001), PCoA (P=0.001) and NMDS(P=0.001, Stress=0.13) analysis results showed that the microbial community compositions of the treatment and model groups exhibited significant phylogenetic distancing from the control and sham-operation groups, showing no overlapping clusters. Notably, post-treatment microbial profiles in the treatment group demonstrated partial overlap with those of the model group. The main bacterial genera in treatment group were Muribaculaceae-unclassified, Escherichia-Shigella, Enterobacter; the main bacterial genera in the model group were Ligilactobacillus, Escherichia-Shigella, and Enterobacter. LEfSe analysis found that the differential bacteria in the treatment group were Enterobacter and Klebsiella, and the model group was Escherichia-Shigella. Compared with the sham operation group, the ratio of Firmicutes to Proteobacteria was reduced in the treatment (P=0.001) and model groups (P=0.001). Compared with the model group, the gut microbiome of the mice in the treatment group were up-regulated in metabolic pathways dominated by Amino acid related enzymes and Cell cycle-Caulobacter, and down-regulated in metabolic pathways dominated by Glycosyltransferases and Bacterial secretion system.

Conclusion In septic mice, increased abundance of pathogenic bacteria in the gut microbiota reduce microbial diversity, whereas MMP8 inhibitor intervention restore diversity, characterized by elevated beneficial bacteria and suppressed harmful bacterial populations.