IL-1β mediates miR-34a promotes bovine endometritis via LGR4-NF-κB axis
Abstract Background Persistent endometritis lead by bacterial infections has lethal effects on the reproductive performance of dairy cattle, which not only compromise animal welfare but also delay or prevent pregnancy. MicroRNA (miRNA) miR-34 family plays a pivotal role in the inflammatory process; however, the precise mechanism of miR-34a in endometritis is still not thoroughly revealed. Methods In this study, we established bovine endometrial epithelial cell (BENDs) inflammation model and mouse model stimulation with Lipopolysaccharide (LPS) in vitro and in vivo. CCK-8 was used to assess cell viability. H&E was used to characterize morphology. Immunohistochemistry, immunofluorescence, qRT-PCR and western blot assays were performed to measure the mRNA or protein expression of related genes. Online database, plasmid construction and dual-luciferase Reporter gene assays were applied to predict and validate the interaction between miR-34a and its target gene LGR4, and mice were injected vaginally with local antagomir to validate the role of miR-34a in murine uterine inflammation. Results Here, we report that miR-34a suppresses LGR4 gene expression by targeting its 3'untranslated regions (3'UTR). The miR-34a was up-regulated in cow uterine tissues and bovine endometrial epithelial cell (BENDs) stimulation with LPS. It further induces the release of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α by activating the phosphorylation level of NF-κB p65. Furthermore, we also revealed that IL-1β was responsible for the upregulation of miR-34a transcription and downregulation of LGR4 in an IL-1β-dependent manner. Conclusions Taken together, our study confirmed that miR-34a is regulated by IL-1β and suppress the level of LGR4 3’UTR which in turn exacerbates the inflammatory response. Thus knockdown miR-34a might be a new indirection for treatment endometritis.