Exosomal miR-193b-5p as a regulator of LPS-induced inflammation in dairy cow mammary epithelial cells.

Exosomes are a type of extracellular vesicle that act as shuttles, transporting certain genetic information to other cells. MiRNA cargo within exosomes can regulate gene expression at the transcriptional level. The objective of this study was to investigate the exosomal miRNAs that regulate lipopolysaccharide (LPS)-induced inflammation in dairy cow mammary alveolar (Mac-T) cells. We found two exosome miRNAs upregulated and five exosomal miRNAs downregulated, respectively, in the LPS-stimulated Mac-T cells. MiR-193b-5p was upregulated 6.3-fold in the LPS-stimulated cell-derived exosome. Target prediction results showed that nuclear factor kappa B (NF-κB) inhibitor delta (NFKBID), transforming growth factor-beta 1 induced transcript 1 (TGFB1I1), interleukin 22 (IL-22), TNF receptor superfamily member 11b (TNFRSF11B), and Janus kinase 3 (JAK3) might be the main target genes of miR-193b-5p. After treatment of Mac-T cells with the miR-193b-5p mimic, the phosphorylation levels of inhibitor of nuclear factor-kappa Bα (IκBα) and p65 were upregulated, the level of IL-6 mRNA was upregulated, and IL-1β, TNF-α, and TGF-β mRNA levels were downregulated. After treatment of Mac-T cells with miR-193b-5p inhibitor, the phosphorylation levels of IκBα and p65 were downregulated. In summary, these findings provide strong evidence that exosomal miR-193b-5p could be a regulator of LPS-induced inflammation in Mac-T cells and reveal a new role of exosomal miRNAs in regulating dairy cow mastitis.