γ-D-glutamyl-meso-diaminopimelic acid (iE-DAP), a bacterial cell wall component, can trigger an inflammatory response. A mammary inflammatory response causes tight junction (TJ) dysfunction. This study aimed to explore the effects and involved mechanisms of iE-DAP-induced inflammatory response on the TJ integrity in bovine mammary epithelial cells (BMECs). The results showed that iE-DAP-induced inflammatory response and TJ disruption was associated with increased expression levels of inflammatory cytokines and decreased gene expression of ZO-1 and Occludin, as well as a reduction in transepithelial electrical resistance and elevation in paracellular dextran passage. While MLCK inhibitor ML-7 reversed the TJ disruption induced by iE-DAP. NF-κB inhibitor BAY 11-7085 hindered the activation of NF-κB and MLCK signaling pathways, the inflammatory response and TJ disruption induced by iE-DAP. NOD1-specific shRNA also inhibited the activation of the NOD1/NF-κB signaling pathway and reversed the inflammatory response and TJ injury in iE-DAP-treated BMECs. Above results suggest that iE-DAP activated the NF-κB and MLCK signaling pathway in NOD1-dependent manner, which promoted the transcription of inflammatory cytokines and altered the expression and distribution of tight junction proteins, finally caused inflammatory response and TJ disruption. This study might provide theoretical basis and scientific support for the prevention and treatment of mastitis.

Metabolism-disorder-induced liver diseases have become increasingly prevalent worldwide and are clinically linked to obesity and type 2 diabetes. In addition, a large number of previous literature studies have indicated that plasma miR-130b is a promising biomarker for the early diagnosis and treatment of obesity. However, whether miRNA-130b that was positively correlated with obesity resulted in hepatic inflammation needs to be further studied. Therefore, the study aims to determine the effect of microvesicle-shuttled miRNA-130b (miR-130b-MV) on the hepatic inflammation and its potential mechanism in high-fat diet-induced obese mice. Three-week-old C57BL/6 mice were fed a high-fat diet for eight weeks. Then, the obese mice received tail vein injections of MV-packaged scrambled control microRNA (miR-SC-MV) or miR-130b-MV every other day for 10 days. Compared with the control group, the miR-130b-MV injection significantly reduced the body weight while increasing the ratio of liver wet weight to total body weight. In addition, the miR-130b-MV injection significantly activated the hepatic inflammation by increasing the expression of proinflammatory genes, although the plasma concentrations of IL-6 and TNF-α were only slightly increased. Furthermore, the miR-130b-MV injection significantly increased the hepatic miR-130b expression while significantly suppressing the protein expression and phosphorylation of GR, a potential target of miR-130b. Moreover, the miR-130b overexpression results in a decrease in the expression of endogenous GR protein and a decrease in the activity of the luciferase reporter of GR 3′-UTR. In addition, the miR-130b-MV injection significantly upregulated NF-kB (p50) in both the cytoplasm and nucleus, showing enhanced proinflammation response. The above results demonstrated that miR-130b-MV activated the hepatic inflammation by inhibiting GR-mediated immunosuppression in high-fat diet-induced obese mice, suggesting a novel mechanism underlying the obesity-induced hepatic inflammation, and the inhibition of miR-130b may serve as a new molecular therapeutic target for the prevention and treatment of hepatic inflammation.