PI3K/AKT/mTOR Signaling Pathway Regulates MMP9 Gene Activation via Transcription Factor NF-κB in Mammary Epithelial Cells of Dairy Cows

Background Matrix metalloproteinase 9 (MMP9) plays a pivotal role in mammary ductal morphogenesis, angiogenesis, and glandular tissue architecture remodeling. However, the molecular mechanism of MMP9 expression in mammary epithelial cells of dairy cows remains unclear. The current study aimed to explore the underlying mechanism of MMP9 expression. Results In this study, to determine whether the PI3K/AKT/mTOR/NF-κB signaling pathway participates in the regulation of MMP9 expression, we treated mammary epithelial cells with specific pharmacological inhibitors of PI3K (LY294002), mTOR (Rapamycin), or NF-κB (Celastrol), respectively. Western blotting results indicated that LY294002, Rapamycin, and Celastrol markedly decreased MMP9 expression and P65 nuclear translocation. Furthermore, we found that NF-κB (P65) overexpression resulted in elevated expression of MMP9 protein and activation of MMP9 promoter. In addition, we observed that Celastrol markedly decreases P65-overexpression-induced MMP9 promoter activity. Moreover, the results of the promoter assay indicated that the core regulation sequence for MMP9 promoter activation may be located -80bp to -420bp downstream from the transcription start site. Conclusions These observations indicated that the PI3K/AKT/mTOR signaling pathway is involved in MMP9 expression by regulating MMP9 promoter activity via NF-κB in the mammary epithelial cells of dairy cows.