14-3-3γ regulates cell viability and milk fat synthesis in lipopolysaccharide-induced dairy cow mammary epithelial cells

Our previous study demonstrated that 14-3-3 gamma overexpression was able to inhibit the production of lipopolysaccharide (LPS) -induced cytokines in dairy cow mammary epithelial cells (DCMECs) by inhibiting the activation of nuclear factor-kappa B (NF-kappa B) signaling pathways. However, the association between 14-3-3 gamma overexpression and milk fat synthesis in LPS-induced DCMECs remains unclear. Therefore, the present study investigated the effect of 14-3-3 gamma on cell viability and milk fat synthesis in LPS-induced DCMECs. The results of the MTT assay and lactate dehydrogenase activity assay demonstrated that 14-3-3 gamma overexpression was able to attenuate LPS-induced cytotoxicity in DCMECs, and increase the viability of the cells. In addition, the results of reverse transcription-quantitative polymerase chain reaction suggested that mRNA expression levels of genes associated with milk fat synthesis, including sterol regulatory element binding protein (SREBP1), peroxisome proliferator-activated receptor-gamma (PPARG), cluster of differentiation 36, acetyl-coA carboxylase (ACC), fatty acid synthase (FAS) and fatty acid binding protein-3, were significantly upregulated in cells overexpressing the 14-3-3 gamma protein. In addition, as compared with the LPS-treated group, the activities of FAS and ACC were significantly increased. Furthermore, western blotting demonstrated that 14-3-3 gamma overexpression enhanced the protein expression levels of phosphorylated SREBP1 and PPARG. These results suggested that high levels of 14-3-3 gamma protein were able to attenuate LPS-induced cell damage and promote milk fat synthesis in LPS-induced DCMECs by increasing the cell viability and upregulating the expression levels of transcription factors associated with milk fat synthesis.