The Role of GSK3β in the Regulation of IL-10 and IL-12 Production Induced by Lipopolysaccharide in PK-15 Cells

GSK3β inhibition attenuates LPS-induced IL-6 expression in porcine adipocytes

IL-6 is not only a proinflammatory cytokine associated with inflammatory responses but also a regulator on the energy and glucose metabolism in adipose tissue. Glycogen synthase kinase 3β (GSK3β) has fundamental roles in the regulation of pro- and anti-inflammatory cytokines production. However, the regulatory role for GSK3β in the pig inflammatory response in adipocytes remains unknown. We show here that SB216763 and LPS increased the phosphorylation of GSK3β (Ser9), and decreased the phosphorylation of GS (Ser641) in adipocytes. The activity of porcine GSK3β was inhibited by SB216763, an inhibitor of GSK3β, attenuated the production of IL-6 in LPS-stimulated adipocytes. Additionally, the essential core region of the pig IL-6 promoter located at -191 bp to -59 bp, and an NF-κBp65 element in this region was responsible for IL-6 promoter activity. The transcription activity of NF-κBp65 was activated by LPS stimulation, and the GSK3β inhibition repressed LPS-induced luciferase activity of the IL-6 promoter. Furthermore, LPS increased p65 binding to the NF-κB site, and GSK3β inhibition had no effect on the association of NF-κBp65 with IL-6 gene promoter after LPS treatment. These results demonstrate that GSK3β has important regulatory roles in the LPS-induced inflammatory response of IL-6 production in pig adipocytes.

Suppression of Virulent Porcine Epidemic Diarrhea Virus Proliferation by the PI3K/Akt/GSK-3α/β Pathway

Porcine epidemic diarrhea virus (PEDV) has recently caused high mortality in suckling piglets with subsequent large economic losses to the swine industry. Many intracellular signaling pathways, including the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, are activated by viral infection. The PI3K/Akt pathway is an important cellular pathway that has been shown to be required for virus replication. In the present study, we found that the PEDV JS-2013 strain activated Akt in Vero cells at early (5-15 min) and late stages (8-10 h) of infection. Inhibiting PI3K, an upstream activator of Akt, enhanced PEDV replication. Inhibiting GSK-3α/β, one of the downstream effectors of PI3K/Akt pathway and regulated by Akt during PEDV infected Vero cells, also enhanced PEDV replication. Collectively, our data suggest that PI3K/Akt/GSK-3α/β signaling pathway is activated by PEDV and functions in inhibiting PEDV replication.