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Background & Aims
In decompensated cirrhosis, the early innate immune response to the Toll-like receptor 4 (TLR4) agonist, lipopolysaccharides (LPS), is characterized by a hyper-production of pro-inflammatory cytokines and hypo-production of the anti-inflammatory cytokine IL-10. In LPS-stimulated non-cirrhotic immune cells, the constitutively active glycogen synthase kinase (GSK) 3 favors pro-
vs. anti-inflammatory cytokines, by acting on gene induction. However, in these cells, TLR4 dampens its own pro-inflammatory response by inducing early (within minutes) AKT-mediated phosphorylation of GSK3¦Â (one of two GSK3 isoforms) on Ser9. Phosphorylation of GSK3¦Â (Ser9) inhibits its activity, decreases pro-inflammatory cytokines, and increases IL-10. Thus, we investigated the role of GSK3 in LPS-induced cytokine production by peripheral blood mononuclear cells (PBMCs) or monocytes from patients with advanced cirrhosis and normal subjects.
Methods
Cells were pre-incubated with or without GSK3 inhibitor (SB216763 or lithium chloride) for 1 h and then stimulated with LPS. Cytokine production was assessed at mRNA and secreted proteins levels, by real-time RT-PCR at 1 h and ELISA at 20 h, respectively. GSK3¦Â phosphorylation was assessed using Western blotting.
Results
In cirrhotic and normal PBMCs pretreated with GSK3 inhibitors, LPS-induced production of pro-inflammatory proteins TNF-¦Á and IL-12p40 was significantly decreased while that of IL-10 was increased. LPS-induced, AKT-mediated phosphorylation of GSK3¦Â on Ser9 found in normal monocytes, was abolished in cirrhotic cells.
Conclusions
GSK3 is involved in the early TLR4-mediated pro-inflammatory response in patients with decompensated cirrhosis. This was associated with a defect in AKT-mediated GSK3¦Â phosphorylation resulting in unrestricted ¡®pro-inflammatory?activity of the enzyme.