OBJECTIVETo investigate the role of glycogen synthase kinase 3β (GSK-3β) in the maturation and function of murine bone marrow-derived dendritic cells (BMDCs).

METHODSMature DCs (mDCs) induced by LPS were examined for GSK-3β phosphorylation level with Western blotting before and after LPS exposure. To explore the role of GSK-3β in maturation and function of DCs, we added SB216763, a selective inhibitor of GSK-3β, in the cell culture of immature DCs (iDCs), and examined CD40 and CD86 expressions in the cells by flow cytometry and the expression of IL-6, IL-12 and IL-10 mRNA by real-time PCR; the changes of the immunogenicity of the cells was evaluated by mixed lymphocyte reaction. The expression of GSK-3β and RelB was examined by Western blotting in DC2.4 cells transfected with a lentiviral vector over-expressing murine GSK-3β gene.

RESULTSLPS exposure significantly lowered GSK-3β activity in iDCs as demonstrated by increased Ser9 phosphorylation and reduced Tyr216 phosphorylation. GSK-3β inhibition induced DC maturation by increasing the expression of surface costimulatory molecules CD40 and CD86, lowered the expressions of IL-6 and IL-12 while enhanced the expression of IL-10 in iDCs, and impaired mixed lymphocyte reaction of the cells. In DC2.4 cells, lentivirus-mediated over-expression of GSK-3β obviously down-regulated the expression of RelB.

CONCLUSIONSGSK-3β is a crucial enzyme involved in the differentiation and maintenance of an immature phenotype of DCs. GSK-3β is constitutively active in iDCs to inhibit their spontaneous maturation. DCs become phenotypically mature after inhibition of GSK-3β, which also executes a proinflammatory task in DC activation. The reduction of RelB protein levels as a result of GSK-3β overexpression supports GSK-3β as a new target for inducing tolerogenic DCs.