OBJECTIVETo investigate whether hepatitis B virus (HBV) can induce the expression of the host-encoded cytokine interleukin-32 (IL-32) and its effects on host signaling mechanisms related to HBV pathogenesis.

METHODSA eukaryotic expression vector harboring an enhanced green fluorescent protein was constructed with HBV genomic sequences (pIRES2-HBV-EGFP) and transfected into HepG2 cells. In addition, the nuclear factor-kappa B (NF-kB) subunits, p50 and p65, were transfected respectively into HepG2 cells. In both cases, 48 hrs after transfection, IL-32 expression was determined at the mRNA and protein levels using real-time PCR and ELISA and western blot, respectively. The HepG2 cells transfected with pIRES2-HBV-EGFP were also treated with the NF-kB inhibitor SN50 at various concentrations, and the effects on IL-32 protein expression 48 hrs later were evaluated by western blot. Significance of between-group differences was assessed by the Student's t-test.

RESULTSTransfection with pIRES2-HBV-EGFP led to significantly higher IL-23 expression than transfection with empty vector (mRNA: 2.8-fold higher and protein: 4.5-fold higher; both P less than 0.05). Transfection of p50 and p65 proteins led to significantly higher IL-32 expression (both P less than 0.05), and NF-kB activation was found to be required for HBV-induced IL-32 expression.

CONCLUSIONIL-32 expression is induced by HBV in HepG2 cells. This host-encoded cytokine, and its downstream activation of NF-kB, may be involved in the pathogenesis of HBV, especially in the subsequent liver inflammation that accompanies HBV infection.