Phosphatidylinositol 3-kinase/Akt signaling mediates interleukin-32α induction in human pancreatic periacinar myofibroblasts

Interleukin (IL)-32 is a recently described proinflammatory cytokine, characterized by the induction of nuclear factor (NF)-κB activation. We studied IL-32α expression in human pancreatic periacinar myofibroblasts, which play important roles in the regulation of extracellular matrix metabolism and inflammatory responses in the pancreas. IL-32α protein expression was evaluated by Western blot analyses, and IL-32α mRNA expression was analyzed by Northern blot and real-time PCR analyses. IL-32α mRNA was weakly expressed without a stimulus, and its expression was markedly enhanced by IL-1β, IFN-γ, and TNF-α. IL-1β, IFN-γ, and TNF-α enhanced intracellular accumulation of IL-32α protein, but IL-32α was not detected in supernatants. Each cytokine dose and time dependently induced IL-32α mRNA expression. An inhibitor of phosphatidylinositol 3-kinase (LY294002) significantly suppressed IL-1β-, IFN-γ-, and TNF-α-induced IL-32α mRNA expression, although MAPK inhibitors had no effect. Akt activation in response to these cytokines was confirmed by Western blot. Furthermore, LY294002 suppressed both IL-1β- and TNF-α-induced NF-κB activation and IL-1β-, TNF-α-, and IFN-γ-induced activated protein-1 (AP-1) activation. Blockade of NF-κB and AP-1 activation by an adenovirus expressing a stable mutant form of IκBα and a dominant negative mutant of c-Jun markedly suppressed IL-1β-, IFN-γ-, and/or TNF-α-induced IL-32α mRNA expression. Human pancreatic periacinar myofibroblasts expressed IL-32α in response to IL-1β, TNF-α, and IFN-γ. IL-32α mRNA expression is dependent on interactions between the phosphatidylinositol 3-kinase/Akt-pathway and the NF-κB/AP-1 system.