IL-27 induces autophagy during monocyte-to-macrophage differentiation through a novel LC3-independent pathway

Abstract

Abstract IL-27, a member of the IL-12 cytokine family composed of IL-12, IL-23 and IL-35, has previously been shown to be an antiviral cytokine inhibiting infection of several viruses, among which HIV-1, HIV-2, HSV, HCV, HBV and Influenza virus. We have already reported that IL-27 induces HIV-1 inhibition in macrophages and dendritic cells in an IFN-independent manner, and that the cytokine enhances potential reactive oxygen species induction from cells. In this study, we demonstrated for the first time that IL-27 triggers autophagy induction in human AB serum-induced macrophages, while other IL-12 cytokine family members did not have such effect on these cells; IL-27 was able to induce autophagy both in terminally differentiated macrophages, causing a 2 to 5-fold increase in autophagosome accumulation, as well as during monocyte-to-macrophage differentiation, where IL-27 effect was even stronger (generating a 20-fold increase in autophagosome formation). Furthermore, we also determined that two key autophagy proteins, mTOR and LC3, were not involved in this phenomenon: while we were able to assess autophagosome accumulation in IL-27-treated cells via electron microscopy and immunofluorescence, this was not linked to either mTOR dephosphorylation nor LC3 lipidation, implying that IL-27 induces autophagy through a novel non-canonical pathway. Finally, we established that blocking IL-27 signaling during macrophage differentiation using both Ruxoliotinib or Tofacitinib, respectively JAK1/2 and JAK3 inhibitors, successfully inhibited autophagy triggering together with STAT3 phosphorylation, which suggests that the JAK-STAT pathway is responsible for regulating IL-27-induced autophagy.