Ubiquitin-specific protease 7 exacerbates acute pancreatitis progression by enhancing ATF4-mediated autophagy.

Abstract

Acute pancreatitis (AP) is a serious inflammatory disease with high incidence rate and mortality. It was confirmed that overactivation of autophagy in acinar cells can increase the risk of AP. Nevertheless, the regulatory mechanism of autophagy in AP is unclear. The role of ubiquitin-specific peptidase 7 (USP7) in controlling autophagy during AP development was examined in this study. AR42J cells were subjected to caerulein to establish a cell model of AP. ELISA utilized to assess IL-6, IL-1β, and TNF-α secretion levels. Cell viability and death were detected using CCK8 assay and flow cytometry, respectively. The interaction between USP7 and ATF4 was analyzed by Co-IP assay. USP7 and ATF4 were abnormally overexpressed in AP patients and cellular models. Loss of function of USP7 increased cell viability, but alleviated cell death and secretions of inflammatory cytokines including IL-6, IL-1β, and TNF-α in AP cellular models. Importantly, autophagy level was activated in AP cells, and could be repressed after USP7 knockdown, and rapamycin treatment greatly diminished the beneficial functions mediated by USP7 downregulation in AP cells. Mechanically, ATF4, an activator of stress autophagy in AP, was proved to be a deubiquitination modification target downstream of USP7, and its protein stability was weakened after USP7 reduction. ATF4 upregulation abolished the protective effect of USP7 silencing on caerulein-induced autophagy, inflammation, and cell injury in AR42J cells. USP7 knockdown reduced inflammation and cell injury during AP progression by inhibiting ATF4-mediated autophagy activation.