Ubiquitin-specific protease 7 regulates macrophage polarization via pyruvate kinase M2-mediated metabolic reprogramming in severe acute pancreatitis

Severe acute pancreatitis (SAP) is a life-threatening inflammatory condition, with macrophage polarization playing a pivotal role in its pathogenesis. This study aims to investigate the role and underlying mechanism of ubiquitin-specific protease 7 (USP7) in regulating macrophage polarization in SAP. The expression of USP7 in the pancreas of SAP mice were assessed to determine its involvement in the disease. Histological evaluation, immunofluorescence, flow cytometry, and Western blotting were utilized to phenotype macrophages and assess the expression of inflammatory markers in both mouse models and cell cultures. Seahorse assays were employed to measure the extracellular acidification rates (ECAR) and oxygen consumption rates (OCR). The interaction between USP7 and pyruvate kinase M2 (PKM2) was determined using co-immunoprecipitation (Co-IP) and ubiquitinated IP assays. Compound 3 K was administered to SAP mice for rescuing the impact of USP7 knockdown. USP7 expression was upregulated in pancreatic macrophages of mice with SAP, and its knockdown alleviated SAP, as evidenced by reduced serum amylase and lipase activities, as well as decreased expression of pro-inflammatory cytokines. USP7 knockdown also shifted macrophage polarization from M1 to M2 types, both in vivo and in vitro. Mechanistically, USP7 modulated the metabolic reprogramming of M1 macrophages by mediating PKM2 deubiquitination, which influenced its phosphorylation and nuclear translocation. Furthermore, a PKM2 inhibitor partially reversed the protective effects of USP7 knockdown in SAP mice, confirming that USP7's regulatory functions depend on PKM2. USP7 regulates macrophage polarization in SAP through PKM2-mediated metabolic reprogramming, providing novel insights into the therapeutic targeting of SAP.