ANGPTL2 regulates autophagy through the MEK/ERK/Nrf-1 pathway and affects the progression of renal fibrosis in diabetic nephropathy

摘要

Background: Diabetic nephropathy (DN) is one of the most important microvascular complications of diabetes mellitus. The present study aims to explore whether angiopoietin-like protein 2 (ANGPTL2) can promote renal tissue fibrosis in DN. Materials and methods: Models includes diabetic SD rats induced by streptozotocin (STZ) and high glucose (HG)-stimulated HK-2 cells. qRT-PCR, western blot and immunohistochemical analysis were performed to explore ANGPTL2 expression. The renal injury and fibrosis were assessed using hematoxylin-eosin staining (H&E) and Masson trichrome staining. Immunofluorescence was conducted to detect the expression of collagen IV and LC3II. The levels of pro-inflammatory factors IL-6, -1β, TNF-α and ANGPTL2 were assessed by an ELISA, and nitric oxide (NO) production was determined using Griess method. Protein levels of iNOS, PTEN, fibronectin (FN), collagen I, IV, p62, beclin1 and MEK/ERK/Nrf-1 pathway in DN rats and HK-2 cells were determined, respectively. Results: When compared with normal rats, DN rats experienced severe renal injury and fibrosis and showed decreased LC3II and beclin1, increased PTEN, FN, collagen I and IV, p62, NO, iNOS and ANGPTL2 in kidney. The pro-inflammatory factors and ANGPTL2 were markedly elevated. Again, knockdown of ANGPTL2 caused an increase in MEK, p-ERK, Nrf-1, LC3II, beclin1, and a decrease in PTEN, FN, collagen I and IV, p62, NO, iNOS and pro-inflammatory factors of HK-2 cells. Furthermore, knockdown of MEK/ERK reversed these changes. Conclusion: ANGPTL2 may serve an important role in the autophagy of DN and activate MEK/ERK/Nrf-1 pathway, which may therefore have potential as a treatment to prevent renal fibrosis in DN.