DMDD, isolated from Averrhoa carambola L., ameliorates diabetic nephropathy by regulating endoplasmic reticulum stress-autophagy crosstalk

Abstract

Studies have shown that Averrhoa carambola L. possesses therapeutic potential for diabetes and related complications. However, the specific beneficial effects and molecular mechanisms of 2-dodecyl-6-meth-oxycyclohexa-2,5-diene-1,4-dione (DMDD) isolated from Averrhoa carambola L. on diabetic nephropathy (DN) require further investigation. 80 C57BL/6 J male mice were subjected to a 1-week adaptive feeding, followed by a high-fat diet and intraperitoneal injection of 100 mg/kg streptozotocin (STZ) to construct an in vivo DN model. Additionally, human renal proximal tubular epithelial cells (HK-2) induced by high glucose (HG) were used as an in vitro DN model. The expression levels of epithelial-mesenchymal transition (EMT), endoplasmic reticulum stress (ERS), and autophagy-related proteins in renal tubular cells were detected by Western Blot, flow cytometry, immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) staining. Transcriptome analysis revealed was conducted to elucidate the specific mechanism of by which DMDD mitigates DN by inhibiting ERS and autophagy. HK-2 cells were transfected with IRE1α overexpression lentivirus to reveal the role of IRE1α overexpression in HG-induced HK-2. The experimental data showed that DMDD significantly reduced blood glucose levels and improved renal pathological alterations in DN mice. Additionally, DMDD inhibited the calcium (Ca2+) pathway, manifested by decreased autophagosome formation and downregulation of LC3II/I, Beclin-1, and ATG5 expression. Moreover, in HG-induced HK-2 cells, DMDD suppressed the overexpression of GRP78, CHOP, LC3II/I, Beclin1, and ATG5. Notably, IRE1α overexpression significantly increased autophagy incidence; however, DMDD treatment subsequently reduced the expression of LC3II/I, Beclin1, and ATG5. DMDD effectively inhibits excessive ERS and autophagy, thereby reducing renal cell apoptosis through the IRE1α pathway and Ca 2+ pathway.