Abstract
Diabetic nephropathy (DN) is one of the causes of end-stage renal failure, featuring renal fibrosis. However, autophagy, a vital process for intracellular homeostasis, can counteract renal fibrosis. Moreover, NAD(P)H: quinone dehydrogenase 1 (NQO1) modulates the ratios of reduced/oxidized nicotinamide nucleotides, exerting a cytoprotective function. Here, to examine the role of NQO1 genes in DN progression, the levels of autophagy-related proteins and pro-fibrotic markers were assessed in silencing or overexpression of NQO1 in human proximal tubular cells (HK2), and C57BL/6 (wild-type) and Nqo1 knockout (KO) mice injected to streptozotocin (50 mg/kg). NQO1 deficiency impaired the autophagy process by suppressing basal expression of ClassⅢ PI 3-kinase (Vps34) and autophagy-related (ATG)14L and inducing the expressions of transforming growth factor beta (TGF-β1), Smad3, and matrix metallopeptidase9 (MMP9) in high-glucose (HG) -treated HK2 cells. Meanwhile, NQO1 overexpression increased the expression of Vps34 and ATG14L, while, reducing TGF-β1, Smad3 and MMP9 expression. In vivo, the expression of Vps34 and ATG14L were suppressed in Nqo1 KO mice indicating aggravated glomerular changes and interstitial fibrosis. Therefore, NQO1 deficiency dysregulated autophagy initiation in HK2 cells, with consequent worsened renal cell damage under HG condition. Moreover, STZ-treated Nqo1 KO mice showed that NQO1 deficiency aggravated renal fibrosis by dysregulating autophagy.