NQO1 alleviates renal fibrosis by inhibiting the TLR4/NF-κB and TGF-β/Smad signaling pathways in diabetic nephropathy

Cell Signal. 2023 Aug:108:110712. doi: 10.1016/j.cellsig.2023.110712. Epub 2023 May 15.

Abstract

Objective: Diabetic nephropathy (DN) is one of the main complications of diabetes, and inflammation and fibrosis play an important role in its progression. NAD(P)H: quinone oxidoreductase 1 (NQO1) protects cells from oxidative stress and damage caused by toxic quinones. In the present study, we aimed to investigate the protective effects of NQO1 against diabetes-induced renal inflammation and fibrosis and the underlying mechanisms.

Methods: In vivo, the kidneys of type 2 diabetes model db/db mice were infected with adeno-associated virus vectors to induce NQO1 overexpression. In vitro, human renal tubular epithelial (HK-2) cells transfected with NQO1 pcDNA3.1(+) were cultured under high-glucose (HG) conditions. Gene and protein expression was assessed by quantitative real-time PCR, Western blotting, immunofluorescence, and immunohistochemical staining. Mitochondrial reactive oxygen species (ROS) were detected with MitoSOX Red.

Result: Our study revealed that the expression of NQO1 was markedly downregulated and that Toll-like receptor (TLR)4 and TGF-β1 expression was upregulated in vivo and in vitro under diabetic conditions. Overexpression of NQO1 suppressed proinflammatory cytokine (IL-6, TNF-α, MCP-1) secretion, extracellular matrix (ECM) (collagen IV, fibronectin) accumulation and epithelial-mesenchymal transition (EMT) (α-SMA, E-cadherin) in the db/db mouse kidneys and HG-cultured HK-2 cells. Furthermore, NQO1 overexpression ameliorated HG-induced TLR4/NF-κB and TGF-β/Smad pathways activation. Mechanistic studies demonstrated that a TLR4 inhibitor (TAK-242) suppressed the TLR4/NF-κB signaling pathway, proinflammatory cytokine secretion, EMT and ECM-related protein expression in HG-exposed HK-2 cells. In addition, we found that the antioxidants N-acetylcysteine (NAC) and tempol increased the expression of NQO1 and decreased the expression of TLR4, TGF-β1, Nox1, and Nox4 and ROS production in HK-2 cells cultured under HG conditions.

Conclusions: These data suggest that NQO1 alleviates diabetes-induced renal inflammation and fibrosis by regulating the TLR4/NF-κB and TGF-β/Smad signaling pathways.

Keywords: Diabetic nephropathy; Fibrosis; Inflammation; NQO1; TLR4.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytokines
  • Diabetes Mellitus, Type 2*
  • Diabetic Nephropathies* / metabolism
  • Epithelial-Mesenchymal Transition
  • Fibrosis
  • Humans
  • Inflammation / metabolism
  • Mice
  • NAD(P)H Dehydrogenase (Quinone)* / metabolism
  • NF-kappa B / metabolism
  • Reactive Oxygen Species / metabolism
  • Signal Transduction*
  • Toll-Like Receptor 4 / metabolism
  • Transforming Growth Factor beta1 / metabolism

Substances

  • Cytokines
  • NAD(P)H Dehydrogenase (Quinone)
  • NF-kappa B
  • NQO1 protein, human
  • Reactive Oxygen Species
  • TLR4 protein, human
  • Toll-Like Receptor 4
  • Transforming Growth Factor beta1