Role of Nox2 in diabetic kidney disease

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333

Diabetic nephropathy may occur, in part, as a result of intrarenal oxidative stress. NADPH oxidases comprise the only known dedicated reactive oxygen species (ROS)-forming enzyme family. In the rodent kidney, three isoforms of the catalytic subunit of NADPH oxidase are expressed (Nox1, Nox2, and Nox4). Here we show that Nox4 is the main source of renal ROS in a mouse model of diabetic nephropathy induced by streptozotocin administration in ApoE 2/2 mice. Deletion of Nox4, but not of Nox1, resulted in renal protection from glomerular injury as evidenced by attenuated albuminuria, preserved structure, reduced glomerular accumulation of extracellular matrix proteins, attenuated glomerular macrophage infiltration, and reduced renal expression of monocyte chemoattractant protein-1 and NF-kB in streptozotocin-induced diabetic ApoE 2/2 mice. Importantly, administration of the most specific Nox1/4 inhibitor, GKT137831, replicated these renoprotective effects of Nox4 deletion. In human podocytes, silencing of the Nox4 gene resulted in reduced production of ROS and downregulation of proinflammatory and profibrotic markers that are implicated in diabetic nephropathy. Collectively, these results identify Nox4 as a key source of ROS responsible for kidney injury in diabetes and provide proof of principle for an innovative small molecule approach to treat and/or prevent chronic kidney failure.

Section: Discussionmentioning

confidence: 99%

Genetic Targeting or Pharmacologic Inhibition of NADPH Oxidase Nox4 Provides Renoprotection in Long-Term Diabetic Nephropathy

Jha

Gray

Barit

et al. 2014

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309

333

“…Deletion of either Nox4 or -2 in STZ-induced diabetes is not beneficial and may even be deleterious in the case of Nox4, supporting studies showing that Nox4 may play a protective role in chronic kidney injury and endothelial dysfunction. [43][44][45][46] However, the role of Nox4 remains controversial in the diabetic setting, because short-term pharmacological Nox4 inhibition reduces renal ROS generation, glomerular hypertrophy, and fibronectin expression. 42 Unlike other Nox family members, nothing is known regarding the function of Nox5 in animal models of disease, owing mainly to its absence from the mouse and rat genome.…”

Section: Discussionmentioning

confidence: 99%

Nephropathy and Elevated BP in Mice with Podocyte-Specific NADPH Oxidase 5 Expression

Holterman¹,

Thibodeau²,

Towaij³

et al. 2014

110

122

NADPH oxidase (Nox) enzymes are a significant source of reactive oxygen species, which contribute to glomerular podocyte dysfunction. Although studies have implicated Nox1, -2, and -4 in several glomerulopathies, including diabetic nephropathy, little is known regarding the role of Nox5 in this context. We examined Nox5 expression and regulation in kidney biopsies from diabetic patients, cultured human podocytes, and a novel mouse model. Nox5 expression increased in human diabetic glomeruli compared with nondiabetic glomeruli. Stimulation with angiotensin II upregulated Nox5 expression in human podocyte cultures and increased reactive oxygen species generation. siRNA-mediated Nox5 knockdown inhibited angiotensin II-stimulated production of reactive oxygen species and altered podocyte cytoskeletal dynamics, resulting in an Rac-mediated motile phenotype. Because the Nox5 gene is absent in rodents, we generated transgenic mice expressing human Nox5 in a podocyte-specific manner (Nox5 pod+ ). Nox5 pod+ mice exhibited early onset albuminuria, podocyte foot process effacement, and elevated systolic BP. Subjecting Nox5 pod+ mice to streptozotocin-induced diabetes further exacerbated these changes. Our data show that renal Nox5 is upregulated in human diabetic nephropathy and may alter filtration barrier function and systolic BP through the production of reactive oxygen species. These findings provide the first evidence that podocyte Nox5 has an important role in impaired renal function and hypertension. Albuminuria is a clinical marker of kidney dysfunction that arises in most glomerulopathies and is associated with poor prognoses for ESRD, hypertension, and cardiovascular mortality. Changes to the podocyte (e.g., foot process effacement, hypertrophy, detachment, and loss) underlie the development and progression of albuminuria and thereby highlight the critical role for these cells in upholding the glomerular filtration barrier. 1,2 Therefore, identifying factors that induce podocyte injury and loss is essential to understanding the mechanisms of filtration barrier dysfunction. Of the many factors implicated in podocyte dysfunction, excessive production of reactive oxygen species (ROS; oxidative stress) may be particularly important. [3][4][5][6] Although sources of ROS are numerous, the NADPH oxidase (Nox) family of enzymes yields significant superoxide production in the

“…At the end of the study period, a 24-hour urine collection was obtained in metabolic cages, blood was obtained by venous puncture, and kidneys were harvested as previously described. 1 Glomeruli were isolated by magnetic bead-based isolation as described. 44 Blood glucose was measured using the Accu-Chek meter system (Roche Diagnostics).…”

Section: C57bl/6-ins2mentioning

confidence: 99%

“…Among the seven members of the NOX family, NOX1, NOX2 (also named gp91 phox ), and NOX4 are expressed in kidneys of humans and mice, whereas NOX5 is expressed only in humans. [1][2][3][4][5] We have been examining the role of NOX isoforms in diabetic kidney disease (DKD) and we recently found that NOX2 did not play a major role in mediating DKD with type 1 diabetes. 1,6 However, NOX4 was upregulated in the NOX2 knockout (KO) diabetic kidney, particularly in glomeruli and podocytes, and thus may play a prominent role.…”

mentioning

confidence: 99%

“…[1][2][3][4][5] We have been examining the role of NOX isoforms in diabetic kidney disease (DKD) and we recently found that NOX2 did not play a major role in mediating DKD with type 1 diabetes. 1,6 However, NOX4 was upregulated in the NOX2 knockout (KO) diabetic kidney, particularly in glomeruli and podocytes, and thus may play a prominent role. Recent studies with total body deletion of NOX4 revealed that NOX4, but not NOX1, is necessary for progression of DKD in ApoE KO mice 7 ; however, in a different mouse model of DKD, the Nox4 KO mouse did not show protection in the B6 background.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Metabolomics Reveals a Key Role for Fumarate in Mediating the Effects of NADPH Oxidase 4 in Diabetic Kidney Disease

You

Quach

Saito

et al. 2016

Self Cite

158

159

The NADPH oxidase (NOX) isoform NOX4 has been linked with diabetic kidney disease (DKD). However, a mechanistic understanding of the downstream effects of NOX4 remains to be established. We report that podocyte-specific induction of NOX4 in vivo was sufficient to recapitulate the characteristic glomerular changes noted with DKD, including glomerular hypertrophy, mesangial matrix accumulation, glomerular basement membrane thickening, albuminuria, and podocyte dropout. Intervention with a NOX1/NOX4 inhibitor reduced albuminuria, glomerular hypertrophy, and mesangial matrix accumulation in the F1 Akita model of DKD. Metabolomic analyses from these mouse studies revealed that tricarboxylic acid (TCA) cyclerelated urinary metabolites were increased in DKD, but fumarate levels were uniquely reduced by the NOX1/ NOX4 inhibitor. Expression of fumarate hydratase (FH), which regulates urine fumarate accumulation, was reduced in the diabetic kidney (in mouse and human tissue), and administration of the NOX1/NOX4 inhibitor increased glomerular FH levels in diabetic mice. Induction of Nox4 in vitro and in the podocyte-specific NOX4 transgenic mouse led to reduced FH levels. In vitro, fumarate stimulated endoplasmic reticulum stress, matrix gene expression, and expression of hypoxia-inducible factor-1a (HIF-1a) and TGF-b. Similar upregulation of renal HIF-1a and TGF-b expression was observed in NOX4 transgenic mice and diabetic mice and was attenuated by NOX1/NOX4 inhibition in diabetic mice. In conclusion, NOX4 is a major mediator of diabetesassociated glomerular dysfunction through targeting of renal FH, which increases fumarate levels. Fumarate is therefore a key link connecting metabolic pathways to DKD pathogenesis, and measuring urinary fumarate levels may have application for monitoring renal NOX4 activity.