Nox4 NAD(P)H Oxidase Mediates Hypertrophy and Fibronectin Expression in the Diabetic Kidney

Abstract

Renal hypertrophy and extracellular matrix accumulation are early features of diabetic nephropathy. We investigated the role of the NAD(P)H oxidase Nox4 in generation of reactive oxygen species (ROS), hypertrophy, and fibronectin expression in a rat model of type 1 diabetes induced by streptozotocin. Phosphorothioated antisense (AS) or sense oligonucleotides for Nox4 were administered for 2 weeks with an osmotic minipump 72 h after streptozotocin treatment. Nox4 protein expression was increased in diabetic kidney cortex compared with non-diabetic controls and was downregulated in AS-treated animals. AS oligonucleotides inhibited NADPH-dependent ROS generation in renal cortical and glomerular homogenates. ROS generation by intact isolated glomeruli from diabetic animals was increased compared with glomeruli isolated from AS-treated animals. AS treatment reduced whole kidney and glomerular hypertrophy. Moreover, the increased expression of fibronectin protein was markedly reduced in renal cortex including glomeruli of AS-treated diabetic rats. Akt/protein kinase B and ERK1/2, two protein kinases critical for cell growth and hypertrophy, were activated in diabetes, and AS treatment almost abolished their activation. In cultured mesangial cells, high glucose increased NADPH oxidase activity and fibronectin expression, effects that were prevented in cells transfected with AS oligonucleotides. These data establish a role for Nox4 as the major source of ROS in the kidneys during early stages of diabetes and establish that Nox4-derived ROS mediate renal hypertrophy and increased fibronectin expression.

Aggravation of diabetic nephropathy in BCL-2 interacting cell death suppressor (BIS)-haploinsufficient mice together with impaired induction of superoxide dismutase (SOD) activity

“…Although multiple enzymatic pathways have been implicated in the generation of ROS in hyperglycaemia, NOX might be an important ROS source in diabetic kidney [32]. In particular, NOX-4 levels were shown to increase early in the STZ-induced diabetic rat model and NOX inhibition prevented diabetic changes of kidney [30,31,33]. On the other hand, the central role of SOD in diabetic nephropathy has been also demonstrated in previous studies.…”

“…Figure 6a shows that the production of NOX-4, which has been implicated as the main superoxide-producing enzyme in the kidney [30,31], was not notably increased by diabetes induction in either BIS-WT or BIS-HT mice. NOX-1 levels were increased in diabetic BIS-WT and BIS-HT mice to a similar extent (1.6-and 1.4-fold increases vs controls, respectively).…”

Nox enzymes, ROS, and chronic disease: An example of antagonistic pleiotropy

“…PKC-beta (−/−) diabetic mice were protected against induction of Nox2, Nox4 and glucose-induced renal dysfunction and fibrosis, indicating a role for PKC in Nox expression and renal pathology [109]. Nox4 is a major source of ROS in diabetic nephropathy, based on protection against high glucose-induced ROS generation and fibronectin expression in kidney cells transfected with Nox4 antisense oligonucleotides [111]. Thus, drugs targeting Nox4 and possibly Nox2 appear to be promising for the treatment and prevention of diabetic nephropathy.…”

The contribution of hypertension to diabetic nephropathy and retinopathy: the role of inflammation and oxidative stress

“…The mitochondrial respiratory chain, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase enzyme system, Nox4 (homologue of gp91phox subunit of NADPH oxidase) and advanced glycation-end productreceptor for advanced glycation end-product interaction have been found to induce oxidative stress in high-glucose conditions. [65][66][67] Oxidative stress is conventionally defined as an imbalance between pro-oxidant stress and antioxidant defense. However, recent evidence indicates that the disruption of redox signaling is an important aspect of oxidative stress, sometimes more important than the pro-oxidant-antioxidant imbalance or the tissue damage induced by such imbalance.…”