Contribution of oxidative stress and NOXes to diabetes-associated vascular and renal injury

Abstract

Diabetes Mellitus stands out as one of the most important non-transmissible chronic diseases worldwide. It has a major negative impact on the quality of life and exerts a heavy economic burden on the society/ health care system. The prevalence of type 2 diabetes mellitus has increased rapidly in Latin America countries and there is an upward trend among the younger age groups. The prognosis of individuals with diabetes continues to be worse than in age matched non-diabetic individuals and this is related primarily to the long term risk of developing renal and vascular complications. Epidemiological, clinical and experimental data indicate a causal association between hyperglycemia and diabetic complications. Exact mechanisms for this remain elusive but hyperglycaemia-induced oxidative stress appears to play an important role in the increased risk of diabetic complications, including diabetic nephropathy, cardiovascular disease and retinopathy. Myriad sources contribute to increased oxidative stress [increased bioavailability of reactive oxygen species (ROS)], but NADPH oxidase (NOX), may be particularly important in diabetes. This proposal aims to determine the role of NOXl/4-derived ROS in the pathogenesis of diabetic vasculopathy and nephropathy due to type 2 diabetes, to elucidate redox-sensitive molecular mechanisms of the disease and to identify novel therapeutic targets. Our hypothesis is that diabetes is associated with tissue-specific activation of different Nox isoforms: hyperactivation of vascular Noxl causing vascular injury and upregulation of renal Nox4 leading to nephropathy. This Nox isoform effect is related to differential expression of p47phox and its isoform NOXOl. We will focus on three specific aims: Aim 1. To elucidate the role of Noxl and Nox4 and p47phox in diabetes-associated renal and vascular complications using models of diabetic nephropathy, db/db mice (C57BLKS/JLepr), crossed with Noxl-/- and Nox4-/- and p47 phox-/- mice. This set of experiments will be performed at the University of Ottawa by Dr. Rhian Touyz's research group. Aim 2. To investigate effects of novel specific Nox inhibitors (e.g. GKT136901) alone and combined with an angiotensin II receptor (AT1R) blocker in the development of nephropathy and vasculopathy in diabetes. These chronic treatments will be performed at the University of Sao Paulo by Dr. Rita Tostes' research group. Aim 3. To determine molecular pathways whereby Nox-mediated ROS generation causes diabetes-associated renal and vascular injury. Studies will be performed in isolated glomeruli and tubules from diabetic mice and in cultured renal (proximal tubular cells, mesangial cells and podocytes) and vascular cells (vascular smooth muscle cells, endothelial cells). Molecular mechanisms in renal and vascular cells will be determined at the University of Ottawa and the University of Sao Paulo, respectively. (AU)