Alagebrium Reduces Glomerular Fibrogenesis and Inflammation Beyond Preventing RAGE Activation in Diabetic Apolipoprotein E Knockout Mice

Abstract

Advanced glycation end products (AGEs) are important mediators of diabetic nephropathy that act through the receptor for AGEs (RAGE), as well as other mechanisms, to promote renal inflammation and glomerulosclerosis. The relative contribution of RAGE-dependent and RAGE-independent signaling pathways has not been previously studied in vivo. In this study, diabetic RAGE apoE double-knockout (KO) mice with streptozotocin-induced diabetes were treated with the AGE inhibitor, alagebrium (1 mg/kg/day), or the ACE inhibitor, quinapril (30 mg/kg/day), for 20 weeks, and renal parameters were assessed. RAGE deletion attenuated mesangial expansion, glomerular matrix accumulation, and renal oxidative stress associated with 20 weeks of diabetes. By contrast, inflammation and AGE accumulation associated with diabetes was not prevented. However, treatment with alagebrium in diabetic RAGE apoE KO mice reduced renal AGE levels and further reduced glomerular matrix accumulation. In addition, even in the absence of RAGE expression, alagebrium attenuated cortical inflammation, as denoted by the reduced expression of monocyte chemoattractant protein-1, intracellular adhesion molecule-1, and the macrophage marker cluster of differentiation molecule 11b. These novel findings confirm the presence of important RAGE-independent as well as RAGE-dependent signaling pathways that may be activated in the kidney by AGEs. This has important implications for the design of optimal therapeutic strategies for the prevention of diabetic nephropathy.

Dicarbonyl Stress in the Absence of Hyperglycemia Increases Endothelial Inflammation and Atherogenesis Similar to That Observed in Diabetes

“…In addition, inhibition of glyoxalase was still proinflammatory in RAGE KO endothelial cells, albeit at a much lower level. These findings are consistent with our previous studies using dicarbonyl scavengers, like alagebrium chloride, aminoguanidine, and pyridoxamine to attenuate diabetic renal complications even in RAGE KO mice (45). The mechanism(s) by which dicarbonyls are able to induce vascular damage independent of RAGE are a matter of ongoing investigation but may result as a functional sequel of increased AGE modification of a broad range of proteins as well as lipids and DNA (46).…”

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

“…Mesangial area was analyzed (percentage of glomerular area) from digital pictures of glomeruli (20 glomeruli per kidney per animal) using Image-Pro plus 6.0 software (Media Cybernetics, Bethesda, MD), as previously described. 56,58 Glomerulosclerotic injury was graded based on the severity of glomerular damage, including mesangial matrix expansion, hyalinosis with focal adhesion, capillary dilation, glomerular tuft occlusion, and sclerosis, as previously described. 12,29,59 Twenty glomeruli per kidney were assessed in a blinded fashion.…”

“…For the quantification of the proportional area of staining, 20 glomeruli (3400) were analyzed using Image-Pro plus 6 (Media Cybernetics). 56,58 All assessments were performed in a blinded manner. Six or eight kidneys were investigated in each group.…”

Combined NOX1/4 inhibition with GKT137831 in mice provides dose-dependent reno- and atheroprotection even in established micro- and macrovascular disease

“…Urinary and serum creatinine concentrations were measured by HPLC [19,20]. The urinary albumin/creatinine ratio (ACR) and creatinine clearance were calculated.…”