Ultrastructure of nonenzymatically glycated mesangial matrix in diabetic nephropathy

Abstract

Advanced protein glycation has been proposed as a major factor in the development of diabetic nephropathy. Advanced glycation end products (AGEs) have altered the structure of extracellular matrix component and impaired self association in vitro. To elucidate the role of AGEs in the progression of diabetic nephropathy, the present study was undertaken to localize glomerular AGEs immunohistochemically. Ultrastructural changes of the mesangial matrix were analyzed with high resolution scanning electron microscopy. No glomerular AGEs staining was noted in normal control kidney specimens, or in tissue from glomerulonephritis patients without diabetes mellitus. The mesangium showed a positive AGEs staining in advanced stages of diabetic nephropathy, and the most characteristic finding was the strong AGEs staining in nodular lesions. By high resolution scanning electron microscopy, control and diabetic mesangial matrices revealed a meshwork structure composed of fine fibrils (10 nm in width) and numerous pores (12 to 13 nm in diameter). In the nodular lesions, however, loosening of the meshwork was significant, and the diameter of the pores was enlarged (approximately 24 nm). This study provides the first immunohistochemical evidence that AGEs are localized in diabetic glomeruli, most notably to nodular lesions. Advanced glycation might play a role in the progression of diabetic nephropathy through impairment of the assembly of matrix proteins in vivo.

Advanced glycation end products-cytokine-nitric oxide sequence pathway in the development of diabetic nephropathy: aminoguanidine ameliorates the overexpression of tumour necrosis factor-α and inducible nitric oxide synthase in diabetic rat glomeruli

“…Immunoreactivity of CML, TNF-a and iNOS was studied with immunoperoxidase techniques by the labelled streptoavidin-biotin method [2]. We evaluated the scoring of immunostaining for CML and TNF-a according to a method described previously [12].…”

“…Further, this augmented expression paralleled intraglomerular expression of TNF-a and NO 2 ± /NO 3 ± in diabetic rat glomeruli. Treatment with aminoguanidine reduced the expression of TNF-a, inducible nitric oxide synthase and intraglomerular NO 2 thase (NOS), of which there are several distinct isoforms. Endothelium-derived NOS (eNOS) and neuronal NOS (nNOS) are constitutive, Ca 2+ -dependent, agonist-triggered enzymes.…”

Intercellular Adhesion Molecule-1–Deficient Mice Are Resistant Against Renal Injury After Induction of Diabetes

“…Tissue preparation for electron microscopy and morphometric analysis of mesangial matrix area. Tissue preparation was performed as previously described (18). Briefly, renal cortical specimens were immersed in 2.5% glutaraldehyde in 0.1 mol/l cacodylate buffer (pH 7.2, 2 h, 4°C), postfixed in 0.1 mol/l osmium tetroxide (2 h, 4°C), and then embedded in Epon following dehydration in a graded series of ethanol preparations.…”

Accumulation of dietary glycotoxins in the reproductive system of normal female rats

“…The mechanisms by which AGE leads to these injuries in multicellular structures remain largely unknown; however, the formation of insoluble cross-links, the induction of oxidative stress, and cell activation play a significant role. Interaction of AGE with specific cellular receptors (RAGE) leads to cell activation, release of cytokines, and growth factors, which contribute to abnormal cell/ matrix proliferation, such as seen in diabetic renal lesions and atheromas [3][4][5]. AGEmodified proteins are continuously formed in the body from the reaction of reducing sugars, but they can also be produced from exogenous sources during contemporary methods of cooking (precooked fast food meals heated in high temperatures) [6][7][8][9].…”