Advanced glycation end products-cytokine-nitric oxide sequence pathway in the development of diabetic nephropathy: aminoguanidine ameliorates the overexpression of tumour necrosis factor-alpha and inducible nitric oxide synthase in diabetic rat glomeruli.
OBJECTIVE
Advanced glycation end products are believed to contribute to diabetic microvascular complications by inducing glomerular damage but their role has not been fully clarified. In this study, we explain their central role in the induction of inducible nitric oxide synthase and production of nitric oxide (NO) in streptozotocin-induced diabetic rat glomeruli.


METHODS
Localization of carboxymethyllysine, which is one of the chemical components of advanced glycation end products, glomerular expression of inducible nitric oxide synthase and urinary excretion and glomerular production of NO2-/NO3- were examined at 0, 26, 51, and 52 weeks after the induction of diabetes. Therapeutic effects of aminoguanidine were also examined.


RESULTS
Carboxymethyllysine was detected in the mesangial area in glomeruli and it progressively accumulated during 52 weeks of observation. Immunohistochemistry and hybridization studies in situ showed that the number of inducible nitric oxide synthase-positive cells was notably increased in diabetic rat glomeruli at 52 weeks. Further, this augmented expression paralleled intraglomerular expression of TNF-alpha and NO2-/NO3- in diabetic rat glomeruli. Treatment with aminoguanidine reduced the expression of TNF-alpha, inducible nitric oxide synthase and intraglomerular NO2-/NO3- production. It also ameliorated proteinuria in diabetic rats.


CONCLUSIONS
This study showed that carboxymethyllysine possibly enhances the expression of inducible nitric oxide synthase by stimulating the expression of TNF-alpha in diabetic rat glomeruli. The carboxymethyllysine-cytokine-NO sequence pathway could be one of the major mechanisms in the development of diabetic nephropathy.
Sugimoto
H
H
Department of Medicine III, Okayama University Medical School, Japan.
Shikata
K
K
Wada
J
J
Horiuchi
S
S
Makino
H
H
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology / Q000503:physiopathology* / Q000628:therapy*; D004791:Enzyme Inhibitors; D019270:Fructosamine / Q000032:analysis; D017127:Glycation End Products, Advanced; D006146:Guanidines / Q000627:therapeutic use; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007668:Kidney; D007678:Kidney Glomerulus / Q000737:chemistry / Q000201:enzymology; D008297:Male; D009252:NADPH Dehydrogenase / Q000378:metabolism; D009566:Nitrates / Q000652:urine; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000652:urine; D011507:Proteinuria; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling; D013311:Streptozocin / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha
D001786:Blood Glucose; D004791:Enzyme Inhibitors; D017127:Glycation End Products, Advanced; D006146:Guanidines; D009566:Nitrates; D009573:Nitrites; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D019270:Fructosamine; D013311:Streptozocin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D009252:NADPH Dehydrogenase; C004479:pimagedine