Ras modulation of superoxide activates ERK-dependent fibronectin expression in diabetes-induced renal injuries.
Although previous studies have demonstrated that diabetic nephropathy is attributable to early extracellular matrix accumulation in glomerular mesangial cells, the molecular mechanism by which high glucose induces matrix protein deposition remains not fully elucidated. Rat mesangial cells pretreated with or without inhibitors were cultured in high-glucose or advanced glycation end product (AGE) conditions. Streptozotocin-induced diabetic rats were given superoxide dismutase (SOD)-conjugated propylene glycol to scavenge superoxide. Transforming growth factor (TGF)-beta1, fibronectin expression, Ras, ERK, p38, and c-Jun activation of glomerular mesangial cells or urinary albumin secretion were assessed. Superoxide, not nitric oxide or hydrogen peroxide, mediated high glucose- and AGE-induced TGF-beta1 and fibronectin expression. Pretreatment with diphenyliodonium, not allopurinol or rotenone, reduced high-glucose and AGE augmentation of superoxide synthesis and fibronection expression. High glucose and AGEs rapidly enhanced Ras activation and progressively increased cytosolic ERK and nuclear c-Jun activation. Inhibiting Ras by manumycin A reduced the stimulatory effects of high glucose and AGEs on superoxide and fibronectin expression. SOD or PD98059 pretreatment reduced high-glucose and AGE promotion of ERK and c-Jun activation. Exogenous SOD treatment in diabetic rats significantly attenuated diabetes induction of superoxide, urinary albumin excretion, 8-hydroxy-2'-deoxyguanosine, TGF-beta1, and fibronectin immunoreactivities in renal glomerular mesangial cells. Ras induction of superoxide activated ERK-dependent fibrosis-stimulatory factor and extracellular matrix gene transcription of mesangial cells. Reduction of oxidative stress by scavenging superoxide may provide an alternative strategy for controlling diabetes-induced early renal injury.
Department of Nephrology, Chiayi Chang Gung Memorial Hospital & Graduate Institute of Clinical Medical Sciences, College of Medicine, Chang Gung University, Chiayi, Taiwan. linchunliang@adm.cgmh.org.tw
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D000818:Animals; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000150:complications; D003928:Diabetic Nephropathies / Q000209:etiology / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005353:Fibronectins / Q000032:analysis / Q000235:genetics*; D005419:Flavonoids / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D015870:Gene Expression; D005947:Glucose / Q000494:pharmacology; D017127:Glycation End Products, Advanced / Q000633:toxicity; D007678:Kidney Glomerulus / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology; D008297:Male; D050527:Mesangial Cells / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D011090:Polyenes / Q000494:pharmacology; D053284:Polyunsaturated Alkamides; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000032:analysis / Q000378:metabolism; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
D005353:Fibronectins; D005419:Flavonoids; D016166:Free Radical Scavengers; D017127:Glycation End Products, Advanced; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D016755:Proto-Oncogene Proteins c-jun; D016212:Transforming Growth Factor beta; D013481:Superoxides; D013482:Superoxide Dismutase; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins; D005947:Glucose; C054474:manumycin; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one