Mice lacking Smad3 are protected against streptozotocin-induced diabetic glomerulopathy.
Transforming growth factor-beta (TGF-beta) has been implicated in the development of diabetic glomerulopathy. In order to evaluate a role of Smad3, one of the major signaling molecules downstream of TGF-beta, in the pathogenesis of diabetic glomerulopathy, Smad3-null mice were made diabetic with streptozotocin injection and analyzed 4 weeks after induction of diabetes. Electron microscopy revealed that the thickness of glomerular basement membrane (GBM) in wild-type diabetic mice was significantly higher than that in non-diabetic mice, whereas no appreciable GBM thickening was found in Smad3-null diabetic mice. Urinary albumin excretion was dramatically increased in wild-type diabetic mice, whereas Smad3-null diabetic mice did not show any overt albuminuria. Northern blotting revealed that mRNA levels of fibronectin and alpha 3 chain of type IV collagen (alpha 3Col4) in renal cortex of wild-type diabetic mice were approximately twice as much as those of non-diabetic mice, whereas their mRNA levels were not increased in Smad3-null diabetic mice. Real-time polymerase chain reaction (PCR) also confirmed diabetes-induced upregulation of fibronectin and alpha 3Col4 in glomeruli of wild-type mice. Glomerular expression of TGF-beta 1, as assessed by real-time PCR, was enhanced to a similar degree in wild-type and smad3-null diabetic mice, indicating that the observed differences between wild-type and Smad3-null mice are not attributable to difference in the expression of TGF-beta 1. These data clearly demonstrate a critical role of Smad3 in the early phase of diabetic glomerulopathy. This may be due at least partly to the present findings that diabetes-induced upregulation of fibronectin and alpha 3Col4 is dependent on Smad3 function.
Fujimoto
Masaki
M
Department of Clinical Cell Biology and Medicine, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chiba 260-8670, Japan.
Maezawa
Yoshiro
Y
Yokote
Koutaro
K
Joh
Kensuke
K
Kobayashi
Kazuki
K
Kawamura
Harukiyo
H
Nishimura
Motonobu
M
Roberts
Anita B
AB
Saito
Yasushi
Y
Mori
Seijiro
S
D000419:Albuminuria / Q000209:etiology; D000818:Animals; D024141:Collagen Type IV / Q000096:biosynthesis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D003921:Diabetes Mellitus, Experimental / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D003928:Diabetic Nephropathies / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D005353:Fibronectins / Q000096:biosynthesis / Q000235:genetics; D007678:Kidney Glomerulus / Q000648:ultrastructure; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D051900:Smad3 Protein; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics; D053773:Transforming Growth Factor beta1
D024141:Collagen Type IV; D004268:DNA-Binding Proteins; D005353:Fibronectins; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; C508961:Tgfb1 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1