Activation of STAT3/Smad1 is a key signaling pathway for progression to glomerulosclerosis in experimental glomerulonephritis.
Mesangial cell proliferation is a significant event in the development of progressive glomerular injuries. However, the issue of how cell proliferation is involved in the development of glomerulosclerosis is unclear. Recently, we showed that the overexpression of type IV collagen (Col IV), a major component of mesangial extracellular matrix, is transcriptionally regulated by Smad1 in diabetic glomerulosclerosis. In this study, we have demonstrated the effect of the administration of an anti-platelet-derived growth factor (PDGF) beta-receptor antibody (APB5) blocking activation by the PDGF-B chain on rat glomerulonephritis and have examined the signaling pathways that regulate both glomerular cell proliferation and glomerulosclerosis in vivo and in vitro. Experimental mesangial proliferative glomerulonephritis (Thy1 GN) was induced by a single intravenous injection of anti-rat Thy-1.1 monoclonal antibody. In Thy1 GN, mesangial cell proliferation and the expression of Col IV peaked at day 6. Immunohistochemical staining for the expression of Smad1, phospho-Smad1 (pSmad1), and phospho-STAT3 (pSTAT3) revealed that the peak for glomerular Smad1 expression occurred at day 6, consistent with the peak for mesangial proliferation. The expression of pSmad1 was up-regulated at day 1, and the peak for glomerular pSmad1 expression occurred at day 4 of the disease. When treated with APB5, both mesangial proliferation and sclerosis were reduced significantly. The expression of Smad1, pSmad1, and pSTAT3 was also significantly reduced by the administration of APB5. PDGF induced both mesangial cell replication and Col IV synthesis in association with an increased expression of pSTAT3 and pSmad1 on cultured mesangial cells. In addition, APB5 reduced mesangial cell proliferation in association with decreased pSmad1, pSTAT3, and Col IV protein expressions in vitro. The introduction of dominant negative STAT3 significantly decreased the expression of Col IV in cultured mesangial cells. These data suggest that the activation of STAT3 and Smad1 participates in the developing process of glomerulosclerosis in experimental glomerulonephritis.
Takahashi
Toshikazu
T
Department of Clinical Biology and Medicine, Course of Biological Medicine, School of Medicine, The University of Tokushima, Tokushima, Japan.
Abe
Hideharu
H
Arai
Hidenori
H
Matsubara
Takeshi
T
Nagai
Kojiro
K
Matsuura
Motokazu
M
Iehara
Noriyuki
N
Yokode
Masayuki
M
Nishikawa
Shinichi
S
Kita
Toru
T
Doi
Toshio
T
D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology; D049109:Cell Proliferation; D024141:Collagen Type IV / Q000032:analysis / Q000235:genetics; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D004195:Disease Models, Animal; D018450:Disease Progression; D005786:Gene Expression Regulation; D005920:Glomerular Mesangium / Q000473:pathology; D005921:Glomerulonephritis / Q000139:chemically induced / Q000473:pathology*; D005923:Glomerulosclerosis, Focal Segmental / Q000209:etiology*; D008297:Male; D010750:Phosphoproteins / Q000032:analysis; D020574:Proto-Oncogene Proteins c-sis / Q000276:immunology / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D051785:Smad Proteins; D051898:Smad1 Protein; D015534:Trans-Activators / Q000032:analysis / Q000235:genetics* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D024141:Collagen Type IV; D004268:DNA-Binding Proteins; D010750:Phosphoproteins; D020574:Proto-Oncogene Proteins c-sis; D050796:STAT3 Transcription Factor; D051785:Smad Proteins; D051898:Smad1 Protein; C497400:Smad1 protein, rat; C494088:Stat3 protein, rat; D015534:Trans-Activators