Repression of let-7 by transforming growth factor-β1-induced Lin28 upregulates collagen expression in glomerular mesangial cells under diabetic conditions

Accumulation of mesangial extracellular matrix (ECM) proteins such as collagen type 1-α2 (Col1a2) and collagen type 4-α1 (Col4a1) is a key feature of diabetic nephropathy (DN). Transforming growth factor (TGF)-β1 plays important roles in ECM accumulation in DN, and evidence shows a mediatory role for microRNAs. In the present study, we found that microRNA let-7 family members (let-7b/c/d/g/i) were downregulated in TGF-β-treated mouse mesangial cells (MMCs) along with upregulation of Col1a2 and Col4a1. Ectopic expression of let-7b in TGF-β-treated MMCs attenuated Col1a2 and Col4a1 upregulation. Conversely, let-7b inhibitors increased Col1a2 and Col4a1 levels. Cotransfection of MMCs with mouse Col1a2 or Col4a1 3′-untranslated region luciferase constructs and let-7b inhibitors increased luciferase activity. However, constructs with let-7 target site mutations were unresponsive to TGF-β. TGF-β-induced 3′-untranslated region activity was attenuated by let-7b mimics, suggesting that Col1a2 and Col4a1 are direct targets of let-7b. In addition, Lin28b, a negative regulator of let-7 biogenesis, was upregulated in TGF-β-treated MMCs. Luciferase assays showed that the Lin28b promoter containing the Smad-binding element (SBE) responded to TGF-β, which was abolished in constructs without SBE. Chromatin immunoprecipitation assays showed TGF-β-induced enrichment of Smad2/3 at the Lin28b promoter, together suggesting that Lin28b is transcriptionally induced by TGF-β through SBE. Furthermore, let-7b levels were decreased, whereas Lin28b, Col1a2, and Col4a1 levels were increased, in glomeruli of diabetic mice compared with nondiabetic control mice, demonstrating the in vivo relevance of this Lin28/let-7/collagen axis. These results identify Lin28 as a new TGF-β target gene and suggest a novel role for the Lin28/let-7 pathway in controlling TGF-β-induced collagen accumulation in DN.

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Suppressions of chronic glomerular injuries and TGF-β1 production by HGF in attenuation of murine diabetic nephropathy

AJP Renal Physiology ◽

10.1152/ajprenal.00199.2003 ◽

2004 ◽

Vol 286 (1) ◽

pp. F134-F143 ◽

Cited By ~ 69

Author(s):

Shinya Mizuno ◽

Toshikazu Nakamura

Keyword(s):

Diabetic Nephropathy ◽

Growth Factor ◽

Renal Dysfunction ◽

Transforming Growth Factor ◽

Mesangial Cells ◽

Renal Diseases ◽

Glomerular Mesangial Cells ◽

Diabetic Mice

Diabetic nephropathy is now the leading cause of end-stage renal diseases, and glomerular sclerotic injury is an initial event that provokes renal dysfunction during processes of diabetes-linked kidney disease. Growing evidence shows that transforming growth factor-β1 (TGF-β1) plays a key role in this process, especially in eliciting hypertrophy and matrix overaccumulation. Thus it is important to find a ligand system to antagonize the TGF-β1-mediated pathogenesis under high-glucose conditions. Herein, we provide evidence that hepatocyte growth factor (HGF) targets mesangial cells, suppresses TGF-β1 production, and minimizes glomerular sclerotic changes, using streptozotocin-induced diabetic mice. In our murine model, glomerular sclerogenesis (such as tuft area expansion and collagen deposition) progressed between 6 and 10 wk after the induction of hyperglycemia, during a natural course of diabetic disease. Glomerular HGF expression levels in the diabetic kidney transiently increased but then declined below a basal level, with manifestation of glomerular sclerogenesis. When anti-HGF IgG was injected into mice for 2 wk (i.e., from weeks 4 to 6 after onset of hyperglycemia), these glomerular changes were significantly aggravated. When recombinant HGF was injected into the mice for 4 wk (i.e., between 6 and 10 wk following streptozotocin treatment), the progression of glomerular hypertrophy and sclerosis was almost completely inhibited, even though glucose levels remained unchanged (>500 mg/dl). Even more important, HGF repressed TGF-β1 production in glomerular mesangial cells even under hyperglycemic conditions both in vitro and in vivo. Consequently, not only albuminuria but also tubulointerstitial fibrogenesis were attenuated by HGF. Overall, HGF therapy inhibited the onset of renal dysfunction in the diabetic mice. On the basis of these findings, we wish to emphasize that HGF plays physiological and therapeutic roles in blocking renal fibrogenesis during a course of diabetic nephropathy.

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Sp1 and Smad proteins cooperate to mediate transforming growth factor-β1-induced α2(I) collagen expression in human glomerular mesangial cells.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(19)37323-5 ◽

2001 ◽

Vol 276 (50) ◽

pp. 47746

Author(s):

Anne-Christine Poncelet ◽

H. William Schnaper

Keyword(s):

Growth Factor ◽

Transforming Growth Factor ◽

Mesangial Cells ◽

Transforming Growth Factor Β1 ◽

Glomerular Mesangial Cells ◽

Collagen Expression ◽

Smad Proteins ◽

Human Glomerular Mesangial Cells

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Sp1 and Smad Proteins Cooperate to Mediate Transforming Growth Factor-β1-induced α2(I) Collagen Expression in Human Glomerular Mesangial Cells

Journal of Biological Chemistry ◽

10.1074/jbc.m006442200 ◽

2000 ◽

Vol 276 (10) ◽

pp. 6983-6992 ◽

Cited By ~ 181

Author(s):

Anne-Christine Poncelet ◽

H. William Schnaper

Keyword(s):

Growth Factor ◽

Transforming Growth Factor ◽

Mesangial Cells ◽

Transforming Growth Factor Β1 ◽

Glomerular Mesangial Cells ◽

Collagen Expression ◽

Smad Proteins ◽

Human Glomerular Mesangial Cells

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LIM-Only Protein FHL2 Is a Negative Regulator of Transforming Growth Factor β1 Expression

Molecular and Cellular Biology ◽

10.1128/mcb.00636-16 ◽

2017 ◽

Vol 37 (10) ◽

Cited By ~ 10

Author(s):

Jennifer Dahan ◽

Florence Levillayer ◽

Tian Xia ◽

Yann Nouët ◽

Catherine Werts ◽

...

Keyword(s):

Growth Factor ◽

Rna Polymerase Ii ◽

Gene Transcription ◽

Wound Repair ◽

Transforming Growth Factor ◽

Transforming Growth Factor Β1 ◽

Negative Regulator ◽

Mesenchymal Transition ◽

Tgf Β1

ABSTRACT Transforming growth factor β1 (TGF-β1) is a master cytokine in many biological processes, including tissue homeostasis, epithelial-to-mesenchymal transition, and wound repair. Here, we report that four and a half LIM-only protein 2 (FHL2) is a critical regulator of TGF-β1 expression. Devoid of a DNA-binding domain, FHL2 is a transcriptional cofactor that plays the role of coactivator or corepressor, depending on the cell and promoter contexts. We detected association of FHL2 with the TGF-β1 promoter, which showed higher activity in Fhl2 −/− cells than in wild-type (WT) cells in a reporter assay. Overexpression of FHL2 abrogates the activation of the TGF-β1 promoter, whereas the upregulation of TGF-β1 gene transcription correlates with reduced occupancy of FHL2 on the promoter. Moreover, ablation of FHL2 facilitates recruitment of RNA polymerase II on the TGF-β1 promoter, suggesting that FHL2 may be involved in chromatin remodeling in the control of TGF-β1 gene transcription. Enhanced expression of TGF-β1 mRNA and cytokine was evidenced in the livers of Fhl2 −/− mice. We tested the in vivo impact of Fhl2 loss on hepatic fibrogenesis that involves TGF-β1 activation. Fhl2 −/− mice developed more severe fibrosis than their WT counterparts. These results demonstrate the repressive function of FHL2 on TGF-β1 expression and contribute to the understanding of the TGF-β-mediated fibrogenic response.

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