Expression of Smad1 is directly associated with mesangial matrix expansion in rat diabetic nephropathy

Matsubara, Takeshi; Abe, Hideharu; Arai, Hidenori; Nagai, Kojiro; Mima, Akira; Kanamori, Hiroshi; Sumi, Eriko; Takahashi, Tomohiro; Matsuura, Motokazu; Iehara, Noriyuki; Fukatsu, Atsushi; Kita, Toru; Doi, Toshio

doi:10.1038/labinvest.3700400

Cited by 67 publications

(50 citation statements)

References 31 publications

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“…Interestingly, recent studies have also shown involvement of ALK1/Smad1 pathways in kidney and liver fibrosis. Elevated expression of Smad1 protein was observed in human diabetic kidney and in animal models of diabetic nephropathy (37)(38)(39). In addition, Smad1 was shown to directly up-regulate expression of the collagen type IV gene in mesangial cells (37).…”

Section: Discussionmentioning

confidence: 95%

Transforming Growth Factor-β Receptor Type I-dependent Fibrogenic Gene Program Is Mediated via Activation of Smad1 and ERK1/2 Pathways

Pannu

Nakerakanti

Smith

et al. 2007

Journal of Biological Chemistry

183

142

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The transforming growth factor (TGF)-␤/Smad3 signaling pathway is considered a central mediator of pathological organ fibrosis; however, contribution of Smad2/3-independent TGF-␤ signaling has not been fully explored. The present study utilized previously a described model of scleroderma (SSc) fibrosis based on forced expression of the TGF-␤RI (ALK5) (Pannu, J., Gardner, H., Shearstone, J. R., Smith, E., and Trojanowska, M. (2006) Arthritis Rheum. 54, 3011-3021). This study was aimed at determining the molecular mechanisms underlying the profibrotic program in this model. We demonstrate that the TGF-␤RI-dependent up-regulation of collagen and CCN2 (CTGF) does not involve Smad2/3 activation but is mediated by ALK1/Smad1 and ERK1/2 pathways. The following findings support this conclusion: (i) Smad2 and -3 were not phosphorylated in response to TGF-␤RI, (ii) a TGF-␤RI mutant defective in Smad2/3 activation, ALK5(3A), potently stimulated collagen production, (iii) elevation of TGF-␤RI triggered sustained association of ALK5 with ALK1 and high levels of Smad1 phosphorylation, (iv) blockade of Smad1 via small interfering RNA abrogated collagen and CCN2 up-regulation in this model, (v) elevated TGF-␤RI led to a prolonged activation of ERK1/2, (vi) the pharmacologic inhibitor of ERK1/2 inhibited Smad1 phosphorylation and abrogated profibrotic effects of elevated TGF␤-RI. Additional experiments demonstrated that a GC-rich response element located ؊6 to ؊16 (upstream of the transcription start site) in the CCN2 promoter mediated Smad1-dependent increased promoter activity in this model. This element was shown previously to mediate up-regulation of the CCN2 promoter in SSc fibroblasts. In conclusion, this study defines a novel ALK1/Smad1-and ERK1/2-dependent, Smad3-independent mode of TGF-␤ signaling that may operate during chronic stages of fibrosis in SSc.

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Section: Discussionmentioning

confidence: 95%

Transforming Growth Factor-β Receptor Type I-dependent Fibrogenic Gene Program Is Mediated via Activation of Smad1 and ERK1/2 Pathways

Pannu

Nakerakanti

Smith

et al. 2007

Journal of Biological Chemistry

183

142

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“…Previously, we reported that Smad1 is induced and phosphorylated by advanced glycation end products and binds to the promoter of Col4a1/a2, thus upregulating its transcriptional activity in mesangial cells (10). We also found that Smad1 is highly expressed in human diabetic glomeruli and that glomerular expression of Smad1 is closely correlated with the severity of mesangial matrix expansion in a rodent model of diabetic nephropathy (15). However, the functional role of Smad1 in diabetic nephropathy in vivo remains unknown.…”

mentioning

confidence: 90%

Bone Morphogenetic Protein 4 and Smad1 Mediate Extracellular Matrix Production in the Development of Diabetic Nephropathy

et al. 2015

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Diabetic nephropathy is the leading cause of end-stage renal disease. It is pathologically characterized by the accumulation of extracellular matrix in the mesangium, of which the main component is a1/a2 type IV collagen (Col4a1/a2). Recently, we identified Smad1 as a direct regulator of Col4a1/a2 under diabetic conditions in vitro. Here, we demonstrate that Smad1 plays a key role in diabetic nephropathy through bone morphogenetic protein 4 (BMP4) in vivo. Smad1-overexpressing mice (Smad1-Tg) were established, and diabetes was induced by streptozotocin. Nondiabetic Smad1-Tg did not exhibit histological changes in the kidney; however, the induction of diabetes resulted in an ∼1.5-fold greater mesangial expansion, consistent with an increase in glomerular phosphorylated Smad1. To address regulatory factors of Smad1, we determined that BMP4 and its receptor are increased in diabetic glomeruli and that diabetic Smad1-Tg and wild-type mice treated with a BMP4-neutralizing antibody exhibit decreased Smad1 phosphorylation and ∼40% less mesangial expansion than those treated with control IgG. Furthermore, heterozygous Smad1 knockout mice exhibit attenuated mesangial expansion in the diabetic condition. The data indicate that BMP4/Smad1 signaling is a critical cascade for the progression of mesangial expansion and that blocking this signal could be a novel therapeutic strategy for diabetic nephropathy.Diabetic nephropathy is a life-threatening complication of diabetes and the leading cause of end-stage renal disease (1). The structural features of diabetic nephropathy include thickening of the glomerular basement membrane (GBM) and mesangial matrix expansion (2,3). Mesangial matrix expansion is pathologically important because it leads to glomerulosclerosis accompanied by various tubulointerstitial damages and subsequent nephron loss (4,5). In addition, the severity of mesangial matrix expansion is clinically important because it is closely associated with the decline of the glomerular filtration rate (6).Mesangial matrix expansion is characterized by increased amounts of extracellular matrix (7), particularly a1/a2 type IV collagen (Col4a1/a2) (8). Although various peptides or growth factors are shown to mediate the regulation of this key component, the protein responsible for its direct regulation remains to be determined.Because various injuries of epithelial, endothelial, and mesangial cells converge on the accumulation of Col4a1/a2 in the mesangium, mesangial cells presumably play a central role for the regulation of Col4a1/a2, even if they are not the primary target of injury (9). Therefore, we attempted to elucidate the direct regulation of Col4a1/a2 under diabetic conditions and demonstrate that Smad1 can transcriptionally regulate Col4a1/a2 in the presence of advanced glycation end products in mesangial cells (10).Smad1 is an intracellular molecule originally cloned as a signal transducer of the transforming growth factor (TGF)-b superfamily (11). In response to these stimuli, Smad1 is phosphorylated at the COOH...

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“…While the specific interactions between ALK-5 and ALK-1 are still not fully elucidated, there is evidence that the relative ratio of these 2 receptor subtypes regulates the switch between proliferation and differentiation of endothelial cells (15). However, recent studies have also shown that the ALK-1/Smad1 pathway may play a role in kidney fibrosis (29)(30)(31). Furthermore, TGF␤ signaling via activation of the ALK-1/Smad1 pathway and subsequent up-regulation of the Id1 gene have been shown to contribute to transdifferentiation of hepatic stellate cells into myofibroblasts (32).…”

Section: Smad1 Signaling Pathway In Ssc 2535mentioning

confidence: 99%

Smad1 pathway is activated in systemic sclerosis fibroblasts and is targeted by imatinib mesylate

Pannu¹,

Asano²,

Nakerakanti³

et al. 2008

Arthritis & Rheumatism

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Objective. Activation of Smad1 signaling has recently been implicated in the development of fibrosis. The goal of the present study was to gain further insights into activation of the Smad1 pathway in fibrosis in systemic sclerosis (SSc) and to determine whether this pathway is targeted by the antifibrotic drug imatinib mesylate.Methods. Levels of phosphorylated Smad1 and total Smad1 were examined in SSc and control skin biopsy samples by immunohistochemistry and in cultured fibroblasts by Western blotting. Activity of the CCN2 promoter was examined by a luciferase reporter gene assay. Interactions of Smad1 with the CCN2 promoter were examined by in vitro and in vivo DNA binding assays. Expression of the nonreceptor tyrosine kinase c-Abl and Smad1 was blocked using respective small interfering RNA.Results. Total and phosphorylated Smad1 levels were significantly elevated in SSc skin biopsy samples and in cultured SSc fibroblasts and correlated with elevated CCN2 protein and CCN2 promoter activity. DNA binding assays demonstrated that Smad1 was a direct activator of the CCN2 gene. Small interfering RNA-mediated depletion of Smad1 in SSc fibroblasts normalized the production of CCN2 and collagen. Imatinib mesylate blocked activation of the Smad1 pathway in transforming growth factor ␤-stimulated control fibroblasts and reversed activation of this pathway in SSc fibroblasts. Likewise, blockade of c-Abl abrogated activation of the Smad1 pathway in SSc fibroblasts.Conclusion. Our findings demonstrate that activation of Smad1 signaling occurs in a subset of SSc patients and contributes to persistent activation of SSc fibroblasts. Demonstration that the Smad1/CCN2 pathway is blocked by imatinib mesylate further clarifies the mechanism of the antifibrotic effects of this compound.

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Expression of Smad1 is directly associated with mesangial matrix expansion in rat diabetic nephropathy

Cited by 67 publications

References 31 publications

Transforming Growth Factor-β Receptor Type I-dependent Fibrogenic Gene Program Is Mediated via Activation of Smad1 and ERK1/2 Pathways

Transforming Growth Factor-β Receptor Type I-dependent Fibrogenic Gene Program Is Mediated via Activation of Smad1 and ERK1/2 Pathways

Bone Morphogenetic Protein 4 and Smad1 Mediate Extracellular Matrix Production in the Development of Diabetic Nephropathy

Smad1 pathway is activated in systemic sclerosis fibroblasts and is targeted by imatinib mesylate

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