Transforming growth factor-beta type 1 receptor (ALK5) and Smad proteins mediate TIMP-1 and collagen synthesis in experimental intestinal fibrosis

Transforming growth factor β (TGF-β) is known to play a key role in intestinal fibrosis; however, the underlying mechanisms are not well understood. TGF-β signal transduction is through TGF-β receptors, including the TGF-β type 1 receptor. Most cell types contain a TGF-β type 1 receptor form known as activin receptor-like kinase 5 (ALK5), which propagates the signal to the nucleus through the phosphorylation of Smad2 and Smad3 proteins. Therefore, we assessed the effect of the disruption of TGF-β/ALK5/Smad signalling by an ALK5 inhibitor (SD-208) in two experimental animal models of intestinal fibrosis: anaerobic bacteria- and trinitrobenzensulphonic acid-induced colitis. In addition, isolated myofibroblasts were pretreated with SD-208 and exposed to recombinant TGF-β1. Finally, myofibroblasts were transfected with ALK5, Smad2, and Smad3-specific siRNA. Up-regulation of ALK5 and TIMP-1, phosphorylation of Smad2 and Smad3 proteins, and increased intestinal wall collagen deposition were found in both experimental animal models. These effects were decreased by SD-208. TGF-β1 treatment also induced phosphorylation of Smad2 and Smad3 and up-regulation of ALK5 protein, TIMP-1, and α2 type 1 collagen gene expression in isolated myofibroblasts. Again these effects were inhibited by SD-208. Also, ALK5, Smad2, and Smad3 siRNA abolished the induction of TIMP-1 and α2 type 1 collagen. Our findings provide evidence that the TGF-β/ALK5/Smad pathway participates in the pathogenesis of experimental intestinal fibrosis. These data show promise for the development of an effective therapeutic intervention in this condition.     

Inhibition of activin receptor-like kinase 5 attenuates bleomycin-induced pulmonary fibrosis

Activin receptor-like kinase 5 (ALK5) is a type I receptor of transforming growth factor (TGF)-beta. ALK5 inhibition has been reported to attenuate the tissue fibrosis including pulmonary fibrosis, renal fibrosis and liver fibrosis. To elucidate the inhibitory mechanism of ALK5 inhibitor on pulmonary fibrosis in vivo, we performed the histopathological assessment, gene expression analysis of extracellular matrix (ECM) genes and immunohistochemistry including receptor-activated Smads (R-Smads; Smad2/3), CTGF, myofibroblast marker (alpha-smooth muscle actin; aSMA) and type I collagen deposition in the lung using Bleomycin (BLM)-induced pulmonary fibrosis model. ALK5 inhibitor, SB-525334 (10 mg/kg or 30 mg/kg) was orally administered at twice a day. Lungs were isolated 5, 7, 9 and 14 days after BLM treatment. BLM treatment led to significant pulmonary fibrotic changes accompanied by significant upregulation of ECM mRNA expressions, Smad2/3 nuclear translocation, CTGF expression, myofibroblast proliferation and type I collagen deposition. SB-525334 treatment attenuated the histopathological alterations in the lung, and significantly decreased the type I and III procollagen and fibronectin mRNA expression. Immunohistochemistry revealed that SB-525334 treatment showed significant attenuation in Smad2/3 nuclear translocation, decrease in CTGF-expressing cells, myofibroblast proliferation and type I collagen deposition. These results suggest that ALK5 inhibition attenuates R-Smads activation thereby attenuates pulmonary fibrosis.     

MicroRNA-21 in Scleroderma Fibrosis and its Function in TGF-β- Regulated Fibrosis-Related Genes Expression

Uncontrolled fibrosis in multiple organs is the main cause of death in systemic sclerosis (SSc), and transforming growth factor-β (TGF-β) activation plays a fundamental role in the process. Our previous study demonstrated that miR-21 was significantly up-regulated in SSc fibroblasts. Here, we found that TGF-β regulated the expression of miR-21 and fibrosis-related genes, and decreased Smad7 expression. Over-expression of miR-21 in fibroblasts decreased the levels of Smad7, whereas knockdown of miR-21 increased its expression. Further study using a reporter gene assay demonstrated Smad7 was a direct target of miR-21. Similar to human SSc, the expression of miR-21 increased in the bleomycin induced skin fibrosis. Inhibition of fibrosis by treatment with anti-fibrosis drug bortezomib restored the levels of miR-21 and Smad7. MiR-21 may function in an amplifying circuit to enhance TGF-β signaling events in SSc fibrosis, and suggesting that miR-21 may act as a potential therapeutic target.     

TGFβ1，CTGF信号转导通路的变化在实验性小鼠肝纤维发生中的作用

 摘要：目的 探讨实验性肝纤维化小鼠肝组织中TGFβ1,CTGF信号转导通路的变化及意义。方法30只C57BL6/J小鼠随机分为正常对照组、肝纤维化模型组,采用10%的CCL4橄榄油腹腔注射诱导小鼠肝纤维化模型,对照组给予生理盐水灌胃,共造模8周。观察血清ALT、HA水平,HE染色、Masson染色观察肝组织炎症及纤维化程度,免疫组化法和RT-PCR法对肝组织α-SMA、TGFβ1、TGFβRⅡ、Smad3,Smad7,CTGF蛋白和mRNA水平进行检测,并与对照组肝组织进行比较。结果 模型组小鼠血清ALT及HA水平明显高于对照组;模型组小鼠肝组织α-SMA、TGFβ1、TGFβRII、Smad3、CTGF蛋白表达和TGFβ1、Smad3、CTGF mRNA表达明显高于对照组,而模型组肝组织Smad7蛋白和Smad7 mRNA表达较对照组小鼠显著降低。结论 TGFβ1和CTGF信号转导通路过度活化,Smad7表达和负调节TGFβ、CTGF信号转导通路的功能被抑制可能与肝纤维化的发生和发展密切相关。     

Anti-fibrotic effect of iguratimod on pulmonary fibrosis by inhibiting the fibroblast–to-myofibroblast transition

PurposePulmonary fibrosis (PF) is a severe lung disease causing significant morbidity and mortality. PF pathogenesis is attributed to the fibroblast-to-myofibroblast transition (FMT) driven by the most potent pro-fibrogenic factor TGF-β1 activating the Smad3-dependent TGF-β1 canonical pathway. Iguratimod (IGU) is a novel anti-rheumatic drug that suppresses the secretion of inflammatory factors, but is also able to modulate the differentiation of multiple cells. Therefore, the aim of this work was to investigate the effect of IGU on FMT.Materials/methodsPF mouse model was induced in C57BL/6 male mice by bleomycin. The effect of IGU was assessed through the evaluation of lung morphology by H&E and through the collagen accumulation in the lung by Masson staining. Primary human lung fibroblasts (pHLFs) were also used to evaluate the effect of IGU in vitro on TGF-β1-stimulated cells, and proliferation, migration and invasion were measured, together with genes and proteins involved in FMT.ResultsIGU attenuated bleomycin-induced PF in mice and improved the pathological changes in their lungs. In addition, IGU significantly inhibited proliferation, migration and invasion in TGF-β1-stimulated pHLFs without causing apoptosis. Moreover, IGU significantly reduced TGF-β1-induced increase of collagen I and III mRNA expression, thus reducing lung function impairment, and α-SMA, Smad2 and Smad3 phosphorylation, fibronectin expression and F-actin microfilament formation, thus attenuating FMT through the inhibition of the Smad3 pathway. Conclusions: Our results collectively revealed the beneficial effect of IGU on the inhibition of FMT, thus suggesting that it might act as an effective anti-fibrotic agent in preventing the progression of PF.     

MicroRNA-21 and microRNA-29a modulate the expression of collagen in dermal fibroblasts of patients with systemic sclerosis

MicroRNAs (miRNAs) are well-known candidates for modulating the dysregulated signaling pathways during fibrosis. In this study, we investigated the expression pattern of 16 miRNAs, which have previously been confirmed or predicted to target genes involved in extracellular matrix (ECM) homeostasis. Primary culture of dermal fibroblasts was obtained from skin biopsies of diffused cutaneous SSc (dcSSc) patients and healthy controls. Expression of let-7a, miR-1, miR-15a, miR-17, miR-19a, miR-20a, miR-21, miR-27b, miR-26a, miR-29a, miR-29b, miR29c, miR-141, miR-125a-5p, miR-193a-3p, and miR-200a were quantified by Real-time PCR. Functional analysis of microRNAs was performed using synthetic oligonucleotides. To further confirm the pro- or anti-fibrotic effects of miRNAs, normal fibroblasts were treated with 10 ng/mL of transforming growth factor (TGF)-β to generate an in vitro model of dermal fibrosis. miR-21 and miR-29a were upregulated and downregulated, respectively, in both dcSSc and TGF-β-treated fibroblasts. We observed that restoration of miR-29a expression or blockade of miR-21 function negatively affected collagen production. COL1A1 expression in SSc fibroblasts is more sensitive to changes of miR-29a and miR-21 expression in compare to normal fibroblasts. miR-29a alone was effective to decrease TGF-β-induced collagen production in dermal fibroblasts. miR-21 and TGF-β had synergistic effects on induction of collagen production. However, neither miR-21 nor miR-29a affected alpha smooth muscle actin (α-SMA) expression in the presence or absence of TGF-β in dermal fibroblasts. miR-21 and miR-29a as pro- and anti-fibrotic miRNAs modulate collagen production in an opposing manner. Focusing on miR-21 and miR-29s as therapeutic targets would be effective in patients with SSc or other fibrotic diseases which show aberrant expression of collagen expression.     

sTβRⅡ拮抗新生大鼠心肌成纤维细胞内TGF-β1诱导的Smad信号和肌成纤维细胞分化

目的研究可溶性转化生长因子-β1Ⅱ型受体(sTβRⅡ)对新生大鼠心肌成纤维细胞内TGF-β1诱导的Smad信号和肌成纤维细胞分化的抑制效应。方法培养新生大鼠的心肌成纤维细胞,随机分为4组:PBS对照组、TGF-β1(5ng/ml)组、sTβRⅡ(50ng/ml)组和TGF-β1+sTβRⅡ组。30min、1h和2h后,免疫细胞化学染色检测P-Smad2和Smad3的表达;24h后,免疫细胞化学染色检测α-SMA的表达。结果与PBS对照组相比,TGF-β1组P-Smad2、Smad3(核阳性率)和α-SMA的表达显著性升高(P0.05);与TGF-β1组相比,TGF-β1+sTβRⅡ组P-Smad2、Smad3(核阳性率)和α-SMA的表达明显降低(P0.05)。结论sTβRⅡ可拮抗新生大鼠心肌成纤维细胞内TGF-β1诱导的Smad2/Smad3蛋白的磷酸化与核转位,阻断Smad信号转导通路,抑制肌成纤维细胞分化。     

Combinatorial activin receptor-like kinase/Smad and basic fibroblast growth factor signals stimulate the differentiation of human embryonic stem cells into the cardiac lineage

The transforming growth factor beta/bone morphogenetic protein-activated Smad signaling pathway plays a complicated role in the maintenance of human embryonic stem cell (hESC) pluripotency and in the cell fate decision of hESCs. Here, we report that sustained inhibition of the transforming growth factor beta type I receptor (also termed activin receptor-like kinase or ALK) using a chemical inhibitor selective for ALK4/5/7 (ALKi) leads to the cardiac differentiation of hESCs under feeder-free and serum-free conditions. Treatment with ALKi reduced Smad2/3 phosphorylation and increased Smad1/5/8 phosphorylation in hESCs, suggesting a requirement for active Smad1/5/8 signaling for cardiac induction in these cells when ALK/Smad2/3 is inhibited. Importantly, active basic fibroblast growth factor (bFGF) signaling was also required for ALKi-mediated cardiac differentiation of monolayer-cultured hESCs. The FGF receptor inhibitor SU5402 blocked ALKi-mediated cardiac induction in hESCs, whereas bone morphogenetic protein-4 enhanced the ALKi-induced increase in phospho-Smad1/5/8 levels but failed to induce the cardiac differentiation of hESCs and instead promoted trophoblastic differentiation. We also confirmed that ALKi potentially enhanced the cardiac differentiation of human embryoid bodies, as determined by expression of cardiac-specific markers, increased beating areas, and action potential recorded from beating areas. These results demonstrate that an ALKi could be used as a potential cardiac-inducing agent and that the development of culture conditions that provide an appropriate balance between ALK/Smad and bFGF signaling is necessary to direct the fate of hESCs into the cardiac lineage.     

Activin A is an acute allergen-responsive cytokine and provides a link to TGF-beta-mediated airway remodeling in asthma

BACKGROUND: Allergic asthma typically shows activated, allergen-specific CD4(+) T cells in the early phase and airway remodeling in the late phase of the disease. Although TGF-beta plays a crucial role in airway remodeling, it is only marginally induced in CD4(+) T cells in the early allergen-dependent activation of the immune system. OBJECTIVE: To elucidate the transition between early- and late-phase events, we investigated the role of activin A, a close family member of TGF-beta. METHODS: Activin A and TGF-beta(1) levels were measured systemically in the serum and in CD4(+) T cells of asthmatic patients, as well as locally in the lung. RESULTS: Activin A serum levels were increased in patients with severe asthma compared with levels in patients with moderate asthma and healthy control subjects, whereas all patients showed significantly increased TGF-beta(1) serum levels independent of disease severity. In T cells only patients with moderate asthma showed increased activin A mRNA expression, whereas TGF-beta(1) expression was equal to that seen in healthy subjects. Accordingly, ovalbumin sensitization in a mouse model of allergic asthma could induce activin A mRNA expression, but not TGF-beta(1) expression, in the lung. Immunohistochemistry of mice and human specimens revealed an abundant expression of activin A by infiltrating lymphocytes and structural cells of the lung. Although TGF-beta(1) more potently enhanced proliferation and Smad 2/3-dependent reporter genes in fibroblasts, activin A was capable of inducing TGF-beta(1) and vice versa. CONCLUSION: Activin A provides a link between acute allergen-specific T-cell responses and chronic TGF-beta(1)-mediated airway remodeling in asthma.     

TGF-β1 induces peritoneal fibrosis by activating the Smad2 pathway in mesothelial cells and promotes peritoneal carcinomatosis

Peritoneal dissemination is one of the main causes of death in gastric cancer patients. Our previous study demonstrated that peritoneal fibrosis induced by transforming growth factor-β1 (TGF-β1) may provide a favorable environment for the dissemination of gastric cancer. The role of Smad3 in the development of dermal fibrosis, subcapsular cataract, and peritoneal fibrosis has been reported. However, the potential role of Smad2 in the development of fibrosis is unclear. The objective of this study was to determine the effect of Smad2 in peritoneal fibrosis, induced by TGF-β1, on dissemination of gastric cancer. Here we demonstrate that TGF-β1 significantly stimulated the expression of collagen?III and fibronectin in mesothelial cells through the Smad2 signal transduction pathway, but knockdown of the Smad2 gene by silencing siRNA partially inhibited these effects. This inhibition was associated with a depressed adhesion and invasiveness of gastric cancer cells. We conclude that peritoneal fibrosis induced by TGF-β1 is dependent on Smad2 signaling and may provide a hospitable environment for carcinomatosis.     

TGF-β1/Smad3信号轴的氧连糖基化修饰对小鼠心脏成纤维细胞活力和分化的影响

目的:探讨TGF-β1/Smad3信号轴的氧连糖基化修饰(O-连接的N-乙酰葡萄糖胺修饰)对体外培养的小鼠心脏成纤维细胞(MCFs)在缺氧/复氧(H/R)后活力和分化的影响及机制.方法:原代培养的MCFs缺氧6 h再恢复常氧24 h建立细胞H/R模型,通过感染O-连接的N-乙酰葡萄糖胺转移酶(OGT)重组腺病毒提高MC...     

Effects of activin A on IgE synthesis and cytokine production by human peripheral mononuclear cells.

Activin A not only stimulates the synthesis and release of pituitary follicle-stimulating hormone, but exerts various effects on haematopoietic cells, embryos, and fibroblasts. In the present study we have examined effects of activin A on IgE synthesis and cytokine production by peripheral blood mononuclear cells (PBMC) in normal humans. When PBMC were cultured in the presence of IL-4, activin A significantly augmented IgE production induced by IL-4. Activin A did not affect, however, IgE production from highly purified B cells when they were stimulated with anti-CD40 MoAb and IL-4. The fact that in the latter condition IgE synthesis was T cell- and monocyte-independent indicated that activin A does not directly influence B cells for IgE synthesis. Rather, production as well as gene expression of IL-6, which is known to enhance IgE synthesis by purified monocytes, was induced by activin A alone. In addition, activin A induced other monokines such as IL-1 and tumour necrosis factor (TNF)-alpha from monocytes. In contrast, activin A neither induced nor augmented the production of TNF-beta or interferon-gamma (IFN-gamma), both of which are known to be exclusively generated by T cells. These data indicate that activin A plays a certain role in physiological functions for monocytes in normal humans.     

Erythropoietin improves skin wound healing and activates the TGF-β signaling pathway

We could recently report that erythropoietin (EPO) accelerates skin wound healing in mice. Now, we provide insight into the molecular mechanisms of this non-hematopoietic property of EPO analyzing the transforming growth factor (TGF)-β signaling pathway. EPO receptor was found expressed in both non-wounded and wounded skin tissue as well as in fibroblasts and keratinocytes. In saline-treated control animals, wounds exhibited a significant upregulation of TGF-β1 and of α-smooth muscle actin (α-SMA) compared with non-wounded skin. EPO treatment accelerated wound epithelialization and induced mRNA expression of TGF-β1 and α-SMA. In addition, EPO significantly enhanced phosphorylation of Smad2 and Smad3 in fibroblasts and also elevated phosphorylation of Smad3 in wound tissue. Blockade of TGF-β using a neutralizing anti-TGF-β antibody attenuated EPO-induced acceleration of wound epithelialization in vivo and markedly reversed EPO effects on mRNA expression of TGF-β1 and α-SMA. In conclusion, EPO caused activation of the Smad-dependent TGF-β signaling pathway, enhanced differentiation of myofibroblasts, and accelerated skin wound closure.     

AGEs对肾小管上皮细胞转分化、1型胶原合成及smad信号通路的影响

目的:观察终末期糖基化终产物(AGEs)对正常大鼠近端肾小管上皮细胞（NRK52E ）转分化、collagenⅠ合成及Smads信号通路的影响。 方法:应用自制的AGEs（AGE-BSA）刺激NRK52E细胞，采用免疫细胞化学方法检测pmad2/3核表达情况；ELISA方法检测细胞培养上清TGF-β₁的浓度；RT-PCR检测TGF-β₁、Smad2、Smad3和Smad7 mRNA的表达；Western印迹检测α-平滑肌肌动蛋白（SMA）、E-钙粘着糖蛋白（cadherin）和1型胶原（collagenⅠ）蛋白的表达。 结果: AGE-BSA刺激15 min后pSmad2/3核表达明显增加，于30 min（68%）和24 h（76%）出现两个高峰，与刺激前及时间匹配的BSA对照组比较均有显著差异（P<0.05）；AGE-BSA以时间依赖方式上调TGF-β₁、Smad2、Smad3和Smad7 mRNA的表达；NRK52E细胞α-SMA和collagenⅠ蛋白表达高于对照组（P<0.01），E-cadherin蛋白表达低于对照组（P<0.01），细胞上清液TGF-β₁的浓度高于对照组（P<0.01）。 结论:AGEs可诱导肾小管上皮细胞Smads信号通路活化，促进肾小管上皮细胞转分化和细胞外基质collagenⅠ的合成。     

Inhibition of p38 mitogen-activated protein kinase and transforming growth factor-beta1/Smad signaling pathways modulates the development of fibrosis in adriamycin-induced nephropathy

Inflammation and fibrogenesis are the two determinants of the progression of renal fibrosis, the common pathway leading to end-stage renal disease. The p38 mitogen-activated protein kinase (MAPK) and transforming growth factor (TGF)-beta1/Smad signaling pathways play critical roles in inflammation and fibrogenesis, respectively. The present study examined the beneficial renoprotective effect of combination therapy using the p38 MAPK pathway inhibitor (SB203580) and a TGF-beta receptor I (ALK5) inhibitor (ALK5I) in a mouse model of adriamycin (ADR) nephrosis. The p38 MAPK and TGF-beta1/Smad2 signaling pathways were activated in ADR-induced nephropathy in a sequential time course manner. Two weeks after ADR injection, the combined administration of SB203580 (1 mg/kg/24 hours) and ALK5I (1 mg/kg/24 hours) markedly reduced p38 MAPK and Smad2 activities. Moreover, the co-administration of SB203580 and ALK5I to ADR-injected mice resulted in a down-regulation of total and active TGF-beta1 production, reduced myofibroblast accumulation, and decreased expression of collagen type IV and fibronectin. In these mice, retardation in the development of glomerulosclerosis and interstitial fibrosis was observed. In conclusion, although p38 MAPK and TGF-beta1/Smad signaling pathways are distinct they coordinate the progression of renal fibrosis in ADR nephrosis. The co-administration of a p38 MAPK inhibitor and an ALK5 inhibitor may have potential applications in the treatment of renal fibrosis.     

Hypoxia induces expression of connective tissue growth factor in scleroderma skin fibroblasts

Connective tissue growth factor (CTGF) plays a role in the fibrotic process of systemic sclerosis (SSc). Because hypoxia is associated with fibrosis in several profibrogenic conditions, we investigated whether CTGF expression in SSc fibroblasts is regulated by hypoxia. Dermal fibroblasts from patients with SSc and healthy controls were cultured in the presence of hypoxia or cobalt chloride (CoCl(2)), a chemical inducer of hypoxia-inducible factor (HIF)-1alpha. Expression of CTGF was evaluated by Northern and Western blot analyses. Dermal fibroblasts exposed to hypoxia (1% O(2)) or CoCl(2) (1-100 microM) enhanced expression of CTGF mRNA. Skin fibroblasts transfected with HIF-1alpha showed the increased levels of CTGF protein and mRNA, as well as nuclear staining of HIF-1alpha, which was enhanced further by treatment of CoCl(2). Simultaneous treatment of CoCl(2) and transforming growth factor (TGF)-beta additively increased CTGF mRNA in dermal fibroblasts. Interferon-gamma inhibited the TGF-beta-induced CTGF mRNA expression dose-dependently in dermal fibroblasts, but they failed to hamper the CoCl(2)-induced CTGF mRNA expression. In addition, CoCl(2) treatment increased nuclear factor (NF)-kappaB binding activity for CTGF mRNA, while decreasing IkappaBalpha expression in dermal fibroblasts. Our data suggest that hypoxia, caused possibly by microvascular alterations, up-regulates CTGF expression through the activation of HIF-1alpha in dermal fibroblasts of SSc patients, and thereby contributes to the progression of skin fibrosis.     

丹参酮ⅡA抑制心肌细胞的纤维化

背景：转化生长因子β-Smads信号通路是心肌纤维化的关键通路;丹参酮ⅡA具有抑制心肌纤维化作用。 目的：验证丹参酮ⅡA对转化生长因子β1致心肌纤维化的作用并探讨其机制。 方法：取出生24 h内的SD大鼠心脏,利用酶消化法结合差速贴壁体外培养心肌成纤维细胞。取上述第3代心肌成纤维细胞,用5 μg/L转化生长因子β1培养15,30,60,120 min或6,12,24 h后收集细胞,用不同浓度(10-5 mol/L、10-4 mol/L)丹参酮ⅡA预处理2 h后再加入5 μg/L转化生长因子β1培养120 min或24 h后收集细胞,并设空白对照组。免疫细胞化学染色法进行细胞鉴定,反转录聚合酶链反应检测结缔组织生长因子及Ⅰ型胶原蛋白mRNA表达,Western Blot检测Smad7及磷酸化Smad3蛋白表达。免疫组织化学染色及免疫荧光法检测磷酸化Smad3、结缔组织生长因子及Ⅰ型胶原蛋白表达。 结果与结论：转化生长因子β1在一定范围内以时间依赖方式诱导结缔组织生长因子、Ⅰ型胶原、磷酸化Smad3及Smad7的表达,刺激终末结缔组织生长因子、Ⅰ型胶原mRNA的表达量明显上升(均P < 0.01);磷酸化Smad3及Smad7蛋白表达量在刺激后1 h达到峰值,表达量显著增加(均P < 0.01)。高浓度丹参酮ⅡA预处理可显著下调磷酸化Smad3、结缔组织生长因子及Ⅰ型胶原表达(均P < 0.01)。两种浓度的丹参酮ⅡA预处理均可上调Smad7蛋白表达(P < 0.05,P < 0.01)。提示丹参酮ⅡA对心肌纤维化有抑制作用,可能与其上调Smad7蛋白表达,抑制转化生长因子β1诱导的Smad3磷酸化,部分阻断转化生长因子β1-Smads信号通路有关。