CTGF基因沉默对肺成纤维细胞增殖及表型转化的影响

近期研究表明,结缔组织生长因子(Connective tissue growth factor,CTGF)参与了肺成纤维细胞表型转化,与肺纤维化的形成关系密切.因此,本研究应用siRNA表达载体介导的RNA干扰(RNA interference,RNAi)技术,将CTGF-siRNA表达质粒稳定转染人肺成纤维细胞MRC-5,并通过定量PCR、Western-blot、细胞生长曲线及群体倍增时间、免疫细胞化学测定等方法检测基因表达、细胞增殖及表型转化等变化.结果显示,与非特异对照Scrambled-siRNA质粒稳定转染的MRC-5细胞或未转染MRC-5细胞相比,CTGF-siRNA表达质粒稳定转染的MRC-5细胞的CTGF表达明显降低;细胞增殖能力明显降低,群体倍增时间延长,由24.63或25.05 h延长至31.14 h(P＜0.05);TGFβ1刺激24 h后,细胞内α-平滑肌肌动蛋白α-smooth muscle actin,α-SMA)、Ⅰ型胶原及纤维连接蛋白(fibronectin,FN)的表达均明显下降.本研究提示,通过RNA干扰使CTGF基因沉默后,在体外可明显抑制MRC-5肺成纤维细胞的增殖、表型转化及细胞外基质的合成,可为基因治疗肺纤维化提供实验依据.     

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.     

Activation of the activin A-ALK-Smad pathway in systemic sclerosis

Systemic sclerosis (SSc) is a chronic disease of unknown etiology that is characterized by multiple tissue fibrosis. Transforming Growth Factor-beta (TGF-β) is thought to be the most important mediator that induces fibrosis. However, the molecular mechanisms by which fibrosis is induced have not been fully elucidated. In this study, the role of activin, a member of the TGF-β superfamily, was investigated in the pathogenesis of fibrosis in SSc. Serum activin A levels in patients with SSc were measured by ELISA, and the expression of the activin receptor type IB (ACVRIB/ALK4) and the activity of the signaling pathway via ACVRIB/ALK4 were investigated using western blotting. To evaluate a potential therapeutic strategy for SSc, we also attenuated the ACVRIB/ALK4 pathway using an inhibitor. Serum activin A levels were significantly higher in SSc patients than in normal controls. Activin A and ACVRIB/ALK4 expression were also higher in cultured SSc fibroblasts. Activin A stimulation induced phosphorylation of Smad2/3 and CTGF expression in SSc fibroblasts. Procollagen production and Col1α mRNA also increased upon stimulation by activin A. The basal level of Smad2/3 phosphorylation was higher in cultured SSc fibroblasts than in control cells, and treatment with the ALK4/5 inhibitor SB431542 prevented phosphorylation of Smad2/3 and CTGF expression. Furthermore, production of collagen was also induced by activin A. Activin A-ACVRIB/ALK4-Smad-dependent collagen production was augmented in SSc fibroblasts, suggesting the involvement of this signaling mechanism in SSc. Inhibition of the activin A-ACVRIB/ALK4-Smad pathway would be a new approach for the treatment of SSc.     

FGF-21和Nrf2对博莱霉素诱导的小鼠肺纤维化的影响

目的:研究成纤维细胞生长因子21(FGF-21)对博莱霉素(BLM)诱导的小鼠肺纤维化炎症应答及氧化应激的影响,并探讨其抗肺纤维化的作用机制。方法:建立BLM诱导的小鼠肺纤维化的模型,40只小鼠随机分为对照组、BLM组及FGF-21(1、2及5 mg/kg)+BLM组。Western blot检测I型胶原蛋白(collagen I)、纤连蛋白(fibronectin)和核因子E2相关因子2(Nrf2)蛋白表达水平。DCFH-DA染色检测活性氧簇(ROS)的生成。ELISA用于测定肺组织炎症因子的表达。试剂盒检测各组小鼠肺组织中的丙二醛(MDA)含量、超氧化物歧化酶(SOD)活性、谷胱甘肽过氧化物酶(GPx)活性和羟脯氨酸(HYP)含量。结果:FGF-21处理显著降低BLM诱导的肺组织炎症介质肿瘤坏死因子α、白细胞介素1β和白细胞介素6的表达水平,减少ROS及MDA的含量,并增加抗氧化酶系统SOD和GPx的活性(P 0. 05)。同时,FGF-21下调BLM诱导的collagen I和fibronectin,并减少TGF-β1及HYP的含量。Nrf2沉默能够逆转FGF-21的抗纤维化作用。结论:FGF-21通过激活Nrf2信号抑制炎症应答进程,减轻氧化损伤,减少细胞外基质沉积,从而缓解BLM诱导的肺纤维化。这可能为肺间质纤维化治疗提供新的靶点。     

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.     

Receptor-activated Smad localisation in bleomycin-induced pulmonary fibrosis

BACKGROUND: Recent advances in fibrosis biology have identified transforming growth factor (TGF)-beta type I receptor-mediated activation of Smads as playing a central part in the development of fibrosis. However, to date, there have been few studies that examined the localisation and distribution of receptor-activated Smads protein (R-Smads: Smad2 and 3) during the fibrosis progression. AIMS: To histopathologically assess the time-course change of the localisation and distribution of the Smads protein in pulmonary fibrosis. METHODS: Pulmonary fibrosis was induced by intranasal injection of bleomycin (0.3 U/mouse). Lungs were isolated 2, 5, 7, 9 and 14 days after bleomycin treatment. Histological changes in the lungs were evaluated by haematoxylin-eosin stain or Masson's trichrome stain, and scored. TGF-beta1, Smad3 and phosphorylated Smad2 localisations in lung tissues were determined by immunohistochemistry. RESULTS: The bleomycin treatment led to considerable pulmonary fibrotic changes accompanied by marked increase in TGF-beta1 expression in infiltrating macrophages. With the progression in fibrosis (day 7-14), marked increases in Smad3-positive and pSmad2-positive cells were observed. There were intense Smad3-positive and pSmad2-positive signals localised to the nuclei of the infiltrating macrophages and to type II epithelial cells, and less intense signals in fibroblasts and hyperplastic alveolar/bronchiolar epithelial cells. CONCLUSIONS: The time-course data of TGF-beta1 and R-Smads indicate that progressive enhancement of TGF-beta1 signalling via R-Smad is activated in the process of fibrosis progression.     

Hepatocyte growth factor inhibits epithelial to myofibroblast transition in lung cells via Smad7

Idiopathic pulmonary fibrosis is a lethal parenchymal lung disease characterized by denudation of the lung epithelium, fibroblast proliferation, and collagen deposition. Cellular changes underlying disease progression involve injury to alveolar epithelial cells, epithelial to mesenchymal transition, proliferation of alpha-smooth muscle actin (alpha-SMA)-expressing myofibroblasts and of fibroblasts resulting in enhanced deposition of extracellular matrix proteins. Hepatocyte growth factor (HGF) inhibits progression of bleomycin-induced pulmonary fibrosis in mice. The mechanism underlying the inhibitory effect of HGF was investigated in an in vitro model. We show that HGF markedly antagonizes basal and transforming growth factor (TGF)-beta-induced expression of myofibroblast markers such as alpha-SMA, collagen type 1, and fibronectin in rat alveolar epithelial cells. HGF also inhibited TGF-beta-induced alpha-SMA expression in primary murine alveolar epithelial cells. Since TGF-beta is known to regulate alpha-SMA expression, the effect of HGF on components of TGF-beta signaling was investigated. HGF induced expression of Smad7, an inhibitor of TGF-beta signaling, in a mitogen-activated protein kinase-dependent manner. HGF also induced the nuclear export of Smad7 and Smad ubiquitin regulatory factor 1 (Smurf1) to the cytoplasm. HGF-dependent decrease in alpha-SMA was abolished with specific siRNAs targeted to Smad7. Thus, induction of Smad7 by HGF serves to limit acquisition of the myofibroblast phenotype in alveolar epithelial cells.     

Heterogeneous response of nasal and lung fibroblasts to transforming growth factor-β1

Background Nasal polyposis is characterized by marked oedema, sparse extracellular matrix (ECM) and proliferating blood vessels. Pulmonary fibrosis is characterized by inflammatory cells accumulation, considerable ECM deposition and vascular abnormalities. Although lung fibrosis is not only and necessarily an inflammatory disorder, we hypothesized that the difference between nasal polyposis and pulmonary fibrosis may, in part, be due to the heterogeneity between nasal and lung fibroblasts. Fibroblasts participate in the inflammatory response by releasing ECM proteins and cytokines. TGF‐β is thought to participate in chronic inflammation and fibrosis. Myofibroblasts are the activated form of fibroblasts. A phenotypic hallmark of myofibroblasts is the expression of smooth muscle α‐actin (SMA). Objective We examined whether there is any heterogeneity between nasal and lung fibroblasts upon stimulation with TGF‐β₁ with regard to the synthesis of SMA, pro‐collagen type I and vascular endothelial growth factor (VEGF) as well as translocation of Smad proteins. Methods Fibroblasts lines were established from human biopsy tissue. The expression of SMA, pro‐collagen type I, VEGF mRNA was evaluated by reverse transciptase RT‐PCR. The amount of pro‐collagen type I and VEGF was measured by ELISA. By immunocytochemistry, we analysed the expression of SMA and Smad2, 3, 4 in cultured fibroblasts. Results TGF‐β₁ induced SMA and pro‐collagen type I synthesis in lung, but not in nasal fibroblasts. By contrast, TGF‐β₁ induced VEGF synthesis in both lung and nasal fibroblasts. After stimulation with TGF‐β₁, Smad2, 3, 4 were translocated from the cytoplasm to the nucleus in lung fibroblasts, whereas only Smad3 was translocated in nasal fibroblasts. Conclusion These results establish the heterogeneous responsiveness of fibroblast populations in the airways to TGF‐β₁ and that such a heterogeneity may contribute, at least in part, to the different pathological outcomes of inflammation in the upper and lower airways.     

Architectural remodelling in lungs of rabbits induced by type V collagen immunization: a preliminary morphologic model to study diffuse connective tissue diseases

The pathogenesis of diffuse connective tissue diseases (DCTD) is still unknown and has been extensively studied regarding its autoimmunity aspects related to extracellular matrix (ECM) remodelling, with an emphasis on the collagens at the inflammatory site. The present paper describes the pulmonary architectural and repair/remodelling responses to injury after immunization of rabbits with human type V collagen. The animal model consisted of rabbits immunized with collagen mixed with Freund's adjuvant and sacrificed 7, 15, 30, 75, and 120 days after the first of four doses of antigen. Pulmonary architecture remodelling response was evaluated by histology, morphometry, and the immunofluorescence method, according to compartments of reference (parenchyma and interstitium) and injury: 1 inflammation (polymorphonuclear and mononuclear cells); 2-repair (fibrosis) and 3-ECM remodelling (collagen system). The results showed an intense inflammatory involvement of the pulmonary vascular and bronchiolar parenchyma, characterized by increased wall thickness in small arteries, infiltrations by pseudoeosinophils, and mononuclear cells. Progressive remodelling of the pulmonary ECM was characterized by collagen deposition in the septal and bronchovascular interstitium, especially in rabbits sacrifices at 75 and 120 days. The ECM remodelling process was not reproduced when rabbits were inoculated with collagen types I and III. We conclude that the model reproduces morphologic changes similar to those observed in many DCTD, encouraging realization of other experiments to gain a better understanding of the pathogenesis of these diseases.     

When the Smad signaling pathway is impaired, fibroblasts advance open wound contraction

In wound healing transforming growth factor β1 (TGFβ1), utilizing the Smad signaling pathway, advances connective tissue deposition, the transformation of fibroblasts into myofibroblasts and wound contraction. The compound SB-505124 disrupts the Smad signaling pathway by blocking activin receptor-like kinase phosphorylation of select Smad signaling proteins. Four full thickness excisional square 2 × 2 cm wounds were made on the rat dorsum. On day 2, the pair of wounds on the left received 1 μM SB-505124 in gel, and the pair on the right, controls, received gel alone. Wounds were covered with nonocclusive dressings and treated redressed daily for 4 days. No differences in day 14 wound sizes between treatment groups were found. H&E stained sections revealed increased cell density in SB-505124 treated wounds. Polarized light microscopy showed collagen fiber bundles birefringence intensity and organization were equivalent between treatment groups. Myofibroblast populations, identified by α-smooth muscle actin staining, were the norm in controls but absent in SB-505124 treated wounds, which was confirmed by Western blot analysis. Blocking the Smad signaling pathway diminished connective tissue deposition and generated a deficiency in myofibroblast numbers, but wound contraction was unimpaired. The absence of myofibroblasts may be related to the blocking of the Smad signaling pathway or it may be related to the generation of less tension in treated wounds, related to reduce deposited connective tissue. These findings support the notion that wound contraction does not require the generation of myofibroblast contractile forces, but rather the organization of newly deposited collagen fiber bundles by forces related to fibroblast locomotion.     

TGFbeta1 induces epithelial-mesenchymal transition, but not myofibroblast transdifferentiation of human kidney tubular epithelial cells in primary culture

The origin and fate of renal interstitial myofibroblasts (MFs), the effector cells of renal fibrosis, are still debated. Experimental evidence suggests that renal MFs derive from tubular epithelial cells throughout the epithelial-mesenchymal transition (EMT) process. Primary human tubular epithelial cells (HUTECs) were cultured for 4 and 6 days on plastic or type I collagen-coated plates with 1, 5, 10 and 50 ng/ml of transforming growth factor beta1 (TGFbeta1). The EMT process was monitored by morphology and immunophenotyping for alphaSMA, cytokeratin 8-18, E-cadherin, vimentin and collagen III. Quantitative comparative RT/PCR and real-time PCR were used to evaluate the expression of collagen III and IV, fibronectin, tenascin, MMP-2, CTGF, E-cadherin and cadherin 11 genes, as well as those of the Smad signalling pathway. TGFbeta1 was found capable of reactivating the mesenchymal programme switched off during tubulogenesis, but it induced no de novo expression of alphaSMA gene or myofibroblast phenotype. We demonstrate that the EMT process is conditioned by the extracellular matrix and characterized by TGFbeta1-driven Smad3 downregulation. Our study results suggest that TGFbeta1 could function as a classic embryonal inducer, initiating a cascade of de-differentiating events that might be further controlled by other factors in the cellular environment.     

Knockdown of elF3a inhibits collagen synthesis in renal fibroblasts via Inhibition of transforming growth factor-β1/Smad signaling pathway

Renal fibrosis is characterized by an exacerbated accumulation of deposition of the extracellular matrix (ECM). The eukaryotic translation initiation factor (eIF) 3a is the largest subunit of the eIF3 complex and has been involved in pulmonary fibrosis. However, the role of eIF3a in rental fibrosis is still unclear. Therefore, in this study, we investigated the role of eIF3a in rental fibrosis and explored the underlying mechanism. Our study found that eIF3a was up-regulated in renal fibrotic tissues and transforming growth factor (TGF)-β1-treated HK-2 cells. In addition, knockdown of eIF3a significantly inhibited TGF-β1-induced expression levels of α-smooth muscle actin (α-SMA) and collagen I. Furthermore, knockdown of eIF3a attenuated TGF-β1-induced Smad3 activation in HK-2 cells. Taken together, these results suggest that knockdown of eIF3a inhibits collagen synthesis in renal fibroblasts via inhibition of TGF-β1/Smad signaling pathway, and eIF3a may be a potential molecular target for the treatment of renal fibrosis.     

小鼠实验性肺纤维化上皮细胞-间充质细胞转变及骨桥蛋白的表达

目的从形态学上证实小鼠实验性肺纤维化上皮细胞-间充质细胞转变(EMT)及骨桥蛋白(OPN)的表达变化。方法将60只健康雄性C57BL/6小鼠随机分为生理盐水对照组和博来霉素(BLM)模型组,采用口咽抽吸法经咽部注入气管50μl博来霉素溶液,对照组注入50μl生理盐水。分别在造模后第3d、7d、14d、21d及28d 5个时间点处死对照组及模型组小鼠。取小鼠左肺制备石蜡切片,行苏木素-伊红(HE)染色及天狼猩红染色观察肺组织形态变化及胶原增生情况;行表面活性物质相关蛋白-C(SP-C)、上皮型钙黏蛋白(E-Cadherin)、波形蛋白(vimentin)、成纤维细胞特异蛋白1(FSP1)和骨桥蛋白(OPN)免疫组织化学染色,观察肺纤维化上皮细胞-间充质细胞转变(EMT)形态与OPN表达,利用图像分析软件Image-Pro Plus 6.0(IPP6.0)测量切片积分吸光度(IA),并进行统计分析。结果HE及天狼猩红染色显示出小鼠肺组织正常结构和纤维化形态变化,并且模型组小鼠肺组织的胶原生成量随时间推移而增加(P<0.05)。免疫组织化学结果显示,模型组小鼠肺OPN表达量随病程进展持续升高,在纤维化期达到峰值,而对照组表达量很少(P<0.05);对照组SP-C在Ⅱ型肺泡细胞恒定表达,模型组SP-C持续增加,且胞体增大;对照组E-Cadherin表达量多,而模型组在肺实变部位几乎不表达,但肺实变部位产生波形蛋白及FSP1,这些蛋白提示肺纤维化存在EMT。结论BLM诱导性肺纤维化中存在EMT,且与显著增加的OPN有潜在关系。     

穿心莲内酯对肺纤维化大鼠BALF中细胞因子和肺组织Ⅰ、Ⅲ型胶原mRNA表达的影响

目的:探讨穿心莲内酯灌胃对博来霉素(BLM)致肺纤维化大鼠支气管肺泡灌洗液(BALF)中TNF-α、TGF-β1浓度和肺组织Ⅰ、Ⅲ型胶原mRNA表达的影响。方法:取健康雄性SD大鼠90只,随机分为生理盐水(NS)组、BLM组、泼尼松(Pred)组、不同剂量穿心莲内酯组(即穿A组62.5mg/kg、穿B组125 mg/kg、穿C组250 mg/kg),各组大鼠15只,分别气管内灌注BLM(BLM组、Pred组、穿A组、穿B组、穿C组)或NS(NS组)后,每天给予NS(NS组、BLM组)、Pred(Pred组)或穿心莲内酯(穿A组、穿B组、穿C组)灌胃,各组分别于气管内灌注药物后第7、14、28天处死大鼠5只。用HE、Masson染色观察肺泡炎症和纤维化改变;实时荧光定量逆转录-聚合酶链反应检测肺组织Ⅰ、Ⅲ型胶原mRNA表达;酶联免疫吸附试验测定BALF中TNF-α、TGF-β1浓度;同时监测肾功能指标血尿素氮(BUN)、肌酐(Cr)及肝功能指标血丙氨酸氨基转移酶(ALT)、天冬氨酸氨基转移酶(AST)。结果:肝肾功能监测显示:不同剂量穿心莲内酯组、NS组、BLM组、Pred组所监测的AST、ALT、BUN、Cr比较,差异无统计学意义(P>0.05)。NS组大鼠肺组织未发现肺泡间隔水肿、炎性细胞浸润和纤维化形成。BLM组第7天时肺泡腔内可见大量炎性细胞浸润,第14天时肺泡炎仍存在,但炎症细胞明显减少,肺泡间隔内成纤维细胞明显增多,肺泡结构破坏,肺泡隔增宽,第28天时炎症较前减轻,肺纤维化程度加重,部分肺泡腔消失,形成严重纤维化。穿A组病理形态改变与BLM组相似。Pred组、穿B组、穿C组大鼠第7天有较多的炎症细胞浸润及局部聚积,第14天和第28天的纤维化病理改变均较BLM组、穿A组明显减轻。NS组各个时间点BALF中TGF-β1、TNF-α含量均明显低于同时间点BLM组、Pred组、穿A组、穿B组、穿C组BALF中的浓度(P<0.05)。BLM组3个时间点BALF中TGF-β1、TNF-α含量较Pred组、穿B、穿C组高(P<0.05)。与BLM组比较,穿A组BALF中TGF-β1、TNF-α含量无统计学意义。NS组各个时间点肺组织Ⅰ、Ⅲ型胶原mRNA表达均明显低于同时间点BLM组、Pred组、穿A组、穿B组、穿C组肺组织中的表达(P<0.05)。BLM组3个时间点Ⅰ、Ⅲ型胶原mRNA表达较Pred组、穿B组、穿C组高(P<0.05)。与BLM组比较,穿A组肺组织Ⅰ、Ⅲ型胶原mRNA表达无统计学差异。结论:穿心莲内酯灌胃可减轻BLM致肺纤维化大鼠肺泡炎和肺纤维化程度,降低肺组织Ⅰ、Ⅲ型胶原mRNA表达,降低BALF中TNF-α、TGF-β1浓度,且对肝肾无明显毒副作用。     

α-Lipoic acid induces collagen biosynthesis involving prolyl hydroxylase expression via activation of TGF-β-Smad signaling in human dermal fibroblasts

The collapse of collagenous networks with aging results in comprehensive changes in the functional properties of skin. α-Lipoic acid (LA) is known to possess beneficial effects against skin aging, effects often presumed to be its antioxidant potential. However, the effects of LA on fibrillogenesis in dermal fibroblasts have not been adequately assessed. In this study, we demonstrated for the first time that LA enhances the biosynthesis of new collagen in normal human dermal fibroblasts (NHDFs). By using a quantitative dye-binding method and immunochemical approaches, we showed that LA effectively increased the expression and subsequently the deposition of type I collagen in NHDFs. LA also facilitated the expression of a collagen-processing enzyme, prolyl-4-hydroxylase, pointing to the existence of a posttranslational mechanism among the LA-mediated effects on collagen synthesis. In addition, we determined that both Smad 2/3 were rapidly phosphorylated by treatment with LA within 30 min, indicating that LA enhances type I collagen synthesis through the activation of Smad signaling. Pretreatment of SB431542, a specific transforming growth factor-β (TGF-β) receptor type I (TβRI) kinase inhibitor, blocked LA-mediated Smad 2/3 phosphorylations and both type I collagen and prolyl-4-hydroxylase expression, suggesting that LA-mediated cell responses are regulated by TβRI kinase-dependent pathway. Levels of TGF-β secretion after 4 hr of treatment with LA were not remarkably elevated, indicating that LA may be able to mimic TGF-β-mediated cell response. The study results produced new insights into the molecular pharmacology of LA in NHDFs, with potential applications in the treatment of aging skin.     

Postmitotic differentiation of rat lung fibroblasts: induction by bleomycin and effect on prolyl 4-hydroxylase

The cytostatic drug bleomycin (BLM) induces pulmonary fibrosis as its main side effect. Fibroblasts in fibrotic foci are the main cellular source for extracellular matrix accumulation that typifies fibrosis. In vitro studies demonstrated the ability of cytotoxic drugs to induce terminal differentiation of fibroblasts. These postmitotic cells are very active in regard to production of collagens. The present study was addressed to investigate the potential of BLM to induce terminal differentiation of rat lung fibroblasts in vitro and the consequences for collagen production and for the expression and activity of the collagen modifying enzyme prolyl 4-hydroxylase (P4H). The BLM effects were compared with those of mitomycin C (MMC), another cytotoxic agent with known potential for initiation of postmitotic differentiation of fibrobasts.

BLM induced postmitotic differentiation of rat lung fibroblasts. The capacity of the cells to form clones was diminished by BLM or MMC in a concentration dependent manner. Both drugs initiated the formation of an increasing number of postmitotic cell clones. The postmitotic differentiation was accompanied by an increase in total collagen production by the cells. Administration of BLM to cultures of lung fibroblasts at concentrations of 1 or 10 mU/ml resulted in an increase of the collagen amount to about the 1.5-fold and 1.6-fold of controls, respectively. Treatment of fibroblasts with MMC elevated the collagen level to about the 2-fold. P4H activity and P4H mRNA levels in cells exposed to BLM or MMC were found to be increased.

We conclude that terminally differentiated fibroblasts might be part of the heterogeneous population of fibroblast-like cells in fibrotic foci responsible for the increased production of collagen during the fibrotic phase of the development of pulmonary fibrosis.     

A phosphodiesterase 4 inhibitor inhibits matrix protein deposition in airways in vitro

BACKGROUND: Airway smooth muscle (ASM) cells may contribute to airway remodeling through the release of growth factors, cytokines, and extracellular matrix (ECM) proteins. The effect of current asthma therapies on this release is not known. OBJECTIVE: We examined the effect of corticosteroids, long-acting beta(2)-agonists, and a phosphodiesterase 4 (PDE4) inhibitor on ASM-released connective tissue growth factor (CTGF), collagen I, fibronectin, versican, and IL-6. METHODS: Airway smooth muscle cells from individuals with and without asthma were stimulated with TGF-beta with or without the drugs and CTGF and ECM protein expression measured by real-time PCR, cell surface, or matrix-associated ELISA. IL-6 release was measured by ELISA. Bronchial rings from individuals without asthma were incubated with TGF-beta with or without the drugs. RESULTS: Neither corticosteroids nor long-acting beta(2)-agonists reduced TGF-beta-induced CTGF, collagen I, or fibronectin in either cell type, whereas corticosteroids alone induced the expression of CTGF, collagen I, and fibronectin. These drugs did not prevent the accumulation of TGF-beta-induced proteins in bronchial rings, whereas the PDE4 inhibitor roflumilast inhibited TGF-beta-induced CTGF, collagen I, and fibronectin. CONCLUSION: In our model, current asthma therapies are not able to inhibit matrix protein deposition from ASM cells. The results of this study suggest that the PDE4 inhibitor roflumilast may have a role in regulating the ECM and therefore aspects of airway remodeling in asthma. CLINICAL IMPLICATIONS: Although current asthma therapies are effective in reducing inflammation and symptoms, reversal or prevention of structural changes contributing to remodeling may require additional therapy, which could include PDE4 inhibitors.