Signaling events required for transforming growth factor-beta stimulation of connective tissue growth factor expression by cultured human lung fibroblasts

Pharmacology Study of the Multiple Angiogenesis Inhibitor RC28-E on Anti-Fibrosis in a Chemically Induced Lung Injury Model

Background: Disease-related injury in any organ triggers a complex cascade of cellular and molecular responses that culminate in tissue fibrosis, inflammation, and angiogenesis simultaneously. Multiple cell angiogenesis is an essential part of the tissue damage response, which is involved in fibrosis development. RC28-E is a novel recombinant dual decoy receptor lgG1 Fc-fusion protein that can block vascular endothelial growth factor (VEGFA), platelet-derived growth factor (PDGF), and fibroblast growth factor-2 (FGF-2) simultaneously. This protein has stepped into clinical trials (NCT03777254) for the treatment of pathological neovascularization-related diseases. Here, we report on the role of RC28-E during anti-fibrosis and its potential multitarget function in regulating fibrosis. Methods: A bleomycin-induced pulmonary fibrosis C57BL/6 mouse model was established. Hematoxylin and eosin staining (HE) and Masson staining (Masson’s) were performed to evaluate the pulmonary fibrosis based on the scoring from, Ashcroft score. Fibrosis related factors and inflammatory cytokines including HYP, α-SMA, procollagen, ICAM, IL-6, IL-1, and TNF-α were also determined at the protein and mRNA levels to characterize the fibrosis. Both mRNA and protein levels of VEGF, FGF, and transforming growth factor (TGF)-β were detected by quantitative real-time PCR (qRT-PCR) and immunohistochemical (IHC) analysis, respectively. Pulmonary fibrosis and related cytokines were re-evaluated in vivo after 3 doses of RC28-E (5 mg/kg, 15 mg/kg, and 50 mg/kg, ip. Tiw × 9) in comparison with a mono-target antagonist treatment (VEGF or FGF blocking). RC28-E attenuated the activation of TGF-β induced fibroblasts in vitro. Expression levels of α-SMA and collagen I, as well as proliferation and migration, were determined with the human skin fibroblast cell line Detroit 551 and primary murine pulmonary fibroblast cells. The mechanism of RC28-E via the TGF-β/Smad pathway was also investigated. Results: RC28-E exhibits significant anti-fibrosis effects on Idiopathic pulmonary fibrosis (IPF) in vivo. Moreover, TGF-β induced fibroblast activation in vitro via the inhibition of the TGF-β downstream Smad pathway, thus providing potential therapeutics for clinical disease-related fibrosis-like IPF as well as chemotherapy-induced fibrosis in cancer therapy.

Quantitative relationships between SMAD dynamics and target gene activation kinetics in single live cells

The transduction of extracellular signals through signaling pathways that culminate in a transcriptional response is central to many biological processes. However, quantitative relationships between activities of signaling pathway components and transcriptional output of target genes remain poorly explored. Here we developed a dual bioluminescence imaging strategy allowing simultaneous monitoring of nuclear translocation of the SMAD4 and SMAD2 transcriptional activators upon TGF-β stimulation, and the transcriptional response of the endogenous connective tissue growth factor (ctgf) gene. Using cell lines allowing to vary exogenous SMAD4/2 expression levels, we performed quantitative measurements of the temporal profiles of SMAD4/2 translocation and ctgf transcription kinetics in hundreds of individual cells at high temporal resolution. We found that while nuclear translocation efficiency had little impact on initial ctgf transcriptional activation, high total cellular SMAD4 but not SMAD2 levels increased the probability of cells to exhibit a sustained ctgf transcriptional response. The approach we present here allows time-resolved single cell quantification of transcription factor dynamics and transcriptional responses and thereby sheds light on the quantitative relationship between SMADs and target gene responses.

Protective Effects of Nintedanib against Polyhexamethylene Guanidine Phosphate-Induced Lung Fibrosis in Mice

Nintedanib (NDN), a tyrosine kinase inhibitor, has been shown to have anti-tumor, anti-inflammatory, and anti-fibrotic effects in several reports. We investigated the protective effects of NDN against polyhexamethylene guanidine phosphate (PHMG)-induced lung fibrosis in mice. The following three experimental groups were evaluated: (1) vehicle control; (2) PHMG (1.1 mg/kg); and (3) PHMG & NDN (60 mg/kg). PHMG induced pulmonary inflammation and fibrosis by intratracheal instillation in mice. In contrast, NDN treatment effectively alleviated the PHMG induced lung injury, and attenuated the number of total cells and inflammatory cells in the bronchoalveolar lavage fluid, including the fibrotic histopathological changes, and also reduced the hydroxyproline content. NDN also significantly decreased the expression of inflammatory cytokines and fibrotic factors, and the activation of the NLRP3 inflammasome in lung tissues. These results suggest that NDN may mitigate the inflammatory response and development of pulmonary fibrosis in the lungs of mice treated with PHMG.

AFAP1 Is a Novel Downstream Mediator of TGF-β1 for CCN2 Induction in Osteoblasts

Background

CCN2 acts as an anabolic growth factor to regulate osteoblast differentiation and function. CCN2 is induced by TGF-β1 and acts as a mediator of TGF-β1 induced matrix production in osteoblasts and Src is required for CCN2 induction by TGF-β1; however, the molecular mechanisms that control CCN2 induction in osteoblasts are poorly understood. AFAP1 binds activated forms of Src and can direct the activation of Src in certain cell types, however a role for AFAP1 downstream of TGF-β1 or in osteoblats is undefined. In this study, we investigated the role of AFAP1 for CCN2 induction by TGF-β1 in primary osteoblasts.

Results

We demonstrated that AFAP1 expression in osteoblasts occurs in a biphasic pattern with maximal expression levels occurring during osteoblast proliferation (~day 3), reduced expression during matrix production/maturation (~day 14–21), an a further increase in expression during mineralization (~day 21). AFAP1 expression is induced by TGF-β1 treatment in osteoblasts during days 7, 14 and 21. In osteoblasts, AFAP1 binds to Src and is required for Src activation by TGF-β1 and CCN2 promoter activity and protein induction by TGF-β1 treatment was impaired using AFAP1 siRNA, indicating the requirement of AFAP1 for CCN2 induction by TGF-β1. We also demonstrated that TGF-β1 induction of extracellular matrix protein collagen XIIa occurs in an AFAP1 dependent fashion.

Conclusions

This study demonstrates that AFAP1 is an essential downstream signaling component of TGF-β1 for Src activation, CCN2 induction and collagen XIIa in osteoblasts.

Nintedanib: evidence for its therapeutic potential in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with poor prognosis. The molecular mechanisms involved in the progression of IPF are not fully understood; however, the platelet-derived growth factor (PDGF)/PDGF receptor pathway is thought to play a critical role in fibrogenesis of the lungs. Other growth factors, including fibroblast growth factor and vascular endothelial growth factor, are also thought to contribute to the pathogenesis of pulmonary fibrosis. Nintedanib is an inhibitor of multiple tyrosine kinases, including receptors for PDGF, fibroblast growth factor, and vascular endothelial growth factor. In the Phase II TOMORROW trial, treatment with 150 mg of nintedanib twice daily showed a trend to slow the decline in lung function and significantly decrease acute exacerbations in patients with IPF, while showing an acceptable safety profile. The Phase III INPULSIS trials demonstrated a significant decrease in the annual rate of decline in forced vital capacity in IPF patients treated with 150 mg nintedanib twice daily. In the INPULSIS-2 trial, the time to the first acute exacerbation significantly increased in IPF patients who were treated with 150 mg of nintedanib twice daily. Pirfenidone, another antifibrotic drug, was shown to limit the decline in pulmonary function in patients with IPF in the ASCEND trial. Combination therapy with nintedanib and pirfenidone is anticipated, although further evaluation of its long-term safety is needed. There is limited evidence for the safety of the combination therapy although a Phase II trial conducted in Japan demonstrated that combination therapy with nintedanib and pirfenidone was tolerable for 1 month. Available antifibrotic agents (ie, pirfenidone and N-acetylcysteine) have limited efficacy as single therapies for IPF; therefore, further study of combination therapy with antifibrotic agents is needed.

Breast cancer anti-estrogen resistance 3 inhibits transforming growth factor β/Smad signaling and associates with favorable breast cancer disease outcomes

INTRODUCTION

This study helps to define the implications of breast cancer anti-estrogen resistance 3 (BCAR3) in breast cancer and extends the current understanding of its molecular mechanism of action. BCAR3 has been shown to promote cell proliferation, migration and attachment to extracellular matrix components. However, in a cohort of metastatic breast cancer patients who received tamoxifen treatment, high BCAR3 mRNA levels were associated with favorable progression-free survival outcome. These results suggest that, besides its established roles, BCAR3 may have additional mechanisms of action that regulate breast cancer aggressive phenotype. In this study, we investigated whether BCAR3 is a novel antagonist of the canonical transforming growth factor β (TGFβ) pathway, which induces potent migration and invasion responses in breast cancer cells.

METHODS

We surveyed functional genomics databases for correlations between BCAR3 expression and disease outcomes of breast cancer patients. We also studied how BCAR3 could regulate the TGFβ/Smad signaling axis using Western blot analysis, coimmunoprecipitation and luciferase assays. In addition, we examined whether BCAR3 could modulate TGFβ-induced cell migration and invasion by using an automated imaging system and a confocal microscopy imaging-based matrix degradation assay, respectively.

RESULTS

Relatively low levels of BCAR3 expression in primary breast tumors correlate with poor distant metastasis-free survival and relapse-free survival outcomes. We also found a strong correlation between the loss of heterozygosity at BCAR3 gene alleles and lymph node invasion in human breast cancer, further suggesting a role for BCAR3 in preventing disease progression. In addition, we found BCAR3 to inhibit Smad activation, Smad-mediated gene transcription, Smad-dependent cell migration and matrix digestion in breast cancer cells. Furthermore, we found BCAR3 to be downregulated by TGFβ through proteasome degradation, thus defining a novel positive feedback loop mechanism downstream of the TGFβ/Smad signaling pathway.

CONCLUSION

BCAR3 is considered to be associated with aggressive breast cancer phenotypes. However, our results indicate that BCAR3 acts as a putative suppressor of breast cancer progression by inhibiting the prometastatic TGFβ/Smad signaling pathway in invasive breast tumors. These data provide new insights into BCAR3's molecular mechanism of action and highlight BCAR3 as a novel TGFβ/Smad antagonist in breast cancer.

Thrombin promotes airway remodeling via protease-activated receptor-1 and transforming growth factor-β1 in ovalbumin-allergic rats

BACKGROUND

Protease-activated receptor-1 (PAR-1) is widely distributed in platelets and involved in coagulation cascade activated by thrombin. In this study, we intend to explore the role of PAR-1 in the process of thrombin-inducing transforming growth factor-β1 (TGF-β1) to promote airway remodeling in ovalbumin (OVA)-allergic rats.

MATERIALS AND METHODS

A rat model of chronic asthma was set up by systemic sensitization and repeated challenge to OVA. The doses of thrombin, recombinant hirudin, PAR-1 inhibitor ER-112780-06 varied for different groups. We evaluated the bronchoalveolar lavage fluid (BALF) concentration of thrombin in these groups. The protein and gene expression of PAR-1 was assessed and the expression of TGF-β1 was also detected.

RESULTS

The PAR-1 mRNA level and the protein level were higher in the airway of asthmatic rats than those of normal rats, and were significantly increased by thrombin treatment but decreased by thrombin-inhibitor treatment. Airway remodeling was strengthened by thrombin but weakened by thrombin inhibitor and PAR-1 antagonist. Expression of TGF-β1 protein in asthmatic rats was significantly increased by thrombin treatment and decreased by thrombin-inhibitor treatment and PAR-1 antagonist treatment.

CONCLUSION

The expression of PAR-1 is regulated by thrombin that induces the expression of TGF-β1 to promote airway remodeling via PAR-1 in OVA-allergic rats.

Connective tissue growth factor/CCN-2 is upregulated in epididymal and subcutaneous fat depots in a dietary-induced obesity model

Connective tissue growth factor (CTGF), also known as CCN-2, is a cysteine-rich secreted protein that is involved in a range of biological processes, including regulation of cell growth and differentiation. Our previous in vitro studies have shown that CCN-2 inhibits adipocyte differentiation, although whether CCN-2 is regulated in vivo in adipogenesis is undetermined and was investigated in this study. C57BL/6 male mice were fed either standard laboratory chow (ND) or a diet high in fat (HFD; 45% fat) for 15 or 24 wk. HFD animals that gained >5 g in weight (termed HFD-fat) were insulin resistant and were compared with HFD-fed animals, which failed to gain weight (termed HFD-lean). HFD-fat mice had significantly increased CCN-2 mRNA levels in both the subcutaneous and epididymal fat pads, whereas CCN-2 mRNA was not induced in the epididymal site in HFD-lean mice. Also in HFD-fed animals, epididymal CCN-2 mRNA correlated positively with key genes involved in adipocyte differentiation, adiponectin and PPARγ (P < 0.001 and P < 0.002, respectively). Additionally, epididymal CCN-2 mRNA correlated positively with two markers of tissue turnover, PAI-1 in HFD-fat mice only and TIMP-1, but only in the HFD-lean mice. Collectively, these findings suggest that CCN-2 plays a role in adipocyte differentiation in vivo and thus in the pathogenesis of obesity linked with insulin resistance.

Wound modulation after filtration surgery

Filtration surgery is the standard invasive procedure for the management of intraocular pressure in advanced glaucoma. The key to a successful outcome is to modulate the normal wound healing cascade that leads to closure of the newly created aqueous outflow pathway. Antifibrotic agents such as mitomycin C and 5-fluorouracil have been increasingly used to modulate the wound healing process and increase surgical success. Although these agents have proven efficacy, they also increase the risk of complications. Efforts have centered on the identification of novel agents and techniques that can influence wound modulation without these complications. We detail new agents and methods under investigation to control wound healing after filtration surgery.

Simvastatin inhibits TGFβ1-induced fibronectin in human airway fibroblasts

Background

Bronchial fibroblasts contribute to airway remodelling, including airway wall fibrosis. Transforming growth factor (TGF)-β1 plays a major role in this process. We previously revealed the importance of the mevalonate cascade in the fibrotic response of human airway smooth muscle cells. We now investigate mevalonate cascade-associated signaling in TGFβ1-induced fibronectin expression by bronchial fibroblasts from non-asthmatic and asthmatic subjects.

Methods

We used simvastatin (1-15 μM) to inhibit 3-hydroxy-3-methlyglutaryl-coenzyme A (HMG-CoA) reductase which converts HMG-CoA to mevalonate. Selective inhibitors of geranylgeranyl transferase-1 (GGT1; GGTI-286, 10 μM) and farnesyl transferase (FT; FTI-277, 10 μM) were used to determine whether GGT1 and FT contribute to TGFβ1-induced fibronectin expression. In addition, we studied the effects of co-incubation with simvastatin and mevalonate (1 mM), geranylgeranylpyrophosphate (30 μM) or farnesylpyrophosphate (30 μM).

Results

Immunoblotting revealed concentration-dependent simvastatin inhibition of TGFβ1 (2.5 ng/ml, 48 h)-induced fibronectin. This was prevented by exogenous mevalonate, or isoprenoids (geranylgeranylpyrophosphate or farnesylpyrophosphate). The effects of simvastatin were mimicked by GGTI-286, but not FTI-277, suggesting fundamental involvement of GGT1 in TGFβ1-induced signaling. Asthmatic fibroblasts exhibited greater TGFβ1-induced fibronectin expression compared to non-asthmatic cells; this enhanced response was effectively reduced by simvastatin.

Conclusions

We conclude that TGFβ1-induced fibronectin expression in airway fibroblasts relies on activity of GGT1 and availability of isoprenoids. Our results suggest that targeting regulators of isoprenoid-dependent signaling holds promise for treating airway wall fibrosis.

CCN2 is required for the TGF-β induced activation of Smad1-Erk1/2 signaling network

Connective tissue growth factor (CCN2) is a multifunctional matricellular protein, which is frequently overexpressed during organ fibrosis. CCN2 is a mediator of the pro-fibrotic effects of TGF-β in cultured cells, but the specific function of CCN2 in the fibrotic process has not been elucidated. In this study we characterized the CCN2-dependent signaling pathways that are required for the TGF-β induced fibrogenic response. By depleting endogenous CCN2 we show that CCN2 is indispensable for the TGF-β-induced phosphorylation of Smad1 and Erk1/2, but it is unnecessary for the activation of Smad3. TGF-β stimulation triggered formation of the CCN2/β₃ integrin protein complexes and activation of Src signaling. Furthermore, we demonstrated that signaling through the α_vβ₃ integrin receptor and Src was required for the TGF-β induced Smad1 phosphorylation. Recombinant CCN2 activated Src and Erk1/2 signaling, and induced phosphorylation of Fli1, but was unable to stimulate Smad1 or Smad3 phosphorylation. Additional experiments were performed to investigate the role of CCN2 in collagen production. Consistent with the previous studies, blockade of CCN2 abrogated TGF-β-induced collagen mRNA and protein levels. Recombinant CCN2 potently stimulated collagen mRNA levels and upregulated activity of the COL1A2 promoter, however CCN2 was a weak inducer of collagen protein levels. CCN2 stimulation of collagen was dose-dependent with the lower doses (<50 ng/ml) having a stimulatory effect and higher doses having an inhibitory effect on collagen gene expression. In conclusion, our study defines a novel CCN2/α_vβ₃ integrin/Src/Smad1 axis that contributes to the pro-fibrotic TGF-β signaling and suggests that blockade of this pathway may be beneficial for the treatment of fibrosis.

CTGF expression is up-regulated by PROK1 in early pregnancy and influences HTR-8/Svneo cell adhesion and network formation

BACKGROUND

Prokineticin-1 (PROK1) and connective tissue growth factor (CTGF) are expressed in human endometrium and first-trimester decidua and have individually been proposed to have roles in implantation and placentation. We have recently demonstrated that CTGF may be a target gene for PROK1 in gene array analysis of a prokineticin receptor-1 stably transfected Ishikawa endometrial epithelial cell line (PROKR1-Ishikawa). The first aim of the study was to determine the effect of PROK1 on CTGF expression in PROKR1-Ishikawa cells and first-trimester decidua samples. Secondly, the effect of CTGF on trophoblast-derived HTR-8/SVneo cell adhesion and network formation was investigated.

METHODS AND RESULTS

Real-time qPCR showed that CTGF expression is elevated in first-trimester decidua compared with non-pregnant endometrium. In decidua, CTGF co-localized with PROKR1 to the glandular epithelium and a subset of stromal cells. PROK1 increased CTGF mRNA and protein expression in PROKR1-Ishikawa cells and first-trimester human decidua (8–12 weeks gestation). Knock down of endogenous PROK1 using micro RNA constructs targeted at PROK1, resulted in decreased expression of CTGF mRNA and protein in decidua. Inhibitors of specific cell signalling molecules demonstrated that PROK1 regulates CTGF expression via the Gq, phospholipase C (PLC), cSrc, epidermal growth factor receptor (EGFR), mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) kinase pathway activation. Treatment of trophoblast-derived HTR-8/Svneo cells with 1 µg/ml CTGF significantly increased adhesion to collagen IV, and differentiation of the cells into tube-like structures in matrigel.

CONCLUSIONS

CTGF expression in early pregnancy decidua is regulated by PROK1, via activation of the Gq, PLC, cSrc, EGFR, MAPK/ERK kinase pathway. CTGF in turn may contribute to the regulation of trophoblast conversion of maternal spiral arteries.

The mevalonate cascade as a target to suppress extracellular matrix synthesis by human airway smooth muscle

Smooth muscle cells promote fibroproliferative airway remodeling in asthma, and transforming growth factor β1 (TGFβ1) is a key inductive signal. Statins are widely used to treat hyperlipidemia. Growing evidence indicates they also exert a positive impact on lung health, but the underlying mechanisms are unclear. We assessed the effects of 3-hydroxy-3-methlyglutaryl-coenzyme A (HMG-CoA) reductase inhibition with simvastatin on the fibrotic function of primary cultured human airway smooth muscle cells. Simvastatin blocked de novo cholesterol synthesis, but total myocyte cholesterol content was unaffected. Simvastatin also abrogated TGFβ1-induced collagen I and fibronectin expression, and prevented collagen I secretion. The depletion of mevalonate cascade intermediates downstream from HMG-CoA underpinned the effects of simvastatin, because co-incubation with mevalonate, geranylgeranylpyrophosphate, or farnesylpyrophosphate prevented the inhibition of matrix protein expression. We also showed that human airway myocytes express both geranylgeranyl transferase 1 (GGT1) and farnesyltransferase (FT), and the inhibition of GGT1 (GGTI inhibitor-286, 10 μM), but not FT (FTI inhibitor-277, 10 μM), mirrored the suppressive effects of simvastatin on collagen I and fibronectin expression and collagen I secretion. Moreover, simvastatin and GGTI-286 both prevented TGFβ1-induced membrane association of RhoA, a downstream target of GGT1. Our findings suggest that simvastatin and GGTI-286 inhibit synthesis and secretion of extracellular matrix proteins by human airway smooth muscle cells by suppressing GGT1-mediated posttranslational modification of signaling molecules such as RhoA. These findings reveal mechanisms related to evidence for the positive impact of statins on pulmonary health.

Hypoxia induces connective tissue growth factor mRNA expression

Connective tissue growth factor (CTGF) is known to be a profibrotic growth factor, which mediate the fibrotic effect of transforming growth factor-beta (TGF-beta) and to stimulate cell proliferation and matrix production. CTGF has been shown to be hypoxia-inducible in several cell types. Here we investigated the effect of hypoxia on CTGF gene expression in cultured mouse renal tubular cells (MTC). Quiescent cultures of MTC were exposed to hypoxia (1% O(2)) or normoxia in serum-free medium. The effects on hypoxia-induced CTGF expression were evaluated by Northern blot and real-time PCR. The roles of mitogen-activated protein kinase (MAPK) and TGF-beta were also determined using specific biochemical inhibitors. Exposure of quiescent tubular cells to hypoxia for 24 hr in a conditioned medium resulted in a significant increase TGF-beta. Hypoxia caused a significant increase in CTGF mRNA expression in MTC. Either JNK or ERK inhibitor did not block the hypoxia-induced stimulation of CTGF, whereas an inhibitor of p38 MAPK reduced the hypoxia-induced changes of CTGF. Although hypoxia stimulated TGF-beta production, neutralizing anti-TGF-beta1 antibody did not abolish the hypoxia-induced CTGF mRNA expression. The data suggest that hypoxia up-regulates CTGF gene expression, and that p38 MAPK plays a role in hypoxic-stimulation of CTGF. We also demonstrated that hypoxia induces CTGF mRNA expression via a TGF-beta1-independent mechanism.

Chondrogenic derivatives of embryonic stem cells seeded into 3D polycaprolactone scaffolds generated cartilage tissue in vivo

In spite of recent scientific advances, treatment and repair of cartilage using tissue engineering techniques remains challenging. The major constraint is the limited proliferative capacity of mature autologous chondrocytes used in the tissue engineering approach. This problem can be addressed by using stem cells, which can self-renew with greater proliferative potential. Cartilage tissue engineering using adult mesenchymal stem cells derived from bone marrows has met with limited success. In this study we explored cartilage tissue generation from embryonic stem cells (ESCs). ESCs were induced to differentiate into chondroprogenitors, capable of proliferating and subsequently differentiating into cartilage-producing cells. The chondrogenic cells expressed chondrocyte-specific markers and deposited extracellular matrix proteins, proteoglycans. ESC-derived chondrogenic cells and polycaprolactone scaffolds seeded with these cells implanted in mice (129 SvImJ) generated cartilage tissue in vivo. Postimplant analysis of the retrieved tissues demonstrated cartilage-like tissue formation in 3-4 weeks. The cells of retrieved tissues also expressed the chondrocyte-specific marker collagen II. These findings suggest that ESCs can be used for tissue engineering and cultivation of cartilage tissues.

Connective tissue growth factor inhibits adipocyte differentiation

Adipocyte differentiation is a key process implicated in the pathogenesis of obesity and insulin resistance. Its regulation is triggered by a cascade of transcription factors, including the CCAAT/enhancer binding proteins (C/EBPs) and peroxisome proliferator-activated receptor-gamma (PPARgamma). Growth factors such as transforming growth factor-beta1 (TGF-beta1) are known to inhibit adipocyte differentiation in vitro, via the C/EBP pathway, and in vivo, but whether a downstream mediator of TGF-beta1, connective tissue growth factor (CTGF), also known as CCN2, has a similar role is unknown. Mouse 3T3-L1 cells were differentiated into adipocytes by using standard methods, and effects and regulation of CTGF were studied. Intervention with recombinant human CTGF during differing stages of differentiation caused an inhibition in the development of the adipocyte phenotype, according to the gene expression of the differentiation markers adiponectin and PPARgamma, as well as suppression of lipid accumulation and expression of the lipogenic enzyme glycerol-3-phosphate dehydrogenase. Whereas CTGF gene expression promptly fell by 90% as 3T3-L1 preadipocytes differentiated into mature adipocytes, CTGF mRNA expression was induced by added TGF-beta1. CTGF applied to cells early in the course of differentiation inhibited total cell protein levels and nuclear localization of the beta-isoform of C/EBP (C/EBP-beta) and, subsequently, total cell C/EBP-alpha levels. CTGF also inhibited the adipocyte differentiation program in primary cultures of mouse preadipocytes. Expression of CTGF mRNA was twofold higher in the central fat depots of mice compared with subcutaneous fat, suggesting a potential role for CTGF in vivo. In summary, these data show that CTGF inhibits the adipocyte differentiation program.

Maintenance of radiation-induced intestinal fibrosis: cellular and molecular features

Recent advances in cell and molecular radiobiology clearly showed that tissue response to radiation injury cannot be restricted to a simple cell-killing process, but depends upon continuous and integrated pathogenic processes, involving cell differentiation and crosstalk between the various cellular components of the tissue within the extracellular matrix. Thus, the prior concept of primary cell target in which a single-cell type (whatever it's epithelial or endothelial cells) dictates the whole tissue response to radiation injury has to be replaced by the occurrence of coordinated multicellular response that may either lead to tissue recovery or to sequel development. In this context, the present review will focus on the maintenance of the radiation-induced wound healing and fibrogenic signals triggered by and through the microenvironment toward the mesenchymal cell compartment, and will highlight how sequential and sustained modifications in cell phenotypes will in cascade modify cell-to-cell interactions and tissue composition.

Regulation of VEGF mRNA expression and protein secretion by TGF-beta2 in human retinal pigment epithelial cells

VEGF secretion by the human retinal pigment epithelium (hRPE) plays an important role in retinal and choroidal neovascularization. In this study, transforming growth factor-beta2 (TGF-beta2)-induced vascular endothelial growth factor (VEGF) gene expression was investigated in hRPE cells. Treatment of hRPE cells with TGF-beta2 for 24 and 48h as compared to 8h resulted in markedly increased VEGF secretion by fivefold and nine-fold, respectively. Induced VEGF mRNA peaked within 3h of stimulation and remained above the basal at 36h. Stimulation of VEGF expression by TGF-beta2 was blocked by cycloheximide, suggesting that de novo protein synthesis is required. Induced VEGF production was strongly inhibited by anti-inflammatory agents, dexamethasone and cyclosporin A. Despite of the weak stimulation of VEGF expression by TNF-alpha or bFGF alone, co-administration of either of these two cytokines synergized the effect of TGF-beta2 on VEGF mRNA expression and protein production. Quantitative RT-PCR revealed that the synergy was predominantly at the level of VEGF transcription. Moreover, TGF-beta2-induced RPE VEGF secretion was significantly reduced by inhibitors of mitogen-activated protein (MAP) kinase (MEK) (U0126), p38 (SB202190), c-Jun NH2-terminal kinase (JNK), Sp600125, protein tyrosine kinase (PTK) (Genistein), and phosphatidylinositol 3-kinase (PI3K) (Ly294002). Induced VEGF expression was completely abrogated by inhibitors of protein kinase C (PKC) (Ro318220), nuclear factor-kappaB (NF-kappaB) [caffeic acid phenethyl ester (CAPE)], and reactive oxygen species (ROS) [N-acetyl-cysteine (Nac) and diphenyleneiodonium (DPI)]. These results suggest that MEK, p38, JNK, PI3K, and NF-kappaB as well as multiple essential signaling intermediates, including PKC, PTK and ROS, are involved in hRPE VEGF up regulation by TGF-beta2.

ALK-5 mediates endogenous and TGF-beta1-induced expression of connective tissue growth factor in embryonic lung

Transforming growth factor-beta1 (TGF-beta1) has been implicated as a major negative regulator of lung branching morphogenesis. Since connective tissue growth factor (CTGF) is a downstream mediator of TGF-beta1 effects on mesenchymal cells, we hypothesized that TGF-beta1 induces CTGF expression in mouse embryonic lung explants and that CTGF mediates TGF-beta1 inhibition of branching morphogenesis. We show that addition of TGF-beta1 to the serum-free medium of embryonic day (E)12.5 lung explant cultures inhibited branching morphogenesis and induced CTGF mRNA expression in time- and dose-dependent manners. In contrast to basal endogenous CTGF protein, which was exclusively localized in the distal airway epithelium, TGF-beta1-induced CTGF protein was localized in both the epithelium and the mesenchyme. Addition of exogenous CTGF to culture medium directly inhibited branching morphogenesis. To identify the signal transduction pathway through which TGF-beta1 induces CTGF, we used SB431542, a specific inhibitor for TGF-beta type I receptor (TbetaRI)/ALK-5 to block TGF-beta1-induced Smad2/3 phosphorylation. Consequently, SB431542 stimulated normal branching morphogenesis and blocked TGF-beta1 inhibition of branching. Furthermore, SB-431542 blocked both endogenous and TGF-beta1-induced expression of CTGF mRNA and protein. These results demonstrate for the first time that TGF-beta1 induces CTGF expression in mouse embryonic lung explants, that CTGF inhibits branching morphogenesis, and that both endogenous and TGF-beta1-induced CTGF expression are mediated by the TbetaRI/ALK-5-dependent Smad2 signaling pathway.

Dominant negative mutation of the TGF-β receptor blocks hypoxia-induced pulmonary vascular remodeling

The present study utilized a novel transgenic mouse model that expresses an inducible dominant negative mutation of the transforming growth factor (TGF)-β type II receptor (DnTGFβRII mouse) to test the hypothesis that TGF-β signaling plays an important role in the pathogenesis of chronic hypoxia-induced increases in pulmonary arterial pressure and vascular and alveolar remodeling. Nine- to 10-wk-old male DnTGFβRII and control nontransgenic (NTG) mice were exposed to normobaric hypoxia (10% O2) or air for 6 wk. Expression of DnTGFβRII was induced by drinking 25 mM ZnSO4 water beginning 1 wk before hypoxic exposure. Hypoxia-induced increases in right ventricular pressure, right ventricular mass, pulmonary arterial remodeling, and muscularization were greatly attenuated in DnTGFβRII mice compared with NTG controls. Furthermore, the stimulatory effects of hypoxic exposure on pulmonary arterial and alveolar collagen content, appearance of α-smooth muscle actin-positive cells in alveolar parenchyma, and expression of extracellular matrix molecule (including collagen I and III, periostin, and osteopontin) mRNA in whole lung were abrogated in DnTGFβRII mice compared with NTG controls. Hypoxic exposure had no effect on systemic arterial pressure or heart rate in either strain. These data support the hypothesis that endogenous TGF-β plays an important role in pulmonary vascular adaptation to chronic hypoxia and that disruption of TGF-β signaling attenuates hypoxia-induced pulmonary hypertension, right ventricular hypertrophy, pulmonary arterial hypertrophy and muscularization, alveolar remodeling, and expression of extracellular matrix mRNA in whole lung.

Induction of CTGF by TGF-beta1 in normal and radiation enteritis human smooth muscle cells: Smad/Rho balance and therapeutic perspectives

BACKGROUND AND PURPOSE

Transforming Growth Factor beta1 (TGF-beta1) and its downstream effector Connective Tissue Growth Factor (CTGF/CCN2), are well known fibrogenic activators and we previously showed that the Rho/ROCK pathway controls CTGF expression in intestinal smooth muscle cells isolated from patients with delayed radiation enteritis. The aim of the present work was to investigate the balance between Smad and Rho signalling pathways in the TGF-beta1 CTGF induction and modulation of radiation-induced fibrogenic differentiation after addition of pravastatin, an inhibitor of Rho isoprenylation.

PATIENTS AND METHODS

Primary human smooth muscle cells isolated from normal (N-SMC) or radiation enteritis (RE-SMC) biopsies were incubated with TGF-beta1 (10 ng/ml). Induction of CTGF, as well as nucleo-cytoplasmic distribution of phospho-Smad2/3, Smad2/3 and Smad4 were analysed by Western blot and immunocytochemistry. Smad DNA binding was assessed by EMSA and Rho activation was measured by pull-down assay.

RESULTS

After TGF-beta1 addition, Smads were translocated to the nucleus in both cell types. Nuclear accumulation of Smad as well as their DNA-binding activity were higher in N-SMC than in RE-SMC, whereas the opposite was observed for Rho activation, suggesting a main involvement of Rho pathway in sustained fibrogenic differentiation. This hypothesis was further supported by the antifibrotic effect observed in vitro after cell treatment with pravastatin (i.e. decreased expression of CTGF, TGF-beta1 and Collagen Ialpha2).

CONCLUSIONS

Our results suggest that TGF-beta1-induced CTGF transactivation mainly depends on the Smad pathway in N-SMC, whereas in RE-SMC, Smad and Rho pathways are involved. Inhibition of Rho activity by pravastatin alters fibrogenic differentiation in vitro which opens up new therapeutic perspectives.

The role of mRNA stability in airway remodelling

As a consequence of long-term exposure to inflammatory mediators, the airways of asthmatics become remodelled. Airway fibrosis becomes apparent, with thickening of the lamina recticularis and increased interstitial matrix deposition being typical features of an asthmatic airway. Mucus hypersecretion occurs, airway smooth muscle mass is increased and neovascularization is evident in the subepithelial mucosa. As development of a remodelled airway is correlated with deterioration of lung function in asthmatics, there is an urgent need for therapies that reduce airway inflammation and reverse structural changes in a remodelled airway. However, in order to design efficacious anti-remodelling agents we first need a greater understanding of the molecular mechanism/s underlying the development of airway remodelling. To date, however, most studies have primarily focused on the transcriptional regulation of genes that promote airway remodelling. Post-transcriptional mechanisms, such as control of mRNA stability, remain largely unexplored. Levels of cellular mRNA transcripts are regulated by controlling the rate at which the mRNA decays, thus investigation into the mechanisms underlying mRNA stability in asthma are of critical importance. Therefore, this review will present an overview of the control of mRNA stability and examine how mRNA stability may play a role in the development of airway remodelling in asthma.

[Physiopathology of pulmonary arterial hypertension. Cellular and molecular aspects]

The combined effects of vasoconstriction, remodelling of the pulmonary vessel walls and in situ thrombosis contribute to the increase in pulmonary vascular resistance during pulmonary arterial hypertension. Vascular remodelling involves all the sheaths of the vessel wall and all the cell types of which it is composed (endothelial cells, smooth muscle cells, fibroblasts, inflammatory cells and platelets). Excessive vasoconstriction has been related to a defect in the function of expression of the potassium channels and endothelial dysfunction. This leads to chronic insufficiency in the production of vasodilators, notably nitrogen monoxide and prostacyclin and the excessive production of vasoconstrictors such as endotheline-1. These defects contribute to the increase in vascular tonus and pulmonary vascular remodelling and represent pertinent pharmacological targets. Certain growth factors, including those of the super-family of transforming growth factor beta, angiopoietine-1 and serotonin, may play a part in the pathogenesis of pulmonary arterial hypertension.

Molecular Mechanisms of Hormonal Activity. II. Kinase Systems. Systems with Intracellular Receptors. Transactivation of STS

Hormone receptors and other components, functional mechanisms, and biological role of analyzed signal transduction systems (STS) are described. The recently revealed module principle of the structure and STS transactivation providing diversity and plasticity of regulation are highlighted. STS activities are significantly changed in many diseases. Novel promising pharmaceuticals targeted to certain components of STS increase in number from year to year. The data published by the beginning of January 2004 are summarized in this review.

Na+/Ca2+ exchanger activity modulates connective tissue growth factor mRNA expression in transforming growth factor beta1- and Des-Arg10-kallidin-stimulated myofibroblasts

Transforming growth factor (TGF)-beta and des-Arg(10)-kallidin stimulate the expression of connective tissue growth factor (CTGF), a matrix signaling molecule that is frequently overexpressed in fibrotic disorders. Because the early signal transduction events regulating CTGF expression are unclear, we investigated the role of Ca(2+) homeostasis in CTGF mRNA expression in TGF-beta1- and des-Arg(10)-kallidin-stimulated human lung myofibroblasts. Activation of the kinin B1 receptor with des-Arg(10)-kallidin stimulated a rise in cytosolic Ca(2+) that was extracellular Na(+)-dependent and extracellular Ca(2+)-dependent. The des-Arg(10)-kallidin-stimulated increase of cytosolic Ca(2+) was blocked by KB-R7943, a specific inhibitor of Ca(2+) entry mode operation of the plasma membrane Na(+)/Ca(2+) exchanger. TGF-beta1 similarly stimulated a KB-R7943-sensitive increase of cytosolic Ca(2+) with kinetics distinct from the des-Arg(10)-kallidin-stimulated Ca(2+) response. We also found that KB-R7943 or 2',4'-dichlorobenzamil, an amiloride analog that inhibits the Na(+)/Ca(2+) exchanger activity, blocked the TGF-beta1- and des-Arg(10)-kallidin-stimulated increases of CTGF mRNA. Pretreatment with KB-R7943 also reduced the basal and TGF-beta1-stimulated levels of alpha1(I) collagen and alpha smooth muscle actin mRNAs. These data suggest that, in addition to regulating ion homeostasis, Na(+)/Ca(2+) exchanger acts as a signal transducer regulating CTGF, alpha1(I) collagen, and alpha smooth muscle actin expression. Consistent with a more widespread role for Na(+)/Ca(2+) exchanger in fibrogenesis, we also observed that KB-R7943 likewise blocked TGF-beta1-stimulated levels of CTGF mRNA in human microvascular endothelial and human osteoblast-like cells. We conclude that Ca(2+) entry mode operation of the Na(+)/Ca(2+) exchanger is required for des-Arg(10)-kallidin- and TGF-beta1-stimulated fibrogenesis and participates in the maintenance of the myofibroblast phenotype.

Smad3 null mice develop airspace enlargement and are resistant to TGF-beta-mediated pulmonary fibrosis

Transforming growth factor-beta 1 plays a key role in the pathogenesis of pulmonary fibrosis, mediating extracellular matrix (ECM) gene expression through a series of intracellular signaling molecules, including Smad2 and Smad3. We show that Smad3 null mice (knockout (KO)) develop progressive age-related increases in the size of alveolar spaces, associated with high spontaneous presence of matrix metalloproteinases (MMP-9 and MMP-12) in the lung. Moreover, transient overexpression of active TGF-beta 1 in lungs, using adenoviral vector-mediated gene transfer, resulted in progressive pulmonary fibrosis in wild-type mice, whereas no fibrosis was seen in the lungs of Smad3 KO mice up to 28 days. Significantly higher levels of matrix components (procollagen 3A1, connective tissue growth factor) and antiproteinases (plasminogen activator inhibitor-1, tissue inhibitor of metalloproteinase-1) were detected in wild-type lungs 4 days after TGF-beta 1 administration, while no such changes were seen in KO lungs. These data suggest a pivotal role of the Smad3 pathway in ECM metabolism. Basal activity of the pathway is required to maintain alveolar integrity and ECM homeostasis, but excessive signaling through the pathway results in fibrosis characterized by inhibited degradation and enhanced ECM deposition. The Smad3 pathway is involved in pathogenic mechanisms mediating tissue destruction (lack of repair) and fibrogenesis (excessive repair).

A New Model of Glaucoma Filtering Surgery in the Rat

PURPOSE

The most common reason for long-term failure of glaucoma filtering surgery (GFS) is scarring of the external filtering "bleb" tissues. The identification of the factors that mediate this process, as well as the development and initial testing of new therapies to limit scarring is enhanced by the use of appropriate animal models. The standard animal model for studying GFS is the rabbit but newer investigative tools that examine changes induced in biologic systems at a genetic level have made development of a rat model desirable.

METHODS

Glaucoma filtering surgery was performed on 20 Sprague-Dawley rats by introducing a 30-gauge silicone cannula through a penetrating scleral tunnel, under a limbal-based conjunctival flap and suturing the conjunctiva closed. Identical GFS was performed on 3 additional rats, which underwent histologic evaluation at days 2, 5, and 11, following surgery.Fistulizing surgery was also performed on 6 Sprague-Dawley rats, for comparison, by creating a full-thickness needle sclerostomy under a limbal-based conjunctival flap and suturing the conjunctiva closed.

RESULTS

Following the cannula GFS, well-elevated filtering blebs formed and these gradually failed over the course of 8 to 13 days. Needle tract sclerostomy filtering blebs formed at the site of the fistulizing surgery but rapidly failed over the course of 2 to 3 days.

CONCLUSION

Cannulated filtering surgery in the rat provides a longer lasting and more predictable model than needle tract sclerostomy for studying wound healing following GFS and may facilitate the study of induced changes at the gene level.

Growth factor combination for chondrogenic induction from human mesenchymal stem cell

During the last decade, many strategies for cartilage engineering have been emerging. Stem cell induction is one of the possible approaches for cartilage engineering. The mesenchymal stem cells (MSCs) with their pluripotency and availability have been demonstrated to be an attractive cell source. It needs the stimulation with cell growth factors to make the multipluripotent MSCs differentiate into chondrogenic lineage. We have shown particular patterns of in vitro chondrogenesis induction on human bone marrow MSCs (hBMSCs) by cycling the growth factors. The pellet cultures of hBMSCs were prepared for chondrogenic induction. Growth factors: TGF-beta3, BMP-6, and IGF-1 were used in combination for cell induction. Gene expression, histology, immunohistology, and real-time PCR methods were measured on days 21 after cell induction. As shown by histology and immunohistology, the induced cells have shown the feature of chondrocytes in their morphology and extracellular matrix in both inducing patterns of combination and cycling induction. Moreover, the real-time PCR assay has shown the expression of gene markers of chondrogenesis, collagen type II and aggrecan. This study has demonstrated that cartilage tissue can be created from bone marrow mesenchymal stem cells. Interestingly, the combined growth factors TGF-beta3 and BMP-6 or TGF-beta3 and IGF-1 were more effective for chondrogenesis induction as shown by the real-time PCR assay. The combination of these growth factors may be the important key for in vitro chondrogenesis induction.

The role of connective tissue growth factor, a multifunctional matricellular protein, in fibroblast biology

Connective tissue growth factor (CTGF, CCN2), a member of the CCN family of proteins, is a cysteine-rich proadhesive matricellular protein that plays an essential role in the formation of blood vessels, bone, and connective tissue. As expression of this protein is potently induced by transforming growth factor-beta (TGFbeta), it has been hypothesized that CTGF mediates several of the downstream actions of TGFbeta. In particular, CTGF is profibrotic, as CTGF is overexpressed in fibrotic disease and synergizes with TGFbeta to promote sustained fibrosis in vivo. Over the last several years, key data regarding the developmental role and structure and function relationship of CTGF have emerged. In addition, increased information concerning the mechanisms underlying the control of CTGF expression in normal and fibrotic cells and the signal transduction pathways through which CTGF acts on cells has been uncovered. This review summarizes the current state of knowledge regarding CTGF biology.

Cellular and molecular pathobiology of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) has a multifactorial pathobiology. Vasoconstriction, remodeling of the pulmonary vessel wall, and thrombosis contribute to increased pulmonary vascular resistance in PAH. The process of pulmonary vascular remodeling involves all layers of the vessel wall and is complicated by cellular heterogeneity within each compartment of the pulmonary arterial wall. Indeed, each cell type (endothelial, smooth muscle, and fibroblast), as well as inflammatory cells and platelets, may play a significant role in PAH. Pulmonary vasoconstriction is believed to be an early component of the pulmonary hypertensive process. Excessive vasoconstriction has been related to abnormal function or expression of potassium channels and to endothelial dysfunction. Endothelial dysfunction leads to chronically impaired production of vasodilators such as nitric oxide and prostacyclin along with overexpression of vasoconstrictors such as endothelin (ET)-1. Many of these abnormalities not only elevate vascular tone and promote vascular remodeling but also represent logical pharmacological targets. Recent genetic and pathophysiologic studies have emphasized the relevance of several mediators in this condition, including prostacyclin, nitric oxide, ET-1, angiopoietin-1, serotonin, cytokines, chemokines, and members of the transforming-growth-factor-beta superfamily. Disordered proteolysis of the extracellular matrix is also evident in PAH. Future studies are required to find which if any of these abnormalities initiates PAH and which ones are best targeted to cure the disease.

TRAIL in the airways

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is an important immunomodulatory factor that may play a role in the structural changes observed in the asthmatic airways. In vitro as well as in vivo studies have evidenced a dual role for TRAIL: it can either function as a pro- or anti-inflammatory cytokine on inflammatory cells, participating in the initiation and resolution of inflammatory and immune responses. TRAIL is expressed in the airways by inflammatory cells infiltrated in the bronchial mucosa, as well as by structural cells of the airway wall including fibroblasts, epithelial, endothelial, and smooth muscle cells. By releasing TRAIL, these different cell types may then participate in the increased levels of TRAIL observed in bronchoalveolar lavage fluid from asthmatic patients. Taken together, this suggests that TRAIL may play a role in inflammation in asthma. However, concerning its role is dual in the modulation of inflammation, further studies are needed to elucidate the precise role of TRAIL in the airways.

Smads as intracellular mediators of airway inflammation

Transforming growth factor-beta (TGF-beta) plays an important role in the pathogenesis of allergic asthma and other airway diseases. Signals from the activated TGF-beta receptor complex are transduced to the nucleus of airway cells by Smad proteins, which represent a family of transcription factors that have recently been implicated to play a major role as intracellular mediators of inflammation. The Smad family consists of the receptor-regulated Smads, a common pathway Smad, and inhibitory Smads. Receptor-regulated Smads (R-Smads) are phosphorylated by the TGF-beta type Ireceptor. They include Smad2 and Smad3, which are recognized by TGF-beta and activin receptors, and Smads 1, 5, 8, and 9, which are recognized by bone morphogenetic protein (BMP) receptors. Smad4 is a common pathway Smad, which is also defined as cooperating Smad (co-Smad) and is not phosphorylated by the TGF-beta type I receptor. Inhibitory Smads(anti-Smads) include Smad6 and Smad7, which down-regulate TGF-beta signaling. To date, the Smads are the only TGF-beta receptor substrates with a demonstrated ability to propagate signals and with regard to the growing number of investigations of Smad-mediated effects in the airways, Smads may prove to be an important target for future development of new therapeutic strategies for asthma and chronic obstructive pulmonary disease.

Differential effects of simvastatin on mesangial cells

BACKGROUND

Statins are increasingly recognized as mediators of direct cellular effects independent of their lipid lowering capacity. Therefore, the time and concentration dependence of various statin-mediated cellular alterations was compared in renal mesangial cells.

METHODS

The effects of statins on cell proliferation, gene expression, cytoskeletal alterations, apoptosis, and cytotoxicity were analyzed in cultured mesangial cells using standard techniques.

RESULTS

Simvastatin and lovastatin decreased proliferation and cell number of rat mesangial cells concentration-dependently. Concurrently, the expression of the fibrogenic protein connective tissue growth factor (CTGF) was impaired and actin stress fibers, which are typical of mesangial cells in culture, became disassembled by simvastatin. A decrease of the posttranslational modification of RhoA by geranylgeranyl moieties was detected, supporting a role for RhoA as mediator of statin effects. Induction of apoptosis, determined by activation of caspase-3 and DNA fragmentation, and necrosis only occurred at later time points, when the morphology of the cells was strongly altered and the cells detached from the surface due to changes in the actin cytoskeleton. Basically, the same results were obtained with a human mesangial cell line. Furthermore, statin effects were mimicked by inhibition of the geranylgeranyltransferase.

CONCLUSION

Most of the cellular effects of the lipophilic statins occurred within the same time and concentration range, suggesting a common molecular mechanism. Only apoptosis and necrosis were observed at later time points or with higher concentrations of simvastatin and thus seem to be secondary to the changes in gene expression and alterations of the actin cytoskeleton.

Interference with transforming growth factor-beta/ Smad3 signaling results in accelerated healing of wounds in previously irradiated skin

Transforming growth factor (TGF)-beta regulates many aspects of wound repair including inflammation, chemotaxis, and deposition of extracellular matrix. We previously showed that epithelialization of incisional wounds is accelerated in mice null for Smad3, a key cytoplasmic mediator of TGF-beta signaling. Here, we investigated the effects of loss of Smad3 on healing of wounds in skin previously exposed to ionizing radiation, in which scarring fibrosis complicates healing. Cutaneous wounds made in Smad3-null mice 6 weeks after irradiation showed decreased wound widths, enhanced epithelialization, and reduced numbers of neutrophils and myofibroblasts compared to wounds in irradiated wild-type littermates. Differences in breaking strength of wild-type and Smad3-null wounds were not significant. As shown previously for neutrophils, chemotaxis of primary dermal fibroblasts to TGF-beta required Smad3, but differentiation of fibroblasts to myofibroblasts by TGF-beta was independent of Smad3. Previous irradiation-enhanced induction of connective tissue growth factor mRNA in wild-type, but not Smad3-null fibroblasts, suggested that this may contribute to the heightened scarring in irradiated wild-type skin as demonstrated by Picrosirius red staining. Overall, the data suggest that attenuation of Smad3 signaling might improve the healing of wounds in previously irradiated skin commensurate with an inhibition of fibrosis.

Angiotensin II increases connective tissue growth factor in the kidney

Connective tissue growth factor (CTGF) has been described as a novel fibrotic mediator. CTGF is overexpressed in several kidney diseases and is induced by different factors involved in renal injury. Angiotensin II (AngII) participates in the pathogenesis of kidney damage, contributing to fibrosis; however, whether AngII regulates CTGF in the kidney has not been explored. Systemic infusion of AngII into normal rats for 3 days increased renal CTGF mRNA and protein levels. At day 7, AngII-infused rats presented overexpression of CTGF in glomeruli, tubuli, and renal arteries, as well as tubular injury and elevated fibronectin deposition. Only treatment with an AT(1) receptor antagonist, but not an AT(2), diminished CTGF and fibronectin overexpression and ameliorated tubular damage. In rats with immune complex nephritis, renal overexpression of CTGF was diminished by the ACE inhibitor quinapril, correlated with a diminution in fibrosis. In cultured renal cells (mesangial and tubular epithelial cells) AngII, via AT(1), increased CTGF mRNA and protein production, and a CTGF antisense oligonucleotide decreased AngII-induced fibronectin synthesis. Our data show that AngII regulates CTGF in the kidney and cultured in mesangial and tubular cells. This novel finding suggests that CTGF could be a mediator of the profibrogenic effects of AngII in the kidney.

Transforming growth factor-beta and its role in asthma

Transforming growth factor-beta (TGF-beta) is an important fibrogenic and immunomodulatory factor that may play a role in the structural changes observed in the asthmatic airways. In vitro as well as in vivo studies have evidenced a dual role for TGF-beta: it can either function as a pro- or anti-inflammatory cytokine on inflammatory cells, participating into the initiation and resultion of inflammatory and immune responses in the airways. TGF-beta is also involved in the remodelling of the airway wall, and has in particular been related to the subepithelial fibrosis. TGF-beta is produced in the airways by inflammatory cells infiltrated in the bronchial mucosa, as well as by structural cells of the airway wall including fibroblasts, epithelial, endothelial and smooth muscle cells. By releasing TGF-beta, these different cell types may then participate into the increased levels of TGF-beta observed in bronchoalveolar lavage fluid from asthmatic patients. Taken together, these results suggest that TGF-beta may play a role in inflammation in asthma. However, as its role is dual in the modulation of inflammation, further studies are needed to elucidate the precise role of TGF-beta in the airways.

Induction of connective tissue growth factor by angiotensin II: integration of signaling pathways

OBJECTIVE

Angiotensin II is recognized as one of the major mediators of cardiovascular pathology. Because connective tissue growth factor (CTGF) is involved in the pathophysiologic processes underlying fibrotic diseases, its regulation by angiotensin II was investigated.

METHODS AND RESULTS

In the 2-kidney, 1-clip model of renovascular hypertension, increased expression of CTGF was detectable in the hypertrophic left ventricle. By activation of angiotensin II type 1 receptors, angiotensin II caused rapid expression of CTGF mRNA and protein in a human fibroblast cell line. Activation of the p42/44 mitogen-activated protein (MAP) kinase signaling pathway proved to be essential for angiotensin II-stimulated CTGF expression. Inhibition of MAP kinase activation by forskolin prevented CTGF induction. Inhibition of the isoprenylation of small GTPases by simvastatin or pretreatment of the cells with toxin B reduced basal CTGF expression below detection limits and prevented induction by angiotensin II. Specific interference with RhoA signaling by Y27632 primarily reduced basal CTGF expression. There was no significant reduction of expression of angiotensin II type 1 receptors by simvastatin. These data indicate cooperation between the Rho signaling and the angiotensin II-activated MAP kinase pathways.

CONCLUSIONS

Direct induction of CTGF by angiotensin II is indicative of a role for CTGF in angiotensin II-mediated fibrosis and might be a target of antifibrotic interventions.

Connective tissue growth factor is a mediator of angiotensin II-induced fibrosis

BACKGROUND

Angiotensin II (Ang II) participates in the development of fibrosis during vascular damage. Connective tissue growth factor (CTGF) is a novel fibrotic mediator. However, the potential link between CTGF and Ang II has not been investigated.

METHODS AND RESULTS

In vivo Ang II effects were studied by systemic infusion into normal rats to evaluate CTGF and extracellular matrix protein (ECM) expression by immunohistochemistry. In aorta of Ang II-infused rats, CTGF staining was markedly increased and ECM overexpression was observed. An AT1 antagonist diminished CTGF and ECM. In growth-arrested vascular smooth muscle cells, Ang II induced CTGF mRNA expression after 1 hour, remained elevated up to 24 hours, and increased CTGF protein production, which was increased up to 72 hours. The AT1 antagonist blocked Ang II-induced CTGF gene and protein expression. Early CTGF upregulation is independent of new protein synthesis. Several intracellular signals elicited by Ang II are involved in CTGF synthesis, including protein kinase C activation, reactive oxygen species, and transforming growth factor-beta endogenous production. Incubation with a CTGF antisense oligonucleotide decreased CTGF and fibronectin upregulation caused by Ang II.

CONCLUSIONS

Our results show that Ang II, via AT1, increases CTGF in vascular cells both in vivo and in vitro. This novel finding suggests that CTGF may be a mediator of the profibrogenic effects of Ang II in vascular diseases.

C-Jun-NH2-terminal kinase mediates expression of connective tissue growth factor induced by transforming growth factor-beta1 in human lung fibroblasts

Many of the fibrogenic effects of transforming growth factor-beta (TGF-beta) might be mediated by connective tissue growth factor (CTGF). The present study investigates the role of mitogen-activated protein (MAP) kinase in the expression of CTGF mRNA in the human lung fibroblast line, HFL-1. TGF-beta1 enhanced CTGF mRNA levels in a time- and concentration-dependent manner, and this enhancement was also dependent upon transcription. Inhibition of p38 MAP kinase or extracellular signal-regulated kinase (ERK) activation did not affect TGF-beta1-induced CTGF expression. On the other hand, specific inhibitors of phosphatidylinositol 3-kinase (PI3K) suppressed TGF-beta1-induced CTGF expression in a concentration-dependent manner. TGF-beta1 activated c-Jun NH2-terminal kinase (JNK) and p38 MAP kinase, but not ERK in HFL-1 cells. PI3K inhibitors dose-dependently suppressed TGF-beta1-induced JNK, but not p38 MAP kinase activation. Finally, JNK1 and JNK2 antisense oligonucleotides attenuated cellular levels of JNK1 and JNK2 protein, respectively, and repressed TGF-beta1-induced CTGF expression. These results suggest that TGF-beta1-induced CTGF mRNA expression is mediated through the JNK-dependent pathway, whereas p38 MAP kinase and ERK pathways minimally contribute.

Molecular and cellular basis of pulmonary vascular remodeling in pulmonary hypertension

Clinical pulmonary hypertension is characterized by a sustained elevation in pulmonary arterial pressure. Pulmonary vascular remodeling involves structural changes in the normal architecture of the walls of pulmonary arteries. The process of vascular remodeling can occur as a primary response to injury, or stimulus such as hypoxia, within the resistance vessels of the lung. Alternatively, the changes seen in more proximal vessels may arise secondary to a sustained increase in intravascular pressure. To withstand the chronic increase in intraluminal pressure, the vessel wall becomes thickened and stronger. This "armouring" of the vessel wall with extra-smooth muscle and extracellular matrix leads to a decrease in lumen diameter and reduced capacity for vasodilatation. This maladaptive response results in increased pulmonary vascular resistance and consequently, sustained pulmonary hypertension. The process of pulmonary vascular remodeling involves all layers of the vessel wall and is complicated by the finding that cellular heterogeneity exists within the traditional compartments of the vascular wall: intima, media, and adventitia. In addition, the developmental stage of the organism greatly modifies the response of the pulmonary circulation to injury. This review focuses on the latest advances in our knowledge of these processes as they relate to specific forms of pulmonary hypertension and particularly in the light of recent genetic studies that have identified specific pathways involved in the pathogenesis of severe pulmonary hypertension.

CTGF expression in mesangial cells: involvement of SMADs, MAP kinase, and PKC

BACKGROUND

The induction of excess matrix in renal fibrosis seems to be mediated, at least in part, by the transforming growth factor-beta (TGF-beta)-mediated induction of connective tissue growth factor (CTGF) in mesangial cells.

METHODS

By examining CTGF protein and mRNA expression and promoter activity in the presence or absence of TGF-beta or inhibitors, the signaling pathways controlling basal and TGF-beta-induced CTGF expression in mesangial cells were investigated.

RESULTS

TGF-beta enhances CTGF mRNA and protein expression in mesangial cells. Mutation of a consensus SMAD binding element in the CTGF promoter completely abolished TGF-beta-induced CTGF expression and reduced basal CTGF expression. The previously identified basal control element-1 (BCE-1) site, but not Sp1 contributes to basal CTGF promoter activity. Ras/MEK/ERK, protein kinase C (PKC) and tyrosine kinase activity also contribute to basal and TGF-beta-induced CTGF promoter activity in cultured mesangial cells.

CONCLUSIONS

The TGF-beta-induction of CTGF in mesangial cells requires SMADs and PKC/ras/MEK/ERK pathways. SMADs are involved in basal CTGF expression, which presumably reflects the fact that mesangial cells express TGF-beta endogenously. TGF-beta also induces CTGF through ras/MEK/ERK. Inhibiting ras/MEK/ERK seems not to reduce phosphorylation (that is, activation) of SMADs, suggesting that SMADs, although necessary, are insufficient for the TGF-beta-stimulation of the CTGF promoter through ras/MEK/ERK. Thus, maximal TGF-beta induction of CTGF requires synergy between SMAD and ras/MEK/ERK signaling.

Keratinocytes inhibit expression of connective tissue growth factor in fibroblasts in vitro by an interleukin-1alpha-dependent mechanism

The wound healing process concludes with downregulation of fibroblast activity. Clinical observations suggest that the regenerating epidermis suppresses this activity. An important regulator of fibroblast activity is the fibrogenic cytokine connective tissue growth factor. We hypothesized that epidermal keratinocytes may affect fibroblast activity via this cytokine. We demonstrate keratinocyte-mediated suppression of connective tissue growth factor at both the mRNA and protein levels by around 50% or more when fibroblasts were cultured in multiwell plates with keratinocyte cultures in accompanying semipermeable cell culture inserts, or stimulated by keratinocyte-conditioned media. Both basal and transforming-growth-factor-beta1-stimulated levels of connective tissue growth factor were inhibited. A 3 h coculture period with keratinocytes was sufficient to suppress connective tissue growth factor expression by fibroblasts, but the inhibition developed over a time period of around 16 h. The putative keratinocyte-derived factor(s) responsible for these effects was found to be soluble and stable. By analyzing cytokines secreted by keratinocytes we identified interleukin-1alpha as a potent inhibitor of connective tissue growth factor mRNA expression in fibroblasts. Involvement of this cytokine in keratinocyte-mediated connective tissue growth factor suppression was confirmed by using anti-interleukin-1alpha antibodies. Tumor necrosis factor alpha or prostaglandins did not appear to be involved. In conclusion, our results indicate that interleukin-1alpha secretion by keratinocytes provides a mechanism for the downregulation of connective tissue activity during the end-stage of wound healing, when epithelia coverage has developed over the wound area.