TNF-α suppressed TGF-β-induced CTGF expression by switching the binding preference of p300 from Smad4 to p65

Deregulation of signaling pathways controlling cell survival and proliferation in cancer cells alters induction of cytochrome P450 family 1 enzymes

Cytochrome P450 family 1 (CYP1) enzymes contribute both to metabolism of xenobiotics and to the control of endogenous levels of ligands of the aryl hydrocarbon receptor (AhR). Their activities, similar to other CYPs, can be altered in tumor tissues. Here, we examined a possible role of proliferative/survival pathways signaling, which is often deregulated in tumor cells, and possible links with p300 histone acetyltransferase (a transcriptional co-activator) in the control of CYP1 expression, focusing particularly on CYP1A1. Using cell models derived from human liver, we observed that the induction of CYP1A1 expression, as well as other CYP1 enzymes, was reduced in exponentially growing cells, as compared with their non-dividing counterparts. The siRNA-mediated inhibition of proliferation/pro-survival signaling pathway effectors (such as β-catenin and/or Hippo pathway effectors YAP/TAZ) increased the AhR ligand-induced CYP1A1 mRNA levels in liver HepaRG cells, and/or in colon carcinoma HCT-116 cells. The activation of proliferative Wnt/β-catenin signaling in HCT-116 cells reduced both the induction of CYP1 enzymes and the binding of p300 to the promoter of CYP1A1 or CYP1B1 genes. These results seem to indicate that aberrant proliferative signaling in tumor cells could suppress induction of CYP1A1 (or other CYP1 enzymes) via competition for p300 binding. This mechanism could be involved in modulation of the metabolism of both endogenous and exogenous substrates of CYP1A1 (and other CYP1 enzymes), with possible further consequences for alterations of the AhR signaling in tumor cells, or additional functional roles of CYP1 enzymes.

Histone deacetylase 7 mediates endothelin-1-induced connective tissue growth factor expression in human lung fibroblasts through p300 and activator protein-1 activation

Background

Histone deacetylase (HDAC) inhibition was reported to ameliorate lung fibrosis in animal models. However, little is known about the underlying mechanism of HDAC7 in the regulation of CTGF production in lung fibroblasts.

Methods

The role of HDAC7 in CTGF production caused by ET-1 stimulation in WI-38 cells (human lung fibroblast) was examined. We also evaluated the expression of HDAC7 in the lung of ovalbumin-induced airway fibrosis model. Statistical data were shown as mean ± standard error.

Results

ET-1-stimulated CTGF and α-SMA expression was attenuated by small interfering (si)RNA interference of HDAC7. ET-1 promoted HDAC7 translocation from the cytosol to nucleus. ET-1-stimulated CTGF expression was reduced by the transfection of p300 siRNA. ET-1 induced an increase in p300 activity. Furthermore, the acetylation of c-Jun was time-dependently induced by ET-1 stimulation, which was reduced by transfection of either HDAC7 or p300 siRNA. Both transfection of HDAC7 and p300 siRNA suppressed the ET-1-increased activity of AP-1-luciferase. Moreover, the presence of HDAC7 was required for ET-1-stimulated formation of HDAC7, p300, and AP-1 complex and recruitment to the CTGF promoter region. In an ovalbumin-induced airway fibrosis model, the protein level of HDAC7 was increased in the lung tissue, and the distribution of HDAC7 was colocalized with α-SMA-positive cells in the subepithelial layer of the airway.

Conclusions

ET-1 activates HDAC7 to initiate AP-1 transcriptional activity by recruiting p300 and eventually promotes the production of CTGF. HDAC7 might play a vital role in airway fibrosis and have the potential to be developed as a therapeutic target.

Epigenetics and expression of key genes associated with cardiac fibrosis: NLRP3, MMP2, MMP9, CCN2/CTGF and AGT

Aims:

Excessive inflammatory signaling and pathological remodeling of the extracellular matrix drive cardiac fibrosis and require changes in gene expression.

Materials and methods:

Using bioinformatics, both tissue-specific expression profiles and epigenomic profiles of some genes critical for cardiac fibrosis were examined, namely, NLRP3, MMP2, MMP9, CCN2/CTGF, AGT (encodes angiotensin II precursors) and hsa-mir-223 (post-transcriptionally regulates NLRP3).

Results:

In monocytes, neutrophils, fibroblasts, venous cells, liver and brain, enhancers or super-enhancers were found that correlate with high expression of these genes. One enhancer extended into a silent gene neighbor. These enhancers harbored tissue-specific foci of DNA hypomethylation, open chromatin and transcription factor binding.

Conclusions:

This study identified previously undescribed enhancers containing hypomethylated transcription factor binding subregions that are predicted to regulate expression of these cardiac fibrosis-inducing genes.

The roles of connective tissue growth factor in the development of anastomotic esophageal strictures

INTRODUCTION

The aim of this study was to investigate the roles of connective tissue growth factor (CTGF) in the development of anastomotic strictures after surgical repair of the esophagus.

MATERIAL AND METHODS

Tissues collected from the patients were divided into three groups based on the results of endoscopy and clinical grading. Patients without dysphagia after esophagectomy were used as the control population. The protein levels of CTGF, TGF-β1, Smad2, and Smad4 were determined by immunohistochemistry (IHC) and western blot analyses, while the mRNA levels of the two growth factors were evaluated by real-time polymerase chain reaction.

RESULTS

Compared with the control group, significantly increased (p < 0.01) levels of CTGF and TGF-β1 protein were observed in the anastomotic stenosis (AS) group, and levels of the two proteins detected by the IHC and western blot analyses were also significantly increased with the increasing severity of stenosis (p < 0.05). The mRNA levels of CTGF and TGF-β1 in the tissues collected from the patients with stenosis were significantly up-regulated (p < 0.05) as compared with those from the control group. In addition, the levels of Smad2 and Smad4 protein were also significantly increased (p < 0.05) with the increasing severity of stenosis, and the protein levels were positively correlated with the levels of CTGF (r = 0.59, p < 0.05) and TGF-β1 (r = 0.63, p < 0.05).

CONCLUSIONS

Inhibition of CTGF protein or mRNA expression may be a distinctive and effective therapy for the treatment of postoperative anastomotic strictures.

Increased serum and musculotendinous fibrogenic proteins following persistent low-grade inflammation in a rat model of long-term upper extremity overuse

We examined the relationship between grip strength declines and muscle-tendon responses induced by long-term performance of a high-repetition, low-force (HRLF) reaching task in rats. We hypothesized that grip strength declines would correlate with inflammation, fibrosis and degradation in flexor digitorum muscles and tendons. Grip strength declined after training, and further in weeks 18 and 24, in reach limbs of HRLF rats. Flexor digitorum tissues of reach limbs showed low-grade increases in inflammatory cytokines: IL-1β after training and in week 18, IL-1α in week 18, TNF-α and IL-6 after training and in week 24, and IL-10 in week 24, with greater increases in tendons than muscles. Similar cytokine increases were detected in serum with HRLF: IL-1α and IL-10 in week 18, and TNF-α and IL-6 in week 24. Grip strength correlated inversely with IL-6 in muscles, tendons and serum, and TNF-α in muscles and serum. Four fibrogenic proteins, TGFB1, CTGF, PDGFab and PDGFbb, and hydroxyproline, a marker of collagen synthesis, increased in serum in HRLF weeks 18 or 24, concomitant with epitendon thickening, increased muscle and tendon TGFB1 and CTGF. A collagenolytic gelatinase, MMP2, increased by week 18 in serum, tendons and muscles of HRLF rats. Grip strength correlated inversely with TGFB1 in muscles, tendons and serum; with CTGF-immunoreactive fibroblasts in tendons; and with MMP2 in tendons and serum. Thus, motor declines correlated with low-grade systemic and musculotendinous inflammation throughout task performance, and increased fibrogenic and degradative proteins with prolonged task performance. Serum TNF-α, IL-6, TGFB1, CTGF and MMP2 may serve as serum biomarkers of work-related musculoskeletal disorders, although further studies in humans are needed.

Interleukin-1 has opposing effects on connective tissue growth factor and tenascin-C expression in human cardiac fibroblasts

Cardiac fibroblasts (CF) play a central role in the repair and remodeling of the heart following injury and are important regulators of inflammation and extracellular matrix (ECM) turnover. ECM-regulatory matricellular proteins are synthesized by several myocardial cell types including CF. We investigated the effects of pro-inflammatory cytokines on matricellular protein expression in cultured human CF. cDNA array analysis of matricellular proteins revealed that interleukin-1α (IL-1α, 10ng/ml, 6h) down-regulated connective tissue growth factor (CTGF/CCN2) mRNA by 80% and up-regulated tenascin-C (TNC) mRNA levels by 10-fold in human CF, without affecting expression of thrombospondins 1-3, osteonectin or osteopontin. Western blotting confirmed these changes at the protein level. In contrast, tumor necrosis factor α (TNFα) did not modulate CCN2 expression and had only a modest stimulatory effect on TNC levels. Signaling pathway inhibitor studies suggested an important role for the p38 MAPK pathway in suppressing CCN2 expression in response to IL-1α. In contrast, multiple signaling pathways (p38, JNK, PI3K/Akt and NFκB) contributed to IL-1α-induced TNC expression. In conclusion, IL-1α reduced CCN2 expression and increased TNC expression in human CF. These observations are of potential value for understanding how inflammation and ECM regulation are linked at the level of the CF.

The role of cardiac fibroblasts in the transition from inflammation to fibrosis following myocardial infarction

Cardiac fibroblasts (CF) play a pivotal role in the repair and remodeling of the heart that occur following myocardial infarction (MI). The transition through the inflammatory, granulation and maturation phases of infarct healing is driven by cellular responses to local levels of cytokines, chemokines and growth factors that fluctuate in a temporal and spatial manner. In the acute inflammatory phase early after MI, CF contribute to the inflammatory milieu through increased secretion of proinflammatory cytokines and chemokines, and they promote extracellular matrix (ECM) degradation by increasing matrix metalloproteinase (MMP) expression and activity. In the granulation phase, CF migrate into the infarct zone, proliferate and produce MMPs and pro-angiogenic molecules to facilitate revascularization. Fibroblasts also undergo a phenotypic change to become myofibroblasts. In the maturation phase, inflammation is reduced by anti-inflammatory cytokines, and increased levels of profibrotic stimuli induce myofibroblasts to synthesize new ECM to form a scar. The scar is contracted through the mechanical force generated by myofibroblasts, preventing cardiac dilation. In this review we discuss the transition from myocardial inflammation to fibrosis with particular focus on how CF respond to alterations in proinflammatory and profibrotic signals. By furthering our understanding of these events, it is hoped that new therapeutic interventions will be developed that selectively reduce adverse myocardial remodeling post-MI, while sparing essential repair mechanisms.

Performance of repetitive tasks induces decreased grip strength and increased fibrogenic proteins in skeletal muscle: role of force and inflammation

BACKGROUND

This study elucidates exposure-response relationships between performance of repetitive tasks, grip strength declines, and fibrogenic-related protein changes in muscles, and their link to inflammation. Specifically, we examined forearm flexor digitorum muscles for changes in connective tissue growth factor (CTGF; a matrix protein associated with fibrosis), collagen type I (Col1; a matrix component), and transforming growth factor beta 1 (TGFB1; an upstream modulator of CTGF and collagen), in rats performing one of two repetitive tasks, with or without anti-inflammatory drugs.

METHODOLOGY/RESULTS

To examine the roles of force versus repetition, rats performed either a high repetition negligible force food retrieval task (HRNF), or a high repetition high force handle-pulling task (HRHF), for up to 9 weeks, with results compared to trained only (TR-NF or TR-HF) and normal control rats. Grip strength declined with both tasks, with the greatest declines in 9-week HRHF rats. Quantitative PCR (qPCR) analyses of HRNF muscles showed increased expression of Col1 in weeks 3-9, and CTGF in weeks 6 and 9. Immunohistochemistry confirmed PCR results, and also showed greater increases of CTGF and collagen matrix in 9-week HRHF rats than 9-week HRNF rats. ELISA, and immunohistochemistry revealed greater increases of TGFB1 in TR-HF and 6-week HRHF, compared to 6-week HRNF rats. To examine the role of inflammation, results from 6-week HRHF rats were compared to rats receiving ibuprofen or anti-TNF-α treatment in HRHF weeks 4-6. Both treatments attenuated HRHF-induced increases in CTGF and fibrosis by 6 weeks of task performance. Ibuprofen attenuated TGFB1 increases and grip strength declines, matching our prior results with anti-TNFα.

CONCLUSIONS/SIGNIFICANCE

Performance of highly repetitive tasks was associated with force-dependent declines in grip strength and increased fibrogenic-related proteins in flexor digitorum muscles. These changes were attenuated, at least short-term, by anti-inflammatory treatments.

Overexpression of tumor necrosis factor-α in the lungs alters immune response, matrix remodeling, and repair and maintenance pathways

Increased production of tumor necrosis factor (TNF)-α and matrix metalloproteinases (MMPs) is a feature of inflammatory lung diseases, including emphysema and fibrosis, but the divergent pathological characteristics that result indicate involvement of other processes in disease pathogenesis. Transgenic mice overexpressing TNF-α in type II alveolar epithelial cells under the control of the surfactant protein (SP)-C promoter develop pulmonary inflammation and emphysema but are resistant to induction of fibrosis by administration of bleomycin or transforming growth factor-β. To study the molecular mechanisms underlying the development of this phenotype, we used a microarray approach to characterize the pulmonary transcriptome of SP-C/TNF-α mice and wild-type littermates. Four-month-old SP-C/TNF-α mice displayed pronounced pulmonary inflammation, airspace enlargement, increased MMP-2 and MMP-9 levels, and altered expression of 2332 probes. The functional assessment of genes with increased expression revealed enrichment of inflammatory/immune responses and proteases, whereas genes involved in protease inhibition, angiogenesis, cross-linking of basement membrane proteins, and myofibroblast differentiation were predominantly decreased. Comparison with multiple lung disease models identified a set of genes unique to the SP-C/TNF-α model and revealed that lack of extracellular matrix production distinguished SP-C/TNF-α mice from fibrosis models. Activation of inflammatory and proteolytic pathways and disruption of maintenance and repair processes are central features of emphysema in this TNF-overexpression model. Impairment of myofibroblast differentiation and extracellular matrix production may underlie resistance to induction of fibrosis.

Runx2/Smad3 complex negatively regulates TGF-β-induced connective tissue growth factor gene expression in vascular smooth muscle cells

AIM

Connective tissue growth factor (CTGF), a direct target gene of transforming growth factor-β (TGF-β) signaling, plays an important role in the development of atherosclerosis. We previously showed that Runx2, a key transcription factor in osteoblast differentiation, regulates osteogenic conversion and dedifferentiation of vascular smooth muscle cells (VSMCs). In this study, we investigated the hypothesis that Runx2 modulates CTGF gene expression via the regulation of TGF-β signaling.

METHODS AND RESULTS

Expression of the Runx2 gene was decreased, and CTGF mRNA levels were reciprocally increased by TGF-β in a time-dependent manner in cultured human aortic smooth muscle cells (HASMCs) and C3H10T1/2 cells. Forced expression of Runx2 decreased and the reduction of Runx2 expression by small interfering RNA enhanced both basal and TGF-β-stimulated CTGF gene expression in HASMCs. Site-directed mutation analysis of the CTGF promoter indicated that transcriptional repression by Runx2 was mediated by the Smad-binding element (SBE) under basal and TGF-β-stimulated conditions. Data obtained from immunoblots of Runx2-, Smad3- or Smad4-transfected cells and chromatin immunoprecipitation analysis indicated that Runx2 interacts with Smad3 at the SBE. Immunohistochemistry revealed that the expression of Runx2 and CTGF was distinct and almost mutually exclusive in human atherosclerotic plaque.

CONCLUSIONS

These results for the first time demonstrate that Runx2/Smad3 complex negatively regulates endogenous and TGF-β-induced CTGF gene expression in VSMCs. Thus, the induction of Runx2 expression contributes to the phenotypic modulation of VSMCs, in which the TGF-β/Smad pathway plays a major role.

NF-κB suppresses HIF-1α response by competing for P300 binding

Hypoxia has emerged as a key determinant of osteogenesis. HIF-1α is the transcription factor mediating hypoxia responses that include induction of VEGF and related bone induction. Inflammatory signals antagonize bone repair via the NF-κB pathway. The present investigation explored the functional relationship of hypoxia (HIF-1α function) and inflammatory signaling (NF-κB) in stem like and osteoprogenitor cell lines. The potential interaction between HIF-1α and NF-κB signaling was explored by co-transfection studies in hFOB with p65, HIF-1α and 9x-HRE-luc or HIF-1α target genes reporter plasmids. Nuclear cross-talk was directly tested using the mammalian Gal4/VP16 two-hybrid, and confirmed by co-immunoprecipitation/western blotting assays. The results show that inflammatory stimulation (TNF-α treatment) causes a marked inhibition of HIF-1α function at the HRE in all cell lines studied. Also, co-transfection with p65 expression vector leads to reduced hVEGFp transcription after DFO-induced hypoxia. However, TNF-α treatment had little effect on HIF-1α mRNA levels. The functional interaction of Gal4-HIF-1α and VP16-p300 fusion proteins is effectively blocked by expression of p65 in a dose dependent manner. It was concluded that NF-κB-mediated inflammatory signaling is able to block HIF-1α transactivation at HRE-encoding genes by direct competition for p300 binding at the promoter. Inflammation may influence the stem cell niche and tissue regeneration by influencing cellular responses to hypoxia.

Connective tissue growth factor promotes articular damage by increased osteoclastogenesis in patients with rheumatoid arthritis

Introduction

A protein analysis using a mass spectrometry indicated that there are serum proteins showing significant quantitative changes after the administration of infliximab. Among them, connective tissue growth factor (CTGF) seems to be related to the pathogenesis of rheumatoid arthritis (RA). Therefore, this study was conducted to investigate how CTGF is associated with the disease progression of RA.

Methods

Serum samples were collected from RA patients in active or inactive disease stages, and before or after treatments with infliximab. CTGF production was evaluated by ELISA, RT-PCR, indirect immunofluorescence microscopy, and immunoblotting. Osteoclastogenesis was evaluated using tartrate-resistant acid phosphatase (TRAP) staining, a bone resorption assay and osteoclasts specific catalytic enzymes productions.

Results

The serum concentrations of CTGF in RA were greater than in normal healthy controls and disease controls. Interestingly, those were significantly higher in active RA patients compared to inactive RA patients. Furthermore, the CTGF levels significantly were decreased by infliximab concomitant with the disease amelioration. In addition, tumour necrosis factor (TNF)α can induce the CTGF production from synovial fibroblasts even though TNFα can oppositely inhibit the production of CTGF from chondrocytes. CTGF promoted the induction of the quantitative and qualitative activities of osteoclasts in combination with M-CSF and receptor activator of NF-κB ligand (RANKL). In addition, we newly found integrin αVβ3 on the osteoclasts as a CTGF receptor.

Conclusions

These results indicate that aberrant CTGF production induced by TNFα plays a central role for the abnormal osteoclastic activation in RA patients. Restoration of aberrant CTGF production may contribute to the inhibition of articular destruction in infliximab treatment.