The transcription of human alpha 1(I) procollagen gene (COL1A1) is suppressed by tumour necrosis factor-alpha through proximal short promoter elements: evidence for suppression mechanisms mediated by two nuclear-factorbinding sites

COL1A1 proximal promoter topology regulates its transcriptional response to transforming growth factor β

OBJECTIVE

The COL1A1 proximal promoter contains two GC-rich regions and two inverted CCAAT boxes. The transcription factors Sp1 and CBF bind to the GC sequence at -122 to -115 bp and the inverted CCAAT box at -101 to -96 bp, respectively, and stimulate COL1A1 transcriptional activity.

METHODS

To further define the regulatory mechanisms controlling COL1A1 expression by Sp1 and CBF, we introduced 2, 4, 6, or 8 thymidine nucleotides (T-tracts) at position -111 bp of the COL1A1 gene promoter to increase the physical distance between these two binding sites and examined in vitro the transcriptional activities of the resulting constructs and their response to TGF-β1.`.

RESULTS

Insertion of 2 or 4 nucleotides decreased COL1A1 promoter activity by up to 70%. Furthermore, the expected increase in COL1A1 transcription in response to TGF-β1 was abolished. Computer modeling of the modified DNA structure indicated that increasing the physical distance between the Sp1 and CBF binding sites introduces a rotational change in the DNA topology that disrupts the alignment of Sp1 and CBF binding sites and likely alters protein-protein interactions among these transcription factors or their associated co-activators.

CONCLUSION

The topology of the COL1A1 proximal promoter is crucial in determining the transcriptional activity of the gene and its response to the stimulatory effects of TGF-β1.

Aberrant miR-3135b and miR-1273g-3p expression in the peripheral blood samples of BRCA1/2 (±) ovarian cancer patients

Ovarian cancer (OC) ranks as the eighth most prevalent malignancy among women globally. The short non-coding RNA molecules, microRNAs (miRNAs) target multiple mRNAs and regulate the gene expression. Here in this study, we aimed to validate miR-3135b and miR-1273g-3p as novel biomarkers for prognostic and diagnostic factor OC. After RNA isolation, we analyzed the miR-3135b and miR-1273g-3p expression in peripheral blood samples derived from 150 OC patients. Subsequently, we compared their expression levels with 100 healthy controls. The differences of miR-3135b and miR-1273g-3p expression were detected using the Quantitative Real Time-PCR (qRT-PCR) technique following miRNA-specific cDNA synthesis pursing miRNA separation. The miR-3135b and miR-1273g-3p were higher in OC patients who tested positive for BRCA1/2 compared to BRCA-negative patients, and healthy cases. The level of miR-3135b demonstrated a roughly 4.82-fold increase in OC patients in comparison to the healthy cases, while miR-1273g-3p expression exhibited a roughly 6.77-fold increase. The receiver operating characteristic (ROC) analysis has demonstrated the potential of miR-3135b and miR-1273g-3p as markers for distinguishing between OC patients and healthy controls. The higher expressions of miR-3135b and miR-1273g-3p could be associated with OC development. Moreover, miR-3135b may have a diagnostic potential and miR-1273g-3p may have both diagnostic and prognostic potential in OC cell differentiation. The string analysis has revealed an association between miR-1273g-3p and the MDM2 gene, suggesting a potential link to tumor formation through the proteasomal degradation of the TP53 tumor suppressor gene. Additionally, the analysis indicates an association of miR-1273g-3p with CHEK1, a gene involved in checkpoint-mediated cell cycle arrest. String analysis also indicates that miR-3135b is associated with the MAPK1 gene, causing activation of the oncogenesis cascade. In conclusion, miR-1273g-3p, and miR-3135b exhibit significant potential as diagnostic markers. However, further research is needed to comprehensively investigate these miRNAs diagnostic and predictive characteristics in a larger cohort.

Male Macrophages and Fibroblasts from C57/BL6J Mice Are More Susceptible to Inflammatory Stimuli

Mounting evidence argues for the significant impact of sex in numerous cardiac pathologies, including myocarditis. Macrophage polarization and activation of cardiac fibroblasts play a key role in myocardial inflammation and remodeling. However, the role of sex in these processes is still poorly understood. In this study, we investigated sex-specific alterations in the polarization of murine bone marrow-derived macrophages (BMMs) and the polarization-related changes in fibroblast activation. Cultured male and female murine BMMs from C57/BL6J mice were polarized into M1 (LPS) and M2 (IL-4/IL-13) macrophages. Furthermore, male and female cardiac fibroblasts from C57/BL6J mice were activated with TNF-α, TGF-β, or conditioned medium from M1 BMMs. We found a significant overexpression of M1 markers (c-fos, NFκB, TNF-α, and IL-1β) and M2 markers (MCP-1 and YM1) in male but not female activated macrophages. In addition, the ROS levels were higher in M1 male BMMs, indicating a stronger polarization. Similarly, the pro-fibrotic markers TGF-β and IL-1β were expressed in activated cardiac male fibroblasts at a significantly higher level than in female fibroblasts. In conclusion, the present study provides strong evidence for the male-specific polarization of BMMs and activation of cardiac fibroblasts in an inflammatory environment. The data show an increased inflammatory response and tissue remodeling in male mice.

Collagen I: a kingpin for rotator cuff tendon pathology

Derangements in tendon matrisome are pathognomonic for musculoskeletal disorders including rotator cuff tendinopathies (RCT). Collagen type-1 accounts for more than 85% of the dry weight of tendon extracellular matrix (ECM). The understanding of basic tendon physiology, organization of ECM, structure and function of component biomolecules of matrisome and the underlying regulatory mechanisms reveal the pathological events associated with RCT. Histomorphological evidence from RCT patients and animal models illustrate that ECM disorganization is the major hallmark in tendinopathy where a significant decrease in type-1 collagen is prevalent. However, the molecular events and regulatory signals associated with the regulation of collagen organization and its composition switch in response to pathological stimuli are largely unknown. The elucidation of various regulatory signalling pathways associated with collagen type-1 gene expression could benefit to develop novel promising therapeutic approaches to restore the tendon ECM. The major focus of the article is to critically evaluate tendon architecture regarding type-1 collagen, the molecular events associated with gene expression, secretion and maturation, the possible mechanisms of type-1 collagen regulation and its translational significance in RCT management.

Hypoxia inducible factor 1 alpha down-regulates type i collagen through Sp3 transcription factor in human chondrocytes

Cartilage engineering is one challenging issue in regenerative medicine. Low oxygen tension or hypoxia inducible factor-1 (HIF-1α) gene therapy are promising strategies in the field of cartilage repair. Previously, we showed that hypoxia and its mediator HIF-1 regulate matrix genes expression (collagens and aggrecan). Here, we investigated the molecular mechanism involved in the regulation of type I collagen (COL1A1) by HIF-1 in human articular chondrocytes. We show that HIF-1α reduces COL1A1 transcription, through a distal promoter (-2300 to -1816 bp upstream transcription initiation site), containing two GC boxes that bind Sp transcription factors (Sp1/Sp3). Sp1 acts as a positive regulator but is not induced by HIF-1. COL1A1 inhibition caused by HIF-1 implies only Sp3, which accumulates and competes Sp1 binding on COL1A1 promoter. Additionally, Sp3 ectopic expression inhibits COL1A1, while Sp3 knockdown counteracts the downregulation of COL1A1 induced by HIF-1. In conclusion, we established a new regulatory model of COL1A1 regulation by HIF-1, and bring out its relationship with Sp3 transcription factor. In a fundamental level, these findings give insights in the mechanisms controlling COL1A1 gene expression. This may be helpful to improve strategies to impair type I collagen expression during chondrocyte differentiation for cartilage engineering. © 2016 IUBMB Life, 68(9):756-763, 2016.

Bioinformatics analysis of molecular mechanisms involved in intervertebral disc degeneration induced by TNF-α and IL-1β

The present study aimed to explore the molecular mechanisms associated with intervertebral disc degeneration (IDD) induced by tumor necrosis factor (TNF)‑α and interleukin (IL)‑1β. The microarray dataset no. GSE42611 was downloaded from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) between four experimental nucleus pulposus samples and four control nucleus pulposus samples were analyzed. Subsequently, Gene Ontology (GO) and pathway enrichment analyses of DEGs were performed, followed by protein‑protein interaction (PPI) network construction and prediction of a regulatory network of transcription factor (TFs). Finally, the transcriptional regulatory network was integrated into the PPI network to analyze the network modules. A total of 246 upregulated and 290 downregulated DEGs were identified. The upregulated DEGs were mainly associated with GO terms linked with inflammatory response and apoptotic pathways, while the downregulated DEGs were mainly associated with GO terms linked with cell adhesion and pathways of extracellular matrix ‑ receptor interaction. In the PPI network, IL6, COL1A1, NFKB1 and HIF1A were hub genes, and in addition, NFKB1 and HIF1A were TFs. Pathways of apoptosis and extracellular matrix ‑ receptor interaction may have important roles in IDD progression. IL6, COL1A1 and the TFs NFKB1 and HIF1A may be used as biomarkers for IDD diagnosis and treatment.

Variations of the COL1A1 gene promoter and the relation to developmental dysplasia of the hip

AIM

Developmental dysplasia of the hip (DDH) is one of the most common hip deformities in children. Since the COL1A1 gene is located in the DDH relating region, we investigated the COL1A1 promoter variations in the development of DDH.

RESULTS

We collected 154 unrelated female patients and 180 matched healthy female children, and then sequenced the COL1A1 gene promoter for detection of variations. Three variations in the COL1A1 gene promoter were detected in ten patients (T-139C, C-106T, and C-35T [rs113647555]), but none of the 180 health controls. The chi-square test showed that the rate of total variations in COL1A1 gene contributed to DDH (p=0.0016).

CONCLUSION

We detected three variations in the COL1A1 gene promoter in patients and first demonstrated that the higher rate of total variations of COL1A1 gene contributed to DDH in Chinese female children; thus, the COL1A1 gene is a new candidate gene for DDH disease.

Benazepril inhibited the NF-κB and TGF-β networking on LV hypertrophy in rats

PURPOSE

Benazepril, an angiotensin-converting enzyme (ACE) inhibitor, has been used to treat hypertension, congestive heart failure, and chronic renal failure. However, its biological activity and mechanism of action in inflammation are not fully identified. The present study was designed to determine the in vivo anti-inflammatory effects of benazepril on LV hypertrophy in rats.

METHODS

LV hypertrophy was produced in rats by abdominal aortic coarctation. They were then divided into the following groups: sham operation; LV hypertrophy; LV hypertrophy+benazepril (1mg/kg in a gavage, once a day for 4 weeks). Both morphological assays (hemodynamic and hemorheological measurement; LV hypertrophy assessment), and molecular assays (protein levels of Collagen type I/III, TNF-α and VCAM-1; TGF-β gene expression; NF-κB or Smad activation; intracellular ROS production) were performed.

RESULTS

The following effects were observed in rats treated with benazepril: (1) marked improvements in hemodynamic and hemorheological parameters; (2) significant reductions in LV hypertrophy, dilatation and fibrosis; (3) significantly attenuated protein levels of Collagen type I/III, TGF-β, TNF-α and VCAM-1, NF-κB or Smad activation, as well as intracellular ROS production.

CONCLUSIONS

These results suggest that the anti-inflammatory properties of benazepril may be ascribed to their down-regulation of both NF-κB and TGF-β signaling pathways by acting on the intracellular ROS production in rats with LV hypertrophy, thus supporting the use of benazepril as an anti-inflammatory agent.

Effect of erythromycin A and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts

Thinning of the dermis is the principal histological change in atrophic skin disorders and aged skin. It is caused due to a decreased amount of collagen in the dermis. Macrolides have been reported to exert various pharmacological activities, including anti-inflammatory activity, tumor angiogenesis inhibition and growth inhibition of fibroblasts, in addition to antimicrobial activity. In this study, we investigated the effects of erythromycin A (EMA) and its new derivative EM201 on type I collagen production by cultured dermal fibroblasts. Dermal fibroblasts were cultured with 10(-9) M-10(-5) M EMA or EM201, and collagen production was measured by incubation with radioactive proline, SDS-polyacrylamide gel electrophoresis and fluorography. mRNA levels were measured by Northern blots analysis, and to investigate transcriptional levels luciferase assays were also performed. The results showed that both EMA and EM201 increased collagen production and type I collagen mRNA level (to a maximum of 200% with EMA and 250% with EM201) in a dose-dependent manner in cultured dermal fibroblasts. Transcription of the type I collagen gene was also increased by both macrolides. These results suggest that EMA and EM201 have the potential to improve the thinning of the dermis in atrophic skin disorders and aged skin.

EM703, the new derivative of erythromycin, inhibits transcription of type I collagen in normal and scleroderma fibroblasts

BACKGROUND

Excessive accumulation of collagen in the skin and internal organs in systemic sclerosis (SSc) is considered to result from enhanced transcription of collagen in fibroblasts. Macrolides have been reported to show various pharmacological activities. Recently, it was reported that EM703, a new derivative of erythromycin, improved bleomycin-induced pulmonary fibrosis in mice.

OBJECTIVE

Therefore, we attempted to examine the effects of EM703 on the type I collagen synthetic activity in normal and SSc dermal fibroblasts.

METHODS

Normal and SSc dermal fibroblasts were cultured with various concentrations of Erythromycin A or EM703 for 48h. Amount of type I collagen in the culture medium was measured with ELISA with anti-type I collagen antibody. Type I collagen mRNA levels were measured by northern blots analysis and type I collagen transcription and regulation of the human COL1A1 promoter activity were examined by transient transfection and luciferase assay. Electrophoretic gel mobility shift assay was also performed for measurement of binding activities of DNA binding factors to the COL1A1 promoter.

RESULTS

We found that EM703 reduced collagen production and the mRNA levels of alpha1(I) collagen in a dose-dependent manner in the normal fibroblasts. The transcription of COL1A1 was downregulated as detected by the luciferase assay. The downregulation was also detected using DNA containing various short lengths of the COL1A1 promoter region. EM703 did not inhibit COL1A1 transcription when the luciferase assay was performed using DNA containing the COL1A1 promoter with a short substitution mutation of the CCAAT box. Decreased production of type I collagen at the transcriptional level was also found in SSc fibroblasts treated with EM703.

CONCLUSION

These results suggest that EM703 inhibits the transcription of type I collagen in both normal and SSc fibroblasts, and that the transcription is inhibited through the CCAAT box of the COL1A1 promoter.

TEF-1 and C/EBPbeta are major p38alpha MAPK-regulated transcription factors in proliferating cardiomyocytes

p38 MAPKs (mitogen-activated protein kinases) play important roles in the regulation of cellular responses to environmental stress. Recently, this signalling pathway has also been implicated in the regulation of processes unrelated to stress, for example, in T lymphocytes and cardiomyocytes. In order to identify molecular targets responsible for the housekeeping functions of p38 MAPKs, we have analysed the differences in the transcriptomes of normally proliferating wild-type and p38alpha knockout immortalized embryonic cardiomyocytes. Interestingly, many potential components of the myocardium extracellular matrix were found to be upregulated in the absence of p38alpha. Further analysis of the microarray data identified TEF-1 (transcriptional enhancer factor-1), a known regulator of heart-specific gene expression, and C/EBPbeta (CCAAT/enhancer-binding protein beta), as the two transcription factors the binding sites of which were most enriched in the promoters of p38alpha-regulated genes. We have focused on the study of the extracellular matrix component COL1A1 (alpha1 chain of type I collagen) and found evidence for the involvement of both TEF-1 and C/EBPbeta in the p38alpha-dependent inhibition of COL1A1 transcription. Our data therefore show that p38 MAPKs regulate TEF-1 and C/EBPbeta transcriptional activity in the absence of environmental stress and suggests a role for p38alpha in the expression of extracellular matrix components that maintain organ architecture.

TGF-beta and TNF-alpha: antagonistic cytokines controlling type I collagen gene expression

The balance between production and degradation of type I collagen plays a critical role in the development and maintenance of organ and tissue integrity. It also represents the most crucial element governing the process of tissue repair. The synthesis of type I collagen gene is highly regulated by different cytokines at the transcriptional level. Especially, transforming growth factor beta (TGF-beta), a key player in the physiopathology of tissue repair, enhances type I collagen gene expression. In contrast, tumor necrosis factor alpha (TNF-alpha), whose matrix-remodelling function is opposite to that of TGF-beta, reduces type I collagen gene expression. This review focuses on transcriptional regulation of type I collagen by TGF-beta and TNF-alpha and on the molecular mechanisms that control the antagonistic activity of TNF-alpha against TGF-beta-driven type I collagen gene expression.

Tumor necrosis factor-α: molecular and cellular mechanisms in skeletal pathology

Tumor necrosis factor-alpha (TNF) is one member of a large family of inflammatory cytokines that share common signal pathways, including activation of the transcription factor nuclear factor kappa B (Nf-kappa B) and stimulation of the apoptotic pathway. Data derived from early work supported a role for TNF as a skeletal catabolic agent that stimulates osteoclastogenesis while simultaneously inhibiting osteoblast function. The finding that estrogen deficiency was associated with increased production of cytokines led to a barrage of studies and lively debate on the relative contributions of TNF and other cytokines on bone loss, on the potential cell sources of TNF in the bone microenvironment, and on the mechanism of TNF action. TNF has a central role in bone pathophysiology. TNF is necessary for stimulation of osteoclastogenesis along with the receptor activator of Nf-kappa B ligand (RANKL). TNF also stimulates osteoblasts in a manner that hinders their bone-formative action. TNF suppresses recruitment of osteoblasts from progenitor cells, inhibits the expression of matrix protein genes, and stimulates expression of genes that amplify osteoclastogenesis. TNF may also affect skeletal metabolism by inducing resistance to 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) by a mechanism that extends to other members of the steroid hormone nuclear receptor family. Thus, TNF assails bone at many levels. This review will focus on the cellular and molecular mechanisms of TNF action in the skeleton that result in increased bone resorption and impaired formation. TNF and its signal pathway remains an important target for the development of new therapies for bone loss from osteoporosis and inflammatory arthritis.

ACL transection influences mRNA levels for collagen type I and TNF-alpha in MCL scar

To assess the mRNA expression of extracellular matrix genes which might correlate with or contribute to mechanically weaker medial collateral ligament (MCL) scars in the ACL-deficient rabbit knee joint compared to those in anterior cruciate ligament (ACL) intact knee joints, a bilateral MCL injury was induced in 10 skeletally mature female NZW rabbits. As part of the same surgical procedure, the ACL was transected in one of the knees while the contralateral knee had a sham procedure. The side having the combined MCL and ACL injury was randomly assigned. After six weeks, the rabbits were euthanized. Histological assessments were performed on samples of the MCL scars from each operated knee (n = 3 animals) and mRNA levels for collagen type I, III, V, decorin, biglycan, lumican, fibromodulin, TGF-beta, IL-1, TNF-alpha, MMP-1, MMP-13, and a housekeeping gene (GAPDH) were assessed using semiquantitative RT-PCR on RNA isolated from the MCL scar tissue of the remaining animals (n = 7 animals). Levels of mRNA for each gene were normalized using the corresponding GAPDH value. Results showed that the total RNA yield (per mg wet weight) in the MCL scar of the ACL-deficient knee was significantly greater than that in the MCL scar from the ACL-intact knee. Collagen type I mRNA levels were significantly lower and mRNA levels for TNF-alpha were significantly greater in the scars of ACL-deficient knees compared to scars from ACL-intact joints. There were no significant differences between ACL-deficient and ACL-intact knees with respect to MCL scar mRNA levels for the remaining genes assessed. Histologically, the "flaw" area, which has been shown to correlate with mechanical properties in previous studies, was significantly greater in MCL scars from ACL-deficient knees than in the ACL-intact MCL scars. The mean number of cells/mm2 in MCL scars from ACL-deficient knees was significantly greater than in MCL scars from ACL-intact knees. The present study suggests that MCL scar cell metabolism is differentially influenced by the combined injury environment.

YY1 is a positive regulator of transcription of the Col1a1 gene

Both cell-specific and ubiquitous transcription factors in fibroblasts have been identified as critical for expression of the Col1a1 gene, which encodes the alpha1 chain of type I collagen. Here, we report that Yin Yang 1 (YY1) binds to the Col1a1 promoter immediately upstream of the TATA box, and we examine the functional implications of YY1 binding for regulation of Col1a1 gene expression in BALBc/3T3 fibroblasts. The Col1a1 promoter region spanning base pairs (bp) -56 to -9 bound purified recombinant YY1 and the corresponding binding activity in nuclear extracts was supershifted using a YY1-specific antibody. Mutation of the TATA box to TgTA enhanced YY1 complex formation. Mutation analysis revealed two YY1 core binding sites at -40/-37 bp (YY1A) and, on the reverse strand, at -32/-29 bp (YY1B) immediately adjacent to the TATA box. In transfections using Col1a1-luciferase constructs, mutation of YY1A decreased activity completely (wild-type p350 (p350wt), -222/+113 bp) or partially (p130wt, -84 bp/+13 bp), whereas mutation of YY1B blocked the expression of both promoter constructs. Cotransfection with pCMV-YY1 increased p350wt and p130wt activities by as much as 10-fold, whereas antisense YY1 decreased constitutive expression and blocked the increased activity due to pCMV-YY1 overexpression. The mTgTA constructs were devoid of activity, arguing for a requirement for cognate binding of the TATA box-binding protein (TBP). Electrophoretic mobility shift assays performed under conditions permitting TBP binding showed that recombinant TBP/TFIID and YY1 could bind to the -56/-9 bp fragment and that YY1B was the preferred site for YY1 binding. Our results indicate that YY1 binds to the Col1a1 proximal promoter and functions as a positive regulator of constitutive activity in fibroblasts. Although YY1 is not sufficient for transcriptional initiation, it is a required component of the transcription machinery in this promoter.

Interstitial fibrosis and growth factors

Interstitial pulmonary fibrosis (IPF) is scarring of the lung caused by a variety of inhaled agents including mineral particles, organic dusts, and oxidant gases. The disease afflicts millions of individuals worldwide, and there are no effective therapeutic approaches. A major reason for this lack of useful treatments is that few of the molecular mechanisms of disease have been defined sufficiently to design appropriate targets for therapy. Our laboratory has focused on the molecular mechanisms through which three selected peptide growth factors could play a role in the development of IPF. Hundreds of growth factors and cytokines could be involved in the complex disease process. We are studying platelet-derived growth factor because it is the most potent mesenchymal cell mitogen yet described, transforming growth factor beta because it is a powerful inducer of extracellular matrix (scar tissue) components by mesenchymal cells, and tumor necrosis factor alpha because it is a pleiotropic cytokine that we and others have shown is essential for the development of IPF in animal models. This review describes some of the evidence from studies in humans, in animal models, and in vitro, that supports the growth factor hypothesis. The use of modern molecular and transgenic technologies could elucidate those targets that will allow effective therapeutic approaches.

Collagen alpha1(I) gene contains an element responsive to tumor necrosis factor-alpha located in the 5' untranslated region of its first exon

The aims of the present study were to identify the cis-acting element through which tumor necrosis factor-alpha (TNFalpha) inhibits collagen alpha1(I) gene transcription and the trans-acting factors involved in this effect in cultured hepatic stellate cells. Deletion analysis of the collagen alpha1(I) promoter demonstrated that TNFalpha inhibited gene expression through an element located between -59 and + 116 bp relative to the transcription start site. DNase I protection assays revealed a footprint between +68 and +86 bp of the collagen first exon, the intensity of which decreased when the DNA probe was incubated with nuclear protein from TNFalpha-treated hepatic stellate cells. This footprint contained a G+C-rich box. Transfection experiments demonstrated that mutations in this G+C-rich element abrogated the inhibitory effect of TNFalpha on the collagen alpha1(I) promoter. Gel retardation experiments using a radiolabeled oligonucleotide containing sequences of this region confirmed that TNFalpha treatment decreased the formation of two complexes between nuclear proteins and DNA. These complexes were efficiently blocked with an oligonucleotide containing an Spl-binding site and were supershifted with specific Spl and Sp3 antibodies. These results suggest that TNFalpha inhibits collagen alpha1(I) gene expression by decreasing the binding of Spl to a G+C-rich box in the 5' untranslated region of its first exon.

Tumor necrosis factor alpha down-regulates expression of the alpha1(I) collagen gene in rat hepatic stellate cells through a p20C/EBPbeta- and C/EBPdelta-dependent mechanism

Tumor necrosis factor alpha (TNF-alpha) is one of the key cytokines of the acute phase response and of many inflammatory processes. This cytokine has several antifibrogenic actions and down-regulates the expression of the type I collagen genes and induces the expression of metalloproteinases. Because TNF-alpha directly antagonizes some fibrogenic actions of transforming growth factor beta(1) (TGF-beta(1)), we considered it important to map the cis-acting regulatory element of the alpha1(I) collagen (col1a1) promoter involved in TNF-alpha responsiveness in hepatic stellate cells (HSC), to investigate the transcription factors that bind to it, and to establish possible mechanisms by which TNF-alpha down-regulates its expression. In this article, we show the presence of a functional TNF-alpha-responsive element (TaRE) in the -378 to -345 region of the col1a1 promoter. This element colocalizes with a previously reported TGF-beta(1)-responsive element. We further demonstrate that TNF-alpha induces nuclear translocation and binding of transcriptional complexes containing p20C/EBPbeta, p35C/EBPbeta, and C/EBPdelta to this sequence of the promoter. Transient overexpression of C/EBPdelta or p20C/EBPbeta, the natural dominant negative form of C/EBPbeta in HSC, down-regulated activity of a CAT reporter vector driven by -412 to +110 of the col1a1 promoter. Taken together, these data suggest that the -378 to -340 region of the col1a1 promoter is the site of convergence of different stimuli that ultimately modulate col1a1 gene transcription.

Wavelength-specific synergy between ultraviolet radiation and interleukin-1 alpha in the regulation of matrix-related genes: mechanistic role for tumor necrosis factor-alpha

Ultraviolet light causes both acute and chronic changes in extracellular matrix. We sought to examine the effects of different ultraviolet wavelengths on expression of matrix-related genes in fibroblasts. We previously reported that tropoelastin gene expression in vivo decreases with acute ultraviolet B exposure, and interleukin-1 alpha-mediated upregulation of tropoelastin is blocked in vitro after ultraviolet B radiation. In this study, we found that only ultraviolet B, but not ultraviolet A or ultraviolet A1, blocked the ability of interleukin-1 alpha to stimulate tropoelastin expression in vitro. Ultraviolet B and interleukin-1 alpha synergistically increased tumor necrosis factor-alpha secretion by fibroblasts, a finding not seen with ultraviolet B alone nor with ultraviolet A or ultraviolet A1 combined with interleukin-1 alpha. Keratinocytes showed a similar ultraviolet B-specific induction of tumor necrosis factor-alpha production. Addition of tumor necrosis factor-alpha to cultured fibroblasts blocked interleukin-1 alpha-induced stimulation of tropoelastin message, and addition of anti-tumor necrosis factor-alpha antibodies restored the responsiveness of tropoelastin and collagen messages to exogenous interleukin-1 alpha after ultraviolet B exposure. We conclude that interleukin-1 alpha in combination specifically with ultraviolet B induces fibroblasts to secrete tumor necrosis factor-alpha, and that this ultraviolet B-specific induction of tumor necrosis factor-alpha secretion is responsible for effects of ultraviolet B on the expression of matrix-related genes in the skin.

Alterations in the regulation of expression of the alpha 1(I) collagen gene (COL1A1) in systemic sclerosis (scleroderma)

At present, the mechanisms that regulate the expression of collagen genes in normal and pathologic fibroblasts are not known. Thus, the detailed study of transcriptional regulation of COL1A1 in SSc cells will increase our current understanding of the pathophysiology of fibrotic diseases. These studies will yield valuable information regarding the important biological process of regulation of collagen gene expression under normal and pathologic conditions, a process that has remained elusive despite intense recent investigations. It is now evident that persistent overproduction of collagen is responsible for the progressive nature of tissue fibrosis in SSc. Up-regulation of collagen gene expression in SSc fibroblasts appears to be a critical event in this process. The coordinate transcriptional activation of numerous collagen genes suggests a fundamental alteration in the regulatory control of gene expression in SSc fibroblasts. Trans-acting nuclear factors which bind to cis-acting elements in enhancer (intronic) and promoter regions of the genes modulate the basal and inducible transcriptional activity of the collagen genes. The identification of the nuclear transcription factors that regulate normal collagen gene expression may provide promising approaches to the therapy of this incurable disease.