Cyclosporin A enhances cytokine and phorbol ester-induced fibroblast collagenase expression

Disruption of Calcium Signaling in Fibroblasts and Attenuation of Bleomycin-Induced Fibrosis by Nifedipine

Fibrotic lung disease afflicts millions of people; the central problem is progressive lung destruction and remodeling. We have shown that external growth factors regulate fibroblast function not only through canonical signaling pathways but also through propagation of periodic oscillations in Ca(2+). In this study, we characterized the pharmacological sensitivity of the Ca(2+)oscillations and determined whether a blocker of those oscillations can prevent the progression of fibrosis in vivo. We found Ca(2+) oscillations evoked by exogenously applied transforming growth factor β in normal human fibroblasts were substantially reduced by 1 μM nifedipine or 1 μM verapamil (both L-type blockers), by 2.7 μM mibefradil (a mixed L-/T-type blocker), by 40 μM NiCl2 (selective at this concentration against T-type current), by 30 mM KCl (which partially depolarizes the membrane and thereby fully inactivates T-type current but leaves L-type current intact), or by 1 mM NiCl2 (blocks both L- and T-type currents). In our in vivo study in mice, nifedipine prevented bleomycin-induced fibrotic changes (increased lung stiffness, overexpression of smooth muscle actin, increased extracellular matrix deposition, and increased soluble collagen and hydroxyproline content). Nifedipine had little or no effect on lung inflammation, suggesting its protective effect on lung fibrosis was not due to an antiinflammatory effect but rather was due to altering the profibrotic response to bleomycin. Collectively, these data show that nifedipine disrupts Ca(2+) oscillations in fibroblasts and prevents the impairment of lung function in the bleomycin model of pulmonary fibrosis. Our results provide compelling proof-of-principle that interfering with Ca(2+) signaling may be beneficial against pulmonary fibrosis.

Calcium Homeostasis and Ionic Mechanisms in Pulmonary Fibroblasts

Fibroblasts are key cellular mediators of many chronic interstitial lung diseases, including idiopathic pulmonary fibrosis, scleroderma, sarcoidosis, drug-induced interstitial lung disease, and interstitial lung disease in connective tissue disease. A great deal of effort has been expended to understand the signaling mechanisms underlying the various cellular functions of fibroblasts. Recently, it has been shown that Ca(2+) oscillations play a central role in the regulation of gene expression in human pulmonary fibroblasts. However, the mechanisms whereby cytosolic [Ca(2+)] are regulated and [Ca(2+)] oscillations transduced are both poorly understood. In this review, we present the general concepts of [Ca(2+)] homeostasis, of ionic mechanisms responsible for various Ca(2+) fluxes, and of regulation of gene expression by [Ca(2+)]. In each case, we then also summarize the original findings that pertain specifically to pulmonary fibroblasts. From these data, we propose an overall signaling cascade by which excitation of the fibroblasts triggers pulsatile release of internally sequestered Ca(2+), which, in turn, activates membrane conductances, including voltage-dependent Ca(2+) influx pathways. Collectively, these events produce recurring Ca(2+) oscillations, the frequency of which is transduced by Ca(2+)-dependent transcription factors, which, in turn, orchestrate a variety of cellular events, including proliferation, synthesis/secretion of extracellular matrix proteins, autoactivation (production of transforming growth factor-β), and transformation into myofibroblasts. That unifying hypothesis, in turn, allows us to highlight several specific cellular targets and therapeutic intervention strategies aimed at controlling unwanted pulmonary fibrosis. The relationships between Ca(2+) signaling events and the unfolded protein response and apoptosis are also explored.

Immunotherapy of systemic sclerosis

Scleroderma is a multisystem autoimmune disease characterized by an abnormal immune activation associated with the development of underlying vascular and fibrotic disease manifestations. This article highlights the current use of drugs targeting the immune system in scleroderma. Nonselective immunosuppression, and in particular cyclophosphamide, remains the main treatment for progressing skin involvement and active interstitial lung disease. Mycophenolate mofetil is a promising alternative to cyclophosphamide. The use of cyclosporine has been limited by modest efficacy and serious renal toxicity. Newer T-cell (sirolimus and alefacept) and B-cell (rituximab)-targeted therapies have provided some encouraging results in small pilot studies. Hematopoietic stem cell transplantation can be effective for severe fibrotic skin disease, but toxicity remains a concern. Clinical efficacy and safety of antifibrotic treatments (e.g., imatinib) await confirmation. Newer biological agents targeting key molecular or cellular effectors in scleroderma pathogenesis are now available for clinical testing.

[Eosynophilic fasciitis. Favorable response to treatment with cyclosporin a]

INTRODUCTION

Eosinophilic fasciitis (EF) is a disease of unknown aetiology characterized by cutaneous swelling and indurations. The disease affects predominantly the extremities and usually show an elevation of serum immunoglobulins, and eosinophilia.

OBJECTIVE

Evaluation of the efficacy of cyclosporine A as a therapeutic alternative in patients with EF refractory to steroids.

PATIENTS AND METHOD

We report 3 patients with clinical, laboratory and pathologic characteristics of EF who did not show a satisfactory response to steroids treatment. All patients disclosed scleroderma-like signs with orange skin, groove sign, and indurations of the affected extremities associated to peipheral eosinophilia and increased creatine-kinase. Epidermis histological findings were normal and intense linfocitary inflammation of the fascia was observed in all patients' biopsies. All patients were treated for average of 8 months with prednisone 30-50 mg daily with an insufficient clinical response.

RESULTS

Patients started on cyclosporine A 5-7mg/kg/day, showing a fast improvement (2 months). The treatment induces a clinical remission that permits to reduce or even stops the cyclosporine A treatment during follow-up.

CONCLUSIONS

It seems that cyclosporine A may be a effective therapeutic alternative in patients with EF refractory to steroids.

MMP-21 is expressed by macrophages and fibroblasts in vivo and in culture

Matrix metalloproteinase (MMP)-21 and MMP-26 (matrilysin-2) are two recently cloned epithelial metalloproteases. Here we examined their expression in various benign skin disorders, in which macrophages and fibroblasts have been implicated as well as in cultures of these cells. Expression of MMP-21 was detected by immunohistochemistry in a subset of macrophages of granulomatous skin lesions and in fibroblasts in dermatofibromas. MMP-21 mRNA was found in THP-1, U937, HEL 299 and Hs68 cells. Furthermore, MMP-21 protein was detected by immunohistochemistry in cultures of the same cell lines. In culture MMP-21 was upregulated by phorbol myristate acetate in THP-1 cells and by retinoic acid (RA) in U937 cells, and downregulated by transforming growth factor beta 1 (TGF-beta1) in HEL 299 as assessed by Taqman quantitative polymerase chain reaction (PCR). Expression of MMP-26 was detected by immunohistochemistry in granulomatous skin diseases and actinic elastosis. MMP-26 at both mRNA and protein levels was only found in HEL 299 cells. In culture it was downregulated by TGF-beta1, RA and IL-1beta as assessed by Taqman quantitative PCR. Our results suggest these two novel MMPs are not only associated with cancer but may be important in connective tissue remodelling and pathobiology of various benign skin disorders.

Relationship between IL-1A polymorphisms and gingival overgrowth in renal transplant recipients receiving Cyclosporin A

AIM

Levels of interleukin-1alpha (IL-1alpha) are elevated in periodontal inflammation. IL-1A gene polymorphisms are associated with inflammatory diseases. This study aimed to investigate IL-1A gene polymorphism in Cyclosporin A (CsA)-treated renal transplant patients and investigate the association between this polymorphism and gingival crevicular fluid (GCF) levels of several cytokines.

MATERIALS AND METHODS

Fifty-one renal transplant patients on CsA treatment (25 with and 26 without gingival overgrowth) and 29 healthy controls were recruited for the study. Demographic, pharmacological and periodontal parameters were recorded and gingival overgrowth was assessed.

RESULTS

Multiple regression analysis showed that genotype was significantly associated with gingival overgrowth (p=0.02). Carriage of the IL-1A (-889) T allele was strongly protective [95% confidence interval (CI): 0.046-0.77], although not significantly associated with IL-1alpha protein levels in GCF. IL-1alpha, IL-1beta and IL-8, but not IL-6, were detected in GCF of CsA-treated patients, but none of them was significantly associated with gingival overgrowth.

CONCLUSIONS

This study is the first to associate a gene polymorphism as a risk factor for CsA-induced gingival overgrowth in renal transplant patients, demonstrating that IL-1A polymorphism might alter individual susceptibility to CsA. However, there was no association between GCF cytokine levels and the presence of gingival overgrowth or patient IL-1A genotype.

Differential expression of matrix metalloproteinase-1 in vitro corresponds to tissue morphogenesis and quality assurance of cultured skin substitutes

OBJECTIVE

To determine if matrix metalloproteinase-1 (MMP-1) was involved in the premature degradation of the dermal component in cultured skin substitutes (CSS) prepared with cells from burn patients.

METHODS AND RESULTS

CSS 645 and 647 were prepared from clinical human fibroblasts (HF) and keratinocytes (HK) that demonstrated premature degradation of collagen-glycosaminoglycan sponges in vitro. The control CSS were prepared from clinical HF and HK, CSS 648, and a pre-clinical cell strain, CSS 644 that did not degrade the sponges. Surface electrical capacitance measures surface hydration and was significantly higher for CSS 647 from days 9 through 14. MTT (3-[4,5-dimethylthiazol-2-yl]- diphenyltetrazolium bromide) conversion, an indicator of cellular viability was significantly lower for the 6-mm punch biopsies from CSS 645 and 647 at day 15 as compared to control CSS. MMP-1 protein levels measured by ELISA were significantly higher in medium from HF 645 and 647 than controls on the day of CSS inoculation. At day 14 of incubation, the mean MMP-1 concentration was significantly elevated in the medium from CSS 645 and 647 versus the controls, CSS 644 and 648. Western blots, and casein zymography demonstrated the presence of the latent and active forms of MMP-1 in the HF and CSS media, respectively.

CONCLUSION

MMP-1 was significantly higher in the media from two of the four HF strains and CSS after a 24 h incubation period. Elevated MMP-1 coincided with premature degradation of the dermal substitute in vitro, and reduced numbers of CSS that met quality assurance standards for clinical transplantation.

Eosinophilic fasciitis successfully treated with cyclosporine

We report on a 45-year-old female who developed eosinophilic fasciitis, characterized by scleroderma-like skin indurations, predominantly on the extremities and chest, with joint contractures and intermittent blood eosinophilia. Histologic examination revealed fibrosis of muscle fascia and eosinophilic infiltration. High-dose systemic corticosteroid therapy was ineffective, but cyclosporine treatment led to remission.

Expression of matrix metalloproteinases in cyclosporin-treated gingival fibroblasts is regulated by transforming growth factor (TGF)-beta1 autocrine stimulation

BACKGROUND

Gingival overgrowth is a common side effect following the administration of cyclosporin A (CsA). The pathogenesis of this condition is not fully understood; however, recent studies show that CsA regulates the transcription of several cytokines including transforming growth factor-beta1 (TGF-beta1). The aim of this study was to investigate the potential role of TGF-beta1 in the pathogenesis of CsA-induced gingival overgrowth, exploring a possible autocrine stimulation of TGF-beta1 as a cellular regulator of synthesis of matrix metalloproteinases (MMPs) and its tissue inhibitors (TIMPs).

METHODS

Gingival fibroblasts from human normal gingiva were incubated with increasing concentrations of CsA, cultured for 24 hours, and the expression and production of TGF-beta1 determined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. MMP and TIMP mRNA expression levels were also analyzed by RT-PCR. To determine the effect of TGF-beta1 on the expression of MMP and TIMP by human gingival fibroblasts under CsA treatment, human gingival fibroblast cultures were treated with sense oligonucleotides (SON) or antisense oligonucleotides (AON).

RESULTS

CsA simultaneously stimulated TGF-beta1 expression and production and inhibited expression of MMP-1 and MMP-2 by human gingival fibroblasts, whereas CsA has a slight effect on TIMP-1 and TIMP-2 expression. AON reduced TGF-beta1 production as demonstrated by ELISA, whereas TGF-beta1 mRNA expression levels were not significantly modified. The inhibition of TGF-beta1 production by AON modulated MMP expression, demonstrating the autocrine inhibitory effect of TGF-beta1 in CsA-treated human gingival fibroblasts.

CONCLUSIONS

The data presented here suggest that TGF-beta1 in an autocrine fashion may contribute to a reduction of proteolytic activity of human gingival fibroblasts in CsA-induced gingival overgrowth, which favors the accumulation of extracellular matrix.

Evaluation of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinase-1 levels in gingival fibroblasts of cyclosporin A-treated patients

BACKGROUND

Cyclosporin A (CsA) is a potent immunosuppressant used to prevent organ transplant rejection and to treat various autoimmune diseases. CsA-induced gingival overgrowth (CsA GO) is the most widely seen side effect of this drug; its pathogenesis is not completely understood. The aim of this study was to identify and compare matrix metalloproteinase-1 (MMP-1) and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels in gingival fibroblast cultures of tissues derived from renal transplant patients receiving CsA and exhibiting gingival overgrowth and from periodontally healthy control subjects.

METHODS

Gingival overgrowth samples were obtained from patients undergoing therapy with CsA, and control tissues were obtained from systemically healthy donors. Gingival fibroblasts were grown using explant cultures. Three different study groups were identified: 1) CsA GO fibroblast culture; 2) CsA-treated healthy gingival fibroblast culture (H+CsA); and 3) healthy gingival fibroblast culture (H). The levels of MMP-1 and TIMP-1 in these groups of gingival fibroblasts were analyzed by enzyme-linked immunoabsorbent assay (ELISA).

RESULTS

The levels of TIMP-1 were significantly lower in CsA GO than H (P < 0.05). There was no statistically significant difference in the levels of MMP-1 between H and CsA GO (P = 0.505). The ratio of MMP-1 to TIMP-1 was significantly higher in CsA GO than H (P < 0.05).

CONCLUSIONS

The results of this study indicate that CsA therapy does not have a significant effect on MMP-1 levels. However, low TIMP-1 levels can be an important factor in the pathogenesis of CsA GO, since the balance between MMP-1 and TIMP-1 levels was changed by CsA.

The effect of cyclosporin A on the activity of matrix metalloproteinases during the healing of rat molar extraction wounds

Cyclosporin A (CyA) is a cyclic peptide used as an immunosuppressive agent because it can block the synthesis of interleukin-2 and other cytokines produced by CD4+ lymphocytes. It is widely used for the prevention of allograft rejection and treatment of autoimmune diseases. Several side-effects of CyA treatment have been reported, among which are chronic nephrotoxicity, hepatotoxicity and neurotoxicity, lymphoproliferative neoplasms, hypertension, thromboembolic complications and gingival overgrowth. Here, using a rat molar model, it is demonstrated that CyA immunosuppression inhibits the activity of matrix metalloproteinases 2 and 9 in the early phase of granulation tissue in the healing dental socket. These observations suggest that CyA may interfere with the wound healing following dental extractions.

Analysis of 16 different matrix metalloproteinases (MMP-1 to MMP-20) in the synovial membrane: different profiles in trauma and rheumatoid arthritis

OBJECTIVE

To define the pattern of mRNA expression of all human matrix metalloproteinases (MMPs) described to date in rheumatoid arthritis (RA) and traumatic synovial membrane, in order to differentiate between a physiological tissue remodelling pattern and that associated with inflammatory tissue destruction.

METHODS

Analysis of SwissProt protein and EMBL/GenBank nucleotide sequence banks, protein sequence alignment, reverse transcriptase-polymerase chain reaction and nucleotide sequencing were used.

RESULTS

MMP-2 (gelatinase A), MMP-3 (stromelysin-1), MMP-11 (stromelysin-3) and MMP-19 were constitutively expressed. MMP-1 (fibroblast type collagenase), MMP-9 (gelatinase B) and MMP-14 (MT1-MMP) were expressed in all RA, but only in 55-80% of trauma samples. MMP-13 (collagenase-3) and MMP-15 (MT2-MMP) were expressed exclusively in RA (80-90% of the samples). MMP-20 (enamelysin) was absent and MMP-8 (collagenase-2) was rarely found in RA or trauma. All other MMPs (-7, -10, -12, -16, -17) had an intermediate pattern of expression.

CONCLUSIONS

Some MMPs without interstitial collagenase activity seem to have a constitutive pattern of expression and probably participate in physiological synovial tissue remodelling. Some MMPs are exclusively associated to RA synovitis, for example, MMP-13, which preferentially degrades type II collagen and aggrecan, and MMP-15, which activates proMMP-2 and proMMP-13 and is involved in tumour necrosis factor alpha processing. This clear cut rheumatoid/inflammatory MMP profile, more complex than has been previously appreciated, may facilitate inflammatory tissue destruction in RA.

Inhibition of the matrix metalloproteinase system in a rat model of chronic cyclosporine nephropathy

BACKGROUND

Chronic cyclosporine A (CsA)-induced nephropathy is histologically characterized by tubular lesions, the interstitial recruitment of inflammatory cells, arteriolopathy and focal interstitial fibrosis. Recent studies show that the intrarenal inhibition of matrix degradation and recruitment of monocytes/ macrophages into the kidney plays a critical role in the development of renal interstitial fibrosis.

METHODS

We examined the expression of components of the matrix metalloproteinase (MMP) system and plasminogen activator inhibitor type-1 (PAI-1) in kidneys from rats injected daily s.c. during three weeks with CsA (10, 15 or 20 mg CsA/kg body wt) or vehicle solution.

RESULTS

In all CsA-treated rats, serum creatinine levels were significantly elevated compared to control levels. The extent of CsA-induced atrophy was not influenced by the dosage during a three-week CsA treatment. The administration of CsA did not significantly increase total cortical interstitial collagen deposition, whereas alpha-smooth muscle actin expression was significantly increased in all CsA-treated rats. Analysis of the different subpopulations of inflammatory cells recruited into the chronically injured kidney revealed a marked influx of macrophages into fibrotic cortical foci of CsA-treated rats. The number of cortical macrophages was highest in the group receiving the highest CsA dose. PAI-1 antigen, present in proximal tubular lysosomes in kidneys from all experimental groups, stained very intensely in atrophic tubules in CsA-treated rats. Both stromelysin and interstitial collagenase mRNA were expressed in the kidneys of control rats, but their message transcription remained unaltered after CsA treatment. In contrast, the expression of tissue inhibitor of matrix metalloproteinase type 1 (TIMP-1) was significantly increased after CsA treatment. TIMP-1 mRNA was undetectable in renal sections from sodium-depleted vehicle-treated animals using the in situ hybridization (ISH) technique. ISH of selected renal sections of CsA-treated rats identified the cells responsible for the increased TIMP-1 message transcription after CsA administration, mainly as interstitial cells and also as visceral and parietal epithelial cells.

CONCLUSIONS

These results suggest that the locally increased expression of TIMP-1 rather than a decrease of matrix metalloprotease expression, contributes to the development of CsA-induced focal interstitial fibrosis in the rat.

Increased gelatinolytic activity in bronchoalveolar lavage fluid in stable lung transplant recipients

Proteolytic enzymes have been proposed to play a role in the pathogenesis of various inflammatory pulmonary diseases accompanied by parenchymal remodeling. To assess the role of inflammatory cells and proteolytic enzymes in the development of chronic allograft rejection after lung transplantation, bronchoalveolar lavage fluid (BALF) samples from clinically stable lung transplant (LT) recipients (i.e., without evidence of active infection or rejection), heart transplant (HT) recipients, and healthy volunteers (NL) were analyzed for total white blood cell (WBC) count and differential cell count, along with gelatinolytic/type IV collagenolytic activity. The LT group displayed a significantly increased total WBC count, neutrophil count, and percent neutrophils compared with the NL group, confirming the presence of inflammation. Furthermore, gelatin zymography revealed a significant increase in activity of the 72 and 92 kD gelatinases in the LT group compared with the NL group. A positive correlation existed between neutrophil counts and the increase in proteolytic activity. Immunosuppressive therapy did not account for the findings, since no significant difference in cell counts or proteolytic activity existed between the NL and HT control groups. These findings, together with those of others that relate chronic lung allograft dysfunction to an increase in BALF neutrophils and collagen matrix remodeling, collectively indicate that up-regulated proteolytic activity may have a role in chronic rejection after lung transplantation.

Effects of the immunosuppressive drugs CsA and FK506 on intracellular signalling and gene regulation

The isolation of Cyclosporin A (CsA) from cultures of the fungus Tolypocladium inflatum and its subsequent elucidation of immunosuppressive properties by Borel et al. (1) was of great clinical consequence. In the early 80s CsA was introduced in the field of organ transplantation resulting in extraordinary improvements of graft survival. CsA has become a first choice drug for patients with allograft organs. The discovery of FK506 by Kino et al. (2) as a novel immuno-suppressant and its introduction into clinics in 1989 (3) extended the available regimen for immunosuppressive therapy. Yet despite their advantages both CsA and FK506 display unwanted side effects and a possible preference of one drug over another remains controversial (4, 5). Although identification of the involvement of the transcription factor NF-AT was an important step forward (6), it has become clear that immunosuppressant action is more complex. CsA and FK506 selectively interact with certain cellular signal transduction pathways. This review briefly describes these effects on signal transduction. We further concentrate on the major known effect of these immunosuppressants, namely the inhibition of the PP2B phosphatase calcineurin. In addition we provide a compilation of effects of CsA and FK506 on gene expression at the level of transcription.

Modulation of intracellular calcium levels inhibits secretion of collagenase 1 by migrating keratinocytes

Calcium concentration influences keratinocyte differentiation, and, following injury, keratinocytes move through an environment of changing calcium levels. Because these migrating cells in wounds invariably express collagenase 1, we assessed if modulation of calcium levels regulates collagenase 1 production by primary human keratinocytes. Accurately reflecting the confined spatial pattern of enzyme production seen in vivo, collagenase 1 mRNA was expressed only by keratinocytes migrating from foci of differentiated cells. Treatment with calcium ionophores A23187 or thapsigargin markedly inhibited the basal and phorbol 12-myristate 13-acetate-(PMA) stimulated accumulation of keratinocyte collagenase 1 in the medium but did not affect collagenase 1 production by control or PMA-treated fibroblasts. A23187-mediated inhibition of collagenase 1 protein was not associated with a decrease in mRNA levels but rather was controlled by a selective and reversible block of enzyme secretion. This block in secretion was likely not due to altered protein folding as the proenzyme within A23187-treated cells remained capable of autolytic activation upon treatment with p-aminophenylmercuric acetate. In contrast, 92-kDa gelatinase mRNA and secreted protein levels were coordinately reduced by A23187. Keratin 14 expression, a basal keratinocyte marker, was reduced with PMA treatment, but A23187 did not affect keratin 14 expression. In human wounds, both basal and suprabasal keratinocytes at the migrating front of epidermis stained for keratin 14, but only the basal cells expressed collagenase 1. These data suggest that collagenase 1 production is not necessarily linked with expression of basal cell markers and that modulation of intracellular calcium levels can block secretion of collagenase 1 by keratinocytes which have moved away from the stratum basalis and from their natural substrate.

Regulation of membrane-type matrix metalloproteinase-1 expression by growth factors and phorbol 12-myristate 13-acetate

Overexpression of membrane-type matrix metalloproteinase (MT-MMP-1) results in the activation of both endogenous and exogenous 72-kDa gelatinase. To understand the effects of MT-MMP-1 on 72-kDa gelatinase activation, we analyzed its expression in human fibroblasts and HT-1080 fibrosarcoma cells. Both cell types expressed the MT-MMP-1 mRNA constitutively at a considerable level and treatment of cells with PMA enhanced the expression about 2-3-fold. Concanavalin A treatment increased MT-MMP-1 mRNA levels in fibroblasts about 4-fold. Induction of MT-MMP-1 by phorbol 12-myristate 13-acetate (PMA) required protein synthesis as shown by cycloheximide inhibition. The induction was also inhibited by dexamethasone. Analysis of MT-MMP-1 mRNA stability using actinomycin D indicated that the half-life was rather long and not affected by PMA, suggesting transcriptional regulation. Only HT-1080 cells had significant 72-kDa gelatinase processing activity after treatment with PMA or concanavalin A, while fibroblasts were virtually negative. Immunoblotting analysis of fibroblast lysates indicated that MT-MMP-1 was present mainly in a 60-kDa form. PMA and concanavalin A caused 2-4-fold increases in its protein levels, while in HT-1080 cells PMA, concanavalin A, or overexpression of MT-MMP-1 did not significantly enhance the level of the 60-kDa protein. Instead, an immunoreactive, proteolytically processed 43-kDa form was observed, and its appearance correlated to 72-kDa gelatinase processing activity. Thus 72-kDa gelatinase activation, while enhanced by MT-MMP-1 expression, needs additional co-operating factors.

TNF-R55-specific form of human tumor necrosis factor-alpha induces collagenase gene expression by human skin fibroblasts

Tumor necrosis factor-alpha (TNF-alpha) is a potent inhibitor of connective tissue formation. The cellular effects of TNF-alpha are mediated by two distinct cell-surface receptors, TNF-R55 and TNF-R75, both present on various types of cells, including fibroblasts. In this study we wanted to elucidate the role of TNF-R55 as a mediator of the connective tissue effects of TNF-alpha by using a mutant, TNF-R55-specific form of human TNF-alpha. This mutant TNF-alpha markedly induced collagenase and stromelysin-1 gene expression in dermal fibroblasts, the maximal activation (up to 42-fold) being 65%-89% of that noted with wild-type human TNF-alpha. In addition, TNF-R55-specific TNF-alpha suppressed type I collagen mRNA levels as potently as wild-type TNF-alpha (by 60%). The enhancement of collagenase gene expression by TNF-R55-specific TNF-alpha was augmented by simultaneous treatment of normal and scleroderma skin fibroblasts with interferon-gamma, indicating specific enhancement of TNF-R55 signaling pathway by interferon-gamma. These results show that stimulation of the TNF-R55 signaling pathway is sufficient for the inhibitory effects of TNF-alpha on extracellular matrix formation by dermal fibroblasts. It is conceivable that due to reduced systemic toxicity, TNF-R55-specific forms of human TNF-alpha may prove to be feasible in the therapy of fibrotic disorders.