Interferon-gamma inhibits experimental renal fibrosis

Cytokine regulation of pulmonary fibrosis in scleroderma

Pulmonary fibrosis occurs in up to 70% of scleroderma patients and progresses to cause severe restrictive lung disease in about 15% of patients. The mechanisms that cause pulmonary fibrosis in scleroderma remain incompletely understood. Increased amounts of mRNA or protein for multiple profibrotic cytokines and chemokines have been identified in lung tissue or broncholveolar lavage samples from scleroderma patients, when compared to healthy controls. These cytokines include transforming growth factor (TGF)-beta, connective tissue growth factor (CTGF), platelet-derived growth factor (PDGF), oncostatin M (OSM), monocyte chemotactic factor-1 and pulmonary and activation-regulated chemokine (PARC). Potential cellular sources of these profibrotic cytokines and chemokines in scleroderma lung disease include alternatively activated macrophages, activated CD8+ T cells, eosinophils, mast cells, epithelial cells and fibroblasts themselves. This review summarizes the literature on involvement of cytokines and chemokines in the development of pulmonary fibrosis in scleroderma.

Mechanisms of pulmonary fibrosis

Tissue injury evokes highly conserved, tightly regulated inflammatory responses and less well-understood host repair responses. Both inflammation and repair involve the recruitment, activation, apoptosis, and eventual clearance of key effector cells. In this review, we propose the concept of pulmonary fibrosis as a dysregulated repair process that is perpetually "turned on" even though classical inflammatory pathways may be dampened or "switched off." Significant regional heterogeneity, with varied histopathological patterns of inflammation and fibrosis, has been observed in individual patients with idiopathic pulmonary fibrosis. We discuss environmental factors and host response factors, such as genetic susceptibility and age, that may influence these varied manifestations. Better understanding of the mechanisms of lung repair, which include alveolar reepithelialization, myofibroblast differentiation/activation, and apoptosis, should offer more effective therapeutic options for progressive pulmonary fibrosis.

Mechanisms of spontaneous resolution versus fibrosis in granulomatous experimental autoimmune thyroiditis

When granulomatous experimental autoimmune thyroiditis (G-EAT) was induced in CBA/J or DBA/1 mice, thyroid lesions resolved in less severe (3+) G-EAT in wild-type mice or severe (5+) G-EAT in IFN-gamma(-/-) mice, but progressed to fibrosis in 5+ G-EAT in wild-type mice. To define the mechanisms leading to these distinct outcomes, the expression of inflammatory and apoptotic molecules and infiltrating cells was evaluated using immunohistochemistry, RT-PCR, and confocal microscopy. The ratio of CD4(+)/CD8(+) T cells in thyroid infiltrates was one factor that predicted G-EAT outcome. CD4(+) T cells outnumbered CD8(+) T cells when lesions progressed to fibrosis, while CD8(+) T cells outnumbered CD4(+) T cells in thyroids that resolved. Fas, Fas ligand, FLIP, TNF-alpha, inducible NO synthase, TGF-beta, and IFN-gamma were highly expressed by infiltrating cells when G-EAT progressed to fibrosis. The expression of active caspase-3 was low, possibly contributing to the persistence of CD4(+) T cells in fibrosis. In contrast, FLIP was mainly expressed by thyrocytes in resolving G-EAT, the expression of active caspase-3 was high, and resolution correlated with apoptosis of infiltrating cells. There was also relatively less expression of TGF-beta, IFN-gamma, TNF-alpha, and inducible NO synthase and higher expression of IL-10 in resolving G-EAT than in G-EAT that progressed to fibrosis. These differences were particularly striking when comparing IFN-gamma(-/-) vs wild-type mice. These results suggest that several opposing biological mechanisms contribute to the outcome of an ongoing autoimmune response. These include differential expression of pro- and antiapoptotic molecules, cytokines, and the ratio of CD4(+) vs CD8(+) T cells.

Gamma interferon as an antifibrosis agent in skeletal muscle

Muscle injuries are a common problem in sports medicine. Skeletal muscle can regenerate itself, but the process is both slow and incomplete. Previously we and others have used growth factors to improve the regeneration of muscle, but the muscle healing was impeded by scar tissue formation. However, when we blocked the fibrosis process with decorin, an antifibrosis agent, we improved the muscle healing. Here we show that gammainterferon (gammaINF)--a cytokine that inhibits the signaling of transforming growth factor beta1 (TGFbeta1), a fibrotic stimulator--reduces fibrosis formation and improves the healing of lacerated skeletal muscle. With gammaINF treatment, the growth rate of muscle-derived fibroblasts was reduced and the level of fibrotic protein expression induced by TGFbeta1 (including TGFbeta1, vimentin, and alpha-smooth muscle actin) was down-regulated in vitro. In a mouse laceration model, the area of fibrosis decreased when gammaINF was injected at either 1 or 2 weeks after injury. More importantly, the injection of gammaINF at either 1 or 2 weeks post-injury was found to improve muscle function in terms of both fast-twitch and tetanic strength. This study demonstrates that gammaINF is a potent antifibrosis agent that can improve muscle healing after laceration injury.

IFN-gamma fails to antagonize fibrotic effect of TGF-beta on keloid-derived dermal fibroblasts

BACKGROUND

Interferon-gamma (IFN-gamma) has been noted as a potential therapeutic agent for various fibrotic disorders, in part, through its antagonistic effect on a fibrogenic cytokine, transforming growth factor-beta (TGF-beta). Keloid is a fibrotic skin disorder that results in an excessive deposition of extracellular matrix, which is associated with altered-expression of or -responses to TGF-beta in dermal fibroblasts.

OBJECTIVE

We sought to determine whether IFN-gamma antagonized TGF-beta-mediated fibrotic response in keloid-derived dermal fibroblasts.

METHODS

Type I collagen production, fibroblast contractile activity, and alpha-smooth muscle actin (alpha-SMA) expression were assessed by using Western blotting, an in vitro type I collagen gel contraction assay, and immunofluorescence study in normal and keloid-derived human dermal fibroblasts in the presence or absence of IFN-gamma and/or TGF-beta.

RESULTS

In contrast to normal dermal fibroblasts, IFN-gamma did not inhibit TGF-beta-induced type I collagen production, contractile activity, and alpha-SMA expression in keloid-derived dermal fibroblasts. In addition, keloid-derived dermal fibroblasts constitutively expressed type I collagen and alpha-SMA with increased capacity to contract a collagen matrix.

CONCLUSION

IFN-gamma failed to antagonize TGF-beta-mediated fibrotic response in keloid-derived dermal fibroblasts. Thus, IFN-gamma may not be therapeutically useful for keloid and clarification of the molecular mechanisms underlying the IFN-gamma resistance should be investigated for therapeutic application of IFN-gamma for keloid.

Effects of caspase inhibition on the progression of experimental glomerulonephritis

BACKGROUND

Caspase-3 has a central role in the execution of apoptosis. In a nephrotoxic nephritis (NTN) model, we previously demonstrated an up-regulation of caspase-3 that was associated with inappropriate renal apoptosis, inflammation, tubular atrophy, and renal scarring.

METHODS

We applied a pan caspase inhibitor, Boc-Asp (OMe)-fluoro-methyl-ketone (B-D-FMK), directly to rat NTN kidney using an intrarenal cannula fed from an osmotic pump. Animals were treated either for the first 7 days (acutely) to determine the effects on renal inflammation (ED-1 staining) and apoptosis (in situ end labeling of fragmented DNA), or for 28 days commencing 15 days after NTN (chronically) to observe the effects on cell death and renal fibrosis. Changes of caspase-3 and caspase-1 activity were detected by fluorometric substrate cleavage assay. Changes in caspase-3 and caspase-1, interleukin-1 beta (IL-1 beta), and collagen I, III, and IV proteins and mRNA were detected by Western blotting and Northern blotting, respectively.

RESULTS

In both treated groups, caspase-3 activity was inhibited, and 17 and 24 kD active caspase-3 proteins were reduced significantly. A compensatory increase of caspase-3 mRNA occurred in the acutely treated group, but decreased in the chronically treated group (P < 0.05). Although there were no significant changes in caspase-1 activity and its active protein, the observed decrease in its precursor in the chronic group was increased by treatment (P < 0.05). Further, IL-1 beta precursor and its mRNA were significantly reduced by treatment only in the chronically treated group. Apoptosis was decreased in the glomeruli of acutely treated rats, and in the tubules and interstitium of chronically treated animals (P < 0.05). Glomerular inflammation was decreased only in the acutely treated group, whereas tubulointerstitial inflammation was lowered in both treated groups (P < 0.05). Glomerulosclerosis was reduced in both inhibitor groups, with a reduction in tubulointerstitial fibrosis and collagen I, III, and IV mRNA restricted to chronically treated animals (P < 0.05). Proteinuria was significantly decreased with caspase inhibition in both treated groups, but not serum creatinine level.

CONCLUSION

This study clearly indicates that caspase inhibition reduces renal apoptosis, ameliorates inflammation and fibrosis, and improves proteinuria in experimental glomerulonephritis, which may mainly be related to changes in the caspase enzymatic system.

Gene therapy and tissue engineering for sports medicine

Sports injuries usually involve tissues that display a limited capacity for healing. The treatment of sports injuries has improved over the past 10 to 20 years through sophisticated rehabilitation programs, novel operative techniques, and advances in the field of biomechanical research. Despite this considerable progress, no optimal solution has been found for treatment of various sports-related injuries, including muscle injuries, ligament and tendon ruptures, central meniscal tears, cartilage lesions, and delayed bone fracture healing. New biological approaches focus on the treatment of these injuries with growth factors to stimulate and hasten the healing process. Gene therapy using the transfer of defined genes encoding therapeutic proteins represents a promising way to efficiently deliver suitable growth factors into the injured tissue. Tissue engineering, which may eventually be combined with gene therapy, may potentially result in the creation of tissues or scaffolds for regeneration of tissue defects following trauma. In this article we will discuss why gene therapy and tissue engineering are becoming increasingly important in modern orthopaedic sports medicine practice. We then will review recent research achievements in the area of gene therapy and tissue engineering for sports-related injuries, and highlight the potential clinical applications of this technology in the treatment of patients with musculoskeletal problems following sports-related injuries.

Complex cytokine regulation of tissue fibrosis

Tissue fibrosis, a serious and even deadly complication of chronic inflammation and environmental exposures, is regulated by a host of factors including interactions with the extracellular matrix, surface of inflammatory cells, hormones, and an extremely complex and redundant network of profibrotic cytokines. The nature of mechanisms by which cytokines regulate fibrosis is dual - indirect, through attraction of inflammatory cells, and direct, through binding to specific receptors on fibroblasts and stimulating proliferation, collagen production and secretion of autocrine factors. This review focuses on systematizing the direct effects of cytokines on fibroblasts. Understanding of the complexity of the cytokine-driven mechanisms of fibrosis is important for identification of potential molecular targets for future pharmacological interventions in prevention and treatment of tissue fibrosis.

[Do the interferons have an antifibrotic action? The internist's point of view]

PURPOSE

The antifibrotic action of interferon alpha on the liver is now established in hepatitis C (cf. article by T. Poynard). Numerous in vitro experimental evidences may lead people into believing in the efficacy of interferon gamma in patients with mucous membrane and pulmonary fibrosis.

CURRENT KNOWLEDGE AND KEY POINTS

A randomized study has confirmed the efficacy of interferon gamma in the idiopathic pulmonary fibrosis, probably by an anti TGF beta action. Several open studies have shown the efficacy of interferon gamma in patients with post-radiation cutaneous fibrosis (Chernobyl survivors, sequelae of radiotherapy for cancer). In systemic sclerosis, several teams have shown that interferon gamma reduced collagen synthesis by sclerodermic fibroblasts in vitro. Four open studies have also confirmed the efficacy of interferon gamma in systemic sclerosis. In our experience concerning 20 patients with diffuse systemic sclerosis, the five years survival with long term therapy was 85% and we observed an improvement in the cutaneous suppleness in 40% of these cases. There was no serious side effect.

FUTURE PROSPECTS AND PROJECTS

These encouraging results need to be confirmed by large randomized studies in pulmonary fibrosis and systemic sclerosis. Other indications should be assessed, particularly extra-cutaneous radiation sequelae and in systemic fibrosis (retroperitoneal, mediastinal and cervical).

Proteoglycan expression in bleomycin lung fibroblasts: role of transforming growth factor-beta(1) and interferon-gamma

Bleomycin (BM)-induced pulmonary fibrosis involves excess production of proteoglycans (PGs). Because transforming growth factor-beta(1) (TGF-beta(1)) promotes fibrosis, and interferon-gamma (IFN-gamma) inhibits it, we hypothesized that TGF-beta(1) treatment would upregulate PG production in fibrotic lung fibroblasts, and IFN-gamma would abrogate this effect. Primary lung fibroblast cultures were established from rats 14 days after intratracheal instillation of saline (control) or BM (1.5 units). PGs were extracted and subjected to Western blot analysis. Bleomycin-exposed lung fibroblasts (BLF) exhibited increased production of versican (VS), heparan sulfate proteoglycan (HSPG), and biglycan (BG) compared with normal lung fibroblasts (NLF). Compared with NLF, BLF released significantly increased amounts of TGF-beta(1). TGF-beta(1) (5 ng/ml for 48 h) upregulated PG expression in both BLF and NLF. Incubation of BLF with anti-TGF-beta antibody (1, 5, and 10 microg/ml) inhibited PG expression in a dose-dependent manner. Treatment of BLF with IFN-gamma (500 U. ml(-1) x 48 h) reduced VS, HSPG, and BG expression. Furthermore, IFN-gamma inhibited TGF-beta(1)-induced increases in PG expression by these fibroblasts. Activation of fibroblasts by TGF-beta(1) promotes abnormal deposition of PGs in fibrotic lungs; downregulation of TGF-beta(1) by IFN-gamma may have potential therapeutic benefits in this disease.

Synergy between CD40 ligation and IL-4 on fibroblast proliferation involves IL-4 receptor signaling

Fibrosis can be an undesired consequence of activated cellular immune responses. The purpose of this work was to determine whether CD40 ligation and the pro-fibrotic cytokine IL-4 interact in regulating fibroblast proliferation and collagen production, and, if so, the mechanisms used. This study found that the combination of IL-4 and ligation of CD40 on the fibroblast cell surface had synergistic effects in stimulating fibroblast proliferation. In contrast, CD40 ligation negated the inhibitory effects of IFN-gamma on fibroblast proliferation. Western blotting analyses of fibroblast crude lysates revealed that a potential mechanism of the synergy between CD40 ligation and IL-4 was the phosphorylation of proteins at 130 kDa and, to a lesser degree, at 95, 85, and 75 kDa. Immunoprecipitation-Western blotting experiments showed that phosphorylation levels of IL-4Ralpha, Janus kinase 1, insulin receptor substrate 1, and insulin receptor substrate 2, factors with molecular mass close to the observed 130 kDa major phosphorylation band, increased in response to the combined CD40 ligation and IL-4 action. In contrast, there was no evidence that synergy was mediated by an increased expression of IL-4Ralpha chain, CD40, or the autocrine profibrotic cytokines IL-6 and TGF-beta. These findings suggest that CD40-CD40 ligand contacts between fibroblasts and cells secreting IL-4 may promote the profibrotic effects of IL-4 by affecting signal transduction and reducing the anti-fibrotic effects of IFN-gamma.

Potential methods to prevent interstitial fibrosis in renal disease

Almost all forms of end stage renal disease (ESRD) are characterised by progressive interstitial fibrosis and tubular atrophy. Since most forms of chronic renal failure are initiated by inflammatory processes, anti-inflammatory strategies can be successful, if initiated early, in preventing progression of the disease process. Unfortunately, in most cases the disease is only detected clinically following robust progression of interstitial fibrosis. In these patients, control of secondary risk factors, such as hypertension and hyperglycaemia, can slow the progression rate but cannot stop the process completely. Certainly, ACE inhibitors remain the mainstay of preserving renal function. However, additional therapies are needed for the effective treatment of progressive renal fibrosis. A number of compounds have shown some very potent antifibrotic properties in vitro and in vivo, and are currently undergoing further evaluation. This review discusses the most promising among them. However, few of the therapeutic agents discussed here have been tested clinically. Studies evaluating the potential of a number of these have just commenced whereas for many others clinical use is still many years away. However, some very promising reagents may enhance our clinical arsenal within a relatively short period of time.

Interleukin-13 induces tissue fibrosis by selectively stimulating and activating transforming growth factor beta(1)

Interleukin (IL)-13 is a key mediator of tissue fibrosis caused by T helper cell type 2 inflammation. We hypothesized that the fibrogenic effects of IL-13 are mediated by transforming growth factor (TGF)-beta. To test this hypothesis we compared the regulation of TGF-beta in lungs from wild-type mice and CC10-IL-13 mice in which IL-13 overexpression causes pulmonary fibrosis. IL-13 selectively stimulated TGF-beta(1) production in transgenic animals and macrophages were the major site of TGF-beta(1) production and deposition in these tissues. IL-13 also activated TGF-beta(1) in vivo. This activation was associated with decreased levels of mRNA encoding latent TGF-beta-binding protein-1 and increased mRNA encoding urinary plasminogen activator, matrix metalloproteinase (MMP)-9, and CD44. TGF-beta(1) activation was abrogated by the plasmin/serine protease antagonist aprotinin. It was also decreased in progeny of crosses of CC10-IL-13 mice and MMP-9 null mice but was not altered in crosses with CD44 null animals. IL-13-induced fibrosis was also significantly ameliorated by treatment with the TGF-beta antagonist soluble TGFbetaR-Fc (sTGFbetaR-Fc). These studies demonstrate that IL-13 is a potent stimulator and activator of TGF-beta(1) in vivo. They also demonstrate that this activation is mediated by a plasmin/serine protease- and MMP-9-dependent and CD44-independent mechanism(s) and that the fibrogenic effects of IL-13 are mediated, in great extent, by this TGF-beta pathway.

Temporary warm ischaemia, 5/6 nephrectomy and single uranyl nitrate administration--comparison of three models intended to cause renal fibrosis in rats

In patients the progression of pathologic renal processes after the treatment of primary disease is a problem of increasing importance and therapeutic strategies are insufficient till now. The aim of this paper was to search for rat models of interstitial fibrosis as a basis for testing therapeutic strategies to prevent end-stage renal failure. Experiments were done on adult female Wistar rats (Han:Wist) to investigate long-term consequences of temporary warm ischaemia, 5/6 nephrectomy (5/6 NX) and single uranyl nitrate (UN) administration (0.3 or 0.5 mg/ 100 g body wt. intraperitoneally). Observation time was 20 weeks after injury in each group. Creatinine clearance, urinary protein excretion and hydroxy-proline (OH-proline) concentration in renal tissue were measured and light microscopic investigations were done to characterise both quality and time course of long-term renal damage in relation to matched control animals. Temporary warm ischaemia and 5/6 NX did not cause any fibrotic changes during the 20 weeks observation period. The higher UN dose led to decreased creatinine clearance, increased urinary protein excretion and enhanced OH-proline concentration in renal tissue. Morphologic investigations showed fibrotic areas containing strongly dilated and atrophic tubules with thickened basal membranes. These effects can be seen from week four after UN administration up to the end of the observation period. In conclusion, administration of one single dose of UN is a simple procedure to induce interstitial renal fibrosis as an experimental model to investigate therapeutic strategies for their prevention.

Fibrosis of the lung and other tissues: new concepts in pathogenesis and treatment

Tissue fibrosis can lead to significant organ dysfunction and resulting patient morbidity and mortality. Unfortunately, the therapeutic repertoire is currently limited, nonspecific, and largely ineffective. While the pathogenesis is incompletely understood, evidence is accumulating that immune and cytokine mediated mechanisms are critical. In this review, data will be provided to support the role of Type 2 cytokines in the pathogenesis of fibrosis. The importance of the role of the pro-fibrogenic cytokine TGF-beta and CD40-CD40 ligand mediated fibroblast activation will also be evaluated. Finally, novel therapeutic options based on inhibiting these pathways will be described.

Renal fibrosis: an update

Tubulointerstitial fibrosis invariably accompanies the course of chronic renal failure towards end-stage renal disease. Tubular epithelial cells, the predominant cell type in the tubulointerstitium, are increasingly being recognized for playing a dominant role as mediators of renal fibrogenesis. Tubular epithelial cells become activated either by the glomerular ultrafiltrate from their apical side or by mononuclear cells from their basolateral side. They initiate the scarring process by secreting chemokines, which in return attract mononuclear cells as well as growth factors that stimulate interstitial fibroblasts. In later phases of renal fibrogenesis, cellular changes of tubular epithelial cells contribute to the chronic impairment of renal function. Whereas tubular epithelial cells react by proliferation or hypertrophy to initial stimuli, they may undergo apoptosis or transdifferentiate into fibroblasts, and thus contribute to tubular atrophy in later stages of progressive renal disease. Resident interstitial fibroblasts are also important in renal fibrogenesis, and recent research has demonstrated that these cells are much more heterogeneous than expected. Cytokines such as fibroblast growth factor type 2 and epithelial growth factor have been shown to be pro-fibrogenic, whereas hepatocyte growth factor and bone morphogenic protein type 7 may inhibit fibrogenesis. Despite recent progress, further research is mandatory for a better understanding and the development of novel therapeutic approaches.

Myofibroblast: a prognostic marker and target cell in progressive renal disease

Myofibroblasts play an important role in many tissue injuries, and particularly in renal disease. The myofibroblast differentiation is an early event in the development of fibrosis. Myofibroblast-like cells express smooth muscle (SM) cytoskeletal markers (alpha-SM actin in particular) and participate actively in the production of extracellular matrix. Identification of early risk factors, particularly histological criteria, could be useful to identify patients at risk of progressive renal failure and needing a treatment. The evaluation of myofibroblast differentiation in renal tissue may reflect the intensity of tissue injury, predict long term outcome of chronic renal disease and help physicians to select therapeutic choices. More than a disease activity indicator. myofibroblasts appear to be a pivotal target for future therapies in progressive renal disease.

Tubulointerstitial renal disease

Tubulointerstitial damage, in progressive chronic renal disease of all types, arises because of a complex interplay between factors in the tubular lumen, tubular epithelial cells, peritubular capillaries, resident and infiltrating interstitial cells and extracellular matrix. Particularly in proteinuric renal disease, tubular epithelial cells play a central role in orchestrating these events. In response to mediators arising systemically, in the tubular lumen or from other renal cells, tubular epithelial cells undergo a complex series of structural and functional changes and produce a bewildering number of soluble and fixed mediators, which in turn lead to interstitial inflammation and fibrosis. Knowledge of these interactions has increased exponentially over the past decade, and has defined a number of new targets for treatment. Both expansion and consolidation of this knowledge is needed to determine which of these targets holds the most promise for future treatment.

Role of cellular infiltrates in response to proteinuria

Tubulointerstitial injury caused by multiple insults, including significant proteinuria, results in interstitial inflammation. Evidence supports the hypothesis that interstitial inflammatory cells initially recruited in response to injury subsequently contribute to interstitial fibrosis. Experimental manipulations that decrease the number of interstitial macrophages (Mphis) preserve renal function. Mphis have the potential to secrete a large number of products, including some with fibrosis-promoting effects. Their most potent profibrotic effect may be the production of soluble fibrogenic factors, such as transforming growth factor-ss, endothelin-1, and tumor necrosis factor-alpha. These factors stimulate the synthesis of extracellular matrix proteins by neighboring myofibroblasts. Mphis may also release inhibitors of such matrix-degrading proteases as tissue inhibitor of metalloproteinase-1 and plasminogen activator inhibitor-1. Protease inhibitors have a role in renal scarring by impairing the process of matrix remodeling and degradation, which normally functions in parallel with matrix synthesis. It is predicted that therapeutic interventions that dampen the interstitial inflammatory response will attenuate the renal fibrogenic response, preserving normal renal architecture and function.