Immune interferon inhibits collagen synthesis by rheumatoid synovial cells associated with decreased levels of the procollagen mRNAs

The systemic administration of gamma interferon inhibits collagen synthesis and acute inflammation in a murine skin wounding model

The ability of gamma interferon (IFN-gamma) to affect cutaneous collagen synthesis in vivo was examined in a murine wounding model. Reproducible areas of full-thickness skin necrosis were produced by argon laser radiation. Mice received recombinant murine IFN-gamma (rMuIFN-gamma) (8.7 X 10(3) units/hr) over 14 d via osmotic pumps implanted subcutaneously or intraperitoneally. At 14 and 21 d after wounding, there was less fibrous tissue in healing scars of treated animals as determined by light and transmission electron microscopy. Associated with the decrease in connective tissue was an increase in the acid mucopolysaccharide content of healing scars, which was largely hyaluronate. Quantitative image analysis of electron micrographs confirmed that less collagen was present in healing scars of animals receiving rMuIFN-gamma. The mean cross-sectional area of collagen fibers was smaller in specimens from treated mice, but no difference was seen in the size of collagen fibrils. The time required to obtain full skin closure was also delayed 23%-27% in treated animals. Using this injury model, we also found that rMuIFN-gamma significantly reduced the degree of perilesional erythema surrounding the laser injury sites and, in the first 6 d after wounding, the degree of polymorphonuclear infiltrate present histologically at lesional sites. Indeed, rMuIFN-gamma also decreased the cutaneous accumulation of neutrophils induced by known proinflammatory mediators, such as interleukin 1 and activated serum. Thus, systemically administered IFN-gamma not only down-regulates collagen synthesis in the skin but also modulates in a previously unrecognized manner: neutrophil accumulation at sites of tissue injury in vivo.

Synergistic effect of tumor necrosis factor-alpha and interferon-gamma on collagen synthesis of human skin fibroblasts in vitro

The effect of tumor necrosis factor-alpha (TNF alpha) and interferon-gamma (IFN gamma) on collagen metabolism by human diploid fibroblasts in confluent monolayer culture was examined. Recombinant TNF alpha reduced collagen mRNA levels 2-fold and stimulated collagenase mRNA levels 5-fold, while recombinant IFN gamma affected only collagen mRNA levels. The combination of TNF alpha (10 ng/ml) and IFN gamma (100 ng/ml) resulted in a much stronger (about 30-fold) reduction of collagen mRNA levels indicating that the two cytokines act synergistically. In contrast no such synergism was observed with respect to collagenase mRNA levels. The effect of TNF alpha and IFN gamma on collagen metabolism reported here indicates a complex interaction of different cytokines in the control of tissue remodeling that occurs during inflammation, repair, or atrophy.

Transcription of human type I collagen genes. Variation in the relative rates of transcription of the pro alpha 1 and pro alpha 2 genes

The relative rates of transcription of the two genes for type I collagen have been measured in a runoff transcription assay using nuclei isolated from cultured human fibroblasts. Control experiments indicated that the ratio of pro alpha 1(I)/pro alpha 2(I) transcripts detected with a given nuclear preparation did not vary over a range of transcription times, nuclei concentrations, and amounts of filter-bound cDNA used in the assay. However, a significant difference in the ratio was observed when nuclei isolated from cells grown under different conditions were used. Nuclei from sub-confluent cultures generally transcribed the two genes in a ratio of 2:1 or lower, while nuclei from post-confluent cultures transcribed the genes in a much higher ratio of about 4:1. Analysis of the amount of pro alpha 1(I) and pro alpha 2(I) RNA transcribed suggests that it is the transcription of the pro alpha 1(I) gene, and not the pro alpha 2(I) gene, that varies with culture conditions. The steady state ratios of pro alpha 1(I)/pro alpha 2(I) RNA remained near 2:1 under all conditions. Thus, some post-transcriptional mechanism apparently results in maintenance of the steady-state pro alpha 1(I)/pro alpha 2(I) RNA ratios at approximately 2:1.

Some recombinant human cytokines stimulate glycosaminoglycan synthesis in human synovial fibroblast cultures and inhibit it in human articular cartilage cultures

Recombinant human cytokines were compared for their effects on glycosaminoglycan (GAG) synthesis in human synovial fibroblast cultures and human articular cartilage explant cultures. In fibroblast cultures, recombinant human interleukin-1 alpha (rHuIL-1 alpha), rHuIL-1 beta, and recombinant human tumor necrosis factor alpha (rHuTNF alpha) stimulated hyaluronic acid (HA) production and, to a lesser extent, sulfated GAG production, while recombinant human gamma-interferon did not have a significant effect. Half-maximal stimulation of HA by rHuIL-1 beta was 0.14 pM, while stimulation for rHuIL-1 alpha and rHuTNF alpha was 1.6 pM and 32 pM, respectively. Indomethacin (10 micrograms/ml) had no influence on HA stimulation by cytokines, while hydrocortisone (2-10 micrograms/ml) caused a significant reduction. In articular cartilage cultures, the cytokines inhibited production of sulfated GAGs. The activity of rHuIL-1 beta was greater than that of rHuIL-1 alpha (half-maximal inhibition at 0.71 pM and 4.7 pM, respectively) and both were considerably more active than rHuTNF alpha; gamma-interferon again had no significant effect. Neither indomethacin nor hydrocortisone influenced cytokine-induced inhibition by either rHuIL-1 preparation. These studies indicate that cytokines released during an inflammatory process may affect GAG synthesis in human joint tissues and may have opposite effects on GAG synthesis in different types of connective tissues.

Interleukin 1 suppresses expression of cartilage-specific types II and IX collagens and increases types I and III collagens in human chondrocytes

In inflammatory diseases such as rheumatoid arthritis, functions of chondrocytes including synthesis of matrix proteins and proteinases are altered through interactions with cells of the infiltrating pannus. One of the major secreted products of mononuclear inflammatory cells is IL-1. In this study we found that recombinant human IL-1 beta suppressed synthesis of cartilage-specific type II collagen by cultured human costal chondrocytes associated with decreased steady state levels of alpha 1 (II) and alpha 1(IX) procollagen mRNAs. In contrast, IL-1 increased synthesis of types I and III collagens and levels of alpha 1(I), alpha 2(I), and alpha 1(III) procollagen mRNAs, as we described previously using human articular chondrocytes and synovial fibroblasts. This stimulatory effect of IL-1 was observed only when IL-1-stimulated PGE2 synthesis was blocked by the cyclooxygenase inhibitor indomethacin. The suppression of type II collagen mRNA levels by IL-1 alone was not due to IL-1-stimulated PGE2, since addition of indomethacin did not reverse, but actually potentiated, this inhibition. Continuous exposure of freshly isolated chondrocytes from day 2 of culture to approximately half-maximal concentrations of IL-1 (2.5 pM) completely suppressed levels of type II collagen mRNA and increased levels of types I and III collagen mRNAs, thereby reversing the ratio of alpha 1(II)/alpha 1(I) procollagen mRNAs from greater than 6.0 to less than 1.0 by day 7. IL-1, therefore, can modify, at a pretranslational level, the relative amounts of the different types of collagen synthesized in cartilage and thereby could be responsible for the inappropriate repair of cartilage matrix in inflammatory conditions.

Ascorbic acid specifically increases type I and type III procollagen messenger RNA levels in human skin fibroblast

In cultured human skin fibroblasts, ascorbic acid stimulates collagen production with no apparent change in the intracellular degradation of newly synthesized procollagen. To understand the basis for this effect, we measured the steady-state levels of type I and type III procollagen mRNAs in cells treated with ascorbic acid. A three- to fourfold increase in collagen synthesis was associated with a two- to threefold increase in the levels of mRNAs for both type I and type III procollagens. These effects of ascorbic acid are explained by a translational control linked either to procollagen gene transcription or mRNA degradation.

Interferon-alpha and interferon-gamma reduce excessive collagen synthesis and procollagen mRNA levels of scleroderma fibroblasts in culture

The effects of interferon-alpha and interferon-gamma on collagen synthesis and mRNA levels of type I and type III procollagens were studied in skin fibroblasts cultured from affected and unaffected skin sites of two patients with localized scleroderma (morphea). Both scleroderma cell lines exhibited elevated type I and type III procollagen mRNA levels to account for the increased procollagen synthesis, when compared to the unaffected controls. Interferon-gamma treatment resulted in a dose-dependent reduction in collagen synthesis and procollagen mRNA levels in scleroderma fibroblasts. A 72-h exposure to interferon-gamma reduced procollagen mRNA levels in the scleroderma fibroblast lines to the levels exhibited by the unaffected control fibroblasts. The suppressive effect of interferon-alpha on procollagen mRNA levels was somewhat weaker than that of interferon-gamma. The results suggest potential use of interferon-gamma in treatment and prevention of human fibrotic conditions.

Effect of murine gamma interferon on the cellular responses to bleomycin in mice

Because in vitro studies have shown inhibition of fibroblast proliferation and collagen synthesis by interferon, we tested the hypothesis that murine gamma interferon inhibits bleomycin-induced pulmonary fibrosis in mice. Mice were divided into the following groups: saline plus vehicle (27), saline plus interferon (29), bleomycin plus vehicle (26), and bleomycin plus interferon (26). Bleomycin or saline were given intratracheally once at the beginning of the experiment and vehicle (phosphate-buffered saline) or interferon was given intramuscularly daily. Mice were killed at 14 or 21 days of the experiment. About half of the mice from each group were used for collagen biochemistry and half for bronchoalveolar lung lavage, transmission electron microscopy (TEM), and morphometry. Hydroxyproline content showed a significant reduction in bleomycin plus interferon compared to bleomycin plus vehicle mice at 21 days. The saline plus vehicle and saline plus interferon mice showed no difference in hydroxyproline content. Similarly, bronchoalveolar lavage showed no differences between saline plus vehicle and saline plus interferon mice; however, all mice treated with bleomycin showed significant increases in total cells as compared to saline treated mice. At 14 and 21 days in bronchoalveolar lavage there were significantly more lymphocytes in bleomycin plus interferon compared to bleomycin plus vehicle mice. In bronchoalveolar lavage, there were usually fewer neutrophils, monocytes and macrophages in bleomycin plus interferon compared to bleomycin plus vehicle mice. Morphometric estimates of the volume of lesion within lung showed no significant differences among the bleomycin treated groups. Stainable collagen fibers were less, but not significantly, in the bleomycin plus interferon compared to bleomycin plus vehicle mice. The number of fibroblasts per volume of lesion was significantly decreased at 14 and 21 days in bleomycin plus interferon compared to bleomycin plus vehicle mice. The total volume of lymphocytes in interstitial lesions was significantly greater at 14 and 21 days in bleomycin plus interferon mice compared to bleomycin plus vehicle mice. These results suggest an inhibitory action of gamma interferon on collagen accumulation and fibroblast proliferation associated with lymphocyte accumulation in the lungs of mice following bleomycin administration.

Interleukin-1 increases collagen production and mRNA levels in cultured skin fibroblasts

In the present study we show that highly purified human interleukin-1 increases collagen production nearly 2-fold and mRNA levels of type I and III collagen over 2.5-fold in cultured normal human dermal fibroblasts. To minimize the effects of transient prostaglanding E2 production in fibroblasts treated with interleukin-1, the cell cultures were preincubated for 24 h before these measurements were made. The effects of interleukin-1 were also tested on scleroderma fibroblasts exhibiting increased collagen production. Although collagen synthesis was stimulated by interleukin-1 to some degree, the cells grown from both affected and unaffected skin areas were found to be relatively unresponsive to the effects of interleukin-1, suggesting a role for this monokine in the earlier stages of the disease process. The results also suggest that interleukin-1 has a role in stimulation of collagen synthesis under certain normal and pathological conditions in addition to stimulating fibroblast proliferation.

Elevated pro alpha 2(I) collagen mRNA levels in cultured scleroderma fibroblasts result from an increased transcription rate of the corresponding gene

Fibroblasts cultured from affected and unaffected skin sites of three scleroderma patients were studied for the activation of type I collagen gene expression. Dot blot hybridizations with pro alpha 2(I) collagen specific cDNA probe revealed 2.9-4.8-fold increases in pro alpha 2(I) mRNA levels in the affected fibroblasts over the unaffected control cells. Transcription rate of the pro alpha 2(I) gene in the nuclei isolated from the same cells was 2.0-3.7-fold higher in the scleroderma fibroblasts than in the controls. The results show that scleroderma fibroblasts have undergone activation of collagen gene expression at the transcriptional level, which subsequently results in elevated procollagen mRNA levels, overproduction of collagen, and development of dermal fibrosis.

Stimulation of procollagenase synthesis parallels increases in cellular procollagenase mRNA in human articular chondrocytes exposed to recombinant interleukin 1 beta or phorbol ester

Interleukin 1, a product predominantly of monocytes, increases the synthesis and release of procollagenase and prostaglandin E2 by mesenchymal target cells such as synovial fibroblasts and articular chondrocytes, an effect mimicked by some phorbol esters. In order to determine the mechanisms underlying these responses primary cultures of human articular chondrocytes were preincubated with recombinant human interleukin 1 beta or the phorbol ester, phorbol 12-myristate 13-acetate, in the presence or absence of the cyclooxygenase inhibitor, indomethacin. Interleukin 1 beta or phorbol ester increased the levels of procollagenase (assayed after trypsin activation) and the labeling of several medium proteins by cells incubated with [35S]methionine, independent of prostaglandin synthesis. The labeling of a 55 kD protein immunocomplexed with antibodies to procollagenase was also increased. The increased synthesis of procollagenase was paralleled by increased cellular levels of procollagenase mRNA, determined with a cDNA probe coding for human procollagenase. Thus the increased synthesis of procollagenase in response to the inflammatory mediator, interleukin 1, is controlled at a pretranslational level, possibly at the level of transcription.

Gamma-interferon inhibits collagen synthesis in vivo in the mouse

Subcutaneous implantation of osmotic pumps into CAF1 mice resulted in the formation of thick fibrous capsules around the pumps. When pumps were loaded with recombinant murine gamma-interferon (rMuIFN-gamma) to deliver 2 X 10(3) U/h for 14 d, there was a marked decrease in thickness and collagen content of the capsules from rMuIFN-gamma-treated animals compared with capsules from animals receiving diluent alone. The collagen content of the capsules was estimated by hydroxyproline analysis of the tissue and by quantitative electron microscopy of collagen bundles. Heat-inactivated rMuIFN-gamma failed to reduce the fibrotic response in this assay. These results provide compelling evidence that gamma-interferon can down-regulate collagen synthesis in vivo and suggest the possibility that this lymphokine may be useful in the treatment of disease states characterized by excessive fibrosis.

Inhibition of fibroblast chemotaxis by recombinant human interferon gamma and interferon alpha

Interferons have recently been recognized as potent mediators in inflammatory processes, exerting profound effects on fibroblasts. The influence of interferons gamma and alpha on the chemotactic movement of fibroblasts toward various attractants was, therefore, investigated. Normal human adult and embryonal dermal fibroblasts, fibrosarcoma-derived fibroblasts and SV40-transformed fibroblasts were tested against conditioned medium from fibroblasts, the chemotactic peptide C-140 of fibronectin, platelet-derived growth factor, and leukotriene B4 as attractants in the presence or absence of the interferons. Interferons gamma and alpha inhibited chemotaxis in a dose-dependent manner and at concentrations at least as low as 10(-2) ng/ml. Inhibition was noticeable when the cells were exposed to interferon for as short a period as 60 minutes, and the effect was not readily reversible. Inhibition occurred when the cells came from sparse or dense cultures, but when platelet-derived growth factor was the attractant and the cells had been grown at low density there was no inhibition. It is concluded that this is a specific effect, not to be wholly explained by overall increase in membrane rigidity. Inhibition of fibroblast chemotaxis by interferons may be an important regulatory mechanism during wound healing or fibrosis and metastatic spread of tumor cells.

Inhibition of excessive scleroderma fibroblast collagen production by recombinant gamma-interferon. Association with a coordinate decrease in types I and III procollagen messenger RNA levels

The effects of recombinant gamma-interferon (rec gamma-IFN) on collagen production by confluent monolayer cultures of progressive systemic sclerosis (PSS) dermal fibroblasts were studied. Five cell lines obtained from patients with rapidly progressive disease of recent onset were examined. All PSS fibroblast cell lines exhibited increased collagen production when compared with normal skin cell lines. It was found that rec gamma-IFN caused potent inhibition of PSS fibroblast collagen production in a concentration-dependent manner. Greater than 50% inhibition was observed with as little as 50 antiviral units/ml, and maximal effects were attained at a concentration of 500 units/ml. The rec gamma-IFN caused reproducible inhibition of collagen production by the 5 PSS fibroblast cell lines, ranging from 58.9% to 85.6% of control values. Measurement of type I and type III procollagen messenger RNA (mRNA) levels with specific complementary DNA probes demonstrated a coordinate reduction of greater than 60% in mRNA for both transcripts in rec gamma-IFN-treated cells, compared with control cells. These findings indicate that rec gamma-IFN can modulate the excessive collagen biosynthesis characteristic of PSS fibroblasts and that this effect can be explained largely by the gamma-IFN-mediated decrease in specific collagen mRNAs.

Regulation of type I collagen mRNA levels in fibroblasts

Type I procollagen mRNA levels, as well as total RNA and poly(A)-rich mRNA, remain constant when rapidly growing human fetal lung fibroblasts (HFL-1 cells) are compared with quiescent cells. Polysome profiles of cells in both growth states revealed that the distribution of type I collagen mRNA in the mRNP fraction and in polysomes also remained constant even though total RNA and poly(A)-rich mRNA were shifted from polysomes to the mRNP pool in resting cells. Similar results were obtained when RNA fractions in polysomes associated with the cytoskeletal framework were examined. It is known that procollagen production is unaffected by the growth state of cells [Breul, S. D., Bradley, K. H., Hance, A. J., Schafer, M. P., Berg, R. A. and Crystal, R. G. (1980) J. Biol. Chem. 255, 5250-5260] although total protein synthesis is markedly decreased in resting cells. It would therefore appear that the translational control responsible for reduced synthesis of non-collagenous proteins in resting cells does not extend to procollagen and that transcriptional control can account for levels of type I procollagen produced by cultured human fibroblasts.

Rheumatoid arthritis: clinical features and pathogenetic mechanisms

Rheumatoid arthritis is a disorder characterized by chronic inflammation affecting predominantly articular tissues, leading in some instances to disruption of the normal structure and function of the joint. In some patients extra-articular manifestations are also present. In the joints, the pathologic lesion consists of synovial cell proliferation with infiltration by inflammatory cells. The complex interaction among these cells is likely responsible for the connective tissue abnormalities that characterize the rheumatoid lesion. The factors responsible for inducing the inflammatory process are unknown.

Transcriptional regulation of fibroblast collagen synthesis by activated mononuclear cell supernatants

Mononuclear cells elaborate effector substances which regulate growth and synthetic activities of fibroblasts. We have studied the mechanism by which activated mononuclear cell supernatants inhibit collagen production. Activated supernatants were prepared by culturing human peripheral mononuclear cells with phytohemagglutinin. Human fibroblasts were exposed to the activated supernatants and total cellular RNA was isolated. Collagen mRNA levels were measured using a pro alpha [I] probe and poly(A+) mRNA was assayed using polyuridylic acid as the probe. Collagen production was measured as collagenase-digestible radioactivity. The results showed that pro alpha 1 [I] mRNA levels were decreased in cells incubated with the activated mononuclear cell supernatants and that the decrease was dose and time dependent. The reduction in the pro alpha 1 [I] mRNA correlated with the decrease in collagen production. No inhibition in the poly(A+) message was observed. We conclude that inhibition of collagen production by activated mononuclear cell supernatant occurs primarily at the transcriptional level and that the inhibition may be selective to collagen.

Influences of gamma interferon on synovial fibroblast-like cells. Ia induction and inhibition of collagen synthesis

The shape and function of adherent cells cultured from rheumatoid synovial membranes are influenced by immune cells, and their products. The synovial cells produce collagenase and prostaglandin E2 (PGE2), the levels of which are increased when the cells are incubated with the monokine, mononuclear cell factor/interleukin 1. The majority of adherent synovial cells are fibroblastlike in appearance and synthesize collagens and fibronectin; the synthesis of collagens and fibronectins are also increased by a monocyte factor. In the present study we found that the fibroblastlike cells expressed major histocompatibility complex class II (Ia-like) antigens after initial dispersion from the synovial membrane. Monocyte lineage antigens were detected on some round cells in early passage, but no T lymphocytes were identified in established cultures. There was loss of Ia expression on the fibroblastlike cells with age and passage in culture. The addition of the lymphokine, gamma interferon (recombinant), induced class II antigen (DR and DS/DQ) expression in early or late passage cells in a time- and dose-dependent manner and required protein synthesis. Furthermore, the adherent synovial fibroblastlike cells continued to be Ia-positive when examined as long as 10 d after the removal of gamma interferon. Ia expression was also induced by gamma interferon in normal skin fibroblasts. Synovial cells that could be induced to express Ia also bound a monoclonal antibody to type III collagen (a fibroblast marker). Gamma interferon, while inducing Ia expression, decreased the binding of type III collagen antibody on unstimulated as well as monokine-stimulated cells. Analysis of [3H]proline-labeled medium by SDS polyacrylamide gel electrophoresis showed that gamma interferon decreased the synthesis of type I and III collagens and fibronectin by adherent synovial cells in a dose-dependent manner. These findings suggest that Ia expression by synovial tissue cells is not cell-specific, but reflects one or several related events, such as the degree of T lymphocyte infiltration, the presence of factors that stimulate gamma interferon release, or an increased sensitivity of the cells to gamma interferon. Whereas the synthesis of class II antigens is enhanced by the lymphokine gamma interferon, and a monocyte factor(s) stimulates collagen, collagenase and PGE2 synthesis by the same cells, gamma interferon inhibits basal and monokine-induced collagen synthesis. Thus, lymphokines and monokines may influence the extent of fibrosis as contrasted to matrix destruction at various stages of the rheumatoid lesion by affecting the function of fibroblastlike synovial cells.