Mode of fibroblast growth enhancement by human interleukin-1

2b or Not 2b: How Opposing FGF Receptor Splice Variants Are Blocking Progress in Precision Oncology

More than ten thousand peer-reviewed studies have assessed the role of fibroblast growth factors (FGFs) and their receptors (FGFRs) in cancer, but few patients have yet benefited from drugs targeting this molecular family. Strategizing how best to use FGFR-targeted drugs is complicated by multiple variables, including RNA splicing events that alter the affinity of ligands for FGFRs and hence change the outcomes of stromal-epithelial interactions. The effects of splicing are most relevant to FGFR2; expression of the FGFR2b splice isoform can restore apoptotic sensitivity to cancer cells, whereas switching to FGFR2c may drive tumor progression by triggering epithelial-mesenchymal transition. The differentiating and regulatory actions of wild-type FGFR2b contrast with the proliferative actions of FGFR1 and FGFR3, and may be converted to mitogenicity either by splice switching or by silencing of tumor suppressor genes such as CDH1 or PTEN. Exclusive use of small-molecule pan-FGFR inhibitors may thus cause nonselective blockade of FGFR2 isoforms with opposing actions, undermining the rationale of FGFR2 drug targeting. This splice-dependent ability of FGFR2 to switch between tumor-suppressing and -driving functions highlights an unmet oncologic need for isoform-specific drug targeting, e.g., by antibody inhibition of ligand-FGFR2c binding, as well as for more nuanced molecular pathology prediction of FGFR2 actions in different stromal-tumor contexts.

In vitro predegeneration of peripheral nerve; the effect of predegeneration period on rat Schwann cell cultures

Peripheral nerve predegeneration has been used as a tool to improve the in vitro cultivation of Schwann cells. The process of predegeneration may be accomplished either in vivo or in vitro. In previously published studies, various predegeneration periods were used, ranging from a few days until up to 5 weeks. The present study systematically evaluated the effect of various durations of in vitro predegeneration on the efficacy of Schwann cell cultivation. The sciatic nerves of adult Wistar rats were harvested and the explanted nerve pieces were maintained in the predegeneration medium for different predegeneration periods. In group A, the dissociation was performed immediately after harvesting. In groups B, C and D, the predegeneration periods were 2, 4 and 6 weeks, respectively. During the predegeneration period, the tissue pieces were repeatedly transferred into new dishes. Afterwards, the nerve tissue was enzymatically dissociated and the cells were seeded onto a six-well culture plate at a defined density. After 3–4 days of incubation, the cultures were passaged by means of the cold jet technique and the cell cultivation was continued for another 21 days. It was observed that the cell cultures in groups A and B were rapidly overgrown by fibroblasts. In group C, numerous wells contained a highly enriched Schwann cell population that had formed a typical monolayer, but in a fraction of the dishes, cultures were debased by fibroblast overgrowth. In group D, all of the cultures had enriched Schwann cell populations. In the experiments of the present study, the positive effect of predegeneration was observed only when the predegeneration periods lasted for 4 weeks or longer. It was concluded that the longer predegeneration periods activated Schwann cells and/or depleted the fibroblast proliferation capacity.

Engineering the healing of the rabbit medial collateral ligament

A biological approach to improve healing of the medial collateral ligament (MCL) was investigated by exploring the use of therapeutic growth factors based on in vitro and in vivo experiments. The in vitro cell culture studies involved screening a variety of growth factors to select those that exhibit the most positive effects on cell proliferation and extracellular matrix synthesis. The selected growth factors were applied in vivo to a rabbit model where the MCL was ruptured. Biomechanical and histological evaluations are performed to determine whether the selected growth factors can enhance the properties of the healed MCL, whether these improvements are dose dependent, and whether combinations of growth factors can enhance MCL healing to a greater extent than individual growth factors. In vitro studies showed that epidermal growth factor (EGF) and platelet derived growth factor-BB (PDGF-BB) have the greatest effect on ligament fibroblast proliferation, whereas transforming growth factor-beta 1 (TGF-beta 1) superiorly promotes extracellular matrix synthesis. These growth factors were then applied in vivo at different dosages, in isolation and in combination, and the ligaments were evaluated six weeks post-operatively. Tensile testing of the femur-MCL-tibia complexes (FMTCs) revealed that the specimens treated with a high dose of PDGF-BB have ultimate load, ultimate elongation and energy absorbed to failure values that are significantly greater than those from the other groups. The high dose of PDGF-BB was more effective than the low dose, indicating a dose dependency. The addition of TGF-beta 1 to PDGF-BB did not lead to any further increases in the structural properties of the FMTC. These encouraging results suggest that PDGF-BB may be a potential growth factor to enhance the quality of the healing ligament.

Trauma and alkali burns induce distinct patterns of cytokine gene expression in the rat cornea

Cytokines such as the interleukins (IL) and tumor necrosis factor alpha (TNF alpha) have traditionally been associated with paracrine regulation of immune reactions. These proteins also have properties suggestive of functional roles in the inflammatory and reparative responses to tissue injury. In this study, mRNA levels for IL-1 alpha, IL-1 beta, IL-6, TNF alpha, interferon gamma, transforming growth factor beta 1, and CD4 were monitored in rat corneas at times from 1 hour through 2 weeks after incisional trauma or alkali burns. Transcripts for IL-1 alpha, TNF alpha, and TGF beta 1 were present in most corneal samples; whereas those for IFN gamma and CD4 were not detected. As early as 1 hour following either of these non-immunologic forms of injury, expression of IL-6 mRNA levels was induced. Only in corneas with alkali burns did IL-6 induction persist from days 1 through 7. The alkali-injured corneas also had markedly increased IL-1 beta mRNA levels from days 1 through 7. These observations indicate that cytokine mRNA is induced in the cornea by trauma without an apparent immunologic stimulus. Our data are consistent with the hypothesis that corneal tissues respond to different types of injury with different patterns of cytokine gene expression.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

Effect of growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments

Growth factors have been shown to stimulate fibroblast division and thus may influence ligament healing. We analyzed the effects of individual growth factors on the proliferation of fibroblasts from the medial collateral and anterior cruciate ligaments of the rabbit in vitro in order to identify growth factors that might enhance proliferation of fibroblasts and to compare the responses of the fibroblasts from the two ligaments to these growth factors. Through measurement of the uptake of [3H]-thymidine into DNA, fibroblasts from these ligaments that had been treated with epidermal growth factor and basic fibroblast growth factor were found to proliferate nearly eight times more than control fibroblasts. Additionally, the fibroblasts of both ligaments proliferated at similar rates when exposed to platelet-derived growth factor-AA, platelet-derived growth factor-BB, basic fibroblast growth factor, insulin-like growth factor-1, and interleukin-1-alpha. However, epidermal growth factor and transforming growth factor-beta caused the fibroblasts from the medial collateral ligament to proliferate at a rate 1.3-1.4 times greater than that of fibroblasts from the anterior cruciate ligament. The reverse was true with acidic fibroblast growth factor, which stimulated the fibroblasts from the anterior cruciate ligament to proliferate at a rate 1.3-1.6 times greater than that of fibroblasts from the medial collateral ligament. This study demonstrated that growth factors can stimulate cell division in ligaments and may be effective in enhancing ligament healing but that these differences were not great enough to explain fully the clinical differences observed between healing of the medial collateral and anterior cruciate ligaments.

Inhibition of endothelial cell proliferation by platelet factor-4 involves a unique action on S phase progression

Modulation of endothelial cell proliferation and cell cycle progression by the "chemokine" platelet factor-4 (PF-4) was investigated. PF-4 inhibited DNA synthesis, as well as proliferation of endothelial cells derived from large and small blood vessels. Inhibition by PF-4 was independent of the type and the concentration of stimuli used for the induction of endothelial cell proliferation. Inhibition of cell growth by PF-4 was reversible. The effects of PF-4 were antagonized by heparin. Cell cycle analysis using [3H]thymidine pulse labeling during traverse of synchronous cells from G0/G1 to S phase revealed that addition of PF-4 during G1 phase completely abolished the entry of cells into S phase. In addition, PF-4 also inhibited DNA synthesis in cells that were already in S phase. In exponentially growing cells, addition of PF-4 resulted in an accumulation of > 70% of the cells in early S phase, as determined by FACS (Becton-Dickinson Immunocytometry Systems, Mountain View, CA). In cells synchronized in S phase by hydroxyurea and then released, addition of PF-4 promptly blocked further progression of DNA synthesis. These results demonstrate that in G0/G1-arrested cells, PF-4 inhibited entry of endothelial cells into S phase. More strikingly, our studies have revealed a unique mode of endothelial cell growth inhibition whereby PF-4 effectively blocked cell cycle progression during S phase.

Interleukin-1 beta stimulates the proliferation of cultured airway smooth muscle cells via platelet-derived growth factor

Bronchoalveolar lavage fluid from symptomatic asthmatics contains elevated levels of several proinflammatory interleukins including interleukin-1 beta (IL-1 beta). Biologic activities of IL-1 beta are considered to be critical in the inflammatory process. Since these characteristics include mitogenic properties, we investigated the effect of IL-1 beta on the proliferation of airway smooth muscle (ASM) cells isolated from guinea pig tracheas. Primary tissue culture of ASM cells was maintained in media containing 0%, 1%, or 10% fetal bovine serum (FBS). Cultures were exposed up to 6 days to human recombinant IL-1 beta (20, 40, or 100 pg/ml) in the presence or absence of indomethacin. The proliferation of ASM cells was assessed with two techniques: a direct counting of cells with a hemocytometer and/or with a [3H]-thymidine incorporation, an established marker of DNA synthesis. The evaluation was done daily, up to the sixth day after exposure of cells to different doses of IL-1 beta. We found that the exposure of ASM cells to human recombinant IL-1 beta significantly (P < 0.01) increased the number of tracheal myocytes as well as the [3H]-thymidine incorporation into ASM cells. These changes were dependent upon the dose of IL-1 beta and the concentration of FBS in the cultured medium. The most active proliferation of ASM cells was observed in medium containing 1% FBS, indomethacin (1 microgram/ml), and IL-1 beta (100 pg/ml). The presence of indomethacin in the culture medium was essential to demonstrate the proliferative effect of IL-1 beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of collagen synthesis by growth factors: the role of ascorbate-stimulated lipid peroxidation

Ascorbic acid has been shown to stimulate collagen synthesis through induction of lipid peroxidation leading to increased transcription of the collagen genes. The mechanism by which lipid peroxidation stimulates collagen transcription is unknown; however, an alteration of cell membranes may affect the activity of serum growth factors leading to a change in gene expression. To test this hypothesis, we treated dermal fibroblasts with transforming growth factor-beta (TGF-beta), epidermal growth factor (EGF), interleukin-1 (IL-1), platelet-derived growth factor (PDGF), or fibroblast growth factor (FGF) in the presence of lipid peroxidation stimulating (200 microM) and nonstimulating (1 microM) concentrations of ascorbic acid. EGF and IL-1 had no effect on collagen synthesis at either concentration of ascorbic acid. FGF affected collagen synthesis only in the presence of 200 microM ascorbic acid, producing both a stimulation (0.4-2 ng/ml) and an inhibition (greater than 50 ng/ml). PDGF and TGF-beta stimulated collagen synthesis in the presence of both concentrations of ascorbic acid, with TGF-beta producing an 11-fold increase in collagen synthesis in the presence of ascorbate. This synergism produced by the combination of ascorbic acid and TGF-beta was inhibitable by the lipid peroxidation inhibitor, propyl gallate. These results indicate that regulation of collagen synthesis by ascorbic acid does not occur through altering the response to EGF or Il-1. Ascorbate has no effect on PDGF but the effects of TGF-beta and FGF on collagen synthesis appear to be sensitive to lipid peroxidation.

Sera but not immunoglobulins of ophthalmic Graves' patients stimulate human embryonal fibroblasts' biosynthetic activity in culture

The retroocular connective tissue changes in the ophthalmopathy of Graves' disease are known, however, the mechanism which leads to the increase in fibroblast number and activity is poorly understood. Using human embryonal fibroblast monolayers, fibroblast biosynthetic activity in the presence of sera, immunoglobulin deprived sera or immunoglobulins of Graves' patients with and without ophthalmopathy has been measured. Both sera and immunoglobulin deprived sera of the ophthalmic Graves' patients caused a marked increase of protein synthesis and a moderate increase of the sulphated glycosaminoglycan synthesis of fibroblasts. The same stimulatory effect was not found when immunoglobulin in fetal calf serum was used instead of sera, though anti-fibroblast IgG-s were present both in the sera and separated immunoglobulin fractions, as it has been demonstrated in an ELISA system. We conclude that the sera of ophthalmic Graves' patients contains a factor which stimulates human embryonal fibroblasts' biosynthetic activity in culture; this factor is not an immunoglobulin. The system described here seems to be suitable for studying the accompanying connective tissue changes in Graves' disease.

Minerals, fibrosis, and the lung

Determinants of pulmonary fibrosis induced by inhaled mineral dusts include quantity retained, particle size, and surface area, together with their physical form and the reactive surface groups presented to alveolar cells. The outstanding problem is to ascertain how these factors exert their deleterious effects. Both compact and fibrous minerals inflict membrane damage, for which chemical mechanisms still leave uncertainty. A major weakness of cytotoxicity studies, even when lipid peroxidation and reactive oxygen species are considered, lies in tacitly assuming that membrane damage suffices to account for fibrogenesis, whereas the parallel occurrence of such manifestations does not necessarily imply causation. The two-phase procedure established that particles, both compact and fibrous, induce release of a macrophage factor that provokes fibroblasts into collagen synthesis. The amino acid composition of the macrophage fibrogenic factor was characterized and its intracellular action explained. Fibrous particles introduce complexities respecting type, durability, and dimensions. Asbestotic fibrosis is believed to depend on long fibers, but scrutiny of the evidence from experimental and human sources reveals that a role for short fibers needs to be entertained. Using the two-phase system, short fibers proved fibrogenic. Other mechanisms, agonistic and antagonistic, may participate. Growth factors may affect the fibroblast population and collagen production, with cytokines such as interleukin-1 and tumor necrosis factor exerting control. Immune involvement is best regarded as an epiphenomenon. Downregulation of fibrogenesis may follow collagenase release from macrophages and fibroblasts, while augmented type II cell secretion of lipid can interfere with the macrophage-particle reaction.

IL-1 beta-induced expression of PDGF-AA isoform in rabbit articular chondrocytes is modulated by TGF-beta 1

Interleukin 1 beta (IL-1 beta) and platelet-derived growth factor (PDGF) induced proliferation in many cell types. Both peptides are released by activated macrophages and other cells in response to injury and are thought to play a crucial role in a number of pathological processes. We found that IL-1 beta stimulates proliferation of rabbit articular chondrocytes and induces synthesis and release of PDGF into their culture medium. This effect, which is time- and dose-dependent (0.05-5 ng/ml), is restricted to PDGF-AA, one of the three PDGF isoforms; IL-1 beta effect on PDGF is inhibited by actinomycin D and alpha-amanitin, suggesting a transcriptional regulation of PDGF-A chain. IL-1 beta stimulates PDGF-AA synthesis also in the presence of indomethacin, a prostaglandin synthesis inhibitor. Transforming growth factor beta 1 (TGF-beta 1), a dimeric polypeptide which displays multiple biological activities, inhibits in a dose-dependent manner (1-10 ng/ml) PDGF-AA production induced by IL-1 beta. In a binding assay, TGF-beta 1 induces 45% decrease in specific binding sites for 125I-IL-1 beta, with no change in affinity.

Fibroblast stimulation by monocytes cultured on protein adsorbed biomedical polymers. I. Biomer and polydimethylsiloxane

The studies presented in this paper evaluate the modulatory role of protein pre-adsorbed polydimethylsiloxane (PDMS) and Biomer on the secretion of fibroblast stimulating growth factors from human monocytes/macrophages. The results of these studies show that Biomer and PDMS selectively activate human monocytes to produce fibroblast "progression-like" and to a lesser extent "competence-like" stimulating growth factors. Polydimethylsiloxane stimulated the monocytes/macrophages to produce more "progression-like" fibro-blast stimulating growth factors than Biomer. The induction of "competence-like" fibroblast stimulating activity from the monocytes was enhanced by preadsorption of PDMS with human derived fibrinogen, fibronectin, IgG, hemoglobin, or albumin. This phenomenon was not observed with protein pre-adsorbed Biomer. These studies support the hypothesis that protein pre-adsorbed polymers will selectively modulate monocyte/macrophage activation and induction of growth factors which have the potential to participate in tissue-implant interactions in vivo.

Inhibition of proliferation of fibroblasts by lazaroids (21-aminosteroids)

Lazaroids (21-aminosteroids) are a novel group of compounds that inhibit lipid peroxidation in biological systems and protect cells from oxidative damage during tissue injury. In vivo efficacy of lazaroids has been demonstrated in a variety of animal models of traumatic or ischemic injury of central nervous system (1-6). However, very little is known about the affects of lazaroids on cellular responses associated with tissue repair and remodeling eg cell proliferation and synthesis of extracellular matrix. In the present study, we show that lazaroids and certain related compounds inhibit cell proliferation in vitro. Light microscopic examination and determination of release of intracellular enzyme, lactate dehydrogenase suggested that cell growth inhibition by lazaroids was not due to cell death resulting from cytotoxic effects. Examination of several lazaroid related antioxidants and other known antioxidants eg vitamin E and Probucol showed that compounds with similar antioxidant potential did not exhibit identical antiproliferative activity, suggesting that cell growth inhibition by lazaroids may be unrelated to their antioxidant action. These results may have implication in the therapeutic actions of lazaroids.

Interleukin-1 beta- and tumor necrosis factor-alpha-independent monocyte stimulation of fibroblast collagenase activity

To investigate the mechanism of cyclosporine (Cs)-induced fibrous gingival enlargement, the indirect effects of Cs on fibroblast collagenolysis via the drug's effect on the synthesis of the fibroblast regulatory monokines interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF alpha) have been studied. Peripheral blood monocytes stimulated with lipopolysaccharide (LPS) for 48 h produced conditioned media (MCM-LPS) that contained 665 pg/ml IL-1 beta and 16 pg/ml TNF alpha and significantly (P less than 0.001) enhanced the collagenase activity of a fibroblast strain (GN 23) derived from a healthy individual with clinically normal gingiva. The concurrent addition of Cs (50, 100, or 150 ng/ml) with LPS to the monocytes (MCM-LPS-Cs) significantly diminished their ability to enhance GN 23 collagenase activity in a dose-dependent manner, with MCM-LPS-Cs (150 ng/ml) causing the greatest effect. Cs also significantly inhibited IL-1 beta and TNF alpha production. Although the greatest inhibition of both cytokines was at 50 ng/ml Cs, the corresponding MCM-LPS-Cs caused the least diminution (16%) of the collagenase stimulation caused by MCM-LPS (no Cs). This suggested that factor(s) other than or in addition to IL-1 beta and TNF alpha might be responsible for the stimulation of GN 23 collagenase activity. MCM-LPS depleted of IL-1 beta by affinity chromatography retained its stimulatory effect on GN 23 collagenolysis, and human recombinant IL-1 beta and TNF alpha, when tested alone or together at levels found in the stimulatory MCM-LPS and MCM-LPS-Cs, did not stimulate GN 23 collagenase activity as did the crude conditioned media. This evidence suggested that the conditioned media contained the complex mixture of cytokines necessary to stimulate collagenase activity of this fibroblast strain and that IL-1 beta and TNF alpha were not necessarily involved. Cs may alter the synthesis of other collagenase-stimulating cytokines, accounting for the diminished ability of Cs-treated monocytes to enhance collagenase activity of susceptible fibroblast strains. Decreased collagenase activity, therefore, resulting from Cs suppression of monokine production, may be an important factor in the development of fibrous gingival enlargement seen in some susceptible patients treated with Cs.

Autocrine regulation of rheumatoid arthritis synovial cell growth in vitro

Rheumatoid arthritis (RA), and not osteoarthritis (OA) synovial cells proliferate in serum-free medium, a finding that suggests that, in vitro, RA synovial cells may be stimulated to grow by the continuous autocrine production of at least one polypeptide growth factor. Adding monoclonal antibody 1D11.16, or rabbit polyclonal anti-tumor growth factor beta (anti-TGF-beta) antibodies (both neutralizing antibodies to TGF-beta 1 and TGF-beta 2) to RA synovial cells, in culture, caused a significant reduction in cell growth, an effect not seen when other growth factor antibodies (platelet-derived growth factor [PDGF], epidermal growth factor [EGF], or EGF receptor) were added to the culture medium. Taken together, these data are consistent with the concept that RA synovial cell growth in vitro is driven endogenous TGF-beta. Moreover, when EGF was added to the culture medium, this caused the numbers of RA, and not OA, synovial cells to increase significantly. This finding suggests that RA synovial cells are in G1 phase of the cell cycle; an effect that could be mediated by endogenous TGF-beta.

Chondrocyte activation by interleukin-1: analysis of the synergistic properties of fibroblast growth factor and phorbol myristate acetate

Following activation, monolayers of lapine articular chondrocytes secreted into their culture media large amounts of prostaglandin E2 (PGE2) and the neutral metalloproteinases collagenase and gelatinase. Partially purified preparations of synovial "chondrocyte activating factors" (CAF), which contain interleukin-1 (IL-1), generally proved stronger activators of chondrocytes than recombinant, human, IL-1 alpha (rHIL-1 alpha) or IL-1 beta (rHIL-1 beta). The presence of synergistic cytokines within the synovial material provides one possible explanation of this discrepancy. As first reported by K. Phadke (1987, Biochem. Biophys. Res. Commun. 142, 448-453) fibroblast growth factor (FGF) synergized with rHIL-1 in promoting the synthesis of neutral metalloproteinases. In our hands FGF alone did not induce neutral metalloproteinases and increased PGE2 synthesis only modestly. However, at doses from 1 ng/ml to 1 microgram/ml, FGF progressively enhanced the synthesis of PGE2, collagenase, and gelatinase by chondrocytes responding to rHIL-1. Acidic and basic FGF synergized equally well with both rHIL-1 alpha and rHIL-1 beta. Phorbol myristate acetate (PMA), but not the Ca2+-ionophore A23187, could substitute for FGF as a synergist. PMA alone was a poor inducer of collagenase or gelatinase but, unlike FGF, it greatly enhanced the synthesis of PGE2 by chondrocytes. Dot-blot analyses with a cDNA probe to collagenase mRNA confirmed that partially purified synovial CAF induced collagenase mRNA more effectively than rHIL-1, with rHIL-1 alpha being superior to rHIL-1 beta in this regard. The synergistic effects of both FGF and PMA upon IL-1-mediated collagenase induction were associated with increased abundance of collagenase mRNA.

Interleukin-1 is a potent regulator of JE and KC gene expression in quiescent BALB/c fibroblasts

Interleukin-1 alpha and beta are polypeptide hormones with a broad range of biological activities. Both interleukins are recognized by a receptor that has been characterized as a member of the immunoglobin superfamily. The interleukin-1 receptor does not appear to be a tyrosine protein kinase. Moreover, the intracellular events that mediate the multiple interleukin-1 responses are poorly understood. Here we show that the JE and KC genes, first isolated and characterized as platelet-derived growth factor inducible in quiescent BALB/c-3T3 fibroblasts, are induced by femtomolar concentrations of recombinant interleukin-1 alpha (rIL-1). The response of JE and KC to IL-1 occurs at the transcriptional level. These observations suggest that an analysis of the JE and KC transcriptional response to rIL-1 may aid in identifying elements involved in interleukin-1-mediated signal transduction

Quantitative immunohistologic assessment of lymphocyte populations in the pulmonary inflammatory response to intratracheal silica

Immunogold-silver staining was used to identify T lymphocytes, T lymphocyte subsets, and B lymphocytes in lung tissue from mice injected intratracheally with silica, titanium dioxide, or saline alone. Morphometric quantitation revealed a marked influx of T lymphocytes in the silica-treated animals during the first 3 weeks after injection. The relative numerical density of these cells remained elevated when compared with saline-treated controls throughout the 12 weeks of the experiment. Cells expressing the CD4 and CD8 antigens were both increased in number, with the former accounting for approximately two-thirds of the T lymphocytes. An increased number of B lymphocytes was also apparent from 6 weeks after treatment with silica. The T lymphocyte response preceded the development of significant pulmonary fibrosis by several weeks. No lymphocyte response was observed in the lungs of mice injected with nonfibrogenic titanium dioxide. These observations are consistent with the hypothesis that lymphokines secreted by T lymphocytes play a role in the pathogenesis of silicotic inflammatory lesions and their progression to fibrosis.

Rapid modulation of a 64 K dalton fibroblast protein: a PDGF mediated early cellular event

The results presented here reveal a novel platelet derived growth factor (PDGF) mediated early cellular event. Treatment of growth arrested Balb/c3T3 fibroblasts with PDGF induces a specific and rapid modulation of a 64,000 Dalton (64 KD) protein preexisting in quiescent cells. The kinetics of 64 KD protein modulation indicate that, temporally, this PDGF mediated step lies between the membrane associated immediate events such as receptor autophosphorylation or ion mobilization and the earliest known transcriptional event, the activation of the proto-oncogene c-fos.

Interleukin 1: a regulator of chondrocyte proliferation

Human interleukin 1 beta (IL-1 beta), at low concentrations (0.3-1 ng/ml), decreased by 95% the efficiency of colony formation in soft agar by rabbit articular chondrocytes. Furthermore, interleukin 1 (IL-1) suppressed by 50-60% the incorporation of [3H]thymidine into DNA in high density chondrocyte cultures on plastic dishes in the presence of 10% serum or fibroblast growth factor, although it increased twofold this incorporation in 0.3% serum alone. This suggests that IL-1 directly inhibits mitogenic response of differentiated chondrocytes to growth factors. In contrast, IL-1 stimulated [3H]thymidine incorporation into DNA in rabbit fibroblasts in the presence of growth factors. The selective suppression of chondrocyte replication by IL-1 may play an important role in cartilage destruction associated with chronic inflammatory joint diseases.

Interleukin-1 mitogenic activity for fibroblasts and smooth muscle cells is due to PDGF-AA

Both interleukin-1 (IL-1) and platelet-derived growth factor (PDGF) induce proliferation of cultured fibroblasts and smooth muscle cells. These polypeptide mediators are released by activated macrophages and other cell types in response to injury and are thought to have a role in tissue remodeling and a number of pathologic processes. Analysis of the kinetics of [3H]thymidine incorporation by cultured fibroblasts demonstrated that the response to IL-1 is delayed approximately 8 hours relative to their response to PDGF. IL-1 transiently stimulated expression of the PDGF A-chain gene, with maximum induction after approximately 2 hours. Subsequent synthesis and release of PDGF activity into the medium was detected as early as 4 hours after IL-1 stimulation, and downregulation of the binding site for the PDGF-AA isoform of PDGF followed PDGF-AA secretion. Antibodies to PDGF completely block the mitogenic response to IL-1. Therefore, the mitogenic activity of IL-1 for fibroblasts and smooth muscle cells appears to be indirect and mediated by induction of the PDGF A-chain gene.

Purification and biochemical properties of a human monocyte-derived growth factor

A monocyte-derived growth factor (MDGF) that stimulates proliferation of fibroblast and smooth muscle cells was purified from mitogen-stimulated human peripheral blood lymphocyte conditioned medium by using anion-exchange, Bio-Sil TSK-250 HPLC gel-permeation chromatography, and NaDodSO4/PAGE. Purified MDGF exhibited acidic charge characteristics (pI 5.0) and migrated with an apparent Mr of 40,000 +/- 2000 in molecular sizing HPLC columns. Elution from NaDodSO4/polyacrylamide gels showed that the growth-promoting activity was associated with three or four protein bands. The highest molecular weight species representing the most intense silver-stained band corresponded to 42,000; the lowest molecular weight species was 33,000. MDGF activity was stable to treatment with acid (pH 2.0) or base (pH 10.0) and heating (100 degrees C, 5 min) but was inactivated upon reduction with 2-mercaptoethanol. The acidic MDGF did not effectively compete with platelet-derived growth factor (PDGF) for receptor binding and was not inhibited by PDGF antibodies. Previous studies have suggested that fibroblast growth-stimulating activity of macrophages is largely due to their secretion of interleukin 1 and a PDGF-like molecule. Our purification and biochemical characterization studies reveal the occurrence of multiple forms of fibroblast growth-stimulating activity in human monocyte conditioned medium. The MDGF activity characterized here appears to be structurally and functionally distinct from the previously described fibroblast growth-promoting activities including interleukin 1, basic fibroblast growth factor, and PDGF.