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Biomedical subjects

R C Chambers

Publications and source records attributed to R C Chambers.

10 recordsLinked to original sources
PubMed1998

Thrombin stimulates fibroblast procollagen production via proteolytic activation of protease-activated receptor 1.

Thrombin is a multifunctional serine protease that has a crucial role in blood coagulation. It is also a potent mesenchymal cell mitogen and chemoattractant and might therefore have an important role in the recruitment and local proliferation of mesenchymal cells at sites of tissue injury. We hypothesized that thrombin might also affect the deposition of connective tissue proteins at these sites by directly stimulating fibroblast procollagen production. To address this hypothesis, the effect of thrombin on procollagen production and gene expression by human foetal lung fibroblasts was assessed over 48 h. Thrombin stimulated procollagen production at concentrations of 1 nM and above, with maximal increases of between 60% and 117% at 10 nM thrombin. These effects of thrombin were, at least in part, due to increased steady-state levels of alpha1(I) procollagen mRNA. They could furthermore be reproduced with thrombin receptor-activating peptides for the protease-activated receptor 1 (PAR-1) and were completely abolished when thrombin was rendered proteolytically inactive with the specific inhibitors d-Phe-Pro-ArgCH2Cl and hirudin, indicating that thrombin is mediating these effects via the proteolytic activation of PAR-1. These results suggest that thrombin might influence the deposition of connective tissue proteins during normal wound healing and the development of tissue fibrosis by stimulating fibroblast procollagen production.

Connective Tissue↗
PubMed1998

Thrombin.

Thrombin is a multifunctional serine protease which plays a central role in haemostasis by regulating platelet aggregation and blood coagulation. It is formed from its precursor prothrombin following tissue injury and converts fibrinogen to fibrin in the final step of the clotting cascade. It also promotes numerous cellular effects including chemotaxis, proliferation, extracellular matrix turnover and release of cytokines. These actions of thrombin on cells have been implicated in tissue repair processes and in the pathogenesis of inflammatory and fibroproliferative disorders such as pulmonary fibrosis and atherosclerosis. Thrombin mediates its cellular effects by proteolytically activating cell surface receptors. Presently, two such receptors have been described and their roles in regulation of these functions are currently being investigated. The discovery of multiple thrombin receptors creates the possibility of selective receptor blockade of specific thrombin mediated events. New drugs with these actions should add to our current repertoire of thrombin inhibitors used to treat thrombotic diseases.

Animals↗
PubMed1998

Increased endothelin-1 and its localization during the development of bleomycin-induced pulmonary fibrosis in rats.

Endothelin-1 (Et-1) has been implicated in the pathogenesis of pulmonary fibrosis with increased levels in the lung tissue of patients with pulmonary fibrosis and profibrotic effects in vitro. In this study we have investigated the temporal changes in lung Et-1 levels and immunohistochemical localization in relation to collagen deposition during the development of bleomycin-induced pulmonary fibrosis in rats. Lung Et-1 content doubled by 3 d following the intratracheal instillation of bleomycin, and continued to increase up to 7 d when values were about threefold greater than controls. Thereafter, the values for bleomycin-treated animals remained constant up to 21 d. There was no change in collagen content at 3 d but after 7 d there was a 25% increase and by 21 d levels were almost double those of the controls. In normal lung, Et-1 was predominantly associated with epithelial cells of conducting and nonconducting airways. Following bleomycin administration, intense staining of macrophages and conducting airway and alveolar epithelial cells was observed with marked staining of perivascular, peribronchiolar, and alveolar septal connective tissue, as well as the venular and arterial intima and media. These results demonstrate elevation of Et-1 levels prior to an increase in collagen content which, along with its localization within developing fibrotic lesions, provides further evidence of a profibrotic role for Et-1 in the pathogenesis of pulmonary fibrosis.

Animals↗
PubMed1998

Cadmium inhibits proteoglycan and procollagen production by cultured human lung fibroblasts.

Chronic inhalation of cadmium at the workplace or in cigarette smoke is associated with emphysema, a disease characterized by extensive disruption of lung connective tissue. We have previously shown that cadmium, at noncytotoxic doses, inhibits fibroblast procollagen production in vitro, with maximal inhibitory effects of 69 +/- 6% (P < 0.01) at 30 &microM cadmium chloride (CdCl2). In this paper we show that at similar doses, cadmium also inhibits proteoglycan synthesis, with values reduced by between 36 +/- 4% (P < 0.01) and 42 +/- 6% (P < 0.01) for proteoglycans secreted into the culture media and associated with the cell layer, respectively. The greatest inhibition was obtained for the major matrix-associated proteoglycans, versican, decorin, and the large heparan sulfate proteoglycans, with synthesis values reduced by between 60 and 70%. Biglycan and other heparan sulfate proteoglycans were also affected, with synthesis values reduced by between 25 and 45%. In contrast, total protein synthesis was unaffected. Furthermore, effects of cadmium at the protein level were mirrored by reduction in messenger RNA levels for alpha1(I) procollagen, versican, and decorin. These data support the hypothesis that cadmium may play an important role in the pathogenesis of emphysema associated with chronic inhalation of cadmium fumes by inhibiting the production of connective tissue proteins.

Administration, Inhalation↗
PubMed1998

Thrombin stimulates smooth muscle cell procollagen synthesis and mRNA levels via a PAR-1 mediated mechanism.

Thrombin is a serine protease involved in haemostasis which exerts a number of cellular effects, including stimulating mesenchymal cell migration, proliferation, and has been implicated both in normal wound healing and pathological conditions associated with hyperproliferation of smooth muscle cells such as atherosclerosis and restenosis. We hypothesize that thrombin, in addition to its proliferative effects, may also influence the deposition of matrix proteins at sites of vascular injury by directly stimulating smooth muscle cell procollagen production. 10 nM thrombin significantly stimulated rat aortic smooth muscle cell procollagen production by 34 +/- 3% compared to media control cells over a 48 h incubation period, and increased steady state alpha1(I) procollagen mRNA levels by up to 104 +/- 22%. These effects are mediated via interaction of thrombin with the PAR-1 receptor since TRAP (Thrombin Receptor Activating Peptide) stimulated procollagen production by 23 +/- 0.5%. In addition, conditioned medium from thrombin-treated cells stimulated procollagen production by 30 +/- 3% suggesting that thrombin is acting via the production and/or release of an autocrine mediator. These data suggest a novel role for thrombin in vascular wound healing and the development of pathological conditions associated with increased connective tissue deposition.

Animals↗
PubMed1995

Role of thrombin in pulmonary fibrosis.

Pulmonary fibrosis commonly develops in systemic sclerosis. We assessed the role of thrombin in promoting fibroblast proliferation in the lungs in this disorder. Bronchoalveolar lavage fluid (BALF) thrombin concentrations were higher in ten patients with systemic sclerosis than in 12 healthy controls (14.6 vs 3.6 nmol/L, p < 0.02), but values in patients with cryptogenic fibrosing alveolitis (n = 10) or sarcoidosis (n = 10) were not increased. BALF from all patients induced fibroblast proliferation. This proliferation was attenuated by thrombin inhibitors for BALF from systemic sclerosis patients only. We suggest thrombin contributes to lung fibroblast proliferation in this disorder.

Alveolitis, Extrinsic Allergic↗
PubMed1995

Regulation of fibroblast procollagen production. Transforming growth factor-beta 1 induces prostaglandin E2 but not procollagen synthesis via a pertussis toxin-sensitive G-protein.

Transforming growth factor-beta 1 (TGF beta 1) initiates a series of signalling events resulting in diverse cellular responses including stimulation of extracellular matrix protein production. In this study we have investigated the role of pertussis toxin-sensitive G-proteins in mediating the effects of TGF beta 1 on fibroblast procollagen metabolism. TGF beta 1 stimulated human fetal lung fibroblast procollagen synthesis and production in a dose-dependent manner which was maximal at 0.5 ng/ml. TGF beta 1 also decreased the proportion of newly synthesized procollagen degraded intracellularly. Pertussis toxin, a G-protein inhibitor, further stimulated TGF beta 1-induced procollagen synthesis and production, but alone it had no effect on fibroblast procollagen metabolism. Addition of indomethacin also potentiated the TGF beta 1-induced increase in procollagen synthesis and production. The effects of pertussis toxin and indomethacin were not additive. Pertussis toxin and indomethacin did not affect the proportion of newly synthesized procollagen degraded intracellularly, either alone or in combination, by control cells. The TGF beta 1-induced decrease in intracellular procollagen degradation was maintained but not further affected by pertussis toxin or indomethacin. TGF beta 1 increased prostaglandin E2 (PGE2) compared with PGE2 production by control cells. Addition of pertussis toxin or indomethacin blocked the TGF beta 1-induced increase in PGE2 production. The TGF beta 1-induced increase in PGE2 preceded the increase in procollagen production. These results demonstrate that TGF beta 1-induced procollagen synthesis by lung fibroblasts is modulated by production of PGE2. Pertussis toxin and indomethacin block the production of PGE2 and enhance the effect of TGF beta 1 on procollagen synthesis. From these data we conclude that the effects of TGF beta 1 on PGE2 production but not procollagen synthesis are mediated via a receptor linked to a pertussis toxin-sensitive G-protein.

Animals↗
PubMed1994

Cadmium selectively inhibits fibroblast procollagen production and proliferation.

Chronic inhalation of cadmium fumes has been associated with the development of emphysema, a disease characterized by extensive disruption of lung connective tissue. Cadmium is also an important contaminant of tobacco and may play a role in cigarette smoking-related emphysema. In this paper we investigated the effect of nontoxic doses of cadmium chloride (CdCl2) on fibroblast procollagen production and proliferation, key features of connective tissue repair following injury. CdCl2 inhibited fibroblast procollagen production in a dose-dependent manner in two different cell lines. For fetal rat fibroblasts, maximal effects were observed at 10 microM CdCl2, with values reduced by 82 +/- 6% (mean +/- SE, n = 6, P < 0.01) relative to control cells. In contrast, noncollagen protein synthesis by these cells was enhanced in the presence of CdCl2. In human fetal lung fibroblasts (HFL1), maximal inhibition of procollagen production (83 +/- 2%, P < 0.01) was observed at 40 microM CdCl2, whereas noncollagen protein synthesis was unaffected. In both cell lines the inhibition of procollagen production was shown to be due to decreased procollagen synthesis and an increase in the proportion of newly synthesized procollagen degraded. Cadmium also affected fibroblast proliferation in response to 2% serum, with values for fetal rat cells depressed by 17 +/- 4, 72 +/- 2, and 86 +/- 4% (all P < 0.01) compared with controls at 1, 5, and 10 microM CdCl2, respectively. These data show that cadmium selectively inhibits fibroblast procollagen production and also attenuates their mitogenic response to serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Eosinophils adhere to and stimulate replication of lung fibroblasts 'in vitro'.

Eosinophils have been implicated in several disorders associated with the development of fibrosis. This led us to investigate the interactions between eosinophils and fibroblasts in vitro. Adhesion between purified guinea pig peritoneal eosinophils and monolayers of human fetal lung fibroblasts was assessed using the rose bengal dye staining assay. Fibroblast replication was assessed using a colorimetric assay based upon the uptake and subsequent release of methylene blue. Addition of phorbol myristate acetate induced a rapid, time-dependent increase in eosinophil adhesion (127% and 328% over basal adhesion after 10 and 30 min, respectively). Phorbol myristate acetate-induced adhesion was inhibited by the peptides RGDS and GRGDS (48% and 42%, respectively using 1 mM peptide) and by nordihydroguaiaretic acid, an inhibitor of the lipoxygenase pathway of arachidonic acid metabolism (46% inhibition at 15 microM). In addition, 24 h culture of fibroblast monolayers with interleukin 1 alpha (IL-1 alpha) or tumour necrosis factor alpha (TNF alpha) resulted in enhanced adhesion (10 U/ml IL-1 alpha stimulated adhesion by 55% of control, 500 U/ml TNF alpha by 75% of control). Conditioned media from cultured eosinophils stimulated fibroblast replication in a time-dependent fashion with maximal stimulation at 3 h. In contrast, media from guinea pig peritoneal macrophages in culture did not show such an effect. This study indicates that eosinophils are capable of both adhering to and releasing mitogens for fibroblasts in vitro. These observations suggest that eosinophils have the capacity to play a role in the development of fibrosis in disorders where they have been shown to be present.

Amino Acid Sequence↗