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Geoffrey J Laurent

Publications and source records attributed to Geoffrey J Laurent.

At least 19 recordsLinked to original sources
PubMed2007

Mice lacking neutrophil elastase are resistant to bleomycin-induced pulmonary fibrosis.

Neutrophil elastase is a serine protease stored in the azurophilic granules of leukocytes. It has been implicated in the pathology of several lung diseases and is generally presumed to contribute to the tissue destruction and extracellular matrix damage associated with these conditions. To delineate the role of neutrophil elastase in pulmonary inflammation and fibrosis, neutrophil elastase-null mice were intratracheally instilled with bleomycin. In neutrophil elastase-null mice, biochemical and morphological characteristics of pulmonary fibrosis were attenuated for at least 60 days after bleomycin administration despite a typical response to bleomycin as evidenced by assessment of indices of DNA and cell damage. Neutrophil burden of bleomycin-treated wild-type and neutrophil elastase-null mice was comparable, and marked neutrophilic alveolitis was manifest in bleomycin-treated neutrophil elastase-null mice. An absence of immunostaining for active transforming growth factor (TGF)-beta in lung tissue from bleomycin-treated neutrophil elastase-null mice suggested a defect in TGF-beta activation, which was confirmed by biochemical assessment of TGF-beta levels in bronchoalveolar lavage fluid and lung tissue. These data point to novel and unexpected fibrogenic consequences of neutrophil elastase activity in the inflamed lung.

Animals↗
PubMed2006

Functional prostaglandin-endoperoxide synthase 2 polymorphism predicts poor outcome in sarcoidosis.

RATIONALE: The majority of patients with sarcoidosis resolve their condition; however 5-10% of patients with sarcoidosis develop pulmonary fibrosis with poor prognosis. Prostaglandin-endoperoxide synthase 2 (PTGS2) is a key regulatory enzyme in the synthesis of the antifibrotic agent prostaglandin E(2) and is reduced in sarcoidosis lung. A promoter polymorphism in PTGS2, -765G>C, is reported to reduce its expression. OBJECTIVES: To investigate if -765G>C is associated with susceptibility to, and poorer outcome within, sarcoidosis and to examine a possible mechanism by which -765G>C reduces PTGS2 expression. METHODS: We used a case-control design study and genotyped -765G>C in a white British population of 198 patients with sarcoidosis and 166 control subjects. Patients with sarcoidosis were classified before genotyping as having persistent or nonpersistent disease using clinical criteria that included chest radiography staging, need for treatment, lung function, and longitudinal follow-up. Electrophoretic mobility shift assays were used to identify changes in transcription factor binding caused by the -765G>C polymorphism. RESULTS: Carriage of the -765C allele was strongly associated with susceptibility to sarcoidosis (odds ratio, 2.50; 95% confidence interval, 1.51-4.13; p=0.006) and, within this disease, with poorer outcome (odds ratio, 3.11; 95% confidence interval, 1.35-7.13; p=0.008). The association with sarcoidosis was replicated in a second Austrian population. Electrophoretic mobility shift assays revealed that the -765C allele causes a loss of Sp1/Sp3 transcription factor binding and an increase in Egr-1 binding to the region. CONCLUSION: Our data suggest that the -765G>C polymorphism identifies individuals who are susceptible to sarcoidosis and, more importantly, at risk of pulmonary fibrotic disease. An altered Sp1/Sp3 binding to the -765 region may contribute to the mechanism by which -765G>C reduces PTGS2 expression.

Adult↗
PubMed2006

Ligation of protease-activated receptor 1 enhances alpha(v)beta6 integrin-dependent TGF-beta activation and promotes acute lung injury.

Activation of latent TGF-beta by the alpha(v)beta6 integrin is a critical step in the development of acute lung injury. However, the mechanism by which alpha(v)beta6-mediated TGF-beta activation is regulated has not been identified. We show that thrombin, and other agonists of protease-activated receptor 1 (PAR1), activate TGF-beta in an alpha(v)beta6 integrin-specific manner. This effect is PAR1 specific and is mediated by RhoA and Rho kinase. Intratracheal instillation of the PAR1-specific peptide TFLLRN increases lung edema during high-tidal-volume ventilation, and this effect is completely inhibited by a blocking antibody against the alpha(v)beta6 integrin. Instillation of TFLLRN during high-tidal-volume ventilation is associated with increased pulmonary TGF-beta activation; however, this is not observed in Itgb6-/- mice. Furthermore, Itgb6-/- mice are also protected from ventilator-induced lung edema. We also demonstrate that pulmonary edema and TGF-beta activity are similarly reduced in Par1-/- mice following bleomycin-induced lung injury. These results suggest that PAR1-mediated enhancement of alpha(v)beta6-dependent TGF-beta activation could be one mechanism by which activation of the coagulation cascade contributes to the development of acute lung injury, and they identify PAR1 and the alpha(v)beta6 integrin as potential therapeutic targets in this condition.

Amides↗
PubMed2006

Aberrant expression of BARD1 in breast and ovarian cancers with poor prognosis.

Mutations in tumor-suppressor gene BARD1 have been found in inherited and spontaneous breast, ovarian and uterine cancers. BARD1 plays a critical role in DNA repair and ubiquitination as binding partner of BRCA1, with which it colocalizes to nuclear dots. Independently of BRCA1, BARD1 can induce p53-dependent apoptosis in response to genotoxic stress. Therefore, BARD1 or p53 might be defective in cancer cells spared from apoptosis. We investigated BARD1 and p53 expression in ovarian, breast and non-small-cell lung cancers. BARD1 expression was highly upregulated and cytoplasmic in most cancer cells, while weak nuclear staining was observed in the surrounding normal tissue. Maximal BARD1 expression was associated with the most malignant ovarian cancer, clear cell carcinoma. In breast cancer, BARD1 expression was correlated with poor differentiation and large tumor size, established factors of poor prognosis, as well as short disease-free survival. In contrast to breast and ovarian cancers, no correlation of BARD1 expression with either grade or stage could be determined for lung cancer. RT-PCR, performed on 10 ovarian cancers, revealed absence of the 5' portion of the BARD1 transcript in 7 tumors, and sequencing of the remaining 3 identified a missense mutation (A1291G) resulting in an amino acid change of glutamine 406 to arginine. These data suggest that genetic and epigenetic changes might lead to elevated cytoplasmic expression of BARD1 and that cytoplasmic BARD1 might be a poor prognostic factor for breast and ovarian cancers.

Adult↗
PubMed2006

Neutrophil elastase: mediator of extracellular matrix destruction and accumulation.

Of the myriad proteolytic enzymes implicated in the development of lung disease, neutrophil elastase has undoubtedly some of the most versatile effects. Although its key physiologic role is in innate host defense, it can also participate in tissue remodeling and possesses secretagogue actions that are now recognized as important to local inflammatory responses. Although unopposed neutrophil elastase activity has been implicated in the development of emphysema for several decades, only relatively recently has a pathogenetic function been ascribed to this serine proteinase in situations where excessive extracellular matrix deposition occurs. The use of genetically manipulated animal models is starting to uncover the potential ways in which its actions might influence fibrotic lung repair. Emerging evidence suggests that the engagement of cellular pathways with more direct effects on fibrogenic mediator generation and collagen synthesis appears to underpin the actions of neutrophil elastase in promoting lung matrix accumulation.

Animals↗
PubMed2005

Quantification of collagen and proteoglycan deposition in a murine model of airway remodelling.

BACKGROUND: Sub-epithelial extracellular matrix deposition is a feature of asthmatic airway remodelling associated with severity of disease, decline in lung function and airway hyperresponsiveness. The composition of, and mechanisms leading to, this increase in subepithelial matrix, and its importance in the pathogenesis of asthma are unclear. This is partly due to limitations of the current models and techniques to assess airway remodelling. METHODS: In this study we used a modified murine model of ovalbumin sensitisation and challenge to reproduce features of airway remodelling, including a sustained increase in sub-epithelial matrix deposition. In addition, we have established techniques to accurately and specifically measure changes in sub-epithelial matrix deposition, using histochemical and immunohistochemical staining in conjunction with digital image analysis, and applied these to the measurement of collagen and proteoglycans. RESULTS: 24 hours after final ovalbumin challenge, changes similar to those associated with acute asthma were observed, including inflammatory cell infiltration, epithelial cell shedding and goblet cell hyperplasia. Effects were restricted to the bronchial and peribronchial regions with parenchymal lung of ovalbumin sensitised and challenged mice appearing histologically normal. By 12 days, the acute inflammatory changes had largely resolved and increased sub-epithelial staining for collagen and proteoglycans was observed. Quantitative digital image analysis confirmed the increased deposition of sub-epithelial collagen (33%, p < 0.01) and proteoglycans (32%, p < 0.05), including decorin (66%, p < 0.01). In addition, the increase in sub-epithelial collagen deposition was maintained for at least 28 days (48%, p < 0.001). CONCLUSION: This animal model reproduces many of the features of airway remodelling found in asthma and allows accurate and reproducible measurement of sub-epithelial extra-cellular matrix deposition. As far as we are aware, this is the first demonstration of increased sub-epithelial proteoglycan deposition in an animal model of airway remodelling. This model will be useful for measurement of other matrix components, as well as for assessment of the molecular mechanisms contributing to, and agents to modulate airway remodelling.

Acute Disease↗
PubMed2005

Pediatric lung disease: from proteinases to pulmonary fibrosis.

One distinctive outcome of interstitial lung diseases in childhood is the abnormal accumulation of pulmonary extracellular matrix. The clinical consequence of such excessive connective tissue accumulation is known as pulmonary fibrosis. While numerous aspects of its pathogenesis have become familiar, many key events involved in its inception and progression still remain unclear. There is now compelling evidence that lung damage due to uncontrolled proteolysis may help drive critical processes that regulate fibrotic matrix remodeling. In this regard, a number of proteinases have been implicated in promoting both the initial lung injury and the fibroproliferative repair that follows. This review summarizes the knowledge of how different matrix-targeting enzymes may act to influence the development of pediatric pulmonary fibrosis. Understanding the scientific basis of this complex process may highlight opportunities to limit unwanted proteolysis and the intensity of its fibrotic sequelae.

Child↗
PubMed2005

Absence of proteinase-activated receptor-1 signaling affords protection from bleomycin-induced lung inflammation and fibrosis.

Activation of the coagulation cascade is commonly observed in the lungs of patients with both acute and chronic inflammatory and fibrotic lung disorders, as well as in animal models of these disorders. The aim of this study was to examine the contribution of the major thrombin receptor, proteinase-activated receptor-1 (PAR-1), during the acute inflammatory and chronic fibrotic phases of lung injury induced by intratracheal instillation of bleomycin in mice. Inflammatory cell recruitment and increases in bronchoalveolar lavage fluid (BALF) protein were attenuated by 56 +/- 10% (P < 0.05) and 53 +/- 12% (P < 0.05), respectively, in PAR-1-deficient (PAR-1-/-) mice compared with wild-type (WT) mice. PAR-1-/- mice were also protected from bleomycin-induced pulmonary fibrosis with total lung collagen accumulation reduced by 59 +/- 5% (P < 0.05). The protection afforded by PAR-1 deficiency was accompanied by significant reductions in pulmonary levels of the potent PAR-1-inducible proinflammatory and profibrotic mediators, monocyte chemoattractant protein-1 (MCP-1), transforming growth factor-beta-1 (TGF-beta1), and connective tissue growth factor/fibroblast-inducible secreted protein-12 (CTGF/FISP12). In addition, PAR-1 was highly expressed in inflammatory and fibroproliferative lesions in lung sections obtained from patients with fibrotic lung disease. These data show for the first time that PAR-1 signaling plays a key role in experimentally induced lung injury, and they further identify PAR-1 as one of the critical receptors involved in orchestrating the interplay between coagulation, inflammation, and remodeling in response to tissue injury.

Animals↗
PubMed2005

Pulmonary fibrosis: searching for model answers.

Substantial challenges remain in our understanding of fibrotic lung diseases. Nowhere is this more true than in the elucidation and verification of the pathogenetic basis upon which they develop. Scientific progress, most recently in the field of experimental therapy, has relied closely on interpreting data derived from animal modeling. Such models are used to identify the cellular interactions and molecular pathways involved in lung tissue repair and fibrosis. Over the coming years, the significance of new discoveries will continue to be evaluated using the in vivo analysis of animal models substituting for patients with actual pulmonary fibrosis. The commonest strategy to induce experimental pulmonary fibrosis is by directly administering a profibrotic agent to either wild-type animals or those that bear a specific genetic modification. The creation of new models has been greatly enhanced by the availability of stem cell lines and methods for introducing genetic mutations into these cells. Despite an increasing choice of models, there are still good reasons to continue adapting and using one of its earliest examples, the bleomycin model, in post-genomic pulmonary fibrosis research. A brief review of the exacting requirements of such research will place the strengths of this particular model in perspective.

Animals↗
PubMed2004

Factor Xa stimulates fibroblast procollagen production, proliferation, and calcium signaling via PAR1 activation.

Fibroblast proliferation and procollagen production are central features of tissue repair and fibrosis. In addition to its role in blood clotting, the coagulation cascade proteinase thrombin can contribute to tissue repair by stimulating fibroblasts via proteolytic activation of proteinase-activated receptor-1 (PAR1). During hemostasis, the coagulation cascade proteinase factor X is converted into factor Xa. We have previously shown that factor Xa upregulates fibroblast proliferation via production of autocrine PDGF. In this study, we further examined the effects of factor Xa on fibroblast function and aimed to identify its signaling receptor. We showed that factor Xa stimulates procollagen promoter activity and protein production by human and mouse fibroblasts. This effect was independent of PDGF and thrombin production, but dependent on factor Xa proteolytic activity. We also showed that PAR1-deficient mouse fibroblasts did not upregulate procollagen production, mobilize cytosolic calcium, or proliferate in response to factor Xa. Desensitization techniques and PAR1-specific agonists and inhibitors were used to demonstrate that PAR1 mediates factor Xa signaling in human fibroblasts. This is the first report that factor Xa stimulates extracellular matrix production. In contrast with endothelial cells and vascular smooth muscle cells, fibroblasts appear to be the only cell type in which the effects of factor Xa are mediated mainly via PAR1 and not PAR2. These findings are critical for our understanding of tissue repair and fibrotic mechanisms, and for the design of novel approaches to inhibit the profibrotic effects of the coagulation cascade without compromising blood hemostasis.

Animals↗
PubMed2004

Differential roles of extracellular signal-regulated kinase 1/2 and p38MAPK in mechanical load-induced procollagen alpha1(I) gene expression in cardiac fibroblasts.

OBJECTIVE AND METHODS: We have previously demonstrated that mechanical loading of cardiac fibroblasts leads to increased synthesis and gene expression of the extracellular matrix protein collagen. We hypothesised that the upregulation of procollagen gene expression in cardiac fibroblasts, in response to cyclic mechanical load, is mediated by one or more members of the MAP kinase family. To test this hypothesis, the effect of mechanical load on the activation of extracellular signal-regulated kinase (ERK) 1/2, p46/54JNK, and p38MAPK was examined in rat cardiac fibroblasts. RESULTS: Peak phosphorylation of ERK 1/2, p38MAPK kinases, and p46/54JNK was observed following 10-20 min of continuous cyclic mechanical load. Mechanical load significantly increased procollagen alpha1(I) mRNA levels up to twofold above static controls after 24 h. This increase was completely abolished by the MEK 1/2 inhibitor U0126, with no effect on basal levels. In contrast, SB203580, a specific inhibitor of p38MAPK, enhanced both basal and stretch-stimulated levels of procollagen mRNA. Consistent with this finding, selective activation of the p38MAPK signalling pathway by expression of MKK6(Glu), a constitutive activator of p38MAPK, significantly reduced procollagen alpha1(I) promoter activity. SB203580-dependent increase in procollagen alpha1(I) was accompanied by ERK 1/2 activation, and inhibition of this pathway completely prevented SB203580-induced procollagen alpha1(I) expression. CONCLUSIONS: These results suggest that mechanical load-induced procollagen alpha1(I) gene expression requires ERK 1/2 activation and that the p38MAPK pathway negatively regulates gene expression in cardiac fibroblasts. These pathways are likely to be key in events leading to matrix deposition during heart growth and remodelling induced by mechanical load.

Animals↗
PubMed2004

Comparison of the morphological and biochemical changes in normal human lung fibroblasts and fibroblasts derived from lungs of patients with idiopathic pulmonary fibrosis during FasL-induced apoptosis.

It is increasingly recognized that the morphological changes of apoptosis vary between cell types. This heterogeneity reflects the wide range of cellular proteins and enzymes involved in apoptotic pathways. Fibroblast apoptosis is crucial to the regression of scars and the restitution of healthy tissue during wound repair and may be aberrant in diseases such as idiopathic pulmonary fibrosis (IPF). The biochemical and morphological changes characterizing fibroblast apoptosis are unknown and may provide insights into the specific enzymatic mediators activated in these cells. This study aimed to examine the morphological changes of fibroblast apoptosis in both primary normal lung fibroblasts (normal-Fb) and fibroblasts obtained from patients with idiopathic pulmonary fibrosis (IPF-Fb) and to correlate these changes with conventional biochemical markers. Transmission electron microscopy (TEM) and video time-lapse microscopy demonstrated no difference in the duration of fibroblast apoptosis in response to FasL (6 +/- 0.3 h in normal-Fb and 6.4 +/- 0.2 h in IPF-Fb). However, IPF-Fb were more resistant to FasL-induced apoptosis compared with normal-Fb. Although the majority of morphological changes of normal-Fb and IPF-Fb were similar, the formation of filopodia and condensation of the cytoskeletal bundles in IPF-Fb, and more prominent vacuolation in normal-Fb, were the significant differences between these cell subtypes. Loss of the mitochondrial membrane potential occurred prior to caspase-3 activation, while phosphatidylserine expression, cytokeratin-18 cleavage, and DNA fragmentation commenced after caspase-3 activation. These observations not only suggest that specific enzymatic effectors may be preferentially activated during fibroblast apoptosis, but also provide potential insights into the pathogenesis of IPF.

Apoptosis↗
PubMed2004

Special Issue on HIV.

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Acquired Immunodeficiency Syndrome↗
PubMed2004

Shooting for PARs in lung diseases.

Proteinase-activated receptors (PARs) are novel G-protein-coupled receptors activated by serine and other proteinases to induce changes in cellular function. There is extensive evidence that PARs are expressed in the airways in a variety of cell types that are relevant to inflammatory lung diseases, and that activation of these receptors might be linked to significant pathological changes. Thus, PARs are exciting new targets in lung disease research. However, much of the data to date has come from in vitro studies using limited pharmacological tools, and considerably more needs to be known about the functions of this family of receptors in the lung before their potential as drug targets can be established.

Animals↗