Biomedical subjects

Marc Chanson

Publications and source records attributed to Marc Chanson.

15 recordsLinked to original sources

PubMed2006

Connexin37 protects against atherosclerosis by regulating monocyte adhesion.

A genetic polymorphism in the human gene encoding connexin37 (CX37, encoded by GJA4, also known as CX37) has been reported as a potential prognostic marker for atherosclerosis. The expression of this gap-junction protein is altered in mouse and human atherosclerotic lesions: it disappears from the endothelium of advanced plaques but is detected in macrophages recruited to the lesions. The role of CX37 in atherogenesis, however, remains unknown. Here we have investigated the effect of deleting the mouse connexin37 (Cx37) gene (Gja4, also known as Cx37) on atherosclerosis in apolipoprotein E-deficient (Apoe(-/-)) mice, an animal model of this disease. We find that Gja4(-/-)Apoe(-/-) mice develop more aortic lesions than Gja4(+/+)Apoe(-/-) mice that express Cx37. Using in vivo adoptive transfer, we show that monocyte and macrophage recruitment is enhanced by eliminating expression of Cx37 in these leukocytes but not by eliminating its expression in the endothelium. We further show that Cx37 hemichannel activity in primary monocytes, macrophages and a macrophage cell line (H36.12j) inhibits leukocyte adhesion. This antiadhesive effect is mediated by release of ATP into the extracellular space. Thus, Cx37 hemichannels may control initiation of the development of atherosclerotic plaques by regulating monocyte adhesion. H36.12j macrophages expressing either of the two CX37 proteins encoded by a polymorphism in the human GJA4 gene show differential ATP-dependent adhesion. These results provide a potential mechanism by which a polymorphism in CX37 protects against atherosclerosis.

Adenosine Triphosphate↗

PubMed2006

Reduced connexin43 expression limits neointima formation after balloon distension injury in hypercholesterolemic mice.

BACKGROUND: Reducing the expression of the gap junction protein connexin43 (Cx43) inhibits the progression of atherosclerosis, a chronic inflammatory disease. Furthermore, acute vascular injury induced by percutaneous coronary interventions is associated with increased Cx43 expression in neointimal smooth muscle cells (SMCs). However, the relevance of Cx43 after acute vascular injury remains unclear. METHODS AND RESULTS: To investigate whether reducing Cx43 expression would affect neointima formation in vivo, we subjected hypercholesterolemic Cx43+/- LDL receptor-deficient (LDLR-/-) mice and Cx43+/+LDLR-/- control littermates to carotid balloon distension injury, which induced marked endothelial denudation and activation of medial SMCs. We observed decreased macrophage infiltration in Cx43+/-LDLR-/- mice 7 days after injury. Similarly, peritoneal macrophages isolated from Cx43+/-LDLR-/- mice showed reduced migration in vitro compared with Cx43+/+LDLR-/- macrophages. Interestingly, Cx43+/-LDLR-/- macrophages also displayed decreased chemotactic activity for SMCs. In addition, we observed less SMC infiltration and proliferation in Cx43+/-LDLR-/- mice 7 and 14 days after balloon angioplasty. Likewise, Cx43+/-LDLR-/- SMCs showed decreased proliferation and migration in vitro compared with Cx43+/+LDLR-/- cells. All these events resulted in a reduction of neointimal thickening after vascular injury in Cx43+/-LDLR-/- mice. CONCLUSIONS: The present study shows for the first time that reducing Cx43 limits neointima formation after acute vascular injury by decreasing the inflammatory response and reducing SMC migration and proliferation. Thus, decreasing Cx43 expression may offer a novel therapeutic strategy for reducing restenosis after percutaneous coronary intervention.

Angioplasty, Balloon↗

PubMed2005

Long-term cultures of polarized airway epithelial cells from patients with cystic fibrosis.

The poor ability of respiratory epithelial cells to proliferate and differentiate in vitro into a pseudostratified mucociliated epithelium limits the general use of primary airway epithelial cell (AEC) cultures generated from patients with rare diseases, such as cystic fibrosis (CF). Here, we describe a procedure to amplify AEC isolated from nasal polyps and generate long-term cultures of the respiratory epithelium. AEC were seeded onto microporous permeable supports that carried on their undersurface a preformed feeder layer of primary human airway fibroblasts. The use of fibroblast feeder layers strongly stimulated the proliferation of epithelial cells, allowing the expansion of the cell pool with successive passages. AEC at increasing passage were seeded onto supports undercoated with airway fibroblasts and exposed to air. Either freshly isolated or amplified AEC could differentiate into a pseudostratified mucociliated epithelium for at least 10 mo. Thus, CF epithelia cultures showed elevated Na+ transport, drastic hyperabsorption of surface liquid, and absence of cAMP-induced Cl- secretion as compared with non-CF cultures. They were also characterized by thick apical secretion that hampered the movement of cell surface debris by cilia. However, CF respiratory epithelia did not show increased production of mucins or IL-8. The method described here is now routinely used in our laboratory to establish long-term cultures of well differentiated respiratory epithelia from human airway biopsies.

Biological Transport↗

PubMed2004

Gap junctional communication in tissue inflammation and repair.

Local injury induces a complex orchestrated response to stimulate healing of injured tissues, cellular regeneration and phagocytosis. Practically, inflammation is defined as a defense process whereby fluid and white blood cells accumulate at a site of injury. The balance of cytokines, chemokines, and growth factors is likely to play a key role in regulating important cell functions such as migration, proliferation, and matrix synthesis during the process of inflammation. Hence, the initiation, maintenance, and resolution of innate responses depend upon cellular communication. A process similar to tissue repair and subsequent scarring is found in a variety of fibrotic diseases. This may occur in a single organ such as liver, kidneys, pancreas, lung, skin, and heart, but fibrosis may also have a more generalized distribution such as in atherosclerosis. The purpose of this review is to summarize recent advances on the contribution of gap junction-mediated intercellular communication in the modulation of the inflammatory response and tissue repair.

Animals↗

PubMed2004

Microelectrodes and their use to assess ion channel function.

Impalement of living cells with microelectrodes (MEs) is a useful approach to measure a variety of biological parameters such as membrane potential (Vm), intracellular free ion concentrations and cell-to-cell communication. Despite such widespread applications, the number of trained researchers capable of using MEs is diminishing. In this article, we describe the fundamentals of the preparation and the proper use of MEs to study the physiology of transepithelial ion transport.

Animals↗

PubMed2004

Role of Toll-like receptor 4 on pancreatic and pulmonary injury in a mice model of acute pancreatitis associated with endotoxemia.

OBJECTIVE: Infection of pancreatic necrosis is a severe complication of acute pancreatitis. Because Toll-like receptor 4 (TLR4) has been identified as a receptor necessary to transduct the signal of bacteria-derived lipopolysaccharide into cells, we investigated the role of TLR4 on pancreatic and pulmonary injury in acute pancreatitis and acute pancreatitis associated with endotoxemia in wild-type and TLR4-deficient mice. DESIGN: Laboratory investigation. SETTING: University laboratory. SUBJECTS: Heterozygous TLR4 mice. INTERVENTIONS: Mice were injected intraperitoneally with a supramaximal dose of cerulein each hour for 10 hrs. To mimic infection, additional groups of mice were injected with lipopolysaccharide in the presence or absence of cerulein injections. MEASUREMENTS AND MAIN RESULTS: The severity of acute pancreatitis was assessed by serum amylase activity, pancreatic edema, acinar cell necrosis, and pancreas myeloperoxidase activity. Lung injury was quantitated by lung microvascular permeability and lung myeloperoxidase activity. Injections of cerulein induced an edematous pancreatitis that was of similar severity in wild-type and TLR4-deficient mice. Lipopolysaccharide alone had no toxic effect on pancreas and lungs and did not worsen the pancreatic injury induced by cerulein in wild-type and TRL4-deficient mice. In contrast, lipopolysaccharide worsened pancreatitis-associated lung injury, and the deficiency in TLR4 fully prevented this aggravation. CONCLUSIONS: TLR4 may not play a role in the pancreatitis-associated lung injury but participates in the pulmonary injury mediated by endotoxemia.

Acute Disease↗

PubMed2003

A tyrosine-based sorting signal is involved in connexin43 stability and gap junction turnover.

The gap junction protein connexin43 is known to have a rapid turnover, involving degradation by both the proteasomal and lysosomal systems, but the structural features of connexin43 that govern these actions are not known. The connexin43 C-terminal sequence contains a proline-rich region corresponding to the consensus of a protein-protein interaction PY-motif (xPPxY), and an overlapping putative tyrosine-based sorting signal (Yxxphi; =hydrophobic), known to play a role in the intracellular trafficking of many membrane proteins. As both motifs may control turnover of connexin43, we used a combination of metabolic radiolabelling, immuno-precipitation and functional assays to determine the possible role of these motifs in controlling degradation of human connexin43 expressed in SKHep1 cells. Mutation V289D in the tyrosine-based sorting motif increased the steady-state pool of connexin43 by approximately 3.5-fold, while mutation P283L in the PY-motif produced a comparatively modest augmentation (1.7-fold). No additive effect was observed when the overlapping tyrosine was mutated. In pulse-chase experiments, the Y286A substitution increased the half-life of connexin43 from 2 to 6 hours, indicating that the increased steady-state levels reflected reduced protein degradation. Moreover, expression at the junctional membrane, as well as gap junction-mediated intercellular communication (GJC), were nearly abolished by lysosomal inhibitors and Brefeldin A in cells expressing wild-type connexin43, but were unaffected in the tyrosine mutant. These results provide strong evidence that the tyrosine-based motif of human connexin43 is a prime determinant controlling connexin43 stability, and consequently GJC, by targeting connexin43 for degradation in the endocytic/lysosomal compartment.

Carcinoma, Hepatocellular↗

PubMed2003

Reduced connexin43 expression inhibits atherosclerotic lesion formation in low-density lipoprotein receptor-deficient mice.

BACKGROUND: Gap junctions allow the direct exchange of ions and small molecules between cells in contact, thus coordinating physiological processes such as cell growth and differentiation. We have recently demonstrated increased expression of the gap junction protein connexin43 (Cx43) in specific subsets of cells in atherosclerotic lesions. Because the development of atherosclerosis depends critically on paracrine cell-to-cell interactions, we hypothesized that direct intercellular communication via gap junctions may be another factor controlling atherogenesis. METHODS AND RESULTS: The role of Cx43 in atherogenesis was examined by use of both a genetic and a pharmacological approach. First, atherosclerosis-susceptible LDL receptor-deficient (LDLR-/-) mice with normal (Cx43+/+) or reduced (Cx43+/-) levels of Cx43 were fed a cholesterol-rich diet for 14 weeks. The progression of atherosclerosis was reduced by 50% (P<0.01) in the thoracoabdominal aorta and in the aortic roots of Cx43+/-LDLR-/- mice compared with Cx43+/+LDLR-/- controls. Atheroma in Cx43+/-LDLR-/- mice contained fewer inflammatory cells and exhibited thicker fibrous caps with more collagen and smooth muscle cells. Next, we observed that HMG-CoA reductase inhibitors, or "statins," lipid-lowering drugs well known for their pleiotropic antiatherogenic effects, reduced Cx43 expression in primary human vascular cells in vitro. Atheroma of LDLR-/- mice treated orally with pravastatin contained fewer inflammatory cells and exhibited thicker fibrous caps than controls. This was associated with reduced Cx43 expression in lesions of statin-treated mice. CONCLUSIONS: These data indicate a critical role for Cx43-mediated gap junctional communication in atherosclerotic plaque formation.

Animals↗

PubMed2003

Severe acute pancreatitis and reduced acinar cell apoptosis in the exocrine pancreas of mice deficient for the Cx32 gene.

BACKGROUND & AIMS: The early events leading to acinar cell injury during acute pancreatitis are poorly characterized. Signaling through gap junction channels contributes to the homeostasis of the exocrine pancreas by coordinating acinar cell activity within an acinus. To explore the role of gap junctional communication in acinar cell response to injury, we analyzed the course of acute pancreatitis induced by injection of cerulein in mice deficient for Cx32, the major gap junction protein expressed in the exocrine pancreas. METHODS: The severity of pancreatitis was evidenced by measuring serum amylase activity, pancreatic edema, acinar cell necrosis, pancreatic tumor necrosis factor alpha concentration, and myeloperoxidase activity. Acinar cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL), caspase-3 activity, and Bax/Bcl-2 expression. Expression and function of connexin were evaluated by immunofluorescence and dye coupling. RESULTS: Cx32-deficient mice exhibited a deleterious course of acute pancreatitis with increased necrosis, edema, and inflammation of the exocrine pancreas. In addition, the exocrine pancreas of Cx32-deficient mice showed a decreased number of TUNEL-positive acinar cells and decreased caspase-3 activity but no change in Bax or Bcl-2 pancreatic expression. Interestingly, chemicals known to induce apoptosis in vivo had no effect on Cx32-deficient pancreatic acinar cells. CONCLUSIONS: Deficiency of a pancreatic connexin converts a mild reversible form of acute pancreatitis into a severe disease and decreases the sensitivity of acinar cells to apoptotic stimuli. The results show that acinar cell-to-cell communication plays a key role in the modulation of severity of acute pancreatitis.

Acute Disease↗

PubMed2002

Defective activation of c-Src in cystic fibrosis airway epithelial cells results in loss of tumor necrosis factor-alpha-induced gap junction regulation.

Tumor necrosis factor-alpha (TNF-alpha) signaling is central to the transmission of the innate immune response and subsequent activation of the adaptive immune system. The functioning of both systems is required for optimal clearance of pathogens from the airways. In cystic fibrosis (CF), dysfunction of the CF transmembrane conductance regulator (CFTR) is associated with recurrent pulmonary infections despite an intense inflammatory and immune response. We reported recently that TNF-alpha decreased gap junction connectivity in non-CF airway cells, a mechanism that was absent in CF cells expressing the DeltaPhe-508 mutant of CFTR. We have now identified the tyrosine kinase c-Src as a possible pathway between the mediators of inflammation and the gap junction protein connexin43 (Cx43). Indeed, TNF-alpha increased the proportion of activated c-Src in non-CF airway cells. Moreover, pharmacological antagonists and expression in non-CF cells of a dominant negative construct of c-Src prevented Cx43 channel closure by TNF-alpha. Finally, gap junction channel closure was prevented by expression of a Cx43 mutant lacking tyrosine phosphorylation sites for c-Src. Additional experiments showed that activation of c-Src was defective in CF airway cells but rescued in CFTR-corrected CF cells. These data suggest that CFTR dysfunction is associated with altered TNF-alpha signaling, resulting in the persistence of gap junction connectivity in CF airway cells. We propose that altered regulation of c-Src may contribute to the dysregulated inflammatory response that is characteristic of the CF phenotype.

Cell Line↗

PubMed2002

Characterization of a novel chemotactic factor for neutrophils in the bronchial secretions of patients with cystic fibrosis.

Chronic airway inflammation is a hallmark of cystic fibrosis (CF). Biological products with chemotactic activity are essential for neutrophil recruitment to sites of inflammation. The presence of a factor with chemotactic activity higher than that of interleukin (IL)-8 in the bronchial secretions of patients with CF has recently been reported. This article reports that the chemotactic activity of this factor remained unaffected by a variety of physical treatments and could be distinguished from those of IL-8, formylmethionylleucylphenylalanine, leukotreine B4, and platelet-activating factor. The factor induced chemotaxis and chemokinesis locomotion of neutrophils, and its chemotactic activity was sensitive to pertussis toxin and thapsigargin. Semipurified preparation of the chemotactic factor increased transiently intracellular Ca(2+) concentration but failed to stimulate the release of neutrophil primary granules and the production of superoxide, suggesting that the semipurified chemotactic factor is a Ca(2+)-dependent chemoattractant of neutrophils, acting via pertussin toxin-sensitive G protein-coupled surface receptors, that directs neutrophil movement toward the airway epithelium.

Adolescent↗

PubMed2002

Role of the carboxyl terminal of connexin43 in transjunctional fast voltage gating.

Previous studies show that chemical regulation of connexin43 (Cx43) gap junction channels depends on the integrity of the carboxyl terminal (CT) domain. Experiments using Xenopus oocytes show that truncation of the CT domain alters the time course for current inactivation; however, correlation with the behavior of single Cx43 channels has been lacking. Furthermore, whereas chemical gating is associated with a "ball-and-chain" mechanism, there is no evidence whether transjunctional voltage regulation for Cx43 follows a similar model. We provide data on the properties of transjunctional currents from voltage-clamped pairs of mammalian tumor cells expressing either wild-type Cx43 or a mutant of Cx43 lacking the carboxyl terminal domain (Cx43M257). Cx43 transjunctional currents showed bi-exponential decay and a residual steady-state conductance of approximately 35% maximum. Transjunctional currents recorded from Cx43M257 channels displayed a single, slower exponential decay. Long transjunctional voltage pulses caused virtual disappearance of the residual current at steady state. Single channel data revealed disappearance of the residual state, increase in the mean open time, and slowing of the transition times between open and closed states. Coexpression of CxM257 with Cx43CT in a separate fragment restored the lower conductance state. We propose that Cx43CT is an effector of fast voltage gating. Truncation of Cx43CT limits channel transitions to those occurring across the higher energy barrier that separates open and closed states. We further propose that a ball-and-chain interaction provides the fast component of voltage-dependent gating between CT domain and a receptor affiliated with the pore.

Animals↗

PubMedDate not supplied

Discrimination between cystic fibrosis and CFTR-corrected epithelial cells by a membrane potential-sensitive probe.

Methods to detect functional cystic fibrosis transmembrane conductance regulator (CFTR) are needed for the assessment of new therapies in cystic fibrosis (CF). We have combined patch-clamp and fluorimetric techniques to investigate whether the fluorescent voltage-sensitive probe bis-(1,3-diethylthiobarbituic anid) trimethine oxonol (Di5BAC2(3)) discriminates between changes of membrane potential (Vm evoked by cAMP in CF and CYFT-corrected epithelial cells. About 60% of the (FTR-correrced cells increased their membrane conductance and depolarized in response to cAMP, as compared to about 20% of CF cells. CFTR was found to contribute only to a fraction of the cAMP-induced responses, as indicated by the differential effects of Cl- channel blockers. Simultaneous reocording of fluorescence (AF) and membrane potential revealed that AF detected Vm changes as small as 10 mV . The relationship between deltaF and deltaVm however, was not proportional. When a large number of cells were analyzed by digital imaging, an increase in deltaF in response to cAMP was detected in the majority of CFTR-corrected cells, but only in a small proportion of CF cells. The results indicate that the DiSBAC2(3) approach is a valid tool to compare cell populations with different proportions of cells responding to CFTR arcivation by cAMP. It cannot be used, however, for quantitative assessment of functional CFTR in individual CF cells.

Cyclic AMP↗

PubMedDate not supplied

Gap junctional communication does not contribute to the interaction between neutrophils and airway epithelial cells.

Cystic fibrosis (CF) is characterized by intense neutrophil migration into the airways. Increasing evidence indicates that interaction between neutrophils and airway epithelial cells contributes to the modulation of the inflammatory response. Blood neutrophils were reported to express connexins and form gap junctions with endothelial cells, thereby establishing gap junctional communication. We tested whether altered communication between human neutrophils and airway epithelial cells may contribute to the exaggerated inflammatory response observed in CF patients. Microinjections did not reveal dye coupling between activated blood neutrophils. By contrast, diffusion of calcein between neutrophils and airway epithelial cells of CF or non-CF origin was observed in transmigration and adhesion assays. This diffusion was prevented with probenicid, an inhibitor of ATP-dependent organic anion pumps, but not with gap junction blockers. Finally, RT-PCR failed to detect mRNAs for six connexins in blood neutrophils. These results suggest that gap junctional communication does not contribute to neutrophil-airway epithelial cell interaction.

Animals↗

PubMedDate not supplied

Src signaling links mediators of inflammation to Cx43 gap junction channels in primary and transformed CFTR-expressing airway cells.

Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) is associated with recurrent pulmonary infections and inflammation. We previously reported that tumor necrosis factor (TNF)-alpha decreases gap junction connectivity in cell lines derived from the airway epithelium of non-cystic fibrosis (non-CF) subjects, a mechanism that was defective in cells derived from CF patients, and identified the tyrosine kinase c-Src as a possible bridge between TNF-alpha and Cx43. To examine whether this modulation also takes place in primary epithelial cells, the functional expression of Cx43 was studied in non-CF and CF airway cells, obtained from surgical polypectomies and turbinectomies, which were grown either on culture dishes or permeable filters. Expression of Cx43 was detected by immunofluorescence on cells grown under both culture conditions. Non-CF and CF airway cells also showed intercellular diffusion of Lucifer Yellow. Dye coupling was rapidly abolished in non-CF cells in the presence of TNF-alpha, lipopolysaccharide and lysophosphatidic acid, and could be prevented by tyrphostin47, an inhibitor of Src tyrosine kinases. This down-regulation, however, was not detected in CF airway cells. These data indicate that CFTR dysfunction is associated with altered Src signaling, resulting in the persistence of gap junction connectivity in primary and transformed CF airway cells.

Caveolin 1↗