Biomedical subjects

Steve Lancel

Publications and source records attributed to Steve Lancel.

12 recordsLinked to original sources

PubMed2007

Inhaled nitric oxide increases endothelial permeability in Pseudomonas aeruginosa pneumonia.

OBJECTIVE: Pneumonia is a frequent cause of acute respiratory distress syndrome (ARDS), and Pseudomonas aeruginosa is a leading pathogen in nosocomial pneumonia. The management of ARDS remains a major problem, and only a limited number of options can improve the oxygenation. Inhaled nitric oxide (iNO) has been widely used, although this molecule is a free radical potentially harmful through the generation of toxic radical derivatives. The goal of our study was to assess the consequences of iNO (10 ppm) in a rat model of P. aeruginosa-induced lung injury. DESIGN: The animals were exposed for 24 h to iNO after instillation of the pathogen. Distal alveolar fluid clearance (DAFC) and epithelial and endothelial permeability were measured with a double flux of radio-labeled albumin. RESULTS: DAFC and epithelial permeability were increased in pneumonia but not influenced by iNO. In contrast, endothelial permeability was statistically significantly higher in the pneumonic animals exposed to iNO than in the pneumonic group without iNO (0.24+/-0.03 vs 0.47+/-0.1, p<0.05). This increase was not related to the production of nitrate/nitrite, nor to the increase of the inflammatory response evaluated by cytokine levels in the bronchoalveolar lavage fluid (TNF-alpha, IL-6, IL-10). The alveolar recruitment of polymorphonuclear neutrophils was comparable in the pneumonic group exposed to iNO and the pneumonic group without iNO. CONCLUSION: iNO increases the endothelial permeability in P. aeruginosa pneumonia. The mechanism is not related to the production of nitrate/nitrite or to a greater inflammatory response.

Administration, Inhalation↗

PubMed2007

Annexin V detection of lipopolysaccharide-induced cardiac apoptosis.

Acute inflammatory response to lipopolysaccharide (LPS) exposure is typically associated with cardiac myocyte apoptosis, which is difficult to quantify because of heart tissue specificity. We report here that radioiodinated Annexin V (I-AnxV), a specific ligand of phosphatidylserine exposed by apoptotic cells, allows tissue detection of apoptosis in LPS-treated rat hearts. Heart I-AnxV uptake was significantly increased in all cardiac territories of LPS-treated rats. In contrast, I-human serum albumin myocardial uptake was only slightly increased in LPS-treated rat hearts, suggesting limited changes in vascular protein permeability. Autoradiography of endotoxin-treated rat heart sections with I-AnxV in association with deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling and caspase 3 staining allows identification of double positive cardiac myocytes. Inhibition of apoptosis by caspase inhibitors (i.e., ZVAD.fmk and DEVD.cmk) reduced I-AnxV myocardial uptake in LPS-treated rats. Eventually, endotoxin-treated rats displayed pathological uptake of Tc-annexin in the cardiac mediastinal region whereas zVAD.fmk reduced Tc-annexin mediastinal uptake. Our results show that radioactive I-AnxV signal emerging from LPS-treated rat hearts could be related to the activation of caspase-dependent apoptotic pathway in cardiac myocytes.

Animals↗

PubMed2006

Inhibition of mitochondrial permeability transition prevents sepsis-induced myocardial dysfunction and mortality.

OBJECTIVES: The purpose of this study was to test whether mitochondrial dysfunction is causative of sepsis sequelae, a mouse model of peritonitis sepsis induced by cecal ligation and perforation. Inhibition of mitochondrial permeability transition was achieved by means of pharmacological drugs and overexpression of the antiapoptotic protein B-cell leukemia (Bcl)-2. BACKGROUND: Sepsis is the leading cause of death in critically ill patients and the predominant cause of multiple organ failure. Although precise mechanisms by which sepsis leads to multiple organ dysfunction are unknown, growing evidence suggests that perturbations of key mitochondrial functions, including adenosine triphosphate production, Ca2+ homeostasis, oxygen-derived free radical production, and permeability transition, might be involved in sepsis pathophysiology. METHODS: Heart and lung functions were evaluated respectively by means of isolated heart preparation, bronchoalveolar lavage fluid protein concentration, lung wet/dry weight ratio, lung homogenate myeloperoxidase activity, and histopathologic grading. Respiratory fluxes, calcium uptake, and membrane potential were evaluated in isolated heart mitochondria. RESULTS: Peritonitis sepsis induced multiple organ dysfunction, mitochondrial abnormalities, and increased mortality rate, which were reduced by pharmacological inhibition of mitochondrial transition by cyclosporine derivatives and mitochondrial Bcl-2 overexpression. CONCLUSIONS: Our study provides strong evidence that mitochondrial permeability transition plays a critical role in septic organ dysfunction. These studies demonstrate that mitochondrial dysfunction in sepsis is causative rather than epiphenomenal and relevant in terms of vital organ function and outcome. Regarding the critical role of heart failure in the pathophysiology of septic shock, our study also indicates a potentially new therapeutic approach for treatment of sepsis syndrome.

Animals↗

PubMed2006

Sphingosine impairs mitochondrial function by opening permeability transition pore.

Growing evidence suggest that, in the heart, sphingosine participates to contractile dysfunction by altering calcium transients and mitochondria function. However, mechanisms underlying sphingosine-induced cardiac mitochondria dysfunction are poorly understood. Here, we studied the effects of sphingosine on isolated cardiac mitochondria of either wild-type or Bcl-2 overexpressing transgenic mice. Sphingosine induced reductions in ADP-coupled respiration, membrane potential, mitochondrial cytochrome c content and ATP production, which were partially prevented by cyclosporine A and mitochondrial Bcl-2 overexpression. These data suggest that sphingosine promotes mitochondrial permeability transition pore opening, which may result in uncoupled respiration and participate in cardiac contractile dysfunction.

Animals↗

PubMed2006

Myocardial dysfunction and potential cardiac hypoxia in rats induced by carbon monoxide inhalation.

BACKGROUND: Results from both animal and human being studies provide evidence that inhalation of concentrations of carbon monoxide (CO) at around 100 ppm has antiinflammatory effects. These low levels of CO are incriminated in ischemic heart diseases experienced by cigarette smokers and, in some cases, from air pollution. Although neurologic mechanisms have been investigated, the effects of CO on cardiovascular function are still poorly understood. METHODS AND RESULTS: The effects of CO (250 ppm; 90 min) inhalation on myocardial function were investigated in isolated heart of rats killed immediately, and 3, 24, 48, and 96 h after CO exposure. CO exposure at 250 ppm resulted in an arterial carboxyhemoglobin (HbCO) level of approximately 11%, which was not associated with changes in mean arterial pressure and heart rate. CO exposure induced coronary perfusion pressure increases, which were associated with endothelium-dependent and -independent vascular relaxation abnormalities. CO-induced coronary vascular relaxation perturbations were observed in the presence of increased heart contractility. Spontaneous peak to maximal Ca(2+)-activated left ventricular pressure ratio was markedly increased in CO-exposed rats, indicating increases in myofilament calcium sensitivity. Heart cyclic guanosine monophosphate/cAMP ratio and myocardial permeabilized fiber respiration (complex intravenous activity) were reduced in CO-exposed rats, which lasted after 48 h of reoxygenation in air. CONCLUSIONS: These findings suggest that CO deteriorates heart oxygen supply to utilization and potentially may induce myocardial hypoxia through mechanisms that include increased oxygen demand due to increased contractility, reduced coronary blood flow reserve, and cardiomyocyte respiration inhibition.

Administration, Inhalation↗

PubMed2006

Cardiovascular protective role for activated protein C during endotoxemia in rats.

OBJECTIVE: We examined whether activated protein C (APC) treatment improves cardiovascular inflammation and dysfunction in endotoxemic rats. DESIGN AND SETTING: Randomized, controlled trial in an experimental laboratory of a university physiology department SUBJECTS: Male Sprague Dawley rats. INTERVENTIONS: Internal carotid artery and external jugular vein were catheterized under sterile conditions in rats. Instrumented rats infused or not with APC (240 microg/kg per hour) were challenged with E. coli endotoxin (10 mg/kg). Four hours after endotoxin challenge rats were prepared for cardiovascular functional studies and tissue and blood analyses. MEASUREMENTS AND RESULTS: Endotoxin administration induced systemic hypotension, depression of myocardial systolic performance and reduction in capillary density of the small intestine muscularis layer. Plasma levels of nitrite/nitrate, tumor necrosis factor alpha and macrophage migration inhibitory factor, mesentery venule leukocyte-endothelium interactions, heart and small intestine myeloperoxidase activities were increased in endotoxin-treated rats. APC largely prevented endotoxin-induced cardiovascular dysfunction with improved systemic hemodynamics, functional capillary density, and myocardial contractile performance. Beneficial cardiovascular effects of APC were associated with attenuation of entotoxin-induced inflammatory response in terms of plasma levels of nitrite/nitrate, tumor necrosis factor alpha, macrophage migration inhibitory factor, and endothelial cell-leukocyte activation. CONCLUSION: APC reduces systemic and tissue inflammation and preserves cardiovascular function during experimental endotoxemia.

Animals↗

PubMed2005

Ventricular myocyte caspases are directly responsible for endotoxin-induced cardiac dysfunction.

BACKGROUND: Although most of the deleterious effects of sepsis-induced apoptosis have been attributed to increased lymphocyte cell death, caspase activation may directly alter cell function of different organ systems. We postulated that left ventricular (LV) cardiomyocyte caspase activation is directly involved in sepsis-induced heart contractile dysfunction. METHODS AND RESULTS: LV cardiomyocytes isolated 4 hours after rat treatment with endotoxin injection (10 mg/kg) displayed major reductions in contractile reserve and myofilament response to Ca2+. Concomitantly, endotoxin also induced increases in LV cardiomyocyte caspase-3, -8, and -9-like activities, which were associated with sarcomeric structure destruction and cleavage of components of the cardiac myofilament. Interestingly, zVAD.fmk treatment of septic rat prevented LV cardiomyocyte contractile dysfunction, reductions in myofilament response to calcium, troponin T cleavage, and sarcomere destruction. Serum (10%) of endotoxin-treated rats induced contractile dysfunction, caspase-3-like activity increase, and troponin T cleavage of naive LV cardiomyocytes. The effects of septic serum were prevented in LV cardiomyocytes isolated from zVAD.fmk- or zDEVD.cmk-treated rats or LV cardiomyocytes preincubated with zVAD.fmk or zDEVD.cmk. CONCLUSIONS: The results show an important relationship between endotoxin-induced caspase activation and reduced contractile reserve and sarcomere disarray at the level of single LV cardiomyocytes.

Actin Cytoskeleton↗

PubMed2005

Expression of apoptosis regulatory factors during myocardial dysfunction in endotoxemic rats.

OBJECTIVES: To document the time course of apoptosis pathway activation in sepsis and to determine whether Bcl-2 overexpression would improve endotoxin-induced myocardial dysfunction and mortality rate. DESIGN: Randomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Male Sprague Dawley rats, wild-type C57BL/6 female mice, C57BL/6 female mice overexpressing Bcl-2. INTERVENTIONS: Hearts were isolated from rats treated with endotoxin (10 mg/kg, intravenously) to perform heart function, immunohistochemistry (terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick 3'-end labeling, caspase 3), RNase protection assay, reverse transcriptase polymerase chain reaction, Western blotting (caspase 3), and radiolabeled annexin V studies. Twenty-four hours before endotoxin challenge (10 mg/kg, intravenously), rats were pretreated with saline or endotoxin (0.5 mg/kg, intraperitoneally), with or without parthenolide (1 mg/kg, intraperitoneally). Isolated hearts were used to test myocardial function. Mortality induced by endotoxin (10 mg/kg, intraperitoneally) was tested on wild-type or mice overexpressing Bcl-2. MEASUREMENTS AND MAIN RESULTS: Endotoxin-induced heart dysfunction was maximal at 4 and 8 hrs postinjection, started to improve, and was fully restored at 24 hrs after endotoxin treatment. Endotoxin also induced phosphatidylserine outer leaflet membrane exposure, caspase 3 activation, nuclear apoptosis, and changes in apoptosis gene expression. Bcl-2 overexpression induced by endotoxin pretreatment prevented endotoxin-induced myocardial dysfunction. Mice overexpressing Bcl-2 had dramatic improvement in survival rate compared with wild-type mice. CONCLUSIONS: These observations suggest that both death receptor and caspase-mediated apoptosis processes are activated in this sepsis model. Bcl-2 overexpression before endotoxin challenge prevents myocardial dysfunction in rats and improves survival rate in mice.

Animals↗

PubMed2004

Mitochondrial proliferation during apoptosis induced by anticancer agents: effects of doxorubicin and mitoxantrone on cancer and cardiac cells.

Doxorubicin is one of the most largely prescribed antitumor drug for the treatment of breast, liver and colon cancers as well as leukemia, but the cardiotoxicity of this anthracycline derivative limits its clinical use. Although doxorubicin is toxic to both cancer and cardiac cells, there are evidences suggesting that the mechanism of cell death is different for the two cell types. To investigate further this issue, we have compared the proapoptotic effects of doxorubicin and the functionally related anthracenedione compound mitoxantrone, which is also used in the clinic for the treatment of cancer. After evaluating the toxicity of the two drugs to mammary adenocarcinoma MTLn3 cells and H9C2 cardiomyocytes, we dissected the drug-induced apoptotic machinery by measuring the effects on the cell cycle progression, DNA condensation and fragmentation, production of endogenous peroxides and caspase activation. Both doxorubicin and mitoxantrone are potent inducers of apoptosis in H9C2 cardiomyocytes and MTLn3 breast cancer cells, but there are significant differences between the two cell types in terms of kinetics and order of the events. In particular, flow cytometry measurements of drug-induced changes in mitochondrial transmembrane potential and mitochondrial mass with different fluorescent probes suggested that the two drugs induced a progressive increase in mitochondrial mass in the cancer cells but not in the cardiac cells. The hypothesis was validated by means of electron microscopy, which revealed a significant increase in the number of mitochondria in drug-treated MTLn3 but not in H9C2 cells. The mitochondrial proliferation precedes the nuclear apoptosis in doxorubicin-treated MTLn3 cells. The changes in the architecture and number of mitochondria are linked to the drug-induced perturbation of the cell cycle progression and apoptosis. The proliferation of mitochondria could explain the higher toxicity of doxorubicin to cancer cells compared to cardiac cells and this suggests novel therapeutic opportunities to better control the cardiotoxicity of anthracyclines.

Adenocarcinoma↗

PubMed2004

Peroxynitrite decomposition catalysts prevent myocardial dysfunction and inflammation in endotoxemic rats.

OBJECTIVES: The aim of this study was to test whether peroxynitrite neutralizers would reduce peroxynitrite accumulation and improve myocardial contractile dysfunction and inflammation in endotoxin-treated rats. BACKGROUND: Release of endogenous proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha in response to endotoxin is responsible for the production of large amounts of nitric oxide (NO), which may exert detrimental effects on the myocardium in animal models, isolated hearts, and isolated cardiac myocytes. Recent studies have indicated that many of the deleterious effects of NO are mediated by peroxynitrite, a powerful oxidant generated from a fast diffusion-limited reaction of NO and superoxide anion. METHODS: We studied the effects of peroxynitrite neutralizers, such as mercaptoethylguanidine (MEG) sodium succinate (10 mg/kg) and 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrinato iron (III) (FeTPPS) (30 mg/kg) on peroxynitrite accumulation, in vivo endothelial cell-leukocyte activation on the mesenteric venule, and myocardial contractile dysfunction and inflammation in a model of sepsis induced by injection of endotoxin (10 mg/kg) in rats. RESULTS: Mercaptoethylguanidine sodium succinate and FeTPPS largely prevented the accumulation of peroxynitrite as measured by plasma rhodamine fluorescence and heart nitrotyrosine staining. Interestingly, MEG sodium succinate and FeTPPS improved endotoxin-induced myocardial contractile dysfunction, which was associated with reduced degradation of nuclear factor kappa B inhibitory protein I-kappa-B, plasma TNF-alpha levels, and microvascular endothelial cell-leukocyte activation. CONCLUSIONS: These observations suggest that the beneficial effects of MEG and FeTPPS on endotoxin-induced myocardial contractile dysfunction could be related to the unique effects of these compounds on cardiovascular inflammation processes.

Animals↗

PubMed2004

Calpain inhibitors improve myocardial dysfunction and inflammation induced by endotoxin in rats.

Excessive activation of calpains has been implicated in the pathophysiology of inflammation, trauma, and ischemia reperfusion injury. Here, we investigated the effects of calpain inhibition on myocardial dysfunction and inflammation induced by endotoxin in rats. Rats were treated i.v. with endotoxin (10 mg/kg) or endotoxin plus calpain inhibitors and were then prepared after 4 h for myocardial contractility assessment, detection of endothelium leukocyte interactions, and plasma TNF-alpha, nitrite/nitrate, and endocan levels. Compared with vehicle-treated rats, hearts from endotoxin-treated rats had reduced systolic performance that was partially prevented by calpain inhibitors, i.e., acetyl-leucyl-leucyl-arginal (leupeptin), carbobenzoxy-valyl-phenylalanial (calpain inhibitor III), and N-acetyl-leucinyl-leucinyl-norleucinal (ALLN). Leupeptin and calpain inhibitor III reduced plasma TNF-alpha levels in endotoxin-treated rats. ALLN reduced plasma TNF-alpha and nitrite/nitrate levels in endotoxin-treated rats. Endotoxin treatment increased mesenteric venule leukocyte rolling (10 +/- 3 leukocytes/min vs. 44 +/- 10 leukocytes/min; P < 0.01) and adhesion (2 +/- 2 leukocytes/min vs. 15 +/- 3 leukocytes/min; P < 0.01), which was reduced by calpain inhibitors. Attenuation of leukocyte endothelium interactions observed in calpain inhibitor-treated rats with sepsis was associated with increases in plasma anti-adhesion molecule endocan. In conclusion, calpain inhibitors improved endotoxin-induced cardiac dysfunction, which may be attributed to the modulation of endothelium leukocyte interactions in the inflamed vasculature.

Animals↗

PubMed2004

Endotoxin-induced myocardial dysfunction: evidence for a role of sphingosine production.

OBJECTIVE: To determine whether sphingomyelinase pathway activation would participate in myocardial depression induced by endotoxin. DESIGN: Randomized, controlled trial. SETTING: Experimental laboratory. SUBJECTS: Male Sprague-Dawley rats, isolated rat heart, and cardiac myocytes. INTERVENTIONS: Cardiovascular function was evaluated in rats injected with saline, endotoxin (10 mg/kg, intravenously), and N-oleoylethanolamine (NOE; 10 mg/kg, intravenously). In ex vivo experiments, isolated rat hearts were perfused with endotoxin (5 microg/mL). For pharmacologic intervention, NOE (1 micromol/L) was admixed to the perfusate 20 mins before endotoxin. In in vitro experiments, ventricular myocytes were incubated with sphingosine (20 microM). Myocyte cell shortening and calcium transient were measured. Mitochondrial membrane potential was measured using the cationic dye tetramethylrhodamine methylester fluorescence technique. MEASUREMENTS AND MAIN RESULTS: Endotoxin treatment at 4 hrs did not alter mean arterial pressure and abdominal blood flow compared with control rats. Left ventricle developed pressure (LVDP) and its first derivatives (i.e., maximal and minimal change in pressure over time [dP/dtmax and dP/dtmin]) were decreased after 4 hrs in endotoxin-treated rats compared with control rats. NOE (10 mg/kg) treatment largely prevented left ventricular systolic function alterations of endotoxin-treated hearts (n = 6 in each group). In isolated rat heart, endotoxin (5 microg/mL) caused increases in tumor necrosis factor-alpha perfusate concentration and delayed depression of LVDP, dP/dtmax, and dP/dtmin after 60 mins, which was partially abrogated in the presence of the ceramidase inhibitor NOE (1 micromol/L). Sphingosine (20 microM) caused decreases in cell fractional shortening, calcium transient, and mitochondrial membrane potential of cardiac myocytes. CONCLUSION: These observations suggest that the sphingomyelinase pathway participates in endotoxin-induced myocardial depression.

Animals↗