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Biomedical subjects

Laurent P Nicod

Publications and source records attributed to Laurent P Nicod.

15 recordsLinked to original sources
PubMed2006

Efficiency and safety of bosentan in child C cirrhosis with portopulmonary hypertension and renal insufficiency.

Bosentan has lately been described as a successful therapeutic agent for portopulmonary hypertension consecutive to child A cirrhosis. This is the first report of the effect of this substance with advanced liver cirrhosis (child C) and renal insufficiency. Low doses of bosentan (initially twice 31.25 mg/day and then 62.5 mg/day) increased cardiac output and allowed correction of renal insufficiency; it allowed one to stop the requirement of oxygen and not only improved the 6-min walking test by more than 400 m, but also decreased the severity of the liver cirrhosis to child B stadium. This suggests that patients, who would be excluded from a liver transplantation program because of their portopulmonary hypertension, could profit from a careful therapy with bosentan.

Adult↗
PubMed2006

Mechanisms of airway obliteration after lung transplantation.

Post-transplant bronchiolitis obliterans, also called bronchiolitis obliterans syndrome, affects up to 50-60% of patients who survive 5 yr after surgery according to its clinical definition, which is based on the degree of obstructive airway disease. Alloimmune-independent and -dependent mechanisms produce injuries and inflammation of epithelial cells and subepithelial structures, leading to aberrant tissue repair. The triggering of innate immunity by various infections or chemical injuries after, for example, gastroesophageal reflux, may lead to the release of danger signals that are able to activate dendritic cells, a crucial link with adaptive immunity. Inflammation can also increase the expression and display of major histocompatibility alloantigens and thus favor the initiation of rejection episodes. These phenomena may be limited in time and location or may be protracted. Reducing the risk of alloimmune-independent factors may be as important as treating acute episodes of lung rejection. Excessive immunosuppression may be deleterious by increasing the risk of infection, thereby triggering innate and adaptive immunity. New potential therapeutic targets are emerging from the research performed on leukotriene receptors, chemokine receptors, and growth factors. Neutralizing these molecules reduces the initial mononuclear and polynuclear infiltrates or the subsequent fibroproliferative process and the neovascular changes, feeding this process.

Bronchiolitis Obliterans↗
PubMed2006

Exovesicles from human activated dendritic cells fuse with resting dendritic cells, allowing them to present alloantigens.

Dendritic cells (DCs) can release microvesicles, but the latter's numbers, size, and fate are unclear. Fluorescently labeled DCs were visualized by laser-scanning microscopy. Using a Surpass algorithm, we were able to identify and quantify per cell several hundred microvesicles released from the surface of stimulated DCs. We show that most of these microvesicles are not of endocytic origin but result from budding of the plasma membrane, hence their name, exovesicle. Using a double vital staining, we show that exovesicles isolated from activated DCs can fuse with the membrane of resting DCs, thereby allowing them to present alloantigens to lymphocytes. We concluded that, within a few hours from their release, exovesicles may amplify local or distant adaptive immunological response.

Antigen Presentation↗
PubMed2005

Severe left ventricular dysfunction secondary to primary pulmonary hypertension: bridging therapy with bosentan before lung transplantation.

When right ventricular failure develops secondary to primary pulmonary hypertension, right-left ventricular interaction may lead to severe impairment of left ventricular function. In such cases, many experts favor combined heart-lung transplantation by fear that the left ventricle may not recover after transplantation of the lungs alone. We report a case of primary pulmonary hypertension with severely diminished right and left ventricular function. The patient was rendered amenable to isolated pulmonary transplantation with the endothelin-receptor antagonist bosentan. The medication improved right and left ventricular function to the point that heart transplantation no longer appeared necessary. After double-lung transplantation the patient's cardiac function made a full recovery. This approach might be particularly welcome considering both the current donor organ shortage and the limited number of surgical teams with expertise in heart-lung transplantation.

Adult↗
PubMed2005

Upregulation of CD40, CD80, CD83 or CD86 on alveolar macrophages after lung transplantation.

BACKGROUND: Alveolar macrophages (AMs) are known to be poor antigen-presenting cells, and lack the accessory molecules such as CD40, CD80 or CD86 to activate T cells. The question raised is about the potential changes in phenotypes after lung transplantation, particularly during acute rejection episodes. METHODS: The present study analyzed the phenotype of AMs longitudinally in 45 lung transplant patients, between August 1997 and April 2002, with a follow-up period of 27.2 +/- 2.5 (mean +/- SEM) months. There were 7.7 +/- 0.6 bronchoalveolar lavage (BAL) assessments performed per patient (i.e., 345 BALs), simultaneously with transbronchial biopsies. Transplantation was soon followed by a progressive upregulation of CD40 on 49.7 +/- 8% of AMs during the first month, and this marker remained elevated at 60 +/- 8% after 5 years. RESULTS: Both CD86 and CD80, as well as CD83, a marker of dendritic cells, were enhanced for most AMs during Grade A2 and A3 rejection episodes. A correlation was found between expression of CD83 and CD86, but not between CD1a and CD86. Immunohistology confirmed that CD40-positive cells in the alveoli corresponded to AMs and to some dendritic cells in the basal layers of the airways. In vitro studies showed that harvested AMs with these enhanced accessory molecules remained poor stimulators of allogeneic cells, a phenomenon that may be related to the ongoing immunosuppressive treatments. CONCLUSIONS: AM phenotypes showed marked changes during early or late acute rejection episodes, acquiring CD80, CD83 and CD86, while CD40 expression was further enhanced. This finding may provide clues on how to monitor the tolerance of transplanted lungs and may also provide new insights into the pathophysiology of lung transplantation.

Adult↗
PubMed2005

Health-related quality of life following single or bilateral lung transplantation: a 7-year comparison to functional outcome.

OBJECTIVES: To compare long-term health-related quality of life (HRQL) in single and bilateral lung transplant recipients independent of the underlying disease, and in a subset of patients with native pulmonary emphysema. METHODS: Forty-four lung transplant recipients (mean [+/- SD] age, 44.8 +/- 11.6 years) were followed up for > 2 years after single lung transplantation (LTx) [14 recipients] or bilateral LTx (30 recipients). Data were prospectively collected, before undergoing LTx and annually after undergoing LTx, measuring FEV1, 6-min walk test (6MWT) results, and quality of life using the St. George respiratory questionnaire (SGRQ) and a visual analog scale (VAS). The SGRQ addresses three domains, namely, respiratory symptoms, accomplishment of routine activities, and disease impact on daily life. RESULTS: Statistically significant correlation coefficients were found comparing the SGRQ and the VAS (r = 0.812; p < 0.0001), the SGRQ and the 6MWT (r = 0.610; p < 0.0001), and the SGRQ and the FEV1 (r = 0.523; p < 0.0001) in all patients. Significant improvements on the FEV1, 6MWT, and SGRQ were observed after LTx in both single and bilateral LTx recipients. Increased risk for the development of bronchiolitis obliterans syndrome (BOS) [relative risk, 2.86; 95% confidence interval, 1.22 to 6.67; p = 0.03] and significantly lower FEV1 values were observed in patients following a single graft, compared to that in patients following a bilateral graft (p < 0.01). In contrast, the 6MWT and the SGRQ scores were not significantly different between recipients of single and double LTx. The same patterns of results were observed in comparisons between single and bilateral lung recipients with prior pulmonary emphysema. CONCLUSIONS: Despite poorer FEV1 recovery and increased risk of BOS after LTx, single lung transplant recipients had comparable long-term exercise tolerance and quality-of-life scores as patients who received bilateral transplants. These results suggest the limited influence of functional performance on objective and subjective markers of HRQL recovery after LTx.

Adult↗
PubMed2004

Respiratory viruses and severe lower respiratory tract complications in hospitalized patients.

BACKGROUND: Acute respiratory viral infections are generally self-limited in healthy subjects but can lead to severe complications in immunocompromised hosts. We report the clinical impact of acute lower respiratory tract viral infections in hospitalized patients. MATERIALS AND METHODS: Of 1,001 fiberoptic bronchoscopies performed during a period of 5 years, 33 BAL samples were positive for respiratory viruses by cell culture. The main diagnosis, length of hospitalization, response to initial treatment, and the mortality rate at 30 days were analyzed. Spirometry performed before and after infection was compared in lung transplant recipients. RESULTS: The following respiratory viruses were identified in 33 cases: influenza A or B (n = 13), parainfluenza virus 1-3 (n = 7), rhinovirus (n = 5), respiratory syncytial virus (n = 4), and adenovirus (n = 4). All cases were immunocompromised patients who acquired new respiratory symptoms and/or radiologic abnormalities suggesting a pulmonary infection. Twenty-five patients (74%) did not respond to initial broad-spectrum antibiotics, and 11 patients (33%) required intensive care for respiratory failure. The overall mortality rate at 1 month was 24%. In patients with a sole viral pathogen identified in their BAL, the mortality rate was 39%. In lung transplant recipients (n = 10), the mean FEV(1) decreased from 2.2 to 1.9 L/s before and during the infection episode, respectively (p < 0.01); 3 months later, 60% of the patients had still not completely recovered to baseline values. CONCLUSION: Respiratory viruses recovered in BAL samples of immunocompromised patients are associated with severe lower respiratory complications. In lung transplant recipients, we observed a persisting impairment of pulmonary function.

Acute Disease↗
PubMed2003

Pulmonary hypertension.

Pulmonary arterial hypertension (PAH) must be classified into primary pulmonary hypertension and PAH related to other diseases such as collagen vascular diseases, HIV infection or portal hypertension. PAH must also be differentiated from other entities, in particular pulmonary hypertension secondary to thromboembolic diseases, requiring specific approaches. All PAH results in similar histological remodelling of pulmonary arteries, with thickening of the intima, proliferation of the media and plexogenic lesions. Today the physiopathology of these lesions is much better understood and has resulted in new therapies involving substances such as prostacyclins, endothelin receptor antagonists or phosphodiesterase inhibitors, aimed not only at dilating arteries but also at preventing their remodelling. Thromboendarterectomy, septostomy and transplantation remain the only option where medical treatment has failed.

Humans↗
PubMed2003

Superoxide anions induce the maturation of human dendritic cells.

Dendritic cells play a key role in immune responses. There is growing evidence that reactive oxygen species participate in signaling pathways involving nuclear factor (NF)-kappaB, leading to expression of important immune system genes. We found that, unlike H2O2, reactive oxygen species generated by the reaction of oxidase on xanthine induced early phenotypic maturation of dendritic cells by upregulating specific markers CD80, CD83, and CD86 and downregulating mannose receptor-mediated endocytosis. Maturation induced by xanthine oxidase was prevented by allopurinol, an inhibitor of xanthine oxidase activity, and by N-acetylcysteine. The proteasome inhibitor MG-132, which blocks NF-kappaB activation, also inhibited CD86 upregulation, but not endocytosis downregulation by reactive oxygen species. Finally, xanthine-xanthine oxidase enhanced or blocked antigen presentation by dendritic cells depending on whether they had been prepulsed or not with the antigen. Taken together, these results demonstrate that oxidative stress induces phenotypic and functional maturation of dendritic cells, partly through an NF-kappaB-dependent mechanism.

Cells, Cultured↗
PubMed2003

DC-SIGN is the major Mycobacterium tuberculosis receptor on human dendritic cells.

Early interactions between lung dendritic cells (LDCs) and Mycobacterium tuberculosis, the etiological agent of tuberculosis, are thought to be critical for mounting a protective anti-mycobacterial immune response and for determining the outcome of infection. However, these interactions are poorly understood, at least at the molecular level. Here we show that M. tuberculosis enters human monocyte-derived DCs after binding to the recently identified lectin DC-specific intercellular adhesion molecule-3 grabbing nonintegrin (DC-SIGN). By contrast, complement receptor (CR)3 and mannose receptor (MR), which are the main M. tuberculosis receptors on macrophages (Mphis), appeared to play a minor role, if any, in mycobacterial binding to DCs. The mycobacteria-specific lipoglycan lipoarabinomannan (LAM) was identified as a key ligand of DC-SIGN. Freshly isolated human LDCs were found to express DC-SIGN, and M. tuberculosis-derived material was detected in CD14(-)HLA-DR(+)DC-SIGN(+) cells in lymph nodes (LNs) from patients with tuberculosis. Thus, as for human immunodeficiency virus (HIV), which is captured by the same receptor, DC-SIGN-mediated entry of M. tuberculosis in DCs in vivo is likely to influence bacterial persistence and host immunity.

Antigens, CD↗
PubMed2003

Pharmacokinetics of mycophenolic acid associated with calcineurin inhibitors: long-term monitoring in stable lung recipients with and without cystic fibrosis.

Pharmacologic interactions and absorption disturbances after transplantation may induce serologic fluctuation of immunosuppression and adversely affect outcome. We present data showing that trough levels of mycophenolic acid decreased by 50% during combined mycophenolate mofetil (MMF) and cyclosporine therapy compared with levels during combined MMF and tacrolimus therapy. In addition, cystic fibrosis patients required 30% higher doses of MMF to achieve the therapeutic levels of recipients without cystic fibrosis.

Adult↗
PubMed2003

Human alveolar macrophages infected by virulent bacteria expressing SipB are a major source of active interleukin-18.

Recent publications have demonstrated that the protease caspase-1 is responsible for the processing of pro-interleukin 18 (IL-18) into the active form. Studies on cell lines and murine macrophages have shown that the bacterial invasion factor SipB activates caspase-1, triggering cell death. Thus, we investigated the role of SipB in the activation and release of IL-18 in human alveolar macrophages (AM), which are the first line of defense against inhaled pathogens. Under steady-state conditions, AM are a more important source of IL-18 than are dendritic cells (DC) and monocytes. Cytokine production by AM and DC was compared after both types of cells had been infected with a virulent strain of Salmonella enterica serovar Typhimurium and an isogenic sipB mutant, which were used as an infection model. Infection with virulent Salmonella led to marked cell death with features of apoptosis while both intracellular activation and release of IL-18 were demonstrated. In contrast, the sipB mutant did not induce such cell death or the release of active IL-18. The specific caspase-1 inhibitor Ac-YVAD-CMK blocked the early IL-18 release in AM infected with the virulent strain. However, the type of Salmonella infection did not differentially regulate IL-18 gene expression. We concluded that the bacterial virulence factor SipB plays an essential posttranslational role in the intracellular activation of IL-18 and the release of the cytokine in human AM.

Amino Acid Chloromethyl Ketones↗
PubMed2002

Salmonella virulence factor SipB induces activation and release of IL-18 in human dendritic cells.

Interleukin-18 (IL-18) plays an important role in innate and acquired immunity, in particular against intracellular pathogens. However, little is known about the microbial factors that trigger IL-18 secretion by dendritic cells (DCs). To determine the influence of bacterial virulence factors on the activation and release of IL-18, we infected human monocyte-derived DCs with virulence mutants of the facultative intracellular pathogen Salmonella typhimurium. Our results show that infection by S. typhimurium causes caspase-1-dependent activation of IL-18 and triggers the release of IL-18 in human DCs. The secretion of IL-18 by the DCs was closely correlated with the ability of the S. typhimurium strains to induce apoptosis. We demonstrate that activation and release of IL-18 are blocked by mutations in the Salmonella sipB gene, which encodes a virulence factor that activates caspase-1 to induce apoptosis. These findings indicate that the activation and release of IL-18 induced by bacterial virulence factors may represent one component of innate immunity against the intracellular bacteria.

Apoptosis↗