Publications (11)59 Total impact
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Article: Transcripts of ceruloplasmin but not hepcidin, both major iron metabolism genes, exhibit a decreasing pattern along the portocentral axis of mouse liver.
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ABSTRACT: During iron overload of dietary origin, iron accumulates predominantly in periportal hepatocytes. A gradient in the basal and normal transcriptional control of genes involved in iron metabolism along the portocentral axis of liver lobules could explain this feature. Therefore, we aimed at characterizing, by quantitative RT-PCR, the expression of iron metabolism genes in adult C57BL/6 mouse hepatocytes regarding lobular localisation, with special emphasis to cell ploidy, considering its possible relationship with lobular zonation. We used two methods to analyse separately periportal and perivenous liver cells: 1) a selective liver zonal destruction by digitonin prior to a classical collagenase dissociation, and 2) laser capture microdissection. We also developed a method to separate viable 4N and 8N polyploid hepatocytes by flow cytometer. Transcripts of ceruloplasmin, involved in iron efflux, were overexpressed in periportal areas and the result was confirmed by in situ hybridization study. By contrast, hepcidin 1, hemojuvelin, ferroportin, transferrin receptor 2, hfe and L-ferritin mRNAs were not differentially expressed according to either lobular zonation or polyploidisation level. At variance with glutamine or urea metabolism, iron metabolism is not featured by a metabolic zonation lying only on a basal transcriptional control. The preferential periportal expression of ceruloplasmin raises the issue of its special role in iron overload disorders involving a defect in cellular iron export.Biochimica et Biophysica Acta 05/2008; 1782(4):239-49. · 4.66 Impact Factor -
Article: Down-modulation of granulocyte macrophage-colony stimulating factor receptor on monocytes during human septic shock.
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ABSTRACT: Loss of surface human leukocyte antigen-DR (HLA-DR) on monocytes is a major factor of immunosuppression in sepsis. Granulocyte macrophage-colony stimulating factor (GM-CSF) up-regulates HLA-DR expression on monocytes via the GM-CSF receptor (GM-CSFr) through a transcriptional mechanism involving the class II transactivator factor (CIITA). We investigated monocyte GM-CSFr expression and its relationship with HLA-DR in septic patients. Prospective clinical experimental study. University hospital intensive care unit and research facility. Septic patients with and without septic shock, control patients. Flow cytometry and real-time quantitative reverse polymerase chain reaction were used to characterize GM-CSFr expression and transcription in septic patients and in ex vivo stimulated healthy monocytes. We showed an early GM-CSFr down-modulation in patients with septic shock compared with those without septic shock and controls. A persistent low GM-CSFr expression was observed in patients who acquired secondary infections or in those who died, and this persistent defect correlated with severity scores. We demonstrated that GM-CSFr down-modulation occurs at a posttranscriptional level since we observed no alteration in GM-CSFr transcription in monocytes isolated from septic patients. Furthermore, we demonstrated that GM-CSFr expression levels on monocytes correlated not only with HLA-DR expression and transcription levels but also with RNA levels of its main transcriptional factor CIITA. Because we previously showed in septic patients a relationship between high cortisol plasma level and low monocyte HLA-DR expression, we investigated the effects of glucocorticoids on monocyte GM-CSFr expression and observed a similar posttranscriptional down-modulation of GM-CSFr by steroids. However, the in vivo putative role of steroids in HLA-DR down-regulation via GM-CSFr down-modulation needs further investigation. Monocyte GM-CSFr down-modulation occurred in septic shock, was associated with severity, and might be either another manifestation of monocyte deactivation linked to sepsis or an additional mechanism participating in immunosuppression.Critical Care Medicine 05/2006; 34(4):1193-201. · 6.33 Impact Factor -
Article: MHC class II signaling function is regulated during maturation of plasmacytoid dendritic cells.
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ABSTRACT: Dendritic cells (DC) play a central role in the immune response, linking innate and adaptative responses to pathogens. Myeloid DC (MDC) produce interleukin-12 in response to bacterial stimuli, whereas plasmacytoid DC (PDC) produce high levels of type I interferon upon viral infection. Human leukocyte antigen (HLA)-DR engagement has been shown to induce apoptosis in various antigen-presenting cells (APC). We now report the consequences of HLA-DR molecule engagement in human PDC, which had thus far not been studied as a result of the difficulty in isolating such cells. HLA-DR engagement on PDC, obtained using a two-step, immunomagnetic separation, led to recruitment of HLA-DR molecules at the site of engagement in mature but not immature PDC. In contrast, relocalization of protein kinase C (PKC) isoenzymes, indicating PKC activation, was observed at the site of HLA-DR engagement and was accompanied by relocalization of a lipid raft marker, the ganglioside M1 staining, in immature and mature PDC. Similar to MDC, HLA-DR-mediated apoptosis was regulated throughout PDC maturation. Freshly isolated PDC were resistant, whereas CD40 ligand-matured PDC were sensitive to HLA-DR-mediated apoptosis. Neither caspase activation nor PKC activation was required for HLA-DR-mediated apoptosis. However, the intrinsic pathway of apoptosis was implicated as mature PDC underwent mitochondrial depolarization in response to HLA-DR engagement. These data provide further arguments for considering HLA-DR-mediated apoptosis as a conserved mechanism of regulating survival of diverse APC and support the ongoing development of humanized ligands for HLA class II molecules as therapeutic tools for use in lymphoproliferative disease.Journal of Leukocyte Biology 05/2005; 77(4):560-7. · 4.99 Impact Factor -
Article: Loss of heterozygosity, a frequent but a non-exclusive mechanism responsible for HLA dysregulation in non-Hodgkin's lymphomas.
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ABSTRACT: The frequent alteration of human leucocyte antigen (HLA) class I molecule expression observed in non-Hodgkin's lymphomas (NHL), similarly to solid tumours, has been reported to favour tumoral escape from the immune system. In order to identify the underlying mechanisms, we analysed 15 HLA defective NHL including partial (n = 10) and total class I (n = 5) loss, as well as HLA class II defects (n = 5). The HLA defect concerned HLA-A and -B antigens in 14 of 15 cases. In the cases with partial defect, the use of specific allelic monoclonal antibodies detected a defect of both alleles of A or B loci in six of seven tested cases. Allelic reverse transcription polymerase chain reaction (RT-PCR) demonstrated defects in six of nine cases, including four alterations of both A and B mRNA alleles. Real-time quantitative RT-PCR (RQ-PCR) did not detect the HLA-DR transcript in the two negative HLA-DR lymphomas, contrasting with the presence of CMH II transactivator (CIITA) transcript. Loss of heterozygosity (LOH) was detected in nine of 14 cases through variable pattern of nine microsatellites markers of the HLA locus. Taken together, these findings demonstrate the complexity and the variability of the mechanisms underlying HLA protein deficiencies with a high frequency of LOH. The diversity of these mechanisms indicates the importance of positive selection of HLA altered clones in the development of these NHL cases.British Journal of Haematology 11/2004; 127(1):40-9. · 4.94 Impact Factor -
Article: Monocyte human leukocyte antigen-DR transcriptional downregulation by cortisol during septic shock.
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ABSTRACT: Monocyte deactivation has been identified as a major factor of immunosuppression in sepsis and is associated with a loss of surface human leukocyte antigen-DR (HLA-DR) expression on circulating monocytes. Using flow cytometry, quantitative reverse transcription-polymerase chain reaction, we investigated this phenomenon in septic patients. We confirmed the early loss of monocyte HLA-DR expression in all infected patients and demonstrated that this persistent lowered expression at Day 6 correlated with severity scores, secondary infection, and death. This phenomenon occurred at a transcriptional level via a decrease in the class II transactivator A (CIITA) transcription. Furthermore, these abnormalities correlated with the high cortisol levels observed in sepsis and not with those of other putative factors such as catecholamines or interleukin-10. Finally, in vitro studies evidenced that glucocorticoids decrease HLA-DR expression at a transcriptional level via a decrease in CIITA mRNA levels, mainly by down modulating its isoforms I and III. We conclude that in human sepsis, the loss of HLA-DR expression on circulating monocytes is associated with a poor outcome. We suggest that the high endogenous cortisol level observed in septic shock may be a possible new factor involved in the loss of HLA-DR expression on monocytes via its effect on HLA-DR and CIITA transcription.American Journal of Respiratory and Critical Care Medicine 06/2004; 169(10):1144-51. · 11.08 Impact Factor -
Article: Soluble HLA-G molecules are increased in lymphoproliferative disorders.
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ABSTRACT: The immunomodulatory properties of soluble human leukocyte antigen G (sHLA-G) explain its potential interest in malignancies. HLA-G frequently transcribed in lymphoproliferative disorders is rarely expressed at cell surface. In this article, we will demonstrate that the plasmatic level of soluble HLA-G was significantly increased in 70% of B chronic lymphocytic leukemia, 53% of non-Hodgkin B lymphoma (B-NHL), and 45% of T-NHL. To explain this variable secretion, the HLA-G secreting cell was searched and was identified as tumoral T4 lymphocytes only in one patient with Sezary syndrome. To approach the mechanisms involved in sHLA-G secretion, the potential role of cytokines has been studied in vitro on T lymphomas. A significant increase of sHLA-G level is observed after activation by cytokines associated with a small increase in the quantity of transcripts using real-time polymerase chain reaction, suggesting an involvement of both transcriptional and post-transcriptional mechanisms. Western Blot analysis reveals no evident variation of the protein expression whatever the conditions, suggesting a continuous secretion and a low intracellular storage. The frequency of the sHLA-G secretion associated to its inhibiting role on T cells and natural killer cells during tumoral lymphoid malignancies suggests a potential role of these molecules as escape mechanism from antitumoral response.Human Immunology 12/2003; 64(11):1093-101. · 2.84 Impact Factor -
Article: HLA-G and lymphoproliferative disorders.
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ABSTRACT: The immunomodulatory properties of the HLA-G molecule explain its relevance in malignancies. Our investigations in lymphoproliferative disorders show (i) a frequent and variable distribution of alternatively spliced HLA-G mRNA isoforms, (ii) a rare cell surface expression in diffuse large cell lymphomas with HLA class I loss in half of cases, and (iii) an increased serum level of sHLA-G in half of cases. The potential role of the microenvironment and/or tumoral process in HLA-G expression is discussed in the light of these data. HLA-G rather through its soluble isoform might provide a new way of immune evasion for lymphoid proliferations.Seminars in Cancer Biology 11/2003; 13(5):379-85. · 6.47 Impact Factor -
Article: Early circulating lymphocyte apoptosis in human septic shock is associated with poor outcome.
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ABSTRACT: The role of lymphocyte apoptosis in septic shock remains a controversial issue. Using Annexin V and flow cytometry analysis on freshly isolated cells, we evaluated circulating lymphocyte apoptosis in 23 septic shock, 25 sepsis without shock, 7 nonseptic critically ill, and 25 control patients. In patients with sepsis, we compared day 1 lymphocyte apoptosis (i.e., within 3 days of the onset of infection) with that observed 5-7 days after (day 6) according to shock state, mortality, and seventy factors. At day 1, patients in septic shock exhibited higher lymphocyte apoptosis than that present in controls (16.5% +/- 3.5% vs. 3% +/- 0.5%, respectively, P = 0.0001). At day 6, patients with sepsis without shock restored undamaged CD4+ T and CD8+ T lymphocyte counts, whereas patients in septic shock increased only CD4+ T cells. Similarly, survivors restored undamaged lymphocyte count at day 6 (+70%, P < 0.001), whereas nonsurvivors did not. Day 6 undamaged lymphocyte count negatively correlated with day 1 SAPS II, day 6 LOD score, mechanical ventilation, and ICU stay duration. We observed no apoptotic effect of septic shock plasma or septic shock circulating mononuclear cells on target lymphoid cell lines. We found no alteration in any death receptors Fas, TRAIL-R1, TRAIL-R2, or in their ligands on circulating blood cells. Catecholamines and interleukin 10 levels significantly increased in patients with septic shock, but did not correlate with apoptosis levels. We conclude that lymphocyte apoptosis is rapidly increased in blood of patients in septic shock and that lymphocyte apoptosis leads to a profound and persistent lymphopenia associated with poor outcome. These results suggest that lymphocyte apoptosis is one of the main components of human septic shock immune dysfunction and could be related more to microcirculatory disturbance than to circulating factors.Shock 01/2003; 18(6):487-94. · 2.85 Impact Factor -
Article: Major histocompatibility complex abnormalities in non-Hodgkin lymphomas.
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ABSTRACT: An optimal antitumoral immune response requires the participation of both CD8 and CD4 T lymphocytes, which are activated by peptide antigen presentation via human leucocyte antigen (HLA) class I and class II molecules respectively. Loss of HLA molecules has been observed in different malignancies, and provides a mechanism for escape from immune surveillance. Furthermore, HLA-G, a class Ib molecule, is considered to be an immune tolerance-inducing molecule. HLA-G expression on tumour cells could provide a further mechanism for immune escape. To determine the frequency and the pattern of HLA defects in non-Hodgkin lymphomas (NHL), HLA expression was prospectively studied in 614 NHL cases, using flow cytometry. Furthermore, HLA-G expression was tested in 50 cases, including 20 cases selected on the basis of their defective HLA class I expression. In 64 cases (10.4%), lymphomatous cells exhibited lower HLA class I mean fluorescence intensity compared with reactive cells. Their characteristics were (1) the diversity of histological entities; (2) the significant frequency of relapse or transformation; (3) the increased incidence of high-grade NHL compared with low-grade; and (4) the severity of the class I defect in 50% of the cases, mainly in high-grade NHL. A defect in HLA-DR expression was always associated with a severe class I defect (12 cases; 2%). The HLA-G protein was detected in three class I defective cases. These HLA alterations frequently appeared as a secondary event at relapse or at transformation, suggesting a direct role in lymphomagenesis.British Journal of Haematology 12/2002; 119(2):417-24. · 4.94 Impact Factor -
Article: MHC class II-mediated apoptosis of mature dendritic cells proceeds by activation of the protein kinase C-delta isoenzyme.
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ABSTRACT: The mature dendritic cell (DC) is considered to be the most potent antigen-presenting cell. Regulation of the DC, particularly its survival, is therefore critical. Mature DC are markedly more sensitive to HLA-DR-mediated apoptosis than immature DC. To further characterize this key survival difference, we compared the intracellular signals initiated via HLA-DR in mature versus immature DC. Apoptosis was unchanged by inhibition of tyrosine kinases or phosphatases. HLA-DR-mediated re-localization of protein kinase C (PKC)-delta to the nucleus was detected in mature DC by confocal microscopy and by immunoblotting. Activation of PKC-delta in mature DC was revealed by the detection of the PKC-delta catalytic fragment in the nuclear fraction isolated from mature DC which had been stimulated via HLA-DR. The broad-spectrum PKC inhibitor, Calphostin C, as well as the PKC-delta-selective inhibitor, Rottlerin, inhibited HLA-DR-mediated apoptosis of mature cells. Taken together, these data reveal a role for the PKC-delta isoenzyme in regulating HLA class II-mediated apoptosis of mature DC. Thus, the lifespan of the mature DC could be controlled by signals generated in the course of antigen presentation, and thereby prevent DC persistence and prolonged stimulation of T and B lymphocytes.International Immunology 09/2002; 14(8):935-42. · 3.41 Impact Factor -
Article: HLA-G and lymphoproliferative disorders
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ABSTRACT: The immunomodulatory properties of the HLA-G molecule explain its relevance in malignancies. Our investigations in lymphoproliferative disorders show (i) a frequent and variable distribution of alternatively spliced HLA-G mRNA isoforms, (ii) a rare cell surface expression in diffuse large cell lymphomas with HLA class I loss in half of cases, and (iii) an increased serum level of sHLA-G in half of cases. The potential role of the microenvironment and/or tumoral process in HLA-G expression is discussed in the light of these data. HLA-G rather through its soluble isoform might provide a new way of immune evasion for lymphoid proliferations.Seminars in Cancer Biology 13(5):379-385. · 6.47 Impact Factor
Top co-authors
Top Journals
Institutions
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2006
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Centre Hospitalier Universitaire Rouen
Rouen, Haute-Normandie, France
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2004
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Centre Hospitalier Universitaire de Rennes
Rennes, Brittany, France -
Université de Rennes 2
Rennes, Brittany, France
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2002–2003
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Université de Rennes 1
- Faculté de Médecine
Rennes, Brittany, France
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