Biomedical subjects

Alexandre Pachot

Publications and source records attributed to Alexandre Pachot.

8 recordsLinked to original sources

PubMed2006

Human CD4+CD25+ regulatory T lymphocytes inhibit lipopolysaccharide-induced monocyte survival through a Fas/Fas ligand-dependent mechanism.

Although it is known that septic shock induces immunosuppression, the mechanism for this phenomenon is not well understood. Monocytes play a central role in septic shock pathophysiology, which is also characterized by an increased proportion of natural regulatory T (Treg) cells. We therefore investigated whether Treg could be involved in the decreased monocyte expression of CD14 and HLA-DR observed during septic shock. We demonstrated that human Treg inhibit LPS-induced retention of monocyte CD14. Because loss of CD14 is a hallmark of monocyte apoptosis, this suggests that Treg inhibit monocyte survival. This effect was largely mediated through the release of a soluble mediator that was not identical with either IL-10 or IL-4. The Fas/FasL pathway participated in the effect as it was blocked by anti-FasL Abs and reproduced by Fas agonist and recombinant soluble FasL. Furthermore, expression of FasL was much higher on Treg than on their CD25(-) counterparts. Collectively, these results indicate that Treg act on monocytes by inhibiting their LPS-induced survival through a proapoptotic mechanism involving the Fas/FasL pathway. This may be an important mechanism for septic shock-induced immunosuppression and may offer new perspectives for the treatment of this deadly disease.

CD4 Antigens↗

PubMed2006

Systemic transcriptional analysis in survivor and non-survivor septic shock patients: a preliminary study.

The second phase of septic shock is characterized by an anti-inflammatory state and patients rapidly develop features consistent with immunosuppression. The mechanisms sustaining this disease step are far from being well understood. The objective of the present study was to perform a genome-wide survey of mRNA expression in septic shock patients in order to investigate the bases of sepsis-induced immunoparalysis. We used Affymetrix HG-U133A oligonucleotide arrays to compare systemic gene expression patterns of survivors and non-survivors after the first 24 h of the syndrome (n = 38 patients). Supervised analysis identified a set of 28 genes efficiently discriminating non-survivors from survivors with a sensitivity of 100% and a specificity of 86%. The microarray findings were confirmed by qRT-PCR and the ability of the selected probe sets to function as a classifier of outcome was verified with an independent set of additional microarray analyses. Noteworthy, of gene overexpressed in survivors, many are known to participate in innate immunity (cytokine, chemokine receptor, effectors of the Toll-receptor pathways). It supports the hypothesis that restoration of inflammatory/immune functions is a key step for survival after septic shock. The consistency of our results into the context of sepsis-induced immunoparalysis tends to indicate that blood transcriptional profiling is a valuable approach not only for patients stratification but also to identity new genes possibly involved in sepsis pathophysiology.

Aged↗

PubMed2005

FcgammaRIIIb and complement component C7 codeficiency in a patient with recurrence of fulminant meningococcal septic shock.

Individuals with deficiencies of the late components of complement exhibit a susceptibility to the recurrence of meningococcal disease with a usually mild clinical presentation. We report the recurrence of fulminant meningococcal disease in a complement component C7-deficient patient. We found a total deficiency of FcgammaRIIIb on neutrophils, which could partially explain the unusually severe clinical presentation.

Adolescent↗

PubMed2005

Longitudinal study of cytokine and immune transcription factor mRNA expression in septic shock.

Success in treating severe sepsis will require relevant tools to monitor the patient immunoinflammatory status. This study aimed to investigate the feasibility of measuring a panel of immunological mediator mRNAs in whole blood and to study their prognostic values in septic shock patients. At the onset of shock, compared to healthy volunteers, mRNA levels in septic shock patients were increased for IL-10, IL-1beta, and high mobility group B1 (HMGB1) and decreased for transforming growth factor beta 1, the Th1, and Th2 transcription factors, T-bet and GATA-3, respectively. Single parameter analysis highlighted an increased expression of IL-10 and HMGB1 mRNA in nonsurvivors and a significant rise over time of GATA3 in survivors. Combining the expression levels of four genes, hierarchical cluster analysis showed that up to 95% of the patients with a similar outcome displayed transcriptional similarities. These results illustrate both the potential of whole blood mRNA quantification assays and the interest of a multiparametric strategy to better stratify septic patients.

Aged↗

PubMed2005

Messenger RNA expression of major histocompatibility complex class II genes in whole blood from septic shock patients.

OBJECTIVE: The decreased expression of human leukocyte antigen (HLA)-DR on monocytes is proposed as a major feature of sepsis-induced immunodepression. The objective of the present study was to investigate, in whole blood from septic shock patients, the messenger RNA (mRNA) expression of a gene panel, which is essential to ensure major histocompatibility complex class II protein structure, transport, and peptide loading. DESIGN: The authors conducted a cohort study. SETTING: This study was conducted in intensive care units at a university hospital. SUBJECTS: The study included septic shock patients (n = 41) and healthy volunteers (n = 15). MEASUREMENTS AND MAIN RESULTS: Using quantitative reverse transcriptase-polymerase chain reaction, we found that the highly polymorphic HLA-DRB1 and nonpolymorphic-DRA mRNA levels were significantly decreased in whole blood from patients with septic shock compared with healthy volunteer both on days 1-3 and 4-10 after the onset of shock. This profile was also observed for genes encoding the invariant chain, the transcription factor class II transactivator (CIITA), and the enzymes involved in the peptide loading cathepsin S, HLA-DMA, and -DMB. The monocyte surface expression of HLA-DR measured by flow cytometry was significantly correlated with the whole-blood mRNA levels of HLA-DRB1 and -DRA and to a lesser extent with the other CIITA-regulated genes HLA-DMA and invariant chain. The correlation between HLA-DRB mRNA and cell-surface expression levels was also observed in a small subset of purified monocyte samples. Regarding the temporal relationship, a significant increase of whole-blood HLA-DRA, -DMA, -DMB, invariant chain, and CIITA mRNA level was observed in survivors (p = .001), whereas expressions remained low in nonsurvivors. CONCLUSIONS: A global transcriptional down regulation of a gene panel required for MHC II-restricted antigen presentation may occur in the course of septic shock. Our results suggest that the transcriptional resumption of CIITA-regulated genes might contribute to the recovery of membrane HLA-DR expression observed in survivors. These results obtained at the mRNA level support previous reports describing the loss of monocyte HLA-DR at the protein level and thus confirm the potential of measuring monocyte HLA-DR in septic patient followup.

Adult↗

PubMed2004

Peptidylpropyl isomerase B (PPIB): a suitable reference gene for mRNA quantification in peripheral whole blood.

Quantitative real-time RT-PCR is a very powerful technique for measuring gene expression at the mRNA level. In order to compare mRNA expression in different experimental or clinical conditions, expression of a target gene has to be normalized to an appropriate internal standard, which is generally a housekeeping gene. In our study, we have tested several housekeeping genes in peripheral whole blood of healthy volunteers and patients suffering from inflammatory diseases. A first analysis of 91 samples illustrated that the mRNA expression of peptidylpropyl isomerase B (PPIB) encoding for cyclophilin B protein, is more stable than beta actin and glyceraldehyde-3-phosphate dehydrogenase, which are both commonly selected as internal standard. Among the three genes tested, beta actin displayed the highest inter-sample variation of expression. The constancy of PPIB mRNA expression was further confirmed by 214 additional samples. In conclusion, we showed that PPIB, in contrast to beta actin and glyceraldehyde-3-phosphate dehydrogenase, is a suitable housekeeping gene in human peripheral blood.

Benchmarking↗

PubMed2004

Increased percentage of CD4+CD25+ regulatory T cells during septic shock is due to the decrease of CD4+CD25- lymphocytes.

OBJECTIVE: The elevation of the percentage of regulatory CD4+CD25+ T lymphocytes (Treg) has been recently described during septic shock. The objective of the present study was to investigate whether this increased percentage was due to Treg proliferation. DESIGN: Observational study. SETTING: Adult intensive care units in a university hospital. SUBJECTS: Patients with septic shock (n = 54) and healthy individuals (n = 30). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: In patients, we first confirmed the increased percentage of Treg among CD4+ lymphocytes in comparison with healthy individuals. Surprisingly, regarding absolute counting, we demonstrated that both T CD4+ lineages (CD25+ and CD25-) were diminished immediately after the onset of shock. Then, whereas Treg returned rapidly to healthy donors values, CD4+CD25- T lymphocytes remained dramatically reduced. Finally, Foxp3 (Treg-related gene) messenger RNA quantification enabled us to definitively rule out a lack of proliferation since it was not increased during shock. CONCLUSION: The increased percentage of Treg after shock is due not to their proliferation but to a decrease in CD4+CD25- T lymphocyte number. We hypothesize that it might be due to a resistance of Treg to apoptosis processes occurring during septic shock.

APACHE↗

PubMed2003

Calcitonin gene related peptide and N-procalcitonin modulate CD11b upregulation in lipopolysaccharide activated monocytes and neutrophils.

OBJECTIVE: Circulating levels of calcitonin gene related peptide (CGRP) and calcitonin precursors, including procalcitonin (PCT) and its free aminopeptide N-procalcitonin (N-PCT), have been found dramatically increased in septic patients. PCT is known to attenuate the chemotaxis of monocytes in response to chemoattractants. This study examined whether CGRP and N-PCT modulate the LPS-induced expression of CD11b, which is one of the major integrins involved in monocyte and neutrophil chemotaxis during a response to microbial infections. DESIGN AND SETTING: In vitro cell culture study in the immunology laboratory of a university hospital. PARTICIPANTS: Healthy volunteers. MEASUREMENTS AND RESULTS: We assessed the effects of N-PCT and CGRP on CD11b expression on monocytes and neutrophils after LPS (2 ng/ml) or fMLP (10(-8) M) challenges. We used a human whole blood model, and measurements were made by flow cytometry. Both peptides in a dose-dependent manner decreased the LPS- and fMLP-induced rise in CD11b in monocytes and neutrophils. As these peptides are thought to act by raising cAMP, we also mimicked their effects with the use of rolipram and forskolin and found similar results. CONCLUSIONS: These findings are in line with recent studies demonstrating anti-inflammatory properties for this family of peptides. CGRP and calcitonin precursors may function as factors suppressing the propagation of inflammation through the inhibition of several processes involved during a response to a bacterial stimulus.

Biomarkers↗