Biomedical subjects

Sandrine Florquin

Publications and source records attributed to Sandrine Florquin.

At least 55 records · Page 3Linked to original sources

PubMed2005

Renal tissue factor expression is increased in streptozotocin-induced diabetic mice.

BACKGROUND: Tissue factor (TF) is the key initiator of the coagulation cascade. Recent evidence suggests that TF plays a role in renal fibrin formation and renal failure in experimental kidney disease. We hypothesized that hyperglycemia is an important stimulus of TF expression in the kidney. METHODS: Mice were injected with streptozotocin (STZ) (200 mg/kg) or with control buffer. Three or 10 weeks after injection, fibrin, thrombin and TF staining and TF activity were evaluated in the kidney. The effect of hyperglycemia on TF expression and secretion by tubular epithelial cells was measured in vitro. RESULTS: Kidneys of STZ-treated mice showed a marked increase in thrombin staining (3.0 +/- 0.5 vs. 1.2 +/- 0.11) (p = 0.002) and an increase in TF clotting activity 10 weeks after STZ injection (33.9 +/- 1.3 vs. 25.4 +/- 1.0 s) (p < 0.0001). Increased glomerular fibrin deposition was present in 3 out of 6 diabetic mice. Tubular cells incubated with D-glucose (25 mmol/l) for 48 h displayed increased cellular TF (p = 0.05). However, soluble TF levels and TF activity in supernatant of cells incubated with D- or L-glucose were not different. CONCLUSIONS: These data suggest that hyperglycemia is a causal factor in procoagulant activity associated with diabetic nephropathy.

Animals↗

PubMed2005

Protection against renal ischemia reperfusion injury by CD44 disruption.

Inflammation contributes to renal ischemia reperfusion (I/R) injury, potentially causing renal dysfunction. The inflammatory infiltrate mainly consists of neutrophils, which are deleterious for the renal tissue. Because CD44 is expressed by neutrophils and is rapidly upregulated by capillary endothelial cells after I/R injury, it was hypothesized that CD44 might play an important role in the development of I/R injury. This study showed that rapid CD44 upregulation on renal capillary endothelial cells mediates neutrophil recruitment to the postischemic tissue. Hence, CD44 deficiency led to decreased influx of neutrophils regardless of comparable levels in chemotactic factors expressed in the kidney. The reduced influx of neutrophils was associated with preserved renal function and morphology. Adoptive transfer experiments of labeled neutrophils revealed that endothelial CD44 rather than neutrophil CD44 mediates neutrophil migration. Activation of neutrophils increased cell-surface expression of hyaluronic acid (HA). Altogether, a novel mechanism in the recruitment of neutrophils that involves interaction of endothelial CD44 and neutrophil HA was found. Either blocking endothelial CD44 or removal of neutrophil HA decreased rolling and adhesion of neutrophils. Administration of anti-CD44 to mice reduced the influx of neutrophils into the postischemic tissue, associated with renal function preservation. Therefore, anti-CD44-based therapies may contribute to prevent or reduce renal I/R injury.

Animals↗

PubMed2005

The cholinergic anti-inflammatory pathway regulates the host response during septic peritonitis.

BACKGROUND: The nervous system, through the vagus nerve, can down-regulate inflammation in vivo by decreasing the release of tumor necrosis factor- alpha by endotoxin-stimulated macrophages. This anti-inflammatory effect is mediated by an interaction between acetylcholine, the principal neurotransmitter of the vagus nerve, and cholinergic nicotinic acetylcholine receptors on macrophages. METHODS: We determined the role of this "cholinergic anti-inflammatory pathway" during septic peritonitis induced in mice by intraperitoneal injection of live Escherichia coli. Septic peritonitis was preceded by inhibition of the cholinergic anti-inflammatory pathway by unilateral cervical vagotomy, by stimulation of this pathway by pretreatment of mice with nicotine, or by a combination of both interventions. RESULTS: Initial cytokine release during septic peritonitis was enhanced after previous vagotomy and was decreased after nicotine pretreatment, independently of the integrity of the vagus nerve. Further study established that vagotomy before septic peritonitis resulted in an enhanced influx of neutrophils and a marked increase in proinflammatory cytokine levels and liver damage. Conversely, nicotine pretreatment strongly decreased cell influx, proinflammatory cytokine levels, and liver damage, whereas bacterial clearance and survival were impaired. DISCUSSION: These data provide the first evidence, to our knowledge, of an important role of the vagus nerve in regulating the innate immune response to a severe bacterial infection.

Animals↗

PubMed2005

Hematopoietic stem cell mobilization therapy accelerates recovery of renal function independent of stem cell contribution.

Acute renal failure and tubular cell loss as a result of ischemia constitute major challenges in renal pathophysiology. Increasing evidence suggests important roles for bone marrow stem cells in the regeneration of renal tissue after injury. This study investigated whether the enhanced availability of hematopoietic stem cells, induced by stem cell factor and granulocyte colony-stimulating factor, to the injured kidney provides an adequate strategy for stem cell-based therapy to counteract renal ischemia/reperfusion injury. It is interesting that cytokine treatment before injury resulted in significant enhancement of function recovery of the kidney. This, however, was not due to increased incorporation of tubular epithelial cells from bone marrow origin. Importantly, cytokine treatment resulted in impaired influx of granulocytes into the injured kidney. Although cytokine treatment improved renal function rapidly after ischemic injury, the results show that the underlying mechanism likely is not based on stem cell transdifferentiation but rather on altered inflammatory kinetics.

Acute Kidney Injury↗

PubMed2005

CD11b limits bacterial outgrowth and dissemination during murine pneumococcal pneumonia.

Expression of CD11b is enhanced on neutrophils recruited to the lungs during bacterial pneumonia. To determine the role that CD11b plays in pneumonia, CD11b gene-deficient (CD11b(-/-)) mice and normal wild-type (wt) mice were intranasally infected with Streptococcus pneumoniae. CD11b(-/-) mice had an enhanced outgrowth of pneumococci in the lungs and an increased dissemination of the infection, which could be reproduced by treatment of wt mice with an anti-CD11b antibody. This reduced resistance was associated with higher neutrophil counts in bronchoalveolar lavage fluid and lung tissue and an exaggerated lung inflammatory response. CD11b is important for an effective defense against S. pneumoniae pneumonia but not for recruitment of neutrophils.

Animals↗

PubMed2005

Specific ICAM-3 grabbing nonintegrin-related 1 (SIGNR1) expressed by marginal zone macrophages is essential for defense against pulmonary Streptococcus pneumoniae infection.

The dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN) homolog, SIGN-related 1 (SIGNR1) is a pathogen receptor expressed by splenic marginal zone and peritoneal macrophages, and is essential for clearance of Streptococcus pneumoniae by phagocytosis after intraperitoneal infection. Here, we identified an important in vivo function for SIGNR1 in S. pneumonia infection induced via its natural entrance route. Upon intranasal infection with S. pneumoniae, SIGNR1-deficient mice did not clear bacteria from lung and blood, and displayed severely enhanced inflammatory parameters compared to the wild-type mice. However, SIGNR1 is not expressed by alveolar macrophages, suggesting that another mechanism than a decrease in phagocytosis is responsible for this difference. Natural anti-phosphorylcholine IgM produced by marginal zone B cells is essential for protection against infection with S. pneumoniae. Strikingly, during infection, SIGNR1-deficient mice failed to produce a rapid anti-phosphorylcholine IgM response. Marginal zone macrophages have been suggested to capture antigens for presentation to marginal zone B cells. We demonstrate that marginal zone macrophages from SIGNR1-deficient mice in contrast to wild-type mice are not able to capture pneumococci from blood, suggesting that SIGNR1 on marginal zone macrophages captures S. pneumoniae for antigen presentation to and activation of marginal zone B cells, resulting in an anti-phosphorylcholine IgM response.

Animals↗

PubMed2005

Lipopolysaccharide binding protein-deficient mice have a normal defense against pulmonary mycobacterial infection.

Lipopolysaccharide (LPS) binding protein (LBP) facilitates the transfer of LPS of Gram-negative bacteria to the pattern recognition receptor CD14, resulting in activation of immunocompetent cells. LBP can also facilitate the binding of lipoarabinomannan, a major cell wall component of mycobacteria, to immune cells. To determine the role of LBP in the immune response to pulmonary Mycobacterium tuberculosis infection, LBP gene-deficient (-/-) and normal wild-type (WT) mice were intranasally infected with M. tuberculosis. LBP-/- mice displayed a similar survival and mycobacterial outgrowth in lungs and liver, although they demonstrated a reduced lymphocyte recruitment and activation during the early stages of infection. The clearance of pulmonary infection with the non-pathogenic M. smegmatis was also unaltered in LBP-/- mice. These data suggest that LBP does not contribute to an effective host response in M. tuberculosis infection.

Acute-Phase Proteins↗

PubMed2005

Therapeutic effects of troglitazone in experimental chronic pancreatitis in mice.

Peroxisome proliferator-activated receptor (PPAR)-gamma controls growth, differentiation, and inflammation. PPAR-gamma agonists exert anti-inflammatory effects in vitro and inhibit the activation of pancreas stellate cells, implicated in the formation and progression of fibrosis. We determined the influence of troglitazone, a ligand for PPAR-gamma, on pancreatic damage and fibrosis in experimental chronic pancreatitis. Mice received six hourly intraperitoneal injections with 50 microg/kg of cerulein or saline, three times a week for 6 weeks. One week after the last injection all mice were sacrificed. Untreated mice were compared with mice treated with troglitazone either during weeks 1 to 6 or weeks 4 to 6. All mice that received cerulein injections displayed histopathological signs of chronic pancreatitis at week 7. Troglitazone treatment improved all markers for severity of pancreatitis. Moreover, early and postponed troglitazone treatments were equally effective in diminishing intrapancreatic fibrosis as quantified by Sirius red staining, hydroxyproline content, and laminin staining as well as the increased number of pancreatic stellate cells and pancreas levels of transforming growth factor-beta. Thus, troglitazone attenuated pancreatic damage and inflammation in experimental chronic pancreatitis and remained beneficial in a therapeutic setting when given after initial damage had been established.

Actins↗

PubMed2005

Posttransplantation cytomegalovirus-induced recurrence of atypical hemolytic uremic syndrome associated with a factor H mutation: successful treatment with intensive plasma exchanges and ganciclovir.

Atypical hemolytic uremic syndrome (HUS) can recur after renal transplantation and often leads to graft loss. In some series of familial HUS, the risk of early graft loss due to recurrence of HUS approaches 100% despite any therapy. This led some authors to claim that kidney transplantation is contraindicated in those patients. The authors describe an 8-year-old girl with end-stage renal failure owing to familial atypical HUS with a factor H mutation who underwent successful transplantation using continuous prophylactic plasma exchange (PE). Twenty-four months after transplantation, plasma creatinine level is 1.2 mg/dL (106 micromol/L) despite 2 recurrences of HUS contemporaneous to 2 cytomegalovirus infections, which resolved with PE intensification and ganciclovir. This strongly suggests that cytomegalovirus infection may trigger posttransplant recurrent HUS. The feasibility of kidney transplantation in case of atypical HUS related to factor H mutation using continuous prophylactic PE intensified during relapses should be confirmed in prospective studies.

Child↗

PubMed2005

Pre-transplant plasma and cellular levels of CD44 correlate with acute renal allograft rejection.

BACKGROUND: Since CD44 is involved in activation, proliferation, rolling and extravasation of lymphocytes, we hypothesized that it could be involved in the pathophysiology of acute renal allograft rejection. METHODS: Plasma and peripheral blood mononuclear cells (PBMCs) were collected from patients 24 h prior to transplantation and analysed retrospectively. Soluble CD44, interleukin-2 receptor (IL-2R), intracellular adhesion molecule-1 (ICAM-1) and C-reactive protein (CRP) in plasma were determined by enzyme-linked immunosorbent assay (ELISA). Cellular CD44 expression on peripheral lymphocytes was determined by flow cytometric analysis. RESULTS: Patients who later developed renal allograft rejection had statistically significantly increased soluble CD44 levels, but not soluble ICAM-1, IL-2R or CRP in plasma prior to transplantation. In addition, cellular CD44 on T-lymphocytes was decreased 24 h prior to transplantation in patients that would reject their allograft, compared with patients without rejection. Additionally, plasma CD44 and cellular CD44 revealed an inversely proportional correlation. Lipopolysaccharide (LPS)-induced immune activation did not influence plasma or cellular CD44 levels in healthy volunteers, suggesting that more specific factors influence the shedding of CD44 on T lymphocytes, leading to increased risk of renal allograft rejection. CONCLUSION: Although the exact mechanism remains to be elucidated and further research is required, soluble CD44 levels and cellular surface CD44 on T lymphocytes prior to transplantation might be useful as predictive markers for the occurrence of acute renal rejection.

Acute Disease↗

PubMed2005

Aspiration pneumonitis primes the host for an exaggerated inflammatory response during pneumonia.

OBJECTIVE: Nosocomial pneumonia is a feared complication in the critically ill patient. Aspiration pneumonitis is frequently complicated by infections. The objective of this study was to determine the influence of aspiration pneumonitis on the host response to a common nosocomial respiratory pathogen. DESIGN: Controlled, in vivo laboratory study. SETTING: Research laboratory of a health sciences university. SUBJECTS: Female C57Bl/6 mice. INTERVENTIONS: Mice received hydrochloric acid or saline intratracheally followed 16 hrs later by Klebsiella pneumoniae. MEASUREMENTS AND MAIN RESULTS: Hydrochloric acid induced a mild aspiration pneumonitis. Nonetheless, hydrochloric acid aspiration resulted in a markedly increased inflammatory response in the lung on infection with K. pneumoniae. This enhanced inflammatory reaction was accompanied by a greatly increased outgrowth of K. pneumoniae in lungs of mice previously exposed to hydrochloric acid. Preexisting aspiration pneumonitis also triggered mouse lungs in vivo and alveolar macrophages ex vivo for enhanced release of proinflammatory mediators on stimulation with Klebsiella lipopolysaccharide. Inhibition of tumor necrosis factor-alpha resulted in an increased inflammatory reaction and enhanced bacterial outgrowth in mice with primary K. pneumoniae pneumonia, whereas it had no effect in mice with preexisting aspiration pneumonitis. CONCLUSIONS: These data indicate a) that aspiration pneumonitis renders the host more susceptible to respiratory tract infection with K. pneumoniae, concurrently priming the lung for an exaggerated inflammatory response; and b) that although tumor necrosis factor-alpha plays a major role in the host response to primary infection, it does not affect lung inflammation or defense after aspiration pneumonitis.

Analysis of Variance↗

PubMed2005

Endogenous interleukin-12 improves the early antimicrobial host response to murine Escherichia coli peritonitis.

Interleukin (IL)-12 is a heterodimeric proinflammatory cytokine formed by a p35 and a p40 subunit. To determine the role of IL-12 in abdominal sepsis, p35 gene-deficient (IL-12 knockout, KO) mice and normal wild-type (WT) mice were injected intraperitoneally with Escherichia coli. Peritonitis was associated with a bacterial dose-dependent increase in IL-12 p40 and IL-12 p75 concentrations in peritoneal fluid and plasma. Whereas at 6 h postinfection, IL-12 KO and WT mice displayed similar bacterial counts, at 20 hours IL-12 KO mice had significantly more bacteria in liver homogenates and were more susceptible to progressing to systemic infection. In addition, IL-12 KO mice demonstrated higher levels of proinflammatory cytokines in peritoneal fluid and increased lung and liver injury. IL-12 deficiency did not influence the recruitment of cells to the site of the infection. These data suggest that endogenous IL-12 is involved in the early antibacterial host response during abdominal sepsis.

Animals↗

PubMed2005

Enhanced viral clearance in interleukin-18 gene-deficient mice after pulmonary infection with influenza A virus.

T helper 1 driven immune responses facilitate host defence during viral infections. Because interleukin-18 (IL-18) mediates T helper 1 driven immune responses, and since mature IL-18 is up-regulated in human macrophages after influenza virus infection in vitro, it has been suggested that IL-18 plays an important role in the immune response to influenza. To determine the role of IL-18 in respiratory tract infection with influenza, IL-18 gene-deficient (IL-18(-/-)) and normal wildtype mice were intranasally inoculated with influenza A virus. Influenza resulted in an increase in constitutively expressed IL-18 in the lungs of wildtype mice. The clearance of influenza A was inhibited by IL-18, as indicated by reduced viral loads on day 8 and day 12 after infection in IL-18(-/-) mice. This enhanced viral clearance correlated with increased CD4(+) T-cell activation in the lungs as reflected by CD69 expression on the cell surface. Surprisingly, interferon-gamma (IFN-gamma) levels were similar in the lungs of IL-18(-/-) mice and wildtype mice. Intracellular IFN-gamma staining revealed similar expression levels in lung-derived natural killer cells, CD4(+) and CD8(+) T cells, indicating that IFN-gamma production is IL-18-independent during influenza virus infection. Tumour necrosis factor-alpha production by CD4(+) T cells was significantly lower in IL-18(-/-) mice than in wildtype mice. Our data indicate that endogenous IL-18 impairs viral clearance during influenza A infection.

Animals↗

PubMed2005

Renal-associated TLR2 mediates ischemia/reperfusion injury in the kidney.

TLRs are conserved pattern recognition receptors that detect motifs of pathogens and host material released during injury. For unknown reasons, renal TLR2 mRNA is mainly expressed by tubular cells and is enhanced upon renal ischemia/reperfusion (I/R) injury. We evaluated the role of TLR2 in I/R injury using TLR2-/- and TLR2+/+ mice, TLR2 antisense oligonucleotides, and chimeric mice deficient in leukocyte or renal TLR2. Tubular cells needed TLR2 to produce significant cytokine and chemokine amounts upon ischemia in vitro. TLR2 played a proinflammatory and detrimental role in vivo after I/R injury, as reflected by a reduction in the amount of local cytokines and chemokines, leukocytes, and the level of renal injury and dysfunction in TLR2-/- mice compared with controls. Analysis of chimeric mice suggested that TLR2 expressed on renal parenchyma plays a crucial role in the induction of inflammation and injury. TLR2-antisense treatment protected mice from renal dysfunction, neutrophil influx, and tubular apoptosis after I/R injury compared with nonsense treatment. In summary, we identified renal-associated TLR2 as an important initiator of inflammatory responses leading to renal injury and dysfunction in I/R injury. These data imply that TLR2 blockade could provide a basis for therapeutic strategies to treat or prevent renal ischemic injury.

Animals↗

PubMed2004

Macrophages play a dual role during pulmonary tuberculosis in mice.

Pulmonary macrophages provide the preferred hiding and replication site of Mycobacterium tuberculosis but display antimicrobial functions. This raises questions regarding the role of macrophages during tuberculosis. We depleted lungs of activated macrophages (activated macrophage(-) mice) and compared this with nonselective macrophage depletion (macrophage(-) mice). Although nonselective depletion of macrophages after infection improved clinical outcome, depletion of activated macrophages led to impaired resistance, reflected by enhanced mycobacterial outgrowth. The production of tumor necrosis factor- alpha and numbers of granuloma decreased after depletion of activated macrophages. Both macrophage(-) and activated macrophage(-) mice showed polarized production of interferon- gamma by splenocytes and lymph-node cells and were able to attract and activate T cells in the lung. These data demonstrate that the dual role of macrophages is associated with the activation state of macrophages and that extensive apoptosis found in patients with tuberculosis could be part of a host defense strategy, as long as these cells are not activated.

Animals↗

PubMed2004

LPS-binding protein-deficient mice have an impaired defense against Gram-negative but not Gram-positive pneumonia.

LPS-binding protein (LBP) can facilitate the transfer of cell wall components of both Gram-negative bacteria (LPS) and Gram-positive bacteria (lipoteichoic acid) to inflammatory cells. Although LBP is predominantly produced in the liver, recent studies have indicated that this protein is also synthesized locally in the lung by epithelial cells. To determine the role of LBP in the immune response to pneumonia, LBP gene-deficient (-/-) and normal wild-type (WT) mice were intra-nasally infected with either Streptococcus pneumoniae or Klebsiella pneumoniae, common Gram-positive and Gram-negative pathogens, respectively. Pneumococcal pneumonia was associated with a 7-fold rise in LBP concentrations in bronchoalveolar lavage fluid of WT mice; LBP-/- mice infected with S. pneumoniae showed a similar survival and a similar bacterial burden in their lungs 48 h post-infection. In Klebsiella pneumonia, however, LBP-/- mice demonstrated a diminished survival together with an enhanced bacterial outgrowth in their lungs. These data suggest that LBP is important for a protective immune response in Klebsiella pneumonia, but does not contribute to an effective host response in pneumococcal pneumonia.

Acute-Phase Proteins↗

PubMed2004

Non-mannose-capped lipoarabinomannan induces lung inflammation via toll-like receptor 2.

Non-mannose-capped lipoarabinomannan (AraLAM) is part of the cell membrane of atypical mycobacteria. To determine the capacity of AraLAM to induce lung inflammation in vivo and to determine the signaling receptors involved herein, wild-type (WT) mice, lipopolysaccharide binding protein knockout mice, CD14-deficient (CD14 KO) mice, Toll-like receptor (TLR) 4 mutant mice, or TLR2 KO mice were intranasally inoculated with purified AraLAM. AraLAM induced high lung levels of tumor necrosis factor, interleukin-1beta, interleukin-6, and cytokine-induced neutrophil chemoattractant (KC) and an influx of neutrophils into the pulmonary compartment of WT mice. Lipopolysaccharide binding protein knockout, CD14 KO, and TLR4 mutant mice displayed similar inflammatory responses as WT mice, whereas in TLR2 KO mice, AraLAM-induced lung inflammation was strongly diminished. In addition, TLR2 KO mice, but not CD14 KO or TLR4 mutant mice, displayed a delayed clearance of pulmonary infection with the atypical AraLAM expressing Mycobacterium smegmatis. These data indicate that TLR2 is the signaling receptor for purified AraLAM in the lung in vivo and that this receptor contributes to an effective clearance of M. smegmatis from the pulmonary compartment.

Animals↗

PubMed2004

Atypical relapse of hemolytic uremic syndrome after transplantation.

Atypical hemolytic uremic syndrome (HUS) frequently leads to end-stage renal failure and can relapse after transplantation. A 12-year-old girl presenting with familial atypical HUS with a factor H mutation was successfully transplanted 6 years after a first transplant that had failed because of immediate recurrent HUS. Prophylactic plasma exchange before and after transplantation was used. Two months after transplantation, concomitant with a reduction in plasma exchange frequency, the plasma creatinine increased from 70 micro mol/l to 194 micro mol/l in 2 weeks without thrombocytopenia or signs of hemolytic anemia. The patient had minimal clinical symptoms and a presumptive diagnosis of graft rejection was made. Despite treatment with six daily pulses of methylprednisolone, plasma creatinine continued to increase and a graft biopsy was therefore undertaken. This showed the typical appearance of a thrombotic microangiopathy without any evidence of rejection. Despite daily plasmapheresis and replacement of cyclosporine with tacrolimus, there was no improvement and transplant nephrectomy was undertaken. This patient demonstrates that HUS can recur in a kidney transplant without the diagnostic hematological features and emphasizes the need for early transplant biopsy in such patients showing a decline in transplant function.

Child↗