[How to investigate sleep related breathing disorders in children?]

Sleep related breathing disorders (SDB) in children has a major negative impact on their neurocognitive development and should be identified and treated early as to decrease morbidity. Children do not usually present daytime fatigue and sleepiness like adults, but rather show abnormal behavior patterns and learning disabilities. The presence of sustained nightime snoring is a good screening toll for SDB. Polysomnography is the gold standard for diagnosis even though nightime oxymetry, with its high positive predictive value, can also be used. The most frequent SDB in childhood is sleep obstructive apnea syndrome (SOAS), which generally requires surgical treatment with adenotonsillectomy. Long term evolution of pediatric SOAS still has to be defined, as the role of other diagnostic tools such as outpatient polygraphy.

Role of CD40-CVD40L in mouse severe malaria

We explored the role of CD40-CD40L (CD154) in the severe malaria elicited by Plasmodium berghei anka infection in mice. Mortality was >90% by day 8 after infection in +/+ mice, but markedly decreased in CD40-/- or in CD40L-/- mice, as well as in +/+ mice treated with anti-CD40L monoclonal antibody. Parasitemia was similar in the different conditions. Breakdown of the blood-brain barrier was evident in infected +/+, but not in CD40-/- mice. Thrombocytopenia was less severe in CD40-/- mice than in the +/+ controls. Sequestration of macrophages in brain venules and alveolar capillaries was reduced in CD40-/- or in CD40L-/- mice, whereas sequestration of parasitized red blood cells or polymorphonuclear leukocytes in alveolar capillaries was CD40-CD40L-independent. CD40 mRNA was increased in the brain and lung of infected mice whereas CD40L was increased in the lung. Tumor necrosis factor plasma levels were similarly increased in infected +/+ or CD40-/- mice. Expression of CD54 and its mRNA levels in the brain were moderately decreased in CD40-deficient mice. Thus the mortality associated with severe malaria requires CD40-CD40L interaction that contributes to the breakdown of the blood-brain barrier, macrophage sequestration, and platelet consumption.

Urokinase receptor (uPAR, CD87) is a platelet receptor important for kinetics and TNF-induced endothelial adhesion in mice

BACKGROUND

Urokinase plasminogen activator receptor (uPAR, CD87) is a widely distributed 55-kD, glycoprotein I-anchored surface receptor. On binding of its ligand uPA, it is known to increase leukocyte adhesion and traffic. Using genetically deficient mice, we explored the role of uPAR in platelet kinetics and TNF-induced platelet consumption.

METHODS AND RESULTS

Anti-uPAR antibody stained platelets from normal (+/+) but not from uPAR-/- mice, as seen by fluorescence-activated cell sorter analysis. 51Cr-labeled platelets from uPAR-/- donors survived longer than those from +/+ donors when injected into a +/+ recipient. Intratracheal TNF injection induced thrombocytopenia and a platelet pulmonary localization, pronounced in +/+ but absent in uPAR-/- mice. Aprotinin, a plasmin inhibitor, decreased TNF-induced thrombocytopenia. TNF injection markedly reduced the survival and increased the pulmonary localization of 51Cr-labeled platelets from +/+ but not from uPAR-/- donors, indicating that it is the platelet uPAR that is critical for their response to TNF. As seen by electron microscopy, TNF injection increased the number of platelets and polymorphonuclear neutrophils (PMNs) in the alveolar capillaries of +/+ mice, whereas in uPAR-/- mice, platelet trapping was insignificant and PMN trapping was slightly reduced. Platelets within alveolar capillaries of TNF-injected mice were activated, as judged from their shape, and this was evident in +/+ but not in uPAR-/- mice.

CONCLUSIONS

These results demonstrate for the first time the critical role of platelet uPAR for kinetics as well as for activation and endothelium adhesion associated with inflammation.

Keratinocyte growth factor protects alveolar epithelium and endothelium from oxygen-induced injury in mice

Keratinocyte growth factor (KGF) has been used successfully to prevent alveolar damage induced by oxygen exposure in rodents. However, this treatment was used intratracheally and before oxygen exposure, which limited its clinical application. In the present study, mice were treated with the recombinant human KGF intravenously before (days -2 and -1) or during (days 0 and +1) oxygen exposure. In both cases, lung damage was attenuated. KGF increased the number of cells incorporating bromodeoxyuridine (BrdU) in the septa and in bronchial epithelium of air-breathing mice but not of oxygen-exposed mice, indicating that the protective effect of KGF is not necessarily associated with proliferation. Oxygen-induced damage of alveolar epithelium and, unexpectedly, of endothelium was prevented by KGF treatment as seen by electron microscopy. We investigated the effect of KGF on different mechanisms known to be involved in oxygen toxicity. The induction of p53, Bax, and Bcl-x mRNAs during hyperoxia was to a large extent prevented by KGF. Surfactant proteins A and B mRNAs were not markedly modified by KGF. The anti-fibrinolytic activity observed in the alveoli during hyperoxia was to a large extent prevented by KGF, most probably by suppressing the expression of plasminogen activator inhibitor-1 (PAI-1) mRNA and protein. As PAI-1 -/- mice are more resistant to hyperoxia, KGF might act, at least in part, by decreasing the expression of this protease inhibitor and by restoring the fibrinolytic activity into the lungs.

TNF-induced enterocyte apoptosis and detachment in mice: induction of caspases and prevention by a caspase inhibitor, ZVAD-fmk

Injection of mouse recombinant TNF to mice induced apoptosis and detachment of the enterocytes of the tip of the villi, evident after 30 to 90 minutes, which resulted in a shrinkage of the villi. Injection of TNF increased the expression of caspase 1, 2, 3, and 6 as well as of cathepsin D in the mucosal wall, which was maximal 30 minutes after TNF injection. Caspase 1 and 3 were not induced in TNFR1-deficient mice in which TNF does not induce apoptosis and detachment. The administration of a caspase inhibitor (ZVAD-fmk, 300 microg) decreased enterocyte detachment and apoptosis, as well as villus atrophy, whereas a caspase 3 inhibitor (Z-DEVD-cmk) had no effect. The results indicate that the induction of caspases by TNF is the cause of their detachment in the lumen and of the resulting villus atrophy.

TNF-induced enterocyte apoptosis in mice is mediated by the TNF receptor 1 and does not require p53

Injection of recombinant mouse TNF into mice is known to induce a shrinkage of the duodenal villi, which becomes evident 30-90 min later and is associated with a detachment of enterocytes in the lumen. These cells can be collected by lavage and are all apoptotic, i.e. hypodiploid as seen by flow cytometric analysis. Thus the count of detached cells was used as an evaluation of the TNF-induced cell loss and apoptosis in the mucosa. TNF injection induced a cell loss of similar magnitude in wild-type (+/+) or in mice lacking the TNF receptor (TNFR)2 (p75, TNFR2-/-), while mice lacking the TNFR1 (p55, TNFR1-/-) were completely resistant to this effect. TNF increased the expression of p53 tumor suppressor gene in the enterocytes from the crypts but not from the villi, as seen by Western blots and histochemistry. TNF increased the expression of p53 in both TNFR2-/- and TNFR1-/- mice. Furthermore, enterocyte cell loss was not attenuated in p53-/- mice. The results indicate that TNF, acting on its receptor 1, induces an apoptotic detachment of the enterocytes from the tip of the villi (i.e. the old enterocytes), while in the enterocytes from the crypts (the young enterocytes) TNF increases, via either TNFR1 or TNFR2, the expression of p53, without inducing apoptosis.

TNF-induced enterocyte apoptosis in mice is mediated by the TNF receptor 1 and does not require p53

Injection of recombinant mouse TNF into mice is known to induce a shrinkage of the duodenal villi, which becomes evident 30-90 min later and is associated with a detachment of enterocytes in the lumen. These cells can be collected by lavage and are all apoptotic, i.e. hypodiploid as seen by flow cytometric analysis. Thus the count of detached cells was used as an evaluation of the TNF-induced cell loss and apoptosis in the mucosa. TNF injection induced a cell loss of similar magnitude in wild-type (+/+) or in mice lacking the TNF receptor (TNFR)2 (p75, TNFR2-/-), while mice lacking the TNFR1 (p55, TNFR1-/-) were completely resistant to this effect. TNF increased the expression of p53 tumor suppressor gene in the enterocytes from the crypts but not from the villi, as seen by Western blots and histochemistry. TNF increased the expression of p53 in both TNFR2-/- and TNFR1-/- mice. Furthermore, enterocyte cell loss was not attenuated in p53-/- mice. The results indicate that TNF, acting on its receptor 1, induces an apoptotic detachment of the enterocytes from the tip of the villi (i.e. the old enterocytes), while in the enterocytes from the crypts (the young enterocytes) TNF increases, via either TNFR1 or TNFR2, the expression of p53, without inducing apoptosis.

TNF-induced enterocyte apoptosis in mice is mediated by the TNF receptor 1 and does not require p53

Injection of recombinant mouse TNF into mice is known to induce a shrinkage of the duodenal villi, which becomes evident 30-90 min later and is associated with a detachment of enterocytes in the lumen. These cells can be collected by lavage and are all apoptotic, i.e. hypodiploid as seen by flow cytometric analysis. Thus the count of detached cells was used as an evaluation of the TNF-induced cell loss and apoptosis in the mucosa. TNF injection induced a cell loss of similar magnitude in wild-type (+/+) or in mice lacking the TNF receptor (TNFR)2 (p75, TNFR2-/-), while mice lacking the TNFR1 (p55, TNFR1-/-) were completely resistant to this effect. TNF increased the expression of p53 tumor suppressor gene in the enterocytes from the crypts but not from the villi, as seen by Western blots and histochemistry. TNF increased the expression of p53 in both TNFR2-/- and TNFR1-/- mice. Furthermore, enterocyte cell loss was not attenuated in p53-/- mice. The results indicate that TNF, acting on its receptor 1, induces an apoptotic detachment of the enterocytes from the tip of the villi (i.e. the old enterocytes), while in the enterocytes from the crypts (the young enterocytes) TNF increases, via either TNFR1 or TNFR2, the expression of p53, without inducing apoptosis.

Oxygen toxicity in mouse lung: pathways to cell death

Mice exposed to 100% O2 die after 3 or 4 d with diffuse alveolar damage and alveolar edema. Extensive cell death is evident by electron microscopy in the alveolar septa, affecting both endothelial and epithelial cells. The damaged cells show features of both apoptosis (condensation and margination of chromatin) and necrosis (disruption of the plasma membrane). The electrophoretic pattern of lung DNA indicates both internucleosomal fragmentation, characteristic of apoptosis, and overall degradation, characteristic of necrosis. Hyperoxia induces a marked increase in RNA or protein levels of p53, bax, bcl-x, and Fas, which are known to be expressed in certain types of apoptosis. However, we did not detect an increased activity of proteases belonging to the apoptosis "executioner" machinery, such as CPP32 (caspase 3), ICE (caspase 1), or cathepsin D. Furthermore, administration of an ICE-like protease inhibitor did not significantly enhance the resistance to oxygen. Additionally, neither p53-deficient mice nor lpr mice (Fas null) manifested an increased resistance to hyperoxia-induced lung damage. These results show that both necrosis and apoptosis contribute to cell death during hyperoxia. Multiple apoptotic pathways seem to be involved in this, and an antiapoptotic strategy does not attenuate alveolar damage.

Role of mast cells and monoamines in the thrombocytopaenia and mortality elicited by tumour necrosis factor in mice

We explored the thrombocytopaenia elicited by the i.v. injection of mouse recombinant tumour necrosis factor (TNF) in mice. Injection of 10 micrograms of TNF led to a thrombocytopaenia (evident after 0.5 hr) which was caused by decreased platelet survival, as seen by the injection of labelled platelets. TNF-induced thrombocytopaenia was not prevented by heparin, nor by depletion of either fibrinogen or C'. TNF-induced thrombocytopaenia was markedly attenuated in mice treated with reserpine, an agent that depletes monoamines from mast cells and other cells, and in the mast-cell-deficient WWv mice. In vitro, TNF elicited a modest release of monoamine from peritoneal mast cells and from a mast cell line. When mice are injected with 3H-serotonin (3H-5HT) before TNF, TNF injection increased the plasma 3H-5HT content 1 hr later, modifications absent in reserpine pretreated or mast-cell-deficient mice. 3H-5HT content of the small intestine was markedly depleted in TNF-injected mice, suggesting that this organ is the source of the plasma 3H-5HT. Drop in body temperature and mortality induced by TNF were also attenuated in mast-cell-deficient, and in reserpine pretreated mice. These results indicate that TNF can induce a release of monoamines from mast cells, mainly from those of the small intestine, a process that contributes to TNF-induced thrombocytopaenia and mortality.

Resistance of TNF/LT alpha double deficient mice to bleomycin-induced fibrosis

In order to evaluate the role and mode of action of TNF in bleomycin-induced lung fibrosis, mice deficient for TNF and LT alpha (delta TNF/LT alpha) were examined at 2 months of age and after 3 weekly i.v. injections of bleomycin. The body weight of the delta TNF/LT alpha mice was 88 +/- 11% of that of the wild type littermates. Lung collagen, evaluated by its hydroxyproline content, was also lower (81 +/- 9%) in mutant than in wild type littermates. Bleomycin induced a diffuse alveolitis with focal areas of alveolar remodelling in wild type but not in delta TNF/LT alpha, mice. Lymphoid infiltration was also prominent in wild type, but absent from delta TNF/LT alpha, mice. Bleomycin injections increased collagen deposition, as evaluated by the lung hydroxyproline content, more markedly in wild type, than in delta TNF/LT alpha, mice. Cell trapping in the alveolar capillaries was evaluated by semi-quantitative electron microscopy. Bleomycin markedly increased platelet trapping in the alveolar capillaries of wild type, but not of delta TNF/LT alpha, mice. This study indicates that the expression of TNF/LT alpha genes increases the deposition of collagen in both untreated and inflamed lung and that these genes may act, at least in part, by promoting platelet trapping.

Plasminogen activator inhibitor-1 in acute hyperoxic mouse lung injury

Hyperoxia-induced lung disease is associated with prominent intraalveolar fibrin deposition. Fibrin turnover is tightly regulated by the concerted action of proteases and antiproteases, and inhibition of plasmin-mediated proteolysis could account for fibrin accumulation in lung alveoli. We show here that lungs of mice exposed to hyperoxia overproduce plasminogen activator inhibitor-1 (PAI-1), and that PAI-1 upregulation impairs fibrinolytic activity in the alveolar compartment. To explore whether increased PAI-1 production is a causal or only a correlative event for impaired intraalveolar fibrinolysis and the development of hyaline membrane disease, we studied mice genetically deficient in PAI-1. We found that these mice fail to develop intraalveolar fibrin deposits in response to hyperoxia and that they are more resistant to the lethal effects of hyperoxic stress. These observations provide clear and novel evidence for the pathogenic contribution of PAI-1 in the development of hyaline membrane disease. They identify PAI-1 as a major deleterious mediator of hyperoxic lung injury.

Hyperoxia induces platelet activation and lung sequestration: an event dependent on tumor necrosis factor-alpha and CD11a

Mice were exposed to pure oxygen for various times to explore the pulmonary platelet trapping associated with alveolar damage, its mechanism, and its role in the lesions. Platelet sequestration, evaluated by electron microscopy and by injection of radiolabeled platelets, was detectable after 72 h and reached a maximum after 96 h of exposure (i.e., shortly before death). Circulating platelets (analyzed by Facscan) showed some increase in the expression of CD11a and CD62, but little change in CD31 and CD61. Both platelet activation and lung sequestration were dependent on TNF-alpha, since antibody against TNF-alpha reduced the expression of CD11a on circulating platelets and their sequestration in the lung. Lung platelet sequestration was also decreased by anti-CD11a MoAb. Northern blot analysis of lung mRNA isolated at 96 h of oxygen exposure revealed a 7-fold increase in CD54 (intercellular adhesion molecule-1 [ICAM-1]) and a 2.5-fold increase in TNF-alpha mRNAs respectively. These results demonstrate that the platelet pulmonary trapping induced by hyperoxia is dependent upon TNF-alpha and the CD11a-CD54 adhesion molecules. However, platelet trapping does not appear to play an important pathogenic role in acute oxygen injury, since treatments that decrease trapping (anti-TNF-alpha, anti-CD11a, or antibody-induced thrombocytopenia) did not markedly attenuate the alveolar damage.

Phagocytosis of Pseudomonas aeruginosa fails to elicit heat shock protein expression in human monocytes

Phagocytosis represents a powerful stress for the phagocytic cells. Phagocytosis of Staphylococcus aureus induces a stress response associated with the synthesis of specific heat shock/stress proteins (HSP). Here we investigated the stress response of human monocyte-macrophages (m phi) to Pseudomonas aeruginosa, a bacterium found, as for S. aureus, in the airways of patients suffering cystic fibrosis. P. aeruginosa activated in m phi the production of both extra- and intracellular O2-; increased Interleukin-1 beta and actin, but failed to induce host HSP. Neither S. aureus' exotoxins nor the scavenging property of P. aeruginosa's alginate, but the lower toxicity of P. aeruginosa and/or differential activation of proteine kinase C (PKC) by the two bacteria, might explain their differences in host HSP induction. While O2- is insufficient to induce HSP synthesis in m phi, hydroxyl radicals, generated in the presence of exogenous iron, is a likely additional signal, along with PKC activation, for HSP induction during bacterial phagocytosis.

Heat-shock proteins in host-pathogen interactions: implications for cystic fibrosis

The expression of heat-shock proteins by both pathogen and host cells during the phagocytosis of Staphylococcus aureus and Pseudomonas aeruginosa, two bacterial species that colonize the airways of patients with cystic fibrosis, probably contributes to pulmonary inflammation in cystic fibrosis. Here, we discuss the likely signals for heat-shock-protein induction within host and bacterial cells.

Childhood tuberculosis at a Swiss university hospital: a 2-year study

The incidence of tuberculosis (TB) presenting to the University Hospital, Geneva, Switzerland, was studied over 2 years. Clinical data on all children receiving antituberculous drug therapy was collected. Of the 43 identified cases, 42% had active disease (i.e. clinical evidence of organ involvement), the remaining 58% being asymptomatic. All 43 children originated from countries other than Switzerland. Symptomatic, drug induced hepatitis necessitated temporary interruption of therapy in 2 children (5%). Contact screening yielded three new cases of pulmonary TB, three previously diagnosed cases and seven instances of a positive medical history in relatives living in other countries. Of the 34 families in this study, contact screening could not be completed in 8. The results of this study indicate that children with TB are primarily associated with families originating from countries other than Switzerland, particularly those in which TB remains endemic. Tuberculin skin testing should therefore be targeted at this group. Contact tracing has also been shown to be beneficial.

Propranolol treatment in children with tetralogy of Fallot alters the response to isoprenaline after surgical repair

When propranolol is given to prevent hypoxaemic episodes in children with tetralogy of Fallot who are awaiting operation it is advisable to continue the treatment until shortly before the induction of anaesthesia. Because catecholamines are often required to maintain adequate cardiac output after surgical correction the effect of preoperative treatment with beta blockers on the response to isoprenaline after the operation was investigated in nine children given propranolol before operation and nine who were not. They were studied three and 24 hours after cardiopulmonary bypass. The haemodynamic response to increasing doses of infused isoprenaline was monitored. Immediately after cardiopulmonary bypass the response to isoprenaline was significantly blunted in the patients who had been given propranolol before operation. Their dose-response curve lay to the right of that for patients not given propranolol, and this indicates competitive inhibition. Propranolol concentrations in the blood and myocardium correlated significantly with the heart rate response to isoprenaline. Twenty four hours after operation the isoprenaline response was similar in both groups and concentrations of propranolol in the blood were minimal or undetectable. beta Blockers given up to the time of operation significantly altered the postoperative response to catecholamines.