Constance Barazzone-Argiroffo

A key role for NOX4 in epithelial cell death during development of lung fibrosis.

UNLABELLED The pathogenesis of pulmonary fibrosis is linked to oxidative stress, possibly generated by the reactive oxygen species (ROS) generating NADPH oxidase NOX4. Epithelial cell death is a crucial early step in the development of the disease, followed only later by the fibrotic stage. We demonstrate that in lungs of patients with idiopathic lung fibrosis, there is strong expression of NOX4 in hyperplastic alveolar type II cells. AIM To study a possible causative role of NOX4 in the death of alveolar cells, we have generated NOX4-deficient mice. RESULTS Three weeks after administration of bleomycin, wild-type (WT) mice developed massive fibrosis, whereas NOX4-deficient mice displayed almost normal lung histology, and only little Smad2 phosphorylation and accumulation of myofibroblasts. However, the protective effects of NOX4 deficiency preceded the fibrotic stage. Indeed, at day 7 after bleomycin, lungs of WT mice showed massive increase in epithelial cell apoptosis and inflammation. In NOX4-deficient mice, no increase in apoptosis was observed, whereas inflammation was comparable to WT. In vitro, NOX4-deficient primary alveolar epithelial cells exposed to transforming growth factor-β(1) did not generate ROS and were protected from apoptosis. Acute treatment with the NOX inhibitors also blunted transforming growth factor-β(1)-induced apoptosis. CONCLUSION ROS generation by NOX4 is a key player in epithelial cell death leading to pulmonary fibrosis.

Alveolar cell death in hyperoxia-induced lung injury

Abstract: Exposure to high oxygen concentration causes direct oxidative cell damage through increased production of reactive oxygen species. In vivo oxygen‐induced lung injury is well characterized in rodents and has been used as a valuable model of human respiratory distress syndrome. Hyperoxia‐induced lung injury can be considered as a bimodal process resulting (1) from direct oxygen toxicity and (2) from the accumulation of inflammatory mediators within the lungs. Both apoptosis and necrosis have been described in alveolar cells (mainly epithelial and endothelial) during hyperoxia. While the in vitro response to oxygen seems to be cell type‐dependent in tissue cultures, it is still unclear which are the death mechanisms and pathways implicated in vivo. Even though it is not yet possible to distinguish unequivocally between apo‐ptosis, necrosis, or other intermediate form(s) of cell death, a great variety of strategies has been shown to prevent alveolar damage and to increase animal survival during hyperoxia. In this review, we summarize the different cell death pathways leading to alveolar damage during hyperoxia, with particular attention to the pivotal role of mitochondria. In addition, we discuss the different protective mechanisms potentially interfering with alveolar cell death.

Pneumonia and pericarditis in a child with HRV-C infection: A case report

Abstract Human rhinovirus type C is a recently discovered species that has been associated with respiratory tract infections of unusual severity in some cases. However, the precise type of diseases associated with this new human rhinovirus needs to be investigated. In the present report, we used adapted real-time PCR assays to screen different clinical specimens collected from a 14-month-old boy presenting an acute lower respiratory tract disease complicated by a severe pericarditis. RT-PCR identified picornavirus RNA in the bronchoalveolar lavage (BAL) specimen, pericardial fluid, plasma and stools. This supported the existence of a disseminated viral infection that extended to the pericardial space. 5′UTR and VP1 sequence analysis performed directly from the BAL sample allowed genotyping of the virus as a human rhinovirus C. This observation highlights the need for adapted diagnostic tools and the potential for the new rhinovirus species C to cause complications, including pericarditis.

NOX enzymes: potential target for the treatment of acute lung injury.

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), is characterized by acute inflammation, disruption of the alveolar-capillary barrier, and in the organizing stage by alveolar pneumocytes hyperplasia and extensive lung fibrosis. The cellular and molecular mechanisms leading to the development of ALI/ARDS are not completely understood, but there is evidence that reactive oxygen species (ROS) generated by inflammatory cells as well as epithelial and endothelial cells are responsible for inflammatory response, lung damage, and abnormal repair. Among all ROS-producing enzymes, the members of NADPH oxidases (NOXs), which are widely expressed in different lung cell types, have been shown to participate in cellular processes involved in the maintenance of lung integrity. It is not surprising that change in NOXs’ expression and function is involved in the development of ALI/ARDS. In this context, the use of NOX inhibitors could be a possible therapeutic perspective in the management of this syndrome. In this article, we summarize the current knowledge concerning some cellular aspects of NOXs localization and function in the lungs, consider their contribution in the development of ALI/ARDS and discuss the place of NOX inhibitors as potential therapeutical target.

Hyperoxia-mediated oxidative stress increases expression of UCP3 mRNA and protein in skeletal muscle

The uncoupling protein‐3 (UCP3) is a mitochondrial protein expressed mainly in skeletal muscle. Among several hypotheses for its physiological function, UCP3 has been proposed to prevent excessive production of reactive oxygen species. In the present study, we evaluated the effect of an oxidative stress induced by hyperoxia on UCP3 expression in mouse skeletal muscle and C2C12 myotubes. We found that the hyperoxia‐mediated oxidative stress was associated with a 5‐fold and 3‐fold increase of UCP3 mRNA and protein levels, respectively, in mouse muscle. Hyperoxia also enhanced reactive oxygen species production and UCP3 mRNA expression in C2C12 myotubes. Our findings support the view that both in vivo and in vitro UCP3 may modulate reactive oxygen species production in response to an oxidative stress.

Macrophage‐specific NOX2 contributes to the development of lung emphysema through modulation of SIRT1/MMP‐9 pathways

Reactive oxygen species (ROS) participate in the pathogenesis of emphysema. Among ROS‐producing enzymes, NOX NADPH oxidases are thought to be responsible for tissue injury associated with several lung pathologies. To determine whether NOX2 and/or NOX1 participate in the development of emphysema, their expression patterns were first studied by immunohistochemistry in the lungs of emphysematous patients. Subsequently, we investigated their contribution to elastase‐induced emphysema using NOX2‐ and NOX1‐deficient mice. In human lung, NOX2 was mainly detected in macrophages of control and emphysematous lungs, while NOX1 was expressed in alveolar epithelium and bronchial cells. We observed an elevated number of NOX2‐positive cells in human emphysematous lungs, as well as increased NOX2 and NOX1 mRNA expression in mouse lungs following elastase exposure. Elastase‐induced alveolar airspace enlargement and elastin degradation were prevented in NOX2‐deficient mice, but not in NOX1‐deficient mice. This protection was independent of inflammation and correlated with reduced ROS production. Concomitantly, an elevation of sirtuin 1 (SIRT1) level and a decrease of matrix metalloproteinase‐9 (MMP‐9) expression and activity were observed in alveolar macrophages and neutrophils. We addressed the specific role of macrophage‐restricted functional NOX2 in elastase‐induced lung emphysema using Ncf1 mutant mice and Ncf1 macrophage rescue mice (Ncf1 mutant mice with transgenic expression of Ncf1 only in CD68‐positive mononuclear phagocytes; the MN mouse). Compared to WT mice, the lack of functional NOX2 led to decreased elastase‐induced ROS production and protected against emphysema. In contrast, ROS production was restored specifically in macrophages from Ncf1 rescue mice and contributes to emphysema. Taken together, our results demonstrate that NOX2 is involved in the pathogenesis of human emphysema and macrophage‐specific NOX2 participates in elastase‐induced emphysema through the involvement of SIRT1/MMP‐9 pathways in mice.

Nicotine mediates oxidative stress and apoptosis through cross talk between NOX1 and Bcl-2 in lung epithelial cells.

Nicotine contributes to the onset and progression of several pulmonary diseases. Among the various pathophysiological mechanisms triggered by nicotine, oxidative stress and cell death are reported in several cell types. We found that chronic exposure to nicotine (48h) induced NOX1-dependent oxidative stress and apoptosis in primary pulmonary cells. In murine (MLE-12) and human (BEAS-2B) lung epithelial cell lines, nicotine acted as a sensitizer to cell death and synergistically enhanced apoptosis when cells were concomitantly exposed to hyperoxia. The precise signaling pathway was investigated in MLE-12 cells in which NOX1 was abrogated by a specific inhibitor or stably silenced by shRNA. In the early phase of exposure (1h), nicotine mediated intracellular Ca(2+) fluxes and activation of protein kinase C, which in its turn activated NOX1, leading to cellular and mitochondrial oxidative stress. The latter triggered the intrinsic apoptotic machinery by modulating the expression of Bcl-2 and Bax. Overexpression of Bcl-2 completely prevented nicotines detrimental effects, suggesting Bcl-2as a downstream key regulator in nicotine/NOX1-induced cell damage. These results suggest that NOX1 is a major contributor to the generation of intracellular oxidative stress induced by nicotine and might be an important molecule to target in nicotine-related lung pathologies.

Early blood exchange transfusion in malignant pertussis: a case report.

Objective: To report early blood exchange transfusion in malignant pertussis and a favorable clinical outcome. Setting: A pediatric intensive care unit in a tertiary hospital in Geneva, Switzerland. Design: A descriptive case report. Patient: An 8-wk-old girl was diagnosed with malignant pertussis (extreme leukocytosis, seizures, pneumonia, and secondary severe hypoxic respiratory failure associated with pulmonary hypertension). After administration of a one-volume blood exchange transfusion, a rapid decrease in white blood cell count (from 119,000/mm3 to 36,500/mm3) was observed and followed by clinical improvement and favorable outcome despite the initial presence of all described risk factors associated with a high mortality. Conclusion: The use of exchange blood transfusion early in the course of the disease might help to prevent a fatal outcome of malignant pertussis.

Prevention of bronchoconstriction in sensitized guinea pigs: efficacy of common prophylactic drugs

Efficacy of beta2-agonists (B2), anticholinergics, corticosteroids, anti-inflammatory drugs or antihistamines against methacholine, histamine, or allergen-induced lung constriction was tested in ovalbumin sensitized guinea pigs. Airway resistance (Raw) and parenchymal damping (G) and elastance (H) were determined from low-frequency forced oscillatory input impedance (ZL). ZL was measured under control conditions, during iv infusions of methacholine, and following iv boluses of histamine or ovalbumin. In decreasing potency, ipratropium, salmeterol, fluticasone or cromoglycate reduced the methacholine-induced increases in Raw and G. Only antihistamines had any effects on the histamine-induced increased in Raw, G, and H. The ovalbumin-induced increases in Raw, G and H in the control animals (120 +/- 90%, 201 +/- 126%, 86 +/- 71%) were markedly reduced by pretreatments with antihistamines (18 +/- 11%, 13 +/- 9%, 3+/- 3%) and cromoglycate (29 +/- 13%, 35 +/- 22%, 18 +/- 10%). Bronchoconstriction induced by muscarinic receptor stimulation is inhibited by anticholinergic, anti-inflammatory or beta2-agonist pretreatment; antihistaminic or anti-inflammatory premedication is beneficial if the release of histamine via an exposure to allergen is responsible for the fall in lung function.

The role of endothelin-1 in hyperoxia-induced lung injury in mice

BackgroundAs prolonged hyperoxia induces extensive lung tissue damage, we set out to investigate the involvement of endothelin-1 (ET-1) receptors in these adverse changes.MethodsExperiments were performed on four groups of mice: control animals kept in room air and a group of mice exposed to hyperoxia for 60 h were not subjected to ET-1 receptor blockade, whereas the dual ETA/ETB-receptor blocker tezosantan (TEZ) was administered via an intraperitoneal pump (10 mg/kg/day for 6 days) to other groups of normal and hyperoxic mice. The respiratory system impedance (Zrs) was measured by means of forced oscillations in the anesthetized, paralyzed and mechanically ventilated mice before and after the iv injection of ET-1 (2 μg). Changes in the airway resistance (Raw) and in the tissue damping (G) and elastance (H) of a constant-phase tissue compartment were identified from Zrs by model fitting.ResultsThe plasma ET-1 level increased in the mice exposed to hyperoxia (3.3 ± 1.6 pg/ml) relative to those exposed to room air (1.6 ± 0.3 pg/ml, p < 0.05). TEZ administration prevented the hyperoxia-induced increases in G (13.1 ± 1.7 vs. 9.6 ± 0.3 cmH2O/l, p < 0.05) and H (59 ± 9 vs. 41 ± 5 cmH2O/l, p < 0.05) and inhibited the lung responses to ET-1. Hyperoxia decreased the reactivity of the airways to ET-1, whereas it elevated the reactivity of the tissues.ConclusionThese findings substantiate the involvement of the ET-1 receptors in the physiopathogenesis of hyperoxia-induced lung damage. Dual ET-1 receptor antagonism may well be of value in the prevention of hyperoxia-induced parenchymal damage.