[Early determinants of chronic obstructive pulmonary disease: Lung regeneration, a new therapeutic target?] / Déterminants précoces de la bronchopneumopathie chronique obstructive : la régénération pulmonaire, une nouvelle piste thérapeutique ?

Chronic obstructive pulmonary disease, a disease of increasing incidence, is related mainly to smoking. Although symptoms only appear at adulthood, the disease can develop from early life events. For example, bronchopulmonary dysplasia, which occurs in preterm infants, is characterized by airspace enlargement and could lead to late lung consequences. Once the lesions are established, no curative treatment is available. Stimulating lung regeneration from endogenous stem cells is therefore an exciting research domain, particularly through the activation of the mesenchymal contingent located in the lung stem cell niche.

Interaction of matrix metalloproteinases with pulmonary pollutants.

An air pollutant consists of any atmospheric substance that may harm humans, animals, vegetation or material. Various air pollutants have been reported, differing in their physicochemical characteristics. They can be grouped into four categories: gaseous pollutants (e.g. ozone, sulfur dioxide, oxides of nitrogen, carbon monoxide and volatile organic compounds), persistent organic pollutants, heavy metals (e.g. cadmium, lead and mercury) and particulate matter (coarse, fine and ultrafine). These pollutants can reach the respiratory system, eliciting pulmonary and/or systemic effects. These effects include inflammation, tissue remodelling and carcinogenesis: all phenomena where matrix metalloproteases (MMPs) play critical roles, given their broad effects on matrix remodelling and modulation of inflammation and cell signalling. Moreover, since expression and activity of MMPs can be induced by such stimuli, the hypothesis has been raised that MMPs could be involved in the health effects of pollutants. Until now, the implication of MMPs in these effects has been studied only for some pollutants and for a restricted selection of MMPs (mainly MMP-1, -2, -9 and -12), while evidence for a link between MMP induction/activation and health effects remains scarce. A larger number of studies is, therefore, needed in order to better understand the implication of MMPs in health effects associated with air pollution.

Respiratory effects of manufactured nanoparticles.

Nanotechnology is the set of techniques used to engineer, characterize, and produce materials that have at least one dimension within the nanoscale. These nanomaterials, or nanoobjects, include nanoparticles and nanotubes. As dictated by the laws of quantum physics, a size within the nanoscale results in unique physicochemical properties and distinctive behaviors. Nanotechnology has a host of applications in fields ranging from cosmetology to the industry and medicine. The production and use of nanomaterials are expanding at a brisk pace. However, concerns are emerging about the potential health effects of nanoparticles in the short and long terms. These concerns are rooted in data on the harmful health effects of micrometric airborne particulate matter. Conceivably, these adverse effects might be amplified when the particles are within the nanoscale. This article is a nonexhaustive overview of current data on the penetration, deposition, translocation, and elimination of inhaled nanoparticles and on the respiratory effects of metallic nanoparticles (with special attention to titanium dioxide) and carbon nanotubes. Both in vivo and in vitro studies consistently found biological effects of nanoparticles on the respiratory system, including oxidative stress generation, proinflammatory and prothrombotic effects, pulmonary fibrosis and emphysema, and DNA damage. Improved knowledge of the potential biological effects of nanoparticles is needed to guide preventive strategies for the workplace and/or general population if needed.

[Respiratory effects of manufactured nanoparticles]. / Effets respiratoires des nanoparticules manufacturées.

Nanotechnology, defined as techniques aimed to design, characterize and produce materials on a nanometer scale, is a fast-growing field today. Nanomaterials are made of nanoobjects (nanoparticles, nanofibers, nanotubes...). The nanoscale confers on these materials their novel, hitherto unknown, chemical and physical properties by the laws of quantum physics which are essentially expressed on this scale. Nanotechnology applications are numerous (e.g., cosmetics, industry and medicine) and they keep growing. We can safely predict that the production and utilization of nanomaterials will increase greatly in the years to come. Nonetheless, the same properties that make these nanomaterials very attractive are a source of concern: there are questions about their potential toxicity, their long-term side effects, and their biodegradability. These questions are based on knowledge of the toxic effects of micrometric particles in air pollution and the fear that these effects will be amplified because of the nanometric size of the new materials. We present in this article a global but not exhaustive summary of current knowledge. We begin by defining lung penetration, deposition, translocation and elimination of nanoparticles. Finally, we consider the respiratory effects of metallic nanoparticles, titanium dioxide nanoparticles in particular, and carbon nanotubes. In vivo and in vitro experimental studies currently available highlight the existence of biological effects of nanoparticles on the respiratory system with generation of oxidative stress, pro-inflammatory and pro-thrombotic effects and the possible development of fibrosis and pulmonary emphysema or DNA damage. A better understanding of the potential biological effects of nanoparticles is required to implement appropriate preventive measures in the workplace and/or in the general population, if this should be necessary.

[Study of cellularity in bronchoalveolar fluid and bronchial reactivity to histamine in a model of asthma in guinea pig]. / Etude de la cellularité bronchoalvéolaire et de la réactivite des voies aériennes a l'histamine dans un modèle d'asthme chez le cobaye.

INTRODUCTION: Several studies showed that the guinea pig represents the animal of choice in the study of the asthma and more exactly in the study of the bronchial hyperreactivity. MATERIALS AND METHOD: In our model of asthma, guinea pigs were made sensitive with ovalbumine (OVA), a protein extracted from the white of egg, and provoked in a way repeated with aerosol challenge of OVA for the group OVA (1 challenge a day during six days). This group was compared with the group controls (C), animals injected with a salt solution (NaCl 0.9%) and receiving aerosol challenge of salt solution. The OVA group was subdivided into two groups: A studied group 6 hours after the aerosol challenge of OVA. A studied group 24 hours after the aerosol challenge of OVA. RESULTS: We showed an increasing increase of airway hyperresponsiveness to increasing doses of histamine in all groups of animals. This increase was significantly more important 6 hours after the last aerosol challenge of OVA (early airway hyperreactivity, OVA-6 group, n = 8) that at 24 hours after the last aerosol challenge (late airway hyperreactivity, OVA-24 group, n = 8). We had also noted a modification of cellularity in bronchoalveolar lavage fluid with an increase of the total number of cells essentially by increase of the rate of eosinophilia in OVA-6 group (n = 6) compared with OVA-24 group (n = 6) and Control group (n = 6). CONCLUSION: The model of bronchial hyperreactivity and modification of cellularity in guinea pig will allow us to envisage studies on the origin of differences of ability to react in the group OVA-6 and OVA-24 and to study the medicinal efficiency of plants used in Senegal in the treatment of the asthma.

Carbon monoxide reduces the expression and activity of matrix metalloproteinases 1 and 2 in alveolar epithelial cells.

Matrix metalloproteinases (MMPs), particularly MMP-1 and MMP-2, are involved in the pathophysiology of emphysema. MMPs contain zinc in the catalytic site and its expression is regulated transcriptionally via mitogen activated protein kinases (MAPKs). Carbon monoxide (CO), one of the end products of heme oxygenase activity, has anti-inflammatory properties, which are mediated, at least in part, by activation of p38 MAPK. Furthermore, CO has the unique ability to bind to metal centers in proteins and can affect their specific activity. Therefore, we hypothesized that CO could inhibit MMPs expression and/or activity. Here we show that a recently identified carbon monoxide-releasing molecule, [Ru(CO)3Cl2]2 (or CORM-2) inhibits MMP-1 and MMP-2 mRNA expression in the human lung epithelial cell line A549. The MMPs mRNA expression was unaffected by the p38 MAPK inhibitor SB203580, but in the case of MMP-1 was reversed by the antioxidant N-acetylcysteine. In addition, CORM-2 inhibited both MMP-1 and MMP-2 activities. Interestingly, no effect was observed with (Ru(DMSO)4Cl2), a negative control that does not contain CO groups. To the best of our knowledge this is the first evidence on the effect of CO on MMPs expression and activity. This effect could have important implications in the pathophysiology of emphysema and other diseases involving proteases/antiproteases imbalance.

[Diaphragmatic weakness in sepsis: the role of oxidant stress]. / Stress oxydant et diaphragme: rôle dans la défaillance contractile au cours du sepsis.

In sepsis contractile weakness of the diaphragm is a major cause of the onset of respiratory failure. This muscular weakness is the result of haemodynamic and metabolic disorders secondary to sepsis and also the damaging effects of inflammatory mediators, among which oxygen free radicals play a crucial role. This role is demonstrated by the protective effect of various exogenous anti-oxidants on diaphragmatic contraction. Early in the course of sepsis there is, in animal models and in man, an increased production of oxygen free radicals and nitric oxide (NO) in the diaphragm, principally within the mitochondria. The formation of peroxinitrite as the result of the action of NO on superoxide anions impairs mitochondrial respiration and consequently the energy production necessary for diaphragmatic contraction. Among the endogenous anti-oxidant systems haem oxygenase, which splits haemoglobin into bilirubin, iron and carbon monoxide, is an effective system for the protection of diaphragmatic function by limiting the damage of oxidant stress. Nevertheless a transient deficiency of local anti-oxidant defences during the early stages of sepsis, when the production of oxygen free radicals is intense, encourages the onset of contractile weakness.

Activation of cardiac endothelium as a compensatory component in endotoxin-induced cardiomyopathy: role of endothelin, prostaglandins, and nitric oxide.

BACKGROUND: In view of growing evidence of an important endothelial paracrine regulation of cardiac function, the present study investigated the role of cardiac endothelium-derived endothelin-1 (ET-1), prostaglandins, and nitric oxide (NO) during endotoxin-induced cardiomyopathy in rabbits. METHODS AND RESULTS: Immunohistochemical studies showed a marked transient coinduction of the inducible isoforms of NO synthase (NOS-2) and cyclooxygenase (COX-2) in endocardial endothelium and coronary arteriolar endothelium of hearts 12 hours after intravenous administration of lipopolysaccharide (LPS+12h); staining for both isoforms was much weaker 24 hours later (LPS+36h). Nitrotyrosine localization was similar to that of NOS-2, suggesting a NOS-2-related endothelial formation of peroxynitrite in septic hearts. Contractile performance of papillary muscles was depressed in both LPS-treated groups. In the LPS+12h group, however, isometric twitches were significantly prolonged (482+/-14 versus 420+/-14 ms in the saline-treated group, P<0.005). This twitch prolongation was completely reversed by simultaneous administration of BQ-123 and indomethacin to block endogenous ET-1 and prostaglandins, respectively. In addition, in the LPS+12h group, myocardial inotropic responsiveness to exogenous ET-1 was enhanced (P<0.01). CONCLUSIONS: Cardiac endothelial activation and myocardial sensitization to endothelium-derived mediators may be part of an adaptive response in the early (12 hours) stages of septic cardiomyopathy.

Sepsis is associated with reciprocal expressional modifications of constitutive nitric oxide synthase (NOS) in human skeletal muscle: down-regulation of NOS1 and up-regulation of NOS3.

OBJECTIVE: To study the expression (mRNA and protein) and activity of the constitutive isoforms of nitric oxide synthase (NOS1 and NOS3) in a skeletal muscle of septic patients. DESIGN: Prospective study. SETTING: An adult trauma/surgical intensive care unit in an urban teaching hospital. PATIENTS: Sixteen septic patients and 21 controls. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Samples of the rectus abdominis muscle were obtained during surgical procedure. NOS mRNA, protein, and activity were detected by reverse-transcriptase polymerase chain reaction, Western blot, and the conversion of [3H]L-arginine to [3H]L-citrulline, respectively. The main results of this study are as follows: a) Levels of NOS1 mRNA and protein were significantly higher than those of NOS3 in the rectus abdominis muscle of control patients; b) NOS1 expression was down-regulated in septic patients, whereas NOS3 was up-regulated; c) these modulations were associated with a reduction in constitutive NOS activity; and d) modifications of NOS1 and NOS3 protein expression were correlated significantly with the severity of sepsis, assessed by the Simplified Acute Physiology Score II. CONCLUSIONS: Sepsis induces reciprocal expressional modifications of NOS1 and NOS3 in human skeletal muscle, which decreases muscular constitutive NOS activity. These modifications may have implications for muscle impairment in septic patients.

Interleukin-13 induces tissue fibrosis by selectively stimulating and activating transforming growth factor beta(1).

Interleukin (IL)-13 is a key mediator of tissue fibrosis caused by T helper cell type 2 inflammation. We hypothesized that the fibrogenic effects of IL-13 are mediated by transforming growth factor (TGF)-beta. To test this hypothesis we compared the regulation of TGF-beta in lungs from wild-type mice and CC10-IL-13 mice in which IL-13 overexpression causes pulmonary fibrosis. IL-13 selectively stimulated TGF-beta(1) production in transgenic animals and macrophages were the major site of TGF-beta(1) production and deposition in these tissues. IL-13 also activated TGF-beta(1) in vivo. This activation was associated with decreased levels of mRNA encoding latent TGF-beta-binding protein-1 and increased mRNA encoding urinary plasminogen activator, matrix metalloproteinase (MMP)-9, and CD44. TGF-beta(1) activation was abrogated by the plasmin/serine protease antagonist aprotinin. It was also decreased in progeny of crosses of CC10-IL-13 mice and MMP-9 null mice but was not altered in crosses with CD44 null animals. IL-13-induced fibrosis was also significantly ameliorated by treatment with the TGF-beta antagonist soluble TGFbetaR-Fc (sTGFbetaR-Fc). These studies demonstrate that IL-13 is a potent stimulator and activator of TGF-beta(1) in vivo. They also demonstrate that this activation is mediated by a plasmin/serine protease- and MMP-9-dependent and CD44-independent mechanism(s) and that the fibrogenic effects of IL-13 are mediated, in great extent, by this TGF-beta pathway.

Protective role of heme oxygenases against endotoxin-induced diaphragmatic dysfunction in rats.

Reactive oxygen species are strongly implicated in diaphragmatic dysfunction during sepsis. We investigated whether the heme oxygenase (HO) pathway, which is a powerful protective cellular system, protects the diaphragm against oxidative stress and contractile failure during sepsis. A basal expression of both the inducible and constitutive HO protein isoforms (HO-1 and HO-2, respectively) was found in the diaphragm. Enhanced HO-1 expression in diaphragmatic myocytes was observed 24 h after Escherichia coli endotoxin (lipopolysaccharide, LPS) inoculation and remained elevated for at least 96 h. Enhanced HO-1 expression was also observed in the rectus abdominis and soleus muscles and in the left ventricular myocardium of endotoxemic animals. Diaphragmatic HO-2 expression was not modified by endotoxin. Diaphragmatic HO activity exhibited a biphasic time course characterized by a transient decrease during the first 12 h followed by a significant increase at 24 h, corresponding to HO-1 induction. Diaphragmatic force was significantly reduced 24 h after LPS, concomitantly with muscular oxidative stress. Administation of an inhibitor of heme oxygenase activity, zinc protoporphyrin IX (ZnPP-IX), further impaired muscular oxidative stress and contractile failure. By contrast, increased levels of HO-1 expression obtained by pretreatment of rats with hemin, a powerful inducer of HO-1, completely prevented LPS-mediated diaphragmatic oxidative stress and contractile failure. This protective effect was reversed by ZnPP-IX. These results show an important protective role for the HO pathway against sepsis-induced diaphragmatic dysfunction, which could be related to its antioxidant properties.

Peroxynitrite-mediated mitochondrial dysfunction.

Peroxynitrite anion (ONOO(-)) is a potent biological oxidant produced by the near diffusion-limited reaction of superoxide and nitric oxide. Peroxynitrite has been implicated in diverse forms of free radical-induced tissue injury. Experimental evidence showed that exogenous and endogenous peroxynitrite causes alterations of the structure and function of mitochondrial proteins, leading to mitochondrial dysfunction and cellular or organ injury. These data are discussed along with its physiopathological implications.

Cardiac contractile impairment associated with increased phosphorylation of troponin I in endotoxemic rats.

The subcellular mechanisms underlying intrinsic myocardial depression during sepsis remain poorly defined, in particular the relative roles of altered intracellular Ca2+ transients versus changes in myofilament properties. We studied contractile function of cardiac myocytes isolated 12 h after induction of endotoxemia (5 mg/kg intravenous E. coli lipopolysaccharide [LPS]) in conscious rats. Cardiomyocytes from LPS-injected rats had depressed twitch shortening compared with control cells (4.10.2% versus 7.80.3%; P2+ transients (peak indo-1 ratio 1.130.02 versus 1.120.02; P = NS). Contractile depression was unaffected by inhibitors of nitric oxide synthase. Steady-state myofilament response to Ca2+, assessed by tetanization of intact cells over a range of [Ca2+], was reduced significantly in the LPS group (P2+ was unaffected by isoproterenol (3 nmol/L) in endotoxemic cells, whereas there was a rightward shift in control cells. A reduction in myofilament response to Ca2+ is the major determinant of intrinsic cardiac depression in systemic endotoxemia. This condition appears to be related to an increase in myocardial troponin I phosphorylation.

Muscular contractile failure in septic patients: role of the inducible nitric oxide synthase pathway.

Skeletal muscle failure is a frequent manifestation of sepsis that affects prognosis and rehabilitation by impairing respiration and ambulation. Animal studies have shown that the inducible NO synthase (NOS2) is expressed in skeletal muscles during sepsis, likely affecting muscular function, by promoting the formation of the strong oxidant peroxynitrite. In contrast, whether human skeletal muscle expresses a functional NOS2 in similar conditions is unknown. We studied NOS2 expression (mRNA and protein) and activity and its role in contractile function in samples from rectus abdominis muscle obtained during surgical procedure in 16 septic patients and in 21 controls. Peroxynitrite formation was detected by immunohistochemical detection of nitrotyrosine residues. The main results of this study are as follows: (1) A significant increase in NOS2 mRNA, protein, and activity was found in muscles from septic patients, the expression of NOS2 protein positively correlating with sepsis severity. (2) Contractile force was significantly lower in septic than in control muscles. This phenomenon was not reverted by muscle incubation ex vivo with the NOS inhibitor L-NMMA, indicating that NO was not involved in force reduction at the time of biopsy. (3) NOS2 expression in skeletal myocytes was strongly co-localized with nitrotyrosine, revealing muscular peroxynitrite generation during the septic process, before the muscle was biopsied. Exposure of control muscles to an amount of peroxynitrite similar to that generated in septic muscles during the septic process resulted in a nonreversible reduction in force generation. These results suggest that NOS2 could be involved in the decreased muscular force of septic patients via the local generation of peroxynitrite.

Anesthetic concentrations of riluzole inhibit neuronal nitric oxide synthase activity, but not expression, in the rat hippocampus.

We hypothesized that anesthetic dose of riluzole, an inhibitor of glutamate neurotransmission, may affect the activity and/or expression of neuronal NOS (nNOS). Riluzole, N(G)-nitro-L-arginine-methyl ester (L-NAME) and 7-nitro indazole (7-NI) produced a concentration-related inhibition of nNOS activity in vitro. Riluzole competed with 7-NI for inhibition of nNOS activity, but had no effect on nNOS or endothelial NOS (eNOS) protein expression. Also, nNOS activity was significantly decreased in riluzole-anesthetized rats (40 mg kg(-1) i.p., -32+/-6% from controls, P<0.05). Therefore, blockade of nNOS activity may be involved in the anesthetic effects of riluzole in vivo.

[Special characteristics of the diaphragm muscle cell]. / Particularités de la cellule musculaire diaphragmatique.

The diaphragm is the main inspiratory muscle, accounting for more than 50% of the tidal volume during quiet breathing. It works continuously, contracting rhythmically and generally at a low intensity. In this respect, it is close to the myocardium, being the only vital skeletal muscle. From a general point of view, functional and biochemical characteristics of the diaphragm are similar to those of other skeletal muscles with a similar fiber type composition. However, the diaphragm presents some specificities allowing a high supply of metabolic substrates. This could serve to preserve contractile function in different physiological and physiopathological situations. Such specificities concern muscular vascularization, the microvascular network and the content of mitochondria and myoglobin. These characteristics are detailed and compared to those of other striated muscles.

[Role of nitric oxide in diaphragmatic dysfunction genesis during sepsis in rats]. / Rôle du monoxyde d'azote (NO) dans la genèse de la dysfonction diaphragmatique au cours du sepsis chez le rat.

Nitric oxide (NO) is a vasodilator agent that is cytotoxic and negatively inotropic in the heart. More recently, it has been shown that during sepsis there is a high amount of NO production by a NO synthase (NOS) that is inducible by cytokines. The aim of this study was to investigate the role of NO in the genesis of diaphragmatic dysfunction during sepsis. Rats were inoculated i.p. injection with 10 mg/kg of Escherichia coil endotoxin (E animals) or saline (C animals). Six hours after endotoxin or saline inoculation, diaphragmatic force and muscularc GMP (Cyclic guanosine monophosphate) were assessed by in vitro force frequency curves and ELISA method, respectively. As compared to C animals, E animals showed a significant decrease in diaphragmatic force for all the frequencies of stimulation (p < 0.01). This reduction was associated with a significant increase in muscular cGMP. Inhibition of NO synthesis in E animals with either dexamethasone (4 mg/kg IV, 45 min before endotoxin or saline) or NG-monomethyl-L-arginine (L-NMMA, 8 mg/kg IV, 90 min after endotoxin or saline) prevented the effects of endotoxin. However, no modification was seen with NG-monomethyl-D-arginine (D-NMMA), a molecule which does not inhibit NO synthesis. Administration of dexamethasone or L-NMMA in C animals did not induce any significant change in diaphragmatic force, and cGMP ratio. We conclude that NO has a contributive role in diaphragmatic dysfunction during Escherichia coli induced sepsis in rats.

Endogenous peroxynitrite mediates mitochondrial dysfunction in rat diaphragm during endotoxemia.

It has been shown that nitric oxide (NO), synthesized by the inducible NO synthase (iNOS) expressed in the diaphragm during endotoxemia, participates in the development of muscular contractile failure. The aim of the present study was to investigate whether this deleterious action of NO was related to its effects on cellular oxidative pathways. Rats were inoculated with E. coli lipopolysaccharide (LPS) or sterile saline solution (controls) and studied at 3 and 6 h after inoculation. iNOS protein and activity could be detected in the rat diaphragm as early as 3 h after LPS, with a sustained steady-state concentration of 0.5 microM NO in the muscle associated with increased detection of hydrogen peroxide (H(2)O(2)). In vitro, the same NO concentration produced a marked increase in H(2)O(2) production by isolated control diaphragm mitochondria, thus reflecting a higher intramitochondrial concentration of nondiffusible superoxide anion (O(2)(-.)). In a similar way, whole diaphragmatic muscle and diaphragm mitochondria from endotoxemic rats showed a progressive increase in H(2)O(2) production associated with uncoupling and decreased phosphorylating capacity. Simultaneous with the maximal impairment in respiration (6 h after LPS), nitration of mitochondrial proteins (a peroxynitrite footprint) was detected and diaphragmatic force was reduced. Functional mitochondrial abnormalities, nitration of mitochondrial proteins, and the decrease in force were significantly attenuated by administration of the NOS inhibitor L-NMMA. These results show that increased and sustained NO levels lead to a consecutive formation of O(2)(-.) that reacts with NO to form peroxynitrite, which in turn impairs mitochondrial function, which probably contributes to the impairment of muscle contractility. during endotoxemia.

Role of nitric oxide on diaphragmatic contractile failure in Escherichia coli endotoxemic rats.

Contractile dysfunction of the respiratory muscles plays an important role in the genesis of respiratory failure during sepsis. Nitric oxide (NO), a free radical that is cytotoxic and negatively inotropic in the heart and skeletal muscle, is produced in large amounts during sepsis by a NO synthase inducible (iNOS) by LPS and/or cytokines. The aim of this study was to investigate whether iNOS was induced in the diaphragm of Escherichia coli endotoxemic rats and whether inhibition of iNOS induction or of NOS synthesis attenuated diaphragmatic contractile dysfunction. Rats were inoculated intravenously (IV) with 10 mg/kg of E. coli endotoxin (LPS animals) or saline (C animals). Six hours after LPS inoculation animals showed a significant increase in diaphragmatic NOS activity (L-citrulline production, P < 0.005). Inducible NOS protein was detected by Western-Blot in the diaphragms of LPS animals, while it was absent in C animals. LPS animals had a significant decrease in diaphragmatic force (P < 0.0001) measured in vitro. In LPS animals, inhibition of iNOS induction with dexamethasone (4 mg/kg IV 45 min before LPS) or inhibition of NOS activity with N(G)-methyl-L-arginine (8 mg/kg IV 90 min after LPS) prevented LPS-induced diaphragmatic contractile dysfunction. We conclude that increased NOS activity due to iNOS was involved in the genesis of diaphragmatic dysfunction observed in E. coli endotoxemic rats.