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]. / 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.

[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.

Dysregulation of elastin expression by fibroblasts in pulmonary emphysema: role of cellular retinoic acid binding protein 2.

BACKGROUND: All-trans retinoic acid (ATRA) stimulates elastin synthesis by lung fibroblasts and induces alveolar regeneration in animal models of pulmonary emphysema. However, ATRA treatment has had disappointing results in human emphysema. It was hypothesised that a defect in the ATRA signalling pathway contributes to the defect of alveolar repair in the human emphysematous lung. METHODS: Fibroblasts were cultured from the lung of 10 control subjects and eight patients with emphysema. Elastin and retinoic acid receptor (RAR)-beta mRNAs were measured in those cells in the presence of incremental concentrations of ATRA. RARs, retinoic X receptors (RXRs) and cellular retinoic acid binding protein (CRABP) 1 and 2 mRNAs were measured as well as CRABP2 protein content. The effect of CRABP2 silencing on elastin and RAR-beta expression in response to ATRA was measured in MRC5 lung fibroblasts. RESULTS: ATRA at 10(-9) M and 10(-8) M increased median elastin mRNA expression by 182% and 126% in control but not in emphysema fibroblasts. RAR-beta mRNA expression was induced by ATRA in control as well as emphysema fibroblasts. RARs, RXRs and CRABP1 mRNAs were similarly expressed in control and emphysema fibroblasts while CRABP2 mRNA and protein were lower in emphysema fibroblasts. CRABP2 silencing abrogated the induction of elastin but not RAR-beta expression by ATRA in MRC5 fibroblasts. CONCLUSION: Pulmonary emphysema fibroblasts fail to express elastin under ATRA stimulation. CRABP2, which is necessary for elastin induction by ATRA in MRC-5 cells, is expressed at low levels in emphysema fibroblasts. This alteration in the retinoic acid signalling pathway in lung fibroblasts may contribute to the defect of alveolar repair in human pulmonary emphysema. These results are the first demonstration of the involvement of CRABP2 in elastin expression.

Altered Nrf2/Keap1-Bach1 equilibrium in pulmonary emphysema.

BACKGROUND: Oxidative stress, resulting from the increased oxidative burden and decreased level of antioxidant proteins, plays a role in the pathophysiology of smoking-related pulmonary emphysema. Expression of several antioxidant proteins, such as heme oxygenase-1 (HO-1), glutathione peroxidase 2 (GPX2) and NAD(P)H:quinone oxidoreductase 1 (NQO1), results from an equilibrium created by positive or negative regulation by the transcription factors Nrf2, Keap1 and Bach1, respectively. However, whether the expression of these transcription factors is altered in emphysema and could account for decreased expression of antioxidant proteins is not known. A study was undertaken to investigate the expression and subcellular localisation of Nrf2, Keap1 and Bach1 as potential regulators of HO-1, GPX2 and NQO1 in alveolar macrophages, a key cell in oxidative stress, in lung surgical specimens from non-smokers without emphysema and smokers with and without emphysema. METHODS AND RESULTS: Western blot, immunohistochemical and laser scanning confocal analysis revealed that the Nrf2 protein level decreased significantly in whole lung tissue and alveolar macrophages (cytosol and nucleus) in patients with emphysema compared with those without emphysema. Conversely, Bach1 and Keap1 levels were increased in patients with emphysema. These modifications were associated with a parallel decrease in the expression of HO-1, GPX2 and NQO1 at the cellular level, which was inversely correlated with airway obstruction and distension indexes, and increased macrophage expression of the lipid peroxidation product 4-hydroxy-2-nonenal. Silencing RNA experiments in vitro in THP-1 cells were performed to confirm the cause-effect relation between the loss of Nrf2 and the decrease in HO-1, NQO1 and GPX2 expression. Nrf2/Keap1-Bach1 equilibrium was altered in alveolar macrophages in pulmonary emphysema, which points to a decreased stress response phenotype. CONCLUSIONS: This finding opens a new view of the pathophysiology of emphysema and could provide the basis for new therapeutic approaches based on preservation and/or restoration of such equilibrium.

Induction of apoptosis and absence of inflammation in rat lung after intratracheal instillation of multiwalled carbon nanotubes.

Several studies performed by intratracheal instillation showed that carbon nanotubes (CNT) induced pulmonary fibrosis, granulomas or inflammation. But, recently, two inhalation studies did not observed such pathological phenomena and suggest that granulomas could be due to the instillation of unbreathable agglomerates. In a previous study, we have described a simple method (using albumin as dispersing agent) which produced solutions containing more than 80% of agglomerate of breathable size. We report here results from intratracheal instillation of rats by 0, 1, 10 or 100 microg of MWCNT dispersed with albumin. After 1, 7, 30, 90, and 180 days, inflammation, apoptosis, fibrosis, respiratory parameters and granuloma formation were assessed. Results obtained by plethysmography, soluble collagen quantification, qRT-PCR and luminex measurement of cytokines expression and histopathological observation showed only evidence of apoptosis of alveolar macrophages. These result underline the importance of controlling MWCNT agglomerate size when exposing animals, through appropriate dispersion methods.

[Characteristics of the patients included in the French cohort of patients with emphysema caused by alpha-1 antitrypsin deficiency]. / Caractéristiques des patients inclus dans la cohorte française de patients emphysémateux déficitaires en alpha-1 antitrypsine.

INTRODUCTION: Alpha-1 antitrypsin deficiency is associated with the occurrence of pulmonary emphysema. The aim of this study is to describe the characteristics of patients with alpha-1 antitrypsin deficiency associated pulmonary emphysema. METHODS: We describe a prospective cohort study including adult patients with alpha-1 antitrypsin deficiency associated pulmonary emphysema confirmed by CT scan living in France. Patients' clinical and functional characteristics, quality of life measures and management were recorded every 6 months during a five-year period. RESULTS: 201 patients were included from 56 centres between 2005 and 2008. The characteristics of 110 patients have been analysed. Mean age was 50 years (SD:11.8), 62.7% were males, 90% were tobacco smokers. The main functional results (% predicted) were: FEV1: 42.8 (19.6), CPT: 128.3 (21.7), CRF: 167.0 (46.0), 6 minute walking distance (meters): 413 (130). 51 (46.4%) patients received augmentation therapy. Augmentation therapy was administered weekly (37.5%), twice a month (35.4%) or monthly (25.5%). Study centre was the only factor associated with the likelihood to received augmentation therapy. CONCLUSIONS: The clinical and functional characteristics as well as management of these patients varied markedly. There is a need for a standardization of the management of patients with alpha-1 antitrypsin deficiency associated pulmonary emphysema.

[Contribution of ATP-dependent potassium channels, nitric oxide and prostaglandins in increase of diaphgram arteriolar blood fow during diaphgram contraction]. / Contribution des canaux potassiques ATP-dépendant, du monoxyde d'azote et des prostaglandines dans l'augmentation du débit artériolaire lors de la contraction du diaphragme.

ATP-sensitive potassium (K(ATP)) channels and nitric oxide (NO) have been suggested to contribute in mediating active hyperemia in diaphragm. However, no data is available in the current literature concerning their comparative contributions to arteriolar dilation during muscle contraction. The aim of this study was therefore to examine, by video microscopy in rats, the effects of superfusing the muscle with Krebs solution alone (group C), or Krebs solution containing either glybenclamide (3mdeltaM, a blocker of K(ATP), group GLY), or Nwdelta-nitro-L-arginine (300 mdeltaM, a NO synthase inhibitor, group NNA), or mefenamic acid (50 mdeltaM, a prostaglandin synthesis inhibitor, group MA) on second and third order of diaphragm (A2 and A3 respectively) arteriolar dilation elicited by 3 min muscle stimulation (40 Hz, train duration: 300 milliseconds, 90 cycles per min). In group C, A2 diameters increased by 67.5 +/- 1.9% referring to baseline at the end of the stimulation. This increase was significantly reduced in groups GLY and NNA (16.7 +/- 2.5% and 47.3 +/- 2.2% respectively, p < 0.001 as compared to group C) and was more important in group GLY than in group NNA (p < 0.001). By contrast, no difference in post-contraction diameter was observed between groups C and MA. Similar results were observed in A3 vessels. These results indicate that K(ATP) are more important mediators of functional diaphragm arteriolar dilation in rat than NO, whereas prostaglandins are not involved in this phenomenon.

Induction of diaphragmatic nitric oxide synthase after endotoxin administration in rats: role on diaphragmatic contractile dysfunction.

Nitric oxide (NO), a free radical that is negatively inotropic in the heart and skeletal muscle, is produced in large amounts during sepsis by an NO synthase inducible (iNOS) by LPS and/or cytokines. The aim of this study was to examine iNOS induction in the rat diaphragm after Escherichia Coli LPS inoculation (1.6 mg/kg i.p.), and its involvement in diaphragmatic contractile dysfunction. Inducible NOS protein and activity could be detected in the diaphragm as early as 6 h after LPS inoculation. 6 and 12 h after LPS, iNOS was expressed in inflammatory cells infiltrating the perivascular spaces of the diaphragm, whereas 12 and 24 h after LPS it was expressed in skeletal muscle fibers. Inducible NOS was also expressed in the left ventricular myocardium, whereas no expression was observed in the abdominal, intercostal, and peripheral skeletal muscles. Diaphragmatic force was significantly decreased 12 and 24 h after LPS. This decrease was prevented by inhibition of iNOS induction by dexamethasone or by inhibition of iNOS activity by N(G)-methyl-L-arginine. We conclude that iNOS was induced in the diaphragm after E. Coli LPS inoculation in rats, being involved in the decreased muscular force.

Association of lung function decline with the heme oxygenase-1 gene promoter microsatellite polymorphism in a general population sample. Results from the European Community Respiratory Health Survey (ECRHS), France.

Inducible heme oxygenase (HO-1) acts against oxidants that are thought to play a major role in the pathogenesis of chronic obstructive pulmonary disease (COPD), characterised by impaired lung function. A (GT)(n) repeat polymorphism in the HO-1 gene promoter can modulate the gene transcription in response to oxidative stress. We hypothesised that this polymorphism could be associated with the level of lung function and decline in subjects exposed to oxidative aggression (smokers). We genotyped 749 French subjects (20-44 years, 50% men, 40% never smokers) examined in both 1992 and 2000 as part of the ECRHS. Lung function was assessed by forced expiratory volume in 1 second (FEV1) and FEV1/forced ventilatory capacity (FVC) ratio. We compared long (L) allele carriers ((GT)(n) > or =33 repeats for one or two alleles) to non-carriers. Cross sectionally, in 2000, L allele carriers showed lower FEV1/FVC than non-carriers. During the 8 year period, the mean annual FEV1 and FEV1/FVC declines were -30.9 (31.1) ml/year and -1.8 (6.1) U/year, respectively. FEV1/FVC decline was steeper in L allele carriers than in non-carriers (-2.6 (5.5) v -1.5 (6.4), p = 0.07). There was a strong interaction between the L allele and smoking. In 2000, the L allele was associated with lower FEV(1) and FEV(1)/FVC in heavy smokers (> or =20 cigarettes/day) only (p for interaction = 0.07 and 0.002 respectively). Baseline heavy smokers carrying the L allele showed the steepest FEV1 decline (-62.0 (29.5 ml/year) and the steepest FEV1/FVC decline (-8.8 (5.4 U/year) (p for interaction = 0.009 and 0.0006). These results suggest that a long (L) HO-1 gene promoter in heavy smokers is associated with susceptibility to develop airway obstruction.

[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.

Theophylline dilates rat diaphragm arterioles via the prostaglandins pathway.

1. We investigated by intravital microscopy in rats, the in vivo direct effects of theophylline on the diameters of second and third order diaphragm arterioles. 2. Theophylline (1-100 microM) dilated second and third order diaphragm arterioles significantly, and with an amplitude which was not statistically different from the one obtained with adenosine (1-100 microM). Enprofylline (1-100 microM), a theophylline analogue with poor adenosine-receptor antagonism but with similar or higher phosphodiesterases inhibition properties than theophylline, also dilated diaphragm arterioles, causing however, a significantly smaller dilatation than theophylline. 3. Neither the A1 adenosine receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (CPX, 50 nM), nor the A2 adenosine receptor antagonist 3,7-dimethyl-1-proparglyxanthine (DMPX, 10 microM) reduced significantly theophylline-induced arteriolar dilatation. 4. Theophylline (100 nM) abolished adenosine-induced arteriolar dilatation. 5. The dilatation induced by theophylline was unchanged by the nitric oxide (NO) synthase inhibitor N(omega)-nitro-L-arginine (NNA, 300 microM). 6. Theophylline-induced arteriolar dilatation was abolished by the prostaglandin synthesis inhibitors mefenamic acid or indomethacin (20 microM). 7. These findings show that theophylline induced a significant dilatation of diaphragm arterioles via the release of prostaglandins.

Predominant role of A1 adenosine receptors in mediating adenosine induced vasodilatation of rat diaphragmatic arterioles: involvement of nitric oxide and the ATP-dependent K+ channels.

1. We investigated, by intravital microscopy in rats, the role of the subtypes of adenosine receptors A1 (A1/AR) and A2 (A2AR) in mediating adenosine-induced vasodilatation of second and third order arterioles of the diaphragm. 2. Adenosine, and the A1AR selective agonists R(-)-N6-(2-phenylisopropyl)-adenosine (R-PIA) and N6-cyclo-pentyl-adenosine (CPA) induced a similar concentration-dependent dilatation of diaphragmatic arterioles. The non selective A2AR subtype agonist N6-[2-(3,5-dimethoxyphenyl)-2-(2-methylphenyl) ethyl]adenosine (DPMA) also dilated diaphragmatic arterioles but induced a significantly smaller dilatation than adenosine. By contrast the selective A(2a)AR subtype agonist 2-[p-(2-carboxyethyl)phenyl amino]-5'-N-ethyl carboxamido adenosine (CGS 21680) did not modify diaphragmatic arteriolar diameter. 3. The non selective adenosine receptor antagonist 1,3-dipropyl-8-p-sulphophenylxanthine (SPX, 100 microM) and the selective A1AR antagonist 8-cyclopentyl-1,3-dipropylxanthine (CPX, 50 nM) significantly attenuated adenosine-induced dilatation of diaphragmatic arterioles. By contrast, adenosine significantly dilated diaphragmatic arterioles in the presence of A2AR antagonist 3,7-dimethyl-1-propargylxanthine (DMPX, 10 microM). 4. The dilatation induced by adenosine was unchanged by the mast cell stabilizing agent sodium cromoglycate (cromolyn, 10 microM). 5. The nitric oxide (NO) synthase inhibitor N omega-nitro-L-arginine (L-NOARG, 300 microM) attenuated the dilatation induced by adenosine, and by the A1AR and A2AR agonists. 6. The ATP-dependent K+ channel blocker glibenclamide (3 microM) significantly attenuated diaphragmatic arteriolar dilatation induced by adenosine and by the A1AR agonists R-PIA and CPA. By contrast, glibenclamide did not significantly modify arteriolar dilatation induced by the A2AR agonist DPMA. 7. These findings suggest that adenosine-induced dilatation of diaphragmatic arterioles in the rat is predominantly mediated by the A1AR, via the release of NO and activation of the ATP-dependent K+ channels.

Early release of proinflammatory cytokines after lung transplantation.

BACKGROUND: Systemic hypotension may complicate the early postoperative period after lung transplantation. A release of proinflammatory cytokines secondary to lung ischemia/reperfusion injury could be involved in the pathogenesis of this early hemodynamic failure (EHF). STUDY OBJECTIVE: To assess prospectively whether the occurrence of EHF is associated with a release of cytokines in the systemic circulation. DESIGN: Blood samples were taken daily during the first postoperative week in 26 patients who underwent a double or a single-lung transplantation. These patients were divided into three groups: 7 patients who experienced EHF and subsequently died (EHF group); 15 patients without EHF (control group); and 4 patients without EHF but with an identified sepsis (sepsis group). The serum levels of interleukin (IL)-1beta, tumor necrosis factor-alpha (TNF-alpha), IL-6, and IL-8 were compared among the three groups. RESULTS: In the EHF group, the levels of each cytokine peaked at day 1 postoperatively. Cytokine levels at day 1 were significantly higher in the EHF group than in the control group (p<0.0006) or in the sepsis group (p<0.003 except for TNF-alpha). CONCLUSION: We conclude that EHF is associated with a massive release of proinflammatory cytokines that could play a determinant role in the pathogenesis of this complication.

Flow limitation and dynamic hyperinflation during exercise in COPD patients after single lung transplantation.

STUDY OBJECTIVE: Using the negative expiratory pressure (NEP) method, we have previously shown that patients receiving single lung transplantation (SLT) for COPD do not exhibit expiratory flow limitation and have little dyspnea at rest. In the present study, we assessed whether SLT patients exhibit flow limitation, overall hyperinflation, and dyspnea during exercise. METHODS: Expiratory flow limitation assessed by the NEP method and inspiratory capacity maneuvers used to determine end-expiratory lung volume (EELV) and end-inspiratory lung volume (EILV) were performed at rest and during symptom-limited incremental cycle exercise in eight SLT patients. RESULTS: At the time of the study, the mean (+/- SD) FEV(1), FVC, functional residual capacity, and total lung capacity (TLC) amounted to 55 +/- 14%, 67 +/- 12%, 137 +/- 16%, and 110 +/- 11% of predicted, respectively. At rest, all patients did not experience expiratory flow limitation and were without dyspnea. At peak exercise, the maximal mechanical power output and maximal oxygen consumption amounted to 72 +/- 20% and 65 +/- 8% of predicted, respectively, with a maximal dyspnea Borg score of 6 +/- 3. All but one patient exhibited flow limitation and dynamic hyperinflation; the EELV and EILV amounted to 74 +/- 5% and 95 +/- 9% TLC, respectively. The patient who did not exhibit flow limitation during exercise had the lowest dyspnea score. CONCLUSION: Most SLT patients for COPD exhibit expiratory flow limitation and dynamic hyperinflation during exercise, whereas maximal dyspnea is variable.

In vivo effects of Escherichia coli endotoxemia on diaphragmatic microcirculation in rats.

We investigated the effects of Escherichia coli endotoxin administration on diaphragmatic microcirculation in rats by in vivo videomicroscopy. Rats were allocated into three groups: 1) intravenous inoculation of 10 mg/kg of E. col endotoxin (group E, n = 25), 2) intravenous inoculation of sterile 0.9% NaCl (group C, n = 20), and 3) induction of a controlled hemorrhage by reducing the vascular volume via an arterial catheter (group H, n = 15). Mean blood pressure (BP) and arteriolar diameters were measured at 15-min intervals and capillary perfusion pattern at 30-min intervals for 1 h. BP decreased similarly in groups E and H, whereas it was maintained in group C. Arterioles were classified as second (A2, n = 46), third (A3, n = 22), and fourth (A4, n = 21) order, according to their relative localization in the network. Basal diameters were the same in the three groups: 38.16, 17.33, and 6.80 microns in group C; 38.17, 17.41, and 7.04 microns in group E; and 37.82, 19.19, and 6.99 microns in group H for A2, A3, and A4, respectively. During the observation period, a significant and similar vasoconstriction of A2 arterioles was observed in groups E and H but not in group C. By contrast, in the three groups, no significant changes in diameter were found for the A3 and A4 arterioles. Capillary perfusion was markedly impaired in group E: at 60 min the percentage of non-perfused capillaries was 40.92 +/- 6.65% in group E compared with 21.17 +/- 5.45% in group C (P less than 0.05) and 18.18 +/- 8.11% in group H (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Role of nitric oxide and prostaglandins in the regulation of diaphragmatic arteriolar tone in the rat.

We evaluated by intravital microscopy in rats the relative importance of nitric oxide (NO) and prostaglandins in 1) the maintenance of basal diaphragmatic arteriolar tone and 2) the response of diaphragmatic arterioles to the endothelium-dependent vasodilator acetylcholine (ACh). One hundred two mechanically ventilated rats were studied. Separate applications of N omega-nitro-L-arginine (L-NNA) and mefenamic acid (MA), which are specific inhibitors of NO and prostaglandin synthesis, respectively, elicited a significant reduction in basal diaphragmatic arteriolar diameter. A dramatic potentiation of the effect of each inhibitor was observed when both agents were applied simultaneously. ACh application induced a significant and dose-dependent increase in arteriolar diameter that was not significantly modified by the separate application of L-NNA or MA. Conversely, the simultaneous administration of L-NNA and MA almost completely prevented ACh-induced arteriolar dilatation. Dilatation in response to sodium nitroprusside was not significantly modified in the presence of both inhibitors. These results suggest that NO and prostaglandins act in concert to regulate basal diaphragmatic arteriolar tone and to mediate diaphragmatic arteriolar response to ACh.

Effects of endotoxic shock on diaphragmatic function in mechanically ventilated rats.

Diaphragmatic function was investigated in mechanically ventilated rats during endotoxic shock (group E, n = 18) and after saline solution injection (group C, n = 8). Endotoxic shock was produced by a 1-min injection of Escherichia coli endotoxin (10 mg/kg iv) suspended in saline. Diaphragmatic strength was assessed before (T0) and 15 (T15) and 60 (T60) min after injection by measuring transdiaphragmatic pressure (Pdi) generated during bilateral phrenic stimulation at 0.5, 10, 20, 30, 50, and 100 Hz. Diaphragmatic neuromuscular transmission was assessed by measuring the integrated electrical activity of the diaphragm. Diaphragmatic endurance was assessed 75 min after injection from the rate of Pdi decline after a 30-s continuous 10-Hz phrenic stimulation. In 16 additional animals, diaphragmatic glycogen content was determined 60 min after inoculation with endotoxin (n = 8) or 0.9% sodium chloride solution (n = 8). Diaphragmatic resting membrane potential (Em) was measured in 16 additional animals 60 min after endotoxin (n = 8) or saline injection (n = 8). Mean blood pressure decreased from 74 +/- 3 to 53 +/- 6 mmHg at T60 in group E, whereas it was maintained in group C. At T60 Pdi was decreased in group E for frequencies of 50 and 100 Hz and was associated with a decreased diaphragmatic electromyographic activity of 25.3 +/- 2.5 and 26.5 +/- 5.2% for 50- and 100-Hz stimulations, respectively, in comparison with T0 values.(ABSTRACT TRUNCATED AT 250 WORDS)