Oxygen free radicals and lungs

Some of the metabolites resulting from the monovalent reduction of O2, superoxide anion and hydroxyl radical, are O2, radicals, whereas H2O2, which is not a radical since having no unpaired electron, is also an active O2 intermediate. These O2 metabolites are formed intracellularly as a result of normal metabolism. Their production can increase following exposure to high O2 concentration, radiations or certain drugs. An increased amount of extracellular O2 metabolites occurs after activation of certain inflammatory cells or during the course of the hypoxanthine-xanthine oxidase reaction. To counteract this oxidative stress, antioxidant defenses exist, whether enzymatic (superoxide dismutase, glutathione peroxidase, catalase, etc.) or nonenzymatic (GSH, vitamin E and C, etc.). Oxidative injury can result from an imbalance between oxidative stress and the defense mechanisms. The main targets are protein, DNA and lipids. The cellular response of the lung is stereotyped and involves cell injury (especially endothelial cells and type I pneumocytes), inflammatory reaction and repair processes.

Hypoxanthine-xanthine oxidase-related defect in polypeptide chain initiation by endothelium

After exposure to O2 intermediates generated by the hypoxanthine-xanthine oxidase system (HX-XO), the rate of [3H]phenylalanine incorporation into total proteins in cultured endothelial cells was markedly reduced. This reduction, which was prevented by catalase, could not be explained by 1) changes in amino acid pools, 2) increased rate of degradation of newly synthesized proteins, 3) impaired poly(A)+ RNA synthesis and efficiency, 4) decreased rate of amino acylation. On the other hand, the increase in the monoribosome-to-polyribosome ratio suggested that translation was affected at the level of chain initiation. Further analysis indicated that 40S initiation complex formation was normal, whereas the assembly of 80S initiation complex was inhibited. Results from reconstitution experiments showed that both normal and treated ribosomes could support normal protein synthesis in the presence of normal initiation factors (IFs). In contrast, IFs from HX-XO lysates did not support normal protein synthesis with ribosomes from either source. Thus, the effect of XO treatment on protein synthesis appears to be an initiation defect related to decreased IF activity and/or availability.

Effects of oleic acid-, alpha-naphthylthiourea-, and phorbol myristate acetate-induced microvascular damage on indexes of pulmonary endothelial function in anesthetized dogs

To study the value of indexes of endothelial cell function in experimentally induced pulmonary microvascular injury, lung damage was produced in anesthetized dogs by intravenous injection of oleic acid (OA; n = 6), alpha-naphthylthiourea (ANTU; n = 5), or phorbol myristate acetate (PMA; n = 6). Angiotensin-converting enzyme (ACE) activity in serum and simultaneous measurements of serotonin (SER) and propranolol (PROP) pulmonary extraction along with several physiologic parameters were determined and compared with those obtained in a control group (n = 5) before and then at 2-h intervals for 8 h after administration of the toxic agent. ACE activity in serum showed a sustained and significant increase in the PMA and OA groups throughout the whole study period, whereas it decreased significantly at 4 h in the ANTU group. SER pulmonary uptake decreased significantly, but slightly, only in the PMA group at 8 h (-5%). At 6 and 8 h respectively, PROP extraction dropped significantly in the PMA (-11 and -13%) and OA (-13 and -19%) groups. This decrease in PROP extraction was likely to result from physiologic changes due to the development of pulmonary edema as suggested by the correlation between the changes in amine uptake and those affecting pulmonary artery pressure and total static respiratory compliance. The lack of effects on SER uptake by the lungs under these experimental conditions indicate that dissociation exists between metabolic dysfunction of pulmonary endothelial cells and fluid leakage.

[Characteristics of respiratory functional involvement in MacLeod's syndrome (or Swyer-James syndrome)]

MacLeod's syndrome (Swyer-James' syndrome in the child) is a radiologic entity: hyperlucency of one or several lobes, or even of one lung, scarce hilar shadow on the same side as the abnormal transradiency, and barely visible arterial network on the abnormal side of the thorax. Distal bronchiectases (bronchography) and abnormal distal bronchi (necropsy) suggest that this disease may be due to bronchiolitis in childhood. An obstructive pulmonary disorder, assessed by pulmonary function tests, has been described in this syndrome. However, neither the prevalence nor the severity or evolution of the obstructive defect are known. We have studied two such patients for 5 and 12 years respectively: during this long follow-up period the obstructive disorder, albeit severe, remained stable. We have also analysed the 75 cases in the literature in which pulmonary function tests are available and comparable. We have been able to show that (1) an obstructive disorder is frequent in MacLeod's syndrome, (2) the severity of this disorder differs markedly between patients, and (3) this airflow limitation is probably stable on a long-term basis. These findings are compatible with the pathogenetic hypothesis at present accepted, ie bronchiolitis during childhood, and suggest that the inflammatory bronchial disease may have been generalized in many such patients.

Comparative study on the selenium- and N-acetylcysteine-related effects on the toxic action of hyperoxia, paraquat and the enzyme reaction hypoxanthine-xanthine oxidase in cultured endothelial cells

The potential protective effect of N-acetylcysteine against various types of oxidative stress (exposure to hyperoxia, treatment with paraquat, incubation in the presence of the hypoxanthine-xanthine oxidase system) was tested in primary cultures of porcine aortic endothelial cells. It was compared to that of selenomethionine (Se-Met), known to increase glutathione peroxidase activity, when given either alone or in combination with N-acetylcysteine. LDH release, 3H-thymidine (TdR) incorporation into DNA and DNA content were measured to assess the cytotoxic effect of the conditions tested. Total and oxidized glutathione content was also determined. Whereas Se-Met had a partial protective effect on all the conditions but paraquat treatment, N-acetylcysteine administration had no effect on the hyperoxia induced changes and significantly worsened the cytotoxic action of paraquat. On the other hand, LDH release following an incubation in the presence of the hypoxanthine-xanthine oxidase was significantly reduced after N-acetylcysteine treatment. No major change in total nor in oxidized glutathione followed N-acetylcysteine treatment in control and experimental conditions. A dose-dependent protective effect of N-acetylcysteine was obtained when this agent was given concomitantly with the xanthine oxidase system. These data suggest that in cultured endothelial cells a N-acetylcysteine-related protective effect, if present, is most likely to result from the direct scavenging action of N-acetylcysteine.

[Case finding in bronchial carcinoma: cost-effectiveness]

The data in the study sponsored by the National Cancer Institute make it possible to calculate the cost of early detection of bronchial carcinoma by radiologic and/or cytologic examination. For the initial series of tests (prevalence study), the cost of one case of screening-related survival amounts to: 417 chest roentgenograms + 417 sputum cytological examinations + 33 investigations to clarify abnormal chest roentgenograms. If cytological investigation alone is performed 2500 examinations are needed for one case of screening-related survival. If these examinations are repeated on a yearly basis, the benefit related to this screening effort is less than 1 case of survival/1000 subjects/year.

Protein synthesis in hyperoxic endothelial cells: evidence for translational defect

To study the effects of hyperoxia on protein synthesis in primary cultures of porcine aortic endothelial cells, we exposed confluent cells to different O2 concentrations for various durations. Exposure to 95% O2 for 5 days resulted in a 71% inhibition of [3H]phenylalanine incorporation into total proteins. When compared with control cells, we observed no changes in 1) the pool size of free cytoplasmic phenylalanine and of phenylalanine attached to transfer RNA (tRNA), 2) the rate of protein degradation, and 3) the rate of charging of tRNA with phenylalanine. We found that under hyperoxic conditions 1) the incorporation of [3H]-uridine into total and polyadenylated RNA was increased, 2) the efficiency of extracted messenger RNA to direct protein synthesis in a reticulocyte lysate was maintained, 3) the proportion of polymeric to monomeric ribosomes was slightly increased, and 4) the rate of elongation, as measured by the ribosomal transit time, was decreased. Thus the reduction in protein synthesis in hyperoxic cells appears to result primarily from defects at the translational level in polypeptide chain elongation.

Effects of oxygen intermediates on cellular functions

This brief illustration of the effects of O2 metabolites and of hyperoxia on some of the main functions of the cells, DNA and protein synthesis, indicates that major changes can occur in cells exposed to oxidative stresses such as those occurring in an inflammatory reaction. The relative sensitivity of the various cell populations may favor the emergence of some cells and the disappearance of others. Depending on the sensitivity of different enzymes to oxidative injury, the response of cells in terms of both mediator production and of response to the action of the mediators themselves may be affected.

Effect of aminophylline and relief from hypoxia on central sleep apnoea due to medullary damage

A 17-year old boy presented with severe, predominantly central sleep apnoeas secondary to structural damage in the medulla. At low O2 saturation, the electroencephalogram showed the sudden onset of slow waves. Hypercapnic ventilatory response was low and hypoxic ventilatory response was absent. Low flow oxygen therapy dramatically improved the apnoea score, probably by relieving hypoxic brain depression. Slow waves also disappeared with oxygen therapy. Aminophylline was effective on apnoea score and duration (p less than 0.001). This beneficial effect could be explained by an improvement of the normal oscillations of respiration at the onset of sleep, a change in arousability or a stimulation of the ascending reticular system. These findings suggest a possible role of hypoxic depression in the manifestations of central sleep apnoeas and demonstrate the beneficial effect of low flow oxygen and aminophylline in treating certain central sleep apnoeas.

Thymidine kinase, thymidylate synthase, and endothelial cell growth under hyperoxia

To determine the respective role of thymidine kinase and thymidylate synthase activities in the hyperoxia-induced decrease in DNA synthesis and their relationship with cell replication, we measured these two enzyme activities in primary cultures of porcine aortic endothelial cells under different O2 concentrations for various durations. In confluent cells, exposure to 95% O2 for 5 days reduced thymidine kinase activity to 15% of control values; thymidylate synthase activity was unaffected. In preconfluent cells exposed to 95% O2 for 2 days, similar results were obtained, together with evidence for arrest in cell proliferation. Thymidylate synthase activity could therefore not be related to decreased cell proliferation under hyperoxia. [3H]thymidine incorporation into DNA, thymidine kinase activity, and cell proliferation were all similarly affected under exposure to graded O2 concentration for 2 days. Thymidine kinase appears to be a key enzyme in the modulation of DNA synthesis from thymidine and in its replication in endothelial cells.

[Aspergillosis with obstruction of the central airways]

Two cases are reported of obstruction of central airways by plugs containing Aspergillus fumigatus. In one case the obstruction was located in the right stem bronchus and, despite treatment with amphotericin B, the immunocompromised patient died from invasive disseminated aspergillosis. In the other case the obstruction was in the trachea and, since the immune function of the patient was normal, she responded favorably to treatment by amphotericin B.

[The role of broncho-alveolar lavage in clinical pneumology and research]

Bronchoalveolar lavage is a recently developed technique which serves to sample the cells free in the alveolar spaces. It has thus been found that many pulmonary interstitial disorders are characterized by increased cellularity involving lymphocytes and/or polymorphonuclears, neutrophils or eosinophils. Bronchoalveolar lavage is rarely of diagnostic use but may provide interesting information on the inflammatory activity of many pulmonary diseases. Bronchoalveolar lavage appears to be a promising tool for study of the pathogenesis of these diseases.

Exercise induced asthma and endogenous opioids

Concentrations of endogenous opioid peptides in the plasma are increased during exercise and these substances have been implicated in the pathogenesis of asthma induced by chloropropramide and alcohol in diabetic patients. This work was undertaken to determine whether exercise induced asthma might be mediated by endogenous opioids. Plasma beta endorphin, met-enkephalin, and adrenocorticotrophic hormone (ACTH) concentrations were measured in five asthmatic patients and five normal volunteers breathing cold air during exercise. In four of the patients the effect of an infusion of naloxone on FEV1 was also measured during exercise induced asthma. Exercise produced acute bronchoconstriction in all asthmatics, characterised by a fall in FEV1; whereas no change occurred in normal subjects. There was no difference in plasma met-enkephalin, beta endorphin, and ACTH concentration between the two groups. Infusion of naloxone neither prevented nor worsened exercise induced asthma. These data suggest that endogenous opioids probably do not play a part in the development of exercise induced asthma.

Data on oxidants and antioxidants

The monovalent reduction of O2 gives rise to highly reactive O2 intermediates, such as superoxide radical (O2-.), hydrogen peroxide (H2O2), and hydroxyl radical (OH.), as well as to singlet O2 (1O2). These O2 metabolites are capable of acting on several groups of substances: enzymes to inactivate them, polyunsaturated fatty acids to form lipid peroxides and DNA to cause single strand breaks and mutations. There are, however, several lines of antioxidant defences, which can be enzymatic (superoxide dismutase, catalase, glutathione peroxidase) or non-enzymatic (glutathione, vitamins C and E, beta-carotene, etc.). These defences are necessary to protect the cell against the intracellular or extracellular generation of O2 metabolites. Since O2 intermediates can affect the general cellular metabolism and inhibit cell replication or reduce protein synthesis, all the biological effects of O2 and its metabolites should therefore be considered in the pathogenesis of emphysematous lesions in the lung.

Comparative effects of acute O2 breathing and terbutaline in patients with chronic obstructive pulmonary disease. A combined hemodynamic and radionuclide study

The acute effects of terbutaline (T) and breathing 100% O2 (O2) on gas exchange, pulmonary hemodynamics and radionuclide angiography were evaluated in 15 patients with severe chronic obstructive pulmonary disease (COPD). O2 breathing resulted in a decrease in mean pulmonary artery pressure (PAP) and cardiac index (CI) without changing pulmonary vascular resistance index (PVRI) or right and left ventricular ejection fractions (RVEF, LVEF). On the other hand, T administration was followed by a decrease in PVRI, an increase in CI, RVEF and LVEF. These effects of T were maintained during exercise. Although RVEF was inversely correlated with basal levels of PAP or PVRI, acute changes in pulmonary hemodynamics were not correlated with significant changes in RVEF. These results suggest that T may be useful in the treatment of patients with COPD prone to develop cor pulmonale. However, the long-term benefit of this treatment remains to be established.

Differential effects of hyperoxia and hydrogen peroxide on thymidine kinase and adenosine kinase activities of cultured endothelial cells

To compare the respective sensitivity of two nucleoside kinases, adenosine kinase and thymidine kinase, to oxidative stress, we measured these enzyme activities in cultured aortic endothelial cells exposed for 48 h to various O2 concentrations, and in cell extracts treated with H2O2 or the enzyme system hypoxanthine-xanthine oxidase. Adenosine kinase activity was not significantly influenced by the exposure to hyperoxia, nor by treatment with the enzyme system hypoxanthine-xanthine oxidase or with H2O2. On the other hand, there was a dose-dependent inhibitory effect on thymidine kinase activity resulting from exposure to various O2 concentrations or from treatment with various amounts of xanthine oxidase. Incubation of cell extracts in the presence of H2O2 also resulted in a significant reduction of thymidine kinase activity. These results indicate that thymidine kinase exhibits a selective sensitivity to the toxic effect of O2 concentrations and of O2 intermediates such as H2O2.

Effects of hyperoxia on DNA synthesis in cultured porcine aortic endothelial cells

The mode of action of hyperoxia on the inhibition of DNA synthesis from thymidine (dThd) was studied in primary cultures of porcine aortic endothelial cells (EC) at confluence. A significant effect of hyperoxia on dThd uptake was detected only after a 48-h exposure to 95% O2. On the other hand, decrease in dThd kinase activity was already observed after a 12-h exposure, and the time course of its reduction followed closely that of the inhibition of dThd incorporation into DNA. The incorporation of dThd triphosphate into DNA in permeabilized EC was unaffected by hyperoxia. Determination of DNA alpha- and beta-polymerase activities showed that hyperoxia reduced the activity of the alpha-polymerase and increased that of the beta-polymerase. We conclude that most of the O2 effects on DNA synthesis from dThd can be attributed to dThd kinase inhibition. The increased activity of DNA beta-polymerase, an enzyme involved in DNA repair, also supports the view that hyperoxia could damage DNA.

Effect of variable glutathione peroxidase activity on H2O2-related cytotoxicity in cultured aortic endothelial cells

Primary cultures of porcine aortic endothelial cells were used to assess the effects of O2 intermediates produced by 10-40 mU/ml xanthine oxidase (XO; +2 mM hypoxanthine) or 25-100 mU/ml glucose oxidase (GO; +5 mM glucose). A 60-min incubation in the presence of the enzyme systems resulted in a dose-dependent toxic effect with evidence of cytolysis (increased LDH release) and cell loss (decrease in DNA and protein content), when these indexes were measured 24 hr after completion of the enzyme reaction. Decreased [3H]thymidine incorporation into DNA was the most sensitive index of cell dysfunction for both enzyme systems. The effects of various scavengers and enzymes indicated that H2O2 was the main O2 intermediate involved in the cytotoxicity resulting from the XO-hypoxanthine reaction. Increased glutathione peroxidase activity associated with the addition of 2 X 10(-7) M selenomethionine to culture medium had a partial protective effect which could be related to an increased rate of H2O2 degradation. Evidence for increased DNA synthesis after injury was found in cells previously exposed to XO-hypoxanthine, the degree of increase in [3H]thymidine incorporation being dependent on the intensity of the initial cytotoxicity. Cultured endothelial cells provide a useful tool to evaluate the role of O2 intermediates in endothelial cell injury, to test the effects of protective agents, and to study the repair process.

[Interauricular right-left shunt: a serious complication of primary pulmonary arterial hypertension]

Primary pulmonary hypertension is a rare and generally progressive disease in which mild hypoxemia at rest, with lower PaO2 during exercise, is consistently reported. Severe hypoxemia at rest suggests the occurrence of a right to left intracardiac shunt, most often due to patency of a foramen ovale. Two cases are reported of primary pulmonary hypertension which rapidly developed severe hypoxemia at rest with worsening of pulmonary hypertension, from which interatrial communication was identified. The prognostic and therapeutic implications of this situation are discussed.

Effects of atelectasis and vascular occlusion on the simultaneous measurement of serotonin and propranolol pulmonary extraction in dogs

To test the relative sensitivity of serotonin and propranolol pulmonary extraction measurements to changes in pulmonary vascular surface, we sequentially subjected anaesthetized dogs to left upper lobe atelectasis, left lung atelectasis and left pulmonary artery occlusion. We used a triple-indicator dilution technique to simultaneously measure the pulmonary extraction of serotonin and propranolol. After an initial series of measurements, dogs received dopamine and dextran to slightly increase pulmonary artery pressure and prevent further recruitment of capillaries. Left upper lobe atelectasis did not modify the pulmonary extraction of serotonin and propranolol. Left lung atelectasis provoked a reduction in the serotonin extraction ratio by only 4%, whereas the propranolol extraction ratio decreased by 13%. After left pulmonary artery occlusion, propranolol and serotonin extraction ratios decreased by 16% and 5% respectively. We conclude that the pulmonary extraction of propranolol is more sensitive to a decrease in pulmonary vascular surface than that of serotonin.

Pulmonary extraction of serotonin and propranolol in patients with adult respiratory distress syndrome

Because injury to the pulmonary vascular endothelium is associated with the development of the adult respiratory distress syndrome (ARDS), we assessed the metabolic function of pulmonary endothelial cells by the measurements of the first-pass pulmonary extraction of [14C]serotonin and [3H]propranolol in 15 patients with ARDS and 15 patients at risk for developing ARDS. Serotonin extraction ratio was lower in patients with ARDS (0.85 +/- 0.10, mean +/- SD) than in patients at risk (0.91 +/- 0.04) (p less than 0.025), and both values were significantly reduced (p less than 0.005) when compared with a control group value (0.97 +/- 0.01). The decrease in serotonin extraction was correlated with the severity of ARDS (r = -0.67) (p less than 0.001) and with pulmonary function changes over time. Propranolol extraction ratio was decreased in patients at risk (0.66 +/- 0.11) (p less than 0.005) but not in patients with ARDS (0.75 +/- 0.11), when compared with those in the control group (0.81 +/- 0.03). Low values in patients at risk were restored to normal by continuous positive airway pressure breathing. We conclude that pulmonary extraction of serotonin, an index of pulmonary endothelial cell function, correlates with the severity of ARDS.