Oxygen radicals and lung injury

Relationship between pulmonary surfactant protein and lipid peroxidation in lung injury due to paraquat intoxication in rats

BACKGROUND

Pulmonary damage resulting from lipid peroxidation is a principal effect of paraquat intoxication. The host-defense functions of surfactant are known to be mediated by the surfactant proteins A and D (SP-A and SP-D, respectively). The primary objective of this study was to evaluate the variations over time in levels of surfactant protein and lipid peroxidation (LPO) in lung tissue following free-radical-induced injury.

METHODS

42 adult, male, Sprague-Dawley rats were administered intraperitoneal injections of paraquat (35 mg/kg body weight). SP-A and SP-D levels were determined via Western blot. LPO in the left lung homogenate was measured via analyses of the levels of thiobarbituric acid-reactive substances.

RESULTS

LPO levels peaked at 6 hours, with no associated histological changes. SP-D levels increased until hour 12 and declined until hour 48; SP-D levels subsequently began to increase again, peaking at hour 72. SP-A levels peaked at hour 6, declining thereafter.

CONCLUSIONS

We suggest that in the early phase of paraquat injury, SP-D levels reflect alveolar damage and that de novo synthesis of SP-D takes 72 hours. Levels of SP-A, on the other hand, reflect abnormalities in the surfactant system in the late stage of paraquat intoxication. Surfactant proteins may play a role in protecting the lungs from reactive oxygen injury. A time-dependent variation has been observed in the levels of surfactant proteins A and D following paraquat injury, and it has been suggested that these proteins play a role in the protection of lung tissue against ROS-induced injuries.

Lipid peroxidation in the skeletal muscle of hamsters with emphysema

Current evidence suggests that skeletal muscle functional impairments present in emphysema and COPD patients may in part be a consequence of the disease condition per se. The mechanistic basis for these impairments is uncertain. Within the human population, it is difficult to control for confounding effects of concomitantly reduced activity levels. To explore this issue, malondialdehyde (MDA), a marker of lipid peroxidation, and enzymes of the glutathione redox system were measured in selected hindlimb muscles of Syrian Golden hamsters 6 months following intratracheal instillation of either saline (CON, n=7) or elastase (25 U/100 g body weight, EMP, n=5) in an accepted model where physical activity levels between control and EMP groups could be equated. Excised lung volume increased with EMP (CON, 1.3+/-0.2 g; EMP, 3.2+/-0.4 g, P<0.01). MDA was increased in the gastrocnemius (CON, 238+/-87; EMP, 371+/-122 nmol/g protein, P<0.05) of EMP hamsters. Antioxidant concentrations had a disparate response; glutathione (CON, 7.68+/-1.53; and EMP, 10.25+/-0.67 &mgr;mol/g protein, P<0.01) and the activity of glutathione reductase (GR) were increased (CON, 1.87+/-0.17; and EMP, 2.46+/-0.31 U/g protein, P<0.01) in the gastrocnemius, whereas the activity of glutathione peroxidase (GPx) was decreased (CON, 12.7+/-2.65; and EMP, 9.46+/-1.88 U/g protein, P<0.05) in the vastus lateralis of EMP hamsters. CONCLUSION: These data indicate that EMP may induce oxidative stress in peripheral skeletal muscle.

Role of neutrophils in xanthine/xanthine oxidase-induced oxidant injury in isolated rabbit lungs

Reactive oxygen species have been shown to play an important role in the pathogenesis of lung injury. This study was designed to clarify the role of intrapulmonary neutrophils in the development of xanthine/xanthine oxidase (X/XO)-induced lung injury in isolated buffer-perfused rabbit lungs. We measured microvascular fluid filtration coefficient (K(f)) and wet-to-dry weight ratio to assess lung injury. X/XO induced a significant increase in K(f) and wet-to-dry weight ratio in neutrophil-replete lungs, whereas the lung injury was attenuated in neutrophil-depleted lungs. A neutrophil elastase inhibitor, ONO-5046, also attenuated the lung injury. In addition, X/XO induced a transient pulmonary arterial pressure (P(pa)) increase. The thromboxane inhibitor OKY-046 attenuated the P(pa) increase but did not alter the increase in permeability. Neutrophil depletion reduced the K(f) increase but had no effect on the P(pa) increase. These results suggest that intrapulmonary neutrophils activated by X/XO play a major role in development of the lung injury, that neutrophil elastase is involved in the injury, and that the X/XO-induced vasoconstriction is independent of intrapulmonary neutrophils.

Adult respiratory distress syndrome after microvascular free tissue reconstruction in head and neck malignancy

Adult respiratory distress syndrome (ARDS) is an important cause of morbidity and mortality after major operations. We undertook a 10 year retrospective analysis of patients undergoing major surgery in combination with microvascular free tissue transfer for head and neck malignancy at a Regional Maxillofacial Unit to try and identify predisposing factors. In the 10 year period to 31 April 1995, roughly 418 patients underwent major head and neck reconstructions, of which 399 (95.5%) were admitted to the intensive care unit (ICU) postoperatively. Thirty patients (7.2%) spent more than 72 h in the ICU, eight developed ARDS (1.9%) of whom four died. The factors that seemed to contribute to the development of ARDS were massive blood transfusion and early postoperative complications that required a further operation under general anaesthesia.

Targeted lung expression of interleukin-11 enhances murine tolerance of 100% oxygen and diminishes hyperoxia-induced DNA fragmentation

Acute lung injury is a frequent and treatment-limiting consequence of therapy with hyperoxic gas mixtures. To determine if IL-11 is protective in oxygen toxicity, we compared the effects of 100% O2 on transgenic mice that overexpress IL-11 in the lung and transgene (-) controls. IL-11 markedly enhanced survival in 100% O2 with 100% of transgene (-) animals dying within 72-96 h and > 90% of transgene (+) animals surviving for more than 10 d. This protection was associated with markedly diminished alveolar-capillary protein leak, endothelial and epithelial membrane injury, lipid peroxidation, and pulmonary neutrophil recruitment. Significant differences in copper zinc superoxide dismutase and catalase activities were not noted and the levels of total, reduced and oxidized glutathione were similar in transgene (+) and (-) animals. Glutathione reductase, glutathione peroxidase, and manganese superoxide dismutase activities were slightly higher in transgene (+) as versus (-) mice after 100% O2 exposure, and IL-11 diminished hyperoxia-induced expression of IL-1 and TNF. Hyperoxia also caused cell death with DNA fragmentation in the lungs of transgene (-) animals and IL-11 markedly diminished this cell death response. These studies demonstrate that IL-11 markedly diminishes hyperoxic lung injury. They also demonstrate this protection is associated with small changes in lung antioxidants, diminished hyperoxia-induced IL-1 and TNF production, and markedly suppressed hyperoxia-induced DNA fragmentation.

Nasal mucosa inflammation induced by oxygen administration in humans

BACKGROUND

The effect of oxygen toxicity in human airways is still poorly documented. We prospectively evaluated the inflammatory reaction induced by nasal oxygen exposure in an experimental setting.

METHODS

Healthy subjects without nasal symptoms were exposed to high FIO2 during 5 h. Oxygen was delivered from a tank at a flow of 4 l/min to one nostril of each subject and both nostrils were studied. Mucociliary clearance was measured as saccharine nasal transit time (SNTT). Nasal lavage was performed with 5 ml normal saline and the fluid recovered was processed for cytology and measurements of cytokines concentrations: TNF alpha, IL-6, IL-8 and soluble ICAM-1. Under local anaesthesia, biopsies were performed for immunochemistry and electron microscopy.

RESULTS

After oxygen exposure mucociliary clearance decreased and SNTT increased from 16 [9-21] to 20.5 [14-32] min (median and extremes; P < 0.1). In the lavage fluid, concentration of IL-6 was higher in the oxygen-exposed nostril (40.5 [11-128] pg/ml) than in the non-exposed one (7 [0-34] pg/ml; P < 0.05). There was also a trend for a higher IL-8 in the exposed than in the non-exposed nostril, (respectively 501 [214-587] pg/ml and 214 [122-616] pg/ml, P < 0.08), and for a higher number of polymorphonuclear cells in exposed nostril. In the mucosal biopsies substance P was not found, but ICAM-1 expression was higher in the mucosa and submucosa of the exposed nostrils where mast cells were also more abundant and showed piecemeal degranulation.

CONCLUSION

In summary, we found clinical, functional and biological evidence of ongoing nasal inflammation following high FIO2 inhalation for 5 h. Since the histology and behaviour of nasal and bronchi mucosa are very similar, the same inflammatory events are likely to be occurring in the bronchi upon high concentrations of inhaled oxygen.

A re-evaluation of the tissue distribution and physiology of xanthine oxidoreductase

Xanthine oxidoreductase is an enzyme which has the unusual property that it can exist in a dehydrogenase form which uses NAD+ and an oxidase form which uses oxygen as electron acceptor. Both forms have a high affinity for hypoxanthine and xanthine as substrates. In addition, conversion of one form to the other may occur under different conditions. The exact function of the enzyme is still unknown but it seems to play a role in purine catabolism, detoxification of xenobiotics and antioxidant capacity by producing urate. The oxidase form produces reactive oxygen species and, therefore, the enzyme is thought to be involved in various pathological processes such as tissue injury due to ischaemia followed by reperfusion, but its role is still a matter of debate. The present review summarizes information that has become available about the enzyme. Interpretations of contradictory findings are presented in order to reduce confusion that still exists with respect to the role of this enzyme in physiology and pathology.

Urine hydrogen peroxide during adult respiratory distress syndrome in patients with and without sepsis

BACKGROUND

The lung injury in adult respiratory distress syndrome (ARDS) has been associated with increased expiratory hydrogen peroxide (H2O2) concentrations. Furthermore, patients with sepsis and ARDS are reported to have greater serum scavenging of H2O2 than patients with ARDS only. We hypothesized that the systemic presence of H2O2 would be detectable in the urine of these two groups of patients and that, in the case of ARDS sepsis, the relative contribution of each disease to the production this analyte would be discernible. Accordingly, we used an in vitro radioisotope assay to follow the weekly course of urine H2O2 levels in ARDS patients with and without sepsis, and in samples from control non-ARDS patients with sepsis with indwelling urinary catheters and in samples provided by healthy volunteers.

METHODS

Thirty patients with ARDS were included in the study: 23 had sepsis and 7 were sepsis free. An indwelling catheter was used to collect urine from each patient over a 24-h period, first within 48 h of ICU admission and then every seventh day over the course of their illness. Urine H2O2 was measured by competitive decarboxylation of 1-14C-alpha-ketoglutaric acid by H2O2. Urine samples were provided by 20 healthy volunteers while, in 10 non-ARDS patients with sepsis, urine was collected over one 24-h period following a 5-day minimum with an indwelling urinary catheter.

RESULTS

Urine H2O2 concentration in healthy control subjects (88 +/- 4 mumol/L) and non-ARDS patients with urinary catheters (96 +/- 5 mumol/L) was not significantly different. During the first 48 h in the ICU, urine H2O2 in patients with ARDS only (295 +/- 29 mumol/L) was significantly lower (p < 0.05) than patients with ARDS and sepsis (380 +/- 13 mumol/L); however, the lung injury scores of these two groups did not differ. Furthermore, within the first 48 h, the urine H2O2 of the patients with ARDS and sepsis who did not survive (427 +/- 19 mumol/L; n = 7) was significantly higher than that in patients who survived sepsis (352 +/- 14 mumol/L; n = 15). Thereafter, the lung injury scores and urine H2O2 levels of the nonsurvivor ARDS-sepsis group remained significantly higher compared with the other two groups. At lung injury scores of 3 and 2, regardless of days in ICU, the patients with ARDS only had significantly lower urine H2O2 (266 +/- 30 mumol/L and 167 +/- 24 mumol/L, respectively) compared with the survivor ARDS-sepsis group (376 +/- 19 mumol/L and 250 +/- mumol/L). When the patients with ARDS (both ARDS only and with sepsis) recovered, their urine H2O2 concentration did not differ from the control groups (healthy donors and patients without ARDS).

CONCLUSION

Lung injury scores did not differentiate patients with ARDS and sepsis from patients with ARDS only during the first 10 days in the ICU; however, urine H2O2 levels were significantly greater in the patients with ARDS and sepsis. Moreover, despite no initial difference in lung injury, patients who did not survive ARDS and sepsis had consistently greater urine H2O2 concentration than patients who survived sepsis. The urine H2O2 level in the ARDS-only group was about 70 percent of the level in the survivor ARDS and sepsis group, suggesting that ARDS alone is the major contributor to the H2O2 oxidant processes during combined ARDS and sepsis. Furthermore, these studies demonstrate that urine H2O2 may be a useful analyte to differentiate the severity of oxidant processes in patients with ARDS and sepsis albeit the prognosis appears to be survival or nonsurvival.

Cigarette smoke oxidation of human plasma constituents

In vitro exposure of fresh human plasma to cigarette smoke (CS) was used as a model for reactions that could be occurring in CS-exposed respiratory tract lining fluids (RTLFs) and lung parenchyma. The central focus of this model was to characterize the consumption of endogenous plasma antioxidants in relationship to the appearance of oxidized proteins and lipids as a consequence of exposure to CS, or to aldehydes present in CS. The amelioration of CS-induced protein and lipid oxidation in plasma by the addition of selective exogenous antioxidants was also assessed. We found that: (i) exposure of human plasma to gas phase CS causes both lipid peroxidation and protein oxidation, and endogenous ascorbic acid protects against lipid, but not protein, oxidation; (ii) whole CS causes protein oxidation, but does not induce lipid peroxidation; (iii) addition to plasma of aldehydes known to be present in CS causes protein damage, but does not induce either lipid peroxidation or oxidation of ascorbic acid; and (iv) exogenously added dihydrolipoic acid (DHLA) preserves ascorbic acid levels in plasma exposed to the gas phase of CS, and protects, to some extent, against lipid peroxidation; DHLA also protects against protein oxidation, whereas added glutathione (GSH) only protects against protein, but not lipid, oxidation.