The effect of lung alpha-tocopherol content on the acute toxicity of nitrogen dioxide

The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

Cellular and biochemical indices of bronchoalveolar lavage for detection of lung injury following insult by airborne toxicants

Cellular and biochemical profiles of bronchoalveolar lavage (BAL) material after inhalation or intratracheal exposure to various airborne toxicants clearly reflect that BAL has the potential of being a useful tool for the rapid screening of lung injury. The cellular and biochemical responses not only predict inflammation, extent of tissue damage and toxic nature of the substances, but could also help in understanding the molecular mechanisms of pathogenicity. Depending upon the changes of BAL in animals acutely exposed to a pulmonary toxicant, future in-depth studies along with complete histopathological evaluations could be made. Also, the assessment of macromolecules of pharmacological importance in the lavage, especially the secretory products of alveolar macrophages and other lung cell types, could be very useful in predicting the toxic potential of various airborne substances and could also serve as important indicators of developing chronic lung diseases and, therefore, necessitate further studies.

Effect of methylprednisolone on nitrogen dioxide (NO2)-induced pulmonary edema in guinea pigs

The treatment of nitrogen dioxide (NO2)-induced lung edema is controversial. In addition, mechanisms and patterns of interstitial edema formation in this form of increased permeability edema are unclear. To ascertain if methylprednisolone (MP) is effective in the therapy of NO2-induced edema, we exposed 108 unaesthetized guinea pigs, in groups of 12, to 277-448 ppm.hr NO2: in 60, we administered MP just before, and in 48 immediately after exposure. In each group, half the animals were randomly assigned to receive 30 mg/kg MP ip, and the other half saline. Mortality rates and lung water with wet weight/dry weight (W/D) ratios were calculated. Alveolar edema, periarterial interstitial edema, and NO2-induced bronchiolitis were graded semiquantitatively by light microscopy from freeze-substituted middle (ML) and lower lobes (LL). We found NO2 produced an exposure-dependent increase in lung water (R = 0.70, p less than 0.01). Treatment with MP preexposure produced a fourfold reduction mortality, and and a significant fall in W/D ratios and in alveolar and interstitial edema. No difference in the degree of acute bronchiolitis was found between treated and untreated animals, although ML had significantly more inflammation than LL. Treatment with MP immediately after NO2 was ineffective since mortality rates, W/D ratios, and alveolar and interstitial edema were not lower in the treated animals; there was significantly more intestitial edema in the middle lobes of the latter. Both LL and ML had equally abundant alveolar edema, but LL had significantly more interstitial edema, supporting our previous findings that in NO2-induced edema interstitial fluid accumulation follows alveolar flooding, with interlobar discrepancies probably due to differences in lung volume or in ventilation.

Protective effect of beta-naphthoflavone against NO2 toxicity in mice with genetically inducible lung cytochrome P450

The effects of the cytochrome P450 inducer beta-naphthoflavone (BNF) on NO2 toxicity were studied in two strains of mice. In one strain (C57B1/6J), cytochrome P450 could be induced by the aromatic hydrocarbon, while in the other strain (DBA/2J) cytochrome P450 was not inducible by this compound. Mice were treated with BNF before and during 4 days of exposure to 20 ppm NO2. The body growth of NO2-exposed mice improved only in BNF-treated C57B1/6J mice. In this strain, BNF reduced both pulmonary edema (as measured by wet and dry lung weights or as assessed by histological studies) and lung peroxidation (as measured by malondialdehyde). This protective effect of BNF on NO2 toxicity in C57B1/6J mice was associated with an increase in the components of the cytochrome P450 system (cytochrome P450 and cytochrome b5), whereas the activities of pulmonary antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and glutathione reductase) were not significantly increased. These data suggest that the induction of the cytochrome P450 system may be important in promoting NO2 tolerance in those strains of mice in which the cytochrome P450 system is genetically inducible.

Mucus protection and airway peroxidation following nitrogen dioxide exposure in the rat

In the current study, biochemical measures of lipid peroxidation following 4-h inhalation exposure to 76 mg/m3 (40 ppm) nitrogen dioxide were correlated with measures of deposition and tissue antioxidant levels in the nasal cavity and the trachea of the Fischer rat. In addition, respiratory-tract mucus samples were collected via esophageal cannulation and nasopharyngeal lavage over known time periods, and were analyzed for phospholipid (PL) content to provide an index of the unsaturated lipids (UL) that they may contain. UL are thought to be important in the scavenging of oxidants by the mucous lining layer. Nasal deposition efficiency, as measured in the surgically isolated upper respiratory tract under unidirectional flow conditions, averaged 25%, corresponding to an absolute deposition rate of 41 nmol/min. Vitamin E levels averaged 1.7, 5.9, and 0.7 nmol/mumol PL in nasal, tracheal, and pulmonary tissues, respectively. The level in the trachea was significantly (p less than 0.005) higher than in the other tissues. As estimated from the increase in lavage PL content over 1 h, the overall mucous PL transport rate was less than 0.013 nmol/min, suggesting the PL of the mucous lining layer could not offer significant protection against the inhaled NO2. Conjugated dienes were detected in two of four pooled nasal tissue samples. Thiobarbituric acid-reactive material levels in tracheal tissues were significantly elevated over control levels by NO2 (p less than 0.05). Thus, despite the relatively high vitamin E levels, 4-h NO2 exposure appeared to result in lipid peroxidation in the trachea and, perhaps, in the nasal airways of the rat, a result that correlated with the apparent lack of oxidant-scavenging species in the mucus lining these airways.

A survey of chemicals inducing lipid peroxidation in biological systems

A great number of drugs and chemicals are reviewed which have been shown to stimulate lipid peroxidation in any biological system. The underlying mechanisms, as far as known, are also dealt with. Lipid peroxidation induced by iron ions, organic hydroperoxides, halogenated hydrocarbons, redox cycling drugs, glutathione depleting chemicals, ethanol, heavy metals, ozone, nitrogen dioxide and a number of miscellaneous compounds, e.g. hydrazines, pesticides, antibiotics, are mentioned. It is shown that lipid peroxidation is stimulated by many of these compounds. However, quantitative estimates cannot be given yet and it is still impossible to judge the biological relevance of chemical-induced lipid peroxidation.