Ozone interactions with lung tissue. Biochemical approaches

Chromium and human low-density lipoprotein oxidation

Chromium is a catalytic metal able to foster oxidant damage, albeit its capacity to induce human LDL oxidation is to date unkown. Thus, we have investigated whether trivalent and hexavalent chromium, namely Cr(III) and Cr(VI), can induce human LDL oxidation. Cr(III) as CrCl₃ is incapable of inducing LDL oxidation at pH 7.4 or 4.5. However, Cr(III), specifically at physiological pH of 7.4 and in the presence of phosphates, causes an absorbance increase at 234 resembling a spectrophotometric kinetics of LDL oxidation with a lag- and propagation-like phase. In this regard, it is conceivable that peculiar Cr(III) forms such as Cr(III) hydroxide and, especially, Cr(III) polynuclear hydroxocomplexes formed at pH 7.4 interact with phosphates generating species with an intrinsic absorbance at 234 nm, which increases over time resembling a spectrophotometric kinetics of LDL oxidation. Cr(VI), as K₂Cr₂O₇, can instead induce substantial human LDL oxidation at acidic pH such as 4.5, which is typical of the intracellular lysosomal compartment. LDL oxidation is related to binding of Cr(VI) to LDL particles with quenching of the LDL tryptophan fluorescence, and it is inhibited by the metal chelators EDTA and deferoxamine, as well as by the chain-breaking antioxidants butylated hydroxytoluene and probucol. Moreover, Cr(VI)-induced LDL oxidation is inhibited by mannitol conceivably by binding Cr(V) formed from LDL-dependent Cr(VI) reduction and not by scavenging hydroxyl radicals (OH); indeed, the OH scavengers sodium formate and ethanol are ineffective against Cr(VI)-induced LDL oxidation. Notably, heightened LDL lipid hydroperoxide levels and decreased LDL tryptophan fluorescence occur in Cr plating workers, indicating Cr-induced human LDL oxidation in vivo. The biochemical, pathophysiological and clinical implications of these novel findings on chromium and human LDL oxidation are discussed.

Einfluss der Umweltnoxe Ozon auf die Haut

The skin is directly and frequently exposed to a pro-oxidative environment, including ozone and UV-radiation. While ozone in the stratosphere protects against mutagenic UVC-radiation, it is also a major air pollutant in urban areas. With its strong oxidizing potential, ozone is perhaps one of the most reactive chemicals the skin ever encounters. Although a large body of evidence exists for ozone- induced oxidative stress in the respiratory tract, the current knowledge on its in vivo effect on cutaneous tissues is based on studies of the last 10 years. Acute ozone exposure damages the stratum corneum, depletes skin vitamin C and E and induces lipid and protein oxidation in upper epidermal layers. Secondary products penetrate into deeper skin layers and are capable of activating signal transduction pathways and inducing cell damage. It has been shown in a murine model, that environmentally relevant ozone concentrations can induce a stress response in the skin.

Cyclooxygenase-2 participates in the late phase of airway hyperresponsiveness after ozone exposure in guinea pigs

We examined the role of cyclooxygenase in airway hyperresponsiveness and inflammation after ozone exposure in guinea pigs using a non-selective (indomethacin) and a selective (JTE-522) cyclooxygenase-2 inhibitor. Spontaneously breathing guinea pigs were exposed to ozone (3 ppm) for 2 h after treatment with vehicle, indomethacin (10 mg/kg) or JTE-522 (10 mg/kg). Airway responsiveness to inhaled histamine (PC(200)) and bronchoalveolar lavage were assessed before, immediately and 5 h after ozone exposure. Ozone caused a significant airway hyperresponsiveness immediately after exposure, which persisted after 5 h. Neither JTE-522 nor indomethacin affected airway hyperresponsiveness immediately after ozone exposure, but significantly attenuated airway hyperresponsiveness 5 h after exposure, suggesting that cyclooxygenase-2 may participate in the late phase of airway hyperresponsiveness but not in the early phase. Ozone caused a significant increase in the concentration of prostaglandin E(2) and thromboxane B(2) in bronchoalveolar lavage fluid immediately after exposure, which decreased to the basal level 5 h after exposure. This increase in prostaglandin E(2) and thromboxane B(2) was significantly inhibited by JTE-522. An expression of cyclooxygenase-2 was detected not only after ozone exposure but also before, and there was no difference in the number of cyclooxygenase-2-positive cells at any time point. An exogenously applied thromboxane A(2) mimetic, U-46619 (10(-5) M), induced airway hyperresponsiveness 5 h after inhalation, but not immediately or 3 h after inhalation. These data suggest that cyclooxygenase-2 may be constitutively expressed before ozone exposure in guinea pig airway and may synthesize prostaglandin E(2) and thromboxane A(2) transiently under ozone stimulation and that thromboxane A(2) may, in turn, induce the late phase of airway hyperresponsiveness.

Acute mild hypothermia caused by a low dose of X-irradiation induces a protective effect against mid-lethal doses of X-rays, and a low level concentration of ozone may act as a radiomimetic

Acute changes in core body temperature following exposure to a low dose of X-rays were assessed in unanaesthetized and unrestrained mice. Radiotelemetry techniques were used to monitor core body temperature continuously. Following exposure to a 20 cGy dose of X-rays, the mice displayed a rapid and significant reduction in core body temperature relative to the sham-treated (non-irradiated) control animals. The present studies, and those by others, showed that pre-exposure to X-rays at doses as low as 20 cGy may result in a reduced mortality rate following subsequent exposure to X-rays at mid-lethal dose levels. This indicates an increased tolerance to radiation. An additional experiment was conducted to examine whether the reduction in the mortality rate following exposure to mid-lethal doses of radiation could be found when mice were subjected to a stressor, ozone inhalation, which induced a suppression in body temperature. The results showed that following inhalation of ozone at a concentration of 0.5 ppm, 93% of the treated animals survived a mid-lethal dose of radiation, whereas 50% of the sham-control animals died within 30 days. These results suggest that low-dose-induced tolerance to radiation may be dependent on a brief exposure to ozone, and a reduction in core temperature may be necessary to obtain tolerance effects in response to a mid-lethal dose of radiation.

Phospholipase A2: its usefulness in laboratory diagnostics

Phospholipase A2 (PLA2) is an enzyme that catalyzes the hydrolysis of membrane phospholipids. This article reviews the source and structure of PLA2, the involvement of the enzyme in various biological and pathological phenomena, and the usefulness of PLA2 assays in laboratory diagnostics. Of particular importance is the role of PLA2 in the cellular production of mediators of inflammatory response to various stimuli. Assays for PLA2 activity and mass concentration are discussed, and the results of enzyme determinations in plasma from patients with different pathological conditions are presented. The determination of activity and mass concentration in plasma is particularly useful in the diagnosis and prognosis of pancreatitis, multiple organ failure, septic shock, and rheumatoid arthritis. A very important result is the demonstration that PLA2 is an acute phase protein, like CRP. Indeed, there is a close correlation between PLA2 mass concentration and CRP levels in several pathological conditions. Although the determination of C-reactive protein is much easier to perform and is routinely carried out in most clinical laboratories, the assessment of PLA2 activity or mass concentration has to be considered as a reliable approach to obtain a deeper understanding of some pathological conditions and may offer additional information concerning the prognosis of several disorders.

Effects of smog on absenteeism in forestry workers

Absenteeism among 161 Dutch forestry workers was investigated in a cohort study. The rate of taking sick leave was related to the concentrations of sulfate and ozone in ambient air, the air temperature, and the relative humidity. The incidence of absenteeism was treated as a Poisson process, with the size of population at risk as the offset factor and with the environmental monitoring data as hazard factors. There appeared to be some overdispersion; therefore, in a second analysis the incidence of absenteeism was also treated as a negative binomial outcome. With the exception of a separate overdispersion parameter in the negative binomial approach, both methods yielded approximately the same results. Although no significant association was found between absence rate and the measured ambient-air-quality data, there appeared to be a time lag of 3 d between a peak in temperature and 1 d in absenteeism.

Mechanisms contributing to ozone-induced bronchial hyperreactivity in guinea-pigs

The effect of ozone (3 ppm, 15-120 min) on bronchial reactivity in the guinea-pig was studied. Ozone induced marked (6-250-fold) bronchial hyperreactivity (BHR) to a range of inhaled, but not intravenous bronchoconstrictors. The degree of BHR was related to the duration of prior ozone exposure. The glutathione redox status was shifted to a more oxidized state in lung after 120 min ozone treatment, although no changes were found in the energy status of lung tissue, as judged by the concentrations of adenosine phosphates. Ascorbic acid pretreatment prevented BHR induced by 30 min ozone exposure. Neutral endopeptidase inhibitors elicited BHR to both substance P and histamine, but did not further enhance bronchoconstriction to substance P after ozone exposure for 120 min. Neither mepyramine, fentanyl, indomethacin nor a 5-lipoxygenase inhibitor (BW B70C), given prior to ozone exposure prevented the induction of BHR to histamine. Atropine or bilateral vagotomy reduced BHR after a 120-min, but not 30-min exposure to ozone. We conclude that in the guinea-pig, ozone induces non-specific, route-dependent BHR by oxidative injury, reducing airway NEP activity and enhancing the cholinergic and peptidergic component to bronchoconstriction. Neither cyclooxygenase nor 5-lipoxygenase products appear to play a role in ozone-induced BHR in this animal model.

Effects of ozone on the respiratory health, allergic sensitization, and cellular immune system in children

To investigate the lasting effects of high ozone concentrations under environmental conditions, we examined the respiratory health, pulmonary function, bronchial hyperresponsiveness to methacholine, allergic sensitization, and lymphocyte subpopulations of 10- to 14-yr-old children. A total of 218 children recruited from an area with high ozone concentrations (Group A) were tested against 281 children coming from an area with low ozone concentrations (Group B). As to subjective complaints, categorized as "usually cough with or without phlegm," "breathlessness," and "susceptibility to chest colds," there was no difference between the two groups. The lung function parameters were similar, but in Group A subjects' bronchial hyperresponsiveness occurred more frequently and was found to be more severe than in Group B (29.4 versus 19.9%, p less than 0.02; PD20 2,100 +/- 87 versus 2,350 +/- 58 micrograms, p less than 0.05). In both groups the number of children who had been suffering from allergic diseases and sensitization to aeroallergens, found by means of the skin test, was the same. Comparison of the total IgE levels showed no difference at all between the two groups. As far as the white blood cells are concerned, the total and differential cell count was the same, whereas lymphocyte subpopulations showed readily recognizable changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of short-term, single and combined exposure to low-level NO2 and O3 on lung tissue enzyme activities in rats

To examine the pulmonary effects of relatively low levels of NO2 and O3, and test for any possible interaction in their effects, we exposed 3-mo-old male Sprague-Dawley rats, free of specific pathogens, to either filtered room air (control) or 1.20 ppm (2256 micrograms/m3) NO2, 0.30 ppm (588 micrograms/m3) O3, or a combination of the two oxidants continuously for 3 d. We studied a series of parameters in the lung, including lung weight, and enzyme activities related to NADPH generation, sulfhydryl metabolism, and cellular detoxification. The results showed that relative to control, exposure to NO2 caused small but nonsignificant changes in all the parameters; O3 caused significant increases in all the parameters except for superoxide dismutase; and a combination of NO2 and O3 caused increases in all the parameters, and the increases were greater than those caused by NO2 or O3 alone. Statistical analysis of the data showed that the effects of combined exposure were synergistic for 6-phosphogluconate dehydrogenase, isocitrate dehydrogenase, glutathione reductase, and superoxide dismutase activities, and additive for glutathione peroxidase and disulfide reductase activities, but indifferent from those of O3 exposure for other enzyme activities.

Effects of ozone inhalation on polyamine metabolism and tritiated thymidine incorporation into DNA of rat lungs

We examined the effects of low-level ozone (O3) inhalation on polyamine metabolism and tritiated thymidine (3H-TdR) incorporation into DNA in rat lungs. We have also compared the activities of ornithine decarboxylase (ODC), the rate-limiting enzyme of polyamine biosynthesis, and glucose-6-phosphate dehydrogenase (G6PD), the key enzyme of the pentose phosphate cycle and a typical marker of oxidant injury, to assess whether ODC can serve as a sensitive marker of O3 effects on the lung. We exposed 90-day-old male specific-pathogen-free Sprague-Dawley rats to either 0.45 +/- 0.05 ppm (882 +/- 98 micrograms/m3) O3 or filtered room air continuously for 3 days. After exposure, the rats were terminated and the lungs examined for enzyme activities, polyamine contents, DNA content, and 3H-TdR incorporation. We found that in exposed rats, the enzyme activities were significantly increased (p less than 0.05) relative to air controls. G6PD, 25%, ODC, 147%, and S-adenosylmethionine decarboxylase (AdoMet DC), 86%. Polyamine contents were also affected by O3; putrescine increased 80%, p less than 0.05, spermidine did not change, and spermine decreased 23%, p less than 0.05. 3H-TdR incorporation into DNA was significantly elevated, 155%, p less than 0.001, after O3 exposure while total lung DNA content remained unchanged. The concomitant and large increase in ODC activity (reflecting polyamine metabolism) and DNA labeling (reflecting DNA synthesis and/or repair), indicates a strong correlation between the two and suggests that polyamine metabolism may play an important role in the accelerated cell proliferation associated with O3 injury. Moreover, the greater increase in lung ODC activity compared to other enzymes offers a sensitive marker of the lung response to inhaled O3. We conclude that inhalation of O3 at levels similar to what may be encountered during some smog episodes can result in significant pulmonary biochemical alterations with a potential for long-term consequences. The possible association between ODC activity and DNA labeling may offer a new insight into the mechanism of tissue injury and repair. We also speculate that the changes in lung polyamines may reflect antioxidant and anti-inflammatory functions associated with the cellular defense against oxidant injury.

Biochemical basis of ozone toxicity

Ozone (O3) is the major oxidant of photochemical smog. Its biological effect is attributed to its ability to cause oxidation or peroxidation of biomolecules directly and/or via free radical reactions. A sequence of events may include lipid peroxidation and loss of functional groups of enzymes, alteration of membrane permeability, and cell injury or death. An acute exposure to O3 causes lung injury involving the ciliated cell in the airways and the type 1 epithelial cell in the alveolar region. The effects are particularly localized at the junction of terminal bronchioles and alveolar ducts, as evident from a loss of cells and accumulation of inflammatory cells. In a typical short-term exposure the lung tissue response is biphasic: an initial injury-phase characterized by cell damage and loss of enzyme activities, followed by a repair-phase associated with increased metabolic activities, which coincide with a proliferation of metabolically active cells, for example, the alveolar type 2 cells and the bronchiolar Clara cells. A chronic exposure to O3 can cause or exacerbate lung diseases, including perhaps an increased lung tumor incidence in susceptible animal models. Ozone exposure also causes extrapulmonary effects involving the blood, spleen, central nervous system, and other organs. A combination of O3 and NO2, both of which occur in photochemical smog, can produce effects which may be additive or synergistic. A synergistic lung injury occurs possibly due to a formation of more powerful radicals and chemical intermediates. Dietary antioxidants, for example, vitamin E, vitamin C, and selenium, can offer a protection against O3 effects.

Structural changes in airways of rats exposed to nitrogen dioxide intermittently for seven days. Comparison between major bronchi and terminal bronchioles

Structural changes caused by exposure to NO2 were compared between the largest intrapulmonary bronchi (major bronchi) and the terminal bronchioles. Rats were exposed to 50 ppm NO2 for 5 h a day for 7 consecutive days, and microscopic findings were assessed subjectively and quantitatively. Destruction of airway epithelium was present on Day 1, and the reparative phase was observed between Days 3 and 7. Light microscopy showed that on Day 1, loss of cilia and disintegration of epithelium occurred, and that the latter was worse in major bronchi than in terminal bronchioles; apical projections of Clara cells in terminal bronchioles were lost almost totally. Recovery of epithelium began by Day 3 and cilia by Day 5, and ciliogenesis progressed less promptly in terminal bronchioles. Clara cells did not return to normal during the experiment. Furthermore, a decrease in the airway diameter occurred in peripheral airways along with an increase in mural thickness in terminal bronchioles. Mural inflammation was also seen more conspicuously in terminal bronchioles. Electron microscopy revealed that epithelial cells lost secretory granules on Day 1 and began to repair them by Day 5 in major bronchi and by Day 7 in terminal bronchioles. It is likely that epithelium in terminal bronchioles is not particularly sensitive to NO2 compared with that in major bronchi, but that recovery occurs more promptly in major bronchi than in terminal bronchioles. Mechanisms underlying bronchoconstriction occurring preferentially in peripheral airways are also discussed.

Airway responsiveness in isolated perfused rat lungs: effect of thoracic irradiation

We developed techniques for assessing airway reactivity in isolated perfused rat lungs by measuring the lung mechanics changes produced by injection of ACh into the pulmonary circulation. Lung resistance (RL) and dynamic compliance (Cdyn) changed in a dose-response fashion after ACh. We used the preparation to examine the effect of thoracic irradiation on airway responsiveness and pulmonary inflammation. Groups of rats were studied after sham irradiation or 24 h or 72 h after a single dose of 1500 rads. Thoracic irradiation did not alter baseline lung mechanics, but did increase the responsiveness of rat lungs to ACh 72 h after radiation. Radiation was not associated with an increase in neutrophils in lung lavage, airways or peripheral lung tissue. We conclude that thoracic irradiation alters airways reactivity without causing overt pulmonary inflammation, and that isolated perfused lungs can be useful for measurement of airway reactivity.

The UCLA population studies of chronic obstructive respiratory disease. 9. Lung function changes associated with chronic exposure to photochemical oxidants; a cohort study among never-smokers

Two cohorts of never-smoking residents of Los Angeles were studied on two occasions five years apart. One cohort (N = 1,099) lived in a community with moderate levels of photochemical pollution and low levels of other pollutants, and the second (N = 1,117) lived in a community with very high levels of photochemical oxidant and relatively high levels of sulfates and particulates. Studies included measurement of forced expiratory volumes and flow rates and single-breath nitrogen washout, as well as use of a standardized questionnaire. The data represent 47 percent of 2,340 and 58 percent of 1,935 residents, respectively, of the original community samples. Mean baseline spirometry and nitrogen washout for those who were and those who were not retested were similar, reflecting the fact that loss to follow-up was primarily due to changes of residence. In the more polluted area there were significantly worse lung function test results for both men and women at baseline and significantly more rapid deterioration at follow-up. Mean changes in nitrogen washout were significantly greater in the more polluted community for both sexes and for all age groups including children. Most of the spirometric test results showed significantly more rapid decline among adults in the more polluted community. These results are consistent with the hypothesis that chronic exposures to a mix of photochemical oxidants, sulfates and particulates are associated with increased loss of lung function, which is especially marked among tests that reflect function of the small airways.

Influence of age on the biochemical response of rat lung to ozone exposure

We have previously examined the influence of animal age on the pulmonary response to ozone (O3) in rats between 7 and 90 days of age (Elsayed et al., 1982a). In the present study, we expanded the age groups of rats, and examined in greater detail the relationship between animal age and pulmonary response to inhaled O3. We exposed 7 groups of specific pathogen free, male Sprague-Dawley rats, aged 24, 30, 45, 60, 90, 180, and 365 days, to 0.8 ppm (1568 micrograms/m3) O3 continuously for 3 days. After O3 exposure, we sacrificed the exposed rats and a matched number of controls from each age group, and analyzed their lungs for a series of physical and biochemical parameters, including glutathione metabolizing and NADPH producing enzyme activities. We observed that in control rats all the parameters increased as a function of age. However, the rate of increase was generally slower after age 60 days. After O3 exposure there was an increase in all the parameters for all age groups relative to their corresponding controls, but the extent of increase was significantly larger in rats 60 days and older than in younger rats. A regression of the difference in mean values between control and exposed animals for each parameter against age showed a linear correlation, indicating that the response was age-dependent. Since the magnitude of such increases is thought to reflect the degree of lung injury, the results suggest that O3 exposure causes greater lung injury in older rats than in younger rats. We tested this assumption by exposing rats from four different age groups (24, 45, 60 and 90 days) to a lethal dose of O3 (4 ppm or 7840 micrograms/m3 for 8 hours). The mortality rates were 50% and 83% for 24 and 45 day old rats, respectively, and 100% for 60 and 90 day old rats. The results of these studies further demonstrate that older rats are more susceptible to lung injury from O3 than younger rats.

Dietary antioxidants and the biochemical response to oxidant inhalation : III. Selenium influence on mouse lung response and tolerance to ozone

We fed female strain A/St mice selenium (Se) test diets containing either no Se (-Se) or 1 ppm Se (+Se) for 11 wk. Both diets contained 55 ppm vitamin E. We then exposed three groups of mice from each dietary regimen to either 0.8 ppm (1568 μg/m(3)) O3 (low-level) continuously for 5 d, 10.0 ppm (19,600 μg/m(3)) O3 (high-level) for 12 h, or filtered room air, where the latter served as a control for both O3 exposures. After O3 exposures we analyzed the lungs for various physical and biochemical parameters, and compared the results to those obtained from the air controls. The results showed that the difference in dietary Se intake produced an eightfold difference in Se content and a three-fold difference in glutathione peroxidase (GP) activity in the lung, but few changes in other lung parameters. With low-level O3 exposure, NADPH production increased significantly in +Se mice, but did not change in -Se mice. With high-level O3 exposure we observed comparable effects for both dietary regimens, including animal mortality, which was 24% for -Se and 14% for +Se mice. Thus, it seems that diminished GP activity resulting from Se deficiency and the ensuing lack of increase in NADPH production were poorly correlated with mouse tolerance to O3. The lung Se content increased in both dietary regimens after O3 exposure, but the increase was greater after high-level O3 exposure. This suggests a "mobilization" of Se to the lung under O3 stress. It is possible that such a mobilization contributes to the lung reserve of antioxidants, and hence the comparable mortality in both dietary Se regimens.

A comparison of biochemical effects of nitrogen dioxide, ozone, and their combination in mouse lung

Swiss Webster mice were exposed to either 4.8 ppm (9024 microgram/m3) nitrogen dioxide (NO2), 0.45 ppm (882 microgram/m3) ozone (O3), or their combination intermittently (8 hr daily) for 7 days, and the effects were studied in the lung by a series of physical and biochemical parameters, including lung weight, DNA and protein contents, oxygen consumption, sulfhydryl metabolism, and activities of NADPH generating enzymes. The results show that exposure to NO2 caused relatively smaller changes than O3, and that the effect of each gas alone under the conditions of exposure was not significant for most of the parameters tested. However, when the two gases were combined, the exposure caused changes that were greater and significant. Statistical analysis of the data shows that the effects of combined exposure were more than additive, i.e., they might be synergistic. The observations suggest that intermittent exposure to NO2 or O3 alone at the concentration used may not cause significant alterations in lung metabolism, but when the two gases are combined the alterations may become significant.

Morphology and fatty acid composition of erythrocytes from monkeys exposed to ozone for one year

Monkeys (Macaca radiata) were exposed to a low dose (0.64 ppm) of ozone (O3) for 8 hr each day over a 1-year period. Control monkeys were exposed to filtered air. The morphology of the red blood cell (RBC) from these monkeys was analyzed by scanning electron microscopy. Red cells from control monkeys had normal morphology with 69% having biconcave shape (discocytes). In O3-exposed animals, blood contained only 35% discocytes. Knizocytes, stomatocytes, and spherocytes each have defined shape which are different from discocytes. The number of knizocytes and stomatocytes in O3-exposed monkeys was twice that of controls. In addition, significant levels of spherocytes were observed while they were absent in the blood of controls. The fatty acid composition of RBC from control and O3-exposed monkeys was the same. These were similar to that of human RBC. However, earlier reports of monkey RBC fatty acid composition differ from our results. These differences are discussed. We conclude that low-dose O3 exposure changes the morphology, but not the fatty acid composition, of erythrocytes in vivo.

Antioxidant system and ozone tolerance

Rats were initially exposed to 2 ppm ozone for 3 hr in order to induce ozone tolerance. The time course of the content of nonprotein SH as well as the activities of glutathione peroxidase, glutathione reductase, and glucose 6-phosphate dehydrogenase (so-called antioxidant system) in lungs of the animals was compared to the development of tolerance in the animals to a challenge exposure of 5.6 ppm ozone for 3 hr. An enhancement of a part of the antioxidant system was detected on the second day and thereafter following the initial exposure, but the clear and complete tolerance to ozone was demonstrated 1 day before the enhancement of the antioxidant system. Alternatively, the induction of tolerance to ozone was found to be experimentally suppressed by actinomycin D or colchicine, but the levels of the antioxidant system in animals thus treated were not significantly different from the matched controls, or only partly enhanced. These events suggest that the tolerance to ozone is not related to an enhancement of the antioxidant system.

Rapid isolation of type II pneumocytes with magnetic removal of macrophages

A method is described for the rapid preparation of lung cell fractions enriched in type II alveolar pneumocytes. Isolated perfused rabbit lungs are exposed to Fe3O4 by tracheal lavage, which permits pulmonary alveolar macrophages to phagocytize the particles. Alveolar epithelial cells are then selectively freed from the basement membrane matrix by critical placement of collagenase and elastase. Detached cells are harvested either by repeated tracheal lavage or by mincing the lobes and filtering freed cells through a series of nylon mesh sieves. Iron oxide-containing macrophages are then removed from the harvested cells by a strong magnetic field. A final sizing of the macrophage-depleted suspension yields a preparation enriched in alveolar type II cells. Eight million viable cells (95% type II) were obtained per rabbit lung when harvested by lavage, while 32 x 10(6) (88% type II) cells were obtained from minced lungs. These values for cell yield and relative purity are comparable to previously described separation methods that depend upon differences in cell density or size. A major advantage of the magnetic separation procedure is the substantially shortened preparation time, typically 2 hr instead of 4. The viability (90-95%), oxygen consumption (88 nmol/10(6) cells/hr), and incorporation of [14C]acetate and [14C]choline (0.44 and 0.115 nmol/10(6) cells/hr, respectively) indicate that these cells will be suitable for pharmacologic and toxicologic investigation.

Age-dependent pulmonary response of rats to ozone exposure

The influence of age on O3 effects in the lung was studied in 8 groups of Sprague-Dawley rats: 7, 12, and 18 d of age (neonatal); 24, 30, and 45 d of age (infant); and 60 and 90 d of age (adult). Lung weight, total lung protein and DNA contents, and a series of marker enzyme activities in lung tissue were determined. After exposure of rats from each group to 0.8 ppm (1568 microgram/m3) O3 continuously for 3 d, a biphasic effect was noted. The biochemical parameters, expressed per lung, in O3-exposed rats relative to their corresponding controls decreased in the 7- and 12-d-old groups, increased or remained unchanged in the 18-d-old group, and increased in the 24- to 90-d-old groups. However, the increases were much greater for 60- to 90-d-old rats than for 24- to 30-d-old rats. The increase in lung biochemical parameters is thought to occur in response to lung injury and subsequent repair processes, and greater increases in the lungs of older rats suggest that they are more responsive to O3 exposure than younger rats. The decrease in lung biochemical parameters and increased mortality in 7- and 24-d-old neonatal rats suggest that they are more susceptible to O3 stress than infant and adult rats.

Ozone sensitivity in aging WI-38 cells based on acid phosphatase content

Young [16-19 population doubling level (PDL)] and senescing (50-53 PDL) WI-38 cell populations were exposed to 1 ppm ozone for 2 hr and the resultant extracellular and intracellular acid phosphatase concentration was measured. Dose-response curves were also determined for surviving populations of young and old cells after a 1 hr ozone exposure ranging in concentration from 0 to 1.00 ppm. Senescing cells released 8 times more acid phosphatase per million cells than the young cells. Both old and young cells showed a clear dose-response to the 1 hr ozone gradient exposure. However, the older cells demonstrated a consistent 17% average lower survival rate than the young cells. The higher acid hydrolase level in older WI-38 cells is probably related to the lower survival rate observed in the older cells in vitro.

The pulmonary and extrapulmonary effects of ozone

The toxicity of ozone is solely due to its action as an oxidant. It is an extremely reactive gas which rapidly forms intermediate oxidizing derivatives after inhalation. High concentrations cause death from pulmonary oedema. Both pulmonary and extrapulmonary toxicity have been observed at lower concentrations of ozone, including those currently present in urban air. Pulmonary cellular and subcellular membranes appear to be particularly susceptible. A primary mechanism of this effect is the oxidative decomposition of polyunsaturated fatty acids, which has been demonstrated in rodent lungs after inhalation of ozone. Supporting evidence includes the potentiation of ozone toxicity by vitamin E deficiency and an increased use of this antioxidant vitamin during repetitive exposure to ozone. Other membrane effects include oxidation of thiol groups and, perhaps, of tryptophan. Microsomal alterations include a loss of lung cytochrome P450 which may also be related to lipid peroxidation. Extrapulmonary toxicity is not directly due to ozone but may represent in effect due to lipid peroxide decomposition products, particularly malonaldehyde. This three-carbon dialdehyde has been shown to alter cell membrane fluidity and to have mutagenic properties; the latter perhaps due to cross-linkage of DNA to histone.

Lactate dehydrogenase activity and isoenzyme pattern in lungs, erythrocytes, and plasma of ozone-exposed rats and monkeys

The effect of low levels of ozone exposure (8 hr daily for 7 days) on lactate dehydrogenase (LDH) activity and isoenzyme pattern was studied in the lungs, plasma, and erythrocytes of rats and monkeys. Exposure to 0.8 or 0.5 ppm ozone resulted in a significant increase in total LDH activvity in the lungs but not in the plasma and erythrocytes of rats. The LDH-5 fraction of the LDH isoenzymes was significantly decreased in terms of percentage distribution in the lungs and plasma of rats exposed to 0.8 ppm ozone, whereas the LDH-4 in the lungs and plasma and LDH-3 in the lungs were increased. At 0.5 ppm ozone, the isoenzyme distribution was not significantly changed in lungs, plasma, or erythrocytes. In monkeys, no significant change in either total LDH activity or isoenzyme pattern was observed in lungs, plasma, or erythrocytes after exposure to 0.8 ppm ozone.

Effect of butylated hydroxytoluene and other antioxidants on mouse lung metabolism

Toxic doses of butylated hydroxytoluene (BHT), a phenolic antioxidant commonly used as a food additive, are known to produce lung damage. In this study, 3 days after a single ip injection of 62.5, 215, or 500 mg/kg BHT in mice there was a dose-dependent increase in lung weight. This concentration dependence with injected BHT was accompanied by increases in lung DNA and nonprotein sulfhydryl levels and in whole lung tissue enzyme activities of glutathione (GSH) peroxidase, GSH reductase, glucose-6-phosphate dehydrogenase, and superoxide dismutase. The increased enzyme activities are considered to correspond to inflammatory and proliferative pulmonary changes resulting from acute lung cell injury and necrosis, which have been described previously, and cannot be construed as evidence for a primary oxidant-induced pulmonary lesion. The mechanism of BHT-induced lung changes may not be related to the antioxidant property of BHT, since vitamin E, n-propyl gallate, ethoxyquin, N,N'-p-phenylenediamine, and the structurally similar compound, butylated hydroxyanisole did not appear to produce the gross anatomical or biochemical lung changes observed with BHT.