Stimulation of oxidant production in alveolar macrophages by pollutant and latex particles

Industrial hygiene and toxicity studies in unorganized bone-based industrial units

A large variety of ornamental and decorative items are manufactured from bone waste by various unorganized sectors in India. An initial survey indicated that workers were exposed at various phases of final product. The subjects (12 industrial units) were tested for total suspended particulate matter (TSPM), particulate matter <10 microm (PM(10)), and particulate matter <2.5 microm (PM(2.5)). Prevalent levels of TSPM ranged between 2.90 and 5.89 mg m(-3). Respirable fractions of occupational dust as PM(10) and PM(2.5) were found in the range of 0.30-2.08 and 0.26-0.50 mg m(-3), respectively. Cytotoxicity study was conducted using hemolysis as a sensitive marker. In an in vitro study, rat RBCs were exposed to the concentration of 25-1,000 microg/ml for 15-120 min. A considerable variation was observed in the hemolytic activity of samples collected from different areas. At 500 microg/ml concentration, the hemolytic activity (12 h) was found to be in the range of 18-25%. Due to limitation in sample mass of respirable fractions, only one concentration (100 microg/ml/2 h) was used for comparative study on hemolysis of RBCs caused by PM(10) and PM(2.5). Interestingly, the hemolytic activity was more at PM(2.5) than PM(10) and TSPM. These results suggest that the respirable particles are capable of reaching deep into the respiratory system. The finding is significant notably when there are no standards available in occupationally exposed populations. This is the first such study. Data could be of importance to policy makers and regulators.

Magnetometric evaluation of cadmium oxide-induced toxicity to pulmonary alveolar macrophages of Syrian golden hamsters

Since alveolar macrophages play an important role in the clearance of inhaled dust from air-ways, these cells have been used as a target for various toxic chemicals. Alveolar macrophages obtained from bronchoalveolar lavage of Syrian golden hamsters were concurrently exposed in vitro to Fe(3)O(4), as an indicator for magnetometry, and various concentrations of cadmium oxide (CdO) in this study. A rapid decrease of the remnant magnetic field, called relaxation, was observed after the cessation of an external magnetic field stimulus in macrophages concurrently exposed to phosphate-buffered saline or CdO at 0.1 microg/ml, while relaxation was delayed in those concurrently exposed to 1, 25, or 50 microg/ml CdO. Therefore, the concentration of CdO affecting relaxation in vitro was estimated at between 0.1 and 1 microg/ml. Release of LDH activity from CdO-exposed macrophages into the medium significantly increased at levels of 25 and 50 microg/ml CdO. Apoptosis was not detected in macrophages exposed to CdO by the DNA ladder detection method or morphological observations. Electron-microscopic examination revealed severe membrane damage and vacuolar changes in macrophages exposed to CdO. Since delayed relaxation is thought to occur by (1). disrupted cytoskeleton-driven random rotation of phagosomes containing iron oxide particles, (2). significant lactate dehydrogenase (LDH) activity release, and (3). detachment of cell membranes, CdO is considered to affect macrophage functions.

Differential particulate air pollution induced oxidant stress in human granulocytes, monocytes and alveolar macrophages

It has been proposed that oxidant stress of cells in the lung is one of the underlying mechanisms of particulate pollution-induced exacerbation of lung disease. Individuals who are considered most sensitive to particulate pollution are those with pre-existing airways inflammation, such as chronic obstructive pulmonary disease (COPD), lung infection or asthma. These diseases are characterized by a presence of inflammatory cells in the airways including neutrophils (PMN), eosinophils and monocytes (Mo), and increased numbers of alveolar macrophages (AM). These cells have a high capacity for production of oxygen radicals, as compared to other cell types of the lung. To assess the oxidative response of these various cell types to pollution particles of various sources, luminol-dependent chemiluminescence was employed. Particles including transition metal-rich residual oil fly ashes (ROFAs), coal fly ashes, diesel, SiO2, TiO2 and fugitive dusts were co-cultured with AM, Mo and PMN in a dose range of 10-100 microg/2 x 10(5) cells and chemiluminescence determined following a 20-min interaction. A strong oxidant response of AM was restricted to oil fly ashes, while the PMN were most reactive to the dusts containing aluminium silicate. In general, the Mo response was less vigorous, but overlapped both AM- and PMN-stimulating dusts. However, in response to SiO2 and volcanic ash the Mo chemiluminescence exceeded that of the other cell types. Oxygen radicals generated in response to ROFA by the AM were likely to be dependent on mitochondrial processes, while the response in PMN involved the membrane NADPH oxidase complex, as determined by targeting inhibitors. The response of AM to SiO2 of various sizes and TiO2 in the fine size range obtained from different commercial sources, was highly variable, implying that composition rather than size was responsible for the oxidant response. A strong chemiluminescence response was not consistently associated with cytotoxicity in the responsive cell. Taken together, these results suggest that oxidant activation by various sources of particulate matter is cell specific. Therefore, the inflamed lung is likely to be more susceptible to harm of ambient air particulates because of the oxidant stress posed by a broader range of particles.

Oxidative interactions of synthetic lung epithelial lining fluid with metal-containing particulate matter

Epidemiology studies show association of morbidity and mortality with exposure to ambient air particulate matter (PM). Metals present in PM may catalyze oxidation of important lipids and proteins present in the lining of the respiratory tract. The present study investigated the PM-induced oxidation of human bronchoalveolar lavage (BAL) fluid (BALF) and synthetic lung epithelial lining fluid (sELF) through the measurement of oxygen incorporation and antioxidant depletion assays. Residual oil fly ash (ROFA), an emission source PM that contains approximately 10% by weight of soluble transition metals, was added (0-200 microg/ml) to BALF or sELF and exposed to 20% (18)O(2) (24 degrees C, 4 h). Oxygen incorporation was quantified as excess (18)O in the dried samples after incubation. BALF and diluted sELF yielded similar results. Oxygen incorporation was increased by ROFA addition and was enhanced by ascorbic acid (AA) and mixtures of AA and glutathione (GSH). AA depletion, but not depletion of GSH or uric acid, occurred in parallel with oxygen incorporation. AA became inhibitory to oxygen incorporation when it was present in high enough concentrations that it was not depleted by ROFA. Physiological and higher concentrations of catalase, superoxide dismutase, and glutathione peroxidase had no effect on oxygen incorporation. Both protein and lipid were found to be targets for oxygen incorporation; however, lipid appeared to be necessary for protein oxygen incorporation to occur. Based on these findings, we predict that ROFA would initiate significant oxidation of lung lining fluids after in vivo exposure and that AA, GSH, and lipid concentrations of these fluids are important determinants of this oxidation.

Chemical reactivity of the carbon-centered free radicals and ferrous iron in coals: role of bioavailable Fe2+ in coal workers pneumoconiosis

Striking differences in the prevalence of coal workers' pneumoconiosis (CWP) exist between different coal mine regions. The major factors responsible for the observed regional differences in CWP have not yet been identified. In the present study, chemical reactivity of the carbon-centered free radicals in coals and lung tissues, as well as ferrous iron in the coals, were studied by ESR techniques. The ESR spectra clearly demonstrated the presence of at least two types of carbon-centered free radical species, which might respectively attribute to the macromolecular phase and the molecular phase of coal. Grinding produced free radicals in coals. Exposure of freshly ground coal to air for 28 h induced a slight increase of free radicals for most of the coals, and a slight decrease after 4 months' exposure. The lung tissue samples of coal workers deceased of CWP showed similar ESR spectra as coal samples, and these radicals were highly stable in the lung. After incubation of coals with glutathione, hydrogen peroxide, sodium formate or oxygen, the coal sample from the Gardanne mine which has never induced CWP, and thus is the least hazardous coal, showed the most significant change in the carbon-centered free radical concentration. No significant changes were observed among other coals reported to induce CWP. On the other hand, we found that the coals released different amounts of Fe2+ in an acidic medium. Interestingly, the prevalence of CWP correlates positively with the released Fe2+ content in these coals and with the amount of oxygen radicals produced by the interaction of Fe2+ with O2 in the acidified coal filtrates. Our studies indicate that the carbon-centered free radicals may not be biologically relevant to coal dust-induced pneumoconiosis, whereas the acid soluble Fe2+, which may be dissolved in the phagolysosomes of macrophages, can then lead to Fe2+-induced oxidative stress and eventual CWP development.

Antiradical and chelating effects in flavonoid protection against silica-induced cell injury

Quercetin, dihydroquercetin, and rutin are capable of scavenging superoxide anion (rate constants of the reaction with superoxide at pH 10 were 1.7 x 10(5), 1.5 x 10(5), and 0.5 x 10(5) M-1 s-1, respectively). At the same time rutin and quercetin but not dihydroquercetin are iron ion chelators. These substances were used to elucidate the role of radical scavenging and iron chelating in flavonoid protection against asbestos-induced oxidative cellular injury. Exposure of rat peritoneal macrophages to chrysotile asbestos fibers resulted in "frustrated" phagocytosis, cell injury, and a LDH release. Quercetin, dihydroquercetin, and rutin were effective in protecting the phagocytic cells against injury caused by asbestos. Moreover, these flavonoids exhibited cellular protection in the same order of effectiveness as that observed for the quenching of superoxide: quercetin > dihydroquercetin > rutin. Exposure of human red blood cells to asbestos fibers also caused progressive cell injury and lysis. Quercetin and rutin protected the red cells (quercetin > rutin), whereas dihydroquercetin was ineffective in preventing asbestos-induced hemolysis. The protective ability of quercetin and rutin may be related to their iron-chelating activity. Due to this these flavonoids can be located on asbestos surface in sites of initiation of free radical reactions and their antiradical moieties can scavenge reactive oxygen species immediately after the appearance. Thus, both antiradical and chelating effects appear to be involved in the flavonoid protection against silica-induced cell injury.

Expression of beta-defensin genes in bovine alveolar macrophages

Bovine alveolar macrophages (BAM) were examined for the expression of beta-defensins and to determine whether their expression could be upregulated by bacterial lipopolysaccharide (LPS), as observed with beta-defensins expressed in bovine tracheal epithelial cells. Four beta-defensins were expressed constitutively in BAM, with bovine neutrophil beta-defensin (BNBD)-4 and BNBD-5 being the most predominant. This is the first evidence of beta-defensin gene expression in a mature myeloid cell. LPS had no effect on beta-defensin expression in BAM, even though tumor necrosis factor alpha (TNF-alpha) production was induced. Nonbacterial inflammatory particles had little effect on beta-defensin gene expression or TNF-alpha production in BAM. We hypothesize that constitutively expressed beta-defensins of alveolar macrophages may have a role in lung host defense.

Diesel exhaust particles induced release of interleukin 6 and 8 by (primed) human bronchial epithelial cells (BEAS 2B) in vitro

Several epidemiological studies have recently shown associations of increased premature mortality rates with ambient particulate air pollution. Diesel exhaust particles (DEP) may constitute an important part of (ultra)fine particulate air pollution in urban areas and may therefore contribute to its toxicity. Epithelial lining of the respiratory tract may be the first target of the toxic effects of DEP, that upon exposure may release pro-inflammatory mediators such as interleukin 6 and 8 (IL-6, IL-8), ultimately causing airway tissue damage and immune alterations. In this study the effects of in vitro DEP exposure (0.04-0.33 mg/mL) on IL-6, IL-8 production by a human bronchial epithelial cell line (BEAS-2B) were investigated. For comparison, the production of interleukins during exposure to silica and titanium oxide (TiO2) were also studied, representing relatively toxic and non-toxic particles, respectively. Scanning and transmission electron microscopy showed that the size of the DEP particles ranged between 25 to 35 nm and that DEP was phagocytized by BEAS-2B cells. An increase in IL-6 and IL-8 production (11- and 4-fold, respectively) was found after 24 or 48 h of exposure to DEP compared to the non-exposed cells. This increase was lower compared to silica (17- and 3.3-fold) and higher as compared to TiO2 which showed no increase for IL-6 and IL-8. To study the DEP effect on inflammation-primed cells, BEAS-2B cells were exposed to both tumor necrosis factor-alpha (TNF-alpha) and subsequently to DEP. Exposure to TNF-alpha caused a strong increase in IL-6 and IL-8 production. Additive effects on the IL-6 and IL-8 production by BEAS-2B cells were found after TNF-alpha priming and subsequently exposure to DEP, only at a low dose of DEP and TNF-alpha (0.05-0.2 ng/mL). In conclusion, BEAS-2B phagocytized DEP and produced an increased amount of IL-6 and IL-8. In TNF-alpha primed BEAS-2B cells, DEP increased interleukin production only at low concentrations of DEP and TNF-alpha. Whether this increased production of pro-inflammatory interleukins affects vulnerable balances in the immune system, such as T help-1 and T help-2 subsets ratios, resulting in an altered resistance to respiratory tract infections or altering the expression of respiratory allergy, is the subject of further studies.

Evidence that exposure of particulate air pollutants to human and rat alveolar macrophages leads to differential oxidative response

Macrophages and inflammatory cells generate active oxygen species in the process of killing and degrading microorganisms. Air pollutant particles may be ingested by macrophages and stimulate the same mechanisms to produce a long term oxidative burden to the lung if particles are not degraded. In the present study human and rat alveolar macrophages (AM) were compared in their response to inhaled particles using luminol dependent chemiluminescence (CL) and peroxide dependent CL assays. Cytotoxicity was measured by the release of lactate dehydrogenase (LDH) activity in the supernatant. Human AM produced more oxidants than rat AM whether, unstimulated, after addition of particles or addition of particles then peroxidase. Human AM also had a different spectrum of response to the same particles. Our results suggest that human macrophages produce more reactive oxygen species in respond to particles than rat AM.

Chrysotile asbestos and H2O2 increase permeability of alveolar epithelium

The alveolar epithelium contains tight junctions and provides a barrier to passage of potentially injurious substances into the pulmonary interstitium. Alveolar epithelial injury is hypothesized to be an important early event in the pathogenesis of asbestosis. Mechanisms that may contribute to alveolar epithelial cell injury following asbestos exposure include the physicochemical interactions between asbestos fibers and cells, and the generation of reactive oxygen species such as hydrogen peroxide (H2O2). The present study examined changes in transepithelial resistance (Rt) (a measure of barrier function) and permeability of alveolar epithelium after chrysotile asbestos and H2O2 exposure. Alveolar epithelial cell monolayers, obtained from isolation of rat alveolar type II cells and grown on porous supports, were exposed to chrysotile asbestos or polystyrene beads (control) at concentrations of 5, 10, and 25 micrograms/cm2 for 24 h. In separate experiments, monolayers were exposed to H2O2 at concentrations of 50, 75, and 100 microM for 1 h Rt was measured using a voltohmmeter. Prior to treatment, monolayers had a high Rt (> 2000 ohms.cm2). Permeability was assessed by measuring flux of [3H]sucrose from apical to basolateral compartments. Cytotoxicity was evaluated by lactate dehydrogenase (LDH) and preincorporated [14C]adenine release. The morphological integrity of the monolayers was evaluated by scanning electron microscopy. Chrysotile asbestos and H2O2 exposure resulted in dose-dependent decrease in alveolar epithelial Rt and increases in permeability under conditions that did not result in over cytotoxicity. These results demonstrate that both chrysotile asbestos and H2O2 have effects on alveolar epithelial Rt and permeability and suggest a potential role for the alveolar epithelium in mediation of asbestos-induced pulmonary interstitial disease.

Inflammatory and fibrotic mediator release by alveolar macrophages from coal miners

Eicosanoids and cytokines produced by alveolar macrophages (AM) are key mediators of pulmonary inflammation and fibrosis. In order to determine if eicosanoid production and cytokine production are altered in AM obtained from coal miners, we compared production of prostaglandin E2 (PGE2), thromboxane A2 (TXA2), leukotriene B4 (LTB4), interleukin-1 beta (IL-1 beta), and tumor necrosis factor alpha (TNF alpha) by cultured AM from normal human subjects and coal miners. The recovery of AM from miners' lungs by bronchoalveolar lavage was significantly greater than that from control subjects. Mean eicosanoid and cytokine production by AM from active miners was also increased compared to AM from control subjects, but this increase was not statistically significant. AM from control subjects produced significantly more TXA2 and TNF alpha when exposed to lipopolysaccharide than did AM from miners. The cyclooxygenase inhibitor suprofen reduced PGF2 and TXA2 production and TNF alpha release but had no effect on LTB4 production of IL-1 beta release by miners' AM. The lipoxygenase inhibitor nordihydroguaiaretic acid attenuated TNF alpha release, as well as that of LTB4, but had no effect on IL-1 beta release. Inhibition of thromboxane synthase by UK 38,485 also reduced TNF alpha release by active miners' AM but had no effect on PGE2, LTB4 production, or IL-1 beta release. The results of these studies suggest that occupational inhalation of coal dust may increase total lung eicosanoid and cytokine levels and reduce the reactivity of AM to bacterial endotoxin. Furthermore, coal dust-induced changes in both eicosanoid and cytokine release may be subject to pharmacological modulation.

Correlation between inflammatory cellular responses and chemotactic activity in bronchoalveolar lavage fluid following intratracheal instillation of nickel sulfate in rats

In a preceding study, we reported that the numbers of macrophages and polymorphonuclear leukocytes (PMN) were increased in bronchoalveolar lavage fluid (BALF) following the intratracheal instillation of nickel sulfate (NiSO4) in rats. In the present study, BALF chemotactic activities for both macrophages and PMN were measured to investigate if the increases of these inflammatory cells in BALF depend on increases in chemotactic activities in epithelial lining fluid (ELF) of the lung. Both the number of PMN and the PMN chemotactic activity peaked at 2 days post-instillation and they were significantly correlated. However, the PMN chemotactic activity was inversely correlated with concentration of leukotriene B4 (LTB4), a well-known chemotaxin. Although PMN were not observed in control BALF, LTB4 concentration in the control ELF (ca. 5 x 10(-7) M) was estimated to have a potential to attract PMN chemotactically through a membrane in in vitro migration assay. These results suggest that the presence of LTB4 in ELF itself does not trigger transpulmonary PMN infiltration. The rat BALF were fractionated by high performance liquid chromatography (HPLC), and PMN chemotactic activity of each fraction was measured. The elution profiles of PMN chemotactic activity showed that there were at least two different chemotaxins in BALF obtained from the NiSO4-exposed rats. Macrophage chemotactic activity in BALF also peaked at 2 days post-instillation. However, the number of macrophages was not significantly correlated with the chemotactic activity for macrophage in BALF.(ABSTRACT TRUNCATED AT 250 WORDS)

Oxidative stress in vivo and in vitro: modulation by quartz dust and hyperbaric atmosphere

Changes in the oxidative status in the soluble proteins of bronchoalveolar lavage (BAL) fluid from monkeys were examined during 26 months of individual or combined exposure to quartz dust (5 mg/m3 of DQ12) and a hyperbaric atmosphere (2.5 bar). The oxidation of BAL proteins, assumed to be an indicator for oxidative stress in the lungs, was determined by measuring the amount of carbonyl groups in their amino acid side chains. The carbonyl content of BAL proteins (nmol carbonyl/mg protein) increased steadily to a maximum value of 156% of the control after 6 months exposure to hyperbaric atmosphere, and decreased below 50% of control levels in both the quartz alone exposed group and the group exposed to quartz in combination with a hyperbaric atmosphere. The effect of quartz on the production of reactive oxygen species by BAL cells was investigated in vitro. BAL cells from healthy monkeys preincubated with quartz and stimulated with phorbol-myristate acetate (PMA) produced reduced levels of extracellular superoxide anion and intracellular hydrogen peroxide compared with PMA-only stimulated cells. Thus the lowered carbonyl content of BAL proteins in the quartz exposed groups may have resulted from reduced production of the hydrogen peroxide which is essential for carbonyl formation by phagocytes. Changes in carbonyl content of BAL protein in vivo may be a new indicator for potential subsequent lung damage.

The role of free radicals in asbestos-induced diseases

Asbestos exposure causes pulmonary fibrosis and malignant neoplasms by mechanisms that remain uncertain. In this review, we explore the evidence supporting the hypothesis that free radicals and other reactive oxygen species (ROS) are an important mechanism by which asbestos mediates tissue damage. There appears to be at least two principal mechanisms by which asbestos can induce ROS production; one operates in cell-free systems and the other involves mediation by phagocytic cells. Asbestos and other synthetic mineral fibers can generate free radicals in cell-free systems containing atmospheric oxygen. In particular, the hydroxyl radical often appears to be involved, and the iron content of the fibers has an important role in the generation of this reactive radical. However, asbestos also appears to catalyze electron transfer reactions that do not require iron. Iron chelators either inhibit or augment asbestos-catalyzed generation of the hydroxyl radical and/or pathological changes, depending on the chelator and the nature of the asbestos sample used. The second principal mechanism for asbestos-induced ROS generation involves the activation of phagocytic cells. A variety of mineral fibers have been shown to augment the release of reactive oxygen intermediates from phagocytic cells such as neutrophils and alveolar macrophages. The molecular mechanisms involved are unclear but may involve incomplete phagocytosis with subsequent oxidant release, stimulation of the phospholipase C pathway, and/or IgG-fragment receptor activation. Reactive oxygen species are important mediators of asbestos-induced toxicity to a number of pulmonary cells including alveolar macrophages, epithelial cells, mesothelial cells, and endothelial cells. Reactive oxygen species may contribute to the well-known synergistic effects of asbestos and cigarette smoke on the lung, and the reasons for this synergy are discussed. We conclude that there is strong evidence supporting the premise that reactive oxygen species and/or free radicals contribute to asbestos-induced and cigarette smoke/asbestos-induced lung injury and that strategies aimed at reducing the oxidant stress on pulmonary cells may attenuate the deleterious effects of asbestos.

Glutathione release by pulmonary alveolar macrophages in response to particles in vitro

We studied whether cultured rat pulmonary alveolar macrophages (PAM) could release glutathione (GSH) in response to latex beads, quartz, and crocidolite asbestos. PAM were exposed for 2 h to 0-100 micrograms of particles per 1 x 10(6) cells. Both quartz and asbestos produced concentration-dependent increases (up to 8-10-fold) in the amount of GSH recovered in the medium and decreases in the cellular GSH levels. In contrast, latex beads did not produce any changes in GSH levels. We also measured lactate dehydrogenase (LDH) levels as an index of toxicity. Only quartz and asbestos were able to produce increases in LDH levels in the medium. The release of GSH occurred at particle concentrations that did not cause release of LDH. Our results indicated that, in vitro, PAM release GSH in response to toxic particles.

Observations on the carcinogenicity of asbestos fibers

This paper summarizes animal experiments and in vitro data carried out to study the oncogenic effects of asbestos fibers on mesothelial cells. An interpretation of the results is made in light of current statements on the carcinogenicity of asbestos fibers. Experimental results appear to show that the carcinogenicity of mineral fibers is a complex, multiparametric phenomenon. Chromosomal mutations and possibly oxygen derivatives are involved in the genesis of the fiber-induced neoplastic process and may be the result of the intrinsic fiber properties, size, and physicochemistry. The role of fiber solubility is discussed; it is suggested that additional experiments are necessary for a better understanding of the importance of solubility in the concept of biopersistence.

Interferon-gamma and immunoglobulin enhance mineral dust-induced production of reactive oxygen metabolites by human macrophages

The modulating effect of interferon-gamma (IFN-gamma) and polyclonal immunoglobulin (poly-Ig) on mineral dust-induced production of reactive oxygen metabolites (ROM) by human monocyte-derived macrophages was investigated using lucigenin-dependent chemiluminescence. Activation of the cell cultures with IFN-gamma enhanced the subsequent quartz- and asbestos-induced production of ROM, while the addition of poly-Ig only stimulated chrysotile asbestos-induced ROM production. The combination of IFN activation and the addition of poly-Ig to the reactions caused a 20-fold enhancement of the responses to chrysotile. As increased levels of IFN-gamma and immunoglobulins have been observed in patients with mineral dust-induced diseases, we suggest that "immunological activation" caused by, for example, autoimmune diseases or recurrent pulmonary infections might amplify the production of potentially tissue-injuring ROM by mononuclear phagocytes and may possibly determine the individual susceptibility to mineral dust-related disorders.

Enhanced lipid peroxidation in lung lavage of rats after inhalation of asbestos

Exposure of phagocytic cells to asbestos in vitro results in an augmented production of reactive oxygen metabolites and increased peroxidation of lipids. The aim of this investigation was to assess the extent of lipid peroxidation both in cells and fluid obtained from bronchoalveolar lavage (BAL), and in lungs of rats exposed to crocidolite asbestos or titanium dioxide (TiO2), a nonfibrous particulate control. In comparison to sham and TiO2-exposed rats, the BAL fluid and cells of crocidolite-exposed animals contained significantly elevated levels of malondialdehyde (MDA), a breakdown product of lipid peroxidation detected using high-pressure liquid chromatography (HPLC). In contrast, no significant differences in MDA were detected in lavaged lung tissue from these animals. Inhalation of crocidolite caused an early inflammatory response characterized by elevated numbers of polymorphonuclear leukocytes and lymphocytes, as well as enhanced total protein in BAL. Pulmonary fibrosis and increased lung hydroxyproline also were observed after 20 days of exposure. Exposure to TiO2 did not cause inflammation, pulmonary fibrosis, or elevated amounts of hydroxyproline in the lung. Our results show that exposure to the fibrogenic and inflammatory mineral, crocidolite, results in an enhanced lipid peroxidation in BAL cells and fluid not observed after inhalation of the particulate TiO2. These novel observations suggest that MDA in BAL may be useful as a biomarker of exposure to inhaled asbestos or other oxidants.

Effect of immunoglobulins on mineral dust-induced production of reactive oxygen metabolites by human macrophages

Mineral dust-induced production of reactive oxygen metabolites (ROMs) by human monocyte-derived macrophages was investigated using lucigenin-dependent chemiluminescence. Chrysotile asbestos alone caused only weak ROM production by macrophages, but the addition of polyclonal immunoglobulin enhanced the reaction strongly. The phenomenon was seen with 1-, 4-, and 7-day-old cell cultures. Polyclonal immunoglobulin also slightly enhanced the ROM responses induced by amosite, crocidolite, and quartz dust. The enhancing effect could be achieved with several monoclonal immunoglobulins (isolated from the sera of myeloma patients), but IgA and IgG had the strongest effects. We suggest that immunoglobulins may interact with mineral dusts in a "nonimmunological," antigen-independent way and that the so-formed dust-immunoglobulin complexes may amplify the production of ROMs by inflammatory cells. This may explain a number of in vivo phenomena in which immune responses (for instance hypergammaglobulinemia and the presence of autoantibodies) have been shown to relate to the progression of mineral dust-induced pulmonary disease.

Quartz-induced production of reactive oxygen metabolites by activated human monocyte-derived macrophages

Quartz but not titanium dioxide (TiO2) induced the production of reactive oxygen metabolites (ROM) by human monocyte-derived macrophages, as measured by lucigenin dependent chemiluminescence. Activation of the macrophages with BCG, bacterial lipopolysaccharide and macrophage-activating factor (MAF) caused a prominent increase of quartz-induced ROM production, MAF having the strongest effect. The activation did not affect the TiO2 responses to the same extent. Assuming that ROM have a role in the pathogenesis of silica-induced disease in man, we suggest that enhancement of quartz-induced production of ROM by activated pulmonary macrophages may at least partly explain the experimental and epidemiological data indicating that activation of the immune system during infection promotes the development of silicosis.

Brief inhalation of asbestos compromises superoxide production in cells from bronchoalveolar lavage

Production of superoxide (O-.2) was measured in alveolar macrophages (AM) exposed to asbestos in vitro and in cells obtained from bronchoalveolar lavage (BAL) of rats inhaling asbestos. Steady state levels of O-.2 released by AM in vitro were dose and time dependent in response to crocidolite, chrysotile, and opsonized zymosan, a particulate used to trigger O-.2 generation. In contrast, an inhalation exposure for 1 h to crocidolite or for 6 days to either crocidolite or chrysotile asbestos resulted in a decreased production of O-.2 by BAL cells. Likewise, BAL cells from rats inhaling chrysotile for 1 h or crocidolite for 9 days exhibited a diminished capacity to secrete O-.2 when challenged with the particulate opsonized zymosan. Diminished generation of O-.2 by asbestos occurred in BAL cell populations containing either significantly increased numbers of polymorphonuclear leukocytes and lymphocytes (6- and 9-day exposures) or 99% AM (1-h exposure). Thus, these novel observations suggest that short-term inhalation of asbestos compromises the ability of BAL cells to produce O-.2 in the presence or absence of an additional phagocytic stimulus.

Toxicity of cadmium oxide instilled into the rat lung. II. Inflammatory responses in broncho-alveolar lavage fluid

Biochemical and cytological responses in the broncho-alveolar lavage fluid were investigated after instillation of cadmium oxide (CdO) or cadmium chloride (CdCl2) into the rat lung. Although biochemical responses of the lung to CdO were similar to the CdCl2-exposed lung, cytological response was more sensitive to CdO than CdCl2. Increases of lactate dehydrogenase, protein content and number of cells in the lavage fluid were proportional to the dose over the range of 0.5-10 micrograms Cd/rat. beta-Glucuronidase activity in the fluid increased with dose at low doses of Cd, but the activity did not continue to increase above 2 micrograms Cd/rat. A dose-response profile of phosphorus content in the lavage fluid, which might indicate amount of surfactant produced by Type II cells was similar to that observed for beta-glucuronidase in CdO-treated rats. Thus, tolerable level of instilled CdO for the rat lung was about 2 micrograms Cd/rat.

Functional and biochemical effects on rat lung following instillation of crocidolite and chrysotile asbestos

Groups of rats received a single intratracheal instillation of saline (control), 1.6 mg crocidolite, and 1.6 mg chrysotile. At 1, 3, 6, 9, and 12 mo after instillation, respiratory functional tests were performed and the lungs were biochemically analyzed. Throughout 12 mo, obstructive small-airway abnormalities with air trapping were observed in the asbestos-treated rats. The degree of airway obstruction and air trapping was higher in the chrysotile-treated group than in the crocidolite-treated group. Lung weight increased significantly in both asbestos-treated groups. Collagen and elastin content of unit lung weight significantly increased in the chrysotile-treated group compared with the control and crocidolite-treated group throughout the experimental period up to 12 mo. However, the collagen and elastin content of unit lung weight in the crocidolite-treated group was not as different from the control group. These results indicate that chrysotile is more fibrogenic than crocidolite, as has been suggested in histopathological studies.

Chromosomal changes induced by chrysotile fibres or benzo-3,4-pyrene in rat pleural mesothelial cells

The induction of chromosomal aberrations in rat pleural mesothelial cells (RPMC) following in vitro treatment with chrysotile fibres has been demonstrated. The production of chromosomal aberrations was also observed after treatment of the cells with benzo-3,4-pyrene (BP). The yield of abnormal metaphases was dose-dependent and reached 58% at a BP dose of 2 micrograms/ml. Chrysotile fibres at 7 micrograms/ml induced 21% abnormal metaphases and the frequency decreased with further increases in fibre concentration. Their decline is possibly related to a lethal effect. Chrysotile-induced chromosomal aberrations were primarily of the chromatid type and included breaks and fragments. BP induced chromosome exchanges which were not seen following chrysotile treatment. Minutes and double minutes were detected in BP-treated RPMC and occasionally found after chrysotile application. These results confirm that chrysotile fibres are clastogenic for some cultured cells and demonstrate that the fibres induce chromosome damage in target RPMC.

Inert particles inhibit natural killer cell function in vitro

Aqueous suspensions of inert particles were found to inhibit the baseline and interferon-enhanced natural killer (NK) cell activity of peripheral blood mononuclear cells (PBMC) and large granular lymphocytes (LGLs). This inhibition was induced with latex, silica, and Sephadex particles. The suppression of NK activity was not related to effector cell death as determined by trypan blue exclusion. The inhibition of NK cell function was more pronounced with prolonged incubation and could be partially reversed with monocyte depletion or the addition of indomethacin, a prostaglandin synthesis inhibitor, but not with the addition of the lipoxygenase inhibitors nordihydroguaiaretic acid and BW755C. Similarly, particle exposure inhibited the NK cell function of monocyte-depleted large granular lymphocytes with and without the add-back of glass adherent cells, implying that monocyte-independent NK suppressive mechanisms were also present. These data demonstrate that inert particles are immunosuppressive in vitro and can inhibit baseline and interferon-stimulated NK cell function of LGLs and PBMC through monocyte-dependent and independent pathways.

Measurement of beta-glucuronidase in effluent of perifused alveolar macrophages challenged with chemically modified chrysotile asbestos

Chrysotile asbestos has been implicated with lung disorders, notably fibrotic lesions and cancer. In vitro, chrysotile fibers are cytotoxic to lung macrophages and stimulate the release of inflammatory mediators. Reports to the effect that chemical modifications of asbestos fibers reduce their cytotoxic and inflammatory potential initiated the present study of three fiber modifications. The cytotoxic and inflammatory effects of magnesium-leached chrysotile, POCL3-treated chrysotile, and CaO-treated chrysotile were studied in a perifused rat alveolar macrophage culture system, relative to untreated fibers. Natural Canadian chrysotile (UICC "B") caused dose-dependent cell mortality and clumping. The release of beta-glucuronidase (beta-Glu), a lysosomal enzyme, was also dose dependent. Rhodesian chrysotile (UICC "A") caused similar cytotoxic and inflammatory effects. However, magnesium-leached chrysotile was less cytotoxic (39% less) and had a lesser clumping capacity (31% less) than untreated chrysotile. Total secretion of beta-Glu elicited by magnesium-leached chrysotile was reduced by 43% from the untreated sample, but kinetic monitoring indicates that this reduction in inflammatory potential is only significant during the first 12 h of an 18-h culture period. POCl3 treatment of chrysotile fibers produced differing effects depending on the length of the fibers under study. Treating fibers with a mean length of 8 micron produced a secretion pattern similar to that produced by acid leaching. The total output for the treated sample was 44% lower than with untreated chrysotile; the difference was only significant during the first 12 h of perifusion. Cell mortality and aggregation were not reduced in any important way with POCl3 treatment of these longer fibers. When ultra-short fibers (mean length = 0.8 micron) were treated with POCl3, the total decrease in beta-Glu output was equal to 41%, and the release of enzyme was significantly lower during the whole 18-h experiment. Cell aggregation was not appreciably affected, but cell mortality was significantly lower than for untreated fibers. CaO treatment did not alter the cytotoxic (cell death and aggregation) or inflammatory (beta-Glu release) effects of chrysotile asbestos. These results suggest that chemical modifications affecting the integrity of the surface magnesium and/or the polarity of the surface charge of chrysotile can reduce to some extent the cytotoxic and inflammatory properties of this type of asbestos.

Role of oxygen radicals in tumor promotion

Tumor promoters provoke the elaboration of oxygen radicals by direct chemical generation and through the indirect activation or alteration of cellular sources including membrane oxidases, peroxisomes, and electron transport chains in mitochondria and endoplasmic reticulum. Although direct measurement of amplified oxygen radical production in response to tumor promoters in target tissues remains problematic, studies with scavengers of reactive oxygen species demonstrate inhibition of biochemical and biological sequelae of tumor promoter exposure and provide strong presumptive evidence for oxygen radical involvement in this late stage of carcinogenesis. The critical macromolecular targets for these oxygen radicals remain undefined; however, they may include lipids, DNA, DNA repair systems, and other enzymes.

Functional and biochemical indicators of pneumoconiosis in mice: comparison with rats

Mice were injected intratracheally with silica or Mt. St. Helens volcanic ash (0.2 mg/g body weight) and examined 6 mo later for changes in pulmonary function, histology, and hydroxyproline content. Results were compared with a similar study using rats. Mice injected with volcanic ash showed significant changes only in wet lung weights. Those injected with silica showed an approximate doubling of lung wet weight and dry weight and hydroxyproline content. Larger increases in lung weight were seen if lymph nodes were left attached. Lung compliance, total lung capacity, and the shape of the pressure-volume curve of the lung were changed as much as 22% in the silica-treated mice. A mild degree of fibrosis with no dense lung consolidation was noted microscopically in silica-treated mice. In contrast, silica-treated rats showed dense lung consolidation, threefold to fivefold increases in both wet and dry lung weights and hydroxyproline content, and up to 40% reductions in pulmonary function measurements. It is concluded that Swiss albino mice develop a milder degree of fibrosis than similarly treated Sprague-Dawley rats and that both biochemical and functional indicators are effective in detecting pneumoconiosis in these species.

Dietary carcinogens and anticarcinogens. Oxygen radicals and degenerative diseases

The human diet contains a great variety of natural mutagens and carcinogens, as well as many natural antimutagens and anticarcinogens. Many of these mutagens and carcinogens may act through the generation of oxygen radicals. Oxygen radicals may also play a major role as endogenous initiators of degenerative processes, such as DNA damage and mutation (and promotion), that may be related to cancer, heart disease, and aging. Dietary intake of natural antioxidants could be an important aspect of the body's defense mechanism against these agents. Many antioxidants are being identified as anticarcinogens. Characterizing and optimizing such defense systems may be an important part of a strategy of minimizing cancer and other age-related diseases.

An overload hypothesis for pulmonary clearance of UICC amosite fibres inhaled by rats

Two types of experiments were carried out to examine the effects of deposition and clearance on the accumulation in the lungs of rats of inhaled fibres of UICC amosite. In the first experiment the mass lung burdens of the dust in question were measured as a function of the time at which animals were killed after the cessation of the six week exposure period, and in the second the masses were measured for rats removed from exposure and killed at intervals during the exposure period itself. The experimental conditions were chosen to complement those of earlier work. Taken together with the results of that earlier work, the new results provide the basis for a simple mathematical model of the kinetics of deposition and clearance which appears to account for the major observed trends. Most significantly, there is strong evidence for an overload of clearance at high lung burdens (exceeding about 1500 micrograms/rat), in which a breakdown occurs of the intermediate rate clearance mechanisms (time constants of the order of 12 days). This hypothesis is supported for inhaled asbestos dust, quartz dust, and diesel fume by results obtained elsewhere. Biological explanations for the clearance overload hypothesis are at present speculative, involving discussion of the role of the macrophage in pulmonary clearance. It is believed that the clearance overload hypothesis could have possible consequences for people occupationally exposed to airborne dusts.

Chemiluminescence response of equine alveolar macrophages during stimulation with latex beads, or IgG-opsonized sheep red blood cells

Isolated equine alveolar macrophages were shown to generate a luminol-dependent light response when challenged with a phagocytic stimulus. The chemiluminescent response was not detected with luminol prepared at 1.0 x 10(-5) or 1.0 x 10(-4) molar concentrations, but was readily quantitated when used at a 1.0 x 10(-3) molar concentration. Challenge of the alveolar macrophages with latex particles or with equine IgG-coated sheep red blood cells elicited the luminol-dependent light response, whereas unchallenged equine alveolar macrophages or those challenged with unopsonized erythrocytes failed to emit light above background levels. Latex-bead-challenged macrophages released 8.06 times the total amount of light as those equine alveolar macrophages challenged with equine IgG-opsonized erythrocytes. This study represents the first investigation on chemiluminescence and equine alveolar macrophages.

Asbestos-induced alterations of human lymphoid cell mitogenic responses

Using mitogenic assays, we have investigated the short term effects of two asbestos (amosite and chrysotile) fibers on lymphocyte functions in vitro. These oppositely charged fibers produced different alterations in mitogenesis. The blastogenic responses of concanavalin-A (Con-A) and pokeweed mitogen stimulated human peripheral blood mononuclear cells (PBMN) were significantly increased by the inclusion of 6 micrograms of chrysotile to the culture media. Amosite fibers proved to be inhibitory in all tests. When PBMN were depleted of monocytes, asbestos-related alterations of Con-A responsiveness were unchanged among the remaining cells. However, the addition of chrysotile to phytohemagglutinin (PHA) cultures resulted in a significant increase of the mitogenic response. When PBMN were enriched for T lymphocytes, and again cultured with the mitogens and fibers, the Con-A response still displayed impressive enhancement with chrysotile. In contrast to an intact PBMN population, PHA-induced blastogenesis among these T-enriched lymphocytes was significantly elevated. These experiments demonstrate that asbestos can induce significant changes in the functional integrity of PBMN following a relatively short exposure time in culture.

The effect of stannous and stannic (tin) chloride on DNA in Chinese hamster ovary cells

Tin(II) at concentrations up to 500 microM stannous chloride (SnCl2), produced extensive DNA damage, as detected by alkaline sucrose gradient (ASG) analysis in Chinese hamster ovary (CHO) cells treated for 1 h at 37 degrees C in serum-free minimal essential medium (MEM). However treatment of cells with tin(IV), as stannic chloride (SnCl4), produced no such DNA damage. There was no loss in colony formation 6 days after either treatment suggesting that the DNA damage induced by the tin(II) was rapidly repaired and/or that DNA synthesis proceeded on the damaged templates permitting cell division to occur. Alternatively, the type of DNA damage caused by tin(II) may not lead to a reduction in colony-forming ability. Tin(II) produced about 200 times more ASG detectable DNA damage on an equi-molar basis than did Cr(VI), a known human carcinogen. This study indicates that tin(II) may be potentially genotoxic.