Mitochondrial oxidant production by a pollutant dust and NO-mediated apoptosis in human alveolar macrophage

Decreased immune response in undernourished rats after air pollution exposure

Children are highly vulnerable subpopulation to malnutrition and air pollution. We investigate, in a rat nutritional growth retardation (NGR) model, the impact of Residual Oil Fly Ash (ROFA) on the lung immune response using in vitro and ex vivo methods. In vitro: Alveolar macrophages (AM) were isolated from Control (C) and NGR animals, cultured and treated with ROFA (1-100 µg/ml) for 24 h. Ex vivo: C and NGR rats were intranasally instilled with ROFA (1 mg/kg BW) or PBS. 24 h post-exposure AM were isolated and cultured. ROFA-treatment increased superoxide anion production and TNFα secretion in C-AM in vitro, though for NGR-AM this response was lower. A similar pattern was observed for TNFα and IL-6 secretion in ex vivo experiments. Regarding the antioxidant response, although NGR-AM showed increased Nrf2, after ROFA instillation an attenuated activation was observed. To conclude, chronic undernutrition altered AM response to ROFA affecting immune responsiveness to air pollutants.

Nitric Oxide Circumvents Virus-Mediated Metabolic Regulation during Human Cytomegalovirus Infection

Nitric oxide is a versatile and critical effector molecule that can modulate many cellular functions. Although recognized as a regulator of infections, the inhibitory mechanism of nitric oxide against human cytomegalovirus (HCMV) replication remains elusive. We demonstrate that nitric oxide attenuates viral replication by interfering with HCMV-mediated modulation of several cellular processes. Nitric oxide exposure reduced HCMV genome synthesis and infectious viral progeny with cell-type-dependent differences observed. Mitochondrial respiration was severely reduced in both uninfected and HCMV-infected cells during exposure with little impact on ATP levels indicating changes in cellular metabolism. Metabolomics identified significantly altered small molecules in multiple pathways during nitric oxide exposure including nucleotide biosynthesis, tricarboxylic acid (TCA) cycle, and glutamine metabolism. Glutathione metabolites were increased coinciding with a reduction in the glutathione precursor glutamine. This shift was accompanied by increased antioxidant enzymes. Glutamine deprivation mimicked defects in HCMV replication and mitochondrial respiration observed during nitric oxide exposure. These data suggest that nitric oxide limits glutaminolysis by shuttling glutamine to glutathione synthesis. In addition, lipid intermediates were severely altered, which likely contributes to the observed increase in defective viral particles. Nitric oxide disrupts multiple cellular processes, and we had limited success in rescuing replication defects by supplementing with metabolic intermediates. Our studies indicate that nitric oxide attenuation of HCMV is multifactorial with interference in viral manipulation of cellular metabolism playing a central role.IMPORTANCE Human cytomegalovirus is a prevalent pathogen that can cause serious disease in patients with compromised immune systems, including transplant patients and during congenital infection. HCMV lytic replication likely occurs in localized sites of infection with immune cells infiltrating and releasing nitric oxide with other effector molecules. This nonspecific immune response results in both uninfected and infected cells exposed to high levels of nitric oxide. The absence of nitric oxide synthase has been associated with lethal HCMV infection. We demonstrate that nitric oxide inhibition of HCMV replication is multifactorial and cell type dependent. Our results indicate that nitric oxide controls replication by interfering with viral modulation of cellular metabolism while also affecting proliferation and mitochondrial respiration of neighboring uninfected cells. These studies identify the mechanism and contribution of nitric oxide during immune control of HCMV infection and provide insight into its role in other viral infections.

Impaired mitochondrial function of alveolar macrophages in carbon nanotube-induced chronic pulmonary granulomatous disease

Human exposure to carbon nanotubes (CNT) has been associated with the development of pulmonary sarcoid-like granulomatous disease. Our previous studies demonstrated that multi-walled carbon nanotubes (MWCNT) induced chronic pulmonary granulomatous inflammation in mice. Granuloma formation was accompanied by decreased peroxisome proliferator-activated receptor gamma (PPARγ) and disrupted intracellular lipid homeostasis in alveolar macrophages. Others have shown that PPARγ activation increases mitochondrial fatty acid oxidation (FAO) to reduce free fatty acid accumulation. Hence, we hypothesized that the disrupted lipid metabolism suppresses mitochondrial FAO. To test our hypothesis, C57BL/6 J mice were instilled by an oropharyngeal route with 100 μg MWCNT freshly suspended in 35 % Infasurf. Control sham mice received vehicle alone. Sixty days following instillation, mitochondrial FAO was measured in permeabilized bronchoalveolar lavage (BAL) cells. MWCNT instillation reduced the mitochondrial oxygen consumption rate of BAL cells in the presence of palmitoyl-carnitine as mitochondrial fuel. MWCNT also reduced mRNA expression of mitochondrial genes regulating FAO, carnitine palmitoyl transferase-1 (CPT1), carnitine palmitoyl transferase-2 (CPT2), hydroxyacyl-CoA dehydrogenase subunit beta (HADHB), and PPARγ coactivator 1 alpha (PPARGC1A). Importantly, both oxidative stress and apoptosis in alveolar macrophages and lung tissues of MWCNT-instilled mice were increased. Because macrophage PPARγ expression has been reported to be controlled by miR-27b which is known to induce oxidative stress and apoptosis, we measured the expression of miR-27b. Results indicated elevated levels in alveolar macrophages from MWCNT-instilled mice compared to controls. Given that inhibition of FAO and apoptosis are linked to M1 and M2 macrophage activation, respectively, the expression of both M1 and M2 key indicator genes were measured. Interestingly, results showed that both M1 and M2 phenotypes of alveolar macrophages were activated in MWCNT-instilled mice. In conclusion, alveolar macrophages of MWCNT-instilled mice had increased miR-27b expression, which may reduce the expression of PPARγ resulting in attenuation of FAO. This reduction in FAO may lead to activation of M1 macrophages. The upregulation of miR-27b may also induce apoptosis, which in turn can cause M2 activation of alveolar macrophages. These observations indicate a possible role of miR-27b in impaired mitochondrial function in the chronic activation of alveolar macrophages by MWCNT and the development of chronic pulmonary granulomatous inflammation.

Oleic acid and derivatives affect human endothelial cell mitochondrial function and vasoactive mediator production

BACKGROUND

Inhalation of common air pollutants such as diesel and biodiesel combustion products can induce vascular changes in humans which may contribute to increased mortality and morbidity associated with fine particulate matter exposures. Diesel, biodiesel, and other combustion byproducts contain fatty acid components capable of entering the body through particulate matter inhalation. Fatty acids can also be endogenously released into circulation following a systemic stress response to some inhaled pollutants such as ozone. When in the circulation, bioactive fatty acids may interact with cells lining the blood vessels, potentially inducing endothelial dysfunction. To examine whether fatty acids could potentially be involved in human vascular responses to air pollutants, we determined the effects of fatty acids and derivatives on important vascular cell functions.

METHODS

Human umbilical vein endothelial cells (HUVEC) were exposed in vitro to oleic acid (OA) or OA metabolites for 4-48 h. Cytotoxicity, vasodilator production (by ELISA measurement), mitochondrial function (using Sea Horse assays), and iron metabolism (inferred by ICP-OES measurements) were examined, with standard statistical testing (ANOVA, t-tests) employed.

RESULTS

Dose-dependent cytotoxicity was noted at 24 h, with 12-hydroxy OA more potent than OA. Mitochondrial stress testing showed that 12-hydroxy OA and OA induce mitochondrial dysfunction. Analysis of soluble mediator release from HUVEC showed a dose-dependent increase in prostaglandin F2α, a lipid involved in control of vascular tone, at 24 h (85% above controls) after OA-BSA exposure. RT-PCR analysis revealed OA did not induce changes in gene expression at noncytotoxic concentrations in exposed HUVEC, but 12-OH OA did alter ICAM and COX2 gene expression.

CONCLUSIONS

Together, these data demonstrate that FA may be capable of inducing cytotoxic effects and altering expression of mediators of vascular function following inhalation exposure, and may be implicated in air pollutant-induced deaths and hospitalizations. (267 of max 350 words).

The influence of PM2.5 on lung injury and cytokines in mice

Exposure to particulate matter ≤2.5 µm in diameter (PM_2.5) profoundly affects human health. However, the role of PM_2.5 on lung injury and cytokine levels in mice is currently unknown. The aim was to examine the effect of PM_2.5 pollution on lung injury in mice fed at an underground parking lot. A total of 20 female Kunming mice were randomly divided into control and polluted groups, with 10 rats in each group. The control group was kept in the laboratory, while the pollution group was fed in an underground parking lot. The concentrations of pollutants were measured using ambient air quality monitoring instruments. After 3 months of treatment, the lungs were collected and examined using electron microscopy, and the morphological structures were assessed using hematoxylin and eosin staining. The polarization of macrophages was evaluated by immunofluorescence. The concentration of interleukin (IL)-4, tumor necrosis factor (TNF)-α and transforming growth factor (TGF)-β1 in peripheral sera were assessed by ELISA. The mRNA and protein levels of IL-4, TNF-α, and TGF-β1 in lung tissues were assessed by reverse transcription-quantitative polymerase chain reaction and western blot analyses, respectively. In the polluted group, the levels of CO, NO_x and PM_2.5 were significantly higher compared with the control group. Compared with the controls, intracellular edema, an increased number of microvilli and lamellar bodies, smaller lamellar bodies in type II alveolar epithelial cells, and abundant particles induced by PM_2.5 in macrophages were observed in the polluted group. The lung ultrastructure changed in the polluted group, revealing exhaust-induced lung injury: The tissues were damaged, and the number of inflammatory cells, neutrophils, polylymphocytes and eosinophils increased in the polluted group compared with the control group. The authors also observed that the number of M1 and M2 macrophages markedly increased after the exhaust treatment. The levels of IL-4, TNF-α and TGF-β1 in the sera and tissues were significantly increased in the polluted group. PM_2.5 pollutants in underground garages can lead to lung injury and have a significant impact on the level of inflammatory cytokines in mice. Therefore, the authors suggest that PM_2.5 can activate the inflammatory reaction and induce immune dysfunction, leading to ultrastructural damage.

Particulate Matter Air Pollution: Effects on the Cardiovascular System

Air pollution is a complex mixture of gaseous and particulate components, each of which has detrimental effects on human health. While the composition of air pollution varies greatly depending on the source, studies from across the world have consistently shown that air pollution is an important modifiable risk factor for significantly increased morbidity and mortality. Moreover, clinical studies have generally shown a greater impact of particulate matter (PM) air pollution on health than the gaseous components. PM has wide-ranging deleterious effects on human health, particularly on the cardiovascular system. Both acute and chronic exposure to PM air pollution is associated with increased risk of death from cardiovascular diseases including ischemic heart disease, heart failure, and ischemic/thrombotic stroke. Particulate matter has also been shown to be an important endocrine disrupter, contributing to the development of metabolic diseases such as obesity and diabetes mellitus, which themselves are risk factors for cardiovascular disease. While the epidemiological evidence for the deleterious effects of PM air pollution on health is increasingly accepted, newer studies are shedding light on the mechanisms by which PM exerts its toxic effects. A greater understanding of how PM exerts toxic effects on human health is required in order to prevent and minimize the deleterious health effects of this ubiquitous environmental hazard. Air pollution is a growing public health problem and mortality due to air pollution is expected to double by 2050. Here, we review the epidemiological evidence for the cardiovascular effects of PM exposure and discuss current understanding about the biological mechanisms, by which PM exerts toxic effects on cardiovascular system to induce cardiovascular disease.

Mitochondria-mediated oxidative stress induced by desert dust in rat alveolar macrophages

Exposure to ambient particulate matter (PM), including PM from resuspension of soils and dusts, increases the risk for respiratory diseases. However, the exact mechanism of PM-mediated damage to the lungs remains unclear. Due to recent increases in the frequency of dust storms in many areas, we examined the cytotoxic effects of soil-dust samples collected in an arid zone in Israel on rat lung macrophages. The desert soil contains soil crusts and low levels of toxic metal content. Exposure of cells to water extracts from the dust samples caused significant reduction in the concentration of live cells and overall cell viability. The dust samples induced cell death through apoptosis, mitochondrial dysfunction, and increased mitochondrial lipid peroxidation. The dust samples generated more reactive oxygen species (ROS) compared to control-treated samples and National Institute of Standards and Technology San Joaquin Valley standard reference material. To assess whether the oxidative imbalance induced by dust extract also interferes with the antioxidant defense, we evaluated phase II detoxifying and antioxidant enzymes, which are Nrf2 classical targets. The Nrf2 transcription factor is a master regulator of cellular adaptation to stress. The dust extracts produced a significant increase in phase II detoxifying genes. This work suggests that the health-related injury observed in rat lung cells exposed to dust extracts is associated with ROS generation, mitochondrial dysfunction, mitochondrial lipid peroxidation, and cellular antioxidant imbalance. Damage to lung mitochondria may be an important mechanism by which dust-containing bacterial material induces lung injury upon inhalation.

In vivo short-term exposure to residual oil fly ash impairs pulmonary innate immune response against environmental mycobacterium infection

Epidemiological studies have shown that pollution derived from industrial and vehicular transportation induces adverse health effects causing broad ambient respiratory diseases. Therefore, air pollution should be taken into account when microbial diseases are evaluated. Environmental mycobacteria (EM) are opportunist pathogens that can affect a variety of immune compromised patients, which impacts significantly on human morbidity and mortality. The aim of this study was to evaluate the effect of residual oil fly ash (ROFA) pre-exposure on the pulmonary response after challenge with opportunistic mycobacteria by means of an acute short-term in vivo experimental animal model. We exposed BALB/c mice to ROFA and observed a significant reduction on bacterial clearance at 24 h post infection. To study the basis of this impaired response four groups of animals were instilled with (a) saline solution (Control), (b) ROFA (1 mg kg(-1) BW), (c) ROFA and EM-infected (Mycobacterium phlei, 8 × 10(6) CFU), and (d) EM-infected. Animals were sacrificed 24 h postinfection and biomarkers of lung injury and proinflammatory madiators were examined in the bronchoalveolar lavage. Our results indicate that ROFA was able to produce an acute pulmonary injury characterized by an increase in bronchoalveolar polymorphonuclear (PMN) cells influx and a rise in O2 (-) generation. Exposure to ROFA before M. phlei infection reduced total cell number and caused a significant decline in PMN cells recruitment (p < 0.05), O2 (-) generation, TNFα (p < 0.001), and IL-6 (p < 0.001) levels. Hence, our results suggest that, in this animal model, the acute short-term pre-exposure to ROFA reduces early lung response to EM infection.

Toxicology of ambient particulate matter

It is becoming increasingly clear that inhalation exposure to particulate matter (PM) can lead to or exacerbate various diseases, which are not limited to the lung but extend to the cardiovascular system and possibly other organs and tissues. Epidemiological studies have provided strong evidence for associations with chronic obstructive pulmonary disease (COPD), asthma, bronchitis and cardiovascular disease, while the evidence for a link with lung cancer is less strong. Novel research has provided first hints that exposure to PM might lead to diabetes and central nervous system (CNS) pathology. In the current review, an overview is presented of the toxicological basis for adverse health effects that have been linked to PM inhalation. Oxidative stress and inflammation are discussed as central processes driving adverse effects; in addition, profibrotic and allergic processes are implicated in PM-related diseases. Effects of PM on key cell types considered as regulators of inflammatory, fibrotic and allergic mechanisms are described.

Combined effects of fine particulate matter and lipopolysaccharide on apoptotic responses in NR8383 macrophages

Alveolar macrophages (AM) are the predominant lung cells responsible for both ingestion and clearance of inhaled particulate matter (PM). The aims of this study were (1) to examine effects of fine PM on rat NR8383 cell line apoptosis, and (2) to determine whether NR8383 cell functions are further affected when exposed to fine PM in the presence of inflammation induced by lipopolysaccharide (LPS). Standard Reference Material 2786 (SRM 2786) for fine PM was used to measure the following parameters: cytotoxicity, apoptotic rate, Bax/Bcl-2 expression, nitric oxide (NO) production, and reactive oxygen species (ROS) generation in NR8383 cells. Data showed that SRM 2786 alone induced damage and apoptosis in NR8383 cells in a concentration-dependent manner as demonstrated by significant decrease in expression of Bcl-2 and increase in expression of Bax, suggesting fine PM might trigger apoptosis involving a mitochondria-mediated apoptotic pathway. In addition, there was elevated production of free radicals, such as NO and ROS, suggesting oxidative stress plays a role in the observed apoptotic responses. Further, LPS pretreatment enhanced apoptosis of NR8383 cells induced by SRM 2786. Consequently, data indicate that SRM 2786 triggered cell apoptosis in NR8383 cells, probably by mechanisms involving oxidative stress, as evidenced by elevated NO and ROS levels, while the degree of apoptosis was further aggravated by inflammation.

Functional and morphological olfactory bulb modifications in mice after vanadium inhalation

Neurodegenerative disorders, such as Parkinson's and Alzheimer's diseases, have olfaction impairment. These pathologies have also been linked to environmental pollutants. Vanadium is a pollutant, and its toxic mechanisms are related to the production of oxidative stress. In this study, we evaluated the effects of inhaled vanadium on olfaction, the olfactory bulb antioxidant, through histological and ultrastructural changes in granule cells. Mice in control group were made to inhale saline; the experimental group inhaled 0.02-M vanadium pentoxide (V2O5) for 1 hr twice a week for 4 weeks. Animals were sacrificed at 1, 2, 3, and 4 weeks after inhalation. Olfactory function was evaluated by the odorant test. The activity of glutathione peroxidase (GPx) and glutathione reductase (GR) was assayed in olfactory bulbs and processed for rapid Golgi method and ultrastructural analysis. Results show that olfactory function decreased at 4-week vanadium exposure; granule cells showed a decrease in dendritic spine density and increased lipofuscin, Golgi apparatus vacuolation, apoptosis, and necrosis. The activity of GPx and GR in the olfactory bulb was increased compared to that of the controls. Our results demonstrate that vanadium inhalation disturbs olfaction, histology, and the ultrastructure of the granule cells that might be associated with oxidative stress, a risk factor in neurodegenerative diseases.

Low levels of residual oil fly ash (ROFA) impair innate immune response against environmental mycobacteria infection in vitro

Epidemiological studies have shown that pollution derived from industrial and vehicular transportation provokes adverse health effects causing broad spectrum of ambient respiratory diseases. Therefore, air pollution should be taken into account when microbial diseases are evaluated. Environmental mycobacteria (EM) are opportunist pathogens in a variety of immunocompromised patients eliciting significant impact on human morbidity and mortality. The aim of this study was to evaluate the in vitro effects of residual oil fly ash (ROFA) on the alveolar macrophages (AMs) response to opportunistic bacteria. AMs from young Wistar rats were obtained by bronchoalveolar lavage and co-cultured with Mycobacterium phlei (MOI 10). We exposed AM cultures to ROFA to characterize the effect of low ROFA concentrations (0, 2.5, and 5μg/ml) and evaluated the response of pre-exposed AM against the bacilli. Low ROFA concentrations induced superoxide anion and nitrites production (p<0.001). Pre-exposure to ROFA (2.5 and 5μg/ml) caused a significant reduction on TNFα (p<0.001) and superoxide anion (p<0.001) production but, did not modify the nitrite production when AM were co-cultured with M. phlei. In addition, ROFA significantly diminished AM killing ability in culture (p<0.001). Hence, our results indicate that pre-exposure to low levels of ROFA modifies the innate pulmonary defence mechanisms against environmental mycobacteria.

Mitochondrial ROS production under cellular stress: comparison of different detection methods

Reactive oxygen species (ROS) are involved in the regulation of many physiological processes. However, overproduction of ROS under various cellular stresses results in cell death and organ injury and thus contributes to a broad spectrum of diseases and pathological conditions. The existence of different cellular sources for ROS and the distinct properties of individual ROS (their reactivity, lifetime, etc.) require adequate detection methods. We therefore compared different models of cellular stress and various ROS-sensitive dyes-2',7'-dichlorodihydrofluorescein diacetate (DCF-DA), MitoSOX™, and MitoTracker® red CM-H(2)XRos-using a confocal fluorescent imaging approach, which has the advantage of not only detecting but also of localizing intracellular sources for ROS. Confocal acquisition of DCF-DA fluorescence can be combined with ROS detection by the mitochondria-specific probes MitoSOX™ and MitoTracker® red CM-H(2)XRos. Specificity was controlled using various antioxidants such as Trolox and N-acetylcysteine. Using different fluorescent ROS-sensitive probes, we detected higher ROS production equally under cell starvation (IL-3 or serum depletion), hypoxia-reoxygenation, or treatment of cells with prooxidants. The detected increase in ROS was approximately threefold in IL-3-depleted 32D cells, approximately 3.5-fold in serum-deprived NIH cells, and 2.5-fold to threefold in hypoxic HL-1 cells, and these findings agree well with previously published spectrofluorometric measurements. In some cases, electron spin resonance (ESR) spectroscopy was used for the validation of results from confocal fluorescent imaging. Our data show that confocal fluorescent imaging and ESR data are in good agreement. Under cellular stress, mitochondrial ROS are released into the cytoplasm and may participate in many processes, but they do not escape from the cell.

Vanadium compounds induced mitochondria permeability transition pore (PTP) opening related to oxidative stress

Vanadium compounds have been regarded as promising in therapeutic treatment of diabetes and in cancer prevention. In the present work, we studied the effects of vanadium compounds on mitochondria to investigate the mechanisms of toxicity. Mitochondria were isolated from rat liver and incubated with a variety of vanadium compounds, i.e. VOSO(4), NaVO(3), and vanadyl complexes with organic ligands. Our studies indicated that VO(2+), VO(3)(-), VO(acac)(2) and VOcit (1-100microM) could induce mitochondrial swelling in a concentration dependent manner and disrupt mitochondrial membrane potential (Deltapsi(m)) in a time dependent manner, which is quite different from the rapid Deltapsi(m) collapse caused by Ca(2+) or CCCP (carbonyl cyanide m-chlorophenylhydrazone, a mitochondrial uncoupling reagent). Release of cytochrome c (Cyt c) was observed and could be inhibited by cyclosporin A (CsA), an inhibitor of the mitochondrial permeability transition pore (PTP). Interestingly, VOdipic caused release of Cyt c without mitochondrial swelling and Deltapsi(m) disruption, an action previously only observed on the Bax protein, suggesting a potentially role of VOdipic in regulating PTP opening. In addition, all the vanadium compounds tested stimulated mitochondrial production of reactive oxygen species (ROS). Antioxidants, i.e. vitamin C and E, significantly delayed the Deltapsi(m) disruption. Overall, our experimental evidence indicated vanadium compounds exhibited multiple actions on mitochondria. Vanadium compounds did induce oxidative stress on mitochondrial and thus caused PTP opening, which led to collapse of Deltapsi(m) and Cyt c release as the initiation of cell apoptosis.

Fine ambient particles induce oxidative stress and metal binding genes in human alveolar macrophages

Exposure to pollutant particles increased respiratory morbidity and mortality. The alveolar macrophages (AMs) are one cell type in the lung directly exposed to particles. Upon contact with particles, AMs are activated and produce reactive oxygen species, but the scope of this oxidative stress response remains poorly defined. In this study, we determined the gene expression profile in human AMs exposed to particles, and sought to characterize the global response of pro- and antioxidant genes. We exposed AMs obtained by bronchoscopy from normal individuals to Chapel Hill particulate matter of 2.5-microm diameter or smaller (PM(2.5); 1 microg/ml) or vehicle for 4 hours (n = 6 independent samples). mRNAs were extracted, amplified, and hybridized to Agilent human 1A microarray. Significant genes were identified by significance analysis of microarrays (false discovery rate, 10%; P < or = 0.05) and mapped with Gene Ontology in the Database for Annotation, Visualization, and Integrated Discovery. We found 34 and 41 up- and down-regulated genes, respectively; 22 genes (approximately 30%) were involved in metal binding, and 11 were linked to oxidative stress, including up-regulation of five metallothionein (MT)-1 isoforms. Exogenous MT1 attenuated PM(2.5)-induced H2O2 release. PM(2.5) premixed with MT1 stimulated less H2O2 release. Knockdown of MT1F gene increased PM(2.5)-induced H2O2 release. PM(2.5) at 1 microg/ml did not increase H2O2 release. Mount St. Helens PM(2.5) and acid-extracted Chapel Hill PM(2.5), both poor in metals, did not induce MT1F or H2O2 release. Our results show that PM(2.5) induced a gene expression profile prevalent with genes related to metal binding and oxidative stress in human AMs, independent of oxidative stress. Metals associated with PM may play an important role in particle-induced gene changes.

Reactive oxygen species- and nitric oxide-mediated lung inflammation and mitochondrial dysfunction in wild-type and iNOS-deficient mice exposed to diesel exhaust particles

Pulmonary responses to diesel exhaust particles (DEP) exposure are mediated through enhanced production of reactive oxygen species (ROS) and nitric oxide (NO) by alveolar macrophages (AM). The current study examined the differential roles of ROS and NO in DEP-induced lung injury using C57B/6J wild-type (WT) and inducible NO synthase knockout (iNOS KO) mice. Mice exposed by pharyngeal aspiration to DEP or carbon black particles (CB) (35 mg/kg) showed an inflammatory profile that included neutrophil infiltration, increased lactate dehydrogenase (LDH) activity, and elevated albumin content in bronchoalveolar lavage fluid (BALF) at 1, 3, and 7 d postexposure. The organic extract of DEP (DEPE) did not induce an inflammatory response. Comparing WT to iNOS KO mice, the results show that NO enhanced DEP-induced neutrophils infiltration and plasma albumin content in BALF and upregulated the production of the pro-inflammatory cytokine interleukin 12 (IL-12) by AM. DEP-exposed AM from iNOS KO mice displayed diminished production of IL-12 and, in response to ex vivo lipopolysaccharide (LPS) challenge, decreased production of IL-12 but increased production of IL-10 when compared to cells from WT mice. DEP, CB, but not DEPE, induced DNA damage and mitochondria dysfunction in AM, however, that is independent of cellular production of NO. These results demonstrate that DEP-induced immune/inflammatory responses in mice are regulated by both ROS- and NO-mediated pathways. NO did not affect ROS-mediated mitochondrial dysfunction and DNA damage but upregulated IL-12 and provided a counterbalance to the ROS-mediated adaptive stress response that downregulates IL-12 and upregulates IL-10.

Apoptotic and Inflammatory Effects Induced by Different Particles in Human Alveolar Macrophages

Pollutant particles induce apoptosis and inflammation, but the relationship between these two biological processes is not entirely clear. In this study, we compared the proapoptotic and proinflammatory effects of four particles: residual oil fly ash (ROFA), St. Louis particles SRM 1648 (SL), Chapel Hill PM10 (CHP), and Mount St. Helens dust (MSH). Human alveolar macrophages (AM) were incubated with these particles at 100 microg/ml. Cell death was assessed by annexin V (AV) expression, histone release, nuclear morphology, caspase 3-like activity and release of caspase 1 for apoptosis, and propidium iodide (PI) for necrosis, and inflammation was measured by interleukin (IL)-1beta and IL-6. We found that particle effects on these cell death measurements varied, and ROFA affected most (four out of five) endpoints, including nuclear morphological changes. CHP and SL also caused necrosis. For cytokine release, the potency was CHP > SL > ROFA > MSH. The proapoptotic and proinflammatory effects induced by the whole particles were unaltered after the particles were washed with water. The water-soluble fraction was relatively inactive, as were individual soluble metals (V, Ni, Fe). ROFA-induced nuclear fragmentation was associated with upregulation and mitochondrial release of apoptosis-inducing factor (AIF), a caspase-independent chromatin condensation factor, and upregulation of DNase II, a lysosomal acid endonuclease. These results indicate that the potential for particles to induce apoptosis does not correlate with their proinflammatory properties, although active components for both processes reside in the water-insoluble core. Both apoptosis and inflammatory endpoints should be included when the toxicity of different pollutant particles is assessed.

Regulation of COX-2 expression and IL-6 release by particulate matter in airway epithelial cells

Particulate matter (PM) in ambient air is a risk factor for human respiratory and cardiovascular diseases. The delivery of PM to airway epithelial cells has been linked to release of proinflammatory cytokines; however, the mechanisms of PM-induced inflammatory responses are not well-characterized. This study demonstrates that PM induces cyclooxygenase (COX)-2 expression and IL-6 release through both a reactive oxygen species (ROS)-dependent NF-kappaB pathway and an ROS-independent C/EBPbeta pathway in human bronchial epithelial cells (HBEpCs) in culture. Treatment of HBEpCs with Baltimore PM induced ROS production, COX-2 expression, and IL-6 release. Pretreatment with N-acetylcysteine (NAC) or EUK-134, in a dose-dependent manner, attenuated PM-induced ROS production, COX-2 expression, and IL-6 release. The PM-induced ROS was significantly of mitochondrial origin, as evidenced by increased oxidation of the mitochondrially targeted hydroethidine to hydroxyethidium by reaction with superoxide. Exposure of HBEpCs to PM stimulated phosphorylation of NF-kappaB and C/EBPbeta, while the NF-kappaB inhibitor, Bay11-7082, or C/EBPbeta siRNA attenuated PM-induced COX-2 expression and IL-6 release. Furthermore, NAC or EUK-134 attenuated PM-induced activation of NF-kappaB; however, NAC or EUK-134 had no effect on phosphorylation of C/EBPbeta. In addition, inhibition of COX-2 partly attenuated PM-induced Prostaglandin E2 and IL-6 release.

Possible role for intracellular cholesteryl ester transfer protein in adipocyte lipid metabolism and storage

Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester (CE) and triglyceride (TG) between lipoproteins in plasma. However, short term suppression of CETP biosynthesis in cells alters cellular cholesterol homeostasis, demonstrating an intracellular role for CETP as well. The consequences of chronic CETP deficiency in lipid-storing cells normally expressing CETP have not been reported. Here, SW872 adipocytes stably expressing antisense CETP cDNA and synthesizing 20% of normal CETP were created. CETP-deficient cells had 4-fold more CE but an approximately 3-fold decrease in cholesterol biosynthesis. This phenotype of cholesterol overload is consistent with the observed 45% reduction in low density lipoprotein receptor and 2.5-fold increase in ABCA1 levels. However, cholesterol mass in CETP-deficient adipocytes was actually reduced. Strikingly, CETP-deficient adipocytes stored <50% of normal TG, principally reflecting reduced synthesis. The hydrolysis of cellular CE and TG in CETP-deficient cells was reduced by >50%, although hydrolase/lipase activity was increased 3-fold. Notably, the incorporation of recently synthesized CE and TG into lipid storage droplets in CETP-deficient cells was just 40% of control, suggesting that these lipids are inefficiently transported to droplets where the hydrolase/lipase resides. The capacity of cellular CETP to transport CE and TG into storage droplets was directly demonstrated in vitro. Overall, chronic CETP deficiency disrupts lipid homeostasis and compromises the TG storage function of adipocytes. Inefficient CETP-mediated translocation of CE and TG from the endoplasmic reticulum to their site of storage may partially explain these defects. These studies in adipocytic cells strongly support a novel role for CETP in intracellular lipid transport and storage.

Hydrogen peroxide is critical for UV-induced apoptosis inhibition

Apoptosis is an important cell death system that deletes damaged and mutated cells, preventing the induction of cancer. We previously have reported that UV irradiation inhibited the apoptosis induced by serum starvation and cell detachment. This phenomenon is suitable for clarifying the relationship between cancer and the dysregulation of apoptosis by UV irradiation. Here, we have studied the factors responsible for this inhibition of apoptosis, focusing on reactive oxygen species (ROS) and DNA damage. Treatment with xanthine oxidase in the presence of hypoxanthine, which is known to produce superoxide anion (O2*-) and hydrogen peroxide (H2O2), inhibited the induction of apoptosis. The xanthine oxidase-induced anti-apoptotic effect was suppressed in the presence of an H2O2-eliminating enzyme, catalase, but not in the presence of an O2*--eliminating enzyme, superoxide dismutase. Treatment with H2O2 itself significantly inhibited the induction of apoptosis. Furthermore, the effect of the inhibition of cell death by UVB irradiation and by H2O2 treatment decreased in H2O2-resistant cells. Although both UVB and H2O2 are known to induce DNA damage, other DNA damaging agents, like gamma-irradiation and treatment with cisplatin and bleomycin, showed no inhibition of apoptosis. These findings suggested that H2O2 was essential to the inhibition of apoptosis, in which DNA damage had no role.

Reactive species and apoptosis of neural precursor cells after gamma-irradiation

This study addresses the participation of radiation-induced free radicals, mainly nitric oxide (NO), in modulating the apoptotic response in an in vitro model of neural cortical precursor cells exposed to gamma-radiation. Cortical cells obtained from rats at 17 gestational day (GD) were irradiated with a dose of 2 Gy. The percentage of apoptotic cells was significantly increased 4h post-irradiation (pi). NO content showed a significant increase after 30 min pi and the rate of generation reached a maximum 1h pi. Luminol-dependent chemiluminescence (CL) was significantly higher in cells after 2h pi as compared to control cells and this profile was maintained up to 4 h pi. Supplementation with L-NAME significantly increased light emission. Administration of superoxide dismutase (SOD) following L-NAME addition prevented the observed changes due to L-NAME administration. The caspase inhibitor zDEVD-fmk significantly reduced the radical generation. Moreover, the cellular decrease in NO content occurred coincidentally with the rise in oxygen radical generation and the activation of caspase-3. In vitro irradiation of neural precursor cells allowed us to suggest that an early radiation-induced generation of NO could exert a neuroprotective role. However, despite this NO initial protective effect and its role modulating the response against gamma-radiation, NO generation was not able of fully preventing radiation-induced apoptosis.

Seasonal variations in air pollution particle-induced inflammatory mediator release and oxidative stress

Health effects associated with particulate matter (PM) show seasonal variations. We hypothesized that these heterogeneous effects may be attributed partly to the differences in the elemental composition of PM. Normal human bronchial epithelial (NHBE) cells and alveolar macrophages (AMs) were exposed to equal mass of coarse [PM with aerodynamic diameter of 2.5-10 microm (PM(2.5-10)], fine (PM(2.5)), and ultrafine (PM(<0.1)) ambient PM from Chapel Hill, North Carolina, during October 2001 (fall) and January (winter), April (spring), and July (summer) 2002. Production of interleukin (IL)-8, IL-6, and reactive oxygen species (ROS) was measured. Coarse PM was more potent in inducing cytokines, but not ROSs, than was fine or ultrafine PM. In AMs, the October coarse PM was the most potent stimulator for IL-6 release, whereas the July PM consistently stimulated the highest ROS production measured by dichlorofluorescein acetate and dihydrorhodamine 123 (DHR). In NHBE cells, the January and the October PM were consistently the strongest stimulators for IL-8 and ROS, respectively. The July PM increased only ROS measured by DHR. PM had minimal effects on chemiluminescence. Principal-component analysis on elemental constituents of PM of all size fractions identified two factors, Cr/Al/Si/Ti/Fe/Cu and Zn/As/V/Ni/Pb/Se, with only the first factor correlating with IL-6/IL-8 release. Among the elements in the first factor, Fe and Si correlated with IL-6 release, whereas Cr correlated with IL-8 release. These positive correlations were confirmed in additional experiments with PM from all 12 months. These results indicate that elemental constituents of PM may in part account for the seasonal variations in PM-induced adverse health effects related to lung inflammation.

ESR investigation of the oxidative damage in lungs caused by asbestos and air pollution particles

Exposure to asbestos and air pollution particles can be associated with increased human morbidity and mortality. However, the molecular mechanism of lung injuries remains unknown. It has been postulated that the in vivo toxicity results from the catalysis of free radical generation. Using electron spin resonance (ESR) in conjunction with the spin trap alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) we previously investigated in vivo free radical production by rats treated with intratracheal instillation of asbestos (crocidolite fibers) and an emission source air pollution particle (oil fly ash). In this report we compare the effect of two different exposures on the type of free radicals they induce in in vivo animal model. Twenty-four hours after the exposure, ESR spectroscopy of the chloroform extract from lungs of animals exposed to either asbestos or oil fly ash gave a spectrum consistent with a carbon-centered radical adduct (aN = 15.01 G and aH = 2.46 G). To test whether free radical formation occurred in vivo and not in vitro, a number of control experiments were performed. Combinations (both individually and together) of asbestos or oil fly ash and 4-POBN were added to lung homogenate of unexposed rats prior to chloroform extraction. No detectable ESR signal resulted. To exclude the possibility of ex vivo free radical generation, asbestos or oil fly ash was added to lung homogenate of an animal treated with 4-POBN. Also, 4-POBN was added to lung homogenate from rats instilled with asbestos or oil fly ash. Neither system produced radical adducts, indicating that the ESR signal detected in the lung extracts of the treated animals must be produced in vivo and not ex vivo or in vitro. In conclusion, ESR analysis of lung tissue demonstrated that both exposures produce lipid-derived radical metabolites despite their different composition and structure. Analogously, both exposures provide evidence of in vivo enhanced lipid peroxidation. Furthermore, it is concluded that without the presence of a spin-trapping agent, no free radical metabolites could be detected directly by ESR in either exposure.

Soluble metals associated with residual oil fly ash increase morbidity and lung injury after bacterial infection in rats

Inhalation of residual oil fly ash (ROFA) has been shown to impair lung defense mechanisms in laboratory animals and susceptible populations. Bioavailability of soluble transition metals has been shown to play a key role in lung injury caused by ROFA exposure. The goal of this study was to evaluate the effect of soluble metals on lung defense and injury in animals preexposed to ROFA followed by pulmonary challenge with a bacterial pathogen. ROFA was suspended in saline (ROFA-TOTAL), incubated overnight at 37 degrees C, and separated by centrifugation into soluble (ROFA-SOL) and insoluble (ROFA-INSOL) fractions. A portion of the soluble sample was treated with the metal-binding resin Chelex for 24 h at 37 degrees C. Sprague-Dawley rats were intratracheally dosed at d 0 with ROFA-TOTAL (1.0 mg/100 g body weight), ROFA-INSOL, ROFA-SOL, saline, saline + Chelex, or ROFA-SOL + Chelex. At d 3, 5 x 10(5) Listeria monocytogenes were intratracheally instilled into rats from each treatment group. At d 6, 8, and 10, left lungs were removed, homogenized, and cultured to assess bacterial clearance. Histopathological analysis was performed on the right lungs. Pulmonary exposure of ROFA-TOTAL or ROFA-SOL before infection led to a marked increase in lung injury and inflammation at all three time points after inoculation, and an increase in morbidity in comparison to saline control rats. Treatment with ROFA-INSOL, saline + Chelex, or ROFA-SOL + Chelex caused no significant increases in lung damage and morbidity when compared to control. By d 10, the ROFA-SOL and ROFA-TOTAL groups had approximately 200-fold more bacteria in the lung than saline control, indicating the inability of these groups to effectively respond to the infection. None of the other treatment groups had significant impairments in bacterial clearance when compared to saline. In conclusion, exposure to ROFA-TOTAL and ROFA-SOL significantly suppressed the lung response to infection. These results suggest that soluble metals present in ROFA may play a key role in increased susceptibility to pulmonary infection in exposed populations.