Histone acetylation regulates epithelial IL-8 release mediated by oxidative stress from environmental particles

Oxidative inactivation of the proteasome in retinal pigment epithelial cells. A potential link between oxidative stress and up-regulation of interleukin-8

Oxidative stress and inflammation are implicated in the pathogenesis of many age-related diseases. Stress-induced overproduction of inflammatory cytokines, such as interleukin-8 (IL-8), is one of the early events of inflammation. The objective of this study was to elucidate mechanistic links between oxidative stress and overproduction of IL-8 in retinal pigment epithelial (RPE) cells. We found that exposure of RPE cells to H(2)O(2), paraquat, or A2E-mediated photooxidation resulted in increased expression and secretion of IL-8. All of these oxidative stressors also inactivated the proteasome in RPE cells. In contrast, tert-butylhydroperoxide (TBH), a lipophilic oxidant that did not stimulate IL-8 production, also did not inactivate the proteasome. Moreover, prolonged treatment of RPE cells with proteasome-specific inhibitors recapitulated the stimulation of IL-8 production. These data suggest that oxidative inactivation of the proteasome is a potential mechanistic link between oxidative stress and up-regulation of the proinflammatory IL-8. The downstream signaling pathways that govern the production of IL-8 include NF-kappaB and p38 MAPK. Proteasome inhibition both attenuated the activation and delayed the turnoff of NF-kappaB, resulting in biphasic effects on the production of IL-8. Prolonged proteasome inhibition (>2 h) resulted in activation of p38 MAPK via activation of MKK3/6 and increased the production of IL-8. Chemically inhibiting the p38 MAPK blocked the proteasome inhibition-induced up-regulation of IL-8. Together, these data indicate that oxidative inactivation of the proteasome and the related activation of the p38 MAPK pathway provide a potential link between oxidative stress and overproduction of proinflammatory cytokines, such as IL-8.

Oxidative stress causes IL8 promoter hyperacetylation in cystic fibrosis airway cell models

Dysregulated inflammation has been implicated in cystic fibrosis (CF) airway pathophysiology. The expression of inflammatory genes, like interleukin 8 (IL8), involves chromatin remodeling through histone acetylation. Inflammatory gene hyperacetylation could explain inflammatory mediator dysregulation seen in CF airways. CF airways are exposed to high levels of oxidative stress, and oxidative stress increases histone acetylation and inflammatory gene transcription. Loss of cystic fibrosis transmembrane conductance regulator (CFTR) may even reduce protection against oxidative stress. Consequently, increasing oxidative stress would likely lead to an imbalance of histone acetyl-transferase (HAT) and deacetylase (HDAC) stoichiometry and contribute to the heightened inflammatory response seen in the CF airway. We hypothesize that oxidative stress in CF airways causes increased acetylation of inflammatory gene promoters, contributing to transcriptional activity of these loci. Messenger RNA levels of IL8, IL6, CXCL1, CXCL2, CXCL3, and IL1 are significantly elevated in CF epithelial cell models. Histone H4 acetylation is lower at the IL8 promoter of the non-CF cell lines than the CF models. The reducing agent N-acetyl-cysteine decreases IL8 message and promoter H4 acetylation to non-CF levels, suggesting that oxidative stress contributes to IL8 expression in these models. H(2)O(2) treatment causes increased IL-8 acetylation and mRNA in all cells, but less in the CF-model cells. Together these data suggest a model in which cells without functional CFTR are under increased oxidative stress. Our data suggest intrinsic alterations in the HAT/HDAC balance in CFTR-deficient cells, and that oxidative stress contributes to this alteration.

Air pollution, ultrafine and nanoparticle toxicology: cellular and molecular interactions

Nanotechnology is involved with the creation and/or manipulation of materials at the nanometer (nm) scale, and has arisen as a consequence of the novel properties that materials exhibit within the "nano" size range. The attraction of producing, and exploiting nanparticles (NPs; one dimension less than 100 nm) is a consequence of the fact that the properties are often strikingly different from bulk forms composed from the same material. As a consequence, the field of nanotechnology has generated substantial interest resulting in incorporation of NPs into a wide variety of products including electronics, food, clothing, medicines, cosmetics and sporting equipment. While there is general recognition that nanotechnology has the potential to advance science, quality of life and to generate substantial financial gains, a number of reports suggest that potential toxicity should be considered in order to allow the safe and sustainable development of such products. For example, substances which are ordinarily innocuous can elicit toxicity due to the altered chemical and physical properties that become evident within nano dimensions leading to potentially detrimental consequences for the producer, consumer or environment. Research into respirable air pollution particles (PM10) has focused on the role of ultrafine particle (diameter less than 100 nm) in inducing oxidative stress leading to inflammation and resulting in exacerbation of preexisting respiratory and cardiovascular disease. Epidemiological studies have repeatedly found a positive correlation between the level of particulate air pollution and increased morbidity and mortality rates in both adults and children. Such studies have also identified a link between respiratory ill health and the number of ambient ultrafine particles. In vivo and in vitro toxicology studies confirm that for low solubility, low toxicity materials such as TiO2, carbon black and polystyrene beads, ultrafine particles are more toxic and inflammogenic than fine particles. In many of these studies the term "ultrafine particle" can be directly exchanged for nanoparticle, as these particles are manufactured industrially. In such studies the NPs generate reactive oxygen species (ROS) to a greater extent than larger particles leading to increased transcription of pro-inflammatory mediators via intracellular signaling pathways including calcium and oxidative stress. To date, only limited NP compositions and structures have been tested, including materials such as carbon, polystyrene beads and TiO2 as surrogate particles that aimed to represent particulate air pollution. All of these materials are generally low toxicity and low solubility. Much work is required to identify whether the conclusions made for such materials can be extrapolated to engineered nanoparticles varying not only in size but also, shape, composition, structure, surface area, surface coating, and aggregation state. Therefore, it is necessary to reveal if the diversity of NPs available will confer to a varied extent and mechanisms of toxicity.

Combined inhaled diesel exhaust particles and allergen exposure alter methylation of T helper genes and IgE production in vivo

Changes in methylation of CpG sites at the interleukin (IL)-4 and interferon (IFN)-gamma promoters are associated with T helper (Th) 2 polarization in vitro. No previous studies have examined whether air pollution or allergen exposure alters methylation of these two genes in vivo. We hypothesized that diesel exhaust particles (DEP) would induce hypermethylation of the IFN-gamma promoter and hypomethylation of IL-4 in CD4+ T cells among mice sensitized to the fungus allergen Aspergillus fumigatus. We also hypothesized that DEP-induced methylation changes would affect immunoglobulin (Ig) E regulation. BALB/c mice were exposed to a 3-week course of inhaled DEP exposure while undergoing intranasal sensitization to A. fumigatus. Purified DNA from splenic CD4+ cells underwent bisulfite treatment, PCR amplification, and pyrosequencing. Sera IgE levels were compared with methylation levels at several CpG sites in the IL-4 and IFN-gamma promoter. Total IgE production was increased following intranasal sensitization A. fumigatus. IgE production was augmented further following combined exposure to A. fumigatus and DEP exposure. Inhaled DEP exposure and intranasal A. fumigatus induced hypermethylation at CpG(-45), CpG(-53), CpG(-205) sites of the IFN-gamma promoter and hypomethylation at CpG(-408) of the IL-4 promoter. Altered methylation of promoters of both genes was correlated significantly with changes in IgE levels. This study is the first to demonstrate that inhaled environmental exposures influence methylation of Th genes in vivo, supporting a new paradigm in asthma pathogenesis.

Environmental exposures and gene regulation in disease etiology

OBJECTIVE

Health or disease is shaped for all individuals by interactions between their genes and environment. Exactly how the environment changes gene expression and how this can lead to disease are being explored in a fruitful new approach to environmental health research, representative studies of which are reviewed here.

DATA SOURCES

We searched Web of Science and references of relevant publications to understand the diversity of gene regulatory mechanisms affected by environmental exposures with disease implications.

DATA SYNTHESIS

Pharmaceuticals, pesticides, air pollutants, industrial chemicals, heavy metals, hormones, nutrition, and behavior can change gene expression through a broad array of gene regulatory mechanisms. Mechanisms include regulation of gene translocation, histone modifications, DNA methylation, DNA repair, transcription, RNA stability, alternative RNA splicing, protein degradation, gene copy number, and transposon activation. Furthermore, chemically induced changes in gene regulation are associated with serious and complex human diseases, including cancer, diabetes and obesity, infertility, respiratory diseases, allergies, and neurodegenerative disorders such as Parkinson and Alzheimer diseases. One of the best-studied areas of gene regulation is epigenetics, especially DNA methylation. Our examples of environmentally induced changes in DNA methylation are presented in the context of early development, when methylation patterns are initially laid down. This approach highlights the potential role for altered DNA methylation in fetal origins of adult disease and inheritance of acquired genetic change.

CONCLUSIONS

The reviewed studies indicate that genetic predisposition for disease is best predicted in the context of environmental exposures. Second, the genetic mechanisms investigated in these studies offer new avenues for risk assessment research. Finally, we are likely to witness dramatic improvements in human health, and reductions in medical costs, if environmental pollution is decreased.

Temporal relationship between air pollutants and hospital admissions for chronic obstructive pulmonary disease in Hong Kong

AIMS

To assess any relationship between the levels of ambient air pollutants and hospital admissions for chronic obstructive pulmonary disease (COPD) in Hong Kong.

METHODS

A retrospective ecological study was undertaken. Data of daily emergency hospital admissions to 15 major hospitals in Hong Kong for COPD and indices of air pollutants (sulphur dioxide (SO(2)), nitrogen dioxide (NO(2)), ozone (O(3)), particulates with an aerodynamic diameter of <10 microm (PM(10)) and 2.5 microm (PM(2.5))) and meteorological variables from January 2000 to December 2004 were obtained from several government departments. Analysis was performed using generalised additive models with Poisson distribution, adjusted for the effects of time trend, season, other cyclical factors, temperature and humidity. Autocorrelation and overdispersion were corrected.

RESULTS

Significant associations were found between hospital admissions for COPD with all five air pollutants. Relative risks for admission for every 10 microg/m(3) increase in SO(2), NO(2), O(3), PM(10) and PM(2.5) were 1.007, 1.026, 1.034, 1.024 and 1.031, respectively, at a lag day ranging from lag 0 to cumulative lag 0-5. In a multipollutant model, O(3), SO(2) and PM(2.5) were significantly associated with increased admissions for COPD. SO(2), NO(2) and O(3) had a greater effect on COPD admissions in the cold season (December to March) than during the warm season.

CONCLUSION

Ambient concentrations of air pollutants have an adverse effect on hospital admissions for COPD in Hong Kong, especially during the winter season. This might be due to indoor exposure to outdoor pollution through open windows as central heating is not required in the mild winter. Measures to improve air quality are urgently needed.

Nanoparticles-a thoracic toxicology perspective

A substantial literature demonstrates that the main ultrafine particles found in ambient urban air are combustion-derived nanoparticles (CDNP) which originate from a number of sources and pose a hazard to the lungs. For CDNP, three properties appear important-surface area, organics and metals. All of these can generate free radicals and so induce oxidative stress and inflammation. Inflammation is a process involved in the diseases exhibited by the individuals susceptible to the effects of PM- development and exacerbations of airways disease and cardiovascular disease. It is therefore possible to implicate CDNP in the common adverse effects of increased PM. The adverse effects of increases in PM on the cardiovascular system are well-documented in the epidemiological literature and, as argued above, these effects are likely to be driven by the combustion-derived NP. The epidemiological findings can be explained in a number of hypotheses regarding the action of NP:-1) Inflammation in the lungs caused by NP causes atheromatous plaque development and destabilization; 2) The inflammation in the lungs causes alteration in the clotting status or fibrinolytic balance favouring thrombogenesis; 3) The NP themselves or metals/organics released by the particles enter the circulation and have direct effects on the endothelium, plaques, the clotting system or the autonomic nervous system/ heart rhythm. Environmental nanoparticles are accidentally produced but they provide a toxicological model for a new class of purposely 'engineered' NP arising from the nanotechnology industry, whose effects are much less understood. Bridging our toxicological knowledge between the environmental nanoparticles and the new engineered nanoparticles is a considerable challenge.

Suppression of lipopolysaccharide- and tumour necrosis factor-alpha-induced interleukin (IL)-8 expression by glucocorticoids involves changes in IL-8 promoter acetylation

There is accumulating evidence that the transrepressional effect of glucocorticoids in down-regulating proinflammatory gene expression might be regulated by an action on histone acetylation. To investigate this, we studied the effect of two glucocorticoids (dexamethasone and triamcinolone acetonide) on reducing lipopolysaccharide (LPS)- and tumour necrosis factor (TNF)-alpha-induced interleukin (IL)-8 release in a monocytic cell line and two lymphocytic cell lines (HUT-78 and Jurkat). The effect of the histone deacetylase inhibitor trichostatin A (TSA) on LPS- and TNF-alpha-induced IL-8 release and its repression by glucocorticoids was also examined. LPS and TNF-alpha induced IL-8 release in all three cell lines and this induction was inhibited by both dexamethasone and triamcinolone. Pretreatment of cells with TSA enhanced basal and LPS- and TNFalpha-stimulated IL-8 release in all three cell lines. TSA also attenuated the inhibitory effect of glucocorticoids on stimulated IL-8 release. Chromatin immunoprecipitation assays confirmed that LPS and TNF-alpha enhanced histone acetylation at the IL-8 promoter and that this was inhibited by triamcinolone in all three cell types. Changes in histone acetylation at the IL-8 are important in its regulation by proinflammatory and anti-inflammatory agents, and modulation of this activity may have therapeutic potential in inflammatory conditions.

Role of metabolic programming in the pathogenesis of beta-cell failure in postnatal life

Intrauterine growth retardation (IUGR) has been linked to later development of type 2 diabetes in adulthood. Human studies indicate that individuals who were growth retarded at birth have impaired insulin secretion and insulin resistance. Multiple animal models of IUGR demonstrate impaired beta-cell function and development. We have developed a model of IUGR in the rat that leads to diabetes in adulthood with the salient features of most forms of type 2 diabetes in the human: progressive defects in insulin secretion and insulin action prior to the onset of overt hyperglycemia. Decreased beta-cell proliferation leads to a progressive decline in beta-cell mass. Using this model, we have tested the hypothesis that uteroplacental insufficiency disrupts the function of the electron transport chain in the fetal beta-cell and leads to a debilitating cascade of events: increased production of reactive oxygen species, which in turn damage mitochondrial (mt) mtDNA and causes further production of reactive oxygen species (ROS). The net result is progressive loss of beta-cell function and eventual development of type 2 diabetes in the adult. Studies in the IUGR rat also demonstrate that an abnormal intrauterine environment induces epigenetic modifications of key genes regulating beta-cell development; experiments directly link chromatin remodeling with suppression of transcription. Future research will be directed at elucidating the mechanisms underlying epigenetic modifications in offspring.

Developmental origins of beta-cell failure in type 2 diabetes: the role of epigenetic mechanisms

Intrauterine growth retardation (IUGR) has been linked to later development of type 2 diabetes in adulthood. An abnormal metabolic intrauterine milieu affects the development of the fetus by permanently modifying gene expression of susceptible cells. Altered gene expression persists after birth, suggesting that an epigenetic mechanism may be responsible for changes in transcription. Uteroplacental insufficiency (IUGR) is associated with hypomethylation and hyperacetylation of genomic DNA in brain and liver of IUGR fetal and juvenile rats. These findings are associated with zinc deficiency that often accompanies fetal growth retardation. Studies in the IUGR rat also demonstrate that an abnormal intrauterine environment induces epigenetic modifications of key genes regulating beta-cell development and experiments directly link chromatin remodeling to suppression of transcription. Dietary protein restriction of pregnant rats causes fetal growth retardation and is associated with hypomethylation of the glucocorticoid receptor (GR) and PPARgamma genes in liver of the offspring. It is postulated that these epigenetic changes result in the observed increase in gene expression of GR and PPARgamma. Future research will be directed at elucidating the mechanisms underlying epigenetic modifications in offspring.

The pro-inflammatory effects of low-toxicity low-solubility particles, nanoparticles and fine particles, on epithelial cells in vitro: the role of surface area

OBJECTIVE

Rats exposed to high airborne mass concentrations of low-solubility low-toxicity particles (LSLTP) have been reported to develop lung disease such as fibrosis and lung cancer. These particles are regulated on a mass basis in occupational settings, but mass might not be the appropriate metric as animal studies have shown that nanoparticles (ultrafine particles) produce a stronger adverse effect than fine particles when delivered on an equal mass basis.

METHODS

This study investigated whether the surface area is a better descriptor than mass of LSLTP of their ability to stimulate pro-inflammatory responses in vitro. In a human alveolar epithelial type II-like cell line, A549, we measured interleukin (IL)-8 mRNA, IL8 protein release and glutathione (GSH) depletion as markers of pro-inflammatory effects and oxidative stress after treatment with a range of LSLTP (fine and nanoparticles) and DQ12 quartz, a particle with a highly reactive surface.

RESULTS

In all the assays, nanoparticle preparations of titanium dioxide (TiO2-np) and of carbon black (CB-np) produced much stronger pro-inflammatory responses than the same mass dose of fine TiO2 and CB. The results of the GSH assay confirmed that oxidative stress was involved in the response to all the particles, and two ultra-fine metal dusts (cobalt and nickel) produced GSH depletion similar to TiO2-np, for similar surface-area dose. As expected, DQ12 quartz was more inflammatory than the low toxicity dusts, on both a mass and surface-area basis.

CONCLUSION

Dose-response relationships observed in the in vitro assays appeared to be directly comparable with dose-response relationships in vivo when the doses were similarly standardised. Both sets of data suggested a threshold in dose measured as surface area of particles relative to the surface area of the exposed cells, at around 1-10 cm2/cm2. These findings are consistent with the hypothesis that surface area is a more appropriate dose metric than mass for the pro-inflammatory effects of LSLTP in vitro and in vivo, and consequently that the high surface area of nanoparticles is a key factor in their inflammogenicity.

Cytotoxic effect of curcumin on malaria parasite Plasmodium falciparum: inhibition of histone acetylation and generation of reactive oxygen species

The emergence of multidrug-resistant parasites is a major concern for malaria control, and development of novel drugs is a high priority. Curcumin, a natural polyphenolic compound, possesses diverse pharmacological properties. Among its antiprotozoan activities, curcumin was potent against both chloroquine-sensitive and -resistant Plasmodium falciparum strains. Consistent with findings in mammalian cell lines, curcumin's prooxidant activity promoted the production in P. falciparum of reactive oxygen species (ROS), whose cytotoxic effect could be antagonized by coincubation with antioxidants and ROS scavengers. Curcumin treatment also resulted in damage of both mitochondrial and nuclear DNA, probably due to the elevation of intracellular ROS. Furthermore, we have demonstrated that curcumin inhibited the histone acetyltransferase (HAT) activity of the recombinant P. falciparum general control nonderepressed 5 (PfGCN5) in vitro and reduced nuclear HAT activity of the parasite in culture. Curcumin-induced hypoacetylation of histone H3 at K9 and K14, but not H4 at K5, K8, K12, and K16, suggested that curcumin caused specific inhibition of the PfGCN5 HAT. Taken together, these results indicated that at least the generation of ROS and down-regulation of PfGCN5 HAT activity accounted for curcumin's cytotoxicity for malaria parasites.

The Effect of Smoking on the Transcriptional Regulation of Lung Inflammation in Patients with Chronic Obstructive Pulmonary Disease

RATIONALE

Chronic obstructive pulmonary disease (COPD) is believed to result from an abnormal inflammatory response in the lungs to noxious particles and gases usually found in cigarette smoke.

OBJECTIVES

In this study, the molecular mechanisms for the enhanced proinflammatory cytokine gene transcription in COPD were investigated.

METHODS

Lung tissue was examined from 56 subjects undergoing resection for peripheral lung tumors as follows: current smokers with (n = 14) and without COPD (n = 17), ex-smokers with COPD (n = 13), and nonsmokers (n = 12). The levels of inhibitor kappaB-alpha (IkappaB-alpha), histone deacetylase 2 (HDAC2), acetylated (ac-) histone H3 and H4, the transcription factor nuclear factor-kappaB (NF-kappaB), proinflammatory cytokine messenger RNA, and 8-isoprostane were measured.

MEASUREMENTS AND MAIN RESULTS

IkappaB-alpha levels were significantly decreased in healthy smokers and current and ex-smoking patients with COPD when compared with nonsmokers (p < 0.001), with an associated increase in NF-kappaB DNA binding in current smokers (p < 0.05). An increase in acetylated histone 4 (ac-H4; p < 0.01) was found in current smokers. Conversely, ex-smokers with COPD showed an increase in ac-H3 (p < 0.05). Decreased levels of cytoplasmic, but not nuclear, HDAC2 protein levels were detected. From the cytokine profiles, no significant differences were detected; however, interleukin-12p40 expression correlated with ac-H4 in current smokers with COPD (p < 0.01).

CONCLUSION

These data propose a role for modification of nucleosomal structure in inflammatory cytokine gene transcription in response to smoking. The imbalance between histone deacetylation and acetylation in favor of acetylation may contribute to the enhanced inflammation in smokers susceptible to the development of COPD.

Zn2+-induced IL-8 expression involves AP-1, JNK, and ERK activities in human airway epithelial cells

Exposure to zinc-laden particulate matter in ambient and occupational settings has been associated with proinflammatory responses in the lung. IL-8 is an important proinflammatory cytokine in the human lung and is induced in human airway epithelial cells exposed to zinc. In this study, we examined the cellular mechanisms responsible for Zn2+-induced IL-8 expression. Zn2+ stimulation resulted in pronounced increases in both IL-8 mRNA and protein expression in the human airway epithelial cell line (BEAS-2B). IL-8 promoter activity was significantly increased by Zn2+ exposure in BEAS-2B cells, indicating that Zn2+-induced IL-8 expression is transcriptionally mediated. Mutation of the activating protein (AP)-1 response element in an IL-8 promoter-enhanced green fluorescent protein construct reduced Zn2+-induced IL-8 promoter activity. Moreover, Zn2+ exposure of BEAS-2B cells induced the phosphorylation of the AP-1 proteins c-Fos and c-Jun. We observed that Zn2+ exposure induced the phosphorylation of ERK, JNK, and p38 MAPKs, whereas inhibition of ERK or JNK activity blocked IL-8 mRNA and protein expression in BEAS-2B cells treated with Zn2+. In addition, we investigated the role of protein tyrosine phosphatases in the activation of signaling by Zn2+. Zn2+ treatment inhibited ERK- and JNK-directed phosphatase activities in BEAS-2B cells. These results suggested that Zn2+-induced inhibition of phosphatase activity is an initiating event in MAPK and AP-1 activation that leads to enhanced IL-8 expression by human airway epithelial cells.

The effect of ozone and PM10 on hospital admissions for pneumonia and chronic obstructive pulmonary disease: a national multicity study

A case-crossover study was conducted in 36 US cities to evaluate the effect of ozone and particulate matter with an aerodynamic diameter of < or =10 microm (PM10) on respiratory hospital admissions and to identify which city characteristics may explain the heterogeneity in risk estimates. Respiratory hospital admissions and air pollution data were obtained for 1986-1999. In a meta-analysis based on the city-specific regression models, several city characteristics were evaluated as effect modifiers. During the warm season, the 2-day cumulative effect of a 5-ppb increase in ozone was a 0.27% (95% confidence interval (CI): 0.08, 0.47) increase in chronic obstructive pulmonary disease admissions and a 0.41% (95% CI: 0.26, 0.57) increase in pneumonia admissions. Similarly, a 10-microg/m(3) increase in PM10 during the warm season resulted in a 1.47% (95% CI: 0.93, 2.01) increase in chronic obstructive pulmonary disease at lag 1 and a 0.84% (95% CI: 0.50, 1.19) increase in pneumonia at lag 0. Percentage of households with central air conditioning reduced the effect of air pollution, and variability of summer apparent temperature reduced the effect of ozone on chronic obstructive pulmonary disease. The study confirmed, in a large sample of cities, that exposure to ozone and PM10 is associated with respiratory hospital admissions and provided evidence that the effect of air pollution is modified by certain city characteristics.

Moraxella catarrhalis induces inflammatory response of bronchial epithelial cells via MAPK and NF-kappaB activation and histone deacetylase activity reduction

Moraxella catarrhalis is a major cause of infectious exacerbations of chronic obstructive lung disease (COPD) and may also contribute to the pathogenesis of COPD. Little is known about M. catarrhalis-bronchial epithelium interaction. We investigated activation of M. catarrhalis infected bronchial epithelial cells and characterized the signal transduction pathways. Moreover, we tested the hypothesis that the M. catarrhalis-induced cytokine expression is regulated by acetylation of histone residues and controlled by histone deacetylase activity (HDAC). We demonstrated that M. catarrhalis induced a strong time- and dose-dependent inflammatory response in the bronchial epithelial cell line (BEAS-2B), characterized by the release of IL-8 and GM-CSF. For this cytokine liberation activation of the ERK and p38 mitogen-activated protein (MAP) kinases and transcription factor NF-kappaB was required. Furthermore, M. catarrhalis-infected bronchial epithelial cells showed an enhanced acetylation of histone H3 and H4 globally and at the promoter of the il8 gene. Preventing histone deacetylation by the histone deacetylase inhibitor trichostatin A augmented the M. catarrhalis-induced IL-8 response. After exposure to M. catarrhalis, we found a decrease in global histone deacetylase expression and activity. Our findings suggest that M. catarrhalis-induced activation of il8 gene transcription was caused by interference with epigenetic mechanisms regulating il8 gene accessibility. Our findings provide insight into important molecular and cellular mechanisms of M. catarrhalis-induced activation of human bronchial epithelium.

Biological targets for therapeutic interventions in COPD: clinical potential

COPD is a widespread inflammatory respiratory disorder characterized by a progressive, poorly reversible airflow limitation. Currently available therapies are mostly based on those used to treat asthma. However, such compounds are not able to effectively reduce the gradual functional deterioration, as well as the ongoing airway and lung inflammation occurring in COPD patients. Therefore, there is an urgent need to improve the efficacy of the existing drug classes and to develop new treatments, targeting the main cellular and molecular mechanisms underlying disease pathogenesis. These therapeutic strategies will be highlighted in the present review.

Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy

The rapid proliferation of many different engineered nanomaterials (defined as materials designed and produced to have structural features with at least one dimension of 100 nanometers or less) presents a dilemma to regulators regarding hazard identification. The International Life Sciences Institute Research Foundation/Risk Science Institute convened an expert working group to develop a screening strategy for the hazard identification of engineered nanomaterials. The working group report presents the elements of a screening strategy rather than a detailed testing protocol. Based on an evaluation of the limited data currently available, the report presents a broad data gathering strategy applicable to this early stage in the development of a risk assessment process for nanomaterials. Oral, dermal, inhalation, and injection routes of exposure are included recognizing that, depending on use patterns, exposure to nanomaterials may occur by any of these routes. The three key elements of the toxicity screening strategy are: Physicochemical Characteristics, In Vitro Assays (cellular and non-cellular), and In Vivo Assays. There is a strong likelihood that biological activity of nanoparticles will depend on physicochemical parameters not routinely considered in toxicity screening studies. Physicochemical properties that may be important in understanding the toxic effects of test materials include particle size and size distribution, agglomeration state, shape, crystal structure, chemical composition, surface area, surface chemistry, surface charge, and porosity. In vitro techniques allow specific biological and mechanistic pathways to be isolated and tested under controlled conditions, in ways that are not feasible in in vivo tests. Tests are suggested for portal-of-entry toxicity for lungs, skin, and the mucosal membranes, and target organ toxicity for endothelium, blood, spleen, liver, nervous system, heart, and kidney. Non-cellular assessment of nanoparticle durability, protein interactions, complement activation, and pro-oxidant activity is also considered. Tier 1 in vivo assays are proposed for pulmonary, oral, skin and injection exposures, and Tier 2 evaluations for pulmonary exposures are also proposed. Tier 1 evaluations include markers of inflammation, oxidant stress, and cell proliferation in portal-of-entry and selected remote organs and tissues. Tier 2 evaluations for pulmonary exposures could include deposition, translocation, and toxicokinetics and biopersistence studies; effects of multiple exposures; potential effects on the reproductive system, placenta, and fetus; alternative animal models; and mechanistic studies.

Transcriptional regulation of cyclooxygenase-2 in response to proteasome inhibitors involves reactive oxygen species-mediated signaling pathway and recruitment of CCAAT/enhancer-binding protein delta and CREB-binding protein

Inhibition of ubiquitin-proteasome pathway has been shown to be a promising strategy for the treatment of inflammation and cancer. Here, we show that proteasome inhibitors MG132, PSI-1, and lactacystin induce COX-2 expression via enhancing gene transcription rather than preventing protein degradation in the human alveolar NCI-H292 and A549, and gastric AGS epithelial cells. NF-IL6 and CRE, but not NF-kappaB elements on the COX-2 promoter were involved in the gene transcription event. The binding of CCAAT/enhancer binding protein (C/EBP)beta and C/EBPdelta to the CRE and NF-IL6 elements, as well as the recruitment of CBP and the enhancement of histone H3 and H4 acetylation on the COX-2 promoter was enhanced by MG132. However, it did not affect the total protein levels of C/EBPbeta and C/EBPdelta. MG132-induced DNA-binding activity of C/EBPdelta, but not C/EBPbeta was regulated by p38, PI3K, Src, and protein kinase C. Small interfering RNA of C/EBPdelta suppressed COX-2 expression, further strengthening the role of C/EBPdelta in COX-2 gene transcription. In addition, the generation of intracellular reactive oxygen species (ROS) in response to MG132 contributed to the activation of MAPKs and Akt. These findings reveal that the induction of COX-2 transcription induced by proteasome inhibitors requires ROS-dependent protein kinases activation and the subsequent recruitments of C/EBPdelta and CBP.

Air pollution and cancer: biomarker studies in human populations

Large cohort studies in the U.S. and in Europe suggest that air pollution may increase lung cancer risk. Biomarkers can be useful to understand the mechanisms and to characterize high-risk groups. Here we describe biomarkers of exposure, in particular DNA adducts as well as markers of early damage, including mutagenicity, other endpoints of genotoxicity and molecular biomarkers of cancer. Several studies found an association between external measures of exposure to air pollution and increased levels of DNA adducts, with an apparent levelling-off of the dose-response relationship. Also, numerous experimental studies in vitro and in vivo have provided unambiguous evidence for genotoxicity of air pollution. In addition, due to the organic extracts of particulate matter [especially various polycyclic aromatic hydrocarbon (PAH) compounds], particulate air pollution induces oxidative damage to DNA. The experimental work, combined with the data on frequent oxidative DNA damage in lymphocytes in people exposed to urban air pollution, suggests 8-oxo-dG as one of the important promutagenic lesions. Lung cancer develops through a series of progressive pathological changes occurring in the respiratory epithelium. Molecular alterations such as loss of heterozygosity, gene mutations and aberrant gene promoter methylation have emerged as potentially promising molecular biomarkers of lung carcinogenesis. Data from such studies relevant for emissions rich in PAHs are also summarized, although the exposure circumstances are not directly relevant to outdoor air pollution, in order to shed light on potential mechanisms of air pollution-related carcinogenesis.

Biomarkers in risk assessment of asbestos exposure

Developments in the field of molecular epidemiology and toxicology have given valuable tools for early detection of impending disease or toxic condition. Morbidity due to respiratory distress, which may be due to environmental and occupational exposure, has drawn attention of researchers worldwide. Among the occupational exposure to respiratory distress factors, fibers and particles have been found to be main culprits in causing diseases like asbestosis, pleural plaques, mesotheliomas and bronchogenic carcinomas. An early detection of the magnitude of exposure or its' effect using molecular end points is of growing importance. The early inflammatory responses like release of the inflammatory cells collected by non-invasive methods give an indication of the unwanted exposure and susceptibility to further complications. Since free radicals like O2-, OH, OOH, NO, NOO, etc. are involved in the progression of asbestos-related diseases and lead to cytogenetic changes, an evaluation of antioxidant states reducing equivalents like GSH and ROS generation can be a good biomarker. The cytogenetic end points like chromosomal aberration, micronucleus formation and sister chromatid exchange give indication of genetic damage, hence they are used as effective biomarkers. New techniques like fluorimetric analysis of DNA unwinding, alkaline elution test, fluorescent in situ hybridization and comet assay are powerful tools for early detection of initiation of disease process and may help in planning strategies for minimizing morbidity related to asbestos fiber exposure. The present review article covers in detail possible biomarkers for risk assessment of morbidity due to fibers/particles in exposed population.

Curcumin-induced histone hypoacetylation: The role of reactive oxygen species

Curcumin (Cur), a well-known dietary pigment derived from Curcuma longa, is a promising anticancer drug, but its in vivo target molecules remain to be clarified. Here we report that exposure of human hepatoma cells to Cur led to a significant decrease of histone acetylation. Histone acetyltransferase (HAT) and histone deacetylase (HDAC) are the enzymes controlling the state of histone acetylation in vivo. Cur treatment resulted in a comparable inhibition of histone acetylation in the absence or presence of trichostatin A (the specific HDAC inhibitor), and showed no effect on the in vitro activity of HDAC. In contrast, the domain negative of p300 (a most potent HAT protein) could block the inhibition of Cur on histone acetylation; and the Cur treatment significantly inhibited the HAT activity both in vivo and in vitro. Thus, it is HAT, but not HDAC that is involved in Cur-induced histone hypoacetylation. At the same time, exposure of cells to low or high concentrations of Cur diminished or enhanced the ROS generation, respectively. And the promotion of ROS was obviously involved in Cur-induced histone hypoacetylation, since Cur-caused histone acetylation and HAT activity decrease could be markedly diminished by the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) or their combination, but not by their heat-inactivated forms. The data presented here prove that HAT is one of the in vivo target molecules of Cur; through inhibiting its activity, Cur induces histone hypoacetylation in vivo, where the ROS generation plays an important role. Considering the critical roles of histone acetylation in eukaryotic gene transcription and the involvement of histone hypoacetylation in the lose of cell viability caused by high concentrations of Cur, these results open a new door for us to further understand the molecular mechanism involved in the in vivo function of Cur.

Histone hypoacetylation is involved in 1,10-phenanthroline?Cu2+-induced human hepatoma cell apoptosis

The 1,10-orthophenanthroline (OP)-Cu(2+) combination, one generally used reactive oxygen species (ROS) generation system, is known to induce cell apoptosis, but the mechanism of ROS generation in this process remains unclear. Here we found that in the presence of 5 microM Cu(2+), OP inhibited histone acetyltransferase (HAT) activity, resulting in decreased acetylation in both histone H3 and H4. This inhibition of histone acetylation and HAT activity was significantly attenuated by preventing or scavenging ROS generation with the Cu(2+) chelator of bathocuproine disulfonate, or the antioxidants of N-acetyl-cysteine and mannitol, respectively, indicating the involvement of ROS generation in OP-Cu(2+) -induced histone hypoacetylation. At the same time, this ROS generation is found to be involved in OP-Cu(2+) -induced apoptosis in human hepatoma Hep3B cells. The important role of histone hypoacetylation in the induction of apoptosis was also proven by the marked diminution of apoptosis by 100 nM trichostatin A, a specific inhibitor of histone deacetylase, or the overexpression of p300, an HAT protein. Collectively, these observations suggest that histone hypoacetylation represents one unrevealed mechanism involved in the in vivo function of OP-Cu(2+) -generated ROS, at least in their induction of cell apoptosis.

Redox regulation of p38 MAPK activation and expression of ICAM-1 and heme oxygenase-1 in human alveolar epithelial (A549) cells

We have explored the potential role of redox events in p38 mitogen-activated protein kinase (MAPK) activation and their relevance to the inducible expression of intercellular adhesion molecule-1 (ICAM-1) and heme oxygenase-1 (HO-1) in A549 cells. Tumor necrosis factor-alpha (TNFalpha) and hydrogen peroxide (H2O2) both activated p38, but only TNFalpha activated nuclear factor-kappaB (NF-kappaB). N-Acetyl-L-cysteine (20 mM) inhibited both H2O2- and TNFalpha-induced p38 phosphorylation (14 +/- 7 and 37 +/- 4% of control, respectively). The mitochondrial complex I and III inhibitors, rotenone and antimycin A, and allopurinol partially inhibited H2O2- but not TNFalpha-induced p38 activation. However, rotenone and antimycin A augmented intracellular oxidative stress measured by dichlorofluorescein fluorescence. TNFalpha, but not H2O2, induced ICAM-1 in A549 cells, which was attenuated by a proteasome inhibitor, but not by the p38 MAPK inhibitor SB203580. In contrast, hemin and hemoglobin, but neither TNFalpha nor H2O2, caused efficient HO-1 expression. However, hemin had no effect on p38 activation and SB203580 did not influence hemin-induced HO-1 protein expression. Collectively, these data suggest that p38 is a cytokine- and oxidative stress-responsive pathway in A549 cells. Whereas NF-kappaB appears crucial in ICAM-1 induction, p38 activation itself is not sufficient to confer HO-1 expression and may not be involved in HO-1 and ICAM-1 induction in A549 cells.

Redox regulation of histone deacetylases and glucocorticoid-mediated inhibition of the inflammatory response

Gene expression, at least in part, is regulated by changes in histone acetylation status induced by activation of the proinflammatory redox-sensitive transcription factors activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB). Hyperacetylated histone is associated with open actively transcribed DNA and enhanced inflammatory gene expression. In contrast, hypoacetylated histone is linked to a closed repressed DNA state and a lack of gene expression. The degree of inflammatory gene expression is a result of a balance between histone acetylation and histone deacetylation. One of the major mechanisms of glucocorticoid function is to recruit histone deacetylase enzymes to the site of active gene expression, thus reducing inflammation. Oxidative stress can enhance inflammatory gene expression by further stimulating AP-1- and NF-kappaB-mediated gene expression and elevating histone acetylation. In addition, oxidants can reduce glucocorticoid function by attenuating histone deacetylase activity and expression. Thus, oxidant stress, acting through changes in chromatin structure, can enhance inflammation and induce a state of relative glucocorticoid insensitivity. This may account for the lack of glucocorticoid sensitivity in patients with chronic obstructive pulmonary disease. Antioxidants should reduce the inflammation and restore glucocorticoid sensitivity in these subjects.

The Role of Oxidative Stress in the Pathogenesis??of COPD

Chronic inflammation and oxidative stress are important features in the pathogenesis of COPD. The increased oxidative stress in patients with COPD is the result of an increased burden of inhaled oxidants, as well as increased amounts of reactive oxygen species (ROS) generated by various inflammatory, immune and epithelial cells of the airways. Oxidative stress has important implications on several events of lung physiology and for the pathogenesis of COPD. These include oxidative inactivation of antiproteases and surfactants, mucus hypersecretion, membrane lipid peroxidation, mitochondrial respiration, alveolar epithelial injury, remodeling of extracellular matrix, and apoptosis. An increased level of ROS produced in the airways is reflected by increased markers of oxidative stress in the airspaces, sputum, breath, lungs, and blood in patients with COPD. The biomarkers of oxidative stress such as H2O2, F2-isoprostanes, malondialdehyde and 4-hydroxy-2-nonenal have been successfully measured in breath condensate. ROS and aldehydes play a key role in enhancing the inflammation through the activation of mitogen-activated protein kinases and redox-sensitive transcription factors such as nuclear factor kappa B and activator protein-1. Oxidative stress also alters nuclear histone acetylation and deacetylation leading to increased gene expression of pro-inflammatory mediators in the lung. Oxidative stress may play a role in the poor clinical efficacy of corticosteroids in the treatment of COPD. Since a variety of oxidants, free radicals, and aldehydes are implicated in the pathogenesis of COPD it is likely that a combination of antioxidants may be effective in the treatment of COPD. Antioxidant compounds may also be of therapeutic value in monitoring oxidative biomarkers indicating disease progression. Various approaches to enhance the lung antioxidant screen and the clinical effectiveness of antioxidant compounds in the treatment of COPD are discussed.

Redox regulation of lung development and perinatal lung epithelial function

Throughout gestation, low oxygen tensions are a dominant feature of the fetal environment and so may be important in sustaining a normal pattern of lung morphogenesis until the moment of birth. As breathing begins, the equilibration of the lung lumen to postnatal PO2 evokes a series of physiologic and morphogenic maturation events that are partially reversible by hypoxia. In this review, we discuss the experimental evidence that fetal and perinatal oxygen tensions differently influence lung morphogenesis through oxygen- and redox-responsive signaling pathways and identify five loci at which this regulation may occur: (I) proliferation of undifferentiated lung mesenchyme as governed by hypoxia-regulated transcription factors (HIF-1alpha, C/EBPbeta); (II) transient production of reactive oxygen species (ROS) and nuclear oxidation of the perinatal lung epithelium; (III) nuclear transport and oxidation of thioredoxin in hand with the acute activation of nuclear factor- kappaB (NF-kappaB); (IV) ROS-evoked chronic rise in intracellular glutathione and thioredoxin redox buffering capacity; and (V) NF-kappaB-dependent increase in transepithelial Na+ transport and lung lumenal fluid clearance. Although not exhaustive, this analysis leads us to the conclusion that redox events that occur in the lung during gestation, parturition, and the early neonatal period may dramatically influence the expression of genes and physiological events that are crucial to the successful transition from fetal to postnatal lung maturation.

Hypertensive rats are susceptible to TLR4-mediated signaling following exposure to combustion source particulate matter

Toll-like receptor 4 (TLR4) has been shown to play a role in cell signaling that results in neutrophilic inflammation in response to lipopolysaccharide and respiratory syncytial virus infection. TLR4 also interacts with CD14, which upon complex formation triggers TLR4-associated signaling pathways to produce a proinflammatory response. This mechanism results in the activation of NF-kappa B and subsequent inflammatory gene induction. In order to determine the effect of combustion source particle matter (PM), rich in zinc and nickel but with negligible endotoxin, on a possible activation of TLR4-mediated cell signaling and inflammation, we intratracheally (IT) instilled 3.3 mg/kg of PM into 12-w-old healthy male Wistar Kyoto (WKY) and susceptible spontaneously hypertensive (SH) rats. Inflammation, inflammatory-mediator gene expression, bronchoalveolar lavage fluid (BALF) protein and LDH, TLR4 and CD14 protein, and NF-kappa B activation in the lung were determined after 24 h. Dose-response data (0.0, 0.83, 3.33, and 8.3 mg/kg PM) for BALF LDH were obtained as a marker of lung cell injury in SH rats. BALF neutrophils, but not macrophages, were significantly increased in the PM-exposed WKY and SH rats. SH rats showed a greater PMN increase than WKY rats. Similarly, BALF protein and LDH levels were also increased following PM exposure but to a significantly greater extent in SH rats. Plasma fibrinogen was increased only in SH rats exposed to PM. The increased inflammation seen in PM-exposed SH rats was accompanied by a significant increase in TLR4 protein in the lung tissue, which was primarily localized in alveolar macrophages and epithelial cells. CD14 was also increased by PM exposure in both SH and WKY rats but was significantly greater in the SH rats. These increases were associated with greater translocation of NF-kappa B in the lungs of SH rather than WKY rats. This was accompanied by increased macrophage inhibitory protein (MIP)-2 mRNA expression at 24 h of exposure. These data suggest that the increased inflammation in the lungs of PM-exposed SH rats compared to WKY rats is accompanied by an increase in TLR4-mediated cell signaling. Thus, one of the mechanisms for greater susceptibility of SH rats to PM exposure may involve an increased activation of the TLR4 signaling pathway.

Effects of hydrogen peroxide on MAPK activation, IL-8 production and cell viability in primary cultures of human bronchial epithelial cells

The airway epithelium is continuously exposed to inhaled oxidants, including airborne pollutants and cigarette smoke, which can exert harmful proinflammatory and cytotoxic effects. Therefore, the aim of our study was to investigate, in primary cultures of human bronchial epithelial cells (HBEC), the signal transduction pathways activated by increasing concentrations (0.25, 0.5, and 1 mM) of hydrogen peroxide (H(2)O(2)), as well as their effects on IL-8 production and cell viability. The reported results show that H(2)O(2) elicited, in a concentration-dependent fashion, a remarkable increase in phosphorylation-dependent activation of mitogen-activated protein kinases (MAPKs), associated with a significant induction of IL-8 synthesis and a dramatically enhanced cell death. Pre-treatment of HBEC with MAPK inhibitors was able to significantly inhibit the effects of H(2)O(2) on IL-8 secretion, and to effectively prevent cell death. Therefore, these findings suggest that MAPKs play a key role as molecular transducers of the airway epithelial injury triggered by oxidative stress, as well as potential pharmacologic targets for indirect antioxidant intervention.

Inhaled particles and lung cancer. Part A: Mechanisms

Both occupational and environmental exposure to particles is associated with an increased risk of lung cancer. Particles are thought to impact on genotoxicity as well as on cell proliferation via their ability to generate oxidants such as reactive oxygen species (ROS) and reactive nitrogen species (RNS). For mechanistic purposes, one should discriminate between a) the oxidant-generating properties of particles themselves (i.e., acellular), which are mostly determined by the physicochemical characteristics of the particle surface, and b) the ability of particles to stimulate cellular oxidant generation. Cellular ROS/RNS can be generated by various mechanisms, including particle-related mitochondrial activation or NAD(P)H-oxidase enzymes. In addition, since particles can induce an inflammatory response, a further subdivision needs to be made between primary (i.e., particle-driven) and secondary (i.e., inflammation-driven) formation of oxidants. Particles may also affect genotoxicity by their ability to carry surface-adsorbed carcinogenic components into the lung. Each of these pathways can impact on genotoxicity and proliferation, as well as on feedback mechanisms involving DNA repair or apoptosis. Although abundant evidence suggests that ROS/RNS mediate particle-induced genotoxicity and mutagenesis, little information is available towards the subsequent steps leading to neoplastic changes. Additionally, since most of the proposed molecular mechanisms underlying particle-related carcinogenesis have been derived from in vitro studies, there is a need for future studies that evaluate the implication of these mechanisms for in vivo lung cancer development. In this respect, transgenic and gene knockout animal models may provide a useful tool. Such studies should also include further assessment of the relative contributions of primary (inflammation-independent) and secondary (inflammation-driven) pathways.

Inhaled particles and lung cancer, part B: paradigms and risk assessment

Poorly soluble particles of low toxicity (PSP), such as CB, TiO(2) and coal mine dust, have been demonstrated to cause lung cancer in rodents, being most pronounced in rats. Adequate epidemiologic studies do not clearly indicate increased lung cancer rates in humans exposed to such particles. This has caused controversial positions in regulatory decisions on PSP on different levels. The present review discusses the current paradigms in rodent particle carcinogenicity, i.e., (i) role of particle overload and of persistent inflammation and (ii) fibrosis as an intermediate step in particle-induced lung cancer with regard to human risk assessment. Fibrosis, which is usually considered a precursor of lung cancer in humans, was not related to lung tumors in an animal study using 6 different particles, each at 3 dosages. Lung tumors after both inhalation and intratracheal instillation of PSP are related to particle surface dose, which forwards hazard assessment at surface-based nonoverload concentrations and a standard setting using surface as an exposure metric. The scarce data available on humans do not support the overload concept but suggest a role for persistent lung inflammation. Differences in antioxidant protection between different rodent species correlate with susceptibility to PSP-induced carcinogenicity and support the need for detailed studies on antioxidant response in humans. Apart from such bridging studies, further focus is also needed on surface chemistry and modifications in relation to their adverse biologic effects.

Peroxide-mediated chromatin remodelling of a nuclear factor kappa B site in the mouse inducible nitric oxide synthase promoter

Hepatocyte expression of iNOS (inducible nitric oxide synthase) and synthesis of nitric oxide convey protective antioxidant functions in models of sepsis, shock and reperfusion. However, the underlying redox-sensitive mechanisms that regulate hepatocyte expression of iNOS and its antioxidant functions are largely unknown. Activity of the transcription factor NF-kappaB (nuclear factor kappaB) is known to be redox-modulated. In this regard, the mouse hepatocyte iNOS promoter has NF-kappaB-binding sites at nt -1044 to -1034 and at nt -114 to -104, which are considered to be critical for iNOS expression in response to pro-inflammatory cytokine stimulation. The relative contribution of these two NF-kappaB-binding sites in the mouse iNOS promoter to hepatocyte iNOS promoter activity in the context of oxidative stress has not been characterized previously. In addition, although the cis - and trans -regulatory factors controlling mouse hepatocyte iNOS expression have been well-characterized, the local changes in chromatin structure that accompany activation of iNOS gene transcription have not been considered. In the present study, we demonstrate that (1) in the absence of exogenous oxidative stress, the NF-kappaB site at nt -114 is inactive and (2) peroxide-mediated oxidative stress induces hyperacetylation and enhanced accessibility of the restriction enzyme to this NF-kappaB region. Our results suggest that chromatin structural changes activate this NF-kappaB site and increase interleukin-1beta-stimulated iNOS expression in the presence of oxidative stress.

Antioxidants in myocardial ischemia-reperfusion injury: therapeutic potential and basic mechanisms

Oxidative stress is a constant threat to all living organisms and an immense repertoire of cellular defense systems is being employed by most pro- and eukaryotic systems to eliminate or to attenuate oxidative stress. Ischemia and reperfusion is characterized by both a significant oxidative stress and characteristic changes in the antioxidant defense. By focusing on this antioxidant response of the cardiovascular system in the setting of ischemia-reperfusion injury, the aim of this review was threefold. First, based on recent animal experiments and clinical studies we shall discuss how endogenous antioxidants respond to oxidative stress during ischemia-reperfusion injury and highlight the results of recent trials on the ability of antioxidants to modulate ischemia-reperfusion injury. In this aspect, we will particularly focus on the emerging concept that various lines of antioxidant defenses do not act individually but are linked to each other in a systematic relationship as part of an antioxidant network. It is well known that enzymatic mechanisms are important components of the endogenous antioxidant repertoire; however, the relative importance of the different enzyme systems and isoforms has been much debated. The second part will focus on recent suggestions attributing a potentially key role of mitochondrial MnSOD in cardiac ischemia-reperfusion injury. Finally, the third part of the review will critically examine how endogenous antioxidants might regulate the complex signal transduction pathways of cellular activation with particular attention to the NF-kappaB and MAPK systems that appears to determine outcome of injury, survival, and adaptation.

Oxidative stress and calcium signaling in the adverse effects of environmental particles (PM10)

This review focuses on the potential role that oxidative stress plays in the adverse effects of PM(10). The central hypothesis is that the ability of PM(10) to cause oxidative stress underlies the association between increased exposure to PM(10) and both exacerbations of lung disease and lung cancer. Pulmonary inflammation may also underlie the cardiovascular effects seen following increased PM(10), although the mechanisms of the cardiovascular effects of PM(10) are not well understood. PM(10) is a complex mix of various particle types and several of the components of PM(10) are likely to be involved in the induction of oxidative stress. The most likely of these are transition metals, ultrafine particle surfaces, and organic compounds. In support of this hypothesis, oxidative stress arising from PM(10) has been shown to activate a number of redox-responsive signaling pathways in lung target cells. These pathways are involved in expression of genes that play a role in responses relevant to inflammation and pathological change, including MAPKs, NF-kappaB, AP-1, and histone acetylation. Oxidative stress from particles is also likely to play an important role in the carcinogenic effects associated with PM(10) and hydroxyl radicals from PM(10) cause DNA damage in vitro.