Chrysotile-mediated imbalance in the glutathione redox system in the development of pulmonary injury

Sinapic Acid Attenuates Cardiovascular Disorders in Rats by Modulating Reactive Oxygen Species and Angiotensin Receptor Expression

The main avoidable risk factor for cardiovascular conditions is high blood pressure (hypertension). At global level, hypertension is believed to be responsible for a 54% stroke-related mortality rate and a 47% mortality rate associated with coronary heart disease. It is postulated that sinapic acid (SA) could help in hypertension management because it displays robust antioxidant, antihyperglycemic, and peroxynitrite scavenging effects. To explore this hypothesis, this work examined the effect of SA on oxidative stress and cardiovascular disease in rats with hypertension by comparison against captopril. For this purpose, 50 male rats were used and equally allocated to five groups, namely, normal control, positive control (L-NAME), L-NAME with concomitant captopril administration, L-NAME with concomitant SA administration, and L-NAME with concomitant administration of both SA and captopril. Results showed that, by contrast to control, L-NAME exhibited marked elevation in serum CK-MB, total cholesterol, triglycerides, VLDL-C, LDL-C, Ang II, AT2R, ET-1, and angiopoietin-2; on the other hand, L-NAME exhibited marked reduction in serum HDL-C, superoxide dismutase (SOD) activity, nitric oxide synthase 3 (NOS3), and glutathione (GSH). Furthermore, joint administration of SA and captopril ameliorated hypertension, enhanced cardiovascular function, hindered hyperlipidemia, and decreased oxidative stress and myocardial hypertrophy displayed by rats with hypertension. Based on such findings, better chemopreventive or therapeutic approaches can be devised to manage hypertension and cardiovascular conditions.

Study on genotoxicity, oxidative stress biomarkers and clinical symptoms in workers of an asbestos-cement factory

The purpose of the present study was to investigate whether the markers of oxidative stress could be altered in workers exposed to asbestos. A comparative cross-sectional research was conducted in a group of 50 subjects exposed to asbestos and another group of 50 with the same age and sex unexposed to asbestos. Malondialdehyde (MDA), total thiol molecule (TTM), total antioxidant capacity (TAC), and DNA damage, were measured in the blood samples of workers and controls. Compared to the control group, the workers showed higher blood levels of DNA damage (P=0.0001) and MDA (P=0.0001). The workers showed lower TTM (P=0.02) as compared with the control group. There was no considerable difference on the level of TAC (P=0.1) between the groups. The workers indicated clinical symptoms such as breathlessness, phlegm, coughing and wheezing. There was a positive correlation between levels of 8-OHdG and MDA of asbestos workers and the smoking status suggesting the negative role of smoking.

Oral administration of veratric acid, a constituent of vegetables and fruits, prevents cardiovascular remodelling in hypertensive rats: a functional evaluation

In our previous studies, veratric acid (VA) shows beneficial effect on hypertension and its associated dyslipidaemia. In continuation, this study was designed to investigate the effect of VA, one of the major benzoic acid derivatives from vegetables and fruits, on cardiovascular remodelling in hypertensive rats, primarily assessed by functional studies using Langendorff isolated heart system and organ bath system. Hypertension was induced in male albino Wistar rats by oral administration of N ω -nitro-l-arginine methyl ester hydrochloride (l-NAME) (40 mg/kg body weight (b.w.)) in drinking water for 4 weeks. VA was orally administered at a dose of 40 mg/kg b.w. l-NAME-treated rats showed impaired cardiac ventricular and vascular function, evaluated by Langendorff isolated heart system and organ bath studies, respectively; a significant increase in the lipid peroxidation products such as thiobarbituric acid-reactive substances and lipid hydroperoxides in aorta; and a significant decrease in the activities of superoxide dismutase, catalase, glutathione peroxidase and levels of GSH, vitamin C and vitamin E in aorta. Fibrotic remodelling of the aorta and heart were assessed by Masson's Trichrome staining and Van Gieson's staining, respectively. In addition, l-NAME rats showed increased heart fibronectin expression assessed by immunohistochemical analysis. VA supplementation throughout the experimental period significantly normalised cardiovascular function, oxidative stress, antioxidant status and fibrotic remodelling of tissues. These results of the present study conclude that VA acts as a protective agent against hypertension-associated cardiovascular remodelling.

Morin attenuates blood pressure and oxidative stress in deoxycorticosterone acetate-salt hypertensive rats: a biochemical and histopathological evaluation

The present study was designed to evaluate the antihypertensive and antioxidant effect of morin, a flavonoid against deoxycorticosterone acetate (DOCA)-salt induced hypertension in male Wistar rats. Hypertension was induced in uninephrectomized rats (UNX) by weekly twice subcutaneous injection of DOCA (25mg/kg) and 1% NaCl in the drinking water for six consecutive weeks. The DOCA-salt hypertensive rats showed significant (P < .05) increase in the systolic and diastolic blood pressure, heart rate, water intake and organ weights (kidney, heart, aorta and liver). DOCA-salt hypertensive rats also showed significant (P < .05) increase in the levels of thiobarbituric acid reactive substances, lipid hydroperoxides and conjugated dienes in plasma and tissues (kidney, heart, aorta and liver), and significant (P < .05) decrease in the body weight, nitrite and nitrate levels in plasma and heart. Furthermore, the activities of enzymic antioxidants such as superoxide dismutase, catalase and glutathione peroxidase in erythrocyte and tissues and the levels of non-enzymic antioxidants such as reduced glutathione, vitamin C and vitamin E in plasma and tissues were significantly (P < .05) decreased in DOCA-salt rats. Morin supplementation (50mg/kg) daily for six weeks brought back all the above parameters to near normal level. The above findings were confirmed by the histopathological examination. No significant (P < .05) effect was observed in UNX-rats treated with morin (50mg/kg). These results suggest that morin acts as an antihypertensive and antioxidant agent against DOCA-salt induced hypertension.

Antioxidant status in MgO nanoparticle-exposed rats

In this present study, antioxidant status was evaluated in rat serum following exposure to magnesium oxide (MgO) nanoparticles. The lungs of rats were intratracheally instilled with (single dose) phosphate-buffered saline (PBS) + 1% of Tween 80 (solvent control) or MgO or carbonyl iron (negative control) or quartz particles (positive control) at a dose of 1 and 5 mg/kg of body weight. The blood samples were collected at 1, 7, and 30 days of postinstillation of nanoparticles after their exposure, and different parameters were estimated to assess the oxidative stress induced by the instillation of MgO. Exposure of rats to MgO produced a significant ( p < 0.05) dose-dependent reduction in blood total antioxidant capacity, superoxide dismutase, and catalase activity levels than PBS + 1% Tween 80 control group. This reduction in the antioxidant capacity in MgO nanoparticle-exposed rats indicates the reduction in antioxidant defense mechanisms due to the instillation of MgO. These results indicate that exposure to MgO nanoparticles induces oxidative stress by reducing the total antioxidant capacity in rats. The findings suggest possible occupational health hazard in chronic exposures.

Antihypertensive and antioxidant potential of vanillic acid, a phenolic compound in L-NAME-induced hypertensive rats: a dose-dependence study

We investigated the antihypertensive and antioxidant potential of vanillic acid (VA) in N(ω)-Nitro-L-arginine methyl ester hydrochloride (L-NAME) - treated adult male albino Wistar rats. Treatment of rats with L-NAME (40 mg/kg Bw for 30 days) caused a sustained increase in systolic- (SBP) and diastolic blood pressure (DBP) and significantly decreased the concentration of nitrite/nitrate (NO(x)) in plasma as compared with that in the control. Rats treated with VA restored SBP and DBP to normal level and preserve the plasma NO metabolites concentration. Moreover, VA reduced lipid peroxidation products (thiobarbituric acid reactive substances, lipid hydroperoxides, conjugated dienes) and significantly restored enzymatic antioxidants (superoxide dismutase, catalase, and glutathione peroxidase), non-enzymatic antioxidants (vitamin C, vitamin E, and reduced glutathione) in the plasma. To assess the toxicity if any of VA treatment, hepatic and renal function markers were measured. Our results showed that the effect at a dose of 50 mg/kg Bw of VA was more pronounced than that of the other two doses, 25 and 100 mg/kg Bw. These results were supported by histopathology studies. We conclude that VA possesses an antihypertensive and antioxidant activity in L-NAME-induced hypertensive rats.

The potential health risk of titania nanoparticles

Widespread use of titania nanoparticles (TNPs) has caused a significant release of TNPs into the environment, increasing human exposure to TNPs. The potential toxicity of TNPs has become an urgent concern. Various models have been used to evaluate the toxic effects of TNPs, but the relationship between TNPs' toxicity and physicochemical properties is largely unknown. This review summarizes relevant reports to support the development of better predictive toxicological models and the safe future application of TNPs.

Hesperidin, a flavanone glycoside, on lipid peroxidation and antioxidant status in experimental myocardial ischemic rats

Myocardial infarction continues to be a leading cause of mortality world-wide. Novel therapies are needed to treat the myocardial ischemia. This study was undertaken to evaluate the cardioprotective role of hesperidin on isoproterenol-induced myocardial ischemia in rats. Myocardial ischemia was induced by subcutaneous injection of isoproterenol hydrochloride (85 mg/kg body weight), for two consecutive days. Isoproterenol-administered rats showed elevated levels of cardiac markers (aspartate transaminase, alanine transaminase, lactate dehydrogenase, creatine kinase, creatine kinase-MB, cardiac troponins T and I) when compared with control and hesperidin treatment groups (100, 200 and 400 mg/kg body weight). The serum levels of cardiac markers were significantly reduced at the doses of 200 mg and 400 mg. All further experiments were carried out at the 200 mg dose. Lipid peroxidation markers (thiobarbituric acid reactive substances, lipid hydroperoxides and conjugated dienes) were elevated significantly in the plasma and heart whereas non-enzymic antioxidants (vitamin C, vitamin E and reduced glutathione) were decreased significantly. Activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and glutathione reductase declined significantly in the heart of ischemic rats. However, after hesperidin treatment, all the above parameters reverted to normal levels. This study demonstrated that the cardioprotective effect of hesperidin on ischemic rats could be due to its anti-lipid peroxidative and antioxidant properties.

Hesperidin pre-treatment attenuates NO-mediated cerebral ischemic reperfusion injury and memory dysfunction

The present study was designed to explore the mechanism of hesperidin action via the nitric oxide pathway in the protection against ischemic reperfusion cerebral injury-induced memory dysfunction. Male Wistar rats (200-220 g) were subjected to bilateral carotid artery occlusion for 30 min followed by 24 h reperfusion. Hesperidin (50 and 100 mg/kg, po) pretreatment was given for 7 days before animals were subjected to cerebral I/R injury. Various behavioral tests (rotarod performance and memory retention), biochemical parameters (lipid peroxidation, nitrite concentration, glutathione levels, superoxide dismutase activity and catalase activity), mitochondrial complex enzyme dysfunctions (complex I, II, III and IV) and histopathological alterations were subsequently assessed in hippocampus. Seven days of hesperidin (50 and 100 mg/kg) treatment significantly improved neurobehavioral alterations (delayed fall off time and increased memory retention), oxidative defense and mitochondrial complex enzyme activities in hippocampus compared to control (I/R) animals. In addition, hesperidin treatment significantly attenuated histopathological alterations compared to control (I/R) animals. L-arginine (100 mg/kg) pretreatment attenuated the protective effect of the lower dose of hesperidin on memory behavior, biochemical and mitochondrial dysfunction compared with hesperidin alone. However, L-NAME pretreatment significantly potentiated the protective effect of hesperidin. The present study suggests that the L-arginine-NO signaling pathway is involved in the protective effect of hesperidin against cerebral I/R-induced memory dysfunction and biochemical alterations in rats.

Roles of oxidative stress in signaling and inflammation induced by particulate matter

This review reports the role of oxidative stress in impairing the function of lung exposed to particulate matter (PM). PM constitutes a heterogeneous mixture of various types of particles, many of which are likely to be involved in oxidative stress induction and respiratory diseases. Probably, the ability of PM to cause oxidative stress underlies the association between increased exposure to PM and exacerbations of lung disease. Mostly because of their large surface area, ultrafine particles have been shown to cause oxidative stress and proinflammatory effects in different in vivo and in vitro studies. Particle components and surface area may act synergistically inducing lung inflammation. In this vein, reactive oxygen species elicited upon PM exposure have been shown to activate a number of redox-responsive signaling pathways and Ca(2+) influx in lung target cells that are involved in the expression of genes that modulate relevant responses to lung inflammation and disease.

Exposure to chrysotile asbestos causes carbonylation of glucose 6-phosphate dehydrogenase through a reaction with lipid peroxidation products in human lung epithelial cells

Exposure to asbestos is known to lead to a reduction in glucose 6-phosphate dehydrogenase (G6PDH) activity and to cause oxidative damage to cells. In the present study, we exposed the human lung carcinoma cell line A549 to chrysotile. We observed an increase in the production of thiobarbituric acid-reactive substances (TBARS, the breakdown products of lipid peroxide) along with a significant decrease in G6PDH activity. Alternatively, when chrysotile was added directly to the cell extract obtained by removing the cell membrane, no loss of G6PDH activity was observed. To elucidate the mechanism of G6PDH inactivation due to exposure to chrysotile, we focused on the TBARS responsible for protein modification via carbonylation. When malondialdehyde or 4-hydroxy-2-nonenal was added to a membrane-free A549 cell extract, G6PDH activity was reduced markedly. However, when t-butylhydroperoxide was added to the extract, there was no significant decrease in G6PDH activity. Western blot analysis and immunoprecipitation of the carbonylated proteins in the A549 cell lysate that was prepared after exposure to chrysotile demonstrated that G6PDH had been carbonylated. Our findings indicate that the decrease in G6PDH activity that occurs after exposure of the cultured cells to chrysotile results from the carbonylation of G6PDH by TBARS.

Oxidative stress and glutathione in TGF-beta-mediated fibrogenesis

Transforming growth factor beta (TGF-beta) is the most potent and ubiquitous profibrogenic cytokine, and its expression is increased in almost all the fibrotic diseases and in experimental fibrosis models. TGF-beta increases reactive oxygen species production and decreases the concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, which mediates many of the fibrogenic effects of TGF-beta in various types of cells. A decreased GSH concentration is also observed in human fibrotic diseases and in experimental fibrosis models. Although the biological significance of GSH depletion in the development of fibrosis remains obscure, GSH and N-acetylcysteine, a precursor of GSH, have been used in clinics for the treatment of fibrotic diseases. This review summarizes recent findings in the field to address the potential mechanism whereby oxidative stress mediates fibrogenesis induced by TGF-beta and the potential therapeutic value of antioxidant treatment in fibrotic diseases.

The oxidation of glutathione by cobalt/tungsten carbide contributes to hard metal-induced oxidative stress

The occupational exposure to cobalt/tungsten carbide (Co/WC) dusts causes asthma and interstitial fibrosis. The International Agency for Research on Cancer (IARC) recently classified the mixture Co/WC as probably carcinogenic to humans (group 2A). The mechanism of action of Co/WC involves particle driven generation of Reactive Oxygen Species (ROS) with consequent oxidative damage. The present study evaluates the reactivity of Co/WC dust toward glutathione (GSH) and cysteine (Cys). Co/WC oxidized thiols through a mechanism involving the generation of sulphur-centred radicals. The results are consistent with the oxidation taking place at surface active sites, a part of which is accessible only to Cys S-H groups, but not to GSH ones. Such a reaction, with consequent irreversible depletion of antioxidant defenses of cells, will potentiate the oxidative stress caused by particle and cell generated ROS.

Antioxidants as potential therapeutics for lung fibrosis

Interstitial lung disease encompasses a large group of chronic lung disorders associated with excessive tissue remodeling, scarring, and fibrosis. The evidence of a redox imbalance in lung fibrosis is substantial, and the rationale for testing antioxidants as potential new therapeutics for lung fibrosis is appealing. Current animal models of lung fibrosis have clear involvement of ROS in their pathogenesis. New classes of antioxidant agents divided into catalytic antioxidant mimetics and antioxidant scavengers are being developed. The catalytic antioxidant class is based on endogenous antioxidant enzymes and includes the manganese-containing macrocyclics, porphyrins, salens, and the non-metal-containing nitroxides. The antioxidant scavenging class is based on endogenous antioxidant molecules and includes the vitamin E analogues, thiols, lazaroids, and polyphenolic agents. Numerous studies have shown oxidative stress to be associated with many interstitial lung diseases and that these agents are effective in attenuating fibroproliferative responses in the lung of animals and humans.

The influence of refractory ceramic fibres on pulmonary morphology, redox and immune system in rats

Refractory ceramic fibres (RCF) were studied in male SPRD rats by both in vivo long term sequential and in vitro methods. RCF was administered by single intratracheal instillation and the lungs were examined at the end of months 1, 3 and 6 after exposure. In addition, the direct toxicity of the fibres was examined in a primary culture of alveolar macrophages (AM) and in pneumocytes type II (T2). Pulmonary morphological changes, a number of parameters of the redox system, such as activity of extracellular Cu,Zn/superoxide dismutase (EC-SOD), total glutathione content of the lungs (GSH) and immunoglobulins in bronchoalveolar lavage (IgA, IgG, IgM) and in the blood were measured. The composition of the original RCF and the elemental content of the lung tissue were compared by energy dispersive x-ray analysis (EDXA) before and after exposure. Macrophage alveolitis became confluent and moderate fibrosis developed by the end of month 3, and after 6 months of exposure the intensity decreased to the level of the first month. The RCF did not significantly influence the activity of EC-SOD or the total glutathione content of the lungs. Although aluminium and silicon could be demonstrated by EDXA in the lung tissue at the end of month 3, these elements were no longer detectable by the end of month 6. The RCF decreased IgA significantly in bronchoalveolar lavage (BAL). The main components of RCF induced pulmonary alterations, whereas no significant change could be detected in EC-SOD and GSH. Injuries caused by direct toxicity could be observed in the cell membranes only at the highest concentration. On the basis of these results RCF can be determined as moderately toxic fibres.

ROS-mediated genotoxicity of asbestos-cement in mammalian lung cells in vitro

Asbestos is a known carcinogen and co-carcinogen. It is a persisting risk in our daily life due to its use in building material as asbestos-cement powder. The present study done on V79-cells (Chinese hamster lung cells) demonstrates the cytotoxic and genotoxic potential of asbestos-cement powder (ACP) in comparison with chrysotile asbestos. A co-exposure of chrysotile and ACP was tested using the cell viability test and the micronucleus assay. The kinetochore analysis had been used to analyse the pathway causing such genotoxic effects. Thiobarbituric acid-reactive substances were determined as evidence for the production of reactive oxygen species. Both, asbestos cement as well as chrysotile formed micronuclei and induced loss of cell viability in a concentration- and time-dependent way. Results of TBARS analysis and iron chelator experiments showed induction of free radicals in ACP- and chrysotile exposed cultures. CaSO4 appeared to be a negligible entity in enhancing the toxic potential of ACP. The co-exposure of both, ACP and chrysotile, showed an additive effect in enhancing the toxicity. The overall study suggests that asbestos-cement is cytotoxic as well as genotoxic in vitro. In comparison to chrysotile the magnitude of the toxicity was less, but co-exposure increased the toxicity of both.

Different cellular responses evoked by natural and stoichiometric synthetic chrysotile asbestos

The carcinogenic potency of asbestos, including chrysotile, is well established. Several physico-chemical features of the fibers appear implied, such as fibrous habit, size, crystallinity, morphology, and surface active metal ions, where free radical generation may take place. In contrast to other asbestos forms, iron is not a stoichiometric component of chrysotile, but is only present together with other extraneous ions as a magnesium- and silicon-replacing contaminant. To determine the role played by contaminating ions and morphological features of the fibers, a stoichiometric chrysotile with constant structure and morphology was synthesized in hydrothermal conditions. Free radical generation and the effects of these fibers on human lung epithelial A549 cells have been compared to that elicited by a well known toxic natural chrysotile (UICC A, from Rhodesia). After a 24-h incubation, the natural, but not the synthetic, form exerted a cytotoxic effect, detected as leakage of lactate dehydrogenase. Homolytic rupture of a C-H bond and lipoperoxidation in A549 cells took place in the presence of the natural, but not of the synthetic, chrysotile. Antioxidant systems were also affected differently. The pentose phosphate pathway and its regulatory enzyme glucose 6-phosphate dehydrogenase were markedly inhibited only by the natural specimen, which also caused a depletion of intracellular reduced glutathione in A549 cells. These results suggest that metal ions, fiber size and state of the surface play a crucial role in the oxidative stress caused by chrysotile asbestos. Stoichiometric synthetic fibers may thus be proposed as a reference standard (negative control) for toxicological studies.

Plasma malondialdehyde and erythrocyte glutathione levels in workers with cement dust-exposure [corrected]

BACKGROUND

Chronic exposure to cement dust has been reported to lead to several health problems. Acute and chronic exposure to quartz are associated with the provocation of an inflammatory response and triggers an extensive host defense mechanism. These inflammatory reactions result in the secretions of cytokines, eicosanoids, lytic enzymes, chemotactic factors and reactive oxygen species (ROS). This study was designed to investigate the plasma oxidant and antioxidant status in cement plant workers.

METHODS

Forty-eight non-smoker volunteer male cement plant workers and 28 non-smoker volunteer office male workers (control) aged between 27 and 56 were recruited. The concentrations of plasma malondialdehyde (p-MDA), and the erythrocyte glutathione (GSH) were measured in both groups. Pulmonary function tests, and exposed free silica fractions were also measured in different working places.

RESULTS

Plasma MDA levels were found to be increased, while erythrocyte GSH levels to be decreased in cement workers (p < 0.001). Although no statistically significance was observed, pulmonary function tests were found to be decreased in cement workers. A negative correlation was observed between MDA levels and FEV1 and FEV1% levels. Although no statistically significant difference was found, MDA levels were found to be increased and GSH levels decreased in the working areas where silisium dioxide concentrations were found to be higher.

CONCLUSIONS

In conclusion, the results presented in this study show that direct measurement of plasma MDA and erythrocyte GSH could be accepted as an indicator of oxidative injury in workers exposed to cement dust.

Reduction of chrysotile asbestos-induced genotoxicity in human peripheral blood lymphocytes by garlic extract

Asbestos fibers are well known environmental carcinogen, however, the underlying mechanisms of their action have still not clearly been identified. Asbestos is capable of depleting glutathione and generating reactive oxygen species (ROS), which are important mediators of damage in biological system. Asbestos-induced mutagenecity, may be mediated by the generation. It is known that a number of scavengers and antioxidants attenuate asbestos-induced ROS release. Furthermore, it is known that garlic, contains numerous sulfur compounds and glutathione precursors which act as antioxidants and also demonstrate anticarcinogenic properties. The aim of this study was to investigate whether garlic extract has any influence on asbestos-mediated genotoxicity. As an assay system, we applied the micronucleus assay, sister chromatid exchanges, and chromosomal aberrations with human peripheral blood lymphocytes, which has already been used to analyze the genotoxicity of asbestos fibers. Our results indicate that garlic extract, when administered to the lymphocytes cell culture simultaneously with chrysotile reduced the rates of micronucleus formation, sister chromatid exchanges, and chromosomal aberrations significantly. We conclude that garlic extract may be an efficient, physiologically tolerable quencher of asbestos-mediated genotoxicity.

Garlic attenuates chrysotile-mediated pulmonary toxicity in rats by altering the phase I and phase II drug metabolizing enzyme system

Asbestos and its carcinogenic properties have been extensively documented. Asbestos exposure induces diverse cellular events associated with lung injury. Previously, we have shown that treatment with chrysotile shows significant alteration in phase I and phase II drug metabolizing enzyme system. In this study we have examined some potential mechanisms by which garlic treatment attenuates chrysotile-mediated pulmonary toxicity in rat. Female Wistar rats received an intratracheal instillation of 5 mg chrysotile (0.5 mL saline) as well as intragastric garlic treatment (1% body weight (v/w); 6 days per week). Effect of garlic treatment was evaluated after 1, 15, 30, 90, and 180 days by assaying aryl hydrocarbon hydroxylase (AHH), glutathione (GSH), glutathione S-transferase (GST), and production of thiobarbituric acid reactive substances (TBARS) in rat lung microsome. The results showed that AHH and TBARS formation were significantly reduced at day 90 and day 180 in chrysotile treated garlic cofed rats; GSH recovered 15 days later to the near normal level and GST elevated significantly after treatment of garlic as compared to chrysotile alone treated rat lung microsome. The data obtained shows that inhibition of AHH activity and induction of GST activity could be contributing factor in chrysotile-mediated pulmonary toxicity in garlic cofed rats. However, recovery of GSH and inhibition of TBARS formation by garlic and its constituent(s) showed that garlic may give protection by altering the drug metabolizing enzyme system.

Reaction of cysteine and glutathione (GSH) at the freshly fractured quartz surface: a possible role in silica-related diseases?

The reactivity of quartz dusts towards glutathione (GSH) and cysteine (Cys) has been investigated. Cys and GSH react, without being adsorbed (UV-Vis spectroscopy), with commercial quartz dusts in an exposed surface-dependent way, but not with amorphous silica. GSH and Cys have been contacted with freshly ground quartz (agate jar QZg-a and steel jar QZg-s) and quartz heated in air at 500 degrees C (QZs-500) and with a dust generated from a purified quartz (99.9999%) to detect the nature of the reacting surface sites. With both GSH and Cys, the highest reactivity was found on the particles ground in a steel jar, while pure quartz was fully inactive. Detection of the radical GS* (spin trapping) suggests a radical mechanism of oxidation to disulphide onto surface-bound iron traces, more abundant on QZg-s and absent on the pure quartz. Oxidation of thiol groups occurs at surface sites different from those involved in the homolytic rupture of a C-H bond. Both reactions are more pronounced on freshly ground samples, but the C-H rupture takes place at silicon-based surface radicals and Fe2+ centers, while oxidation of GSH and Cys requires Fe3+ centers. As all commercial quartz dusts contain surface iron as an impurity, depletion of extracellular or intracellular GSH may contribute to the oxidative damage caused by particle-derived and cell-derived reactive oxygen species.

Differential responses of rat alveolar macrophages to carpet dust in vitro

Epidemiological studies of workers in carpet weaving units in carpet industries have shown a direct relation between the concentration of carpet dust in the air and respiratory symptoms. To predict the health risk of carpet weavers, this preliminary study was conducted to evaluate the toxic potential of different types of workplace dust by using alveolar macrophages (AMs). Several parameters were observed for cytotoxicity such as cell viability, the release of lactate dehydrogenase (LDH) in rat AMs treated with different concentration of carpet dust and haemolytic potential of erythrocytes. In addition, reactive oxygen/nitrogen species-inducing effects of carpet dust were assessed by nitric oxide (NO), reduced glutathione (GSH) release and hydrogen peroxide (H2O2) generation in AMs. Results of cell viability and hemolytic assay showed a direct correlation between increasing the dust concentration with enhancing the toxic effect. Knotted and tufted carpet dust increases the release of LDH, NO, GSH and H2O2 production with increasing dust concentration. Present observations have revealed that dusts collected from tufted carpet weaving units exhibited more toxicity to AMs than knotted carpet dust. These data further suggest that injurious effects of carpet dust to AMs could pave a way to evaluate the toxic potential of the different types of workplace dusts and component(s) involved in it.

Crocidolite asbestos inhibits pentose phosphate oxidative pathway and glucose 6-phosphate dehydrogenase activity in human lung epithelial cells

The cytotoxicity of asbestos has been related to its ability to increase the production of reactive oxygen species (ROS), via the iron-catalyzed reduction of oxygen and/or the activation of NADPH oxidase. The pentose phosphate pathway (PPP) is generally activated by the cell exposure to oxidant molecules. Contrary to our expectations, asbestos (crocidolite) fibers caused a dose- and time-dependent inhibition of PPP and decreased its activation by an oxidative stress in human lung epithelial cells A549. In parallel, the intracellular activity of the PPP rate-limiting enzyme, glucose 6-phosphate dehydrogenase (G6PD), was significantly diminished by crocidolite exposure. This inhibition was selective, as the activity of other PPP and glycolysis enzymes was not modified, and was not attributable to a decreased expression of G6PD. On the opposite, the incubation with glass fibers MMVF10 did not modify PPP and G6PD activity. PPP and G6PD inhibition did not correlate with the increased nitric oxide (NO) production elicited by crocidolite in A549 cells. Experiments with the purified enzyme suggest that crocidolite inhibits G6PD by directly interacting with the protein. We propose here a new mechanism of asbestos-evoked oxidative stress, wherein fibers increase the intracellular ROS levels also by inhibiting the main antioxidant pathway of the cell.

Rethinking cystic fibrosis pathology: the critical role of abnormal reduced glutathione (GSH) transport caused by CFTR mutation

Though the cause of cystic fibrosis (CF) pathology is understood to be the mutation of the CFTR protein, it has been difficult to trace the exact mechanisms by which the pathology arises and progresses from the mutation. Recent research findings have noted that the CFTR channel is not only permeant to chloride anions, but other, larger organic anions, including reduced glutathione (GSH). This explains the longstanding finding of extracellular GSH deficit and dramatically reduced extracellular GSH:GSSG (glutathione disulfide) ratio found to be chronic and progressive in CF patients. Given the vital role of GSH as an antioxidant, a mucolytic, and a regulator of inflammation, immune response, and cell viability via its redox status in the human body, it is reasonable to hypothesize that this condition plays some role in the pathogenesis of CF. This hypothesis is advanced by comparing the literature on pathological phenomena associated with GSH deficiency to the literature documenting CF pathology, with striking similarities noted. Several puzzling hallmarks of CF pathology, including reduced exhaled NO, exaggerated inflammation with decreased immunocompetence, increased mucus viscoelasticity, and lack of appropriate apoptosis by infected epithelial cells, are better understood when abnormal GSH transport from epithelia (those without anion channels redundant to the CFTR at the apical surface) is added as an additional explanatory factor. Such epithelia should have normal levels of total glutathione (though perhaps with diminished GSH:GSSG ratio in the cytosol), but impaired GSH transport due to CFTR mutation should lead to progressive extracellular deficit of both total glutathione and GSH, and, hypothetically, GSH:GSSG ratio alteration or even total glutathione deficit in cells with redundant anion channels, such as leukocytes, lymphocytes, erythrocytes, and hepatocytes. Therapeutic implications, including alternative methods of GSH augmentation, are discussed.

4-Hydroxy-2-nonenal increases gamma-glutamylcysteine synthetase gene expression in alveolar epithelial cells

Previous studies from this laboratory demonstrated that 4-hydroxy-2-nonenal (4HNE), a lipid peroxidation product, induces expression of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in de novo glutathione (GSH) synthesis, in rat alveolar epithelial L2 cells. The present study demonstrates that 4HNE also induces GCS in primary cultured alveolar epithelial type II (AT2) cells. Enzyme activity, protein content, and messenger RNA levels of both the catalytic (GCS-HS) and regulatory (GCS-LS) subunits were significantly increased in AT2 cells treated with 5 or 10 microM 4HNE, the same concentrations that induced GCS expression in L2 cells. As in L2 cells, 4HNE induced a greater AT2-cell increase in GCS-LS than in GCS-HS, suggesting that modulation of GCS-LS may play a dominant role in regulating GSH concentration in response to oxidative stress. Additional studies using mitogen-activated protein kinase pathway inhibitors showed that induction by 4HNE of GCS-HS, but not GCS-LS, was mediated through activation of the extracellular regulated kinase pathway in L2 cells. The results demonstrate that L2 cells maintain the same responsiveness to oxidant challenge as do primary cultured AT2 cells in terms of increasing GSH synthetic capacity, and that different pathways are involved in the induction of two GCS subunits by 4HNE.

Possible role of ascorbic acid in the oxidative damage induced by inhaled crystalline silica particles

The selective interaction of ascorbic acid with crystalline silica (quartz) has been studied by measuring the ascorbic acid consumption (by means of UV/vis and IR spectroscopy) and the release of silicon when quartz particles or amorphous silica (Aerosil 50) is incubated in ascorbic acid solution. At a physiological ascorbic acid concentration, quartz, and not amorphous silica, reacts, suggesting the formation of a 1:1 silicon-ascorbate complex, while at higher concentrations, the reacting amount of ascorbic acid exceeds the amount of silicon that is released. Silicon tetrahedra bearing free silanols at the quartz surface are selectively attached by ascorbic acid. The particle-derived hydroxyl radical yield in the presence of hydrogen peroxide is increased on ascorbic acid-treated quartz in comparison with the original sample. The results presented herein are relevant because the depletion of ascorbic acid from the lung lining layer and the increased potential in particle-derived free radical generation may both contribute to the oxidative damage following inhalation of crystalline silica.

N-acetyl L-cysteine attenuates oxidant-mediated toxicity induced by chrysotile fibers

Chrysotile, an important commercial variety of asbestos, is known to cause oxidative stress by enhancing production of hydrogen peroxide (H(2)O(2)) and thiobarbituric acid reactive substances (TBARS), depleting glutathione (GSH) and altering levels of GSH redox system enzymes. N-acetyl L-cysteine (NAC), a compound that increases GSH levels, protects cells against chrysotile toxicity. In the present study, rats were exposed intratracheally to a single dose (5 mg/rat) of chrysotile. This was followed by a daily dose of NAC 50 mg/kg. b. wt., i.p. At 1, 4, 8 and 16 days post chrysotile exposure lung lavage fluid was collected to determine H(2)O(2) generation, TBARS production, GSH level and its redox system enzymes activities. A significant decrease in H(2)O(2) and TBARS, an increase in GSH content and its redox system enzymes was observed in chrysotile+NAC animals in comparison to chrysotile-exposed animals. In this preliminary study it appears that NAC may be protecting cells against oxidative damage. This protection may be due to its ability to maintain intracellular GSH/oxidative scavenging capability.