The expressions of protooncogenes and CYP1A in lungs of rats exposed to sulfur dioxide and benzo(a)pyrene

Synergistic effects of sulfur dioxide and polycyclic aromatic hydrocarbons on pulmonary pro-fibrosis via mir-30c-1-3p/ transforming growth factor β type II receptor axis

SO₂ and PAHs are well-known pollutants of coal burning and significant contributors to haze episodes. The purpose of the study is to determine whether the combined effects of SO₂ and BaP are synergetic and to investigate the pro-fibrotic influences and possible mechanism from the aspect of microRNAs. In the present study cellular metabolic activity of BEAS-2B was assessed using MTT probe. C57BL/6 mice were exposed to BaP (40 mg/kg b.w.) for 5 days or SO₂ (7 mg/m³) inhalation for 4 weeks alone or together. Lung tissues were processed for histology to assess pulmonary fibrosis. The protein level of pulmonary pro-fibrotic genes (Col1a1, Col3a1, alpha-SMA, fibronectin) and TGFβR2 were analyzed by Western blot and immunofluorescence in vivo and in vitro. Furthermore, we clarified that the microRNA expression of mir-30c-1-3p by real-time RT-PCR. The luciferase reporter assay was used to determine the binding sites of mir-30c-1-3p in the 3'-UTR of TGFβR2. It was confirmed that SO₂ and BaP acted together to produce synergistic effects in cellular metabolic activity. Coexisting of SO₂ and BaP increased the protein expression of pro-fibrotic genes and TGFβR2 and decreased mir-30c-1-3p in vivo and in vitro. Dual-luciferase reporter gene assays showed that TGFβR2 was a validated target of mir-30c-1-3p. All above results demonstrated that mir-30c-1-3p was involved in the synergistic pro-fibrotic effects of SO₂ and BaP in lung via targeting TGFβR2. This work implies the potential risk of pulmonary fibrosis from the co-existence of SO₂ and PAHs and provides new insights into the molecular markers for relevant diseases.

The effect of exposure of SO2 in high concentrations on CD19+ cells in reactive airway dysfunction syndrome in rat

Reactive airway dysfunction syndrome (RADS) has a clinical manifestation similar to asthma, but some features are different between both the diseases. To probe the effect of CD19+ cells in RADS pathogenesis by inhalation of sulfur dioxide (SO2), rats were exposed to SO2 at 600 ppm for 2 h per day for 7 days and the CD19 expression in lung tissue was detected both at mRNA and protein levels by RT-PCR and western blot. The percentages of CD19+ and CD19+ CD23+ cells were measured by flow cytometry. IgG, IgA, and IgE in serum and bronchoalveolar lavage fluid (BALF) were detected by enzyme-linked immunosorbent assay (ELISA). Histological analysis was performed. The results showed that expression of CD19 in SO2 exposure group was lower than that in the control both at mRNA and protein levels ( P < 0.05). Flow cytometry analysis showed that the percentages of CD19+ and CD19+ CD23+ were significantly lower in the SO2 exposed group than that in the control ( P < 0.05). There was no difference between the control and SO2 exposed groups in both serum and BALF levels of IgG, IgA, and IgE. Pathological changes, such as chronic bronchitis, local alveolar hemorrhage, and lymphocytes infiltration were observed in SO2 exposed. RADS is a non-immunogenicity, chronic airway inflammatory disease caused by irritation of harmful factor and manifests as airway hyperresposiveness.

Sulfur dioxide and benzo(a)pyrene trigger apoptotic and anti-apoptotic signals at different post-exposure times in mouse liver

There is considerable concern that exposure to PAHs in combination with other air pollutants may lead to cancer or apoptosis in different cells. This study investigated the interaction effects between SO2 and BaP in mouse liver after long-term exposure. Mice were exposed to BaP for 5days or SO2 inhalation for 4weeks alone or together. The mitochondrial membrane potential (MMP) was assessed using the lipophilic cationic probe JC-1. The mRNA and protein level of several mitochondrial respiratory complex subunits and apoptosis-related genes were analyzed by real-time RT-PCR and/or western blot, respectively. We observed the pathology change of the mouse liver after 4-week treatments. It was revealed that MMP was reduced after co-exposure of SO2 and BaP after a 4-week treatment (1day post-exposure, p.e. 1d), with the suppression of the mRNA expression of complexes IV and V subunits, CO1, CO4, and ATP6. Co-exposure of SO2 and BaP appeared to be able to cause apoptotic signals, as judged by the suppression of bcl-2 and the bcl-2/bax ratio and the elevation of bax, caspase 3 activation, p53 accumulation and phosphorylation 1d post-exposure to SO2 and BaP, while the anti-apoptotic signal was detected by the elevation of bcl-2 and the bcl-2/bax ratio as well as the suppression of bax and p53 expression after a 13-week post-exposure (p.e. 13w) of SO2 and BaP. These results indicate that co-exposure to SO2 and BaP appears to lead to apoptotic as well as anti-apoptotic signals at different post-exposure times.

Stress response, biotransformation effort, and immunotoxicity in captive birds exposed to inhaled benzene, toluene, nitrogen dioxide, and sulfur dioxide

In the oil sands of Alberta, Canada, toxicology research has largely neglected the effects of air contaminants on biota. Captive Japanese quail (Coturnix c. japonica) and American kestrels (Falco sparverius) were exposed to mixtures of volatile organic compounds and oxidizing agents (benzene, toluene, NO2 and SO2) in a whole-body inhalation chamber, to test for toxicological responses. Hepatic biotransformation measured through 7-ethoxyresorufin-O-dealkylase (EROD) tended to be increased in exposed kestrels (p=0.06) but not in quail (p=0.15). Plasma corticosterone was increased in the low dose group for quail on the final day of exposure (p=0.0001), and midway through the exposure period in exposed kestrels (p=0.04). For both species, there was no alteration of T and B-cell responses, immune organ mass, or histology of immune organs (p>0.05). This study provides baseline information valuable to complement toxicology studies and provides a better understanding of potential health effects on wild avifauna.

Effects of intravenous benzo[a]pyrene dose administration on levels of exposure biomarkers, DNA adducts, and gene expression in rats

The effects of benzo[a]pyrene (BaP) administration on biomarkers of exposure and early effects were studied in male Sprague-Dawley rats intravenously injected with doses of 0.4, 4, 10, or 40 μmol BaP/kg . Blood, tissues, and excreta were collected 8 and 24 h posttreatment. BaP and several of its metabolites were simultaneously measured in blood, tissues and excreta by ultra-high-performance liquid chromatography (UHPLC)/fluorescence. DNA adducts of BaP diol epoxide (BaPDE) in lungs were quantified using an ultrasensitive immunoassay with chemiluminescence detection. Expression of selected genes in lungs of treated rats (lung RNA) compared to control rats was also assessed by quantitative real-time polymerase chain reaction. There was a dose-dependent increase in blood, tissue, and excreted levels of BaP metabolites. At 8 and 24 h postinjection, BaP and hydroxyBaP were found in higher concentrations in blood and tissues compared to other analytes. However, diolBaP were excreted in greater amounts in urine and apparently more rapidly than hydroxyBaP. Mean percentages (± SD) of injected dose excreted in urine as 4,5-diolBaP during the 0-8 h and 0-24 h period posttreatment were 0.16 ± 0.027% and 0.14 ± 0.083%, respectively. Corresponding values for 3-OHBaP were 0.0045 ± 0.0009% and 0.026 ± 0.014%. BaP-diones were not detectable in blood, tissues, and excreta; 7,8-diolBaP and BaPtetrol were found to be minor metabolites. There was also a dose-dependent increase in DNA adduct formation in lung. Analysis of gene expression further showed a modulation of Cyp1a1, Cyp1b1, Nqo1, Nrf2, Fos, and Ahr expression at 10- and 40-μmol/kg doses, but not at the lower doses. This study provided a better assessment of the influence of absorbed BaP doses on biological levels of diolBaP and OHBaP exposure biomarkers and association of the latter with early biological alterations, such as DNA adducts and gene expression.

Kinetics of Diol and Hydroxybenzo[a]pyrene Metabolites in Relation to DNA Adduct Formation and Gene Expression in Rats

Benzo[a]pyrene (BaP) is a human carcinogen, but there are no validated biomarkers of exposure and the relationship of carcinogenesis with early biological alterations is not fully documented. This study aimed at better documenting the toxicokinetics of diolBaP and hydroxyBaP metabolites as potential biomarkers of exposure to BaP in relation to DNA adduct formation and gene expression. Rats were intravenously (iv) injected with 40 μmol/kg BaP. BaP and several metabolites were measured in blood, tissues, and excreta collected at frequent intervals over 72 h posttreatment. BaP diol epoxide (BaPDE)-DNA adduct formation and gene expression were assessed in lungs. 3-HydroxyBaP (3-OHBaP) and 4,5-diolBaP were the most abundant measured metabolites, and differences in time courses were apparent between the two metabolites. Over the 0-72 h period, mean proportions of BaP dose recovered in urine as 3-OHBaP and 4,5-diolBaP (±SD) were 0.017 ± 0.003% and 0.1 ± 0.03%. Corresponding values in feces were 1.5 ± 0.5% and 0.42 ± 0.052%. BaPDE-DNA adducts were significantly increased in lungs and a correlation was observed with urinary 3-OHBaP and 4,5-diolBaP. Analysis of gene expression showed a modulation of expression of metabolic genes (Cyp1a1, Cyp1b1, Nqo1, Ahr) and oxidative stress and repair genes (Nrf2, Rad51). However, BaPDE adducts formation did not exhibit any significant correlation with expression of genes, except a negative correlation with Rad51 expression. Similarly, there was no significant correlation between urinary excretion of OHBaP and diolBaP and expression of genes, except for urinary 7-OHBaP excretion, which was negatively correlated with Rad51 expression. Results indicate that concomitant measurements of diolBaP and OHBaP may serve to better assess the extent of exposure as compared to single metabolite measurements, given kinetic differences between metabolites. Further, although some urinary metabolites were correlated with BaPDE adducts, links with gene expression need to be further investigated.

Bisulfite and sulfite as derivatives of sulfur dioxide alters biomechanical behaviors of airway smooth muscle cells in culture

Sulfur dioxide (SO2) is a common air pollutant that triggers asthmatic symptoms, but its toxicological mechanisms are not fully understood. Specifically, it is unclear how SO2 in vivo affects airway smooth muscle (ASM) cells of which the mechanics is known to ultimately mediate airway hyperresponsiveness (AHR) - a hallmark feature of asthma. To this end, we investigated the effects of bisulfite/sulfite (1:3 M/M in neutral fluid to simulate the in vivo derivatives of inhaled SO2 in the airways), on the viability, migration, stiffness and contractility of ASM cells cultured in vitro. The results showed that bisulfite/sulfite consistently increased viability, migration, F-actin intensity and stiffness of ASM cells in similar fashion as concentration increasing from 10(-4) to 10(-1) mmol/L. However, bisulfite/sulfite increased the ASM cell contractility induced by KCl only at the concentration between 10(-4) and 10(-3) mmol/L (p < 0.05), while having no consistent effect on that induced by histamine. At the concentration of 10(0) mmol/L, bisulfite/sulfite became acutely toxic to the ASM cells. Taken together, the data suggest that SO2 derivatives at low levels in vivo may directly increase the mass, stiffness and contractility of ASM cells, which may help understand the mechanism in which specific air pollutants contribute in vivo to the pathogenesis of asthma.

Alcoholic lung injury: metabolic, biochemical and immunological aspects

Chronic alcohol abuse is a systemic disorder and a risk factor for acute respiratory distress syndrome (ARDS) and chronic obstructive pulmonary disease (COPD). A significant amount of ingested alcohol reaches airway passages in the lungs and can be metabolized via oxidative and non-oxidative pathways. About 90% of the ingested alcohol is metabolized via hepatic alcohol dehydrogenase (ADH)-catalyzed oxidative pathway. Alcohol can also be metabolized by cytochrome P450 2E1 (CYP2E1), particularly during chronic alcohol abuse. Both the oxidative pathways, however, are associated with oxidative stress due to the formation of acetaldehyde and/or reactive oxygen species (ROS). Alcohol ingestion is also known to cause endoplasmic reticulum (ER) stress, which can be mediated by oxidative and/or non-oxidative metabolites of ethanol. An acute as well as chronic alcohol ingestions impair protective antioxidants, oxidize reduced glutathione (GSH, cellular antioxidant against ROS and oxidative stress), and suppress innate and adaptive immunity in the lungs. Oxidative stress and suppressed immunity in the lungs of chronic alcohol abusers collectively are considered to be major risk factors for infection and development of pneumonia, and such diseases as ARDS and COPD. Prior human and experimental studies attempted to identify common mechanisms by which alcohol abuse directly causes toxicity to alveolar epithelium and respiratory tract, particularly lungs. In this review, the metabolic basis of lung injury, oxidative and ER stress and immunosuppression in experimental models and alcoholic patients, as well as potential immunomodulatory therapeutic strategies for improving host defenses against alcohol-induced pulmonary infections are discussed.

Benzo[a]pyrene decreases global and gene specific DNA methylation during zebrafish development

DNA methylation is important for gene regulation and is vulnerable to early-life exposure to environmental contaminants. We found that direct waterborne benzo[a]pyrene (BaP) exposure at 24μg/L from 2.5 to 96hpf to zebrafish embryos significantly decreased global cytosine methylation by 44.8% and promoter methylation in vasa by 17%. Consequently, vasa expression was significantly increased by 33%. In contrast, BaP exposure at environmentally relevant concentrations did not change CpG island methylation or gene expression in cancer genes such as ras-association domain family member 1 (rassf1), telomerase reverse transcriptase (tert), c-jun, and c-myca. Similarly, BaP did not change gene expression of DNA methyltransferase 1 (dnmt1) and glycine N-methyltransferase (gnmt). While total DNMT activity was not affected, GNMT enzyme activity was moderately increased. In summary, BaP is an epigenetic modifier for global and gene specific DNA methylation status in zebrafish larvae.

Chronic exposure to sulfur dioxide enhances airway hyperresponsiveness only in ovalbumin-sensitized rats

Sulfur dioxide (SO(2)) is a common air pollutant that triggers asthmatic symptoms, but its toxicological mechanisms are not fully understood. Specifically, it is unclear how airborne SO(2) affects airway hyperresponsiveness (AHR) - a hallmark feature of asthma. To this end, we investigated the effects of chronic exposure to SO(2) on AHR, airway inflammation, tissue remodeling, cell stiffness (G') and contractility of the airway smooth muscle cell (ASMC). Newborn Sprague-Dawley (SD) rats sensitized to ovalbumin (OVA) was used as the model to mimic asthmatic symptoms. The experimental results show that exposure to SO(2): (1) significantly increased Penh (an indicator of AHR) in the OVA-sensitized rats (p<0.01) but not in the normal rats (p>0.05), which correlated with the increase of airway smooth muscle mass; (2) increased IL-4 production in BALF of both the normal (p<0.05) and OVA-sensitized rats (p<0.001), but decreased IFN-γ in BALF of only the normal rats, and in serum only increased IL-4 production of the OVA-sensitized rats (p<0.001); (3) increased ASMC stiffness (G') and contractility only in the OVA-sensitized rats (p<0.001, p<0.05, respectively). Taken together, these results demonstrate that SO(2) may be a universal airway inflammatory factor, but more importantly, specific to exacerbating AHR in asthmatics only. These findings uncover a potential mechanism of SO(2)-induced health effects and may provide a basis for therapeutic targets.

The negative inotropic effects of gaseous sulfur dioxide and its derivatives in the isolated perfused rat heart

Epidemiological investigations have revealed that sulfur dioxide (SO(2) ) exposure is linked to cardiovascular diseases. The present study was designed to investigate the negative inotropic effects of gaseous SO(2) and its derivatives in the isolated perfused rat heart and the possible mechanisms involved in their effects. The results showed that both SO(2) and SO(2) derivatives elicited a negative inotropic effect in a dose-dependent manner, and SO(2) produced a higher negative effect than SO(2) derivatives. The mechanism of SO(2) -induced negative inotropic effects at low concentrations was different from that at high concentrations. At low concentrations, the mechanism of SO(2) -induced negative inotropic effects might occur through promoting the activities of protein kinase C (PKC), cycloxygenase, and cGMP, while the mechanism of SO(2) derivatives-induced effects might be related to the opening of ATP-sensitive K(+) (K(ATP) ) channel and the inhibition of Ca(2+) influx via L-type calcium-channel. At high concentrations, the mechanisms of SO(2) and SO(2) derivatives-induced negative inotropic effects were similar, which might be related to the K(ATP) channel and L-type calcium-channel as well as the possible alterations in PKC, cycloxygenase, and cGMP. Further work is needed to determine the relative contribution of each pathway in SO(2) -mediated inotropic effect.

Ethanol induced induction of cytochrome P450 2E1 and activation of mitogen activated protein kinases in peripheral blood lymphocytes

Cytochrome P450 2E1 (CYP2E1), which induces oxidative stress that leads to alcohol-mediated toxicity in liver, is expressed in peripheral blood lymphocytes. To validate blood lymphocyte CYP2E1 as a biomarker of alcohol-induced diseases, studies were initiated to investigate similarities in CYP2E1 induction and associated cell signalling pathways in freshly prepared blood lymphocytes with the liver in rats exposed to alcohol. Acute or chronic treatment of ethanol produced significant increase in enzyme activity and lipid peroxidation in blood lymphocytes. As observed in liver, this increase was associated with the enrichment of CYP2E1 protein and mRNA. Similar pattern of increase in the mRNA and protein expression of c-jun and c-fos was also observed in blood lymphocytes and liver. Acute exposure to ethanol activated ERK and JNK MAP kinases and c-jun in the blood lymphocytes and liver. The present data demonstrating similarities in the induction of CYP2E1 and lipid peroxidation and activation of MAP Kinases in blood lymphocytes with liver after acute or chronic exposure of ethanol have suggested that blood lymphocytes could be used to monitor ethanol induced CYP2E1 induction and associated oxidative stress in liver.

Evidence for cytochrome P450 2B1/2B2 isoenzymes in freshly prepared peripheral blood lymphocytes

Cytochrome P450 2B1 and 2B2, the major hepatic drug metabolizing enzymes belonging to CYP2 family and associated constitutive androstane receptor (CAR) were found to be expressed in peripheral blood lymphocytes (PBL) isolated from rats. As observed in liver, pretreatment of phenobarbital (PB) or phenytoin were found to increase the expression of CYP2B1, CYP2B2 and associated enzyme activity in PBL. Like in liver, blood lymphocyte CYP2B1/2B2 catalyzed the activity of 7-pentoxyresorufin O-dealkylase (PROD). The present data, demonstrating similarities in the regulation of blood lymphocyte CYP2B-isoenzymes with the liver enzymes, suggests that blood lymphocyte CYP2B-isoenzymes could be used as a biomarker to monitor tissue levels.

Sulfur dioxide upregulates the aortic nitric oxide pathway in rats

Sulfur dioxide (SO(2)) is a common gaseous pollutant. It is also, however, endogenously generated from sulfur-containing amino acids. Recent studies have demonstrated that rat blood pressure can be lowered by SO(2)-exposure in vivo and that vasodilation caused by SO(2) at low concentrations (<450 microM) is endothelium-dependent in rat aorta. However, effects of SO(2) on nitric oxide synthase (NOS) and nitric oxide (NO) production have not been previously studied in rat aorta. The objective of the present study is to assess the effects of acute (10 min) and prolonged (2h) stimulation with different concentrations of SO(2) on NO/cGMP pathway in isolated rat aorta. The results show that: (1) the acute and prolonged pretreatments with SO(2) produced an inhibition of vasoconstrictions induced by norepinephrine. (2) SO(2) potentiated activity of endothelial nitric oxide synthase (eNOS), but not of induced NOS (iNOS). (3) SO(2) could increase expression of eNOS gene on the transcription and translation levels in rat aorta. (4) SO(2) enhanced NO formation in aortic tissue. (5) The level of cGMP in rat aorta was increased by SO(2) and no change of cAMP. These findings led to the conclusion: there were acute and prolonged effects of SO(2) on the NO/cGMP signalling pathway; and SO(2) could upregulate the eNOS-NO-cGMP pathway and at least partly by which the SO(2) might cause vasodilation and inhibition to vasoconstriction.

Sulfur dioxide and benzo(a)pyrene modulates CYP1A and tumor-related gene expression in rat liver

Sulfur dioxide (SO(2)) and benzo(a)pyrene (B(a)P) are common industrial and environmental contaminants. However, few data are available on the effects of SO(2) on proto-oncogenes and tumor suppressor genes, as well as the interactions between SO(2) and other xenobiotics regulating proto-oncogenes or tumor suppressor genes expression. To investigate the interactions between SO(2) and B(a)P, male Wistar rats were exposed to intratracheally instilled with B(a)P or SO(2) inhalation alone or together. We detected mRNA expression of CYP1A1 and 1A2, 7-ethoxyresorufin O-deethylase (EROD), and methoxyresorufin O-demethylase (MROD) activities in livers. The mRNA and protein levels of several cancer-related genes were analyzed in livers by real-time RT-PCR and Western blot, respectively. The EROD/MROD activities and CYP1A1/2 expression were down-regulated by SO(2) but up-regulated by B(a)P alone. Exposure of SO(2) alone induced c-fos, c-jun, c-myc, H-ras, and p53 expression, and depressed p16 and Rb expression in livers. The effects of B(a)P on the above gene were similar to SO(2) except c-fos expression. Furthermore, SO(2) + B(a)P exposure increased the expression of c-fos, c-jun, c-myc, and p53, and decreased p16 and Rb expression in livers compared with exposed to SO(2) or B(a)P alone. However, no synergistic effects were observed on H-ras and CYP1A1/2 after SO(2) + B(a)P exposure. Our findings indicate that multiple cell cycle regulatory proteins play key roles in the toxicity of SO(2) and B(a)P in livers. It might involve the activation of c-fos, c-jun, c-myc, and p53. And p16-Rb pathway might also participate in the progress. Although the gene products we studied are classed as oncogenes and tumor suppressor genes, their functions actually relate to more general processes of control of cell proliferation, survival, and/or apoptosis.

Effects of sulfur dioxide on expressions of p53, bax and bcl-2 in lungs of asthmatic rats

Inhibition of cell apoptosis is an increasingly important factor in modulating airway inflammation in asthma, which is related to environmental pollutants. To investigate the effects of sulfur dioxide (SO(2)) on the mRNA and protein expressions of apoptosis-related genes in lungs from asthmatic rats, male Wistar rats were challenged by ovalbumin (OVA) or SO(2) (2 ppm) inhalation alone or together. Examinations were performed 24 h after the last treatment. The mRNA and protein levels of p53, bax, and bcl-2 were analyzed in lungs using real-time reverse transcription-polymerase chain reaction (RT-PCR) assay and Western blot analysis, respectively. The results indicated that increases of bcl-2 or decreases of p53 and bax mRNA and protein levels were not significant in lungs of rats exposed to SO(2) alone, compared with controls, but elevated or reduced levels of these genes appeared in lungs of asthmatic rats exposed to SO(2) plus OVA, compared with controls, suggesting that SO(2) exposure could result in OVA-induced increases or decreases of transcription and translation levels of these apoptosis-related genes in rat lungs, and may have relations to airway inflammation in asthma. The regulation mechanism of apoptosis in asthma disease exposure to SO(2) needs further study.

Polycyclic aromatic hydrocarbon metabolizing cytochrome P450s in freshly prepared uncultured rat blood lymphocytes

In an attempt to develop blood lymphocyte cytochrome P450 expression profile as a surrogate to monitor tissue enzyme, the present study aimed to identify the expression and regulation of polycyclic aromatic hydrocarbons (PAHs) responsive CYPs in freshly prepared rat blood lymphocytes. Semi-quantitative and RT-PCR studies demonstrated constitutive and inducible mRNA expression of CYP1A1, 1A2, 1B1 isoenzymes and the associated transcription factors, aryl hydrocarbon receptor (AhR) and AhR translocator (ARNT) in blood lymphocytes. Absolute quantification using RT-PCR revealed several fold lower basal expression of CYP1A1, 1A2 and 1B1 in lymphocytes when compared to the liver. However, significant increase in the mRNA expression of these isoenzymes as well as AhR and ARNT in lymphocytes following pretreatment with 3-methylcholanthrene (MC) have demonstrated that responsiveness is retained in the blood lymphocytes, though the magnitude of increase is several fold lower when compared to liver. This increase in the mRNA expression was found to be associated with an increase in the protein expression of CYP1A1 and 1A2 in blood lymphocytes. Further, CYPs expressed in blood lymphocytes catalysed the O-dealkylation of 7-ethoxy- and 7-methoxyresorufins (ER or MR), though the reactivity was several fold lower in lymphocytes when compared to the liver enzyme. Our data providing quantitative evidence for similarities in the regulation of PAH-regulated CYP in uncultured and non-mitogen stimulated blood lymphocytes with the liver enzyme has led us to suggest that blood lymphocytes could be used as a surrogate to monitor tissue expression of CYPs.

Protective effects of salicylic acid and vitamin C on sulfur dioxide-induced lipid peroxidation in mice

The antioxidant effects of exogenous salicylic acid (SA) and vitamin C (Vit C) on the oxidative stress induced by 56 mg/m(3) of sulfur dioxide (SO2) in mouse livers and brains were investigated. The exposure of SO2 caused significant elevation of thiobarbituric acid-reactive substance (TBARS) levels and reduction of enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in brain and liver, accompanied by a decrease in relative growth rate, when compared with controls. Application of moderate concentrations of SA and Vit C markedly reduced the SO2-induced elevation of TBARS levels, with 5.5 mg/kg SA or 200 mg/kg Vit C being most effective. In contrast to the decrease of TBARS levels, the levels of SOD, POD, and CAT in liver and brain were significantly increased in comparison with controls. The polyacrylamide gel electrophoresis (PAGE) of total liver proteins showed that the SO2 inhalation caused a 30-kD protein band disappearance compared with the control. However, the band remained unchanged in the samples treated with 5.5 and 8.25 mg/kg SA or 100, 200, and 400 mg/kg Vit C. Therefore, this protein band may serve as a marker for the damage induced by SO2 and an additional basis for drug screening and selection.

Effects of sulfur dioxide on the expressions of EGF, EGFR, and COX-2 in airway of asthmatic rats

The pathogenesis of asthma involves a combination of genetic and environmental factors. The epidemiology studies have shown that SO(2)might play an important role in the initiation or exacerbation of the asthma disease. To investigate the asthmatic molecular mechanisms exposed to SO(2), male Wistar rats were divided randomly into four equal groups of six animals each: (1) SO(2) group, (2) ovalbumin (OVA) group (asthma group), (3) SO(2)plus OVA group, and (4) control group. The rats were challenged by ovalbumin (OVA) or SO(2) (5.6 mg/m(3)) inhalation alone or together. The mRNA and protein levels of asthma-related genes (EGF, EGFR, and COX-2) were analyzed in lungs and tracheas using real-time reverse transcription-polymerase chain reaction assay, radioimmunoassay method, and Western blot analysis, respectively. The results showed that inhaled SO(2) alone increased the mRNA and protein expressions of three tested genes in lung and trachea tissues, but only the mRNA levels of EGFR and COX-2 in tracheas were significantly increased compared with the control. However, OVA exposure significantly induced the mRNA and protein expressions of EGF, EGFR, and COX-2 compared with the control. Meanwhile, OVA plus SO(2) inhalation enhanced the mRNA and protein levels of these genes in rat airways, versus exposure to OVA alone. These results suggested that SO(2) could increase the expressions of EGF, EGFR, and COX-2 on the transcription and translation levels in the lungs and tracheas from asthmatic rats, which might be one of the possible mechanisms by which SO(2) pollution aggravates asthma disease.

Effects of SO2 derivatives on expressions of MUC5AC and IL-13 in human bronchial epithelial cells

Sulfur dioxide (SO2) is a common air pollutant, and inhaled SO2 in airway epithelium easily forms its soluble derivatives in vivo (bisulfite and sulfite), which are toxic to the respiratory system and related to the exacerbation of asthma. To investigate the effects of SO2 derivatives on the expressions of asthma related genes (MUC5AC and IL-13), the mRNA and protein levels of the two genes in cultured human bronchial epithelial (BEP2D) cells were analyzed using real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay, immunocytochemistry method and enzyme-linked immunosorbent assay (ELISA), respectively. The results showed that the mRNA expressions of MUC5AC and IL-13 were significantly increased at different concentrations of SO2 derivatives (0.0001, 0.001, 0.01, 0.1 and 1.0 mM), and the maximum appeared at 0.01 mM for MUC5AC (3.9-fold) or at 0.001 mM for IL-13 (4.7-fold). Meanwhile, SO2 derivatives significantly increased the mRNA levels at 0, 0.5, 1, 4 and 24 h post-exposure with the maximum at 4 h post-exposure (25-fold for MUC5AC and 41-fold for IL-13). Furthermore, the protein levels of MUC5AC and IL-13 in BEP2D cells were significantly increased at different concentrations and different time courses exposed to SO2 derivatives, along with the maximum at 4 h post-exposure. These results lead to a conclusion that SO2 derivatives can increase the expressions of MUC5AC and IL-13 genes on the transcription and translation levels, and it suggests that SO2 derivatives can induce mucus over-production and inflammation responses in human bronchial epithelial cells and may have relations with asthma diseases. This might be one of the possible mechanisms that SO2 aggravates asthma disease.

Effects of sulfur dioxide on the expressions of MUC5AC and ICAM-1 in airway of asthmatic rats

Asthma is a chronic inflammatory disease characterized by infiltration and activation of various inflammatory cells and mucus secretion. To investigate the effects of SO(2) on the expressions of asthma related-genes, male Wistar rats were challenged by ovalbumin (OVA) or SO(2) (2 ppm) inhalation alone or together. Bronchoalveolar lavage and histopathologic examination were performed 24h after the last treatment. The mRNA and protein levels of MUC5AC and ICAM-1 were analyzed in lungs and tracheas using real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay, immunohistochemistry method and Western blot analysis, respectively. Exposure to OVA or to OVA plus inhaled SO(2) significantly caused increases of the mRNA and protein levels of MUC5AC and ICAM-1 in lungs and tracheas of rats compared with the control (P <0.05 or P <0.01), but the increases of mRNA and protein levels after SO(2) inhalation were not statistically significant. Exposure to OVA plus inhaled SO(2) significantly not only induced the mRNA and protein expressions of these genes, but also induced the infiltration of inflammatory cells in lungs and tracheas and the increase of the numbers of inflammatory cells in bronchoalveolar lavage fluids (BALF), versus exposure to OVA alone. Meanwhile, a synergistic effect on the pathological changes between SO(2) and OVA was observed in lungs after SO(2) and OVA exposure. These results suggested that SO(2) could increase the expressions of MUC5AC and ICAM-1 on the transcription and translation levels in the lungs and tracheas from asthmatic rats, which might be one of the possible mechanisms that SO(2) pollution aggravates asthma disease.