Polymerase chain reaction-based deletion screening of bisulfite (sulfur dioxide)-enhanced gpt-mutants in CHO-AS52 cells

S-Sulfocysteine's toxic effects on HT-22 cells are not triggered by glutamate receptors, nor do they involve apoptotic or genotoxicity mechanisms

S-Sulfocysteine (SSC) is a metabolite derived from the metabolism of sulfur-containing amino acids. It has been implicated in neurotoxicity observed in children with sulfite oxidase deficiency. The aim of our study was to confirm the neurotoxic effects of SSC using a mouse hippocampal cell line (HT-22) and to investigate the role of apoptosis in these effects, especially in terms of caspase-3 activation and genotoxicity. Based on the viability graph obtained following increasing concentrations of SSC, we determined the LC50 dose of SSC to be 125 µM by probit analysis. The cytotoxic effects of SSC were not reversed by glutamate receptor blocker administration. However, SSC treatment did not induce caspase-3 activation or induce DNA damage. Our results showed that SSC has a cytotoxic effect on neurons like glutamate, but glutamate receptor blockers reversed glutamate-induced toxicity, while these blockers did not protect neurons from SSC toxicity. The absence of caspase-3 activation and DNA fragmentation, which are indicative of apoptosis, in SSC-induced cell death suggests that alternative cell death pathways, such as necrosis and oxytosis may be implicated. Further research is necessary to fully elucidate SSC-induced cell death. The aim of our study was to confirm the neurotoxic effects of SSC using a mouse hippocampal cell line (HT-22) and to investigate the role of apoptosis in these effects, especially in terms of caspase-3 activation and genotoxicity.

Effects of NaHSO3 on Cellular Metabolic Energy, Photosynthesis and Growth of Iris pseudacorus L

According to the law of energy conservation, the energy consumed by plants to resist adversity is equal to the difference between photosynthetic energy and growth energy consumption and cellular metabolic energy in plants. The cellular metabolic energy is calculated based on the electrical signals in plants. This study mainly investigated the effect of NaHSO3 on the growth and energy traits of the aquatic plant Iris pseudacorus L. and explored the effect of NaHSO3 on energy consumption in the process of plant development. In this study, NaHSO3 was used for simulating sulfur pollution in water medium. During the 20-day experiment period, the response of I. pseudocorus to the polluted water sources simulated by adding different concentrations of NaHSO3 (0, 0.5, 2, 4, 10 mmol·L−1) was monitored, and the internal mechanism of the relationship between the forms of energy and the removal of sulfur pollution was analyzed. After the 20-day exposure experiment, the growth and nutrient absorption capacity were significantly inhibited, and this inhibition proved to be concentration-dependent. In addition, high concentrations (4 and 10 mmol·L−1) of NaHSO3 might affect photosynthesis by disrupting cell membrane systems as it may interfere with membrane proteins and lipids and thus alter membrane integrity. Therefore, the cellular metabolic energy was increased and the sulfur absorption by I. pseudocorus was promoted under the low concentration (0.5 mmol/L−1) compared with the control, the role of NaHSO3 in promoting the growth of I. pseudocorus is much greater than its toxic effect under low concentrations. Under the hydroponic culture which contained 0.5 mmol·L−1 of NaHSO3, I. pseudocorus grew well and absorbed more sulfur. The results can be used as a reference for the cultivation of aquatic plants dealing with sulfur pollution, and dilution strategy can be set up to treat water medium that is seriously polluted with sulfur.

Sulfur dioxide inhibits expression of mitochondrial oxidative phosphorylation genes encoded by both nuclear DNA and mitochondrial DNA in rat lungs

Epidemiological studies show that sulfur dioxide (SO₂), a major air pollutant, is associated with the morbidity and mortality of respiratory tract diseases. The aim of the present study was to determine the effects of SO₂ on mitochondria and the corresponding molecular characterization in the lung. Male Wistar rats were exposed to 0, 3.5, 7, and 14 mg/m³ SO₂ (4 h/day, 30 days). Mitochondrial dysfunction including decreases of cytochrome c oxidase (COX) activity and mitochondrial membrane potential (MMP) was observed in the lungs of rats after SO₂ inhalation. We showed that total mitochondrial DNA (mtDNA) content was significantly decreased in the lungs from rats exposed to SO₂. Furthermore, SO₂ repressed the expression of complex IV and V subunits encoded by both nuclear DNA (nDNA) and mtDNA. Moreover, such changes were accompanied by depressions of three regulatory factors: peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (TFAM). The findings suggest that SO₂ exposure induced mitochondrial dysfunction in rat lungs. Both nDNA and mtDNA are involved in SO₂-induced depression of mitochondrial biogenesis in the lungs. There might be a tissue-specific response of mitochondrial biosynthesis to SO₂ inhalation. Such impairment may lead to cellular dysfunction and eventually lung diseases.

The PI3K/Akt pathway mediates the protection of SO(2) preconditioning against myocardial ischemia/reperfusion injury in rats

AIM

To explore the mechanisms underlying the protection by SO2 preconditioning against rat myocardial ischemia/reperfusion (I/R) injury.

METHODS

Male Wistar rats underwent 30-min left coronary artery ligation followed by 120-min reperfusion. An SO2 donor (1 μmol/kg) was intravenously injected 10 min before the ischemia, while LY294002 (0.3 mg/kg) was intravenously injected 30 min before the ischemia. Plasma activities of LDH and CK were measured with an automatic enzyme analyzer. Myocardial infarct size was detected using Evans-TTC method. The activities of caspase-3 and -9 in myocardium were assayed using a commercial kit, and the levels of p-Akt, Akt, PI3K and p-PI3K were examined with Western blotting.

RESULTS

Pretreatment with SO2 significantly reduced the myocardial infarct size and plasma LDH and CK activities, as well as myocardial caspase-3 and -9 activities in the rats. Furthermore, the pretreatment significantly increased the expression levels of myocardial p-Akt and p-PI3K p85. Administration of the PI3K inhibitor LY294002 blocked all the effects induced by SO2 pretreatment.

CONCLUSION

The results suggest that the PI3K/Akt pathway mediates the protective effects of SO2 preconditioning against myocardial I/R injury in rats.

Genotoxic effects of sulfur dioxide in human lymphocytes

Sulfur dioxide (SO2), which is used as food preservative in apricot sulfurization and several fabricated foods, is a common air pollutant. The aim of this study was to reveal the possible genotoxic effects of SO2 using in vitro human lymphocytes. The different endpoints of genotoxicity: sister chromatid exchange (SCE), micronuclei (MN) tests and cell growth kinetics such as mitotic index (MI) and replication index (RI) were studied. The cells were treated with 0.1, 0.5 and 1.0 ppm concentrations of SO2. It was shown that SO2 caused significant increases in the frequency of SCE and MN in the middle and high dosage groups and also induced mitotic delays and decreased MI and RI. In conclusion, the results have confirmed that SO2 has potent mutagenicity and it can cause genetic damage leading to a malignancy.

Sulfur dioxide attenuates LPS-induced acute lung injury via enhancing polymorphonuclear neutrophil apoptosis

AIM

We speculated that the enhanced apoptosis of polymorphonuclear neutrophil (PMN) might be responsible for the inhibition of PMN infiltration in the lung. This study was designed to investigate the effects of sulfur dioxide (SO(2)) on PMN apoptosis in vivo and in vitro, which may mediate the protective action of SO(2) on pulmonary diseases.

METHODS

Acute lung injury (ALI) was induced by intratracheally instillation of lipopolysaccharide (LPS, 100 μg/100 g, in 200 μL saline) in adult male SD rats. SO(2) solution (25 μmol/kg) was administered intraperitoneally 30 min before LPS treatment. The rats were killed 6 h after LPS treatment. Lung tissues were collected for histopathologic study and SO(2) concentration assay. Bronchoalveolar lavage fluid (BALF) was collected for the measurement of PMN apoptosis. For in vitro experiments, rat peripheral blood PMNs were cultured and treated with LPS (30 mg/L) and SO(2) (10, 20 and 30 μmol/L) for 6 h, and apoptosis-related protein expression was detected by Western blotting, and apoptosis rate was measured with flow cytometry.

RESULTS

LPS treatment significantly reduced the SO(2) concentrations in the lung tissue and peripheral blood, as compared with the control group. Pretreatment with SO(2) prevented LPS-induced reduction of the SO(2) concentration in the lung tissue and peripheral blood. LPS treatment significantly reduced PMN apoptosis both in vivo and in vitro, which could be prevented by the pretreatment with SO(2). The protein levels of Caspase-3 and Bax was significantly increased, but Bcl-2 was decreased by the pretreatment with SO(2), as compared with LPS administration alone.

CONCLUSION

SO(2) plays an important role as the modulator of PMN apoptosis during LPS-induced ALI, which might be one of the mechanisms underlying the protective action of SO(2) on pulmonary diseases.

Effect of sulfur dioxide on expression of proto-oncogenes and tumor suppressor genes from rats

Sulfur dioxide (SO(2)) is a ubiquitous air pollutant that is present in low concentrations in the urban air, and in higher concentrations in the working environment. In the present study, male Wistar rats were housed in exposure chambers and treated with 14.00 +/- 1.01, 28.00 +/- 1.77 and 56.00 +/- 3.44 mg m(-3) SO(2) for 6 h/day for 7 days, while control group was exposed to filtered air in the same condition. The mRNA and protein levels of proto-oncogenes (c-fos, c-jun, c-myc, and Ki-ras) and tumor suppressor genes (p53, Rb, and p16) were analyzed in lungs using a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay and Western blot analysis. The results showed that mRNA and protein levels of c-fos, c-jun, c-myc, Ki-ras, and p53 in lungs were increased in a dose-dependent manner, while mRNA and protein levels of Rb and p16 were decreased in lungs of rats after SO(2) inhalation. These results lead to a conclusion that SO(2) exposure could activate expressions of proto-oncogenes and suppress expressions of tumor suppressor genes, which might relate to the molecular mechanism of cocarcinogenic properties and potential carcinogenic effects of SO(2). According to previous studies, the results also indicated that promoter genes of apoptosis and tumor suppressor genes could produce apoptotic signals to antagonize the growth signals that arise from oncogenes. Understanding its molecular controls will benefit development of treatments for many diseases.

SO(2) inhalation induces protein oxidation, DNA-protein crosslinks and apoptosis in rat hippocampus

Previous studies provide evidence for the possible neurotoxicity of SO(2), but little information is available about its mechanisms. In the present study, SO(2) inhalation-induced effects on the protein oxidation, DNA-protein crosslinks and apoptosis in rat hippocampus were studied, by exposing Wistar rats to SO(2) at 14, 28 and 56mg/m(3). The results indicate that the protein carbonyl content, an indicator of protein oxidation, and DNA-protein crosslink coefficient were significantly augmented with concentration-dependent properties. In addition, SO(2) inhalation at all concentrations tested caused the increases of caspase-3 activity and number of TUNEL positive staining neuron and the statistical difference was observed after 28 and 56mg/m(3) exposure, suggesting the occurrence of apoptosis. The results imply that attacking protein, nucleic acids and lipids by free radicals, generated via SO(2) derivatives in vivo, is one of the main mechanisms for SO(2)-induced injuries in central neuronal system.

The Vasodilator Effect and Its Mechanism of Sulfur Dioxide-Derivatives on Isolated Aortic Rings of Rats

The vasodilator effect of exogenous sulfur dioxide (SO(2)) derivatives (mixture of sodium bisulfite and sodium sulfite, 3:1 M/M in neutral solution) on rat vascular system was studied in order to explore the mechanism of blood pressure lowered by SO(2) and its derivatives. Isolated rat aortic rings were perfused in bath tubes containing various chemicals and their tensions were recorded. The results showed: (1) The SO(2) derivatives could relax isolated aorta precontracted by norepinephrine (NE) or potassium chloride (KCl) in a dose-dependent manner. (2) This vasodilator effect was attenuated after preincubation with indomethacin, but was not affected by N-L-nitro-arginine, methylene blue, and propranolol, and was independent of the aorta endothelium. (3) The vasoconstriction responses induced by NE, KCl, or Ca(2+) were antagonized by SO(2) derivatives in a noncompetitive manner. (4) The vasoconstrictions of two components (initial fast vasoconstriction induced by intracellular Ca(2+) release and sustained vasoconstriction evoked by extracellular Ca(2+) influx) were also inhibited by SO(2) derivatives. These results led to the conclusions: The SO(2) derivatives could cause vasorelaxation by a direct role of the chemicals on aortic smooth muscle cells. It was not dependent on vascular endothelium and was independent of nitric oxide (NO). It is suggested that SO(2) and its derivatives might be also vasoactive substances that modulate changes of blood pressure, like other gasotransmitters. The vasorelaxation might be related to the inhibition effects of SO(2) derivatives on Ca(2+) entry through both potential-dependent calcium channels and receptor-operating calcium channels, and also to the inhibition of intracellular Ca(2+) release. The vasorelaxation was at partly related to the increase of prostacyclin (PGI(2)) induced by SO(2) derivatives.

Cell Morphological Ultrastructural Changes in Various Organs from Mice Exposed by Inhalation to Sulfur Dioxide

Sulfur dioxide (SO2) is a common air pollutant, present in low concentrations in the community air as well as in higher concentrations in some workplaces. Our previous studies demonstrated that SO2 can cause oxidative stress and DNA damage to multiple organs of mice. However, there was no direct proof if and how the morphological changes are caused by SO2. In this study, the ultrastructural morphologies of lungs, livers, spleens, testis, brains, hearts, and kidneys from mice exposed by inhalation to SO2 at 28.00 +/- 1.98 and 56.00 +/- 3.11 mg/m3 were observed with electron microscopy. Our results show that (1) type II alveolar cells of lungs in SO2-exposure groups had obvious pathological changes including vacuolation of osmiophilic multilamellar bodies, a decrease in microvilli content and mitochondrial pyknosis or swelling, as well as various changes in the structure of the nucleus and chromatin. Meanwhile obvious changes in the mitochondrial and nuclear compartments, in type II alveolar cells were also observed. (2) A series of pathological changes was discovered in hepatic cells in SO2-exposure groups, such as swelling of the nucleus, dispersion of lipid droplets, degenerated mitochondria, and dilatation of rough endoplasmic reticulum. For mice exposed to SO2 at 56 mg/m3, necrosis of hepatocytes with unclear karyotheca or nearly dissolved karyotheca and decreases in organelles were observed. (3) The numbers of apoptotic splenocytes from mice exposed to SO2 were increased by SO2 inhalation in a dose-dependent manner. (4) In SO2-exposure groups, some of the cerebral cortex neurons, many glial cells and nerve fibers were damaged. (5) Mitochondrial swelling, decrease or disappearance of mitochondria crista, myocardial myofibril disorder, various changes of nucleus and chromatin, intercalated discs dissociation, and endothelium edema caused by SO2 exposure in heart tissues were found. In addition, other effects, such as myofibrillar fragmentation and dissolution, some myocardial cell membranes breach, and inflammatory cell infiltration, were observed in groups exposed to SO2 at 56 mg/m3. (6) SO2 exposure induced serious ultrastructural lesions in renal proximal tubular lining cells; moreover glomeruli and distal tubular lining cells were damaged in a dose-dependent manner. (7) Compared with the control group, the basement membranes, various seminiferous cells, as well as spermatozoa, and Sertoli cells of testes were altered in the SO2-exposure groups in a dose-dependent manner. In the aggregate, these results lead to a conclusion that inhalation of SO2 can cause the ultrastructure cellular damage of multiple organs in mice. Thus, inhalation of sulfur dioxide appears to be not only toxic to the respiratory system, but also a systemic toxin as well.

The genotoxic effect of potassium metabisulfite using chromosome aberration, sister chromatid exchange, micronucleus tests in human lymphocytes and chromosome aberration test in bone marrow cells of rats

Potassium metabisulfite (PMB) is used as an antimicrobial substance in many kinds of foods. In the present study, the effects of PMB on chromosome aberrations (CAs), sister chromatid exchanges (SCEs), and micronucleus (MN) formation in human lymphocytes and as well as its effect on CAs in bone marrow cells of rats were investigated. The human lymphocytes were treated with 25, 50, 100, and 200 microg/ml of PMB for 24 and 48 hr. PMB was also intraperitoneally (ip) injected to the rats as a single dose of 150, 300, and 600 mg/kg body weight (b.w.) for 12 and 24 hr before sacrifice. PMB induced abnormalities such as structural and numerical (total) CAs, SCEs, and MN formations in a dose dependent manner in the lymphocytes of the 24- and 48-hr treatment periods. In addition, PMB showed a cytotoxic effect by decreasing the replication index (RI), mitotic index (MI) and nuclear division index (NDI) in a dose dependent manner in human lymphocytes. The compound induced CA as well and decreased the MI in bone marrow cells of rats. It might be concluded that PMB had a high genotoxic and cytotoxic risk.

Vasodilatation of sulfur dioxide derivatives and signal transduction

The vasodilatation of sulfur dioxide (SO(2)) derivatives on the rat thoracic aortic rings and its cell signal transduction pathway were studied. The levels of cAMP, cGMP, PGI(2), TXA(2) and activities of PKA and adenylyl cyclase (AC) in the rings exposed to SO(2) derivatives were determined. The results indicated that SO(2) derivatives could dose-dependently relax the isolated rat aorta rings with or without endothelium precontracted by NE, no difference was found between the rings with and without endothelium; Levels of cAMP, PGI(2), AC activity and PKA activity in the aortic rings were significantly increased by the derivatives in a dose-related way; No change of cGMP and TXA(2) levels in rings was observed; cAMP/cGMP and PGI(2)/TXA(2) ratios were increased significantly by the SO(2) derivatives. These results led to the conclusions that SO(2) derivatives might cause the endothelium-independent vasorelaxation effect, and the vasorelaxation was mediated in partly by the signal transduction pathway of PGI(2)-AC-cAMP-PKA.

Protein oxidation and DNA-protein crosslink induced by sulfur dioxide in lungs, livers, and hearts from mice

In this article, protein oxidative damage and DNA-protein crosslinks (DPC) induced by sulfur dioxide (SO(2)) in lungs, livers, and hearts of mice were studied. The protein carbonyl (PCO) content was measured using spectrophotometric DNPH assay to reflect the degree of protein oxidative damage, and the DPC coefficient was measured by using a KCl-sodium dodecyl sulfate (SDS) assay to show the degree of DNA damage in lungs, livers, and hearts from mice exposed to SO(2) at various concentrations (0, 14, 28, and 56 mg-m(- 3)) for 6 h per day for 7 days. The results indicate that SO(2) caused an increase of PCO and DPC level in all organs tested from mice in a concentration-dependent manner. The concentration-response relationships in all organs tested of both female and male mice could be fitted well with monolinear regression equations. The adjusted coefficient R squared of all equations is more than 0.9. These results lead to a conclusion that SO(2) may cause an increase of protein oxidation damage and DNA-protein crosslinking in lungs, livers, and hearts from mice. The rank order of absolute increase in PCO contents and DPC coefficient in three organs from mice compared with controls was lung > liver > heart. Our results also indicated the regulation of PCO and that of DPC induced by SO(2) were conformed to each other; this implies that the protein oxidative damage may be associated with the emergence of DPC.

The effect of sulfur dioxide inhalation on active avoidance learning, antioxidant status and lipid peroxidation during aging

The effect of SO2 was examined on active avoidance learning, thiobarbituric acid reactive substances (TBARS), and the activities of Cu, Zn superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in young (3 months), middle-age (12 months ), and old (24 months) Swiss male albino rats. Ten ppm SO2 was administered to the animals of SO2 groups in an exposure chamber for 1 h/day x 7 days/week x 6 weeks while control groups were exposed to filtered air in the same condition. The most prominent effect of aging on active performance was also observed in the older group. SO2 exposure significantly decreased the active avoidance learning in the young group, but it had no effect on this parameter in the middle-aged and the older group compared with their corresponding control groups. SO2 exposure resulted in increased levels of Cu, Zn-SOD activity while decreased level of GSH-Px activity in all experimental groups compared with their corresponding control groups. CAT activities were unaltered. TBARS levels of all SO2 exposed groups were significantly increased compared with their respective control groups. In conclusion, results from the present research showed that SO2 exposure resulted in an increase in the lipid peroxidation and caused alterations in antioxidant enzyme activities. Additionally, SO2 exposure impaired cognitive function only in the young rats during the acquisition phase of active avoidance learning.

Effect of sodium sulfite on mast cell degranulation and oxidant stress

BACKGROUND

Sulfur dioxide is 1 of 6 environmental pollutants monitored by the Environmental Protection Agency. Its ability to induce bronchoconstriction is well documented. It is highly soluble, initially forming sulfite ions in solution. Sulfur oxides are important constituents of other pollutants, such as diesel exhaust and fine particulates.

OBJECTIVE

To investigate the cellular responses of sulfite on cultured mast cells (rat basophilic leukemia [RBL-2H3] cells) and human peripheral blood basophils.

METHODS

Sulfite-induced mast cell degranulation and intracellular production of reactive oxygen species were evaluated in the presence and absence of antioxidants and inhibitors of redox metabolism. Degranulation was determined using beta-hexosaminidase, serotonin, and histamine release assays. Induction of intracellular reactive oxygen species generation was determined using the redox-sensitive dye 2',7'-dichlorofluorescein diacetate.

RESULTS

Sodium sulfite induced degranulation and the generation of intracellular reactive oxygen species in RBL-2H3 cells. These responses were inhibited by the free radical scavenger tetramethylthiourea and the flavoenzyme inhibitor diphenyliodinium but not by depletion of extracellular calcium. Peripheral blood basophils also showed histamine release after exposure to sodium sulfite

CONCLUSIONS

Sulfite, the aqueous ion of sulfur dioxide, induces cellular activation, leading to degranulation in mast cells through a non-IgE-dependent pathway. The response also differs from IgE-mediated degranulation in that it is insensitive to the influx of extracellular calcium. The putative pathway seems to rely on activation of the reduced form of nicotinamide adenine dinucleotide phosphate oxidase complex, leading to intracellular oxidative stress.

Modulation of L-type calcium current in rat cardiac myocytes by sulfur dioxide derivatives

The effects of sulfur dioxide (SO(2)) derivatives (bisulfite and sulfite, 1:3M/M) on voltage-dependent L-type calcium current (I(Ca,L)) in isolated rat ventricular myocytes were studied using the whole cell patch-clamp technique. SO(2) derivatives increased I(Ca,L) in a concentration-dependent manner. SO(2) derivatives shifted both the steady-state activation and the inactivation curves of I(Ca,L) to more positive potentials, the effect on the latter being more pronounced. SO(2) derivatives markedly accelerated the recovery of I(Ca,L) from inactivation. SO(2) derivatives also significantly shortened the fast and slow time constants of inactivation. These results suggested that SO(2) inhalation might cause cardiac myocyte injury through increasing intracellular calcium via voltage-gated calcium channels.

Study of the interaction of sulfur dioxide derivative with cardiac sodium channel

The effects of sulfur dioxide (SO(2)) derivatives (bisulfite and sulfite, 1:3 M/M) on voltage-dependent sodium channel in isolated rat ventricular myocyte were studied using the whole cell patch-clamp technique. SO(2) derivatives increased sodium current (I(Na)) in a concentration-dependent manner. SO(2) derivatives at 10 microM significantly shifted steady-state inactivation curve of I(Na) to more positive potentials, but did not affect the activation curve. SO(2) derivatives markedly shifted the curve of time-dependent recovery of I(Na) from inactivation to the left, and accelerated the recovery of I(Na). SO(2) derivatives also significantly shortened the activation and inactivation time constants of I(Na). These results indicated that SO(2) derivatives produced concentration-dependent stimulation of cardiac sodium channels, which due mainly to the interaction of the drug with sodium channels in the inactivated state.

DNA damage in mice treated with sulfur dioxide by inhalation

Sulfur dioxide (SO2) is a ubiquitous air pollutant produced by the burning of fossil fuels. In this study, single-cell gel electrophoresis (the Comet assay) was used to evaluate the DNA damage produced by inhalation exposure of mice to SO2. Male and female mice were housed in exposure chambers and treated with 14.00 +/- 1.25, 28.00 +/- 1.98, 56.00 +/- 3.11, and 112.00 +/- 3.69 mg/m3 SO2 for 6 hr/day for 7 days, while control groups were exposed to filtered air. Comet assays were performed on blood lymphocytes and cells from the brain, lung, liver, spleen, kidney, intestine, and testicles of the animals. SO2 caused significant, dose-dependent increases in DNA damage, as measured by Olive tail moment, in all the cell types analyzed from both sexes of mice. The results indicate that inhalation exposure to SO2 damages the DNA of multiple organs in addition to the lung, and suggests that this damage could result in mutation, cancer, and other diseases related to DNA damage. Further work will be required to understand the ultimate toxicological significance of this damage. These data also suggest that detecting DNA damage in blood lymphocytes, using the Comet assay, may serve as a useful tool for evaluating the impact of pulmonary SO2 exposure in human biomonitoring studies.

Sulfur dioxide derivative modulation of potassium channels in rat ventricular myocytes

The effects of sulfur dioxide (SO2) derivatives (bisulfite and sulfite, 1:3 M/M) on voltage-dependent potassium current in isolated adult rat ventricular myocyte were investigated using the whole cell patch-clamp technique. SO2 derivatives (10 microM) increased transient outward potassium current (I(to)) and inward rectifier potassium current (I(K1)), but did not affect the steady-state outward potassium current (I(ss)). SO2 derivatives significantly shifted the steady-state activation curve of I(to) toward the more negative potential at the V(h) point, but shifted the inactivation curve to more positive potential. SO2 derivatives markedly shifted the curve of time-dependent recovery of I(to) from the steady-state inactivation to the left, and accelerated the recovery of I(to) from inactivation. In addition, SO2 derivatives also significantly change the inactivation time constants of I(to) with increasing fast time constant and decreasing slow time constant. These results indicated a possible correlation between the change of properties of potassium channel and SO2 inhalation toxicity, which might cause cardiac myocyte injury through increasing extracellular potassium via voltage-gated potassium channels.

Oxidation damage of sulfur dioxide on testicles of mice

The effects of sulfur dioxide (SO2) on levels of thiobarbituric acid reactive substances (TBARS), levels of reduced glutathione (GSH), and the activities of Cu,Zn-superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were investigated in testicles of Kunming albino male mice. SO2 at different concentrations (22, 56, and 112 mg/m3) was administered to animals of SO2 groups in different exposure chambers for 6 h/day for 7 days, while control groups were exposed to filtered air under the same conditions. Our results show that SO2 caused lipid peroxidation and changes in antioxidative status in testicles of mice. Exposure to SO2 at all concentrations tested significantly increased TBARS levels in testicles of mice. SO2 at all concentrations tested tended to decrease activities of SOD and GPx enzymes and levels of GSH relative to control animals, but only the decreases in SOD and GPx activities caused by SO2 exposures of higher concentrations were statistically significant. SO2 at all concentrations tested tended to increase activities of CAT relative to control animals, but the increases of CAT activities caused by SO2 exposures of low concentrations (22 and 56 mg/m3) were statistically significant. These results lead to the conclusion that SO2 exposure can cause oxidative damage to testicles of male mice, and SO2 is a toxin to the reproductive system of mammals, not only to the respiratory system. Further work is required to understand the toxicological role of SO2 in reproduction organs or even sperm from humans and animals.

Effects of derivatives of sulfur dioxide on transient outward potassium currents in acutely isolated hippocampal neurons

The effect of SO2 derivatives, a common air pollutant and exists in vivo as an equilibrium between bisulfate and sulfite, on transient outward currents (TOCS) in hippocampal neurons were studied using the whole cell configuration of patch-clamp technique. TOCS that preliminary included a fast inactivating (A-current or IA) and a slow inactivating (D-current or ID ) current, were isolated based on the kinetics and pharmacological properties in the presence of 50 mM TEA. The results showed that SO2 derivatives reversibly increased the amplitudes of TOCS in a concentration dependent and voltage dependent. Half-increase dose on TOCS was 25 microM. In vivo, SO2 derivatives shifted the steady-state inactivation curve of TOCS in the depolarizing direction but had little effect on the activation curve. Half-maximal inactivation voltage of TOCS was -69.6+/-1.0 mV before and -56.8+/-0.4 mV after application of 10 microM SO2 derivatives. SO2 derivatives increased the maximal conductance and delayed the inactivation process of TOCS. These results suggest that SO2 derivatives would increase the excitability of hippocampal neurons.

Modulation of sodium currents in rat dorsal root ganglion neurons by sulfur dioxide derivatives

The effect of sulfur dioxide (SO2) derivatives, a common air pollutant and exists in vivo as an equilibrium between bisulfate and sulfite, on tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium channels in cultured post-natal dorsal root ganglion (DRG) neurons were studied using the whole cell configuration of patch-clamp technique. SO2 derivatives on two types of sodium currents were either inhibitory or stimulatory depending on the kinetic parameters tested. At a holding potential of -80 mV, SO2 derivatives suppressed TTX-S sodium currents when depolarizing potential was negative to -30 mV and TTX-R sodium currents when negative to -10 mV but they increased them when the depolarizing potential was positive to -30 or -10 mV. SO2 derivatives shifted the conductance-voltage curve for TTX-R sodium currents in the depolarizing direction but had little effect on that for TTX-S sodium currents. The steady-state inactivation curve for TTX-R sodium channel was shifted by SO2 derivatives in the depolarizing direction as that for TTX-S sodium channel. SO2 derivatives changed the reversal potential and increased the maximum conductance of two types of sodium channels. SO2 derivatives postponed the activating time and delayed the inactivation of sodium currents. The results suggest that SO2 derivatives would increase the excitability of neurons and alter the ion selectivity for two types of sodium currents.

Oxidative damage of sulfur dioxide inhalation on lungs and hearts of mice

Effects of sulfur dioxide (SO2) on concentrations of thiobarbituric acid-reactive substances (TBARS) and reduced glutathione (GSH), activities of Cu,Zn-superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were investigated in lungs and hearts of Kunming albino mice of both sexes. The mice of SO2 groups were exposed to various concentrations (22, 56, and 112 mg/m3) of SO2 in separate exposure chambers for 6 h/day for 7 days, whereas control groups were exposed to filtered air under otherwise the same conditions. Our results show that SO2 caused lipid peroxidation and changes of antioxidative status in both lungs and hearts of mice. Exposure to SO2 at all concentrations tested caused a significant increase of TBARS and a significant decrease in GSH content in lungs and hearts of mice, with the exception of GSH content in the hearts of female mice. For lungs, SO2 at low concentrations significantly increased SOD and GPx activities, whereas at high concentrations it significantly decreased these same activities in mice of both sexes. For hearts, SO2 at all tested concentrations significantly decreased activities of SOD from mice of both sexes, as well as that of GPx from male mice, but the decrease of GPx activities in hearts from female mice was statistically insignificant. SO2 inhalation tended to decrease activities of CAT in lungs and hearts from mice of both sexes, whereas only the decrease of CAT activities caused by SO2 in lungs from male mice was statistically significant, at 112 mg/m3. The results also show a gender difference in oxidative stress and antioxidation status caused by SO2 exposure. These results lead us to conclude that SO2 exposure can cause oxidative damage to lungs and hearts of mice, and SO2 is toxic not only to the respiratory system, but to the heart as well. Additional work is required to understand the toxicological role of SO2 on many or even all mammalian organs.

Genotoxicity of hydrated sulfur dioxide on root tips of Allium sativum and Vicia faba

Genotoxicity of sulfur dioxide (SO(2)) and its hydrates (bisulfite and sulfite) in human lymphocytes and other mammalian cells have been found earlier in our laboratory. In the present studies, we used Allium stavium and Vicia faba cytogenetic tests, which are the highly sensitive and simple plant bioassays. A mixture of sodium bisulfite and sodium sulfite (1:3), at various concentrations from 1 x 10(-4) to 2 x 10(-3)M was used for the treatment. Genotoxicity was expressed in terms of anaphase aberration (AA) frequencies in the Vicia-AA test and in terms of micronuclei (MCN) frequencies in both Vicia-MCN test and Alllium-MCN test. On average, the results showed a 1.7-3.9-fold increase of AA frequencies and a 3.5-4.5-fold increase of MCN frequencies in Vicia root tips as compared with the negative control. Similarly, results of Allium-MCN test also showed a significant increase in MCN frequencies in the treated samples. In addition, pycnotic cells (PNC) appeared in Allium root tips of treated groups. The frequencies of MCN, AA and PNC increased dose-dependently and the cell cycle delayed at the same time in bisulfite treated samples. Results of the present study suggest that the Vicia and Allium cytogenetic bioassays are efficient, simple and reproducible in genotoxicity studies of bisulfite.

Oxidative damage of sulfur dioxide inhalation on stomachs and intestines of mice

Effects of exposure to sulfur dioxide (SO(2)) on levels of thiobarbituric acid-reactive substances (TBARS), levels of reduced glutathione (GSH), and the activities of Cu,Zn-superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were investigated in stomachs and intestines of Kunming albino mice of both sexes. SO(2) exposure at different concentrations (22, 56, and 112 mg/m(3)) was administered to the animals of SO(2) groups in the exposure chambers for 6 h/day for 7 days, while control groups were exposed to filtered air under the same condition. Our results show that SO(2) caused lipid peroxidation and changes of antioxidative status in stomachs and intestines of mice. Exposure to SO(2) at all concentrations tested caused significantly the increase of TBARS levels in stomachs and intestines of mice. For the stomachs, activities of these antioxidant enzymes and levels of GSH were significantly unaltered by SO(2) at low concentrations, except significant increase of SOD activity in the stomachs of male mice. However, higher SO(2) caused the significant increases of CAT activities and the significant decreases of GSH levels and activities of SOD and GPx. For intestines, SO(2) at all concentrations tested decreased significantly activities of SOD relative to control animals; SO(2) caused the decreases of GPx activities, but only the decreases of GPx activities caused by SO(2) exposures at higher concentrations (56 and 112 mg/m(3)) were statistically significant. SO(2) at all concentrations tested tended to increase the CAT activities in a dose-dependent manner, but the decreases of CAT activities caused by higher SO(2) were significant. SO(2) at all concentrations tested decreased significantly levels of GSH in intestines of both sexual mice. These results lead to conclusion that SO(2) exposure can caused oxidative damage to stomachs and intestines of mice, and SO(2) is a toxic agent to stomachs and intestines of mammals, not only to respiratory system. Further work is required to understand toxicological role of SO(2) on multiple or even all organs in human and animal.

Oxidative damage of sulfur dioxide inhalation on brains and livers of mice

The effects of sulfur dioxide (SO(2)) on levels of thiobarbituric acid reactive substances (TBARS), levels of reduced glutathione(GSH) and the activities of Cu,Zn-superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase (CAT) were investigated in brains and livers of Kunming albino mice of both sexes. SO(2) at different concentrations (22, 56 and 112 mg/m(3)) was administered to animals of SO(2) groups in different exposure chambers for 6 h/day for 7 days, while control groups were exposed to filtered air in the same condition. Our results show that SO(2) caused lipid peroxidation and changes of antioxidative status in brains and livers of mice. Exposure to SO(2) at all concentrations tested caused significantly the increase of TRARS levels in brains and livers of mice. For the brains, activities of these antioxidant enzymes and levels of GSH were significantly unaltered by SO(2) at low concentrations, except significant increase of GSH levels in the brains of male mice; however, SO(2) at higher concentrations caused significantly decreases of GSH levels and activities of these antioxidant enzymes. For livers, SO(2) at all concentrations tested decreased significantly activities of SOD relative to control animals; SO(2) tended to decrease activities of GPx and CAT, but only the decreases of GPx and CAT activities caused by SO(2) exposures of higher concentrations (56 and 112 mg/m(3)) were statistically significant. SO(2) also tended to decrease levels of GSH, but only at 112 mg/m(3) caused significantly decrease of GSH levels in livers of both sexual mice. Unexpectedly, the decreases of activities of these antioxidative enzymes caused by SO(2) at different concentrations in brains and livers of mice did not follow a linear dose-response curves. In many respects, the decreased percentages of the activities of each antioxidative enzyme (SOD or GPx or CAT) caused by SO(2) at 22, 56 and 112 mg/m(3) in brains and livers of mice were similar. These results lead to conclusion that SO(2) exposure can caused oxidative damage to brains and livers of mice, and SO(2) is a toxin to brain and liver of mammals, not only to respiratory system. Further work is required to understand toxicological role of SO(2) on multiply or even all organs in human and animal.

Chromosome aberrations and sister chromatid exchanges in cultured human lymphocytes treated with sodium metabisulfite, a food preservative

The aim of this study was to investigate the ability of sodium metabisulfite (SMB) which is used as an antimicrobial substance in food, to induce chromosome aberrations (CA) and sister chromatid exchanges (SCE) in human lymphocytes. SMB-induced CAs and SCEs at all concentrations (75, 150 and 300 microg/ml) and treatment periods (24 and 48h) dose-dependently. However, SMB decreased the replication index (RI) and the mitotic index (MI) at the concentrations of 150 and 300 microg/ml for 24 and 48h treatment periods. This decrease was dose-dependent as well.