Neurochemical changes by inhalation of environmental pollutants sulfur dioxide and hydrogen sulfide: degradation of total lipids, elevation of lipid peroxidation and enzyme activity in discrete regions of the guinea pig brain and spinal cord

SO(2) inhalation modulates the expression of pro-inflammatory and pro-apoptotic genes in rat heart and lung

SO(2) is a common air pollutant, and human exposure to SO(2) has become increasingly widespread due to the combustion of fossil fuels. The epidemiological studies have linked SO(2) exposure not only with many respiratory responses, but also with cardiovascular diseases. Also, its possible toxicity has been implicated by determining oxidative stress, DNA damage and membrane channel alteration in rat heart and lung. However, its detailed mechanisms remain unclear. In the present study, rats were treated with 7, 14 and 28 mg/m(3) SO(2) for 6h/day for 7 days, and the mRNA levels of TNF-α, IL-1β, iNOS, ICAM-1, Bax and Bcl-2 and subsequent insults were determined in the heart and lung. The results indicate that SO(2) inhalation markedly elevated TNF-α and IL-1β mRNA levels and secretions, enhanced iNOS and ICAM-1 mRNA levels and the ratio of Bax/Bcl-2 in a concentration-dependent manner, and induced occurrence of apoptosis. This suggests that SO(2) inhalation induced an inflammatory response and subsequent insults via modulating pro-inflammatory and pro-apoptotic genes in the heart and lung, which contributed to the increased risk of respiratory and cardiovascular diseases.

Expression of caspase and apoptotic signal pathway induced by sulfur dioxide

Sulfur dioxide (SO(2)) is a common air pollutant that is released in low concentrations into the atmosphere and in higher concentrations in some work places. 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 7 days (6 hr/day), while control rats were exposed to filtered air under the same conditions. The mRNA and protein levels of caspase-3, caspase-8, and caspase-9 were analyzed using a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay and an immunohistochemistry method. Activities of caspases were detected using colorimetric and fluorescent assays. Chromatin degradation and cell morphological changes were investigated by TUNEL assay and H&E staining in livers and lungs, respectively. The results showed that mRNA levels, protein levels and activities of caspase-3, caspase-8, and caspase-9 were increased in a dose-dependent manner in livers and lungs of rats after SO(2) inhalation. In addition, livers were infiltrated with lymphocytes, congestion and inflammation occurred in lungs, and eosinophil cells and apoptotic cells increased in both livers and lungs after SO(2) inhalation. These results suggest that SO(2) exposure increases the expression and activity of both initiator and and effector caspases, and may induce apoptosis in liver and lung of rats through both death receptor and mitochondrial pathways.

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.

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.

Effects of sulfur dioxide on apoptosis-related gene expressions in lungs from rats

Sulfur dioxide (SO2) is an air pollutant in densely populated areas as well as in areas polluted by coal-fired power plants, smelters, and sulfuric acid factories. 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/m3 SO2 for 6 h/day for 7 days, while control rats were exposed to filtered air in the same condition. The mRNA and protein levels of three apoptosis-related genes (p53 and bax are promoters of apoptosis, whereas bcl-2 is apoptotic suppressor) were analyzed in lungs using a real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) assay and immunohistochemistry method, and caspase-3 activities were detected. The results showed that mRNA levels of p53 and bax were increased in a dose-dependent manner and at the concentrations of 28.00 and 56.00 mg/m3 SO2 the increases were significant (for p53: 1.23-fold at 28 mg/m3 and 1.39-fold at 56 mg/m3; for bax: 1.77-fold at 28 mg/m3 and 2.26-fold at 56 mg/m3, respectively), while mRNA levels of bcl-2 were decreased significantly (0.78-fold at 28 mg/m3 and 0.73-fold at 56 mg/m3) in lungs of rats exposed to SO2. Dose-dependent increase of p53 and bax proteins in the lungs was observed after SO2 inhalation, while decrease of bcl-2 protein levels was obtained using immunohistochemistry method. Caspase-3 activities were increased in lungs of rats after SO2 inhalation. These results lead to a conclusion that SO2 exposure can change the expression of apoptosis-related genes, and it suggests that SO2 can induce apoptosis in lung of rat and may have relations with some apoptosis-related diseases. Elucidating the expression patterns of those factors after SO2 inhalation may be critical to our understanding mechanisms of SO2 toxicity and helpful for the therapeutic intervention.

The effects of ageing and sulfur dioxide inhalation exposure on visual-evoked potentials, antioxidant enzyme systems, and lipid-peroxidation levels of the brain and eye

The effects of ageing and 10 ppm sulfur dioxide (SO(2)) inhalation exposure on visual-evoked potentials (VEPs), thiobarbituric acid reactive substances (TBARS), a product of lipid peroxidation, and the activities of Cu, Zn superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) of brain and eye were investigated in young (3-month), adult (12-month), and mature (24-month) Swiss male albino rats. The experimental groups were placed in an exposure chamber containing a constant level of 10 ppm SO(2), while control groups were placed in an exposure chamber, which was continually pumped with filtered air, for 1 h/day x 7 days/week for 6 weeks. SO(2) inhalation exposure caused increased levels of brain, retina, and lens Cu, Zn SOD activity, and decreased levels of brain and lens GSH-Px activity in all experimental groups with respect to their corresponding control groups, whereas no change was observed in the level of retina GSH-Px activity. No alterations were observed in brain CAT activity. On the other hand, retina CAT activity was slightly decreased in SO(2)-exposed rats, but no change was observed in their lens CAT activity. The brain and lens TBARS levels of all SO(2)-exposed groups were significantly increased in comparison with their respective control groups. The amount of TBARS was only increased in the retina of the SO(2)-exposed 3-month group compared with its control. Of the SO(2)-exposed rats, the mean latencies of the P(1), N(1), P(2), and P(3) components of the 3-month group, P(1), N(1), and N(2) components of the 12-month group, and only P(3) of the 24-month group were significantly prolonged in comparison with those of their control groups. The amplitudes of N(1)P(2) and P(2)N(2) in the 12- and 24-month control groups were significantly decreased compared with those of the 3-month group. On the other hand, no differences were observed among those of SO(2)-exposed groups. These findings suggest that ageing and SO(2) inhalation exposure have the potential to induce antioxidant enzymes in the brain and eye, and VEP alterations, which are the primary target for air pollutants. It could be concluded that lipid peroxidation could play a critical role in the mechanism responsible for VEP alterations with ageing.

High-performance liquid chromatography detection of sulfide in tissues from sulfide-treated mice

The biological and forensic use of ion-interaction reversed-phase high-performance liquid chromatography for the determination of hydrogen sulfide-derived methylene blue is evaluated by measuring the sulfide content in tissues from sulfide-treated mice. Various preparative conditions were examined. The determinations of background levels of sulfide from brain, liver and kidney were compared to sulfide levels from mice exposed to 60 micrograms g-1 sodium hydrosulfide. At the time of death, significant increases above background sulfide levels were measured for all three biological tissues. To evaluate its forensic potential, we used this sulfide detection methodology to evaluate comparatively the sulfide levels from fresh and frozen samples of brain, liver and kidney. The stability of sulfide levels obtained from frozen brain makes this tissue the most reliable tissue for forensic evaluation. Samples of brain, liver and kidney obtained within 24 h of death by sulfide intoxication had demonstrable elevations in sulfide concentration.