| ObjectiveAluminum (Al) is one of the most abundant elements in the natural environment which widely exists in air, soil, water, and human food, second only to oxygen and silicon. With the rapid development of industrialization, people are more frequently exposed to aluminum and it can cause chronic toxic effects when it accumulates in human body. The neurotoxicity induced by aluminum has been paid close attention in recent years. Al can produce toxic effect in nerve cells by generating reactive oxygen species (ROS) which cause lipid peroxidation, and ultimately lead to apoptosis. Taurine (Tau),2-aminoethanesulphonic acid, one of the most abundant amino acid in cells, serving a variety of functions in central nervous system,respiratory system and hepatobiliary system, but very little is known yet about its protection against Al-induced oxidative damage and apoptosis. In the present study, Wistar rats were administered with Aluminum Chloride Hexahydrate (AlCl3·6H2O) intragastrically to build animal models, and then were treated with Tau in aspect of prevention and treatment. We determined element contents, peroxidation indices, adenosine triphosphatase (ATPase) activity, and expression of apoptosis-related gene, to study and discuss the protective role of Tau against Al-induced neural apoptosis and oxidative injuries in rats.Methods1. Animal experimentSixty male Wistar rats (185-225g) were radomized into six groups of ten animals each based on their body weights:control group, Al-treated group, low, mid and high-dose Tau groups, and prevention group. After seven days of acclimatization, the rats began to receive drugs by gavage once a day, five days a week. In the first four weeks, the Al-treated group received AlCl3·6H2O dissolved in double-distilled water at a dose of 281.40 mg/(kg·d). The control group was administered normal saline 1.0 mL/d. The low-dose Tau group, the mid-dose Tau group and the high-dose Tau group received the same treatment as the Al-treated group during this period. The prevention group was also given AlCl3·6H2O 281.40 mg/(kg·d) but received Tau at a dose of 400 mg/(kg·d) 4h later. In the subsequent four weeks, the Al-treated group was administered an equal volume of normal saline, as given to the control group. The low-dose Tau group received Tau at a dose of 200 mg/(kg·d). The mid-dose Tau group and the prevention group were both administered Tau 400 mg/(kg·d). The high-dose Tau group was given 800 mg/(kg·d).Three rats selected from each group were perfused by 4% paraformaldehyde for the use of making paraffin sections and immunohistochemical assay. The other rats were fasted for 24h after the treatments and then were sacrificed, their brains were quickly removed and blood was collected. All the samples were stored at -20℃ for the use of bioassays.2. Effect of Tau on growth and development of rats exposed to AlThe eating situation and behavior change of rats were observed everyday during the whole animal experiment, the rats were weighed every three days and the growth of body weight in each stage was calculated. The brains were separated and weighed after sacrifice, and the brain coefficient was calculated to study the accelerative effect of Tau on the growth and development of Al-exposed rats.3. Effect of Tau on antioxidant system in Al-exposed rats’brainAfter the rats were sacrificed, brains were separated and made into tissue homogenate with normal saline. The Malondialdehyde (MDA) content, the activities of Glutathione peroxidase (GSH-Px) and Superoxide dismutase (SOD) were determined by thibabituric acid (TBA) method,5,5’-Dithio bis-(2-nitrobenzoic acid) (DTNB) method and xanthine oxidase (XO) method respectively, to investigate the protective role of Tau against Al-induced oxidative injuries in brain of rats.4. Effect of Tau on antioxidant system in serum of rats exposed to AIAll the rats were sacrificed after the treatments. Blood was immediately collected in centrifuge tubes and centrifuged to collect serum. The MDA content, the activities of GSH-Px and SOD were determined by TBA method, DTNB method and XO method respectively, to study the effect of Tau on improving the antioxidant indices in serum of Al-exposed rats.5. Effect of Tau on the activity of ATPase in Al-exposed rats’brainAfter the rats were sacrificed, brains were separated and made into tissue homogenate. The activities of Na+K+-ATPase, Ca2+-ATPase and Mg2+-ATPase were tested by inorganic phosphorus method, to investigate antagonistic effect of Tau on Al-induced reduction of ATPase activities in brain of rats.6. Effect of Tau on the activity of ATPase in blood of rats exposed to AlThe blood of was immediately collected after they were sacrificed and a part of it was made into dissolving blood. The activities of Na+K+-ATPase, Ca2+-ATPase and Mg2+-ATPase in blood were tested by inorganic phosphorus method, to study the protective role of Tau on ATPase in blood of rats exposed to Al.7. Effect of Tau on contents of Al and other essential elements in Al-exposed rats’ serumAll the rats were sacrificed after the treatments. Blood was immediately collected in centrifuge tubes and centrifuged to collect serum. The contents of Ca, Mg, Cu, Fe and Zn were measured by Atomic Absorption Spectrometry (AAS), and the Al content in serum was analyzed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), aiming to discuss the effect of Tau on removing Al and regulating essential elements in serum of Al-exposed rats.8. Effect of Tau on the expression of Bcl-2 and Box in brain of rats exposed to AlAfter all the treatments, the rats were administered with cardiac perfusion by 4% paraformaldehyde to fixate brain tissues and make paraffin sections. The expression of Bcl-2 and Box were analyzed by ready-to-use SABC immunohistochemical dyeing test kit, to investigate antagonistic effect of Tau on Al-induced apoptosis in brain of rats.Results1. Effect of Tau on growth and development of rats exposed to AlThe growth and development of rats in Al-treated group were slower and they appeared listlessness and dizziness. However, the developing conditions in other groups were much better. There has been a significant decline in the growth of body weight from the sixth week compared to control group (P<0.05). Until the eighth week, the growth of body weight is significantly higher in the prevention group than in the Al-treated group (P<0.05), the brain coefficient in control group and prevention group were obviously lower compared to Al-treated group (P<0.05).2. Effect of Tau on antioxidant system in Al-exposed rats’ brainThe brain displayed significantly higher level of MDA in the Al-treated group than in the control group (P<0.05). The activities of SOD and GSH-Px were both significantly reduced in the Al-treated group (P<0.05). However, the content of MDA was lowered in all the Tau-treated groups in a dose-dependent manner, and it was significantly declined in the high-dose group and prevention group than in the Al-treated group (P<0.05). The results showed that Tau significantly improved the activities of SOD in the high-dose group and prevention group (P<0.05). The GSH-Px activities were also significantly increased in the prevention group, the mid-dose and high-dose groups (P<0.05). No significant difference was observed among all the Tau-treated groups compared to normal group (P>0.05).3. Effect of Tau on antioxidant system in serum of rats exposed to AlTreating rats with Al resulted in significant increasement of MDA content in the serum compared to the control group (P<0.05). Conversely, treatments with Tau at mid-dose and high-dose caused significant decrement of MDA content compared to the Al-treated group (P<0.05). The activitity of GSH-Px was markedly reduced in the Al-intoxicated rats’ serum (P<0.05) while significant elevation was observed in the mid-dose Tau group (P<0.05). However, neither Al nor Tau resulted in significant changes of the SOD activities in rats’serum (P>0.05).4. Effect of Tau on the activity of ATPase in Al-exposed rats’brainAl caused significant reduction of Na+K+-ATPase and Mg2+ -ATPase activities compared to the control group (P<0.05). The activities of Na+K+-ATPase were significantly increased in the brain of rats treated with Tau at mid-dose and high-dose compared to the Al-treated group (P<0.05). The brain also displayed significant higher activity of Mg2+-ATPase in the high-dose taurine group (P<0.05). However, no significant difference of Ca2+-ATPase activity was observed among all the groups (P>0.05).5. Effect of Tau on the activity of ATPase in blood of rats exposed to AlThe activities of Ca2+-ATPase and Mg2+-ATPase were significantly reduced in the blood of rats treated with Al compared to the control group (P<0.05). On the contrary, significant elevation of Ca2+-ATPase activity was found in high-dose Tau group and prevention group compared to the Al-treated group (P<0.05). No significant difference of Na+K+-ATPase activity was found among all the groups (P>0.05). Although the activity of Mg2+-ATPase was increased in all the Tau-treated groups compared to Al-treated group, none of them achieve a statistical significance (P>0.05).6. Effect of Tau on contents of Al and other essential elements in Al-exposed rats’ serumThe content of Al in rats’ serum was significantly elevated in the Al-treated group compared to the control group (P<0.05). On the contrary, significant reduction of Al contents were found in mid-dose Tau group and high-dose Tau group compared to the Al-treated group (P<0.05).The contents of Fe in rats’ serum were significantly higher but the contents of Mg and Zn in rats’ serum were significantly lower in the Al-treated group compared to the control group (P<0.05). Compared to the Al-treated group, the Fe content was significantly lower in the high-dose Tau group (P<0.05) but the Zn content was significantly elevated (P<0.05). The Mg contents were significantly increased in mid-dose Tau group and prevention group compared to the control group (P<0.05). However, neither Al nor Tau resulted in significant changes of Cu and Ca contents in rats’serum (P>0.05).7. Effect of Tau on the expression of Bcl-2 and Box in brain of rats exposed to AlThe results of the expression of Bcl-2 in rats’brain showed that most of the cells in the control group had irregular shapes and processes, the cytoplast of positive cells were dyed dark claybank and obviously different from negative cells. Compared to control group, the number of positive cells presented a certain degree of decline. However, the number of positive cells was obviously increased in Tau-treated groups compared to Al-treated group and the cytoplast of positive cells were deep-dyed.The results of the expression of Bax in rats’brain showed that most of the cells in the control group had regular shapes and distributed uniformly, almost no positive expression was observed. The cytoplast of most of the cells in the Al-treated group were dyed dark claybank and irregular bulges can be observed. However, the numbers of positive cells were all decreased in Tau-treated groups, the result were more noticeable in mid- and high-dose Tau groups, and the positive cells were dyed more lightly.Conclusions1. Tau could promote the growth and development of rats, and improve Al-induced growth retardation to a certain extent.2. Tau plays a role in protecting rats’brain and serum from Al-induced oxidative injuries.3. Tau could inhibit the significant reduction of ATPase activity induced by Al in rats’brain and serum.4. Tau could promote the elimination of Al and regulate the imbalance of homeostasis of other essential elements induced by Al.5. Tau could regulate the expression of neural apoptosis related gene, and thus alleviate the toxic effect of Al on nervous system of rats.In conclusion, Tau can effectively antagonize neural oxidative injuries and apoptosis induced by Al and thus play a role in protecting rats’nervous system. |
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