The Mechanism Of1-Bromopropane Neurotoxicity On The Central Nervous System Of Rats

Objective1-Bromopropane (1-BP), also named brompropane. Due to its noninflammability, volatility, and lower ozone-depleting potency, it is now used as an alternative to ozone-depleting solvents. With the widely use of1-BP, the number of worker exposed occupationally to1-BP is increasing. The occupational poisoning also emerged. Epidemiological and laboratory studies indicate that the nervous systems are the one targets of the1-BP toxicity, the central nervous system (CNS) is demonstrated the more sensitive than the peripheral nervous system (PNS). However, the exactly underlying toxicology mechanisms of1-BP remain unclear, and there is no effective therapeutic remedy for1-BP so far as well. Therefore, the study addressed on the mechanisms of CNS and tried to provide some useful information for preventing and curing1-BP toxicityDocosahexaenoic acid (DHA) is an necessary n-3polyunsaturated fatty acids, mainly derived from fish oil and micro algae oil. DHA is able to influence the activity of cells, regluate physiological reaction to oxidative stress, and reduce the oxidative stress injury. Previous research indicated that DHA has neutoprotective effection, and DHA is improtant for the development of nervous system. Recently research showed that DHA has antioxidant and anti-inflammatory effect.1-BP induced toxicity of CNS is related to oxidative stress and inflammation. Therefore we hypothesis that DHA could exert protection for1-BP induced injury of nervous system.Nervonic acid is a kind of long chain monounsaturated fatty acids which mainly comes from shark brain and shark oil. NA is a major component of cell membrane of white matter, which can promote recovery of nervous system effectively, and prevent brain aging. Studies found that NA has an important role in treatment of Parkinson and alzheimer. With its strong antioxidant ability, NA could increase the activity of SOD, and decrease the level of MDA. We hypothesized that NA maybe has a certain degree protection for1-BP caused central nervous system injury.In order to choose the optimal intervention and to study the underlying mechanism, the rats were given corresponding test material by gavage, and the Morris water maze was applied to evaluate learning and memory of rats. The biochemical parameters were used to determine the function of DHA and NA. After intervention, we adopt Morris water maze to evalutate the intervention effect. We detected astrocytes activation, the expression of nucler factor-kappa B (NF-κB) and transcription factor NF-E2-related factor-2(Nrf2) to illustrate the mechanism of1-BP.Methods1DHA and NA against1-BP neurotoxicity on the central nervous system40Wistar male rats were randomly divided into4groups with10in each, i.e. control group,1-BP group, NA intervention group and DHA intervention group. The rats of1-BP group, NA intervention, and DHA intervention group received800mg/kg.bw1-BP by gavage, while the rats in control group received eauivalent corn oil. After4hours of giving1-BP, NA intervention group and DHA intervention group orally administered150mg/kg.bw NA and500mg/kg.bw DHA respectively, for consecutive12days. Rats in each group were given in accordance with their material for7days, and then Morris water maze was used to detect learning and memory ability of rats in each group. After the Morris water maze test, rats were sacrificed; the cerebral cortex and hippocampus were quickly dissected. The cerebral cortexes were homogenized, and levels of glutathione (GSH) and malondialdehyde (MDA), the activity of glutathione reductase (GR) and y-Glutamate cysteine ligase (y-GCL) were determined by biochemical method.2The antagonistic effects of DHA on1-BP neurotoxicity48male healthy Wistar rats were randomly divided into4groups with12in each group, i.e. control group,1-BP group, low-dose DHA intervention and high-dose DHA intervention. Low-dose DHA intervention and high-dose DHA intervention group were treated250mg/kg.bw and500mg/kg.bw DHA respectively, while control group and1-BP group received equivalent corn oil. On day8of DHA treatment,1-BP group, low-dose DHA intervention and high-dose DHA intervention were given800mg/kg.bw1-BP, whereas control received corn oil. The Morris water maze test was applied to detect the ability of learning and memory fuction. After the Morris water maze, rats were sacrificed and the cerebral cortexes were removed. Biochemical methods detected the levels of GSH and MDA. Using immunofluorescence and western blotting determine the protein expression of glial fibrillary acidic protein (GFAP), NF-κB and Nrf2.Results1DHA and NA against1-BP neurotoxicity on the central nervous system1.1The results of the Morris water mazeCompared to control group, the latency and swim distance of rats in1-BP group were prolonged significantly (P<0.05,P<0.01). In the spatial probe test, the number of crossing the platform in1-BP group decreased evidently (P<0.05). While the latency and swim distance of rats treated with NA and DHA were much less than the value of1-BP group, and the number of crossing the platform in NA intervention group and DHA intervention group increased evidently (P<0.05).1.2The changes of biochemical indicatorsIn our study, the level of GSH in1-BP group which compared with control group was decreased by18.1%. While compared with the1-BP group, the GSH content in NA intervention group and DHA intervention group were increased significantly (P<0.05).Results showed that exposed1-BP resulted in lipid peroxidation of cortex. Compared with control group, the MDA content in1-BP group was increased by14.3%. While the levels of MDA in NA treatment group and DHA treatment group were decreased significantly, when compared with1-BP group.In addition, the activity of GR and y-GCL in1-BP group reduced evidently, when compared with the value of control group, while DHA treatment could increase the GR activity (P<0.05) and NA administration could increase y-GCL activity (P<0.05) respectively.2The antagonistic effects of DHA on1-BP neurotoxicity2.1The result of Morris water mazeIn place navigation test, compared with control group, the latency and total swim distance of rats in1-BP group were prolonged significantly (P<0.05). While compared to1-BP group, low-dose DHA intervention group and high-dose DHA intervention group both could decrease the latency and swim distance evidently (P<0.01). 2.2The change of biochemical indicatorsIn our study, the level of GSH of rats in1-BP group was much lower than of control group. Compared with control group, the GSH content in1-BP group was decreased by48.1%(P<0.01). While compared with1-BP group, the GSH content of cerebral cortex in low and high dose DHA intervention group were increased by59.9%(P<0.01) and81.9%(P<0.01) respectively.The content of MDA of cortex in1-BP group was increased by27.0%(P<0.01), when compared with control group. After supplement of low and high dose DHA, the levels of MDA were decresased significantly (P<0.01).2.3Expression of GFAP in cerebral cortexImmunofluorescence showed that astrocytes in control group express very low levels. But the GFAP protein expression in the cerebral cortex of1-BP group was significantly larger, when compared to the control group. As expected, DHA treatment exhibited the astroctytes activation, indicated by the reduction of GFAP, with stronger effect in high dose group.The reactive astrocytes were also evidenced by Western blotting analysis. The results showed that the levels of GFAP in1-BP group were significantly increased, compared to that control group (P<0.05). While low-dose and high-dose DHA treatment could inhibit this increase (P<0.05,P<0.01).2.4Expression of NF-κB and Nrf2in cerebral cortexIn this study, the protein expressions of NF-κB in1-BP group were higher than that of control group in cytoplasm and nuclear extraction of cerebral cortex. The levels of NF-κB in DHA treatment group in cell nuclear were significantly decreased (P<0.05), compared to that of1-BP group.Western blotting for Nrf2protein showed that both1-BP treatment and DHA intervention group were factors that significantly increased Nrf2protein content. As a result, the high-dose DHA treatment group, which had both the1-BP and the DHA factors, had the highest brain content of Nrf2protein of all the groups. Furthermore, treatment with DHA not only increased the total content of Nrf2protein but also increased its nuclear translocation in with1-BP treatment rats, as shown by increased Nrf2nuclear accumulation. Conclusion11-BP could result in the CNS damage, evidenced by the disorder of Morris Water Maze appearances. NA (150mg/kg.bw) and DHA (500mg/kg.bw) both could effectively attenuate1-BP (800mg/kg.bw) neurtoxicity on central nevours system.21-BP exposure could decrease the GSH contents, GR and y-GCL activities. NA and DHA could significantly increase the content of GSH and upregulate the activity of GR andy-GCL, which were two important enzymes in GSH synthesis process.3The1-BP neurotoxicity might be related to the astrocyte activation mediated by the NF-κB pathway of the brain in rats. DHA could increase the protein level of Nrf2and decrease the expression of NF-κB, which could ameliorate the activation of astocytes.