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  • 學位論文

奈米氧化鋅微粒對中樞神經影響之研究

Effects of zinc oxide nanoparticles exposure on central nervous system in Sprague-Dawley rats

指導教授 : 鄭尊仁

摘要


近年來因為奈米科技快速蓬勃發展,奈米微粒在生活中的應用廣泛,奈米氧化鋅(Zinc oxide, ZnO-NPs)是最常使用且重要的奈米材料之一,也是工作常見的毒性物質。先前研究顯示奈米微粒相較於粒徑大的微粒,其對身體產生的毒性和風險較大,其中在許多種類的奈米微粒之中,ZnO-NPs相較於CuO、TiO2等金屬氧化物,有著較強的毒性,因此探討暴露ZnO-NPs對健康潛在的毒性成為了重要的議題。有許多文獻探討奈米氧化鋅對呼吸道的毒性,顯示ZnO-NPs會誘發呼吸道過敏相關的反應、肺部發炎反應、氧化壓力增加還有系統性的發炎及心肺損傷。但對於ZnO-NPs的中樞神經毒性尚不明確,有研究顯示ZnO-NPs會造成大鼠空間學習能力受損,但結果並不一致。此外,有關ZnO-NPs中樞神經系統毒性還缺乏急性呼吸道暴露的探討,因此,本研究目的主要是想探討奈米氧化鋅微粒急性呼吸道暴露對大鼠中樞神經系統的影響。 本研究使用了八周大的SD健康大鼠,分別配置5 mg/kg、10 mg/kg、20 mg/kg三種劑量的ZnO-NPs懸浮液以及控制組,以氣管灌注(Intratracheal Instillation)方式進行急性暴露且分為兩組,第一組為暴露完24hr後隔天進行舉臂式十字型迷宮後進行犧牲,並取出大鼠腦部將海馬迴、大腦皮質、小腦三個區域進行促發炎細胞激素分析、分析8-OHdG、8-NO2Gua和鋅濃度,第二組是暴露完後隔天進行5天的莫氏水迷津及舉臂式十字型迷宮行為實驗後,取腦部及肺部進行病理切片。 本研究的行為實驗結果顯示暴露不同劑量的奈米氧化鋅,沒有造成大鼠空間學習及焦慮情緒的產生。量測海馬迴、大腦皮質、小腦細胞激素,結果顯示,在海馬迴的IL-1α,小腦的IL-6、TNF-α,大腦皮質的IL-1α、IL-1β、IL-6,ZnO-NPs在高劑量暴露組,其細胞激素濃度顯著低於控制組。8-OHdG的部分,海馬迴及小腦的高劑量組8-OHdG顯著增加,8-NO2Gua則沒有顯著差異。在鋅濃度的部分,小腦高劑量組的鋅顯著較控制組高,但皮質則無變化。行為實驗組的病理結果顯示於腦部無病理變化的產生,肺部則是隨著暴露ZnO-NPs的劑量越高,肺部的病理變化較嚴重。 本研究結論是ZnO-NPs暴露對中樞神經產生的影響,機制上鋅離子似乎扮演重要的角色,會造成氧化壓力增加、細胞激素下降,但產生的效應會根據腦區的不同有所差異,小腦可能較容易受到影響。本研究對ZnO-NPs急性呼吸道暴露影響中樞神經的可能機制和效應提供一些初步的結果,實際的機制和其毒性仍需要進一步的探討。

並列摘要


With the rapid development of nanotechnology, nanomaterials have been used widely in human life. Studies have shown that nanomaterials have greater toxicity than larger particles on the same masses. Zinc oxide as one of the most important and useful nanomaterials, have been widely applied in commercial products. Thus, the potential toxicity of zinc oxide has become an important issue. Many researchers have explored the respiratory toxicity of ZnO-NPs. However, few studies investigated central nervous system toxicity of ZnO-NPs. Previous studies showed that ZnO-NPs might impair spatial learning ability in rats, however, the outcome was inconsistent. Thus, the aim of our study is to explore central nervous system toxicity and the underlying mechanisms induced by ZnO-NPs. In our present study, 8-week-old Sprague-Dawley rats were exposed to ZnO-NPs at the dose of 5 mg/kg, 10 mg/kg and 20 mg/kg respectively via intratracheal instillation (IT). One group (N=5) was sacrificed 24 hrs after the exposure to ZnO-NPs. We collected brain tissue including hippocampus, cerebellum and cortex to analyze proinflammatory cytokines, oxidative stress, nitrative stress and zinc content. Another group (N=10) underwent morris water maze and elevated-plus maze for 5 days. In the next day, rats were sacrificed and the brain and lung tissue were collected for pathological examination. Our results showed that ZnO-NPs exposure didn’t affect spatial learning ability and anxiety. Results showed that ZnO-NPs exposure caused decreased cytokine level in high dose such as IL-1α in hippocampus, IL-1β, IL-6 and TNF-αin cerebellum and IL-1α、IL-1βand IL-6 in cortex. Oxidative stress marker 8-OHdG increased in hippocampus and cerebellum. There was no difference between groups for 8-NO2Gua. Zinc levels increased in cerebellum but not in cortex. Histology examination showed a dose-response inflammation in lung. However, there was no changes in brain. We conclude that zinc might play an important role in central nervous system toxicity caused by ZnO-NPs. Zinc cause a decrease in cytokines and an increase in oxidative stress, but the effects are not consistent through brain regions. Cerebellum seems vulnerable to ZnO-NPs. Our study sheds some light on the possible mechanisms and effects caused by ZnO-NPs, however, the exact mechanisms required further study.

參考文獻


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