系統農藥芬普尼對斑馬魚神經系統的影響

Abstract

芬普尼 (fipronil) 是一種苯基吡唑類殺蟲劑，可選擇性抑制昆蟲中的γ-氨基丁酸（GABA）受體。儘管芬普尼已成為在水生環境中使用最廣泛的藥物，但很少有研究評估芬普尼的神經毒性對於水生脊椎動物的感覺和運動系統的影響。在本碩士論文的研究中，我們選擇斑馬魚（Danio rerio）實驗動物來探討芬普尼對感覺與運動系統的神經毒理作用。我們評估了急性芬普尼暴露對斑馬魚存活率，側線毛細胞數量以及神經毒性的影響，此外，我們比較了正常與芬普尼處理下斑馬魚的游泳軌跡熱圖、速度和距離的差異。我們的實驗結果發現成年斑馬魚暴露在0.5、1.0和2.0 ppm芬普尼的水中環境24小時，與正常處理斑馬魚比較，存活率隨著芬普尼濃度顯著遞減。而斑馬魚胚胎暴露在0.1、0.5和1.0 ppm芬普尼的水中環境24小時，與正常處理斑馬魚比較，側線毛細胞數量也是隨著芬普尼濃度顯著遞減。透過組織病理學和西方墨點法研究發現，成年斑馬魚暴露於1.0 ppm芬普尼的水中環境24小時，大腦組織的氧化壓力、發炎與細胞凋亡，與正常處理斑馬魚比較，則是顯著增加。通過影像追蹤觀察，成年斑馬魚暴露在0.1和0.5 ppm芬普尼的水中環境24小時，游泳軌跡的速度和距離隨著芬普尼濃度顯著遞減，儘管芬普尼的神經毒性主要針對無脊椎動物昆蟲的GABA受體而開發，但我們的研究結果發現，芬普尼不但會減低斑馬魚的存活率，還會透過損傷側線的毛細胞數量以及產生氧化壓力、發炎與細胞凋亡來損傷大腦組織來影響斑馬魚的感覺和運動系統。這結果推論系統農藥芬普尼誘導的神經毒性會損傷水生脊椎動物的感覺與運動系統。

Fipronil is a phenylpyrazole insecticide that may selectively inhibit gamma- aminobutyric acid (GABA) receptors in the insect. Although fipronil have become the most widely used in aquatic environments, few studies have evaluated neurotoxicity of fipronil in sensory and motor systems of the aquatic vertebrates. In the research of this master thesis, the zebrafish (Danio rerio) experimental model system was selected to explored the neurotoxicological effects of fipronil in sensory and motor systems. We assessed effects of acute fipronil exposure in the survival rate, the number of hair cell of lateral lines, and the brain neurotoxicity in the zebrafish, In addition, heat maps, speed, and distance of swimming trajectory were compared between the zebrafish with sham and fipronil treatments. Our results showed the survival rates of the adult zebrafish exposed to fipronil at 0.5, 1.0 and 2.0 ppm were significantly decreased from 24 hours of exposure. The number of hair cell of lateral lines of the zebrafish embryos exposed to fipronil at 0.1, 0.5 and 1.0 ppm were significantly decreased. As the fipronil concentration increased, the degree of reduction was enhanced in both of the survival rate of the adult zebrafish and the number of hair cell of the zebrafish embryos. Through histopathological and western blots observations, significant oxidative stress, inflammation, and apoptosis were observed in the brain of the adult zebrafish exposed to fipronil at 1.0 ppm. Through video tracking observations, the speed, and distance of swimming trajectory in the adult zebrafish exposed to fipronil at 0.1, and 0.5 ppm were significantly decreased from 24 hours of exposure. Although fipronil neurotoxicity specifically developed to target insect GABA receptors with low vertebrate toxicity, our results suggest that fipronil impairs sensory and motor systems in zebrafish by reducing the number of hair cell of lateral lines, and damaging neurons in the brain tissue via oxidative stress, inflammation, and apoptosis. Therefore, neurotoxicity of fipronil can reduce survival rate and movement in the zebrafish. The results also imply that fipronil-induced neurotoxicity could damage sensory and motor systems in the aquatic vertebrates.