砷是本省主要的環境污染源之一，近年來的研究指出砷是誘發血管病變，癌症及免疫毒性的危險因子。由於巨噬細胞在先天性免疫及引發動脈粥狀硬化上扮演重要角色，因此人類單核球受砷影響造成的分化不全及基因表達異常是近年研究砷毒性的熱門主題之一。天然物(例如硫辛酸)已被證實可緩解砷引起的毒性。動物實驗顯示，硫辛酸可提高受砷毒害的動物的glutathione含量，也可改善因餵食高脂飼料所引發的apoE小鼠的動脈粥狀硬化的病灶。本研究室今年更首次發現硫辛酸可以降低受砷刺激的THP-1細胞的清道夫受體(CD36)的表達。許多研究也顯示其他的含硫天然物(如N-acetyl cysteien, NAC)對砷所引起的氧化傷害也具保護作用。本計畫擬結合成大環醫所王應然教授多年的毒理研究及致病動物模式的經驗，配合本人分子生物及營養免疫研究的心得，探討天然抗氧化物(硫辛酸、NAC等)對砷所誘發的血管粥狀硬化及免疫毒性的保護效果及機轉。第一年的計畫重點包括有二: 第一是利用人類全血，探討砷對PMN，monocyte及NK的毒性；並在抗氧化物如lipoic acid、NAC等的共同作用下，對砷所誘導的指標物及基因的影響，並與砷對PBMC作用的結果比較。第二部份則為建立砷所誘發的動脈粥狀硬化的動物模式及病理分析平台。第二年除了繼續第一年的in vitro 實驗，測試其他天然物對砷的免疫毒害的抑制效果及機轉。另外主要的重點是動物實驗，可分為兩部份：第一部份為在第一年所建立砷所誘發的心血管疾病的apoE剔除鼠動物模式的基礎上，以餵食方式測試天然物的功效。第二部份則是建立砷所產生的免疫毒性的動物模式。本實驗室已發表有關免疫活性分析的細胞實驗，並建立免疫分析的動物實驗平台，因此第二年將仿照他人之文獻，分析砷在小鼠上對免疫功能的影響，以確定作用濃度及培養時間。第三年的重點為繼續上述兩個動物實驗，探討天然抗氧化物在砷所引發的免疫毒性上的抑制活性及機制。尤其重要的是分析在apoE剔除小鼠所建立砷所誘發的心血管疾病的動物模式，分析其免疫能力是否下降，以期探討兩者間的關連性。期待本研究團隊可以建立一個營養學與環境毒物研究的合作模式，並對台灣本土特有的疾病的照顧及研究，盡一份微薄的貢獻。 Chronic exposure to inorganic arsenic, a widely distributed environmental contaminant, can lead to toxic effects, including atherosclerosis, immunosuppression and cancer. Owing to the established roles of human macrophages in immune defect and atherogenesis, the arsenic exposure on the gene expression and differentiation of human monocytes/macrophages has been an interest for many current researches. Natural component, such as α-lipoic acid, has been demonstrated effectively inhibiting arsenic-induced toxicity. α-lipoic acid can increase the glutathione level in arsenic-treated animals and prevent atherosclerosis in high-fat/low-cholesterol diet- fed apoE knockout mice. We recently found that α-lipoic acid was able to attenuate CD36 expression in arsenic-induced THP-1 cells, indicating that α-lipoic acid may also be involved in inhibiting atherogenic gene expression. Several literatures have revealed the protective effects of another thio-compound, N-actyl cysteine (NAC), on arsenic-induced toxicity by inhibiting oxidative stress. All of these results suggest that thio-antioxidants are potent agents for preventing arsenic-induced toxicity. The aim of the project is to investigate the effect and mechanism of natural antioxidants such as α-lipoic acid and NAC on arsenic-induced atherogenesis and immunotoxicity. This project would combine the expertise of Professor YJ Wang』s toxicology and disease animal research as well as mine in molecular biology and immuno-modulatory study. In the first year, two goals will be achieved: the first is the use of human PBMC-derived macrophages or peripheral blood as an in vitro platform for screening the natural compounds for inhibition of arsenic-induced immunotoxicity. The second goal is to establish an animal model of arsenic-induced atherosclerosis. There are also two focuses in the second year research. The first is to investigate the possible protective effect of lipoic acid on arsenic-induced atherosclerosis in apoE knockout mice. In addition, we will use BALB/c mice to establish an arsenic-induced immunosuppression animal model. In the final year, we will use the effective natural compounds obtained from the 1st year in vitro system to test in BALB/c immunosupression mice. In addition, the relationship between immunosuppression and atherosclerosis will also be investigated in arsenic-treated apoE knockout mice. In conclusion, we wish to provide the information for the anti-atherogenic and immuno-modulatory effects of natural compounds against arsenic toxicity both in vitro and in vivo.
