| 摘要: | 亞砷酸鈉是一種著名的致癌物質，並且也會導致如動脈粥狀硬化、烏腳病等心臟血管疾病。血色素加氧?-1 (HO-1) 為一種誘導型的酵素，其功能是將血色素 (heme) 代謝變為鐵離子 (iron)、膽紅素(bilirubin) 及一氧化碳 (carbon monoxide)。血色素加氧?-1會被許多物質誘導出來包括血色素、氧化性壓力 (oxidative stress)、熱刺激 (heat shock)、紫外線照射 (UV irradiation) 及一些如砷、鎘金屬物質等。血色素加氧?-1被認為在細胞遭受氧化性傷害上，扮演著雙重的角色，即具有保護或促進作用。本研究中發現在牛大動脈血管內皮細胞中，血色素加氧?-1的蛋白質和mRNA會被低濃度 (< 1 micro mol/L) 的亞砷酸鈉誘導出來。為了要找出低濃度亞砷酸鈉誘導血色素加氧?-1的途徑及參與的分子，本研究中用了許多種的酵素抑制劑。其中以蛋白質激?C (PKC) 的抑制劑包括H7, staurosporine, 及 chelerythine chloride可以減低亞砷酸鈉誘導血色素加氧?-1的表現，而酪胺酸激?抑制劑、一氧化氮合成?抑制劑、ERK抑制劑或是PI-3 kinase抑制劑則都無法抑制血色素加氧?-1的表現。另外，在本實驗中也利用組織免疫螢光染色的方法來觀察蛋白質激?C轉位 (translocation) 的現象。從目前的結果顯示，蛋白質激?C-eta 及蛋白質激?C-epsilon 在 1 micro mol/L 的亞砷酸鈉處理下，會由細胞質轉位到細胞膜。因此，在牛大動脈血管內皮細胞中，蛋白質激?C-eta 及 蛋白質激?C-epsilon 可能參與低濃度亞砷酸鈉誘導血色素加氧?-1的表現。 Sodium arsenite is a well-known carcinogen and may cause cardiovascular disease, such as atherosclerosis and blackfoot disease. Heme oxygenase-1 (HO-1) is an inducible enzyme that catalyzes heme degradation into iron, biliverdin, and carbon monoxide. HO-1 is induced by a variety of agents, such as heme, oxidative stress, heat shock, UV irradiation, and some heavy metals (arsenite and cadmium). HO-1 has been proposed to play a dual role in protecting cells against or stimulating intracellular oxidative injury. We investigated the induction of HO-1 by low doses of sodium arsenite (< 1 micro mol/L) in bovine aortic endothelial cells (BAEC). Our results show that both HO-1 protein and mRNA are significantly induced by treatment of BAEC cells with 1mM sodium arsenite. To examine which pathway or which signaling molecule is involved in low dose sodium arsenite-mediated induction of HO-1, several enzyme inhibitors were adopted in this study. Among these inhibitors, protein kinase C (PKC) inhibitors such as H7, staurosporine, and chelerythrine chloride decreased 1 mM sodium arsenite-induced HO-1 expression, whereas inhibitors of tyrosine kinase, nitric oxide synthase (NOS), extracellular-regulated kinase (ERK), and PI-3 kinase are unable to inhibit HO-1 induction. Furthermore, the translocation of various PKC isoforms is then examined by histoimmunochemical technique. The present results have shown that PKC-eta and PKC-epsilon are apparently translocated from cytosol to membrane after 1 micro mol/L sodium arsenite treatment. Therefore PKC-eta and PKC-epsilon is probably involved in low dose sodium arsenite-indued HO-1 expression in BAEC. |
