| 摘要: | 中文摘要 Thioredoxin peroxidase II (TPx II)是一種氧化壓力所誘導的酵素，具有保護其他蛋白質免於受到氧化傷害的功能，也參與細胞分裂及分化的訊息傳遞。砷化物暴露可能導致人類皮膚癌、肺癌、肝癌及心血管疾病的發生。近年來研究指出，砷化物的毒性與自由基有關；細胞為了抵抗氧化壓力，會啟動許多防護機制。 本研究探討亞砷酸鈉(As(III))及氧化性壓迫對老鼠纖維母細胞(3T3) TPx II表現的影響及調控機制。結果顯示As(III)處理可誘導老鼠纖維母細胞TPx II蛋白及mRNA之表現。此外其他氧化性藥劑(H2O2, CdCl2, DPPH)的處理，皆可造成TPx II蛋白表現量增加，而H2O2及DPPH處理，亦可造成TPx II mRNA之表現增加。 本研究進一步研究As(III)誘導TPx II表現之機制；結果顯示ERKs磷酸化受到As(III)處理明顯增加，蛋白質激酶C (PKC)的抑制劑(Staurosprine、Calphostin C) ，可以抑制As(III)所誘導TPx II的表現，鈣離子螯合劑EGTA對As(III)所誘導TPx II表現並沒有抑制作用，此外，Rotterlin (PKC δ專一性抑制劑)也能有效抑制As(III)所誘導TPx II表現。然而這些蛋白質激酶C (PKC)抑制劑對過氧化氫所誘導TPx II表現不具抑制作用，此一結果顯示As(III)誘導老鼠纖維母細胞TPx II表現的機制與PKC δ有關，並與H2O2和DPPH明顯不同。此外TPx II驅動子位於269-169鹼基位置，對As(III)誘導TPx II表現具有重要之影響；且藉由FKHR調控因子(與氧化性壓迫有關的調控因子) 可有效提高As(III)誘導TPx II轉錄活性。FKHR對H2O2, CdCl2, DPPH誘導TPx II轉錄並沒有影響。此一結果顯示As(III)誘導TPx II表現機制可能與H2O2, CdCl2, DPPH明顯不同，且與其對細胞產生氧化性壓迫有關。 Abstract Thioredoxin peroxidase II (TPx II) is an oxidative stress-inducible enzyme that functions in cell proliferation and differentiation, and protects other proteins from oxidative damage. Arsenic is an environmental pollutant associated with human skin, lung, liver cancers and cardiovascular diseases. Recent studies suggested that arsenic-induced toxicity is associated with the generation of free radicals. This study investigates the mechanism of sodium arsenite (As(III))- and other oxidative stress-induced TPx II expression in murine fibroblast cells (3T3). The results showed that As(III), H2O2, CdCl2 and DPPH dose-dependently induced TPx II protein expression in 3T3 cell. The mRNA level of TPx II were also induced by As(III), H2O2, and DPPH, but not CdCl2. In addition, the phospho-ERK protein level was significantly enhanced in response to As(III) treatment. The As(III)-induced TPx II expression could be dose-dependently abolished by the presence of Rotterlin (PKC δ specific inhibitor); however, Rotterlin showed no effect on H2O2- and DPPH-induced TPx II expression. We further investigated the effect of As(III) on TPx II expression in transcription level. The results showed that a DNA response element located at TPx II promoter 269-169 pair was critical for As(III) inductory effect on TPx II gene expression. The As(III)-induced TPx II expression was further enhanced by another transcriptional factor FKHR that had no effect on H2O2-, CdCl2- and DPPH-induced TPx II expression. These results indicated that the mechanism of As(III) induces TPx II protein expression likely through oxidative stress pathway by which is dependent on FKHR and distinct from that induced by H2O2, CdCl2 and DPPH. |
