| 摘要: | 棒曲毒素（PAT）是由Penicillium 和Aspergillus 所分泌的黴菌毒素，通常在發霉的水果和汙染物中被發現。在人類胚胎腎細胞的實驗中，PAT 會隨著劑量及時間來增加extracellular signal-regulated protein kinases 1 and 2 (ERK1/2)的磷酸化現象，且在人類周邊血液單核球細胞及鼠類腎臟細胞中都得到相同的結果。當HEK293 暴露在5 μM PAT 下30 分鐘會導致ERK1/2 的磷酸化現象，而在0.05 μM PAT 處理24小時下也同樣發現活化ERK1/2 的情形。而用30 μM PAT 處理人類周邊血液單核球細胞30 分鐘也發現ERK1/2 磷酸化上升的現象。在HEK293 或 MDCK 細胞中，不論MEK1/2 的抑制劑U0126 或PD98059，都可以抑制ERK1/2 的活性。在HEK293細胞中利用單細胞電泳實驗所取得的tail moment 數值中發現，使用U0126 來降低ERK1/2 磷酸化發現可以顯著的降低DNA 的損傷。另ㄧ方面，U0126 並不會降低PAT處理後的細胞存活率、乳酸去氫脢活性疾DNA 合成的速率。當HEK293 細胞暴露在15 μM PAT 下90 分鐘時，會使得early growth response gene-1 (egr-1)的mRNA 表達量升高，但c-fos, fosB, 和 junB 的mRNA 並沒有這種現象。這結果指出在人類細胞中，PAT 會快速活化ERK1/2 且這一條訊息傳導途徑在PAT 所誘導的DNA 損傷及egr-1 基因的表現上扮演了重要的角色。
Patulin (PAT), a mycotoxin produced by certain species of Penicillium and Aspergillus, is often detectable in moldy fruits and their derivative products. PAT led to a concentration-dependent and time-dependent increase in phosphorylation of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in human embryonic kidney (HEK293) cells, human peripheral blood mononuclear cells (PBMCs), and Madin-Darby canine kidney (MDCK) cells. Exposure of HEK293 cells to concentrations above 5 .mu.M. PAT for 30 min induced ERK1/2 phosphorylation; activation of ERK1/2 was also observed after 24 h incubation with 0.05 .mu.M of PAT. Treatment of human PBMCs for 30 min with 30 .mu.M. PAT dramatically increased the phosphorylated ERK1/2 levels. Both MEK1/2 inhibitors, U0126 and PD98059, suppressed ERK1/2 activation in either HEK293 or MDCK cells. In HEK293 cells, U0126-mediated inhibition of PAT-induced ERK1/2 phosphorylation resulted in a significant decrease in levels of DNA damage, expressed as tail moment values, in the single cell gel electrophoresis assay. Conversely, U0126 did not affect cell viability, lactate dehydrogenase release, and the DNA synthesis rate in PAT-treated cultures. Exposure of HEK293 cells for 90 min to 15 .mu.M PAT elevated the levels of early growth response gene-1 (egr-1) mRNA, but not of c-fos, fosB, and junB mRNAs. These results indicate that in human cells, PAT causes a rapid and persistent activation of ERK1/2 and this signaling pathway plays an important role in mediating PAT-induced DNA damage and egr-1 gene expression. |
