鄰苯二甲酸酯類對於心臟毒性的探討-從細胞到動物模式

Abstract

DEHP鄰苯二甲酸二(2-乙基己基)酯【Bis (2-ethylhexyl) phthalate】是一種常用的塑化劑，可以增加塑膠的延展性與彈性，為一種環境荷爾蒙。在哺乳類中， DEHP進入體內後會快速的代謝產生其代謝物鄰苯二甲酸- 單- 乙基己基酯 (MEHP, mono-ethylhexyl phthalate)和2-辛醇（2-ethylhexanol），在醫療環境下，血液樣本中都可測得DEHP及MEHP的濃度，在先前的許多文獻中以指出DEHP可於生殖系統造成毒性以並且增加罹患乳癌及子宮頸癌風險已被廣泛研究；然而鄰苯二甲酸鹽對於心臟的不利影響相關文獻報導有限。而這些塑化劑暴露是否會造成臨床上心臟功能的變化就是我們要探討的題目本研究為了瞭解心臟手術醫療環境中的塑化劑對心肌功能的影響。 從細胞層次，動物實驗二方面分析。然而鄰苯二甲酸鹽對於心臟的不利影響相關文獻報導有限。其中有文獻指出在暴露臨床相關濃度DEHP處理之下的新生大鼠心肌細胞以微陣列晶片分析基因表現，其結果顯示DEHP會造成與心律不整相關基因受到改變，並且造成心肌細胞中重要的連接蛋白connexin 43喪失造成心肌損傷，但影響機制仍然不明白。本研究主在探討臨床相關濃度的DEHP對於心臟功能之影響，以小鼠口服暴露DEHP 八週之後，以心臟超音波分析心臟功能，研究中發現暴露DEHP之下的小鼠心跳頻率(heart rate)及左心室收縮能力(Left-ventricular fractional shortening)與單純服用玉米 油控制組有統計意義上的差異，在第十六週以微導管測量舒張末期容積與壓力(pv-loop)，在pv-loop檢測下發現暴露DEHP的小鼠收縮功能下降，包括，在低劑量組及高劑量組別之收縮末期壓力 -容積關係(ESPVR)斜率比控制組小並且造成預緊搏出功(PRSW)及末期收縮壓的下降。在細胞實驗方面的研究結果顯示以大鼠心肌細胞暴露DEHP 及其代謝產物MEHP後造成胞內處主要儲存鈣離子胞器肌漿網(SR) 上回收鈣離子通道SERCA2(SR Ca2+-ATPase)表現量下降，進一步探討病理組織鑑定以確認經DEHP所造成的心肌受損程度，這可能導致心臟功能障礙，此研究顯示了長期暴露於DEHP具有在雌性小鼠的造成心血管不良影響的第一個證據。

Di(2-ethylhexyl) phthalate (DEHP) is a plasticizer have been added to polyvinyl chloride (PVC) products to enhance PVC flexibility and durability. DEHP is a well- known endocrine-disrupting chemical. In mammals, DEHP is rapidly hydrolyzed to its monoester, mono-(2-ethylhexyl) phthalate (MEHP) by esterase. The level of DEHP and its metabolite MEHP could be detectable before and after cardiopulmonary bypass (CPB) in the blood sample. The developmental and reproductive toxicity of DEHP are well recognized, however, little is known about the potential adverse effects and the mechanism of phthalates on the heart. Here, the effects and mechanism of DEHP exposure on cardiomyocytes were examined in both in vitro and in vivo models. Our data showed that high dosage DEHP and MEHP (10-100 μM) treatment for 48hr could causes the reduce of the cells viability, as well as, the activity of sarcoplasmic/endoplasmic reticulum Ca2+-ATPase2 (SERCA2) in H9C2 cardiomyoblast. The mRNA and protein level of SERCA2 declined after treating with DEHP and MEHP. Most importantly, long term exposure of DEHP could significantly affect cardiac functions in female mice . Left ventricular (LV) pressure–volume analysis revealed that less steep ESPVR and PRSW was markly drecreased in DEHP-treated animals.Left ventricular end-systoloic pressure(ESP) was decreased in DEHP-treated mice compared with control group. All these indicated exposure to DEHP would causes cadiac dysfunction at the level readurable clincal medial of heart.Our data documented that exposure to DEHP can lead to cardiac toxicity effects by reducing cardiomyocytes viability and decreasing SERCA2 expression, which may lead to cadiac dysfunction . This is the first evidence showing that long term exposure to DEHP has adverse cardiovascular effects in the adult female mice.