利用心肌損傷大鼠探討濃縮大氣懸浮微粒對血漿磷脂醯膽鹼類的影響

Abstract

許多流行病學研究都已證實細懸浮微粒(PM2.5)會對心血管系統產生負面的健康效應，尤其對本身已罹患心血管疾病的病人會產生更嚴重的反應。大氣中懸浮微粒對心血管系統的致病機制有直接作用和間接作用兩個假說，其中心血管系統的損傷都與體內脂質的平衡擾亂有很大的相關性；磷脂醯膽鹼類，在磷脂質內佔最大比例的脂質，可能與懸浮微粒暴露誘導心血管系統異常有密切的關係。本研究比較心肌受損大鼠暴露到濃縮大氣懸浮微粒後血漿內脂質，尤其是磷脂醯膽鹼類的變異，希望能觀察到濃縮大氣懸浮微粒對易感受族群的分子層次影響。 雄性SD大鼠注射isoproterenol使其發展成為心肌受損大鼠後，會暴露65天濃縮大氣細懸浮微粒(平均濃度149 µg/m3)再進行犧牲，取大鼠血漿樣本，以Folch萃取法萃取脂溶性代謝物並使用核磁共振儀與質譜儀進行分析，得到的圖譜以多變相檢定法觀察暴露組與控制組血漿內脂溶性代謝物是否有差異。 統計結果顯示心肌受損大鼠暴露到濃縮大氣細懸浮微粒後，血漿內的脂質含量出現變動，核磁共振圖譜可發現暴露組的總脂肪酸鏈雙鍵數顯著下降，細懸浮微粒造成生物體內氧化壓力提升可能是雙鍵數下降的一個原因；質譜儀的資料則顯示單碳鏈的磷脂醯膽鹼類在暴露組會有一致的下降趨勢，可能是血小板凝結因子大量消耗，促使單碳鏈磷脂醯膽鹼類以特殊途徑生成血小板凝結因子而降低在血漿中的濃度；某些雙碳鏈的磷脂醯膽鹼類則會提高在血漿中的濃度。找出這些在血漿內出現變動的脂質與磷脂醯膽鹼類，可以提供後續研究一些線索與方向並縮小分析範圍，針對這幾個物質進行更進一步的研究，以解釋濃縮大氣細懸浮微粒的可能致病機制並發掘可能的生物標誌以做為前期預防的指標。

Many epidemiologic studies have demonstrated that fine particles (PM2.5) will produce cardiovascular adverse effects, especially for those who already have cardiovascular disease. There have been two hypotheses about the mechanisms of ambient particulate in cardiovascular system. The first one is through direct effect. PM or its’ soluble materials activate the neural reflexes and disarray the heart rate rhythm, which sequentially conducting the cardiac arrhythmias. The other one is the indirect effect, which caused by increased oxidative stress and inflammation, then inducing the thrombosis and the atherosclerosis. Either direct effects or indirect effects will disturb the lipids’ balance during the course of cardiovascular disease. Glycerophosphocholine (PC), which accounted the most ratios in phospholipids, are likely to be affected by PM2.5 exposure and cause cardiovascular abnormal. In our study, we compare the differences of PC in myocardial rat plasma between PM2.5 exposure and control group. We intend to examine the molecular events of concentrated ambient particles in plasma of susceptible population. Male SD rats were exposed to PM2.5 for 65 days after they became myocardial damaging rats by isoproterenol(150 mg/kg). After animals were scarified, plasma samples were taken and snap frozen. The samples were extracted by Folch’s extraction method and the hydrophobic layer was removed for farther analysis. Both NMR and MS were used to analyze the hydrophobic metabolite extracts of the rat plasma. The data from NMR and MS were pretreated for multivariate analysis to examine the hydrophobic metabolic variation among samples. The statistic results demonstrated lipid fluctuations in rat plasma after PM2.5 exposure. NMR data showed that fatty acyl chain -CH2CH= and =CHCH2CH= decreased in exposure group. The raised oxidative stress after PM2.5 exposure may explain the decline of unstaurated fatty acyl chain. MS data indicated that the concentrations of lysoPCs were declined in exposure group. Moreover, numerous diacyl-phosphatidylcholine and alkyl-acyl-phosphatidylcholine were increased in the plasma of PM2.5 exposed rats. Understanding the fluctuations of PC in plasma can help us to elucidate the possible mechanism of PM2.5 toxicity and to mine the possible biomarkers for cardiovascular disease progress.