雙酚合成物對抗神經毒素所引起神經細胞傷害的保護功效

Abstract

環境毒素如百草枯 (paraquat, PQ)，為非選擇性的除草劑，與一種被廣泛使用的除蟲劑魚藤酮 (rotenone, ROT)，皆會引起氧化壓力增加而造成多巴胺神經元 (dopaminergic neuron) 死亡，並可能為導致帕金森氏症 (Parkinson`s disease, PD) 的原因，因此百草枯與魚藤酮經常作為神經毒素引發神經傷害的體外模式。MH101 為一種合成的雙酚化合物，先前文獻發現它在體內及體外模式中皆具有抗氧化效果。故本研究進一步探討新穎的合成雙酚化合物 MH101 與結構相似的 MH102 在對於神經毒素百草枯及魚藤酮造成的多巴胺神經損傷的體外模式，是否具有保護的效果。透過腎上腺髓質嗜鉻細胞瘤 PC12 細胞預先處理 MH101 及 MH102，並以不同濃度及不同時間點的百草枯和魚藤酮暴露細胞，使用 MTT assay 觀測對細胞存活的影響。實驗結果指出 MH101 及 MH102 於對抗百草枯和魚藤酮所造成的神經傷害具有顯著的保護作用。利用Griess test 測量 NO 含量，結果顯示百草枯、MH101 及 MH102 不影響 NO 的產生。相反地，使用 DCFH-DA assay 偵測細胞內活性氧 (reactive oxygen species, ROS) 含量，發現 MH101 及 MH102 能夠顯著地減少 H2O2 和百草枯所誘發的 ROS。然而，PC12 細胞預先處理 MH101 及 MH102 與單獨處理百草枯和魚藤酮相比並不會改變酪胺酸羥化酶 (tyrosine hydroxylase, TH)、多巴胺轉運蛋白 (dopamine transporter, DAT) 與過氧化體增生活化受體γ (peroxisome proliferator-activated receptor, PPARγ) 的蛋白質表現量。使用 PolarScreenTM PPARγ Competitor Assay Kit 測量 MH101 及 MH102 與 PPARγ 的結合能力，結果得知 MH102 的結合能力較佳。由此推論，合成的雙酚化合物 MH101 和 MH102 在百草枯及魚藤酮引起多巴胺神經毒害的體外模式中具備神經保護的能力。此外，MH101 和 MH102 對抗百草枯及魚藤酮之毒害的保護作用可能是藉由減少 ROS 的產生。

Environmental toxicants such as paraquat (PQ), a nonselective herbicide, and rotenone (ROT), a widely used pesticide are known to induce the increase of oxidative stress and death of dopaminergic neurons, which might lead to Parkinson`s disease (PD). Thus, PQ and ROT were used as the neurotoxins to induce neuronal damage in vitro studies. Previous findings showed that MH101, a synthetic biphenyl compound, has the anti-oxidant effect in in vivo and in vitro model. In this study, we evaluated whether the newly synthetic compounds MH101 and MH102, which structure is similar to MH101, have the neuroprotective activities in PQ- and ROT-induced neuronal cell death in vitro studies. It was observed that PC12 cells exposed to PQ and ROT resulted in neuronal cell death, determined by the 3-(4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, in a concentration- and time-dependent manners. Our data further indicated that MH101 and MH102 revealed a significant protective action against PQ- and ROT-induced neuronal damage. PQ, MH101 and MH102 didn’t affect NO production, assessed by Griess test. In contrast, MH101 and MH102 significantly decreased the level of ROS induced by H2O2 and PQ, measured by DCFH- DA assay. However, pretreatment of PC12 cells with MH101 and MH102 did not show significant changes in the protein expression of tyrosine hydroxylase (TH), dopamine transporter (DAT) and peroxisome proliferator-activated receptor γ (PPARγ) compared with the PQ-treated cells. However MH102 compared with MH101 had higher PPARγ binding affinity, measured by PolarScreenTM PPARγ Competitor Assay Kit. In this study, we concluded that the synthetic compounds MH101 and MH102 have the neuronal protective activities in PQ- or ROT-induced cell death in vitro studies. Furthermore, the neuroprotection of the synthetic biphenyl compounds in preventing PQ- or ROT- induced toxicity may be related to reduction of ROS production.