以基因體層面探討天麻水萃物之抗憂鬱功效

Abstract

憂鬱症是精神疾病中盛行率極高的情感性疾病，並且根據 WHO 公佈的統計顯示， 全球憂鬱症患者逐年攀升，並且將會在2020年成為精神疾病之首。由於目前抗憂鬱劑治療方式會帶給許多病人嚴重的副作用，例如焦慮，腸胃問題，以及性功能衰減。因此如何預防憂鬱症是個重要的課題。本研究應用中藥食療預防醫學探討天麻水萃物對大鼠情感相關腦組織之影響，如前額葉皮質，海馬迴，以及紋狀體。本研究以管餵的方式將0.5 g/kg BW劑量之天麻水萃物 (WGE) 給予 Sprangue-Dawley大鼠，每日一次並為期連續21天，並進一步利用強迫游泳試驗(FST) 來誘導憂鬱症。研究結果顯示，天麻水萃物試驗組 (WGE) 的大鼠在FST 中比控制組 (NE) 的老鼠取得有顯著性差異較低的不活動時間，顯示 FST有成功的誘導大鼠憂鬱症行為。在 21天試驗期結束後，將大鼠犧牲，並取得前額葉皮質，海馬迴，紋狀體等憂鬱症相關之大腦區域組織，接著萃取total mRNA. 進一步利用微陣列分析來探討可能的天麻抗憂鬱機制，並運用即時聚合酶鏈式反應來驗證實驗結果。微陣列分析結果顯示在大鼠前額葉皮質以及海馬迴中，axongenesis, neurogenesis, nervous system development, 以及多巴胺分泌 (dopamine secretion) 為最有可能的機制，根據與資料庫的資料比對後取得的p-value值大小排列，最有可能的機制為最小的數值。然而紋狀體的微陣列分析結果並沒有顯式與憂鬱症有關的機制。即時聚合酶鏈式反應實驗結果驗證了WGE確實有顯著性的提升與神經可塑性 (neuroplasticity) 相關的基因表現量， 如Map1b,RhoA, profilin-1, 以及CRMP2 (p < 0.05).因此，神經可塑性為天麻水萃物之可能的抗憂鬱機制。本研究結果可為未來同一試驗模式但不同體系之研究做為參考，並為未來抗憂鬱製藥的研究有所貢獻，尤其是中藥天麻在基因體學中之抗憂鬱研究領域。

Depression has been a serious issue, as the annual worldwide reported cases of depression have been constantly increasing, according to the statistics published by WHO. In fact, WHO predicts that it will be the leading psychological disease by year 2020. However, antidepressants generally demonstrate serious side-effects, such as anxiety disorders, gastrointestinal problems, and sexual dysfunction in patients; therefore, it is important to find an effective way to prevent the occurrence of depression. In this research, Gastrodia eleta Bl., an Oriental herb that has been shown to demonstrate anti-depression effects, was investigated in the form of water extraction. In the present study, the water extract of Gastrodia eleta Bl. (WGE) was orally administered to Sprague-Dawley rats at the dose of 0.5 g/kg BW each day for 21 consecutive days. Forced swimming test (FST) was performed to induce depression in the rodent model, and results showed that the WGE group demonstrated shorter immobile time compared to the negative control group, indicating that FST has successfully induced depression-like behaviours in these rats. Total mRNA samples were then obtained from the frontal cortex, hippocampus, and striatum, after having sacrificed the rats after 21 days. In order to deduce a possible anti-depression pathway at the genomic level, cDNA microarray was performed to generate gene expression profiles of depression relevant brain regions: cortex, hippocampus, and striatum. To confirm the findings, real-time polymerase chain reaction (QRT-PCR) analysis of several neuroplasticity-related, differentially expressed genes, was performed. The microarray data showed that WGE altered axongenesis/neurogenesis, nervous system development, and dopamine secretion pathways in cortex and hippocampus, from the evidence that they yield the lowest p-values from all other pathway matches with the KEGG database. However, there were no depression-related pathways shown in the results of the microarray data for the striatum. QRT-PCR results validated that genes involved in neurogenesis, such as Map1b, RhoA, profilin-1, and CRMP2 were significantly altered (p < 0.05) in the cortex and hippocampus. Therefore, neuroplasticity might be the mechanism that WGE takes. The neuroplasticity effects of WGE in the rodent model of antidepressant action strengthen the case for further testing the results in the same context using other tools, and can serve as the basis of future antidepressant drugs, especially in the area of WGE demonstrating anti-depressant effects in the aspect of genomics.