| 摘要: | 我的研究興趣主要是在探討常見的神經精神疾病的致病危險因子，包括精神分裂病、躁鬱症、甲基安非他命成癮和阿茲海默失智症（Alzheimer disease, AD）。
研究的第一個部分是探討精神病症狀的成因。精神病症狀主要包括妄想和幻覺，常見於精神分裂病患者和甲基安非他命成癮者中。已知腦內的多巴胺系統的過度活化和精神病症狀的產生和成癮行為有密切的關係。腦內細胞突觸的多巴胺主要透過節前神經元上的多巴胺轉送器（dopamine transporter，DAT）將多巴胺轉送回節前神經元，來維持多巴胺系統的穩定。所以我們假設DAT功能上的變異也許和多巴胺系統的過度活化有關，進而導致精神病症狀。所以我們檢測DAT基因變異與精神分裂病與甲基安非他命精神病患者之間的關係。DAT基因的多型性變異中有一個位置是在3’非轉譯端，帶有40個鹼基的不固定多重複（variable number tandem repeats，VNTR）。然而，我們並未發現這個多型性變異和精神病症狀之間有相關聯性。
多巴胺的第一型受體的A-48G多型性變異被發現和成癮行為有關，另外身體的內因性大麻（endocannabinoid）系統的fatty acid amide hydrolase (FAAH)基因的C385A多型性變異也發現和成癮行為有關。我們藉由嚴重的甲基安非他命施用者來檢測這個關聯性，結果我們並未發現類似現象。我們再次分析前人的研究結果，發現過去報告的基因型分佈都偏離了Hardy-Weinberg平衡率。所以我們推測過去的結果為偽陽性，可能來自於取樣的偏差。
精神分裂病的成因中，愈來愈多的證據顯示和神經發育有關。一些發育相關的基因也被證實和精神分裂病有關聯。最近的學者發現Akt1在精神分裂病患者的週邊血球和腦皮質中都有下降的現象，對Akt1缺損的老鼠投予安非他命也會發現出現prepulse inhibition異常的現象。所以我們假設較低的Akt1是產生精神病症狀的危險因子，也會產生較多的神經學異常。另外最近發現一個新的和精神分裂病相關的基因disrupted-in-schizophrenia (DISC1)，當DISC1有突變時會導致腦部發育的異常，所以我們一同檢測是否在精神分裂病病患也有DISC1表現量的差異。目前我們的實驗結果顯示，於甲基安非他命使用者身上，在急性期甲基安非他命會升高Akt1與DISC1 mRNA，這個增加在兩週後會消失。我們並未發現精神分裂病患者Akt1和DISC1 mRNA的表現量與控制組有何不同，且未證實這兩個基因的表現量和神經學異常的嚴重度有關。然而我們發現Akt1 和DISC1二者的表現有強烈的正相關。在基因型研究上，我們發現Akt1基因的SNP2 (rs1130214)的G對偶基因型和精神分裂病有關，另外SNP4 (rs1130233)的A對偶基因和甲基安非他命使用者與精神分裂病患者有關。這些結果能解釋的範圍有限，更需要更多的實驗來證實Akt1和 DISC1在精神病的角色。
第二部分的研究是在探討躁症病患的精神神經免疫功能。過去已知免疫細胞激素會作用於下視丘和顳葉邊緣系統，進而影響下視丘-腦下垂體-腎上腺系統與一些神經行為變化。例如接受細胞激素治療的病患容易產生憂鬱症。我們比較躁症病患在治療前後的免疫因子的變化，我們發現細胞免疫功能（cell-mediated immunity）在躁症患者確有改變。
第三部分的研究為針對AD病患。我們首先探討類澱粉產生的速率決定步驟的酵素BACE(beta-site APP cleaving enzyme)的基因變異。我們發現了這個基因的786C/G多型性變異，但這個變異和我們的AD病患並無相關聯性。我們另外嘗試尋找AD的可能週邊組織的生物標記，我們以蛋白質體（proteomics）的方式發現AD病患的血清中的apolipoprotein A-I (ApoA-I)較對照組低。這個發現的臨床和疾病愈後的意義需要進一步研究。
總之，我的研究興趣在探討一些神經精神疾病的致病危險因子。其中尤其是針對精神病症狀和AD的成因。除了基因的多型性變異研究之外，我們希望能找到有效的週邊組織即可取得的生物標記，可作為疾病早期診斷與病程愈後推估之使用。
My researches are trying to identify the molecular risk factors in various neuropsychological disorders, including schizophrenia, bipolar mania patients, methamphetamine (MAP) addiction patients and Alzheimer’s disease (AD).
The first part of my study was to deal the issue of psychosis in schizophrenia patients and MAP abusers. It is well known that dopaminergic pathway is the major neuronal substrate in the pathophysiology of psychosis development and in the rewarding process of addictive behaviors. The majority of released dopamine is reuptaked by the presynaptic dopamine transporter (DAT) to maintain the homeostasis of dopamine system. It is reasonabe to postulate that hyperdopaminergic state in psychosis might be in part due to the DAT dysfunction. Therefore, we first targeted the association of DAT and psychosis in MAP abusers and schizophrenia patients. One of the DAT gene polymorphism is 40-bp VNTR (variable number tandem repeats) which is located at the 3’-untranslated region of the DAT. However, we did not find the association of this DAT VNTR polymorphism with psychosis, neither in MAP psychosis nor schizophrenia patients.
Dopaminergic rewarding system is the main pathway to be activated in addiction behavior. It has been also reported that DRD1A-48G polymorphism was associated with substance abuse. In addition to the dopaminergic rewarding, endocannabinoid system was noted to be a new target for addiction behavior through modulation of dopamine activity. Fatty acid amide hydrolase (FAAH) is the main catabolic enzyme in degradation of endocannabinoid and FAAH C385A polymorphism has been reported to be strongly associated with addiction behaviors. Therefore, we tested these two loci in our MAP addiction patients, but we could not replicate the positive association results in our patient samples. Our sample size is pretty large and the most important of all, our genetic distribution was no deviated from the Hardy-Weinberg equilibrium. We re-analyzed previous studies and showed that previous positive association study results might be false positive, because their genetic distribution was apparently deviated from the Hardy-Weinberg equilibrium.
Compelling evidence suggests that neurodevelopment anomaly might be one of the major factors in the development of schizophrenia. Several molecules involved in the developmental process have been shown to the candidate genes in the pathogenesis of schizophrenia, such as Akt1, neuregulin, calcineurin and disrupted-in-schizophrenia 1(DISC1). Akt1 was shown to be lower in the peripheral lymphocytes and brain of schizophrenia patients. Akt1 deletion mice were shown to have impaired prepulse inhibition after amphetamine challenge. Therefore, lower Akt1 might be a risk factor to develop psychosis. Lower Akt1 might be also associated with neurodevelopment abnormalities which could be identified by clinical neurological soft sign evaluation. DISC1 is also shown to influence the cortical development. We also examine the DISC1 level in schizophrenia patients and MAP abusers simultaneously. The purpose to this study was trying to test if the lower Akt1 and DISC1 level was also a risk factor for development of MAP psychosis and the neurological abnormalities in schizophrenia patients. The results showed MAP would up-regulate Akt1 and DISC1 mRNA in the MAP abusers during acute phase. The Akt1 and DISC1 mRNA levels were of no difference between schizophrenia patients and controls. The expression level was also not associated with severity of neurological anomaly. However, we found a strong positive correlation between Akt1 and DISC1 level. The genetic association study showed an increase of G allele of SNP2 (rs1130214) in schizophrenia patients. The A allele of SNP4 (rs1130233) was shown to be associated with MAP abusers and schizophrenia. Further experiments are necessary to delineate the role of Akt1 and DISC1 in the development of psychosis.
The second part of our study is to deal with the psychoneuroimmunology in bipolar mania patients. Psychological and physical stressors are known to induce immune alteration. The immunological cytokines may act as neurotransmitters in the CNS to modulate the hypothalamus-pituitary-adrenal (HPA) axis to control the stress hormone release and then modulate the immune response in a feedback mechanism. In addition to the well known HPA axis, the immune modulation in the hypothalamus might also induce circadian rhythm changes and affect the nearby limbic system, and then alter the neurobehavioral expression. Administration of cytokines would induce mood instability as depression in humans and experimental animals. Actually the interaction between nervous and immune system is complicated. Our study was trying to investigate the plasma levels of several immunologic variables in patients with bipolar mania. IL-1RA and sCD8 were found different in remitted bipolar patients as compared to normal controls. For TH1 cytokines, culture supernatant level of IFN-γ was found significantly lower in manic patients of both acute and remission stages as compared to normal controls. No significant difference was found in IL-2 level in pre-medicated acute manic patients compared to controls. For TH2 cytokines, no significant differences in IL-4 and IL-10 levels were observed. We showed that cell-mediated immune response was activated in patients with bipolar disorder during the pre-medication, medication, and the remission stages.
The third part of our study was focusing upon AD patients. According the amyloid hypothesis of AD, the molecules involved in the amyloidogenic pathway would be the candidate genes associated with AD. BACE (beta-site APP cleaving enzyme) cleaves APP (amyloid precursor protein) is the rate-limiting step in the process of amyloidogenesis. Therefore, BACE polymorphisms would be the potential candidate markers associated with AD. We used SSCP (single strand conformational polymorphism) to find a 786C/G polymorphism in the BACE gene. However, this polymorphism was not associated with AD in our patients.
In addition to the genetic marker association studies for AD patients, we were trying to survey other potential peripheral markers which could be of either diagnostic or prognostic value for clinical use. We used the proteomics method to screen the potential biomarkers in the sera of AD patients in comparison to the controls. Lower apolipoprotein A-I (ApoA-I) was noted in proteomics study and the lower ApoA-I was confirmed by direct assay of the serum of AD patients. The significance of lower ApoA-I in AD patients need further clarification.
In summary, our research interest is to survey the molecular risk factors in neuropsychiatric disorders. The main topics were the etiology and psychosis and AD. In addition to the genetic polymorphism association study, we are trying to investigate the signaling molecules and other potential peripheral markers. The ultimate goal is to identify factors to be useful in diagnosis or prognosis prediction. |
