王玉敏，崔其福，趙偉麗，張俊毅，王洪權(quán)*

(赤峰學院 醫(yī)學院 附屬醫(yī)院 1.腫瘤內(nèi)科；2.神經(jīng)內(nèi)五科；3.病理科, 內(nèi)蒙古 赤峰 024000)

短篇綜述

Nrf2/ARE/HO-1通路是治療帕金森病的作用新靶點

王玉敏1，崔其福2，趙偉麗2，張俊毅3，王洪權(quán)2*

(赤峰學院 醫(yī)學院 附屬醫(yī)院 1.腫瘤內(nèi)科；2.神經(jīng)內(nèi)五科；3.病理科, 內(nèi)蒙古 赤峰 024000)

調(diào)節(jié)Nrf2/ARE/HO-1通路在氧化應(yīng)激相關(guān)性疾病中具有神經(jīng)保護作用。通過藥理學途徑調(diào)節(jié)Nrf2/ARE/HO-1通路，可以抑制帕金森病神經(jīng)毒劑誘導(dǎo)的神經(jīng)毒性損傷。因此，篩選調(diào)節(jié)此通路的化合物有可能成為治療帕金森病潛在的新靶點。

Nrf2；血紅素加氧酶-1；帕金森病；神經(jīng)保護

帕金森病(Parkinson’s disease，PD)是一種以黑質(zhì)多巴胺能神經(jīng)元丟失為特征的氧化損傷相關(guān)性神經(jīng)退行性疾病。其主要的病理特征是種黑質(zhì)多巴胺能神經(jīng)元丟失以及細胞內(nèi)以α-突觸核蛋白(α-synuclein)為主要成分的路易小體(lewy body)形成。越來越多的證據(jù)表明氧化應(yīng)激 (oxidative stress,OS) 損傷在PD的發(fā)病機制及其多巴胺能神經(jīng)元死亡中發(fā)揮重要作用。PD患者腦內(nèi)脂質(zhì)過氧化、DNA損傷和羰基化作用蛋白的增多[1]，均提示OS損傷參與PD的發(fā)病機制。鑒于此，針對抗OS的策略則成為PD有效的治療途徑。

1 Nrf2/ARE/HO-1通路

機體細胞本身具有一套復(fù)雜的抗氧化系統(tǒng)，此系統(tǒng)組成Nrf2-ARE-抗氧化酶通路。生理狀態(tài)下，在胞漿內(nèi)的核轉(zhuǎn)錄因子Nrf2 (nuclear factor-erythroid 2-related factor-2) 與細胞骨架相關(guān)性抑制蛋白Keap1(kelch-like ECH-associated protein 1)結(jié)合形成一個復(fù)合體，使Nrf2經(jīng)泛素蛋白酶途徑降解。當細胞或機體暴露于活性氧簇(reactive oxygen species, ROS)時，ROS可引起Keap1的修飾(如磷酸化)，從而使Keap1募集Nrf2的功能發(fā)生改變，Keap1-Nrf2復(fù)合體解離，Nrf2從胞質(zhì)轉(zhuǎn)位到胞核，與受其調(diào)控的抗氧化酶基因的抗氧化反應(yīng)元件(antioxidant response element, ARE)結(jié)合，從而啟動編碼解毒和抗氧化的基因表達，使其表達上調(diào)，促進細胞存活。血紅素加氧酶-1(heme oxygenase, HO-1) 即是受其調(diào)控的一個非常重要的酶類。此外，Nrf2的激活除了受 Keap1調(diào)控外, 一些上游的激酶如蛋白激酶-C (protein kinase, PKC), MAPKs (mitogen-activated protein kinase) 和PI3K/Akt也可以調(diào)節(jié)Nrf2的激活[2], 因此可以形成一個Nrf2/ARE/HO-1通路 (圖1)。此通路在以O(shè)S損傷為特征的PD中發(fā)揮重要的作用。

圖1 Nrf2/ARE/HO-1通路及其激活機制Fig 1 The Nrf2/ARE/HO-1 pathway and a proposed mechanism responsible for its activation

2 Nrf2在PD中的神經(jīng)保護作用

調(diào)控HO-1表達的上游轉(zhuǎn)錄因子Nrf2在PD中的發(fā)揮重要作用。第1，隨著年齡(PD危險因素之一)的增加Nrf2的活性降低，而在老化動物中通過藥理學途徑可以恢復(fù)Nrf2的轉(zhuǎn)錄活性[3]。第2，Nrf2表達于黑質(zhì)多巴胺能神經(jīng)元胞質(zhì)內(nèi)，而在PD患者中Nrf2表達于存活的黑質(zhì)多巴胺能神經(jīng)元胞核內(nèi)，表明細胞正通過Nrf2依賴的抗氧化酶來試圖減弱氧化應(yīng)激損傷。Nrf2在PD中的神經(jīng)保護作用越來越引起研究者的注意。在動物模型中的研究也支持Nrf2在PD中發(fā)揮重要作用，在Nrf2缺失的小鼠模型中，神經(jīng)元更易受MPTP誘導(dǎo)的神經(jīng)退變和炎性反應(yīng)的發(fā)生[4]，Nrf2的缺失加重腹側(cè)中腦內(nèi)α-synuclein過表達引起的多巴胺能神經(jīng)元的死亡，并促進α-synuclein的聚集，表明Nrf2在PD中具有神經(jīng)保護作用。另外，通過siRNA抑制Keap1活性，進而激活Nrf2可以在體內(nèi)抑制MPTP引起的多巴胺能神經(jīng)元的損傷[5]，而通過藥理學途徑激活Nrf2可以在體內(nèi)或體外抑制6-OHDA[6]、MPP+[7]以及MPTP[8]引起的引起的神經(jīng)元損傷。綜上所述，Nrf2在PD中具有神經(jīng)保護作用，而通過激活Nrf2可能成為治療PD的潛在靶點。

3 HO-1在PD中的神經(jīng)保護作用

HO-1為游離血紅素(heme)降解的限速酶，能夠催化Heme產(chǎn)生一氧化碳、膽綠素和游離鐵，是應(yīng)激早期發(fā)揮保護作用的抗氧化酶蛋白。PD患者腦內(nèi)在黑質(zhì)多巴胺能神經(jīng)元胞質(zhì)中HO-1表達升高，在路易小體內(nèi)HO-1呈免疫強陽性[9]。研究者們陸續(xù)對不同PD模型中HO-1的表達進行了研究，顯示引起PD的相關(guān)毒素，如百草枯(paraquat)、MPP+和MPTP等可以在體內(nèi)或體外上調(diào)HO-1的表達，HO-1在PD中的作用日益凸顯。HO-1的表達上調(diào)可能是對PD相關(guān)毒素引起的神經(jīng)損傷具有神經(jīng)保護作用, 證據(jù)如下, 1)編碼HO-1蛋白的Hmox1基因啟動子單核苷酸多態(tài)性與PD具有高度關(guān)聯(lián)性。HO-1(-413)TT基因型較AA基因型的HO-1的表達水平低[10]，暗示HO-1蛋白水平的降低可以升高氧化應(yīng)激的敏感性。2)PD患者血漿內(nèi)HO-1的水平升高，與對抗持續(xù)慢性氧化損傷相關(guān)。3)腺病毒介導(dǎo)的HO-1過表達可以保護受MPP+毒性損傷的黑質(zhì)多巴胺能神經(jīng)元[11]。在神經(jīng)母細胞瘤M17細胞中，HO-1過表達降低α-突觸核蛋白的水平[12]，PINK1 G309D突變體促進H2O2誘導(dǎo)的SH-SY5Y凋亡的發(fā)生，而HO-1過表達可以促進細胞的存活[13]。4)上調(diào)HO-1的表達可以抑制亞鐵離子(ferrous Iron, Fe2+)誘導(dǎo)的SK-N-SH細胞損傷[14]。

3.1上調(diào)HO-1抑制6-OHDA引起的神經(jīng)毒性損傷

通過藥理學手段誘導(dǎo)上調(diào)HO-1的表達在PD中具有神經(jīng)保護作用[15- 17]，可以抑制6-OHDA引起的神經(jīng)毒性損傷。在SH-SY5Y細胞，人參皂甙Rb1(ginsenoside Rb1)通過上調(diào)HO-1的表達，抑制6-OHDA引起的神經(jīng)毒性損傷[18]?？Х劝字?kahweol)可通過PI3K和P38 MAPK激活來活化Nrf2，再上調(diào)HO-1的表達，從而抑制6-OHDA引起的SH-SY5Y細胞的氧化應(yīng)激損傷[19]。蛋白酶體活性抑制劑MG-132可上調(diào)原代培養(yǎng)的中腦星形膠質(zhì)細胞HO-1的表達，并抑制6-OHDA誘導(dǎo)的毒性損傷，而HO-1抑制劑鋅原卟啉(zinc protoporphyrin IX, ZnPP)可以減弱MG-132的這種神經(jīng)保護作用，這表明MG-132介導(dǎo)的HO-1的表達上調(diào)參與其抑制6-OHDA誘導(dǎo)的毒性損傷機制[20]。在Mes23.5多巴胺能細胞中，地昔帕明(desipramine)可通過ERK和JNK激活來活化Nrf2，進而上調(diào)HO-1的表達，從而抑制魚藤酮和6-OHDA引起的神經(jīng)毒性損傷[21]。萊菔硫烷(sulforaphane,SFN)能夠通過PI3K/Akt通路激活Nrf2，從而上調(diào)HO-1進而抑制6-OHDA誘導(dǎo)的神經(jīng)毒性損傷[22]。

3.2上調(diào)HO-1抑制MPP+引起的神經(jīng)毒性損傷

通過藥理學途徑上調(diào)HO-1表達可抑MPP+引起的神經(jīng)毒性損傷。在Raw 264.7巨噬細胞中，HO-1抑制劑錫原卟啉Ⅸ(tin protoporphyrin-Ⅸ，SnPP-Ⅸ)加重MPP+誘導(dǎo)的氧化損傷，而HO-1誘導(dǎo)劑鈷原卟啉Ⅸ(cobalt protoporphyrin-Ⅸ,CoPP-Ⅸ)可逆轉(zhuǎn)MPP+誘導(dǎo)的氧化損傷，最新研究表明，MPP+可以促進HO-1的表達，而抑制HO-1的表達反過來促進MPP+誘導(dǎo)的氧化損傷[23]，為HO-1參與抑制MPP+誘導(dǎo)損傷提供了直接的證據(jù)。蝦青素(astaxanthin) 可通過促進HO-1的表達從而保護PC12細胞受MPP+介導(dǎo)的NOX2來源的ROS氧化損傷[24]。1,2,3,4,6-O-五沒食子酰葡萄糖(1,2,3,4,6-penta-o-galloyl-β-d-glucopyranose)通過PI3K和ERK/Nrf2通路促進HO-1的表達從而保護PC12細胞受MPP+介導(dǎo)的氧化損傷[25]。綜上所述，上調(diào)HO-1表達在PD具有神經(jīng)保護作用。

4 結(jié)語

綜上所述，調(diào)控Nrf2/ARE/HO-1通路，即激活Nrf2進而上調(diào)HO-1的表達成為PD 潛在的治療靶標。以此為切入點，篩選出具有調(diào)節(jié)Nrf2/ARE/HO-1通路的天然化合物，將成為人們探索治療PD的新措施。

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Nrf2/ARE/HO-1 signaling pathway isa new neuroprotective target for Parkinson’s disease

WANG Yu-min1, CUI Qi-fu2, ZHAO Wei-li2, ZHANG Jun-yi3, WANG Hong-quan2*

(1.Dept. of Oncology; 2.Dept. of Neurology; 3.Dept. of Pathology, Affiliated Hospital of Chifeng Medical CollegeChifeng University, Chifeng 024000，China)

Recent studies have shown that regulation of Nrf2/ARE/HO-1 provides neuroprotection against oxidative stress-induced neurotoxicity. The specific activation of Nrf2/ARE/HO-1 gene expression by pharmacological modulation may represent a novel approach for therapeutic treatment of Parkinson’s. There is, therefore, an excellent rationale for the development of new neuroprotective agents, based on their ability to enhance activity of Nrf2 and upregulate HO-1 expression.

Nrf2；heme oxygenase-1(HO-1); Parkinson’s disease; neuroprotection

2013- 10- 23

2013- 12- 23

國家自然科學基金(81260196, 81201844);內(nèi)蒙古自治區(qū)高等學校青年科技英才支持計劃(NJYT-13-B20);內(nèi)蒙古自治區(qū)高等學?？茖W研究重點項目(NJSZ12306)

*通信作者(correspondingauthor)： whongquan@alu.fudan.edu.cn

1001-6325(2014)08-1125-04

R 741.05

A