馮 杰,鄧子輝,張金英,薛 輝,梁 辰,李建華,顏光濤
解放軍總醫(yī)院,北京 1008531基礎(chǔ)所生化研究室;2生化科
高脂飲食誘導(dǎo)的肥胖對顳葉癲癇小鼠海馬損傷的影響
馮 杰1,鄧子輝1,張金英1,薛 輝1,梁 辰1,李建華1,顏光濤2
解放軍總醫(yī)院,北京 1008531基礎(chǔ)所生化研究室;2生化科
目的 探討肥胖對顳葉癲癇發(fā)生、發(fā)展的影響。方法 高脂飼料喂養(yǎng)C57BL/6J小鼠建立肥胖小鼠模型,建模成功后單側(cè)海馬微量注射200 ng海人酸(kainic acid,KA)誘導(dǎo)顳葉癲癇,記錄小鼠癲癇評分,測定血清肌酸激酶同工酶(creatine kinase isoenzyme,CK-MB)濃度,Western blot檢測海馬S-100β的表達(dá)。海人酸注射5周后,觀察小鼠海馬病理結(jié)構(gòu)改變。結(jié)果 海人酸注射后,肥胖小鼠的癲癇行為評分較野生型鼠顯著增高;海人酸注射24 h后,與野生型鼠相比,肥胖小鼠海馬血清CK-MB濃度和海馬S-100β表達(dá)升高;海人酸注射后,病理切片顯示肥胖鼠海馬CA3區(qū)神經(jīng)元丟失和星形膠質(zhì)細(xì)胞活化較野生型鼠更嚴(yán)重,肥胖鼠星形膠質(zhì)細(xì)胞形態(tài)發(fā)生明顯變化。結(jié)論 肥胖可能加重了小鼠對海人酸誘導(dǎo)顳葉癲癇的損傷。
肥胖;海人酸;星形膠質(zhì)細(xì)胞;顳葉癲癇;C57BL/6J小鼠
網(wǎng)絡(luò)出版時間:2015-05-05 14:17 網(wǎng)絡(luò)出版地址:http://www.cnki.net/kcms/detail/11.3275.R.20150505.1417.002.html
肥胖癥是21世紀(jì)人類面臨的最嚴(yán)峻的公共衛(wèi)生問題之一,不良的生活方式和不健康的飲食習(xí)慣是目前導(dǎo)致肥胖的最主要原因。肥胖癥既是一種疾病,也是其他疾病的重要誘因,包括常見的糖尿病、心血管疾病和神經(jīng)系統(tǒng)疾病等[1-2]。流行病學(xué)調(diào)查發(fā)現(xiàn),在難治型癲癇患者中超重和肥胖患者所占比例高,肥胖可能是影響癲癇病理過程的重要因素。癲癇是第二大神經(jīng)系統(tǒng)性頑癥,是由于神經(jīng)元的同步異常放電引起的一種短暫腦功能障礙疾病。其中顳葉癲癇(temporal lobe epilepsy,TLE)是最常見的局灶性癲癇綜合征,異常放電來源于顳葉[3-4]。臨床病理研究發(fā)現(xiàn),顳葉癲癇患者具有異常的海馬形態(tài),并且伴有特征的病理改變包括神經(jīng)元的丟失和星形膠質(zhì)細(xì)胞活化,尤其是海馬CA3區(qū)[5-6]。目前,C57BL/6J小鼠單側(cè)海馬微量注射海人酸是常見的顳葉癲癇的動物模型建模方法[7]。本研究通過高脂飼料喂養(yǎng)C57BL/6J小鼠建立肥胖模型[8],然后注射海人酸誘導(dǎo)顳葉癲癇小鼠模型,檢測小鼠行為學(xué)、病理學(xué)上的變化,初步探討肥胖與顳葉癲癇的關(guān)系。
1 動物和試劑 C57BL/6J小鼠(SPF級),90只,4周齡,雄性,體質(zhì)量14 ~ 15 g,購自解放軍總醫(yī)院醫(yī)學(xué)實(shí)驗(yàn)動物中心;標(biāo)準(zhǔn)飼料(10% kJ%fat,北京中興飼料);高脂飼料(40% kJ%fat,上海實(shí)驗(yàn)動物中心);海人酸(Sigma Chemical Co. St Louis,MO,USA);腦立體定位儀(ZS-B/C,北京眾實(shí)迪創(chuàng)科技發(fā)展有限責(zé)任公司);5 μl微量進(jìn)樣器Microliter Syringes(上海高鴿工貿(mào)有限公司);乙醚(北京益利精細(xì)化學(xué)品公司);甲苯胺藍(lán)(Sigma Chemical Co. St Louis,MO,USA);一抗:膠質(zhì)纖維酸性蛋白(GFAP,Cell Signaling Technology Inc. #3670),S-100β(Santa Cruz Biotechnology,SC-28533);二抗:山羊抗小鼠IgG/辣根酶標(biāo)記、山羊抗兔IgG/辣根酶標(biāo)記(北京中衫金橋公司);檸檬酸鹽緩沖液(北京普利萊公司);DAB顯色液(北京中衫金橋公司)。
2 高脂飲食誘導(dǎo)肥胖小鼠模型的建立 C57BL/6J飼養(yǎng)于無特定病原體動物房,溫度22 ~ 24℃,維持12 h晝夜交替。小鼠用標(biāo)準(zhǔn)飼料適應(yīng)性喂養(yǎng)1周,1周后稱體質(zhì)量。小鼠按隨機(jī)數(shù)字表法分為2組,肥胖組給予高脂飼料飼養(yǎng),標(biāo)準(zhǔn)飼料飼養(yǎng)組給予標(biāo)準(zhǔn)飼料飼養(yǎng),均自由飲水和進(jìn)食。體質(zhì)量記錄:稱質(zhì)量前1 d于下午18:00禁食,第2天9:00稱量。飼養(yǎng)12周后,肥胖組小鼠體質(zhì)量高于野生型組小鼠20%以上,肥胖小鼠模型構(gòu)建成功。
3 顳葉癲癇小鼠模型的建立 將肥胖小鼠分為氯化鈉注射組(OS組,15只)和海人酸注射組(OK組,30只),野生型小鼠分為氯化鈉注射組(WS組,15只)和海人酸注射組(WK組,30只)。將小鼠乙醚麻醉后,置于腦立體定位儀上,以大腦Bregma為原點(diǎn)的海馬定位注射坐標(biāo):-2.0、-1.8、-2.3(右側(cè)海馬),進(jìn)行單側(cè)注射海人酸200 ng(100 ng/μl,2 μl)后,速度2 μl/5 min,注射結(jié)束留注射器5 min,去除吸入麻醉機(jī)后,觀察行為表現(xiàn)。氯化鈉組以0.9%氯化鈉注射液代替海人酸,其余步驟和注射方式同海人酸小鼠。
4 行為學(xué)觀察 海人酸注射后,根據(jù)Racine分級標(biāo)準(zhǔn)[9]進(jìn)行癇性評分:0分:無驚厥;1分:咀嚼運(yùn)動、眨眼、胡須顫抖等面部肌肉抽搐;2分:頸部肌肉抽搐,節(jié)律點(diǎn)頭;3分:單側(cè)前肢震顫,頸部肌肉痙攣;4分:雙前肢陣攣,后肢站立;5分:身體持續(xù)性強(qiáng)直,跌倒伴陣攣。
5 血清肌酸激酶同工酶的測定 海人酸注射24 h,小鼠麻醉后,摘眼球取血,靜置4℃過夜,3 000 r/ min離心15 min后取上清液,采用比色法,通過Roche Cobas 8000 Modular Analyser儀器測定。
6 尼式染色 4 μm石蠟切片脫蠟至水,用磷酸鹽緩沖溶液洗2 min,放1%甲苯胺藍(lán)溶液中室溫20 min,用梯度乙醇依次脫水,結(jié)果尼式小體呈深藍(lán)色顆粒,細(xì)胞核呈淡藍(lán)色,背景基本無色。
7 免疫組化法觀察GFAP的表達(dá)和形態(tài)變化4 μm石蠟切片脫蠟至水,檸檬酸鹽緩沖溶液高壓修復(fù)5 min,37℃ 5%的山羊血清封閉20 min,GFAP(1:400) 4℃過夜,漂洗后,加辣根過氧化物酶標(biāo)記的二抗37℃孵育40 min,DAB顯示,蘇木素染核,漂洗后封片,置于顯微鏡下觀察并拍照,GFAP顯黃色,細(xì)胞核顯淡藍(lán)色。
8 Western blot檢測S-100β表達(dá) 小鼠處死后,取腦剝離右側(cè)海馬,放入RIPA蛋白裂解液,勻質(zhì)離心提取總蛋白,BCA法蛋白定量。蛋白上樣量為100 μg,在質(zhì)量分?jǐn)?shù)為12%的SDS-PAGE上進(jìn)行垂直電泳,然后電轉(zhuǎn)移到硝酸纖維素膜上(100 V,80 min),將硝酸纖維素膜放入含5%脫脂奶粉(TBST溶解)塑料袋中,放入搖床37℃封閉1 h,將稀釋好的一抗,S-100β(1∶1 000)、β-actin(1∶500),4℃封閉過夜。取出后放室溫30 min,TBS/T漂洗膜3次×10 min,加入稀釋好的二抗(1∶3 000),37℃孵育30 min,TBS/T漂洗硝酸纖維素膜3次×10 min,加入發(fā)光液,暗室曝光。掃描后,使用Image Plus 6.0軟件,分析其灰度值,3次獨(dú)立實(shí)驗(yàn)求平均值。
9 統(tǒng)計學(xué)方法 采用GraphPad Prism軟件進(jìn)行統(tǒng)計分析,數(shù)據(jù)以±s表示,組間比較用t檢驗(yàn),與對照組比較采用LSD-t檢驗(yàn)。P<0.05為差異有統(tǒng)計學(xué)意義。
1 高脂飲食誘導(dǎo)的肥胖模型建立 經(jīng)過12周喂養(yǎng),高脂飼料飼養(yǎng)組小鼠體質(zhì)量比標(biāo)準(zhǔn)飼料飼養(yǎng)組高出20%以上(P<0.05),高脂飼料喂養(yǎng)的小鼠脂肪墊濕重是標(biāo)準(zhǔn)飼料喂養(yǎng)小鼠的2倍以上,肥胖小鼠模型建立成功(圖1)。
2 顳葉癲癇肥胖小鼠行為學(xué)評分和血清肌酸激酶同工酶(creatine kinase isoenzyme,CK-MB)增高海人酸注射后4 h內(nèi),肥胖組每只小鼠Racine最高評分平均值顯著高于野生型小鼠(P<0.05),OK組每只小鼠最高評分均值為4.6,WK組每只小鼠最高評分均值為3.2(圖2A)。海人酸注射后,小鼠血清內(nèi)肌酸激酶同工酶顯著增加(P<0.05),肥胖鼠和標(biāo)準(zhǔn)飼料喂養(yǎng)鼠差異無統(tǒng)計學(xué)意義,但肥胖組血清肌酸激酶同工酶的平均濃度高于標(biāo)準(zhǔn)飼料喂養(yǎng)組(P>0.05)(圖2B)。
圖 1 肥胖模型的建立(aP<0.05, vs wild mice group)Fig. 1 Establishment of obesity model (aP<0.01, vs wild mice group)
圖 2 肥胖對海人酸誘導(dǎo)的顳葉癲癇小鼠抽搐評分與血清肌酸激酶同工酶的影響(aP<0.05, vs WS group;bP<0.05, vs OS group;cP<0.05, vs WK group)Fig. 2 Effect of obesity on seizure scores and serum CK-MB after KA-induced mice model of TLE (aP<0.05, vs WS group;bP<0.05, vs OS group;cP<0.05, vs WK group)
3 顳葉癲癇肥胖小鼠海馬CA3區(qū)神經(jīng)元丟失嚴(yán)重及星形膠質(zhì)細(xì)胞過度活化 海人酸注射后繼續(xù)飼養(yǎng)5周,小鼠腦冠狀面切片尼式染色結(jié)果顯示,與野生型小鼠海馬注射側(cè)CA3區(qū)相比,肥胖組小鼠神經(jīng)元丟失更重,神經(jīng)元彌散(圖3A)。免疫組化結(jié)果顯示,星形膠質(zhì)細(xì)胞過度活化和星形膠質(zhì)細(xì)胞形態(tài)改變(星形膠質(zhì)細(xì)胞胞體變粗,細(xì)胞足加長,細(xì)胞聚集成簇)(圖3B)。顳葉癲癇肥胖小鼠海馬S-100β(活化星形膠質(zhì)細(xì)胞分泌蛋白)表達(dá)升高(圖4)。
肥胖患者多為單純性肥胖,占總肥胖人數(shù)90%以上,主要由不健康的飲食習(xí)慣和缺乏鍛煉引起。本研究采用高脂飲食誘導(dǎo)方式建立肥胖模型很好的模仿單純性肥胖,避免使用基因缺陷鼠如ob/ob或db/db,基因缺陷鼠會產(chǎn)生嚴(yán)重的代謝紊亂[10]。肥胖是高血壓、冠心病、心肌梗死、糖尿病、腦梗死、阿爾茨海默病等多種疾病的主要危險因素。目前觀點(diǎn)認(rèn)為,癲癇患者發(fā)生體質(zhì)量增加是抗癲癇藥物如丙戊酸鈉的不良反應(yīng)[11-13],但流行病學(xué)調(diào)查發(fā)現(xiàn),在未經(jīng)藥物治療的難治性癲癇中肥胖者患病率高于正常體質(zhì)量者[14-15],本文探究肥胖是否加重顳葉癲癇。
顳葉癲癇發(fā)病率高,治療效果不佳,嚴(yán)重影響病人生活和工作。目前認(rèn)為,神經(jīng)元離子通道改變、突觸傳遞異常、神經(jīng)元微環(huán)境發(fā)生變化導(dǎo)致興奮性與抑制性的不平衡,從而導(dǎo)致神經(jīng)元異常同步放電[16-17]。本研究探討肥胖與癲癇的關(guān)系可能會為顳葉癲癇發(fā)生、發(fā)展的研究提供一個新思路。病理研究發(fā)現(xiàn),顳葉癲癇大部分由顳葉海馬組織的變形引起的,神經(jīng)元丟失和星形膠質(zhì)細(xì)胞活化是海馬變形的主要特征,因此本研究主要觀察小鼠注射海人酸后海馬組織的病理變化。研究發(fā)現(xiàn),在顳葉小鼠模型中,肥胖小鼠的行為學(xué)Racine評分要明顯高于野生型小鼠。研究表明,全身痙攣發(fā)作可引起血清肌酸激酶同工酶升高[18],肥胖小鼠血清肌酸激酶同工酶濃度平均值高于標(biāo)準(zhǔn)飼料飼養(yǎng)組小鼠,但無統(tǒng)計學(xué)差異,可能與小鼠數(shù)量少有關(guān)。病理切片顯示,與野生型小鼠相比,肥胖小鼠神經(jīng)元丟失和擴(kuò)散加重;免疫組化顯示,星形膠質(zhì)細(xì)胞過度活化以及星形膠質(zhì)細(xì)胞胞體加粗,星形膠質(zhì)細(xì)胞足加長,細(xì)胞聚集。S100β是活化星形膠質(zhì)細(xì)胞的分泌蛋白,在唐氏綜合征、阿爾茲海默病、癲癇中都過表達(dá),是判斷腦損傷的常用指標(biāo)[19],在肥胖鼠海馬中大量表達(dá),表明星形膠質(zhì)細(xì)胞過度活化?;罨男切文z質(zhì)細(xì)胞可以遷移聚集在損傷部位形成瘢痕,阻礙了營養(yǎng)物質(zhì)向神經(jīng)元的運(yùn)輸,同時活化的星形膠質(zhì)細(xì)胞興奮性氨基酸轉(zhuǎn)運(yùn)受體和谷氨酸合成酶活力降低,導(dǎo)致神經(jīng)元外興奮性氨基酸濃度升高,最終影響神經(jīng)元的微環(huán)境[20],與癲癇的反復(fù)發(fā)作密切相關(guān)。因此,肥胖可能促進(jìn)了顳葉癲癇的發(fā)生、發(fā)展。肥胖小鼠海馬中神經(jīng)元的大量丟失和星形膠質(zhì)細(xì)胞的過度活化可能與肥胖小鼠血清相關(guān)因子變化有關(guān),研究表明,肥胖小鼠具有高瘦素水平,JAK2/ STAT3是瘦素主要下游信號通路,JAK2/STAT3信號通路的激活可以促進(jìn)星形膠質(zhì)細(xì)胞的活化,星形膠質(zhì)細(xì)胞活化可以促進(jìn)癲癇的發(fā)生[21-23]。提示肥胖的顳葉癲癇患者減輕體質(zhì)量可能有利于疾病的治療,同時對了解顳葉癲癇的機(jī)制提供了一個新思路。因此,肥胖影響顳葉癲癇的機(jī)制值得進(jìn)一步研究。
圖 3 肥胖對海人酸誘導(dǎo)的顳葉癲癇小鼠海馬CA3區(qū)神經(jīng)元(A)和星形膠質(zhì)細(xì)胞的影響(B)Fig. 3 Effect of obesity on neurons and astrocytes in hippocampal CA3 after KA-induced mice model of TLE
圖 4 肥胖對海人酸誘導(dǎo)顳葉癲癇小鼠海馬S-100β表達(dá)的影響Fig. 4 Effect of obesity on hippocampal S-100βexpression after KA-induced mice model of TLE (aP<0.05, vs WS group,bP<0.05, vs OS group,cP<0.05, vs WK group)
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Effect of high fat diet induced-obesity on hippocampal damage of temporal lobe epilepsy in mice
FENG Jie1, DENG Zihui1, ZHANG Jinying1, XUE Hui1, LIANG Chen1, LI Jianhua1, YAN Guangtao2
1Bichemistry Laboratory of Basic Medical Institute;2Department of Clinic Biochemistry Chinese PLA General Hospital, Beijing 100853, China
Corresponding author: YAN Guangtao. Email: yan301@263.net
Objective To study the effect of obesity in pathogenesis of temporal lobe epilepsy. Methods A high-fat diet induced obesity model of C57BL/6J mice was established and then a normal dose of kainic acid (KA, 200 ng per mouse) were microinjected into the hippocampus of mice to induce temporal lobe epilepsy and seizures were scored with the Racine scores. The concentration of serum CK-MB was tested and the expression of S-100β was measured by Western blot. Then, the hippocampal pathogenesis of mice was observed 5 weeks after KA injection. Results The mean peak seizure scores of obese mice significantly increased compared with the wild mice after KA injection. After 24 h of injection of KA, the mean serum CK-MB concentration and hippocampal S-100βexpression of obese mice were higher than wild mice. The neuron loss and astrocyte activation significantly increased in hippocampal CA3 region of obese mice compared with these of the wild mice after KA injection, there were significantly morphologic change of reactive astrocyte in obese mice. Conclusion Obesity may be detrimental to KA-induced brain injury.
obesity; kainic acid; astrocyte; temporal lobe epilepsy; C57BL/6J mice
R 363.2
A
2095-5227(2015)07-0724-05
10.3969/j.issn.2095-5227.2015.07.023
2014-11-20
科技基礎(chǔ)性工作專項(xiàng)項(xiàng)目(2011FY130100);國家科技支撐計劃項(xiàng)目(2012BAK25B01)
Supported by National Basic Research Development Program of the Ministry of Science and Technology of China (2011FY130100);The National Key Technology R&D Program (2012BAK25B01)
馮杰,男,在讀碩士。研究方向:神經(jīng)退行性疾病的機(jī)制。Email: fengjie654321@126.com
顏光濤,男,研究員,主任,博士生導(dǎo)師。Email: yan3 01@263.net