劉韋鋆,余劍波,蔡 旺,李東華,張 一,聶 衛(wèi),劉大衛(wèi),劉洪斌1,
實(shí)驗(yàn)研究
重型胰腺炎大鼠血漿線粒體DNA變化與器官損傷的關(guān)系
劉韋鋆1,2,余劍波2,蔡 旺2,李東華1,2,張 一1,2,聶 衛(wèi)3,劉大衛(wèi)3,劉洪斌1,3
目的:檢測(cè)重型急性胰腺炎(SAP)模型大鼠血漿線粒體DNA(mtDNA)濃度,探討循環(huán)血中mtDNA水平與SAP器官損傷的關(guān)系。方法:健康成年雄性Wistar大鼠30只,隨機(jī)分為假手術(shù)組和SAP模型組,以5%?;悄懰徕c膽胰管逆行注射法制備SAP大鼠模型,24 h后麻醉,取全血,留取血漿,測(cè)定淀粉酶和脂肪酶水平;提取血漿中游離DNA,采用線粒體細(xì)胞色素B和細(xì)胞色素C氧化酶亞基Ⅲ引物,進(jìn)行熒光定量PCR擴(kuò)增,以其擴(kuò)增產(chǎn)物量代表循環(huán)血中mtDNA水平;取肺臟、肝臟、腎臟組織,一部分行HE染色、病理組織學(xué)檢查及評(píng)分,一部分勻漿提取組織上清液,ELISA法檢測(cè)TNF-α、IL-1及IL-6水平,兩組間各指標(biāo)的比較采用單因素方差分析;mtDNA水平與病理組織評(píng)分相關(guān)性分析采用Spearman秩相關(guān)分析。結(jié)果:與假手術(shù)組比較,SAP模型組大鼠血中淀粉酶活性[(10 444.5±1863.2)U/L]和脂肪酶活性[(1751.3±121.3) U/L]顯著升高(P< 0.01);各臟器損傷評(píng)分和 TNF-α[肺臟(88.4±15.4) pg/mg ;肝臟(79.3±10.3) pg/mg;腎臟(69.5±9.6) pg/mg]、IL-1[肺臟(0.68±0.11) μg/g ;肝臟(0.72±0.17) μg/g ;腎臟(0.85±0.17) μg/g]、IL-6[肺臟(252.1±18.7) pg/mg;肝臟(107.5±12.3) pg/mg;腎臟(118.5±15.2) pg/mg]水平顯著升高(P< 0.01);模型組循環(huán)血中線粒體細(xì)胞色素B(0.4891±0.0921)及線粒體細(xì)胞色素C氧化酶亞基Ⅲ相對(duì)表達(dá)量(0.6082±0.1142)均較假手術(shù)組[細(xì)胞色素B (0.2856±0.0878);細(xì)胞色素C氧化酶亞基Ⅲ (0.1985±0.0854)]顯著升高(P< 0.01),且二者水平與臟器損傷評(píng)分顯著正相關(guān)(P< 0.05)。結(jié)論:SAP大鼠循環(huán)血中mtDNA水平升高與器官損傷程度相關(guān)。
重型急性胰腺炎;線粒體DNA;損傷相關(guān)分子模式;細(xì)胞色素B;細(xì)胞色素C氧化酶
重型急性胰腺炎(severe acute pancreatitis,SAP)起病急,進(jìn)展快,尤其早期病情復(fù)雜多變,累及器官多,并發(fā)癥多,病死率高[1]。目前多認(rèn)為胰腺腺泡細(xì)胞內(nèi)酶原顆粒過早激活、腺泡細(xì)胞壞死以及啟動(dòng)的多種炎性因子釋放發(fā)生瀑布樣級(jí)聯(lián)反應(yīng),是SAP發(fā)生全身炎性反應(yīng)綜合征、多器官功能障礙以致死亡的主要機(jī)制之一[2]。新近研究表明,線粒體DNA(mitochondrial DNA,mtDNA)作為一種損傷相關(guān)分子模式(damage associated molecular pattern molecules,DAMP),在引起炎性介質(zhì)釋放過程中起到重要作用。已有研究發(fā)現(xiàn),mtDNA與膿毒癥、創(chuàng)傷、心肌梗塞等的嚴(yán)重程度及預(yù)后關(guān)系密切[3-4]。本研究旨在分析SAP模型大鼠血漿mtDNA濃度變化,探討循環(huán)血中mtDNA水平與SAP器官損傷的關(guān)系。
1.1 材料 健康雄性Wistar大鼠,由北京維通利華實(shí)驗(yàn)動(dòng)物技術(shù)有限公司提供;?;悄懰徕c為Sigma公司產(chǎn)品;TNF-α、IL-1、IL-6 ELISA kit為TPI公司產(chǎn)品;淀粉酶、脂肪酶測(cè)定試劑盒購自南京建成生物技術(shù)研究所。
1.2 大鼠重癥急性胰腺炎模型的建立 參照Aho[5]的方法并加以改進(jìn),建立大鼠重癥急性胰腺炎模型。術(shù)前12 h禁食不禁水,以10%水合氯醛(0.3 g/kg)腹腔注射麻醉,無菌條件下經(jīng)腹壁正中切口入腹。于膽管出肝門端以無損傷小動(dòng)脈夾暫時(shí)阻斷膽管,尋找到膽胰管十二指腸乳頭開口處。在其對(duì)系膜緣用4號(hào)注射針頭刺一小孔,用PE50導(dǎo)管經(jīng)乳頭部逆行插入膽胰管0.5 cm,妥善固定。以5%?;悄懰徕c勻速注入(1 mL/kg,0.1 mL/min),5 min后去除小動(dòng)脈夾。以無損傷縫線縫合十二指腸穿刺孔,縫合腹壁。
1.3 分組 健康雄性Wistar大鼠30只,體質(zhì)量220~250 g。隨機(jī)分為假手術(shù)組和模型組,每組15只。假手術(shù)組只開腹翻動(dòng)腹腔臟器數(shù)次即關(guān)腹;模型組經(jīng)膽胰管逆行注射5%?;悄懰徕c誘發(fā)SAP。兩組24 h后在麻醉狀態(tài)下經(jīng)腹主動(dòng)脈取血,測(cè)定血清淀粉酶、脂肪酶;取左肺一部分勻漿,測(cè)定TNF-α、IL-1、IL-6,一部分經(jīng)10%甲醛固定作病理組織學(xué)檢;留取肺臟、肝臟、腎臟組織進(jìn)行組織病理學(xué)觀察。
1.4 檢測(cè)指標(biāo)
1.4.1 血清AMY測(cè)定 采用碘比色法,結(jié)果以U/L蘇氏單位表示。
1.4.2 血清脂肪酶測(cè)定 按試劑盒方法,即甲基試鹵靈底物法進(jìn)行檢測(cè)。準(zhǔn)確稱取組織質(zhì)量,質(zhì)量(g):體積(mL)1:9,加入9倍體積的生理鹽水,冰水浴條件下機(jī)械勻漿,制成10%的勻漿,2500 r/min,離心10 min,取上清測(cè)定,結(jié)果以U/L單位表示。
1.4.3 組 織 TNF-α、IL-1、IL-6測(cè) 定 采 用ELISA法檢測(cè)。
1.4.4 循環(huán)血中mtDNA的PCR擴(kuò)增反應(yīng) 血漿中mtDNA采用QIAamp DNA Mini and Blood Mini kit提?。喝?%肝素鈉抗凝處理的血漿,加入proteinase K,加入Buffer AL,渦旋徹底混勻。56 ℃孵育血液樣品10 min,加入無水乙醇,渦旋徹底混勻,吸取混合液至一個(gè)裝有DNeasy Mini spin column 的收集管。依次加入Buffer AW1,Buffer AW2洗脫,棄去流出液和收集管。加入Buffer AE洗脫,收集DNA流出液,進(jìn)行PCR分析。引物序列如下:rat cytochrome B(forward 5' -tccacttcatcctcccattc-3' 、reverse 5' -ctgcgtcggagtttaatcct-3'),rat cytochrome C oxidase subunit III(forward 5' -acataccaaggccaccaac-3'、reverse 5'-cagaaaaatccggcaaagaa-3'),rat NADH dehydrogenase(forward 5' -caataccccacccccttatc-3'、reverse' -gaggctcatcccgatcatag-3'), 其 中 以 NADH為內(nèi)參?;虮磉_(dá)差異 =2-(?CtTS-?CtCS),其中 ?CtTS為待測(cè)樣品目的基因與待測(cè)樣品參照基因Ct值的差;?CtCS為空白樣品目的基因與空白樣品參照基因Ct值的差。
1.4.5 病理學(xué)評(píng)分 留取肺、肝、腎標(biāo)本做HE染色,光鏡下觀察,按參考文獻(xiàn)進(jìn)行病理組織學(xué)評(píng)分[6]。病理改變嚴(yán)重程度分為輕(1分)、中(2分)、重(3分)。評(píng)分標(biāo)準(zhǔn)見表1。
表1 大鼠肺、肝、腎病理改變?cè)u(píng)分標(biāo)準(zhǔn)
1.5 統(tǒng)計(jì)學(xué)分析 數(shù)據(jù)及統(tǒng)計(jì)處理采用SPSS11.0統(tǒng)計(jì)分析軟件計(jì)算機(jī)處理,各組數(shù)據(jù)以表示,各組計(jì)量資料的平均數(shù)間的差異采用單因素方差分析進(jìn)行檢驗(yàn);其中mtDNA水平與病理組織評(píng)分相關(guān)性分析采用Spearman秩相關(guān)分析,以P< 0.05為差異有統(tǒng)計(jì)學(xué)意義。
2.1 大鼠死亡情況 模型組24 h內(nèi)死亡6只,存活9只,死亡率為40%;假手術(shù)組無死亡。
2.2 血清淀粉酶及脂肪酶水平 模型組血清淀粉酶及脂肪酶水平較假手術(shù)組顯著增高(P< 0.01)。見表2。
表2 兩組大鼠血清淀粉酶及脂肪酶水平比較()
表2 兩組大鼠血清淀粉酶及脂肪酶水平比較()
注:與假手術(shù)組比,aP < 0.01
n 淀粉酶(U/L) 脂肪酶(U/L)假手術(shù)組 1 5 4 9 9.4±8 6.3 4 9 2.5±5 7.4模型組 9 1 0 4 4 4.5±1 8 6 3.2 a 1 7 5 1.3±1 2 1.3 a
2.3 肺臟、腎臟、肝臟組織TNF-α、IL-1、IL-6水平 與假手術(shù)組比較,模型組大鼠肺臟、腎臟、肝臟組織TNF-α、IL-1、IL-6水平均顯著升高(P< 0.01)。見表 3。
表3 兩組大鼠肺臟、腎臟、肝臟組織TNF-α、IL-1、IL-6水平比較()
表3 兩組大鼠肺臟、腎臟、肝臟組織TNF-α、IL-1、IL-6水平比較()
注:與假手術(shù)組比,aP < 0.01
n 肺臟 肝臟 腎臟TNF-α (pg/mg)假手術(shù)組 15 17.0± 8.4 11.5± 2.7 15.3±2.5模型組 9 88.4±15.4a 79.3±10.3a 69.5±9.6a IL-1 (μg/g)假手術(shù)組 15 0.19±0.07 0.16±0.04 0.18±0.05模型組 9 0.68±0.11a 0.72±0.17a 0.85±0.17a IL-6 (pg/mg)假手術(shù)組 15 59.5±10.6 39.2± 9.1 18.1± 7.9模型組 9 252.1±18.7a 107.5±12.3a 118.5±15.2a
2.4 循環(huán)血中mtDNA水平 模型組大鼠線粒體細(xì)胞色素B相對(duì)表達(dá)量為0.4891±0.0921,線粒體細(xì)胞色素C氧化酶亞基Ⅲ相對(duì)表達(dá)量為0.6082±0.1142,分別較假手術(shù)組(0.2856±0.0878,P< 0.05 和 0.1985±0.0854,P< 0.01)顯著升高。見圖1、2。
圖1 兩組大鼠循環(huán)血中線粒體細(xì)胞色素B基因相對(duì)表達(dá)量比較
圖2 兩組大鼠循環(huán)血中線粒體細(xì)胞色素C氧化酶亞基Ⅲ基因相對(duì)表達(dá)量比較
2.5 肺、肝、腎組織HE病理學(xué)觀察及評(píng)分 模型組肺組織間質(zhì)炎性細(xì)胞浸潤(rùn)明顯、肺泡壁增厚;肝細(xì)胞排列紊亂、肝細(xì)胞變性、肝血竇擴(kuò)張;腎小管上皮細(xì)胞腫脹變性、腎間質(zhì)小血管和毛細(xì)血管擴(kuò)張、腎小管間充血、腎小管擴(kuò)張。假手術(shù)組基本正常。模型組各臟病理評(píng)分顯著增高(P< 0.01,表4)。見圖3。
圖3 肺、肝、腎組織HE染色
表4 兩組大鼠肺、肝、腎組織病理評(píng)分比較()
表4 兩組大鼠肺、肝、腎組織病理評(píng)分比較()
注:與假手術(shù)組比,aP < 0.01。
n 肺臟 肝臟 腎臟假手術(shù)組 15 0.20±0.02 0 0模型組 9 2.10±0.57a 1.90±0.32a 2.00±0.47a
2.6 模型組mtDNA水平與病理組織評(píng)分相關(guān)性分析 采用Spearman秩相關(guān)分析,mtDNA水平(細(xì)胞色素B和細(xì)胞色素C氧化酶亞基Ⅲ)與病理學(xué)評(píng)分顯著正相關(guān)(P< 0.05,P< 0.01)。見表5。
表5 模型組mtDNA水平與病理組織評(píng)分相關(guān)性
SAP是一多因素,累及多環(huán)節(jié)的全身性疾病,其發(fā)病機(jī)制至今尚未完全闡明[7]。目前的主要觀點(diǎn)有“白細(xì)胞過度激活-炎性因子級(jí)聯(lián)瀑布效應(yīng)”學(xué)說[8-9]、“胰腺微循環(huán)障礙”學(xué)說[10]、“細(xì)胞凋亡”學(xué)說、“腸道細(xì)菌易位”學(xué)說[11-12]、“二次打擊”學(xué)說等。國際上近年來關(guān)于固有免疫與炎癥關(guān)系的免疫學(xué)新機(jī)制,提出了DAMP,尤其是線粒體DAMP分子(mitochondrial DAMPs,MTD)炎癥信號(hào)通路在創(chuàng)傷、膿毒癥、急性胰腺炎及其器官損傷中起重要作用[3-4]。
多數(shù)DAMP在胞內(nèi)有確定的功能,但一旦因損傷而釋放到細(xì)胞外,即可發(fā)生功能變性,引起免疫反應(yīng)。DAMP可以特異性結(jié)合模式識(shí)別受體(pattern recognition receptors,PRRs),激活機(jī)體固有免疫系統(tǒng),導(dǎo)致組織器官進(jìn)一步損傷[13]。DAMP可來自胞內(nèi)和胞外,其中胞內(nèi)DAMP最受關(guān)注,最主要的胞內(nèi)DAMP由受損細(xì)胞特別是壞死細(xì)胞所釋放。現(xiàn)在認(rèn)為,最主要的胞內(nèi)DAMP分子是組織細(xì)胞破裂后釋放的MTD。MTDs主要包括甲酰肽和線粒體DNA(mtDNA),其中甲酰肽激活免疫細(xì)胞表面的甲酰肽受體(formyl peptide receptor,F(xiàn)PR),mtDNA活化細(xì)胞內(nèi)TLR-9觸發(fā)多條炎性信號(hào)傳導(dǎo)通路。mtDNA與細(xì)菌DNA相似,而與機(jī)體細(xì)胞核DNA差別巨大。細(xì)菌和mtDNA具有未甲基化的CPG二核苷為核心的回形序列,人體細(xì)胞通常為甲級(jí)化的CPG結(jié)構(gòu),CPG特征結(jié)構(gòu)是機(jī)體免疫系統(tǒng)識(shí)別自身和異體的物質(zhì)基礎(chǔ),被稱為“免疫刺激DNA序列”?;诰€粒體結(jié)構(gòu)上的差異,有研究證實(shí)創(chuàng)傷后組織細(xì)胞破裂釋放mtDNA,通過與細(xì)胞內(nèi)TLR-9結(jié)合,募集趨化嗜中性粒細(xì)胞脫顆粒引起全身性炎性反應(yīng),造成遠(yuǎn)隔器官的損傷[14-15]。
臨床對(duì)膿毒癥研究發(fā)現(xiàn),其循環(huán)血中mtDNA濃度顯著升高,并且與膿毒癥休克發(fā)生率及病死率顯著正相關(guān),提示其可作為一種診斷膿毒癥嚴(yán)重程度和判斷病情預(yù)后的重要指標(biāo)[3]。目前,在重癥急性胰腺炎與循環(huán)血mtDNA的相關(guān)性方面還缺乏相關(guān)研究。本研究采用線粒體細(xì)胞色素B和細(xì)胞色素C氧化酶亞基Ⅲ引物,進(jìn)行熒光定量PCR擴(kuò)增,以其擴(kuò)增產(chǎn)物量代表循環(huán)血中mtDNA水平。結(jié)果顯示,SAP造模24 h大鼠循環(huán)血中mtDNA水平與假手術(shù)組比顯著升高。此外,研究結(jié)果發(fā)現(xiàn),SAP大鼠循環(huán)血中mtDNA水平與主要器官病理損傷程度(病理組織學(xué)評(píng)分)呈顯著正相關(guān),提示循環(huán)血中mtDNA水平有可能作為一種判斷SAP嚴(yán)重程度及器官損傷程度的分子指標(biāo)。當(dāng)然這還需要進(jìn)行進(jìn)一步研究,特別是進(jìn)行臨床SAP患者循環(huán)血中mtDNA水平的測(cè)定,以及與臨床應(yīng)用廣泛的一些生化指標(biāo)或判斷標(biāo)準(zhǔn)比較,如CRP、馬歇爾評(píng)分系統(tǒng)、改良CT嚴(yán)重指數(shù)、APACHE-II、Ranson評(píng)分系統(tǒng)等。
SAP大鼠循環(huán)血中mtDNA濃度顯著升高,且與器官損傷程度相關(guān),提示其有可能成為輔助判斷SAP嚴(yán)重程度及器官損傷程度的一項(xiàng)指標(biāo),但需要進(jìn)一步的基礎(chǔ)與臨床研究加以驗(yàn)證。
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Relationship between Plasma Mitochondrial DNA and Organ Damage in Rat Model of Severe Acute Pancreatitis
LIU Wei-jun, YU Jian-bo, CAI Wang, et al. Tianjin Institute of Acute Abdominal Disease, Tianjin(300100), China
ObjectiveTo detect the concentration of plasma mitochondrial DNA (mtDNA) in rat model of severe acute pancreatitis (SAP) and investigate the relationship between mtDNA level and organ damage.MethodsThirty healthy adult male Wistar rats were randomly divided into Sham operation group and SAP model group with 15 rats in each group. The rat SAP model was induced by retrogradely injection of 5%sodium taurocholate through the biliopancreatic duct. After 24 h, the whole blood was taken and the plasma was separated to measure the levels of amylase and lipase. The dissociative DNA was extracted from plasma and amplified by fluorescent quantitative PCR amplification using mitochondrial cytochrome B and cytochrome oxidase subunit III primers. The level of mtDNA in circulating blood was represented by the PCR amplification product. The lung, liver and kidney tissues were collected. One part was used for HE staining, histopathological examination and scoring, and the other part was homogenized to extract the supernatant and used to measure the levels of TNF-α, IL-1 and IL-6 by ELISA method. The two groups were compared using the index single factor variance analysis. Correlation analysis between the mtDNA level and pathological score was performed by Spearman rank correlation analysis.ResultsCompared with Sham operationgroup, the levels of amylase [(10444.5±1863.2 )U/L] and lipase [(1751.3±121.3)U/L] in SAP model rats were significantly increased (P< 0.01). The pathological scores and levels of TNF-α [(88.4±15.4) pg/mg in lung,(79.3±10.3) pg/mg in liver, (69.5±9.6) pg/mg in kidney], IL-1 [(0.68±0.11) μg/g in lung, (0.72±0.17)μg/g in liver, (0.85±0.17) μg/g in kidney] and IL-6 [(252.1±18.7) pg/mg in lung, (107.5±12.3) pg/mg in liver, (118.5±15.2) pg/mg in kidney] were significantly increased (P< 0.01). The circulating mtDNA level was also increased significantly and had a significant positive correlation with organ injury score (P< 0.05). The relative expression of cytochrome B (0.4891±0.0921) and cytochrome oxidase subunit III (0.6082±0.1142)in mitochondria of model group was increased significantly compared with that in Sham operation group(0.2856±0.0878) and (0.1985±0.0854), respectively) (P< 0.01). The expression levels were positively correlated with the organ damage score.ConclusionThe increase of mtDNA concentration in circulating blood of SAP model rats is related to the degree of organ damage.
Severe acute pancreatitis; mitochondrial DNA; damage associated molecular pattern;cytochrome B; cytochrome C oxidase
Q95-33;R657.5+1
A
1007-6948(2017)06-0633-05
10.3969/j.issn.1007-6948.2017.06.014
國家自然科學(xué)基金資助項(xiàng)目(81373854)
1.天津市中西醫(yī)結(jié)合急腹癥研究所(天津 300100)
2.天津市南開醫(yī)院(天津 300100)
3.天津市醫(yī)藥科學(xué)研究所(天津 300020)
劉洪斌,E-mail:jtss@sina.com
(收稿:2017-04-12 修回:2017-11-02)
張淑坤 屈振亮)