表1 實驗前后各組豚鼠AL變化Table 1 AL changes of guinea pigs before and after experiment in each group(±s,l/mm)
2.2各組豚鼠后鞏膜干質(zhì)量的比較右眼后鞏膜干質(zhì)量組間相比:C組>A組>B組,差異有統(tǒng)計學意義(F=38.294,P=0.000,見表2);左眼后鞏膜干質(zhì)量組間相比,A組、B組明顯低于C組,差異有顯著統(tǒng)計學意義(F=22.966,P=0.000),A 組與B組左眼后鞏膜干質(zhì)量差異無統(tǒng)計學意義(P=0.342)。各組豚鼠左右眼比較發(fā)現(xiàn):A組和B組豚鼠兩眼間均存在顯著差異,右眼后鞏膜干質(zhì)量明顯高于左眼(均為P=0.000);C組豚鼠兩眼間后鞏膜干質(zhì)量差異無統(tǒng)計學意義(P=0.163;見表2)。
表2 實驗4周后各組豚鼠后鞏膜干質(zhì)量比較Table 2 Dry weight of posterior scleral of guinea pigs after 4 weeks in each group
2.3視網(wǎng)膜VIP表達的比較免疫組織化學顯示在豚鼠視網(wǎng)膜中VIP在細胞胞漿中表達,呈棕黃、棕色顆粒狀。VIP強表達部位主要位于內(nèi)叢狀層(雙極細胞、無長突細胞與神經(jīng)節(jié)細胞相互接觸形成突觸的部位)、神經(jīng)節(jié)細胞層以及內(nèi)核層(雙極細胞、無長突細胞、水平細胞的細胞核組成),在光感受器細胞層亦有表達(圖1)。右眼視網(wǎng)膜VIP陽性細胞計數(shù)組間相比:A組0.05;見表3)。
表3 實驗4周后各組豚鼠視網(wǎng)膜VIP陽性細胞數(shù)Table 3 Number of VIP positive cells of guinea pigs after 4 weeks in each group
2.4后鞏膜組織MMP-2表達的比較以C組豚鼠左眼活化MMP-2表達OD值為參照,即100.0%±4.0%,各組左右眼相比發(fā)現(xiàn):A組和B組豚鼠兩眼間均存在顯著差異,右眼后鞏膜組織活化MMP-2表達量明顯低于左眼(t=20.366、-13.043,均為P=0.000);C組豚鼠兩眼間后鞏膜組織活化MMP-2表達差異無統(tǒng)計學意義(t=1.823,P=0.098;見表4)。
表4 實驗4周后各組豚鼠后鞏膜MMP-2表達值OD值Table 4 OD values of MMP-2 expression in posterior scleral of guinea pigs after 4 weeks in each group
2.5后鞏膜組織TIMP-2的表達比較
2.5.1繪制標準曲線ELISA法檢測TIMP-2的表達線性范圍限制在4.0~80.0 μg·L-1。以空白孔調(diào)零,各標準品吸光度(y)值對標準品濃度(x)作線性回歸的方程式為:y=0.037x+0.111(R2=0.990 1,P>0.05)。
2.5.2各組豚鼠眼球后鞏膜組織TIMP-2的含量
2.5.2.1右眼后鞏膜組織TIMP-2的表達實驗4周,A、B、C三組豚鼠右眼后鞏膜TIMP-2的含量分別為:(67.10±6.67)μg·L-1、(55.12±7.28)μg·L-1、(76.53±8.66)μg·L-1。三組豚鼠右眼組間比較發(fā)現(xiàn),C組高于A組、B組,差異有顯著統(tǒng)計學意義(F=12.864,P=0.001)。
Figure 1 Expression of VIP in retina of guinea pigs at 4 weeks after VIPhybrid injection (×400).A1:Right eye in group A;A2:Left eye in group A;B1:Right eye in group B;B2:Left eye in group B;C1:Right eye in group C;C2:Left eye in group C VIPhybrid注射4周后豚鼠視網(wǎng)膜VIP表達情況(×400 )。A1:A組右眼;A2:A組左眼;B1:B組右眼;B2:B組左眼;C1:C組右眼;C2:C組左眼
2.5.2.2左眼后鞏膜組織TIMP-2的表達實驗4周,A、B、C三組豚鼠左眼后鞏膜TIMP-2的含量分別為:(40.09±4.57)μg·L-1、(43.01±4.18)μg·L-1、(73.86±5.30)μg·L-1。A組、B組豚鼠左眼TIMP-2表達均低于C組,差異有顯著統(tǒng)計學意義(F=26.855,P=0.000);A組、B組比較差異無統(tǒng)計學意義(P=0.336)。
各組豚鼠左右眼比較:A組、B組豚鼠右眼TIMP-2的表達均明顯高于同組左眼,差異有顯著統(tǒng)計學意義(q=11.043、7.563,均為P=0.000);C組豚鼠兩眼間TIMP-2表達差異無統(tǒng)計學意義(q=-0.602,P=0.000)。
3 討論
VIP屬于小分子生物活性肽,廣泛分布于神經(jīng)系統(tǒng)和消化系統(tǒng)。既往研究證實視網(wǎng)膜細胞群中廣泛表達VIP參與多種視覺信號通路的調(diào)控,是功能性視網(wǎng)膜發(fā)育分化的促進因子。Seltner等[5]建立雛雞單眼形覺剝奪性近視模型,發(fā)現(xiàn)玻璃體內(nèi)注射VIP拮抗劑能完全消除形覺剝奪性近視的發(fā)生。前期研究發(fā)現(xiàn)長波長紅光環(huán)境中豚鼠視網(wǎng)膜VIP 表達明顯上升,且與后部鞏膜干質(zhì)量呈顯著負相關(guān)[4]。提示VIP可能在視網(wǎng)膜水平對近視眼后部鞏膜的主動重塑起重要調(diào)控作用。
VIP的生物學效應通過與其受體結(jié)合實現(xiàn)的,VIP受體(VIP-R)共分為三類:VPAC1受體,與腺苷酸環(huán)化酶系統(tǒng)偶聯(lián);VPAC2受體,與腺苷酸環(huán)化酶和鈣-氯通道偶聯(lián);PAC1受體,與腺苷酸環(huán)化酶和磷脂酶C偶聯(lián)[9]。VIP-R廣泛表達于視網(wǎng)膜內(nèi)網(wǎng)狀層的無長突細胞,其次是雙極細胞和神經(jīng)節(jié)細胞,以VPAC2受體為主,其次為VPAC1受體。VIPhybrid為非選擇性VIP受體拮抗劑,是血管緊張素(Ang)與VIP氨基酸片段的雜合物,即血管緊張素(6-11)-VIP(7-28)[10-11]。該物質(zhì)可以非選擇性同時作用于VPAC1和VPAC2兩種受體,競爭性抑制VIP與這兩種受體的結(jié)合,拮抗VIP的生理作用[12]。這也是本研究選擇VIPhybrid的依據(jù)。本實驗結(jié)果顯示,紅光照射明顯誘導豚鼠AL增長,對應豚鼠視網(wǎng)膜VIP高表達,選用不同濃度VIPhybrid進行玻璃體內(nèi)注射可抑制VIP表達,一定程度抑制紅光照射引起的眼球生長發(fā)育,進一步證明了VIP高表達與軸性近視的關(guān)系。VIP抑制長波長紅光誘導的近視化過程,且呈濃度依賴關(guān)系(高濃度VIPhybrid抑制作用更為明顯)。但與白光照射豚鼠相比,仍表現(xiàn)為近視化狀態(tài),即不能完全消除近視化過程。
既往研究證實鞏膜是近視發(fā)生機制的最終靶器官,尤其是后極部鞏膜細胞外基質(zhì)重塑與病理性近視的發(fā)生密切相關(guān)[13-14]。本實驗中也比較各組后鞏膜干質(zhì)量的變化,以白光照射條件下豚鼠鞏膜干質(zhì)量為參照,發(fā)現(xiàn)紅光使豚鼠后部鞏膜變薄,干質(zhì)量減輕;玻璃體內(nèi)注射VIPhybrid后能部分抑制鞏膜的重塑變薄,抑制程度呈劑量依賴性。提示拮抗VIP的作用可以抑制后部鞏膜的重塑變薄,延緩眼軸的延長、近視發(fā)展。
鞏膜主要由大量的膠原纖維和彈性纖維組成,調(diào)節(jié)膠原纖維、基質(zhì)合成與降解最關(guān)鍵的一類蛋白酶為MMP-2及TIMP-2間的動態(tài)平衡。許多研究報道MMP-2/TIMP-2參與形覺剝奪性及透鏡誘導性近視的發(fā)生[15-16]。Western blot檢測結(jié)果發(fā)現(xiàn),紅光抑制豚鼠鞏膜TIMP-2表達,導致MMP-2表達增高,玻璃體內(nèi)注射VIPhybrid后能部分調(diào)控鞏膜MMP-2/TIMP-2表達,TIMP-2表達增高,MMP-2表達下調(diào),抑制程度呈劑量依賴性。但鞏膜中MMP-2/TIMP-2表達變化與視網(wǎng)膜VIP表達不一致。說明VIPhybrid能有效拮抗視網(wǎng)膜VIP的表達;同時鞏膜MMP-2/TIMP-2表達平衡除受到視網(wǎng)膜VIP表達的影響外,還由其他多種可能的生物活性物質(zhì)調(diào)控。上述實驗結(jié)果提示,VIPhybrid抑制視網(wǎng)膜VIP表達后,一定程度下調(diào)鞏膜MMP-2表達,伴TIMP-2表達上調(diào),進而抑制后鞏膜重塑變薄及眼軸的延長,延緩近視化過程。
另外本研究比較了各組豚鼠左右眼及不同組豚鼠非注射眼間各指標的差異,發(fā)現(xiàn)白光環(huán)境下高濃度VIPhybrid注射沒有影響豚鼠眼球的生長發(fā)育及后極部組織VIP、MMP-2/TIMP-2的表達。說明VIPhybrid對正常環(huán)境下眼球生長及屈光發(fā)育無明顯影響,但可以延緩長波長紅光誘導眼球近視的進展。
綜上所述,VIPhybrid能夠一定程度地抑制鞏膜組織MMP-2表達,伴 TIMP-2表達上調(diào),鞏膜細胞外基質(zhì)重塑過程受阻,抑制眼軸的延長,繼而長波長光誘導的近視化過程延緩,并且在一定范圍內(nèi)呈現(xiàn)濃度依賴關(guān)系。提示視網(wǎng)膜VIP-鞏膜MMP-2/TIMP-2可能是長波長紅光誘導近視化過程的一條蛋白通路。但是研究中存在一些未明確的地方:包括視網(wǎng)膜VIP與鞏膜MMP-2之間的具體分子信號通路;其他神經(jīng)遞質(zhì)與VIP、MMP-2在近視化過程中的相互聯(lián)系;以及該拮抗劑對白光環(huán)境中眼球生長無明顯影響的原因都有待于研究。
1 Kroger RH,Binder S.Use of paper selectively absorbing long wavelengths to reduce the impact of edueational near work on human refractive development[J].BrJOphthalmol,2000,84(8):890-893.
2 Seidemann A,Schaeffel F.Effects of longitudinal chromatic aberration on accommodation and emmetropization[J].VisionRes,2002,42(21):2409-2417.
3 陳冬紅,褚仁遠,周國民, 胡誕寧.不同波長有色光對豚鼠眼球生長發(fā)育的影響[J].眼視光學雜志,2003,5(3):144-146.
4 劉鵬飛,肖林,暢立斌.不同波長單色光對豚鼠視網(wǎng)膜血管活性腸肽動態(tài)表達的影響[J].眼科,2012,21(3):181-186.
5 Seltner RL,Stell WK.The effect of vasoactive intestinal peptide on development of form deprivation myopia in the chick:a pharmacological and immunocytochemical study[J].VisionRes,1995,35(9):1265-1270.
6 王平寶,王華,劉雙珍,蔣晶晶.血管活性腸肽受體拮抗劑VIPhybrid對雞形覺剝奪性近視眼發(fā)展的影響[J].中南大學學報(醫(yī)學版), 2008,33(8):669-675.
7 Long Q,Chen D,Chu R.Illumination with monochromatic long-wavelength light promotes myopic shift and ocular elongation in newborn pigmented guinea pigs[J].JCutanOculToxicol,2009,28(4):176-180.
8 Kroger RH,Knoblaueh B,Wagner HJ.Rearing in different photic and spectral environments changes the optomotor response to chromatic stimuli in the cichlid fish aequidens puleher[J].JExpBiol,2003,206(10):1643-1648.
9 Rucker FJ,Wallman J.Chick eyes compensate for chromatic simulations of hyperopic and myopic defocus:evidence that the eye uses longitudinal chromatic aberration to guide eye-growth[J].VisionRes,2009,49(14):1775-1783.
10 Sreedharan SP,Patel DR,Huang JX,Goetzl EJ.Cloning and functional expression of a human neuroendocrine vasoactive intestinal peptide receptor[J].BiochemBiophysResCommun,1993,193(2):546-553.
11 Sreedharan SP,Patel DR,Xia M,Ichikawa S,Goetzl EJ.Human vasoactive intestinal peptide1 receptors expressed by stable transfectants couple to two distinct signaling pathways[J].BiochemBiophysResCommun,1994,203(1):141-148.
12 Moody TW,Jensen RT,F(xiàn)ridkin M,Gozes I.(N-stearyl,norleucine17)VIPhybrid is a broad spectrum vasoactive intestinal peptide receptor antagonist[J].JMolNeurosci,2002,18(1-2):29-35.
13 Shelton L,Rada JA.Inhibition of human scleral fibroblast cell attachment to collagen type I by TGFBIp[J].InvestOphthalmolVisSci,2009,50(8):3542-3552.
14 Frost MR,Norton TT.Alterations in protein expression in tree shrew sclera during development of lens-induced myopia and recovery[J].InvestOphthalmolVisSci,2012,53(1):322-336.
15 Gong B,Liu X,Zhang D,Wang P.Evaluation of MMP2 as a candidate gene for high myopia[J].MolVis,2013,19(1):121-127.
16 Leung KH,Yiu WC,Yap MK.Systematic investigation of the relationship between high myopia and polymorphisms of the MMP2,TIMP2,and TIMP3 genes by a DNA pooling approach[J].InvestOphthalmolVisSci,2011,52(6):3893-3900.
date:Aug 13,2013
Effects of VIPhybrid on long wave red light induced myopia
CHANG Li-Bin,LIU Peng-Fei,JIN En-Zhong,CHEN Si,XIAO-Lin
long wave-length light;myopia;vasoactive intestinal polypeptide;sclera
Objective To observe the effects of a non-specific vasoactive intestinal polypeptide (VIP) receptor antagonist (VIPhybrid) on progression of long wavelength red light induced myopia in guinea pigs,and investigate the expression changes of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) in sclera tissues,and find the possible protein pathway of myopia formation induced by red light.Methods Myopia models induced by long wave red light were established.Thirty-six guinea pigs were divided into three groups,the cases in group A and group B were intravitreal injected VIPhybrid with high and low concentrations into right eyes and bred in red light,the cases in group C were intravitreal injected VIPhybrid with high concentrations into right eyes and bred in white light.The ocular bioparameters and posterior scleral morphous were observed,and the expression of retinal VIP,scleral MMP-2/TIMP-2 were detected.Results After 4 weeks of VIPhybrid injection,the red light could induce the long ocular axis,the ocular axis of left eye in group A,B,C were (8.10±0.09)mm,(8.13±0.08)mm and (7.78±0.07)mm,respectively,group A and B were longer than group C (allP<0.05).The ocular axis of right eye in group A,B and C were (7.85±0.09)mm,(8.01±0.07)mm and (7.76±0.08)mm,respectively,there was statistical difference between group A and B (P<0.05),group A and B were longer than group C (bothP<0.05).In group A,the posterior scleral dry weight was relatively high,the expression of VIP was decreased,and the expression of MMP-2 was also decreased,the expression of TIMP-2 was increased.In group B,the changes were same as above in group A,but lighter than group A (bothP<0.05).The posterior scleral dry weight and expression of VIP and TIMP-2 in group A and B were lower than those in group C,and the expression of MMP-2 was higher than group C (bothP<0.05).Conclusion VIP plays a role in the red light induced myopia of the guinea pigs,VIPhybrid can alleviate the myopia partly,and the inhibiting effect is positively related with reagent concentration.
暢立斌,男,1982年10月出生。聯(lián)系電話:010-63926275;E-mail:mdchang@yeah.net
AboutCHANGLi-Bin:Male,born in October,1982.Tel:+86-10-63926275;E-mail:mdchang@yeah.net
2013-08-13
100038 北京市, 首都醫(yī)科大學附屬北京世紀壇醫(yī)院
肖林, E-mail:xiaolin1957@126.com
暢立斌,劉鵬飛,金恩忠,陳思,肖林.VIPhybrid對長波長紅光誘導近視化作用的影響[J].眼科新進展,2014,34(5):428-432.
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10.13389/j.cnki.rao.2014.0117
修回日期:2014-01-06
本文編輯:方紅玲
Accepteddate:Jan 6,2014
From theDepartmentofOphthalmology,BeijingShijitanHospital,CapitalMedicalUniversity,Beijing100038,China
Responsibleauthor:XIAO Lin,E-mail:xiaolin1957@126.com
[RecAdvOphthalmol,2014,34(5):428-432]