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肽核酸是20世纪80年代由有机化学家Ole Buchardt和生化学家Peter Nielsen共同研制合成的一种新型的序列特异性核酸制剂,是以不带电的、非手性的肽键(NH-CO)替代核酸的天然骨架3’,5’-磷酸二酯键的核酸类似物[1-2]。尽管肽核酸的骨架不同于天然核酸,但是它仍然遵守Watson-Crick原则,肽核酸与DNA或RNA的亲和力比DNA与DNA、DNA与RNA的亲和力强[3]。核酸在体内容易被核酸内切酶和核酸外切酶水解,而肽核酸不易被蛋白酶和核酸酶水解。有研究通过在肽核酸分子上连接正电荷基团,如赖氨酸或精氨酸残基,或通过配体、核定位信号(nuclear localization signal, NLS)提高细胞对肽核酸的通透性[4-6]。
自身免疫性甲状腺疾病(autoimmune thyroid disease, AITD)主要包括Graves病、桥本氏甲状腺炎和原发黏液性水肿,它们的临床表现为甲状腺功能亢进或低下,以及甲状腺组织的病理损伤。迄今为止,国内外学者对AITD的发病机理尚存在许多争议,但多数学者倾向于认为AITD是由与促甲状腺激素受体(thyroid stimulating hormone receptor, TSHR)结合的抗体所引起的[7]。这一论点不仅通过Graves病患者血清中检测到的高水平甲状腺刺激性抗体(thyroid stimulating antibody,TSAb)得到证明,而且新生儿Graves病是由母亲胎盘中的TSAb引发的事实也支持了这一论点。既然AITD是由于TSHR结合抗体引起的,我们可以通过减少TSHR的受体数目达到控制AITD进程的目的。
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细胞涂片后经荧光显微镜观察发现,单纯的FRTL细胞(即A组)经过碘化丙啶染色后细胞核为红色(图 1a)。而在B、C、D 3组中,由于肽核酸上标记的GITC所发出的荧光为黄绿色,在红色的细胞核周围即胞浆中,我们可以见到黄绿色荧光,提示NLS-asPNA可以进入到细胞中(图 1b)。
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将3种肽核酸分别加入细胞培养基中与细胞一起培养,分别于24、48、72 h后测定T/C值(表 1),经统计学分析后发现,B、C、D 3组在不同时间的T/C值之间差异无统计学意义(F= 0.0006、0.0007和0.0004,P均 > 0.05),表明NLS-asPNA对细胞没有毒性作用。
组别 T/C值 24 h 48 h 72 h B组(NLS-asPNA1) 1.036±0.01 1.051±0.02 1.048±0.01 C组(NLS-asPNA2) 1.051±0.03 0.982±0.02 0.987±0.01 D组(NLS-scrPNA) 1.007±0.02 1.039±0.01 1.064±0.02 注:表中,T代表NLS-asPNA1、NLS-asPNA2和NLS-scrPNA组在各个时间点的光密度值,C代表对照组在各个时间点的光密度值;NLS:核定位信号;asPNA:反义肽核酸;scrPNA:干扰肽核酸。 表 1 3种肽核酸与细胞培养不同时间后的T/C值
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从图 3我们可以看出,NLS-asPNA1和NLS-asPNA2均可以抑制FRTL细胞TSHR mRNA的表达,NLS-asPNA1和NLS-asPNA2分别与细胞培养12、24、48 h后,TSHR cDNA的拷贝数与0 h相比逐渐降低,且呈现出时间依赖性。而NLS-scrPNA与细胞培养12、24、48 h后,TSHR cDNA的拷贝数与0 h相比,没有明显的变化。
反义肽核酸对促甲状腺激素受体mRNA表达的影响
The effects of antisense peptide nucleic acid on the expression of thyroid stimulating hormone receptor mRNA
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摘要:
目的 探讨反义肽核酸(asPNA)对大鼠甲状腺细胞的细胞膜表面促甲状腺激素受体(TSHR)表达的影响。 方法 设计两种与TSHR mRNA不同片段互补的asPNA,分别为核定位信号-asPNA1(NLS-asPNA1)和NLS-asPNA2,另外合成一段非相关的干扰肽核酸(NLS-scrPNA)序列,用荧光显微镜观察NLS-asPNA能否进入细胞,采用噻唑蓝法检测asPNA对细胞是否具有毒性作用,然后用实时定量RT-PCR检测NLS-asPNA对TSHR mRNA表达的影响。 结果 荧光显微镜观察发现,asPNA可以进入到细胞中去。噻唑蓝法检测发现asPNA对细胞没有毒性作用。实时定量RT-PCR结果显示,NLS-asPNA1和NLS-asPNA2可以抑制TSHR mRNA表达,表现为随着NLS-asPNA与细胞培养时间的延长,TSHR cDNA的拷贝数逐渐下降,且呈现时间依赖性,而NLS-scrPNA对TSHR mRNA的表达没有明显的影响。 结论 NLS-asPNA可以进入到细胞中去,并且能够下调TSHR mRNA的表达。 Abstract:Objective To study the effects of antisense peptide nucleic acid(asPNA)on thyroid stimulating hormone receptor(TSHR)of Fisher rat thyroid cells membrane. Methods Two kinds of asPNA which could hybridized to the TSHR mRNA named as nuclear localization signal-asPNA1(NLS-asPNA1) and NLS-asPNA2 were designed, and a control PNA with a scramble sequence named as NLS-scrPNA was synthetized. The cellular uptake of peptide nucleic acids were analyzed by fluorescence microscopy, and the toxic effect of asPNA to Fisher rat thyroid cells was evaluated by MTT assay. The effect of NLS-asPNA on the expression of TSHR mRNA was detected by realtime quantitative RT-PCR. Results Fluorescence microscopy indicated that asPNA were taken up by the cells. The results of MTT assay showed that all the asPNA had no toxic effect on the cells. The results of realtime quantitative RT-PCR showed that NLS-asPNA1 and NLS-asPNA2 could inhibit the expression of TSHR mRNA, the copies of TSHR cDNA decreased gradually along with the prolongation of culture time. But NLS-scrPNA had no significant effect on the expression of TSHR mRNA. Conclusion NLS-asPNA could be taken up by the cells and down-regulate the expression of TSHR mRNA. -
Key words:
- Peptide nucleic acids /
- Receptors, thyrotropin /
- RNA, messenger
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表 1 3种肽核酸与细胞培养不同时间后的T/C值
组别 T/C值 24 h 48 h 72 h B组(NLS-asPNA1) 1.036±0.01 1.051±0.02 1.048±0.01 C组(NLS-asPNA2) 1.051±0.03 0.982±0.02 0.987±0.01 D组(NLS-scrPNA) 1.007±0.02 1.039±0.01 1.064±0.02 注:表中,T代表NLS-asPNA1、NLS-asPNA2和NLS-scrPNA组在各个时间点的光密度值,C代表对照组在各个时间点的光密度值;NLS:核定位信号;asPNA:反义肽核酸;scrPNA:干扰肽核酸。 -
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