左甲状腺素钠联合多奈哌齐治疗对成年甲减大鼠后扣带回SNAP-25表达的影响

Effects of levothyroxine sodium combined with donepezil on expression of SNAP-25 in posterior cingulate gyrus of adult hypothyroidism rats

目的研究左甲状腺素钠(L-T4)与多奈哌齐(DON)联合治疗对甲状腺功能减退症(简称甲减)大鼠后扣带回突触相关蛋白25(SNAP-25)表达的影响。方法 40只清洁级SD雄性大鼠,适应性饲养1周后随机分为正常对照组(CON组)、甲减组(Hypo组)、L-T4替代治疗组(L-T4组)、多奈哌齐治疗组(DON组)、联合治疗组(L-T4+DON组)。CON组正常饲养,余4组通过给予0.05%丙硫氧嘧啶(PTU)水饮用6周建立甲减大鼠模型。造模5周开始,给予左甲状腺素钠、多奈哌齐、左甲状腺素钠联合多奈哌齐治疗2周。通过放射免疫法测定血清甲状腺激素水平,尼氏染色法观察尼氏体数量,免疫组化法、Western blot法观察大鼠后扣带回SNAP-25的表达。结果 Hypo组、DON组大鼠较CON组血清甲状腺激素水平显著降低(P<0.01),L-T4组、L-T4+DON组血清甲状腺素水平与正常对照组差异无统计学意义。尼氏染色显示Hypo组较CON组尼氏体数量降低(P<0.05),DON组尼氏体数量较Hypo组增加(P<0.05),未恢复至CON组水平(P<0.05),L-T4+DON组尼氏染色显示与CON组比较差异无统计学意义,尼氏体数量恢复。免疫组化染色、Western blot法显示Hypo组、DON组后扣带回SNAP-25表达高于CON组(P<0.05);L-T4组SNAP-25表达低于Hypo组(P<0.05),未恢复至CON组水平(P<0.05);L-T4+DON组后扣带回SNAP-25表达与CON组差异无统计学意义。结论成年期甲减大鼠后扣带回SNAP-25蛋白表达量升高(P<0.05)、尼氏体数量减少(P<0.05),左甲状腺素钠与多奈哌齐联合治疗能够有效恢复突触蛋白和尼氏体的损伤。

Objective To study the effect of combination therapy of L-T4 and donepezil（ DON） on the expression of synaptic-associated protein 25（ SNAP-25） in posterior cingulate gyrus of hypothyroidism rats. Methods Forty healthy male SD rats were randomly divided into normal control group（ CON group）,hypothyroid group（ Hypo group）,L-T4 substitution group（ L-T4 group）,donepezil treatment group（ DON group）,combined therapy group（ L-T4 ＋ DON group）. The rats were treated with 0. 05% propylthiouracil（ PTU） for 6 weeks to establish a hypothyroidism model except for the CON group. 5 weeks after the model establishment,levothyroxine sodium,donepezil,levothyroxine sodium and donepezil were given for 2 weeks. The radioimmunoassay was used to measure the level of serum thyroid hormones. he Nissl＇s staining method was applied in the observation of Nissl body number,and we also determined the the expression of SNAP-25 by immunohistochemistry and Western blot. Results The level of serum thyroxine in the Hypo and DON group were significantly lower than those in the CON group（ P〈0. 01）. There was no significant difference between the L-T4 and the L-T4 ＋ DON group as well as the CON group. The number of Nissl bodies in Hypo group was decreased as compared to the CON group（ P 〈0. 05）,while DON group increased the number of Nissl bodies in the hypothyroid rats（ P〈 0. 05）,however,it was still lower than that in CON group（ P〈 0. 05）. Interestingly,the number of Nissl body was up-regulated nearly to that in the CON group by the combination therapy of L-T4 ＋ DON group. The expression of SNAP-25 was significantly up-regulated in the hypothyroid or the DON group treated rats than that in CON group（ P 〈0. 05）,while the level of SNAP-25 was repressed by L-T4 comparing to the Hypo group（ P 〈0. 05）,but still higher than that in CON group（ P〈 0. 05）. And of note,the level of SANP-25 in the L-T4 ＋ DON group treated rats was not altered as compared to the CON group.Conclusion The expression of SNAP-25 is increased and the number of Nissl body is reduced in posterior cingulate gyrus in adult hypothyroid rats（ P 〈0. 05）,and the combined treatment of levothyroxine sodium and donepezil can effectively protect the synaptic protein and Nissl body against injury.