磷酸化c-Jun表达对亚急性帕金森病MPTP模型小鼠黑质COX-2表达的影响

Effect of phosphorylated c-Jun expression on COX-2 expression in the substantia nigra of MPTP mouse model of subacute Parkinson disease

目的研究磷酸化c-Jun(p-c-Jun)在1-甲基-4-苯基-1,2,3,6-四氢吡啶(MPTP)所致亚急性帕金森病(PD)小鼠模型中对环氧合酶-2(COX-2)的表达调控作用,以探讨PD黑质多巴胺(DA)能神经元变性失活的可能机制。方法采用MPTP制备亚急性PD小鼠模型。通过行为学观察,免疫组织化学SP法,免疫荧光双标记法和免疫蛋白印记法,观察模型小鼠行为学变化,观察PD模型小鼠黑质区酪氨酸羟化酶(TH)、COX-2和p-c-Jun免疫组织化学变化以及中脑黑质TH、COX-2和p-c-Jun表达水平的变化;观察给予JNK通路特异性剂SP-600125对上述变化的影响。结果与对照组小鼠相比,模型组小鼠出现典型PD症状。黑质区TH阳性神经元下降约65%(P<0.001),中脑黑质TH表达水平显著降低约75%;黑质区COX-2阳性细胞显著增加,中脑黑质COX-2表达水平明显升高;p-c-Jun特异性表达于黑质区细胞核内,p-c-Jun表达水平显著升高。免疫荧光双标记染色可见,COX-2和p-c-Jun共同表达于TH阳性细胞。抑制剂组,经SP600125处理后,模型小鼠PD症状减轻,与对照组比较,在MPTP第5次注射后七天,TH阳性细胞数和TH表达水平仅下降约15%和20%,与模型组比较,黑质区COX-2阳性细胞明显减少,中脑黑质COX-2表达水平明显降低,p-c-Jun仅表达于黑质区细胞的胞浆内,中脑黑质p-c-Jun表达水平明显下降。结论p-c-Jun表达对亚急性帕金森病MPTP模型中脑黑质COX-2表达中可能起重要调控作用;抑制p-c-Jun表达对帕金森病小鼠可能具有一定的神经保护作用。

Objective To investigate the effect ofphophorylated c-Jun （p-c-Jun） expression on the expression of COX-2 in the substantia nigra （SN） of the MPTP mouse model of subacute Parkinson disease （PD） and explore the possible mechanism of the dopaminergic （DA） neuron death in PD. Methods C57BL/6N mice were treated with MPTP to establish subacute PD model. The changes of TH-, COX-2- and p-c-Jun-positive cells, and the expression levels of TH, COX-2 and p-c-Jun in the SN in the midbrain were observed with inmmunohistochemistry and Western blotting before and after administration of SP600125, a specific JNK inhibitor. Results Compared with the mice in control group, the PD mice exhibited typical symptoms of PD. The number of TH-positive neurons and expression level of TH in the model group were significantly reduced in the substantia nigra by about 65% and 75% （P〈0.001） 7 days alter the fifth injection of MPTP. The number of COX-2-immunoreactive cells and the expression level of COX-2 were significantly increased. P-c-Jun was specifically expressed in the nuclei of neurons and p-c-Jun expression level was significantly increased in the SN 6 h after the third injection of MPTP. Double-labeling immunofluorescence assay showed coexpression of COX-2 and p-c-Jun in TH-positive neurons in the SN. In mice treated with JNK inhibitor, the number of TH-positive neurons and TH expression level in the SN was only decreased by 15% and 20% as compared with the control group （P〈0.001） 7 days after the fifth injection of MPTP, COX-2-positive cell number and COX-2 expression level were obviously reduced as compared with the model group （P〈 0.001）, and p-c-Jun was expressed mainly in the cytoplasm of the neurons whose expression level in SN were significantly decreased 6 h after the third injection of MPTP. The PD mice treated with SP600125 showed slight behavioral symptoms.Conclusion P-c-Jun expression may play an important role in mediating COX-2 expression in the SN in the MPTP model of subacute PD, and inhibiting p-c-Jun activity may provide neuroprotection to the mouse model.