| Parkinson's disease(PD)is one of the most common neurodegenerative diseases,which has a higher incidence in middle-aged and elderly people and is called “the third killer”.Recently,China has the largest number of PD patients in the world.Either from social or family aspect,PD has become the serious social issue influencing quality of life,family health,and social economy development.PD's major pathologic features can be characterized by the selective loss of dopamine(DA)neurons in the substantia nigra pars compacta(SNc)and the reduction of DA in the striatum.These would result in a series of relative symptoms,especially motor symptoms(e.g.static tremor,muscle rigidity,akinesia,and postural reflex disorder).Many pathologic mechanisms have been proved to be associated with PD,such as oxidative stress,inflammatory response,mitochondrial dysfunction,iron deposition,abnormal protein aggregation,and apoptosis.These pathologic mechanisms make the treatment of PD extremely complex.At the same time,the side effects of tranditional PD drugs cannot be ignored.Therefore,it is vital significance to search for a new and effective target for relieving and healing PD.In recently years,studies have shown that PD is closely related to dysfunction of potassium channels.It is hence called channelopathy.Kv7/KCNQ/M potassium channels(also known as KCNQ channels)are voltage-dependent potassium channels,which have a wide distribution in basal ganglia.Our previous study has first recorded the KCNQ current in DA neurons of SNc area,and it is also confirmed that using KCNQ specificity channel blocker 10,10-bis(2-fluoro-4-pyridinylmethyl)-9(10H)-anthracenone(XE991)could significantly inhibit the KCNQ current,enhance the excitability of DA neurons,increase the spontaneous discharge frequency,and cluster discharge.However,these studies merely focused on the function of KCNQ channel under normal physiological conditions,and the biological effect of KCNQ channel in the pathogenesis of PD remains unknown.Therefore,we aimed to explore the modulatory effect of KCNQ channel during the process of PD.In this study,6-OHDA-induced damage in PD model rat was prepared.Immunofluorescence and immunohistochemistry were adopted to explore the effect of lateral ventricle administration of XE991 on the number of positive neurons of tyrosine hydroxylase(TH)in substantia nigra(SN)and Str,as well as TH protein expression;the changes of DA and its metabolites in Str were detected by high-performance liquid chromatography(HPLC);to further evaluate the effect of XE991 on the rats' balance ability,coordination ability,muscle rigidity,and motor speed,rotation behavior,open field test,balance beam,and grip strength test induced by apomorphine(APO)were executed,respectively;Finally,Retigabine,a KCNQ channel opener,was further given in lateral ventricle to observe changes in above tests.The results are as follows:1.By Western blots,it is verified that the expression of KCNQ4 was abundant in the normal rat's SNc region.2.In the 6-OHDA-induced PD model rats,the expression of TH protein in SN had significantly decreased to 12.5% of that in control group(P < 0.001).After continuous injection of different concentrations of XE991(1 ?mol/L,5 ?mol/L,and 10 ?mol/L)in lateral ventricle for 21 days,5 ?mol/L and 10 ?mol/L XE991 groups were able to antagonize the damage of DA neuron caused by 6-OHDA,respectively(P < 0.05,P < 0.01).3.For 6-OHDA group,the number of TH positive neurons in the lesioned region of SN decreased by 83.3%(P < 0.001).After treatment of 10 ?mol/L XE991 for 21 days,it was observed that the number of TH positive neurons increased to 45.6% of that in control group(P < 0.001).4.In 6-OHDA group,on the lesioneded region of the Str,the amount of DA and dihydroxyphenylacetic acid(DOPAC)and homovanillic acid(HVA)decreased by 84.5%,53.2% and 53.6% compared with the control group(P < 0.001).After treatment of 10 ?mol/L XE991 for 21 days,the amount of DA,DOPAC and HVA significantly increased(PDA < 0.01,PDOPAC < 0.001,PHVA < 0.01).5.Compared with control group,the number of TH-immunoreactive fibers markedly reduced in 6-OHDA group.After treatment of 10 ?mol/L XE991 for 21 days,the amount of positive TH-immunoreactive fibers significantly rose.6.The dyskinesia of PD rats was greatly improved by XE991.In the rotation test induced by APO,6-OHDA-lesioned rats display a significant increase of the number of contralateral rotations compared to the control group(P < 0.001);While,the rotation number of rats in XE991 group(10 ?mol/L)significantly reduced(P < 0.001).In the open field test,the mean velocity of the rats in 6-OHDA group was slower than that in control group(P < 0.05);after it is treated with XE991(10 ?mol/L)for 21 days,the mean motor speed was significantly improved compared with 6-OHDA group(P < 0.05).In the balanced beam test,the rats in 6-OHDA group had less score than the control group,and the balance and exercise coordination ability decreased much compared with control group(P < 0.001);Compared with 6-OHDA group,the score of XE991 group was significantly higher(P < 0.05),with the ability of balance and exercise coordination improving a lot.In the grip strength test,6-OHDA group showed a significant increase in the suspension time on steel wire compared with control group(P < 0.01);Compared with 6-OHDA group,XE991 could significantly improve the muscle rigidity(P < 0.05).7.In 6-OHDA group,the amount of TH protein in the SN region and the amount of DA,DOPAC and HVA in Str,slow motor speed,grip strength,and the balance and exercise coordination ability were significantly lower than that of control group(P < 0.01).And those results obviously improved in XE991 group(P < 0.05).Retigabine,a postassium channel operner,could completely antagonize the protective effect of XE991.The results showed that treating with XE991 could improve the damage of DA neuron in SN region of 6-OHDA-induced PD model rats,increase the expression of TH protein and the number of TH positive neurons in SN region,and promote the release of DA and TH positive TH neuronal fibers in Str area,thereby improving the function of SN-Str system and alleviating PD rats' dyskinesia.Further experimental results showed that the neuroprotective effects of XE991 could totally antagonized by the KCNQ channel opener Retigabine These results provided a new theoretical basis for involvement of KCNQ channel in PD,and provided a new strategy for medical treatment towards PD. |
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