Kaempferol ameliorated levodopa-induced dyskinesia in experimental rats: A role of brain monoamines, cFOS, FosB, Parkin, Pdyn, TH, and p-JNK

Background:L-dopa(Levodopa)is well known for managing PD(Parkinson’s disease);however,its prolonged use caused dyskinesia(LID).Due to the varied presentation of LID,effective treatment options are scarce.Flavonoids reported their neuroprotective activity by ameliorating acetylcholinesterase,monoamine oxidase,and neuroinflammation.Kaempferol is anotherflavonoid bearing these potentials.Aim:To evaluate neuroprotective activity of kaempferol in dyskinetic rats.Methods:PD was developed in Sprague-Dawley rats by injecting combination of L-ascorbic acid(10µL)+6-OHDA(12µg)in medial forebrain bundle to induce neuronal damage in substantial nigra(SNr).LID was induced by administrating combination of L-dopa(20 mg/kg)+benserazide HCl(5 mg/kg)for 42 days.Rats were concomitantly treated with amantadine(40 mg/kg)or kaempferol(25,50,and 100 mg/kg,p.o.).Results:Kaempferol(50 and 100 mg/kg)markedly(p<0.05)inhibited LID-induced abnormal involuntary movements(AIMs)and alternation in motor function.Kaempferol administration considerably(p<0.05)inhibited reduced mitochondrial complex activities,serotonin and dopamine levels,Bcl-2,and Tyrosine hydroxylase protein expressions in SNr.Additionally,kaempferol considerably(p<0.05)attenuated increased cFOS,FosB,Parkin,and Pdyn mRNAs expressions,Bax,cleaved caspase-3,caspase-3,and pJNK proteins levels;DOPAC and 5-HIAA levels in SNr.A positive correlation was reported between cFOS,FosB,Parkin,Pdyn,apoptosis,and TH with AIMs.Conclusion:Kaempferol effectively attenuated L-dopa-induced AIMs and dyskinesia via amelioration of alterations in cFOS,FosB,Parkin,Pdyn,Tyrosine hydroxylase,and apoptosis in the brain SNr.

Mechanism of over-activation in direct pathway mediated by dopamine D_1 receptor in rats with levodopa-induced dyskinesias

Objective To study the changes of prodynorphin （PDyn） gene expression and dopamine and cAMPregulated phosphoprotein of 32 kDa （DARPP-32） phosphorylation in rats with levodopa-induced dyskinesias （LID）, and to explore the mechanism of over-activation in direct pathway mediated by dopamine D1 receptor. Methods Parkinson＇s disease （PD） rats were received levodopa （10 mg/kg, i.p.） for 28 d to get the LID rats. According to the behavior scale, LID rats were divided into mild （n=8） and severe （n=16） groups. On day 29, 8 rats in severe LID group were given an acute intraperitoneal injection of MK-801 （0.1 mg/kg） 15 min before levodopa treatment （MK-801 group, n=8）. The normal rats received same course and dosage of levodopa as the control group （n=8）. Hybridization in situ was used to measure the expression of PDyn mRNA in striatum. Protein and mRNA levels of total DARPP-32 and phospho-Thr-34 DARPP-32 level were measured by immunoblotting and RT-PCR, respectively. Results The levels of PDyn mRNA and phospho-Thr-34 DARPP-32 increased significantly in LID rats compared with control rats （P〈0.01）, and they also increased markedly in severe LID group compared with mild group （P〈0.01）. Conclusion Phospho-Thr-34 DARPP-32 level was increased in LID rats, which contributed to the over-activation of direct pathway mediated by dopamine D1 receptor.

Quantitative Autoradiographic Study on Receptor Regulation in the Basal Ganglia in Rat Model of Levodopa-induced Motor Complications

In order to study neurotransmitter receptor regulation in the basal ganglia involved in the functional changes underlying levodopa-induced motor complications, quantitative autoradiography was used to observe receptor bindings of dopamine D1 and D2, N-methyl-D-aspartate （NMDA）, amino-3-hydroxy-5-methylisoxazole propionic acid （AMPA） and amino butyric acid （GABA） in the basal ganglia of rats that had unilateral nigrostriatal lesions and had been chronically treated with levodopa until motor complications developed. The rats were randomly assigned to three groups： normal, denervated and treatment-complicated groups. The results showed that response duration to levodopa became progressively shorter and abnormal involuntary movement （AIM） score was progressively increased during the course of levodopa treatment. Chronic treatment augmented D1 receptors more than denervation, and reduced D2 receptors that were also increased by dopamine denervation. Striatal NMDA receptors were substantially up-regulated in the treatment-complicated group. Levodopa treatment did not change receptors of nigral AMPA, pallidal GABA, and subthalamic GABA, which remained the same as that in denervation group. However, chronic treatment reversed the increase of nigral GABA receptors caused by the lesion. It was concluded that a shortening of response duration and AIM mimicked levodopa-induced motor complications of Parkinson＇s patients. These data suggested that up-regulation of dopamine D1 and NMDA receptors in the striatum leads to an imbalance of stimulation through the striatal output pathways, which is associated with levodopa-induced motor complications.

Effect of Antisense FosB and CREB on the Expression of Prodynor- phin Gene in Rats with Levodopa-induced Dyskinesias

The effects of antisense FosB and CREB intra-striatum injection on the expression of prodynorphin （PDyn） gene in striatal neurons of Levodopa-induced dyskinesias （LID） rats with Parkinson disease （PD） were explored. PD model in rats was established by 6-OHDA microinjection stereotaxically. The rats were treated with chronic intermittent Levodopa celiac injection for 28 days to get the LID rats. Antisense FosB and cAMP response element-binding protein （CREB） were injected into striatum of all rats respectively. In situ hybridization was used to measure the changes in the expression of PDyn mRNA in striatum and behavior changes were observed. The results showed after administration of antisense FosB, abnormal involuntary movement （AIM） was decreased and the expression of PDyn mRNA in striatum was increased in LID rats as compared with sense FosB group （P〈0.01, respectively）. As compared with the control group, the expression of PDyn mRNA in striatum was decreased by antisense CREB-treated LID group （P〈0.0 l） and compared with sense CREB treated LID group, antisense CREB-treated LID group showed no changes in AIM scores and the expressions of PDyn mRNA （both P〉0.05）. In conclusion, FosB protein, which replaced the CREQ could regulate the expression of PDyn mRNA and play critical role in the pathogenesis of LID.

The role of nerve growth factor inducible protein B in the pathogenesis of levodopa-induced dyskinesias

Objective： To study the role of the expression of nerve growth factor inducible protein B gene （NGFI-B） in striatum in the pathogenesis of levodopa-induced dyskinesias （LID）. Methods： The rat model of LID was treated with SCH 23390（1 mg/kg ip,a dopamine D1 antagonist） and haloperidol （1 mg/kg ip,a dopanfme D2 antagonist） respectively. Reverse transcriptase-polymerase chain reaction （RT-PCR） was used to measure the expression of NGFI-B mRNA in stiiatam and the behavior changes were observed. Resuits： After treatment with SCH23390, abnormal involuntary movement （AIM） in LID rats was decreased （ P 〈 0.05 ） and the expression of NGFI-B mRNA in striatum did not change significantly. After treatment with haloperidol, the changes of AIM in LID rats were not significant and the expression of NGFI-B mRNA was increased significantly（ P 〈 0.01）. Conclusion： LID is associated with over-expression of NGFI-B in striatum. Abnormal activity in the direct pathway and the basal ganglia circuit could be involved in the occurrence of LID.

Efficacy and safety of Tianqi Pingchan Granule,a compound Chinese herbal medicine,for levodopa-induced dyskinesia in Parkinson’s disease:A randomized double-blind placebo-controlled trial

Background Patients with Parkinson’s disease(PD)undergoing long-term levodopa therapy are prone to develop levodopa-induced dyskinesia(LID).Amantadine is the main drug recommended for the treatment of LID by current guidelines,but it is far from meeting clinical needs.Tianqi Pingchan Granule(TPG),a compound Chinese herbal medicine,has been developed to relieve symptom of LID.Objective This randomized controlled trial evaluated the efficacy and safety of the combination of TPG and amantadine for LID.Design,setting,participants and interventions This is a randomized double-blind placebo-controlled trial,conducted from January 2020 to August 2021 at 6 sites in Jiangsu,Zhejiang and Shanghai,China.One hundred PD patients with≥0.5 h of LID were randomly assigned to either the TPG plus amantadine group(TPG group)or the placebo plus amantadine group(placebo group),and treated for a period of 12 weeks.To ensure unbiased results,all study participants,investigators and sponsors were unaware of group allocations.Additionally,the data analysts remained blinded until the analysis was finalized.Main outcome measures The primary outcome was assessed using the Unified Dyskinesia Rating Scale(UDysRS)(Range 0–104).The key secondary end point was improvement of motor and non-motor symptoms.Safety analyses included all enrolled patients.Results One hundred patients were enrolled and randomized into the two treatment groups.The changes in UDysRS at week 12 were–11.02 for the TPG group and–4.19 for the placebo group(treatment difference–6.83[–10.53 to–3.12];P=0.0004).Adverse events were reported for 2 of 50 patients(4.0%)in each of the groups.Conclusion This study indicated that a 12-week treatment of amantadine plus TPG effectively reduced UDysRS scores and was well tolerated,demonstrating the efficacy and safety of TPG for the treatment of LID in PD.

The dual role of striatal interneurons:circuit modulation and trophic support for the basal ganglia

Striatal interneurons play a key role in modulating striatal-dependent behaviors,including motor activity and reward and emotional processing.Interneurons not only provide modulation to the basal ganglia circuitry under homeostasis but are also involved in changes to plasticity and adaptation during disease conditions such as Parkinson's or Huntington's disease.This review aims to summarize recent findings regarding the role of striatal cholinergic and GABAergic interneurons in providing circuit modulation to the basal ganglia in both homeostatic and disease conditions.In addition to direct circuit modulation,striatal interneurons have also been shown to provide trophic support to maintain neuron populations in adulthood.We discuss this interesting and novel role of striatal interneurons,with a focus on the maintenance of adult dopaminergic neurons from interneuronderived sonic-hedgehog.