Inhibition Of Baicalein On Tremor In Parkinsonian Animal Models And Mechanism Study

Baicalein (5, 6, 7-trihydroxyflavone) is one of the major flavonoids originally isolated from the roots of the traditional Chinese herbal medicine Huangqin,Huangqin Scutellaria baicalensis Georgi. Baicalein is a major active ingredient of Huangqin. Baicalein has a variety of biological activities, such as antibacterial, antiviral, anti-inflammatory, anti-allergies,antioxidant and free radical scavenger, anti-tumor, antithrombotic. Baicalein is commonly used for treating inflammatory, tumor, fibrous degeneration, cardiovascular and cerebral vessels disease. Recent studies had shown that baicalein had neuron-protection against neuronal injury secondary to ischemia insult, and attenuated inflammation-mediated degeneration of dopaminergic neurons. These pharmacologic properties suggest that baicalein may be a useful agent for prevention or treatment of neurodegenerative diseases such as Parkinson's disease.Baicalein showed a significant neuron-protection by high-flux screening in our laboratory in 2007,and was determined to be a lead compound. However, baicalein has a pool dissolvability and scarcely dissolve in water. Thus, our topic group further studied the crystal form of the chemical composition of baicalein. The result showed that baicalein possessed polymorphism. Moreover, ? crystal form of baicalein was determined to be a superiority drug crystal because of its dominant position in stability and absorbance by constancy and biological test. The result of preclinical studies showed that baicalein reduced PD tremors and related symptom such as neurosis and daily living dyskinesia. These pharmacologic properties suggest baicalein may be a distinct agent for treatment of Parkinson's disease, and has a favorable drug worth and exploitation perspective.Chapter ? Progress of research on baicalein for treating central nervous system degenerative diseaseFirst of all, this chapter has reviewed the progress in pharmacological research in a great deal of literature on the basis of baicalein in recently several decades. This review included the following seven areas: antibacterial and antiviral, anti-inflammatory and anti-allergies,anti-oxidation, anti-tumor, anti-fibrosis, the protective effect on the cardiovascular, the protective effect of the brain and the protective effect of neuron. And then in section II, we chose baicalein and central nervous system degenerative disease as the subject and discussed the science nature of baicalein in treating central nervous system degenerative disease. The content includes the inhibiting of promoter of cellula nervosa degenerative disease, the interrupting of the cellula nervosa in signal transmission and activating the nerve protective mechanism of internal source. In section ?, baicalein and Parkinson's disease were discussed.Finally, this chapter points out the current study about baicalein of existing problems, and the research behind the idea put forward.Chapter ? Assessment of the treatment effect of baicalein in 6-OHDA - model of Parkinsonian tremor and elucidation of the mechanismIn this chapter, we evaluated the effects of baicalein on the parkinsonian tremor using unilateral 6-OHDA lesions of the medial forebrain bundle (MFB) in rats, and examine the changes of neurotransmitter concentrations, neuronal activity and TH, DAT, VMAT2,GFAP,OX42, GS,GABA-T, A2A,D1 R ? D2Rprotein expression. The aim is to elucidata the mechanism of baicalein on the parkinsonian tremor. The results further confirmed results of the preliminary research from our laboratory and came to the following conclusions:1. 6-OHDA could significantly augment the burst frequency and burst amplitude in a dose -response manner. Time-response of baicalein showed that baicalein reduced the amplitude and frequency of tremors at 10 minutes post-dose, with peak effects appearing at about 30 minutes,continuing for further 5 hours, which is similar to madopar.2. The difference of Pathophysiology between tremor predominant PD rats and rotation predominant PD rats showed that in rats with tremor only, dopaminergic lesions were mostly confined to SNc and the degree of injury was relatively slight, resulting in neuronal dysfunction in the connections of the SNc with the pallidum and the STN. However, in rats with tremor only, dopaminergic lesions were mostly confined to SNM and SNL, and the degree of injury was relative severity, resulting in neuronal dysfunction in the connections of the SN with the striatum.3. Baicalein facilitation of inhibitory output of the GPe and suppression of excitatory output of the STN caused reversed inhibitory outflow and normalized motor functional of basal ganglia through balancing the disorder of neurotransmitter including DA?Glu and GABA in basal ganglia. The regulation of baicalein on DA inferior to Glu and GABA explained that baicalein had significantly anti-tremor action, but no effect in rotation.4. Baicalein exerts the ability to balance neurotransmitter through increasing DAT and GS expression and decreasing GABA-T expression.5. The effect of anti - tremor of baicalein may be related to up regulating D1 and D2 receptor and down regulating A2A receptor.6. Baicalein exerts the neuronal protection action through attenuating the excessive activation of astrocyte and glial cell.Chapter ? Assessment of the treatment effect of baicalein in model of MPTP - Macaca fascicularis and elucidation of the mechanismIn order to further confirming the anti-tremor of baicalein, in this chapter, we evaluated the effects of baicalein and elucidatad of the mechanism on the parkinsonian using MPTP -Macaca fascicularis models which mimics human PD in symptom, pathology and biochemistry, and much more stable and reliable. The present study showed that baicalein can significantly improve the abnormal behavior in MPTP-treated monkeys including arm movements disturbance, freezing,bradykinesia and resting tremor. Following the assessment of ethology, we studied the change of parkinsonian - related zymology in mRNA level by realtime RT-PCR. The results showed that baicalein up regulated TH mRNA expression,confirming its neuronal protection action. Besides, baicalein down regulated COMT, MAO-B and GABA-T mRNA levels and up regulated GS mRNA levels, further confirming the balancing action of baicalein on the disorder of neurotransmitter including DA?Glu and GABA in basal ganglia in PD. The results of COI?GAD67 and GDH showed that baicalein facilitate the inhibitory output of the GPe, and suppress the excitatory output of the STN and inhibitory output of the GPi. These results further confirmed that baicalein exerts the ability to anti-tremor through balancing neurotransmitter disorder and normalizing the neuronal activity of GPi?GPe ? STN.Chapter IV Mechanism Study of Baicalein on Glu Induced Neurotoxicity in Cultured Dopaminergic Neurons.The important role of Glu in PD was gradually realized following the study on parkinsonian disease. Glu could potentiate dopaminergic neurodegeneration via excitotoxicity and oxidative toxicity. Besides, as a compensatory mechanism in order to maintain dopamine homeostasis, the increase in glutamate release of STN neurons contributed to the disorder of mortor circle of basal ganglia and the generate of mortor symptom of PD. We found that baicalein had a significant inhibition on Glu transmitter in experiment of Chapter II and III.Based on these contexts, we investigated the antagonism of baicalein on Glu -induced excitotoxicity and oxidative toxicity in cultured mesencephalic dopaminergic cells, and the expression of downstream protein of Glu were examined. The results showed that baicalein significantly inhibited the Glu - induced oxidative toxicity through increasing the cell viability and mitochondrial membrane potential, decreasing the contents of ROS, inhibiting LDH leakage, and the last inhibiting cell apoptosis. Baicalein could inhibit the [Ca2+] i and NO increase induced by Glu using Fura-2 microfluorimetry and chromium reduction method.These results suggest that baicalein could inhibit the Glu -induced excitotoxicity, and suppress the excitatory output of the STN and improve the motor symptom of PD. The result in western blotting showed that the inhibition of baicalein on the P-nNOS expression seems to be responsible for the anti- excitatory glutamate toxicity of baicalein. The result of FOS protein suggests that baicalein could a long-term regulation action on anti-PD tremor through down regulating the FOS expression. Baicalein had no effect on the P-CaMKII expression.Recent studies have shown T-type Ca2+ channels may be a new target on treatment of parkinsonian tremor. In PD, the Reticular Nucleus of the thalamus (NRT)-mediated inhibitory post-synaptic potentials, as a result of the disorder of mortor circle of basal ganglia, active T-type Ca2+ channels and trigger the low threshold Ca+ spike (LTS). LTS allows the NRT neurons produced rhythmicity burst, moreover serves to amplify and drive thalamocortical rhythmicity and muscle tremor in periphery. This process was regard as the final pathway in tremor production. Based on these contexts, we investigated the effect of baicalein on the expression of T-type Ca2+ channels protein CAV3.1 and CAV3.3. The results showed that baicalein significantly down regulated the expression of CAV3.1 and CAV3.3. The results suggest that the effect may be a new target on the treatment of parkinsonian tremor.Chapter V Comparation of the effect among flavonoids and combination on the treatment of parkinsonian tremorIn this chapter, we compared the effect among flavonoids and combination on the treatment of parkinsonian tremor. The results showed that the anti-PD tremor of flavonoid had significant preponderance compared with the essential tremor inhibitor Inderal and the classical anti-PD Madopar. The results of symphysial medication showed that the flavonoids may be a similarly or homoplastic mechanism. Thus, further studying the mechanism of anti-PD of flavonoids, searching the active lead compound of neuronal system and finding the potential high performance and low toxin medicine would be a far-reaching significance.The various chapters of the above research findings, we conclude that the anti-PD tremor of baicalein mainly through:1. balancing the disorder of neurotransmitter including DA?Glu and GABA in basal ganglia.2. Up regulating DAT and GS expression, down regulating GABA-T expression, inhibiting COMT and MAO-B mRNA expression.3. Up regulating D1 and D2 receptor, and down regulating A2A receptor.4. Inhibiting the Glu -induced oxidative toxicity through increasing the cell viability and mitochondrial membrane potential, decreasing the contents of ROS, inhibiting LDH leakage,and the last inhibiting cell apoptosis.5. Inhibiting the Glu -induced excitotoxicity through inhibit the [Ca2+] i, nNOS expression and NO increase.6. Down regulating the increased FOS expression induced by Glu.7. Down regulating the expression of T-type Ca2+ channels protein CAV3.1 and CAV3.3.