| Parkinson’s disease(PD)is a progressive neurodegenerative disease common in middleaged and elderly people.Common motor symptoms of PD include impaired motor function,bradykinesia,quiescent tremor,and balance disorders.The neuropathological features of PD are progressive loss of dopaminergic neurons in substantia nigra(SN)and dopamine(DA)depletion in the striatum.The pathogenesis of PD is related to aging,environmental toxins,oxidative stress,neuroinflammation and other factors.However,up to now,the degeneration and death mechanism of DA-capable neurons in SN region during the pathogenesis of PD has not yet been clarified.In recent years,more and more evidences have shown that the iron content of SN in the midbrain is increased in PD patients and PD models,and abnormal iron accumulation of SN in the midbrain can cause damage to DA neurons.Cannabinoid 2 receptor(CB2 receptor)is expressed in both human and rodent brains.Studies have shown that activation of CB2 receptor in glial cells can protect DA neurons by inhibiting inflammatory response.Recent studies have found that human and mouse SN have co-localization of tyrosine hydroxylase(TH)positive neurons and CB2 receptors,but it is unclear whether the CB2 receptors in the DA neurons of the SN are involved in the pathogenesis of PD.To explore the mechanism of CB2 receptor’s involvement in the pathogenesis of PD,we study studied the effects of CB2 receptor agonist JWH133 on DA neurons in the SN region of the rat model with unilateral 6-OHDA damage,using behavioral,immunofluorescence,Western bolts and iron staining methods.The experimental results are as follows:1.The co-localization of TH positive cells and CB2 receptor-positive cells in SN region of rats was observed by double immunofluorescence staining.2.Compared with the control group,the 6-OHDA rats showed significant contralateral rotation behavior after subcutaneously injected Apomorphine(APO)on the neck at 7d,14 d,21d and 28d(P<0.001);Compared with the 6-OHDA group,the contralateral rotation behavior of rats with unilateral 6-OHDA damage was significantly improved in the CB2 agonist JWH133 co-treatment group,with the most significant decrease in the number of turns at 28d(P<0.001).3.Compared with the control group,the number of TH positive neurons in SN region on the damaged side was significantly decreased after 28 days of unilateral 6-OHDA damage(P<0.001);Compared with the 6-OHDA treatment group,the number of TH positive neurons in the SN area of the damaged side of rats with unilateral 6-OHDA damage in the JWH133co-treatment group was significantly increased(P<0.01).4.Compared with the control group,the expression level of TH protein in SN region on the damaged side of 6-OHDA rats was significantly decreased on d 7,14,21 and 28(P<0.001);Compared with the 6-OHDA group,the TH protein expression level in the SN region of the damaged side was significantly increased after JWH133 treatment for 7,14,21 and 28 days,and the difference was statistically significant.The expression level of TH protein in SN region of 6-OHDA rats was significantly decreased with time,The ratio of TH protein expression between JWH133 co-treatment group and 6-OHDA treatment group increased significantly over time.5.Compared with the control group,the number of iron staining positive cells in SN region of 6-OHDA rats increased significantly on day 28(P<0.001);Compared with the 6-OHDA group,the number of iron-stained positive cells in the damaged SN region of rats treated with JWH133 for a total of 28 days was significantly decreased(P<0.001).6.Compared with the control group,the expression of Ferroportin1(FPN1)protein in the SN region on the unilateral damage side of 6-OHDA rats on 28 days was decreased(P<0.05).Compared with the 6-OHDA treatment group,the expression of FPN1 protein in the damaged SN area of rats in the JWH133 co-treatment group was significantly increased(P<0.05).7.Compared with the control group,the expression of cyclooxygenase-2(COX-2)protein in SN region of the 6-OHDA rats increased on day 28(P<0.05);Compared with the 6-OHDA treatment group,the expression of COX-2 protein in the damaged SN region of rats in the JWH133 co-treatment group was decreased(P<0.05).These results indicate that CB2 receptor agonist JWH133 can improve the rotation behavior of APO-induced PD model rats with unilateral 6-OHDA damage,inhibit the damage of DA neurons in the SN region of the damaged side of rats with unilateral 6-OHDA damage,and play a neuroprotective role.We speculate the mechanism may be related to antagonism against 6-OHDA induced downregulation of FPN1 expression and up-regulation of COX-2expression,inhibiting brain iron accumulation,and thus playing an anti-inflammatory role or reducing iron poisoning.This study provides new experimental data for understanding the biological function of CB2 receptor and drug therapy for PD. |
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