Controlled-release levodopa methyl ester/benserazide-loaded nanoparticles ameliorate levodopa-induced dyskinesia in rats

Abstract

Xinxin Yang1*, Ruiyuan Zheng2*, Yunpeng Cai2, Meiling Liao2, Weien Yuan1,2, Zhenguo Liu11Department of Neurology, Xinhua Hospital (affiliated to Shanghai Jiaotong University School of Medicine), 2School of Pharmacy, Shanghai Jiaotong University, Shanghai, People's Republic of China*Xinxin Yang and Ruiyuan Zheng contributed equally to this workBackground: Levodopa remains the most effective drug in the treatment of Parkinson's disease. However, long-term administration of levodopa induces motor complications, such as levodopa-induced dyskinesia. The mechanisms underlying levodopa-induced dyskinesia are not fully understood.Methods: In this study, we prepared levodopa methyl ester (LDME)/benserazide-loaded nanoparticles, which can release LDME and benserazide in a sustained manner. Dyskinesia was induced in rats by repeated administration of levodopa then treated with LDME plus benserazide or the same dose of LDME/benserazide-loaded nanoparticles. Apomorphine-induced rotations and abnormal involuntary movements (AIMs) were measured on treatment days 1, 5, 10, 15, and 20. In addition, the levels of phosphorylated dopamine- and cyclic adenosine monophosphate-regulated phosphoprotein of 32 kDa, extracellular signal-regulated kinases 1/2, and ΔfosB were determined by Western blot. Tau levels were determined by Western blot and immunohistochemistry. Dynorphin levels in the striatum and cortex of rats were measured using enzyme-linked immunosorbent assay.Results: Over the course of levodopa treatment, the rats developed abnormal AIMs, classified as locomotive, axial, orolingual, and forelimb dyskinesia. The degree of reduction of apomorphine-induced rotations was comparable in dyskinetic rats treated with LDME plus benserazide or LDME/benserazide-loaded nanoparticles. The axial, limb, and orolingual (ALO) AIMs of dyskinetic rats treated with LDME/benserazide-loaded nanoparticles were 14 ± 2.5, 9 ± 2.0, and 10 ± 2.1 on treatment days 10, 15, and 20, respectively, which were significantly reduced compared with dyskinetic rats treated with LDME plus benserazide (25 ± 3.7, 27 ± 3.8, and 25 ± 3.5, respectively). The locomotive AIMs of dyskinetic rats treated with LDME/benserazide-loaded nanoparticles were 2.3 ± 0.42, 1.7 ± 0.35, and 1.6 ± 0.37 on treatment days 10, 15, and 20, respectively, which were also reduced compared with dyskinetic rats treated with LDME plus benserazide (4.4 ± 0.85, 4.7 ± 0.95 and 4.8 ± 0.37, respectively). Western blot showed that the levels of phosphorylated dopamine- and cyclic adenosine monophosphate-regulated phosphoprotein of 32 kDa, extracellular signal-regulated kinases 1/2, tau, and ΔfosB in dyskinetic rats treated with LDME/benserazide-loaded nanoparticles were 134.6 ± 14.1, 174.9 ± 15.1, 134.2 ± 19.3, and 320.5 ± 32.8, respectively, which were significantly reduced compared with those of dyskinetic rats treated with LDME plus benserazide (210.3 ± 19.7, 320.8 ± 21.9, 340.4 ± 27.1, and 620.7 ± 48.3, respectively). Immunohistochemistry indicated that the level of phosphorylated tau was (7.2 ± 1.1) × 104 in dyskinetic rats treated with LDME/benserazide-loaded nanoparticles. However, the tau level was only (14.6 ± 2.3) × 104 in LDME plus benserazide-treated dyskinetic rats. There was a significant difference between the two groups. Enzyme-linked immunosorbent assay showed that dynorphin levels in the striatum and cortex of dyskinetic rats treated with LDME/benserazide-loaded nanoparticles were 5.7 ± 1.2 and 4.8 ± 0.87, respectively, which were significantly reduced compared with LDME plus benserazide-treated dyskinetic rats (13.3 ± 2.1 and 8.1 ± 1.1 for the striatum and cortex, respectively).Conclusion: Results suggest that LDME/benserazide-loaded nanoparticles can be used to reduce the expression of dyskinesia in dyskinetic rats.Keywords: Parkinson’s disease, levodopa-induced dyskinesia, ∆fosB, dopamine, cAMP-regulated phosphoprotein of 32 kDa, extracellular signal-regulated kinases 1/2, tau