Immunomodulatory drugs alleviate l-dopa-induced dyskinesia in a rat model of Parkinson's disease

Abstract

Background: Thalidomide and closely related analogues are used clinically for their immunomodulatory and antiangiogenic properties mediated by the inhibition of the proinflammatory cytokine tumor necrosis factor α. Neuroinflammation and angiogenesis contribute to classical neuronal mechanisms underpinning the pathophysiology of l-dopa-induced dyskinesia, a motor complication associated with l-dopa therapy in Parkinson's disease. The efficacy of thalidomide and the more potent derivative 3,6'-dithiothalidomide on dyskinesia was tested in the 6-hydroxydopamine Parkinson's disease model.

Methods: Three weeks after 6-hydroxydopamine infusion, rats received 10 days of treatment with l-dopa plus benserazide (6 mg/kg each) and thalidomide (70 mg/kg) or 3,6'-dithiothalidomide (56 mg/kg), and dyskinesia and contralateral turning were recorded daily. Rats were euthanized 1 hour after the last l-dopa injection, and levels of tumor necrosis factor-α, interleukin-10, OX-42, vimentin, and vascular endothelial growth factor immunoreactivity were measured in their striatum and substantia nigra reticulata to evaluate neuroinflammation and angiogenesis. Striatal levels of GLUR1 were measured as a l-dopa-induced postsynaptic change that is under tumor necrosis factor-α control.

Results: Thalidomide and 3,6'-dithiothalidomide significantly attenuated the severity of l-dopa-induced dyskinesia while not affecting contralateral turning. Moreover, both compounds inhibited the l-dopa-induced microgliosis and excessive tumor necrosis factor-α in the striatum and substantia nigra reticulata, while restoring physiological levels of the anti-inflammatory cytokine interleukin-10. l-Dopa-induced angiogenesis was inhibited in both basal ganglia nuclei, and l-dopa-induced GLUR1 overexpression in the dorsolateral striatum was restored to normal levels.

Conclusions: These data suggest that decreasing tumor necrosis factor-α levels may be useful to reduce the appearance of dyskinesia, and thalidomide, and more potent derivatives may provide an effective therapeutic approach to dyskinesia. © 2019 International Parkinson and Movement Disorder Society.

Keywords: l-dopa; 3,6′-dithiothalidomide; dyskinesia; immunomodulation; thalidomide.

FIG. 1.

TLD and DTT reduced the development of LID in hemiparkinsonian rats. Representative image of the 6-OHDA-infused SNc. (A) Development of AIMs during 10 days of treatment, score is shown as total seconds spent in AIMs in daily session, and linear regression of AIM development during 10 days of treatment (S, slope). (B) Development of AIMs (C) and contralateral turning (D) post-L-dopa injection during daily sessions (days 5 and 9); total limb and axial AIM score (E) and contralateral turns (F) in the whole treatment. Values represent the mean ± SEM. ^#P < 0.0001 for main treatment effect (B); *P < 0.05 versus V + dopa (B, D, F, I); ^{^}P < 0.01 vs TLD + dopa (F).

FIG. 2.

TLD and DTT reduced L-dopa-induced microgliosis and microglial TNF-α content in the dopamine-depleted Str and SNr. Representative confocal images showing TNF-α (yellow) in OX-42 (red)-positive cells in the Str (A–G); total volume occupied by OX-42 and colocalized with TNF-α (red columns) in the Str and SNr (H). Values represent the mean ± SEM. *P < 0.0001; ^#P < 0.05; ^P < 0.0001 versus unlesioned; °P < 0.05 versus Veh (1-way ANOVA followed by Tukey HSD post hoc test).

FIG. 3.

TLD and DTT reverted L-dopa-induced decrease of IL-10 content in the dopamine-depleted Str (A). Representative confocal images showing IL-10 (yellow) in OX-42 (red)-positive cells (B–H); volume of OX-42 colocalized with IL-10 (I). Total OX-42-occupied volume is shown in Figure 2. TNF-α/IL-10 volume ratio expressed as % versus OX-42 volume (L). Values represent the mean ± SEM.^{^}*P < 0.0001; °P < .0001 versus Veh. DL, dorsolateral striatum.

FIG. 4.

DTT prevented L-dopa-induced angiogenesis in the SNr. Representative confocal images showing GFAP (red) and vimentin (green, A–E) or VEGF (yellow, G–M) in the SNr, and total volume occupied by vimentin (F) and VEGF (N). Values represent the mean ± SEM. *P < 0.0001.

FIG. 5.

Representative confocal images of GLUR1 protein expression in the dopamine-depleted Str (A) and GLUR1 levels expressed as % of the analyzed volume (B).