Higher alpha-synuclein aggregate density does not lead to more severe dopaminergic cell loss in the AAV-mediated overexpression model of Parkinson’s Disease: A time- course study

Year 2021, Volume: 25 Issue: 3, 352 - 358, 27.06.2025

Banu Cahide Tel , Inci Kazkayası , Gökçen Telli Elif Çinar Sevgi Uğur Mutluay , Gül Yalçin-çakmakli Esen Saka Bülent Elibol

https://doi.org/10.29228/jrp.25

Abstract

Pathological intracellular aggregation of alpha-synuclein (a-syn) is the hallmark of Parkinson’s disease (PD). Our aim is to explore the outcomes of long-term a-syn pathology with its functional correlates in the PD model by AAV (adeno-associated virus)-mediated a-syn overexpression in substantia nigra (SN). Female Wistar rats (220-260 g) received a unilateral injection of AAV-human-a-syn or green fluorescent protein (GFP) gene into the SN. The animals were tested for motor functions with cylinder test at 8, 12 weeks or 9 months post-injection. The intensity of a-syn accumulation or GFP in striatum and dopaminergic neuronal loss in SN, dopaminergic terminal loss in striatum and synaptic integrity were analyzed by a-syn, GFP, tyrosine hydroxylase (TH) and synaptophsin immunohistochemistry, respectively. At all time-points, AAV-human-a-syn injected animals displayed more motor dysfunction and TH- positive cell loss compared to AAV-GFP injected group. A-syn immunoreactivity was present in the nigral neurons as well as the striatal terminals in all animals that received AAV-a-syn. Striatal TH density analysis showed a decrease in both 12-weeks and 9 months a-syn groups compared to controls. However, TH-positive neuron count was lower in 9- months group compared to 12-weeks group. Hence, the motor performance of 9-month group showed an improvement which may be a sign of a compensatory mechanisms against a-syn-induced neurodegeneration. The findings of this study implicate that higher a-syn density in SN does not always lead to worse motor function or more severe dopaminergic cell loss. This may support the hypothesis that a-syn aggregates are the end-product of a cellular defense mechanism rather than being causative pathology.

Keywords

Alpha-synuclein , Parkinson’s disease , adeno associated viral vectors , animal model.

References

• [1] Chartier S, Duyckaerts C. Is Lewy pathology in the human nervous system chiefly an indicator of neuronal protection or of toxicity? Cell Tissue Res. 2018; 373(1): 149-60. [CrossRef]
• [2] Titova N, Schapira AHV, Chaudhuri KR, Qamar MA, Katunina E, Jenner P. Nonmotor Symptoms in Experimental Models of Parkinson's Disease. Int Rev Neurobiol. 2017; 133: 63-89. [CrossRef]
• [3] Chiu WH, Depboylu C, Hermanns G, Maurer L, Windolph A, Oertel WH, Ries V, Höglinger GU. Long-term treatment with L-DOPA or pramipexole affects adult neurogenesis and corresponding non-motor behavior in a mouse model of Parkinson's disease. Neuropharm. 2015; 95: 367-76. [CrossRef]
• [4] Kirik D, Rosenblad C, Burger C, Lundberg C, Johansen TE, Muzyczka N, et al. Parkinson-like neurodegeneration induced by targeted overexpression of alpha-synuclein in the nigrostriatal system. J Neurosci. 2002; 22(7): 2780-91. [CrossRef]
• [5] Decressac M, Mattsson B, Lundblad M, Weikop P, Bjorklund A. Progressive neurodegenerative and behavioural changes induced by AAV-mediated overexpression of alpha-synuclein in midbrain dopamine neurons. Neurobiol Dis. 2012; 45(3): 939-53. [CrossRef]
• [6] Gombash SE, Manfredsson FP, Kemp CJ, Kuhn NC, Fleming SM, Egan AE, et al. Morphological and behavioral impact of AAV2/5-mediated overexpression of human wildtype alpha-synuclein in the rat nigrostriatal system. PLoS One. 2013; 8(11): e81426. [CrossRef]
• [7] Oliveras-Salva M, Van der Perren A, Casadei N, Stroobants S, Nuber S, D'Hooge R, et al. rAAV2/7 vector-mediated overexpression of alpha-synuclein in mouse substantia nigra induces protein aggregation and progressive dose-dependent neurodegeneration. Mol Neurodegener. 2013; 8: 44. [CrossRef]
• [8] Van der Perren A, Van den Haute C, Baekelandt V. Viral vector-based models of Parkinson's disease. Curr Top Behav Neurosci. 2015; 22: 271-301. [CrossRef]
• [9] Bourdenx M, Dovero S, Engeln M, Bido S, Bastide MF, Dutheil N, et al. Lack of additive role of ageing in nigrostriatal neurodegeneration triggered by alpha-synuclein overexpression. Acta Neuropathol Commun. 2015; 3: 46. [CrossRef]
• [10] Ulusoy A, Decressac M, Kirik D, Bjorklund A. Viral vector-mediated overexpression of alpha-synuclein as a progressive model of Parkinson's disease. Prog Brain Res. 2010; 184: 89-111. [CrossRef]
• [11] Mutluay SU, Çınar E, Yalçın Çakmaklı G, Ulusoy A, Elibol B, Tel BC. Modelling Non-motor Symptoms of Parkinson’s Disease: AAV Mediated Overexpression of Alpha-synuclein in Rat Hippocampus and Basal Ganglia. Turk J Neurol. 2020; 26(4): 322-329. [CrossRef]
• [12] Albert K, Voutilainen MH, Domanskyi A, Airavaara M. AAV Vector-Mediated Gene Delivery to Substantia Nigra Dopamine Neurons: Implications for Gene Therapy and Disease Models. Genes (Basel). 2017; 8(2): 63. [CrossRef]
• [13] Koprich JB, Johnston TH, Huot P, Reyes MG, Espinosa M, Brotchie JM. Progressive neurodegeneration or endogenous compensation in an animal model of Parkinson's disease produced by decreasing doses of alpha-synuclein. PLoS One. 2011; 6(3): e17698. [CrossRef]
• [14] Landeck N, Buck K, Kirik D. Toxic effects of human and rodent variants of alpha-synuclein in vivo. Eur J Neurosci. 2017; 45(4): 536-547. [CrossRef]
• [15] Cinar E, Yalcin-Cakmakli G, Saka E, Ulusoy A, Yuruker S, Elibol B, et al. Modelling cognitive deficits in Parkinson's disease: Is CA2 a gateway for hippocampal synucleinopathy? Exp Neurol. 2020; 330: 113357. [CrossRef]
• [16] Albert K, Voutilainen MH, Domanskyi A, Piepponen TP, Ahola S, Tuominen RK, et al. Downregulation of tyrosine hydroxylase phenotype after AAV injection above substantia nigra: Caution in experimental models of Parkinson's disease. J Neurosci Res. 2019; 97(3): 346-61. [CrossRef]
• [17] Delenclos M, Faroqi AH, Yue M, Kurti A, Castanedes-Casey M, Rousseau L, et al. Neonatal AAV delivery of alpha-synuclein induces pathology in the adult mouse brain. Acta Neuropathol Commun. 2017; 5(1): 51. [CrossRef]
• [18] Eslamboli A, Romero-Ramos M, Burger C, Bjorklund T, Muzyczka N, Mandel RJ, et al. Long-term consequences of human alpha-synuclein overexpression in the primate ventral midbrain. Brain. 2007; 130(Pt 3): 799-815. [CrossRef]
• [19] Paxinos G WC. The Rat Brain in Stereotaxic Coordinates: Hard Cover Edition: AcademicPress; 2006.
• [20] Schneider CA, Rasband WS, Eliceiri KW. NIH Image to ImageJ: 25 years of image analysis. Nat Methods. 2012; 9(7):671-5. [CrossRef] [3] Chiu WH, Depboylu C, Hermanns G, Maurer L, Windolph A, Oertel WH, Ries V, Höglinger GU. Long-term treatment with L-DOPA or pramipexole affects adult neurogenesis and corresponding non-motor behavior in a mouse model of Parkinson's disease. Neuropharm. 2015; 95: 367-76. [CrossRef]