Reelin protects against pathological α-synuclein accumulation and dopaminergic neurodegeneration after environmental enrichment in Parkinson's disease.

Two of the primary features of Parkinson's disease (PD) are the accumulation of α-synuclein (α-Syn) and the depletion of lysosomal-associated membrane protein 1 (LAMP1) in the brain. Beneficial effects of environmental enrichment (EE) have been reported on the activation of lysosomal function and the amelioration of PD symptoms. Furthermore, Reelin could be a novel therapeutic target in PD. Hence, in this study, we validated the effects of EE on the activation of LAMP1 via Reelin in PD. Heterogeneous α-Syn (A53T)-overexpressing transgenic mice (age 6 and 16 months) were exposed to EE for 8 weeks. After motor and cognitive tests, brain tissues were obtained from mice and subjected to immunohistochemistry and molecular analyses. EE ameliorated motor and non-motor symptoms, protected dopamine neurons, and reduced pathological α-Syn accumulation in the early stage of PD. Striatal Reelin levels were altered depending on the disease stage and regulated by EE in PD mice. To elucidate the underlying mechanism of the effect of EE on PD, we performed further molecular and cellular analyses using activated preformed fibril (PFF)-induced SH-SY5Y cells, an in vitro model of PD, which were treated with recombinant Reelin protein and a Reelin blocker, CR-50. The CR-50 increased pathological α-Syn accumulation and accelerated dopamine neuronal degeneration by decreasing LAMP1 in the PFF-induced PD model. Our results showed that Reelin increased LAMP1 after EE and decreased pathological α-Syn accumulation, thus protecting dopamine neurons from degeneration in the striatum and substantia nigra, and ameliorating neurobehavioral deficits. These results suggest that Reelin is a promising target in treating histopathological changes and improving behavioral symptoms associated with PD.

Environmental Enrichment and Estrogen Upregulate Beta-Hydroxybutyrate Underlying Functional Improvement.

Environmental enrichment (EE) is a promising therapeutic strategy in improving metabolic and neuronal responses, especially due to its non-invasive nature. However, the exact mechanism underlying the sex-differential effects remains unclear. The aim of the current study was to investigate the effects of EE on metabolism, body composition, and behavioral phenotype based on sex. Long-term exposure to EE for 8 weeks induced metabolic changes and fat reduction. In response to the change in metabolism, the level of ßHB were influenced by sex and EE possibly in accordance to the phases of estrogen cycle. The expression of ß-hydroxybutyrate (ßHB)-related genes and proteins such as monocarboxylate transporters, histone deacetylases (HDAC), and brain-derived neurotrophic factor (BDNF) were significantly regulated. In cerebral cortex and hippocampus, EE resulted in a significant increase in the level of ßHB and a significant reduction in HDAC, consequently enhancing BDNF expression. Moreover, EE exerted significant effects on motor and cognitive behaviors, indicating a significant functional improvement in female mice under the condition that asserts the influence of estrogen cycle. Using an ovariectomized mice model, the effects of EE and estrogen treatment proved the hypothesis that EE upregulates ß-hydroxybutyrate and BDNF underlying functional improvement in female mice. The above findings demonstrate that long-term exposure to EE can possibly alter metabolism by increasing the level of ßHB, regulate the expression of ßHB-related proteins, and improve behavioral function as reflected by motor and cognitive presentation following the changes in estrogen level. This finding may lead to a marked improvement in metabolism and neuroplasticity by EE and estrogen level.

Reduced Interaction of Aggregated α-Synuclein and VAMP2 by Environmental Enrichment Alleviates Hyperactivity and Anxiety in a Model of Parkinson's Disease.

Parkinson's disease (PD) is a prevalent motor disease caused by the accumulation of mutated α-synuclein (α-Syn); however, its early stages are also characterized by non-motor symptoms, such as olfactory loss, cognitive decline, depression, and anxiety. The therapeutic effects of environmental enrichment (EE) on motor recovery have been reported, but its effects on non-motor symptoms remain unclear. Herein, we reveal the beneficial effects of EE on PD-related non-motor symptoms and changes in synaptic plasticity in the nucleus accumbens. To investigate its therapeutic effects in the early phase of PD, we randomly assigned eight-month-old mice overexpressing human A53T (hA53T) α-Syn to either the EE or standard condition groups for two months. Next, we performed behavioral tests and biochemical and histological analyses at 10 months of age. EE significantly alleviated locomotor hyperactivity and anxiety during the early stages of PD. It normalized the levels of tyrosine hydroxylase, phosphorylated and oligomeric α-Syn, and soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex-forming proteins, including synaptosomal-associated protein, 25 kDa, syntaxin1, and vesicle-associated membrane protein 2 (VAMP2). Moreover, the interactions between VAMP2 and pSer129 α-Syn were markedly reduced following EE. The restoration of synaptic vesicle transportation status may underlie the neuroprotective effects of EE in hA53T α-Syn mice.

Reelin Alleviates Mesenchymal Stem Cell Senescence and Reduces Pathological α-Synuclein Expression in an In Vitro Model of Parkinson's Disease.

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. The mechanisms underlying PD remain to be fully elucidated, and research into treatments for this condition is ongoing. Recent advances in genetic research have shed light on the mechanisms underlying PD. In this study, we used PD and control mesenchymal stem cells (MSCs) obtained from adipose tissues to confirm the differences between groups at the cellular and molecular levels. The results revealed that in PD MSCs, cell viability was clearly lower, and the rate of cell senescence was higher compared to the controls. Next, to compare the gene expression in PD and control cells, transcriptome analysis was performed. Genes in pathways, including extracellular matrix (ECM) receptor interaction, P53 signaling, and focal adhesion, were down-regulated in PD. Among genes related to ECM receptor interaction, RELN gene expression was markedly decreased in PD cells; however, after being treated with recombinant Reelin protein, a significant increase in cell viability and a decrease in α-Synuclein aggregation and cell senescence were observed. In conclusion, Reelin affects PD by positively influencing the cell characteristics. Our findings will facilitate research into new treatments for PD.

Environmental Enrichment Attenuates Oxidative Stress and Alters Detoxifying Enzymes in an A53T α-Synuclein Transgenic Mouse Model of Parkinson's Disease.

Although environmental enrichment (EE) is known to reduce oxidative stress in Parkinson's disease (PD), the metabolic alternations for detoxifying endogenous and xenobiotic compounds according to various brain regions are not fully elucidated yet. This study aimed to further understand the role of EE on detoxifying enzymes, especially those participating in phase I of metabolism, by investigating the levels of enzymes in various brain regions such as the olfactory bulb, brain stem, frontal cortex, and striatum. Eight-month-old transgenic PD mice with the overexpression of human A53T α-synuclein and wild-type mice were randomly allocated to either standard cage condition or EE for 2 months. At 10 months of age, the expression of detoxifying enzymes was evaluated and compared with wild-type of the same age raised in standard cages. EE improved neurobehavioral outcomes such as olfactory and motor function in PD mice. EE-treated mice showed that oxidative stress was attenuated in the olfactory bulb, brain stem, and frontal cortex. EE also reduced apoptosis and induced cell proliferation in the subventricular zone of PD mice. The overexpression of detoxifying enzymes was observed in the olfactory bulb and brain stem of PD mice, which was ameliorated by EE. These findings were not apparent in the other experimental regions. These results suggest the stage of PD pathogenesis may differ according to brain region, and that EE has a protective effect on the PD pathogenesis by decreasing oxidative stress.