Findings reveal an age-dependent progression of mitochondrial dysfunction in BAC-hR1441G SNc DA neurons, and dysregulation of calcium channels and uncoupling proteins emerges as a key mechanism contributing to bioenergetic failure, suggesting potential therapeutic targets to mitigate PD progression.
Abstract
Background
Mitochondrial dysfunction and oxidative stress are central to the pathogenesis of Parkinson's disease (PD), particularly affecting substantia nigra pars compacta (SNc) dopamine (DA) neurons. Here, we investigate how the R1441G mutation in leucine-rich repeat kinase 2 (LRRK2), a key genetic contributor to familial and sporadic PD, impacts mitochondrial function in midbrain DA neurons.
Methods
We employed a BAC transgenic mouse model overexpressing human LRRK2-R1441G (BAC-hR1441G) and crossed it with TH-mito-roGFP mice to enable mitochondria-targeted redox imaging specifically in DA neurons. Acute midbrain slices from 3-, 6-, and 10-month-old mice were imaged using two-photon microscopy to assess mitochondrial oxidative stress. In parallel, mitochondrial respiratory function, membrane potential flickering events, and expression of uncoupling proteins (UCP4/UCP5) were analyzed. Spatial transcriptomic profiling was performed using the GeoMx® Digital Spatial Profiler to uncover associated molecular alterations.
Results
We observed a progressive increase in mitochondrial oxidative stress in SNc DA neurons of BAC-hR1441G mice at 3, 6, and 10 months of age. This was accompanied by reduced respiratory complex activity, attenuated mitochondrial membrane potential flickering, and diminished expression of UCP4 and UCP5. Spatial transcriptomic analysis revealed dysregulation of genes linked to mitochondrial uncoupling, calcium signaling, and redox regulation in BAC-hR1441G SNc DA neurons.
Conclusions
These findings reveal an age-dependent progression of mitochondrial dysfunction in BAC-hR1441G SNc DA neurons. Dysregulation of calcium channels and uncoupling proteins emerges as a key mechanism contributing to bioenergetic failure, suggesting potential therapeutic targets to mitigate PD progression.
Dopaminergic neurons in the substantia nigra pars compacta are key targets of α-synuclein pathology and neurodegeneration in Parkinson’s disease (PD). It is thought that pathological accumulation of α-synuclein significantly contributes to nigral neuronal dysfunction and ensuing neuronal demise. In this study, we further assessed this possibility and interrogated the role of α-synuclein burden in compromising neuronal function and altering physiological neuronal pathways. In particular, we focused on nigral mitochondrial impairment and disruption of circadian regulatory pathways triggered by sustained α-synuclein expression. Using an in vivo AAV-mediated model, we show that α-synuclein accumulation over a period of 12 weeks is associated with mitochondrial complex I and IV deficits and leads to dopaminergic cell loss. Proximity ligation assays revealed association of both total and phosphorylated α-synuclein with mitochondrial proteins at a time (between 4 and 12 weeks) that paralleled the development of mitochondrial dysfunction. Spatial transcriptomic analysis of the substantia nigra identified coordinated alterations in genes involved in mitochondrial, metabolic, and circadian pathways, including increased expression of circadian-associated genes such as Nr1d1, Nr1d2, Cry2, Arntl2, and Csnk1e. At the protein level, α-synuclein overexpression was associated with a differential shift in cryptochrome protein expression, characterized by reduced CRY1 and increased CRY2. Data provide evidence of a specific window of time during which sustained α-synuclein burden results in direct α-synuclein-mitochondria interactions and nigral mitochondrial damage. During the same time period, a specific remodeling of molecular clock components occurs, providing a potential new mechanism contributing to metabolic and mitochondrial dysregulations and, ultimately, neuronal injury and degeneration.
S. O’Sullivan, Adrian Kacperczyk-Perdyan, A. Ulusoy et al.· bioRxiv· 0 citations
This work generates human induced pluripotent stem cell-derived midbrain dopaminergic neurons using both a 2D differentiation protocol and a recently developed 3D method based on the microencapsulation of hiPSCs in small alginate/fibronectin beads.
A. Zanon, E. Kerschbamer, D. Riekschnitz et al.· Communications Biology· 0 citations
Introduction: Parkinson’s disease (PD) is the most prevalent movement disorder, with global prevalence increasing by 153% since 1990. It is characterized by dopaminergic neuronal loss in the substantia nigra, driven in part by mitochondrial dysfunction and neuroinflammation. High-mobility group box 1 (HMGB1), a nuclear protein that acts as a damage-associated molecular pattern (DAMP) upon extracellular release, has been implicated in both processes, yet its role in PD remains underexplored. Hence, this study aims to investigate the role of HMGB1 and the effects of its inhibition in a zebrafish model of parkinsonism.
Materials and methods: Adult zebrafish were administered a single dose of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) via intraperitoneal (i/p) injection, followed by two doses of glycyrrhizin, an HMGB1 inhibitor, at day 1 and day 2 post-MPTP exposure. At day 3 post-injection, locomotor activity, gene expression, tissue morphology, and blood–brain barrier (BBB) permeability were assessed.
Results: HMGB1 inhibition improved locomotor deficits, reduced gene expression of inflammatory mediators: toll-like receptor 4b duplicate a (tlr4ba), nuclear factor kappa light polypeptide gene enhancer in B-cells 1 (nfκb), tumor necrosis factor alpha (tnfα), interleukin-1β (il1β), normalized mitochondrial quality control markers: PTEN-induced kinase 1 (pink1), parkin RBR E3 ubiquitin protein ligase (prkn), fission mitochondrial 1 (fis1), and attenuated BBB disruption. However, morphological alterations in the posterior tuberculum and subpallium regions of the brain persisted. Additionally, in silico analyses showed strong molecular interactions between 1-methyl-4-phenylpyridinium (MPP+) and dopamine transporter, as well as glycyrrhizin to HMGB1 in zebrafish, supporting translational relevance.
Conclusions: These findings suggest that HMGB1 is closely associated with the intersection of neuroinflammation and mitochondrial dysfunction in MPTP-induced parkinsonism. Modulating HMGB1 pathways helps mitigate these downstream functional and molecular impairments, highlighting its potential utility as an indirect biomarker and therapeutic target. Ultimately, this study supports the translational value of the zebrafish PD model for investigating complex neurodegenerative mechanisms.
Khairiah Razali, Mohd Hamzah Mohd Nasir, Jaya Kumar et al.· Academia Neuroscience and Br...· 0 citations
Findings support a model in which MCU-1-dependent elevation of [Ca2+]mito contributes to oxidative mitochondrial defects in PDR-1/Parkin-deficient muscle.
Masahiro Kawasumi, Mika Teranishi· Antioxidants· 0 citations
Astrocyte-specific mitochondrial dysfunctions and calcium dysregulation are identified as key features of LRRK2- and PRKN-related pathology, providing new insights into how glial metabolic alterations contribute to neurodegeneration in PD.
Giovanna C. Cavalcante, Camille C. Caldeira da Silva, É. Vogt et al.· bioRxiv· 0 citations
OBJECTIVE
To investigate the effects of targeting DYNC1I1 in cellular and mouse models of Parkinson's disease (PD). Methods The scRNA-seq dataset GSE243639 was analyzed to prioritize autophagy- and transport-related candidate genes in post-mortem substantia nigra samples from patients with PD and controls. SH-SY5Y cells were treated with 1mM MPP⁺ for 48h, and male C57BL/6 mice received MPTP at 30mg/kg/day for 5 consecutive days. DYNC1I1 was silenced with siRNA in cells and targeted with AAV-DYNC1I1 in mice. Autophagic-lysosomal status was evaluated using tandem mCherry-GFP-LC3B fluorescence and autophagy- and lysosome-related markers. Motor performance was assessed using the pole and rotarod tests.
RESULTS
DYNC1I1 was prioritized as a candidate gene on the basis of PD-associated differential expression, overlap with autophagy-related genes, enrichment in a dopaminergic neuron-related subpopulation, and biological relevance to intracellular transport. In MPP⁺-treated cells, DYNC1I1 knockdown reduced α-synuclein accumulation and phosphorylation and improved autophagic-lysosomal marker profiles. In MPTP-treated mice, AAV-DYNC1I1 treatment improved motor performance and TH-positive signal and reduced α-synuclein pathology and autophagic-lysosomal impairment. AAV-DYNC1I1 treatment was also associated with higher p-PI3K/PI3K and p-AKT/AKT ratios.
CONCLUSIONS
DYNC1I1-targeting interventions attenuated PD-related phenotypes in cellular and mouse models. The observed effects were accompanied by improved autophagic-lysosomal marker profiles and increased PI3K/AKT phosphorylation.
Yuyu Li, Li Xu, Hui Sun et al.· Brain Research Bulletin· 0 citations
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