Objective: Our objective in this study was to elucidate the mechanisms underlying the release of mtDNA in cellular models of Parkin-associated Parkinson’s disease and to intervene in these processes using mitochondrially targeted drugs
Background: Dysregulated trafficking of mitochondrial content, specifically the release of mitochondrial DNA (mtDNA) into the cytosol or blood circulation, are well-documented phenotypes in PINK1– and PRKN-associated Parkinson’s disease (PD)1. This observation is of high clinical relevance due to the immunogenic properties of circulating cell-free and cytosolic mtDNA. Extra-mitochondrial mtDNA has been linked to the upregulation of inflammatory pathways; namely cGAS-STING, NLRP3, and TLR9 signalling2. We previously investigated PRKN KO SH-SY5Y cells, a PD model system associated with significant levels of extra-mitochondrial mtDNA. We observed an increase in the lactate-to-pyruvate ratio in these cells, which is indicative of a metabolic shift towards glycolysis3. We also detected a decline in TFAM abundance – a known trigger of mtDNA release; as well as Sirt1 and PGC-1α. From these results, we proposed that NAD+ metabolism drives mtDNA release via SIRT1, and thus by regulating NAD+/NADH levels, we can modulate mtDNA release.
Method: Combining high-throughput imaging analyses, PCR, and Western blotting, we accessed the impact of several mitochondrial drugs on mtDNA release and biogenesis. To simulate the metabolic shift detected in PRKN-deficient cells in a wild-type SH-SY5Y line, we induced chemical hypoxia with cobalt chloride. We analysed mtDNA release with high throughput imaging and qPCR, and performed analyses of the biogenesis pathway using western blots.
Results: Our results revealed that decreasing the NAD+/NADH ratio in wildtype SH-SY5Y cells results in a disruption of the mitochondrial biogenesis pathway and an increase in cytosolic mtDNA, mirroring the situation in PRKN-PD. We now intend to further validate our hypothesis of a link between cellular metabolism and mito-inflammation and are currently testing the impact of different NAD+ enhancers on mtDNA release.
Conclusion: Our current results support the premise that metabolic modulation of NAD+/NADH levels could be a promising method for regulating mtDNA release. We hope that our work will advance personalized medicine approaches in PD by uncovering novel therapeutic entry points.
References: 1. Borsche M, König IR, Delcambre S, et al. Mitochondrial damage-associated inflammation highlights biomarkers in PRKN/PINK1 parkinsonism. Brain. Oct 1 2020;143(10):3041-3051. doi:10.1093/brain/awaa246
2. Riley JS, Tait SW. Mitochondrial DNA in inflammation and immunity. EMBO Rep. Apr 3 2020;21(4):e49799. doi:10.15252/embr.201949799
3. Wasner K, Smajic S, Ghelfi J, et al. Parkin Deficiency Impairs Mitochondrial DNA Dynamics and Propagates Inflammation. Movement Disorders. 2022;37(7):1405-1415. doi:https://doi.org/10.1002/mds.29025
To cite this abstract in AMA style:G. Agyeah, P. Antony, K. Wasner, A. Rakovic, S. Pereira, A. Grünewald. Metabolic modulation of mitochondrial DNA release in cellular models of Parkin-associated Parkinson’s disease [abstract]. Mov Disord. 2023; 38 (suppl 1). https://www.mdsabstracts.org/abstract/metabolic-modulation-of-mitochondrial-dna-release-in-cellular-models-of-parkin-associated-parkinsons-disease/. Accessed September 23, 2023.
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MDS Abstracts - https://www.mdsabstracts.org/abstract/metabolic-modulation-of-mitochondrial-dna-release-in-cellular-models-of-parkin-associated-parkinsons-disease/