REGULATORS OF MTDNA RELEASE IN PRKN-ASSOCIATED PARKINSON’S DISEASE

Abstract
Mitochondrial DNA (mtDNA) release has emerged as a key factor in cellular stress responses, inflammation, and neurodegenerative disease pathology. Building on the foundational work of Wasner et al. (2022), this study investigates the physiological factors governing mtDNA release in PRKN-deficient cellular models, focusing on mitochondrial dynamics, quality control, and metabolic regulation as potential therapeutic strategies. Employing high-throughput imaging and quantitative PCR (qPCR), we quantified cytosolic mtDNA levels and assessed mitochondrial dysfunction in response to various cellular stressors.
Our findings demonstrate that chemical hypoxia in wild-type (WT) SH-SY5Y cells replicates several hallmarks of PRKN deficiency, including increased glycolysis, suppressed mitochondrial biogenesis markers, impaired mtDNA transcription, and elevated mtDNA release. Expanding on this, we examined the impact of mitochondrial physiological changes (mitochondrial fragmentation and mitophagy) on mtDNA release in both WT and PRKN knockout (KO) cells. These cells were exposed to thapsigargin, hydrogen peroxide, rotenone, and paraquat. All stressors induced significant mtDNA release, with the strongest effects observed under thapsigargin and hydrogen peroxide treatment. Notably, mitochondrial fragmentation strongly correlated with mtDNA release, supporting a mechanistic link rather than a coincidental association. PRKN KO cells exhibited increased fragmentation and impaired mitophagy, suggesting that diminished mitochondrial quality control exacerbates mtDNA release. Importantly, thapsigargin uniquely triggered fragmentation without inducing mitophagy, underscoring PRKN’s essential role in mitochondrial maintenance.
Given the association between mitochondrial dysfunction and neurodegeneration, we explored potential therapeutic interventions. Quercetin emerged as a promising candidate, effectively mitigating mtDNA release, restoring mitochondrial membrane potential, and reducing mitochondrial fragmentation in both WT and PRKN KO cells. The observed stabilization of mitochondrial dynamics positions quercetin as a potential modulator of mitochondrial dysfunction and inflammatory responses in neurodegenerative diseases linked to PRKN mutations.
This study provides novel insights into mtDNA release mechanisms, reinforcing the role of mitochondrial fragmentation and quality control in regulating mtDNA dynamics. The identification of quercetin as a protective agent highlights the therapeutic potential of metabolic modulators in addressing mitochondrial dysfunction. Future investigations should explore the long-term efficacy of quercetin and other metabolic interventions in neurodegenerative disease models, further refining therapeutic strategies targeting mitochondrial homeostasis.