Mitophagy modulation rescues single large-scale mitochondrial DNA deletion (SLSMD) disease symptoms in the C. elegans uaDf5 animal model

S ingle large s cale m itochondrial DNA (mtDNA) d eletions (SLSMD) underlie a range of sporadic or maternally inherited primary mitochondrial diseases having significant morbidity and mortality, including Pearson syndrome, Kearns-Sayre Syndrome, or Chronic Progressive External Ophthalmoplegia. Therapeutic development has been hindered by limited existing knowledge on mtDNA quality control and a lack of SLSMD animal models. To address this challenge, we utilized the C. elegans heteroplasmic SLSMD strain, uaDf5, to objectively screen for potential therapies. As mitophagy modulation has been implicated in mtDNA homeostasis, we screened a library of mitophagy modulating compounds to determine their comparative effects to rescue mitochondrial unfolded protein (UPR ^mt ) stress induction in in uaDf5 SLSMD worms. Interestingly, Thiamine was discovered to be an effective positive control, significantly reducing mitochondrial stress in this model. Two lead therapeutic candidates from the mitophagy library screen were Hemin and Celastrol (Tripterin). Celastrol is a mitophagy activating anti-inflammatory and metabolic modifying natural product derived compound, that rescued multiple fitness outcomes (thrashing, development, survival) and reduced the mitochondrial stress in uaDf5 animals in a mitophagy-dependent fashion. This study highlights the utility of the uaDf5 worm model to enable preclinical identification of therapeutic candidate leads for SLSMD-based heteroplasmic mtDNA diseases and identifies possible therapeutic candidates that serve as mitophagy modulators to improve health and specifically reduce heteroplasmy levels in SLSMD diseases.