Drug repurposing for mitochondrial diseases using a pharmacological model of complex I deficiency in the yeast Yarrowia lipolytica

Mitochondrial diseases affect 1 in 5,000 live births around the world. They are caused by inherited or de novo mutations in over 350 nuclear-encoded and mtDNA-encoded genes. There is no approved treatment to stop the progression of any mitochondrial disease despite the enormous global unmet need. Affected families often self-compound cocktails of over-the-counter vitamins and generally recognized as safe nutritional supplements that have not received regulatory approval for efficacy. Finding a new use for an approved drug is called repurposing, an attractive path for mitochondrial diseases because of the reduced safety risks, low costs and fast timelines to a clinic-ready therapy or combination of therapies. Here I describe the first-ever drug repurposing screen for mitochondrial diseases involving complex I deficiency, e.g., Leigh syndrome, using the yeast Yarrowia lipolytica as a model system. Unlike the more commonly used yeast Saccharomyces cerevisiae but like humans, Yarrowia lipolytica has a functional and metabolically integrated respiratory complex I and is an obligate aerobe. In 384-well-plate liquid culture format without shaking, Yarrowia lipolytica cells grown in either glucose-containing media or acetate-containing media were treated with a half-maximal inhibitory concentration (3{micro}M and 6M, respectively) of the natural product and complex I inhibitor piericidin A. Out of 2,560 compounds in the Microsource Spectrum collection, 24 suppressors of piercidin A reached statistical significance in one or both media conditions. The suppressors include calcium channel blockers nisoldipine, amiodarone and tetrandrine as well as the farnesol-like sesquiterpenoids parthenolide, nerolidol and bisabolol, which may all be modulating mitochondrial calcium homeostasis. Estradiols and synthetic estrogen receptor agonists are the largest class of suppressors that rescue growth of piericidin-A-treated Yarrowia lipolytica cells in both glucose-containing and acetate-containing media. Analysis of structure-activity relationships suggests that estrogens may enhance bioenergetics by evolutionarily conserved interactions with mitochondrial membranes that promote mitochondrial filamentation and mitochondrial DNA replication.