Aminolevulinate/iron exposure elicited Nrf-2-mediated cytoprotection in DARS2 deficient fibroblasts with impaired energy and antioxidant metabolisms

Leukoencephalopathy with brain stem and spinal cord involvement and lactate elevation (LBSL) is a disorder caused by mutations in the mitochondrial aspartyl-tRNA synthetase gene DARS2, which compromises mitochondrial protein translation. The typical presentation is juvenile in onset with gradually progressive spasticity and ataxia. Only palliative treatment is available for LBSL individuals. Here we showed that the use of the Food and Drug Administration-approved heme precursors, aminolevulinate plus ferrous iron (ALA/Fe), can result in a novel pharmacological treatment that increases energy status in DARS2 deficient cells. The marked mitochondrial and antioxidant deficiencies observed in fibroblasts from two LBSL-affected brothers, harboring intron-2 (c.228-17C > G) and intron-5 (c.492 + 2 T > C) DARS2 mutations, were rescued by ALA/Fe exposure, and the use of dexamethasone, a known Nrf-2 inhibitor, blocked the positive effects of ALA/Fe. Altogether, this study showed that fibroblasts can be used as a biological system to identify potential new treatments for LBSL that can reduce morbidity and mortality, and that the activation of Nrf-2-mediated cytoprotection can be targeted for the treatment of LBSL and other mitochondrial diseases.