Evaluation of mitochondrial bioenergetics, dynamics, superoxide levels and endoplasmic reticulum-mitochondria crosstalk in fibroblasts from patients with ETHE1 and MOCS1 deficiencies

Mateus Grings, PhDa,b, Bianca Seminotti, PhDa,b, Anuradha Karunanidhi, MSb, Lina Ghaloul-Gonzalez, PhDb, Al-Walid Mohsen, PhDb, Peter Wipf, PhDc, Johan Palmfeldt, PhDd, Jerry Vockley, PhDb, Guilhian Leipnitz, PhDa,b*
aPPG Ciências Biológicas: Bioq, Dept Bioquímica, Univ Fed do Rio Grande do Sul, Porto Alegre, RS, Brazil
bDiv Med Genet, Dept Pediatrics, Univ Pittsburgh, Pittsburgh, PA, USA
cDept Chem, Univ Pittsburgh, Pittsburgh, PA, USA
dRes Unit Mol Med, Aarhus Univ Hosp, Aarhus, Denmark
*e-mail: guilhian@ufrgs.br / phone: +55 51996958682

Background: ETHE1 and molybdenum cofactor deficiency (MOCS1 deficiency) are inborn errors that affect the metabolism of sulfur amino acids and characterized by neurological dysfunction. Previous data showed that bioenergetic impairment and oxidative stress are mechanisms underlying the pathophysiology of symptoms observed in these disorders. Since these defects may affect mitochondria function and disturb their interaction with other organelles, we evaluated mitochondrial bioenergetics, dynamics, endoplasmic reticulum (ER)-mitochondria communication, superoxide production and apoptosis in fibroblasts from patients with ETHE1 and MOCS1 deficiencies.

Methods: Content of proteins involved in mitochondrial dynamics and ER-mitochondria crosstalk, oxygen consumption, superoxide levels and apoptosis were measured in primary human dermal fibroblasts obtained from four patients with ETHE1 deficiency and one with MOCS1 deficiency.

Results: Mitochondrial respiration was decreased in all cell lines while ATP levels were reduced in two ETHE1 deficient cell lines and MOCS1 deficient cells. Moreover, two ETHE1 cell lines and the MOCS1 fibroblasts showed increased mitochondrial mass. Variable alterations were seen in MFN1 and DRP1, reflecting dynamics dysregulation. High superoxide levels were also found in all cells. Content of VDAC1 and IP3R, proteins found in ER- mitochondria communication, were decreased, while DDIT3, a marker of ER stress, and apoptosis were increased in all cell lines.

Discussion: These data identify that disturbances in mitochondrial bioenergetics and dynamics, ER-mitochondria crosstalk, as well as increased superoxide contribute for the onset or progression of symptoms of ETHE1 and MOCS1 deficiencies. These mechanisms may play a key role in the
pathophysiology of fatty acid oxidation disorders that are also characterized by impairment of bioenergetics and oxidative stress.