D-2-hydroxyglutaric acid disrupts heart mitochondrial calcium retention capacity and causes cardiomyocyte death

Rafael Teixeira Ribeiro ¹ Ana Cristina Roginski ² Rafael Aguiar Marschner ³ Simone Magagnin Wajner ³ Roger Frigerio Castilho ⁴ Alexandre Umpierrez Amaral ^1,5 Moacir Wajner ^1,6

¹PPG Ciências Biológicas: Bioquímica, Departamento De Bioquímica, Universidade Federal Do Rio Grande Do Sul, Brazil
²Biodesign Center for Immunotherapy, Vaccines and Virotherapy, Arizona State University, USA
³Departamento De Medicina Interna, Faculdade De Medicina, Universidade Federal Do Rio Grande Do Sul, Brazil
⁴Departamento de Patologia Clínica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, Brazil
⁵PPG Atenção Integral à Saúde, Universidade Regional Integrada Do Alto Uruguai E Das Missões, Brazil
⁶Serviço De Genética Médica, Hospital De Clínicas De Porto Alegre, Brazil

Background: D-2-hydroxyglutaric acid (D-2-HG) accumulates in D-2-hydroxyglutaric aciduria type I and more accentuated in D-2-hydroxyglutaric aciduria type II (D2HGA2). D2HGA2 is an inherited metabolic disease caused by gain-of-function mutations in the gene isocitrate dehydrogenase 2. It is clinically characterized by neurological abnormalities and a severe cardiomyopathy whose pathogenesis is still poorly established. The present work investigated the potential cardiotoxicity of D-2-HG, by evaluating its in vitro effects on heart calcium retention capacity and cardiomyocyte viability. Methods: The evaluation of calcium retention capacity was performed in heart mitochondria isolated from 30-day-old rats and supported by glutamate plus malate, whereas cardiomyocyte viability was tested by the MTT assay and propidium iodide incorporation into H9c2 myoblasts. Results: D-2-HG compromised calcium retention capacity in heart mitochondrial preparations, therefore compromising mitochondrial calcium homeostasis in the heart. Noteworthy, D-2-HG-induced decrease of calcium retention capacity was totally prevented by cyclosporin A, implying that mitochondrial permeability transition pore opening was involved in this effect. In addition, this organic acid significantly reduced the viability of H9c2 cardiac cells, as determined by a decreased MTT assay and by increased propidium iodide incorporation. Discussion/Conclusion: It is presumed that D-2-HG-induced disruption of heart calcium homeostasis and reduction of cardiomyocyte viability may be possibly involved in the cardiomyopathy commonly observed in D2HGA2.

Financial support: PROPESQ/UFRGS, FAPERGS, INCT and CNPq.