Loss of mitochondrial exo/endonuclease EXOG affects mitochondrial respiration and induces ROS-mediated cardiomyocyte hypertrophy.
Recently, a locus at the mitochondrial exo/endonuclease EXOG gene, which has been implicated in mitochondrial DNA repair, was associated with cardiac function. The function of EXOG in cardiomyocytes is still elusive. Here we investigated the role of EXOG in mitochondrial function and hypertrophy in cardiomyocytes. Depletion of EXOG in primary neonatal rat ventricular cardiomyocytes (NRVCs) induced a marked increase in cardiomyocyte hypertrophy. Depletion of EXOG, however, did not result in loss of mitochondrial DNA integrity. Although EXOG depletion did not induce fetal gene expression and common hypertrophy pathways were not activated, a clear increase in ribosomal S6 phosphorylation was observed, which readily explains increased protein synthesis. With the use of a Seahorse flux analyzer, it was shown that the mitochondrial oxidative consumption rate (OCR) was increased 2.4-fold in EXOG-depleted NRVCs. Moreover, ATP-linked OCR was 5.2-fold higher. This increase was not explained by mitochondrial biogenesis or alterations in mitochondrial membrane potential. Western blotting confirmed normal levels of the oxidative phosphorylation (OXPHOS) complexes. The increased OCR was accompanied by a 5.4-fold increase in mitochondrial ROS levels. These increased ROS levels could be normalized with specific mitochondrial ROS scavengers (MitoTEMPO, mnSOD). Remarkably, scavenging of excess ROS strongly attenuated the hypertrophic response. In conclusion, loss of EXOG affects normal mitochondrial function resulting in increased mitochondrial respiration, excess ROS production, and cardiomyocyte hypertrophy.
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and.
Wardit
W
Tigchelaar
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and Department of Hematology, The First Clinical College of Harbin Medical University, Harbin, China.
Hongjuan
H
Yu
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and.
Anne Margreet
AM
de Jong
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and.
Wiek H
WH
van Gilst
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and.
Pim
P
van der Harst
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and.
B Daan
BD
Westenbrink
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and.
Rudolf A
RA
de Boer
University Medical Center Groningen, University of Groningen, Department of Cardiology, Groningen, The Netherlands; and h.h.w.sillje@umcg.nl.
Herman H W
HH
Silljé
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D019069:Cell Respiration / Q000235:genetics / Q000502:physiology*; D004272:DNA, Mitochondrial / Q000235:genetics; D004720:Endonucleases / Q000235:genetics / Q000378:metabolism*; D005092:Exonucleases / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression / Q000235:genetics; D006984:Hypertrophy / Q000235:genetics / Q000378:metabolism*; D053078:Membrane Potential, Mitochondrial / Q000235:genetics / Q000502:physiology; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D032383:Myocytes, Cardiac / Q000378:metabolism* / Q000502:physiology; D010084:Oxidation-Reduction; D010085:Oxidative Phosphorylation; D010766:Phosphorylation / Q000235:genetics / Q000528:radiation effects; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
D004272:DNA, Mitochondrial; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D004720:Endonucleases; D005092:Exonucleases
ROS; cardiomyocytes; hypertrophy; mitochondria; mitochondrial respiration