Loss of cardiomyocyte CYB5R3 impairs redox equilibrium and causes sudden cardiac death
Nolan T. Carew, … , Guy Salama, Adam C. Straub
Nolan T. Carew, … , Guy Salama, Adam C. Straub
Published September 15, 2022
Citation Information: J Clin Invest. 2022;132(18):e147120. https://doi.org/10.1172/JCI147120.
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Loss of cardiomyocyte CYB5R3 impairs redox equilibrium and causes sudden cardiac death

Abstract

Sudden cardiac death (SCD) in patients with heart failure (HF) is allied with an imbalance in reduction and oxidation (redox) signaling in cardiomyocytes; however, the basic pathways and mechanisms governing redox homeostasis in cardiomyocytes are not fully understood. Here, we show that cytochrome b5 reductase 3 (CYB5R3), an enzyme known to regulate redox signaling in erythrocytes and vascular cells, is essential for cardiomyocyte function. Using a conditional cardiomyocyte-specific CYB5R3-knockout mouse, we discovered that deletion of CYB5R3 in male, but not female, adult cardiomyocytes causes cardiac hypertrophy, bradycardia, and SCD. The increase in SCD in CYB5R3-KO mice is associated with calcium mishandling, ventricular fibrillation, and cardiomyocyte hypertrophy. Molecular studies reveal that CYB5R3-KO hearts display decreased adenosine triphosphate (ATP), increased oxidative stress, suppressed coenzyme Q levels, and hemoprotein dysregulation. Finally, from a translational perspective, we reveal that the high-frequency missense genetic variant rs1800457, which translates into a CYB5R3 T117S partial loss-of-function protein, associates with decreased event-free survival (~20%) in Black persons with HF with reduced ejection fraction (HFrEF). Together, these studies reveal a crucial role for CYB5R3 in cardiomyocyte redox biology and identify a genetic biomarker for persons of African ancestry that may potentially increase the risk of death from HFrEF.

Authors

Nolan T. Carew, Heidi M. Schmidt, Shuai Yuan, Joseph C. Galley, Robert Hall, Helene M. Altmann, Scott A. Hahn, Megan P. Miller, Katherine C. Wood, Bethann Gabris, Margaret C. Stapleton, Sean Hartwick, Marco Fazzari, Yijen L. Wu, Mohamed Trebak, Brett A. Kaufman, Charles F. McTiernan, Francisco J. Schopfer, Placido Navas, Patrick H. Thibodeau, Dennis M. McNamara, Guy Salama, Adam C. Straub

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Figure 7

Cardiomyocyte CYB5R3 is critical for myoglobin reduction and maintenance of intracellular oxygen tension.

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Cardiomyocyte CYB5R3 is critical for myoglobin reduction and maintenance...
(A) In vitro purified colorimetric assay showing absorbance shift of oxidized myoglobin to reduced myoglobin (B) after the addition of electron donor NADH. (C) Rate of absorbance changes at 540 nm, with observation of increasing amounts of reduced myoglobin over time. (D) Schematic of hypothesized redox regulation of myoglobin by CYB5R3 and the relevant impact on oxygen binding. (E) Western blot of heart lysates measuring myoglobin and β-actin as a loading control with quantification of relative integrated intensities (ac-WT, n = 8; ac-CYB5R3–KO, n = 13). (F) HO-1 and β-actin loading control Western blot with quantification of relative integrated intensities. (G) Hypoxyprobe staining (green) of heart sections from control (ac-WT n = 3) and Cyb5R3-KO (ac-CYB5R3–KO, n = 3) heart sections, counterstained with wheat germ agglutinin (red) and DAPI (blue). Original magnification, ×3 (right panels). (H) Quantification of Hypoxyprobe-positive cells relative to total cells. Data are represented as SEM. P values were calculated by Student’s t test. Scale bar: 50 m.