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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Research Article Cardiology

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 8

CYB5R3 T117S is a partial loss-of-function variant that associates with accelerated death in African American HF patients.

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CYB5R3 T117S is a partial loss-of-function variant that associates with ...
(A) Structure of membrane and soluble CYB5R3. Red colored area shows T117 residue (dark red) of the reductase. Below, the green-blue-yellow figure shows the FAD prosthetic group of the reductase. (B) Amino acid sequence aligned across mammals showing conserved threonine (highlighted in yellow) in the 117 position of membrane CYB5R3. (C) Comparison of known allele frequency of T117S in African Americans (left pie chart) compared with allele frequency of T117S in African Americans with HF that received transplant or LV assist devices (LVAD). Gray represents the proportion of noncarriers relative to red region representing pooled heterozygous and homozygous CYB5R3 T117S carriers. (D) Reduced myoglobin over time in vitro comparing 23 T117S (soluble) with WT 23 CYB5R3 (soluble) with and without CYB5B. (E) Change in myoglobin reduction rates detected at 540 nm/s (n = 4–9). (F) Western blot of reexpressed CYB5R3 WT, CYB5R3 T117S, 23 CYB5R3 WT, and 23 CYB5R3 T117S in HEK293 FT CYB5R3-KO≈cells (n = 3). (G) CYB5R3 activity over time measured by 2,6-dichlorophenolindophenol (DCPIP) reduction, comparing CYB5R3 WT, CYB5R3 T117S, 23 CYB5R3 WT, and 23 CYB5R3 T117S (n = 3). (H) Total cGMP in heart lysates from African Americans receiving ventricular assist devices, comparing noncarriers (gray) and T117S carriers (red) (n = 13–19). (I) Event-free survival curve comparing African American CYB5R3 T117S CC versus CG/GG from the GRACE and GRAHF trials. Data are represented as SEM. P values were calculated by Student’s t test (G and H), 1-way ANOVA (E), or a log-rank test (I).