Mitochondrial oxidative stress contributes to diastolic dysfunction through impaired mitochondrial dynamics

Andrey Lozhkin; Aleksandr E Vendrov; R Ramos-Mondragón; Chandrika Canugovi; Mark D Stevenson; Todd J Herron; Scott L Hummel; C Alberto Figueroa; Dawn E Bowles; Lori L Isom; Marschall S Runge; Nageswara R Madamanchi

doi:10.1016/j.redox.2022.102474

Mitochondrial oxidative stress contributes to diastolic dysfunction through impaired mitochondrial dynamics

Redox Biol. 2022 Nov:57:102474. doi: 10.1016/j.redox.2022.102474. Epub 2022 Sep 17.

Affiliations

¹ 1150 West Medical Center Drive, 7200 Medical Science Research Building III, Department of Internal Medicine, Frankel Cardiovascular Center, University of Michigan, Ann Arbor, MI, 48019, USA.
² Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA.
³ Frankel Cardiovascular Regeneration Core Laboratory, Ann Arbor, MI, 48109, USA.
⁴ Department of Internal Medicine, Division of Cardiovascular Medicine, University of Michigan, Ann Arbor, MI, 48109, USA; Ann Arbor Veterans Affairs Health System, Ann Arbor, MI, USA.
⁵ Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
⁶ Department of Surgery, Duke University School of Medicine, Durham, NC, USA.
⁷ Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA; Department of Neurology, University of Michigan, Ann Arbor, MI, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA.
⁸ 1150 West Medical Center Drive, 7200 Medical Science Research Building III, Department of Internal Medicine, Frankel Cardiovascular Center, University of Michigan, Ann Arbor, MI, 48019, USA. Electronic address: madamanc@med.umich.edu.

Abstract

Diastolic dysfunction (DD) underlies heart failure with preserved ejection fraction (HFpEF), a clinical syndrome associated with aging that is becoming more prevalent. Despite extensive clinical studies, no effective treatment exists for HFpEF. Recent findings suggest that oxidative stress contributes to the pathophysiology of DD, but molecular mechanisms underpinning redox-sensitive cardiac remodeling in DD remain obscure. Using transgenic mice with mitochondria-targeted NOX4 overexpression (Nox4TG618) as a model, we demonstrate that NOX4-dependent mitochondrial oxidative stress induces DD in mice as measured by increased E/E', isovolumic relaxation time, Tau Glantz and reduced dP/dt_min while EF is preserved. In Nox4TG618 mice, fragmentation of cardiomyocyte mitochondria, increased DRP1 phosphorylation, decreased expression of MFN2, and a higher percentage of apoptotic cells in the myocardium are associated with lower ATP-driven and maximal mitochondrial oxygen consumption rates, a decrease in respiratory reserve, and a decrease in citrate synthase and Complex I activities. Transgenic mice have an increased concentration of TGFβ and osteopontin in LV lysates, as well as MCP-1 in plasma, which correlates with a higher percentage of LV myocardial periostin- and ACTA2-positive cells compared with wild-type mice. Accordingly, the levels of ECM as measured by Picrosirius Red staining as well as interstitial deposition of collagen I are elevated in the myocardium of Nox4TG618 mice. The LV tissue of Nox4TG618 mice also exhibited increased I_CaL current, calpain 2 expression, and altered/disrupted Z-disc structure. As it pertains to human pathology, similar changes were found in samples of LV from patients with DD. Finally, treatment with GKT137831, a specific NOX1 and NOX4 inhibitor, or overexpression of mCAT attenuated myocardial fibrosis and prevented DD in the Nox4TG618 mice. Together, our results indicate that mitochondrial oxidative stress contributes to DD by causing mitochondrial dysfunction, impaired mitochondrial dynamics, increased synthesis of pro-inflammatory and pro-fibrotic cytokines, activation of fibroblasts, and the accumulation of extracellular matrix, which leads to interstitial fibrosis and passive stiffness of the myocardium. Further, mitochondrial oxidative stress increases cardiomyocyte Ca²⁺ influx, which worsens CM relaxation and raises the LV filling pressure in conjunction with structural proteolytic damage.

Keywords: Cardiomyocyte; Diastolic dysfunction; Heart failure with preserved ejection fraction; Interstitial fibrosis; Mitochondrial dysfunction; NADPH oxidase 4; NOX4 inhibitor.