Apocynin Treatment Prevents Cardiac Connexin 43 Hemichannels Hyperactivity by Reducing Nitroso-Redox Stress in Mdx Mice.

Alejandra Z Vielma,Mauricio P Boric,Daniel R Gonzalez

doi:10.3390/ijms21155415

Alejandra Z Vielma, Mauricio P Boric + Show 1 more

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https://doi.org/10.3390/ijms21155415

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Abstract

Duchenne muscular dystrophy (DMD) is a fatal disease that causes cardiomyopathy and is associated with oxidative stress. In the heart, oxidative stress interferes with the location of connexin 43 (Cx43) to the intercalated discs causing its lateralization to the plasma membrane where Cx43 forms hemichannels. We tested the hypothesis that in DMD cardiomyopathy, increased oxidative stress is associated with the formation and activation of Cx43 hemichannels. For this, we used mdx mice as a DMD model and evaluated cardiac function, nitroso-redox changes and Cx43 hemichannels permeability. Mdx hearts presented increased NADPH oxidase-derived oxidative stress and increased Cx43 S-nitrosylation compared to controls. These redox changes were associated with increased Cx43 lateralization, decreased cardiac contractility and increased arrhythmic events. Pharmacological inhibition of NADPH oxidase using apocynin (one month) reduced systemic oxidative stress and reversed the aforementioned changes towards normal, except Cx43 lateralization. Opening of Cx43 hemichannels was blocked by apocynin treatment and by acute hemichannel blockade with carbenoxolone. NADPH oxidase inhibition also prevented the occurrence of apoptosis in mdx hearts and reversed the ventricular remodeling. These results show that NADPH oxidase activity in DMD is associated with S-nitrosylation and opening of Cx43 hemichannels. These changes lead to apoptosis and cardiac dysfunction and were prevented by NADPH oxidase inhibition.

Highlights

Duchenne muscular dystrophy (DMD) is a genetic disease caused by mutations of a gene located in the X chromosome that codifies for dystrophin, a protein that connects the cytoskeleton with the sarcolemma, stabilizing the cell membrane [1]
We decided to investigate the state of NADPH oxidase-derived oxidative stress and its impact on connexin 43 (Cx43) subcellular location and redox state in mdx mice, an established animal model for DMD
As previously described, mdx hearts presented increased expression of the NADPH oxidase subunits NOX2 and p22 compared to age-matched controls (Figure 1B) at both ages

Summary

Introduction

Duchenne muscular dystrophy (DMD) is a genetic disease caused by mutations of a gene located in the X chromosome that codifies for dystrophin, a protein that connects the cytoskeleton with the sarcolemma, stabilizing the cell membrane [1]. The lack of dystrophin results in progressive skeletal muscle damage and degeneration [2]. Besides the skeletal muscle complications, patients with DMD and related forms of muscular dystrophy such as Becker dystrophy develop cardiac alterations such as arrhythmias and heart failure. 20% of DMD patients die around the age of 20, mainly due to severe cardiac complications [3]. Despite important efforts to find an effective treatment for the disease, current therapeutic approaches are mostly palliative: physical therapy, psychomotor support and symptom therapy [4,5]. Dystrophic cardiomyopathy can be treated pharmacologically with angiotensin-converting enzyme (ACE) inhibitors, β-adrenergic blockade and glucocorticoid therapy [6], approaches that ameliorate the symptoms and delay the progression to cardiac failure; they neither arrest nor reverse the disease [7]

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