Interventricular Differences of Signaling Pathways-Mediated Regulation of Cardiomyocyte Function in Response to High Oxidative Stress in the Post-Ischemic Failing Rat Heart.

Judit Barta,Melina Tangos,Attila Tóth,Árpád Kovács,Andreas Mügge,Nazha Hamdani,Melissa Herwig,Saltanat Zhazykbayeva,Carsten Tschöpe,Ágnes Balogh,Beáta Bódi,Naranjan S Dhalla,Sophie Van Linthout,Roua Hassoun,Zoltán Papp,Simin Delalat,Dániel Czuriga,Detmar Kolijn,Heidi Budde

doi:10.3390/antiox10060964

Abstract

Standard heart failure (HF) therapies have failed to improve cardiac function or survival in HF patients with right ventricular (RV) dysfunction suggesting a divergence in the molecular mechanisms of RV vs. left ventricular (LV) failure. Here we aimed to investigate interventricular differences in sarcomeric regulation and function in experimental myocardial infarction (MI)-induced HF with reduced LV ejection fraction (HFrEF). MI was induced by LAD ligation in Sprague–Dawley male rats. Sham-operated animals served as controls. Eight weeks after intervention, post-ischemic HFrEF and Sham animals were euthanized. Heart tissue samples were deep-frozen stored (n = 3–5 heart/group) for ELISA, kinase activity assays, passive stiffness and Ca2+-sensitivity measurements on isolated cardiomyocytes, phospho-specific Western blot, and PAGE of contractile proteins, as well as for collagen gene expressions. Markers of oxidative stress and inflammation showed interventricular differences in post-ischemic rats: TGF-β1, lipid peroxidation, and 3-nitrotyrosine levels were higher in the LV than RV, while hydrogen peroxide, VCAM-1, TNFα, and TGF-β1 were increased in both ventricles. In addition, nitric oxide (NO) level was significantly decreased, while FN-1 level was significantly increased only in the LV, but both were unchanged in RV. CaMKII activity showed an 81.6% increase in the LV, in contrast to a 38.6% decrease in the RV of HFrEF rats. Cardiomyocyte passive stiffness was higher in the HFrEF compared to the Sham group as evident from significantly steeper Fpassive vs. sarcomere length relationships. In vitro treatment with CaMKIIδ, however, restored cardiomyocyte passive stiffness only in the HFrEF RV, but had no effect in the HFrEF LV. PKG activity was lower in both ventricles in the HFrEF compared to the Sham group. In vitro PKG administration decreased HFrEF cardiomyocyte passive stiffness; however, the effect was more pronounced in the HFrEF LV than HFrEF RV. In line with this, we observed distinct changes of titin site-specific phosphorylation in the RV vs. LV of post-ischemic rats, which may explain divergent cardiomyocyte stiffness modulation observed. Finally, Ca2+-sensitivity of RV cardiomyocytes was unchanged, while LV cardiomyocytes showed increased Ca2+-sensitivity in the HFrEF group. This could be explained by decreased Ser-282 phosphorylation of cMyBP-C by 44.5% in the RV, but without any alteration in the LV, while Ser-23/24 phosphorylation of cTnI was decreased in both ventricles in the HFrEF vs. the Sham group. Our data pointed to distinct signaling pathways-mediated phosphorylations of sarcomeric proteins for the RV and LV of the post-ischemic failing rat heart. These results implicate divergent responses for oxidative stress and open a new avenue in targeting the RV independently of the LV.

Highlights

Right ventricular (RV) function is an independent prognostic factor and determinate of survival in patients with chronic heart failure (HF)
Lipid peroxidation (Figure 1B) and 3-Nitrotyrosine (Figure 1C) levels were increased in the left ventricular (LV), but unaltered in the right ventricular (RV) of HF with reduced LV ejection fraction (HFrEF) animals compared to the Sham group
Lipid peroxidation (Figure 1B) and 3-Nitrotyrosine (Figure 1C) levels were higher in the LV vs. RV of HFrEF animals

Summary

Introduction

Right ventricular (RV) function is an independent prognostic factor and determinate of survival in patients with chronic heart failure (HF). RV dysfunction cardinally influences symptoms and predicts poor prognosis in HF patients with reduced left ventricular (LV) ejection fraction (EF), i.e., HFrEF [1]. Whereas RV dysfunction is associated with poor clinical outcomes independently of the underlying mechanism of the disease [3], no therapeutic options are available in today’s clinical routine that target the right heart and even diagnostic approaches are limited. Standard HF therapies have failed to improve cardiac function or survival in HF patients with impaired RV function, which suggests a divergence in the molecular mechanisms of RV vs LV failure [8]. Improving RV function by medical therapy implies better survival in HFrEF patients with RV dysfunction than those with persistently abnormal or worsening RV function [10]

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