The inotropic agent digitoxin strengthens desmosomal adhesion in cardiac myocytes in an ERK1/2-dependent manner

Angela Schlipp,Jens Waschke,Silvana Olivares-Florez,Ellen Kempf,Camilla Schinner,Desalegn Tadesse Egu,Manouk Feinendegen,Heinrich Flaswinkel,Sebastian Trenz,Sunil Yeruva

doi:10.1007/s00395-020-0805-3

Angela Schlipp, Jens Waschke + Show 8 more

Open Access

https://doi.org/10.1007/s00395-020-0805-3

Copy DOI

Abstract

Desmosomal proteins are components of the intercalated disc and mediate cardiac myocyte adhesion. Enhancement of cardiac myocyte cohesion, referred to as “positive adhesiotropy”, was demonstrated to be a function of sympathetic signaling and to be relevant for a sufficient inotropic response. We used the inotropic agent digitoxin to investigate the link between inotropy and adhesiotropy. In contrast to wild-type hearts, digitoxin failed to enhance pulse pressure in perfused mice hearts lacking the desmosomal protein plakoglobin which was paralleled with abrogation of plaque thickening indicating that positive inotropic response requires intact desmosomal adhesion. Atomic force microscopy revealed that digitoxin increased the binding force of the adhesion molecule desmoglein-2 at cell–cell contact areas. This was paralleled by enhanced cardiac myocyte cohesion in both HL-1 cardiac myocytes and murine cardiac slices as determined by dissociation assays as well as by accumulation of desmosomal proteins at cell–cell contact areas. However, total protein levels or cytoskeletal anchorage were not affected. siRNA-mediated depletion of desmosomal proteins abrogated increase of cell cohesion demonstrating that intact desmosomal adhesion is required for positive adhesiotropy. Mechanistically, digitoxin caused activation of ERK1/2. In line with this, inhibition of ERK1/2 signaling abrogated the effects of digitoxin on cell–cell adhesion and desmosomal reorganization. These results show that the positive inotropic agent digitoxin enhances cardiac myocyte cohesion with reorganization of desmosomal proteins in an ERK1/2-dependent manner. Desmosomal adhesion seems to be important for a sufficient positive inotropic response of digitoxin treatment, which can be of medical relevance for the treatment of heart failure.

Highlights

For a coordinated contraction and structural integrity of the myocardium, mechanical and electrical coupling of the cardiac myocytes via the intercalated disc (ICD) is essential
We demonstrate that the positive inotropic agent digitoxin strengthens adhesion between adjacent cardiac myocytes in a desmosome-dependent manner with recruitment of DSG2, DP, and PG at cell–cell contacts paralleled with thickening of the ICD plaque
Given the positive inotropic effect of digitoxin and the data on cardiac myocyte cohesion presented in this study, we aimed to evaluate the interplay of both signals on the mechanical coupling of ICDs

Summary

Introduction

For a coordinated contraction and structural integrity of the myocardium, mechanical and electrical coupling of the cardiac myocytes via the intercalated disc (ICD) is essential. The transmembrane adhesion molecule N-cadherin (NCAD) is coupled to the actin filament system [1]. AC becomes evident in patients by ventricular arrhythmia, which may cause sudden death with increased prevalence in young athletes. It is characterized by progressive loss of cardiac myocytes and fibrotic tissue replacement [41]. Physical exercise, which is paralleled with elevated adrenergic signaling, seems to be an important factor in the progression of the disease as it may aggravate mechanical uncoupling of cardiac myocytes and triggers malignant ventricular arrhythmias [4]

Objectives

Methods

Results

Conclusion