Crosstalk between cardiomyocytes and noncardiomyocytes is essential to prevent cardiomyocyte apoptosis induced by proteasome inhibition

Fang Guo,Cheng-Hu Fang,Xi-Biao He,Chen-Chen Zhang,Xi-Hui Yin,Ting Li

doi:10.1038/s41419-020-03005-8

Abstract

Heart is a multi-cellular organ made up of various cell types interacting with each other. Cardiomyocytes may benefit or suffer from crosstalk with noncardiomyocytes in response to diverse kinds of cardiac stresses. Proteasome dysfunction is a common cardiac stress which causes cardiac proteotoxicity and contributes to cardiac diseases such as heart failure and myocardial infarction. The role of crosstalk between cardiomyocytes and noncardiomyocytes in defense of cardiac proteotoxicity remains unknown. Here, we report a cardiomyocyte-specific survival upon proteasome inhibition in a heterogeneous culture consisting of cardiomyocytes and other three major cardiac cell types. Conversely, cardiomyocyte apoptosis is remarkably induced by proteasome inhibition in a homogeneous culture consisting of a majority of cardiomyocytes, demonstrating an indispensable role of noncardiomyocytes in the prevention of cardiomyocyte apoptosis resulting from proteasome inhibition. We further show that cardiomyocytes express brain natriuretic peptide (BNP) as an extracellular molecule in response to proteasome inhibition. Blockade of BNP receptor on noncardiomyocytes significantly exacerbated the cardiomyocyte apoptosis, indicating a paracrine function of cardiomyocyte-released extracellular BNP in activation of a protective feedback from noncardiomyocytes. Finally, we demonstrate that proteasome inhibition-activated transcriptional up-regulation of BNP in cardiomyocytes was associated with the dissociation of repressor element 1 silencing transcription factor (REST)/ histone deacetylase 1 (HDAC1) repressor complex from BNP gene promoter. Consistently, the induction of BNP could be further augmented by the treatment of HDAC inhibitors. We conclude that the crosstalk between cardiomyocytes and noncardiomyocytes plays a crucial role in the protection of cardiomyocytes from proteotoxicity stress, and identify cardiomyocyte-released BNP as a novel paracrine signaling molecule mediating this crosstalk. These findings provide new insights into the key regulators and cardioprotective mechanism in proteasome dysfunction-related cardiac diseases.

Highlights

Ubiquitin-proteasome system (UPS) is critical for the protein quality control in the heart
To investigate the proteotoxic effect of proteasome inhibition on different cardiac cell populations, we employed a heterogeneous cell culture extracted from neonatal mouse hearts which consisted of 10.54 ± 2.06% sarcomeric α-actinin (SAA) + cardiomyocytes, 10.13 ± 1.59% smooth muscle actin (SMA) + vascular smooth muscle cells, 26.43 ± 2.83% discoidin domain-containing receptor 2 (DDR2) + cardiac fibroblasts, and 29.02 ± 2.09% Lectin+ endothelial cells (Supplementary Fig. 1A)
Immunostaining analysis with each cell type marker showed that DDR2 + cardiac fibroblasts and Lectin+ endothelial cells were significantly lost when exposed to MG132 at 25 μM, whereas the number of SMA + smooth muscle cells was not significantly decreased until the concentration reached 50 μM

Summary

Introduction

Ubiquitin-proteasome system (UPS) is critical for the protein quality control in the heart. UPS dysfunction induced by proteasome inhibition disrupts intracellular protein turnover and degradation of misfolded, oxidized, and damaged proteins, thereby causing cellular proteotoxicity. Protective cellular response to proteasome inhibition is critical for cell survival, as the continued presence of proteotoxicity usually leads to apoptosis in different cell types including cardiac cells[1,2,3,8]. A number of studies have provided in vitro evidence of proteasome inhibition-induced apoptosis in cultured cardiomyocytes[9,10,11,12]. Systemic proteasome inhibition in vivo prefers cardiomyopathies rather than cardiomyocyte apoptosis[5,9,13]. Given that cardiomyocytes communicate with a variety of noncardiomyocytes in the myocardium in response to pathophysiological stresses[16], crosstalk between cardiomyocytes and noncardiomyocytes is likely to play a protective role in cardiomyocytes’ response to proteasome inhibition, the evidence of which remains lacking

Methods

Results

Conclusion