# Suppressing Endothelial–Mesenchymal Transition Through the Histone Deacetylase 1/GATA Binding Protein 4 Pathway: The Mechanism of Protocatechuic Acid Against Myocardial Fibrosis Revealed by an Integrated Study

## TL;DR

This study shows that protocatechuic acid, a natural compound, can reduce heart scarring by targeting a specific protein pathway, offering a new treatment for heart disease.

## Contribution

The study reveals a novel mechanism by which protocatechuic acid suppresses heart fibrosis through the HDAC1/GATA4 pathway.

## Key findings

- Protocatechuic acid improved heart function and reduced fibrosis in rat models.
- It inhibited inflammation and endothelial-mesenchymal transition via the HDAC1/GATA4 pathway.
- Molecular simulations confirmed stable binding of protocatechuic acid to HDAC1.

## Abstract

This study examines a potential new approach to treating myocardial fibrosis, a major pathology contributing to heart failure. We investigated protocatechuic acid, a natural compound widely distributed in plants with known anti-inflammatory effects, to see if it could ameliorate myocardial fibrosis and elucidate the underlying mechanism. By using animal models, human umbilical vein endothelial cells and human cardiomyocytes, as well as computer simulations, we found that protocatechuic acid ameliorated cardiac function and alleviated myocardial fibrosis through regulating a specific protein pathway in vascular cells. In summary, this natural compound is effective in delaying disease progression by anti-inflammation and protecting heart cells. These promising results indicate that protocatechuic acid is expected to be a new drug candidate for the prevention or treatment of cardiovascular diseases.

Background: Myocardial fibrosis, a central pathological process leading to heart failure, lacks specific mechanism-based therapies. Although the anti-inflammatory activity of the natural compound protocatechuic acid is recognized, its direct anti-fibrotic mechanism, particularly concerning the critical role of endothelial–mesenchymal transition (EndMT), remains unexplored. This study aimed to investigate the protective effects and underlying mechanisms of protocatechuic acid. Methods: The study employed both in vivo and in vitro models. For in vivo evaluation, a rat model of myocardial fibrosis was induced by isoproterenol hydrochloride (ISO). For in vitro analysis, human umbilical vein endothelial cells (HUVECs) were stimulated with angiotensin II (Ang II) and subjected to siRNA-mediated histone deacetylase 1 (HDAC1) knockdown, alongside a co-culture model involving HUVECs and the AC16 human cardiomyocyte cells. Additionally, molecular docking and dynamics simulations were performed to evaluate the binding affinity and stability of protocatechuic acid with the target protein, HDAC1. Results: In vivo, protocatechuic acid significantly improved cardiac function, attenuated pathological injury, and reduced collagen deposition in ISO-induced fibrotic rats. It also potently suppressed inflammatory responses and inhibited the EndMT process. These beneficial effects were associated with decreased HDAC1 and increased GATA binding protein 4 (GATA4) expression in perivascular regions, which suggests the modulation of the HDAC1/GATA4 pathway. In vitro, protocatechuic acid suppressed Ang II-induced endothelial inflammation in HUVECs. This effect was replicated by HDAC1 knockdown, thus confirming that the HDAC1/GATA4 pathway mediates its anti-inflammatory action at the cellular level. Furthermore, molecular docking and dynamics simulations indicated that protocatechuic acid stably binds to a key target, HDAC1. Conclusions: Protocatechuic acid alleviates inflammation and EndMT by inhibiting the HDAC1/GATA4 signaling pathway, thereby preserving cardiac function and retarding the progression of myocardial fibrosis. These findings provide a theoretical and experimental foundation for the potential application of protocatechuic acid in treating cardiovascular diseases.