Inhibition of TLR4/MAPKs Pathway Contributes to the Protection of Salvianolic Acid A Against Lipotoxicity-Induced Myocardial Damage in Cardiomyocytes and Obese Mice.

Zhen Yang,Xiangyao Wu,Songtao Li,Zhaoyuan Yan,Tian Tian Xu,Yanli Chen,Hui Chai,Aiwen Pi,Qingsheng Liu,Xiaobing Dou

doi:10.3389/fphar.2021.627123

Abstract

The occurrence of lipotoxicity during obesity-associated cardiomyopathy is detrimental to health. Salvianolic acid A (SAA), a natural polyphenol extract of Salvia miltiorrhiza Bunge (Danshen in China), is known to be cardioprotective. However, its clinical benefits against obesity-associated cardiomyocyte injuries are unclear. This study aimed at evaluating the protective effects of SAA against lipotoxicity-induced myocardial injury and its underlying mechanisms in high fat diet (HFD)-fed mice and in palmitate-treated cardiomyocyte cells (H9c2). Our analysis of aspartate aminotransferase and creatine kinase isoenzyme-MB (CM-KB) levels revealed that SAA significantly reversed HFD-induced myocardium morphological changes and improved myocardial damage. Salvianolic acid A pretreatment ameliorated palmitic acid-induced myocardial cell death and was accompanied by mitochondrial membrane potential and intracellular reactive oxygen species improvement. Analysis of the underlying mechanisms showed that SAA reversed myocardial TLR4 induction in HFD-fed mice and H9c2 cells. Palmitic acid-induced cell death was significantly reversed by CLI-95, a specific TLR4 inhibitor. TLR4 activation by LPS significantly suppressed SAA-mediated lipotoxicity protection. Additionally, SAA inhibited lipotoxicity-mediated expression of TLR4 target genes, including MyD88 and p-JNK/MAPK in HFD-fed mice and H9c2 cells. However, SAA did not exert any effect on palmitic acid-induced SIRT1 suppression and p-AMPK induction. In conclusion, our data shows that SAA protects against lipotoxicity-induced myocardial damage through a TLR4/MAPKs mediated mechanism.

Highlights

Obesity is a global epidemic that is characterized by excessive amounts of circulating free fatty acids (FFAs), resulting in a variety of metabolic disorders, including lipotoxic cardiomyopathy (Schrammel et al, 2013)
We have shown that Salvianolic acid A (SAA), a phytochemical found in Danshen, protects against lipotoxicity in high fat diet (HFD)-fed mice and cultured cardiomyocytes
Its benefits are associated with its effects on toll-like-receptor 4 (TLR4)/mitogenactivated protein kinase (MAPK) signaling

Summary

Introduction

Obesity is a global epidemic that is characterized by excessive amounts of circulating free fatty acids (FFAs), resulting in a variety of metabolic disorders, including lipotoxic cardiomyopathy (Schrammel et al, 2013). TLR4 is a well-known activator of innate immune responses against pathogens and has recently been shown to mediate obesity-induced cardiac inflammation, glucose metabolic derangement and injury (Jackson et al, 2015; Chen et al, 2020; Liu et al, 2020). Studies on HFD-induced obesity have shown that myocardial damage is significantly alleviated by TLR4 depletion (Wang et al, 2017). MyD88 or MAPKs (including JNK and ERK1/2) inhibition has been shown to improve lipotoxicity-induced cardiac injury in both obese mice and cultured cardiomyocytes (Liu et al, 2014; Wang et al, 2016). Adenosine monophosphate activated protein kinase (AMPK), a key cellular energy sensor, has been implicated in HFDinduced cardiac hypertrophy, palmitate-induced apoptosis, and cardiomyocytes lipid deposit (Gélinas et al, 2018; Yang et al, 2018; Zhang et al, 2019). AMPK activation inhibits myocardial hypertrophy by regulating energy metabolism through sirtuin 1 (SIRT1) (Ma et al, 2018)

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