Epigallocatechin-3-gallate inhibits osteogenic differentiation of vascular smooth muscle cells through the transcription factor JunB

Abstract

Medial arterial calcification (MAC) accompanying chronic kidney disease (CKD) leads to increased vessel wall stiffness, myocardial ischemia, heart failure, and increased cardiovascular morbidity and mortality. Unfortunately, there are currently no drugs available to treat MAC. The natural polyphenol epigallocatechin-3-gallate (EGCG) has been demonstrated to protect against cardiovascular disease; however, whether EGCG supplementation inhibits MAC in CKD remains unclear. In this study, we utilize a CKD-associated MAC model to investigate the effects of EGCG on vascular calcification and elucidate the underlying mechanisms involved. Our findings demonstrate that EGCG treatment significantly reduces calcium phosphate deposition and osteogenic differentiation of VSMCs in vivo and in vitro in a dose-dependent manner. In addition, through RNA sequencing (RNA-seq) analysis, we show a significant activation of the transcription factor JunB both in CKD mouse arteries and in osteoblast-like VSMCs. Notably, EGCG effectively suppresses CKD-associated MAC by inhibiting the activity of JunB. In addition, overexpression of JunB can abolish while knockdown of JunB can enhance the inhibitory effect of EGCG on the osteogenic differentiation of VSMCs. Furthermore, EGCG supplementation inhibits MAC in CKD via modulation of the JunB-dependent Ras/Raf/MEK/ERK signaling pathway. In conclusion, our study highlights the potential therapeutic value of EGCG for managing CKD-associated MAC, as it mitigates this pathological process through targeted inactivation of JunB.

1. Introduction

In recent decades, the incidence of cardiovascular disease has steadily increased, rendering it the primary cause of death for numerous ethnic groups globally [1]. Vascular calcification plays a pivotal role in the pathogenesis of cardiovascular disease by causing ectopic deposition of calcium hydroxyapatite minerals in the arterial wall [1,2]. Previous studies have shown that patients with vascular calcification associated with chronic kidney disease (CKD) have a significant increase in major adverse cardiovascular events [3]. Depending on where calcium phosphate deposits occur, vascular calcification is typically classified as intimal or medial calcification. Although both types are present in CKD patients, previous studies have demonstrated that mortality is more closely linked to medial arterial calcification (MAC) [4]. Therefore, identifying drugs to inhibit MAC or uncovering its molecular mechanisms is crucial for intervening in CKD.

Recent studies indicated that the osteogenic differentiation of vascular smooth muscle cells (VSMCs) is essential in this CKD-associated MAC [5]. When exposed to pathological stimuli, such as calcium and phosphate metabolism disorders, VSMCs undergo a phenotypic switch from a contracted state to an osteogenic phenotype [1]. These osteoblast-like VSMCs are capable of secreting various osteogenic differentiation proteins, including alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), and bone morphogenetic protein-2 (BMP2), to promote the progression of MAC in CKD [6]. However, the precise pathophysiological mechanisms underlying the osteogenic differentiation of VSMCs remain poorly defined, and effective approaches for inhibiting the osteogenic differentiation of VSMCs are still lacking.

Epigallocatechin-3-gallate (EGCG) is a monomeric polyphenol compound extracted from green tea and is the primary component responsible for the pharmacological effects of green tea. EGCG has a variety of biological activities. EGCG has been recognized for its pharmacological effects on inflammatory bowel disease (IBD) due to its anti-inflammatory properties [7]. EGCG has antioxidant and free radical scavenging activities and is thus beneficial against metabolic diseases such as non-alcoholic fatty liver disease, obesity, and type 2 diabetes [8]. EGCG selectively induces the death of cancer cells by modulating antioxidant pathways, which can improve antitumor effects [9]. Numerous studies have shown that EGCG plays a protective role in cardiovascular diseases, but its specific effect on CKD-associated MAC remains to be explored.