The Inhibitory Effect of Quercetin on Asymmetric Dimethylarginine-Induced Apoptosis Is Mediated by the Endoplasmic Reticulum Stress Pathway in Glomerular Endothelial Cells

Weikang Guo,Liyan Wang,Sha Liu,Wendi Dai,Aihua Zhang,Jiaxiang Ding,Zongli Diao,Xue Han,Wenhu Liu

doi:10.3390/ijms15010484

Abstract

Asymmetric dimethylarginine (ADMA) is considered an independent mortality and cardiovascular risk factor in chronic kidney disease (CKD) patients, and contributes to the development of renal fibrosis. Quercetin (QC), a natural component of foods, protects against renal injury. Here, we explored the possible mechanisms that are responsible for ADMA-induced renal fibrosis and the protective effect of QC. We found that ADMA treatment activated the endoplasmic reticulum (ER) stress sensor proteins phosphorylated protein kinase RNA-activated-like ER kinase (PERK) and inositol requiring-1α (IRE1), which correspondingly induced C/EBP homologous protein (CHOP) expression and phosphorylated c-Jun N-terminal kinase (JNK) phosphorylation in glomerular endothelial cells (GEnCs). Following this, ADMA promoted ER stress-induced apoptosis and resulted in transforming growth factor β (TGF-β) expression in GEnCs. SP600125, an inhibitor of JNK, and CHOP siRNA protected against ADMA-induced cell apoptosis and TGF-β expression. QC prevented ADMA-induced PERK and IRE1 apoptotic ER stress pathway activation. Also, ADMA-induced GEnCs apoptosis and TGF-β expression was reduced by QC. Overexpression of CHOP blocked QC-mediated protection from apoptosis in ER stressed cells. Overall, these observations indicate that ADMA may induce GEnCs apoptosis and TGF-β expression by targeting the PERK-CHOP and IRE1-JNK pathway. In addition, drugs such as QC targeting ER stress may hold great promise for the development of novel therapies against ADMA-induced renal fibrosis.

Highlights

Asymmetric dimethylarginine (ω-NG, NG-asymmetric dimethylarginine; ADMA) is a residue of the proteolysis of arginine methylated proteins, and an endogenous competitive inhibitor of nitric oxide synthase (NOS) enzymes at supraphysiological concentrations, the physiological relevance of this inhibition remains unclear [1]
It was revealed that treatment with ADMA (100 μM) for 12–48 h increased the percentage of apoptotic cells (Figure 1A,B)
We found that the expression of activating transcription factor 4 (ATF4) mRNA, C/EBP homologous protein (CHOP) protein and mRNA were increased after treatment with 100 μM ADMA for 12–48 h (Figure 2A,B)

Summary

Introduction

Asymmetric dimethylarginine (ω-NG, NG-asymmetric dimethylarginine; ADMA) is a residue of the proteolysis of arginine methylated proteins, and an endogenous competitive inhibitor of nitric oxide synthase (NOS) enzymes at supraphysiological concentrations, the physiological relevance of this inhibition remains unclear [1]. Blood concentrations of ADMA are markedly increased at a very early stage, even when glomerular filtration rate (GFR) is still within the normal range [2]. Increased ADMA induces glomerular and tubulointerstitial fibrosis and accelerates renal dysfunction progression [3,4,5,6]. Apoptosis of glomerular endothelial cells (GEnC) is known to correlate directly with the development of glomerular scarring, which eventually leads to glomerular sclerosis [7,8]. The mechanism of GEnC apoptosis is not well understood.

Methods

Results

Conclusion