Apoptosis signal-regulating kinase 1 inhibition attenuates cardiac hypertrophy and cardiorenal fibrosis induced by uremic toxins: Implications for cardiorenal syndrome

Feby Savira,Kevin Huang,Ian Wang,Robert N Willette,Zhiliang Li,Longxing Cao,Beat M Jucker,Bing Hui Wang,Qiang Fu,Henry Krum,Yue Hua,Wendi Yang,Li Huang

doi:10.1371/journal.pone.0187459

Abstract

Intracellular accumulation of protein-bound uremic toxins in the setting of cardiorenal syndrome leads to adverse effects on cardiorenal cellular functions, where cardiac hypertrophy and cardiorenal fibrosis are the hallmarks. In this study, we sought to determine if Apoptosis Signal-Regulated Kinase 1 (ASK1), an upstream regulator of cellular stress response, mediates cardiac hypertrophy and cardiorenal fibrosis induced by indoxyl sulfate (IS) and p-cresol sulfate (PCS) in vitro, and whether ASK1 inhibition is beneficial to ameliorate these cellular effects. PCS augmented cardiac myocyte hypertrophy and fibroblast collagen synthesis (as determined by 3H-leucine and 3H-proline incorporation, respectively), similar to our previous finding with IS. IS and PCS also increased collagen synthesis of proximal tubular cells and renal mesangial cells. Pro-hypertrophic (α-skeletal muscle actin and β-MHC) and pro-fibrotic genes (TGF-β1 and ctgf) were induced by both IS and PCS. Western blot analyses revealed the activation of ASK1 and downstream mitogen activated protein kinases (MAPKs) (p38MAPK and ERK1/2) as well as nuclear factor-kappa B (NF-κB) by IS and PCS. ASK1, OAT1/3, ERK1/2 and p38MAPK inhibitors suppressed all these effects. In summary, IS and PCS exhibit pro-hypertrophic and pro-fibrotic properties, at least in part, via the activation of ASK1 and its downstream pathways. ASK1 inhibitor is an effective therapeutic agent to alleviate protein-bound uremic toxin-induced cardiac hypertrophy and cardiorenal fibrosis in vitro, and may be translated further for cardiorenal syndrome therapy.

Highlights

Cardiorenal syndrome remains a global challenge, with patients relentlessly faced with high morbidity and mortality rates and significant burden of healthcare-related costs [1]
Dose-dependent inhibitions were seen in p-cresol sulfate (PCS)-stimulated Neonatal rat cardiac myocyte (NCM) hypertrophy (100 μM) after co-treatment with G226 (Fig 2C), OAT1/3 antagonist (Probenecid) (Fig 2D) as well as p38MAPK and ERK1/2 inhibitors (RWJ-67657 and U0126, respectively) (Fig 2E and 2F) at indicated concentrations
Mechanistic studies reveal the activation of Apoptosis Signal-Regulated Kinase 1 (ASK1) and downstream mitogen activated protein kinases (MAPKs), ERK1/2 and p38MAPK as well as NFκB pathways as well as the increase in pro-hypertrophic and pro-fibrotic genes by Indoxyl sulfate (IS) and PCS, all of which were suppressed by G226

Summary

Introduction

Cardiorenal syndrome remains a global challenge, with patients relentlessly faced with high morbidity and mortality rates and significant burden of healthcare-related costs [1]. Cardiac hypertrophy as well as cardiac and renal fibrosis are the hallmarks of pathological changes within the heart and the kidneys Excessive activation of these cellular processes is critical in mediating both cardiac and renal impairment, contributing to CRS pathophysiology. Serum levels of IS and PCS are elevated by 54 and 17 times, respectively, whereas their amounts are undetectable in healthy individuals [5] Both toxins are associated with increased mortality in patients with cardiovascular disease (CVD) and renal impairment [8,9,10]. Targeting these toxic solutes and related pathways may be of a high therapeutic value to attenuate CRS progression [11]

Methods

Results

Conclusion