ALK5 deficiency inhibits macrophage inflammation and lipid loading by targeting KLF4.

Wenyan Li,Zhaofeng Li,Junhua Wang

doi:10.1042/bsr20194188

Abstract

The transforming growth factor type-β (TGF-β) has been demonstrated to play an important role in the development of atherosclerosis through binding to the serine/threonine kinase transmembrane type I and type II receptors. However, as a key type I receptor for TGF-β, the exact role and the underlying mechanism of Activin receptor-like kinase 5 (ALK5) on macrophage activation involved in atherogenesis remain unclear. In the present study, enhanced ALK5 expression was found in bone marrow derived macrophages (BMDMs) upon OX-LDL stimulation tested by RT-PCR and Western blot, which was further verified by co-immunofluorescence staining. Next, the loss-of-function of ALK5 used AdshALK5 transfection was performed to test the effect of ALK5 on macrophage activation. We observed that ALK5 silencing inhibited pro-inflammatory but promoted anti-inflammatory macrophage markers expression. Moreover, decreased foam cell formation was found in ALK5 knockdown macrophages accompanied by increased cholesterol efflux. Mechanistically, ALK5 knockdown significantly increased KLF4 expression that was responsible for the attenuated macrophage activation induced by ALK5 knockdown. Collectively, these findings suggested that neutralization of ALK5 may act as a promising strategy for the management of atherosclerosis.

Highlights

Atherosclerosis is well recognized as a chronic inflammatory disease [1] and accounts for the development of cardiovascular diseases (CVDs) that is the leading cause of mortality and morbidity worldwide, including myocardial infarction, sudden cardiac death and stroke [2]
The present study exhibited that Activin receptor-like kinase 5 (ALK5) expression was significantly up-regulated in bone marrow derived macrophage (BMDM) with OX-LDL administration and primary located in cytoplasm of macrophages
To explore the effect of ALK5 on macrophage activation involved in the development of atherosclerosis, we first examined whether ALK5 expression was changed in isolated BMDMs upon OX-LDL administration

Summary

Introduction

Atherosclerosis is well recognized as a chronic inflammatory disease [1] and accounts for the development of cardiovascular diseases (CVDs) that is the leading cause of mortality and morbidity worldwide, including myocardial infarction, sudden cardiac death and stroke [2]. Macrophage has emerged to show plastic properties and can regulate inflammatory response by shifting the activation of classically pro-inflammatory M1 macrophages and resolving M2 macrophages [4]. The excess engulfment of oxidized low-density lipoprotein gives rise to foam cell formation and accelerates atherogenesis associated with the vulnerable plaques [5]. Exploring the key regulator of macrophage activation implicated in atherogenesis may provide an effective strategy for preventing atherosclerosis. The present study exhibited that ALK5 expression was significantly up-regulated in BMDMs with OX-LDL administration and primary located in cytoplasm of macrophages. Loss-of-function study demonstrated that ALK5 silencing dramatically inhibited inflammatory response and foam cell formation. We found that ALK5 knockdown significantly promoted KLF4 expression and the effect of ALK5 silencing on macrophage activation was largely reversed by KLF4 inactivation

Methods

Results

Conclusion