ARRB1 suppresses the activation of hepatic macrophages via modulating endoplasmic reticulum stress in lipopolysaccharide-induced acute liver injury

Yiming Lei,Haoxiong Zhou,Sizhe Wan,Bin Wu,Huiling Liu,Lingjun Chen,Yidong Yang

doi:10.1038/s41420-021-00615-9

Abstract

Acute liver injury (ALI) caused by multiple inflammatory responses is a monocyte-/macrophage-mediated liver injury that is associated with high morbidity and mortality. Liver macrophage activation is a vital event that triggers ALI. However, the mechanism of liver macrophage activation has not been fully elucidated. This study examined the role of β-arrestin1 (ARRB1) in wild-type (WT) and ARRB1-knockout (ARRB1-KO) mouse models of ALI induced by lipopolysaccharide (LPS), and ARRB1-KO mice exhibited more severe inflammatory injury and liver macrophage activation compared to WT mice. We found that LPS treatment reduced the expression level of ARRB1 in Raw264.7 and THP-1 cell lines, and mouse primary hepatic macrophages. Overexpression of ARRB1 in Raw264.7 and THP-1 cell lines significantly attenuated LPS-induced liver macrophage activation, such as transformation in cell morphology and enhanced expression of proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), while downregulation of ARRB1 by small interfering RNA and ARRB1 deficiency in primary hepatic macrophages both aggravated macrophage activation. Moreover, overexpression of ARRB1 suppressed LPS-induced endoplasmic reticulum (ER) stress in liver macrophages, and inhibition of ER stress impeded excessive hepatic macrophage activation induced by downregulation of ARRB1. Our data demonstrate that ARRB1 relieves LPS-induced ALI through the ER stress pathway to regulate hepatic macrophage activation and that ARRB1 may be a potential therapeutic target for ALI.

Highlights

Acute liver injury (ALI) is a complex and life-threatening disease caused by multiple inflammation-related etiologies, such as sepsis, alcohol addiction, metabolic syndrome, drug-induced liver disease, and virus or bacterial infection [1, 2], and is associated with high mortality due to a lack of specific therapy
LPS from gramnegative bacteria can activate macrophages to release a variety of inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6, which in turn lead to massive hepatocyte apoptosis or necrosis along with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) release into peripheral blood [8]. β-Arrestin1 (ARRB1) belongs to the arrestin family originally identified as a multifunctional adaptor protein that negatively regulates the desensitization and internalization of G-proteincoupled receptors (GPCRs) [9]
We found that Raw264.7 and THP-1 cells cell activation, we tested the levels of TNF-α, IL-1β, and IL-6 by realobviously exhibited characteristics of activated macrophages time PCR in vector- or ARRB1-overexpressing Raw264.7 and THP-1 when stimulated with LPS (1 μg/ml), such as increased size, cells treated with LPS (1 μg/ml) treatment for 6 h and mouse primary hepatic macrophages (PHMs) polygonization, and much more and longer pseudopodia (Fig. 2A). with LPS (0.5 μg/ml) treatment

Summary

Introduction

Acute liver injury (ALI) is a complex and life-threatening disease caused by multiple inflammation-related etiologies, such as sepsis, alcohol addiction, metabolic syndrome, drug-induced liver disease, and virus or bacterial infection [1, 2], and is associated with high mortality due to a lack of specific therapy. Despite considerable differences in these etiologies, the pathophysiological manifestations of ALI are mainly hepatocyte injury, inflammatory cell infiltration and activation, and disordered inflammatory response [3]. In this pathologic process, liver macrophages (Kupffer cells) play a crucial role as modulators of the immune system [4], and activated macrophages regulate the immune response by recognizing and expressing antigens and releasing inflammatory cytokines [5]. LPS from gramnegative bacteria can activate macrophages to release a variety of inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6, which in turn lead to massive hepatocyte apoptosis or necrosis along with aspartate aminotransferase (AST) and alanine aminotransferase (ALT) release into peripheral blood [8]. There are few Received: 7 May 2021 Revised: 7 July 2021 Accepted: 26 July 2021

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