Elsevier

Biochemical Pharmacology

Volume 86, Issue 6, 15 September 2013, Pages 836-843
Biochemical Pharmacology

Role of hepatic resident and infiltrating macrophages in liver repair after acute injury

https://doi.org/10.1016/j.bcp.2013.07.006Get rights and content

Abstract

Treatment of liver disease, caused by hepatotoxins, viral infections, alcohol ingestion, or autoimmune conditions, remains challenging and costly. The liver has a powerful capacity to repair and regenerate, thus a thorough understanding of this tightly orchestrated process will undoubtedly improve clinical means of restoring liver function after injury. Using a murine model of acute liver injury caused by overdose of acetaminophen (APAP), our studies demonstrated that the combined absence of liver resident macrophages (Kupffer cells, KCs), and infiltrating macrophages (IMs) resulted in a marked delay in liver repair, even though the initiation and extent of peak liver injury was not impacted. This delay was not due to impaired hepatocyte proliferation but rather prolonged vascular leakage, which is caused by APAP-induced liver sinusoidal endothelial cell (LSEC) injury. We also found that KCs and IMs express an array of angiogenic factors and induce LSEC proliferation and migration. Our mechanistic studies suggest that hypoxia-inducible factor (HIF) may be involved in regulating the angiogenic effect of hepatic macrophages (Macs), as we found that APAP challenge resulted in hypoxia and stabilization of HIF in the liver and hepatic Macs. Together, these data indicate an important role for hepatic Macs in liver blood vessel repair, thereby contributing to tissue recovery from acute injury.

Introduction

Liver disease is a significant health problem, affecting millions of people in the world. Currently, transplantation is the only effective treatment for acute liver failure and end-stage chronic liver injury. However, transplantation is costly, challenging, and well-matched donor tissues are not readily available. Therefore, there is a pressing need to develop pharmacological treatments. One area of research that holds promise of breakthrough discoveries is better understanding of the liver's own repair and regeneration processes. The majority of studies of liver regeneration have used animal models of partial hepatectomy. However, hepatectomy often lacks the cell death and tissue inflammation that are commonly observed in acute and chronic liver injury. Therefore, the present study aimed to investigate liver repair processes after overdose of acetaminophen (APAP)-induced liver injury (AILI), which itself is a significant clinical problem [1]. Macrophages/monocytes play important roles in liver injury and liver repair. They produce pro- and anti-inflammatory mediators which can trigger hepatocytic cell death pathways as well as activate protective signaling pathways [2], [3]. Damage-associated molecular pattern molecules (DAMPS), such as high-mobility group box 1 protein and heat shock proteins [4] [5], are released during liver injury and activate macrophages to produce cytokines and chemokines. Macrophage-derived soluble mediators can exacerbate cellular injury or inhibit cell death and promote hepatocyte proliferation [2]. Another important function of macrophages is to phagocytose dead cells and cellular debris [6], [7], [8]. As result, these cells produce angiogenic factors and growth factors, thereby promoting tissue repair.

There are at least two types of macrophages in the liver after acute injury, resident macrophages (Kupffer cells, KCs) and infiltrating macrophages. We have reported that APAP challenge causes hepatic recruitment of circulating monocytes in C–C chemokine receptor type 2 (CCR2)-dependent manner [9]. Our studies also demonstrated that the lack of infiltrating macrophages (IMs) in CCR2−/− mice resulted in a slight delay in tissue recovery from APAP-induced liver injury (AILI). However, the observation that liver repair was completed by 72 h in CCR2−/− mice (versus 48 h in WT mice) suggested that resident Kupffer cells are also involved in liver repair and can compensate for the lack of IMs. Hence, the present study aims to investigate the combined role of resident and infiltrating hepatic Macs during tissue repair.

We developed a mouse model in which either or both populations of hepatic Macs (resident KCs and IMs) could be depleted. We found that the liver repaired and histology returned to normal by day 3 after APAP in mice with intact hepatic Macs or lack of either population of Macs; however, necrotic areas remained prominent in mice with the combined absence of both populations of Macs. Moreover, our data revealed an important angiogenic function of hepatic Macs that plays an integral role in liver repair from AILI.

Section snippets

Animal treatment and assessment of hepatotoxicity

Seven–ten week old male BALB/cJ wild-type (WT, Jackson Laboratories, Bar Harbor, ME) and CCR2−/− mice [on Balb/cJ background, provided by Cara L. Mack, M.D. (Department of Pediatrics, School of Medicine, University of Colorado Denver)] were used. All animal procedures were approved by the Institutional Animal Care and Use Committee of the University of Colorado Anschutz Medical Campus. Animals were fasted overnight for approximately 16 h to deplete glutathione levels, prior to intraperitoneal

The combined absence of KCs and IMs markedly delays liver repair after AILI

In the present study we developed an in vivo approach to assess the roles of KCs and IMs in the progression and regression of AILI by using 4 groups of mice having none, either, or both populations of the hepatic Macs (see Section 2).

At 24 h after APAP treatment, the ALT levels (Fig. 1B) were similar and liver histopathology (Fig. 1A, 24 h) was comparable across the 4 groups. These data suggested that the extent of initial hepatic injury was not impacted by the absence of either or both

Discussion

Liver disease caused by various etiologies, such as viral infection, alcohol or drug ingestion, metabolic disorders, and autoimmunity affect approximately 150,000 new patients in the U.S. each year [18]. Although liver transplantation is an effective treatment for chronic and acute liver failure, the limited options for therapeutic interventions remain a pressing issue of treating liver disease. A better understanding the liver's own repair and regeneration processes may lead to discoveries of

References (36)

  • H.W. Zimmermann et al.

    Functional role of monocytes and macrophages for the inflammatory response in acute liver injury

    Front Physiol

    (2012)
  • D.J. Antoine et al.

    High-mobility group box-1 protein and keratin-18, circulating serum proteins informative of acetaminophen-induced necrosis and apoptosis in vivo

    Toxicol Sci

    (2009)
  • V.A. Fadok et al.

    Macrophages that have ingested apoptotic cells in vitro inhibit proinflammatory cytokine production through autocrine/paracrine mechanisms involving TGF-beta, PGE2, and PAF

    J Clin Invest

    (1998)
  • P.P. McDonald et al.

    Transcriptional and translational regulation of inflammatory mediator production by endogenous TGF-beta in macrophages that have ingested apoptotic cells

    J Immunol

    (1999)
  • M.L. Huynh et al.

    Phosphatidylserine-dependent ingestion of apoptotic cells promotes TGF-beta1 secretion and the resolution of inflammation

    J Clin Invest

    (2002)
  • M.P. Holt et al.

    Identification and characterization of infiltrating macrophages in acetaminophen-induced liver injury

    J Leukoc Biol

    (2008)
  • C. Ju et al.

    Immunohistochemical detection of protein adducts of 2,4-dinitrochlorobenzene in antigen presenting cells and lymphocytes after oral administration to mice: lack of a role of Kupffer cells in oral tolerance

    Chem Res Toxicol

    (2001)
  • C. Meijer et al.

    Kupffer cell depletion by CI2MDP-liposomes alters hepatic cytokine expression and delays liver regeneration after partial hepatectomy

    Liver

    (2000)
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    Financial support: U.S. National Institutes of Health grant RO1 ES012914 (to C.J.) and The ALSAM Foundation Skaggs Scholars Program Award (to C.J.).

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