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Luyendyk JP, Morozova E, Copple BL. Good cells go bad: immune dysregulation in the transition from acute liver injury to liver failure after acetaminophen overdose. Drug Metab Dispos 2023:DMD-MR-2023-001280. [PMID: 38050055 DOI: 10.1124/dmd.123.001280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 11/12/2023] [Accepted: 11/27/2023] [Indexed: 12/06/2023] Open
Abstract
The role of inflammatory cells and other components of the immune system in acetaminophen (APAP)-induced liver injury and repair has been extensively investigated. Although this has resulted in a wealth of information regarding the function and regulation of immune cells in the liver after injury, apparent contradictions have fueled controversy around the central question of whether the immune system is beneficial or detrimental after APAP overdose. Ultimately, this may not be a simple assignment of "good" or "bad." Clinical studies have clearly demonstrated an association between immune dysregulation and a poor outcome in patients with severe liver damage/liver failure induced by APAP overdose. To date, studies in mice have not uniformly replicated this connection. The apparent disconnect between clinical and experimental studies has perhaps stymied progress and further complicated investigation of the immune system in APAP-induced liver injury. Mouse models are often dismissed as not recapitulating the clinical scenario. Moreover, clinical investigation is most often focused on the most severe APAP overdose patients, those with liver failure. Notably, recent studies have made it apparent that the functional role of the immune system in the pathogenesis of APAP-induced liver injury is highly context dependent and greatly influenced by the experimental conditions. In this review, we highlight some of these recent findings, and suggest strategies seeking to resolve and build on existing disconnects in the literature. Significance Statement Acetaminophen overdose is the most frequent cause of acute liver failure in the United States. Studies indicate that dysregulated innate immunity contributes to the transition from acute liver injury to acute liver failure. In this review, we discuss the evidence for this and the potential underlying causes.
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Affiliation(s)
- James P Luyendyk
- Pathobiology and Diagnostic Investigation, Michigan State University, United States
| | - Elena Morozova
- Pathobiology and Diagnostic Investigation, Michigan State University, United States
| | - Bryan L Copple
- Department of Pharmacology and Toxicology, Michigan State University, United States
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Roth K, Strickland J, Pant A, Freeborn R, Kennedy R, Rockwell CE, Luyendyk JP, Copple BL. Interleukin-10 disrupts liver repair in acetaminophen-induced acute liver failure. Front Immunol 2023; 14:1303921. [PMID: 38094302 PMCID: PMC10716295 DOI: 10.3389/fimmu.2023.1303921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2023] [Accepted: 11/13/2023] [Indexed: 12/18/2023] Open
Abstract
Introduction Systemic levels of the anti-inflammatory cytokine interleukin 10 (IL-10) are highest in acetaminophen (APAP)-induced acute liver failure (ALF) patients with the poorest prognosis. The mechanistic basis for this counterintuitive finding is not known, as induction of IL-10 is hypothesized to temper the pathological effects of immune cell activation. Aberrant production of IL-10 after severe liver injury could conceivably interfere with the beneficial, pro-reparative actions of immune cells, such as monocytes. Methods To test this possibility, we determined whether IL-10 levels are dysregulated in mice with APAP-induced ALF and further evaluated whether aberrant production of IL-10 prevents monocyte recruitment and/or the resolution of necrotic lesions by these cells. Results Our studies demonstrate that in mice challenged with 300 mg/kg acetaminophen (APAP), a hepatotoxic dose of APAP that fails to produce ALF (i.e., APAP-induced acute liver injury; AALI), Ly6Chi monocytes were recruited to the liver and infiltrated the necrotic lesions by 48 hours coincident with the clearance of dead cell debris. At 72 hours, IL-10 was upregulated, culminating in the resolution of hepatic inflammation. By contrast, in mice treated with 600 mg/kg APAP, a dose that produces clinical features of ALF (i.e., APAP-induced ALF; AALF), IL-10 levels were markedly elevated by 24 hours. Early induction of IL-10 was associated with a reduction in the hepatic numbers of Ly6Chi monocytes resulting in the persistence of dead cell debris. Inhibition of IL-10 in AALF mice, beginning at 24 hours after APAP treatment, increased the hepatic numbers of monocytes which coincided with a reduction in the necrotic area. Moreover, pharmacologic elevation of systemic IL-10 levels in AALI mice reduced hepatic myeloid cell numbers and increased the area of necrosis. Discussion Collectively, these results indicate that during ALF, aberrant production of IL-10 disrupts the hepatic recruitment of monocytes, which prevents the clearance of dead cell debris. These are the first studies to document a mechanistic basis for the link between high IL-10 levels and poor outcome in patients with ALF.
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Affiliation(s)
- Katherine Roth
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, United States
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI, United States
- College of Human Medicine, Michigan State University, East Lansing, MI, United States
| | - Jenna Strickland
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, United States
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI, United States
- College of Human Medicine, Michigan State University, East Lansing, MI, United States
| | - Asmita Pant
- Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, MI, United States
| | - Robert Freeborn
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, United States
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
| | - Rebekah Kennedy
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, United States
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
| | - Cheryl E. Rockwell
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, United States
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI, United States
- College of Human Medicine, Michigan State University, East Lansing, MI, United States
| | - James P. Luyendyk
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
- Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, MI, United States
| | - Bryan L. Copple
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, United States
- Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
- Cell and Molecular Biology Program, Michigan State University, East Lansing, MI, United States
- College of Human Medicine, Michigan State University, East Lansing, MI, United States
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Copple BL, Rockwell CE. Preface. Adv Pharmacol 2021; 91:xi-xii. [PMID: 34099114 DOI: 10.1016/s1054-3589(21)00040-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
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Zagórska A, Través PG, Jiménez-García L, Strickland JD, Oh J, Tapia FJ, Mayoral R, Burrola P, Copple BL, Lemke G. Differential regulation of hepatic physiology and injury by the TAM receptors Axl and Mer. Life Sci Alliance 2020; 3:e202000694. [PMID: 32571802 PMCID: PMC7335405 DOI: 10.26508/lsa.202000694] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 05/28/2020] [Accepted: 05/29/2020] [Indexed: 12/15/2022] Open
Abstract
Genome-wide association studies have implicated the TAM receptor tyrosine kinase (RTK) Mer in liver disease, yet our understanding of the role that Mer and its related RTKs Tyro3 and Axl play in liver homeostasis and the response to acute injury is limited. We find that Mer and Axl are most prominently expressed in hepatic Kupffer and endothelial cells and that as mice lacking these RTKs age, they develop profound liver disease characterized by apoptotic cell accumulation and immune activation. We further find that Mer is critical to the phagocytosis of apoptotic hepatocytes generated in settings of acute hepatic injury, and that Mer and Axl act in concert to inhibit cytokine production in these settings. In contrast, we find that Axl is uniquely important in mitigating liver damage during acetaminophen intoxication. Although Mer and Axl are protective in acute injury models, we find that Axl exacerbates fibrosis in a model of chronic injury. These divergent effects have important implications for the design and implementation of TAM-directed therapeutics that might target these RTKs in the liver.
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Affiliation(s)
- Anna Zagórska
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA, USA
| | - Paqui G Través
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA, USA
- Instituto de Investigaciones Biomédicas Alberto Sols (CSIC-UAM), Madrid, Spain
| | | | - Jenna D Strickland
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, USA
| | - Joanne Oh
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA, USA
| | - Francisco J Tapia
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA, USA
| | - Rafael Mayoral
- Division of Endocrinology & Metabolism, Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Patrick Burrola
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA, USA
| | - Bryan L Copple
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, MI, USA
| | - Greg Lemke
- Molecular Neurobiology Laboratory, The Salk Institute, La Jolla, CA, USA
- Immunobiology and Microbial Pathogenesis Laboratory, The Salk Institute, La Jolla, CA, USA
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Poole LG, Pant A, Cline‐Fedewa HM, Williams KJ, Copple BL, Palumbo JS, Luyendyk JP. Liver fibrosis is driven by protease-activated receptor-1 expressed by hepatic stellate cells in experimental chronic liver injury. Res Pract Thromb Haemost 2020; 4:906-917. [PMID: 32685902 PMCID: PMC7354391 DOI: 10.1002/rth2.12403] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Accepted: 05/14/2020] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND Blood coagulation protease activity is proposed to drive hepatic fibrosis through activation of protease-activated receptors (PARs). Whole-body PAR-1 deficiency reduces experimental hepatic fibrosis, and in vitro studies suggest a potential contribution by PAR-1 expressed by hepatic stellate cells. However, owing to a lack of specific tools, the cell-specific role of PAR-1 in experimental hepatic fibrosis has never been formally investigated. Using a novel mouse expressing a conditional PAR-1 allele, we tested the hypothesis that PAR-1 expressed by hepatic stellate cells contributes to hepatic fibrosis. METHODS PAR-1flox/flox mice were crossed with mice expressing Cre recombinase controlled by the lecithin retinol acyltransferase (LRAT) promoter, which induces recombination in hepatic stellate cells. Male PAR-1flox/flox/LRATCre and PAR-1flox/flox mice were challenged twice weekly with carbon tetrachloride (CCl4, 1 mL/kg i.p.) for 6 weeks to induce liver fibrosis. RESULTS PAR-1 mRNA levels were reduced (>95%) in hepatic stellate cells isolated from PAR-1flox/flox/LRATCre mice. Hepatic stellate cell activation was evident in CCl4-challenged PAR-1flox/flox mice, indicated by increased α-smooth muscle actin labeling and induction of several profibrogenic genes. CCl4-challenged PAR-1flox/flox mice displayed robust hepatic collagen deposition, indicated by picrosirius red staining and type I collagen immunolabeling. Notably, stellate cell activation and collagen deposition were significantly reduced (>30%) in PAR-1flox/flox/LRATCre mice. Importantly, the reduction in liver fibrosis was not a consequence of reduced acute CCl4 hepatotoxicity in PAR-1flox/flox/LRATCre mice. CONCLUSIONS The results constitute the first direct experimental evidence that PAR-1 expressed by stellate cells directly promotes their profibrogenic phenotype and hepatic fibrosis in vivo.
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Affiliation(s)
- Lauren G. Poole
- Institute for Integrative ToxicologyMichigan State UniversityEast LansingMIUSA
- Department of Pathobiology & Diagnostic InvestigationMichigan State UniversityEast LansingMIUSA
| | - Asmita Pant
- Department of Pathobiology & Diagnostic InvestigationMichigan State UniversityEast LansingMIUSA
| | - Holly M. Cline‐Fedewa
- Department of Pathobiology & Diagnostic InvestigationMichigan State UniversityEast LansingMIUSA
| | - Kurt J. Williams
- Department of Pathobiology & Diagnostic InvestigationMichigan State UniversityEast LansingMIUSA
| | - Bryan L. Copple
- Department of Pharmacology and ToxicologyMichigan State UniversityEast LansingMIUSA
| | - Joseph S. Palumbo
- Cancer and Blood Diseases InstituteCincinnati Children’s Hospital Medical Center and the University of Cincinnati College of MedicineCincinnatiOHUSA
| | - James P. Luyendyk
- Institute for Integrative ToxicologyMichigan State UniversityEast LansingMIUSA
- Department of Pathobiology & Diagnostic InvestigationMichigan State UniversityEast LansingMIUSA
- Department of Pharmacology and ToxicologyMichigan State UniversityEast LansingMIUSA
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Roth K, Strickland J, Copple BL. Regulation of macrophage activation in the liver after acute injury: Role of the fibrinolytic system. World J Gastroenterol 2020; 26:1879-1887. [PMID: 32390699 PMCID: PMC7201151 DOI: 10.3748/wjg.v26.i16.1879] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 03/31/2020] [Accepted: 04/08/2020] [Indexed: 02/06/2023] Open
Abstract
The liver functions, in part, to prevent exposure of the body to potentially harmful substances ingested in the diet. While it is highly efficient at accomplishing this, it is frequently prone to liver injury due to the biotransformation of xenobiotics into toxic metabolites. To counter this injury, the liver has evolved a unique capacity to rapidly and efficiently repair itself. Successful resolution of acute liver injury relies on hepatic macrophage populations that orchestrate the reparative response. After injury, Kupffer cells, the resident macrophages of the liver, become activated and secrete proinflammatory cytokines. These cytokines recruit other immune cells, including monocyte-derived macrophages, to the liver where they contribute to the repair process. Monocyte-derived macrophages traffic into the necrotic foci where they rapidly phagocytose dead cell debris. Simultaneous with this process, these cells change phenotype from a proinflammatory macrophage to a pro-restorative macrophage that produce pro-mitogenic growth factors and anti-inflammatory cytokines. Ultimately this process triggers resolution of inflammation, and along with proliferation of other hepatic cells, restores the liver architecture and function. While the mechanisms regulating specific macrophage functions during repair remain to be elucidated, recent studies indicate a key role for the fibrinolytic system in coordinating macrophage function during repair. In this review, we will highlight the function and role of hepatic macrophages in repair after acute liver injury, and will discuss the role of the fibrinolytic enzyme, plasmin, in regulation of these various processes.
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Affiliation(s)
- Katherine Roth
- Department of Pharmacology and Toxicology, Institute for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, United States
| | - Jenna Strickland
- Department of Pharmacology and Toxicology, Institute for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, United States
| | - Bryan L Copple
- Department of Pharmacology and Toxicology, Institute for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, United States
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Strickland J, Garrison D, Copple BL. Hypoxia upregulates Cxcl12 in hepatocytes by a complex mechanism involving hypoxia-inducible factors and transforming growth factor-β. Cytokine 2020; 127:154986. [PMID: 31951966 PMCID: PMC7255688 DOI: 10.1016/j.cyto.2020.154986] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 12/26/2019] [Accepted: 01/03/2020] [Indexed: 02/08/2023]
Abstract
INTRODUCTION Cxcl12, or stromal-derived factor-1, is a chemokine produced by several hepatic cell types, including hepatocytes, after liver injury and surgical resection. Studies have revealed that Cxcl12 is important for regeneration of the liver after surgical resection and for development of liver fibrosis during chronic liver injury. While the function of Cxcl12 in the liver is well established, the mechanism by which Cxcl12 is upregulated is not fully understood. Because regions of hypoxia develop in the liver following injury, we tested the hypothesis that hypoxia upregulates Cxcl12 in hepatocytes by a hypoxia-inducible factor (HIF)-dependent mechanism. METHODS To test this hypothesis, primary mouse hepatocytes were isolated from the livers of HIF-1α-deficient mice or HIF-1β-deficient mice and exposed to 1% oxygen. Cxcl12 expression was increased following exposure of primary mouse hepatocytes to 1% oxygen. Previously we have shown, that in addition to HIFs, transforming growth factor-β is required for upregulation of a subset of genes in hypoxic hepatocytes. To examine the role of TGF-β in regulation of Cxcl12 during hypoxia, hepatocytes were pretreated with the TGF-β receptor I inhibitor, SB431542. RESULTS Upregulation of Cxcl12 by hypoxia was partially prevented in hepatocytes from HIF-1α-deficient mice and completely prevented in hepatocytes from HIF-1β-deficient hepatocytes. This suggests that under hypoxic conditions, both HIF-1α and HIF-2α regulate Cxcl12 in hepatocytes. Pretreatment of hepatocytes with SB431542 completely prevented upregulation Cxcl12 by hypoxia. Further, treatment of hepatocytes with recombinant TGF-β1 upregulated Cxcl12 in hepatocytes cultured in room air. CONCLUSION Collectively, these studies demonstrate that hypoxia upregulates Cxcl12 in primary mouse hepatocytes by a mechanism that involves HIFs and TGF-β.
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Affiliation(s)
- Jenna Strickland
- Department of Pharmacology and Toxicology and the Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
| | - Domonique Garrison
- Department of Pharmacology and Toxicology and the Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States
| | - Bryan L Copple
- Department of Pharmacology and Toxicology and the Institute for Integrative Toxicology, Michigan State University, East Lansing, MI, United States.
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Roth K, Strickland J, Joshi N, Deng M, Kennedy RC, Rockwell CE, Luyendyk JP, Billiar TR, Copple BL. Dichotomous Role of Plasmin in Regulation of Macrophage Function after Acetaminophen Overdose. Am J Pathol 2019; 189:1986-2001. [PMID: 31381887 DOI: 10.1016/j.ajpath.2019.07.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/13/2019] [Revised: 06/25/2019] [Accepted: 07/01/2019] [Indexed: 12/21/2022]
Abstract
Kupffer cells and monocyte-derived macrophages are critical for liver repair after acetaminophen (APAP) overdose. These cells produce promitogenic cytokines and growth factors, and they phagocytose dead cell debris, a process that is critical for resolution of inflammation. The factors that regulate these dynamic functions of macrophages after APAP overdose, however, are not fully understood. We tested the hypothesis that the fibrinolytic enzyme, plasmin, is a key regulator of macrophage function after APAP-induced liver injury. In these studies, inhibition of plasmin in mice with tranexamic acid delayed up-regulation of proinflammatory cytokines after APAP overdose. In culture, plasmin directly, and in synergy with high-mobility group B1, stimulated Kupffer cells and bone marrow-derived macrophages to produce cytokines by a mechanism that required NF-κB. Inhibition of plasmin in vivo also prevented trafficking of monocyte-derived macrophages into necrotic lesions after APAP overdose. This prevented phagocytic removal of dead cells, prevented maturation of monocyte-derived macrophages into F4/80-expressing macrophages, and prevented termination of proinflammatory cytokine production. Our studies reveal further that phagocytosis is an important stimulus for cessation of proinflammatory cytokine production as treatment of proinflammatory, monocyte-derived macrophages, isolated from APAP-treated mice, with necrotic hepatocytes decreased expression of proinflammatory cytokines. Collectively, these studies demonstrate that plasmin is an important regulator of macrophage function after APAP overdose.
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Affiliation(s)
- Katherine Roth
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan; Cell and Molecular Biology Program, Michigan State University, East Lansing, Michigan
| | - Jenna Strickland
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan
| | - Nikita Joshi
- Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan; Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - Meihong Deng
- Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Rebekah C Kennedy
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan
| | - Cheryl E Rockwell
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan; Cell and Molecular Biology Program, Michigan State University, East Lansing, Michigan
| | - James P Luyendyk
- Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan; Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - Timothy R Billiar
- Department of Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
| | - Bryan L Copple
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan; Institute for Integrative Toxicology, Michigan State University, East Lansing, Michigan; Cell and Molecular Biology Program, Michigan State University, East Lansing, Michigan.
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Strickland JD, Roth KJ, Copple BL. Failed Phenotype Switching by Hepatic Macrophages Produces Persistent Inflammation in Acute Liver Failure. FASEB J 2019. [DOI: 10.1096/fasebj.2019.33.1_supplement.369.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | - Katherine J Roth
- Cell and Molecular BiologyMichigan State UniversityEast LansingMI
| | - Bryan L Copple
- Pharmacology and ToxicologyMichigan State UniversityEast LansingMI
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Roth K, Rockwell CE, Copple BL. Differential Sensitivity of Kupffer Cells and Hepatic Monocyte-Derived Macrophages to Bacterial Lipopolysaccharide. Clin Exp Gastroenterol Hepatol 2019; 1:106. [PMID: 31555773 PMCID: PMC6759814 DOI: 10.31531/edwiser.jcegh.1000106] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/20/2023]
Abstract
The liver contains two distinct populations of macrophages, monocyte-derived macrophages (MDMs), which primarily reside proximal to the Glisson's capsule and Kupffer cells, which reside within the sinusoids. Kupffer cells infiltrate the liver during embryogenesis and are replenished from local proliferation of mature Kupffer cells. By contrast MDMs arise from hematopoietic stem cells in the bone marrow and are replenishedfrom circulating monocytes. Studies have revealed that these two hepatic macrophage populations possess distinct transcriptomic profiles, suggesting that they may be functionally distinct. In the present study, we tested the hypothesis that MDMs and Kupffer cells are differentially sensitive to bacterial lipopolysaccharide (LPS). MDMs and Kupffer cells were purified to greater than 90% from the livers of mice by using magnetic beads labeled with Cx3cr1 antibody for MDMs and F4/80 antibody for Kupffer cells. Basal levels of tumor necrosis factor-α (TNF-α) mRNA were higher in MDMs when compared to Kupffer cells. After treatment with LPS, mRNA levels of TNF-α, Cxcll, and Cxcl2 were increased to a greater extent in MDMs when compared to Kupffer cells. To confirm these findings, Kupffer cells and MDMs were isolated from mice in which bone marrow transplantation was used to selectively tag cells arising from hematopoietic stem cells in adult mice. Similar to above, treatment of MDMs with LPS increased TNF-α, Cxcll, and Cxcl2 to a greater extent when compared to Kupffer cells. Collectively, these results indicate that MDMs exhibit a greater pro-inflammatory phenotype in the liver when exposed to LPS.
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Affiliation(s)
| | | | - Bryan L. Copple
- Corresponding author: Bryan L. Copple, Department of Pharmacology and Toxicology, Michigan State University, B403 Life Sciences, 1355 Bogue Street, East Lansing, USA, Tel: (517) 884-6691;
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Abstract
Liver fibrosis remains a significant clinical problem in the United States and throughout the world. Although important advances in the understanding of this disease have been made, no effective pharmacologic agents have been developed that directly prevent or reverse the fibrotic process. Many of the successes in liver fibrosis treatment have been targeted toward treating the cause of fibrosis, such as the development of new antivirals that eradicate hepatitis virus. For many patients, however, this is not feasible, so a liver transplant remains the only viable option. Thus, there is a critical need to identify new therapeutic targets that will slow or reverse the progression of fibrosis in such patients. Research over the last 16 years has identified hypoxia-inducible factors (HIFs) as key transcription factors that drive many aspects of liver fibrosis, making them potential targets of therapy. In this review, we discuss the latest work on HIFs and liver fibrosis, including the cell-specific functions of these transcription factors in the development of liver fibrosis.
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Key Words
- BDL, bile duct ligation
- CCl4, carbon tetrachloride
- Ccr, C-C chemokine receptor
- FGF, fibroblast growth factor
- HGF, hepatocyte growth factor
- HIFs, hypoxia-inducible factors
- HSC, hepatic stellate cell
- Hepatic Stellate Cells
- Hypoxia-Inducible Factors
- Jmjd, Jumonji domain-containing
- Kupffer Cells
- Liver Fibrosis
- PAI-1, plasminogen activator inhibitor-1
- PDGF, platelet-derived growth factor
- Rgs, regulator of G-protein signaling
- TGF-β, transforming growth factor β
- VEGF, vascular endothelial growth factor
- α-SMA, α-smooth muscle actin
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Affiliation(s)
| | - Bryan L. Copple
- Correspondence Address correspondence to: Bryan L. Copple, PhD, Department of Pharmacology and Toxicology, Michigan State University, 1355 Bogue Street, B403 Life Sciences Building, East Lansing, Michigan 48824.Department of Pharmacology and ToxicologyMichigan State University1355 Bogue Street, B403 Life Sciences BuildingEast LansingMichigan 48824
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Joshi N, Kopec AK, O'Brien KM, Towery KL, Cline-Fedewa H, Williams KJ, Copple BL, Flick MJ, Luyendyk JP. Coagulation-driven platelet activation reduces cholestatic liver injury and fibrosis in mice. J Thromb Haemost 2015; 13:57-71. [PMID: 25353084 PMCID: PMC4487795 DOI: 10.1111/jth.12770] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Accepted: 10/17/2014] [Indexed: 01/14/2023]
Abstract
BACKGROUND The coagulation cascade has been shown to participate in chronic liver injury and fibrosis, but the contribution of various thrombin targets, such as protease activated receptors (PARs) and fibrin(ogen), has not been fully described. Emerging evidence suggests that in some experimental settings of chronic liver injury, platelets can promote liver repair and inhibit liver fibrosis. However, the precise mechanisms linking coagulation and platelet function to hepatic tissue changes following injury remain poorly defined. OBJECTIVES To determine the role of PAR-4, a key thrombin receptor on mouse platelets, and fibrin(ogen) engagement of the platelet αII b β3 integrin (αIIb β3 ) in a model of cholestatic liver injury and fibrosis. METHODS Biliary and hepatic injury was characterized following 4 week administration of the bile duct toxicant α-naphthylisothiocyanate (ANIT) (0.025%) in PAR-4-deficient mice, mice expressing a mutant form of fibrin(ogen) incapable of binding integrin αII b β3 (Fibγ(Δ5) ), and wild-type mice. RESULTS Elevated plasma thrombin-antithrombin and serotonin levels, hepatic fibrin deposition, and platelet accumulation in liver accompanied hepatocellular injury and fibrosis in ANIT-treated wild-type mice. PAR-4 deficiency reduced plasma serotonin levels, increased serum bile acid concentration, and exacerbated ANIT-induced hepatocellular injury and peribiliary fibrosis. Compared with PAR-4-deficient mice, ANIT-treated Fibγ(Δ5) mice displayed more widespread hepatocellular necrosis accompanied by marked inflammation, robust fibroblast activation, and extensive liver fibrosis. CONCLUSIONS Collectively, the results indicate that PAR-4 and fibrin-αII b β3 integrin engagement, pathways coupling coagulation to platelet activation, each exert hepatoprotective effects during chronic cholestasis.
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MESH Headings
- 1-Naphthylisothiocyanate
- Animals
- Antithrombin III
- Bile Acids and Salts/blood
- Blood Coagulation/genetics
- Blood Platelets/metabolism
- Chemical and Drug Induced Liver Injury/blood
- Chemical and Drug Induced Liver Injury/genetics
- Chemical and Drug Induced Liver Injury/pathology
- Chemical and Drug Induced Liver Injury/prevention & control
- Cholestasis/blood
- Cholestasis/chemically induced
- Cholestasis/genetics
- Cholestasis/pathology
- Cholestasis/prevention & control
- Fibrinogens, Abnormal/genetics
- Fibrinogens, Abnormal/metabolism
- Genotype
- Liver/metabolism
- Liver/pathology
- Liver Cirrhosis, Experimental/blood
- Liver Cirrhosis, Experimental/chemically induced
- Liver Cirrhosis, Experimental/genetics
- Liver Cirrhosis, Experimental/pathology
- Liver Cirrhosis, Experimental/prevention & control
- Male
- Mice, Inbred C57BL
- Mice, Knockout
- Mutation
- Necrosis
- Peptide Hydrolases/blood
- Phenotype
- Platelet Activation/genetics
- Platelet Glycoprotein GPIIb-IIIa Complex/metabolism
- Receptors, Thrombin/deficiency
- Receptors, Thrombin/genetics
- Serotonin/blood
- Signal Transduction
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Affiliation(s)
- N Joshi
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI, USA; Center for Integrative Toxicology, Michigan State University, East Lansing, MI, USA
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13
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Mochizuki A, Pace A, Rockwell CE, Roth KJ, Chow A, O'Brien KM, Albee R, Kelly K, Towery K, Luyendyk JP, Copple BL. Hepatic stellate cells orchestrate clearance of necrotic cells in a hypoxia-inducible factor-1α-dependent manner by modulating macrophage phenotype in mice. J Immunol 2014; 192:3847-3857. [PMID: 24639359 DOI: 10.4049/jimmunol.1303195] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Hypoxia-inducible factor-1α (HIF-1α) is activated in hepatic stellate cells (HSCs) by hypoxia and regulates genes important for tissue repair. Whether HIF-1α is activated in HSCs after acute injury and contributes to liver regeneration, however, is not known. To investigate this, mice were generated with reduced levels of HIF-1α in HSCs by crossing HIF-1α floxed mice with mice that express Cre recombinase under control of the glial fibrillary acidic protein (GFAP) promoter (i.e., HIF-1α-GFAP Cre+ mice). These mice and control mice (i.e., HIF-1α-GFAP Cre- mice) were treated with a single dose of carbon tetrachloride, and liver injury and repair were assessed. After carbon tetrachloride, HIF-1α was activated in HSCs. Although liver injury was not different between the two strains of mice, during resolution of injury, clearance of necrotic cells was decreased in HIF-1α-GFAP Cre+ mice. In these mice, the persistence of necrotic cells stimulated a fibrotic response characterized by extensive collagen deposition. Hepatic accumulation of macrophages, which clear necrotic cells from the liver after carbon tetrachloride, was not affected by HIF-1α deletion in HSCs. Conversion of macrophages to M1-like, proinflammatory macrophages, which have increased phagocytic activity, however, was reduced in HIF-1α-GFAP Cre+ mice as indicated by a decrease in proinflammatory cytokines and a decrease in the percentage of Gr1(hi) macrophages. Collectively, these studies have identified a novel function for HSCs and HIF-1α in orchestrating the clearance of necrotic cells from the liver and demonstrated a key role for HSCs in modulating macrophage phenotype during acute liver injury.
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Affiliation(s)
- Akie Mochizuki
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Aaron Pace
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Cheryl E Rockwell
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Katherine J Roth
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Aaron Chow
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Kate M O'Brien
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Ryan Albee
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Kara Kelly
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
| | - Keara Towery
- Department of Pathobiology and Diagnostic Investigation Michigan State University, East Lansing, MI 48824
| | - James P Luyendyk
- Department of Pathobiology and Diagnostic Investigation Michigan State University, East Lansing, MI 48824
| | - Bryan L Copple
- Department of Pharmacology and Toxicology Michigan State University, East Lansing, MI 48824
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14
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Yang M, Ramachandran A, Yan HM, Woolbright BL, Copple BL, Fickert P, Trauner M, Jaeschke H. Osteopontin is an initial mediator of inflammation and liver injury during obstructive cholestasis after bile duct ligation in mice. Toxicol Lett 2013; 224:186-95. [PMID: 24188933 DOI: 10.1016/j.toxlet.2013.10.030] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 10/24/2013] [Accepted: 10/25/2013] [Indexed: 12/13/2022]
Abstract
Osteopontin (OPN) is a chemotactic factor which can be cleaved to the pro-inflammatory form by matrix metalloproteinases (MMPs). To test the hypothesis that OPN can modulate inflammatory liver injury during cholestasis, wild-type (WT) C57BL/6 and OPN knockout (OPN-KO) mice underwent bile duct ligation (BDL). OPN-KO mice showed significant reduction in liver injury (plasma ALT and necrosis) and neutrophil recruitment compared with WT animals at 24h but not 72h after BDL. In WT mice, a 4-fold increase in hepatic MMP-3 mRNA and elevated MMP activities and cleaved OPN levels were observed in bile. WT mice subjected to BDL in the presence of the MMP inhibitor BB-94 showed reduced liver injury, less neutrophil extravasation and diminished levels of cleaved OPN in bile. Thus, during obstructive cholestasis, OPN released from biliary epithelial cells could be cleaved by MMPs in bile. When the biliary system leaks, cleaved OPN enters the parenchyma and attracts neutrophils. In the absence of OPN, other chemoattractants, e.g. chemokines, mediate a delayed inflammatory response and injury. Taken together, our data suggest that OPN is the pro-inflammatory mediator that initiates the early neutrophil-mediated injury phase during obstructive cholestasis in mice.
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Affiliation(s)
- Min Yang
- Department of Pharmacology, Toxicology & Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA
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15
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O'Brien KM, Allen KM, Rockwell CE, Towery K, Luyendyk JP, Copple BL. IL-17A synergistically enhances bile acid-induced inflammation during obstructive cholestasis. Am J Pathol 2013; 183:1498-1507. [PMID: 24012680 DOI: 10.1016/j.ajpath.2013.07.019] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 06/20/2013] [Accepted: 07/12/2013] [Indexed: 12/13/2022]
Abstract
During obstructive cholestasis, increased concentrations of bile acids activate ERK1/2 in hepatocytes, which up-regulates early growth response factor 1, a key regulator of proinflammatory cytokines, such as macrophage inflammatory protein 2 (MIP-2), which, in turn, exacerbates cholestatic liver injury. Recent studies have indicated that IL-17A contributes to hepatic inflammation during obstructive cholestasis, suggesting that bile acids and IL-17A may interact to regulate hepatic inflammatory responses. We treated mice with an IL-17A neutralizing antibody or control IgG and subjected them to bile duct ligation. Neutralization of IL-17A prevented up-regulation of proinflammatory cytokines, hepatic neutrophil accumulation, and liver injury, indicating an important role for IL-17A in neutrophilic inflammation during cholestasis. Treatment of primary mouse hepatocytes with taurocholic acid (TCA) increased the expression of MIP-2. Co-treatment with IL-17A synergistically enhanced up-regulation of MIP-2 by TCA. In contrast to MIP-2, IL-17A did not affect up-regulation of Egr-1 by TCA, indicating that IL-17A does not affect bile acid-induced activation of signaling pathways upstream of early growth response factor 1. In addition, bile acids increased expression of IL-23, a key regulator of IL-17A production in hepatocytes in vitro and in vivo. Collectively, these data identify bile acids as novel triggers of the IL-23/IL-17A axis and suggest that IL-17A promotes hepatic inflammation during cholestasis by synergistically enhancing bile acid-induced production of proinflammatory cytokines by hepatocytes.
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Affiliation(s)
- Kate M O'Brien
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Katryn M Allen
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - Cheryl E Rockwell
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan
| | - Keara Towery
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - James P Luyendyk
- Department of Pathobiology and Diagnostic Investigation, Michigan State University, East Lansing, Michigan
| | - Bryan L Copple
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan.
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16
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O'Brien KM, Copple BL. Bile acids elicit production of Interleukin‐23 by hepatocytes. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.387.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kate M O'Brien
- Pharmacology and ToxicologyMichigan State UniversityEast LansingMI
| | - Bryan L Copple
- Pharmacology and ToxicologyMichigan State UniversityEast LansingMI
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17
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Kassel KM, Sullivan BP, Copple BL, Luyendyk JP. Therapeutic administration of a direct thrombin inhibitor reduces hepatic inflammation in a mouse model of hypercholesterolemia. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.405.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Karen M. Kassel
- Pharmacology, Toxicology and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Bradley P. Sullivan
- Pharmacology, Toxicology and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Bryan L. Copple
- Pharmacology, Toxicology and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - James P. Luyendyk
- Pharmacology, Toxicology and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
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18
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OˈBrien KM, Copple BL. Interleukin‐17A promotes inflammation and hepatocellular injury during obstructive cholestasis. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.lb471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Kate M OˈBrien
- Pharmacology and ToxicologyMichigan State UniversityEast LansingMI
| | - Bryan L Copple
- Pharmacology and ToxicologyMichigan State UniversityEast LansingMI
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19
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Hossain MA, Kim DH, Jang JY, Kang YJ, Yoon JH, Moon JO, Chung HY, Kim GY, Choi YH, Copple BL, Kim ND. Aspirin enhances doxorubicin-induced apoptosis and reduces tumor growth in human hepatocellular carcinoma cells in vitro and in vivo. Int J Oncol 2012; 40:1636-42. [PMID: 22322725 DOI: 10.3892/ijo.2012.1359] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 12/20/2011] [Indexed: 12/31/2022] Open
Abstract
Combined therapy with multiple drugs is a common practice in the treatment of cancer, which can achieve better therapeutic effects than a single drug, and can reduce the side effects as well as drug resistance. This study aimed to determine whether aspirin (ASA) shows synergism with doxorubicin (DOX) in HepG2 human hepatocellular carcinoma cells in vitro and in a HepG2 cell xenograft model in BALB/c nude mice. When treated in combination, DOX (0.25 nmol/ml) and ASA (5 µmol/ml) produced strong synergy in growth inhibition, cell cycle arrest and importantly, apoptosis in vitro in comparison to single treatments. Moreover, ASA (100 mg/kg/day orally) and DOX (1.2 mg/kg biweekly ip) induced synergistic antitumor activity in the HepG2 cell xenograft model in nude mice. Therefore, the combination of ASA and DOX could be used as a novel combination regimen which provides a strong anticancer synergy in the treatment of hepatocellular carcinoma.
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Affiliation(s)
- Mohammad Akbar Hossain
- Division of Pharmacy, College of Pharmacy, Molecular Inflammation Research Center for Aging Intervention, Pusan National University, Busan 609-735, Republic of Korea
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20
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Copple BL, Kaska S, Wentling C. Hypoxia-inducible factor activation in myeloid cells contributes to the development of liver fibrosis in cholestatic mice. J Pharmacol Exp Ther 2012; 341:307-16. [PMID: 22271822 DOI: 10.1124/jpet.111.189340] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Macrophages play an integral role in the development of liver fibrosis by releasing mediators, such as platelet-derived growth factor-B (PDGF-B) and transforming growth factor-β1, which stimulate hepatic stellate cell proliferation, chemotaxis, and collagen production. However, the mechanism by which chronic liver injury stimulates macrophages to release these mediators is not completely understood. We tested the hypothesis that chronic liver injury activates hypoxia-inducible factor (HIF) transcription factors in macrophages that regulate the production of mediators that promote fibrosis. To test this hypothesis, Cre/lox technology was used to generate myeloid cell-specific HIF-1α or HIF-1β knockout mice. When these mice were subjected to bile duct ligation (BDL), levels of α-smooth muscle actin and type I collagen in the liver were reduced compared with those of mice with normal levels of HIFs. The deficiency of HIFs in macrophages did not affect liver injury or inflammation after BDL but reduced PDGF-B mRNA and protein, suggesting that HIF activation in macrophages may promote fibrosis by regulating the production of PDGF-B. Consistent with a role for HIFs in liver fibrosis in cholestatic liver disease, nuclear HIF-1α protein was present in macrophages, hepatocytes, and fibroblasts in the livers from patients with primary biliary cirrhosis and primary sclerosing cholangitis. These studies demonstrate that HIFs are important regulators of profibrotic mediator production by macrophages during the development of liver fibrosis and suggest that HIFs may be a novel therapeutic target for the treatment of chronic liver disease in patients.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology and Toxicology, Michigan State University, B403 Life Sciences Building, East Lansing, MI 48823, USA.
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21
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Zhang Y, Hong JY, Rockwell CE, Copple BL, Jaeschke H, Klaassen CD. Effect of bile duct ligation on bile acid composition in mouse serum and liver. Liver Int 2012; 32:58-69. [PMID: 22098667 PMCID: PMC3263524 DOI: 10.1111/j.1478-3231.2011.02662.x] [Citation(s) in RCA: 133] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Accepted: 09/10/2011] [Indexed: 12/12/2022]
Abstract
BACKGROUND Cholestatic liver diseases can be caused by genetic defects, drug toxicities, hepatobiliary malignancies or obstruction of the biliary tract. Cholestasis leads to accumulation of bile acids (BAs) in hepatocytes. Direct toxicity of BAs is currently the most accepted hypothesis for cholestatic liver injury. However, information on which bile acids are actually accumulating during cholestasis is limited. AIM To assess the BA composition in liver and serum after bile duct ligation (BDL) in male C57Bl/6 mice between 6 h and 14 days and evaluate toxicity of the most abundant BAs. RESULTS Bile acid concentrations increased in liver (27-fold) and serum (1400-fold) within 6 h after surgery and remained elevated up to 14 days. BAs in livers of BDL mice became more hydrophilic than sham controls, mainly because of increased 6β-hydroxylation and taurine conjugation. Among the eight unconjugated and 16 conjugated BAs identified in serum and liver, only taurocholic acid (TCA), β-muricholic acid (βMCA) and TβMCA were substantially elevated representing >95% of these BAs over the entire time course. Although glycochenodeoxycholic acid and other conjugated BAs increased in BDL animals, the changes were several orders of magnitude lower compared with TCA, βMCA and TβMCA. A mixture of these BAs did not cause apoptosis or necrosis, but induced inflammatory gene expression in cultured murine hepatocytes. CONCLUSION The concentrations of cytotoxic BAs are insufficient to cause hepatocellular injury. In contrast, TCA, βMCA and TβMCA are able to induce pro-inflammatory mediators in hepatocytes. Thus, BAs act as inflammagens and not as cytotoxic mediators after BDL in mice.
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Affiliation(s)
- Youcai Zhang
- Department of Pharmacology, Toxicology and Therapeutics; University of Kansas Medical Center; Kansas City; KS; USA
| | - Ji-Young Hong
- Department of Pharmacology, Toxicology and Therapeutics; University of Kansas Medical Center; Kansas City; KS; USA
| | - Cheryl E. Rockwell
- Department of Pharmacology, Toxicology and Therapeutics; University of Kansas Medical Center; Kansas City; KS; USA
| | - Bryan L. Copple
- Department of Pharmacology, Toxicology and Therapeutics; University of Kansas Medical Center; Kansas City; KS; USA
| | - Hartmut Jaeschke
- Department of Pharmacology, Toxicology and Therapeutics; University of Kansas Medical Center; Kansas City; KS; USA
| | - Curtis D. Klaassen
- Department of Pharmacology, Toxicology and Therapeutics; University of Kansas Medical Center; Kansas City; KS; USA
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22
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Hossain MA, Kim DH, Jang JY, Kang YJ, Yoon JH, Moon JO, Chung HY, Kim GY, Choi YH, Copple BL, Kim ND. Aspirin induces apoptosis in vitro and inhibits tumor growth of human hepatocellular carcinoma cells in a nude mouse xenograft model. Int J Oncol 2011; 40:1298-304. [PMID: 22179060 PMCID: PMC3584583 DOI: 10.3892/ijo.2011.1304] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2011] [Accepted: 11/29/2011] [Indexed: 12/21/2022] Open
Abstract
Nonsteroidal anti-inflammatory drugs (NSAIDs) are known to induce apoptosis in a variety of cancer cells, including colon, prostate, breast and leukemia. Among them, aspirin, a classical NSAID, shows promise in cancer therapy in certain types of cancers. We hypothesized that aspirin might affect the growth of liver cancer cells since liver is the principal site for aspirin metabolism. Therefore, we investigated the effects of aspirin on the HepG2 human hepatocellular carcinoma cell line in vitro and the HepG2 cell xenograft model in BALB/c nude mice. We found that treatment with aspirin inhibited cell growth and induced apoptosis involving both extrinsic and intrinsic pathways as measured by DNA ladder formation, alteration in the Bax/Bcl-2 ratio, activation of the caspase activities and related protein expressions. In vivo antitumor activity assay also showed that aspirin resulted in significant tumor growth inhibition compared to the control. Oral administration of aspirin (100 mg/kg/day) caused a significant reduction in the growth of HepG2 tumors in nude mice. These findings suggest that aspirin may be used as a promising anticancer agent against liver cancer.
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Affiliation(s)
- Mohammad Akbar Hossain
- Division of Pharmacy, College of Pharmacy, Molecular Inflammation Research Center for Aging Intervention, Pusan National University, Busan 609-735, Republic of Korea
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23
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Sullivan BP, Cui W, Copple BL, Luyendyk JP. Early growth response factor-1 limits biliary fibrosis in a model of xenobiotic-induced cholestasis in mice. Toxicol Sci 2011; 126:267-74. [PMID: 22094456 DOI: 10.1093/toxsci/kfr311] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Hepatic expression of the transcription factor early growth response-1 (Egr-1) is increased in livers of patients with cholestatic liver disease. Bile acid induction of inflammatory genes in hepatocytes is Egr-1 dependent, and Egr-1 expression is increased in livers of mice after bile duct ligation. Of importance, Egr-1 deficiency reduces liver inflammation and injury in that model. However, it is not known whether Egr-1 promotes inflammation in other models of cholestasis. We tested the hypothesis that Egr-1 contributes to liver inflammation in mice exposed chronically to the bile duct epithelial cell (BDEC) toxicant alpha-naphthylisothiocyanate (ANIT). Egr-1-knockout (Egr-1(-/-)) mice and wild-type mice were fed a diet containing 0.025% ANIT for 2 weeks. Expression of Egr-1 mRNA and protein was significantly increased in livers of mice fed ANIT diet. Egr-1 deficiency did not significantly affect ANIT diet-induced hepatocellular injury, inflammatory gene induction, BDEC hyperplasia, or hepatic neutrophil accumulation. In contrast, the deposition of Type 1 collagen was significantly increased in livers of Egr-1(-/-) mice fed ANIT diet compared with wild-type mice fed ANIT diet. Interestingly, this increase in liver fibrosis occurred in association with elevated expression of the β6 integrin (Itgb6) gene, suggesting the potential for increased local activation of transforming growth factor beta. Taken together, the results indicate that Egr-1 does not contribute to liver injury or inflammation in mice fed a diet containing ANIT. Rather, these studies indicate that Egr-1 deficiency worsens liver fibrosis in conjunction with enhanced expression of the profibrogenic Itgb6 gene.
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Affiliation(s)
- Bradley P Sullivan
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
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24
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Mei S, Ni HM, Manley S, Bockus A, Kassel KM, Luyendyk JP, Copple BL, Ding WX. Differential roles of unsaturated and saturated fatty acids on autophagy and apoptosis in hepatocytes. J Pharmacol Exp Ther 2011; 339:487-98. [PMID: 21856859 DOI: 10.1124/jpet.111.184341] [Citation(s) in RCA: 226] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Fatty acid-induced lipotoxicity plays a critical role in the pathogenesis of nonalcoholic liver disease. Saturated fatty acids and unsaturated fatty acids have differential effects on cell death and steatosis, but the mechanisms responsible for these differences are not known. Using cultured HepG2 cells and primary mouse hepatocytes, we found that unsaturated and saturated fatty acids differentially regulate autophagy and apoptosis. The unsaturated fatty acid, oleic acid, promoted the formation of triglyceride-enriched lipid droplets and induced autophagy but had a minimal effect on apoptosis. In contrast, the saturated fatty acid, palmitic acid, was poorly converted into triglyceride-enriched lipid droplets, suppressed autophagy, and significantly induced apoptosis. Subsequent studies revealed that palmitic acid-induced apoptosis suppressed autophagy by inducing caspase-dependent Beclin 1 cleavage, indicating cross-talk between apoptosis and autophagy. Moreover, our data suggest that the formation of triglyceride-enriched lipid droplets and induction of autophagy are protective mechanisms against fatty acid-induced lipotoxicity. In line with our in vitro findings, we found that high-fat diet-induced hepatic steatosis was associated with autophagy in the mouse liver. Potential modulation of autophagy may be a novel approach that has therapeutic benefits for obesity-induced steatosis and liver injury.
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Affiliation(s)
- Shuang Mei
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center MS 1018, 3901 Rainbow Blvd., Kansas City, KS 66160, USA
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25
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Luyendyk JP, Kassel KM, Allen K, Guo GL, Li G, Cantor GH, Copple BL. Fibrinogen deficiency increases liver injury and early growth response-1 (Egr-1) expression in a model of chronic xenobiotic-induced cholestasis. Am J Pathol 2011; 178:1117-25. [PMID: 21356363 DOI: 10.1016/j.ajpath.2010.11.064] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 10/15/2010] [Accepted: 11/09/2010] [Indexed: 01/26/2023]
Abstract
Chronic cholestatic liver injury induced by cholestasis in rodents is associated with hepatic fibrin deposition, and we found evidence of fibrin deposition in livers of patients with cholestasis. Key components of the fibrinolytic pathway modulate cholestatic liver injury by regulating activation of hepatocyte growth factor. However, the exact role of hepatic fibrin deposition in chronic cholestasis is not known. We tested the hypothesis that fibrinogen (Fbg) deficiency worsens liver injury induced by cholestasis. Fbg-deficient mice (Fbgα(-/-) mice) and heterozygous control mice (Fbgα(+/-) mice) were fed either the control diet or a diet containing 0.025% α-naphthylisothiocyanate (ANIT), which selectively injures bile duct epithelial cells in the liver, for 2 weeks. Hepatic fibrin and collagen deposits were evident in livers of heterozygous control mice fed the ANIT diet. Complete Fbg deficiency was associated with elevated serum bile acids, periportal necrosis, and increased serum alanine aminotransferase activity in mice fed the ANIT diet. Fbg deficiency was associated with enhanced hepatic expression of the transcription factor early growth response-1 (Egr-1) and enhanced induction of genes encoding the Egr-1-regulated proinflammatory chemokines monocyte chemotactic protein-1, KC growth-regulated protein, and macrophage inflammatory protein-2. Interestingly, peribiliary collagen deposition was not evident near necrotic areas in Fbg-deficient mice. The results suggest that in this model of chronic cholestasis, fibrin constrains the release of bile constituents from injured intrahepatic bile ducts, thereby limiting the progression of hepatic inflammation and hepatocellular injury.
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Affiliation(s)
- James P Luyendyk
- Department of Pharmacology, Toxicology, and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
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26
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Sparkenbaugh EM, Saini Y, Greenwood KK, LaPres JJ, Luyendyk JP, Copple BL, Maddox JF, Ganey PE, Roth RA. The role of hypoxia-inducible factor-1α in acetaminophen hepatotoxicity. J Pharmacol Exp Ther 2011; 338:492-502. [PMID: 21576378 DOI: 10.1124/jpet.111.180521] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Hypoxia-inducible factor-1α (HIF-1α) is a critical transcription factor that controls oxygen homeostasis in response to hypoxia, inflammation, and oxidative stress. HIF has been implicated in the pathogenesis of liver injury in which these events play a role, including acetaminophen (APAP) overdose, which is the leading cause of acute liver failure in the United States. APAP overdose has been reported to activate HIF-1α in mouse livers and isolated hepatocytes downstream of oxidative stress. HIF-1α signaling controls many factors that contribute to APAP hepatotoxicity, including mitochondrial cell death, inflammation, and hemostasis. Therefore, we tested the hypothesis that HIF-1α contributes to APAP hepatotoxicity. Conditional HIF-1α deletion was generated in mice using an inducible Cre-lox system. Control (HIF-1α-sufficient) mice developed severe liver injury 6 and 24 h after APAP overdose (400 mg/kg). HIF-1α-deficient mice were protected from APAP hepatotoxicity at 6 h, but developed severe liver injury by 24 h, suggesting that HIF-1α is involved in the early stage of APAP toxicity. In further studies, HIF-1α-deficient mice had attenuated thrombin generation and reduced plasminogen activator inhibitor-1 production compared with control mice, indicating that HIF-1α signaling contributes to hemostasis in APAP hepatotoxicity. Finally, HIF-1α-deficient animals had decreased hepatic neutrophil accumulation and plasma concentrations of interleukin-6, keratinocyte chemoattractant, and regulated upon activation normal T cell expressed and secreted compared with control mice, suggesting an altered inflammatory response. HIF-1α contributes to hemostasis, sterile inflammation, and early hepatocellular necrosis during the pathogenesis of APAP toxicity.
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Affiliation(s)
- Erica M Sparkenbaugh
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824, USA
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Copple BL, Bai S, Burgoon LD, Moon JOK. Hypoxia-inducible factor-1α regulates the expression of genes in hypoxic hepatic stellate cells important for collagen deposition and angiogenesis. Liver Int 2011; 31:230-44. [PMID: 20880076 PMCID: PMC3099214 DOI: 10.1111/j.1478-3231.2010.02347.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND/AIMS Several studies have shown that regions of hypoxia develop in the liver during chronic injury. Furthermore, it has been demonstrated that hypoxia stimulates the release of mediators from hepatic stellate cells (HSCs) that may affect the progression of fibrosis. The mechanism by which hypoxia modulates gene expression in HSCs is not known. Recent studies demonstrated that the hypoxia-activated transcription factor, hypoxia-inducible factor (HIF)-1α, is critical for the development of fibrosis. Accordingly, the hypothesis was tested that HIF-1α is activated in HSCs and regulates the expression of genes important for HSC activation and liver fibrosis. METHODS Hepatic stellate cells were isolated from mice and exposed to hypoxia. HIF-1α and HIF-2α activation were measured, and gene expression was analysed by gene array analysis. To identify the genes regulated by HIF-1α, HSCs were isolated from control and HIF-1α-deficient mice. RESULTS Exposure of primary mouse HSCs to 0.5% oxygen activated HIF-1α and HIF-2α. mRNA levels of numerous genes were increased in HSCs exposed to 0.5% oxygen, many of which are important for HSC function, angiogenesis and collagen synthesis. Of the mRNAs increased, chemokine receptor (Ccr) 1, Ccr5, macrophage migration inhibitory factor, interleukin-13 receptor α1 and prolyl-4-hydroxylase α2 (P4h α2) were completely HIF-1α dependent. Upregulation of the vascular endothelial growth factor and the placental growth factor was partially HIF-1α dependent and upregulation of angiopoietin-like 4 and P4h α1 was HIF-1α independent. CONCLUSIONS Results from these studies demonstrate that hypoxia, through activation of HIF-1α, regulates the expression of genes that may alter the sensitivity of HSCs to certain activators and chemotaxins, and regulates the expression of genes important for angiogenesis and collagen synthesis.
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Affiliation(s)
- Bryan L. Copple
- Department of Pharmacology, Toxicology, and Experimental Therapeutics University of Kansas Medical Center, Kansas City, KS 66160
| | - Shan Bai
- Department of Pharmacology, Toxicology, and Experimental Therapeutics University of Kansas Medical Center, Kansas City, KS 66160
| | - Lyle D. Burgoon
- Department of Biochemistry and Molecular Biology, Department of Quantitative Biology Initiative, Michigan State University, East Lansing, MI 48824
| | - Jeon-OK Moon
- Department of Pharmacology, Toxicology, and Experimental Therapeutics University of Kansas Medical Center, Kansas City, KS 66160,School of Pharmacy, Pusan National University, Busan 609-735, South Korea
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Abstract
AIM Liver fibrosis develops when chronic liver injury stimulates cells in the liver to produce mediators that activate hepatic stellate cells and stimulate them to secrete collagen. Recent studies suggest that the hypoxia-regulated transcription factor, hypoxia-inducible factor-1alpha, is essential for upregulation of profibrotic mediators, such as platelet-derived growth factor, in the liver during the development of liver fibrosis. What remains unknown, however, is the cell type-specific regulation of profibrotic mediators by hypoxia-inducible factors. Accordingly, in the present study the hypothesis tested was that hypoxia-inducible factors regulate production of profibrotic mediators by hypoxic Kupffer cells. METHODS Kupffer cells were isolated from control mice and hypoxia-inducible factor-1beta-deficient mice and exposed to room air or 1% oxygen (i.e. hypoxia). Levels of profibrotic mediators were quantified by real-time polymerase chain reaction. RESULTS Exposure of Kupffer cells isolated from control mice to 1% oxygen activated hypoxia-inducible factor-1alpha, and increased mRNA levels of platelet-derived growth factor-B, vascular endothelial growth factor, angiopoietin-1 and monocyte chemotactic protein-1. Upregulation of all of these mediators by hypoxia was prevented in Kupffer cells isolated from hypoxia-inducible factor-1beta-deficient mice. CONCLUSION RESULTS from these studies suggest that hypoxia-inducible factors are critical regulators of profibrotic mediator production by hypoxic Kupffer cells.
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Affiliation(s)
- Bryan L. Copple
- Department of Pharmacology, Toxicology, and Experimental Therapeutics University of Kansas Medical Center, Kansas City, KS 66160
| | - Shan Bai
- Department of Pharmacology, Toxicology, and Experimental Therapeutics University of Kansas Medical Center, Kansas City, KS 66160
| | - Jeon-OK Moon
- Department of Pharmacology, Toxicology, and Experimental Therapeutics University of Kansas Medical Center, Kansas City, KS 66160,Department of Pharmacy, Pusan National University, Busan 609-735, South Korea
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Abstract
BACKGROUND/AIMS During development of liver fibrosis, an important source of myofibroblasts is hepatocytes, which differentiate into myofibroblasts by epithelial to mesenchymal transition (EMT). In epithelial tumours and kidney fibrosis, hypoxia, through activation of hypoxia-inducible factors (HIFs), is an important stimulus of EMT. Our recent studies demonstrated that HIF-1alpha is important for the development of liver fibrosis. Accordingly, the hypothesis was tested that hypoxia stimulates hepatocyte EMT by a HIF-dependent mechanism. METHODS Primary mouse hepatocytes were exposed to room air or 1% oxygen and EMT evaluated. In addition, bile duct ligations (BDLs) were performed in control and HIF-1alpha-deficient mice and EMT quantified. RESULTS Exposure of hepatocytes to 1% oxygen increased expression of alpha-smooth muscle actin, vimentin, Snail and fibroblast-specific protein-1 (FSP-1). Levels of E-cadherin and zona occludens-1 were decreased. Upregulation of FSP-1 and Snail by hypoxia was completely prevented in HIF-1beta-deficient hepatocytes and by pretreatment with SB431542, a transforming growth factor-beta (TGF-beta) receptor inhibitor. HIFs promoted TGF-beta-dependent EMT by stimulating activation of latent TGF-beta1. To determine whether HIF-1alpha contributes to EMT in the liver during the development of fibrosis, control and HIF-1alpha-deficient mice were subjected to BDL. FSP-1 was increased to a greater extent in the livers of control mice when compared with HIF-1alpha-deficient mice. CONCLUSIONS Results from these studies demonstrate that hypoxia stimulates hepatocyte EMT by a HIF and TGF-beta-dependent mechanism. Furthermore, these studies suggest that HIF-1alpha is important for EMT in the liver during the development of fibrosis.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
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Abstract
Cholestasis is a reduction in bile flow that occurs from a variety of causes in humans. This produces hepatocellular injury and fibrosis. Considering that there are limited therapies for this disease, there has been interest in understanding the mechanism by which cholestasis produces injury. Studies have demonstrated that oxidative stress occurs in livers of humans with cholestasis. In vitro studies have demonstrated that bile acids kill hepatocytes by a mechanism that depends upon reactive oxygen species (ROS). Further studies, however, have demonstrated that this mechanism is of limited importance in vivo. Cholestasis also initiates an inflammatory response resulting in accumulation of neutrophils in the liver. Inhibition of neutrophil function reduces oxidative stress and liver injury suggesting that neutrophils are an important source of damaging ROS in vivo. Furthermore, inhibition of ROS during cholestasis reduces fibrosis. Collectively, these studies suggest that ROS are important for pathologic changes that occur during cholestasis.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
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Copple BL, Sullivan B, Bai S. Hypoxia Stimulates Hepatocyte Epithelial to Mesenchymal Transition. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.236.9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bryan L Copple
- Pharmacology, Toxicology, and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Bradley Sullivan
- Pharmacology, Toxicology, and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Shan Bai
- Pharmacology, Toxicology, and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
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Abstract
BACKGROUND Maternal metabolic demands change dramatically during the course of gestation and must be co-ordinated with the needs of the developing placenta and fetus. The liver is critically involved in metabolism and other important functions. However, maternal hepatic adjustments to pregnancy are poorly understood. AIM The aim of the study was to evaluate the influences of pregnancy on the maternal liver growth and gene expression profile. METHODS Holtzman Sprague-Dawley rats were mated and sacrificed at various stages of gestation and post-partum. The maternal livers were analysed in gravimetric response, DNA content by PicoGreen dsDNA quantitation reagent, hepatocyte ploidy by flow cytometry and hepatocyte proliferation by ki-67 immunostaining. Gene expression profiling of non-pregnant and gestation d18.5 maternal hepatic tissue was analysed using a DNA microarray approach and partially verified by northern blot or quantitative real-time PCR analysis. RESULTS During pregnancy, the liver exhibited approximately an 80% increase in size, proportional to the increase in body weight of the pregnant animals. The pregnancy-induced hepatomegaly was a physiological event of liver growth manifested by increases in maternal hepatic DNA content and hepatocyte proliferation. Pregnancy did not affect hepatocyte polyploidization. Pregnancy-dependent changes in hepatic expression were noted for a number of genes, including those associated with cell proliferation, cytokine signalling, liver regeneration and metabolism. CONCLUSIONS The metabolic demands of pregnancy cause marked adjustments in maternal liver physiology. Central to these adjustments are an expansion in hepatic capacity and changes in hepatic gene expression. Our findings provide insights into pregnancy-dependent hepatic adaptations.
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Affiliation(s)
- Juan J. Bustamante
- Institute of Maternal-Fetal Biology, Division of Cancer & Developmental Biology, Departments of Pathology & Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160
| | - Bryan L. Copple
- Department of Pharmacology and Toxicology, University of Kansas Medical Center, Kansas City, KS 66160
| | - Michael J. Soares
- Institute of Maternal-Fetal Biology, Division of Cancer & Developmental Biology, Departments of Pathology & Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160
| | - Guoli Dai
- Institute of Maternal-Fetal Biology, Division of Cancer & Developmental Biology, Departments of Pathology & Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160
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Copple BL. Hypoxia stimulates hepatocyte epithelial to mesenchymal transition by hypoxia-inducible factor and transforming growth factor-beta-dependent mechanisms. Liver Int 2010. [PMID: 20158611 DOI: 10.1111/j.1478-3231.2010.02205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
BACKGROUND/AIMS During development of liver fibrosis, an important source of myofibroblasts is hepatocytes, which differentiate into myofibroblasts by epithelial to mesenchymal transition (EMT). In epithelial tumours and kidney fibrosis, hypoxia, through activation of hypoxia-inducible factors (HIFs), is an important stimulus of EMT. Our recent studies demonstrated that HIF-1alpha is important for the development of liver fibrosis. Accordingly, the hypothesis was tested that hypoxia stimulates hepatocyte EMT by a HIF-dependent mechanism. METHODS Primary mouse hepatocytes were exposed to room air or 1% oxygen and EMT evaluated. In addition, bile duct ligations (BDLs) were performed in control and HIF-1alpha-deficient mice and EMT quantified. RESULTS Exposure of hepatocytes to 1% oxygen increased expression of alpha-smooth muscle actin, vimentin, Snail and fibroblast-specific protein-1 (FSP-1). Levels of E-cadherin and zona occludens-1 were decreased. Upregulation of FSP-1 and Snail by hypoxia was completely prevented in HIF-1beta-deficient hepatocytes and by pretreatment with SB431542, a transforming growth factor-beta (TGF-beta) receptor inhibitor. HIFs promoted TGF-beta-dependent EMT by stimulating activation of latent TGF-beta1. To determine whether HIF-1alpha contributes to EMT in the liver during the development of fibrosis, control and HIF-1alpha-deficient mice were subjected to BDL. FSP-1 was increased to a greater extent in the livers of control mice when compared with HIF-1alpha-deficient mice. CONCLUSIONS Results from these studies demonstrate that hypoxia stimulates hepatocyte EMT by a HIF and TGF-beta-dependent mechanism. Furthermore, these studies suggest that HIF-1alpha is important for EMT in the liver during the development of fibrosis.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS, USA.
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Allen K, Kim ND, Moon JO, Copple BL. Upregulation of early growth response factor-1 by bile acids requires mitogen-activated protein kinase signaling. Toxicol Appl Pharmacol 2009; 243:63-7. [PMID: 19931294 DOI: 10.1016/j.taap.2009.11.013] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 11/04/2009] [Accepted: 11/10/2009] [Indexed: 01/13/2023]
Abstract
Cholestasis results when excretion of bile acids from the liver is interrupted. Liver injury occurs during cholestasis, and recent studies showed that inflammation is required for injury. Our previous studies demonstrated that early growth response factor-1 (Egr-1) is required for development of inflammation in liver during cholestasis, and that bile acids upregulate Egr-1 in hepatocytes. What remains unclear is the mechanism by which bile acids upregulate Egr-1. Bile acids modulate gene expression in hepatocytes by activating the farnesoid X receptor (FXR) and through activation of mitogen-activated protein kinase (MAPK) signaling. Accordingly, the hypothesis was tested that bile acids upregulate Egr-1 in hepatocytes by FXR and/or MAPK-dependent mechanisms. Deoxycholic acid (DCA) and chenodeoxycholic acid (CDCA) stimulated upregulation of Egr-1 to the same extent in hepatocytes isolated from wild-type mice and FXR knockout mice. Similarly, upregulation of Egr-1 in the livers of bile duct-ligated (BDL) wild-type and FXR knockout mice was not different. Upregulation of Egr-1 in hepatocytes by DCA and CDCA was prevented by the MEK inhibitors U0126 and SL-327. Furthermore, pretreatment of mice with U0126 prevented upregulation of Egr-1 in the liver after BDL. Results from these studies demonstrate that activation of MAPK signaling is required for upregulation of Egr-1 by bile acids in hepatocytes and for upregulation of Egr-1 in the liver during cholestasis. These studies suggest that inhibition of MAPK signaling may be a novel therapy to prevent upregulation of Egr-1 in liver during cholestasis.
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Affiliation(s)
- Katryn Allen
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, 4063 KLSIC, 3901 Rainbow Boulevard, Kansas City, KS 66160, USA
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Abstract
BACKGROUND/AIMS During the development of liver fibrosis, mediators are produced that stimulate cells in the liver to differentiate into myofibroblasts and to produce collagen. Recent studies demonstrated that the transcription factor, hypoxia-inducible factor-1alpha (HIF-1alpha), is critical for upregulation of profibrotic mediators, such as platelet-derived growth factor-A (PDGF-A), PDGF-B and plasminogen activator inhibitor-1 (PAI-1) in the liver, during the development of fibrosis. What remains unknown is the cell type-specific regulation of these genes by HIF-1alpha in liver cell types. Accordingly, the hypothesis was tested that HIF-1alpha is activated in hypoxic hepatocytes and regulates the production of profibrotic mediators by these cells. METHODS In this study, hepatocytes were isolated from the livers of control and HIF-1alpha- or HIF-1beta-deficient mice and exposed to hypoxia. RESULTS Exposure of primary mouse hepatocytes to 1% oxygen stimulated nuclear accumulation of HIF-1alpha and upregulated PAI-1, vascular endothelial cell growth factor and the vasoactive peptides adrenomedullin-1 (ADM-1) and ADM-2. In contrast, the levels of PDGF-A and PDGF-B mRNAs were unaffected in these cells by hypoxia. Exposure of HIF-1alpha-deficient hepatocytes to 1% oxygen only partially prevented upregulation of these genes, suggesting that other hypoxia-regulated transcription factors, such as HIF-2alpha, may also regulate these genes. In support of this, HIF-2alpha was activated in hypoxic hepatocytes, and exposure of HIF-1beta-deficient hepatocytes to 1% oxygen completely prevented upregulation of PAI-1, vascular endothelial cell growth factor and ADM-1, suggesting that HIF-2alpha may also contribute to upregulation of these genes in hypoxic hepatocytes. CONCLUSIONS Collectively, our results suggest that HIFs may be important regulators of profibrotic and vasoactive mediators by hypoxic hepatocytes.
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Affiliation(s)
- Bryan L. Copple
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160
| | - Juan J. Bustamante
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160
| | - Timothy P. Welch
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160
| | - Nam Deuk Kim
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160, School of Pharmacy, Pusan National University, Busan 609-735, South Korea
| | - Jeon-OK Moon
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160, School of Pharmacy, Pusan National University, Busan 609-735, South Korea
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Luyendyk JP, Cantor GH, Kirchhofer D, Mackman N, Copple BL, Wang R. Tissue factor-dependent coagulation contributes to alpha-naphthylisothiocyanate-induced cholestatic liver injury in mice. Am J Physiol Gastrointest Liver Physiol 2009; 296:G840-9. [PMID: 19179621 PMCID: PMC2670671 DOI: 10.1152/ajpgi.90639.2008] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Separation of concentrated bile acids from hepatic parenchymal cells is a key function of the bile duct epithelial cells (BDECs) that form intrahepatic bile ducts. Using coimmunostaining, we found that tissue factor (TF), the principal activator of coagulation, colocalized with cytokeratin 19, a marker of BDECs in the adult mouse liver. BDEC injury induced by xenobiotics such as alpha-naphthylisothiocyanate (ANIT) causes cholestasis, inflammation, and hepatocellular injury. We tested the hypothesis that acute ANIT-induced cholestatic hepatitis is associated with TF-dependent activation of coagulation and determined the role of TF in ANIT hepatotoxicity. Treatment of mice with ANIT (60 mg/kg) caused multifocal hepatic necrosis and significantly increased serum biomarkers of cholestasis and hepatic parenchymal cell injury. ANIT treatment also significantly increased liver TF expression and activity. ANIT-induced activation of the coagulation cascade was shown by increased plasma thrombin-antithrombin levels and significant deposition of fibrin within the necrotic foci. ANIT-induced coagulation and liver injury were reduced in low-TF mice, which express 1% of normal TF levels. The results indicate that ANIT-induced liver injury is accompanied by TF-dependent activation of the coagulation cascade and that TF contributes to the progression of injury during acute cholestatic hepatitis.
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Affiliation(s)
- James P. Luyendyk
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas; Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey; Department of Protein Engineering, Genentech, South San Francisco, California; and Division of Hematology/Oncology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Glenn H. Cantor
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas; Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey; Department of Protein Engineering, Genentech, South San Francisco, California; and Division of Hematology/Oncology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Daniel Kirchhofer
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas; Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey; Department of Protein Engineering, Genentech, South San Francisco, California; and Division of Hematology/Oncology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Nigel Mackman
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas; Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey; Department of Protein Engineering, Genentech, South San Francisco, California; and Division of Hematology/Oncology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Bryan L. Copple
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas; Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey; Department of Protein Engineering, Genentech, South San Francisco, California; and Division of Hematology/Oncology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina
| | - Ruipeng Wang
- Department of Pharmacology, Toxicology and Therapeutics, The University of Kansas Medical Center, Kansas City, Kansas; Discovery Toxicology, Bristol-Myers Squibb, Princeton, New Jersey; Department of Protein Engineering, Genentech, South San Francisco, California; and Division of Hematology/Oncology, Department of Medicine, University of North Carolina, Chapel Hill, North Carolina
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Wood JG, Font R, Moncure M, Thomas JH, Holloway NB, Blanco VG, Copple BL, Casillan AJ, West CE, Gonzalez NC. Heme Oxygenase‐1 Upregulation Following Prolyl Hydroxylase Inhibition Attenuates Hypoxia‐Induced Microvascular Inflammation. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.762.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
| | | | | | | | | | | | - Bryan L. Copple
- Pharmacology, Toxicology, & TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
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Abstract
Liver fibrosis is characterized by excessive deposition of extracellular matrix in the liver during chronic injury. During early stages of this disease, cells begin to synthesize and secrete profibrotic proteins that stimulate matrix production and inhibit matrix degradation. Although it is clear that these proteins are important for development of fibrosis, what remains unknown is the mechanism by which chronic liver injury stimulates their production. In the present study, the hypothesis was tested that hypoxia-inducible factor-1alpha (HIF-1alpha) is activated in the liver during chronic injury and regulates expression of profibrotic proteins. To investigate this hypothesis, mice were subjected to bile duct ligation (BDL), an animal model of liver fibrosis. HIF-1alpha protein was increased in the livers of mice subjected to BDL by 3 days after surgery. To test the hypothesis that HIF-1alpha is required for the development of fibrosis, control and HIF-1alpha-deficient mice were subjected to BDL. Levels of type I collagen and alpha-smooth muscle actin mRNA and protein were increased in control mice by 14 days after BDL. These levels were significantly reduced in HIF-1alpha-deficient mice. Next, the levels of several profibrotic mediators were measured to elucidate the mechanism by which HIF-1alpha promotes liver fibrosis. Platelet-derived growth factor (PDGF)-A, PDGF-B, and plasminogen activator inhibitor-1 mRNA levels were increased to a greater extent in control mice subjected to BDL compared with HIF-1alpha-deficient mice at 7 and 14 days after BDL. Results from these studies suggest that HIF-1alpha is a critical regulator of profibrotic mediator production during the development of liver fibrosis.
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Affiliation(s)
- Jeon-OK Moon
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, Kansas; Department of Pharmacy, Pusan National University, Busan, South Korea; and Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Timothy P. Welch
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, Kansas; Department of Pharmacy, Pusan National University, Busan, South Korea; and Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Frank J. Gonzalez
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, Kansas; Department of Pharmacy, Pusan National University, Busan, South Korea; and Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
| | - Bryan L. Copple
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, Kansas; Department of Pharmacy, Pusan National University, Busan, South Korea; and Laboratory of Metabolism, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland
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Welch TP, Bustamante J, Moon J, Copple BL. Hypoxia‐inducible Factor‐dependent Production of Profibrotic Mediators by Hypoxic Hepatocytes. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.1190.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Timothy Paul Welch
- PharmacologyToxicology, & TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Juan Bustamante
- PharmacologyToxicology, & TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Jeon‐Ok Moon
- Department of PharmacyPusan National UniversityBusanRepublic of Korea
| | - Bryan L. Copple
- PharmacologyToxicology, & TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
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Affiliation(s)
- Bryan L Copple
- PharmacologyToxicology, and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
| | - Jeon‐OK Moon
- PharmacologyToxicology, and TherapeuticsUniversity of Kansas Medical CenterKansas CityKS
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Copple BL, Roth RA, Ganey PE. Anticoagulation and inhibition of nitric oxide synthase influence hepatic hypoxia after monocrotaline exposure. Toxicology 2006; 225:128-37. [PMID: 16828949 DOI: 10.1016/j.tox.2006.05.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2005] [Revised: 05/16/2006] [Accepted: 05/17/2006] [Indexed: 02/04/2023]
Abstract
Monocrotaline (MCT) is a pyrrolizidine alkaloid plant toxin that produces hepatotoxicity in humans and animals. Administration of MCT to rats causes rapid sinusoidal endothelial cell (SEC) injury, hemorrhage, pooling of blood and fibrin deposition in centrilobular regions of liver. These events precede hepatic parenchymal cell (HPC) injury and produce marked changes in the microvasculature of the liver, which could interrupt blood flow and produce hypoxia in affected regions. To test the hypothesis that hypoxia occurs in liver after MCT exposure, rats were treated with 300mgMCT/kg, and hypoxia was detected immunohistochemically. MCT produced significant hypoxia in centrilobular regions of livers by 8h after treatment. Inasmuch as fibrin deposition can impair oxygen delivery by reducing blood flow, the effect of anticoagulant treatment on MCT-induced hypoxia was determined. Administration of warfarin to MCT-treated rats reduced hypoxia in the liver by approximately 70%, suggesting that fibrin deposition plays a causal role in the development of hypoxia in the liver. Conversely, administration of l-NAME, a nonspecific inhibitor of nitric oxide synthases (NOSs), enhanced MCT-induced hypoxia and HPC injury. l-NAME did not, however, affect SEC injury or coagulation system activation. Results from these studies show that hypoxia occurs in the liver after MCT exposure. Furthermore, hypoxia precedes HPC injury, and manipulations that modify hypoxia also modulate HPC injury.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology and Toxicology, Center for Integrative Toxicology, and National Food Safety and Toxicology Center, 214 Food Safety and Toxicology Building, Michigan State University, East Lansing, MI 48824, USA
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Abstract
Hepatocyte injury during cholestasis depends in part on the release of proinflammatory mediators that cause neutrophils to accumulate in the liver and become activated to damage hepatocytes. The mechanism by which cholestasis stimulates production of proinflammatory mediators in the liver is not completely understood. The studies presented here tested the hypothesis that the transcription factor early growth response factor-1 (Egr-1) is required for inflammation to occur in the liver during cholestasis. The results of these studies show that Egr-1 was rapidly upregulated, primarily in hepatocytes, in mice subjected to bile duct ligation, an animal model of cholestasis. To determine whether Egr-1 was required for inflammation and hepatocyte injury during cholestasis, bile duct ligation was performed in wild-type and Egr-1 knockout mice. Hepatocyte injury, neutrophil accumulation, and upregulation of macrophage inflammatory protein-2 (MIP-2) and intercellular adhesion molecule-1 (ICAM-1) in the liver were significantly reduced in Egr-1 knockouts. By contrast, levels of tumor necrosis factor-alpha (TNF-alpha) and collagen (i.e., a biomarker of liver fibrosis) were not different between wild-types and Egr-1 knockouts subjected to bile duct ligation. Because hepatocytes are exposed to elevated concentrations of bile acids during cholestasis, it was determined that bile acids upregulate Egr-1 in primary mouse hepatocytes. Deoxycholic acid dose-dependently increased Egr-1 protein in hepatocytes. Results from these studies suggest a scenario in which elevated concentrations of bile acids during cholestasis increase expression of Egr-1 in hepatocytes. Egr-1 then upregulates proinflammatory mediators that cause neutrophils to accumulate in the liver and become activated to damage hepatocytes.
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Affiliation(s)
- Nam Deuk Kim
- Department of Pharmacology, Toxicology, and Experimental Therapeutics, University of Kansas Medical Center, Kansas City, Kansas 66160, USA
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43
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Abstract
Monocrotaline (MCT) is a pyrrolizidine alkaloid (PA) plant toxin that produces sinusoidal endothelial cell (SEC) injury, hemorrhage, fibrin deposition, and coagulative hepatic parenchymal cell (HPC) oncosis in centrilobular regions of rat livers. Cells with apoptotic morphology have been observed in the livers of animals exposed to other PAs. Whether apoptosis occurs in the livers of MCT-treated animals and whether it is required for full manifestation of pathological changes is not known. To determine this, rats were treated with 300 mg MCT/kg, and apoptosis was detected by transmission electron microscopy and the TUNEL (TdT-mediated dUTP nick end labeling) assay. MCT produced significant apoptosis in the liver by 4 h after treatment. To determine if MCT kills cultured HPCs by apoptosis, HPCs were isolated from the livers of rats and exposed to MCT. MCT caused a concentration-dependent release of alanine aminotransferase (ALT), a marker of HPC injury. Furthermore, caspase 3 was activated and TUNEL staining increased in MCT-treated HPCs. MCT-induced TUNEL staining and release of ALT into the medium were completely prevented by the pancaspase inhibitors z-VAD.fmk and IDN-7314, suggesting that MCT kills cultured HPCs by apoptosis. To determine if caspase inhibition prevents MCT-induced apoptosis in the liver, rats were cotreated with MCT and IDN-7314. IDN-7314 reduced MCT-induced TUNEL staining in the liver and release of ALT into the plasma. Morphometric analysis confirmed that IDN-7314 reduced HPC oncosis in the liver by approximately 50%. Inasmuch as HPC hypoxia occurred in the livers of MCT-treated animals, upregulation of the hypoxia-regulated cell-death factor, BNIP3 (Bcl2/adenovirus EIB 19kD-interacting protein 3), was examined. BNIP3 was increased in the livers of mice treated 24 h earlier with MCT. Results from these studies show that MCT kills cultured HPCs by apoptosis but causes both oncosis and apoptosis in the liver in vivo. Furthermore, caspase inhibition reduces both apoptosis and HPC oncosis in the liver after MCT exposure.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology and Toxicology, Institute for Environmental Toxicology, and National Food Safety and Toxicology Center, Michigan State University, East Lansing, Michigan 48824, USA
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Hanumegowda UM, Copple BL, Shibuya M, Malle E, Ganey PE, Roth RA. Basement membrane and matrix metalloproteinases in monocrotaline-induced liver injury. Toxicol Sci 2003; 76:237-46. [PMID: 12970574 DOI: 10.1093/toxsci/kfg222] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Monocrotaline (MCT) is a pyrrolizidine alkaloid that causes liver injury in animals. In rats, injury is characterized by sinusoidal endothelial cell (SEC) damage and centrilobular parenchymal cell necrosis. Loss of endothelium is a possible outcome of the action of matrix metalloproteinases (MMPs), specifically MMP-9 from neutrophils and SECs and MMP-2 from SECs, on basement membrane collagen. Accordingly, the dynamics of MMPs in MCT-induced SEC damage were studied. Rats were treated with MCT (300 mg/kg, ip), and livers were collected at 8, 12, and 18 h. Immunofluorescence analysis of frozen sections of livers from MCT-treated rats revealed a progressive reduction in basement membrane heparan sulfate proteoglycan and collagen IV. A time-dependent increase in total type IV collagenase activity and MMP-9 content occurred in the livers of MCT-treated rats, as measured by fluorescent collagenase activity assay and gelatin zymography, respectively. Progressive neutrophil accumulation and activation in the liver after MCT treatment were demonstrated by an increased activity of myeloperoxidase and pronounced staining for hypochlorite-modified proteins generated via the myeloperoxidase-hydrogen peroxide-halide system. However, neutrophil depletion did not protect against MCT-induced SEC injury. Treatment of NP-26 cells, a sinusoidal endothelial cell line, with MCT resulted in dose-dependent release of MMP-9 from the cells. The results demonstrate the degradation of basement membrane components with a concurrent increase in the amount and activity of MMP-9, likely originating from sinusoidal endothelial cells, neutrophils, and probably other cell types. This suggests the possibility of a role for MMPs in the SEC detachment and loss that occurs during MCT hepatotoxicity.
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Affiliation(s)
- Umesh M Hanumegowda
- Department of Pharmacology and Toxicology, Michigan State University, East Lansing, Michigan 48824, USA
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45
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Abstract
Monocrotaline (MCT) is a pyrrolizidine alkaloid (PA) plant toxin that causes hepatotoxicity in humans and animals. Human exposure occurs from consumption of contaminated grains and herbal teas and medicines. Intraperitoneal injection (i.p.) of 300 mg/kg MCT in rats produced time-dependent hepatic parenchymal cell (HPC) injury beginning at 12 h. At this time, an inflammatory infiltrate consisting of neutrophils (PMNs) appeared in areas of hepatocellular injury, and activation of the coagulation system occurred. PMN accumulation was preceded by up-regulation of the PMN chemokines cytokine-induced neutrophil chemoattractant-1 (CINC-1) and macrophage inflammatory protein-2 (MIP-2) in the liver. The monocyte chemokine, monocyte chemoattractant protein-1 (MCP-1), was also upregulated. Inhibition of Kupffer cell function with gadolinium chloride (GdCl(3)) significantly reduced CINC-1 protein in plasma after MCT treatment but had no effect on hepatic PMN accumulation. Since inflammation can contribute to either pathogenesis or resolution of tissue injury, we explored inflammatory factors as a contributor to MCT hepatotoxicity. To test the hypothesis that PMNs contribute to MCT-induced HPC injury, rats were depleted of PMNs with a rabbit anti-PMN serum prior to MCT treatment. Anti-PMN treatment reduced hepatic PMN accumulation by 80% but had no effect on MCT-induced HPC injury or activation of the coagulation system. To test the hypothesis that Kupffer cells and/or tumor necrosis factor-alpha (TNF-alpha) are required for MCT-induced HPC injury, rats were treated with either GdCl(3) to inhibit Kupffer cell function or pentoxifylline (PTX) to prevent synthesis of TNF-alpha. Neither treatment prevented MCT-induced HPC injury. Results from these studies suggest that PMNs, Kupffer cells and TNF-alpha are not critical mediators of MCT hepatotoxicity. Accordingly, although inflammation occurs in the liver after MCT treatment, it is not required for HPC injury and possibly occurs secondary to hepatocellular injury.
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Affiliation(s)
- Bryan L Copple
- Institute for Environmental Toxicology, B-346 Life Sciences Building, Michigan State University, East Lansing, MI 48824, USA
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46
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Yee SB, Hanumegowda UM, Copple BL, Shibuya M, Ganey PE, Roth RA. Endothelial cell injury and coagulation system activation during synergistic hepatotoxicity from monocrotaline and bacterial lipopolysaccharide coexposure. Toxicol Sci 2003; 74:203-14. [PMID: 12730616 DOI: 10.1093/toxsci/kfg106] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
A small, noninjurious dose of bacterial lipopolysaccharide (LPS; 7.4 x 106 EU/kg) administered 4 h after a small, nontoxic dose of monocrotaline (MCT; 100 mg/kg) produces synergistic hepatotoxicity in rats within 6 to 12 h after MCT exposure. The resulting centrilobular (CL) and midzonal (MZ) liver lesions are characterized by hepatic parenchymal cell (HPC) necrosis. Pronounced hemorrhage, disruption of sinusoidal architecture, and loss of central vein intima suggest that an additional component to injury may be the liver vasculature. In the present investigation, the hypothesis that sinusoidal endothelial cell (SEC) injury and coagulation system activation occur in this model was tested. Plasma hyaluronic acid (HA) concentration, a biomarker for SEC injury, was significantly increased in cotreated animals before the onset of HPC injury and remained elevated through the time of maximal HPC injury (i.e., 18 h). SEC injury was confirmed by immunohistochemistry and electron microscopy. Pyrrolic metabolites were produced from MCT by SECs in vitro, which suggests that MCT may injure SECs directly through the formation of its toxic metabolite, monocrotaline pyrrole. Inasmuch as SEC activation and injury can promote hemostasis, activation of the coagulation system was evaluated. Coagulation system activation, as marked by a decrease in plasma fibrinogen, occurred before the onset of HPC injury. Furthermore, extensive fibrin deposition was observed immunohistochemically within CL and MZ regions after MCT/LPS cotreatment. Taken together, these results suggest that SEC injury and coagulation system activation are components of the synergistic liver injury resulting from MCT and LPS coexposure.
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Affiliation(s)
- Steven B Yee
- Department of Pharmacology, National Food Safety and Toxicology Center, Institute for Environmental Toxicology, Michigan State University, East Lansing, USA
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Copple BL, Moulin F, Hanumegowda UM, Ganey PE, Roth RA. Thrombin and protease-activated receptor-1 agonists promote lipopolysaccharide-induced hepatocellular injury in perfused livers. J Pharmacol Exp Ther 2003; 305:417-25. [PMID: 12606620 DOI: 10.1124/jpet.102.046391] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Bacterial lipopolysaccharide (LPS) is a potent inflammatory agent capable of producing liver injury, the pathogenesis of which depends on numerous mediators, including thrombin. Previous studies showed that thrombin promotes LPS-induced liver injury independent of its ability to form fibrin clots. In isolated, buffer-perfused livers from LPS-treated rats, thrombin added to the perfusion buffer caused dose-dependent liver injury with an EC(50) value of 0.4 nM, consistent with activation by thrombin of a protease-activated receptor (PAR). Actions of thrombin at PARs can be mimicked by thrombin receptor-activating peptides (TRAPs). TRAPs for PAR-1 reproduced the injury caused by thrombin in isolated livers, suggesting that one mechanism by which thrombin promotes LPS-induced liver injury is by activating PAR-1. Immunocytochemistry demonstrated the presence of PAR-1 on sinusoidal endothelial cells and Kupffer cells but not on parenchymal cells or neutrophils. Previous studies showed that thrombin interacts with neutrophils in the genesis of liver injury after LPS treatment. To explore this interaction further, the influence of thrombin on mediators that modulate neutrophil function were evaluated. Inhibition of thrombin in LPS-treated rats prevented liver injury but did not prevent up-regulation of cytokine-induced neutrophil chemoattractant-1, macrophage inflammatory protein-2, or intercellular adhesion molecule-1. Thrombin inhibition did, however, prevent neutrophil (PMN) degranulation in vivo as measured by plasma elastase levels. In addition, elastase concentration was increased in the perfusion medium of livers isolated from LPS-treated rats and perfused with TRAPs. These results suggest that activation of PAR-1 after LPS exposure promotes PMN activation and hepatic parenchymal cell injury.
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Affiliation(s)
- Bryan L Copple
- Department of Pharmacology and Toxicology, B-346 Life Sciences Bldg., Michigan State University, East Lansing, MI 48824, USA
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48
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Luyendyk JP, Copple BL, Barton CC, Ganey PE, Roth RA. Augmentation of aflatoxin B1 hepatotoxicity by endotoxin: involvement of endothelium and the coagulation system. Toxicol Sci 2003; 72:171-81. [PMID: 12604847 DOI: 10.1093/toxsci/kfg007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Aflatoxin B(1) (AFB(1)) is a fungal toxin that causes both acute hepatotoxicity and liver carcinoma in exposed humans and animals. Previous studies have shown that exposure of rats to nontoxic doses of bacterial lipopolysaccharide (LPS) augments AFB(1) acute hepatotoxicity, resulting in enhanced injury to hepatic parenchymal cells and bile ducts. At larger doses, LPS causes damage to sinusoidal endothelial cells (SECs) and activation of the coagulation system. Accordingly, we tested the hypothesis that treatment of rats with AFB(1) and LPS damages SECs and activates the coagulation system, which is critical for potentiation of AFB(1) hepatotoxicity by LPS. Male, Sprague-Dawley rats were given 1 mg/kg AFB(1) (ip), then 4 hours later 7.4 x 10(6) EU/kg LPS was administered (iv). A time-dependent injury to SECs and parenchymal cells was observed in AFB(1)/LPS-cotreated animals that became significant by 12 h, as estimated by increases in plasma hyaluronic acid (HA) and alanine aminotransferase (ALT) activities, respectively. Immunohistochemical analysis revealed that endothelial cell immunostaining was decreased in both centrilobular and periportal regions after AFB(1)/LPS treatment. Immunohistochemical evidence of fibrin deposition was found in both centrilobular and periportal regions by 12 h, but these deposits persisted only in periportal regions by 24 h. Administration of the anticoagulant heparin to AFB(1)/LPS-cotreated animals markedly attenuated increases in markers of hepatic parenchymal cell injury but provided only minimal amelioration of bile duct injury. These results suggest that AFB(1)/LPS coexposure results in SEC injury and activation of the coagulation system, and that the coagulation system is required for the development of hepatic parenchymal cell injury but not bile duct injury in this model.
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Affiliation(s)
- James P Luyendyk
- Department of Pharmacology and Toxicology, National Food Safety and Toxicology Center, Institute for Environmental Toxicology, Michigan State University, East Lansing, Michigan 48824-1224, USA
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49
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Abstract
Noninjurious doses of bacterial endotoxin (lipopolysaccharide; LPS) enhance allyl alcohol-induced liver damage in rats in a Kupffer cell (KC)-dependent fashion. To investigate the mechanism by which KCs contribute to liver injury in this model, isolated KCs and hepatocytes (HCs) were cocultured. Addition of LPS to the cocultured cells did not enhance allyl alcohol-induced cytotoxicity. In addition, recirculating perfusion of isolated livers from naïve rats with LPS for 2 h did not significantly enhance allyl alcohol-induced toxicity as measured by release of alanine aminotransferase (ALT). These results suggest an extrahepatic factor is required for LPS potentiation of allyl alcohol hepatotoxicity. To examine whether the coagulation cascade contributes to injury in this model, rats were given either warfarin at 42 and 18 h before LPS, or heparin at 1 h before LPS, and were treated with allyl alcohol 2 h after LPS. Warfarin and heparin each significantly blocked the decrease in plasma fibrinogen levels and attenuated the increase in plasma ALT activity in rats treated with LPS and allyl alcohol. To assess the role of thrombin in this injury, isolated livers from rats pretreated with LPS were perfused with thrombin or vehicle and allyl alcohol. Though LPS pretreatment enhanced the toxicity of allyl alcohol compared with livers from naïve rats, perfusion with thrombin did not increase sensitivity to allyl alcohol. In summary, LPS augments the hepatotoxicity of allyl alcohol through a mechanism involving extrahepatic factors, one of which may be a component of the coagulation cascade.
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Affiliation(s)
- Shawn Kinser
- Department of Pharmacology and Toxicology, Institute for Environmental Toxicology, 214 Food Safety and Toxicology Building, Michigan State University, East Lansing, MI 48824, USA
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50
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Yee SB, Copple BL, Ganey PE, Roth RA. The temporal relationship between bacterial lipopolysaccharide and monocrotaline exposures influences toxicity: shift in response from hepatotoxicity to nitric oxide-dependent lethality. J Toxicol Environ Health A 2002; 65:961-976. [PMID: 12133231 DOI: 10.1080/00984100290071261] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Liver injury from a variety of hepatotoxicants, including the food-borne phytotoxin monocrotaline (MCT), can be augmented by exposure to a noninjurious dose of the inflammagen bacterial lipopolysaccharide (LPS). In a previous study, a nontoxic dose of LPS given 4 h after MCT resulted in synergistic hepatotoxicity within 12-18 h. This study was designed to determine whether temporal differences in MCT and LPS exposure affect toxicity. When LPS (3.4 x 10(6) EU/kg; iv) was given one hour before MCT (100 mg/kg; ip), hepatotoxicity developed between 4 and 8 h after MCT administration, and mortality was much greater than when LPS was administered 4 h after MCT. To explore this difference, the temporal relationship between LPS and MCT exposure (7.4 x 10(6) EU/kg and 100 mg/kg, respectively) was altered. Twenty-four-hour survival was high in animals that received LPS 4 h before (86%) or after (88%) MCT, but it decreased markedly when LPS was administered 1 h before MCT (17%). Using this latter dosing regimen, animals became moribund as early as 4 h after MCT administration. Since liver injury was similar from regimens that differed greatly in mortality, death appeared to result from extrahepatic causes. To explore a role for nitric oxide (NO)-induced shock in this regimen, animals were treated with aminoguanidine (AG), an inhibitor of inducible NO synthase, prior to administration of LPS given an hour before MCT. In the cotreated animals, AG significantly attenuated mortality and decreased plasma nitrate/nitrite concentrations, markers of NO biosynthesis. Hence, the primary target of toxicity from MCT and LPS cotreatment appeared to shift from the liver to an extrahepatic site or sites as exposure to these agents occurred closer together temporally. NO appears to be causally involved in the deaths of animals treated with LPS 1 h before MCT.
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Affiliation(s)
- Steven B Yee
- Department of Pharmacology and Toxicology, National Food Safety and Toxicology Center, and Institute for Environmental Toxicology, Michigan State University, East Lansing, Michigan 48824, USA
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