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      The UII/UT System Mediates Upregulation of Proinflammatory Cytokines through p38 MAPK and NF-κB Pathways in LPS-Stimulated Kupffer Cells

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          Abstract

          The urotensin II (UII)/UII receptor (UT) system is closely related to immune inflammation. In acute liver failure (ALF), the UII/UT system can promote the production and release of proinflammatory cytokines, inducing an inflammatory injury response in liver tissue. However, the mechanism by which the hepatic UII/UT system promotes proinflammatory cytokine production and release is not clear. To solve this problem, we used primary Kupffer cells (KCs) as the model system in the current study. The results showed that after lipopolysaccharide (LPS) stimulation, KCs showed significantly increased expression and release of UII/UT and proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β). Pretreatment with urantide, which is a UT receptor antagonist, significantly inhibited the LPS-stimulated expression and release of UII/UT, TNF-α, and IL-1β by KCs. In addition, LPS stimulation induced nuclear p38 mitogen-activated protein kinase (MAPK) protein phosphorylation and expression of the nuclear nuclear factor κB (NF-κB) p65 subunit in KCs and enhanced the binding activity of NF-κB to DNA molecules, whereas urantide pretreatment significantly inhibited the LPS-stimulated nuclear expression and activity of these molecules in KCs. Therefore, our conclusion is that the UII/UT system mediates LPS-stimulated production and release of proinflammatory cytokine by KCs, and this mediating effect at least partially relies on the inflammatory signaling pathway molecules p38 MAPK and NF-κB.

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          Most cited references25

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          Acute liver failure: mechanisms of immune-mediated liver injury.

          Acute liver failure (ALF) is a syndrome of diverse aetiology, including hepatic encephalopathy, renal, cardiac and pulmonary failures, which result in a rapid loss of hepatic function. The mechanisms of liver injury contributing to ALF can be summarized into two categories: direct damage and immune-mediated liver injury. This review summarizes current concepts of immune-mediated liver injury from both clinical studies and animal models. We highlight immune responses of ALF from the liver injury perspective, which combines a variety of molecular and cellular mechanisms, particularly, the contribution of cytokines and the innate immune system. Hepatic and circulating inflammatory cytokines play a significant role in the pathophysiology of ALF including hepatocyte necrosis, extrahepatic complications and hepatocyte regeneration. Overproduction of cytokines, if unchecked, is hazardous to the host and may cause severe outcomes. Measuring pro-inflammatory cytokines in ALF may be of value for predictors of outcome. Innate and adaptive immune systems both involved in ALF contribute to immune-mediated liver injury. The innate immune response is activated much more rapidly compared with adaptive immunity, particularly in acute liver injury where the host has little time to trigger an effective adaptive immune response. From this point of view, the innate immune system may make a more profound contribution than the adaptive immune system. Furthermore, immune responses crosstalk with other physiological or pathophysiological factors, for example, coagulation factors which in turn determine the outcome of ALF and these are discussed.
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            Mechanisms of immune-mediated liver injury.

            Hepatic inflammation is a common finding during a variety of liver diseases including drug-induced liver toxicity. The inflammatory phenotype can be attributed to the innate immune response generated by Kupffer cells, monocytes, neutrophils, and lymphocytes. The adaptive immune system is also influenced by the innate immune response leading to liver damage. This review summarizes recent advances in specific mechanisms of immune-mediated hepatotoxicity and its application to drug-induced liver injury. Basic mechanisms of activation of lymphocytes, macrophages, and neutrophils and their unique mechanisms of recruitment into the liver vasculature are discussed. In particular, the role of adhesion molecules and various inflammatory mediators in this process are explored. In addition, the authors describe mechanisms of liver cell damage by these inflammatory cells and critically evaluate the functional significance of each cell type for predictive and idiosyncratic drug-induced liver injury. It is expected that continued advances in our understanding of immune mechanisms of liver injury will lead to an earlier detection of the hepatotoxic potential of drugs under development and to an earlier identification of susceptible individuals at risk for predictive and idiosyncratic drug toxicities.
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              Kupffer cells are associated with apoptosis, inflammation and fibrotic effects in hepatic fibrosis in rats.

              Hepatocellular apoptosis, hepatic inflammation, and fibrosis are prominent features in chronic liver diseases. However, the linkage among these processes remains mechanistically unclear. In this study, we examined the apoptosis and activation of Kupffer cells (KCs) as well as their pathophysiological involvement in liver fibrosis process. Hepatic fibrosis was induced in rats by dimethylnitrosamine (DMN) or carbon tetrachloride (CCl4) treatment. KCs were isolated from normal rats and incubated with lipopolysaccharide (LPS) or from fibrotic rats. The KCs were stained immunohistochemically with anti-CD68 antibody, a biomarker for KC. The level of expression of CD68 was analyzed by western blot and real-time PCR methods. The apoptosis and pathophysiological involvement of KCs in the formation of liver fibrosis were studied using confocal microscopy. The mRNA and protein expression of CD68 were significantly increased in DMN- and CCL4-treated rats. Confocal microscopy analysis showed that CD68-positive KCs, but not α-smooth muscle actin (SMA)-positive cells, underwent apoptosis in the liver of DMN- and CCL4-treated rats. It was also revealed that the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and CD68-double-positive apoptotic KCs located in the portal or fibrotic septa area were situated next to hepatic stellate cells (HSCs). Tumor necrosis factor-α (TNF-α) and KC co-localized in the liver in the neighbor of HSCs. The double α-SMA- and collagen type I-positive cells predominantly existed in fibrotic septa, and those cells were co-localized clearly with CD68-positive cells. Interestingly, some CD68 and Col (1) double positive, but completely negative for α-SMA, were found in the portal areas and hepatic sinusoids; this phenomenon was also validated in primary isolated KCs after 6 h LPS exposure or fibrotic rats in vitro. These results show that KCs are associated with hepatocellular apoptosis, inflammation, and fibrosis process in a liver fibrosis models.
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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                24 March 2015
                2015
                : 10
                : 3
                : e0121383
                Affiliations
                [001]Department of Hepatology, Songjiang Hospital Affiliated to the First People’s Hospital Shanghai Jiaotong University, Shanghai, China
                Harvard Medical School, UNITED STATES
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: LML. Performed the experiments: DYL CGY WJT TZ. Analyzed the data: LML DYL CGY. Contributed reagents/materials/analysis tools: LML. Wrote the paper: LML.

                Article
                PONE-D-14-48893
                10.1371/journal.pone.0121383
                4372515
                25803040
                9dfc65bb-a738-4b2b-88af-e3d407b8ada7
                Copyright @ 2015

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

                History
                : 30 October 2014
                : 31 January 2015
                Page count
                Figures: 7, Tables: 2, Pages: 13
                Funding
                The work was supported by grants from National Natural Science Foundation of China (No. 81070357, No. 30660066) ( http://www.nsfc.gov.cn/Portal0/default152.htm). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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                Research Article
                Custom metadata
                All relevant data are within the paper and its Supporting Information files.

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