Interleukin-1α is mainly expressed on the cell membrane, but can also be secreted during inflammation. The roles of secreted and membrane IL-1α in acute liver inflammation are still not known. Here, we examined the functions of secreted and membrane IL-1α in a mouse model of carbon tetrachloride-induced acute liver injury. We show that secreted IL-1α aggravates liver damage and membrane IL-1α slightly protects mice from liver injury. Further studies showed that secreted IL-1α promotes T-cell activation. It also increased the expansion of CD11b + Gr1 + myeloid cells, which may serve as a negative regulator of acute liver inflammation. Moreover, secreted IL-1α induced IL-6 production from hepatocytes. IL-6 neutralization reduced the proliferation of CD11b + Gr1 + myeloid cells in vivo. CCL2 and CXCL5 expression was increased by secreted IL-1α in vitro and in vivo. Antagonists of the chemokine receptors for CCL2 and CXCL5 significantly reduced the migration of CD11b + Gr1 + myeloid cells. These results demonstrate that secreted and membrane IL-1α play different roles in acute liver injury. Secreted IL-1α could promote Tcell activation and the recruitment and expansion of CD11b + Gr1 + myeloid cells through induction of CCL2, CXCL5, and IL-6. The controlled release of IL-1α could be a critical regulator during acute liver inflammation.Keywords: Acute liver injury r CD11b + Gr1 + myeloid cells r Membrane IL-1α r Secreted IL-1α r T-cell activation Additional supporting information may be found in the online version of this article at the publisher's web-site Correspondence: Dr. Haiyan Liu e-mail: hliu@suda.edu.cn
IntroductionThe liver plays a central role in metabolic homeostasis [1]. Liver injury is mainly caused by various insults such as drug, chemical agents, viral hepatitis (hepatitis B or C viruses), alcohol, and C 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu Eur. J. Immunol. 2015. 45: 2084-2098 Molecular immunology 2085 autoimmune attack of hepatocytes [2]. Liver damage by proinflammatory cytokines induced by these causes is a relevant mechanism for liver cell death [3]. Acute liver injury remains one of the most challenging problems in liver diseases, and new therapeutic options for treatment of acute liver injury are urgently needed [4]. Carbon tetrachloride (CCl 4 ) is widely used as a chemical inducer of acute or chronic liver injury in rodents depending on the dosage and administration frequency [5]. ROS and oxidative stress are then generated and inflammatory cells are recruited, which leads to hepatocyte degeneration and necrosis [6,7]. Parenchymal cells could regenerate that involves a complex regulated response after CCl 4 -induced acute liver injury [8]. Therefore, anti-oxidative and anti-inflammatory therapies are thought to be the effective ways to prevent and attenuate CCl 4 -induced liver damage. IL-1 is a pleiotropic cytokine and affects inflammatory immune responses. The IL-1 family includes two important agonistic proteins, IL-1α and IL-1β, which play an important role in ...