Microparticles mediate hepatic ischemia-reperfusion injury and are the targets of Diannexin (ASP8597)

Abstract

BACKGROUND & AIMS: Ischemia-reperfusion injury (IRI) can cause hepatic failure after liver surgery or transplantation. IRI causes oxidative stress, which injures sinusoidal endothelial cells (SECs), leading to recruitment and activation of Kupffer cells and platelets (by unknown processes) and microcirculatory impairment. We investigated whether injured SECs release microparticles (small fragments shed from outer leaf of the plasma membrane) with inflammatory effects that contribute to IRI pathogenesis. METHODS: C57BL6 mice underwent 60min of partial hepatic ischemia followed by 15min-24hrs of reperfusion. We collected blood and liver samples, isolated and measured circulating microparticles, and determined protein and lipid content. In mouse primary hepatocytes, we investigated features of microparticles and mechanisms of production. We analyzed the effects of an annexin V-homodimer (diannexin or ASP8597) on post-ischemia microparticle production and function. RESULTS: Circulating microparticles released 15-30min after ischemic reperfusion contained markers of SECs, platelets, natural killer T cells, and CD8+ cells; 4 hrs later, they contained markers of macrophages. Microparticles also contained F2- isoprostanes, markers of oxidative damage to membrane lipids. Injection of mice with TNF-alfa increased formation of microparticles, whereas injection with diannexin substantially reduced release of microparticles and prevented IRI. Hypoxia followed by re-oxygenation of primary hepatocytes generated microparticles via processes that involved oxidative stress and Ca2+. Circulating microparticles were engulfed by cultured hepatocytes, injuring them via the mitochondrial membrane permeability transition. Microparticles also activated platelets and induced migration of inflammatory cells in vitro. The inflammatory properties of microparticles involved activation of the transcription factor NF-kB, JNK and increased levels of E-selectin, P-selectin, Icam1, and Vcam1; these processes were blocked by coating microparticles with Diannexin. CONCLUSIONS: Following ischemia and reperfusion of mouse liver, microparticles (derived from SECs, platelets, and lymphocytes) are taken up by hepatocytes, where they activate signaling pathways that mediate inflammation and hepatocyte injury. Diannexin prevents microparticle formation and subsequent inflammation. Show more