Then, tissue sections were exposed to diluted primary antibody for overnight at 4

Then, tissue sections were exposed to diluted primary antibody for overnight at 4. a marked neutrophil recruitment and CD44 expression into the ischemic livers. Administration of anti-CD44 antibody to mice reduced the infiltration of neutrophil into the ischemic tissue, associated with liver function preservation. These results support crucial roles of CD44 in neutrophil recruitment and infiltration leading to liver damage in hepatic I/R injury. Moreover, they provide the rationale for targeting to CD44 as a potential therapeutic approach Fluvastatin in liver I/R injury. Keywords:Liver, Ischemia/Reperfusion, CD44, Inflammation, Neutrophils, Recruitment == INTRODUCTION == Hepatic ischemia reperfusion (I/R) injury is a pathophysiologic process whereby hypoxic organ damage is accentuated following return of blood flow and oxygen delivery (1-3). Transient episodes of tissue ischemia are encountered during solid organ transplantation, trauma, hypovolemic shock and elective liver resection, when inflow occlusion or total vascular exclusion is used to minimize blood loss. In these situations, after a period of ischemia, the liver can be significantly injured upon its reperfusion. If the injury is severely uncontrolled, this can lead to liver failure, systemic inflammatory response syndrome and multiple organ failure which are associated with high rates of morbidity and mortality (4). I/R injury is characterized by an excessive inflammatory response after reperfusion, which exert a crucial role in the pathophysiology of postischemic hepatic failure (5). The injury occurs in a biphasic pattern: The early pattern is characterized by hepatic injury occurring within 1-6 hr after reperfusion, associated Fluvastatin with Kupffer cell activation and up-regulation of reactive oxygen species, the inducible nitric oxide synthase and the pro-inflammatory cytokines (6,7). Subsequently, the injury is aggravated by a massive neutrophil infiltration, peaking 9-24 hr following reperfusion. The neutrophils are recruited into the liver vasculature, which is activated by various cellular adhesion molecules. These neutrophils cause hepatocyte necrosis through the release of cytotoxic proteases and oxygen-derived radicals. The neutrophil recruitment during inflammation is classically attributed to a multi-step cascade involving initial tethering and rolling Fluvastatin along the vessel wall, followed by firm adhesion to the vascular endothelium and emigration out of the vasculature. This classical paradigm is well characterized for a number of organ microvasculatures including mesentery, peritoneum, skeletal muscle, and skin (8). Within the post-capillary vessels of these tissues, the classical paradigm of neutrophil recruitment involve selectin mediated tethering and rolling, followed by integrin mediated firm adhesion (9). The liver has two principal vascular beds for neutrophil recruitment during reperfusion: sinusoids and postsinusoidal venules. The evidence for transmigration from postsinusoidal venules is limited. In contrast, sinusoids were identified as the dominant sites Fluvastatin for neutrophil extravasation (10). The sinusoidal endothelium is the unique structure of the liver, which is Fluvastatin discontinuous, fenestrated, and lacking basal lamina and tight junction. And then in these narrow capillaries, the recruitment of slow-moving leukocytes is selectin independent, and the rolling process is likely to be unnecessary. In short, the liver presents an apparent exception to this classical paradigm of neutrophil recruitment in three ways: 1) in addition to the postsinusoidal venules, neutrophils also adhere to the endothelium of capillaries called sinusoids, 2) within the sinusoids, neutrophils appear not to roll for a significant distance, but rather tether and immediately adhere and 3) the adhesion in the sinusoids is shown to be completely independant of selectin (11,12). Some clinical trials of anti-adhesion therapy in an attempt to reduce CD177 injury associated with I/R injury failed to show a significant benefit, despite very strong preclinical data (13). Recently, several adhesion molecules, including VAP-1, CD44, CD43, and Fc RIII for lymphocyte adhesion in sinusoidal endothelium have been proposed (14). Therefore, we examined the role of CD44 in liver reperfusion injury, at various lengths of reperfusion time. In current study, we sought to test whether or not hepatic I/R injury would be attenuated in mice treated with anti-CD44 antibody before I/R insult, at time points most consistent with the neutrophil-mediated phage of liver.