P-Selectin Mediates Platelet-Endothelial Cell Interactions and Reperfusion Injury in the Mouse Liver In Vivo

Abstract

Platelets are suggested to participate in the pathogenesis of hepatic ischemia-reperfusion (I/R) injury. This study was designed to analyze platelet-endothelial cell interactions in the postischemic mouse liver in vivo and to define the role of endothelial versus platelet P-selectin for these interactions. Platelet-endothelial cell interactions were quantitatively analyzed using intravital fluorescence microscopy after lobar hepatic I/R in C57BL/6 wild-type and P-selectin-deficient mice after infusion of ex vivo rhodamine-6G-labeled wild-type and P-selectin-deficient platelets. Reperfusion injury and apoptosis were assessed by established methods. In wild-type animals, hepatic I/R caused significantly enhanced platelet-endothelial cell interactions in terminal arterioles and postsinusoidal venules as well as platelet stagnation in sinusoids. Concomitantly, transaminase and caspase-3 activities were elevated and sinusoidal perfusion was impaired. In contrast, platelet-endothelial cell interactions were nearly absent in arterioles and venules of mice lacking endothelial P-selectin, irrespective of the presence of P-selectin on infused platelets, but still significantly elevated in sinusoids. Simultaneously, sinusoidal perfusion failure was ameliorated, and transaminase- and caspase-3 activities were significantly reduced in P-selectin-deficient mice as compared with wild-type animals. The present intravital microscopic study provides, for the first time, quantitative analyses of platelet-endothelial cell interactions in the postischemic hepatic microcirculation. Our in vivo data show that endothelial P-selectin is critical for postischemic platelet-endothelial cell interactions within hepatic presinusoidal arterioles and postsinusoidal venules. P-selectin deficiency prevents microvascular injury and apoptosis after warm hepatic I/R.

Ultrafine Particles Exert Prothrombotic but Not Inflammatory Effects on the Hepatic Microcirculation in Healthy Mice In Vivo

“…Therefore, the character of UFP-induced platelet-endothelial cell interactions seems to be different from that of inflammation-associated interactions of platelets with the endothelium as observed in the postischemic liver in our previous investigations. 21,22,26 After hepatic ischemiareperfusion, in contrast to UFP exposure, platelet rolling precedes permanent adhesion, and platelet adhesion is not restricted to venules and sinusoids but rather is also observed in terminal arterioles. 20 Although UFPs were recently shown to enhance ADPinduced platelet activation, 14 we addressed the issue of whether platelet recruitment can be mediated by prothrombotic changes on the hepatic endothelium in response to the systemic infusion of particles.…”

“…P-selectin, which is stored in granules of arteriolar/venular endothelial cells and platelets, is rapidly mobilized onto the endothelial surface on stimulation by various proinflammatory agents (ie, thrombin, histamine, oxidants) and is responsible for leukocyte and platelet rolling on hepatic endothelium. 22,29 Indeed, almost no staining for P-selectin was observed in animals subjected to UFP application followed by 2 hours of exposure (Table). This fact may explain the lack of leukocyte and platelet rolling in response to UFP exposure.…”

CD4+ T cells contribute to postischemic liver injury in mice by interacting with sinusoidal endothelium and platelets

“…[1][2][3][4] The microvascular hepatic I/R injury is initiated by the release and action of proinflammatory cytokines and oxygen radicals, which trigger upregulation of adhesion molecules, intravascular deposition of fibrinogen, and interaction of neutrophils as well as platelets with the endothelial lining of the hepatic microvasculature. [5][6][7][8] The failure of nutritive sinusoidal perfusion results in prolongation of focal hypoxia or anoxia and loss of endothelial integrity, which together lead to edema formation and oncotic necrosis. 1 Recent studies suggest that, in addition to neutrophils and platelets, T cells are involved in the induction of I/R injury of the liver.…”

“…The surgical procedure has been described in detail. 8 Shortly, under inhalation anesthesia with isoflurane-N 2 O, a catheter was inserted into the left carotid artery for measurement of mean arterial pressure and application of fluorescence dyes. A warm reversible ischemia of the left liver lobe was induced for 90 minutes by clamping the supplying nerve vessel bundle using a microclip.…”

“…7,8 To analyze leukocyte-endothelial cell interactions, all fractions of circulating leukocytes were labeled by an intravenous application of rhodamine 6G (0.1 mL, 0.05%, Sigma-Aldrich, Deisenhofen, Germany) and visualized using an N2 filter block (excitation: 530-560 nm, emission: Ͼ580 nm; Leitz). Sinusoidal perfusion was analyzed after intravenous application of fluorescein isothiocyanate-labeled dextran (MW 150,000; 0.1 mL, 5%, Sigma-Aldrich) using an I2/3 filter block (excitation: 450-490 nm, emission: Ͼ515 nm; Leitz) in sinusoids within 5 to 7 acini.…”