Important Role of P-Selectin for Leukocyte Recruitment, Hepatocellular Injury, and Apoptosis in Endotoxemic Mice

Abstract

Leukocyte recruitment in the liver includes a two-step procedure in which selectin-dependent leukocyte rolling is a prerequisite for subsequent CD18-dependent leukocyte firm adhesion in postsinusoidal venules. However, the roles of the individual selectins in leukocyte rolling and adhesion, hepatocellular injury, and apoptosis remain elusive. Therefore, we examined the pathophysiological role of P-, E-, and L-selectin in male C57BL/6 mice challenged with lipopolysaccharide (LPS) and D-galactosamine (Gal) by use of intravital microscopy of the liver microcirculation. In control animals, administration of LPS-Gal provoked reproducible hepatic damage, including marked increases of leukocyte recruitment, liver enzymes, and hepatocyte apoptosis and reduced sinusoidal perfusion. Interestingly, pretreatment with an anti-P-selectin antibody (RB40.34) markedly reduced leukocyte rolling and firm adhesion by 65 and 71%, respectively. Moreover, interference with P-selectin function significantly improved sinusoidal perfusion and reduced the increase in liver enzymes by 49 to 84% in endotoxemic mice. Moreover, the activity of caspase-3 and the number of apoptotic hepatocytes were significantly reduced by 55 and 54%, respectively, in RB40.34-treated animals. In contrast, administration of an anti-E-selectin antibody (10E9.6) and an anti-L-selectin antibody (Mel-14) did not protect against endotoxin-induced leukocyte responses or hepatic injury. In conclusion, our novel findings document a principal role of P-selectin in mediating leukocyte rolling, a precondition to the subsequent firm adhesion of leukocytes in liver injury. Furthermore, our novel data demonstrate that inhibition of P-selectin function reduces hepatocellular injury and apoptosis, suggesting a causal relationship between leukocyte recruitment on one hand and hepatocellular injury and apoptosis on the other hand. Based on these findings, it is suggested that P-selectin may be an important therapeutic target in endotoxin-induced liver injury.Activation and recruitment of leukocytes are features associated with liver injury in, e.g., ischemia-reperfusion and endotoxemia (10,12,23). In general, studies of various tissues have shown that infiltration of leukocytes involves a multistep cascade in which the initial rolling interaction between leukocytes and the endothelium is predominately mediated by the selectin family of adhesion molecules, including P-, E-, and L-selectin (1,15,20,31). Subsequent firm adhesion of leukocytes to the endothelium is dependent on the function of ␤ 1 -and ␤ 2 -integrins (CD11/18) on leukocytes, interacting with members of the immunoglobulin supergene family expressed on activated endothelial cells, such as ICAM-1 and -2 and VCAM-1 (1,12,15,16,20,21,31).However, the literature on the specific roles of P-, E-, and L-selectin and the relationship between leukocyte recruitment, cellular injury, and apoptosis is contradictory. For example, when blood flow velocity and shear rates are reduced, it has been suggested that leukocytes may bypass...

Sepsis-associated cholestasis is critically dependent on P-selectin-dependent leukocyte recruitment in mice

“…Our study did not address which stage in the transmigration process of leukocytes that P-selectin supports. However, a recent intravital microscopic study demonstrated that P-selectin supports LPS-induced leukocyte rolling in the liver (14), which helps explain our present findings showing that inhibition of P-selectin substantially blocks endotoxin-provoked accumulation of leukocytes in the extravascular space in the liver. Thus it appears that the recruitment process of leukocytes in the liver is similar to that observed in other organs.…”

“…The host response to endotoxin challenge provokes upregulation of specific endothelial cell adhesion molecules. Interestingly, it has been shown that P-selectin supports leukocyte rolling and lymphocyte function antigen-1 mediates firm adhesion of leukocytes in postsinusoidal venules in septic liver injury (14,15). Moreover, hepatic accumulation of leukocytes in response to endotoxin challenge is dependent on CXC chemokines, including macrophage inflammatory protein-2 (MIP-2) and cytokineinduced neutrophil chemoattractant (KC), which trigger tissue extravasation of leukocytes (16).…”

Molecular Characterization of Rat Leukocyte P-Selectin Glycoprotein Ligand-1 and Effect of Its Blockade: Protection from Ischemia-Reperfusion Injury in Liver Transplantation

“…The protein encoded by Bcl-2 gene has been implicated in prolongation of cell survival by blocking apoptosis and preventing hepatic IRI (42,43). Although the protective effect of the blockade of leukocyte-endothelial cell interaction on the induction of apoptosis has been reported in liver injury models (17,44,45), the exact mechanism remains unclear. Khandoga et al (45) reported that P-selectin KO mice prevented microvascular injury and apoptosis after hepatic warm I/R.…”

Compound Danshen injection improves endotoxin-induced microcirculatory disturbance in rat mesentery

“…Up-regulation of a variety of adhesion molecules was evoked following the LPS stimulation, mediating different phases of leukocyte recruitment in microvessels, with L-selectin in leukocytes and E-selectin in endothelial cells [7,28,29] being involved in leukocyte rolling along vascular endothelium [7] , and CD11b/CD18 in leukocytes and ICAM-1 in endothelial cells implicated in firm adhesion of leukocytes to vascular wall [5,15,30,31] . The fact that compound Danshen injection did not display any effect on the LPS-induced leukocyte rolling implies that it might reduce leukocytes adhering to venular wall through its inhibitory effect on the expression of adhesion molecules either CD11b/CD18 in neutrophils or ICAM-1 in endothelial cells or both rather than selectins.…”