Leukocyte recruitment in hepatic injury: selectin-mediated leukocyte rolling is a prerequisite for CD18-dependent firm adhesion

Background/Aims: This study was designed to examine the role of selectins and CD18 in leukocyte recruitment in hepatic injury induced by tumor necrosis factor-α (TNF-α) and galactosamine (Gal) in vivo. Methods: Intravital fluorescence microscopy of the hepatic microcirculation was used to quantify leukocyte–endothelium interactions provoked by 24 h of systemic TNF-α/Gal challenge in rats. Hepatic injury was evaluated with liver enzymes. Results: When administered after 24 h of TNF-α/Gal challenge, fucoidan, a selectin-function inhibitor, reduced leukocyte rolling by 69%, whereas firm adhesion was unaltered. In contrast, passive immunization against CD18 decreased leukocyte adhesion by 60%, whereas rolling remained unchanged. Notably, when administered prior to TNF-α/Gal, fucoidan attenuated both leukocyte rolling and adhesion, by 57 and 69%, respectively. Pretreatment with an anti-CD18 antibody decreased TNF-α/Gal-induced rolling and firm adhesion by 25 and 90%, respectively. Moreover, pretreatment with fucoidan and the anti-CD18 antibody both protected against TNF-α/Gal-induced increases in liver enzymes. For example, the pretreatments reduced alanine aminotransferase by 59 and 87%, respectively. Conclusions: Our data suggest that TNF-α/Gal-induced leukocyte rolling is selectin-mediated and a precondition for CD18-dependent firm adhesion in hepatic venules. Thus, reducing leukocyte recruitment by inhibition of selectins or CD18 may be useful to control TNF-α-induced liver injury