Selectin-mediated rolling of neutrophils is essential for their activation and retention in the reperfused coronary system

Abstract

Neutrophil adhesion to coronary endothelium is a key event for cardiac reperfusion injury. Adhesion is proposed to be a multi-step event, consisting of selectin-mediated rolling, chemotactic activation, and subsequent integrin-mediated firm attachment. However, it is not clear whether this sequence also occurs in the coronary circulation with its unique hemodynamic properties (turbulent flow, flow reversal). We have studied neutrophil adhesion in the coronary system of isolated perfused guinea pig hearts under basal and reperfusion conditions (15 min global ischemia). Adhesion was manipulated by an anti-CD18 antibody (blocking firm adhesion) and fucoidin (reducing rolling). Neutrophil behavior during coronary passage was assessed by measurement of CD11b expression, forward scatter (FSC, indicating polarization), and sideward scatter (SSC, measure for granularity) via flow cytometry. Adhesion rose from 21 % (basal) to 35 % after ischemia. Anti-CD18 decreased adhesion to 11 % and 14 %, respectively; fucoidin altered only the postischemic increase (23 %). CD11b was unchanged by passage through the non-ischemic coronaries, but rose postischemically (139 % increase). CD18 blockade did not reduce the postischemic rise of CD11b, while fucoidin was inhibitory (24 % increase). FSC did not differ between controls and ischemic hearts in any group, while SSC decreased most in postischemic hearts after CD18 blockade. Blockade of rolling and of firm attachment both reduce neutrophil retention, while only inhibition of rolling reduces intracoronary activation. Thus, rolling seems to be mandatory for endothelial-leukocyte communication in the coronary system.