Selectins and β 2 -integrins mediate post-ischaemic venular adhesion of polymorphonuclear leukocytes, but not capillary plugging, in isolated hearts

Abstract

Leukocytes adhering to venular endothelium and emigrating into the tissue contribute to myocardial reperfusion injury. The aim of the present study was to characterize the contribution of two different families of adhesion molecules, selectins and integrins, to post-ischaemic capillary plugging and venular adhesion of leukocytes in an isolated heart model. Guinea-pig hearts were perfused using the Langendorff technique. After 20 min stabilization global ischaemia was induced for 15 min at 37 degrees C. With the onset of reperfusion 10(7) isolated polymorphonuclear leukocytes (PMN), prelabelled with rhodamine 6G, were infused within 1 min. Perfusion was continued for 2 min to wash out all cells not firmly adhering to the vascular endothelium. Hearts were then arrested, mounted on a microscope stage and perfused with a cardioplegic solution containing 0.01% fluorescein isothiocyanate (FITC)-dextran (MW 150,000). In situ videofluorescence microscopy was used to quantify PMN plugging and adherent PMN. Four groups were studied: control (no treatment or ischaemia, n = 6); ischaemia (no treatment and 15 min ischaemia, n = 5); fucoidin (pretreatment of hearts and PMN with 0.3 mg/ml selectin inhibitor fucoidin and 15 min ischaemia, n = 5) and CD18 (pretreatment of PMN with 0.1 mg monoclonal antibody against CD18 and 15 min ischaemia, n = 5). Capillary plugging by PMN was 25 +/- 5 PMN/mm2 epicardial surface area and increased moderately to 55 +/- 6 PMN/mm2 in reperfused hearts. This increase was not affected by fucoidin or CD18 antibody. In contrast, post-ischaemic adhesion of PMN in small venules increased ninefold from 21 +/- 5 to 196 +/- 23 PMN/mm2 endothelial surface area. The increase in PMN adhesion to venular endothelium was blocked completely by pretreatment with fucoidin (19 +/- 5 PMN/mm-2) or CD18 antibody (7 +/- 2 PMN/mm-2). We conclude that selectin interaction alone is not sufficient to account for post-ischaemic PMN adhesion in the small venules of the coronary vasculature, because blocking the integrin subunit CD18 also inhibited PMN adhesion completely. On the other hand, neither integrins nor selectins seem to be involved in post-ischaemic capillary plugging by PMN in our perfused heart model.

Microcirculatory function monitoring at the bedside—a view from the intensive care

“…Endothelial swelling, leucocyte plugging, disseminated intravascular clot formation, tissue edema and the build up of vasoactive mediators (e.g. nitric oxide, arachidonic acid metabolites, histamine, serotonine, adenosin) may lead to increasing heterogeneity of microvascular blood flow, thereby decreasing tissue oxygen supply and promoting organ failure (Ellis et al 2002, Mazzoni et al 1989, Talbott et al 1994, Eichelbronner et al 2003, Gando et al 1999, Habazettl et al 1999 (figure 1). In addition, systemic hemodynamic failure due to downregulation of adrenergic receptors on vascular smooth muscle cells, depletion of endogenous vasoactive hormones (e.g.…”

Capillary pericytes mediate coronary no-reflow after myocardial ischaemia

“…No-reflow has been attributed to swollen endothelial cells and/or cardiomyocytes compressing the lumen of capillaries ( Kloner, 2011 ), or to leukocytes adhering to and plugging capillaries ( Engler et al, 1983 ). However, although depleting blood of granulocytes reduces no-reflow ( Engler et al, 1986 ), leukocyte adhesion to capillaries in reperfused hearts is modest compared to the adhesion seen in post-capillary venules ( Habazettl et al, 1999 ). No treatment exists for coronary no-reflow after decades of investigation, even though it predicts a worse outcome after myocardial ischaemia ( Niccoli et al, 2009 ; Wu et al, 1998 ; Morishima et al, 2000 ; Ørn et al, 2009 ; Kloner, 2011 ).…”

Regulation of blood flow and volume exchange across the microcirculation

“…Inflammatory growth factors such as VEGF have been reported to act as venodilators [ 21 ]. On the other hand, in inflammatory and in postischemic, reperfused tissue, leukocytes adhere in large numbers to the walls of the venules and small collecting veins [ 22 ]. This will cause partial obstruction to flow, also increasing upstream intravascular pressure with consequences for fluid filtration, a topic to be discussed more fully below.…”

“…On top of that, shedding of the glycocalyx leads to breakdown of the oncotic pressure gradient at the endothelial surface, and inflammatory mediators generally induce widening of the interendothelial clefts. They also directly and indirectly enhance sticking of inflammatory leukocytes and of blood platelets to the walls of venules and collecting veins, thereby effectively leading to a narrowing of the microvascular outflow tract [ 22 , 28 , 29 ]. All of this is bad news for fluid homeostasis.…”