ABSTRACT
Endothelial basement membranes constitute barriers to extravasating leukocytes during inflammation, a process where laminin isoforms define sites of leukocyte exit; however, how this occurs is poorly understood. In addition to a direct effect on leukocyte transmigration, we show that laminin 511 affects endothelial barrier function by stabilizing VE-cadherin at junctions and downregulating expression of CD99L2, correlating with reduced neutrophil extravasation. Binding of endothelial cells to laminin 511, but not laminin 411 or non-endothelial laminin 111, enhanced transendothelial cell electrical resistance (TEER) and inhibited neutrophil transmigration. Data suggest that endothelial adhesion to laminin 511 via ß1 and ß3 integrins mediates RhoA-induced VE-cadherin localization to cell-cell borders, and while CD99L2 downregulation requires integrin ß1, it is RhoA-independent. Our data demonstrate that molecular information provided by basement membrane laminin 511 affects leukocyte extravasation both directly and indirectly by modulating endothelial barrier properties.
Subject(s)
Basement Membrane/metabolism , Cell Movement/physiology , Endothelial Cells/metabolism , Endothelium, Vascular/metabolism , Laminin/metabolism , Leukocytes/metabolism , Animals , Antigens, CD/metabolism , Cadherins/metabolism , Cell Adhesion/physiology , Cells, Cultured , Male , Mice , Mice, Knockout , Neutrophils/metabolism , Neutrophils/physiologyABSTRACT
Acute peritonitis is a frequent medical condition that can trigger severe sepsis as a life-threatening complication. Neutrophils are first-responders in infection but recruitment mechanisms to the abdominal cavity remain poorly defined. Here, we demonstrate that high endothelial venules (HEVs) of the greater omentum constitute a main entry pathway in TNFα-, Escherichia coli (E. coli)- and caecal ligation and puncture-induced models of inflammation. Neutrophil transmigration across HEVs is faster than across conventional postcapillary venules and requires a unique set of adhesion receptors including peripheral node addressin, E-, L-selectin and Mac-1 but not P-selectin or LFA-1. Omental milky spots readily concentrate intra-abdominal E. coli where macrophages and recruited neutrophils collaborate in phagocytosis and killing. Inhibition of the omental neutrophil response exacerbates septic progression of peritonitis. This data identifies HEVs as a clinically relevant vascular recruitment site for neutrophils in acute peritonitis that is indispensable for host defence against early systemic bacterial spread and sepsis.
