Transendothelial migration of effector T cells across inflamed endothelial barriers does not require heparan sulfate proteoglycans.
Leukocyte diapedesis is a chemotactic multistep process that requires optimal chemoattractant presentation by the endothelial barrier. Recent studies have described a critical role for heparan sulfate glycosaminoglycans (HSGAGs) in the presentation and functions of chemokines essential for lymphocyte interactions with the lymph node vasculature. We wished to test whether HS expression by a prototypic endothelial cell type, i.e. human umbilical vein endothelial cells (HUVECs), is critical for their ability to support neutrophil and lymphocyte adhesion and transendothelial migration (TEM) under shear flow. We found that HUVECs deposit HS GAGs mainly at their basolateral compartments in both their resting and inflamed states. We next inactivated the key enzyme involved in HS biosynthesis, exostosin-1 (Ext1). Silencing Ext1 resulted in a complete loss of HS biosynthesis; nonetheless, TNF-α and IL-1β stimulation of key adhesion molecules and inflammatory chemokines necessary for neutrophil or lymphocyte adhesion and TEM remained intact. Ext1 silencing reduced neutrophil arrest and markedly impaired TEM, consistent with a role of basolateral HS GAGs in directing neutrophil crossing of inflamed endothelial barriers. Strikingly, however, the TEM of effector T cells across identically Ext1-silenced HUVECs remained normal. Importantly, the biosynthesis of the main promigratory chemokines for effector T cells and neutrophils, respectively, CCL2 and CXCL1, and their vesicle distributions were also Ext1 independent. These results suggest that transmigrating neutrophils must respond to chemokines transiently presented by apical and basolateral endothelial HS GAGs. In contrast, effector T cells can integrate chemotactic TEM signals directly from intra-endothelial chemokine stores rather than from externally deposited chemokines.
['Stoler-Barak|Liat|L|', 'Barzilai|Sagi|S|', 'Zauberman|Ayelet|A|', 'Alon|Ronen|R|']
D002460:Cell Line D018932:Chemokine CCL2 D054360:Chemokine CXCL1 D002633:Chemotaxis D004730:Endothelium, Vascular D006493:Heparin D006801:Humans D007249:Inflammation D053583:Interleukin-1beta D017351:N-Acetylglucosaminyltransferases D009504:Neutrophils D011509:Proteoglycans D034741:RNA, Small Interfering D013601:T-Lymphocytes D057705:Transendothelial and Transepithelial Migration D014409:Tumor Necrosis Factor-alpha
neutrophils Ext1 inflammation leukocyte trafficking