Inflammation- and ischemia-induced shedding of venular glycocalyx

• Published in: American journal of physiology. Heart and circulatory physiology 2004-05, Vol.286 (5), p.H1672-H1680
• Main Authors: Mulivor, A. W, Lipowsky, H. H
• Format: Article
• Language: English
• Subjects: Animals; Cell Adhesion; Endothelium, Vascular - physiopathology; Fluorescein-5-isothiocyanate; Fluorescent Dyes; Glycocalyx - drug effects; Glycocalyx - metabolism; Glycosaminoglycans - metabolism; Ischemia - physiopathology; Leukocytes; Male; Membrane Glycoproteins - metabolism; N-Formylmethionine Leucyl-Phenylalanine - pharmacology; Plant Lectins - metabolism; Proteoglycans - metabolism; Rats; Rats, Sprague-Dawley; Splanchnic Circulation; Syndecan-1; Syndecans; Vasculitis - physiopathology; Venules - drug effects; Venules - metabolism
• ISSN: 0363-6135; 1522-1539
• DOI: 10.1152/ajpheart.00832.2003

Department of Bioengineering, Pennsylvania State University, University Park, Pennsylvania 16802 Submitted 2 September 2003 ; accepted in final form 23 December 2003 Alterations in the composition of the glycocalyx of venular endothelium in postcapillary venules (rat mesentery) were explored in models of inflammation and ischemia-reperfusion injury. Lectins were covalently linked to fluorescently labeled microspheres (0.1-µm diameter) or directly labeled with FITC. Adhesion of lectins specific for glucose and galactose residues of glycosaminoglycans (GAGs) and other components of the endothelial glycocalyx decreased dramatically after superfusion of the mesentery with the chemoattractant N -formylmethionyl-leucyl-phenylalanine and during reperfusion after 60-min ischemia. These reductions were significantly attenuated by superfusion with pertussis toxin (PTX), suggesting that shedding of glycocalyx was mediated by G proteins. Adhesion of microspheres linked with antibody for syndecan-1, a major proteoglycan to which GAGs are bound, revealed increased labeling as GAGs were lost and permitted greater numbers of spheres to adhere to the protein core, which was not shed. Induction of ischemia by occluding proximal microvessels for 60 min resulted in a 40% increase in galactosaminoglycans and a 15% increase in glucosaminoglycans on the endothelium, which was not inhibited by PTX. Reperfusion of vessels led to a rapid loss of GAGs that was inhibited by pretreatment with PTX, with 40% of galactosaminoglycans and 25% of glucosaminoglycans accumulated being removed by G protein-mediated shedding and the remainder freely convected away by fluid shear. We conclude that the composition of the glycocalyx results from a balance of the rate of biosynthesis of GAGs by the endothelial cell and their shedding, which may be mediated by intracellular and/or membrane-bound proteases or lyases released or activated by G protein signaling. endothelium; venules Address for reprint requests and other correspondence: H. H. Lipowsky, Dept. of Bioengineering, Penn State Univ., 233 Hallowell Bldg, Univ. Park, PA 16802 (E-mail: hhlbio{at}engr.psu.edu ).