Reactive oxygen species mediate modification of glycocalyx during ischemia-reperfusion injury

1 Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia; and 2 Universities Space Research Association, Division of Space Life Sciences, National Aeronautics and Space Center, Johnson Space Center, Houston, Texas Submitted 26 July 2005 ; accepted in final form 1 January 2006 The glycocalyx (Gcx) is a complex and poorly understood structure covering the luminal surface of endothelial cells. It is known to be a determinant of vascular rheology and permeability and may be a key control site for the vascular injuries caused by ischemia-reperfusion (I/R). We used intravital-microscopy to evaluate the effects of I/R injury on two properties of Gcx in mouse cremasteric microvessels: exclusion of macromolecules (anionic-dextrans) and intracapillary distribution of red blood cells (RBC). In this model, the Gcx is rapidly modified by I/R injury with an increase in 70-kDa anionic-dextran penetration without measurable effect on the penetration of 580-kDa anionic-dextran or on RBC exclusion. The effects of I/R injury appear to be mediated by the rapid production of reactive oxygen species (ROS) because they are ameliorated by the addition of exogenous superoxide dismutase-catalase. Intravenous application of allopurinol or heparin also inhibited the effects of I/R injury, and we interpret efficacy of allopurinol as evidence for a role for xanthine-oxidoreductase (XOR) in the response to I/R injury. Heparin, which is hypothesized to displace XOR from a heparin-binding domain in the Gcx, reduced the effects of I/R. The effects of I/R injury were also partially prevented or fully reversed by the intravascular infusion of exogenous hyaluronan. These data demonstrate: 1 ) the liability of Gcx during I/R injury; 2 ) the importance of locally produced ROS in the injury to Gcx; and 3 ) the potential importance of heparin-binding sites in modulating the ROS production. Our findings further highlight the relations between glycosaminoglycans and the pathophysiology of Gcx in vivo. glycosaminoglycans; heparin-binding domain; xanthine oxidoreductase Address for reprint requests and other correspondence: B. R. Duling, Cardiovascular Research Center, Dept. of Molecular Physiology and Biological Physics, 409 Lane Rd., MR-4 Bldg., Rm. 6051; Univ. of Virginia, School of Medicine, Charlottesville, VA 22908 (e-mail: brd{at}virginia.edu )