High-molecular-weight hyaluronan is a novel inhibitor of pulmonary vascular leakiness

Abstract

Endothelial cell (EC) barrier dysfunction results in increased vascular permeability, a perturbation observed in inflammatory states, tumor angiogenesis, atherosclerosis, and both sepsis and acute lung injury. Therefore, agents that enhance EC barrier integrity have important therapeutic implications. We observed that binding of high-molecular-weight hyaluronan (HMW-HA) to its cognate receptor CD44 within caveolin-enriched microdomains (CEM) enhances human pulmonary EC barrier function. Immunocytochemical analysis indicated that HMW-HA promotes redistribution of a significant population of CEM to areas of cell-cell contact. Quantitative proteomic analysis of CEM isolated from human EC demonstrated HMW-HA-mediated recruitment of cytoskeletal regulatory proteins (annexin A2, protein S100-A10, and filamin A/B). Inhibition of CEM formation [caveolin-1 small interfering RNA (siRNA) and cholesterol depletion] or silencing (siRNA) of CD44, annexin A2, protein S100-A10, or filamin A/B expression abolished HMW-HA-induced actin cytoskeletal reorganization and EC barrier enhancement. To confirm our in vitro results in an in vivo model of inflammatory lung injury with vascular hyperpermeability, we observed that the protective effects of HMW-HA on LPS-induced pulmonary vascular leakiness were blocked in caveolin-1 knockout mice. Furthermore, targeted inhibition of CD44 expression in the mouse pulmonary vasculature significantly reduced HMW-HA-mediated protection from LPS-induced hyperpermeability. These data suggest that HMW-HA, via CD44-mediated CEM signaling events, represents a potentially useful therapeutic agent for syndromes of increased vascular permeability.

Role of hyaluronan and hyaluronan-binding proteins in lung pathobiology

“…We recently demonstrated that intravenous administration of HMW-HA (ϳ1 ϫ 10 6 ) 4 h after intratracheal administration of LPS protects against lung injury in mice (125,126). This finding is consistent with results from the study of Nadkarni et al (97), who demonstrated that pretreatment of hamsters with aerosolized HMW-HA protects against endotoxin-induced lung injury.…”

“…2). In addition, we have demonstrated that targeted deletion of CD44 in the mouse pulmonary vasculature increases basal leakiness in the lungs (125). In contrast, pulmonary vascular leak caused by intraperitoneal administration of IL-2 is attenuated in CD44 knockout mice and by CD44 antibody blockage (51,95,111).…”

“…These differences are likely accounted for by the different modes of delivery (intratracheal vs. aerosolized) and lower LPS concentration, leading to a milder inflammatory response and faster resolution. One common finding in all these studies is the increased concentration of HA in the BAL fluid of CD44 knockout mice (56,75,125). CD44 AND PNEUMONIA.…”

“…HMW-HA can induce cyclooxygenase-2 expression in endothelial cells via cluster of differentiation 44 (CD44) (94), mediate epithelialmesenchymal transition during heart valve formation via ErbB2 (13), and enhance endothelial cell barrier function in the lung via CD44, the sphingosine 1-phosphate (S1P1) receptor, Akt, and Rac signaling (124,125). Low-molecular-weight HA (LMW-HA), on the other hand, has been shown to decrease endothelial cell barrier function (124,125), stimulate angiogenesis (30), and induce expression of a host of inflammatory mediators in alveolar macrophages, including macrophage inflammatory protein-1␣ (MIP-1␣), regulated upon activation, normal T cell expressed and secreted (RANTES), Mig, IFN-␥-induced protein 10, and plasminogen activator inhibitor 1, via CD44 and Toll-like receptor (TLR) 2 and TLR4 (57,58,60,86). Therefore, the effects of HA are wide-ranging and are dependent not only on its molecular weight, but also on the specific receptors expressed and the cell type involved.…”

Safe and Curative Brachytherapy Reirradiation with Organ-Sparing Hyaluronate Gel Injection

“…Recent reports state that HMW-HA inhibits the production of matrix metalloproteinases [Hashizume, 2010] as well as vascular leakiness [Singleton, 2010], and that there is a size function of hyaluronate [Wolny. 2010].…”