Rhamnan sulfate enhances the endothelial glycocalyx and decreases the LDL permeability of human coronary artery endothelial cells in vitro

Abstract

Human coronary artery endothelial cell monolayers were incubated with two rhamnan sulfate isoforms (RS1 and RS2) for 24 hrs before the permeability of low density lipoprotein (LDL) was measured. In addition, some monolayers were induced to undergo apoptosis with tumor necrosis factor‐α/cycloheximide (TNF‐α/CHX ) in the presence or absence of RS1 or RS2 and the permeability of LDL was measured. Both RS1 and RS2 significantly reduced the LDL permeability of control monolayers by 5‐fold. When the monolayers were induced to undergo apoptosis to increase their permeability, incubation with both RS1 and RS2 completely abolished the TNF‐α/CHX‐induced increase. Neither RS1 nor RS2 had any effect on the apoptosis rate of control or TNF‐α/CHX‐treated monolayers indicating that their effects were not mediated by apoptosis inhibition. Immunostaining of RS1 and RS2‐treated monolayers for a major gycocalyx component, heparan sulfate (HS), showed a significant increase in the coverage of HS compared to control monolayers. This suggests that enhanced HS synthesis may mediate the reduction in LDL permeability associated with RS1 and RS2. We believe that the enhanced glycocalyx provides added resistance to the leaky junction pathway that is the main pathway for LDL transport across the endothelium. Research supported by NIH HL094889 and Daniels Health Sciences.