The Glycocalyx and Pressure-Dependent Transcellular Albumin Transport

Abstract

Purpose Acute increases in hydrostatic pressure activate endothelial signaling pathways that modulate barrier function and vascular permeability. We investigated the role the glycocalyx and established mechanotransduction pathways in pressure-induced albumin transport across rat lung microvascular endothelial cells. Methods Rat lung microvascular endothelial cells (RLMEC) were cultured on Costar Snapwell chambers. Cell morphology was assessed using silver nitrate staining. RLMEC were exposed to zero pressure (Control) or 30 cmH2O (Pressure) for 30 or 60 min. Intracellular albumin uptake and transcellular albumin transport was quantified. Transcellular transport was reported as solute flux (Js) and an effective permeability coefficient (Pe). The removal of cell surface heparan sulfates (heparinase), inhibition of NOS (L-NAME) and reactive oxygen species (apocynin, Apo) was investigated. Results Acute increase in hydrostatic pressure augmented albumin uptake by 30–40% at 60 min and Js and Pe both increased significantly. Heparinase increased albumin uptake but attenuated transcellular transport while L-NAME attenuated both pressure-dependent albumin uptake and transport. Apo interrupted albumin uptake under both control and pressure conditions, leading to a near total lack of transcellular transport, suggesting a different mechanism and/or site of action. Conclusion Pressure-dependent albumin uptake and transcellular transport is another component of endothelial mechanotransduction and associated regulation of solute flux. This novel albumin uptake and transport pathway is regulated by heparan sulfates and eNOS. Albumin uptake is sensitive to ROS. The physiological and clinical implications of this albumin transport are discussed.

The Pulmonary Endothelial Glycocalyx Modifications in Glypican 1 Knockout Mice Do Not Affect Lung Endothelial Function in Physiological Conditions

“…A decreased glycocalyx was observed at arterial branch points, prone to the development of atherogenic lesions [33]. Additionally, glycocalyx perturbation is associated with impaired endothelial mechanotransduction [34,35], adhesion of platelets [36], and leukocytes [37] to the endothelial surface and endothelial hyperpermeability [7,38,39]. Therefore, we decided to explore if the structural and chemical changes observed in the lung endothelial glycocalyx of glypican 1 knockout mice were associated with lung endothelial barrier disruption, a known process in the early stages of pulmonary vascular diseases.…”

“…Among the many factors that regulate lung endothelial barrier stability, eNOS-dependent mechanisms stand out as a common pathway for the glycocalyx effects on lung endothelial barrier function and the effects of glypican 1 on aortic endothelial function. eNOS was shown to be a target of the glycocalyx in conditions of increased pulmonary pressure [7,31,40] and shear stress [26]. Although no studies have reported a link between glypican 1 and eNOS in the lungs, reduced eNOS phosphorylation at S1177 has been associated with decreased glypican 1 in aortic vessels of aged mice [25].…”

“…This cellular coat was first observed in endothelial cells, where it was described to be a physical barrier to the passage of solutes and proteins from the circulation to the interstitium [2,3]. It is currently known that the glycocalyx is a dynamic signaling layer that is involved in cellular homeostasis and pathological processes such as inflammation [4], hyperpermeability [5][6][7], coagulation [8,9], and leukocyte migration [5,10,11]. Moreover, degradation of the glycocalyx is often seen during disease development [12][13][14] and thus, the glycocalyx is seen as a gatekeeper for cellular homeostasis.…”

Special Issue on Professor John M. Tarbell’s Contribution to Cardiovascular Engineering

“…MENSAH ET AL. 26 11 Hydrostatic pressure is known to activate endothelial signaling pathways that modulate barrier function and vascular permeability. His team used rat lung microvascular endothelial cells to measure uptake and transcellular uptake of albumin in response to hydrostatic pressure.…”