Endothelial functional responses and increased vascular permeability induced by polycations

Area of Science:

• Vascular Biology
• Endothelial Cell Function
• Pharmacology

Background:

• Polycations are known to interact with biological systems.
• Endothelial cells play a crucial role in vascular health and inflammation.
• Prostacyclin and purines are important mediators released by endothelial cells.

Purpose of the Study:

• To investigate the effects of polycations, specifically poly-L-lysine, on vascular endothelium in vitro and in vivo.
• To determine the role of charge and molecular weight (size) in polycation-induced endothelial responses.
• To elucidate the mechanisms underlying polycation-mediated endothelial stimulation and edema formation.

Main Methods:

• Cultured porcine aortic endothelial cells were stimulated with poly-L-lysine.
• In vivo studies involved intradermal injection of poly-L-lysine in rabbits.
• Enzyme treatments (heparinase, trypsin, neuraminidase) and pharmacological inhibitors (indomethacin, trasylol, soybean trypsin inhibitor) were used to probe mechanisms.

Main Results:

• Poly-L-lysine stimulated endothelial cells to release prostacyclin and cytoplasmic purines in a dose- and size-dependent manner.
• In vivo, poly-L-lysine induced charge- and size-dependent local edema.
• Responses were reduced by heparin/trypsin pretreatment, indomethacin, and trasylol, suggesting involvement of membrane proteins, prostaglandins, and proteases.

Conclusions:

• Polycations, such as poly-L-lysine, potently stimulate vascular endothelium.
• Both charge and molecular size are critical determinants of polycation effects on endothelium.
• Naturally occurring polycations may contribute to pathological processes due to their size-dependent interactions with the vasculature.