Mechanism for the increased permeability in endothelial monolayers induced by elastase

Area of Science:

• Biochemistry
• Cell Biology
• Physiology

Background:

• Endothelial permeability is crucial for regulating substance exchange.
• Human neutrophil elastase (HNE) is implicated in inflammatory conditions.
• The precise mechanism of HNE-induced endothelial permeability remains unclear.

Purpose of the Study:

• To elucidate the mechanism by which HNE increases endothelial permeability.
• To differentiate between proteolytic and charge-dependent effects of HNE.

Main Methods:

• Bovine pulmonary artery endothelial cells (BPAEC) were treated with varying concentrations of HNE.
• Albumin clearance assays were used to measure endothelial permeability.
• Inhibitors of xanthine oxidase (sodium tungstate, oxypurinol), heparin, heat-inactivated HNE, and a specific HNE inhibitor (ONO-5046) were employed.

Main Results:

• HNE caused a concentration-dependent increase in endothelial permeability, measured by (125)I-albumin clearance.
• This effect was reversible and not due to cell lysis.
• Inhibiting xanthine oxidase, neutralizing HNE's charge with heparin, or using heat-inactivated HNE did not prevent the permeability increase; however, the specific HNE inhibitor ONO-5046 did.

Conclusions:

• The findings strongly suggest that the proteolytic activity of HNE, rather than its cationic charge, is the primary driver of increased endothelial permeability.
• This mechanism is independent of xanthine oxidase pathways.
• Understanding this mechanism offers potential therapeutic targets for conditions involving HNE-mediated vascular leakage.