Anthrax lethal toxin downregulates claudin-5 expression in human endothelial tight junctions

Area of Science:

• Pathology
• Molecular Biology
• Toxicology

Background:

• Vascular leakage, including pleural effusion and hemorrhage, is characteristic of anthrax.
• Anthrax lethal toxin (LT) is a primary virulence factor.
• Previous studies showed LT reduces barrier function in human microvascular endothelial cells.

Purpose of the Study:

• To investigate the molecular mechanisms by which anthrax lethal toxin (LT) disrupts endothelial barrier function.
• To identify specific endothelial junction proteins affected by LT exposure.
• To determine the role of claudin-5 in LT-induced vascular leakage.

Main Methods:

• In vitro studies using cultured primary human microvascular endothelial cells.
• Analysis of tight junction (TJ) and adherens junction (AJ) protein expression (claudin-5, occludin, ZO-1, ZO-2, VE-cadherin).
• Measurement of transendothelial electrical resistance (TEER).
• In vivo studies using a mouse model challenged with LT.
• Pharmacological inhibition of MEK-1/2 kinases.

Main Results:

• LT exposure led to reduced expression of the TJ protein claudin-5, without affecting other TJ/AJ components.
• Downregulation of claudin-5 correlated with decreased TEER in a time- and dose-dependent manner.
• LT-induced claudin-5 loss was independent of cell death and preceded cytoskeletal changes.
• LT reduced claudin-5 mRNA levels, suggesting transcriptional regulation.
• Mice challenged with LT exhibited reduced claudin-5 expression.

Conclusions:

• Anthrax lethal toxin (LT) specifically downregulates endothelial claudin-5 expression.
• Reduced claudin-5 expression is a key mechanism contributing to LT-induced vascular leakage.
• These findings highlight the role of TJ disruption in anthrax pathogenesis.