Impaired function of the Tie-2 receptor contributes to vascular leakage and lethality in anthrax

Area of Science:

• Vascular Biology
• Toxinology
• Immunology

Background:

• Anthrax lethal toxin (LT) is known to affect host cells, but its precise role in disease lethality, particularly concerning vascular permeability, is not fully understood.
• Published research suggests LT may directly impact vascular integrity, yet the underlying molecular mechanisms remain unclear.

Purpose of the Study:

• To investigate the molecular mechanisms by which anthrax lethal toxin (LT) causes death, focusing on its effects on the vascular endothelium.
• To determine the role of Tie-2 receptor tyrosine kinase signaling in the response to LT challenge and its potential as a therapeutic target.

Main Methods:

• LT challenge in mouse models to assess Tie-2 signaling disruption and vascular permeability.
• Genetic manipulation to enhance Tie-2 activation and evaluate its protective effects.
• Analysis of MEK cleavage and its necessity for LT-induced endothelial barrier dysfunction.
• Examination of Tie-2 ligand imbalance in primates infected with Bacillus anthracis.

Main Results:

• LT challenge in mice disrupts endothelial Tie-2 signaling, leading to increased vascular permeability.
• Enhanced Tie-2 activation in mice conferred protection against lethal LT doses by strengthening interendothelial junctions and preventing leakage.
• MEK cleavage by LT was essential for endothelial barrier dysfunction, while activated Tie-2 signaled through uncleaved MEKs to counteract LT's effects.
• Primates infected with Bacillus anthracis showed a significant imbalance in Tie-2 ligands, mirroring findings in LT-challenged mice.

Conclusions:

• Bacillus anthracis LT impairs vascular barrier integrity by blunting Tie-2 signaling, contributing to disease lethality.
• Targeting Tie-2 activity and measuring circulating Tie-2 ligands present potential future strategies for diagnosing and treating anthrax exposure.