Poly(I:C) Induces Human Lung Endothelial Barrier Dysfunction by Disrupting Tight Junction Expression of Claudin-5

Area of Science:

• Immunology
• Cell Biology
• Pathology

Background:

• Viral infections often cause pulmonary microvascular leakage and endothelial dysfunction.
• Mechanisms underlying viral-induced vascular damage are not fully understood.

Purpose of the Study:

• To investigate the impact of polyinosinic-polycytidylic acid [Poly(I:C)], a Toll-like receptor 3 (TLR3) ligand mimicking viral double-stranded RNA (dsRNA), on human lung microvascular endothelial cell barrier function.
• To elucidate the role of TLR3 signaling in dsRNA-induced endothelial dysfunction.

Main Methods:

• Primary human lung microvascular endothelial cells were treated with Poly(I:C).
• Cytokine production (IL-6, IL-8, TNFα, IFNβ), NF-κB and IRF3 activation, and endothelial permeability were assessed.
• Expression and localization of claudin-5 and its mRNA levels were analyzed using quantitative PCR and immunofluorescence.
• Inhibitors of TLR3 (chloroquine) and NF-κB (Bay11-7082) were used to assess protective effects.

Main Results:

• Poly(I:C) induced production of inflammatory cytokines and activation of NF-κB and IRF3.
• Poly(I:C) increased endothelial monolayer permeability in a dose- and time-dependent manner.
• Poly(I:C) treatment led to decreased claudin-5 expression and mRNA levels, with cytoplasmic redistribution and lysosomal co-localization.
• Chloroquine and Bay11-7082 treatment protected against Poly(I:C)-induced claudin-5 loss.

Conclusions:

• dsRNA-activated TLR3 signaling disrupts lung microvascular endothelial barrier integrity.
• The disruption involves downregulation and mislocalization of the tight junction protein claudin-5.
• These findings offer insights into mechanisms of viral-induced vascular leakage and endothelial dysfunction.