# Molecular Mechanism of Lung Barrier Dysfunction

> **NIH NIH R01** · UNIVERSITY OF ALABAMA AT BIRMINGHAM · 2020 · $371,250

## Abstract

Project Summary/Abstract
Increased paracellular permeability is a hallmark of acute lung injury and the mechanisms underlying failure of
both epithelial and endothelial barriers need to be further investigated. High morbidity and mortality in patients
with acute lung injury is characterized by flooding of the airspaces with protein-rich edema. We previously
reported that Rho GTPase activation plays a critical role in permeability derangements and actin stress fiber
formation in lung microvascular endothelial and alveolar epithelial cells. Additionally, inhibition of Rho GTPase
preserved the integrity of lung endothelial and alveolar epithelial barrier function and promoted alveolar fluid
clearance in a murine model of Pseudomonas aeruginosa (P. aeruginosa) pneumonia. However, the molecular
downstream mechanism(s) by which Rho GTPases alter cytoskeletal dynamics of lung microvascular
endothelial and alveolar epithelial cells, and causes paracellular permeability derangements, is not fully
understood. Active small Rho GTPase unlocks Neuronal Wiskott–Aldrich syndrome protein (NWASP) from an
autoinhibited conformation for activation. NWASP transmits upstream signals to the cellular machinery directly
involved in modulation of cytoskeletal dynamics. Our preliminary data and published work indicate that (a)
NWASP downregulation inhibits actin stress fiber formation and reduces paracellular permeability in lung
microvascular endothelial and alveolar epithelial cells after exposure to P. aeruginosa or TGF-β1; (b)
Furthermore, inhibition of N-WASP protects mice against lung injury and improves survival in a murine model
of P. aeruginosa pneumonia. We hypothesize that activation of the GBD domain of NWASP functions as a
critical switch (the “GBD-switch”) in the development of lung edema associated with bacteria-induced lung
injury, through recruiting downstream signaling molecules, promoting cytoskeletal dynamics, and disrupting
barrier function of both lung endothelium and alveolar epithelium. To test this hypothesis, we propose three
specific aims: (Aim 1) to define the downstream partner(s), and critical domain(s), of NWASP that are essential
to promote lung microvascular endothelial and alveolar epithelial permeability induced by P. aeruginosa; (Aim
2) to determine the common, and differential, molecular mechanisms, by which the activated GBD
switch alters cytoskeletal dynamics, disrupts barrier function, and causes paracellular permeability in lung
microvascular endothelial cells and alveolar epithelial cells in response to P. aeruginosa; (Aim 3) to define the
in vivo, and cell-type-specific, role of NWASP in a murine model of acute lung injury caused by P. aeruginosa
pneumonia. The findings from these studies will help to delineate the molecular mechanisms regulating
cytoskeletal dynamics, barrier function, and permeability in P. aeruginosa-induced acute lung injury.

## Key facts

- **NIH application ID:** 9937796
- **Project number:** 5R01HL143017-03
- **Recipient organization:** UNIVERSITY OF ALABAMA AT BIRMINGHAM
- **Principal Investigator:** QIANG DING
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $371,250
- **Award type:** 5
- **Project period:** 2018-07-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9937796

## Citation

> US National Institutes of Health, RePORTER application 9937796, Molecular Mechanism of Lung Barrier Dysfunction (5R01HL143017-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9937796. Licensed CC0.

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