Loss of endothelial cell (EC) barrier function is important in the development of indirect acute lung injury (ALI). We have shown, in a novel murine model of hemorrhage (shock) with a subsequent septic challenge caused by cecal ligation and performation (CLP), that neutrophil (PMN) interactions with resident pulmonary cells are central to this pathology. In ALI, unresolved inflammation elicits a pathological process with loss of EC barrier integrity and impaired lung function. EC growth factors, Angiopoietin (Ang)-i and 2, under physiological conditions, maintain vascular homeostasis through competitive interactions wdth the t3T:osine kinase receptor, Tie2, expressed on ECs. Ang-1/Tie2 binding has been shown to stabilize vessels and stimulate down stream pro-survival/anti-inflammatory signaling, in contrast, Ang-2, released from storage granules of activated ECs, destabilizes vessels. Recent findings report that plasma Ang-2 levels are significantly elevated in patients that develop ALI. We find similar elevation in the lungs and plasma in our shock/CLP model, and we have found that depletion of PMNs prior to shock abrogates Ang-2 elevation. We propose the following central hypothesis: Ang-2 causes loss of pulmonary EC barrier function in ALI due to shock/CLP, initiated by EC interaction with shock-primed PMNs. We propose the following specific aims:
Aim 1 will determine the kinetics of change in Ang-1:Ang-2 and Ang-2 expression and re-synthesis as well as its relationship to changes in indices of inflammation. We will use Ang-2 (si)RNA to suppress lung tissue expression, Ang-2 protein specific inhibition, and Ang-1 competitive inhibition of Ang-2/Tie2 binding to assess the contribution of Ang-2 release in shock priming for the development of ALI.
Aim 2 will determine mechanisms by which Ang-2 changes pulmonary EC phenotype/activation in response to plasma from mice with ALI/ARDS.
Aim 3 will determine mechanisms by which Ang-2 mediates changes in EC phenotype /activation in cultured mouse ECs following co-culture with shock-primed PMNs. The studies in this proposal will provide novel insights into the mechanisms of PMN associated, Ang-2 mediated ALI and will elucidate pathways that hold potential for therapeutic intervention.

Public Health Relevance

Acute lung injury (ALI) is a progressive syndrome with significant mortality in trauma patients. Identifying the cellular interactions and protein mediators involved in the development of indirect ALI is a critical step in the discovery of effective therapies. This project will identity mechanisms by which endothelial growth factor, Angiopoietin-2, and shock primed neutrophils contribute to lung edema in the development of ALI.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Exploratory Grants (P20)
Project #
1P20GM103652-01A1
Application #
8465678
Study Section
Special Emphasis Panel (ZGM1-TWD-B (CB))
Project Start
Project End
Budget Start
2013-09-20
Budget End
2014-05-31
Support Year
1
Fiscal Year
2013
Total Cost
$250,305
Indirect Cost
Name
Ocean State Research Institute, Inc.
Department
Type
DUNS #
848476271
City
Providence
State
RI
Country
United States
Zip Code
02908
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