This project will test the overall hypothesis that angiopoietins influence the severity and duration of inflammatory responses in the airways and lung, by regulating the remodeling of blood vessels and lymphatics. This property makes angiopoietins important therapeutic targets. The goal is to determine in preclinical experiments the actions of angiopoietins that can be exploited in the treatment of human inflammatory lung disease, through the use of angiopoietin agonists and inhibitors currently under development. Angiopoietins control the growth and stability of blood vessels and lymphatics: angiopoietin-1 (Ang1) activates Tie2 receptors on endothelial cells, and angiopoietin-2 (Ang2) inhibits or activates Tie2 signaling, depending on context and temporal-spatial concentrations. The project will explore evidence that angiopoietins have potent actions on two interrelated processes: (1) blood vessel remodeling, which influences the amount of plasma leakage and leukocyte influx, and (2) lymphatic remodeling, which influences edema fluid clearance and immune cell traffic to lymph nodes. The approach will use three mouse models of lung inflammation, due to mycoplasmal infection, fungal allergen challenge, or pulmonary fibrosis, with complementary gain or loss of function reagents and transgenic mice, as tools to interrogate the actions of angiopoietins in clinically relevant inflammatory conditions.
Specific Aim #1 will assess the benefit of manipulating angiopoietin actions in two phases of blood vessel remodeling in inflammation. In Phase I, suppression of Tie2 signaling by Ang2 promotes loosening of pericyte-endothelial cell attachment, vessel destabilization, leakiness, and expression of leukocyte-adhesion proteins. In Phase II, pericytes proliferate and reinforce the abnormal vascular phenotype that sustains leakage and leukocyte traffic.
Aim #1 will test the hypothesis that Ang2 inhibition or Tie2 activation by Ang1 can reduce lung inflammation by reversing vascular remodeling that leads to and sustains leakage and leukocyte influx.
Specific Aim #2 will explore strategies for correcting lymphatic defects at sites of inflammation, where remodeling of lymphatics impairs fluid clearance and immune cell traffic.
Aim #2 will test the hypothesis that Ang2 inhibition or Tie2 activation by Ang1 promotes lymphatic maturation and formation of specialized button-like endothelial junctions necessary for efficient fluid drainage.
Aim #2 will also investigate the benefit of manipulating angiopoietin actions in pulmonary lymphangiectasia and chylothorax, where dilated fluid-filled channels replace normal lung lymphatics, by studying a novel transgenic mouse with conditional VEGF-C overexpression in the respiratory epithelium. Together, the experiments will explore the therapeutic potential of manipulating angiopoietin actions to reduce edema and inflammation in the airways and lung by regulating the remodeling of blood vessels and lymphatics.
Angiogenesis and remodeling of blood vessels contribute to the severity of inflammatory conditions of the airways and lung by being the source of edema fluid and inflammatory cells that lead to tissue changes and persistence of the inflammatory response. Lymphatic vessels also participate, by serving as a route for edema fluid and immune cells to leave inflamed tissues. This project has the goal of identifying novel mechanisms and treatment strategies for reducing the severity and duration of chronic inflammation in the airways and lung by manipulating the actions of the angiopoietin family of growth factors on blood vessels and lymphatic vessels.
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