Immunomodulation of Galectin-3 to Prevent Radiation-Induced Myocardial Fibrogenesis This application addresses the scientific goals of FOA-PA-19-112. More than half of life-threatening thoracic cancers are treated with repeated doses of ionizing radiation. Unfortunately, the pro-inflammatory and pro-fibrotic properties of ionizing radiation increase the cumulative risk of cardiac damage. Galectin-3 (gal3) is a unique carbohydrate and peptide-binding molecule widely implicated in myocardial inflammation and fibrosis. Increased myocardial gal3 expression is reported in models of cardiac irradiation, but it is unclear whether gal3 directly contributes to radiation-induced cardiac fibrosis.
We aim to determine the function of gal3 in mediating the inflammatory and fibrotic effects of radiation. We propose to test the hypothesis that gal3 mediates radiation-induced myocardial inflammation and fibrosis, and that genetic or immunological modulation of gal3 expression or function neutralizes these effects and is thus cardioprotective. The unique features of this hypothesis are the concept that radiation exposure activates cardiomyocytes and macrophages to release gal3, which then binds to high-affinity mast cell surface receptors inducing the release of inflammatory and fibrotic mediators. Moreover, we have designed a new gal3 immunomodulatory vaccine that neutralizes gal3 after single-dose intramuscular administration in a mouse model. To test the general hypothesis, we propose three specific aims.
In Aim I, we will determine the effects of gal3 modulation on inflammation, fibrosis, and cardiac function after repeated exposure to thoracic radiation. We will use genetically engineered cardiomyocyte-selective gal3 gain-of-function mice to study gal3-myocyte-fibroblast pathways, and bone marrow transplanted mice to study gal3-macrophage-fibroblast pathways.
In Aim II, we will determine the contribution of gal3 released by cardiomyocytes and macrophages to activate mast cells after in vitro irradiation, as well as the downstream effects on cardiac fibroblast growth and collagen synthesis using a state-of-the art microchamber system.
In Aim III, we will compare the preventive and therapeutic effects of a new gal3-immunomodulatory vaccine on radiation- induced cardiac fibrogenesis and dysfunction. The feasibility of this project is confirmed by the a) availability of gal3 knockout mice for gal3 loss-of-function studies, b) cardio-selective and global gal3 overexpression mice for cardiac and systemic gain-of-function studies, and c) Myeloablated mice engrafted with gal3-null or gal3- overexpressing progenitor cells for macrophage-targeted gal3 loss-and gain-of-function studies. A safe and highly potent gal3 inhibitor vaccine has been designed in our laboratory to study the therapeutic potential of gal3 inhibition. Expected project outcomes include the evidence that gal3 mediates cardiac fibrosis and dysfunction after cumulative radiation exposure, and pre-clinical data on the protective effects of early gal3 immunomodulation. These studies have important therapeutic implications for timely and targeted interventions in cancer patients susceptible to radiotherapy-induced myocardial fibrogenesis and loss of cardiac function.
In this interdisciplinary project, we will use cell- and tissue-specific galectin-3 loss- and gain-of-function mouse models to determine the causative effects and the mechanisms mediated by galectin-3 in cardiac fibrosis and myocardial dysfunction after repetitive exposure to ionizing radiation. In addition, we will test the efficacy of a new galectin-3 inhibitor vaccine in preventing radiation-induced cardiotoxicity.
