Project Summary Inflammatory immune responses dictate cardiac healing post-myocardial infarction (MI) and are temporally regulated to initiate wound-healing and scar formation. Recent studies have shown that, in addition to immediately after myocardial infarction (MI), circulating, splenic and cardiac inflammatory cells (monocytes, macrophages, and T-lymphocytes) are augmented even at 8-weeks post-MI (chronic HF), and promote pathological left ventricular (LV) remodeling. Moreover, we and others have shown that depletion of specific cell types, including monocytes/macrophages or T-cells during chronic HF blunts LV remodeling and prevents progressive decline in cardiac function, suggesting a critical role of immune cells in this disease. These findings underscore the necessity for identifying specific molecular mechanisms that can be targeted to restrain pathological immune activation for therapeutic immune-modulation. Recent studies have shown that CD4+ T-cells are obligatory for efficient healing, neovascularization, and to check excessive fibrosis during MI. However, global knockout mouse models (such as CD4-/-) fail to consider spatio-temporal alterations that we see during progression from acute-MI to chronic HF. Indeed, our previous studies showed that CD4+ T-cells undergo a phenotypic shift specifically during chronic HF, promote LV remodeling in an antigen-dependent manner, and their depletion from 4 to 8 weeks post-MI blunts progressive cardiac dysfunction. Nonetheless, the molecular signatures that mediate this transition from being protective during MI to pathological during chronic HF are not known. Using RNA sequencing on cardiac CD4+ T-cells flow-sorted from the failing hearts of male mice, we showed that, as opposed to MI, T-cells activated during HF possess upregulated estrogen receptor (ER) α signaling. Since ERα effects are opposed by ERβ activation, we identified a novel ERβ agonistic drug (OSU-ERb-012). Our preliminary data show that OSU-ERb-012 is highly efficacious at inhibiting anti-CD3/CD28 (T-cell receptor) mediated T-cell proliferation and expression of pro- inflammatory cytokines, ex-vivo and in-vivo. Moreover, at 10 mg/kg dose OSU-ERb-012 significantly blunted LV remodeling and HF progression when administered from 4 to 8 weeks post-MI suggesting its therapeutic efficacy. Thus, we hypothesize that OSU-ERb-012 selectively inhibits antigenically activated pathological CD4+ T-cells at clinically translatable doses, ameliorate LV remodeling and progressive cardiac dysfunction during chronic HF, and that ERβ agonists could be used as selective immuno-modulatory drugs. We will test this hypothesis by i) delineating dose-dependent effects of OSU-ERb-012 in ameliorating LV remodeling, ii) testing whether the protective effects of OSU-ERb-012 are mediated through T-cell specific ERβ agonism, and iii) identify effects of OSU-ERb-012 on cardiomyocyte function and cardiac physiology.

Project Narrative Despite the knowledge that CD4+ T-cells mediate wound healing during myocardial infarction (MI) but exacerbate left-ventricular remodeling and cardiac dysfunction during heart failure (HF), the specific mechanisms that mediate this phenotypic shift in T-cell biology are not known. Our published results suggest an important role of estrogen receptor (ER) α signaling in mediating this phenotypic shift, and autoimmune activation of T-cells during chronic HF. In this proposal, PI intends to develop a novel ERβ agonist (OSU-ERb- 012), to functional oppose ERα signaling, by studying i) therapeutic efficacy of OSU-ERb-012 at clinically translatable low doses and ii) dissect, in detail, its effects on the cardiomyocytes and CD4+ T-cells using relevant cell-specific ERβ-/- HF mice.