Abstract P319: Eliminating Cardiotoxicity In Alpha1-adrenergic Receptor Antagonists

• Published in: Hypertension (Dallas, Tex. 1979) Tex. 1979), 2023-09, Vol.80 (Suppl_1)
• Main Authors: Healy, Chastity L, Puccini, Sara J, Aragon, Ingrid R, Dodda, Vasudeva, Muthyala, Ramaiah, Sham, Yuk, O'Connell, Timothy D
• Format: Article
• Language: English
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/hyp.80.suppl_1.P319

Abstract only Introduction: Alpha-1 adrenergic receptor (α1-AR) antagonists (α1-blockers) are efficacious antihypertensives, but ALLHAT found that doxazosin (Dzn) doubled the risk of heart failure (HF). We previously demonstrated that α1-ARs, specifically the α1A-AR, protect the heart, explaining the worse outcomes with Dzn in ALLHAT. Interestingly, α1-ARs localize to and signal at the nucleus in cardiac myocytes (CM), whereas α1-ARs localize to the sarcolemma in smooth muscle (SM). Hypothesis: We hypothesize that a membrane impermeant α1-blocker would inhibit α1-ARs in SM, reducing blood pressure, but preserve protective α1-signaling in CMs, preventing HF. Methods: We developed an α1A-AR homology model to define the structural basis of α1-blocker binding and modified existing α1-blocker structure to reduce cardiotoxicity. Using this model, we designed 30 compounds, synthesized 9 in gram quantities, and tested 2 compounds. Results and Conclusions: Binding assays identified 2 novel high affinity α1-ligands; α1705 (IC50 = 5.2 [CI:3.5,7.6] nM, n=3) and α1707 (5.8 [CI:4.2,8.1] nM, n=3) (Dzn: 7.7 [CI:6.3,9.2] nM, n=6). Uptake assays in cultured CM indicated uptake of Prazosin (10 μM Prz: 230 nM in CMs detected by mass spectrometry), whereas α1705 and α1707 were not detected. In HEK cells expressing α1A-AR at the cell surface, Prz, α1705, and α1707 (all 2 μM) inhibited Ca2+ transients (90%, 76%, 88%) induced by the α1A agonist A61603 (20 μM). In CM, A61603 increased ERK phosphorylation (1.55±0.04 fold, n=7, P