Abstract P1170: Changes In Endothelin Signaling In A Long-term Rat Coronary Culture Resembles Chronic Coronary Syndrome

Abstract

Background: Coronary artery disease generates changes in the structure and function of the blood vessels. 48hrs organ culture (mimicking the acute loss of blood flow) of coronary arteries induces the upregulation of contractile endothelin type B (ETB) receptors, resembling the pattern seen in ischemic heart disease. MEK inhibitors (U0126 and Trametinib), can acutely inhibit the upregulation of these receptors, illustrating the importance of this pathway. The 48hrs organ culture model has been proven successful for translation in acute ischemic disease, but arterial changes have not been studied in a long-term chronic model which could be important for chronic coronary syndrome. Purpose: 1) Investigate the changes of ETB receptors after incubation in a long-term optimized medium for organ culture, mimicking the reduction of blood flow in chronic coronary syndrome and 2) determine whether Trametinib, would have treatment effect on the upregulation of ETB receptors in both long term and short term culture. Methods: Rat coronary arteries were incubated in organ culture for 48hrs in DMEM ± trametinib (“acute”) or in a long-term optimized medium for organ culture for 14 days (“chronic”). After the incubation, arteries were mounted stainless steel wires (40 μm) on a Mulvany-Halpern arterial wire myograph and cumulative concentration response curves were made to measure arterial contractility to the ETB receptor specific agonist Sarafotoxin (S6c). Trametinib was added at time 0 (for both the acute and chronic organ culture) or 7 days delayed. Results: For the “acute” culture, we observed a high contractile effect in response to S6c (Emax=136.5±18%). The presence of Trametinib greatly reduced this contractile effect (Emax=10±1.9%) and arteries were comparable to fresh (Emax=0.8±0.7%). The rat coronary arteries in the “chronic” culture maintained their ability to contract in response to potassium, and S6c had a strong contractile effect (Emax=74.64±17%). Interestingly, neither trametinib addition at time 0 nor at day 7 could inhibit the functional upregulation of ETB in the chronic model. Conclusion: Chronic coronary syndrome may require new inhibitors of ETB receptor upregulation. This could be investigated with our new long-term rat coronary artery model.