Thursday, April 25, 2024
4/25/2024
Project Summary/Abstract: Ventricular Arrhythmia is a leading cause of death following Myocardial Infarction (MI), with high incidence among aging populations. Recent data from our laboratory show that the osmotically activated Transient Receptor Potential Vanilloid 4 (TRPV4) cation channel increases expression in ventricular cardiomyocytes with advancing age. Ischemia-Reperfusion (I/R) is associated with both Ca2+ overload and hypoosmotic stress on the myocardium. Ca2+ overload disturbs excitation-contraction coupling and promotes arrhythmia by increasing diastolic Ca2+ release and membrane depolarization. Thus, this proposal tests the hypothesis that hypoosmotic stress during I/R activates TRPV4-mediated Ca2+ influx, which contributes to Ca2+ overload and arrhythmogenesis. Specific Aim 1 is to investigate the role of TRPV4 in isolated cardiomyocyte Ca2+ influx, membrane potential, and Ca2+ homeostasis following hypoosmotic stress. Patch clamp recording of membrane potential and membrane Ca2+ currents will be measured in cardiomyocytes from Aged mice (24-26 month, with high TRPV4 expression), Young mice (3-6 month, with low TRPV4 expression), and Young mice with inducible transgenic cardiac-specific TRPV4 overexpression (Young TRPV4 Overexpressors). Isolated cardiomyocytes from the same groups, but with an additional GCaMP6f Ca2+ sensor transgenewill also be subjected to hypoosmotic stress and intracellular Ca2+ homeostasis will be assessed using laser scanning confocal microscopy in the presence and absence of TRPV4 antagonism (HC067047, 1 M). Specific Aim 2 is to investigate the arrhythmogenic role of TRPV4 in Langendorff-perfused isolated hearts subjected to I/R. Reversible ligation of the left anterior descending artery (LAD) will induce I/R in Aged, Young, and Young TRPV4 Overexpressor hearts. Sharp microelectrode recordings of cardiomyocytes from LAD-supplied myocardium will be taken prior to, during, and following I/R in the presence and absence of TRPV4 antagonism. The same protocol will be conducted on Langendorff perfused Young and Young TRPV4 Overexpressor isolated hearts (with the GCaMP6f Ca2+ sensor) while imaging of the left-ventricular free wall by laser scanning confocal microscopy. This in situ imaging will allow for measurement of arrhythmogenic diastolic Ca2+ release events in the intact heart during I/R. This project investigates a novel therapeutic target for preventing Ca2+-dependent ventricular arrhythmias following myocardial infarction in aging populations. Additionally, the proposal provides valuable training to the applicant in conducting cardiovascular research.
HHS’ Tracking Accountability in Government Grants System (TAGGS) website provides access to detailed descriptions of grants, loans, aggregated direct payments and other types of financial assistance awarded by the HHS Operating Divisions (OPDIVs) and the Office of the Secretary Staff Divisions (STAFFDIVs).
