AIMS: Cardiovascular disease remains the greatest cause of mortality in Americans over 65. The stretch-activated transient receptor potential vanilloid-4 (TRPV4) ion channel is expressed in cardiomyocytes of the aged heart. This investigation tests the hypothesis that TRPV4 alters Ca2+ handling and cardiac function in response to increased ventricular preload and cardiomyocyte stretch. METHODS AND RESULTS: Left ventricular maximal pressure (PMax) was monitored in isolated working hearts of Aged (24-27 months) mice following preload elevation from 5 to 20mmHg, with and without TRPV4 antagonist HC067047 (HC, 1 µmol/L). In preload responsive hearts, PMax prior to and immediately following preload elevation (i.e. Frank-Starling response) was similar between Aged and Aged+HC. Within 1 min following preload elevation, Aged hearts demonstrated secondary PMax augmentation (Aged>Aged+HC) suggesting a role for stretch-activated TRPV4 in cardiac hypercontractility. However, after 20 min at 20 mmHg Aged exhibited depressed PMax (Aged<Aged+HC) suggestive of TRPV4-dependent contractile dysfunction with sustained stretch. To examine stretch-induced Ca2+ homeostasis at the single-cell level, isolated cardiomyocytes were stretched 10-15% of slack length while measuring intracellular Ca2+ with fura-2. Uniaxial longitudinal stretch increased intracellular Ca2+ levels and triggered Ca2+ overload and terminal cellular contracture in Aged, but not Aged+HC. Preload elevation in hearts of young/middle-age (3-12 months) mice produced an initial PMax increase (Frank-Starling response) without secondary PMax augmentation, and cardiomyocyte stretch did not affect intracellular Ca2+ levels. Hearts of transgenic mice with cardiac-specific TRPV4 expression exhibited PMax similar to 3- to 12-month control mice prior to and immediately following preload elevation but displayed secondary PMax augmentation. Cardiomyocytes of mice with transgenic TRPV4 expression were highly sensitive to mechanical stimulation and exhibited elevated Ca2+ levels, Ca2+ overload, and terminal contracture upon cellular attachment and stretch. CONCLUSION: TRPV4 contributes to a stretch-induced increase in cardiomyocyte Ca2+ and cardiac hypercontractility, yet sustained stretch leads to cardiomyocyte Ca2+ overload and contractile dysfunction in the aged heart. Published on behalf of the European Society of Cardiology. All rights reserved.
AIMS: Cardiovascular disease remains the greatest cause of mortality in Americans over 65. The stretch-activated transient receptor potential vanilloid-4 (TRPV4) ion channel is expressed in cardiomyocytes of the aged heart. This investigation tests the hypothesis that TRPV4 alters Ca2+ handling and cardiac function in response to increased ventricular preload and cardiomyocyte stretch. METHODS AND RESULTS: Left ventricular maximal pressure (PMax) was monitored in isolated working hearts of Aged (24-27 months) mice following preload elevation from 5 to 20mmHg, with and without TRPV4 antagonist HC067047 (HC, 1 µmol/L). In preload responsive hearts, PMax prior to and immediately following preload elevation (i.e. Frank-Starling response) was similar between Aged and Aged+HC. Within 1 min following preload elevation, Aged hearts demonstrated secondary PMax augmentation (Aged>Aged+HC) suggesting a role for stretch-activated TRPV4 in cardiac hypercontractility. However, after 20 min at 20 mmHg Aged exhibited depressed PMax (Aged<Aged+HC) suggestive of TRPV4-dependent contractile dysfunction with sustained stretch. To examine stretch-induced Ca2+ homeostasis at the single-cell level, isolated cardiomyocytes were stretched 10-15% of slack length while measuring intracellular Ca2+ with fura-2. Uniaxial longitudinal stretch increased intracellular Ca2+ levels and triggered Ca2+ overload and terminal cellular contracture in Aged, but not Aged+HC. Preload elevation in hearts of young/middle-age (3-12 months) mice produced an initial PMax increase (Frank-Starling response) without secondary PMax augmentation, and cardiomyocyte stretch did not affect intracellular Ca2+ levels. Hearts of transgenic mice with cardiac-specific TRPV4 expression exhibited PMax similar to 3- to 12-month control mice prior to and immediately following preload elevation but displayed secondary PMax augmentation. Cardiomyocytes of mice with transgenic TRPV4 expression were highly sensitive to mechanical stimulation and exhibited elevated Ca2+ levels, Ca2+ overload, and terminal contracture upon cellular attachment and stretch. CONCLUSION:TRPV4 contributes to a stretch-induced increase in cardiomyocyte Ca2+ and cardiac hypercontractility, yet sustained stretch leads to cardiomyocyte Ca2+ overload and contractile dysfunction in the aged heart. Published on behalf of the European Society of Cardiology. All rights reserved.
Authors: Nicholas E Hoffman; Barbara A Miller; JuFang Wang; John W Elrod; Sudasan Rajan; Erhe Gao; Jianliang Song; Xue-Qian Zhang; Iwona Hirschler-Laszkiewicz; Santhanam Shanmughapriya; Walter J Koch; Arthur M Feldman; Muniswamy Madesh; Joseph Y Cheung Journal: Am J Physiol Heart Circ Physiol Date: 2015-01-09 Impact factor: 4.733
Authors: B S Cain; D R Meldrum; K S Joo; J F Wang; X Meng; J C Cleveland; A Banerjee; A H Harken Journal: J Am Coll Cardiol Date: 1998-08 Impact factor: 24.094
Authors: Hiroyuki Nakayama; Xiongwen Chen; Christopher P Baines; Raisa Klevitsky; Xiaoying Zhang; Hongyu Zhang; Naser Jaleel; Balvin H L Chua; Timothy E Hewett; Jeffrey Robbins; Steven R Houser; Jeffery D Molkentin Journal: J Clin Invest Date: 2007-09 Impact factor: 14.808
Authors: John L Jones; Deborah Peana; Adam B Veteto; Michelle D Lambert; Zahra Nourian; Natalia G Karasseva; Michael A Hill; Brian R Lindman; Christopher P Baines; Maike Krenz; Timothy L Domeier Journal: Cardiovasc Res Date: 2019-01-01 Impact factor: 10.787
Authors: Fuzhong Qin; Deborah A Siwik; Steve Lancel; Jingmei Zhang; Gabriela M Kuster; Ivan Luptak; Lei Wang; Xiaoyong Tong; Y James Kang; Richard A Cohen; Wilson S Colucci Journal: J Am Heart Assoc Date: 2013-08-20 Impact factor: 5.501