TY - JOUR
T1 - Calcium-independent negative inotropy by β-myosin heavy chain gene transfer in cardiac myocytes
AU - Herron, Todd J.
AU - Vandenboom, Rene
AU - Fomicheva, Ekaterina
AU - Mundada, Lakshmi
AU - Edwards, Terri
AU - Metzger, Joseph M.
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2007/4
Y1 - 2007/4
N2 - Increased relative expression of the slow molecular motor of the heart (β-myosin heavy chain [MyHC]) is well known to occur in many rodent models of cardiovascular disease and in human heart failure. The direct effect of increased relative β-MyHC expression on intact cardiac myocyte contractility, however, is unclear. To determine the direct effects of increased relative β-MyHC expression on cardiac contractility, we used acute genetic engineering with a recombinant adenoviral vector (AdMYH7) to genetically titrate β-MyHC protein expression in isolated rodent ventricular cardiac myocytes that predominantly expressed α-MyHC (fast molecular motor). AdMYH7-directed β-MyHC protein expression and sarcomeric incorporation was observed as soon as 1 day after gene transfer. Effects of β-MyHC expression on myocyte contractility were determined in electrically paced single myocytes (0.2 Hz, 37°C) by measuring sarcomere shortening and intracellular calcium cycling. Gene transfer-based replacement of α-MyHC with β-MyHC attenuated contractility in a dose-dependent manner, whereas calcium transients were unaffected. For example, when β-MyHC expression accounted for ≈18% of the total sarcomeric myosin, the amplitude of sarcomere-length shortening (nanometers, nm) was depressed by 42% (151.0±10.7 [control] versus 87.0±5.4 nm [AdMYH7 transduced]); and genetic titration of β-MyHC, leading to 38% β-MyHC content, attenuated shortening by 57% (138.9±13.0 versus 59.7±7.1 nm). Maximal isometric cross-bridge cycling rate was also slower in AdMYH7-transduced myocytes. Results indicate that small increases of β-MyHC expression (18%) have Ca transient-independent physiologically relevant effects to decrease intact cardiac myocyte function. We conclude that β-MyHC is a negative inotrope among the cardiac myofilament proteins.
AB - Increased relative expression of the slow molecular motor of the heart (β-myosin heavy chain [MyHC]) is well known to occur in many rodent models of cardiovascular disease and in human heart failure. The direct effect of increased relative β-MyHC expression on intact cardiac myocyte contractility, however, is unclear. To determine the direct effects of increased relative β-MyHC expression on cardiac contractility, we used acute genetic engineering with a recombinant adenoviral vector (AdMYH7) to genetically titrate β-MyHC protein expression in isolated rodent ventricular cardiac myocytes that predominantly expressed α-MyHC (fast molecular motor). AdMYH7-directed β-MyHC protein expression and sarcomeric incorporation was observed as soon as 1 day after gene transfer. Effects of β-MyHC expression on myocyte contractility were determined in electrically paced single myocytes (0.2 Hz, 37°C) by measuring sarcomere shortening and intracellular calcium cycling. Gene transfer-based replacement of α-MyHC with β-MyHC attenuated contractility in a dose-dependent manner, whereas calcium transients were unaffected. For example, when β-MyHC expression accounted for ≈18% of the total sarcomeric myosin, the amplitude of sarcomere-length shortening (nanometers, nm) was depressed by 42% (151.0±10.7 [control] versus 87.0±5.4 nm [AdMYH7 transduced]); and genetic titration of β-MyHC, leading to 38% β-MyHC content, attenuated shortening by 57% (138.9±13.0 versus 59.7±7.1 nm). Maximal isometric cross-bridge cycling rate was also slower in AdMYH7-transduced myocytes. Results indicate that small increases of β-MyHC expression (18%) have Ca transient-independent physiologically relevant effects to decrease intact cardiac myocyte function. We conclude that β-MyHC is a negative inotrope among the cardiac myofilament proteins.
KW - Adenovirus
KW - Contractility
KW - Gene transfer
KW - Intracellular calcium
KW - Muscle contraction
KW - Myosin
KW - Ventricular myocytes
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U2 - 10.1161/01.RES.0000264102.00706.4e
DO - 10.1161/01.RES.0000264102.00706.4e
M3 - Article
C2 - 17363698
AN - SCOPUS:34247585621
SN - 0009-7330
VL - 100
SP - 1182
EP - 1190
JO - Circulation research
JF - Circulation research
IS - 8
ER -