Alterations of Excitation-Contraction Coupling in the Failing Human Heart

198 Pages·1998·6.02 MB·English

by  Donald M. Bers PhD (auth.)

Alterations of Excitation-Contraction Coupling in the Failing Human Heart
G. Hasenfuss . H. Just
Editors
Alterations
of Excitation
Contraction Coupling
in the
Failing Human Heart
Springer
Editors' addresses:
Prof. Dr. G. Hasenfuss . Prof. Dr. H. Just
Universitat Freiburg - Med. Klinik III
Abt. Kardiologie und Angiologie
Hugstetter StraBe 55
79106 Freiburg
Die Deutsche Bibliothek - CIP-Einheitsaufnahme
Alterations of excitation contraction coupling in the failing human
heart / G. Hasenfuss ; H. Just, ed. - Darmstadt: Steinkopff; New
York: Springer, 1998
ISBN-13: 978-3-642-48672-2 e-ISBN-13: 978-3-642-48670-8
DOl: 10.1007/978-3-642-48670-8
This work is subject to copyright. All rights are reserved, whether the whole or part of the material
is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,
broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplica
tion of this publication or parts thereof is permitted only under the provisions of the German
Copyright Law of September 9, 1965, in its current version, and permission for use must always
be obtained from SteinkopffVerlag. Violations are liable for prosecution under the German Copy
right Law.
© 1998 by Dr. Dietrich SteinkopffVerlag GmbH & Co. KG, Darmstadt
Softcover reprint of the hardcover 1st edition 1998
Medical Editor: Beate Rilhlemann - English Editor: James C. Willis - Production: Heinz J. Schafer
Cover Design: Erich Kirchner, Heidelberg
The use of general descriptive names, registered names, trademarks, etc. in this publication does
not imply, even in the absence of a specific statement, that such names are exempt from the relevant
protective laws and regulations and therefore free for general use.
Typesetting: Typoservice, Griesheim
Printed on acid-free paper
Preface and Introduction
Alteration of excitation-contraction coupling in the failing human heart was deemed
an interesting subject for a dialogue between basic scientists and clinical researchers
in continuation of previous Gargellen Conferences concerned with the function of
the normal and failing human myocardium.
In 1987 basic mechanisms and clinical implications of then new insights into cardiac
energetics was followed by a comprehensive review of inotropic stimulation and
myocardial energetics in 1989. Here, we undertook a re-evaluation of the principles
of inotropic stimulation and of its potential therapeutic value, based on new observa
tions from experiments with human myocardium. In 1992 the risk due to myocardial
phenotype change as a consequence of adaptation in heart failure was published.
Here, alterations of subcellular structures and functions as a consequence of chronic
heart failure, summarized as phenotype change, could be described as an essential
characteristic of the failing human myocardium. This topic was discussed in greater
depth in the volume "Cellular and Molecular Alterations in the Failing Human
Heart", considering both the sarcolemma and the phosphodiesterases, as well as
excitation-contraction coupling and contractile proteins, extracellular matrix, and
mitrochondrial function. Since it soon became apparent that myocardial ischemia
represents a special case of chronic alteration to the human myocardium and that an
intimate connection exists between excitation-contraction coupling and contractile
performance within the framework of myocardial phenotype change on the one hand
and the propensity to develop arrhythmias on the other hand, yet another conference
was conducted and published on the topic of "Myocardial Ischemia and Arrhythmia"
in 1994.
The rapid development of new observations and concepts has prompted us to
again deal with the alteration of excitation-contraction coupling in the failing human
heart and the proceedings are presented here.
This series of supplements to Basic Research in Cardiology has been the result of a
larger series of conferences dedicated to the dialogue between basic scientists and
clinicians and is named, according to the little village where the conferences take
place, the "Gargellen" conferences. These conferences have been concerned with a
rather wide spectrum of topics and is always characterized by an open dialogue
between experts from all parts of the world, organized by the Society for Coopera
tion in Medical Sciences. This Society and its numerous conferences is based on the
personal initiative of Prof. H. Just, the late Prof. Dr. med. Felix Burkart, Basel, Prof.
Dr. jur. Albin Eser, Freiburg, Prof. Dr. med. Detlef Ganten, Berlin, Prof. Dr. med.
H. R. Kirchheim, Heidelberg, Prof. Dr. med. Thomas Meinertz, Hamburg, Prof. Dr.
med. Wilhelm Rutishauser, Genf, Prof. Dr. med. Hasso Scholz, Hamburg, and Prof.
Dr. med. Stanley H. Taylor, Leeds. The broader, more general interest of the Society
in the interdisciplinary exchange of thought in various fields of medicine and natural
science is focused on specific topics with the collaboration of experts in the field to be
dealt with.
My Co-worker Prof. Dr. med. Gerd Hasenfuss, Freiburg, organized the confer
ence in 1995. It represents a field of research which has been subject of intense efforts
of our group in Freiburg. Both conference and extended publication of its proceedings
would not have been possible without the generous support of the Boehringer
VI Preface and Introduction
Ingelheim Pharmaceutical Company through its affiliate Dr. Carl Thomae GmbH,
BiberachiRiss, Germany, as well as the Bayer AG, Leverkusen, Germany. In particu
lar we thank Dr. Manfred Haehl from Boehringer Ingelheim Zentrale, Ingelheim,
Germany, for his continued interest and generous support.
It should not go unnoticed that the Dr. D. Steinkopff-Verlag, Darmstadt,
Germany, a subsidiary of the Springer-Verlag, Berlin - Heidelberg - New York, has
been a most helpful and understanding partner in publishing this series of books. In
particular we thank Ms. Sabine Ibkendanz for her continued interest and help.
Regarding the topic of this volume a brief introductory note is in order:
Recently, the possibilities to study human myocardium, both normal, as well as in
the failing state with and without hypertrophy, have led us to revise earlier concepts,
primarily derived from animal experimentation. It could be shown that in the human
myocardium a characteristic phenotyp prevails, which at a subcellular level may be
quite different from the animal model. As a matter of fact in the state of hypertrophy
and under the conditions of heart failure a very characteristic change of myocardial
phenotype can be observed. This results from altered gene expression under the spe
cific internal and external conditions of the failing human heart, which increases wall
tension under the conditions of altered contractile geometry and tissue composition,
as well as an activation of the sympatho-adrenal system, the renin-angiotensin
system, and the nitric oxide-endothelin system. As a consequence of myocardial
regeneration or growth myocyte hypertrophy, sometimes hypoplegia and fibroblast
growth with connective tissue development occurs. The altered gene expression
under these conditions leads primarily to an alteration of the structures of excitation
contraction coupling. To a lesser extent the contractile apparatus may show certain
alterations. In the center of functional consequences of myocardial phenotype
change is an alteration of calcium homeostasis. This may characteristically lead to
diastolic as well as to systolic dysfunction. In particular in the presence of maintained
Frank-Starling mechanism, the force-frequency relationship (Bowditch Treppe
phenomenon) is altered. While unter normal conditions with any increase in heart
rate the force of contraction increases, this effect is attenuated or reversed in hyper
trophy and heart failure. It could be shown that primarily the sarcoplasmic calcium
ATPase pumping of calcium into the sarcoplasmic reticulum is reduced, therefore,
rendering SR-calcium stores insufficient. This will lead to an attenuation ofthe force
of contraction with increasing heart rates, i.e., with shortening of diastole, the time
for pumping available to the sarcoplasmic calcium ATPase. Here the renin-angioten
sin system seems to play the decisive role together with altered tension conditions of
the working myocardium. If this were the only change, then diastolic dysfunction
would have to be expected due to increased diastolic calcium content in the cytosol.
This, however, is not the case. The explanation rests with a concomitant or sub
sequent up-regulation of the sarcolemmal sodium-calcium exchanger. A component
of the myocardial phenotype change which is probably brought about due to chronic
activation of the sympatho-adrenergic system.
All variations of systolic and/or diastolic dysfunction can be seen as a consequence
of the specific alteration of these two proteins and their function. As a consequence
of these alterations an increased sodium content in the cytosol can be anticipated.
This is indeed the case and can be held responsible for a wide spectrum of ventricular
arrhythmias and a propensity to develop life-threatening arrhythmias under these
conditions. In addition, specific alterations of the responsiveness of the myocyte to
sympathetic innervation is seen. This alteration may be considered protective to
myocyte integrity and function, especially from an energetic point of view. Further-
Preface and Introduction VII
more, the cardiac endothelin system seems to be activated. The consequences of this
phenomenon are, however, not yet defined.
The improved methodology and the availability of normal myocardium and of
myocardial specimen from end-stage failing human hearts, obtained at the time of
transplantation, has uncovered these alterations, specific to the human myocardium.
A further clarification of the subsequent subcellular changes of structure and func
tion can be considered a major advancement in the understanding of the state of
heart failure and will lead to improved therapeutic techniques and to new drugs. In
fact a paradigmatic change to the treatment of congestive heart failure can be fore
seen: While in the sixties the retention of sodium and water was considered a main
problem in heart failure, diuretics and digitalis glycosides were used. With better
understanding of myocardial mechanics the principal of unloading to the heart was
then developed in the seventies. Here the introduction of vasodilators into the treat
ment was effected. In the eighties and nineties, however, it became increasingly clear
that neurohumoral changes are very basic to the condition of heart failure and that
their interception or correction can be utilized to the greatest advantage to the failing
human heart. The introduction of renin-angiotensin system blockers, the ACE
inhibitors, and more recently the angiotensin II-receptor antagonists were developed
as well as the introduction of the beta-receptor blockade. Currently, we are expecting
a group of new drugs interfering with the endothelin system.
We consider the contribution of this volume to the understanding of the failing
human myocardium as another step forward, prompting yet new studies and new dis
cussions in order to further deepen and clarify our understanding of the complex
nature of the clinically significant syndrome of heart failure.
Freiburg, January 1998 Prof. Dr. H. Just
REFERENCES
1. Just H, Holubarsch Ch, Scholz H (1989) Inotropic stimulation and myocardial energetics. Steinkopff
Verlag Darmstadt, Springer-Verlag New York
2. Holtz J, Drexler H, Just H (1992) Cardiac adaptation in heart failure. SteinkopffVeriag Darmstadt,
Springer-Verlag New York
3. Hasenfuss G, Holubarsch Ch, Just H, Alpert NR (1992) Cellular and molecular alterations in the
failing human heart. SteinkopffVeriag Darmstadt, Springer-Verlag New York
4. Zehender M, Meinertz T, Just H (1994) Myocardial ischemia and arrhythmia. Steinkopff Verlag
Darmstadt, Springer-Verlag New York
Contents
Preface and Introduction v
Ca transport during contraction and relaxation in mammalian ventricular
muscle
Bers, D. M. ........................................ 1
Sites of regulatory interaction between calcium ATPases and phospholamban
MacLennan, D. H., T. Toyofuku, Y. Kimura ...... . .. . . . .... 17
The relative phospholamban and SERCA2 ratio: a critical determinant
of myocardial contractility
Koss, K. L., I. L. Grupp, E. G. Kranias .. . . . . . . . . . . . . . . . . . . 25
Phosphorylation and regulation of the CaH -pumping ATPase in cardiac
sarcoplasmic reticulum by calcium/calmodulin-dependent protein kinase
Narayanan, N., A. Xu .............. .. . . . . ...... . ... . 39
Site-specific phosphorylation of a phospholamban peptide by cyclic
nucleotide-and CaH /calmodulin-dependent protein kinases of cardiac
sarcoplasmic reticulum
Karczewski, P., M. Kuschel, L. G. Baltas, S. Bartel, E.-G. Krause 55
Sodium-calcium exchange: Recent advanves
Hryshko, L. v., K. D. Philipson ..... . .. . 67
Expression and function of the cardiac Na + /eaH exchanger in postnatal
development of the rat, in experimental-induced cardiac hypertrophy, and
in the failing human heart
Studer, R., H. Reinecke, R. Vetter, J. Holtz, H. Drexler ........... 77
Plasma membrane calcium pump: structure, function, and relationships
Carafoli, E. ............................... ... .. 85
Regulation ofmRNA-expression ofthe sarcolemmal calmodulin
dependent calcium pump in cardiac hypertrophy
Krain, B.,A. Hammes, L. Neyses . . ...... . ............ 89
Molecular mechanisms regulating the myofilament response to Ca2+:
Implications of mutations causal for familial hypertrophic cardiomyopathy
Palmiter, K. A., R. J. Solaro .............................. 105
X _______________________________________________________
~C~on=t~en=ts~
Ca2+ -dependent and Ca2+ -independent regulation of contractility in isolated
human myocardium
Pieske, B K. Schlotthauer, J Schattmann, F. Beyersdorf, J Martin,
0, 0 0
Ho Just, Go Hasenfuss 123
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Calcium handling proteins in the failing human heart
Hasenfuss, Go, Mo Meyer, W. Schillinger, Mo Preuss, Bo Pieske, Ho Just 141
Role of cAMP in modulating relaxation kinetics and the force-frequency
relation in mitral regurgitation heart failure
Mulieri, L. A., B. Jo Leavitt, R. K. Wright, No R. Alpert 153
0 0 0 0 0 0 0 0 0 0 0 0
Contributions of Ca2+ -influx via the L-type Ca2+ -current and Ca2+ -release
from the sarcoplasmic reticulum to [Ca2+]i-transients in human myocytes
Beuckelmann, Do Jo 169
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Molecular and cellular aspects ofre-entrant arrhythmias
Kleber, A. Go, V. Fast 179
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
SUbject Index 195
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Ca transport during contraction and relaxation in mammalian
ventricular muscle
D. M. Bers
Department of Physiology, Loyola University School of Medicine, Maywood, USA
Abstract
During relaxation of cardiac muscle four Ca transport systems can compete to
remove Ca from the myoplasm. These are 1) the SR Ca-ATPase, 2) the sarcolemmal
Na/Ca exchange, 3) the sarcolemmal Ca-ATPase, and 4) the mitochondrial Ca
uniporter. Isolated ventricular myocytes loaded with the intracellular fluorescent Ca
indicator indo-1 were used to study [Cali decline during relaxation. By selective
inhibition of the various Ca transporters above the dynamic interaction of these sys
tems during relaxation was evaluated. Quantitatively the SR Ca-ATPase and Na/Ca
exchange are clearly the most important (accounting for> 95 % of Ca removal).
However, the balance of Ca fluxes between these systems vary in a species dependent
manner. For example, the SR is much more strongly dominant in rat ventricular
myocytes, where ~ 92 % of Ca removal is via SR Ca-ATPase and only 7 % via Na/Ca
exchange during a twitch. In other species (rabbit, ferret, cat, and guinea-pig) the
balance is more in the range of 70-75% SR Ca-ATPase and 25-30% Na/Ca
exchange. Ferret ventricular myocytes also exhibit a unusually strong sarcolemmal
Ca-ATPase. During the normal steady state cardiac contraction-relaxation cycle the
same amount of Ca must leave the cell as enters over a cardiac cycle. This implies that
25-30 % of the Ca required to activate contraction must enter the cell at each cardiac
cycle. Experiments using voltage clamp to measure both Ca current and Na/Ca
exchange current demonstrate that this amount of Ca may be supplied by the L-type
Ca current.
The ability of the SR Ca-ATPase to reduce [Cali may also be modified both acutely
(e.g. by catecholamines) as well as chronically (e.g. during cardiac hypertrophy and
heart failure). Using tissue cultured neonatal rat ventricular myocytes, we studied
the effect of chronic arrest or stimulation with phorbol esters (to stimulate protein
kinase C). Verapamil-induced arrest increased the SR Ca-ATPase at the level of
mRNA, protein expression and functional ability to lower [Cali in intact cells. Con
versely, stimulation or protein kinase C reduced SR Ca-ATPase at all three of these
levels.
Key words Rat - rabbit - ferret - shortening - fluorescence - cardiac myocyte -
sarcoplasmic reticulum - cardiac hypertrophy
2 D.M.Bcrs
Introduction
For the activation of cardiac ventricular muscle contraction a large amount of Ca
must enter the cytosol, resulting in an increase in cytoplasmic [Cal ([Ca]i) and Ca
binding to troponin C (thereby activating the myofilaments). During the cardiac
action potential Ca influx occurs via L-type Ca channels and some amount of Ca
influx may also be expected via NaiCa exchange (1). In several species sufficient Ca
can enter the cell during the action potential to activate substantial contraction even
in the absence of a functional sarcoplasmic reticulum (SR, e.g. rabbit and guinea
pig), while in rat this does not seem to be the case (2, 3). Furthermore, under normal
conditions the quantity of Ca entry via Na/Ca exchange is probably small compared
to that which enters via Ca current (lca) , although Ca influx via NaiCa exchange can
be greatly increased when intracellular [Na] ([Nal) is elevated (e.g. 4,5).
Nevertheless, when the SR is functional in mammalian ventricular myocytes most
of the activating Ca is released from the SR during excitation-contraction (E-C)
coupling. While it is clear that L-type ICa can trigger SR Ca release via Ca-induced
Ca-release (6, 7). Ca entry via NaiCa exchange can also trigger SR Ca release under
certain conditions (8-10). The physiological importance of NaiCa exchange in trig
gering SR Ca release remains to be clarified.
For ventricular relaxation to occur [Ca]i must be lowered by transporting Ca out of
the cytosol, allowing Ca to dissociate from troponin C. There are four Ca transport
systems which compete for cytosolic Ca in cardiac myocytes: 1) the SR Ca-ATPase,
2) the sarcolemmal NaiCa exchange, 3) the sarcolemmal Ca-ATPase, and 4) the
mitochondrial Ca uniporter (11-13). Indeed, in the steady state, the amount of Ca
which enters the cytosol (from the extracellular space or the SR) must be restored
between beats to prevent net shifts in Ca content. This implies an intrinsic link
between Ca fluxes involved in activation of contraction and relaxation under steady
state conditions.
There is substantial evidence that during the course of cardiac hypertrophy and
heart failure, there are chronic changes in relaxation (slowing) and down-regulation
of the SR Ca-ATPase (for review see 14). Cultured neonatal rat ventricular myocytes
have also been a valuable tool to study alterations of gene expression accompanying
myocyte hypertrophy in a more controlled setting (e.g. 15).
In this paper, I will describe collaborative work with Drs. R. A. Bassani, J. W. M.
Bassani, L. M. D. Delbridge, M. Qi and A. M. Samarel in which we have: 1) quan
titatively characterized the relative contributions of the 4 Ca transport systems con
tributing to relaxation during the normal twitch contraction in various mammalian
species, 2) compared the amount of Ca entry via Ca current to the amount extruded
via NaiCa exchange, and 3) evaluated changes in SR Ca-ATPase expression and func
tion in conditions that alter hypertrophic state in cultured neonatal rat ventricular
myocytes.
Methods
Individual freshly dissociated ventricular myocytes were studied in a chamber on the
stage of an inverted microscope equipped for epifluorescence measurement of [Cali