Table Of ContentPhagocytosis of Dying Cells: From Molecular
Mechanisms to Human Diseases
Phagocytosis of Dying Cells:
From Molecular Mechanisms
to Human Diseases
Dmitri V. Krysko • Peter Vandenabeele
Editors
Department for Molecular Biomedical Research,
VIB, Ghent, Belgium
Department of Molecular Biology,
Ghent University, Ghent, Belgium
1 J
Editors
Dr. Dmitri V. Krysko, M.D., Ph.D. Prof. Dr. Peter Vandenabeele, Ph.D.
VIB Department for Molecular Biomedical VIB Department for Molecular Biomedical
Research, VIB and Ghent University, Research, VIB and Ghent University,
Technologiepark 927 Technologiepark 927
9052 Ghent, Belgium 9052 Ghent, Belgium
[email protected] [email protected]
ISBN 978-1-4020-9292-3 e-ISBN 978-1-4020-9293-0
Library of Congress Control Number 2008939363
© 2009 Springer Science+Business Media B.V.
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Cover illustration: Based on scanning electron micrograph of necrotic cell internalization by macro-
phage. Kindly provided by Prof. Dr. Katharina D’Herde, Ghent University, Ghent, Belgium.
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Preface
Phagocytosis has been at the forefront of cell biology for more than a century.
Initially, phagocytosis, which comes from Greek words meaning “devouring cells,”
was discovered in the late 19th century by Ilya Metchnikoff, who was awarded,
together with Paul Ehrlich, the Nobel Prize in Physiology and Medicine in 1908
“in recognition of their work on immunity.” At that time Metchnikoff had already
identified a function for phagocytes not only in host defense but also as scavengers
of degenerating host cells during metamorphosis of tadpoles, thus providing one of
the first descriptions of apoptotic cell clearance by macrophages (Kaufmann 2008).
Since then, much has been learned about phagocytosis, and the previous several
decades have witnessed outstanding progress in understanding the functions and the
molecular mechanisms of phagocytosis. Two main types of targets are cleared by
phagocytosis: microbial pathogens and dying cells. Rapid recognition and clearance
of dying cells by phagocytes plays a pivotal role in development, maintenance of
tissue homeostasis, control of immune responses, and resolution of inflammation.
Clearance of dying cells can be divided into several stages, including sensing, rec-
ognition, binding and signaling, internalization, and immunological responses.
In this book, our contributors address these different stages of dead cell clear-
ance and examine how impaired clearance of dying cells may lead to human dis-
eases. We have attempted to provide sufficient cross-referencing and indexing to
enable the reader to easily locate the ideas elaborated in the different chapters.
These cross-references to other chapters in the book are indicated by [brackets] in
the text. We have divided the book into two major parts: Part I “Molecular mecha-
nisms of phagocytosis of dying cells” and Part II “Impairment of phagocytosis of
dying cells and its role in the development of diseases”. The first part addresses the
issues of the attraction of phagocytes, the recognition of dying cells, genetic path-
ways, and immunological responses of professional and non-professional phago-
cytes. This part we begin with two introductory chapters to provide the reader with
an overview of cell death types: apoptotic, autophagic and necrotic cell death. In
the first chapter, Krysko, Kaczmarek and Vandenabeele provide a general overview
of the molecular pathways responsible for the execution of apoptotic, necrotic and
autophagy-associated cell death. We distinguish between accidental necrosis, which
is due to direct physiochemical damage, and programmed necrosis, by some others
also called necroptosis, which is mediated by Rip1-kinase dependent signaling. We
v
vi Preface
also highlight the multiple roles of autophagy, such as in cell survival, death and
clearance, and also its contribution to pathogenesis of human diseases. Diez-Fraile,
Lammens and D’Herde continue with this subject by considering examples from
embryonic development, tissue and organ remodeling, and age-related diseases in
which apoptotic, necrotic and autophagic cell death play an important role. They
also address the issue of cell death types in invertebrate and plant systems.
It is striking that about 500 x 109 cells in the human body die each day. These
cells are either shed off directly from body surfaces or continuously removed by a
remarkably efficient phagocytic system without causing inflammation or scar for-
mation. This raises the question of how phagocytes, which are usually not close to
the dying cells, manage to reach their targets in time. The answer to this question
is provided by Peter, Wesselborg and Lauber, who review what is currently known
about attraction and danger signals. These “eat me” signals, released from apoptotic
and necrotic cells, direct phagocytes to the site of dead cells and contribute to their
clearance as well as to the immunological response. Once phagocytes arrive at the
site of cell death, they first have to distinguish dying cells from living cells, and
then adhere to and bind them. These steps involve a complex and redundant array of
ligands and receptors located on the surface of dying cells and phagocytes, respec-
tively. Napirei and Mannherzs provide a global view of how phagocytes continually
sense dead and dying cells by means of a set of cell surface receptors and ligands.
(These themes are picked up later by Ucker; Gregory and Pound; Lucy-Hubert).
Napirei and Mannherzs also emphasize the extracellular mechanisms involved in the
degradation of dying cells with subsequent clearance of debris by phagocytes, and
they elaborate on the role of nucleases and proteases in these processes. Recogni-
tion and binding of phagocytes to their dying targets is followed by signaling events
leading to initiation of engulfment. Gronski and Ravichandran provide an in-depth
comparative study of the biochemical pathways involved in clearance of dead cells
in phylogenetically diverse multicellular organisms ranging from C. elegans and
D. melanogaster to mammals. In the following two chapters, Ucker and Lacy-Hul-
bert address the issue of phagocyte responses to dying cells. Ucker emphasizes that
apoptotic cells exert anti-inflammatory effects on phagocytes at the transcriptional
level independently of engulfment. He also provides examples of how immunosup-
pressive pathways engaged by apoptotic cells are targeted by pathogens. In this dis-
cussion he also proposes two dimensions of immune recognition. In addition to the
unidimensional view of immune discrimination as a self-versus-non-self phenom-
enon to signal danger, apoptotic “calm” (conserved apoptotic ligand for response
modulation) determinants engage a second dimension of immune discrimination
devoted to the maintenance of homeostasis and tolerance. Lacy-Hubert continues
by dealing with the responses of different classes of professional and non-profes-
sional phagocytes to apoptotic cells. He emphasizes that their responses are more
than waste disposal, and that they have immunomodulatory effects as well as pro-
moting proliferation, angiogenesis and tissue regeneration. Aspects of the immu-
nomodulatory properties of apoptotic cells are also touched upon by Divito and
Morelli in the second part of this book. Finally, Trahtemberg and Mevorach close
Part I with a chapter devoted to discussion of different methods and models that are
Preface vii
widely used to study the clearance of dying cells in vitro and in vivo, together with
their pros and cons and some practical advice. Researchers studying the clearance
of dying cells can derive particular benefit from this chapter, especially in view of
the potential bias to which these methods may lead.
Part II, “Impairment of phagocytosis of dying cells and its role in the devel-
opment of diseases,” turns to a different, more clinically relevant viewpoint. The
authors examine whether dysregulation of dying cell clearance may alter immune
responses in ways that contribute to human diseases. Gregory and Pound start
this part with one of today’s most intriguing themes: mouse knock-out models of
clearance. In this well-detailed essay, there is again emphasis on the complexity of
the array of molecules implicated in the removal of dying cells. They look at the
association between defects in cell clearance and development of autoimmunity
and inflammatory disorders in several knock-out mouse models, a matter that has
been far from clear. Indeed, great benefit may be derived from knock-out mod-
els of clearance because they provide not only a basis for understanding clearance
mechanisms, but also for identification of molecular targets for therapeutic manipu-
lation of the clearance process. Mevorach continues by discussing mechanisms that
might link the defective clearance of apoptotic cells with increased autoimmune
responses in the development and acceleration of systemic lupus erythematosus
(SLE), a multisystem autoimmune disease of unknown etiology, and drug-induced
lupus. In this chapter, the following subjects are discussed: altered clearance of
dying cells, accelerated leukocyte apoptosis, genetic or functional deficiencies of
natural opsonins, the presence of autoantibodies, and dysfunction of phagocytes.
Mevorach concludes that all these events could lead to an autoimmune response and
persistence of inflammation.
We placed the chapter written by Divito and Morelli in the second part of the
book because, besides discussing the mechanisms of down-regulation of adap-
tive immune responses by apoptotic cells, they focus on the effects of apoptotic
cells on allograft survival in experimental models, as well as on the potential use
of apoptotic cells in the prevention and treatment of graft rejection and autoim-
mune disorders. Bartunkova and Spisek overview the rapid developments in the
use of dying cells as immunotherapy for cancer, as well as its advantages and dis-
advantages. The authors also outline the molecular markers of immunogenic cell
death and delineate the future goals of immunotherapy. Martinet, Schrijvers and
De Meyer focus on atherosclerosis and state that unstable rupture-prone plaques
are characterized by the accumulation of macrophages and non-engulfed apoptotic
cells, which points to inefficient removal of dying cells. They consider mechanisms
contributing to the defective clearance of apoptotic cells in atherosclerosis and the
consequences of this defect, and discuss therapeutic strategies that could be used
to limit the detrimental effects of impaired phagocytosis of dying cells. However,
it remains unclear whether the number of non-engulfed apoptotic cells in advanced
human plaques is large enough to evoke the plaque-destabilizing events. Reynolds
and Hodge critically examine the hypothesis of defective clearance of apoptotic
material in the pathogenesis of chronic lung diseases, such as chronic obstructive
pulmonary disease (COPD), asthma and cystic fibrosis. They emphasize that on
viii Preface
one hand there is evidence for increased apoptosis, and on the other hand that the
phagocytic capacity of macrophages derived from patients is deficient as a result
of defects related to the expression levels of cell surface receptors. However, the
link between defective clearance of apoptotic cells and lung disease requires a lot
more work before its potential as a therapeutic target can be properly assessed. Dini
and Vergallo continue the discussion of COPD but from another point of view, by
assessing the relationship between cigarette smoke, one of the main risk factors in
the development of chronic pulmonary diseases, and phagocytosis of dying cells.
They follow by pointing out that other environmental factors, including static mag-
netic fields, also may affect the phagocytosis of dying cells and potentially lead to
the diseases. This mostly uninvestigated area of research deserves more attention,
especially in view of the increasing rate of environmental pollution.
Phagocytosis on its own and in relation to dying cells is a very important aspect
of life, and gaining the ability to manipulate it will have far-reaching consequences
in many fields of medicine. Future insights into the molecular mechanisms of cell
death and phagocytosis and their immunomodulatory features will open new ave-
nues for research on autoimmunity and cancer and should eventually facilitate the
development of new classes of therapeutics and disease-modifying agents. Recogni-
tion of impaired phagocytosis as one of the mechanisms of certain human diseases
may give rise to new therapeutic approaches based on manipulating this fundamen-
tal and highly conserved process. All these authors recognize the complexity of the
link between defective clearance of dying cells and development of the above-men-
tioned human diseases. Elucidating this link is of great importance to biology and
medicine, and our authors pose this challenging question to our readers. We hope
that this book will stimulate future research on phagocytosis of dying cells, from its
molecular and cellular basis up to human pathologies, and that it will inspire new
and insightful experiments.
Sincere thanks are given to the outstanding contributors of this book for their
time and effort. We would like to express our special acknowledgement to Dr. A.
Bredan for editing the chapters and working over the proofs. We are also deeply
thankful to BD Biosciences, whose generous support made it possible to publish all
illustrations in color.
Ghent, Belgium Dmitri V. Krysko and Peter Vandenabeele
July 2008 Editors
Reference
Kaufmann SH (2008) Immunology’s foundation: the 100-year anniversary of the Nobel Prize to
Paul Ehrlich and Elie Metchnikoff. Nat Immunol 9, 705–712
Contents
Part I. Molecular Mechanisms of Phagocytosis of Dying Cells
1. Molecular Pathways of Different Types of Cell Death:
Many Roads to Death
Dmitri V. Krysko, Agnieszka Kaczmarek
and Peter Vandenabeele. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Apoptotic, Autophagic and Necrotic Cell Death Types
in Pathophysiological Conditions: Morphological
and Histological Aspects
Araceli Diez-Fraile, Tim Lammens and Katharina D’Herde . . . . . . . . . . 33
3. Role of Attraction and Danger Signals in the Uptake
of Apoptotic and Necrotic Cells and its Immunological Outcome
Christoph Peter, Sebastian Wesselborg and Kirsten Lauber. . . . . . . . . . . . 63
4. Molecules Involved in Recognition and Clearance
of Apoptotic/Necrotic Cells and Cell Debris
Markus Napirei and Hans Georg Mannherz. . . . . . . . . . . . . . . . . . . . . . . 103
5. Evolutionarily Conserved Pathways Regulating
Engulfment of Apoptotic Cells
Matthew A. Gronski and Kodi S. Ravichandran. . . . . . . . . . . . . . . . . . . . 147
6. Innate Apoptotic Immunity: A Potent Immunosuppressive
Response Repertoire Elicited by Specific Apoptotic Cell Recognition
David S. Ucker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
7. Comparative Characterization of Non-professional
and Professional Phagocyte Responses to Apoptotic Cells
Adam Lacy-Hulbert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
ix
x Contents
8. Methods Used to Study Apoptotic Cell Clearance
Uriel Trahtemberg and Dror Mevorach. . . . . . . . . . . . . . . . . . . . . . . . . . . 217
Part II. Impairment of Phagocytosis of Dying Cells
and its Role in the Development of Diseases
9. Results of Defective Clearance of Apoptotic Cells:
Lessons from Knock-out Mouse Models
Christopher D. Gregory and John D. Pound. . . . . . . . . . . . . . . . . . . . . . . 271
10. Clearance of Dying Cells and Systemic Lupus Erythematosus
Dror Mevorach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
11. Apoptotic Cells for Therapy of Transplant Rejection
Sherrie J. Divito and Adrian E. Morelli . . . . . . . . . . . . . . . . . . . . . . . . . . 319
12. Impact of Tumour Cell Death on the Activation
of Anti-tumour Immune Response
Ji(cid:284)ina Bart(cid:292)(cid:278)ková and Radek Špíšek . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
13. Phagocytosis of Dying Cells in the Pathogenesis
of Atherosclerosis
Wim Martinet, Dorien M. Schrijvers and Guido R.Y. De Meyer. . . . . . . 371
14. The Impact of Defective Clearance of Apoptotic Cells
in the Pathogenesis of Chronic Lung Diseases: Chronic
Obstructive Pulmonary Disease, Asthma and Cystic Fibrosis
Paul N. Reynolds and Sandra J. Hodge. . . . . . . . . . . . . . . . . . . . . . . . . . . 393
15. Environmental Factors Affecting Phagocytosis of Dying Cells:
Smoking and Static Magnetic Fields
Luciana Dini and Cristian Vergallo. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 409
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 439
Part I
Molecular Mechanisms of Phagocytosis
of Dying Cells
