Preconditioning and the Developing Brain
Henrik Hagberg, MD, PhD,* Olaf Dammann, MD, MSc,† Carina Mallard, PhD,‡
and Alan Leviton, MD, PhD§
Preconditioning occurs when a subinjurious exposure renders the brain less vulnerable to a
subsequent damaging exposure. In this essay, various models of preconditioning in the
immature brain are discussed. Adenosine, excitatory amino acids, nitric oxide, hypoxia-inducible factor, ATP-sensitive Kⴙ channels, caspases, heat shock proteins, inflammatory mediators
and gene expression all seem to be involved in sensing, transducing and executing preconditioning resistance. Also reviewed in this essay is evidence that some subinjurious exposures
render the brain more vulnerable to a subsequent damaging exposure. We believe that
unraveling the mechanisms of how the developing brain becomes inherently resilient or
vulnerable will offer important insights into the pathogenesis of injury. Preconditioning of the
brain or induction of tolerance of the immune system might be utilized in the future to decrease
CNS vulnerability and the occurrence of perinatal brain injury.
Semin Perinatol 28:389-395 © 2004 Elsevier Inc. All rights reserved.
I
n light of recent advances in the field of preconditioning
(PC), we consider it appropriate to review this area of
research. Elucidating the endogenous mechanisms involved in PC might provide information that can guide us
to a better understanding of the critical events leading to
brain injury. This, in turn, would help us design prophylactic and therapeutic interventions. Because our major
goal is to find ways to protect the developing brain, we
have emphasized PC effects in the immature central nervous system.
Background and Definition
In a seminal paper published in 1986, Murray and his
colleagues reported that the extent of myocardial infarction resulting from a sustained coronary occlusion was
diminished if the heart had been subjected previously to
brief periods of sublethal ischemia.1 This modulation of a
response to an otherwise lethal exposure by a preceding
*Department of Obstetrics and Gynecology, Institute of Women’s and Children’s Health, Göteborg University, Göteborg.
†Perinatal Infectious Disease Epidemiology Unit, Department of Obstetrics,
Prenatal Medicine, and General Gynecology, Department of Pediatric
Pneumology and Neonatology, Hannover Medical School, Hannover.
‡Department of Physiology and Pharmacology, Göteborg University, Göteborg.
§Neuroepidemiology Unit, Children’s Hospital, Boston, MA.
Address reprint requests to: Professor Henrik Hagberg, Perinatal Center,
Department of Obstetrics and Gynecology, Sahlgrenska University Hospital, Göteborg University, Göteborg, Sweden 416 85. E-mail:
henrik.hagberg@obgyn.gu.se
0146-0005/04/$-see front matter © 2004 Elsevier Inc. All rights reserved.
doi:10.1053/j.semperi.2004.10.006
sublethal exposure defines PC. Similar PC effects on the
heart have been observed in humans.2,3 One report suggests that transient ischemic attacks (TIA) induce ischemic
PC in the brain.4
PC, also sometimes known as tolerance, occurs in a number of organs, can be induced by different sublethal insults,
and can occur at remote sites. For example, ischemia in one
cerebral hemisphere can induce tolerance in both hemispheres to subsequent forebrain ischemia.5 Moreover, this
concept of “remote PC” can be extended to include PC of one
organ protecting another organ.6 This suggests that a circulating substance is involved in communicating the PC message to other organs. Although early studies used the same PC
exposure as the potentially toxic exposure, subsequent studies documented that PC to a toxic exposure could be
achieved with exposure to subtoxic levels of a different exposure, so called cross-tolerance.7,8 Usually PC means that a
prior sublethal exposure renders the tissue less sensitive to
the severe insult. In this sense, PC protects the organ. Some
recent studies, however, have demonstrated that a sublethal
exposure (eg, to lipopolysaccharide or “in vitro ischemia”)
increases vulnerability to further insults.9 In this sense, PC, or
perhaps more appropriately, “negative PC,” is a sensitizing
factor (Fig. 1).
Here we limit the expression PC to illustrate the reduction
in the brain’s vulnerability made possible by a previous subthreshold exposure (chemicals, toxins, hypoxia, epilepsy, cytokines or any other exposure). We use the term sensitization
to describe a situation where the brain is rendered more
vulnerable by a previous subthreshold exposure.
389
390
H. Hagberg et al.
the vulnerability of the cell or tissue. Single factors can sometimes act both as a sensor and part of the cellular signal transduction/effector system (eg, HIF-1, caspases and nitric oxide).
Adenosine
PC stimuli (eg, hypoxia or ischemia) disturb the energy balance resulting in an accumulation of adenosine. The subsequent activation of adenosine A1 receptors seems to be a
critical early step in tolerance. A1 receptor antagonists inhibit
PC protection in a number of tissues, including the adult
CNS.19,20 The role of adenosine A1 receptors has not been
explored in PC models of immature animals and may actually
be less critical as A1 receptors do not appear to function
during the neonatal period.21
Figure 1 The interaction between a sub-threshold insult and a severe
insult may result in decreased brain injury, so called preconditioning. In contrast, the term sensitization describes a situation where
the brain is rendered more vulnerable by a previous sub-threshold
exposure. (Color version of figure is available online.)
Cellular Biology of
Preconditioning in the Brain
Models of PC in Immature Animals
A number of different insults can induce PC in adult animals,
including hypoxia, ischemia, inflammatory cytokines, endotoxin, spreading depression, seizures, excitotoxins, hyperthermia and mitochondrial toxins. Usually, a certain time period
(typically 12-72 hours) between PC and the severe insult is
required to achieve tolerance. For example, induction of hyperthermia (41.5-42°C for 15 minutes) 6 to 24 hours before hypoxia–ischemia conferred a considerable reduction of brain injury in postnatal day 7 rats.10,11 Longer lasting protection is
suggested by the observation that transient (30 minute) intrauterine ischemia 12 days before an hypoxic–ischemic insult on
postnatal day 7 still increased neuronal survival from 44% to
74%.12 On the other hand, the salutary effects of PC are partly
lost when the interval between the threshold exposure and evaluation is prolonged (eg, weeks), especially in young animals.13,14
Although no study has demonstrated that the benefits of PC are
permanent, they do seem to last for weeks, if not months. In
immature rats, 3 hours of exposure to 8% oxygen, 24 hours
before a prolonged hypoxic–ischemic insult, reduces brain injury by 70 to 90%,15,16 which persists up to 3 weeks.17 Indeed,
we recently found that the structural damage and the functional
deficits following the severe insult were still markedly (by 72%)
reduced after 8 weeks of recovery in the PC compared with the
sham control group.18
Mechanisms of PC
Acquisition of tolerance appears to depend on stress sensors,
signal transduction and effectors of protection (Fig. 2). Stress
sensors (or proximal triggers) detect various stressful conditions
and convert the information into an intracellular stress response.
The signal is thereafter processed through the signal transduction system, activating various effector systems that will reduce
Glutamate
Glutamate is also released in response to PC insults, leading to
activation of both N-methyl-D-aspartate (NMDA) and alphaamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)
receptors. Indeed, PC can be induced by administration of glutamate receptor agonists. NMDA receptor antagonists block tolerance in the adult brain,22,23 but not in the immature brain.17
Preconditioning might also prevent the downregulation of
GluR2 AMPA type of receptors, which would decrease intracellular calcium overload.24 In the immature white matter, the situation appears to be quite the opposite, as sublethal exposure to
oxygen– glucose deprivation down-regulates GluR2 receptors,
increases Ca2⫹ uptake and increases the vulnerability of oligodendroglial precursor cells.9 This is an example of the sensitization (“negative PC”) we refer to above.
Nitric Oxide (NO)
NO may be involved in hypoxic PC in the immature brain. In
one study of 7-day-old rats, the nonspecific NOS inhibitor
L-nitroarginine almost completely inhibited PC protection.16
Specific inhibitors of the neuronal and inducible isoforms of
NOS, however, had no effect on the PC response, indicating
the importance of endothelial NOS (eNOS).
Hypoxia Inducible Factor 1 (HIF-1)
HIF-1 is a heterodimeric transcription factor composed of
HIF-1␤, which is constitutively expressed, and HIF-1␣,
which is tightly regulated by the oxygen concentration.25
Consequently, HIF-1␣, is rapidly induced by hypoxia in the
neonatal brain26 and may thereby serve as a stress sensor.
HIF-1 may actually also function as an effector to promote
cell survival by inducing genes that contain a hypoxia response element that includes binding sites for HIF-1.27 Indeed, hypoxic PC induces the expression of a number of
HIF-1 target proteins (or mRNAs) like glucose transporter 1,
aldolase, phosphofructokinase, lactate dehydrogenase,
erythropoietin and vascular endothelial growth factor28,29
that may make the brain resistant to further insults.30,31
Both desferrioxamine and CoCl2, each known to protect the
immature brain (see below), also induce HIF-1␣ expression.26
However, HIF-1 target genes expressed after hypoxia were not
induced by CoCl228 and there is currently no direct evidence yet
that HIF-1 is responsible for PC protection in the immature
brain.
Preconditioning and the developing brain
391
Preconditioning insults
hypoxia, ischemia, proinflammatory cytokines, endotoxins, spreading
depression, seizures, excitotoxins, hyperthermia, mitochondrial toxins
Stress sensors
ATP-sensitive K-channels; NMDA receptors (?), i.c. Ca2+, NO, adenosine A1 receptors (?), oxygen free radicals;
activation of caspase-3; Heat shock proteins;
Signal transduction
Kinases
Transcription factors
PKC
NFkB
Raf-1, P42/p44(Erks), p38, p21ras, MEKs, JNK/SAP
ceramide
Jak-2
HIF-1a
CREB
Effectors of protection
Altered synthesis of proteins or posttranslational modification
hypoxia-inducible factor
ATP sensitive K channels (mitochondria)
HIF-1a target genes
preservation of mitochondrial function
heat shock protein 72 & 27
Erythropoietin
Bcl-2-family of proteins
12-lipoxygenase
heme oxygenase-1
eNOS
MnSOD
metallothionein-1 and-2
MKP-1
block of GluR2 (?)
Figure 2 Acquisition of tolerance depends on stress sensors, signal transduction and effectors of protection. Stress
sensors detect various stressful conditions and convert the information into an intracellular stress response. The signal
is thereafter processed through the signal transduction system, activating various effector systems that will reduce the
vulnerability of the cell or tissue.
ATP-Sensitive Kⴙ Channels,
Caspases and Heat Shock Proteins
ATP-sensitive K⫹ channels, which may be important at the
signal transduction/effector level, can be activated by adenosine A1 receptors, oxygen free radicals and through a complicated kinase cascade involving both the protein kinase C
family and mitogen-activated protein kinases.20
Channel blockers inhibit PC and channel openers can induce
tolerance in many systems.19,20 The mechanisms are partly unresolved, but activation of these channels in the plasma membrane leads to hyperpolarization that may prevent or delay deleterious depolarizations. Alternatively, opening of ATP-sensitive
K⫹ channels in mitochondria may dissipate the potential across
the inner membrane that would prevent wasteful ATP-hydrolysis or increase mitochondrial buffering of cytosolic Ca2⫹.20 Another possibility is that opening of ATP-sensitive K⫹ channels
leads to a limited release of mitochondrial cytochrome C and
activation of caspase-3, which will turn on compensatory systems like the heat shock proteins (HSPs). HSPs are intracellular
molecular chaperones of naive, aberrantly folded or mutated
proteins, but they also prevent the assembly of the apoptosome
and inactivate caspase-3.32,33
Such a sequence of events may be relevant for the immature brain because administration of an ATP sensitive K⫹
channel opener (diazoxide) protects against hypoxia–ischemia,34 heat shock protein 72 is induced in response to stimuli that promote PC10 and caspases play a key role in immature cell injury.35-37 Preconditioning-induced activation of
caspase-3 may also cleave and inactivate poly(ADP-ribose)polymerase-1 (PARP-1), which would add to the tolerant state as activation of PARP-1 enhances brain injury also in
the immature brain.38,39
Preconditioning and Gene Expression
In most cases a certain time lag (typically 12-72 hours) is required between the PC stimulus and the severe insult to obtain
PC protection (at least for the brain). This has led to the inference that protein synthesis is needed for PC. This inference is
supported by the observation that the protein synthesis inhibitor cycloheximide inhibits ischemic PC40 and by the evidence
that proteins play an important role in PC (including such transcription factors as HIF-1, nuclear factor kappa B (NF-kB), ceramide, activator protein-1, early growth response gene-1 and
cAMP response element-binding protein).41,42
392
A number of these genes/proteins, besides HIF-1 target
genes and heat shock proteins, are expressed after PC. Based
on their specific properties, some of them may be anticipated
to act as intermediates between the PC stimulus and the
observed protection. For example, metallothionein-1 and -2
are expressed in the immature brain after hypoxic PC29 and
even though the functions of these proteins are unknown,
they are protective in models of ischemia.43 Furthermore,
MAP-kinase phosphate-1 (MKP-1) mRNA, which is induced
after hypoxia,29 improves survival by antagonizing c-Jun Nterminal kinase (JNK) activation, a contributor to CNS injury.44 A considerable number of other genes are also induced
by the PC process (eg, lipoxgenases, cytokines, chemokines,
etc). With the increased availability of micro-arrays, we expect that more will be identified.
Vascular Effects: Cerebral Blood Flow
Although some PC-related phenomena10,29,45 lead to the inference that improved cerebral blood flow accounts for some of the
PC effects, studies in the adult CNS have shown that PC does not
affect cerebral blood flow during or after ischemia.40,46,47 In addition, the fact that PC can be induced in vitro provides additional support for the view that factors unrelated to blood flow
are at play. No studies have been published on PC and cerebral
blood flow in the immature brain. However, in an immature
(6-day-old) rat model of 2.5 hours of systemic hypoxia followed
24 hours later by the same systemic hypoxia accompanied by
unilateral common carotid artery ligation, the rate of energy
failure was significantly delayed in PC rats compared with that
seen in rats exposed to hypoxia–ischemia alone.48 These results
suggest an effect on cerebral blood flow or a direct effect on
energy metabolism.
Cytokines
Under certain circumstances pro-inflammatory cytokines afford protection against cerebral ischemia.49 Both IL-1␤ and
TNF-␣ are up-regulated following sublethal ischemia in
vivo.50,51 Ischemic preconditioning appears to be dependent
on TNF-␣ release as inhibition of TNF-␣ convertase (TACE/
ADAM17, which is involved in TNF-␣ release), blocked both
the increase in TNF-␣ and the neuroprotective effects of preconditioning.51 Pretreatment of hippocampal cell cultures
with TNF-␣ induces protection against subsequent oxidative
insults such as FeSO4 or amyloid b-peptide exposure.52
TNF-␣ pretreatment also protects against focal cerebral ischemia in mice, however, only when given intracisternally.53
Furthermore, both TNF-␣ and IL-1␤ protect neurons in culture against subsequent hypoxic or excitotoxic injury.54,55 In
the adult gerbil, repeated administration of IL-1 over several
days protects hippocampal neurons from subsequent ischemic injury, an effect that is blocked by coadministering of
IL-1 receptor antagonist (IL-1ra).56
In neuron cultures, the protective effects of TNF-␣ appear
to reflect activation of NF-kB with subsequent induction of
manganese superoxide dismutase (Mn-SOD) and suppression of both peroxynitrite formation and apoptosis.52,57 Nuclear translocation of NF-kB plays a central role following
several PC stimuli as inhibition of NF-kB activation abolishes
the preconditioning effects of sublethal ischemia, as well as
H. Hagberg et al.
epileptic and polyunsaturated fatty acid insults.58 In astrocyte
cultures, TNF-␣-induced tolerance is associated with the inhibition of the phosphorylation of the NF-kB subunit, p65/
RelA, resulting in suppression of the ICAM-1 gene, while
other NF-kB dependent genes such as Mn-SOD are not affected.59 These results therefore suggest that cytokine-induced tolerance is associated with different mechanisms in
different cell types.
Other possible down-stream beneficial effect of the induction of TNF-␣ and IL-1␤ is the production of neurotrophins,
which are markedly induced by pro-inflammatory cytokines55,60,61 and by PC.62 In support of neurotrophins as PC
intermediaries, is the observation that intracerebral administration of BDNF for 7, 10 or 14 days before ischemia reduces
infarction volume, without affecting CBF.63 BDNF may exert
its PC effects via crosstalk between the TrkB receptor and the
NMDA receptor.64
Thus, under certain circumstances and at relatively low
levels, pro-inflammatory cytokines appear to participate
in a physiologic stress response that contributes to the
development of tolerance in adult animals and in vitro.
The role of cytokines in PC in the immature brain is complex and still unclear. Cytokines play important roles in
the developing brain, are easily induced following ischemia, and might contribute to damage. We await evidence
that cytokines and neurotrophins are involved in PC in the
immature brain.
Lipopolysaccharide (LPS)
In the adult, the endotoxin LPS and the endotoxin analog
diphoporyl lipid A confer tolerance to cerebral ischemia.65,66
LPS priming that increases tolerance against focal cerebral
ischemia could be due to its stimulation of cytokines, such as
TNF-␣ expression.67 Furthermore, ceramide, a down stream
messenger of TNF-␣ signaling, contributes to LPS-induced
tolerance to cerebral ischemia.68 PC induced by LPS is also
associated with the induction of TGF-␤1, which has neuroprotective properties.69
LPS pretreatment does not appear to affect the cerebral
blood flow immediately after MCA occlusion, but may
diminish the severity of secondary microvascular perfusion deficits.70,71 In support of this concept, endothelial
NOS is up-regulated following LPS and administration of
the NOS inhibitor L-NAME abolishes the preconditioning
effects of LPS.72 Other studies suggest that up-regulation
of antioxidants (superoxide dismutase) following low
doses of endotoxin may be important in LPS-induced tolerance.73,74
To our knowledge, endotoxin-induced PC has not been
studied in the immature brain. We have recently found that
LPS sensitizes the immature rat brain.75 Repeated daily doses
of LPS, in utero, have been shown to induce cardiovascular
tolerance but without cerebral protection in the fetal sheep.76
These observations suggest that effects of LPS priming may be
variable depending on the physiological state, the presence of
certain risk factors for vascular injury and age.
Preconditioning and the developing brain
Brain Injury
Protection Analogies to PC
Chemical Protection
Some chemicals that protect the immature brain might do so
by means other than those that characterize PC. Thus, we are
not yet prepared to consider glucocorticoids, desferrioxamine and cobalt chloride as “chemical” preconditioners. Nevertheless, some of the similarities deserve attention. For example, glucocorticoids do not provide brain protection
against hypoxia/ischemia if given immediately prior, during
or after the insult in immature77 or adult78,79 animals. However, if dexamethasone, is given 4 to 24 hours before hypoxia–ischemia, brain injury is prevented in 1 to 2 weeks old,
but not in 4-week-old pups80,81 demonstrating that not only
the interval between the protector and the insult can be critical but also the age of the animals. The relatively long halflife of glucocorticoids would allow their effects to be exerted
in the brain for days after administration and their presence
might therefore contribute to a direct protective effect.82
Thus, a PC like mechanism needs not to be invoked, although it remains a possibility.
As previously mentioned, HSPs are seen as protectors of the
cell after exposure to stressful stimuli and may have a role in PC.
The primary mediator of the heat shock response is the heat
shock transcription factor 1 (HSF1). When HSF1 binds to one
of the HSPs, a conformational switch occurs that rapidly activates HSF1 in a manner that mimics the kinetics of glucocorticoid receptor pathways mediated by cochaperones.83,84 Thus,
steroid receptor function might be analogous to some phenomena presumed to be similar to some PC processes.
Other examples of “chemical” preconditioners in immature animals are desferrioxamine and CoCl2. Giving either of
these substances 24 hours before hypoxia–ischemia in 7-dayold rats reduces brain injury by more than 50%.26 Desferrioxamine has a half-life of only 3 hours in the rat.85 Thus, it is
unlikely that enough desferrioxamine is available, in the
brain, 24 hours later when the rat is exposed to the insult.
The inference is that desferrioxamine has changed something
that might be an approximation of what occurs with PC.
Until the mechanisms of action are known, it is difficult to
separate a PC effect of these agents from alternative explanations for brain protection.
Immunization
Immunization is defined as the induction of an immune response that is beneficial to the host in halting a pathological
process.86 The earliest, and most current, immunizations
promote the organisms’ ability to respond vigorously to an
infectious organism (eg, H influenza). When an inflammatory response is damaging, however, the goal should be to
turn down the ability to respond vigorously to a stimulus.
Progress has been made recently in efforts to induce tolerance
to CNS components, thereby promoting the development of
regulatory/suppressor cells that modulate subsequent potentially damaging inflammatory phenomena.
Antigen(s) can be injected, although risk of adversities may
393
be heightened.86 An alternative approach exposes the animal
or person to the antigen(s) via the nose or mouth.87 Nasaland gut-associated lymphoid tissues are thought to have
evolved to prevent the host from reacting to inhaled or ingested proteins that are nonpathogenic.88 T cells in the nose
and bowel can be made tolerant with a low-dose regimen of a
CNS antigen. For multiple sclerosis, the preferred antigens
have been synthetic polypeptides whose components are
present in myelin basic protein.89 For Alzheimer disease, the
antigen has been amyloid-beta (A␤) protein.90 In animals
studies intended to reduce infarct size, the antigens have
been myelin basic protein,91 ovalbumin,91 and selectin.88
These tolerized cells become a form of regulatory T cell called
Tr3 cells, which secrete cytokines such as IL-10 and transforming growth factor-␤1 on antigen restimulation. These Tr3 cells
thereby modulate the brain-damaging inflammatory response
by “active cellular regulation” or “bystander suppression.”92
PC-induced tolerance differs considerably from immunization-induced tolerance. Nevertheless, they can be viewed as
analogous, at least in that both are prophylactic procedures intended to diminish the effects of insults that would otherwise
lead to brain cell death. We offer this detail about immunizationinduced tolerance because it is a possible alternative to PC or a
supplemental therapeutic approach. This alternative/supplement might be especially attractive if circulating inflammatory
cells are shown to adversely affect the immature brain.93
Concluding Remarks
Although PC does occur in the immature brain, very few
investigators have addressed this topic. The complexity of PC
needs to be much better understood before PC is considered
a viable prophylactic approach to prevent brain damage in
the newborn. For example, the possibility exists that a PC
stimulus intended to protect the brain might instead sensitize
the brain to an insult. On the other hand, the potential for PC
to reduce the occurrence/severity of brain damage in the most
vulnerable humans is sufficient reason to explore this topic in
greater detail. Perhaps chemical preconditioners can be
found that do not have this sensitizing capability. Other possibilities to protect the brain may be to induce tolerance in
circulating inflammatory cells as activation of these are
known to adversely affect the immature brain. Might such
immuno-modulating interventions help to minimize perinatal brain damage in the future?
Acknowledgments
This work was supported by the Swedish Medical Research
Council (09455 and K2004-33X-14185-03A), the Åhlén Foundation, the Sven Jerring Foundation, the Magnus Bergvall Foundation, the Wilhelm and Martina Lundgren Foundation, the
Linnéa and Josef Carlsson Foundation, the Frimurare Barnhus
Foundation, Göteborg Medical Society, Åke Wibergs Foundation, Wilhelm-Hirte Stiftung, Hannover Medical School, a cooperative agreement with the National Institutes of Health of the
United States (NS40069) and by grants to researchers in the
public health service from the Swedish government.
H. Hagberg et al.
394
References
1. Murray CE, Jennings RB, Reimer KA: Preconditioning with ischemia: A
delay of lethal cell injury in ischemic myocardium. Circulation 74:
1124-1136, 1986
2. Tomai F, Crea F, Chiariello L, et al: Preinfarction angina and myocardial preconditioning. Cardiologia 44:963-967, 1999
3. Yellon DM, Dana A: The preconditioning phenomenon: A tool for the
scientist or a clinical reality? Circ Res 87:543-550, 2000
4. Wegener S, Gottschalk B, Jovanovic V, et al: Transient ischemic attacks
before ischemic stroke: Preconditioning the human brain? A multicenter magnetic resonance imaging study. Stroke 35:616-621, 2004
5. Belayev L, Ginsberg MD, Alonso OF, et al: Bilateral ischemic tolerance
of rat hippocampus induced by prior unilateral transient focal ischemia: Relationship to c-fos mRNA expression. Neuroreport 8:55-59,
1996
6. Takaoka A, Nakae I, Mitsunami K, et al: Renal ischemia/reperfusion
remotely improves myocardial energy metabolism during myocardial
ischemia via adenosine receptors in rabbits: Effects of “remote preconditioning.” J Am Coll Cardiol 33:556-564, 1999
7. Plamondon H, Blondeau N, Heurteaux C, et al: Mutually protective
actions of kainic acid epileptic preconditioning and sublethal global
ischemia on hippocampal neuronal death: Involvement of adenosine
A1 receptors and K(ATP) channels. J Cereb Blood Flow Metab 19:
1296-1308, 1999
8. Meng X, Brown JM, Ao L, et al: Myocardial gene reprogramming associated with a cardiac cross-resistant state induced by LPS preconditioning. Am J Physiol 275:C475-C483, 1998
9. Deng W, Rosenberg PA, Volpe JJ, et al: Calcium-permeable AMPA/
kainate receptors mediate toxicity and preconditioning by oxygen-glucose deprivation in oligodendrocyte precursors. Proc Natl Acad Sci U S A
100:6801-6806, 2003
10. Ikeda T, Ikenoue T, Xia XY, et al: Important role of 72-kd heat shock
protein expression in the endothelial cell in acquisition of hypoxic–
ischemic tolerance in the immature rat. Am J Obstet Gynecol 182:380386, 2000
11. Wada T, Kondoh T, Tamaki N: Ischemic “cross” tolerance in hypoxic
ischemia of immature rat brain. Brain Res 847:299-307, 1999
12. Cai Z, Fratkin JD, Rhodes PG: Prenatal ischemia reduces neuronal
injury caused by neonatal hypoxia–ischemia in rats. Neuroreport
8:1393-1398, 1997
13. Corbett D, Crooks P: Ischemic preconditioning: A long term survival
study using behavioural and histological endpoints. Brain Res 760:129136, 1997
14. Dowden J, Corbett D: Ischemic preconditioning in 18- to 20-monthold gerbils: Long-term survival with functional outcome measures.
Stroke 30:1240-1246, 1999
15. Gidday JM, Fitzgibbons JC, Shah AR, et al: Neuroprotection from ischemic brain injury by hypoxic preconditioning in the neonatal rat.
Neurosci Lett 168:221-224, 1994
16. Gidday JM, Shah AR, Maceren RG, et al: Nitric oxide mediates cerebral
ischemic tolerance in a neonatal rat model of hypoxic preconditioning.
J Cereb Blood Flow Metab 19:331-340, 1999
17. Vannucci RC, Towfighi J, Vannucci SJ: Hypoxic preconditioning and
hypoxic–ischemic brain damage in the immature rat: Pathologic and
metabolic correlates. J Neurochem 71:1215-1220, 1998
18. Gustavsson M, Anderson M, Mallard C, et al: Hypoxic preconditioning
confers long-term reduction of brain injury and improvement of neurological ability in immature rats. Pediatr Res 2004 (in press)
19. Heurteaux C, Lauritzen I, Widmann C, et al: Essential role of adenosine,
adenosine A1 receptors, and ATP-sensitive K⫹ channels in cerebral ischemic preconditioning. Proc Natl Acad Sci U S A 92:4666-4670, 1995
20. Cohen MV, Baines CP, Downey JM: Ischemic preconditioning: From
adenosine receptor of K ATP channel. Annu Rev Physiol 62:79-109, 2000
21. Ådén U, Leverin AL, Hagberg H, et al: Adenosine A1 receptor agonism in
the immature rat brain and heart. Eur J Pharmacol 426:185-192, 2000
22. Grabb MC, Choi DW: Ischemic tolerance in murine cortical cell culture: Critical role for NMDA receptors. J Neurosci 19:1657-1662, 1999
23. Aizenman E, Sinor JD, Brimecombe JC, et al: Alterations of N-methyl-
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
41.
42.
43.
44.
45.
46.
D-aspartate receptor properties after chemical ischemia. J Pharmacol
Exp Ther 295:572-577, 2000
Tanaka H, Calderone A, Jover T, et al: Ischemic preconditioning acts
upstream of GluR2 down-regulation to afford neuroprotection in the
hippocampal CA1. Proc Natl Acad Sci U S A 99:2362-2367, 2002
Huang LE, Arany Z, Livingston DM, et al: Activation of hypoxia-inducible transcription factor depends primarily upon redox-sensitive stabilization of its alpha subunit. J Biol Chem 271:32253-32259, 1996
Bergeron M, Gidday JM, Yu AY, et al: Role of hypoxia-inducible factor-1
in hypoxia-induced ischemic tolerance in neonatal rat brain. Ann Neurol 48:285-296, 2000
Gregg L, Semenza GL: Surviving ischemia: Adaptive responses mediated by hypoxia-inducible factor 1. J Clin Invest 106:809-812, 2000
Jones NM, Bergeron M: Hypoxic preconditioning induces changes in
HIF-1 target genes in neonatal rat brain. J Cereb Blood Flow Metab
21:1105-1114, 2001
Bernaudin M, Tang Y, Reilly M, et al: Brain genomic response following
hypoxia and re-oxygenation in the neonatal rat. Identification of genes
that might contribute to hypoxia-induced ischemic tolerance. J Biol
Chem 277:39728-39738, 2002
Juul S: Erythropoietin in the central nervous system, and its use to
prevent hypoxic–ischemic brain damage. Acta Paediatr Suppl 91:3642, 2002
Sun Y, Jin K, Xie L, et al: VEGF-induced neuroprotection, neurogenesis, and angiogenesis after focal cerebral ischemia. J Clin Invest 111:
1843-1851, 2003
McLaughlin B, Hartnett KA, Erhardt JA, et al: Caspase 3 activation is
essential for neuroprotection in preconditioning. Proc Natl Acad Sci
U S A 100:715-720, 2003
Parcellier A, Gurbuxani S, Schmitt E, et al: Heat shock proteins, cellular
chaperones that modulate mitochondrial cell death pathways. Biochem
Biophys Res Commun 304:505-512, 2003
Rajapakse N, Shimizu K, Kis B, et al: Activation of mitochondrial ATPsensitive potassium channels prevents neuronal cell death after ischemia in neonatal rats. Neurosci Lett 327:208-212, 2002
Cheng Y, Deshmukh M, D’Costa A, et al: Caspase inhibitor affords
neuroprotection with delayed administration in a rat model of neonatal
hypoxic–ischemic brain injury. J Clin Invest 101:1992-1999, 1998
Nakajima W, Ishida A, Lange MS, et al: Apoptosis has a prolonged role
in the neurodegeneration after hypoxic ischemia in the newborn rat.
J Neurosci 20:7994-8004, 2000
Zhu C, Wang X, Hagberg H, et al: Correlation between caspase-3 activation and three different markers of DNA damage in neonatal cerebral
hypoxia–ischemia. J Neurochem 75:819-829, 2000
Ducrocq S, Benjelloun N, Plotkine M, et al: Poly(ADP-ribose) synthase
inhibition reduces ischemic injury and inflammation in neonatal rat
brain. J Neurochem 74:2504-2511, 2000
Hagberg H, Wilson M-A, Mutsushita H, et al: Hypoxia–ischemia in immature mice: Disruption of the poly(ADP-ribose) and the polymerase
(PARP)-1 gene modifies responses to injury. Dev Neurosci 24:446, 2002
Barone FC, White RF, Spera PA, et al: Ischemic preconditioning and
brain tolerance: Temporal histological and functional outcomes, protein synthesis requirement, and interleukin-1 receptor antagonist and
early gene expression. Stroke 29:1937-1950, 1998
Semenza GL: Regulation of mammalian O2 homeostasis by hypoxiainducible factor 1. Annu Rev Cell Dev Biol 15:551-578, 1999
Baxter GF, Ferdinandy P: Delayed preconditioning of myocardium:
Current perspectives. Basic Res Cardiol 96:329-344, 2001
Giralt M, Penkowa M, Lago N, et al: Metallothionein-1⫹2 protect the
CNS after a focal brain injury. Exp Neurol 173:114-128, 2002
Kuan CY, Whitmarsh AJ, Yang DD, et al: A critical role of neuralspecific JNK3 for ischemic apoptosis. Proc Natl Acad Sci U S A 100:
15184-15189, 2003
Wick A, Wick W, Waltenberger J, et al: Neuroprotection by hypoxic
preconditioning requires sequential activation of vascular endothelial
growth factor receptor and Akt. J Neurosci 22:6401-6407, 2002
Matsushima K, Hakim AM: Transient forebrain ischemia protects
against subsequent focal cerebral ischemia without changing cerebral
perfusion. Stroke 26:1047-1052, 1995
Preconditioning and the developing brain
47. Chen J, Graham SH, Zhu R, et al: Stress proteins and tolerance to focal
cerebral ischemia. J Cereb Blood Flow Metab 16:566-577, 1996
48. Vannucci SJ, Brucklacher RM, Vannucci RC: Hypoxic preconditioning
increases brain glycogen, delays energy depletion, and prevents secondary energy failure following hypoxia–ischemia in the immature rat.
J Cereb Blood Flow Metab 23:440, 2003
49. Bruce AJ, Boling W, Kindy MS, et al: Altered neuronal and microglial
responses to excitotoxic and ischemic brain injury in mice lacking TNF
receptors. Nat Med 2:788-794, 1996
50. Wang X, Li X, Currie RW, et al: Application of real-time polymerase
chain reaction to quantitate induced expression of interleukin-1␤
mRNA in ischemic brain tolerance. J Neurosci Res 59:238-246, 2000
51. Cardenas A, Moro MA, Leza JC, et al: Upregulation of TACE/ADAM17
after ischemic preconditioning is involved in brain tolerance. J Cereb
Blood Flow Metab 22:1297-1302, 2002
52. Mattson MP, Goodman Y, Luo H, et al: Activation of NF-kappaB protects hippocampal neurons against oxidative stress-induced apoptosis:
Evidence for induction of manganese superoxide dismutase and suppression of peroxynitrite production and protein tyrosine nitration.
J Neurosci Res 49:681-697, 1997
53. Nawashiro H, Tasaki K, Ruetzler CA, et al: TNF-alpha pretreatment
induces protective effects against focal cerebral ischemia in mice.
J Cereb Blood Flow Metab 17:483-490, 1997
54. Cheng B, Christakos S, Mattson MP: Tumor necrosis factors protect
neurons against metabolic– excitotoxic insults and promote maintenance of calcium homeostasis. Neuron 12:139-153, 1994
55. Strijbos PJ, Rothwell NJ: Interleukin-1 beta attenuates excitatory amino
acid-induced neurodegeneration in vitro: Involvement of nerve growth
factor. J Neurosci 15:3468-3474, 1995
56. Ohtsuki T, Ruetzler CA, Tasaki K, et al: Interleukin-1 mediates induction of tolerance to global ischemia in gerbil hippocampal CA1 neurons. J Cereb Blood Flow Metab 16:1137-1142, 1996
57. Van Antwerp DJ, Martin SJ, Verma IM, et al: Inhibition of TNF-induced
apoptosis by NF-kappa B. Trends Cell Biol 8:107-111, 1998
58. Blondeau N, Widmann C, Lazdunski M, et al: Activation of the nuclear
factor-kappaB is a key event in brain tolerance. J Neurosci 21:46684677, 2001
59. Ginis I, Jaiswal R, Klimanis D, et al: TNF-alpha-induced tolerance to
ischemic injury involves differential control of NF-kappaB transactivation: The role of NF-kappaB association with p300 adaptor. J Cereb
Blood Flow Metab 22:142-152, 2002
60. Lindholm D, Heumann R, Meyer M, et al: Interleukin-1 regulates synthesis of nerve growth factor in non-neuronal cells of rat sciatic nerve
Nature 330:658-659, 1987
61. Heese K, Hock C, Otten U: Inflammatory signals induce neurotrophin
expression in human microglial cells. J Neurochem 70:699-707, 1998
62. Truettner J, Busto R, Zhao W, et al: Effect of ischemic preconditioning
on the expression of putative neuroprotective genes in the rat brain.
Mol Brain Res 103:106-115, 2002
63. Yanamoto H, Nagata I, Sakata M, et al: Infarct tolerance induced by
intra-cerebral infusion of recombinant brain-derived neurotrophic factor. Brain Res 859:240-248, 2000
64. Jiang X, Zhu D, Okagaki P, et al: N-methyl-D-aspartate and TrkB receptor activation in cerebellar granule cells: An in vitro model of preconditioning to stimulate intrinsic survival pathways in neurons. Ann
N Y Acad Sci 993:134-145, 2003
65. Ahmed SH, He YY, Nassief A, et al: Effects of lipopolysaccharide priming on acute ischemic brain injury. Stroke 31:193-199, 2000
66. Toyoda T, Kassell NF, Lee KS: Induction of tolerance against ischemia/
reperfusion injury in rat brain by preconditioning with the endotoxin
analog diphosphoryl lipid A. J Neurosurg 92:435-441, 2000
67. Tasaki K, Ruetzler CA, Ohtsuki T, et al: Lipopolysaccharide pre-treatment
induces resistance against subsequent focal cerebral ischemic damage in
spontaneously hypertensive rats. Brain Res 748:267-270, 1997
68. Zimmermann C, Ginis I, Furuya K, et al: Lipopolysaccharide-induced
ischemic tolerance is associated with increased levels of ceramide in
brain and in plasma. Brain Res 895:59-65, 2001
69. Boche D, Cunningham C, Gauldie J, et al: Transforming growth factor-
395
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
91.
92.
93.
beta 1-mediated neuroprotection against excitotoxic injury in vivo.
J Cereb Blood Flow Metab 23:1174-1182, 2003
Dawson DA, Furuya K, Gotoh J, et al: Cerebrovascular hemodynamics
and ischemic tolerance: Lipopolysaccharide-induced resistance to focal
cerebral ischemia is not due to changes in severity of the initial ischemic
insult, but is associated with preservation of microvascular perfusion.
J Cereb Blood Flow Metab 19:616-623, 1999
Bastide M, Gele P, Petrault O, et al: Delayed cerebrovascular protective
effect of lipopolysaccharide in parallel to brain ischemic tolerance.
J Cereb Blood Flow Metab 23:399-405, 2003
Puisieux F, Deplanque D, Pu Q, et al: Differential role of nitric oxide
pathway and heat shock protein in preconditioning and lipopolysaccharide-induced brain ischemic tolerance. Eur J Pharmacol 389:71-78, 2000
Kramer BC, Yabut JA, Cheong J, et al: Lipopolysaccharide prevents cell
death caused by glutathione depletion: Possible mechanisms of protection. Neuroscience 114:361-372, 2002
Bordet R, Deplanque D, Maboudou P, et al: Increase in endogenous
brain superoxide dismutase as a potential mechanism of lipopolysaccharide-induced brain ischemic tolerance. J Cereb Blood Flow Metab
20:1190-1196, 2000
Eklind S, Mallard C, Leverin AL, et al: Bacterial endotoxin sensitizes the
immature brain to hypoxic–ischaemic injury. Eur J Neurosci 13:11011106, 2001
Duncan JR, Cock ML, Scheerlinck JP, et al: White matter injury after
repeated endotoxin exposure in the preterm ovine fetus. Pediatr Res
52:941-949, 2002
Altman DI, Young RS, Yagel SK: Effects of dexamethasone in hypoxic–
ischemic brain injury in the neonatal rat. Biol Neonate 46:149-156, 1984
Sapolsky RM, Pulsinelli WA: Glucocorticoids potentiate ischemic injury to
neurons: Therapeutic implications. Science 229:1397-1400, 1985
Koide T, Wieloch TW, Siesjo BK: Chronic dexamethasone pretreatment aggravates ischemic neuronal necrosis. J Cereb Blood Flow Metab
6:395-404, 1986
Barks JD, Post M, Tuor UI: Dexamethasone prevents hypoxic–ischemic
brain damage in the neonatal rat. Pediatr Res 29:558-563, 1991
Chumas PD, Del Bigio MR, Drake JM, et al: A comparison of the protective effect of dexamethasone to other potential prophylactic agents
in a neonatal rat model of cerebral hypoxia–ischemia. J Neurosurg
79:414-420, 1993
Tuor UI, Chumas PD, Del Bigio MR: Prevention of hypoxic–ischemic
damage with dexamethasone is dependent on age and not influenced
by fasting. Exp Neurol 132:116-122, 1995
Williams RS, Benjamin IJ: Protective responses in the ischemic myocardium. J Clin Invest 106:813-818, 2000
Beato M, Klug J: Steroid hormone receptors: An update. Hum Reprod
Update 6:225-236, 2000
Palmer C, Roberts RL, Bero C: Deferoxamine posttreatment reduces
ischemic brain injury in neonatal rats. Stroke 25:1039-1045, 1994
Nicoll JA, Wilkinson D, Holmes C, et al: Neuropathology of human
Alzheimer disease after immunization with amyloid-␤ peptide: A case
report. Nat Med 9:448-452, 2003
Weiner HL, Selkoe DJ: Inflammation and therapeutic vaccination in
CNS diseases. Nature 420:879-884, 2002
Chen Y, Ruetzler C, Pandipati S, et al: Mucosal tolerance to E-selectin
provides cell-mediated protection against ischemic brain injury. Proc
Natl Acad Sci U S A 100:15107-15112, 2003
Arnon R, Sela M: Immunomodulation by the copolymer glatiramer
acetate. J Mol Recognit 16:412-421, 2003
Lemere CA, Maron R, Selkoe DJ, et al: Nasal vaccination with betaamyloid peptide for the treatment of Alzheimer’s disease. DNA Cell Biol
20:705-711, 2001
Becker K, Kindrick D, McCarron R, et al: Adoptive transfer of myelin
basic protein-tolerized splenocytes to naïve animals reduces infarct
size: A role for lymphocytes in ischemic brain injury? Stroke 34:18091815, 2003
Faria AM, Weiner HL: Oral tolerance: Mechanisms and therapeutic
applications. Adv Immunol 73:153-264, 1999
Cavaillon JM: The nonspecific nature of endotoxin tolerance. Trends
Microbiol 3:320-324, 1995