J Appl Physiol 102: 2389 –2397, 2007;
doi:10.1152/japplphysiol.01202.2006.
HIGHLIGHTED TOPIC
Invited Review
Free Radical Biology in Skeletal Muscle
Oxidative stress and disuse muscle atrophy
Scott K. Powers, Andreas N. Kavazis, and Joseph M. McClung
Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida
oxidants; proteasome; calpain; caspase-3; reactive oxygen species
of skeletal muscle inactivity (e.g., limb immobilization, chronic bed rest, or spaceflight) result in a loss of
muscle mass and strength (1, 11, 83). Knowledge of the cell
signaling pathways that regulate disuse muscle atrophy is
important in developing an anti-catabolic strategy to prevent or
retard protein loss and maintain physiological function (12).
Ongoing research in cell signaling has led to an improved
understanding of those factors that contribute to muscle atrophy during both disuse and pathologies that promote muscle
wasting. In particular, a large volume of research indicates that
oxidative stress is an important contributor to numerous cellular signaling pathways that modulate muscle atrophy during
prolonged inactivity. For example, exposure of skeletal muscle
myotubes to oxidative stress (i.e., hydrogen peroxide) increases the expression of important components of the proteasome proteolytic system (58). Moreover, other signaling pathways exist to connect oxidative stress with cellular processes
leading to a loss of cellular protein (44).
The objective of this review is to provide a synopsis of our
present knowledge regarding the link between reactive oxygen
species (ROS) and proteolytic components of disuse skeletal
muscle atrophy. The first segment of this article will introduce
experimental models to study muscle atrophy. We will then
present an overview of the biochemical events leading to the
loss of myonuclei in atrophying muscle followed by a discussion of the principal proteolytic pathways that contribute to
EXTENDED PERIODS
Address for reprint requests and other correspondence: S. K. Powers, Dept.
of Applied Physiology and Kinesiology, PO Box 118205, Univ. of Florida,
Gainesville, FL 32611 (e-mail: [email protected]).
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disuse muscle atrophy. Next, we will outline the major pathways involved in skeletal muscle radical production followed
by a discussion of the signaling pathways linking oxidative
stress to increased proteolysis and loss of myonuclei. The final
segment of this treatise will identify voids in our knowledge
about oxidative stress and disuse muscle atrophy in hopes of
stimulating future research in this field.
EXPERIMENTAL MODELS TO INVESTIGATE DISUSE
MUSCLE ATROPHY
Skeletal muscle atrophy can occur due to pathology (e.g.,
cancer, sepsis, or diabetes) and in the absence of disease during
extended durations of inactivity (33, 39). For example, long
periods of bed rest, limb immobilization, spaceflight, or unloading the diaphragm via mechanical ventilation is associated
with skeletal muscle atrophy in humans and other animals. Due
to the complexities involved in investigating the mechanisms
responsible for disuse muscle atrophy in humans, numerous
experimental animal models have evolved to simulate unloading conditions that lead to disuse muscle atrophy (Fig. 1). For
example, animal models of limb immobilization (i.e., casting)
have been used to investigate the impact of muscle inactivity
on muscle size and function (11). Moreover, rodent animal
models using a tail suspension technique to unload the hindlimb locomotor muscles have been used to simulate prolonged
spaceflight or bed rest in humans (1, 83).
An interesting and clinically relevant model of inactivityinduced skeletal muscle atrophy is controlled mechanical ventilation (i.e., ventilator delivers all of the breaths; Fig. 1). In
human medicine, controlled mechanical ventilation is used to
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Powers SK, Kavazis AN, McClung JM. Oxidative stress and disuse muscle atrophy.
J Appl Physiol 102: 2389–2397, 2007; doi:10.1152/japplphysiol.01202.2006.—Skeletal
muscle inactivity is associated with a loss of muscle protein and reduced forcegenerating capacity. This disuse-induced muscle atrophy results from both increased
proteolysis and decreased protein synthesis. Investigations of the cell signaling
pathways that regulate disuse muscle atrophy have increased our understanding of
this complex process. Emerging evidence implicates oxidative stress as a key
regulator of cell signaling pathways, leading to increased proteolysis and muscle
atrophy during periods of prolonged disuse. This review will discuss the role of
reactive oxygen species in the regulation of inactivity-induced skeletal muscle
atrophy. The specific objectives of this article are to provide an overview of muscle
proteases, outline intracellular sources of reactive oxygen species, and summarize
the evidence that connects oxidative stress to signaling pathways contributing to
disuse muscle atrophy. Moreover, this review will also discuss the specific role that
oxidative stress plays in signaling pathways responsible for muscle proteolysis and
myonuclear apoptosis and highlight gaps in our knowledge of disuse muscle
atrophy. By presenting unresolved issues and suggesting topics for future research,
it is hoped that this review will serve as a stimulus for the expansion of knowledge
in this exciting field.
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OXIDATIVE STRESS AND DISUSE MUSCLE ATROPHY
Fig. 1. Human conditions that promote skeletal muscle atrophy and the
corresponding animal models that are used to investigate them.
BIOCHEMICAL ALTERATIONS IN SKELETAL MUSCLE
DURING PROLONGED INACTIVITY
Well-controlled studies, using both the tail suspension and
limb immobilization models of muscle inactivity, indicate that
disuse muscle atrophy occurs due to both an increase in
proteolysis and a decrease in muscle protein synthesis (13, 82).
For example, a study using the hindlimb suspension model of
muscle atrophy reported that the rate of protein synthesis
declines quickly after the onset of muscle unloading (82). This
decrease in muscle protein synthesis reaches a new “lower”
steady-state rate of protein synthesis at ⬃48 h (82). Furthermore, this disuse-induced decrease in muscle protein synthesis
is followed by a large increase in muscle protein degradation.
Hence, reduced activity of skeletal muscle results in a net loss
of total muscle protein due to both a decrease in protein
synthesis and an increase in proteolysis.
Similar to studies using locomotor skeletal muscle, recent
studies indicate that mechanical ventilation-induced diaphragmatic atrophy is a result of both elevated proteolysis and
decreased protein synthesis (19, 73, 74). However, during
prolonged mechanical ventilation, the time course of disuseinduced proteolysis in the diaphragm is more rapid than the
rate of protein breakdown observed in limb muscles exposed to
PATHWAYS RESPONSIBLE FOR MYONUCLEAR APOPTOSIS
Myonuclear apoptosis can be induced by three overlapping
pathways: 1) sarcoplasmic (endoplasmic) reticulum (SR), 2)
receptor mediated, or 3) mitochondrial. Each of these apoptotic
pathways can trigger the activation of a unique group of
proteases called “caspases.” To date, over 14 different caspases
have been identified in mammalian cells (66). Collectively,
caspases are endoproteases responsible for the final execution
of cell death or nuclear destruction. In the cell, caspases are
expressed as inactive precursors (i.e., procaspases), which
activate on cleavage, resulting in a series of events leading to
Fig. 2. Alterations in myonuclear number
during skeletal muscle hypertrophy and atrophy. Note that during hypertrophy or disuse
atrophy, myonuclear number is altered in
conjunction with changes in myofibrillar protein content and myofiber cross-sectional
area (CSA), resulting in a constant ratio of
cytoplasmic area to nuclear number (myonuclear domain).
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maintain alveolar ventilation in patients incapable of sustaining
adequate ventilation. Common applications for mechanical
ventilation in medicine include respiratory failure, sepsis, drug
overdose, spinal cord injury, and surgery (34). Numerous
human and animal studies have reported that prolonged mechanical ventilation results in a rapid onset of diaphragmatic
fiber atrophy (25, 54, 56, 75).
periods of unloading. In fact, it would take at least 96 h to
achieve the same level of atrophy in locomotor muscle unloaded by hindlimb suspension as observed in the diaphragm
following 12 h of mechanical ventilation (61, 82). In addition,
the rate of mechanical ventilation-induced atrophy also exceeds that reported in the diaphragm with denervation (26),
spinal cord hemisection (91), and corticosteroid administration
(87). These facts suggest that the signaling associated with
myofiber atrophy during mechanical ventilation may involve
different or accelerated mechanisms compared with other models of muscle atrophy.
Moreover, it is now clear that muscular dystrophy (72)-,
denervation (14)-, aging (20, 78)-, hindlimb unloading (4, 5,
22)-, and mechanical ventilation (61)-induced disuse muscle
atrophy are associated with a loss of myonuclei, and growing
evidence indicates that the loss is due to a form of apoptosis
called “myonuclear apoptosis” (3, 4, 71). Apoptosis is a highly
regulated form of programmed cell death that is characterized
by specific morphological and biochemical events (55, 66).
Recently it has been reported that a loss of myonuclei via
apoptotic pathways can occur without cell death in multinucleated muscle fibers during disuse muscle atrophy (4, 66, 71).
The loss of nuclei within atrophying muscle fibers appears to
be a strategy to maintain a constant ratio of nuclei per fiber area
(4, 71). It has been postulated that this constant ratio of nuclei
to fiber area (i.e., myonuclear domain) within skeletal muscle
is intended to maintain an optimal nuclear-to-cytoplasm ratio
such that nuclei are added to muscle fibers during growth and
nuclei are lost during atrophy (Fig. 2; Refs. 4, 71).
Identical to locomotor skeletal muscle, our laboratory recently discovered that unloading the diaphragm during prolonged mechanical ventilation results in caspase-3 activation
and myonuclear apoptosis (61). The pathways responsible for
this disuse-induced myonuclear apoptosis are a hot topic of
debate and potential candidate pathways will be outlined in the
next segment.
Invited Review
OXIDATIVE STRESS AND DISUSE MUSCLE ATROPHY
a ligand to one or more extracellular receptors. These ligandreceptor complexes transmit their signals via a series of protein-protein interactions (66). The tumor necrosis factor receptor super family is a critical trans-membrane receptor class that
binds both the cytokine tumor necrosis factor-␣ (TNF-␣) and
Fas Ligand (a transmembrane protein on cytotoxic T lymphocytes and other immune cells; Ref. 52). Receptor-mediated
apoptotic pathways can be initiated by ligand-induced (e.g.,
TNF-␣) binding, leading to the activation of caspase-8 and -10,
promoting the activation of caspase-3 and subsequent damage
to genomic DNA (66).
Mitochondrial-mediated apoptosis. The mitochondrial pathway of apoptosis can be initiated via various signals, including
ROS (i.e., oxidative stress) and high levels of cellular calcium.
These factors can induce opening of the mitochondrial permeability transition pore and promote the release of cytochrome c
from the mitochondria into the cytosol (Fig. 3; Ref. 66). In the
cytosol, cytochrome c triggers a signaling pathway leading to
the activation of caspase-9 and subsequently promoting
caspase-3-mediated nuclear DNA fragmentation. Independent
of caspase activation, mitochondrial release of apoptosis-inducing factor (AIF) or endonuclease G (Endo G) can also
induce nuclear DNA fragmentation in atrophying skeletal muscle (22, 66).
In general, the release of mitochondrial apoptotic factors
into the cytoplasm is regulated by the Bcl-2 family of apoptotic
regulators (17, 24, 66). Within this family, several pro-apoptotic (e.g., Bax, Bid, PUMA, etc.) and anti-apoptotic (e.g.,
Bcl-2, Bcl-XL, etc.) members exist (66). For example, Bcl-2
protects the mitochondria against the release of pro-apoptotic
molecules, whereas Bax (Bcl2-associated X-protein) and Bid
facilitate apoptosis by contributing to the opening of the
mitochondrial permeability transition pore, resulting in the
release of cytochrome c and AIF (24, 66). Interestingly, Bcl-2
and Bax influence each other’s function such that the relative
Fig. 3. Pathways involved in myonuclear apoptosis in atrophying skeletal muscle. Apoptosis
can be initiated by receptor signaling, sarcoplasmic reticulum (SR), and/or mitochondrialregulated pathways in skeletal muscle. Ligand
receptor (FAS/TNF) binding results in
caspase-3 dependent DNA fragmentation
and/or myofilament release. Reactive oxygen
species (ROS) dysregulation of sarcoplasmic
reticulum calcium (Ca) handling results in
caspase-7 and calpain activation. ROS also
acts on the mitochondria to influence the
opening of the mitochondrial permeability
transition pore to release cytochrome c (Cyt
C). Independent of caspase activity, mitochondrial endonuclease G (Endo G), and/or
apoptosis inducing factor (AIF) are also capable of inducing DNA fragmentation in skeletal
muscle. Note the multiple lines of cross talk
between pathways.
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apoptosis. An illustration of the three primary apoptotic pathways along with selected caspases and pro/anti-apoptotic proteins is presented in Fig. 3.
SR stress-induced apoptosis. The SR-mediated pathway of
apoptosis is activated via SR stress, resulting in calcium release
leading to activation of caspase-12 (due to either caspase-7 or
calpain activation). Activation of caspase-12 can then lead to
activation of caspase-3 (Fig. 3). Activated caspase-3 then
translocates to the nucleus where it cleaves and deactivates
“inhibitor of caspase-activated DNase” (66). This liberates
caspase-activated DNase, an endonuclease, to fracture genomic
DNA, leading to one of the most important morphological
events of apoptosis (i.e., DNA fragmentation; Ref. 66). This
apoptotic DNA fragmentation can be identified via histological
techniques, including fluorescent labeling of damaged DNA
via probes for single-stranded DNA or terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)
or electrophoretic procedures to reveal DNA fragmentation
(i.e., DNA laddering).
Note that increases in cytosolic calcium due to SR stress can
also promote apoptosis via activation of calpain. Calciummediated activation of calpain has been postulated to contribute to apoptosis in several ways. For example, calpain can
cleave the Bcl2 (B-cell CLL/lymphoma-2) family member Bid
(BH3 interacting domain death agonist), to an active pro-apoptotic molecule, tBid (truncated Bid). tBid promotes the formation of the mitochondrial permeability transition pore and
cytochrome c release from the mitochondria, leading to nuclear
apoptosis (15). Moreover, it has been reported that calpain
cleaves a variety of other proteins to promote apoptosis (15).
Hence it is possible that calpain activation is an important
stimulus to promote myonuclear apoptosis in skeletal muscle
during prolonged periods of unloading.
Receptor-mediated apoptosis. A widely studied pathway
leading to apoptosis is the corridor induced by the binding of
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concentration of these two proteins may determine whether the
cell undergoes apoptosis when faced with stimuli such as
oxidative stress or calcium overload (24, 66).
PROTEOLYTIC PATHWAYS IN SKELETAL MUSCLE
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Numerous proteolytic systems contribute to the degradation
of muscle proteins. The principal proteases in skeletal muscle
can be classified into three major categories: 1) lysosomal
proteases, 2) Ca2⫹-activated proteases (i.e., calpain), and 3) the
proteasome system. Furthermore, recent evidence reveals that
another protease, caspase-3, may also contribute to select
forms of muscle atrophy (21, 61). A brief overview of each of
these major proteolytic systems follows.
Lysosomal proteases. Lysosomes are a component of the
degradative machinery in many mammalian cells. Lysosomes
are membrane-bound vesicles containing acid hydrolases that
include proteases, glycosidases, lipases, and phosphatases (8).
Therefore, lysosomes are intracellular compartments dedicated
to the degradation of macromolecules.
The four major lysosomal proteases are cathepsins L, B, D,
and H (8, 79). Although these cathepsins are ubiquitously
expressed in all tissues, the concentrations of cathepsins in
cells vary, with the greatest levels found in tissues containing
inherently high rates of protein turnover (i.e., kidney, liver, and
spleen), whereas tissues with slow protein turnover (i.e., skeletal muscle) possess much lower levels (8). Moreover, cathepsin levels differ between skeletal muscle fiber types. Type I
(slow, oxidative) fibers exhibit higher levels of cathepsins
compared with type IIb (fast, glycolytic) fibers (8).
Although some debate continues, it is generally agreed that
lysosomal protease activity increases in disuse muscle atrophy
(8, 27, 79, 85). For instance, work by Taillandier et al. (79)
indicates that 9 days of hindlimb suspension promoted a 2.5-fold
increase in lysosomal protease activity in rat soleus muscle. In an
effort to determine the quantitative contribution of cathepsins to
muscle atrophy, these investigators inhibited cathepsin activity
during periods of muscle disuse and evaluated the rate of muscle
atrophy. Their results revealed that inhibition of cathepsin activity
resulted in only a small decrease (⬍18%) of the loss of muscle
protein associated with disuse muscle atrophy. Furthermore, because lysosomal proteases are not involved in the degradation of
myofibrillar proteins, it seems unlikely that cathepsins play a
dominant role in the proteolysis associated with inactivity in
skeletal muscles (79).
Calpain-mediated proteolysis. Calpains are Ca2⫹-dependent
cysteine proteases that are found in all vertebrate cells (28).
Although numerous members of the calpain family of proteases exist, the two best-characterized calpains found in skeletal muscle are termed ␮-calpain and m-calpain and refer to
micromolar and millimolar amounts of calcium required to
activate each respective calpain isoform (28). Although
calpains are not at present known to directly degrade the
contractile proteins actin and myosin, they participate in
sarcomeric protein release by cleaving cytoskeletal proteins
(e.g., titin, nebulin) that anchor contractile elements (43,
67). Moreover, calpain is known to degrade several kinases
and phosphatases, including calcium/calmodulin-dependent
kinase (CaM kinase II), protein kinase C (PKC-␣, PKC-␤I,
PKC-␤II, and PKC-␥), and calcineurin (28, 32, 81).
In vivo calpain activity is regulated by several factors
including cytosolic calcium levels and the concentration of the
endogenous calpain inhibitor, calpastatin (28). More specifically, calpain activity is increased by a sustained elevation in
free calcium in the cytosol and/or a decrease in cytosolic
calpastatin levels (28). In regard to calpain’s contribution to
disuse muscle atrophy, it is clear that skeletal muscle inactivity
is associated with an increase in both cytosolic calcium levels
and calpain activity (51). Although the mechanism responsible
for this inactivity-mediated calcium overload is unknown, it is
possible that intracellular production of ROS could play a key
role in disturbances in calcium homeostasis (42). A potential
biochemical mechanism to link oxidative stress with calcium
overload is that ROS-mediated formation of reactive aldehydes
(i.e., 4-hydroxy-2,3-trans-nonenal) can inhibit plasma membrane Ca2⫹-ATPase activity (77). Hence, an oxidative stressinduced decrease in membrane Ca2⫹-ATPase activity would
impede Ca2⫹ removal from the cell and promote intracellular
Ca2⫹ accumulation. Nonetheless, it is currently unknown as to
whether this mechanism is the single explanation for inactivitymediated calcium overload in muscle.
Caspase-3 and muscle atrophy. Recent evidence suggests
that the protease caspase-3 contributes to protein degradation
and muscle atrophy (21, 61). In this regard, caspase-3 activation promotes degradation of actomyosin complexes, and inhibition of caspase-3 activity suppresses the overall rate of
proteolysis in diabetes-mediated cachexia and myofiber atrophy in mechanical ventilation disuse (21, 61).
As discussed previously, control of caspase-3 activity in the
cell is complex and involves numerous interconnected signaling pathways. In the case of diabetes-induced muscle atrophy,
it seems possible that caspase-3 is activated by caspase-12 (via
a calcium release pathway) and/or activation of caspase-9 (via
a mitochondrial pathway). A potential interaction between
these caspase-3 activation pathways is that both of these can be
activated by ROS (Fig. 3; Ref. 66).
Moreover, note that calpastatin is a substrate for both
caspase-3 and calpain. It follows that increases in caspase-3 or
calpain activity lower calpastatin levels in cells and promote
calpain activation (21, 28, 88). Furthermore, increased calpain
activity can lead to the activation of caspase-3 (15). Therefore,
cross-talk between the calpain and caspase-3 proteolytic systems could play a role in the regulation of myofilament release
in skeletal muscle during periods of disuse.
The proteolytic release of myofilaments during disuse muscle atrophy is important because the bulk of muscle proteins
(50 –70%) exist in actomyosin complexes (84). Although the
proteasome system can degrade monomeric contractile proteins (i.e., actin and myosin), it is unable to break down intact
actomyosin complexes (28). Hence, myofilaments must be
released from the sarcomere as monomeric proteins prior to
degradation by the proteasome system (84, 89). This fact
dictates that the release of myofilaments is potentially the
rate-limiting step in muscle protein degradation. Again, evidence reveals that both calpain and caspase-3 are capable of
producing actomyosin disassociation (21, 28, 84). Hence, activation of one or both of these proteases is a requirement for
proteolytic degradation of myofilaments during conditions that
result in muscle atrophy.
Proteasome-mediated proteolysis. The total proteasome
complex (26S) is comprised of a core proteasome subunit
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OXIDATIVE STRESS AND DISUSE MUSCLE ATROPHY
PRODUCTION OF ROS IN QUIESCENT SKELETAL MUSCLES
It is now clear that ROS are produced in both inactive and
contracting skeletal muscles (44, 69). When ROS production in
cells exceeds the antioxidant capacity to eliminate these oxidants, oxidative stress occurs. A pro-oxidant state in cells can
alter the structure and function of proteins, lipids, and nucleic
acids, resulting in cellular injury and, in extreme circumstances, cell death.
Until the early 1990s it was widely believed that ROS
production was limited in noncontracting skeletal muscle and
that oxidative injury does not occur in inactive muscles. However, many studies indicate that oxidative injury occurs during
periods of disuse in locomotor skeletal muscles (45, 47–50, 53)
and in the unloaded diaphragm during prolonged mechanical
ventilation (23, 75, 90). It is currently unknown which ROS
producing pathways are dominant contributors to inactivityinduced oxidative injury in skeletal muscles. Indeed, it is
possible that oxidative stress in inactive skeletal muscle may be
due to the interaction of several major oxidant production
pathways, including xanthine oxidase production of superoxide, nitric oxide synthase production of nitric oxide, NADPH
oxidase-mediated production of superoxide, and mitochondrial
production of superoxide (7, 23, 37, 38, 50, 86; Fig. 4).
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Fig. 4. Simplified diagram illustrating pathways capable of producing superoxide (O䡠2) and nitric oxide (NO䡠) in skeletal muscle during periods of disuse.
Candidates for the production of reactive oxygen include NADPH oxidase,
xanthine oxidase, and muscle mitochondria. Nitric oxide is likely produced by
skeletal muscle nitric oxide synthase.
WHAT INTRACELLULAR SIGNALING PATHWAYS LINK
OXIDATIVE STRESS TO MUSCLE ATROPHY?
Recent studies reveal that ROS species can serve as second
messengers in cellular signal transduction pathways that regulate both normal physiological signaling and pathological signaling leading to proteolysis and cell death via apoptosis. This
seemingly contradictory signaling function of ROS is presumably linked to the level of ROS and the overall redox state in
the cell. That is, low levels of ROS promote cell adaptation and
survival, whereas high levels of ROS modulate signaling
pathways that lead to proteolysis and cell death.
Abundant research demonstrates that oxidative stress contributes to disuse muscle atrophy. The first evidence that
oxidants played a key signaling role in the regulation of disuse
muscle atrophy was provided by Kondo et al. (46). The
pioneering work of Kondo and colleagues revealed that immobilization of skeletal muscles is associated with increased
radical production, resulting in oxidative injury in inactive
muscle fibers (46, 47, 50). Importantly, this work also demonstrated that disuse muscle atrophy could be delayed by exogenous antioxidants. These early observations have subsequently been confirmed by others (6, 9, 60).
How does inactivity-induced oxidative stress in skeletal
muscle contribute to muscle atrophy? At present, a complete
answer to this question is not available. Nonetheless, it appears
that oxidative stress could contribute to disuse muscle atrophy
by influencing one or more of the following cell signaling
pathways: 1) regulation of cytosolic calcium levels and subsequent activation of calpain (as previously discussed); 2) control
of mitogen activated protein kinase (MAPK) signaling; and
3) activation of the nuclear factor (NF)-␬B pathway. A brief
discussion of these possibilities follows.
OXIDATIVE STRESS ACTIVATES MAPK SIGNALING
The redox regulation of MAPK provides another potential
link between oxidative stress and skeletal muscle atrophy. It is
well established that MAPKs play a key role in cell signaling
because control of numerous cellular signaling pathways is
achieved via activation or deactivation of regulatory proteins
through phosphorylation (16). Indeed, the highly conserved
MAPK family is one of the major kinase families that regulate
the conversion of cell signals into cellular responses. These
protein kinases contribute to the regulation of life and death
decisions made in response to various stress signals (e.g.,
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(20S) coupled with a regulatory complex (19S) connected to
each end of the 20S core (30, 31, 33, 84). Interestingly,
proteins can be degraded by either the 26S proteasome or the
20S protease core.
The 26S proteasome degrades ubiquitinated proteins. It
follows that the 26S proteasome degradation pathway is only
active after ubiquitin covalently binds to protein substrates and
marks them for degradation. The binding of ubiquitin to
protein substrates is often a three-step process that initially
requires the ubiquitin-activating enzyme (E1). Following activation, the ubiquitination of specific proteins is provided by
one of a variety of E2s and by specialized E3s that recognize
specific protein substrates. In this regard, numerous studies
reveal that the ubiquitin-conjugating enzyme E214k is an important regulator of skeletal muscle ubiquitin-protein conjugation (58, 70, 80). Furthermore, E214k interacts with a specific
E3 ligase (i.e., E3␣) to promote muscle protein degradation in
catabolic states. In addition, other unique ubiquitin E3 ligases
(e.g., atrogin1/muscle atrophy F-box and muscle ring finger-1)
exist in skeletal muscle, and these ligases play essential roles in
skeletal muscle atrophy (10, 29, 70, 80).
The process of ubiquinated protein degradation requires a
coordinated effort of both the 19S regulatory complex and the
20S proteasome core. The 19S regulatory complex possesses
inherent ATPase activity and is a required participant in ATPdependent degradation of ubiquitinated proteins (18). The
ubiquitinated protein is recognized and bound by the 19S
regulators of the 26S proteasome, and energy from ATP
hydrolysis removes the polyubiquitin chain and unfolds the
substrate protein. The unfolded protein then enters the 20S core
proteasome and is degraded in a process that does not require
energy from ATP (31, 70). Also, note that evidence reveals that
the 20S core proteasome can degrade oxidized proteins without
ubiquitination (30, 31). Therefore, ROS-mediated oxidation of
proteins can promote muscle protein breakdown via 20S core
proteasome alone.
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stress, endotoxins, and oxidative stress (64). The link between
oxidative stress and p38 activation occurs via apoptosis stimulating kinase 1 (ASK1; Ref. 59). ASK1 is a ubiquitously
expressed member of the MAPK family that activates both p38
and JNK by phosphorylating and activating respective MAPK
kinases (Fig. 5). Five isoforms of p38 have been identified:
p38␣, p38␤, p38␤2, p38␥, and p38␦ and expression of these
isoforms varies among tissues (16). For example, p38␣ is
highly expressed in bone morrow and leukocytes, p38␤ is
expressed in heart and brain, and p38␥ is predominantly
expressed in skeletal muscle (16).
Among the phosphorylation targets of p38 are several important transcription factors, including p53, NF-␬B, and ATF2.
Of particular importance to apoptosis is the fact that activation
of the tumor suppressor protein p53 results in the expression of
the pro-apoptosis protein Bax. Moreover, p38 signaling has
been shown to promote the expression of atrogin 1 in myotubes
(57). Collectively, these data suggest a potential role for
oxidative stress-induced activation of p38 in disuse muscle
atrophy.
JNK. JNK (also known as stress-induced kinase) has three
isoforms (JNK1, JNK2, JNK3) that are encoded by three different
genes. JNK1 and JNK2 are ubiquitously expressed, whereas
JNK3 is only expressed in brain, heart, and testis (16). JNK can be
activated in response to many of the same stimuli that activate
p38, such as osmotic stress, endotoxins, and oxidative stress.
Moreover, similar to p38, oxidative stress-induced activation of
JNK occurs via the ASK1 pathway (Fig. 5; Ref. 76).
The specific molecular targets of JNK include the transcriptional factors AP-1, p53, and c-Myc and many other nontranscriptional factors such as Bcl-2 family members. In this
regard, there is growing evidence that JNK plays an important
role in oxidative stress-mediated apoptosis. Indeed, because
ROS themselves are not able to activate caspases, ROSmediated apoptosis requires another death-signaling pathway
Fig. 5. Simplified overview of ROS signaling
pathways leading to activation of mitogen activated protein kinases in skeletal muscle.
Skeletal muscle cytosolic or mitochondrial
ROS activates apoptosis-stimulating kinase 1
(ASK1) stimulating phosphorylation (p) of jun
NH2-terminal kinase (JNK) and/or p38 regulation of myonuclear apoptosis-associated transcription factors (AP1, p53, c-Myc, NF␬B).
JNK/p38 activation by ASK1 can lead to cytochrome c release and caspase-3 activation. In
contrast, low levels of ROS (dashed lines) can
result in the phosphorylation of the extracellular regulated kinases 1 and 2 (ERK 1/2), which
functions in cellular survival. mtPTP, mitochondrial permeability transition pore.
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oxidative stress), as the actions of both pro- and antiapoptotic
factors are often regulated by the phosphorylation status of key
elements in the execution of apoptosis or survival (59).
All eurkaryotic cells possess multiple MAPK pathways. The
three best characterized MAPK subfamilies are c-Jun NH2terminal kinase (JNK), p38 MAPK, and extracellular signalregulated kinase (ERK; Ref. 64). All three of these MAPK
pathways are structurally similar, but functionally distinct.
Importantly, ERK, JNK, and p38 have all been shown to be
activated by oxidative stress and could potentially participate
in pathways influencing muscle protein breakdown or myonuclear apoptosis. The classic MAPK activation cascade consists of three sequential intracellular protein kinase activation
steps leading to the activation of numerous protein kinases,
nuclear proteins, and transcription factors, resulting in downstream signal transduction (16, 64). A brief overview of the
functions of ERK, p38, and JNK follows.
ERK1/2. The first identified and best studied MAPK cascade
is the ERK pathway (16). ERK is composed of two isoforms,
ERK1 and ERK2, and are collectively referred to as ERK1/2
(16, 64). ERK1/2 can be activated by a number of mitogens,
including epidermal growth factor, platelet-derived growth
factor, transforming growth factor, and insulin. In addition,
ERK1/2 can be activated by endotoxin and oxidative stress
(16). The activation of ERK1/2 by oxidative stress is consistent
with the hypothesis that low and adequate levels of ROS are
mitogenic (64, 68). Activation of ERK1/2 regulates the transcriptional activity of AP-1, NF-␬B, c-Myc, and the cell
survival protein Bcl-2 (68). Although it has been reported that
ERK1/2 can promote apoptosis, ERK1/2 can also function as
an anti-apoptotic factor following oxidative stress (64). To
date, however, there is little evidence to link ERK1/2 activation
with disuse muscle atrophy.
p38. p38 is an important MAPK member that is activated in
response to various physiological stresses such as osmotic
Invited Review
OXIDATIVE STRESS AND DISUSE MUSCLE ATROPHY
REDOX REGULATION OF NF-␬B SIGNALING
Another potential link between oxidative and muscle disuse
atrophy involves the redox regulation of the NF-␬B family of
transcriptional activators. NF-␬B comprises a family of five
transcription factors (p65, Rel B, c-rel, p52, and p50) and,
when activated, can promote a wide range of cellular outcomes
depending on the cell type (reviewed in Refs. 36, 41, 42). All
five of the NF-␬B family members are expressed in skeletal
muscle and Hunter et al. (35) first reported that skeletal muscle
inactivity leads to increased NF-␬B transcriptional activity.
Since this discovery in 2002, accumulating evidence indicates
that a specific NF-␬B pathway is required for disuse muscle
atrophy (reviewed in Refs. 36, 41). Nonetheless, although
NF-␬B regulates the expression of over 100 genes, a detailed
understanding of the specific NF-␬B targets required for disuse
muscle atrophy remains incomplete.
Although it has long been believed that NF-␬B activation is
under redox control, how ROS regulate NF-␬B transcriptional
activity remains contentious. For example, ROS are known to
enhance the signal transduction pathways (e.g., activation of
kinases) that promote both NF-␬B activation in the cytoplasm
and translocation to the nucleus (40, 62). This observation is
consistent with the concept that ROS can promote NF-␬B
activation and subsequent gene expression. In contrast, the
DNA binding activity of oxidized NF-␬B is diminished, suggesting that ROS may also inhibit NF-␬B transcriptional activity (40). Therefore, although NF-␬B was once considered to
be a prototypic redox sensitive transcription factor, the fact that
ROS can both promote and inhibit NF-␬B transcriptional
activation has lead to considerable debate regarding the redox
control of NF-␬B signaling (62). Clearly, future research will
be required to unravel the uncertainties about the redox regulation of NF-␬B in physiologically relevant settings in skeletal
muscle during prolonged periods of inactivity.
J Appl Physiol • VOL
CONCLUSIONS AND UNANSWERED QUESTIONS
Inactivity-induced skeletal muscle atrophy can occur due to
a variety of conditions, including prolonged bed rest, limb
immobilization, and spaceflight. Several lines of evidence
directly link ROS to disuse muscle atrophy via ROS-mediated
regulation of proteolysis. Importantly, several studies suggest
that antioxidants can serve as therapeutic agents in delaying the
rate of disuse muscle atrophy.
Although it is clear that ROS-mediated signaling contributes
to disuse muscle atrophy, numerous unanswered questions
remain. For example, does the role that ROS play in muscle
atrophy differ between different models of skeletal muscle
inactivity (e.g., immobilization vs. microgravity)? Another key
question is “which ROS pathways are active in unloaded
skeletal muscle”? Moreover, “if multiple oxidant production
pathways are active, what is the relative contribution of each
pathway to the regulation of cell signaling pathways involved
in disuse muscle atrophy”? Resolution of these issues will
provide the information needed to develop therapeutic strategies to prevent oxidant production or scavenge ROS to prevent
oxidative injury in the muscle fiber during prolonged periods of
inactivity.
Is the production of ROS a requirement for disuse muscle
atrophy or does oxidative stress merely regulate the rate of
muscle atrophy? A related question is, “do ROS simply act as
second messengers to control muscle atrophy or is ROSmediated oxidative injury a requirement for oxidant regulation
of muscle atrophy”? Both of these questions are important and
unresolved.
Another unresolved question is “does oxidative stress negatively influence the rate of protein synthesis in skeletal muscle
during periods of inactivity”? To date, the majority of previous
research related to ROS and muscle atrophy has focused on
proteolysis, and it is unclear if ROS contribute to the downregulation of protein synthesis that occurs during disuse in skeletal
muscle; hence, this is an interesting area for future work. In this
regard, emerging evidence reveals that oxidative stress can inhibit
protein synthesis in several cell types (2, 63, 65).
A final area for future research relates to the pathways
responsible for myonuclear apoptosis in skeletal muscle. As
discussed earlier, disuse muscle atrophy is associated with a
loss of myonuclei from muscle fibers due to myonuclear
apoptosis (3, 71). Although it is well known that ROS can
contribute to signaling pathways, leading to apoptosis, it is
unknown if ROS represent the primary signal to promote
myonuclear apoptosis in atrophying skeletal muscle (55, 66).
Hopefully, questions outlined in this review stimulate muscle
biologists to pursue research in the area of ROS and skeletal
muscle atrophy. Future scientific advances in cell signaling
will provide the tools required to answer these important
questions that will ultimately result in therapeutic approaches
to prevent or diminish disuse muscle atrophy.
GRANTS
Our work in this research area has been supported by National Heart, Lung,
and Blood Institute Grants R01-HL-62361 and R01-HL-072789.
REFERENCES
1. Adams GR, Caiozzo VJ, Baldwin KM. Skeletal muscle unweighting:
spaceflight and ground-based models. J Appl Physiol 95: 2185–2201,
2003.
102 • JUNE 2007 •
www.jap.org
Downloaded from http://jap.physiology.org/ by 10.220.33.6 on June 16, 2017
such as JNK (59, 76). Preliminary evidence implicating JNK as
a mediator of ROS-induced apoptosis can be summarized in
three observations. First, JNK is readily activated in cells by
exposure to physiological levels of ROS (59, 76). Secondly, in
ASK1⫺/⫺ cells, JNK is not activated in response to ROS and
ASK⫺/⫺ cells are resistant to ROS-mediated apoptosis, although the role of p38 could not be eliminated (76). Finally,
overexpression of a dominant negative mutant of JNK provides
some resistance to ROS-induced apoptosis (76). Collectively,
these findings support a link between ROS, JNK, and apoptosis. However, it is currently unknown if JNK activation is
responsible for the myonuclear apoptosis that occurs during
disuse muscle atrophy.
MAPK cross talk. While each member of the MAPK super
family is considered unique, each member forms only a part of the
complex and interactive network of phosphorylation signaling
pathways (16). Indeed, each member of the MAPK cascade shares
communication with a number of upstream and downstream
kinases along with transcription factors that interact and integrate
these different pathways. Therefore, this redundancy results in a
complex cross-talk and signal convergence among MAPK family
members. Moreover, each MAPK family member has feedback
loops that impact their activation and regulate the activation of
other MAPK family members (16).
2395
Invited Review
2396
OXIDATIVE STRESS AND DISUSE MUSCLE ATROPHY
J Appl Physiol • VOL
26. Geiger PC, Bailey JP, Zhan WZ, Mantilla CB, Sieck GC. Denervationinduced changes in myosin heavy chain expression in the rat diaphragm
muscle. J Appl Physiol 95: 611– 619, 2003.
27. Goldspink DF, Morton AJ, Loughna P, Goldspink G. The effect of
hypokinesia and hypodynamia on protein turnover and the growth of four
skeletal muscles of the rat. Pflügers Arch 407: 333–340, 1986.
28. Goll DE, Thompson VF, Li H, Wei W, Cong J. The calpain system.
Physiol Rev 83: 731– 801, 2003.
29. Gomes MD, Lecker SH, Jagoe RT, Navon A, Goldberg AL. Atrogin-1,
a muscle-specific F-box protein highly expressed during muscle atrophy.
Proc Natl Acad Sci USA 98: 14440 –14445, 2001.
30. Grune T, Davies KJ. The proteasomal system and HNE-modified proteins. Mol Aspects Med 24: 195–204, 2003.
31. Grune T, Merker K, Sandig G, Davies KJ. Selective degradation of
oxidatively modified protein substrates by the proteasome. Biochem Biophys Res Commun 305: 709 –718, 2003.
32. Hajimohammadreza I, Raser KJ, Nath R, Nadimpalli R, Scott M,
Wang KK. Neuronal nitric oxide synthase and calmodulin-dependent
protein kinase IIalpha undergo neurotoxin-induced proteolysis. J Neurochem 69: 1006 –1013, 1997.
33. Hasselgren PO, Fischer JE. The ubiquitin-proteasome pathway: review
of a novel intracellular mechanism of muscle protein breakdown during
sepsis and other catabolic conditions. Ann Surg 225: 307–316, 1997.
34. Hess DaRK. Essentials of Mechanical Ventilation. New York: McGrawHill, 1996.
35. Hunter RB, Stevenson E, Koncarevic A, Mitchell-Felton H, Essig DA,
Kandarian SC. Activation of an alternative NF-␬B pathway in skeletal
muscle during disuse atrophy. FASEB J 16: 529 –538, 2002.
36. Jackman RW, Kandarian SC. The molecular basis of skeletal muscle
atrophy. Am J Physiol Cell Physiol 287: C834 –C843, 2004.
37. Jackson MJ. Reactive oxygen species and redox-regulation of skeletal
muscle adaptations to exercise. Philos Trans R Soc Lond B Biol Sci 360:
2285–2291, 2005.
38. Jackson MJ, Papa S, Bolanos J, Bruckdorfer R, Carlsen H, Elliott
RM, Flier J, Griffiths HR, Heales S, Holst B, Lorusso M, Lund E,
Oivind Moskaug J, Moser U, Di Paola M, Polidori MC, Signorile A,
Stahl W, Vina-Ribes J, Astley SB. Antioxidants, reactive oxygen and
nitrogen species, gene induction and mitochondrial function. Mol Aspects
Med 23: 209 –285, 2002.
39. Jagoe RT, Goldberg AL. What do we really know about the ubiquitinproteasome pathway in muscle atrophy? Curr Opin Clin Nutr Metab Care
4: 183–190, 2001.
40. Kabe Y, Ando K, Hirao S, Yoshida M, Handa H. Redox regulation of
NF-␬B activation: distinct redox regulation between the cytoplasm and the
nucleus. Antioxid Redox Signal 7: 395– 403, 2005.
41. Kandarian SC, Jackman RW. Intracellular signaling during skeletal
muscle atrophy. Muscle Nerve 33: 155–165, 2006.
42. Kandarian SC, Stevenson EJ. Molecular events in skeletal muscle
during disuse atrophy. Exerc Sport Sci Rev 30: 111–116, 2002.
43. Koh TJ, Tidball JG. Nitric oxide inhibits calpain-mediated proteolysis of
talin in skeletal muscle cells. Am J Physiol Cell Physiol 279: C806 –C812,
2000.
44. Kondo H. Oxidative stress in skeletal muscle atrophy. In: Handbook of
Oxidants and Antioxidants in Exercise, edited by Sen C, Packer L, and
Hanninen O. Amsterdam: Elsevier, 2000, p. 631– 653.
45. Kondo H, Miura M, Itokawa Y. Antioxidant enzyme systems in skeletal
muscle atrophied by immobilization. Pflügers Arch 422: 404 – 406, 1993.
46. Kondo H, Miura M, Itokawa Y. Oxidative stress in skeletal muscle
atrophied by immobilization. Acta Physiol Scand 142: 527–528, 1991.
47. Kondo H, Miura M, Kodama J, Ahmed SM, Itokawa Y. Role of iron
in oxidative stress in skeletal muscle atrophied by immobilization.
Pflügers Arch 421: 295–297, 1992.
48. Kondo H, Miura M, Nakagaki I, Sasaki S, Itokawa Y. Trace element
movement and oxidative stress in skeletal muscle atrophied by immobilization. Am J Physiol Endocrinol Metab 262: E583–E590, 1992.
49. Kondo H, Nakagaki I, Sasaki S, Hori S, Itokawa Y. Mechanism of
oxidative stress in skeletal muscle atrophied by immobilization. Am J
Physiol Endocrinol Metab 265: E839 –E844, 1993.
50. Kondo H, Nishino K, Itokawa Y. Hydroxyl radical generation in skeletal
muscle atrophied by immobilization. FEBS Lett 349: 169 –172, 1994.
51. Kourie JI. Interaction of reactive oxygen species with ion transport
mechanisms. Am J Physiol Cell Physiol 275: C1–C24, 1998.
52. Krammer PH. CD95’s deadly mission in the immune system. Nature
407: 789 –795, 2000.
102 • JUNE 2007 •
www.jap.org
Downloaded from http://jap.physiology.org/ by 10.220.33.6 on June 16, 2017
2. Alirezaei M, Marin P, Nairn AC, Glowinski J, Premont J. Inhibition of
protein synthesis in cortical neurons during exposure to hydrogen peroxide. J Neurochem 76: 1080 –1088, 2001.
3. Allen DL, Linderman JK, Roy RR, Bigbee AJ, Grindeland RE,
Mukku V, Edgerton VR. Apoptosis: a mechanism contributing to remodeling of skeletal muscle in response to hindlimb unweighting. Am J
Physiol Cell Physiol 273: C579 –C587, 1997.
4. Allen DL, Roy RR, Edgerton VR. Myonuclear domains in muscle
adaptation and disease. Muscle Nerve 22: 1350 –1360, 1999.
5. Allen DL, Yasui W, Tanaka T, Ohira Y, Nagaoka S, Sekiguchi C,
Hinds WE, Roy RR, Edgerton VR. Myonuclear number and myosin
heavy chain expression in rat soleus single muscle fibers after spaceflight.
J Appl Physiol 81: 145–151, 1996.
6. Appell HJ, Duarte JA, Soares JM. Supplementation of vitamin E may
attenuate skeletal muscle immobilization atrophy. Int J Sports Med 18:
157–160, 1997.
7. Bailey DM, Davies B, Young IS, Jackson MJ, Davison GW, Isaacson
R, Richardson RS. EPR spectroscopic detection of free radical outflow
from an isolated muscle bed in exercising humans. J Appl Physiol 94:
1714 –1718, 2003.
8. Bechet D, Tassa A, Taillandier D, Combaret L, Attaix D. Lysosomal
proteolysis in skeletal muscle. Int J Biochem Cell Biol 37: 2098 –2114,
2005.
9. Betters JL, Criswell DS, Shanely RA, Van Gammeren D, Falk D,
Deruisseau KC, Deering M, Yimlamai T, Powers SK. Trolox attenuates
mechanical ventilation-induced diaphragmatic dysfunction and proteolysis. Am J Respir Crit Care Med 170: 1179 –1184, 2004.
10. Bodine SC, Latres E, Baumhueter S, Lai VK, Nunez L, Clarke BA,
Poueymirou WT, Panaro FJ, Na E, Dharmarajan K, Pan ZQ, Valenzuela DM, DeChiara TM, Stitt TN, Yancopoulos GD, Glass DJ.
Identification of ubiquitin ligases required for skeletal muscle atrophy.
Science 294: 1704 –1708, 2001.
11. Booth FW. Effect of limb immobilization on skeletal muscle. J Appl
Physiol 52: 1113–1118, 1982.
12. Booth FW, Criswell DS. Molecular events underlying skeletal muscle
atrophy and the development of effective countermeasures. Int J Sports
Med18, Suppl 4: S265–269, 1997.
13. Booth FW, Seider MJ. Early change in skeletal muscle protein synthesis
after limb immobilization of rats. J Appl Physiol 47: 974 –977, 1979.
14. Borisov AB, Carlson BM. Cell death in denervated skeletal muscle is
distinct from classical apoptosis. Anat Rec 258: 305–318, 2000.
15. Chen M, Won DJ, Krajewski S, Gottlieb RA. Calpain and mitochondria
in ischemia/reperfusion injury. J Biol Chem 277: 29181–29186, 2002.
16. Cuschieri J, Maier RV. Mitogen-activated protein kinase (MAPK). Crit
Care Med 33: S417– 419, 2005.
17. Dejean LM, Martinez-Caballero S, Manon S, Kinnally KW. Regulation of the mitochondrial apoptosis-induced channel, MAC, by BCL-2
family proteins. Biochim Biophys Acta 1762: 191–201, 2006.
18. DeMartino GN, Ordway GA. Ubiquitin-proteasome pathway of intracellular protein degradation: implications for muscle atrophy during unloading. Exerc Sport Sci Rev 26: 219 –252, 1998.
19. DeRuisseau KC, Kavazis AN, Deering MA, Falk DJ, Van Gammeren
D, Yimlamai T, Ordway GA, Powers SK. Mechanical ventilation
induces alterations of the ubiquitin-proteasome pathway in the diaphragm.
J Appl Physiol 98: 1314 –1321, 2005.
20. Dirks A, Leeuwenburgh C. Apoptosis in skeletal muscle with aging.
Am J Physiol Regul Integr Comp Physiol 282: R519 –R527, 2002.
21. Du J, Wang X, Miereles C, Bailey JL, Debigare R, Zheng B, Price SR,
Mitch WE. Activation of caspase-3 is an initial step triggering accelerated
muscle proteolysis in catabolic conditions. J Clin Invest 113: 115–123,
2004.
22. Dupont-Versteegden EE, Strotman BA, Gurley CM, Gaddy D, Knox
M, Fluckey JD, Peterson CA. Nuclear translocation of EndoG at the
initiation of disuse muscle atrophy and apoptosis is specific to myonuclei.
Am J Physiol Regul Integr Comp Physiol 291: R1730 –R1740, 2006.
23. Falk DJ, Deruisseau KC, Van Gammeren DL, Deering MA, Kavazis
AN, Powers SK. Mechanical ventilation promotes redox status alterations
in the diaphragm. J Appl Physiol 101: 1017–1024, 2006.
24. Garrido C, Galluzzi L, Brunet M, Puig PE, Didelot C, Kroemer G.
Mechanisms of cytochrome c release from mitochondria. Cell Death
Differ 13: 1423–1433, 2006.
25. Gayan-Ramirez G, de Paepe K, Cadot P, Decramer M. Detrimental
effects of short-term mechanical ventilation on diaphragm function and
IGF-I mRNA in rats. Intens Care Med 29: 825– 833, 2003.
Invited Review
OXIDATIVE STRESS AND DISUSE MUSCLE ATROPHY
J Appl Physiol • VOL
74. Shanely RA, Van Gammeren D, Deruisseau KC, Zergeroglu AM,
McKenzie MJ, Yarasheski KE, Powers SK. Mechanical ventilation
depresses protein synthesis in the rat diaphragm. Am J Respir Crit Care
Med 170: 994 –999, 2004.
75. Shanely RA, Zergeroglu MA, Lennon SL, Sugiura T, Yimlamai T,
Enns D, Belcastro A, Powers SK. Mechanical ventilation-induced diaphragmatic atrophy is associated with oxidative injury and increased
proteolytic activity. Am J Respir Crit Care Med 166: 1369 –1374, 2002.
76. Shen HM, Liu ZG. JNK signaling pathway is a key modulator in cell
death mediated by reactive oxygen and nitrogen species. Free Radic Biol
Med 40: 928 –939, 2006.
77. Siems W, Capuozzo E, Lucano A, Salerno C, Crifo C. High sensitivity
of plasma membrane ion transport ATPases from human neutrophils
towards 4-hydroxy-2,3-trans-nonenal. Life Sci 73: 2583–2590, 2003.
78. Strasser H, Tiefenthaler M, Steinlechner M, Eder I, Bartsch G,
Konwalinka G. Age dependent apoptosis and loss of rhabdosphincter
cells. J Urol 164: 1781–1785, 2000.
79. Taillandier D, Aurousseau E, Meynial-Denis D, Bechet D, Ferrara M,
Cottin P, Ducastaing A, Bigard X, Guezennec CY, Schmid HP,
Attaix D. Coordinate activation of lysosomal, Ca 2⫹-activated and
ATP-ubiquitin-dependent proteinases in the unweighted rat soleus muscle.
Biochem J 316: 65–72, 1996.
80. Taillandier D, Combaret L, Pouch MN, Samuels SE, Bechet D, Attaix
D. The role of ubiquitin-proteasome-dependent proteolysis in the remodelling of skeletal muscle. Proc Nutr Soc 63: 357–361, 2004.
81. Tallant EA, Brumley LM, Wallace RW. Activation of a calmodulindependent phosphatase by a Ca2⫹-dependent protease. Biochemistry 27:
2205–2211, 1988.
82. Thomason DB, Biggs RB, Booth FW. Protein metabolism and betamyosin heavy-chain mRNA in unweighted soleus muscle. Am J Physiol
Regul Integr Comp Physiol 257: R300 –R305, 1989.
83. Thomason DB, Booth FW. Atrophy of the soleus muscle by hindlimb
unweighting. J Appl Physiol 68: 1–12, 1990.
84. Tidball JG, Spencer MJ. Expression of a calpastatin transgene slows
muscle wasting and obviates changes in myosin isoform expression during
murine muscle disuse. J Physiol 545: 819 – 828, 2002.
85. Tischler ME, Rosenberg S, Satarug S, Henriksen EJ, Kirby CR, Tome
M, Chase P. Different mechanisms of increased proteolysis in atrophy
induced by denervation or unweighting of rat soleus muscle. Metabolism
39: 756 –763, 1990.
86. Van Gammeren D, Falk DJ, Deering MA, Deruisseau KC, Powers SK.
Diaphragmatic nitric oxide synthase is not induced during mechanical
ventilation. J Appl Physiol 102: 157–162, 2007.
87. Verheul AJ, Mantilla CB, Zhan WZ, Bernal M, Dekhuijzen PN, Sieck
GC. Influence of corticosteroids on myonuclear domain size in the rat
diaphragm muscle. J Appl Physiol 97: 1715–1722, 2004.
88. Wang KK, Posmantur R, Nadimpalli R, Nath R, Mohan P, Nixon RA,
Talanian RV, Keegan M, Herzog L, Allen H. Caspase-mediated fragmentation of calpain inhibitor protein calpastatin during apoptosis. Arch
Biochem Biophys 356: 187–196, 1998.
89. Wray CJ, Sun X, Gang GI, Hasselgren PO. Dantrolene downregulates
the gene expression and activity of the ubiquitin-proteasome proteolytic
pathway in septic skeletal muscle. J Surg Res 104: 82– 87, 2002.
90. Zergeroglu MA, McKenzie MJ, Shanely RA, Van Gammeren D,
DeRuisseau KC, Powers SK. Mechanical ventilation-induced oxidative
stress in the diaphragm. J Appl Physiol 95: 1116 –1124, 2003.
91. Zhan WZ, Miyata H, Prakash YS, Sieck GC. Metabolic and phenotypic
adaptations of diaphragm muscle fibers with inactivation. J Appl Physiol
82: 1145–1153, 1997.
102 • JUNE 2007 •
www.jap.org
Downloaded from http://jap.physiology.org/ by 10.220.33.6 on June 16, 2017
53. Lawler JM, Song W, Demaree SR. Hindlimb unloading increases
oxidative stress and disrupts antioxidant capacity in skeletal muscle. Free
Radic Biol Med 35: 9 –16, 2003.
54. Le Bourdelles G, Viires N, Boczkowski J, Seta N, Pavlovic D, Aubier
M. Effects of mechanical ventilation on diaphragmatic contractile properties in rats. Am J Respir Crit Care Med 149: 1539 –1544, 1994.
55. Leeuwenburgh C. Role of apoptosis in sarcopenia. J Gerontol A Biol Sci
Med Sci 58: 999 –1001, 2003.
56. Levine STN, Friscia M, Kaiser L, Shrager J. Ventilator-induced atrophy
in human diaphragm myofibers. Proc Am Thoracic Soc 3: A27, 2006.
57. Li YP, Chen Y, John J, Moylan J, Jin B, Mann DL, Reid MB.
TNF-alpha acts via p38 MAPK to stimulate expression of the ubiquitin
ligase atrogin1/MAFbx in skeletal muscle. FASEB J 19: 362–370, 2005.
58. Li YP, Chen Y, Li AS, Reid MB. Hydrogen peroxide stimulates ubiquitin-conjugating activity and expression of genes for specific E2 and E3
proteins in skeletal muscle myotubes. Am J Physiol Cell Physiol 285:
C806 –C812, 2003.
59. Matsuzawa A, Ichijo H. Stress-responsive protein kinases in redoxregulated apoptosis signaling. Antioxid Redox Signal 7: 472– 481, 2005.
60. Matuszczak Y, Arbogast S, Reid MB. Allopurinol mitigates muscle
contractile dysfunction caused by hindlimb unloading in mice. Aviat Space
Environ Med 75: 581–588, 2004.
61. McClung JM, Kavazis AN, DeRuisseau KC, Falk DJ, Deering MA,
Lee Y, Sugiura T, Powers SK. Caspase-3 regulation of diaphragm
myonuclear domain during mechanical ventilation-induced atrophy. Am J
Respir Crit Care Med. 175:150 –159, 2007.
62. Pantano C, Reynaert NL, Vliet AV, and Janssen-Heininger YM.
Redox-sensitive kinases of the nuclear factor-kappaB signaling pathway.
Antioxid Redox Signal 8: 1791–1806, 2006.
63. Patel J, McLeod LE, Vries RG, Flynn A, Wang X, Proud CG. Cellular
stresses profoundly inhibit protein synthesis and modulate the states of
phosphorylation of multiple translation factors. Eur J Biochem 269:
3076 –3085, 2002.
64. Pearson G, Robinson F, Beers Gibson T, Xu BE, Karandikar M,
Berman K, Cobb MH. Mitogen-activated protein (MAP) kinase pathways: regulation and physiological functions. Endocr Rev 22: 153–183,
2001.
65. Pham FH, Sugden PH, Clerk A. Regulation of protein kinase B and
4E-BP1 by oxidative stress in cardiac myocytes. Circ Res 86: 1252–1258,
2000.
66. Primeau AJ, Adhihetty PJ, Hood DA. Apoptosis in heart and skeletal
muscle. Can J Appl Physiol 27: 349 –395, 2002.
67. Purintrapiban J, Wang MC, Forsberg NE. Degradation of sarcomeric
and cytoskeletal proteins in cultured skeletal muscle cells. Comp Biochem
Physiol B Biochem Mol Biol 136: 393– 401, 2003.
68. Qi M, Elion EA. MAP kinase pathways. J Cell Sci 118: 3569 –3572,
2005.
69. Reid MB. Redox modulation of skeletal muscle contraction: what we
know and what we don’t. J Appl Physiol 90: 724 –731, 2001.
70. Reid MB. Response of the ubiquitin-proteasome pathway to changes in
muscle activity. Am J Physiol Regul Integr Comp Physiol 288: R1423–
R1431, 2005.
71. Sandri M. Apoptotic signaling in skeletal muscle fibers during atrophy.
Curr Opin Clin Nutr Metab Care 5: 249 –253, 2002.
72. Sandri M, Carraro U, Podhorska-Okolov M, Rizzi C, Arslan P, Monti
D, Franceschi C. Apoptosis, DNA damage and ubiquitin expression in
normal and mdx muscle fibers after exercise. FEBS Lett 373: 291–295,
1995.
2397