Mitochondria-associated apoptotic signalling in denervated rat skeletal muscle

Parco M. Siu, Stephen Alway

Research output: Contribution to journalArticle

142 Citations (Scopus)

Abstract

Apoptosis has been implicated in the regulation of denervation-induced muscle atrophy. However, the activation of apoptotic signal transduction during muscle denervation has not been fully elucidated. The present study examined the apoptotic responses to denervation in rat gastrocnemius muscle. Following 14 days of denervation, the extent of apoptotic DNA fragmentation as determined by a cytosolic nucleosome ELISA was increased by 100% in the gastrocnemius muscle. RT-PCR and immunoblot analyses indicated that Bax was dramatically upregulated while Bcl-2 was modestly increased; however, the Bax/Bcl-2 ratio was significantly increased in denervated muscles relative to control muscles. Analyses of ELISA and immunoblots from mitochondria-free cytosol extracts showed a significant increase in mitochondria-associated apoptotic factors, including cytochrome c, Smac/DIABLO and apoptosis-inducing factor (AIF). In addition to the upregulation of caspase-3 and -9 mRNA, pro-/deaved caspase protein and proteolytic activity levels, the X-linked inhibitor of apoptosis (XIAP) protein level was downregulated. The cleaved product of poly(ADP-ribose) polymerase (PARP) was detected in muscle samples following denervation. Although we did not find a difference in the inhibitor of DNA binding/differentiation-2 (Id2) and c-Myc protein contents between the denervated and control muscles, the protein content of tumour suppressor p53 was significantly increased in both the nuclear and the cytosolic fractions with denervation. Moreover, denervation increased the protein content of HSP70, whereas the MnSOD (a mitochondrial isoform of superoxide dismutase) protein content was diminished, which indicated that denervation might have induced cellular and/or oxidative stress. Our data show that mitochondria-associated apoptotic signalling is upregulated during muscle denervation. We interpret these findings to indicate that apoptosis has a physiologically important role in regulating denervation-induced muscle atrophy.

Original languageEnglish (US)
Pages (from-to)309-323
Number of pages15
JournalJournal of Physiology
Volume565
Issue number1
DOIs
StatePublished - May 15 2005
Externally publishedYes

Fingerprint

Denervation
Mitochondria
Skeletal Muscle
Muscle Denervation
Muscular Atrophy
Muscles
Enzyme-Linked Immunosorbent Assay
X-Linked Inhibitor of Apoptosis Protein
Apoptosis Inducing Factor
Proto-Oncogene Proteins c-myc
Apoptosis
Proteins
Poly(ADP-ribose) Polymerases
Caspase 9
Muscle Proteins
Nucleosomes
DNA Fragmentation
Caspases
Cytochromes c
Caspase 3

All Science Journal Classification (ASJC) codes

  • Physiology

Cite this

Mitochondria-associated apoptotic signalling in denervated rat skeletal muscle. / Siu, Parco M.; Alway, Stephen.

In: Journal of Physiology, Vol. 565, No. 1, 15.05.2005, p. 309-323.

Research output: Contribution to journalArticle

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