Apoptosis is suspended in muscle of mitochondrial encephalomyopathies.
Over the past few years, many studies have been done on the apoptotic involvement in muscle fiber degeneration in various myopathies, but the occurrence of apoptosis in muscles of mitochondrial encephalomyopathies is still controversial. To confirm whether apoptotic processes are truly related to muscle fiber degeneration in mitochondrial encephalomyopathies, we performed the TUNEL method not only at the light microscopic (LM) but also at the electron microscopic (EM) level for muscles of five MELAS, five CPEO and five MERRF patients and five control muscles. Immunohistochemical studies of Bcl-2, Bax, cytochrome c, Apaf-1, activated caspase-3 and human inhibitor of apoptosis protein XIAP, and immunoblotting of Apaf-1 and XIAP were also carried out. In LM-TUNEL, MELAS, CPEO and MERRF patients had only very small numbers of TUNEL-positive myonuclei: 0.13+/-0.10%, 0.15+/-0.14% and 0.04+/-0.09%, respectively. Almost all of them were seen in ragged-red fibers (RRFs). EM-TUNEL showed no significant increase of DNA fragmentation in RRFs despite mild peripheral chromatin condensation. However, Bax and Apaf-1 expression and cytochrome c release from mitochondria were seen in RRFs. Caspase-3 activation was confirmed in 9.0+/-3.7%, 12.0+/-4.4% and 12.4+/-3.8% of RRFs in MELAS, CPEO and MERRF, respectively, but not in control muscles. Almost all RRFs showed sarcoplasmic expression of XIAP. Thus, there is a possibility that, although apoptotic reactions started in muscles of mitochondrial encephalomyopathies, their execution is rarely completed. Sarcoplasmic expression of XIAP probably leads to the suspension of the apoptotic process in mitochondrial encephalomyopathies.
Ikezoe
Koji
K
Department of Neurology, Kyushu Koseinenkin Hospital, Kitakyushu, Fukuoka, 806-8501, Japan.
Nakagawa
Masahiro
M
Yan
Chuanzhu
C
Kira
Jun-Ichi
J
Goto
Yu-Ichi
Y
Nonaka
Ikuya
I
D000293:Adolescent; D000328:Adult; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053477:Apoptotic Protease-Activating Factor 1; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D002648:Child; D002675:Child, Preschool; D003574:Cytochrome c Group / Q000378:metabolism; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D017237:Mitochondrial Encephalomyopathies / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D013950:Thymus Gland / Q000378:metabolism / Q000648:ultrastructure; D051636:X-Linked Inhibitor of Apoptosis Protein; D051028:bcl-2-Associated X Protein
C506592:APAF1 protein, human; C506594:Apaf1 protein, rat; D053477:Apoptotic Protease-Activating Factor 1; C494826:BAX protein, human; C494828:Bax protein, rat; D003574:Cytochrome c Group; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051636:X-Linked Inhibitor of Apoptosis Protein; C496866:XIAP protein, human; D051028:bcl-2-Associated X Protein; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases