Expression of autophagy-associated genes in skeletal muscle: an experimental model of chloroquine-induced myopathy.
OBJECTIVE
Chloroquine modulates autophagocytic protein degradation in the lysosome system, thereby inducing the formation of rimmed vacuoles consisting of autophagosomes and autolysosomes in skeletal muscle. The goal of this study was to investigate the contribution of the lysosomal system, particularly autophagosome formation (an autophagic process) at the molecular level, to the abnormal accumulation of vacuoles in an experimental model of chloroquine-induced myopathy.


METHODS
Histological, immunohistochemical and semiquantitative reverse transcriptase-polymerase chain reaction studies were performed on innervated and denervated rat soleus muscles after treatment with either saline or chloroquine.


RESULTS
Accumulation of rimmed vacuoles was observed only in chloroquine-treated denervated muscles. Microtubule-associated protein-1 light chain-3 (LC3) protein and mRNA levels were significantly increased exclusively in denervated muscles from chloroquine-treated rats, whereas Apg5 and Apg12 mRNA levels did not change significantly. Further, the mRNA levels of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE), which are associated with distal myopathy with rimmed vacuoles showing numerous rimmed vacuoles in its skeletal muscle, were not decreased in denervatedmuscles treated with chloroquine.


CONCLUSIONS
LC3 mRNA may increase in association with rimmed vacuole formation in denervated muscles from chloroquine-treated rats, suggesting an increase in autophagy at the molecular level. Abnormal accumulation of rimmed vacuoles in this myopathy does not appear to be mediated by inhibition of autophagosome-related genes or GNE gene.
Kimura
Noriyuki
N
Department of Neurology and Neuromuscular Disorders, Faculty of Medicine, Oita University, Yufu, Oita, Japan.
Kumamoto
Toshihide
T
Kawamura
Yosuke
Y
Himeno
Takahiro
T
Nakamura
Ken-Ichro
KI
Ueyama
Hidetsugu
H
Arakawa
Ryuki
R
D000818:Animals; D018501:Antirheumatic Agents / Q000633:toxicity*; D001343:Autophagy / Q000187:drug effects / Q000235:genetics*; D002738:Chloroquine / Q000633:toxicity*; D004195:Disease Models, Animal; D007274:Injections, Intraperitoneal; D008026:Ligation; D008297:Male; D008869:Microtubule-Associated Proteins / Q000235:genetics* / Q000378:metabolism; D009097:Multienzyme Complexes / Q000235:genetics* / Q000378:metabolism; D009121:Muscle Denervation; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation / Q000378:metabolism* / Q000473:pathology; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012584:Sciatic Nerve / Q000293:injuries / Q000601:surgery; D014617:Vacuoles / Q000187:drug effects / Q000473:pathology
D018501:Antirheumatic Agents; C490546:Map1a protein, rat; D008869:Microtubule-Associated Proteins; D009097:Multienzyme Complexes; D012333:RNA, Messenger; C482901:UDP-N-acetylglucosamine 2-epimerase - N-acetylmannosamine kinase; D002738:Chloroquine