title: Amyloid-beta accumulation caused by chloroquine injections precedes ER stress and autophagosome formation in rat skeletal muscle.
abstract: Chloroquine, an anti-malaria drug, is known to cause myopathy with rimmed vacuole formation. Although it disrupts the lysosomal degradation of proteins, the precise mechanism underlying muscle fiber degeneration has remained unclear. We investigated the temporal profiles of muscle fiber degeneration in chloroquine-treated rats, paying special attention to endoplasmic reticulum (ER) stress and autophagy. Male Wistar rats were intraperitoneally injected with chloroquine diphosphate at a dosage of 50 mg/kg body weight every day. We examined the localization and levels of proteins related to ER stress and autophagy in soleus muscle by means of immunohistochemistry and Western blotting at 3, 5, and 7 weeks after the beginning of the treatment. At 3 weeks, the levels of LC3-II and amyloid-beta (Abeta) were increased. At 5 weeks, an unfolded protein response took place. At 7 weeks, rimmed vacuole formation became obvious. Interestingly, SERCA2, a Ca2+ -pump ATPase located in the endoplasmic/sarcoplasmic reticulum membrane was up-regulated at 5 weeks after treatment, but declined to the control level by 7 weeks. Taken together, these findings suggest that Abeta accumulation (at 3 weeks) caused by the disruption of lysosomal enzymes precedes an unfolded protein response (at 5 weeks). Next, activation of autophagy occurs (at 7 weeks), probably using sarcoplasmic reticulum membrane, the amount of which was increased. Chloroquine-treated rats could be useful for investigating the pathogenesis of diseases related to Abeta accumulation.
authors.affiliation: Department of Neurology, Neurological Institute, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. kikezoe@neuro.med.kyushu-u.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Ikezoe
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Furuya
authors.forename: Hajime
authors.initials: H
authors.lastname: Arahata
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nakagawa
authors.forename: Takahisa
authors.initials: T
authors.lastname: Tateishi
authors.forename: Naoki
authors.initials: N
authors.lastname: Fujii
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Kira
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D000818:Animals; D000962:Antimalarials / Q000008:administration & dosage / Q000633:toxicity*; D001343:Autophagy / Q000187:drug effects; D015153:Blotting, Western; D002738:Chloroquine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000633:toxicity; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D007150:Immunohistochemistry; D007274:Injections, Intraperitoneal; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D017510:Protein Folding / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014617:Vacuoles / Q000187:drug effects
chemical_list: D016229:Amyloid beta-Peptides; D000962:Antimalarials; C023676:chloroquine diphosphate; D002738:Chloroquine