title: The effect of hindlimb immobilization on acid phosphatase, metalloproteinases and nuclear factor-kappaB in muscles of young and old rats.
abstract: Age-associated muscle wasting (sarcopenia of old age) is a major problem in elderly people, however, the mechanisms of muscle proteolysis in aging remain obscure and enigmatic. Possible reasons for loss of skeletal muscle mass with aging may be attributed to multiple and complex proteolytic systems. The purpose of the present study was to explore the kinetics of activation of extracellular hydrolytic and proteolytic systems in muscles of hindlimbs immobilized by external fixation of 24-month-old female Wistar rats, in comparison with those of 6-month-old rats. Results show that elevated acid phosphatase activities (lysosomal hydrolytic enzyme activated mainly in macrophages) in immobilized limb muscles of young animals, differ from old animals. In young rats external fixation resulted in significantly elevated acid phosphatase activities (50-55%; p<0.05) after 4 weeks of immobilization, whereas in old animals similar increases were observed already during the first and second weeks of immobilization. The extracellular proteolytic enzymes, matrix metalloproteinases (MMP-2 and -9), were also differentially activated in old animals compared to young animals. In young animals, as shown in previous studies, both MMP-2 and -9 activities were elevated significantly in immobilized muscles. In this study of old animals, only MMP-2 activity was detected, with no significant elevation in the immobilized muscles of old animals. In addition, the levels of the transcription factor Nuclear Factor-kappaB (NF-kappaB) in nuclear extracts of old rat muscles, as detected by ELISA, showed a biphasic pattern after immobilization, suggesting that NF-kappaB could be activated by different processes in the atrophy process, at least in the old age. In conclusion, it seems that the kinetics of activation of extracellular hydrolytic and proteolytic systems differ in muscles of old animals compared to young animals.
authors.affiliation: Department of Anatomy and Cell Biology, Bruce Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, P.O. Box 9649, Haifa 31096, Israel.
authors.forename: Marina
authors.initials: M
authors.lastname: Bar-Shai
authors.forename: Eli
authors.initials: E
authors.lastname: Carmeli
authors.forename: Raymond
authors.initials: R
authors.lastname: Coleman
authors.forename: Nimrod
authors.initials: N
authors.lastname: Rozen
authors.forename: Shoshan
authors.initials: S
authors.lastname: Perek
authors.forename: Dror
authors.initials: D
authors.lastname: Fuchs
authors.forename: Abraham Z
authors.initials: AZ
authors.lastname: Reznick
mesh_terms: D000135:Acid Phosphatase / Q000096:biosynthesis* / Q000378:metabolism; D000375:Aging; D000818:Animals; D003720:Densitometry; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019417:Hindlimb Suspension; D007150:Immunohistochemistry; D008264:Macrophages / Q000378:metabolism; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis*; D020780:Matrix Metalloproteinase 9 / Q000096:biosynthesis*; D045726:Metalloproteases / Q000096:biosynthesis*; D018482:Muscle, Skeletal / Q000378:metabolism* / Q000473:pathology; D009132:Muscles / Q000473:pathology; D009133:Muscular Atrophy / Q000473:pathology*; D016328:NF-kappa B / Q000096:biosynthesis* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D051996:Transcription Factor RelA
chemical_list: D016328:NF-kappa B; D012333:RNA, Messenger; D051996:Transcription Factor RelA; D000135:Acid Phosphatase; D045726:Metalloproteases; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9