title: Antioxidant administration attenuates mechanical ventilation-induced rat diaphragm muscle atrophy independent of protein kinase B (PKB Akt) signalling.
abstract: Oxidative stress promotes controlled mechanical ventilation (MV)-induced diaphragmatic atrophy. Nonetheless, the signalling pathways responsible for oxidative stress-induced muscle atrophy remain unknown. We tested the hypothesis that oxidative stress down-regulates insulin-like growth factor-1-phosphotidylinositol 3-kinase-protein kinase B serine threonine kinase (IGF-1-PI3K-Akt) signalling and activates the forkhead box O (FoxO) class of transcription factors in diaphragm fibres during MV-induced diaphragm inactivity. Sprague-Dawley rats were randomly assigned to one of five experimental groups: (1) control (Con), (2) 6 h of MV, (3) 6 h of MV with infusion of the antioxidant Trolox, (4) 18 h of MV, (5) 18 h of MV with Trolox. Following 6 h and 18 h of MV, diaphragmatic Akt activation decreased in parallel with increased nuclear localization and transcriptional activation of FoxO1 and decreased nuclear localization of FoxO3 and FoxO4, culminating in increased expression of the muscle-specific ubiquitin ligases, muscle atrophy factor (MAFbx) and muscle ring finger-1 (MuRF-1). Interestingly, following 18 h of MV, antioxidant administration was associated with attenuation of MV-induced atrophy in type I, type IIa and type IIb/IIx myofibres. Collectively, these data reveal that the antioxidant Trolox attenuates MV-induced diaphragmatic atrophy independent of alterations in Akt regulation of FoxO transcription factors and expression of MAFbx or MuRF-1. Further, these results also indicate that differential regulation of diaphragmatic IGF-1-PI3K-Akt signalling exists during the early and late stages of MV.
authors.affiliation: Department of Applied Physiology and Kinesiology, University of Florida, Room 25 Florida Gym, Gainesville, FL 32611, USA. mmcclung@hhp.ufl.edu
authors.forename: J M
authors.initials: JM
authors.lastname: McClung
authors.forename: A N
authors.initials: AN
authors.lastname: Kavazis
authors.forename: M A
authors.initials: MA
authors.lastname: Whidden
authors.forename: K C
authors.initials: KC
authors.lastname: DeRuisseau
authors.forename: D J
authors.initials: DJ
authors.lastname: Falk
authors.forename: D S
authors.initials: DS
authors.lastname: Criswell
authors.forename: S K
authors.initials: SK
authors.lastname: Powers
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology / Q000627:therapeutic use*; D002839:Chromans / Q000494:pharmacology / Q000627:therapeutic use; D003964:Diaphragm / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D007328:Insulin / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000502:physiology; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D009133:Muscular Atrophy / Q000209:etiology* / Q000517:prevention & control*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial / Q000009:adverse effects*; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D000071161:Forkhead Box Protein O1
chemical_list: D000975:Antioxidants; D002839:Chromans; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D044843:SKP Cullin F-Box Protein Ligases; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases; C499515:FOXO3 protein, rat; C524737:FOXO4 protein, rat; C074639:Foxo1 protein, rat; D000071161:Forkhead Box Protein O1; C486692:Fbxo32 protein, rat; C499086:Trim63 protein, rat; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid