title: Muscle-specific calpastatin overexpression prevents diaphragm weakness in cecal ligation puncture-induced sepsis.
abstract: Recent work indicates that infections are a major contributor to diaphragm weakness in patients who are critically ill and mechanically ventilated, and that diaphragm weakness is a risk factor for death and prolonged mechanical ventilation. Infections activate muscle calpain, but many believe this is an epiphenomenon and that other proteolytic processes are responsible for infection-induced muscle weakness. We tested the hypothesis that muscle-specific overexpression of calpastatin (CalpOX; an endogenous calpain inhibitor) would attenuate diaphragm dysfunction in cecal ligation puncture (CLP)-induced sepsis. We studied 1) wild-type (WT) sham-operated mice, 2) WT CLP-operated mice, 3) CalpOX sham-operated mice, and 4) CalpOX CLP-operated mice (n = 9-10/group). Twenty-four hours after surgery, we assessed the diaphragm force-frequency relationship, diaphragm mass, and total protein content and diaphragm levels of talin and myosin heavy chain (MHC). CLP markedly reduced diaphragm-specific force generation (force/cross-sectional area), which was prevented by calpastatin overexpression (force averaged 21.4 ± 0.5, 6.9 ± 0.8, 22.4 ± 1.0, and 18.3 ± 1.3 N/cm(2), respectively, for WT sham, WT CLP, CalpOX sham, and CalpOX CLP groups, P < 0.001). Diaphragm mass and total protein content were similar in all groups. CLP induced talin cleavage and reduced MHC levels; CalpOX prevented these alterations. CLP-induced sepsis rapidly reduces diaphragm-specific force generation and is associated with cleavage and/or depletion of key muscle proteins (talin, MHC), effects prevented by muscle-specific calpastatin overexpression. These data indicate that calpain activation is a major cause of diaphragm weakness in response to CLP-induced sepsis.
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine; Department of Internal Medicine, University of Kentucky, Lexington, Kentucky; Center for Muscle Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Supinski
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine; Department of Internal Medicine, University of Kentucky, Lexington, Kentucky; Center for Muscle Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine; Department of Internal Medicine, University of Kentucky, Lexington, Kentucky; Center for Muscle Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Xiao-Hong
authors.initials: XH
authors.lastname: Song
authors.affiliation: Department of Physiology, University of Kentucky, Lexington, Kentucky; and Center for Muscle Biology, University of Kentucky, Lexington, Kentucky.
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Moylan
authors.affiliation: Division of Pulmonary, Critical Care and Sleep Medicine; Department of Internal Medicine, University of Kentucky, Lexington, Kentucky; Center for Muscle Biology, University of Kentucky, Lexington, Kentucky lacall2@email.uky.edu.
authors.forename: Leigh Ann
authors.initials: LA
authors.lastname: Callahan
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002154:Calpain / Q000378:metabolism; D002432:Cecum / Q000378:metabolism* / Q000473:pathology; D003964:Diaphragm / Q000378:metabolism* / Q000473:pathology*; D008026:Ligation / Q000379:methods; D051379:Mice; D009124:Muscle Proteins / Q000378:metabolism; D018908:Muscle Weakness / Q000378:metabolism* / Q000473:pathology; D009132:Muscles / Q000378:metabolism* / Q000473:pathology; D018995:Myosin Heavy Chains / Q000378:metabolism; D018805:Sepsis / Q000378:metabolism* / Q000473:pathology; D016608:Talin / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D009124:Muscle Proteins; D016608:Talin; C033668:calpastatin; D002154:Calpain; D018995:Myosin Heavy Chains
keywords: calpain; cecal ligation puncture; diaphragm; proteolysis; sepsis