title: Treatment of rats with calpain inhibitors prevents sepsis-induced muscle proteolysis independent of atrogin-1/MAFbx and MuRF1 expression.
abstract: Muscle wasting in sepsis is a significant clinical problem because it results in muscle weakness and fatigue that may delay ambulation and increase the risk for thromboembolic and pulmonary complications. Treatments aimed at preventing or reducing muscle wasting in sepsis, therefore, may have important clinical implications. Recent studies suggest that sepsis-induced muscle proteolysis may be initiated by calpain-dependent release of myofilaments from the sarcomere, followed by ubiquitination and degradation of the myofilaments by the 26S proteasome. In the present experiments, treatment of rats with one of the calpain inhibitors calpeptin or BN82270 inhibited protein breakdown in muscles from rats made septic by cecal ligation and puncture. The inhibition of protein breakdown was not accompanied by reduced expression of the ubiquitin ligases atrogin-1/MAFbx and MuRF1, suggesting that the ubiquitin-proteasome system is regulated independent of the calpain system in septic muscle. When incubated muscles were treated in vitro with calpain inhibitor, protein breakdown rates and calpain activity were reduced, consistent with a direct effect in skeletal muscle. Additional experiments suggested that the effects of BN82270 on muscle protein breakdown may, in part, reflect inhibited cathepsin L activity, in addition to inhibited calpain activity. When cultured myoblasts were transfected with a plasmid expressing the endogenous calpain inhibitor calpastatin, the increased protein breakdown rates in dexamethasone-treated myoblasts were reduced, supporting a role of calpain activity in atrophying muscle. The present results suggest that treatment with calpain inhibitors may prevent sepsis-induced muscle wasting.
authors.affiliation: Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
authors.forename: Moin U
authors.initials: MU
authors.lastname: Fareed
authors.forename: Amy R
authors.initials: AR
authors.lastname: Evenson
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Michael
authors.initials: M
authors.lastname: Menconi
authors.forename: Vitaliy
authors.initials: V
authors.lastname: Poylin
authors.forename: Victoria
authors.initials: V
authors.lastname: Petkova
authors.forename: Bernadette
authors.initials: B
authors.lastname: Pignol
authors.forename: Per-Olof
authors.initials: PO
authors.lastname: Hasselgren
mesh_terms: D000818:Animals; D002135:Calcium-Binding Proteins / Q000235:genetics; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism; D002460:Cell Line; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000235:genetics; D006023:Glycoproteins / Q000494:pharmacology*; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D009124:Muscle Proteins / Q000235:genetics* / Q000378:metabolism; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D009133:Muscular Atrophy / Q000209:etiology / Q000378:metabolism*; D032448:Myoblasts, Skeletal / Q000187:drug effects / Q000378:metabolism; D010436:Pepstatins / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics*; D018805:Sepsis / Q000150:complications*; D014162:Transfection; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000235:genetics*
chemical_list: D002135:Calcium-Binding Proteins; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D006023:Glycoproteins; D009124:Muscle Proteins; D010436:Pepstatins; D061988:Proteasome Inhibitors; D000070584:Tripartite Motif Proteins; C039304:calpain inhibitors; C071482:calpeptin; C033668:calpastatin; D003907:Dexamethasone; D006861:Hydrogen Peroxide; C486692:Fbxo32 protein, rat; D044843:SKP Cullin F-Box Protein Ligases; C499086:Trim63 protein, rat; D044767:Ubiquitin-Protein Ligases; D002154:Calpain; D046988:Proteasome Endopeptidase Complex; C031375:pepstatin