Energy-ubiquitin-dependent muscle proteolysis during sepsis in rats is regulated by glucocorticoids.
Recent studies suggest that sepsis-induced increase in muscle proteolysis mainly reflects energy-ubiquitin-dependent protein breakdown. We tested the hypothesis that glucocorticoids activate the energy-ubiquitin-dependent proteolytic pathway in skeletal muscle during sepsis. Rats underwent induction of sepsis by cecal ligation and puncture or were sham-operated and muscle protein breakdown rates were measured 16 h later. The glucocorticoid receptor antagonist RU 38486 or vehicle was administered to groups of septic and sham-operated rats. In other experiments, dexamethasone (2.5 or 10 mg/kg) was injected subcutaneously in normal rats. Total and myofibrillar proteolysis was determined in incubated extensor digitorum longus muscles as release of tyrosine and 3-methylhistidine, respectively. Energy-dependent proteolysis was determined in incubated muscles depleted of energy with 2-deoxyglucose and 2,4-dinitrophenol. Levels of muscle ubiquitin mRNA and free and conjugated ubiquitin were determined by Northern and Western blot, respectively. RU 38486 inhibited the sepsis-induced increase in total and myofibrillar energy-dependent protein breakdown rates and blunted the increase in ubiquitin mRNA levels and free ubiquitin. Some, but not all, sepsis-induced changes in ubiquitin protein conjugates were inhibited by RU 38486. Injection of dexamethasone in normal rats increased energy-dependent proteolysis and ubiquitin mRNA levels. The results suggest that glucocorticoids regulate the energy-ubiquitin-dependent proteolytic pathway in skeletal muscle during sepsis.
Tiao
G
G
Department of Surgery, University of Cincinnati Medical Center, Ohio 45267, USA.
Fagan
J
J
Roegner
V
V
Lieberman
M
M
Wang
J J
JJ
Fischer
J E
JE
Hasselgren
P O
PO
D000818:Animals; D001483:Base Sequence; D004734:Energy Metabolism; D015870:Gene Expression; D005786:Gene Expression Regulation / Q000187:drug effects; D005938:Glucocorticoids / Q000502:physiology*; D006727:Hormone Antagonists / Q000494:pharmacology; D008297:Male; D015735:Mifepristone / Q000494:pharmacology; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D015345:Oligonucleotide Probes / Q000737:chemistry; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011965:Receptors, Glucocorticoid / Q000037:antagonists & inhibitors; D018805:Sepsis / Q000378:metabolism*; D014452:Ubiquitins / Q000235:genetics / Q000502:physiology*
D005938:Glucocorticoids; D006727:Hormone Antagonists; D009124:Muscle Proteins; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D011965:Receptors, Glucocorticoid; D014452:Ubiquitins; D015735:Mifepristone