Effect of proteasome inhibitors on endotoxin-induced diaphragm dysfunction.
Infections produce severe respiratory muscle dysfunction. It is known that the proteasome proteolytic system is activated in skeletal muscle in sepsis, and it has been postulated that this degradative pathway is responsible for inducing skeletal muscle weakness and wasting. The objective of this study was to determine if administration of proteasomal inhibitors (MG132, epoxomicin, bortezomib) can prevent sepsis-induced diaphragm weakness. Rats were given either 1) saline (0.5 ml ip), 2) endotoxin (12 mg/kg ip), 3) endotoxin plus MG132 (2.5 mg/kg), 4) endotoxin plus epoxomicin (1 micromol/kg), or 5) endotoxin plus bortezomib (0.05 mg/kg). Animals were killed either 48 or 96 h after injections, and assessments were made of diaphragm proteolysis, force-frequency relationships, mass, protein content, and caspase activation. Endotoxin increased proteolysis (P <0.001). MG132, epoxomicin, and bortezomib each prevented the endotoxin-induced increase in proteolysis (P <0.01). Endotoxin induced severe reductions in diaphragm force generation by 48 h (P <0.01); none of the proteasomal inhibitors prevented loss of force. Endotoxin induced significant reductions in diaphragm mass and protein content by 96 h (P <0.01); neither MG132 nor epoxomicin prevented loss of mass or protein, but bortezomib attenuated the reduction in protein content (P <0.05). Endotoxin increased diaphragm caspase-3 activity (P <0.01); caspase-3 activity remained high when either MG132, epoxomicin, or bortezomib were given. These data suggest proteasomal inhibitors are not an adequate treatment to prevent endotoxin-induced diaphragmatic dysfunction.
Supinski
G S
GS
Division of Pulmonary, Critical Care, and Sleep Medicine, University of Kentucky, Lexington, KY 40536-0284, USA. gsupi2@email.uky.edu
Vanags
J
J
Callahan
L A
LA
D000818:Animals; D001284:Atrophy; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D053148:Caspase 3 / Q000378:metabolism; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects* / Q000201:enzymology* / Q000473:pathology; D019446:Endotoxemia / Q000150:complications; D004789:Enzyme Activation / Q000187:drug effects; D007976:Leupeptins / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018908:Muscle Weakness / Q000188:drug therapy* / Q000209:etiology / Q000473:pathology; D009842:Oligopeptides / Q000494:pharmacology; D009929:Organ Size; D011480:Protease Inhibitors / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018805:Sepsis / Q000150:complications; D014443:Tyrosine / Q000378:metabolism
D001897:Boronic Acids; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D009842:Oligopeptides; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D014443:Tyrosine; D000069286:Bortezomib; C505410:Casp3 protein, rat; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde; C078846:epoxomicin