Bortezomib partially protects the rat diaphragm from ventilator-induced diaphragm dysfunction.
OBJECTIVE
Controlled mechanical ventilation leads to diaphragmatic contractile dysfunction and atrophy. Since proteolysis is enhanced in the diaphragm during controlled mechanical ventilation, we examined whether the administration of a proteasome inhibitor, bortezomib, would have a protective effect against ventilator-induced diaphragm dysfunction.


METHODS
Randomized, controlled experiment.


METHODS
Basic science animal laboratory.


METHODS
Anesthetized rats were submitted for 24 hrs to controlled mechanical ventilation while receiving 0.05 mg/kg bortezomib or saline. Control rats were acutely anesthetized.


RESULTS
After 24 hrs, diaphragm force production was significantly lower in mechanically ventilated animals receiving an injection of saline compared to control animals (-36%, p<.001). Importantly, administration of bortezomib improved the diaphragmatic force compared to mechanically ventilated animals receiving an injection of saline (+15%, p<.01), but force did not return to control levels. Compared to control animals, diaphragm cross-sectional area of the type IIx/b fibers was significantly decreased by 28% in mechanically ventilated animals receiving an injection of saline (p<.01) and by 16% in mechanically ventilated animals receiving an injection of bortezomib (p<.05). Diaphragmatic calpain activity was significantly increased in mechanically ventilated animals receiving an injection of saline (+52%, p<.05) and in mechanically ventilated animals receiving an injection of bortezomib (+36%, p<.05). Caspase-3 activity was increased after controlled mechanical ventilation with saline by 55% (p<.05), while it remained similar to control animals in mechanically ventilated animals receiving an injection of bortezomib. Diaphragm 20S proteasome activity was slightly increased in both ventilated groups, and the amount of ubiquitinated proteins was significantly and similarly enhanced in mechanically ventilated animals receiving an injection of saline and mechanically ventilated animals receiving an injection of bortezomib.


CONCLUSIONS
These data show that the administration of bortezomib partially protects the diaphragm from controlled mechanical ventilation-induced diaphragm contractile dysfunction without preventing atrophy. The fact that calpain activity was still increased after bortezomib treatment may explain the persistence of atrophy. Part of bortezomib effects might have been due to its ability to inhibit caspase-3 in this model.
Respiratory Muscle Research Unit, Laboratory of Pneumology and Respiratory Division, Katholieke Universiteit Leuven, Leuven, Belgium.
Anouk
A
Agten
Karen
K
Maes
Debby
D
Thomas
Nele
N
Cielen
Hieronymus W H
HW
Van Hees
Richard P N
RP
Dekhuijzen
Marc
M
Decramer
Ghislaine
G
Gayan-Ramirez
D000818:Animals; D001897:Boronic Acids / Q000627:therapeutic use*; D000069286:Bortezomib; D002154:Calpain / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D003964:Diaphragm / Q000187:drug effects* / Q000503:physiopathology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009133:Muscular Atrophy / Q000209:etiology / Q000517:prevention & control; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D012121:Respiration, Artificial / Q000009:adverse effects*
D001897:Boronic Acids; D061988:Proteasome Inhibitors; D011719:Pyrazines; D000069286:Bortezomib; D002154:Calpain; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex