Submitted on January 18, 2008
Accepted on April 15, 2008
Proteasome inhibition improves diaphragm function in congestive heart failure rats
Hieronymus W.H. van Hees1*, Yi-Ping Li2, Coen A.C. Ottenheijm3, Bingwen Jin2, Cindy J.C. Pigmans1, Marianne Linkels1, P N. Richard Dekhuijzen4, and Leo M.A. Heunks5
1 Pulmonary Diseases, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands
2 Medicine, Baylor College of Medicine, Houston, Texas, United States
3 Molecular and Cellular Biology, University of Arizona, Tucson, Arizona, United States
4 Dept. of Pulmonary Diseases (549), University Medical Centre Nijmegen, Nijmegen, Netherlands
5 Intensive Care Medicine, Radboud University Nijmegen Medical Centre, Netherlands
* To whom correspondence should be addressed. E-mail: h.vanhees{at}long.umcn.nl.
Rationale: In congestive heart failure (CHF) diaphragm weakness is known to occur and is associated with myosin loss and activation of the ubiquitin-proteasome pathway. The effect of modulating proteasome activity on myosin loss and diaphragm function is unknown. The present study investigated the effect of in vivo proteasome inhibition on myosin loss and diaphragm function in CHF rats.
Methods: Coronary artery ligation was used as animal model for CHF. Sham-operated rats served as controls. Animals were treated with the proteasome inhibitor bortezomib (iv) or received saline (0.9%) injections. Force generating capacity, cross-bridge cycling kinetics and myosin content were measured in diaphragm single fibers. Proteasome activity, caspase-3 activity and MuRF-1 and MAFbx mRNA levels were determined in diaphragm homogenates.
Results: Proteasome activities in the diaphragm were significantly reduced by bortezomib. Bortezomib treatment significantly improved diaphragm single fiber force generating capacity (~30-40%) and cross-bridge cycling kinetics (~20%) in CHF. Myosin content was ~30% higher in diaphragm fibers from bortezomib treated CHF rats than saline. Caspase-3 activity was decreased in diaphragm homogenates from bortezomib treated rats. CHF increased MuRF-1 and MAFbx mRNA expression in the diaphragm and bortezomib treatment diminished this rise.
Conclusions: The present study demonstrates that treatment with a clinically used proteasome inhibitor improves diaphragm function by restoring myosin content in CHF.
