title: Blockage of the Ryanodine Receptor via Azumolene Does Not Prevent Mechanical Ventilation-Induced Diaphragm Atrophy.
abstract: Mechanical ventilation (MV) is a life-saving intervention for patients in respiratory failure. However, prolonged MV causes the rapid development of diaphragm muscle atrophy, and diaphragmatic weakness may contribute to difficult weaning from MV. Therefore, developing a therapeutic countermeasure to protect against MV-induced diaphragmatic atrophy is important. MV-induced diaphragm atrophy is due, at least in part, to increased production of reactive oxygen species (ROS) from diaphragm mitochondria and the activation of key muscle proteases (i.e., calpain and caspase-3). In this regard, leakage of calcium through the ryanodine receptor (RyR1) in diaphragm muscle fibers during MV could result in increased mitochondrial ROS emission, protease activation, and diaphragm atrophy. Therefore, these experiments tested the hypothesis that a pharmacological blockade of the RyR1 in diaphragm fibers with azumolene (AZ) would prevent MV-induced increases in mitochondrial ROS production, protease activation, and diaphragmatic atrophy. Adult female Sprague-Dawley rats underwent 12 hours of full-support MV while receiving either AZ or vehicle. At the end of the experiment, mitochondrial ROS emission, protease activation, and fiber cross-sectional area were determined in diaphragm muscle fibers. Decreases in muscle force production following MV indicate that the diaphragm took up a sufficient quantity of AZ to block calcium release through the RyR1. However, our findings reveal that AZ treatment did not prevent the MV-induced increase in mitochondrial ROS emission or protease activation in the diaphragm. Importantly, AZ treatment did not prevent MV-induced diaphragm fiber atrophy. Thus, pharmacological inhibition of the RyR1 in diaphragm muscle fibers is not sufficient to prevent MV-induced diaphragm atrophy.
authors: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, United States of America.
authors: Erin E
authors: EE
authors: Talbert
authors: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, United States of America.
authors: Ashley J
authors: AJ
authors: Smuder
authors: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, United States of America.
authors: Oh Sung
authors: OS
authors: Kwon
authors: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, United States of America.
authors: Kurt J
authors: KJ
authors: Sollanek
authors: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, United States of America.
authors: Michael P
authors: MP
authors: Wiggs
authors: Department of Applied Physiology and Kinesiology, University of Florida, Gainesville, Florida, United States of America.
authors: Scott K
authors: SK
authors: Powers
mesh_terms: D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects* / Q000473:pathology*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D007093:Imidazoles / Q000494:pharmacology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009133:Muscular Atrophy / Q000201:enzymology / Q000209:etiology / Q000378:metabolism / Q000517:prevention & control*; D010080:Oxazoles / Q000494:pharmacology*; D010447:Peptide Hydrolases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D012121:Respiration, Artificial / Q000009:adverse effects*; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D007093:Imidazoles; D010080:Oxazoles; D017382:Reactive Oxygen Species; D019837:Ryanodine Receptor Calcium Release Channel; C061387:azumolene; D010447:Peptide Hydrolases