Apocynin attenuates diaphragm oxidative stress and protease activation during prolonged mechanical ventilation.
OBJECTIVE
To investigate whether apocynin protects the diaphragm from wasting and oxidative stress during mechanical ventilation (MV).


METHODS
Prospective, randomized, controlled study.


METHODS
Research laboratory.


METHODS
Adult female Sprague-Dawley rats.


METHODS
Rats were randomly assigned to one of five experimental groups: 1) acutely anesthetized control, 2) spontaneous breathing control, 3) spontaneously breathing control with administration of the nicotinamide adenine dinucleotide phosphate oxidase inhibitor, apocynin, 4) mechanically ventilated, and 5) mechanically ventilated with apocynin.


RESULTS
Apocynin attenuated MV-induced diaphragmatic oxidative stress, contractile dysfunction, and type I, type IIa, and type IIb/IIx myofiber atrophy. The apocynin-induced attenuation of MV-induced diaphragmatic atrophy and contractile dysfunction occurred in conjunction with a reduction in the small increase in nicotinamide adenine dinucleotide phosphate oxidase activity as well as the preservation of total glutathione levels, glutathione peroxidase protein abundance, and a decrease in the activation of the cysteine proteases, calpain-1 and caspase-3. Interestingly, independent of MV, apocynin increased diaphragmatic levels of calpastatin, an endogenous calpain inhibitor. Furthermore, treatment of skeletal muscle cells in culture (C2C12 myotubes) with apocynin resulted in an increase in both calpastatin mRNA levels and protein abundance.


CONCLUSIONS
Our results suggest that the protective effects of apocynin on the diaphragm during prolonged MV seem to be linked to both its functions as an antioxidant and role in cellular signaling regulating the cysteine protease inhibitor calpastatin.
McClung
Joseph M
JM
Department of Applied Physiology and Kinesiology, Center for Exercise Science, University of Florida, Gainesville, FL, USA. joseph.mcclung@duke.edu
Van Gammeren
Darin
D
Whidden
Melissa A
MA
Falk
Darin J
DJ
Kavazis
Andreas N
AN
Hudson
Matt B
MB
Gayan-Ramirez
Ghislaine
G
Decramer
Marc
M
DeRuisseau
Keith C
KC
Powers
Scott K
SK
D000098:Acetophenones / Q000627:therapeutic use*; D000818:Animals; D000975:Antioxidants / Q000627:therapeutic use*; D003964:Diaphragm / Q000187:drug effects* / Q000378:metabolism*; D005260:Female; D018384:Oxidative Stress / Q000187:drug effects*; D010447:Peptide Hydrolases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012121:Respiration, Artificial; D013997:Time Factors
D000098:Acetophenones; D000975:Antioxidants; C056165:acetovanillone; D010447:Peptide Hydrolases