Mechanical ventilation (MV) is used clinically as a life saving intervention to sustain adequate pulmonary gas exchange in patients that are incapable of maintaining sufficient alveolar ventilation (e.g., patients in respiratory failure). The removal of patients from MV is termed "weaning" and problems in weaning are extremely common. The inability to wean patients from MV results in increased risk of morbidity and mortality along with higher health care costs. Studies indicate that MV-induced diaphragmatic weakness, due to both atrophy and contractile dysfunction, is a significant contributor to weaning difficulties. Our research reveals that prolonged MV is associated with diaphragmatic oxidative stress and that the activation of two proteases, calpains and caspase-3, is required for MV-induced diaphragmatic atrophy and contractile dysfunction. The mechanism(s) that regulate the activity of these proteases in the diaphragm during prolonged MV are currently unknown and will be addressed in this application. HYPOTHESES:
Aim 1 will test the hypothesis that oxidative stress is essential for activation of both calpain and caspase-3 in the diaphragm during prolonged MV.
Aim 2 will test the postulate that oxidative modification of diaphragmatic myofilament proteins increases their susceptibility to degradation by calpains-1/2 and/or caspase-3.
Aim 3 will test the hypothesis that regulatory cross-talk between calpain and caspase-3 plays a vital role in determining the individual activity of these proteases. APPROACH: We will test these hypotheses using a combination of experimental paradigms including an animal model of MV, peptide mapping, and cell-signaling experiments performed in rat primary skeletal muscle cell culture. Cause and effect will be determined by prevention of MV-induced oxidative stress in the diaphragm and by the independent inhibition of calpains and caspase-3 in primary skeletal muscle myotubes using innovative approaches. SIGNIFICANCE AND LONG-TERM GOAL: Failure to wean patients from MV is an important clinical problem and respiratory muscle weakness is a major contributor to weaning difficulties. Hence, our long-term goal is to develop methods for the prevention of MV-induced diaphragmatic weakness based on an understanding of the cellular mechanisms responsible for MV-induced atrophy in the diaphragm. Moreover, the results of these experiments should provide important information for broader topics such as skeletal muscle wasting due to prolonged bed rest, immobilization, and disease states.

Public Health Relevance

Mechanical ventilation (MV) is used to sustain pulmonary gas exchange in patients that are incapable of maintaining adequate alveolar ventilation;the withdrawal of MV from patients is referred to as "weaning" and problems in weaning from MV are extremely common. Numerous studies reveal that MV-induced diaphragmatic weakness, due to both atrophy and contractile dysfunction, is an important contributor to weaning difficulties. Our long-term goal is to develop methods for the prevention of MV-induced diaphragmatic weakness based on an understanding of the cellular mechanisms responsible for MV-induced diaphragmatic atrophy and contractile dysfunction.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL087839-04
Application #
8252152
Study Section
Skeletal Muscle and Exercise Physiology Study Section (SMEP)
Program Officer
Harabin, Andrea L
Project Start
2009-06-01
Project End
2014-04-30
Budget Start
2012-05-01
Budget End
2014-04-30
Support Year
4
Fiscal Year
2012
Total Cost
$357,732
Indirect Cost
$110,232
Name
University of Florida
Department
None
Type
Other Domestic Higher Education
DUNS #
969663814
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Powers, Scott K (2014) Can antioxidants protect against disuse muscle atrophy? Sports Med 44 Suppl 2:S155-65
Smuder, Ashley J; Nelson, W Bradley; Hudson, Matthew B et al. (2014) Inhibition of the ubiquitin-proteasome pathway does not protect against ventilator-induced accelerated proteolysis or atrophy in the diaphragm. Anesthesiology 121:115-26
Powers, Scott K; Wiggs, Michael P; Duarte, Jose A et al. (2012) Mitochondrial signaling contributes to disuse muscle atrophy. Am J Physiol Endocrinol Metab 303:E31-9
Powers, Scott K; Smuder, Ashley J; Judge, Andrew R (2012) Oxidative stress and disuse muscle atrophy: cause or consequence? Curr Opin Clin Nutr Metab Care 15:240-5
Nelson, W Bradley; Smuder, Ashley J; Hudson, Matthew B et al. (2012) Cross-talk between the calpain and caspase-3 proteolytic systems in the diaphragm during prolonged mechanical ventilation. Crit Care Med 40:1857-63
Powers, Scott K; Hudson, Matthew B; Nelson, W Bradley et al. (2011) Mitochondria-targeted antioxidants protect against mechanical ventilation-induced diaphragm weakness. Crit Care Med 39:1749-59
Agten, Anouk; Maes, Karen; Smuder, Ashley et al. (2011) N-Acetylcysteine protects the rat diaphragm from the decreased contractility associated with controlled mechanical ventilation. Crit Care Med 39:777-82
Powers, Scott K; Smuder, Ashley J; Criswell, David S (2011) Mechanistic links between oxidative stress and disuse muscle atrophy. Antioxid Redox Signal 15:2519-28
Smuder, Ashley J; Kavazis, Andreas N; Hudson, Matthew B et al. (2010) Oxidation enhances myofibrillar protein degradation via calpain and caspase-3. Free Radic Biol Med 49:1152-60
Powers, Scott K; Smuder, Ashley J; Kavazis, Andreas N et al. (2010) Experimental guidelines for studies designed to investigate the impact of antioxidant supplementation on exercise performance. Int J Sport Nutr Exerc Metab 20:2-14