Caspase-3 Regulation of Diaphragmatic Myonuclear Apoptosis during prolonged Mechanical Ventilation

Abstract

PURPOSE: Unloading the diaphragm via mechanical ventilation (MV) results in a rapid decrease in myonuclear content and diaphragmatic myofiber atrophy. We tested the hypothesis that caspase-3 activation is a critical component of the MV-induced myonuclear loss. METHODS: To test this postulate, Sprague-Dawley rats were randomly assigned to one of five experimental groups: control, 6-hour MV, 12-hour MV, 6-hour MV with a highly specific caspase-3 inhibitor (DEVD-CHO), and 12-hour MV with DEVD-CHO. RESULTS: Decreases in myonuclear content and increases in the number of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) positive nuclei were observed in diaphragm muscle fibers following 6-and 12-hours of MV. DEVD-CHO administration attenuated the decrease in both myonuclear content and the increase in TUNEL positive myonuclei at both 6-and 12-hours of MV. In addition, decreases in both Type I and Type IIa diaphragm myofiber cross sectional areas with 12-hours of MV were attenuated by DEVD-CHO administration. CONCLUSIONS: Collectively, these data support the hypothesis that caspase-3 activation is a critical component of myonuclear loss occurring during rapid MV induced myofiber atrophy. This work was supported by National Institutes of Health (R01 HL072789).