Newly Published
Critical Care Medicine  |   June 2019
Oxidants Regulated Diaphragm Proteolysis during Mechanical Ventilation in Rats
Author Notes
  • From the Meakins–Christie Laboratories, Translational Research in Respiratory Diseases Program, and Department of Critical Care, McGill University Health Centre Research Institute, Montréal, Québec, Canada (N.M., J.-P.L.-G., P.G., B.J.P., D.M., S.N.H.); the Respiratory Muscle Research Unit, Laboratory of Pneumology, Katholieke Universiteit Leuven, Leuven, Belgium (K.M., G.G.-R.); the Department of Critical Care, Pulmonary Unit, Evangelismos General Hospital, National and Kaposdistrian University of Athens Medical School, Athens, Greece (T.V.); and the Department of Kinesiology and Physical Education, Muscle Physiology and Biophysics Laboratory, McGill University, Montréal, Québec, Canada (D.R.).
  • Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).
    Supplemental Digital Content is available for this article. Direct URL citations appear in the printed text and are available in both the HTML and PDF versions of this article. Links to the digital files are provided in the HTML text of this article on the Journal’s Web site (www.anesthesiology.org).×
  • Part of the work presented in this article has been presented at the American Thoracic Society International Meeting in Denver, Colorado, May 15 to 20, 2015, and the European Respiratory Society International Congress in London, September 3 to 7, 2016.
    Part of the work presented in this article has been presented at the American Thoracic Society International Meeting in Denver, Colorado, May 15 to 20, 2015, and the European Respiratory Society International Congress in London, September 3 to 7, 2016.×
  • Submitted for publication October 8, 2018. Accepted for publication May 9, 2019.
    Submitted for publication October 8, 2018. Accepted for publication May 9, 2019.×
  • Correspondence: Address correspondence to Dr. Hussain: Room EM2.2224, Research Institute of the McGill University Health Centre, 1001 Décarie Boulevard, Montréal, Québec H4A 3J1, Canada. sabah.hussain@muhc.mcgill.ca. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Critical Care Medicine / Critical Care / Respiratory System / Technology / Equipment / Monitoring
Critical Care Medicine   |   June 2019
Oxidants Regulated Diaphragm Proteolysis during Mechanical Ventilation in Rats
Anesthesiology Newly Published on June 28, 2019. doi:10.1097/ALN.0000000000002837
Anesthesiology Newly Published on June 28, 2019. doi:10.1097/ALN.0000000000002837
Abstract

Editor’s Perspective:

What We Already Know about This Topic:

  • Diaphragm dysfunction and atrophy develop during controlled mechanical ventilation. Although oxidative stress injures muscle during controlled mechanical ventilation, it is unclear whether it causes autophagy or fiber atrophy.

What This Article Tells Us That Is New:

  • Pretreatment of rats undergoing 24 h of mechanical ventilation with N-acetylcysteine prevents decreases in diaphragm contractility, inhibits the autophagy and proteasome pathways, but has no influence on the development of diaphragm fiber atrophy.

Background: Diaphragm dysfunction and atrophy develop during prolonged controlled mechanical ventilation. Fiber atrophy has been attributed to activation of the proteasome and autophagy proteolytic pathways. Oxidative stress activates the proteasome during controlled mechanical ventilation, but it is unclear whether it also activates autophagy. This study investigated whether pretreatment with the antioxidant N-acetylcysteine affects controlled mechanical ventilation–induced diaphragm contractile dysfunction, fiber atrophy, and proteasomal and autophagic pathway activation. The study also explored whether proteolytic pathway activity during controlled mechanical ventilation is mediated by microRNAs that negatively regulate ubiquitin E3 ligases and autophagy-related genes.

Methods: Three groups of adult male rats were studied (n = 10 per group). The animals in the first group were anesthetized and allowed to spontaneously breathe. Animals in the second group were pretreated with saline before undergoing controlled mechanical ventilation for 24 h. The animals in the third group were pretreated with N-acetylcysteine (150 mg/kg) before undergoing controlled mechanical ventilation for 24 h. Diaphragm contractility and activation of the proteasome and autophagy pathways were measured. Expressions of microRNAs that negatively regulate ubiquitin E3 ligases and autophagy-related genes were measured with quantitative polymerase chain reaction.

Results: Controlled mechanical ventilation decreased diaphragm twitch force from 428 ± 104 g/cm2 (mean ± SD) to 313 ± 50 g/cm2 and tetanic force from 2,491 ± 411 g/cm2 to 1,618 ± 177 g/cm2. Controlled mechanical ventilation also decreased diaphragm fiber size, increased expression of several autophagy genes, and augmented Atrogin-1, MuRF1, and Nedd4 expressions by 36-, 41-, and 8-fold, respectively. Controlled mechanical ventilation decreased the expressions of six microRNAs (miR-20a, miR-106b, miR-376, miR-101a, miR-204, and miR-93) that regulate autophagy genes. Pretreatment with N-acetylcysteine prevented diaphragm contractile dysfunction, attenuated protein ubiquitination, and downregulated E3 ligase and autophagy gene expression. It also reversed controlled mechanical ventilation–induced microRNA expression decreases. N-Acetylcysteine pretreatment had no affect on fiber atrophy.

Conclusions: Prolonged controlled mechanical ventilation activates the proteasome and autophagy pathways in the diaphragm through oxidative stress. Pathway activation is accomplished, in part, through inhibition of microRNAs that negatively regulate autophagy-related genes.