Oxidants Regulated Diaphragm Proteolysis during Mechanical Ventilation in Rats

Area of Science:

• Muscle physiology
• Respiratory medicine
• Cellular biology

Background:

• Diaphragm dysfunction and atrophy are known complications of controlled mechanical ventilation.
• Oxidative stress is implicated in muscle injury during ventilation, but its role in autophagy and atrophy is unclear.

Purpose of the Study:

• To investigate the effects of N-acetylcysteine (NAC) on mechanical ventilation-induced diaphragm dysfunction, atrophy, and proteolytic pathway activation.
• To explore the role of microRNAs in regulating these pathways during ventilation.

Main Methods:

• Adult male rats were divided into three groups: spontaneous breathing, ventilation with saline pretreatment, and ventilation with NAC pretreatment.
• Diaphragm contractility, proteasome and autophagy pathway activation, and microRNA expression were measured.
• Quantitative PCR was used to assess microRNA and gene expression.

Main Results:

• Controlled mechanical ventilation reduced diaphragm force and fiber size, while increasing autophagy gene expression and E3 ligase levels.
• Ventilation decreased specific microRNAs that regulate autophagy genes.
• NAC pretreatment prevented contractile dysfunction, attenuated protein ubiquitination, and modulated gene and microRNA expression, but did not affect fiber atrophy.

Conclusions:

• Prolonged mechanical ventilation activates diaphragm proteasome and autophagy pathways via oxidative stress.
• This activation is partly mediated by the downregulation of microRNAs that regulate autophagy-related genes.
• NAC mitigates ventilation-induced diaphragm dysfunction by targeting these pathways but does not prevent fiber atrophy.