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.) the Department of Kinesiology and Physical Education, Muscle Physiology and Biophysics Laboratory, McGill University, Montréal, Québec, Canada (D.R.).
Anesthesiology. 2019 Sep;131(3):605-618. doi: 10.1097/ALN.0000000000002837.
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.
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.
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.
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.
Controlled mechanical ventilation decreased diaphragm twitch force from 428 ± 104 g/cm (mean ± SD) to 313 ± 50 g/cm and tetanic force from 2,491 ± 411 g/cm to 1,618 ± 177 g/cm. 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.
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.
在控制性机械通气期间，膈肌功能障碍和萎缩会发展。虽然氧化应激会在控制性机械通气期间损伤肌肉，但目前尚不清楚它是否会引起自噬或纤维萎缩。
在接受 24 小时机械通气的大鼠中，用 N-乙酰半胱氨酸预处理可防止膈肌收缩力下降，抑制自噬和蛋白酶体途径，但对膈肌纤维萎缩的发展没有影响。
在长时间的控制性机械通气过程中，膈肌功能障碍和萎缩会发展。纤维萎缩归因于蛋白酶体和自噬蛋白水解途径的激活。氧化应激在控制性机械通气期间激活蛋白酶体，但尚不清楚它是否也激活自噬。本研究旨在探讨抗氧化剂 N-乙酰半胱氨酸预处理是否会影响控制性机械通气引起的膈肌收缩功能障碍、纤维萎缩以及蛋白酶体和自噬途径的激活。该研究还探讨了控制性机械通气期间的蛋白水解途径活性是否受负调控泛素 E3 连接酶和自噬相关基因的 microRNAs 调节。
研究了三组成年雄性大鼠（每组 10 只）。第一组动物麻醉后允许自主呼吸。第二组动物在接受 24 小时控制性机械通气前用生理盐水预处理。第三组动物在接受 24 小时控制性机械通气前用 N-乙酰半胱氨酸（150mg/kg）预处理。测量膈肌收缩性和蛋白酶体和自噬途径的激活。用定量聚合酶链反应测量负调控泛素 E3 连接酶和自噬相关基因的 microRNAs 的表达。
控制性机械通气使膈肌的单次抽搐力从 428±104g/cm（均值±标准差）降至 313±50g/cm，强直力从 2491±411g/cm 降至 1618±177g/cm。控制性机械通气还减小了膈肌纤维的大小，增加了几种自噬基因的表达，并使 Atrogin-1、MuRF1 和 Nedd4 的表达分别增加了 36 倍、41 倍和 8 倍。控制性机械通气还降低了 6 种 microRNAs（miR-20a、miR-106b、miR-376、miR-101a、miR-204 和 miR-93）的表达，这些 microRNAs 调节自噬基因。N-乙酰半胱氨酸预处理可预防膈肌收缩功能障碍，减轻蛋白泛素化，并下调 E3 连接酶和自噬基因的表达。它还逆转了控制性机械通气诱导的 microRNA 表达下降。N-乙酰半胱氨酸预处理对纤维萎缩没有影响。
在氧化应激的作用下，长时间的控制性机械通气会使膈肌的蛋白酶体和自噬途径激活。途径的激活部分是通过抑制负调控自噬相关基因的 microRNAs 来完成的。
