The role of Akt and JNK in mechanical ventilation-induced diaphragmatic dysfunction in mice

• Main Authors: Mei Ling Tien, 田美齡
• Other Authors: M. C. Lin
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/32328127688131993990

碩士 === 長庚大學 === 臨床醫學研究所 === 99 === Purpose: Controlled mechanical ventilation (MV) provides life Support for patients who are unable to maintain adequate alveolar ventilation. However, unloading the diaphragm via MV for extended periods (i.e., 3 days or more) leads to weaning difficulties in as many as 20% of patients Although the causes responsible for difficult weaning continue to be investigated, respiratory muscle weakness is a key potential mechanism. Alterations in the (PI3-K)/Akt pathway have been demonstrated to be involved in the atrophying skeletal muscles. The aim of the study is to examine the role of serine/threonine kinase/protein kinase B (Akt)/ c-Jun NH2-terminal kinase (JNK) in the mechanical ventilation-induced diaphragm muscle injury in mice. Materials and methods: Male C57BL/6J, either wild-type or Akt deficient (Akt+/-) on a C57BL/6J background, aged between 6 and 8 weeks, weighing between 20 and 25 g, were randomly assigned to one of three experimental groups: 1) Sham group: tracheostomized and nonventilated wild type, 2) Tidal volume (VT) 30ml/kg, wild type, 3) VT30ml/kg, Akt+/- 4) Tidal volume (VT) 30ml/kg, wild type +SP600126. For ventilator protocol, tracheostomy was performed under general anesthesia with intraperitoneal ketamine (90 mg/kg) and xylazine (10 mg/kg) followed by ketamine (0.1 mg/g/hr) and xylazine (0.01 mg/g/hr) at a rate of 0.09 ml/10g/hr by a continuous intraperitoneal infusion. Mice were ventilated 30 ml/kg at 65 breaths/min[39] without PEEP for 2 to 8 hrs while breathing room air. Transmission electromicroscopy, Western blot, and malondialdehyde (free radical) were measured. The expression of phospho-Akt was studied by immunohistochemistry. Results: High tidal volume mechanical ventilation induced Akt, JNK, and fork-head homeobox type O (FOXO) 4 activation in a time-dependent manner, disrupted myofibrils in diaphragm, positive staining of phospho-Akt in diaphragm membrane, and production of free radicals. Mechanical ventilation of Akt deficient mice attenuated diaphragmatic injury, Akt, JNK, and Foxo4 activation, and free radical production. Conclusions: We conclude that large tidal volume mechanical ventilation induces diaphragmatic dysfunction and free radical production hrough activation of the Akt and JNK pathways.