Increased Proteolysis, Myosin Depletion, and Atrophic AKT-FOXO Signaling in Human Diaphragm Disuse
Increased Proteolysis, Myosin Depletion, and Atrophic AKT-FOXO Signaling in Human Diaphragm Disuse
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DOI：
10.1164/rccm.200910-1487oc
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发表时间：
2011-02-15
影响因子：
24.7
通讯作者：
Budak, Murat T.
中科院分区：
文献类型：
--
作者：
Levine, Sanford;Biswas, Chhanda;Budak, Murat T.
基本原理：机械通气的患者长时间表现出膈肌不活动（病例受试者）发展为横膈膜力产生能力下降，伴有横膈膜肌纤维萎缩。我们的目的是检验通过泛素-蛋白酶体途径增加蛋白水解，降低肌球蛋白重链（MyHC）水平，和萎缩的AKT-FOXO信号在引起这些与膈肌废用相关的病理变化中起主要作用。18例受试者于取材前取肋膈活检标本例并与11名因良性病变或局部肺癌接受手术的患者（对照组）的横膈膜的术中标本进行比较。病例受试者有隔膜不活动，并进行机械通气18至72小时，而这种状态在对照组被限制为2至4 hours.Measurements和主要结果：相对于细胞质组分中的蛋白水解，情况下隔膜表现出更高水平的泛素化蛋白结合物，增加活性的265蛋白酶体，和降低水平的MyHCs和α-肌动蛋白。关于核组分中的萎缩信号传导，病例横膈膜显示磷酸化AKT、磷酸化FOXO 1减少，Atrogin-1和MuRF-1与共有DNA序列的结合增加，DNA-FOXO 1复合物与针对FOXO 1的特异性抗体的超移位增加，以及整个肌纤维裂解物中Atrogin-1和MuRF-1转录物增加。我们的研究结果表明，泛素-蛋白酶体途径的活性增加，MyHCs的显着减少，以及萎缩的AKT-FOXO信号在引起肌纤维萎缩和膈肌力量产生与长期人类膈肌废用相关的减少中发挥重要作用。
Rationale: Patients on mechanical ventilation who exhibit diaphragm inactivity for a prolonged time (case subjects) develop decreases in diaphragm force-generating capacity accompanied by diaphragm myofiber atrophy.Objectives: Our objectives were to test the hypotheses that increased proteolysis by the ubiquitin-proteasome pathway, decreases in myosin heavy chain (MyHC) levels, and atrophic AKT-FOXO signaling play major roles in eliciting these pathological changes associated with diaphragm disuse.Methods: Biopsy specimens were obtained from the costal diaphragms of 18 case subjects before harvest (cases) and compared with intraoperative specimens from the diaphragms of 11 patients undergoing surgery for benign lesions or localized lung cancer (control subjects). Case subjects had diaphragm inactivity and underwent mechanical ventilation for 18 to 72 hours, whereas this state in controls was limited to 2 to 4 hours.Measurements and Main Results: With respect to proteolysis in cytoplasm fractions, case diaphragms exhibited greater levels of ubiquitinated-protein conjugates, increased activity of the 265 proteasome, and decreased levels of MyHCs and a-actin. With respect to atrophic signaling in nuclear fractions, case diaphragms exhibited decreases in phosphorylated AKT, phosphorylated FOXO1, increased binding to consensus DNA sequence for Atrogin-1 and MuRF-1, and increased supershift of DNA-FOXO1 complexes with specific antibodies against FOXO1, as well as increased Atrogin-1 and MuRF-1 transcripts in whole myofiber lysates.Conclusions: Our findings suggest that increased activity of the ubiquitin-proteasome pathway, marked decreases in MyHCs, and atrophic AKT-FOXO signaling play important roles in eliciting the myofiber atrophy and decreases in diaphragm force generation associated with prolonged human diaphragm disuse.