Godar Rebecca J, Ma Xiucui, Liu Haiyan, Murphy John T, Weinheimer Carla J, Kovacs Attila, Crosby Seth D, Saftig Paul, Diwan Abhinav
a Division of Cardiology and Center for Cardiovascular Research ; Department of Internal Medicine; Washington University School of Medicine ; St. Louis , MO USA.
b John Cochran VA Medical Center ; St. Louis , MO USA.
Autophagy. 2015;11(9):1537-60. doi: 10.1080/15548627.2015.1063768.
Autophagy, a lysosomal degradative pathway, is potently stimulated in the myocardium by fasting and is essential for maintaining cardiac function during prolonged starvation. We tested the hypothesis that intermittent fasting protects against myocardial ischemia-reperfusion injury via transcriptional stimulation of the autophagy-lysosome machinery. Adult C57BL/6 mice subjected to 24-h periods of fasting, every other day, for 6 wk were protected from in-vivo ischemia-reperfusion injury on a fed day, with marked reduction in infarct size in both sexes as compared with nonfasted controls. This protection was lost in mice heterozygous null for Lamp2 (coding for lysosomal-associated membrane protein 2), which demonstrate impaired autophagy in response to fasting with accumulation of autophagosomes and SQSTM1, an autophagy substrate, in the heart. In lamp2 null mice, intermittent fasting provoked progressive left ventricular dilation, systolic dysfunction and hypertrophy; worsening cardiomyocyte autophagosome accumulation and lack of protection to ischemia-reperfusion injury, suggesting that intact autophagy-lysosome machinery is essential for myocardial homeostasis during intermittent fasting and consequent ischemic cardioprotection. Fasting and refeeding cycles resulted in transcriptional induction followed by downregulation of autophagy-lysosome genes in the myocardium. This was coupled with fasting-induced nuclear translocation of TFEB (transcription factor EB), a master regulator of autophagy-lysosome machinery; followed by rapid decline in nuclear TFEB levels with refeeding. Endogenous TFEB was essential for attenuation of hypoxia-reoxygenation-induced cell death by repetitive starvation, in neonatal rat cardiomyocytes, in-vitro. Taken together, these data suggest that TFEB-mediated transcriptional priming of the autophagy-lysosome machinery mediates the beneficial effects of fasting-induced autophagy in myocardial ischemia-reperfusion injury.
自噬是一种溶酶体降解途径，在心肌中可被禁食强烈刺激，并且在长期饥饿期间对于维持心脏功能至关重要。我们检验了这样一种假说，即间歇性禁食通过对自噬-溶酶体机制的转录刺激来预防心肌缺血-再灌注损伤。成年C57BL/6小鼠每隔一天进行24小时禁食，持续6周，在喂食日可免受体内缺血-再灌注损伤，与未禁食的对照组相比，两性的梗死面积均显著减小。这种保护作用在Lamp2（编码溶酶体相关膜蛋白2）杂合缺失的小鼠中丧失，这些小鼠在禁食时自噬受损，心脏中自噬体和自噬底物SQSTM1积累。在Lamp2基因敲除小鼠中，间歇性禁食引发进行性左心室扩张、收缩功能障碍和肥大；心肌细胞自噬体积累恶化，对缺血-再灌注损伤缺乏保护作用，这表明完整的自噬-溶酶体机制对于间歇性禁食期间的心肌稳态以及随之而来的缺血性心脏保护至关重要。禁食和再喂食周期导致心肌中自噬-溶酶体基因的转录诱导，随后下调。这与禁食诱导的自噬-溶酶体机制的主要调节因子TFEB（转录因子EB）的核转位相关；再喂食后核TFEB水平迅速下降。在新生大鼠心肌细胞体外实验中，内源性TFEB对于重复饥饿减轻缺氧-复氧诱导的细胞死亡至关重要。综上所述，这些数据表明，TFEB介导的自噬-溶酶体机制的转录启动介导了禁食诱导的自噬在心肌缺血-再灌注损伤中的有益作用。
