Fleck Courtney C, Carey Hannah V
Dept. of Comparative Biosciences, University of Wisconsin, 2015 Linden Drive, Madison, WI 53706, USA.
Am J Physiol Regul Integr Comp Physiol. 2005 Aug;289(2):R586-R595. doi: 10.1152/ajpregu.00100.2005. Epub 2005 Apr 14.
Mammalian hibernation is associated with several events that can affect programmed cell death (apoptosis) in nonhibernators, including marked changes in blood flow, extended fasting, and oxidative stress. However, the effect of hibernation on apoptosis is poorly understood. Here, we investigated apoptosis and expression of proteins involved in apoptotic pathways in intestinal mucosa of summer and hibernating ground squirrels. We used terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) to identify possible apoptotic enterocytes in small intestine of summer squirrels and hibernating squirrels throughout the winter. Nuclear TUNEL staining increased as hibernation progressed, but the staining pattern was diffuse and not accompanied by chromatin condensation or apoptotic bodies. Electrophoresis of mucosal DNA revealed no ladders typical of apoptosis. Nuclear levels of proapoptotic p53 protein were fourfold less in hibernators compared with summer squirrels. A 12-fold increase in anti-apoptotic Bcl-x(L) compared with a 2-fold increase in proapoptotic Bax suggested a balance in favor of antiapoptotic signaling in hibernators. There was no change in Bcl-2 protein expression but phospho-Bcl-2 increased in mucosa of hibernators. Hibernation had minimal effects on expression of active caspase-8 or -9, whereas caspase-3-specific activity was lower in hibernators during an interbout arousal compared with summer squirrels. Expression of the prosurvival protein Akt increased 20-fold during hibernation, but phospho-Akt was not altered. These data provide evidence for enhanced expression of antiapoptotic proteins during hibernation that may promote enterocyte survival in a pro-oxidative, proapoptotic environment.
哺乳动物的冬眠与一些会影响非冬眠动物程序性细胞死亡（凋亡）的事件有关，包括血流量的显著变化、长期禁食和氧化应激。然而，冬眠对凋亡的影响却知之甚少。在此，我们研究了夏季和冬眠地松鼠肠道黏膜中凋亡情况以及凋亡途径相关蛋白的表达。我们使用末端脱氧核苷酸转移酶介导的dUTP缺口末端标记法（TUNEL）来识别整个冬季夏季松鼠和冬眠松鼠小肠中可能发生凋亡的肠上皮细胞。随着冬眠进程的推进，细胞核TUNEL染色增加，但染色模式呈弥散状，且未伴有染色质凝聚或凋亡小体。黏膜DNA电泳未显示出典型的凋亡梯状条带。与夏季松鼠相比，冬眠动物促凋亡p53蛋白的细胞核水平降低了四倍。抗凋亡蛋白Bcl-x(L)增加了12倍，而促凋亡蛋白Bax仅增加了2倍，这表明冬眠动物中抗凋亡信号占优势。Bcl-2蛋白表达没有变化，但冬眠动物黏膜中磷酸化Bcl-2增加。冬眠对活性半胱天冬酶-8或-9的表达影响极小，而与夏季松鼠相比，冬眠动物在一次间眠觉醒期间半胱天冬酶-3的特异性活性较低。促生存蛋白Akt在冬眠期间表达增加了20倍，但磷酸化Akt未发生改变。这些数据为冬眠期间抗凋亡蛋白表达增强提供了证据，这可能在促氧化、促凋亡环境中促进肠上皮细胞存活。
