Stefanelli C, Stanic I, Bonavita F, Flamigni F, Pignatti C, Guarnieri C, Caldarera C M
Department of Biochemistry G. Moruzzi, University of Bologna, Italy.
Biochem Biophys Res Commun. 1998 Feb 24;243(3):821-6. doi: 10.1006/bbrc.1998.8154.
The AMP-activated protein kinase (AMPK) is related to a growing family of protein kinases that are believed to protect cells against environmental and nutritional stress. In the present study the hypothesis of a protective role for AMPK against thymocyte apoptosis has been tested. It is shown that AMPK is expressed in rat thymocytes that contain the transcript for the a1 isoform of the AMPK catalytic subunit and can be activated by treatment with 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR), a well-established activator of AMPK. AICAR is not toxic and prevents glucocorticoid-induced apoptosis in the same concentration range used to activate AMPK. At concentrations higher than 1 mM, AICAR fully restores cell viability and inhibits DNA laddering in dexamethasone-treated thymocytes. Furthermore, AICAR blocks the dexamethasone-induced activation of caspase 3-like enzymes, which are believed to play a pivotal role in apoptotic cell death. Activation of AMPK by oligomycin, which depletes thymocytes of ATP, is also correlated to inhibition of caspase 3-like activity in dexamethasone-treated cells. However, AICAR and oligomycin do not exert any protective action when apoptosis is induced by staurosporine. These results indicate that AICAR is a powerful inhibitor of glucocorticoid-induced apoptosis and suggest that AMPK activation may interfere with a step in the apoptotic cascade triggered by dexamethasone.
AMP激活的蛋白激酶（AMPK）与越来越多的蛋白激酶家族相关，这些蛋白激酶被认为能保护细胞免受环境和营养应激的影响。在本研究中，对AMPK在保护胸腺细胞免受凋亡方面的作用这一假说进行了验证。结果表明，AMPK在大鼠胸腺细胞中表达，这些细胞含有AMPK催化亚基α1亚型的转录本，并且可以通过用5-氨基咪唑-4-甲酰胺核苷（AICAR）处理来激活，AICAR是一种公认的AMPK激活剂。AICAR无毒，并且在用于激活AMPK的相同浓度范围内可防止糖皮质激素诱导的凋亡。在高于1 mM的浓度下，AICAR能完全恢复细胞活力并抑制地塞米松处理的胸腺细胞中的DNA梯状条带形成。此外，AICAR可阻断地塞米松诱导的caspase 3样酶的激活，这些酶被认为在凋亡性细胞死亡中起关键作用。通过寡霉素激活AMPK（寡霉素会耗尽胸腺细胞中的ATP）也与抑制地塞米松处理细胞中的caspase 3样活性相关。然而，当由星形孢菌素诱导凋亡时，AICAR和寡霉素没有发挥任何保护作用。这些结果表明，AICAR是糖皮质激素诱导凋亡的有力抑制剂，并提示AMPK激活可能会干扰地塞米松触发的凋亡级联反应中的一个步骤。
