Ma Tao, Zhao YongBo, Kwak Young-Don, Yang Zhangmin, Thompson Robert, Luo Zhijun, Xu Huaxi, Liao Francesca-Fang
Department of Pharmacology, University of Tennessee Health Science Center, College of Medicine, Memphis, Tennessee 38163, USA.
J Neurosci. 2009 Sep 9;29(36):11226-36. doi: 10.1523/JNEUROSCI.6150-08.2009.
The widely used cholesterol-lowering drugs, statins, were reported to reduce the incidence of stroke and the progression of Alzheimer's disease. However, little is known on how statins exert these beneficial effects. In this study, we investigated the molecular mechanisms underlying the neuroprotective actions of statins in primary cultured cortical neurons. We found that chronic treatment of neurons with a low dosage of two CNS-permeable statins (lovastatin and simvastatin) selectively reduced NMDA-induced cell death but not the caspase-mediated apoptosis. The protective effects of stains were inhibited by mevalonate, a PI3K inhibitor, and tyrphostin AG538, suggesting roles for cholesterol and insulin/IGF-1 signaling in the neurotoxic response. We further demonstrate that statins block calcium-dependent calpain activation, resulting in complete suppression of protein truncation events on multiple calpain substrates that are involved in neuronal death including CDK5 coactivator p35 cleavage to p25, GSK3 and beta-catenin. This is followed by reduced and increased nuclear translocation of p25 and beta-catenin, respectively. Under excitotoxic conditions, the activities of CDK5 and beta-catenin are exclusively regulated by calpain-mediated cleavage while apoptosis modulates beta-catenin mainly through phosphorylation. Strikingly, our data demonstrate that the calpain-blocking effect of statins is largely mediated by stimulation of alpha-secretase cleavage of APP, resulting in increased secretion of its soluble form, sAPP. Finally, our data suggest that statin-regulated sAPP secretion occurs via activation of the PI3K pathway and inhibition of ROCK signaling. Altogether, our study provides novel insights into statin-mediated neuronal excitoprotection through both cholesterol-dependent and -independent mechanisms and links them to calpain-mediated neuronal death.
广泛使用的降胆固醇药物他汀类药物据报道可降低中风发病率和阿尔茨海默病的进展。然而，关于他汀类药物如何发挥这些有益作用却知之甚少。在本研究中，我们调查了他汀类药物在原代培养皮质神经元中神经保护作用的分子机制。我们发现，用两种可透过中枢神经系统的低剂量他汀类药物（洛伐他汀和辛伐他汀）长期处理神经元，可选择性降低N-甲基-D-天冬氨酸（NMDA）诱导的细胞死亡，但不影响半胱天冬酶介导的细胞凋亡。甲羟戊酸、一种磷脂酰肌醇-3-激酶（PI3K）抑制剂和 tyrphostin AG538可抑制他汀类药物的保护作用，提示胆固醇和胰岛素/胰岛素样生长因子-1（IGF-1）信号在神经毒性反应中发挥作用。我们进一步证明，他汀类药物可阻断钙依赖性钙蛋白酶激活，从而完全抑制多个参与神经元死亡的钙蛋白酶底物上的蛋白质截断事件，包括细胞周期蛋白依赖性激酶5（CDK5）共激活因子p35裂解为p25、糖原合成酶激酶3（GSK3）和β-连环蛋白。随后，p25和β-连环蛋白的核转位分别减少和增加。在兴奋性毒性条件下，CDK5和β-连环蛋白的活性仅由钙蛋白酶介导的裂解调节，而细胞凋亡主要通过磷酸化调节β-连环蛋白。引人注目的是，我们的数据表明，他汀类药物的钙蛋白酶阻断作用很大程度上是通过刺激淀粉样前体蛋白（APP）的α-分泌酶裂解介导的，导致其可溶性形式sAPP的分泌增加。最后，我们的数据表明，他汀类药物调节的sAPP分泌是通过激活PI3K途径和抑制Rho相关卷曲螺旋形成蛋白激酶（ROCK）信号发生的。总之，我们的研究通过胆固醇依赖性和非依赖性机制为他汀类药物介导的神经元兴奋保护作用提供了新的见解，并将它们与钙蛋白酶介导的神经元死亡联系起来。
