Department of Pharmacology, Second Military Medical University, Shanghai, China.
Ann Neurol. 2011 Feb;69(2):360-74. doi: 10.1002/ana.22236. Epub 2011 Jan 19.
Stroke is a leading cause of mortality and disability. Nicotinamide phosphoribosyltransferase (Nampt) is the rate-limiting enzyme in mammalian nicotinamide adenine dinucleotide (NAD)(+) biosynthesis and contributes to cell fate decisions. However, the role of Nampt in brain and stroke remains to be investigated.
We used lentivirus-mediated Nampt overexpression and knockdown to manipulate Nampt expression and explore the effects of Nampt in neuronal survival on ischemic stress both in vivo and in vitro. We also used adenosine monophosphate (AMP)-activated kinase-α2 (AMPKα2) and silent mating type information regulation 2 homolog 1 (SIRT1) knockout mice to investigate the underlying mechanisms of Nampt neuroprotection.
Nampt inhibition by a highly-specific Nampt inhibitor, FK866, aggravated brain infarction in experimentally cerebral ischemia rats, whereas Nampt overexpression in local brain and Nampt enzymatic product nicotinamide mononucleotide (NMN) reduced ischemia-induced cerebral injuries. Nampt overexpression and knockdown regulated neuron survival via the AMPK pathway. Neuroprotection of Nampt was abolished in AMPKα2(-/-) neurons. In neurons, Nampt positively modulated NAD(+) levels and thereby controlled SIRT1 activity. SIRT1 coprecipitated with serine/threonine kinase 11 (LKB1), an upstream kinase of AMPK, and promoted LKB1 deacetylation in neurons. Nampt-induced LKB1 deacetylation and AMPK activation disappeared in SIRT1(-/-) neurons. In contrast, Ca(2+) /calmodulin-dependent protein kinase kinase-β (CaMKK-β), another upstream kinase of AMPK, was not involved in the neuroprotection of Nampt. More important, Nampt overexpression-induced neuroprotection was abolished in SIRT1(+/-) and AMPKα2(-/-) mice.
Our findings reveal that Nampt protects against ischemic stroke through rescuing neurons from death via the SIRT1-dependent AMPK pathway and indicate that Nampt is a new therapeutic target for stroke.
中风是导致死亡和残疾的主要原因。烟酰胺磷酸核糖转移酶（Nampt）是哺乳动物烟酰胺腺嘌呤二核苷酸（NAD +）生物合成的限速酶，有助于细胞命运的决定。然而，Nampt 在大脑和中风中的作用仍有待研究。
我们使用慢病毒介导的 Nampt 过表达和敲低来操纵 Nampt 表达，并在体内和体外探索 Nampt 对缺血应激下神经元存活的影响。我们还使用单磷酸腺苷（AMP）激活的蛋白激酶-α2（AMPKα2）和沉默交配型信息调节 2 同源物 1（SIRT1）敲除小鼠来研究 Nampt 神经保护的潜在机制。
高度特异性的 Nampt 抑制剂 FK866 抑制 Nampt 加重了实验性脑缺血大鼠的脑梗死，而局部脑 Nampt 过表达和 Nampt 酶产物烟酰胺单核苷酸（NMN）减少了缺血引起的脑损伤。Nampt 过表达和敲低通过 AMPK 途径调节神经元存活。AMPKα2（-/-）神经元中的 Nampt 神经保护作用被消除。在神经元中，Nampt 正向调节 NAD +水平，从而控制 SIRT1 活性。SIRT1 与丝氨酸/苏氨酸激酶 11（LKB1）共沉淀，LKB1 是 AMPK 的上游激酶，并促进神经元中 LKB1 的去乙酰化。在 SIRT1（-/-）神经元中，Nampt 诱导的 LKB1 去乙酰化和 AMPK 激活消失。相反，钙/钙调蛋白依赖性蛋白激酶激酶-β（CaMKK-β），另一种 AMPK 的上游激酶，不参与 Nampt 的神经保护作用。更重要的是，在 SIRT1（+/-）和 AMPKα2（-/-）小鼠中，Nampt 过表达诱导的神经保护作用被消除。
我们的研究结果表明，Nampt 通过 SIRT1 依赖性 AMPK 途径挽救神经元免于死亡来保护缺血性中风，并表明 Nampt 是中风的一个新的治疗靶点。
