Silent Information Regulator 1 (SIRT1), an NAD+-dependent deacetylase, contributes to the neuroprotective effect. However, intracellular signaling pathways that affect SIRT1 function remain unknown. It is well known that N-methyl-D-aspartate (NMDA) receptor activation induces calcium influx which then activates PKC, and SIRT1 is a mRNA target for HuR protein. We hypothesize that Ca2+-PKC-HuR-SIRT1 pathway modulates SIRT1 function. The present study is to investigate the potential pathway of SIRT1 in the SH-SY5Y cell line as an in vitro model of NMDA-induced neurotoxicity. The results showed that: (1) SIRT1 levels were downregulated in NMDA model; (2) NMDA induced an increase in serine phosphorylation of HuR, while inhibition of serine phosphorylation of HuR increased SIRT1 levels, promoting cell survival; (3) PKC inhibitor (Gö 6976) reversed NMDA insults and also suppressed serine phosphorylation of HuR; (4) 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA-AM), an intracellular calcium chelator, fully reversed NMDA insults and also inhibited PKC activity evoked by NMDA. These results indicate that intracellular elevated Ca2+ activates PKC, which phosphorylates HuR and then promotes SIRT1 mRNA decay and subsequent neuronal death in NMDA model. Therefore, the study suggests that inhibition of Ca2+-PKC-HuR-SIRT1 pathway could be an effective strategy for preventing certain neurological diseases related to NMDA excitotoxicity.

中文翻译：

---

NMDA 诱导的兴奋性毒性中 SIRT1 信号通路的调节

Silent Information Regulator 1 (SIRT1) 是一种 NAD+ 依赖性脱乙酰酶，有助于神经保护作用。然而，影响 SIRT1 功能的细胞内信号通路仍然未知。众所周知，N-甲基-D-天冬氨酸 (NMDA) 受体激活会诱导钙内流，然后激活 PKC，而 SIRT1 是 HuR 蛋白的 mRNA 靶标。我们假设 Ca2+-PKC-HuR-SIRT1 通路调节 SIRT1 功能。本研究旨在研究 SIRT1 在 SH-SY5Y 细胞系中作为 NMDA 诱导的神经毒性体外模型的潜在途径。结果表明：（1）NMDA模型中SIRT1水平下调；(2)NMDA诱导HuR丝氨酸磷酸化增加，而抑制HuR丝氨酸磷酸化增加SIRT1水平，促进细胞存活；(3) PKC 抑制剂 (Gö 6976) 逆转 NMDA 损伤并抑制 HuR 的丝氨酸磷酸化；(4) 1,2-双(2-氨基苯氧基)乙烷-N,N,N',N'-四乙酸 (BAPTA-AM)，一种细胞内钙螯合剂，可完全逆转 NMDA 损伤并抑制 NMDA 引起的 PKC 活性. 这些结果表明细胞内升高的 Ca2+ 激活 PKC，PKC 使 HuR 磷酸化，然后促进 NMDA 模型中的 SIRT1 mRNA 衰减和随后的神经元死亡。因此，该研究表明，抑制 Ca2+-PKC-HuR-SIRT1 通路可能是预防某些与 NMDA 兴奋性毒性相关的神经系统疾病的有效策略。完全逆转 NMDA 损伤并抑制 NMDA 引起的 PKC 活性。这些结果表明细胞内升高的 Ca2+ 激活 PKC，PKC 使 HuR 磷酸化，然后在 NMDA 模型中促进 SIRT1 mRNA 衰减和随后的神经元死亡。因此，该研究表明，抑制 Ca2+-PKC-HuR-SIRT1 通路可能是预防某些与 NMDA 兴奋性毒性相关的神经系统疾病的有效策略。完全逆转 NMDA 损伤并抑制 NMDA 引起的 PKC 活性。这些结果表明细胞内升高的 Ca2+ 激活 PKC，PKC 使 HuR 磷酸化，然后促进 NMDA 模型中的 SIRT1 mRNA 衰减和随后的神经元死亡。因此，该研究表明，抑制 Ca2+-PKC-HuR-SIRT1 通路可能是预防某些与 NMDA 兴奋性毒性相关的神经系统疾病的有效策略。