Choi Ji Woong, Yoo Byoung-Kwon, Shin Chan Young, Ryu Mi-Kyoung, Ryu Jong Hoon, el Kouni Mahmoud H, Lee Jae-Chul, Kim Won-Ki, Ko Kwang Ho
Department of Pharmacology, College of Pharmacy, Seoul National University, Shillim-Dong, Kwanak-Gu, Seoul, Republic of Korea.
Neurosci Res. 2006 Sep;56(1):111-8. doi: 10.1016/j.neures.2006.06.004. Epub 2006 Jul 12.
We previously reported that in immunostimulated astrocytes, glucose deprivation induced cell death via the loss of ATP, reduced glutathione, and mitochondrial transmembrane potential. The cytotoxicity was due to reactive nitrogen and oxygen species and blocked by adenosine, a purine nucleoside, via the preservation of cellular ATP. Here, we investigated whether uridine, a pyrimidine nucleoside, could prevent the glucose deprivation-induced cytotoxicity in LPS+IFN-gamma-treated (immunostimulated) astrocytes. Glucose deprivation induced the death of immunostimulated cells, which was significantly reduced by uridine. Glucose deprivation rapidly decreased cellular ATP levels in immunostimulated astrocytes, which was also reversed by uridine. The inhibition of cellular uptake of uridine by S-(4-nitrobenzyl)-6-thioinosine attenuated the protective effect of uridine. mRNA and protein expression for uridine phosphorylase, an enzyme catalyzing reversible phosphorolysis of uridine, were observed in rat brain as well as primary astrocytes. 5-(Phenylthio)acyclouridine (PTAU), a specific inhibitor of uridine phosphorylase, inhibited the protective effect of uridine. Additionally, the loss of mitochondrial transmembrane potential and reduced glutathione by glucose deprivation in immunostimulated cells was attenuated by uridine, which was also reversed by PTAU. These results provide the first evidence that uridine protects immunostimulated astrocytes against the glucose deprivation-induced death by preserving intracellular ATP through the action of uridine phosphorylase.
我们之前报道过，在免疫刺激的星形胶质细胞中，葡萄糖剥夺通过ATP、还原型谷胱甘肽的丧失以及线粒体跨膜电位的降低诱导细胞死亡。细胞毒性归因于活性氮和氧物种，并被嘌呤核苷腺苷通过保存细胞ATP所阻断。在此，我们研究了嘧啶核苷尿苷是否能预防LPS + IFN-γ处理（免疫刺激）的星形胶质细胞中葡萄糖剥夺诱导的细胞毒性。葡萄糖剥夺诱导免疫刺激细胞死亡，而尿苷可显著减少这种死亡。葡萄糖剥夺迅速降低免疫刺激星形胶质细胞中的细胞ATP水平，这也被尿苷逆转。S-(4-硝基苄基)-6-硫代肌苷对尿苷细胞摄取的抑制减弱了尿苷的保护作用。在大鼠脑以及原代星形胶质细胞中观察到了尿苷磷酸化酶（一种催化尿苷可逆磷酸解的酶）的mRNA和蛋白表达。尿苷磷酸化酶的特异性抑制剂5-(苯硫基)阿昔洛韦（PTAU）抑制了尿苷的保护作用。此外，免疫刺激细胞中葡萄糖剥夺导致的线粒体跨膜电位丧失和还原型谷胱甘肽减少被尿苷减弱，而PTAU也可使其逆转。这些结果提供了首个证据，即尿苷通过尿苷磷酸化酶的作用保存细胞内ATP，从而保护免疫刺激的星形胶质细胞免受葡萄糖剥夺诱导的死亡。
