Investigation of mechanism of developing neonatal hypoxic ischemic encephalopathy establishment of novel therapy.

本研究观察了新生儿缺氧缺血性脑病模型仔猪12小时后神经元中诱导型一氧化氮合酶（inducible nitric oxide synthase，iNOS）的表达。血液中的生物蝶呤（称为iNOS的辅助因子）水平也有所增加。NMDA受体拮抗剂MK-801可抑制这种增加。但iNOS的表达不受影响。鸟苷三磷酸环化水解酶I（GTPCH）是生物蝶呤合成途径的限速酶。先前的报道描述了促炎细胞因子上调GTPCH的活性。提示兴奋性神经传递影响促炎细胞因子的合成。另一方面，用谷氨酸类似物海人酸建立的大鼠癫痫持续状态模型，神经元中iNOS无明显增加。以上结果提示，猪与啮齿类动物的信号转导途径不同，人Segawa病是由GTPCH缺陷引起的。一般来说，生物喋呤缺乏会导致高苯丙氨酸血症。而Segawa病患者的血苯丙氨酸浓度在正常范围内，因为Segawa病患者的GTPCH突变是杂合的。我们比较了Segawa病患者和对照组之间的血苯丙氨酸水平。结果表明，濑川病患者血苯丙氨酸水平在正常范围内，但明显高于对照组。

In this study, we found the expression of inducible nitric oxide synthase (iNOS) in neurons of severe neonatal hypoxic ischemic encephalopathy model piglets after 12 hours. Level of blood biopterin, known as a co-factor of iNOS, was also increased. The increase was inhibited by MK-801, one of NMDA receptor antagonist. However, expression of iNOS was not affected. Guanosine triphosphate cyclohydrolase I (GTPCH) is the rate-limiting enzyme of biopterin synthesis pathway. Previous reports described that proinflammatory cytokines up-regulated the activity of GTPCH. It was suggested that excitatory neurotransmission affected the synthesis of proinflammatory cytokines. On the other hand, rat model of status epilepticus by using kainic acid, an analogue of glutamate, indicated no increase of iNOS in neuron. Those results suggested that the pathways of signal transductions were different between swine and rodents.Human Segawa Disease was caused by the defect of GTPCH. Generally, biopterin shortage causes hyperphenylalaninemia. However blood phenylalanine concentration of Segawa disease patients was within normal range, for the mutations of GTPCH in Segawa disease were heterozygous. We compared blood phenylalanine levels between patients of Segawa disease and controls. The result was that the blood phenylalanine level in Segawa disease was within normal range however the values were significantly higher than those of controls.