Experimental Evidence that Phenylalanine Provokes Oxidative Stress in Hippocampus and Cerebral Cortex of Developing Rats
Experimental Evidence that Phenylalanine Provokes Oxidative Stress in Hippocampus and Cerebral Cortex of Developing Rats
复制标题
DOI：
10.1007/s10571-009-9455-6
复制
发表时间：
2010-03-01
影响因子：
4
通讯作者：
Wajner, Moacir
中科院分区：
文献类型：
--
作者：
Fernandes, Carolina G.;Leipnitz, Guilhian;Wajner, Moacir
高水平的苯丙氨酸 (Phe) 是苯丙酮尿症 (PKU) 的生化标志，苯丙酮尿症 (PKU) 是一种神经代谢紊乱，临床特征为严重智力低下和其他大脑异常，包括皮质萎缩和小头畸形。考虑到导致脑损伤的病理机制，特别是这种疾病中明显的认知障碍，我们知之甚少，在本研究中，我们研究了与 PKU 患者大脑中发现的浓度相似的 Phe 对发育中大鼠海马和大脑皮层氧化应激重要参数的体外影响。我们发现 Phe 在两个大脑结构中诱导体外脂质过氧化（TBA-RS 值增加）和蛋白质氧化损伤（巯基氧化）。此外，这些作用可能是由活性氧介导的，因为自由基清除剂α-生育酚和褪黑激素完全可以防止脂质氧化损伤，但一氧化氮合酶的有效抑制剂L-NAME则不能。因此，Phe 不会诱导一氧化氮合成，但会显着降低海马和大脑皮层上清液中还原型谷胱甘肽 (GSH) 的水平，GSH 是大脑主要的抗氧化防御手段。 Phe 还可以还原无细胞培养基中商业 GSH 溶液的硫醇基团。我们还发现 Phe 分解代谢的主要代谢物苯丙酮酸、苯乳酸和苯乙酸也会增加大脑皮层中的 TBA-RS 水平，但程度较小。数据表明，Phe 会引起海马体（主要与学习/记忆相关的结构）以及大脑皮层的氧化应激，而 PKU 患者的大脑皮层严重受损。因此推测这种病理机制可能至少部分涉及严重认知缺陷以及与这种疾病中观察到的髓鞘形成障碍和脑白质营养不良相关的特征性皮质萎缩。
High levels of phenylalanine (Phe) are the biochemical hallmark of phenylketonuria (PKU), a neurometabolic disorder clinically characterized by severe mental retardation and other brain abnormalities, including cortical atrophy and microcephaly. Considering that the pathomechanisms leading to brain damage and particularly the marked cognitive impairment in this disease are poorly understood, in the present study we investigated the in vitro effect of Phe, at similar concentrations as to those found in brain of PKU patients, on important parameters of oxidative stress in the hippocampus and cerebral cortex of developing rats. We found that Phe induced in vitro lipid peroxidation (increase of TBA-RS values) and protein oxidative damage (sulfhydryl oxidation) in both cerebral structures. Furthermore, these effects were probably mediated by reactive oxygen species, since the lipid oxidative damage was totally prevented by the free radical scavengers alpha-tocopherol and melatonin, but not by L-NAME, a potent inhibitor of nitric oxide synthase. Accordingly, Phe did not induce nitric oxide synthesis, but significantly decreased the levels of reduced glutathione (GSH), the major brain antioxidant defense, in hippocampus and cerebral cortex supernatants. Phe also reduced the thiol groups of a commercial GSH solution in a cell-free medium. We also found that the major metabolites of Phe catabolism, phenylpyruvate, phenyllactate and phenylacetate also increased TBA-RS levels in cerebral cortex, but to a lesser degree. The data indicate that Phe elicits oxidative stress in the hippocampus, a structure mainly involved with learning/memory, and also in the cerebral cortex, which is severely damaged in PKU patients. It is therefore presumed that this pathomechanism may be involved at least in part in the severe cognitive deficit and in the characteristic cortical atrophy associated with dysmyelination and leukodystrophy observed in this disorder.