da Silva Janaína Camacho, Amaral Alexandre Umpierrez, Cecatto Cristiane, Wajner Alessandro, Dos Santos Godoy Kálita, Ribeiro Rafael Teixeira, de Mello Gonçalves Aline, Zanatta Ângela, da Rosa Mateus Struecker, Loureiro Samanta Oliveira, Vargas Carmen Regla, Leipnitz Guilhian, de Souza Diogo Onofre Gomes, Wajner Moacir
Programa de Pós-Graduação em Ciências Biológicas: Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Departamento de Ciências Biológicas, Universidade Regional Integrada do Alto Uruguai e das Missões, Erechim, RS, Brazil.
Neurotox Res. 2017 Aug;32(2):276-290. doi: 10.1007/s12640-017-9735-8. Epub 2017 Apr 20.
Tissue accumulation of α-ketoadipic (KAA) and α-aminoadipic (AAA) acids is the biochemical hallmark of α-ketoadipic aciduria. This inborn error of metabolism is currently considered a biochemical phenotype with uncertain clinical significance. Considering that KAA and AAA are structurally similar to α-ketoglutarate and glutamate, respectively, we investigated the in vitro effects of these compounds on glutamatergic neurotransmission in the brain of adolescent rats. Bioenergetics and redox homeostasis were also investigated because they represent fundamental systems for brain development and functioning. We first observed that AAA significantly decreased glutamate uptake, whereas glutamate dehydrogenase activity was markedly inhibited by KAA in a competitive fashion. In addition, AAA and more markedly KAA induced generation of reactive oxygen and nitrogen species (increase of 2',7'-dichloroflurescein (DCFH) oxidation and nitrite/nitrate levels), lipid peroxidation (increase of malondialdehyde concentrations), and protein oxidation (increase of carbonyl formation and decrease of sulfhydryl content), besides decreasing the antioxidant defenses (reduced glutathione (GSH)) and aconitase activity. Furthermore, KAA-induced lipid peroxidation and GSH decrease were prevented by the antioxidants α-tocopherol, melatonin, and resveratrol, suggesting the involvement of reactive species in these effects. Noteworthy, the classical inhibitor of NMDA glutamate receptors MK-801 was not able to prevent KAA-induced and AAA-induced oxidative stress, determined by DCFH oxidation and GSH levels, making unlikely a secondary induction of oxidative stress through overstimulation of glutamate receptors. In contrast, KAA and AAA did not significantly change brain bioenergetic parameters. We speculate that disturbance of glutamatergic neurotransmission and redox homeostasis by KAA and AAA may play a role in those cases of α-ketoadipic aciduria that display neurological symptoms.
α-酮己二酸（KAA）和α-氨基己二酸（AAA）在组织中的蓄积是α-酮己二酸尿症的生化标志。这种先天性代谢缺陷目前被认为是一种临床意义尚不明确的生化表型。鉴于KAA和AAA在结构上分别与α-酮戊二酸和谷氨酸相似，我们研究了这些化合物对青春期大鼠大脑谷氨酸能神经传递的体外影响。还对生物能量学和氧化还原稳态进行了研究，因为它们代表了大脑发育和功能的基本系统。我们首先观察到AAA显著降低了谷氨酸摄取，而谷氨酸脱氢酶活性则被KAA以竞争性方式显著抑制。此外，AAA以及更显著的KAA诱导了活性氧和氮物种的生成（2',7'-二氯荧光素（DCFH）氧化增加以及亚硝酸盐/硝酸盐水平升高）、脂质过氧化（丙二醛浓度增加）和蛋白质氧化（羰基形成增加以及巯基含量降低），同时还降低了抗氧化防御（还原型谷胱甘肽（GSH））和乌头酸酶活性。此外，抗氧化剂α-生育酚、褪黑素和白藜芦醇可预防KAA诱导的脂质过氧化和GSH降低，这表明活性物种参与了这些效应。值得注意的是，NMDA谷氨酸受体的经典抑制剂MK-801无法预防由DCFH氧化和GSH水平所确定的KAA诱导和AAA诱导的氧化应激，这使得通过谷氨酸受体过度刺激继发氧化应激的可能性不大。相比之下，KAA和AAA并未显著改变大脑生物能量学参数。我们推测，KAA和AAA对谷氨酸能神经传递和氧化还原稳态的干扰可能在那些表现出神经症状的α-酮己二酸尿症病例中起作用。
