Parmeggiani Belisa, Moura Alana Pimentel, Grings Mateus, Bumbel Anna Paula, de Moura Alvorcem Leonardo, Tauana Pletsch Julia, Fernandes Carolina Gonçalves, Wyse Angela T S, Wajner Moacir, Leipnitz Guilhian
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600 - Anexo - CEP, 90035-003 Porto Alegre, RS, Brazil.
Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600 - Anexo - CEP, 90035-003 Porto Alegre, RS, Brazil; Serviço de Genética Médica, Hospital de Clínicas de Porto Alegre, Rua Ramiro Barcelos, 2350 - CEP, 90035-003 Porto Alegre, RS, Brazil.
Int J Dev Neurosci. 2015 May;42:68-75. doi: 10.1016/j.ijdevneu.2015.03.005. Epub 2015 Mar 13.
Sulfite oxidase (SOX) deficiency is an inherited neurometabolic disorder biochemically characterized by tissue accumulation and high urinary excretion of sulfite and thiosulfate. Affected patients present severe neurological dysfunction accompanied by seizures, whose pathophysiology is poorly known. In the present study we evaluated the in vitro effects of sulfite and thiosulfate on important parameters of glutamatergic neurotransmission and redox homeostasis in rat cerebral cortex slices. We verified that sulfite, but not thiosulfate, significantly decreased glutamate uptake when cerebral cortex slices were exposed during 1h to these metabolites. We also observed that thiosulfate inhibited glutamine synthetase (GS) activity. A pronounced trend toward GS inhibition induced by sulfite was also found. Regarding redox homeostasis, sulfite, at the concentration of 10 μM, increased thiobarbituric acid-reactive substances and decreased glutathione concentrations after 1h of exposure. In contrast, thiosulfate did not alter these parameters. We also found that 500 μM sulfite increased sulfhydryl group content in rat cerebral cortex slices and increased GSH levels in a medium containing oxidized GSH (GSSG) and devoid of cortical slices, suggesting that sulfite reacts with disulfide bonds to generate sulfhydryl groups. Moreover, sulfite and thiosulfate did not alter the activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST) and glucose-6-phosphate dehydrogenase (G6PDH) after 1h of incubation. However, sulfite inhibited the activities of GPx, GST and G6PDH when cortical slices were exposed for 3h to sulfite. We finally verified that sulfite did not induce cell death after 1h of incubation. Our data show that sulfite impairs glutamatergic neurotransmission and redox homeostasis in cerebral cortex. Therefore, it may be presumed that these pathomechanisms contribute, at least in part, to the seizures observed in patients affected by SOX deficiency.
亚硫酸盐氧化酶（SOX）缺乏症是一种遗传性神经代谢疾病，其生化特征是组织中亚硫酸盐和硫代硫酸盐蓄积以及尿中排泄量增加。受影响的患者表现出严重的神经功能障碍并伴有癫痫发作，其病理生理学尚不清楚。在本研究中，我们评估了亚硫酸盐和硫代硫酸盐对大鼠大脑皮层切片中谷氨酸能神经传递和氧化还原稳态重要参数的体外影响。我们证实，当大脑皮层切片在1小时内暴露于这些代谢物时，亚硫酸盐而非硫代硫酸盐会显著降低谷氨酸摄取。我们还观察到硫代硫酸盐抑制谷氨酰胺合成酶（GS）活性。还发现亚硫酸盐诱导GS抑制有明显趋势。关于氧化还原稳态，在暴露1小时后，10 μM浓度的亚硫酸盐会增加硫代巴比妥酸反应性物质并降低谷胱甘肽浓度。相比之下，硫代硫酸盐不会改变这些参数。我们还发现500 μM亚硫酸盐会增加大鼠大脑皮层切片中的巯基含量，并在含有氧化型谷胱甘肽（GSSG）且无皮层切片的培养基中增加谷胱甘肽水平，这表明亚硫酸盐与二硫键反应生成巯基。此外，孵育1小时后，亚硫酸盐和硫代硫酸盐不会改变谷胱甘肽过氧化物酶（GPx）、谷胱甘肽还原酶（GR）、谷胱甘肽S-转移酶（GST）和葡萄糖-6-磷酸脱氢酶（G6PDH）的活性。然而，当皮层切片暴露于亚硫酸盐3小时时，亚硫酸盐会抑制GPx、GST和G6PDH的活性。我们最终证实孵育1小时后亚硫酸盐不会诱导细胞死亡。我们的数据表明亚硫酸盐会损害大脑皮层中的谷氨酸能神经传递和氧化还原稳态。因此，可以推测这些发病机制至少部分导致了SOX缺乏症患者所观察到的癫痫发作。
