Laboratório de Neuroproteção e DoençasMetabólicas, Departamento de Bioquímica, Instituto de CiênciasBásicas da Saúde, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
Departamento de Bioquímica, Instituto de CiênciasBásicas da Saúde, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2600-Anexo, CEP, Porto Alegre, RS, 90035-003, Brazil.
Mol Neurobiol. 2018 Jun;55(6):5111-5124. doi: 10.1007/s12035-017-0749-2. Epub 2017 Aug 24.
Kynurenic acid (KYNA) is a neuroactive metabolite of tryptophan known to modulate a number of mechanisms involved in neural dysfunction. Although its activity in the brain has been widely studied, the effect of KYNA counteracting the actions of quinolinic acid (QUIN) remains unknown. The present study aims at describing the ability of 100 μM KYNA preventing cytoskeletal disruption provoked by QUIN in astrocyte/neuron/microglia mixed culture. KYNA totally preserved cytoskeletal organization, cell morphology, and redox imbalance in mixed cultures exposed to QUIN. However, KYNA partially prevented morphological alteration in isolated primary astrocytes and failed to protect the morphological alterations of neurons caused by QUIN exposure. Moreover, KYNA prevented QUIN-induced microglial activation and upregulation of ionized calcium-binding adapter molecule 1 (Iba-1) and partially preserved tumor necrosis factor-α (TNF-α) level in mixed cultures. TNF-α level was also partially preserved in astrocytes. In addition to the mechanisms dependent on redox imbalance and microglial activation, KYNA prevented downregulation of connexin-43 and the loss of functionality of gap junctions (GJs), preserving cell-cell contact, cytoskeletal organization, and cell morphology in QUIN-treated cells. Furthermore, the toxicity of QUIN targeting the cytoskeleton of mixed cultures was not prevented by the N-methyl-D-aspartate (NMDA) antagonist MK-801. We suggest that KYNA protects the integrity of the cytoskeleton of mixed cultures by complex mechanisms including modulating microglial activation preventing oxidative imbalance and misregulated GJs leading to disrupted cytoskeleton in QUIN-treated cells. This study contributed to elucidate the molecular basis of KYNA protection against QUIN toxicity.
犬尿酸（KYNA）是色氨酸的一种神经活性代谢产物，已知可调节多种与神经功能障碍相关的机制。尽管其在大脑中的活性已得到广泛研究，但 KYNA 对抗喹啉酸（QUIN）作用的效果仍不清楚。本研究旨在描述 100μM KYNA 防止星形胶质细胞/神经元/小胶质细胞混合培养物中 QUIN 引起的细胞骨架破坏的能力。在暴露于 QUIN 的混合培养物中，KYNA 完全保留了细胞骨架组织、细胞形态和氧化还原失衡。然而，KYNA 部分防止了原代星形胶质细胞的形态改变，并未能保护神经元暴露于 QUIN 引起的形态改变。此外，KYNA 可防止 QUIN 诱导的小胶质细胞激活和离子钙结合接头分子 1（Iba-1）的上调，并部分保留混合培养物中 QUIN 诱导的肿瘤坏死因子-α（TNF-α）水平。星形胶质细胞中 TNF-α 水平也部分保留。除了依赖于氧化还原失衡和小胶质细胞激活的机制外，KYNA 还可防止连接蛋白 43 的下调和缝隙连接（GJ）的功能丧失，从而维持 QUIN 处理细胞中的细胞-细胞接触、细胞骨架组织和细胞形态。此外，NMDA 拮抗剂 MK-801 并不能防止 QUIN 靶向混合培养物细胞骨架的毒性。我们认为，KYNA 通过复杂的机制保护混合培养物细胞骨架的完整性，包括调节小胶质细胞激活、防止氧化失衡和调节 GJ 导致 QUIN 处理细胞中的细胞骨架破坏。本研究有助于阐明 KYNA 对抗 QUIN 毒性的分子基础。
