Mechanism for Quinolinic Acid Cytotoxicity in Human Astrocytes and Neurons
Mechanism for Quinolinic Acid Cytotoxicity in Human Astrocytes and Neurons
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DOI：
10.1007/s12640-009-9051-z
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发表时间：
2009-07-01
影响因子：
3.7
通讯作者：
Guillemin, Gilles J.
中科院分区：
文献类型：
--
作者：
Braidy, Nady;Grant, Ross;Guillemin, Gilles J.
越来越多的证据表明犬尿氨酸途径(KP)，特别是其代谢物之一的喹啉酸(Quin)，是几种脑部疾病中神经炎症的重要因素。虽然奎宁已被证明可以诱导神经细胞和星形胶质细胞的凋亡，但导致细胞死亡的确切机制仍不清楚。为了探讨Quin对人脑细胞的兴奋毒性作用机制，我们测定了Quin对原代培养的人脑神经元和星形胶质细胞的细胞内NAD(+)和聚腺苷二磷酸核糖聚合酶(PARP)水平及细胞外乳酸脱氢酶(LDH)活性的影响。我们发现，在神经元和星形胶质细胞中，Quin在极低浓度(<；50 nM)下作为NAD(+)合成的底物，但在亚生理浓度(>；150 nM)下在这两种细胞中都具有细胞毒性。我们发现，离子通道阻断剂MK801和美金刚以及一氧化氮合酶抑制剂L-NAME显著抑制Quin介导的神经元和星形胶质细胞PARP激活、NAD(+)耗竭和LDH释放。Quin作用后，诱导型(INOS)和神经型(NNOS)型一氧化氮合酶的mRNA和蛋白表达均增加。综上所述，这些结果表明，Quin对神经元和星形胶质细胞的细胞毒作用可能是通过NMDA样受体的过度激活以及随后的NOS诱导和过量的一氧化氮(NOaEuro Cent)介导的自由基损伤来实现的。这些结果有助于我们理解奎宁神经和神经胶质毒性的病理生理学机制，并对神经炎性疾病的治疗发展具有重要意义。
There is growing evidence implicating the kynurenine pathway (KP) and particularly one of its metabolites, quinolinic acid (QUIN), as important contributors to neuroinflammation in several brain diseases. While QUIN has been shown to induce neuronal and astrocytic apoptosis, the exact mechanisms leading to cell death remain unclear. To determine the mechanism of QUIN-mediated excitotoxicity in human brain cells, we measured intracellular levels of nicotinamide adenine dinucleotide (NAD(+)) and poly(ADP-ribose) polymerase (PARP) and extracellular lactate dehydrogenase (LDH) activities in primary cultures of human neurons and astrocytes treated with QUIN. We found that QUIN acts as a substrate for NAD(+) synthesis at very low concentrations (< 50 nM) in both neurons and astrocytes, but is cytotoxic at sub-physiological concentrations (> 150 nM) in both the cell types. We have shown that the NMDA ion channel blockers, MK801 and memantine, and the nitric oxide synthase (NOS) inhibitor, L-NAME, significantly attenuate QUIN-mediated PARP activation, NAD(+) depletion, and LDH release in both neurons and astrocytes. An increased mRNA and protein expression of the inducible (iNOS) and neuronal (nNOS) forms of nitric oxide synthase was also observed following exposure of both cell types to QUIN. Taken together these results suggests that QUIN-induced cytotoxic effects on neurons and astrocytes are likely to be mediated by an over activation of an NMDA-like receptor with subsequent induction of NOS and excessive nitric oxide (NOaEuro cent)-mediated free radical damage. These results contribute significantly to our understanding of the pathophysiological mechanisms involved in QUIN neuro- and gliotoxicity and are relevant for the development of therapies for neuroinflammatory diseases.