Fragoso Gabriela, Martínez-Bermúdez Ana Katherine, Liu Hsueh-Ning, Khorchid Amani, Chemtob Sylvain, Mushynski Walter E, Almazan Guillermina
Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada.
J Neurochem. 2004 Jul;90(2):392-404. doi: 10.1111/j.1471-4159.2004.02488.x.
The molecular mechanisms underlying H(2)O(2)-induced toxicity were characterized in rat oligodendrocyte cultures. While progenitor cells were more sensitive than mature oligodendrocytes to H(2)O(2), the antioxidant, N-acetyl-L-cysteine, blocked toxicity at both stages of development. Differentiated oligodendrocytes contained more glutathione than did progenitors and were less susceptible to decreases in glutathione concentration induced by H(2)O(2) stress. As free radicals have been considered to serve as second messengers, we examined the effect of H(2)O(2) on activation of the mitogen-activated protein kinases (MAPK), extracellular signal-regulated kinases (ERK) 1/2 and p38. H(2)O(2) caused a time- and concentration-dependent increase in MAPK phosphorylation, an effect that was totally blocked by N-acetyl-L-cysteine. Further exploration of potential mechanisms involved in oligodendrocyte cell death showed that H(2)O(2) treatment caused DNA condensation and fragmentation at both stages of development, whereas caspase 3 activation and poly (ADP-ribose) polymerase cleavage were significantly increased only in oligodendrocyte progenitors. The pan-caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone, blocked DNA fragmentation in progenitors and produced a small but significant level of protection from H(2)O(2) toxicity in progenitors and mature oligodendrocytes. In contrast, inhibitors of both p38 and MEK reduced H(2)O(2)-induced death most significantly in oligodendrocytes. The poly (ADP-ribose) polymerase inhibitor, PJ34, reduced H(2)O(2)-induced toxicity on its own but was most effective when combined with benzyloxycarbonyl-Val-Ala-Asp fluoromethyl ketone or PD169316. The finding that molecular mechanisms conferring resistance to reactive oxygen species toxicity are regulated during oligodendrocyte differentiation may be of importance in designing therapies for certain neurological diseases affecting white matter.
在大鼠少突胶质细胞培养物中对H₂O₂诱导毒性的分子机制进行了表征。虽然祖细胞比成熟少突胶质细胞对H₂O₂更敏感，但抗氧化剂N-乙酰-L-半胱氨酸在发育的两个阶段均能阻断毒性。分化的少突胶质细胞比祖细胞含有更多的谷胱甘肽，并且对H₂O₂应激诱导的谷胱甘肽浓度降低更不敏感。由于自由基被认为可作为第二信使，我们研究了H₂O₂对丝裂原活化蛋白激酶（MAPK）、细胞外信号调节激酶（ERK）1/2和p38激活的影响。H₂O₂导致MAPK磷酸化呈时间和浓度依赖性增加，这一效应被N-乙酰-L-半胱氨酸完全阻断。对少突胶质细胞死亡潜在机制的进一步探索表明，H₂O₂处理在发育的两个阶段均导致DNA浓缩和片段化，而仅在少突胶质细胞祖细胞中半胱天冬酶3激活和聚（ADP-核糖）聚合酶裂解显著增加。泛半胱天冬酶抑制剂苄氧羰基-Val-Ala-Asp氟甲基酮可阻断祖细胞中的DNA片段化，并在祖细胞和成熟少突胶质细胞中产生少量但显著的对H₂O₂毒性的保护作用。相比之下，p38和MEK的抑制剂在少突胶质细胞中对H₂O₂诱导的死亡抑制作用最为显著。聚（ADP-核糖）聚合酶抑制剂PJ34自身可降低H₂O₂诱导的毒性，但与苄氧羰基-Val-Ala-Asp氟甲基酮或PD169316联合使用时效果最佳。在少突胶质细胞分化过程中，赋予对活性氧毒性抗性的分子机制受到调控，这一发现可能对设计影响白质的某些神经疾病的治疗方法具有重要意义。
