Studies on mechanism of neuronal death induced by an amyotrophic lateral sclerosis

S-烯丙基-L-半胱氨酸是陈化大蒜提取物中的一种有机硫化合物，具有包括神经营养活性在内的多种生物学效应。我们研究了淀粉样β蛋白(A-β)、4-羟基壬烯醛(HNE)、衣霉素(TM)和营养因子剥夺诱导的神经元死亡，并研究了SAC是否以及如何预防这些神经元的死亡。SAC对A和衣霉素诱导的神经元死亡有保护作用，其主要机制是以浓度依赖的方式下调内质网应激(ER)反应。相反，它对HNE和营养因子剥夺诱导的细胞死亡没有保护作用，而caspase-3在这些神经元死亡中发挥了关键作用。提示SAC对内质网功能障碍所致的海马神经细胞死亡具有保护作用，对依赖caspase-3途径的神经细胞死亡无明显影响。我们还检测了在没有和存在L-谷氨酸(Glu)的情况下，HNE对6天或7天大鼠的器官型海马和脊髓切片的神经毒性。在脑片培养中，HNE(25-100μM)或Aβ(25和50 mM)单独作用时，神经毒性较小。单独应用谷氨酸(2.5和5.0 mM)可引起培养脊髓神经元轻度死亡，但加入HNE(5 0μM)后，神经元死亡明显增加。泛型半胱氨酸氨基转移酶抑制剂z-VAD-fmk可部分保护Glu和HNE诱导的神经元死亡。这些结果表明，半胱氨酸天冬氨酸酶介导的通路至少在一定程度上导致了神经元的死亡。

S-allyl-L-cysteine (SAC), one of the organosulfur compounds in aged garlic extract, has been shown to possess various biological effects including neurotrophic activity. We characterized neuronal death induced by amyloid beta-protein (Aβ), 4-hydroxynonenal (HNE), Tunicamycin (Tm) and trophic factor deprivation, and investigated whether and how SAC could prevent these neuronal deaths in cultured hippocampal neurons in rats. Treatment with SAC protected against A- and tunicamycin-induced neuronal death which has been shown to be mediated predominantly through the down regulation of endoplasmic reticurum (ER) stress (ER) response in a concentration-dependent manner. In contrast, it afforded no protection against HNE- and trophic factor deprivation-induced cell death, in which caspase-3 played a pivotal role in these neuronal deaths. These results suggest that SAC could protect against neuronal cell death which is triggered by ER dysfunction in the hippocampus, and that it has no effect on neuronal death which is dependent on caspase-3 mediated pathway. We also examined HNE-induced neurotoxicity in the absence and presence of L-glutamic acid (Glu) in organotypic hippocampal and spinal cord slice coltures prepared from 6- or 7-day-old rats. In slice cultures, little neurotoxicity was observed by the treatment with HNE (25-100 μM) or Aβ (25 and 50 mM) alone. Although Glu (2.5 and 5.0 mM) alone exhibited slight neuronal death in cultured spinal cord, this neuronal death was dramatically increased in the presence of HNE (50 μM). A pan-caspase inhibitor, z-VAD-fmk, partially protected neurons from neuronal death induced by Glu in combination with HNE. These results suggest that caspases-mediated pathway is, at lease in part, responsible for this neuronal death.