Diwakar Latha, Kenchappa Rajappa S, Annepu Jayasree, Ravindranath Vijayalakshmi
Division of Molecular and Cellular Neuroscience, National Brain Research Centre, Nainwal Mode, Manesar 122050, India.
Neurochem Int. 2007 Jul;51(1):37-46. doi: 10.1016/j.neuint.2007.03.008. Epub 2007 Apr 5.
Oxidative stress, excitotoxicity and mitochondrial dysfunction play synergistic roles in neurodegeneration. Maintenance of thiol homeostasis is important for normal mitochondrial function and dysregulation of protein thiol homeostasis by oxidative stress leads to mitochondrial dysfunction and neurodegeneration. We examined the critical roles played by the antioxidant, non-protein thiol, glutathione and related enzyme, glutaredoxin in maintaining mitochondrial function during excitotoxicity caused by beta-N-oxalyl amino-L-alanine (L-BOAA), the causative factor of neurolathyrism, a motor neuron disease involving the pyramidal system. L-BOAA causes loss of GSH and inhibition of mitochondrial complex I in lumbosacral cord of male mice through oxidation of thiol groups, while female mice are resistant. Reducing GSH levels in female mice CNS by pretreatment with diethyl maleate or L-propargyl glycine did not result in inhibition of complex I activity, unlike male mice. Further, treatment of female mice depleted of GSH with L-BOAA did not induce inhibition of complex I indicating that GSH levels were not critical for maintaining complex I activity in female mice unlike their male counterpart. Glutaredoxin, a thiol disulfide oxidoreductase helps maintain redox status of proteins and downregulation of glutaredoxin results in loss of mitochondrial complex I activity. Female mice express higher levels of glutaredoxin in certain CNS regions and downregulation of glutaredoxin using antisense oligonucleotides sensitizes them to L-BOAA toxicity seen as mitochondrial complex I loss. Ovariectomy downregulates glutaredoxin and renders female mice vulnerable to L-BOAA toxicity as evidenced by activation of AP1, loss of GSH and complex I activity indicating the important role of glutaredoxin in neuroprotection. Estrogen protects against mitochondrial dysfunction caused by excitotoxicity by maintaining cellular redox status through higher constitutive expression of glutaredoxin in the CNS. Therapeutic interventions designed to upregulate glutaredoxin may offer neuroprotection against excitotoxicity in motor neurons.
氧化应激、兴奋性毒性和线粒体功能障碍在神经退行性变中起协同作用。维持硫醇稳态对正常线粒体功能很重要，氧化应激导致蛋白质硫醇稳态失调会引发线粒体功能障碍和神经退行性变。我们研究了抗氧化剂、非蛋白质硫醇、谷胱甘肽以及相关酶谷氧还蛋白在由β-N-草酰基氨基-L-丙氨酸（L-BOAA）引起的兴奋性毒性过程中对维持线粒体功能所起的关键作用，L-BOAA是致运动神经元疾病神经性豆状核变性（涉及锥体系统）的病因。L-BOAA通过硫醇基团氧化导致雄性小鼠腰骶脊髓中谷胱甘肽（GSH）丧失并抑制线粒体复合体I，而雌性小鼠具有抗性。与雄性小鼠不同，用马来酸二乙酯或L-炔丙基甘氨酸预处理降低雌性小鼠中枢神经系统中的GSH水平，并不会导致复合体I活性受到抑制。此外，用L-BOAA处理耗尽GSH的雌性小鼠，不会诱导复合体I受到抑制，这表明与雄性小鼠不同，GSH水平对维持雌性小鼠的复合体I活性并不关键。谷氧还蛋白是一种硫醇二硫化物氧化还原酶，有助于维持蛋白质的氧化还原状态，谷氧还蛋白的下调会导致线粒体复合体I活性丧失。雌性小鼠在某些中枢神经系统区域表达较高水平的谷氧还蛋白，使用反义寡核苷酸下调谷氧还蛋白会使它们对L-BOAA毒性敏感，表现为线粒体复合体I丧失。卵巢切除术下调谷氧还蛋白并使雌性小鼠易受L-BOAA毒性影响，AP1激活、GSH丧失和复合体I活性降低证明了谷氧还蛋白在神经保护中的重要作用。雌激素通过在中枢神经系统中更高的组成性表达谷氧还蛋白来维持细胞氧化还原状态，从而防止兴奋性毒性引起的线粒体功能障碍。旨在上调谷氧还蛋白的治疗干预措施可能为运动神经元的兴奋性毒性提供神经保护。
