| Summary: | 碩士 === 國立成功大學 === 生理學研究所 === 91 === 3-nitropropionic acid (3-NP) is an irreversible inhibitor of succinate dehydrogenase (complexⅡ) in the mitochondria. Systemic administration of 3-NP causes selective striatal lesions in rats and has gained acceptance as an experimental model of huntington’s disease (HD). Although a number of molecules and pathways in response to oxidative stress induced by mitochondrial energy impairment have been implicated, the interaction of these molecules remains unclear. In this study, the relationship of GSH, NF-κB and Bcl-2 protein family that are redox sensitive and responsible for 3-NP neurotoxicity has been explored. The results indicated that 3-NP causes human SK-N-SH neuroblastoma cell death, which represents PS (phosphatidylserine) and DNA condensation but not fragmentation, in a dose dependent manner 24 h after treatment. We also found an increase of the nuclear NF-kB-p65 protein expression as earlier as 30 min after 3-NP treatment, but a decrease of its DNA binding activity in a time dependent manner, and an elevation of the oxidative stress indicated by the high GSSG/GSH ratio and a reduction of glutathione (GSH) level at 2 h, as well as the final down-regulation of Bcl-2 and up-regulation of Bax at 18 h. To further clarify the death signaling cascade triggered by 3-NP, we used antioxidant of melatonin and NF-kB inhibitor of bay and cell permeable GSH and IPTG-induced or transient Bcl-2 overexpressed cells. Our results demonstrated that co-treatment of GSH or melatonin significantly attenuated the 3-NP-induced oxidative stress, the decrease of NF-kB activity and Bcl-2/Bax expression, as well as cell death. However, the inhibition of NF-kB activation by its inhibitor of bay did not prevent the high GSSG/GSH ratio and the low Bcl-2 expression and cell death induced by 3-NP. In addition, the Bcl-2 overexpressed SK cells could significantly attenuated 3-NP cytotoxicity, but the changes of GSH redox status, NF-kB activity, Bax expression induced by 3-NP could not be prevented. These results suggest that 3-NP-trigged death signal cascade was the impairment of GSH redox system, inhibition of NF-kB activity, and the final down-regulation of Bcl-2/Bax expression. Furthermore, the present and other previous results demonstrated that melatonin significantly blocked the oxidative stress of initial death signal and preserved the mitochondrial function to effectively protect cells from the attack of mitochondrial toxins. The novel finding demonstrates here that melatonin dramatically prevents the inhibition of Nrf-1 (nuclear respiratory factor 1, Nrf-1) activity, which is characterized as a transcriptional activator of many genes encoding subunits from all five mitochondrial respiratory complexes, induced by 3-NP to achieve a well neuroprotective effect.
|
|---|
