| ObjectiveNeurodegenerative diseases are a heterogeneous group of disorders characterized by gradually progressive, selective loss of anatomically or physiologically related neuronal systems. With the social development and aging population, the risk of these diseases is elevated. Because the brain tissue is sensitive to ischemia and hypoxia, ischemia-reperfusion is the key factor which leads to neurodegenerative diseases. It is important to investigate the mechanism of neurodegenerative diseases induced by ischemia/reperfusion for discovering new therapeutic targets and drugs.Superoxide dismutase(SOD) is the main enzyme that involves in the scavenge of reactive oxygen species in brain. SOD1(Cu-ZnSOD) and SOD2(Mn-SOD) are the main forms that function to eliminate reactive oxygen species in all three SOD isoforms. In the past, the research was focused on the effects of SOD1 and SOD2 on brain damage causad by acute cerebral ischemia-reperfusion. There were limited reports of the effects of SOD1 and SOD2 in the development of neurodegenerative diseases.In this study, we investigated the relationship between SOD and neurodegeneration, and further explored the possible mechanism of neurodegeneration induced by ischemia-reperfusion at the levels of entirety, subcell and molecular in order to develop effective neural protectants.Method1. Animal model:The mouse cerebral ischemia/reperfusion model was established through drawing out and reperfusing 40% of the whole blood volume in combination with clamping the carotid arteries for 20 min after anesthesia with 40 g.L-1chloral hydrate (400 mg.kg-1 ip). The sham operation mouse only received similar anesthesia and exposure of carotid arteries and the right jugular vein for 20 min above.2. Behavior test, pathological observation, and malondialdehyde (MDA) determination were performed on the d 5, d 15, d 30, and d 60 after the operation to evaluate the neurodegenerative model induced by ischemia-reperfusion.3. The mRNA and protein expressions of SOD1 and SOD2 were also detected by RT-PCR and Western blot, respectively on the same dates above after the operation to study the relationship between SOD and neurodegeneration and its possible mechanism.4. In order to investigate the relationship between mitochondrial disfunction and neurodegeneration induced by ischemia-reperfusion, the activity of mitochondrial respiratory chain complexâ… -â…£was detected by spectrophotometer on the 5th d, 15th d, 30th d, and 60th d after the operation.Result1. Compared with sham operation group, the learning and memory ability of cerebral ischemia-reperfusion group was decreased significantly, and the brain MDA level of ischemia-reperfusion group was significantly increased in a time-dependent manner. Pathological test indicated there existed the loss and karyopyknosis of neurons in hippocampi of ischemia-reperfusion group.2. The biological test indicated that the SOD1 activity of the 5th d and 15th d group of ischemia-reperfusion group was lower than that of corresponding sham operation group significantly (P<0.05), and there was no difference of SOD-1 activity between sham opration group and the 30th d and 60th d group of ischemia-reperfusion group (P>0.05). RT-PCR showed there was no difference of SOD1 mRNA expression of cortex and hippocampus between sham operation group and ischemia-reperfusion group (P>0.05). Western blot indicated the SOD1 protein of the 5th d and 15th d group was decreased significantly, and it was up-regulated significantly on the 30th d and 60th d group, compared with sham operation group (P<0.05).3. The biological experiment indicated the activity of brain SOD2 of ischemia-reperfusion group was lower than that of sham operation group dramatically (P<0.05). RT-PCR indicated there was no difference of brain SOD2 mRNA between sham operation group and ischemia-reperfusion group (P>0.05). Western blot identified the expression of SOD2 protein of ischemia-reperfusion group was deceased significantly, compared with sham operation group (P<0.05).4. The test of mitochondrial function showed the activity of mitochondrial respiratory chain complexâ… -â…£of the ischemia-reperfusion group was lower than that of sham operation group on the 5th d (P<0.01). On the 15th d, 30th d, and 60th d there was no difference of activity of mitochondrial respiratory chain complexâ… andâ…¡between sham operation group and ischemia-reperfusion group (P>0.05); however, the activity of complexâ…¢andâ…£of ischemia-reperfusion group was decreased significantly (P<0.05), compared with sham operation group.Conclusion1. The neurodegenerative model can be built effectively in this way.2. The suppression of normal SOD1 and over-expression of abnormal SOD1 as well as the down-regulation of SOD2 may involve in the neurodegeneration induced by ischemia-reperfusion.3. The disfunction of mitochondrial respiratory chain complexâ…¢andâ…£involves in the development of neurodegeneration induced by ischemia-reperfusion.All above indicate that disfunction of SOD involves in the neurodegeneration caused by ischemia-reperfusion. Its mechanism may be related to the down-regulation of SOD2 and over-expression of abnormal SOD1. The decline of SOD activity can lead to the disruption of oxidative stress balance, which inhibits the activity of mitochondrial respiratory chain complex and causes neurodegeneration. |
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