The Possible Roles And The Mechanisms Underly Of COX5A And The Associated SCN2B In Brain Aging

[Object] In order to explore the possible roles of one subunit V-a of cytochrome c oxidase (COX5A) and the assocaited SCN2B in aging-related neurodegenerative disorders of mice.[Methods] To investigate the exact roles of COX5A as well as SCN2B in aging related proceduces, COX5A over-expression, SCN2B upregulated and SCN2B down-regulated transgenic mice were generated and employed. Firstly, RT-PCR and Western blot were employed to evaluate the COX5A and SCN2B expressions of both the mRNA and protein in different parts of transgenic mice brain. The relative over-expressional or down-regulated rates were then calculated. The4-month-old and12-month-old transgenic mice were employedin the present study. Morris Water Maze (MWM) Test and hippacampus-depended Long-term potentiation (LTP) were used to evaluate the learning and memory funtions. Immunohistochemistry for NeuN, GFAP, NF, COX5A as well as SCN2B was preceded. Golji staining was used to detect the changes of synapy of neurons. Finally, mRNA expressions of mutiply genes in transgenic mice brain were detected by RT-PCR. These genes were described as BDNF, PDGF-B, TGF-β1, TGF-β2, IGF-1, bFGF, APP, SCN2B, COX5A, AKT, ERK-1and GSK-3β. The wild type mice were severd as control. [Results]1. Five heterozygous transgenic offspring of COX5A upregulated transgenic mice lines were obtained. Only four of them could produce offsprings. These were designated Founder35, Founder22, Founder26and Founder28. The transgenic mice with inserted fragment, identified by PCR, were regarded as positive transgenic mice. Results of Western blot, which detected in the four genotypes in the brains of transgenic mice, showed that Cox5a expressions were up-regulated by51%,31%,20%and16%in Founder35, Founder22, Founder26and Founder28mice respectively. The results revealed a51%increase in Cox5a expressions in transgenic mice Founder35. This increase resulted in:ⅰ) improvement in the hippocampus-dependent spatial recognition memory evaluated by Morris Water Test (MWT); ⅱ) significant increase in long-term potentiation (LTP) of the field excitatory postsynaptic potential (fEPSP) slope at Schaffer collateral/commissural fiber synapses; ⅲ) recovery of hippocampal CA1apical/basal dendrites; ⅳ) up-regulation of BDNF, IGF-1, PDGF-B, AKT, ERK1and down-regulation of SCN2B, bFGF and GSK-3β mRNA expressions.2. Four heterozygous transgenic offspring of SCN2B upregulated transgenic mice lines were obtained. All of them could produce offsprings. These were designated Founder19, Founder41, Founder66and Founder61. Results of Western blot, which detected in the four genotypes in the brains of transgenic mice, showed that SCN2B expressions were up-regulated by48%,32%,19%and17%in Founder19, Founder41, Founder66and Founder61mice, respectively. The results revealed a48%increase in SCN2B expressions in transgenic mice Founder19. This increase showed no effect in:ⅰ) the hippocampus-dependent spatial recognition memory evaluated by MWT; ⅱ) LTP of the fEPSP slope at Schaffer collateral/commissural fiber synapses; ⅲ) hippocampal CA1apical/basal dendrites; ⅳ) expressions of BDNF, PDGF-B, TGF-β1, TGF-β2, IGF-1, bFGF, APP, COX5A, AKT, ERK-1and GSK-3p mRNA expressions.3. Four heterozygous transgenic offspring of SCN2B down-regulated transgenic mice lines were obtained. These were designated Founder36, Founder41, Founder18and Founder38. Results of Western blot, which detected in the four genotypes in the brains of transgenic mice, showed that SCN2B expressions were up-regulated by60.58%,53%,33%and30%in Founder36, Founder41, Founder18and Founder38 mice, respectively. The data revealed a60.58%decrease in SCN2B expressions, in transgenic mice Founder36, resluted in:ⅰ) improvement in the hippocampus-dependent spatial recognition memory; ⅱ) increases in LTP of the fEPSP slope at Schaffer collateral fiber synapses; ⅲ) recovery of hippocampal CA1apical/basal dendrites; ⅳ) up-regulation in mRNA expressions of BDNF, ERK-1, AKT, COX5A and IGF-1, as well as down-regulations in GSK-3β and bFGF levels.[Conclusion]1. The present results generated four genotypes COX5A TG mice of expressional up-regulated, as well as the SCN2B TG mice either of expressional up-regulated or down-regulated by different folds, which supplied multiply genotypes TG mice sources for different researches.2. The results revealed either a51%increase in COX5A or a60.58%decrease in SCN2B expressions in transgenic mice improved the hippocampus-dependent spatial recognition memory and recover the hippocampal CA1apical/basal dendrites. It was possible that the neuroprotective effects of Cox5a in aging might be associated with:ⅰ) the increased synaptic excitatory of hippacmpus; ⅱ) increase in dendritic branching points in the hippocampal CA1; ⅲ) compensational up-regulation of COX5A which lost and impaired in aging progress; ⅳ) increase the aupregulation of NTFs and the down-steam signal pathway moculars.3. The48%increase in SCN2B expressions showed no effect on recognition memory nor the hippocampal CA1apical/basal dendrites. These resluts suggested that the increase in SCN2B levels by48%was not sufficient to trigger the serial changes intransgenic mice. It is indicated that SCN2B upregulation may not the key factors in learning and memory improvement of mice.4. The present data demonstrated that COX5A and the assocaited SCN2B in the hippocampus played a crucial role in aging-related cognitive deterioration via BDNF regulation, compensational COX5A lost in aging brain and may be potential targets for anti-senescence drugs.