Effect of mitochondrial aconitase activity on energy synthesis during aging

AIM：To investigate the effect of mitochondrial aconitase (ACO2) on energy synthesis during aging in male SD rats and D-galactose-induced cell aging model. METHODS：D-galactose at concentration of 55 mmol/L was used to establish MRC-5 cell aging model. Intact mitochondria in the rat brain and MRC-5 cells were isolated by a sucrose density gradient centrifugation. The formation of NADPH was used to represent the ACO2 activity and determined by observation of the absorbance at 340 nm. Fluorescence quantitative PCR and Western blotting were applied to detected ACO2 expression. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) content were measured by the commercial assay kits. The tissue iron content was detected by ferrozine method. Mitochondrial membrane potential was detected by JC-1 mitochondrial membrane potential detection kit. The content of ATP, ADP and AMP was measured by HPLC analysis, and the energy charge was then calculated by the formula. RESULTS：ACO2 activity and iron content presented age-related decline and increase, respectively, while the expression level of ACO2 kept stable. ACO2 activity significantly declined when the cells were treated with hydrogen peroxide at different concentrations. In the aging cells, SOD activity and ACO2 activity were decreased and MDA content was increased significantly, while the expression level of ACO2 was unchanged. During aging, mitochondrial membrane potential, ATP synthesis and energy charge presented significant reduction. CONCLUSION：The activity of ACO2, which is sensitive to oxidative stress, declines during aging, and may affect the efficiency of the Krebs cycle. At the same time, mitochondrial membrane potential decreases, thus reducing the energy synthesis in mitochondria.