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DOI: 10.1055/s-0035-1549588
Age-related carbonylation in glomeruli of diabetic mice influences anti-oxidative defense mechanisms
Background: In addition to the well-established role of protein carbonylation in oxidative stress, this oxidation process may also play a role in cell signal transduction. This study aims to investigate the influence of age-dependent protein carbonylation in the kidney of diabetic mice on the expression and activity of the cytosolic anti-oxidative selenoenzyme glutathione peroxidase (GPx).
Methods: In addition to standard methods, dinitrophenylhydrazine (DNPH) derivatization has been used to detect carbonylated proteins in diabetic Ins2Akita mice. GPx activity was determined using a luminescent activity assay.
Results: Protein carbonylation, GPx1 and GPx4 expression were found to be increased in kidneys of diabetic but not non-diabetic mice with age and co-localized with podocytes and mesangial cells in glomeruli. In addition, GPx activity was augmented in diabetic animals, especially in young (1 month) Ins2Akita mice that did not show a simultaneous upregulation of GPx on the protein level. In these young animals, immunoprecipitated GPx1 was found to be carbonylated. Using recombinant GPx1 protein, a marked increase in activity after mild in vitro carbonylation was detected. In podocytes cultured under high glucose conditions (25 mM for 7 days), GPx protein expression was increased as well, whereas its activity was found to be decreased.
Conclusion: GPx carbonylation in the kidney is associated with an increase in its activity at early stages of diabetes whereas this effect was absent in animals with end-stage disease. These results indicate that there might be a threshold for beneficial carbonylation-dependent redox signaling during the progression of diabetic nephropathy.