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Medina-Navarro R.,Center for Biomedical Research of Michoacan | Duran-Reyes G.,Biochemistry Medical Research Unit | Diaz-Flores M.,Biochemistry Medical Research Unit | Vilar-Rojas C.,Biochemistry Medical Research Unit
PLoS ONE | Year: 2010

Background:Proteins have long been considered a principal target for oxidants as a result of their abundance in biological systems. However, there is increasing evidence about the significant antioxidant activity in proteins such as albumin. It is leading to new concepts that even consider albumin not only as an antioxidant but as the major antioxidant in plasma known to be exposed to continuous oxidative stress. Evidence presented here establishes a previously unrecognized relationship between proteins' antioxidant capacity and structural stress. Methodology/Principal Findings:A chemiluminiscence based antioxidant assay was achieved to quantify the antioxidant capacity of albumin and other proteins. The capabilities of proteins as antioxidants were presented, but in addition a new and powerful component of the protein antioxidant capacity was discovered. The intrinsic component, designated as Response Surplus (RS), represents a silent reserve of antioxidant power that awakens when proteins face a structural perturbation (stressor) such as temperature, short wave UV light, the same reactive oxygen species, and more extreme changes like glucose or aldehyde-mediated structural modifications. The work also highlights the importance of structural changes in protein antioxidant properties and the participation of sulfhydryl groups (SHs) in the RS antioxidant component. Based on recent evidence about the SH group chemistry, a possible model for explaining RS is proposed. Conclusions/Significance:The data presented show the significant antioxidant behavior of proteins and demonstrate the existence of a previously unrecognized antioxidant response to the stress. Several implications, including changes in elementary concepts about antioxidants and protein function, should emerge from here. © 2010 Medina-Navarro et al.


Medina-Navarro R.,Center for Biomedical Research of Michoacan | Nieto-Aguilar R.,Center for Biomedical Research of Michoacan | Nieto-Aguilar R.,Universidad Michoacana de San Nicolas de Hidalgo | Alvares-Aguilar C.,Center for Biomedical Research of Michoacan
Lipids in Health and Disease | Year: 2011

Background: One of the well-defined and characterized protein modifications usually produced by oxidation is carbonylation, an irreversible non-enzymatic modification of proteins. However, carbonyl groups can be introduced into proteins by non-oxidative mechanisms. Reactive carbonyl compounds have been observed to have increased in patients with renal failure. In the present work we have described a procedure designed as aldehyde capture to calculate the protein carbonyl stress derived solely from lipid peroxidation. Methods. Acrolein-albumin adduct was prepared as standard at alkaline pH. Rat liver microsomal membranes and serum samples from patients with diabetic nephropathy were subjected to the aldehyde capture procedure and aldol-protein formation. Before alkalinization and incubation, samples were precipitated and redisolved in 6M guanidine. The absorbances of the samples were read with a spectrophotometer at 266 nm against a blank of guanidine. Results: Evidence showed abundance of unsaturated aldehydes derived from lipid peroxidation in rat liver microsomal membranes and in the serum of diabetic patients with advanced chronic kidney disease. Carbonyl protein and aldol-proteins resulted higher in the diabetic nephropathy patients (p < 0.004 and p < 0.0001 respectively). Conclusion: The aldehyde-protein adduct represents a non oxidative component of carbonyl stress, independent of the direct amino acid oxidation and could constitute a practical and novelty strategy to measure the carbonyl stress derived solely from lipid peroxidation and particularly in diabetic nephropathy patients. In addition, we are in a position to propose an alternative explanation of why alkalinization of urine attenuates rhabdomyolysis-induced renal dysfunction. © 2011 Medina-Navarro et al; licensee BioMed Central Ltd.


Rosas-Diaz M.,Center for Biomedical Research of Michoacan | Camarillo-Cadena M.,Metropolitan Autonomous University | Hernandez-Arana A.,Metropolitan Autonomous University | Ramon-Gallegos E.,Environmental Cytopathology Laboratory | Medina-Navarro R.,Center for Biomedical Research of Michoacan
Molecular and Cellular Biochemistry | Year: 2015

Changes in the antioxidant capacity of albumin and alterations of the albumin structural conformation were examined in patients in advanced stages of diabetes nephropathy. Human serum albumin was purified from diabetic patients in pre-dialysis (glomerular filtration rate [GFR] between 15 and 29 ml min−1 1.73 m−2) and those in dialysis (GFR ≤ 15 ml min−1 1.73 m−2) and then compared with albumin from patients with a normal GFR (>90 ml min−1 m−2). We evaluated the antioxidant capacity of albumin using an enhanced chemiluminescence-based assay and thiol group content, and the structural changes were evaluated by circular dichroism and fluorescence spectroscopy. The antioxidant capacity and thiol content of albumin from patients in advanced stages of diabetic nephropathy were markedly reduced. The circular dichroism spectra showed a mean albumin α-helix content reduction from 44 to 37 % and from 44 to 30 % between the control group and pre-dialysis and dialysis patients, respectively. Additionally, the fluorescence intensity was reduced by 4.2 and 13 % for the groups 4 and 5, respectively, in relation with the control. These data provide evidence for the partial denaturation of albumin and exacerbated oxidative stress among patients in advanced stages of diabetes nephropathy before and even after dialysis. © 2015, Springer Science+Business Media New York.

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