Determination of autofluorescence of red blood cells (RbCs) in uremic patients as a marker of oxidative damage.

Abstract

It is suggested that the red blood cells (RBCs) of uremic patients have increased oxidative damage. The activities of different antioxidant enzymes and the levels of several antioxidants or lipid peroxidation products in RBCs are usually determined to estimate the oxidative stress in uremia. The autofluorescence of RBCs as measured by flow cytometry is caused by the formation of conjugated Schiff base compounds from aldehydes derived from lipid peroxidation and amino groups of phospholipids or cell proteins, and has been proposed as a marker of oxidative stress. The aim of this study was to evaluate if this method is suitable for estimation of oxidative stress in the RBCs of patients with different degrees of renal insufficiency. To determine the oxidative damage in RBCs in uremia, the autofluorescence of RBCs was measured by flow cytometry in the following 3 groups of patients: group A: 16 patients with chronic renal failure (CRF); group B: 16 hemodialysis (HD) patients; group C: 16 patients with a well-functioning renal allograft. Twenty-four healthy volunteers served as controls. The basal value of RBC autofluorescence and the autofluorescence of RBCs after oxidative damage by treatment with 0.1 mM hydrogen peroxide (H2O2)/0.7 mM sodium azide were determined. In basal RBC autofluorescence values, no differences were found between the 3 groups and the controls. However, there was a significant correlation between the increase of serum creatinine and RBC autofluorescence in the group of patients with CRF (r = 0.521; p = 0.038). After H2O2 treatment, the RBC autofluorescence rose markedly in all individuals. This increase in RBC autofluorescence was significantly higher in the patients with CRF (p = 0.003) and in the HD patients (p = 0.001) compared to the controls. In contrast, there was no difference in RBC autofluorescence between the patients with renal allograft and the controls after H2O2 treatment. In conclusion, flow cytometry is a useful tool for determining oxidative damage in RBCs. The RBCs of uremic patients are more susceptible to oxidative damage induced by H2O2, likely caused by diminished antioxidant defense in the RBC membrane. Successful renal transplantation leads to a normal autofluorescence response in the RBCs after H2O2 treatment.