Apoptosis and antioxidant defense in the nephrotic syndrome

Nephrotic syndrome (NS) is accompanied, and probably caused by, abnormalities in T lymphocyte function. The aim of this study was to investigate the antioxidant status of children with NS and its influence on the apoptosis of T cells. Fifty-seven children with NS were studied, aged 4-16 years (mean 7.4 years), 34 with a first episode (group I) and 23 in remission (>6 months) of NS (group II). The control group comprised 26 healthy children matched for age. Annexin V-FITC was used as a sensitive probe for identifying cells undergoing apoptosis. We found that apoptotic T lymphocytes occurred more frequently in patients with a first episode of NS than in children in remission and in the controls. In group I, total antioxidant status (TAS, plasma) was significantly reduced compared with controls (0.77+/-0.14 vs. 1.18+/-0.42 mmol/l, P<0.001). In group I children, glutathione reductase (GR, red blood cells) and glutathione peroxidase (GPX, red blood cells) activity was lower than in controls (GR 8.10+/-2.40 vs.10.55+/-3.81 U/g Hb, P<0.001) (GPX 28.65+/-6.99 vs. 33.84+/-13.11 U/g Hb, P=0.010). TAS levels and GR activity in group II were also lower than in the controls. A negative correlation between GR activity and the apoptosis rate of T lymphocytes was found. We conclude that in patients with NS, reduced antioxidant defense may contribute to an increase in the apoptosis rate of circulating lymphocytes.