Expression of P-glycoprotein in lymphocytes of children with nephrotic syndrome treated with glucocorticoids.

INTRODUCTION: Glucocorticoids are still the mainstay of therapy for nephrotic syndrome (NS) in children. Poor response to glucocorticoids may relate, in part, to the overexpression of P-glycoprotein (P-gp). The aim of the present study was to determine the expression of P-gp in lymphocytes (CD3) in the peripheral blood of children with steroid-sensitive nephrotic syndrome in the dynamics of the disease. The study group (I) consisted of 18 children, median age 5.75 years, with steroid-sensitive nephrotic syndrome, in whom the examinations were carried out three times: (A) before treatment, during relapse; (B) after 3-4 weeks of prednisone treatment; (C) 2 months after finishing prednisone treatment. The control group (II) consisted of 18 healthy children of the same age. P-gp expression in CD3 lymphocytes of peripheral blood was measured using flow cytometry. During NS relapse and prior to glucocorticoid administration, the CD3/P-gp level was higher (median 3.20%, range 0.80-7.80%) when compared to healthy controls (1.10%, range 0.30- 2.20%) (p<0.01). During glucocorticoid treatment, CD3/P-gp increased significantly and was much higher than in the control group (p<0.01) and in the NS children before treatment (p<0.01). In remission, the P-gp expression decreased, but did not achieve the values of the controls (p<0.05). Fourteen out of eighteen (14/18) children still showed P-gp values above the cut-off level. We also found a positive correlation between the P-gp expression and total prednisone dose in the NS children in all examinations: A: (r=0.540, p<0.05); B: (r=0.630, p<0.01); C: (r=0.653, p<0.01).
CONCLUSION: In conclusion, the overexpression of P-gp in remission, after finishing glucocorticoid treatment, may indicate that P-gp plays a role in the response to corticosteroids in nephrotic children.