Heat shock protein 70 levels in children with nephrotic syndrome

Background: Idiopathic nephrotic syndrome (NS) is the most prevalent glomerular disease in children. Heat shock protein 70 (HSP70) is synthesized in response to diverse stress factors like infections and oxidative stress. We aimed to evaluate serum and urine levels of HSP70 in children with steroid-sensitive nephrotic syndrome (SSNS) and to assess changes in HSP70 levels with prednisolone treatment. Additionally, we seek to determine whether serum and urine levels of HSP70 can differentiate between frequently relapsing and infrequently relapsing cases in children with SSNS.

Methods: A total of 36 patients with SSNS and 35 healthy children were included in the study. Samples were taken from all patients at four time points; before corticosteroid treatment (day 0) and on days 15, 30, and 90 after the initiation of corticosteroid treatment. Serum and urine levels of HSP70 were measured by enzyme-linked immunosorbent assay (ELISA).

Results: In the NS group before steroid treatment (day 0), urine HSP70 (uHSP70) levels and urine HSP70/creatinine (uHSP70/Cre) ratios were significantly higher (p<0.0001), whereas serum HSP70 (sHSP70) levels were lower (p=0.002), compared to the healthy group. uHSP70 levels decreased gradually during prednisolone treatment in the patient group (p<0.0001). There was no difference in terms of sHSP70, uHSP70, and uHSP70/Cre ratios between patients with frequently relapsing and infrequently relapsing.

Conclusions: Our study demonstrates that uHSP70 levels are elevated in SSNS prior to treatment and decrease with prednisolone therapy, reflecting reduced renal stress and damage. uHSP70 may be a useful biomarker for monitoring renal damage and treatment response. Serum and urine levels of HSP70, as well as uHSP70/Cre ratios, did not differentiate between frequent and infrequent relapses.