Inhibition of heparin-binding epidermal growth factor-like growth factor increases albuminuria in puromycin aminonucleoside nephrosis

Background. Our previous work in the acute puromycin aminonucleoside nephro sis (PAN) model has demonstrated up-regulation of heparin-binding epidermal growth factor-like growth factor (HB-EGF) mRNA and protein within glomerul ar epithelial cells (GECs) prior to the onset of proteinuria. Methods. To determine whether increased HB-EGF expression in the acute PAN model contributes to the pathogenesis of proteinuria, a monoclonal antibody (DE10) was produced against recombinant human HB-ECF. Results. The specificity of DE10 for human HB-EGF was confirmed by enzyme-l inked immunosorbent assay, immunohistochemical staining, and how cytometry of transfected cells expressing human and rat HE EGF. and inhibition of cel l proliferation. DE10 also reacted with cells transfected with rat HB-EGF c DNA. Administration of 0.5 mg affinity-purified DE10 to normal rats did not cause significant albuminuria compared with controls. Five days after the induction of the acute PAN model, albuminuria was significantly greater in animals treated with 0.5 mg DE10 than a control mAb (162.6 +/- 32.4 vs. 64. 8 +/- 10.2 mg/day, respectively, P < 0.01). Rats treated with DE10 had an e arlier onset of severe albuminuria, but no increase in maximal albuminuria at later time points. Electron microscopy showed marked podocyte effacement in both DE10-treated and control animals, but no obvious difference betwee n groups. However, adhesion of the human GEC line 56/10 Al to laminin and f ibronectin, but not to collagens I or IV, was reduced by DE10. Conclusions. This study suggests that HB-EGF contributes to the integrity o f the glomerular filtration barrier, particularly when the podocyte has bee n injured. Following podocyte injury, adhesion to laminin in the glomerular basement membrane by HB-EGF may be important in reducing albuminuria.