suPAR and WT1 modify the adhesion of podocytes and are related to proteinuria in class IV lupus nephritis

Introduction

Lupus nephritis (LN) affects up to 60 % of the patients with Systemic Lupus Erythematosus (SLE) and renal damage progression is associated with proteinuria, caused in part by the integrity of the glomerular basement membrane (GBM) and by podocyte injury. The soluble urokinase plasminogen activator receptor (suPAR) and Wilms Tumor 1 (WT1) have been related to podocyte effacement and consequently with proteinuria which raises questions about its pathogenic role in LN.

Objective

Define whether suPAR levels and WT1 expression influence in podocyte anchorage destabilization in LN class IV.

Materials and methods

This is a cross-sectional study of cases and controls. We studied patients with SLE without renal involvement (n = 12), SLE and LN class IV with proteinuria ≤0.5 g/24 h (n = 12), LN class IV with proteinuria ≥0.5 g/24 h (n = 12) and compared them with renal tissue control (CR) (n = 12) and control sera (CS) (n = 12). The CR was integrated by cadaveric samples without SLE or renal involvement and the CS was integrated by healthy participants. The expression and cellular localization of WT1, urokinase-type plasminogen activator receptor (uPAR), ac-α-tubulin, vimentin, and β3-integrin was assessed by immunohistochemistry (IHC). The concentration of suPAR in serum was analyzed by enzyme-linked immunosorbent assay (ELISA).

Results

In patients with LN, the activation of anchoring proteins was increased, such as podocyte β3-integrin, as well as the acetylation of alpha-acetyl-tubulin and uPAR, in contrast to the decrease in vimentin; interestingly, the cellular localization of WT1 was cytoplasmic and the number of podocytes per glomerulus decreased. The concentrations of suPAR was increased in patients with LN.

Conclusion

The destabilization of podocyte anchorage modulated by β3-integrin activation, and tubulin acetylation, associated with decreased WT1 cytoplasmic expression, and increased suPAR levels could be involved in kidney damage in patients with LN class IV.