TWEAK Activates the Non-Canonical NFκB Pathway in Murine Renal Tubular Cells: Modulation of CCL21

TWEAK is a member of the TNF superfamily of cytokines that contribute to kidney tubulointerstitial injury. It has previously been reported that TWEAK induces transient nuclear translocation of RelA and expression of RelA-dependent cytokines in renal tubular cells. Additionally, TWEAK induced long-lasting NF kappa B activation suggestive of engagement of the non-canonical NF kappa B pathway. We now explore TWEAK-induced activation of NF kappa B2 and RelB, as well as expression of CCL21, a T-cell chemotactic factor, in cultured murine tubular epithelial cells and in healthy kidneys in vivo. In cultured tubular cells, TWEAK and TNF alpha activated different DNA-binding NF kappa B complexes. TWEAK-induced sustained NF kappa B activation was associated with NF kappa B2 p100 processing to p52 via proteasome and nuclear translocation and DNA-binding of p52 and RelB. TWEAK, but not TNF alpha used as control), induced a delayed increase in CCL21a mRNA (3.5 +/- 1.22-fold over control) and CCL21 protein (2.5 +/- 0.8-fold over control), which was prevented by inhibition of the proteasome, or siRNA targeting of NIK or RelB, but not by RelA inhibition with parthenolide. A second NF kappa B2-dependent chemokine, CCL19, was upregulates by TWEAK, but not by TNF alpha. However, both cytokines promoted chemokine RANTES expression (3-fold mRNA at 24 h). In vivo, TWEAK induced nuclear NF kappa B2 and RelB translocation and CCL21a mRNA (1.5 +/- 0.3-fold over control) and CCL21 protein (1.6 +/- 0.5-fold over control) expression in normal kidney. Increased tubular nuclear RelB and tubular CCL21 expression in acute kidney injury were decreased by neutralization (2 +/- 0.9 vs 1.3 +/- 0.6-fold over healthy control) or deficiency of TWEAK (2 +/- 0.9 vs 0.8 +/- 0.6-fold over healthy control). Moreover, anti-TWEAK treatment prevented the recruitment of T cells to the kidney in this model (4.1 +/- 1.4 vs 1.8 +/- 1-fold over healthy control). Our results thus identify TWEAK as a regulator of non-canonical NF kappa B activation and CCL21 expression in tubular cells thus promoting lymphocyte recruitment to the kidney during acute injury.