Carboxymethyl lysine induces EMT in podocytes through transcription factor ZEB2: Implications for podocyte depletion and proteinuria in diabetes mellitus

Advanced glycation end-products (AGEs) are implicated in the pathogenesis of diabetic nephropathy (DN). N-carboxymethyl-lysine (CML) is one of the predominant AGEs that accumulate in all renal compartments of diabetic patients. Nevertheless, the direct effect of CML on podocyte biology has not been explored. In this study, we demonstrate the induction of the transcription factor Zeb2 in podocytes upon exposure to CML through activation of NF-kB signaling cascade. Zeb2 orchestrates epithelial-mesenchymal transformation (EMT), during which cell-cell and cell-extracellular matrix interactions are feeble and enable epithelial cells to become invasive. CML treatment induced both NF-kB and Zeb2 promoter activity and suppressed E-cadherin promoter activity. Inhibition of NF-kB activity prevented CML dependent induction of Zeb2 and loss of E-cadherin. While the exposure of podocytes to CML results in increased podocyte permeability, shRNA-mediated knockdown of Zeb2 expression abrogated CML-mediated podocyte permeability. Further, in vivo findings of elevated CML levels concurrent with increased expression of ZEB2 in glomeruli and proteinuria in diabetic rats confirm that CML-mediated manifestations in the kidney under chronic diabetes conditions. These in vitro and in vivo results envisage the novel axis of NFkB-ZEB2 in podocytes playing a significant role in eliciting EMT and pathogenesis of DN.