The TGF-β profibrotic cascade targets ecto-5′-nucleotidase gene in proximal tubule epithelial cells and is a traceable marker of progressive diabetic kidney disease

Progressive diabetic nephropathy (DN) and loss of renal function correlate with kidney fibrosis. Crosstalk between TGF-beta and adenosinergic signaling contributes to the phenotypic transition of cells and to renal fibrosis in DN models. We evaluated the role of TGF-beta on NT5E gene expression coding for the ecto-5'-nucleotidase CD73, the limiting enzyme in extracellular adenosine production. We showed that high D-glucose may predispose HK-2 cells towards active transcription of the proximal promoter region of the NT5E gene while additional TGF-beta results in full activation. The epigenetic landscape of the NT5E gene promoter was modified by concurrent TGF-beta with occupancy by the p300 co-activator and the phosphorylated forms of the Smad2/3 complex and RNA Pol II. Transcriptional induction at NT5E in response to TGF-beta was earlier compared to the classic responsiveness genes PAI-1 and Fnl. CD73 levels and AMPase activity were concomitantly increased by TGF-beta in HK-2 cells. Interestingly, we found increased CD73 content in urinary extracellular vesicles only in diabetic patients with renal repercussions. Further, CD73-mediated AMPase activity was increased in the urinary sediment of DN patients. We conclude that the NT5E gene is a target of the profibrotic TGF-beta cascade and is a traceable marker of progressive DN.