High Glucose Up-regulates ADAM17 through HIF-1α in Mesangial Cells

Background: ADAM17 is an important promoter of fibrosis in diabetic kidney disease. Results: ADAM17 is transcriptionally up-regulated by glucose through HIF-1 in kidney mesangial cells, associated with enhanced enzymatic activity. Conclusion: ADAM17 induces its own up-regulation, thereby augmenting its activity, in response to glucose. Significance: These studies provide a strong foundation for further evaluation of the role of ADAM17 in the profibrotic response of kidney cells to high glucose. We previously showed that ADAM17 mediates high glucose-induced matrix production by kidney mesangial cells. ADAM17 expression is increased in diabetic kidneys, suggesting that its up-regulation may augment high glucose profibrotic responses. We thus studied the effects of high glucose on ADAM17 gene regulation. Primary rat mesangial cells were treated with high glucose (30 mm) or mannitol as osmotic control. High glucose dose-dependently increased ADAM17 promoter activity, transcript, and protein levels. This correlated with augmented ADAM17 activity after 24 h versus 1 h of high glucose. We tested involvement of transcription factors shown in other settings to regulate ADAM17 transcription. Promoter activation was not affected by NF-B or Sp1 inhibitors, but was blocked by hypoxia-inducible factor-1 (HIF-1) inhibition or down-regulation. This also prevented ADAM17 transcript and protein increases. HIF-1 activation by high glucose was shown by its increased nuclear translocation and activation of the HIF-responsive hypoxia-response element (HRE)-luciferase reporter construct. Assessment of ADAM17 promoter deletion constructs coupled with mutation analysis and ChIP studies identified HIF-1 binding to its consensus element at -607 as critical for the high glucose response. Finally, inhibitors of epidermal growth factor receptor (EGFR) and downstream PI3K/Akt, or ADAM17 itself, prevented high glucose-induced HIF-1 activation and ADAM17 up-regulation. Thus, high glucose induces ADAM17 transcriptional up-regulation in mesangial cells, which is associated with augmentation of its activity. This is mediated by HIF-1 and requires EGFR/ADAM17 signaling, demonstrating the potentiation by ADAM17 of its own up-regulation. ADAM17 inhibition thus provides a potential novel therapeutic strategy for the treatment of diabetic nephropathy.