HB-EGF release mediates glucose-induced activation of the epidermal growth factor receptor in mesangial cells

Abstract

Glomerular matrix accumulation is a hallmark of diabetic nephropathy. We showed that transactivation of the epidermal growth factor receptor (EGFR) is an important mediator of matrix upregulation in mesangial cells (MC) in response to high glucose (HG). Here, we study the mechanism of EGFR transactivation. In primary MC, EGFR transactivation by 1 h of HG (30 mM) was unaffected by inhibitors of protein kinase C, reactive oxygen species, or the angiotensin II AT1 receptor. However, general metalloprotease inhibition, as well as specific inhibitors of heparin-binding EGF-like growth factor (HB-EGF), prevented both EGFR and downstream Akt activation. HB-EGF was released into the medium by 30 min of HG, and this depended on metalloprotease activity. One of the metalloproteases shown to cleave proHB-EGF is ADAM17 (TACE). HG, but not an osmotic control, activated ADAM17, and its inhibition prevented EGFR and Akt activation and HB-EGF release into the medium. siRNA to either ADAM17 or HB-EGF prevented HG-induced EGFR transactivation. We previously showed that EGFR/Akt signaling increases transforming growth factor (TGF)-β1 transcription through the transcription factor activator protein (AP)-1. HG-induced AP-1 activation, as assessed by EMSA, was abrogated by inhibitors of metalloproteases, HB-EGF and ADAM17. HB-EGF and ADAM17 siRNA also prevented AP-1 activation. Finally, these inhibitors and siRNA prevented TGF-β1 upregulation by HG. Thus, HG-induced EGFR transactivation in MC is mediated by the release of HB-EGF, which requires activity of the metalloprotease ADAM17. The mechanism of ADAM17 activation awaits identification. Targeting upstream mediators of EGFR transactivation including HB-EGF or ADAM17 provides novel therapeutic targets for the treatment of diabetic nephropathy.

ADAM17 mediates Nox4 expression and NADPH oxidase activity in the kidney cortex of OVE26 mice

“…Glucose increases ADAM17 activity and/or EGFR transactivation causing increased ECM or fibrotic factors within the kidney (48,(51)(52)(53). Exposure of primary cultures of rat mesangial cells to a high concentration of D-glucose activates ADAM17 and results in an increase in TGF␤ promoter activity and an increase in TGF␤ transcripts (48).…”

“…Exposure of primary cultures of rat mesangial cells to a high concentration of D-glucose activates ADAM17 and results in an increase in TGF␤ promoter activity and an increase in TGF␤ transcripts (48). Additional data in mesangial cells suggest that the increase in collagen I and fibronectin expression in response to glucose depends on the activation of ADAM17, EGFR transactivation, and activation of downstream signals such as the phosphoinositide 3-kinaseAkt pathway (48,(51)(52)(53). Other than these limited publications, glucose-induced ADAM17 expression or activity influencing the progression of DN has not been thoroughly investigated.…”

“…ADAM17, a member of this ADAM family of MMPs, was originally described as the sheddase of tumor necrosis factor-␣, referred to as TNF␣-converting enzyme (4, 34). In addition, ADAM17 is also responsible for cleaving membrane-bound growth factors and receptors such as transforming growth factor-␣ (TGF␣), heparin-bound epidermal growth factor (HB-EGF), TNF receptor I and II, adhesion molecules, proinflammatory molecules, amyloid precursor protein, and ErbB4 (4,12,17,28,34,39,41).There is evidence that ADAM17 plays a role in the pathogenesis of DN (1,3,10,11,20,21,26,29,33,35,40,42,47,48). Studies in mesangial cells showed that glucose activates ADAM17 and EGF receptor (EGFR) and regulates profibrotic TGF␤ and the accumulation of matrix proteins (48,(51)(52)(53).…”

“…There is evidence that ADAM17 plays a role in the pathogenesis of DN (1,3,10,11,20,21,26,29,33,35,40,42,47,48). Studies in mesangial cells showed that glucose activates ADAM17 and EGF receptor (EGFR) and regulates profibrotic TGF␤ and the accumulation of matrix proteins (48,(51)(52)(53).…”

“…Studies in mesangial cells showed that glucose activates ADAM17 and EGF receptor (EGFR) and regulates profibrotic TGF␤ and the accumulation of matrix proteins (48,(51)(52)(53). However, the mechanisms by which glucose-mediated ADAM17 activity contributes to increased matrix production and fibrosis are still not fully understood.…”