Heparin binding EGF is necessary for vasospastic response to endothelin

Area of Science:

• Cardiovascular Biology
• Molecular Cell Biology
• Pharmacology

Background:

• Endothelin-1 (ET-1) is a potent vasoconstrictor implicated in vasospastic diseases and fibrotic remodeling.
• Epidermal growth factor receptor (EGFR) transactivation is known to mediate ET-1 signaling in vascular smooth muscle cells (VSMCs) and arteries.
• The precise mechanisms of ET-1-induced EGFR transactivation remain unidentified.

Purpose of the Study:

• To investigate the role of heparin-binding EGF-like growth factor (HB-EGF) in ET-1-induced EGFR transactivation.
• To elucidate the involvement of HB-EGF in ET-1-mediated intracellular calcium mobilization and VSMC contraction.
• To explore the functional cascade involving EGFR and PI3K in ET-1 signaling.

Main Methods:

• Utilized HB-EGF-deficient (HB-EGF-/-) mice and wild-type littermates.
• Employed isolated mouse carotid artery segments and VSMCs for functional assays.
• Administered ET-1, EGFR inhibitors (AG1478), PI3K inhibitors (LY294002, wortmannin), metalloproteinase inhibitor (batimastat), and CRM197.

Main Results:

• ET-1-induced vasoconstriction was significantly attenuated in HB-EGF-/- mice.
• ET-1-induced calcium transients in VSMCs were reduced in HB-EGF-/- and waved-2 (EGFR partial loss-of-function) mice.
• Inhibition of EGFR, PI3K, or metalloproteinases blunted ET-1 responses, indicating a role for HB-EGF and EGFR signaling.

Conclusions:

• ET-1-induced vasoconstriction is mediated by HB-EGF-dependent transactivation of EGFR.
• This pathway involves rapid modulation of calcium transients by EGFR and PI3K.
• The findings suggest a novel paradigm for G-protein coupled receptor (GPCR)-mediated calcium signaling with potential therapeutic implications.