Induction of heparin-binding epidermal growth factor-like growth factor mRNA by phorbol ester and angiotensin II in rat aortic smooth muscle cells.

To determine whether the gene encoding the recently identified heparin-binding epidermal growth factor-like growth factor (HB-EGF), a potent smooth muscle cell (SMC) mitogen of macrophage origin, is transcribed and regulated in vascular SMC, we isolated cDNA clones encoding rat HB-EGF from a macrophage library. Using the rat HB-EGF cDNA as a probe for RNA blot analysis, we detected low levels of HB-EGF mRNA in rat aortic SMC in culture. However, 20 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) and 10(-6) M angiotensin II (AII) induced a marked increase in HB-EGF mRNA levels in rat aortic SMC (11- and 4.6-fold, respectively) that was both dose- and time-dependent. In response to TPA and AII, HB-EGF mRNA levels increased rapidly, peaked at 2 h, and returned to base line at 7 h. This effect of AII on HB-EGF induction was specific, as evidenced by the fact that it could be completely blocked by the AII antagonist saralasin. This is the first demonstration that HB-EGF is transcribed and regulated in SMC. The inducible transcription of this potent SMC mitogen gene in vascular SMC suggests that HB-EGF may have an important autocrine role in the proliferation of SMC in vascular diseases such as atherosclerosis and hypertension.