Angiotensin II stimulates DNA and protein synthesis in vascular smooth muscle cells from human arteries: role of extracellular signal-regulated kinases

Objective This study investigates the growth effects and associated signali ng pathways of angiotensin II (Ang II) in human vascular smooth muscle cell s. Methods Cultured vascular smooth muscle cells derived from resistance arter ies (< 300 mu m diameter) from subcutaneous gluteal biopsies of healthy sub jects (n = 6) and human aortic vascular smooth muscle cells were used. Cell s were studied between passages 3 and 6. Both H-3-thymidine and H-3-leucine incorporation were measured as indices of vascular smooth muscle cell hype rplasia (DNA synthesis) and cell hypertrophy (protein synthesis), respectiv ely, Growth effects of Ang II (10(-12) - 10(-6) mol/l), in the absence and presence of 10(-5) mol/l losartan (AT(1) antagonist) and PD123319 (AT(2) an tagonist), were determined. Ang II-induced effects were compared to those o f endothelin-1. To determine whether extracellular signal-regulated kinase (ERK)-dependent pathways play a role in Ang II-mediated growth, cells were pretreated with the selective ERK kinase (MEK) inhibitor, PD98059 (10-5 mol /l), ERK activation was determined by Western blot in the absence and prese nce of PD98059, Results Ang II dose-dependently increased 3H-thymidine incorporation in cel ls from aorta (E-max = 276 +/- 10.4% of control) and resistance arteries (E -max = 284 +/- 5.1% of control). Ang II also stimulated 3H-leucine incorpor ation in cells from aorta (E-max = 162 +/- 11.6 of control) and resistance arteries (E-max 175 +/- 10% of control). Unlike Ang II, endothelin-1 failed to significantly alter cellular growth, except at high concentrations (> 1 0(-7) mol/l), where it had a weak stimulatory effect. Losartan, but not PD1 23319, blocked Ang II-stimulated growth responses. Ang II significantly inc reased phosphorylation of ERK-1 and ERK-2, with maximum responses obtained at 5 min. PD98059 inhibited Ang II-stimulated ERK activity and abrogated ag onist-induced DNA and protein synthesis. Losartan, but not PD123319 inhibit ed Ang II-induced phosphorylation of ERK-1 and ERK-2, Conclusions Ang II stimulates both hyperplasia and hypertrophy in vascular smooth muscle cells from human arteries. These growth effects are mediated via Ang II receptors of the AT(1) subtype that are linked to ERK-dependent signaling pathways. I Hypertens 1999, 17:907-916 (C) Lippincott Williams & Wilkins.