Abstract
Heme oxygenase (HO)-1 is a well-known cytoprotectant against oxidative stress and exhibits an antiproliferative effect in vascular smooth muscle cells (VSMCs). The purpose of the present study was to test whether isoproterenol, one of the synthetic catecholamines having β-adrenergic activity, affected angiotensin II (Ang II)-induced cell proliferation and reactive oxygen species (ROS) production. Also, the presumptive underlying signaling pathways in VSMCs were studied. Aortic VSMCs from 11-week-old male Sprague-Dawley rats were used. Isoproterenol dose-dependently increased HO-1 expression through β2-adrenoceptor (AR) and protein kinase A (PKA) pathway, and isoproterenol concentration-dependently increased β2-AR mRNA expression. Isoproterenol attenuated Ang II-induced cell proliferation, as evidenced by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide (MTT) assay. This effect of isoproterenol was inhibited by pretreatment of the cells with β2-AR antagonist butoxamine, PKA inhibitor H-89 and HO inhibitor Tin Protoporphyrin IX (SnPP IX), respectively. Isoproterenol inhibited phosphorylation level of Ang II-induced extracellular signal-regulated kinase (ERK1/2). Isoproterenol significantly inhibited Ang II-induced ROS production through the ERK1/2 pathway. These findings suggest that isoproterenol, via induction of HO-1, inhibits Ang II-stimulated proliferation and ROS production in cultured VSMCs.
