The regulation of mitogenesis and apoptosis in response to the persistent stimulation of alpha1-adrenoceptors: a possible role of 15-lipoxygenase.
1. Activation of alpha1-adrenoceptor stimulation regulates eicosanoid metabolism and growth in vascular smooth muscle cells (VSMCs). The purpose of this study was to investigate the functional implications of lipoxygenase pathway in alpha1-adrenoceptor-stimulated VSMCs growth through mutually exclusive biological functions, that is cell proliferation and cell death. 2. Phenylephrine (10 microM), a specific alpha1-adrenoceptor agonist, enhanced [3H]-thymidine incorporation by 300% above basal. Nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, caused 36 and 50% decrease in phenylephrine (10 microM)-stimulated [3H]-thymidine incorporation at concentrations of 1 microM and 10 microM respectively. 3. Inversely, treatment of phenylephrine (10 microM)-stimulated VSMCs with NDGA induced DNA fragmentation in a dose-dependent fashion. The level of induction of DNA fragmentation by NDGA was 225, 319 and 406% above the phenylephrine (10 microM)-level at concentrations of 0.1 microM, 1 microM and 10 microM, respectively. This induction of DNA fragmentation was partially prevented by exogenous 15-hydroxyeicosatetraenoic acid (15-HETE). The inhibition of apoptosis was 53 and 63% at concentrations of 5 microM and 10 microM of 15HETE, respectively, as compared with phenylephrine (10 microM) in the presence of NDGA (10 microM). 4. Furthermore, we performed the time-course analysis of Bcl-2 protein expression in phenylephrine (10 microM)-stimulated VSMCs. The expression of Bcl-2 protein disappeared after a 2 h incubation in the presence of NDGA (10 microM), but remained stable after a 2 h incubation period in the absence of NDGA (10 microM). 5, These results suggest that the lipoxygenase pathway is involved in cell proliferation by preventing apoptosis through the level of Bcl-2 protein expression.
Nishio
E
E
Department of Pharmacology, National Defence Medical College 3-2, Namiki, Tokorozawa, Japan.
Watanabe
Y
Y
D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001093:Arachidonate 15-Lipoxygenase / Q000187:drug effects* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects*; D004789:Enzyme Activation; D005260:Female; D019254:Genes, bcl-2 / Q000187:drug effects; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D008297:Male; D009637:Masoprocol / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D011817:Rabbits; D018340:Receptors, Adrenergic, alpha-1 / Q000187:drug effects*
D058646:Adrenergic alpha-1 Receptor Agonists; D000316:Adrenergic alpha-Agonists; D016859:Lipoxygenase Inhibitors; D018340:Receptors, Adrenergic, alpha-1; D010656:Phenylephrine; D009637:Masoprocol; D001093:Arachidonate 15-Lipoxygenase