title: Alpha1D-adrenergic receptors and mitogen-activated protein kinase mediate increased protein synthesis by arterial smooth muscle.
abstract: Catecholamines may influence vascular smooth muscle cell (SMC) growth and vascular hypertrophic diseases. We previously demonstrated that stimulation of alpha1-adrenoceptors (AR) causes hypertrophy of vascular SMCs in vitro and in situ. Here, we used adult rat aorta SMCs that express alpha1D- and alpha1B-ARs (but not alpha1A-ARs) in vitro to examine the mechanisms and alpha1-AR subtypes involved. Norepinephrine (NE) increased protein synthesis and content in a time- and dose-dependent manner. To identify the responsible alpha1-AR subtype, we first documented the selectivity of two alpha1-AR subtype antagonists, BMY 7378 (alpha1D-AR antagonist) and chloroethylclonidine (CEC; alpha1B-AR antagonist), using Rat-1 fibroblasts stably transfected with the three different rodent alpha1-AR cDNAs. NE dose-dependently increased protein synthesis in each cell line. In alpha1D fibroblasts, BMY 7378 inhibited growth and protected alpha1D-ARs from CEC alkylation while having little blocking or protecting effect on the growth induced by stimulation of fibroblasts that express alpha1A- or alpha1B-ARs. In rat aorta SMCs, pretreatment with CEC in the presence of BMY 7378 to protect alpha1D-ARs had no effect on NE-induced protein synthesis. BMY 7378 inhibited the SMC growth response with a pKb of 8.4. NE caused rapid and transient p42-p44 mitogen-activated protein kinase (MAPK) activation that was alpha1D-AR dependent. Furthermore, NE caused tyrosine phosphorylation of multiple cellular proteins, phosphorylation of Raf-1, and stimulation of c-fos mRNA expression in aorta SMCs. The selective MAPK kinase inhibitor PD 98059 inhibited NE-induced protein synthesis and MAPK activation with IC50 values of 2.3 and 1.6 microM, respectively. These data demonstrate that SMC growth induced by NE is mediated by alpha1D-ARs that couple to activation of the MAPK cascade.
authors.affiliation: Department of Physiology, University of North Carolina, Chapel Hill 27599-7545, USA.
authors.forename: X
authors.initials: X
authors.lastname: Xin
authors.forename: N
authors.initials: N
authors.lastname: Yang
authors.forename: A D
authors.initials: AD
authors.lastname: Eckhart
authors.forename: J E
authors.initials: JE
authors.lastname: Faber
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004789:Enzyme Activation; D007700:Kinetics; D008297:Male; D009124:Muscle Proteins / Q000096:biosynthesis*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D019908:Proto-Oncogene Proteins c-raf; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism
chemical_list: C547721:Adra1d protein, rat; D009124:Muscle Proteins; D010879:Piperazines; D011518:Proto-Oncogene Proteins; D016760:Proto-Oncogene Proteins c-fos; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D014443:Tyrosine; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C053428:BMY 7378; D009638:Norepinephrine