Noradrenergic stimulation of BDNF synthesis in astrocytes: mediation via alpha1- and beta1/beta2-adrenergic receptors.
Brain-derived neurotrophic factor (BDNF) synthesis in astrocytes induced by noradrenaline (NA) is a receptor-mediated process utilizing two parallel adrenergic pathways: beta1/beta2-adrenergic/cAMP and the novel alpha1-adrenergic/PKC pathway. BDNF is produced by astrocytes, in addition to neurons, and the noradrenergic system plays a role in controlling BDNF synthesis. Since astrocytes express various subtypes of alpha- and beta-adrenergic receptors that have the potential to be activated by synaptically released NA, we focused our present study on the mediatory role of adrenergic receptors in the noradrenergic up-regulation of BDNF synthesis in cultured neonatal rat cortical astrocytes. NA (1 microM) elevates BDNF levels by four-fold after 6 h of incubation. Its stimulation was partly inhibited by either the beta1-adrenergic antagonist atenolol, the beta2-adrenergic antagonist ICI 118,551, or by the alpha1-adrenergic antagonist prazosin, while the alpha2-adrenergic antagonist yohimbine showed no effect. BDNF levels in astrocytes were increased by the specific beta1-adrenergic agonist dobutamine and the beta2-adrenergic agonist salbutamol, as well as by adenylate cyclase activation (by forskolin) and PKA activation (by dBcAMP). However, none of the tested agonists or mediators of the intracellular beta-adrenergic pathways were able to reach the level of NA's stimulatory effect. BDNF cellular levels were also elevated by the alpha1-adrenergic agonist methoxamine, but not by the alpha2-adrenergic agonist clonidine. The increase in intracellular Ca2+ by ionophore A23187 showed no effect, whereas PKC activation by phorbol 12-myristate 13-acetate (TPA) potently stimulated BDNF levels in the cells. The methoxamine-stimulated BDNF synthesis was inhibited by desensitizing pretreatment with TPA, indicating that the alpha1-stimulation was mediated via PKC activation. In conclusion, the synthesis of astrocytic BDNF stimulated by noradrenergic neuronal activity is an adaptable process using multiple types (alpha1 and beta1/beta2) of adrenergic receptor activation.
Juric
Damijana Mojca
DM
Department of Pharmacology and Experimental Toxicology, Faculty of Medicine, University of Ljubljana, Korytkova 2, Ljubljana SI-1000, Slovenia. damijana-mojca.juric@mf.uni-lj.si
Loncar
Darja
D
Carman-Krzan
Marija
M
D018663:Adrenergic Agents / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D019208:Brain-Derived Neurotrophic Factor / Q000096:biosynthesis*; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D011941:Receptors, Adrenergic / Q000502:physiology*
D018663:Adrenergic Agents; D019208:Brain-Derived Neurotrophic Factor; D011941:Receptors, Adrenergic