brl-37344 and Neuroblastoma

Loss of brain-derived neurotrophic factor (BDNF)/TrkB (tropomyosin kinase receptor B) signaling accounts for brain and cardiac disorders. In neurons, β-adrenergic receptor stimulation enhances local BDNF expression. It is unclear if this occurs in a pathophysiological relevant manner in the heart, especially in the β-adrenergic receptor-desensitized postischemic myocardium. Nor is it fully understood whether and how TrkB agonists counter chronic postischemic left ventricle (LV) decompensation, a significant unmet clinical milestone.. We conducted in vitro studies using neonatal rat and adult murine cardiomyocytes, SH-SY5Y neuronal cells, and umbilical vein endothelial cells. We assessed myocardial ischemia (MI) impact in wild type, β3AR knockout, or myocyte-selective BDNF knockout (myoBDNF KO) mice in vivo (via coronary ligation [MI]) or in isolated hearts with global ischemia-reperfusion (I/R).. In wild type hearts, BDNF levels rose early after MI (<24 hours), plummeting at 4 weeks when LV dysfunction, adrenergic denervation, and impaired angiogenesis ensued. The TrkB agonist, LM22A-4, countered all these adverse effects. Compared with wild type, isolated myoBDNF KO hearts displayed worse infarct size/LV dysfunction after I/R injury and modest benefits from LM22A-4. In vitro, LM22A-4 promoted neurite outgrowth and neovascularization, boosting myocyte function, effects reproduced by 7,8-dihydroxyflavone, a chemically unrelated TrkB agonist. Superfusing myocytes with the β3AR-agonist, BRL-37344, increased myocyte BDNF content, while β3AR signaling underscored BDNF generation/protection in post-MI hearts. Accordingly, the β1AR blocker, metoprolol, via upregulated β3ARs, improved chronic post-MI LV dysfunction, enriching the myocardium with BDNF. Last, BRL-37344-imparted benefits were nearly abolished in isolated I/R injured myoBDNF KO hearts.. BDNF loss underscores chronic postischemic heart failure. TrkB agonists can improve ischemic LV dysfunction via replenished myocardial BDNF content. Direct cardiac β3AR stimulation, or β-blockers (via upregulated β3AR), is another BDNF-based means to fend off chronic postischemic heart failure.

Topics: Animals; Brain-Derived Neurotrophic Factor; Endothelial Cells; Heart Failure; Humans; Mice; Myocardial Ischemia; Myocytes, Cardiac; Neuroblastoma; Rats; Receptors, Adrenergic, beta; Ventricular Dysfunction, Left

In SK-N-MC human neuroblastoma cells, the cAMP response to 10 nM isoproterenol (ISO) is mediated primarily by beta 1-adrenergic receptors. However, responses to higher concentrations of ISO (100-1000 nM) were only weakly blocked by beta 1- and beta 2-selective antagonists. When beta 1 receptors were blocked with 10 microM CGP 20712A, catecholamines still maximally activated cAMP accumulation, with only small decreases in potency. In the presence of CGP 20712A, beta blockers inhibited the response to ISO stereoselectively but with relatively low potencies. Pindolol derivatives were partial agonists with low potencies, and the atypical agonist BRL 37344 was a partial agonist with an intermediate potency. All binding sites in these cells labeled by 125I-cyanopindolol were of the beta 1 subtype. Nuclease protection assays indicated that SK-N-MC cells contain mRNA for both the human beta 1- and beta 3-adrenergic receptors, with the beta 3 subtype mRNA being expressed 25-50% more abundantly than that for the beta 1 subtype. Northern blot hybridizations showed the presence of two beta 3 mRNA transcripts of 3.1 and 2.4 kilobases. These results suggest that beta 1- and atypical beta-adrenergic receptors coexist in these cells and cause redundant increases in cAMP formation. Although molecular approaches suggest that the atypical subtype is the beta 3, the observed drug specificity differs from that reported for the expressed recombinant human beta 3 receptor.

Topics: Adrenergic beta-Agonists; Adrenergic beta-Antagonists; Cyclic AMP; Ethanolamines; Humans; Imidazoles; Isoproterenol; Neuroblastoma; Pindolol; Radioligand Assay; Receptors, Adrenergic, beta; RNA, Messenger; Tumor Cells, Cultured