Huang R, Tamalunas A, Waidelich R, Strittmatter F, Stief CG, Hennenberg M. Antagonism of α
1-adrenoceptors by β
3-adrenergic agonists: Structure-function relations of different agonists in prostate smooth muscle contraction.
Biochem Pharmacol 2022;
202:115148. [PMID:
35716783 DOI:
10.1016/j.bcp.2022.115148]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Revised: 06/09/2022] [Accepted: 06/10/2022] [Indexed: 11/29/2022]
Abstract
Effects of β3-adrenergic agonists on prostate smooth muscle contraction are poorly characterized, although mirabegron is used for treatment of lower urinary tract symptoms. Off-target effects of several β3-adrenergic agonists include antagonism of α1-adrenoceptors. Proposed, but unconfirmed explanations include phenylethanolamine backbones, found in some β3-adrenergic agonists and imparting interaction with catecholamine binding pockets of adrenoceptors. Here, we examined effects of β3-adrenergic agonists on contractions of human prostate tissues, including ZD7114 (without phenylethanolamine moiety), ZD2079 (phenylethanolamine backbone), BRL37344 and CL316243 (chloride-substituted phenylethanolamine deriatives). Prostate tissues were obtained from radical prostatectomy. Contractions by α1-adrenergic agonists and electric field stimulation (EFS) were studied in an organ bath. ZD7114 (10 µM) right-shifted concentration responses curves for α1-adrenergic agonists, resulting in increased EC50 values for phenylephrine, methoxamine and noradrenaline up to one magnitude, without affecting Emax values. ZD7114 (10 µM) inhibited EFS-induced contractions, resulting in reduced Emax values. All effects of ZD7114 were resistant to the β3-adrenergic antagonist L-748337, including increases in EC50 values for α1-adrenergic agonists, up to more than two magnitudes. Using 10 µM, neither ZD2079, BRL37344 or CL316243 affected α1-adrenergic or EFS-induced contractions. At escalated concentrations, BRL37344 (200 µM) right-shifted concentration response curves for phenylephrine, increased EC50 values for phenylephrine, and inhibited EFS-induced contractions, while CL316243 (300 µM) did not affect phenylephrine- or EFS-induced contractions. In conclusion, phenylethanolamine backbones are not decisive to impart α1-adrenoceptor antagonism to β3-agonists. Effects of β3-adrenergic agonists on prostate smooth muscle contraction are limited to off-target effects, including α1-adrenoceptor antagonism by ZD7114 and BRL37344.
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