Tsotinis A, Afroudakis PA, Papanastasiou IP, Sakellaropoulou A, Boniakou M, Komiotis D, Garratt PJ, Delagrange P, Bocianowska-Zbrog A, Sugden D. Mapping the Melatonin Receptor. 8. Selective MT2 Agonists derived from 5,6-dihydroindolo[2,1-a]isoquinolines and related systems.
ChemMedChem 2022;
17:e202200129. [PMID:
35478275 DOI:
10.1002/cmdc.202200129]
[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: 03/11/2022] [Revised: 04/15/2022] [Indexed: 11/10/2022]
Abstract
A series of substituted indolo[2,1- a ]isoquinolines and indolo[1,2- a ]benzoxazines have been prepared, as melatonin analogues, to investigate the nature of the binding site of the melatonin receptor. Agonist and antagonist potency of all the analogues was measured using the [35S]GTPγS binding assay protocol. The binding affinity of the analogues were measured by competition binding studies against the human MT1 (hMT1) and MT2 (hMT2) receptors stably transfected in Chinese Hamster Ovarian (CHO) cells, using 2-[ 125 I]-iodomelatonin, as a ligand. N -Acetyl 2-(10-methoxy-5,6-dihydroindolo[2,1- a ]isoquinolin-12-yl)propyl-1-amine (12a) binds strongly to both the hMT1 and hMT2 receptors, and shows a preference for the hMT2, as does Its propanamido counterpart 12b . The introduction of two methyl groups into their side chain, analogues 15a and 1 5b, leads to antagonism, in the case of the former, and drastically diminishes its hMT1 binding; an analogous profile is seen for 15b , which, however, is a partial agonist.. Introduction of chlorine or methoxyl groups into ring 4 gives compounds, that are weakly binding, with a preference for MT2. Substitution of oxygen for carbon at position 5 gives the indolo[1,2- c ]benzoxazines 33 , 36a and b , that bind strongly to the human receptors, 33 , 36b are potent agonists at the melatonin receptors, but do not discriminate between hMT1 and hMT2.
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