title: The melatonin analog 5-MCA-NAT increases endogenous dopamine levels by binding NRH:quinone reductase enzyme in the developing chick retina.
abstract: NRH:quinone reductase (QR2) is present in the retinas of embryonic and post-hatched (PH) chicks. 5-Methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT) is a QR2 ligand that increases cAMP levels in developing retinas, but it does not affect cAMP levels in CHO-QR2 cells. The dopamine quinone reductase activity of QR2 retrieves dopamine, which increases cAMP levels in developing retinas. The objective of the present study was to investigate whether 5-MCA-NAT increases endogenous dopamine levels in retinas from chick embryos and post-hatched chicks. Endogenous dopamine was measured by enzyme-linked immunosorbent assay (ELISA). 5-MCA-NAT increased retinal endogenous dopamine levels at all developmental stages studied and in PH chicks (-logEC50=11.62±0.34 M). This effect was inhibited by non-selective antagonists of receptors and melatonin binding sites N-acetyl-2-benzyltryptamine (luzindole, 5 μM), but it was not inhibited by the Mel1b melatonin receptor antagonist 4-phenyl-2-propionamidotetralin (4-P-PDOT, 10 nM). The QR2 cosubstrate, N-methyl-dihydronicotinamide (NMH) (-logEC50=6.74±0.26 M), increased endogenous dopamine levels in controls and in retinas stimulated with 5-MCA-NAT (3 nM). The QR2 inhibitor benzo[e]pyrene inhibited endogenous dopamine levels in both control (-logIC50=7.4±0.28 M) and NMH-stimulated (at 100 nM and 1 μM benzo[e]pyrene concentrations) retinas. Theoretical studies using Molegro Virtual Docking software corroborated these experimental results. We conclude that 5-MCA-NAT increases the level of endogenous dopamine via QR2. We suggest that this enzyme triggers double reduction of the dopamine quinone, recovering dopamine in retinal development.
authors.affiliation: Lab. de Bioquímica do Desenvolvimento do Sistema Nervoso, Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa No. 1, CEP: 66075-110 Belém, PA, Brazil. Electronic address: lsampaio@ufpa.br.
authors.forename: Lucia de Fatima Sobral
authors.initials: Lde F
authors.lastname: Sampaio
authors.affiliation: Lab. de Bioquímica do Desenvolvimento do Sistema Nervoso, Instituto de Ciências Biológicas, Universidade Federal do Pará, Rua Augusto Corrêa No. 1, CEP: 66075-110 Belém, PA, Brazil.
authors.forename: Felipe Pantoja
authors.initials: FP
authors.lastname: Mesquita
authors.affiliation: Lab. de Planejamento e Desenvolvimento de Fármacos, Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, Rua Augusto Corrêa No. 1, CEP: 66075-110 Belém, PA, Brazil.
authors.forename: Paulo Robson Monteiro
authors.initials: PR
authors.lastname: de Sousa
authors.affiliation: Lab. de Planejamento e Desenvolvimento de Fármacos, Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, Rua Augusto Corrêa No. 1, CEP: 66075-110 Belém, PA, Brazil.
authors.forename: Jerônimo Lameira
authors.initials: JL
authors.lastname: Silva
authors.affiliation: Lab. de Planejamento e Desenvolvimento de Fármacos, Instituto de Ciências Exatas e Naturais, Universidade Federal do Pará, Rua Augusto Corrêa No. 1, CEP: 66075-110 Belém, PA, Brazil.
authors.forename: Claudio Nahum
authors.initials: CN
authors.lastname: Alves
mesh_terms: D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D002642:Chick Embryo; D002645:Chickens; D004298:Dopamine / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004797:Enzyme-Linked Immunosorbent Assay; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D016660:NAD(P)H Dehydrogenase (Quinone) / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D044123:Receptor, Melatonin, MT2 / Q000037:antagonists & inhibitors*; D012160:Retina / Q000187:drug effects / Q000196:embryology / Q000201:enzymology / Q000254:growth & development*; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D014363:Tryptamines / Q000494:pharmacology*
chemical_list: C114459:4-phenyl-2-propionamidotetraline; C413586:5-methoxycarbonylamino-N-acetyltryptamine; D044123:Receptor, Melatonin, MT2; D013764:Tetrahydronaphthalenes; D014363:Tryptamines; C057154:luzindole; D016660:NAD(P)H Dehydrogenase (Quinone); D004298:Dopamine
keywords: 5-MCA-NAT; Benzo[e]pyrene; Dopamine; Melatonin receptors; NRH:quinone reductase; Retina