Enhancement of nitric oxide production by methylecgonidine in cultured neonatal rat cardiomyocytes

Abstract

1 In the present experiments, we investigated the eects of methylecgonidine (MEG) on nitric oxide (NO) production in cultured neonatal rat cardiomyocytes. Incubation of cultured cardiomyocytes with carbachol or MEG for 48 h signi®cantly enhanced NO production. No release was increased from 1.48+0.13 mM (mg protein) 71 for control to 5.73+0.19 mM (mg protein) 71 for 1 mM carbachol treated cells (P50.001). In addition, incubation with 1 mM MEG enhanced NO production to 5.55+0.28 mM (mg protein) 71. The eects of MEG on NO production were concentrationdependent. The muscarinic antagonist atropine prevented the enhancement of NO production induced by carbachol or MEG. Compared to MEG-induced NO production, cocaine was much less potent. 2 The enhancement of NO production by carbachol or MEG was even greater in cultured cardiomyocytes transfected with the M 2 cDNA. After 48-h incubation with 1 mM carbachol or 1 mM MEG, NO production was increased by 6.5 and 6.7 fold, respectively, in cardiomyocytes overexpressing M 2 receptors. Coincubation with atropine or N G -nitro-L-arginine methyl ester abolished the enhancement of NO production. In contrast, NO production enhanced by carbachol or MEG in M 1 -or M 3 -transfected cardiomyocytes was similar to the level in non-transfected cells. 3 Western blot analysis showed that the protein levels of M 1 , M 2 , and M 3 were signi®cantly increased in cardiomyocytes transfected with the receptor cDNAs, but MEG had no eect on the expressions. It is interesting that both carbachol and MEG caused a signi®cant increase in constitutive endothelial NO synthase (eNOS) only in M 2 -transfected cardiomyocytes, not in nontransfected, M 1 -or M 3 -transfected cells. Again, atropine blocked the MEG-produced induction of eNOS. 4 Our data demonstrate that MEG signi®cantly enhanced NO production in cultured cardiomyocytes and that the enhancement of NO production may result from MEG stimulation of muscarinic M 2 receptors.

Pharmacokinetics and Pharmacodynamics of Methylecgonidine, a Crack Cocaine Pyrolyzate

“…This work does support the hypothesis that methylecgonidine may play a role in cardiovascular toxicity associated with crack use (Yang et al, 2002). Our results confirm that methylecgonidine does produce hypotension, an effect consistent with methylecgonidine stimulation of nitric-oxide synthase as shown in cell preparations (Yang et al, 2001(Yang et al, , 2002.…”

“…This contrasted with methacholine, which produced marked bradycardia. The lack of methylecgonidine-induced bradycardia seems to contrast with reports of in vitro M 2 agonist properties in myocardium , myocytes Yang et al, 2002), and human embryonic lung cells expressing M 2 receptors (Yang et al, 2001). Data from these reports relate to muscarinic signaling pathways involved in decreasing contractility and vasodilation.…”

“…These responses to methylecgonidine mimic muscarinic agonism (Brown and Taylor, 1996). Several in vitro studies have demonstrated that methylecgonidine acts as M 2 muscarinic agonist Woolf et al, 1997;Yang et al, 2001Yang et al, , 2002. Therefore, we wanted to test the hypothesis that the pharmacodynamics of methylecgonidine are consistent with muscarinic agonism in awake sheep.…”

Ações da metilecgonidina sobre a síntese de melatonina na glândula pineal de ratos.

“…Jacob et al (1990) sugeriram que ela poderia estar agindo como agonista colinérgico, isso provavelmente devido a sua estrutura ser semelhante à arecolina, um agonista de receptores muscarinícos (XIE et al, 2004) e à anatoxina-a, uma cianotoxina que atua como bloqueador muscular (WOOD et al, 2007). Vários estudos in vitro mostraram que AEME age como agonista muscarínico do receptor M 2 (HUANG et al, 1997;WOOLF et al, 1997;YANG et al,2001YANG et al, , 2002.…”

“…Em cultura de cardiomiócitos de ratos neonatais a AEME aumentou a produção de NO, a qual foi revertida com a adição de 1µM atropina (YANG et al, 2002). Isso sugere que essa produção de NO provavelmente se deva também à estimulação de receptores muscarínicos.…”