RESUMEN
Cigarette smoking is the leading cause of preventable disease and death in the United States, with more persons dying from nicotine addiction than any other preventable cause of death. Even though smoking cessation incurs multiple health benefits, the abstinence rate remains low with current medications. Here we show that the AMP-activated protein kinase (AMPK) pathway in the hippocampus is activated following chronic nicotine use, an effect that is rapidly reversed by nicotine withdrawal. Increasing pAMPK levels and, consequently, downstream AMPK signaling pharmacologically attenuate anxiety-like behavior following nicotine withdrawal. We show that metformin, a known AMPK activator in the periphery, reduces withdrawal symptoms through a mechanism dependent on the presence of the AMPKα subunits within the hippocampus. This study provides evidence of a direct effect of AMPK modulation on nicotine withdrawal symptoms and suggests central AMPK activation as a therapeutic target for smoking cessation.
Asunto(s)
Proteínas Quinasas Activadas por AMP/efectos de los fármacos , Trastornos de Ansiedad/tratamiento farmacológico , Hipocampo/efectos de los fármacos , Metformina/uso terapéutico , Proteínas del Tejido Nervioso/efectos de los fármacos , Nicotina/efectos adversos , Síndrome de Abstinencia a Sustancias/tratamiento farmacológico , Proteínas Quinasas Activadas por AMP/genética , Proteínas Quinasas Activadas por AMP/fisiología , Aminoimidazol Carboxamida/análogos & derivados , Aminoimidazol Carboxamida/farmacología , Animales , Trastornos de Ansiedad/inducido químicamente , Trastornos de Ansiedad/enzimología , Evaluación Preclínica de Medicamentos , Activación Enzimática/efectos de los fármacos , Conducta Alimentaria/efectos de los fármacos , Técnicas de Silenciamiento del Gen , Hipocampo/enzimología , Masculino , Metformina/farmacología , Ratones , Ratones de la Cepa 129 , Ratones Endogámicos C57BL , Proteínas del Tejido Nervioso/fisiología , Ribonucleótidos/farmacología , Transducción de Señal/efectos de los fármacos , Síndrome de Abstinencia a Sustancias/enzimología , Tabaquismo/enzimología , Tabaquismo/psicologíaRESUMEN
The human cytochrome P450 2A6 (CYP2A6) and monoamine oxidases (MAO-A and MAO-B), catalyzing nicotine and dopamine metabolisms, respectively, are two therapeutic targets of nicotine dependence. Vernonia cinerea, a medicinal plant commonly used for treatment of diseases such as asthma and bronchitis, has been shown reducing tobacco dependence effect among tobacco users. In the present study, we found eight active compounds isolated from V. cinerea that comprise inhibitory activity toward CYP2A6 and MAO-A and MAO-B enzymes using activity-guided assays, with coumarin as substrate of CYP2A6 and kynuramine of MAOs. These compounds were three flavones (apigenin, chrysoeriol, luteolin), one flavonol (quercetin), and four hirsutinolide-type sesquiterpene lactones (8α-(2-methylacryloyloxy)-hirsutinolide-13-O-acetate, 8α-(4-hydroxymethacryloyloxy)-hirsutinolide-13-O-acetate, 8α-tigloyloxyhirsutinolide-13-O-acetate, and 8α-(4-hydroxytigloyloxy)-hirsutinolide-13-O-acetate). Modes and kinetics of inhibition against the three enzymes were determined. Flavonoids possessed strong inhibitory effect on CYP2A6 in reversible mode, while inhibition by hirsutinolides was mechanism-based (NADPH-, concentration-, and time-dependence) and irreversible. Inhibition by hirsutinolides could not be reversed by dialysis and by addition of trapping agents or potassium ferricyanide. Flavonoids inhibited MAOs with variable degrees and were more prominent in inhibition toward MAO-A than hirsutinolides, while two of hirsutinolides inhibited MAO-B approximately comparable to two flavonoids. These results could have implications in combination of drug therapy for smoking cessation.