RESUMO
Major depression brings about a heavy socio-economic burden worldwide due to its high prevalence and the low efficacy of antidepressant drugs, mostly inhibiting the serotonin transporter (SERT). As a result, ~80% of patients show recurrent or chronic depression, resulting in a poor quality of life and increased suicide risk. RNA interference (RNAi) strategies have been preliminarily used to evoke antidepressant-like responses in experimental animals. However, the main limitation for the medical use of RNAi is the extreme difficulty to deliver oligonucleotides to selected neurons/systems in the mammalian brain. Here we show that the intranasal administration of a sertraline-conjugated small interfering RNA (C-SERT-siRNA) silenced SERT expression/function and evoked fast antidepressant-like responses in mice. After crossing the permeable olfactory epithelium, the sertraline-conjugated-siRNA was internalized and transported to serotonin cell bodies by deep Rab-7-associated endomembrane vesicles. Seven-day C-SERT-siRNA evoked similar or more marked responses than 28-day fluoxetine treatment. Hence, C-SERT-siRNA (i) downregulated 5-HT1A-autoreceptors and facilitated forebrain serotonin neurotransmission, (ii) accelerated the proliferation of neuronal precursors and (iii) increased hippocampal complexity and plasticity. Further, short-term C-SERT-siRNA reversed depressive-like behaviors in corticosterone-treated mice. The present results show the feasibility of evoking antidepressant-like responses by selectively targeting neuronal populations with appropriate siRNA strategies, opening a way for further translational studies.
Assuntos
Antidepressivos/administração & dosagem , Depressão/tratamento farmacológico , RNA Interferente Pequeno/administração & dosagem , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Sertralina/administração & dosagem , Administração Intranasal , Animais , Proteínas de Arabidopsis/metabolismo , Encéfalo/citologia , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Corticosterona/sangue , DNA Antissenso/farmacologia , Depressão/patologia , Modelos Animais de Doenças , Endocitose/efeitos dos fármacos , Comportamento Exploratório/efeitos dos fármacos , Fluoxetina/administração & dosagem , Regulação da Expressão Gênica/efeitos dos fármacos , Transferases Intramoleculares/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Fosfopiruvato Hidratase/metabolismo , Serotonina/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Fatores de TempoRESUMO
Current antidepressants, which inhibit the serotonin transporter (SERT), display limited efficacy and slow onset of action. Here, we show that partial reduction of SERT expression by small interference RNA (SERT-siRNA) decreased immobility in the tail suspension test, displaying an antidepressant potential. Moreover, short-term SERT-siRNA treatment modified mouse brain variables considered to be key markers of antidepressant action: reduced expression and function of 5-HT(1A)-autoreceptors, elevated extracellular serotonin in forebrain and increased neurogenesis and expression of plasticity-related genes (BDNF, VEGF, Arc) in hippocampus. Remarkably, these effects occurred much earlier and were of greater magnitude than those evoked by long-term fluoxetine treatment. These findings highlight the critical role of SERT in serotonergic function and show that the reduction of SERT expression regulates serotonergic neurotransmission more potently than pharmacological blockade of SERT. The use of siRNA-targeting genes in serotonin neurons (SERT, 5-HT(1A)-autoreceptor) may be a novel therapeutic strategy to develop fast-acting antidepressants.
Assuntos
Antidepressivos/farmacologia , Fluoxetina/farmacologia , Hipocampo/efeitos dos fármacos , Neurogênese/genética , RNA Interferente Pequeno/genética , Receptor 5-HT1A de Serotonina/genética , Proteínas da Membrana Plasmática de Transporte de Serotonina/genética , Análise de Variância , Animais , Antidepressivos/metabolismo , Autorreceptores/genética , Autorreceptores/metabolismo , Fator Neurotrófico Derivado do Encéfalo/efeitos dos fármacos , Fator Neurotrófico Derivado do Encéfalo/genética , Proteínas do Citoesqueleto/efeitos dos fármacos , Proteínas do Citoesqueleto/genética , Fluoxetina/metabolismo , Expressão Gênica , Hipocampo/citologia , Hipocampo/metabolismo , Imuno-Histoquímica , Hibridização In Situ , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Proteínas do Tecido Nervoso/efeitos dos fármacos , Proteínas do Tecido Nervoso/genética , Neurogênese/fisiologia , Interferência de RNA/fisiologia , RNA Interferente Pequeno/metabolismo , RNA Interferente Pequeno/farmacologia , Receptor 5-HT1A de Serotonina/efeitos dos fármacos , Receptor 5-HT1A de Serotonina/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/farmacologia , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/genética , Fator A de Crescimento do Endotélio Vascular/efeitos dos fármacos , Fator A de Crescimento do Endotélio Vascular/genéticaAssuntos
Antidepressivos/uso terapêutico , Autorreceptores/antagonistas & inibidores , RNA Interferente Pequeno/uso terapêutico , Receptor 5-HT1A de Serotonina/genética , Animais , Antidepressivos/administração & dosagem , Camundongos , RNA Mensageiro/efeitos dos fármacos , RNA Interferente Pequeno/administração & dosagem , Sertralina/administração & dosagemRESUMO
Depression is a major health problem worldwide. Most prescribed anti-depressants, the selective serotonin reuptake inhibitors (SSRI) show limited efficacy and delayed onset of action, partly due to the activation of somatodendritic 5-HT(1A)-autoreceptors by the excess extracellular serotonin (5-HT) produced by SSRI in the raphe nuclei. Likewise, 5-HT(1A) receptor (5-HT(1A)R) gene polymorphisms leading to high 5-HT(1A)-autoreceptor expression increase depression susceptibility and decrease treatment response. In this study, we report on a new treatment strategy based on the administration of small-interfering RNA (siRNA) to acutely suppress 5-HT(1A)-autoreceptor-mediated negative feedback mechanisms. We developed a conjugated siRNA (C-1A-siRNA) by covalently binding siRNA targeting 5-HT(1A) receptor mRNA with the SSRI sertraline in order to concentrate it in serotonin axons, rich in serotonin transporter (SERT) sites. The intracerebroventricular (i.c.v.) infusion of C-1A-siRNA to mice resulted in its selective accumulation in serotonin neurons. This evoked marked anti-depressant-like effects in the forced swim and tail suspension tests, but did not affect anxiety-like behaviors in the elevated plus-maze. In parallel, C-1A-siRNA administration markedly decreased 5-HT(1A)-autoreceptor expression and suppressed 8-OH-DPAT-induced hypothermia (a pre-synaptic 5-HT(1A)R effect in mice) without affecting post-synaptic 5-HT(1A)R expression in hippocampus and prefrontal cortex. Moreover, i.c.v. C-1A-siRNA infusion augmented the increase in extracellular serotonin evoked by fluoxetine in prefrontal cortex to the level seen in 5-HT(1A)R knockout mice. Interestingly, intranasal C-1A-siRNA administration produced the same effects, thus opening the way to the therapeutic use of C-1A-siRNA. Hence, C-1A-siRNA represents a new approach to treat mood disorders as monotherapy or in combination with SSRI.