RESUMO
The Zika virus (ZIKV) epidemic declared in Brazil between 2015 and 2016 was associated with an increased prevalence of severe congenital malformations, including microcephaly. The distribution of microcephaly cases was not uniform across the country, with a disproportionately higher incidence in the Northeast region (NE). Our previous work demonstrated that saxitoxin (STX), a toxin present in the drinking water reservoirs of the NE, exacerbated the damaging effects of ZIKV on the developing brain. We hypothesized that the impact of STX might vary among different neural cell types. While ZIKV infection caused severe damages on astrocytes and neural stem cells (NSCs), the addition of STX did not exacerbate these effects. We observed that neurons subjected to STX exposure were more prone to apoptosis and displayed higher ZIKV infection rate. These findings suggest that STX exacerbates the harmful effects of ZIKV on neurons, thereby providing a plausible explanation for the heightened severity of ZIKV-induced congenital malformations observed in Brazil's NE. This study highlights the importance of understanding the interactive effects of environmental toxins and infectious pathogens on neural development, with potential implications for public health policies.
Assuntos
Astrócitos , Células-Tronco Neurais , Neurônios , Saxitoxina , Infecção por Zika virus , Zika virus , Células-Tronco Neurais/virologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Humanos , Zika virus/fisiologia , Astrócitos/virologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Neurônios/virologia , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Infecção por Zika virus/virologia , Infecção por Zika virus/patologia , Saxitoxina/toxicidade , Apoptose/efeitos dos fármacos , Microcefalia/virologia , Morte Celular/efeitos dos fármacos , Brasil , Células CultivadasRESUMO
Crude extracts and three isolated alkaloids from Erythrina mulungu plants have shown anxiolytic effects in different animal models. We investigated whether these alkaloids could affect nicotinic acetylcholine receptors and if they are selective for different central nervous system (CNS) subtypes. Screening experiments were performed using a single concentration of the alkaloid co-applied with acetylcholine in whole cell patch-clamp recordings in three different cell models: (i) PC12 cells natively expressing α3* nicotinic acetylcholine receptors; (ii) cultured hippocampal neurons natively expressing α7* nicotinic acetylcholine receptors; and (iii) HEK 293 cells heterologoulsy expressing α4ß2 nicotinic acetylcholine receptors. For all three receptors, the percent inhibition of acetylcholine-activated currents by (+)-11á-hydroxyerysotrine was the lowest, whereas (+)-erythravine and (+)-11á-hydroxyerythravine inhibited the currents to a greater extent. For the latter two substances, we obtained concentration-response curves with a pre-application protocol for the α7* and α4ß2 nicotinic acetylcholine receptors. The IC50 obtained with (+)-erythravine and (+)-11á-hydroxyerythravine were 6 µM and 5 µM for the α7* receptors, and 13 nM and 4 nM for the α4ß2 receptors, respectively. Our data suggest that these Erythrina alkaloids may exert their behavioral effects through inhibition of CNS nicotinic acetylcholine receptors, particularly the α4ß2 subtype.
Assuntos
Alcaloides/farmacologia , Erythrina/química , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Antagonistas Nicotínicos/farmacologia , Receptores Nicotínicos/metabolismo , Alcaloides/química , Animais , Linhagem Celular , Relação Dose-Resposta a Droga , Feminino , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Humanos , Antagonistas Nicotínicos/química , Gravidez , RatosRESUMO
Assembly of synapses requires proper coordination between pre- and postsynaptic elements. Identification of cellular and molecular events in synapse formation and maintenance is a key step to understand human perception, learning, memory, and cognition. A key role for astrocytes in synapse formation and function has been proposed. Here, we show that transforming growth factor ß (TGF-ß) signaling is a novel synaptogenic pathway for cortical neurons induced by murine and human astrocytes. By combining gain and loss of function approaches, we show that TGF-ß1 induces the formation of functional synapses in mice. Further, TGF-ß1-induced synaptogenesis involves neuronal activity and secretion of the co-agonist of the NMDA receptor, D-serine. Manipulation of D-serine signaling, by either genetic or pharmacological inhibition, prevented the TGF-ß1 synaptogenic effect. Our data show a novel molecular mechanism that might impact synaptic function and emphasize the evolutionary aspect of the synaptogenic property of astrocytes, thus shedding light on new potential therapeutic targets for synaptic deficit diseases.
Assuntos
Astrócitos/citologia , Córtex Cerebral/metabolismo , Neurônios/metabolismo , Serina/química , Sinapses/metabolismo , Fator de Crescimento Transformador beta/metabolismo , Animais , Células Cultivadas , Cognição , Meios de Cultivo Condicionados/farmacologia , Eletrofisiologia , Humanos , Camundongos , Modelos Biológicos , Técnicas de Patch-Clamp , Transdução de Sinais , TransfecçãoRESUMO
Schizophrenia has been defined as a neurodevelopmental disease that causes changes in the process of thoughts, perceptions, and emotions, usually leading to a mental deterioration and affective blunting. Studies have shown altered cell respiration and oxidative stress response in schizophrenia; however, most of the knowledge has been acquired from postmortem brain analyses or from nonneural cells. Here we describe that neural cells, derived from induced pluripotent stem cells generated from skin fibroblasts of a schizophrenic patient, presented a twofold increase in extramitochondrial oxygen consumption as well as elevated levels of reactive oxygen species (ROS), when compared to controls. This difference in ROS levels was reverted by the mood stabilizer valproic acid. Our model shows evidence that metabolic changes occurring during neurogenesis are associated with schizophrenia, contributing to a better understanding of the development of the disease and highlighting potential targets for treatment and drug screening.
Assuntos
Células-Tronco Pluripotentes Induzidas/citologia , Espécies Reativas de Oxigênio/metabolismo , Células Cultivadas , Feminino , Fibroblastos/citologia , Expressão Gênica/efeitos dos fármacos , Humanos , Pessoa de Meia-Idade , Células-Tronco Neurais/citologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Neurogênese , Esquizofrenia/metabolismo , Esquizofrenia/patologia , Pele/citologia , Ácido Valproico/farmacologiaRESUMO
Hippocampal alpha7(*) nicotinic acetylcholine receptors modulate the release of GABA and glutamate. The control of functional receptor pools by cell firing or synaptic activity could therefore allow for a local adjustment of the sensitivity to cholinergic input upon changes in neuronal activity. We first investigated whether tonic depolarization or cell firing affected the function of alpha7(*). The amplitude of alpha7(*)-gated whole-cell currents in cultured rat hippocampal neurons exposed to high-extracellular K(+) (40 mM KCl) for 24 to 48 h increased 1.3 to 5.5 times. The proportion of alpha7(*)-responsive neurons (99%), the potency of acetylcholine, and the sensitivity to nicotinic antagonists were all unaffected. In contrast, block of spontaneous cell firing with tetrodotoxin for 24 h led to a 37% reduction in mean current amplitude. Reduced alpha7(*) responses were seen after a 24-h blockade of N-type calcium channels but not of L-type calcium channels, N-methyl-d-aspartate (NMDA), or non-NMDA receptor channels, protein kinase C, or calcium-calmodulin kinases II and IV. The N-type or L-type calcium channel antagonists omega-conotoxin GVIA and nifedipine did not prevent the current-potentiating effect of KCl. The GABA(A) antagonist picrotoxin led to a 44% reduction of the currents, despite increasing action potential firing, and also reversed the potentiating effect of KCl. Treatment with GABA, midazolam, or a GABA uptake blocker led to increased currents. These data indicate that alpha7(*)-gated currents in hippocampal neurons are regulated by GABAergic activity and suggest that depolarization-induced GABA release may underlie the effect of increased extracellular KCl.