RESUMO
OBJECTIVE: This study aimed to investigate the connection between the mutation of the Sip1 transcription factor and impaired Ca2+-signaling, which reflects changes in neurotransmission in the cerebral cortex in vitro. METHODS: We used mixed neuroglial cortical cell cultures derived from Sip1 mutant mice. The cells were loaded with a fluorescent ratiometric calcium-sensitive probe Fura-2 AM and epileptiform activity was modeled by excluding magnesium ions from the external media or adding a GABA(A) receptor antagonist, bicuculline. Intracellular calcium dynamics were recorded using fluorescence microscopy. To identify the level of gene expression, the Real-Time PCR method was used. RESULTS: It was found that cortical neurons isolated from homozygous (Sip1fl/fl) mice with the Sip1 mutation demonstrate suppressed Ca2+ signals in models of epileptiform activity in vitro. Wild-type cortical neurons are characterized by synchronous high-frequency and high-amplitude Ca2+ oscillations occurring in all neurons of the network in response to Mg2+-free medium and bicuculline. But cortical Sip1fl/fl neurons only single Ca2+ pulses or attenuated Ca2+ oscillations are recorded and only in single neurons, while most of the cell network does not respond to these stimuli. This signal deficiency of Sip1fl/fl neurons correlates with a suppressed expression level of the genes encoding the subunits of NMDA, AMPA, and KA receptors; protein kinases PKA, JNK, CaMKII; and also the transcription factor Hif1α. These negative effects were partially abolished when Sip1fl/fl neurons are grown in media with anti-inflammatory cytokine IL-10. IL-10 increases the expression of the above-mentioned genes but not to the level of expression in wild-type. At the same time, the amplitudes of Ca2+ signals increase in response to the selective agonists of NMDA, AMPA and KA receptors, and the proportion of neurons responding with Ca2+ oscillations to a Mg2+-free medium and bicuculline increases. CONCLUSION: IL-10 restores neurotransmission in neuronal networks with the Sip1 mutation by regulating the expression of genes encoding signaling proteins.
Assuntos
Cálcio , Interleucina-10/metabolismo , Animais , Bicuculina/farmacologia , Cálcio/metabolismo , Células Cultivadas , Córtex Cerebral/fisiologia , Camundongos , N-Metilaspartato , Receptores de Glutamato/metabolismo , Fatores de Transcrição/metabolismo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol PropiônicoRESUMO
The aim of the study was to investigate the mechanisms of Ca2+ oscillation generation upon activation of connexin-43 and regulation of the lipolysis/lipogenesis balance in white adipocytes through vesicular ATP release. With fluorescence microscopy it was revealed that a decrease in the concentration of extracellular calcium ([Ca2+]ex) results in two types of Ca2+ responses in white adipocytes: Ca2+ oscillations and transient Ca2+ signals. It was found that activation of the connexin half-channels is involved in the generation of Ca2+ oscillations, since the blockers of the connexin hemichannels-carbenoxolone, octanol, proadifen and Gap26-as well as Cx43 gene knockdown led to complete suppression of these signals. The activation of Cx43 in response to the reduction of [Ca2+]ex was confirmed by TIRF microscopy. It was shown that in response to the activation of Cx43, ATP-containing vesicles were released from the adipocytes. This process was suppressed by knockdown of the Cx43 gene and by bafilomycin A1, an inhibitor of vacuolar ATPase. At the level of intracellular signaling, the generation of Ca2+ oscillations in white adipocytes in response to a decrease in [Ca2+]ex occurred due to the mobilization of the Ca2+ ions from the thapsigargin-sensitive Ca2+ pool of IP3R as a result of activation of the purinergic P2Y1 receptors and phosphoinositide signaling pathway. After activation of Cx43 and generation of the Ca2+ oscillations, changes in the expression levels of key genes and their encoding proteins involved in the regulation of lipolysis were observed in white adipocytes. This effect was accompanied by a decrease in the number of adipocytes containing lipid droplets, while inhibition or knockdown of Cx43 led to inhibition of lipolysis and accumulation of lipid droplets. In this study, we investigated the mechanism of Ca2+ oscillation generation in white adipocytes in response to a decrease in the concentration of Ca2+ ions in the external environment and established an interplay between periodic Ca2+ modes and the regulation of the lipolysis/lipogenesis balance.
Assuntos
Adipócitos Brancos/metabolismo , Cálcio/metabolismo , Conexina 43/fisiologia , Lipogênese , Lipólise , Adipócitos Brancos/citologia , Animais , Sinalização do Cálcio , Células Cultivadas , CamundongosRESUMO
Transcription factors Satb1 and Satb2 are involved in the processes of cortex development and maturation of neurons. Alterations in the expression of their target genes can lead to neurodegenerative processes. Molecular and cellular mechanisms of regulation of neurotransmission by these transcription factors remain poorly understood. In this study, we have shown that transcription factors Satb1 and Satb2 participate in the regulation of genes encoding the NMDA-, AMPA-, and KA- receptor subunits and the inhibitory GABA(A) receptor. Deletion of gene for either Satb1 or Satb2 homologous factors induces the expression of genes encoding the NMDA receptor subunits, thereby leading to higher amplitudes of Ca2+-signals in neurons derived from the Satb1-deficient (Satb1fl/+ * NexCre/+) and Satb1-null mice (Satb1fl/fl * NexCre/+) in response to the selective agonist reducing the EC50 for the NMDA receptor. Simultaneously, there is an increase in the expression of the Gria2 gene, encoding the AMPA receptor subunit, thus decreasing the Ca2+-signals of neurons in response to the treatment with a selective agonist (5-Fluorowillardiine (FW)). The Satb1 deletion increases the sensitivity of the KA receptor to the agonist (domoic acid), in the cortical neurons of the Satb1-deficient mice but decreases it in the Satb1-null mice. At the same time, the Satb2 deletion decreases Ca2+-signals and the sensitivity of the KA receptor to the agonist in neurons from the Satb1-null and the Satb1-deficient mice. The Satb1 deletion affects the development of the inhibitory system of neurotransmission resulting in the suppression of the neuron maturation process and switching the GABAergic responses from excitatory to inhibitory, while the Satb2 deletion has a similar effect only in the Satb1-null mice. We show that the Satb1 and Satb2 transcription factors are involved in the regulation of the transmission of excitatory signals and inhibition of the neuronal network in the cortical cell culture.
Assuntos
Sinalização do Cálcio , Proteínas de Ligação à Região de Interação com a Matriz/fisiologia , Neuroglia , Receptores de Glutamato/metabolismo , Transmissão Sináptica , Fatores de Transcrição/fisiologia , Animais , Células Cultivadas , Feminino , Masculino , Camundongos , Camundongos Knockout , Neuroglia/citologia , Neuroglia/metabolismo , Receptores de GABA/metabolismoRESUMO
Various types of cells demonstrate ubiquitous rhythmicity registered as simple and complex Ca2+-oscillations, spikes, waves, and triggering phenomena mediated by G-protein and tyrosine kinase coupled receptors. Phospholipase C/IP3-receptors (PLC/IP3R) and endothelial NO-synthase/Ryanodine receptors (NOS/RyR)-dependent Ca2+ signaling systems, organized as multivariate positive feedback generators (PLC-G and NOS-G), underlie this rhythmicity. Loss of rhythmicity at obesity may indicate deregulation of these signaling systems. To issue the impact of cell size, receptors' interplay, and obesity on the regulation of PLC-G and NOS-G, we applied fluorescent microscopy, immunochemical staining, and inhibitory analysis using cultured adipocytes of epididumal white adipose tissue of mice. Acetylcholine, norepinephrine, atrial natriuretic peptide, bradykinin, cholecystokinin, angiotensin II, and insulin evoked complex [Ca2+]i responses in adipocytes, implicating NOS-G or PLC-G. At low sub-threshold concentrations, acetylcholine and norepinephrine or acetylcholine and peptide hormones (in paired combinations) recruited NOS-G, based on G proteins subunits interplay and signaling amplification. Rhythmicity was cell size- dependent and disappeared in hypertrophied cells filled with lipids. Contrary to control cells, adipocytes of obese hyperglycemic and hypertensive mice, growing on glucose, did not accumulate lipids and demonstrated hormonal resistance being non responsive to any hormone applied. Preincubation of preadipocytes with palmitoyl-L-carnitine (100 nM) provided accumulation of lipids, increased expression and clustering of IP3R and RyR proteins, and partially restored hormonal sensitivity and rhythmicity (5-15% vs. 30-80% in control cells), while adipocytes of diabetic mice were not responsive at all. Here, we presented a detailed kinetic model of NOS-G and discussed its control. Collectively, we may suggest that universal mechanisms underlie loss of rhythmicity, Ca2+-signaling systems deregulation, and development of general hormonal resistance to obesity.
Assuntos
Adipócitos Brancos/metabolismo , Sinalização do Cálcio , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 2/metabolismo , Obesidade/metabolismo , Adipócitos Brancos/citologia , Adipócitos Brancos/efeitos dos fármacos , Animais , Sinalização do Cálcio/efeitos dos fármacos , Tamanho Celular , Células Cultivadas , Diabetes Mellitus Tipo 2/etiologia , Dieta Hiperlipídica/efeitos adversos , Epididimo , Proteínas de Ligação ao GTP/metabolismo , Masculino , Camundongos , Óxido Nítrico Sintase Tipo III/metabolismo , Obesidade/induzido quimicamente , Palmitoilcarnitina/farmacologia , Periodicidade , Cultura Primária de Células , Fosfolipases Tipo C/metabolismoRESUMO
The Sip1 mutation plays the main role in pathogenesis of the Mowat-Wilson syndrome, which is characterized by the pronounced epileptic symptoms. Cortical neurons of homozygous mice with Sip1 mutation are resistant to AMPA receptor activators. Disturbances of the excitatory signaling components are also observed on such a phenomenon of neuroplasticity as hypoxic preconditioning. In this work, the mechanisms of loss of the AMPA receptor's ability to precondition by episodes of short-term hypoxia were investigated on cortical neurons derived from the Sip1 homozygous mice. The preconditioning effect was estimated by the level of suppression of the AMPA receptors activity with hypoxia episodes. Using fluorescence microscopy, we have shown that cortical neurons from the Sip1fl/fl mice are characterized by the absence of hypoxic preconditioning effect, whereas the amplitude of Ca2+-responses to the application of the AMPA receptor agonist, 5-Fluorowillardiine, in neurons from the Sip1 mice brainstem is suppressed by brief episodes of hypoxia. The mechanism responsible for this process is hypoxia-induced desensitization of the AMPA receptors, which is absent in the cortex neurons possessing the Sip1 mutation. However, the appearance of preconditioning in these neurons can be induced by phosphoinositide-3-kinase activation with a selective activator or an anti-inflammatory cytokine interleukin-10.
Assuntos
Córtex Cerebral/fisiopatologia , Hipóxia/fisiopatologia , Interleucina-10/fisiologia , Mutação , Proteínas do Tecido Nervoso/fisiologia , Neurônios/fisiologia , Receptores de AMPA/fisiologia , Alanina/análogos & derivados , Alanina/farmacologia , Animais , Cálcio/metabolismo , Sinalização do Cálcio , Ativação Enzimática , Agonistas de Aminoácidos Excitatórios/farmacologia , Camundongos , Microscopia de Fluorescência , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Pirimidinas/farmacologia , Receptores de AMPA/agonistasRESUMO
Smad-interacting protein-1 (Sip1) [Zinc finger homeobox (Zfhx1b), Zeb2] is a transcription factor implicated in the genesis of Mowat-Wilson syndrome (MWS) in humans. MWS is a rare genetic autosomal dominant disease caused by a mutation in the Sip1 gene (aka Zeb2 or Zfhx1b) mapped to 2q22.3 locus. MWS affects 1 in every 50-100 newborns worldwide. It is characterized by mental retardation, small stature, typical facial abnormalities as well as disturbances in the development of the cardio-vascular and renal systems as well as some other organs. Sip1 mutations cause abnormal neurogenesis in the brain during development as well as susceptibility to epileptic seizures. In the current study we investigated the role of the Sip1 gene in the activity of NMDA-, AMPA- and KA- receptors. We showed that a particular Sip1 mutation in the mouse causes changes in the activity of both NMDA- and AMPA- receptors in the neocortical neurons in vitro. We demonstrate that neocortical neurons that have only one copy of Sip1 (heterozygous, Sip1fI/wt), are more sensitive to both NMDA- and AMPA- receptors agonists as compared to wild type neurons (Sip1wt/wt). This is reflected in higher amplitudes of agonist induced Ca2+ signals as well as a lower half maximal effective concentration (ÐC50). In contrast, neurons from homozygous Sip1 mice (Sip1fI/fI), demonstrate higher resistance to these respective receptor agonists. This is reflected in lower amplitudes of Ca2+-responses and so a higher concentration of receptor activators is required for activation.
Assuntos
Sinalização do Cálcio/fisiologia , Córtex Cerebral/fisiologia , Proteínas do Tecido Nervoso/genética , Neurônios/fisiologia , Receptores de AMPA/metabolismo , Receptores de Ácido Caínico/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Potenciais de Ação/fisiologia , Animais , Variações do Número de Cópias de DNA/genética , Camundongos , Camundongos Transgênicos , MutaçãoRESUMO
In the present work we compared the protective effect of anti-inflammatory cytokine IL-10 with the action of a PI3-kinase selective activator 740 Y-P, selective agonists of alpha-2 adrenoreceptor, guanfacine and UK-14,304, and compounds having antioxidant effect: recombinant human peroxiredoxin 6 and B27, in hippocampal cell culture during OGD (ischemia-like conditions). It has been shown that the response of cells to OGD in the control includes two phases. The first phase was accompanied by an increase in the frequency of spontaneous synchronous Ca2+-oscillations (SSCO) in neurons and Ca2+-pulse in astrocytes. Spontaneous Ca2+ events in astrocytes during ischemia in control experiments disappeared. The second phase started after a few minutes of OGD and looked like a sharp/avalanche, global synchronic (within 20 s) increase in [Ca2+]i in many cells. Within 1 h after OGD, a mass death of cells, primarily astrocytes, was observed. To study the protective action of the compounds, cells were incubated in the presence of the neuroprotective agents for 10-40 min or 24 h before ischemia. All the neuroprotective agents delayed a global [Ca2+]i increase during OGD or completely inhibited this process and increased cell survival.
Assuntos
Antioxidantes/metabolismo , Hipocampo/citologia , Interleucina-10/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Receptores Adrenérgicos alfa 2/metabolismo , Agonistas Adrenérgicos/metabolismo , Animais , Astrócitos/citologia , Encéfalo/metabolismo , Cálcio/metabolismo , Morte Celular , Sobrevivência Celular , Células Cultivadas , Guanfacina/química , Isquemia/metabolismo , Oscilometria , RatosRESUMO
Angiotensin II (Ang II) is an important mammalian neurohormone involved in reninangiotensin system. Ang II is produced both constitutively and locally by RAS systems, including white fat adipocytes. The influence of Ang II on adipocytes is complex, affecting different systems of signal transduction from early Са(2+) responses to cell proliferation and differentiation, triglyceride accumulation, expression of adipokine-encoding genes and adipokine secretion. It is known that white fat adipocytes express all RAS components and Ang II receptors (ÐТ1 and ÐТ2). The current work was carried out with the primary white adipocytes culture, and Са(2+) signaling pathways activated by Ang II were investigated using fluorescent microscopy. Са(2+)-oscillations and transient responses of differentiated adipocytes to Ang II were registered in cells with both small and multiple lipid inclusions. Using inhibitory analysis and selective antagonists, we now show that Ang II initiates periodic Са(2+)-oscillations and transient responses by activating ÐТ1 and ÐТ2 receptors and involving branched signaling cascades: 1) Ang II â Gq â PLC â IP3 â IP3Rs â Ca(2+) 2) Gßγ â PI3Kγ â PKB 3) PKB â eNOS â NO â PKG 4) CD38 â cADPR â RyRs â Ca(2+) In these cascades, AT1 receptors play the leading role. The results of the present work open a perspective of using Ang II for correction of signal resistance of adipocytes often observed during obesity and type 2 diabetes.
Assuntos
Adipócitos Brancos/metabolismo , Angiotensina II/metabolismo , Sinalização do Cálcio , Adipócitos Brancos/citologia , Adipócitos Brancos/efeitos dos fármacos , Angiotensina II/farmacologia , Animais , Cálcio/metabolismo , Diferenciação Celular , Gotículas Lipídicas/ultraestrutura , Camundongos , Cultura Primária de Células , Receptor Tipo 1 de Angiotensina/metabolismo , Receptor Tipo 2 de Angiotensina/metabolismoRESUMO
It is suggested that anti-inflammatory cytokine interleukin-10 (IL-10) mediates the delayed protective effects through activation of Jak-Stat3, PI3K-Akt and NF-κB signaling pathways. However, our previous experiments have demonstrated that IL-10 is capable to exert the rapid neuroprotective action through modulation of hypoxia-induced intracellular Ca(2+) ([Ca(2+)]i) response. The first purpose of the present study was to evaluate the neuroprotective effects of IL-10 using three models of the ischemic insults in rats: permanent middle cerebral artery occlusion, ischemia in acute hippocampal slices in vitro and ischemia in cultured hippocampal cells in vitro. The second purpose of the study was to elucidate a role of [Ca(2+)]i changes in the mechanisms underlying IL-10 elicited protection of neurons and astrocytes from ischemia-induced death in cultures of primary hippocampal cells. The data presented here shown that anti-inflammatory cytokine IL-10 is capable to induce a resistance of the brain cells to ischemia-evoked damages in in vivo and in vitro models of the ischemic insults in rats. This protective effect in cultured hippocampal cells is developed rapidly after application of IL-10 and strongly associated with the IL-10 elicited elimination of [Ca(2+)]i response to ischemia. Thus, our results provide the evidence that anti-inflammatory cytokine IL-10, in addition to an activation of the canonical signaling pathways, is capable to exert the rapid neuroprotective effects through transcription-independent modulation of ischemia-induced intracellular Ca(2+) responses in the brain cells.
Assuntos
Isquemia Encefálica/patologia , Cálcio/metabolismo , Interleucina-10/metabolismo , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Astrócitos/patologia , Infarto Encefálico/etiologia , Infarto Encefálico/metabolismo , Infarto Encefálico/patologia , Isquemia Encefálica/etiologia , Isquemia Encefálica/metabolismo , Morte Celular , Hipóxia Celular , Células Cultivadas , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Hipocampo/patologia , Infarto da Artéria Cerebral Média/complicações , Infarto da Artéria Cerebral Média/metabolismo , Infarto da Artéria Cerebral Média/patologia , Interleucina-10/farmacologia , Masculino , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Cultura Primária de Células , Ratos Sprague-Dawley , Ratos WistarRESUMO
We have previously developed a rat hippocampal neuronal cell model for the registration of the preconditioning effect and posthypoxic hyperexcitability (Turovskaya et al., 2011). Repeated episodes of short-term hypoxia are reported to suppress the amplitude of Ca(2+) response to NMDA in majority of neurons, reflecting the effect of preconditioning in the culture. In addition, exposure to hypoxia causes posthypoxic hyperexcitability: this is characterized by the onset of spontaneous synchronous Ca(2+) transients in a population of neurons in a neural network during the period of reoxygenation after each hypoxic episode. The nature of this phenomenon is unknown, although it has been observed that there always exists a minority of neurons in which there is no effect of hypoxic preconditioning. In this small population of neurons, the amplitude of Ca(2+) response to NMDA is not suppressed, but rather increases after each episode of hypoxia. Here we report the type of these neurons and their role in the generation of posthypoxic hyperexcitability. We compared the effect of short-term hypoxia on the amplitude of the Ca(2+) response to NMDA and the Ca(2+) transient generation in two populations of neurons - inhibitory GABAergic and excitatory glutamatergic. We have demonstrated that the neurons in which the preconditioning effect was not observed are GABAergic. Moreover at the instant moment of the posthypoxic synchronous Ca(2+)-transient generation (during reoxygenation) there is a global increase of [Ca(2+)]i and subsequent apoptosis in some GABAergic neurons. Anti-inflammatory cytokine interleukin-10 prevents the development of posthypoxic hyperexcitability, inhibiting the spontaneous synchronous Ca(2+) transients. At the same time, interleukin-10 protects GABAergic neurons from death, by restoring the effect of hypoxic preconditioning in them. Activation of one of the signaling pathways initiated by interleukin-10 appears to be necessary for the development of hypoxic preconditioning in GABAergic neurons. Overall our results indicate that short-term episodes of hypoxia can damage GABAergic neurons and weaken the inhibitory action of GABAergic neurons in a neural network. Activation of PI3K-dependent survival signaling pathways in neurons of this type is a possible strategy to protect these cells against hypoxia.