RESUMO
Our previous reports showed that 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) has antiproliferative actions in endothelial cells stably expressing viral G protein-coupled receptor (vGPCR) associated with the pathogenesis of Kaposi's sarcoma. It has been reported that COX-2 enzyme, involved in the tumorigenesis of many types of cancers, is induced by vGPCR. Therefore, we investigated whether COX-2 down-regulation is part of the growth inhibitory effects of 1α,25(OH)2D3. Proliferation was measured in presence of COX-2 inhibitor Celecoxib (10-20 µM) revealing a decreased in vGPCR cell number, displaying typically apoptotic features in a dose dependent manner similarly to 1α,25(OH)2D3. In addition, the reduced cell viability observed with 20 µM Celecoxib was enhanced in presence of 1α,25(OH)2D3. Remarkably, although COX-2 mRNA and protein levels were up-regulated after 1α,25(OH)2D3 treatment, COX-2 enzymatic activity was reduced in a VDR-dependent manner. Furthermore, an interaction between COX-2 and VDR was revealed through GST pull-down and computational analysis. Additionally, high-affinity prostanoid receptors (EP3 and EP4) were found down-regulated by 1α,25(OH)2D3. Altogether, these results suggest a down-regulation of COX-2 activity and of prostanoid receptors as part of the antineoplastic mechanism of 1α,25(OH)2D3 in endothelial cells transformed by vGPCR.
RESUMO
Iron overload is a hallmark of many neurodegenerative processes such as Alzheimer's, Parkinson's, and Huntington's diseases. Unbound iron accumulated as a consequence of brain aging is highly reactive with water and oxygen and produces reactive oxygen species (ROS) or free radicals. ROS are toxic compounds able to damage cell membranes, DNA, and mitochondria. Which are the mechanisms involved in neuronal iron homeostasis and in neuronal response to iron-induced oxidative stress constitutes a cutting-edge topic in metalloneurobiology. Increasing our knowledge about the underlying mechanisms that operate in iron accumulation and their consequences would shed light on the comprehension of the molecular events that participate in the pathophysiology of the abovementioned neurodegenerative diseases. In this review, current evidences about iron accumulation in the brain, the signaling mechanisms triggered by metal overload, as well as the interaction between amyloid ß (Aß) and iron, will be summarized.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Ferro/metabolismo , Humanos , Doenças Neurodegenerativas/metabolismo , Doenças Neurodegenerativas/fisiopatologia , Estresse OxidativoRESUMO
We have previously demonstrated that oligomeric amyloid ß peptide (oAß) together with iron overload generates synaptic injury and activation of several signaling cascades. In this work, we characterized hippocampal neuronal response to oAß. HT22 neurons exposed to 500 nM oAß showed neither increased lipid peroxidation nor altered mitochondrial function. In addition, biophysical studies showed that oAß did not perturb the lipid order of the membrane. Interestingly, although no neuronal damage could be demonstrated, oAß was found to trigger bifurcated phosphoinositide-dependent signaling in the neuron, on one hand, the phosphorylation of insulin receptor, the phosphatidylinositol 3-kinase (PI3K)-dependent activation of Akt, its translocation to the nucleus and the concomitant phosphorylation, inactivation, and nuclear exclusion of the transcription factor Forkhead Box O3a (FoxO3a), and on the other, phosphoinositide-phospholipase C (PI-PLC)-dependent extracellular signal-regulated kinase 1/2 (ERK1/2) activation. Pharmacological manipulation of the signaling cascades was used in order to better characterize the role of oAß-activated signals, and mitochondrial function was determined as a measure of neuronal viability. The inhibition of PI3K, PI-PLC, and general phosphoinositide metabolism impaired neuronal mitochondrial function. Furthermore, increased oAß-induced cell death was observed in the presence of phosphoinositide metabolism inhibition. Our results allow us to conclude that oAß triggers the activation of phosphoinositide-dependent signaling, which results in the subsequent activation of neuroprotective mechanisms that could be involved in the determination of neuronal fate.
Assuntos
Peptídeos beta-Amiloides/toxicidade , Fosfatidilinositóis/metabolismo , Multimerização Proteica , Transdução de Sinais , Animais , Linhagem Celular , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Proteína Forkhead Box O3/metabolismo , Humanos , Camundongos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Neurônios/patologia , Fosfatidilinositol 3-Quinases/metabolismo , Agregados Proteicos , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos , Receptor de Insulina/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Metal-imbalance has been reported as a contributor factor for the degeneration of dopaminergic neurons in Parkinson Disease (PD). Specifically, iron (Fe)-overload and copper (Cu) mis-compartmentalization have been reported to be involved in the injury of dopaminergic neurons in this pathology. The aim of this work was to characterize the mechanisms of membrane repair by studying lipid acylation and deacylation reactions and their role in oxidative injury in N27 dopaminergic neurons exposed to Fe-overload and Cu-supplementation. N27 dopaminergic neurons incubated with Fe (1 mM) for 24 hs displayed increased levels of reactive oxygen species (ROS), lipid peroxidation and elevated plasma membrane permeability. Cu-supplemented neurons (10, 50 µM) showed no evidence of oxidative stress markers. A different lipid acylation profile was observed in N27 neurons pre-labeled with [3H] arachidonic acid (AA) or [3H] oleic acid (OA). In Fe-exposed neurons, AA uptake was increased in triacylglycerols (TAG) whereas its incorporation into the phospholipid (PL) fraction was diminished. TAG content was 40% higher in Fe-exposed neurons than in controls. This increase was accompanied by the appearance of Nile red positive lipid bodies. Contrariwise, OA incorporation increased in the PL fractions and showed no changes in TAG. Lipid acylation profile in Cu-supplemented neurons showed AA accumulation into phosphatidylserine and no changes in TAG. The inhibition of deacylation/acylation reactions prompted an increase in oxidative stress markers and mitochondrial dysfunction in Fe-overloaded neurons. These findings provide evidence about the participation of lipid acylation mechanisms against Fe-induced oxidative injury and postulate that dopaminergic neurons cleverly preserve AA in TAG in response to oxidative stress.
Assuntos
Acilação/fisiologia , Neurônios Dopaminérgicos/fisiologia , Sobrecarga de Ferro/fisiopatologia , Metabolismo dos Lipídeos/fisiologia , Estresse Oxidativo/fisiologia , Animais , Ácido Araquidônico/química , Linhagem Celular , Cobre/metabolismo , Ferro/metabolismo , Peroxidação de Lipídeos/fisiologia , Potencial da Membrana Mitocondrial/fisiologia , Mitocôndrias/fisiologia , Ácido Oleico/química , Oxirredução , Doença de Parkinson/patologia , Fosfolipídeos/metabolismo , Ratos , Espécies Reativas de Oxigênio/metabolismo , Triglicerídeos/metabolismoRESUMO
We have previously demonstrated that Lactobacillus reuteri CRL1098 soluble factors were able to reduce TNF-α production by human peripheral blood mononuclear cells. The aims of this study were to determine whether L. reuteri CRL1098 soluble factors were able to modulate in vitro the inflammatory response triggered by LPS in murine macrophages, to gain insight into the molecular mechanisms involved in the immunoregulatory effect, and to evaluate in vivo its capacity to exert anti-inflammatory actions in acute lung injury induced by LPS in mice. In vitro assays demonstrated that L. reuteri CRL1098 soluble factors significantly reduced the production of pro-inflammatory mediators (NO, COX-2, and Hsp70) and pro-inflammatory cytokines (TNF-α, and IL-6) caused by the stimulation of macrophages with LPS. NF-kB and PI3K inhibition by L. reuteri CRL1098 soluble factors contributed to these inhibitory effects. Inhibition of PI3K/Akt pathway and the diminished expression of CD14 could be involved in the immunoregulatory effect. In addition, our in vivo data proved that the LPS-induced secretion of the pro-inflammatory cytokines, inflammatory cells recruitment to the airways and inflammatory lung tissue damage were reduced in L. reuteri CRL1098 soluble factors treated mice, providing a new way to reduce excessive pulmonary inflammation.
Assuntos
Lesão Pulmonar Aguda/tratamento farmacológico , Anti-Inflamatórios/farmacologia , Extratos Celulares/farmacologia , Limosilactobacillus reuteri/química , Macrófagos/efeitos dos fármacos , Lesão Pulmonar Aguda/etiologia , Animais , Anti-Inflamatórios/uso terapêutico , Extratos Celulares/uso terapêutico , Linhagem Celular , Ciclo-Oxigenase 2/genética , Ciclo-Oxigenase 2/metabolismo , Citocinas/sangue , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico HSP70/metabolismo , Lipopolissacarídeos/toxicidade , Macrófagos/metabolismo , Camundongos , Óxido Nítrico/metabolismoRESUMO
The PI3K/Akt pathway is a key component in synaptic plasticity and neuronal survival. The aim of this work was to investigate the participation of the PI3K/Akt pathway and its outcome on different molecular targets such as glycogen synthase kinase 3ß (GSK3ß) and Forkhead box-O (FoxO) transcription factors during mild oxidative stress triggered by iron overload. The exposure of mouse hippocampal neurons (HT22) to different concentrations of Fe(2+) (25-200 µm) for 24 h led us to define a mild oxidative injury status (50 µm Fe(2+)) in which cell morphology showed changes typical of neuronal damage with increased lipid peroxidation and cellular oxidant levels but no alteration of cellular viability. There was a simultaneous increase in both Akt and GSK3ß phosphorylation. Levels of phospho-FoxO3a (inactive form) increased in the cytosolic fraction of cells treated with iron in a PI3K-dependent manner. Moreover, PI3K and Akt translocated to the nucleus in response to oxidative stress. Iron-overloaded cells harboring a constitutively active form of Akt showed decreased oxidants levels. Indeed, GSH synthesis under oxidative stress conditions was regulated by activated Akt. Our results show that activation of the PI3K/Akt pathway during iron-induced neurotoxicity regulates multiple targets such as GSK3ß, FoxO transcriptional activity, and glutathione metabolism, thus modulating the neuronal response to oxidative stress.
Assuntos
Hipocampo/enzimologia , Ferro/farmacologia , Neurônios/enzimologia , Estresse Oxidativo/efeitos dos fármacos , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/efeitos dos fármacos , Transporte Ativo do Núcleo Celular/efeitos dos fármacos , Transporte Ativo do Núcleo Celular/genética , Animais , Linhagem Celular , Núcleo Celular/enzimologia , Núcleo Celular/patologia , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/genética , Proteína Forkhead Box O3 , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Quinase 3 da Glicogênio Sintase/genética , Quinase 3 da Glicogênio Sintase/metabolismo , Glicogênio Sintase Quinase 3 beta , Hipocampo/metabolismo , Humanos , Ferro/metabolismo , Peroxidação de Lipídeos/efeitos dos fármacos , Peroxidação de Lipídeos/genética , Camundongos , Neurônios/patologia , Estresse Oxidativo/genética , Fosfatidilinositol 3-Quinases/genética , Fosforilação/efeitos dos fármacos , Fosforilação/genética , Proteínas Proto-Oncogênicas c-akt/genética , Transdução de Sinais/genéticaRESUMO
Insulin receptor substrate-4 (IRS-4) has a limited tissue expression and its modulation by tyr-phosphorylation is still controversial. We evaluated the participation of IRS-4 in the cross-talk between Angiotensin II (Ang II) and Insulin (Ins) receptors in HepG2 cells. Ins (10(-7)M) induced tyr-phosphorylation of IRS-4 (maximal at 5 min), an effect potentiated by Ang II AT(1) receptors. Phosphatydilinositol-3 kinase (PI3-K) inhibitors Wortmanin or LY294002 reduced Ang II effect on tyr-phosphorylation of IRS-4 to a level comparable to that of Ins alone. Physical association between IRS-4 substrate and PI3-K was demonstrated by co-immunoprecipitation. Recruitment of PI3-K by IRS-4 was induced by Ins (10(-7)M, 5 min) not by Ang II (10(-7)M) and this was inhibited by Wortmanin and LY294002. Ang II did not modify either the association or activation of PI3-K in immunocomplexes. The present data provide novel evidence of IRS-4 phosphorylation mediated by Ins, an effect modulated by Ang II. We report also Ins-induced PI3-K activation mediated by IRS-4. Our findings suggest a role for IRS-4 as a docking protein in the Ins signaling pathway that involves PI3-K association and activation. The present data suggest a possible participation of IRS-4 in cell proliferation Ins-induced.
Assuntos
Angiotensina II/farmacologia , Ativação Enzimática/efeitos dos fármacos , Proteínas Substratos do Receptor de Insulina/metabolismo , Insulina/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Angiotensina II/metabolismo , Western Blotting , Eletroforese em Gel de Poliacrilamida , Células Hep G2 , Humanos , Imunoprecipitação , Fosforilação/efeitos dos fármacos , Ligação ProteicaRESUMO
In this work we study the state of phosphoinositide-3-kinase/Akt/glycogen synthase kinase 3 beta (PI3K/Akt/GSK3beta) signaling during oxidative injury triggered by free iron using cerebral cortex synaptic endings isolated from adult (4-month-old) and aged (28-month-old) rats. Synaptosomes were exposed to FeSO4 (50 microM) for different periods of time and synaptosomal viability and the state of the PI3K/Akt/GSK3beta pathway were evaluated in adult and aged animals. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction and lactate dehydrogenase leakage were significantly affected in both age groups. However, aged animals showed a greater susceptibility to oxidative stress. In adults, Akt was activated after a brief exposure time (5 min), whereas in aged animals activation occurred after 5 and 30 min of incubation with the metal ion. GSK3beta phosphorylation showed the same activation pattern as that observed for Akt. Both Akt and GSK3beta phosphorylation were dependent on PI3K activation. Extracellular signal-regulated kinases 1 and 2 (ERK1/2) activation was temporally coincident with Akt activation and was PI3K dependent in adults, whereas ERK1/2 activation in aged rats was higher than that observed in adults and showed no dependence on PI3K activity. We demonstrate here that synaptic endings from adult and aged animals subjected to iron-induced neurotoxicity show a differential profile in the activation of PI3K/Akt/GSK3beta. Our results strongly suggest that the increased susceptibility of aged animals to oxidative injury provokes a differential modulation of key signaling pathways involved in synaptic plasticity and neuronal survival.