RESUMO
The incidence of neurodegenerative disease like Parkinson's disease and Alzheimer's disease (AD) increases dramatically with age; only a small percentage is directly related to familial forms. The etiology of the most abundant, sporadic forms is complex and multifactorial, involving both genetic and environmental factors. Several environmental pollutants have been associated with neurodegenerative disorders. The present article focuses on results obtained in experimental neurotoxicology studies that indicate a potential pathogenic role of lead and mercury in the development of neurodegenerative diseases. Both heavy metals have been shown to interfere with a multitude of intracellular targets, thereby contributing to several pathogenic processes typical of neurodegenerative disorders, including mitochondrial dysfunction, oxidative stress, deregulation of protein turnover, and brain inflammation. Exposure to heavy metals early in development can precondition the brain for developing a neurodegenerative disease later in life. Alternatively, heavy metals can exert their adverse effects through acute neurotoxicity or through slow accumulation during prolonged periods of life. The pro-oxidant effects of heavy metals can exacerbate the age-related increase in oxidative stress that is related to the decline of the antioxidant defense systems. Brain inflammatory reactions also generate oxidative stress. Chronic inflammation can contribute to the formation of the senile plaques that are typical for AD. In accord with this view, nonsteroidal anti-inflammatory drugs and antioxidants suppress early pathogenic processes leading to Alzheimer's disease, thus decreasing the risk of developing the disease. The effects of lead and mercury were also tested in aggregating brain-cell cultures of fetal rat telencephalon, a three-dimensional brain-cell culture system. The continuous application for 10 to 50 days of non-cytotoxic concentrations of heavy metals resulted in their accumulation in brain cells and the occurrence of delayed toxic effects. When applied at non-toxic concentrations, methylmercury, the most common environmental form of mercury, becomes neurotoxic under pro-oxidant conditions. Furthermore, lead and mercury induce glial cell reactivity, a hallmark of brain inflammation. Both mercury and lead increase the expression of the amyloid precursor protein; mercury also stimulates the formation of insoluble beta-amyloid, which plays a crucial role in the pathogenesis of AD and causes oxidative stress and neurotoxicity in vitro. Taken together, a considerable body of evidence suggests that the heavy metals lead and mercury contribute to the etiology of neurodegenerative diseases and emphasizes the importance of taking preventive measures in this regard.
Assuntos
Exposição Ambiental/efeitos adversos , Chumbo/toxicidade , Mercúrio/toxicidade , Doenças Neurodegenerativas/induzido quimicamente , Encéfalo/patologia , Humanos , Doenças Neurodegenerativas/patologiaRESUMO
BACKGROUND: Transplantation of endothelial progenitor cells (EPCs) improves neovascularization after ischemia, but patients with coronary artery disease (CAD) or diabetes mellitus show a reduced number of EPCs and impaired functional activity. Therefore, we investigated the effects of risk factors, such as glucose and TNF-alpha, on the number of EPCs in vitro to elucidate the underlying mechanisms. METHODS AND RESULTS: EPCs of patients or healthy subjects were isolated from peripheral blood. Incubation with glucose or TNF-alpha dose-dependently reduced the number of EPCs (79.9+/-1.3% and 74.3+/-8.1% of control; P<0.05, respectively). This reduction was not caused by apoptosis. TNF-alpha and glucose induced a dose- and time-dependent activation of the p38 MAP kinase, the downstream kinase mitogen- and stress-activated kinase 1, and the transcription factor cAMP-responsive element-binding protein (CREB), in EPCs. Moreover, EPCs from CAD patients had significantly higher basal p38-phosphorylation levels (1.83+/-0.2-fold increase; P<0.05) compared with healthy subjects. The inhibition of the p38-kinase by SB203580 or infection with a dominant negative p38 kinase adenovirus significantly increased basal number of EPCs (136.7+/-6.3% and 142.9+/-18% versus control, respectively). Likewise, ex vivo cultivation of EPCs from patients with CAD with SB203580 significantly increased the number of EPCs and partially reversed the impaired capacity for neovascularization of EPCs in vivo (relative blood flow: 0.40+/-0.03 versus 0.64+/-0.08, P<0.05). The increased numbers of EPCs by SB203580 were associated with an augmentation of EPC proliferation and a reduction of cells expressing the monocytic marker proteins CD14 and CD64, suggesting that p38 regulates proliferation and differentiation events. CONCLUSIONS: These results demonstrate that p38 MAP kinase plays a pivotal role in the signal transduction pathways regulating the number of EPCs ex vivo. SB203580 can prevent the negative effects of TNF-alpha and glucose on the number of EPCs and may be useful to improve the number of EPCs for potential cell therapy.
Assuntos
Doença das Coronárias/enzimologia , Células-Tronco/enzimologia , Proteínas Quinases p38 Ativadas por Mitógeno/fisiologia , Fator 2 Ativador da Transcrição , Adulto , Idoso , Sequência de Aminoácidos , Animais , Apoptose , Contagem de Células , Diferenciação Celular , Divisão Celular/efeitos dos fármacos , Células Cultivadas/citologia , Células Cultivadas/efeitos dos fármacos , Comorbidade , Doença das Coronárias/epidemiologia , Doença das Coronárias/patologia , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Feminino , Glucose/farmacologia , Membro Posterior/irrigação sanguínea , Humanos , Imidazóis/farmacologia , Isquemia/enzimologia , Isquemia/patologia , Isoquinolinas/farmacologia , Masculino , Camundongos , Camundongos Nus , Pessoa de Meia-Idade , Dados de Sequência Molecular , Fosforilação/efeitos dos fármacos , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Piridinas/farmacologia , Proteínas Quinases S6 Ribossômicas 90-kDa/metabolismo , Fatores de Risco , Transdução de Sinais/efeitos dos fármacos , Transplante de Células-Tronco , Células-Tronco/citologia , Sulfonamidas/farmacologia , Fatores de Transcrição/metabolismo , Transplante Heterólogo , Fator de Necrose Tumoral alfa/farmacologia , Proteínas Quinases p38 Ativadas por Mitógeno/antagonistas & inibidoresRESUMO
Interleukin (IL)-18 is the interferon-gamma-inducing factor and has potent proinflammatory activities. IL-18 has been recently implicated in atherosclerotic plaque instability and myocardial ischemia-reperfusion injury. However, it is unknown whether IL-18 expression is increased in human myocardium or if it has any role in heart failure. We analyzed the expression of IL-18, its receptor IL-18Ralpha, and its endogenous inhibitor, IL-18 binding protein (IL-18BP) in myocardial tissue from patients with end-stage heart failure (ischemic or dilated cardiomyopathy) and controls by use of quantitative real-time reverse transcriptase polymerase chain reaction, Western blot or immunohistochemical techniques. Plasma levels of IL-18 were also determined in 48 patients with heart failure. IL-18 mRNA and protein levels were up-regulated in the myocardium of patients with ischemic cardiomyopathy. Both ischemic and dilated myocardium showed increased IL-18Ralpha levels, suggesting potential biological effects. In addition, mRNA levels of IL-18 BP were down-regulated in the failing myocardium. Finally, plasma IL-18 levels were significantly elevated in patients with heart failure and were higher in those who died at follow-up than in survivors. The results suggest a potential role for the immunoinflammatory IL-18 signaling pathway in the pathophysiology of heart failure and identify novel therapeutic targets for future testing.
Assuntos
Baixo Débito Cardíaco/imunologia , Interleucina-18/metabolismo , Baixo Débito Cardíaco/genética , Baixo Débito Cardíaco/mortalidade , Glicoproteínas/biossíntese , Glicoproteínas/genética , Humanos , Imuno-Histoquímica , Peptídeos e Proteínas de Sinalização Intercelular , Interleucina-18/biossíntese , Interleucina-18/genética , Subunidade alfa de Receptor de Interleucina-18 , Isquemia Miocárdica/genética , Isquemia Miocárdica/imunologia , Miocárdio/química , Miocárdio/imunologia , RNA Mensageiro/biossíntese , Receptores de Interleucina/análise , Receptores de Interleucina/biossíntese , Receptores de Interleucina/genética , Receptores de Interleucina-18 , Regulação para CimaRESUMO
Identification of factors that may stimulate ischemia-induced neovascularization without increasing atherosclerotic plaque progression is of major therapeutic importance. We hypothesized that interleukin-18 binding protein (IL-18BP), a major antiinflammatory protein with plaque-stabilizing activities, may affect the neovascularization in mice ischemic hindlimb. Ischemia was produced by artery femoral occlusion in mice that were subjected to in vivo intramuscular electrotransfer of either an empty plasmid or a murine IL-18BP plasmid. Angiographic score, capillary density (CD31 staining), and laser Doppler perfusion data at day 28 showed significant improvement in ischemic/nonischemic leg ratio by respectively 1.6-, 1.4-, and 1.5-fold in IL-18BP-treated mice compared with controls (P<0.01). This was associated with a significant 2-fold increase in both vascular endothelial growth factor (VEGF) and phospho-Akt protein content in the ischemic hindlimb of IL-18BP-treated mice (P<0.05). Similar results were obtained in IL-18-deficient mice. Because bone marrow-derived endothelial progenitor cells (BM-EPCs) are involved in postnatal vasculogenesis, EPCs were isolated and cultivated from bone marrow mononuclear cells. IL-18BP treatment led to a significant 1.8-fold increase in the percentage of BM-EPCs characterized as cells positive for both AcLDL-Dil and von Willebrand factor (P<0.001). In conclusion, IL-18BP stimulates ischemia-induced neovascularization in association with an activation of VEGF/Akt signaling and an increase in BM-EPCs mobilization and differentiation. Our findings strongly suggest a major antiangiogenic role of endogenous IL-18 in postischemic injury.
Assuntos
Glicoproteínas/fisiologia , Membro Posterior/irrigação sanguínea , Interleucina-18/fisiologia , Isquemia/fisiopatologia , Neovascularização Patológica/fisiopatologia , Proteínas Serina-Treonina Quinases , Angiografia , Animais , Células da Medula Óssea/citologia , Células da Medula Óssea/efeitos dos fármacos , Células da Medula Óssea/fisiologia , Linhagem Celular , Fatores de Crescimento Endotelial/metabolismo , Fatores de Crescimento Endotelial/farmacologia , Endotélio Vascular/citologia , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/metabolismo , Glicoproteínas/genética , Membro Posterior/metabolismo , Humanos , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular/farmacologia , Interleucina-18/genética , Interleucina-18/farmacologia , Fluxometria por Laser-Doppler , Linfocinas/metabolismo , Linfocinas/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Neovascularização Fisiológica/efeitos dos fármacos , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase Tipo II , Óxido Nítrico Sintase Tipo III , Fosforilação , Plasmídeos/administração & dosagem , Plasmídeos/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas c-akt , Fator A de Crescimento do Endotélio Vascular , Fatores de Crescimento do Endotélio VascularRESUMO
The pathogenesis of Crohn's disease (CD) remains under intense investigation. Increasing evidence suggests a role for mature IL-18 in the induction of proinflammatory cytokines and Th1 polarization in CD lesions. The aim of this study was to investigate the contribution of the IL-18-neutralizing (a and c) and non-neutralizing (b and d) isoforms of IL-18-binding protein (IL-18BP) during active CD. Intestinal endothelial cells and macrophages were the major source of IL-18BP within the submucosa, and this IL-18BP production was also found to be relevant to other types of endothelial cells (HUVEC) and macrophages (peripheral monocytes). IL-18BP messenger transcript and protein were significantly increased in surgically resected specimens from active CD compared with control patients, correlating with an up-regulation of IL-18. Analysis of the expression of the four IL-18BP isoforms as well as being free or bound to IL-18 was reported and revealed that unbound IL-18BP isoforms a and c and inactive isoform d were present in specimens from active CD and control patients while isoform b was not detected. IL-18/IL-18BP complex was also detected. Interestingly, although most was complexed, free mature IL-18 could still be detected in active CD specimens even in the presence of the IL-18BP isoform a/c. These results demonstrate that the appropriate neutralizing isoforms are present in the intestinal tissue of patients with active CD and highlights the complexity of IL-18/IL-18BP biology.