RESUMO
Acetylcholine (ACh), the neurotransmitter of the cholinergic system, regulates inflammation in several diseases including pulmonary diseases. ACh is also involved in a non-neuronal mechanism that modulates the innate immune response. Because inflammation and release of pro-inflammatory cytokines are involved in pulmonary emphysema, we hypothesized that vesicular acetylcholine transport protein (VAChT) deficiency, which leads to reduction in ACh release, can modulate lung inflammation in an experimental model of emphysema. Mice with genetical reduced expression of VAChT (VAChT KDHOM 70%) and wild-type mice (WT) received nasal instillation of 50 uL of porcine pancreatic elastase (PPE) or saline on day 0. Twenty-eight days after, animals were evaluated. Elastase instilled VAChT KDHOM mice presented an increase in macrophages, lymphocytes, and neutrophils in bronchoalveolar lavage fluid and MAC2-positive macrophages in lung tissue and peribronchovascular area that was comparable to that observed in WT mice. Conversely, elastase instilled VAChT KDHOM mice showed significantly larger number of NF-κB-positive cells and isoprostane staining in the peribronchovascular area when compared to elastase-instilled WT-mice. Moreover, elastase-instilled VAChT-deficient mice showed increased MCP-1 levels in the lungs. Other cytokines, extracellular matrix remodeling, alveolar enlargement, and lung function were not worse in elastase-instilled VAChT deficiency than in elastase-instilled WT-controls. These data suggest that decreased VAChT expression may contribute to the pathogenesis of emphysema, at least in part, through NF-κB activation, MCP-1, and oxidative stress pathways. This study highlights novel pathways involved in lung inflammation that may contribute to the development of chronic obstrutive lung disease (COPD) in cholinergic deficient individuals such as Alzheimer's disease patients.
Assuntos
Acetilcolina/deficiência , Enfisema/imunologia , Pneumonia/etiologia , Acetilcolina/metabolismo , Animais , Líquido da Lavagem Broncoalveolar/citologia , Citocinas/metabolismo , Modelos Animais de Doenças , Enfisema/metabolismo , Inflamação/patologia , Pulmão/patologia , Macrófagos/metabolismo , Masculino , Camundongos , NF-kappa B/metabolismo , Neutrófilos/metabolismo , Elastase Pancreática/efeitos adversos , Elastase Pancreática/farmacologia , Pneumonia/fisiopatologia , Enfisema Pulmonar/metabolismo , Transdução de Sinais , Proteínas Vesiculares de Transporte de Acetilcolina/deficiência , Proteínas Vesiculares de Transporte de Acetilcolina/genética , Proteínas Vesiculares de Transporte de Acetilcolina/metabolismoRESUMO
The cholinergic anti-inflammatory pathway has been shown to regulate lung inflammation and cytokine release in acute models of inflammation, mainly via α7 nicotinic receptor (α7nAChR). We aimed to evaluate the role of endogenous acetylcholine in chronic allergic airway inflammation in mice and the effects of therapeutic nAChR stimulation in this model. We first evaluated lung inflammation and remodeling on knock-down mice with 65% of vesicular acetylcholine transport (VAChT) gene reduction (KDVAChT) and wild-type(WT) controls that were subcutaneously sensitized and then inhaled with ovalbumin(OVA). We then evaluated the effects of PNU-282987(0.5-to-2mg/kg),(α7nAChR agonist) treatment in BALB/c male mice intraperitoneal sensitized and then inhaled with OVA. Another OVA-sensitized-group was treated with PNU-282987 plus Methyllycaconitine (MLA,1 mg/kg, α7nAChR antagonist) to confirm that the effects observed by PNU were due to α7nAChR. We showed that KDVAChT-OVA mice exhibit exacerbated airway inflammation when compared to WT-OVA mice. In BALB/c, PNU-282987 treatment reduced the number of eosinophils in the blood, BAL fluid, and around airways, and also decreased pulmonary levels of IL-4,IL-13,IL-17, and IgE in the serum of OVA-exposed mice. MLA pre-treatment abolished all the effects of PNU-282987. Additionally, we showed that PNU-282987 inhibited STAT3-phosphorylation and reduced SOCS3 expression in the lung. These data indicate that endogenous cholinergic tone is important to control allergic airway inflammation in a murine model. Moreover, α7nAChR is involved in the control of eosinophilic inflammation and airway remodeling, possibly via inhibition of STAT3/SOCS3 pathways. Together these data suggest that cholinergic anti-inflammatory system mainly α7nAChR should be further considered as a therapeutic target in asthma.
Assuntos
Asma/imunologia , Proteínas Vesiculares de Transporte de Acetilcolina/deficiência , Receptor Nicotínico de Acetilcolina alfa7/imunologia , Remodelação das Vias Aéreas , Alérgenos , Animais , Asma/etiologia , Benzamidas/farmacologia , Compostos Bicíclicos com Pontes/farmacologia , Líquido da Lavagem Broncoalveolar/citologia , Líquido da Lavagem Broncoalveolar/imunologia , Doença Crônica , Citocinas/imunologia , Modelos Animais de Doenças , Inflamação/etiologia , Inflamação/imunologia , Contagem de Leucócitos , Pulmão/efeitos dos fármacos , Pulmão/imunologia , Pulmão/patologia , Masculino , Camundongos Endogâmicos BALB C , Camundongos Knockout , Ovalbumina , Fator de Transcrição STAT3/antagonistas & inibidores , Proteína 3 Supressora da Sinalização de Citocinas/antagonistas & inibidores , Proteínas Vesiculares de Transporte de Acetilcolina/genética , Receptor Nicotínico de Acetilcolina alfa7/agonistasRESUMO
Endogenous acetylcholine (ACh), which depends of the levels of vesicular ACh transport (VAChT) to be released, is the central mediator of the cholinergic anti-inflammatory system. ACh controls the release of cytokine in different models of inflammation. Diesel exhaust particles (DEP) are one of the major environmental pollutants produced in large quantity by automotive engines in urban center. DEP bind the lung parenchyma and induce inflammation. We evaluated whether cholinergic dysfunction worsens DEP-induced lung inflammation. Male mice with decreased ACh release due to reduced expression of VAChT (VAChT-KD mice) were submitted to DEP exposure for 30 days (3â¯mg/mL of DEP, once a day, five days a week) or saline. Pulmonary function and inflammation as well as extracellular matrix fiber deposition were evaluated. Additionally, airway and nasal epithelial mucus production were quantified. We found that DEP instillation worsened lung function and increased lung inflammation. Higher levels of mononuclear cells were observed in the peripheral blood of both wild-type (WT) and VAChT-KD mice. Also, both wild-type (WT) and VAChT-KD mice showed an increase in macrophages in bronchoalveolar lavage fluid (BALF) as well as increased expression of IL-4, IL-6, IL-13, TNF-α, and NF-κB in lung cells. The collagen fiber content in alveolar septa was also increased in both genotypes. On the other hand, we observed that granulocytes were increased only in VAChT-KD peripheral blood. Likewise, increased BALF lymphocytes and neutrophils as well as increased elastic fibers in alveolar septa, airway neutral mucus, and nasal epithelia acid mucus were observed only in VAChT-KD mice. The cytokines IL-4 and TNF-α were also higher in VAChT-KD mice compared with WT mice. In conclusion, decreased ability to release ACh exacerbates some of the lung alterations induced by DEP in mice, suggesting that VAChT-KD animals are more vulnerable to the effects of DEP in the lung.
Assuntos
Pulmão/efeitos dos fármacos , Emissões de Veículos/toxicidade , Proteínas Vesiculares de Transporte de Acetilcolina/genética , Animais , Líquido da Lavagem Broncoalveolar/citologia , Citocinas/genética , Citocinas/metabolismo , Pulmão/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/metabolismo , Masculino , Camundongos , Tecido Parenquimatoso/efeitos dos fármacos , Tecido Parenquimatoso/metabolismo , Pneumonia/induzido quimicamente , Pneumonia/diagnóstico , Proteínas Vesiculares de Transporte de Acetilcolina/deficiência , Proteínas Vesiculares de Transporte de Acetilcolina/metabolismoRESUMO
Estrogens positively affect object recognition memory (ORM). However, whether this effect rely on acetylcholine is unknown. Here we investigated if 17ß-estradiol (E2) would be able to recover ORM deficits in animals with decreased expression of the Vesicular Acetylcholine Transporter (VAChT KDHET). We found that E2 improved short-term ORM (STM) in VAChT KDHET male and in OVX female mutant mice. However, E2 did not recover long-term (LTM) ORM in both sexes. Next, we tested whether hippocampal ERs activation could also rescue STM in mutant mice. Our results showed that ERα seems to be both sufficient and necessary for STM consolidation in female VAChT KDHET. Differently, in male, both ERα and ERß activation recovered STM. In addition, we tested whether mRNA level of estrogen receptors (ER) is also sensitive to VAChT expression. Female mutant mice showed lower levels of ER alpha (ERα) mRNA in the hippocampus, while no differences in male were observed. Together, our results showed that under hypocholinergic function, E2 improve short-term object recognition in both male and female. Furthermore, we showed that changes in VAChT expression might potentially modulate hippocampal ERα expression in a sex-dependent-manner.
Assuntos
Estradiol/farmacologia , Transtornos da Memória/tratamento farmacológico , Memória de Curto Prazo/efeitos dos fármacos , Nootrópicos/farmacologia , Reconhecimento Psicológico/efeitos dos fármacos , Proteínas Vesiculares de Transporte de Acetilcolina/deficiência , Acetilcolina/metabolismo , Animais , Estrogênios/farmacologia , Feminino , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Masculino , Transtornos da Memória/metabolismo , Memória de Curto Prazo/fisiologia , Camundongos Transgênicos , Ovariectomia , RNA Mensageiro/metabolismo , Receptores de Estrogênio/metabolismo , Reconhecimento Psicológico/fisiologia , Fatores Sexuais , Proteínas Vesiculares de Transporte de Acetilcolina/genéticaRESUMO
The pilocarpine (PILO) animal model of Temporal Lobe Epilepsy (TLE) portrays the most common changes in hippocampal circuitry found in human TLE. The acute cholinergic insult induces status epilepticus (SE), which triggers an overwhelming set of plastic events that result on late spontaneous recurrent limbic seizures. It has been suggested that the cholinergic system plays an important role in the synchronization required for ictogenesis. We took advantage of a knock-down animal model for the vesicular acetylcholine transporter (VAChT KD) to investigate seizure genesis in a model of cholinergic dysfunction. We induced SE in VAChT KD and wild-type (WT) mice by a single intraperitoneal injection of PILO in order to evaluate susceptibility to seizures. Video-EEG recordings evaluated epileptiform activity and ictal behavior onset. The hypothesis tested is that innate cholinergic hypofunction could result in increased susceptibility to PILO. VAChT KD(HOM) mice showed shorter latency for the first epileptiform discharge and for the first seizure episode, when compared to other groups. The duration of these seizure episodes, however, were not statistically different among experimental groups. On the other hand, VAChT KD(HOM) had the shortest latency to isoelectric EEG, when compared to WT and KD(HET). Our results indicate that a reduction of brain VAChT protein to the levels found in VAChT KD(HOM) mice alters the epileptic response to PILO. Thus, fine-tuning modulation of cholinergic tone can affect the susceptibility of epileptic responses to pilocarpine.
Assuntos
Suscetibilidade a Doenças , Pilocarpina , Estado Epiléptico/induzido quimicamente , Proteínas Vesiculares de Transporte de Acetilcolina/deficiência , Animais , Modelos Animais de Doenças , Camundongos , Camundongos Knockout , Estado Epiléptico/genéticaRESUMO
An important step for cholinergic transmission involves the vesicular storage of acetylcholine (ACh), a process mediated by the vesicular acetylcholine transporter (VAChT). In order to understand the physiological roles of the VAChT, we developed a genetically altered strain of mice with reduced expression of this transporter. Heterozygous and homozygous VAChT knockdown mice have a 45% and 65% decrease in VAChT protein expression, respectively. VAChT deficiency alters synaptic vesicle filling and affects ACh release. Whereas VAChT homozygous mutant mice demonstrate major neuromuscular deficits, VAChT heterozygous mice appear normal in that respect and could be used for analysis of central cholinergic function. Behavioral analyses revealed that aversive learning and memory are not altered in mutant mice; however, performance in cognitive tasks involving object and social recognition is severely impaired. These observations suggest a critical role of VAChT in the regulation of ACh release and physiological functions in the peripheral and central nervous system.