RESUMO
The M2 muscarinic receptor (M2R) is a prototypic class A G protein-coupled receptor (GPCR). Interestingly, Fasciani et al. recently identified an internal translation start site within the M2 receptor mRNA, directing the expression of a C-terminal receptor fragment. Elevated during cellular stress, this polypeptide localizes to mitochondria where it inhibits oxidative phosphorylation.
Assuntos
Receptor Muscarínico M2 , Humanos , Receptor Muscarínico M2/metabolismo , Receptor Muscarínico M2/genética , Animais , Mitocôndrias/metabolismo , Fosforilação OxidativaRESUMO
Glioblastoma (GB) is a very aggressive human brain tumor. The high growth potential and invasiveness make this tumor surgically and pharmacologically untreatable. Our previous work demonstrated that the activation of the M2 muscarinic acetylcholine receptors (M2 mAChRs) inhibited cell proliferation and survival in GB cell lines and in the cancer stem cells derived from human biopsies. The aim of the present study was to investigate the ability of M2 mAChR to modulate cell migration in two different GB cell lines: U87 and U251. By wound healing assay and single cell migration analysis performed by time-lapse microscopy, we demonstrated the ability of M2 mAChRs to negatively modulate cell migration in U251 but not in the U87 cell line. In order to explain the different effects observed in the two cell lines we have evaluated the possible involvement of the intermediate conductance calcium-activated potassium (IKCa) channel. IKCa channel is present in the GB cells, and it has been demonstrated to modulate cell migration. Using the perforated patch-clamp technique we have found that selective activation of M2 mAChR significantly reduced functional density of the IKCa current in U251 but not in U87 cells. To understand whether the M2 mAChR mediated reduction of ion channel density in the U251 cell line was relevant for the cell migration impairment, we tested the effects of TRAM-34, a selective inhibitor of the IKCa channel, in wound healing assay. We found that it was able to markedly reduce U251 cell migration and significantly decrease the number of invadopodia-like structure formations. These results suggest that only in U251 cells the reduced cell migration M2 mAChR-mediated might involve, at least in part, the IKCa channel.
Assuntos
Glioblastoma , Humanos , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Glioblastoma/metabolismo , Receptor Muscarínico M2/metabolismo , Receptores Muscarínicos/metabolismoRESUMO
Beta-adrenoceptor (ß-AR) agonists inhibit cholinergic contractions of airway smooth muscle (ASM), but the underlying mechanisms are unclear. ASM cells express M3 and M2 muscarinic receptors, but the bronchoconstrictor effects of acetylcholine are believed to result from activation of M3Rs, while the role of the M2Rs is confined to offsetting ß-AR-dependent relaxations. However, a profound M2R-mediated hypersensitization of M3R-dependent contractions of ASM was recently reported, indicating an important role for M2Rs in cholinergic contractions of ASM. Here, we investigated if M2R-dependent contractions of murine bronchial rings were inhibited by activation of ß-ARs. M2R-dependent contractions were apparent at low frequency (2Hz) electric field stimulation (EFS) and short (10s) stimulus intervals. The ß1-AR agonist, denopamine inhibited EFS-evoked contractions of ASM induced by reduction in stimulus interval from 100 to 10 s and was more effective at inhibiting contractions evoked by EFS at 2 than 20 Hz. Denopamine also abolished carbachol-evoked contractions that were resistant to the M3R antagonist 4-DAMP, similar to the effects of the M2R antagonists, methoctramine and AFDX-116. The inhibitory effects of denopamine on EFS-evoked contractions of ASM were smaller in preparations taken from M2R -/- mice, compared to wild-type (WT) controls. In contrast, inhibitory effects of the ß3-AR agonist, BRL37344, on EFS-evoked contractions of detrusor strips taken from M2R -/- mice were greater than WT controls. These data suggest that M2R-dependent contractions of ASM were inhibited by activation of ß1-ARs and that genetic ablation of M2Rs decreased the efficacy of ß-AR agonists on cholinergic contractions.
Assuntos
Contração Muscular , Receptores Muscarínicos , Camundongos , Animais , Receptor Muscarínico M2/genética , Antagonistas Muscarínicos/farmacologia , Agonistas Adrenérgicos beta/farmacologia , Músculo Liso , Receptores AdrenérgicosRESUMO
Ovarian cancer is the fifth leading cause of cancer-related deaths in females. Many ovarian tumor cell lines express muscarinic receptors (mAChRs), and their expression is correlated with reduced survival of patients. We have characterized the expression of mAChRs in two human ovarian carcinoma cell lines (SKOV-3, TOV-21G) and two immortalized ovarian surface epithelium cell lines (iOSE-120, iOSE-398). Among the five subtypes of mAChRs (M1-M5 receptors), we focused our attention on the M2 receptor, which is involved in the inhibition of tumor cell proliferation. Western blot analysis and real-time PCR analyses indicated that the levels of M2 are statistically downregulated in cancer cells. Therefore, we investigated the effect of arecaidine propargyl ester hydrobromide (APE), a preferential M2 agonist, on cell growth and survival. APE treatment decreased cell number in a dose and time-dependent manner by decreasing cell proliferation and increasing cell death. FACS and immunocytochemistry analysis have also demonstrated the ability of APE to accumulate the cells in G2/M phase of the cell cycle and to increase the percentage of abnormal mitosis. The higher level of M2 receptors in the iOSE cells rendered these cells more sensitive to APE treatment than cancer cells. The data here reported suggest that M2 has a negative role in cell growth/survival of ovarian cell lines, and its downregulation may favor tumor progression.
Assuntos
Hominidae , Neoplasias Ovarianas , Animais , Carcinoma Epitelial do Ovário , Ciclo Celular , Proliferação de Células , Ésteres/farmacologia , Feminino , Hominidae/metabolismo , Humanos , Neoplasias Ovarianas/genética , Receptor Muscarínico M2/metabolismo , Receptores MuscarínicosRESUMO
Abstract Background: Different immune mechanisms of myocardial damage involved in the pathophysiology of Chagas disease coexist with high titers of autoantibodies induced by T. cruzi . There are few studies in the literature about the adaptive role of anti-β1 and anti-M2 antibodies in chronic Chagas cardiomyopathy (CCC). Objectives: To evaluate the association between anti-β1 and anti-M2 antibodies with heart rate variability (HRV) parameters on 24h Holter monitoring and the rate-pressure product (RPP) on cardiopulmonary exercise testing (CPET). Methods: Anti-β1 and anti-M2 antibody titers were measured by enzyme-linked immunosorbent assay (ELISA) in 64 patients affected by CCC. Analysis of HRV was performed through the time-domain indices NNs, mean NN, SDNN, SDANN, SDNN index, NNNs, RMSSD, and pNN50. Spearman's correlation coefficient was used to assess the association between antibody titers and numerical variables. The Mann-Whitney test was used for comparison between two groups. Multiple linear regression was used to identify independent variables capable of explaining anti-β1 and anti-M2 antibody titers at the 5% significance level. Results: On 24h Holter, during the period of greatest parasympathetic activation (2:00-6:00 a.m.), an inverse association was found between anti-β1 titers and SDNN (rs=-0.13, p =0.041, n=43), as well as a direct association between anti-M2 titers and SDANN ( r s=0.317, p =0.039, n=43). Regarding CPET variables, anti-β1 titers were directly associated with RPP (rs=0.371, p =0.005, n=56). The subgroup of patients with a normal chronotropic response showed higher anti-β1 titers than the subgroup with an impaired response (p=0.023). RPP was an independent explanatory variable for anti-β1 titers, although with a low coefficient of determination (R2=0.147). Conclusion: The findings of this study suggest that, in patients with CCC, anti-β1 and anti-M2 antibodies may affect HRV parameters. RPP was directly associated with higher anti-β1 titers.
Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Idoso de 80 Anos ou mais , Adulto Jovem , Sistema Nervoso Autônomo/fisiologia , Cardiomiopatia Chagásica/fisiopatologia , Receptores Adrenérgicos beta 1/fisiologia , Receptor Muscarínico M2/fisiologia , Doença Crônica , Estudos Transversais , Anticorpos Biespecíficos , Teste de EsforçoRESUMO
BACKGROUND: Donepezil, a cholinesterase inhibitor approved in Alzheimer's disease, has demonstrated analgesic and preventive effects in animal models of oxaliplatin-induced neuropathy. To improve the clinical interest of donepezil for the management and prevention of chemotherapy-induced peripheral neuropathy (CIPN), a broader validation is required in different animal models of CIPN. METHODS: using rat models of CIPN (bortezomib, paclitaxel, and vincristine), the analgesic and preventive efficacies of donepezil were evaluated on tactile, cold and heat hypersensitivities. The involvement of muscarinic M2 acetylcholine receptors (m2AChRs) in analgesic effects was investigated at the spinal level. The absence of interference of donepezil with the cytotoxic effect of chemotherapy has been controlled in cancer cell lines. RESULTS: the analgesic efficacy of donepezil was demonstrated for all CIPN models, mainly on tactile hypersensitivity (maximal efficacy at 60 min, p < 0.05 vs. vehicle group). This effect was suppressed by an intrathecal injection of methoctramine (m2AChR antagonist). Regarding preventive effects, donepezil limited tactile hypersensitivity induced by paclitaxel, but not for other CIPN models. Donepezil did not modify the viability of cancer cells or the efficacy of anticancer drugs. CONCLUSIONS: donepezil had a broad analgesic effect on animal models of CIPN and this effect involved spinal m2AChRs. This work validates the repositioning of donepezil in the management of CIPN.
Assuntos
Antineoplásicos , Leucemia Mieloide Aguda , Doenças do Sistema Nervoso Periférico , Acetilcolina , Analgésicos/efeitos adversos , Animais , Antineoplásicos/toxicidade , Inibidores da Colinesterase/farmacologia , Inibidores da Colinesterase/uso terapêutico , Donepezila , Modelos Animais , Paclitaxel/efeitos adversos , Doenças do Sistema Nervoso Periférico/induzido quimicamente , Doenças do Sistema Nervoso Periférico/tratamento farmacológico , Doenças do Sistema Nervoso Periférico/prevenção & controle , Ratos , Receptor Muscarínico M2 , Receptores MuscarínicosRESUMO
PURPOSE: Activation of muscarinic receptors located in bladder sensory pathways is generally considered to be the primary contributor for driving the pathogenesis of neurogenic detrusor overactivity following spinal cord injury. The present study is undertaken to examine whether moxibustion improves neurogenic detrusor overactivity via modulating the abnormal muscarinic receptor pathway. MATERIALS AND METHODS: Female Sprague-Dawley rats were subjected to spinal cord injury with T9-10 spinal cord transection. Fourteen days later, animals were received moxibustion treatment for one week. Urodynamic parameters and pelvic afferents discharge were measured. Adenosine triphosphate (ATP) content in the voided cystometry fluid was determined. Expressions of M2, M3, and P2X3 receptors in the bladder mucosa were evaluated. RESULTS: Moxibustion treatment prevented the development of detrusor overactivity in spinal cord injury rats, with an increase in the intercontraction interval and micturition pressure threshold and a decrease in afferent activity during filling. The expression of M2 was markedly suppressed by moxibustion, accompanied by a reduction in the levels of ATP and P2X3. M2 receptor antagonist methoctramine hemihydrate had similar effects to moxibustion on bladder function and afferent activity, while the M2-preferential agonist oxotremorine methiodide abolished the beneficial effects of moxibustion. CONCLUSION: Moxibustion is a potential candidate for treating neurogenic bladder overactivity in a rat model of spinal cord injury, possibly through inhibiting the M2/ATP/P2X3 pathway.
Assuntos
Trifosfato de Adenosina , Moxibustão , Receptor Muscarínico M2 , Traumatismos da Medula Espinal , Bexiga Urinária Hiperativa , Trifosfato de Adenosina/antagonistas & inibidores , Trifosfato de Adenosina/metabolismo , Animais , Diaminas/farmacologia , Feminino , Antagonistas do Receptor Purinérgico P2X/farmacologia , Ratos , Ratos Sprague-Dawley , Receptor Muscarínico M2/antagonistas & inibidores , Receptor Muscarínico M2/metabolismo , Receptores Muscarínicos , Receptores Purinérgicos P2X3/metabolismo , Traumatismos da Medula Espinal/metabolismo , Bexiga Urinaria Neurogênica/tratamento farmacológico , Bexiga Urinaria Neurogênica/metabolismo , Bexiga Urinaria Neurogênica/terapia , Bexiga Urinária Hiperativa/tratamento farmacológico , Bexiga Urinária Hiperativa/metabolismo , Bexiga Urinária Hiperativa/terapiaRESUMO
The cross-talk between axon and glial cells during development and in adulthood is mediated by several molecules. Among them are neurotransmitters and their receptors, which are involved in the control of myelinating and non-myelinating glial cell development and physiology. Our previous studies largely demonstrate the functional expression of cholinergic muscarinic receptors in Schwann cells. In particular, the M2 muscarinic receptor subtype, the most abundant cholinergic receptor expressed in Schwann cells, inhibits cell proliferation downregulating proteins expressed in the immature phenotype and triggers promyelinating differentiation genes. In this study, we analysed the in vitro modulation of the Neuregulin-1 (NRG1)/erbB pathway, mediated by the M2 receptor activation, through the selective agonist arecaidine propargyl ester (APE). M2 agonist treatment significantly downregulates NRG1 and erbB receptors expression, both at transcriptional and protein level, and causes the internalization and intracellular accumulation of the erbB2 receptor. Additionally, starting from our previous results concerning the negative modulation of Notch-active fragment NICD by M2 receptor activation, in this work, we clearly demonstrate that the M2 receptor subtype inhibits erbB2 receptors by Notch-1/NICD downregulation. Our data, together with our previous results, demonstrate the existence of a cross-interaction between the M2 receptor and NRG1/erbB pathway-Notch1 mediated, and that it is responsible for the modulation of Schwann cell proliferation/differentiation.
Assuntos
Neurregulinas , Receptor ErbB-2 , Receptor Muscarínico M2/metabolismo , Receptores Notch , Células de Schwann , Transdução de Sinais , Proliferação de Células , Células Cultivadas , Neurregulinas/metabolismo , Receptor ErbB-2/metabolismo , Receptores Notch/metabolismo , Células de Schwann/citologia , Células de Schwann/metabolismoRESUMO
Inhibitory regulation of the heart is determined by both cholinergic M2 receptors (M2R) and adenosine A1 receptors (A1R) that activate the same signaling pathway, the ACh-gated inward rectifier K+ (KACh) channels via Gi/o proteins. Previously, we have shown that the agonist-specific voltage sensitivity of M2R underlies several voltage-dependent features of IKACh, including the 'relaxation' property, which is characterized by a gradual increase or decrease of the current when cardiomyocytes are stepped to hyperpolarized or depolarized voltages, respectively. However, it is unknown whether membrane potential also affects A1R and how this could impact IKACh. Upon recording whole-cell currents of guinea-pig cardiomyocytes, we found that stimulation of the A1R-Gi/o-IKACh pathway with adenosine only caused a very slight voltage dependence in concentration-response relationships (~1.2-fold EC50 increase with depolarization) that was not manifested in the relative affinity, as estimated by the current deactivation kinetics (τ = 4074 ± 214 ms at -100 mV and τ = 4331 ± 341 ms at +30 mV; P = 0.31). Moreover, IKACh did not exhibit relaxation. Contrarily, activation of the M2R-Gi/o-IKACh pathway with acetylcholine induced the typical relaxation of the current, which correlated with the clear voltage-dependent effect observed in the concentration-response curves (~2.8-fold EC50 increase with depolarization) and in the IKACh deactivation kinetics (τ = 1762 ± 119 ms at -100 mV and τ = 1503 ± 160 ms at +30 mV; P = 0.01). Our findings further substantiate the hypothesis of the agonist-specific voltage dependence of GPCRs and that the IKACh relaxation is consequence of this property.
Assuntos
Acetilcolina/farmacologia , Agonistas do Receptor A1 de Adenosina/farmacologia , Adenosina/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Miócitos Cardíacos/metabolismo , Canais de Potássio/metabolismo , Receptor A1 de Adenosina/metabolismo , Animais , Feminino , Cobaias , Masculino , Receptor Muscarínico M2/agonistas , Receptor Muscarínico M2/metabolismoRESUMO
BACKGROUND: Cholinergic neurons utilize choline (Ch) to synthetize acetylcholine (ACh) and contain a high-affinity Ch transporter, Ch acetyltransferase (ChAT), ACh receptors, and acetylcholinesterase (AChE). As the depletion or malfunction of each component of the cholinergic system has been reported in patients with dementia, many studies have sought to evaluate whether treatment candidates affect each of the cholinergic components. The associated changes in the cholinergic components may be reflected by intra- or extra-cellular ACh levels, with an increase in extracellular ACh levels occurring following AChE inhibition. We hypothesized that increases in intracellular ACh levels can be more sensitively detected than those in extracellular ACh levels, thereby capturing subtle effects in the cholinergic components other than AChE. The objective of this study was to test this hypothesis. METHODS: We developed an in vitro model to measure both extracellular and intracellular ACh levels using the human cholinergic neuroblastoma cell line, LA-N-2, which have been reported to express Ch transporter, ChAT, muscarinic ACh receptor (mAChR), and AChE. With this model, we evaluated several drug compounds and food constituents reported to improve cholinergic function through various mechanisms. In addition, we conducted western blotting to identify the subtype of mAChR that is expressed on the cell line. RESULTS: Our cell-based assay system was capable of detecting increases in extracellular ACh levels induced by an AChE inhibitor at relatively high doses, as well as increases in intracellular ACh levels following the administration of lower AChE-inhibitor doses and an mAChR agonist. Moreover, increases in intracellular ACh levels were observed even after treatment with food constituents that have different mechanisms of action, such as Ch provision and ChAT activation. In addition, we revealed that LA-N-2 cells expressed mAChR M2. CONCLUSION: The findings support our hypothesis and indicate that the developed assay model can broadly screen compounds from drugs to food ingredients, with varying strengths and mechanisms of action, to develop treatments for ACh-relevant phenomena, including dementia and aging-related cognitive decline.
Assuntos
Acetilcolina/metabolismo , Colinérgicos/farmacologia , Neurônios/efeitos dos fármacos , Antocianinas/farmacologia , Linhagem Celular Tumoral , Colina/metabolismo , Inibidores da Colinesterase/farmacologia , Humanos , Neurônios/citologia , Neurônios/metabolismo , Fisostigmina/farmacologia , Receptor Muscarínico M2/metabolismoRESUMO
BACKGROUND: Glioblastoma multiforme (GBM) is characterized by several genetic abnormalities, leading to cell cycle deregulation and abnormal mitosis caused by a defective checkpoint. We previously demonstrated that arecaidine propargyl ester (APE), an orthosteric agonist of M2 muscarinic acetylcholine receptors (mAChRs), arrests the cell cycle of glioblastoma (GB) cells, reducing their survival. The aim of this work was to better characterize the molecular mechanisms responsible for this cell cycle arrest. METHODS: The arrest of cell proliferation was evaluated by flow cytometry analysis. Using immunocytochemistry and time-lapse analysis, the percentage of abnormal mitosis and aberrant mitotic spindles were assessed in both cell lines. Western blot analysis was used to evaluate the modulation of Sirtuin2 and acetylated tubulin-factors involved in the control of cell cycle progression. RESULTS: APE treatment caused arrest in the M phase, as indicated by the increase in p-HH3 (ser10)-positive cells. By immunocytochemistry, we found a significant increase in abnormal mitoses and multipolar mitotic spindle formation after APE treatment. Time-lapse analysis confirmed that the APE-treated GB cells were unable to correctly complete the mitosis. The modulated expression of SIRT2 and acetylated tubulin in APE-treated cells provides new insights into the mechanisms of altered mitotic progression in both GB cell lines. CONCLUSIONS: Our data show that the M2 agonist increases aberrant mitosis in GB cell lines. These results strengthen the idea of considering M2 acetylcholine receptors a novel promising therapeutic target for the glioblastoma treatment.
Assuntos
Glioblastoma/metabolismo , Glioblastoma/patologia , Mitose , Receptor Muscarínico M2/metabolismo , Fuso Acromático/metabolismo , Acetilação/efeitos dos fármacos , Arecolina/análogos & derivados , Arecolina/farmacologia , Linhagem Celular Tumoral , Núcleo Celular/efeitos dos fármacos , Núcleo Celular/metabolismo , Humanos , Metáfase/efeitos dos fármacos , Sirtuína 2/metabolismo , Imagem com Lapso de Tempo , Tubulina (Proteína)/metabolismoAssuntos
Diabetes Mellitus Experimental/patologia , Diabetes Mellitus Tipo 1/patologia , Modelos Animais de Doenças , Coração/fisiopatologia , Pâncreas/patologia , Animais , Glicemia/metabolismo , Diabetes Mellitus Experimental/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Feminino , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/imunologia , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/imunologia , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Insulina/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Pâncreas/metabolismo , Canais de Potássio Corretores do Fluxo de Internalização/imunologia , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Receptor Muscarínico M2/imunologia , Receptor Muscarínico M2/metabolismo , Fator de Necrose Tumoral alfa/imunologia , Fator de Necrose Tumoral alfa/metabolismoRESUMO
BACKGROUND: Glioblastoma multiforme (GBM) is characterized by heterogeneous cell populations. Among these, the Glioblastoma Stem Cells (GSCs) fraction shares some similarities with Neural Stem Cells. GSCs exhibit enhanced resistance to conventional chemotherapy drugs. Our previous studies demonstrated that the activation of M2 muscarinic acetylcholine receptors (mAChRs) negatively modulates GSCs proliferation and survival. The aim of the present study was to analyze the ability of the M2 dualsteric agonist Iper-8-naphthalimide (N-8-Iper) to counteract GSCs drug resistance. METHODS: Chemosensitivity to M2 dualsteric agonist N-8-Iper and chemotherapy drugs such as temozolomide, doxorubicin, or cisplatin was evaluated in vitro by MTT assay in two different GSC lines. Drug efflux pumps expression was evaluated by RT-PCR and qRT-PCR. RESULTS: By using sub-toxic concentrations of N-8-Iper combined with the individual chemotherapeutic agents, we found that only low doses of the M2 agonist combined with doxorubicin or cisplatin or temozolomide were significantly able to counteract cell growth in both GSC lines. Moreover, we evaluated as the exposure to high and low doses of N-8-Iper downregulated the ATP-binding cassette (ABC) drug efflux pumps expression levels. CONCLUSIONS: Our results revealed the ability of the investigated M2 agonist to counteract drug resistance in two GSC lines, at least partially by downregulating the ABC drug efflux pumps expression. The combined effects of low doses of conventional chemotherapy and M2 agonists may thus represent a novel promising pharmacological approach to impair the GSC-drug resistance in the GBM therapy.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Neoplasias Encefálicas/tratamento farmacológico , Resistencia a Medicamentos Antineoplásicos , Glioblastoma/tratamento farmacológico , Agonistas Muscarínicos/farmacologia , Naftalimidas/farmacologia , Células-Tronco Neoplásicas/efeitos dos fármacos , Transportadores de Cassetes de Ligação de ATP/genética , Transportadores de Cassetes de Ligação de ATP/metabolismo , Neoplasias Encefálicas/genética , Neoplasias Encefálicas/metabolismo , Neoplasias Encefálicas/patologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Cisplatino/farmacologia , Doxorrubicina/farmacologia , Regulação Neoplásica da Expressão Gênica , Glioblastoma/genética , Glioblastoma/metabolismo , Glioblastoma/patologia , Humanos , Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Receptor Muscarínico M2/agonistas , Receptor Muscarínico M2/genética , Receptor Muscarínico M2/metabolismo , Transdução de Sinais , Temozolomida/farmacologiaRESUMO
The family of human muscarinic acetylcholine receptors (MRs) is characterized by a high sequence homology among the five subtypes (M1R-M5R), being the reason for a lack of subtype selective MR ligands. In continuation of our work on dualsteric dibenzodiazepinone-type M2R antagonists, a series of M2R ligands containing a dibenzodiazepinone pharmacophore linked to small basic peptides was synthesized (64 compounds). The linker moiety was varied with respect to length, number of basic nitrogens (0-2) and flexibility. Besides proteinogenic basic amino acids (Lys, Arg), shorter homologues of Lys and Arg, containing three and two methylene groups, respectively, as well as D-configured amino acids were incorporated. The type of linker had a marked impact on M2R affinity and also effected M2R selectivity. In contrast, the structure of the basic peptide rather determined M2R selectivity than M2R affinity. For example, the most M2R selective compound (UR-CG188, 89) with picomolar M2R affinity (pKi 9.60), exhibited a higher M2R selectivity (ratio of Ki M1R/M2R/M3R/M4R/M5R: 110:1:5200:55:2300) compared to the vast majority of reported M2R preferring MR ligands. For selected ligands, M2R antagonism was confirmed in a M2R miniG protein recruitment assay.
Assuntos
Aminoácidos/antagonistas & inibidores , Benzodiazepinonas/farmacologia , Antagonistas Muscarínicos/farmacologia , Peptídeos/farmacologia , Receptor Muscarínico M2/antagonistas & inibidores , Aminoácidos/metabolismo , Animais , Benzodiazepinonas/síntese química , Benzodiazepinonas/química , Células Cultivadas , Relação Dose-Resposta a Droga , Humanos , Simulação de Acoplamento Molecular , Estrutura Molecular , Antagonistas Muscarínicos/síntese química , Antagonistas Muscarínicos/química , Peptídeos/química , Receptor Muscarínico M2/metabolismo , Relação Estrutura-AtividadeRESUMO
One of the major limits of chemotherapy is depending on the ability of the cancer cells to elude and adapt to different drugs. Recently, we demonstrated how the activation of the M2 muscarinic receptor could impair neuroblastoma cell proliferation. In the present paper, we investigate the possible effects mediated by the preferential M2 receptor agonist arecaidine propargyl ester (APE) on drug resistance in two neuroblastoma cell lines, SK-N-BE and SK-N-BE(2C), a sub-clone presenting drug resistance. In both cell lines, we compare the expression of the M2 receptor and the effects mediated by the M2 agonist APE on cell cycle, demonstrating a decreased percentage of cells in S phase and an accumulation of SK-N-BE cells in G1 phase, while the APE treatment of SK-N-BE(2C) cells induced a block in G2/M phase. The withdrawal of the M2 agonist from the medium shows that only the SK-N-BE(2C) cells are able to rescue cell proliferation. Further, we demonstrate that the co-treatment of low doses of APE with doxorubicin or cisplatin significantly counteracts cell proliferation when compared with the single treatment. Analysis of the expression of ATP-binding cassette (ABC) efflux pumps demonstrates the ability of the M2 agonist to downregulate their expression and that this negative modulation may be dependent on N-MYC decreased expression induced by the M2 agonist. Our data demonstrate that the combined effect of low doses of conventional drugs and the M2 agonist may represent a new promising therapeutic approach in neuroblastoma treatment, in light of its significant impact on drug resistance and the possible reduction in the side effects caused by high doses of chemotherapy drugs.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Arecolina/análogos & derivados , Neuroblastoma/tratamento farmacológico , Receptor Muscarínico M2/agonistas , Transportadores de Cassetes de Ligação de ATP/genética , Arecolina/administração & dosagem , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Cisplatino/administração & dosagem , Doxorrubicina/administração & dosagem , Resistencia a Medicamentos Antineoplásicos , Expressão Gênica/efeitos dos fármacos , Humanos , Neuroblastoma/metabolismo , Neuroblastoma/patologia , Receptor Muscarínico M2/genéticaRESUMO
G protein-coupled receptors (GPCRs) initiate signaling cascades via G-proteins and beta-arrestins (ßarr). ßarr-dependent actions begin with recruitment of ßarr to the phosphorylated receptor tail and are followed by engagement with the receptor core. ßarrs are known to act as adaptor proteins binding receptors and various effectors, but it is unclear whether in addition to the scaffolding role ßarrs can allosterically activate their downstream targets. Here we demonstrate the direct allosteric activation of proto-oncogene kinase Src by GPCR-ßarr complexes in vitro and establish the conformational basis of the activation. Whereas free ßarr1 had no effect on Src activity, ßarr1 in complex with M2 muscarinic or ß2-adrenergic receptors reconstituted in lipid nanodiscs activate Src by reducing the lag phase in Src autophosphorylation. Interestingly, receptor-ßarr1 complexes formed with a ßarr1 mutant, in which the finger-loop, required to interact with the receptor core, has been deleted, fully retain the ability to activate Src. Similarly, ßarr1 in complex with only a phosphorylated C-terminal tail of the vasopressin 2 receptor activates Src as efficiently as GPCR-ßarr complexes. In contrast, ßarr1 and chimeric M2 receptor with nonphosphorylated C-terminal tail failed to activate Src. Taken together, these data demonstrate that the phosphorylated GPCR tail interaction with ßarr1 is necessary and sufficient to empower it to allosterically activate Src. Our findings may have implications for understanding more broadly the mechanisms of allosteric activation of downstream targets by ßarrs.
Assuntos
Receptor Muscarínico M2/metabolismo , Receptores Adrenérgicos beta 2/metabolismo , Receptores de Vasopressinas/metabolismo , beta-Arrestina 1/metabolismo , Quinases da Família src/metabolismo , Regulação Alostérica , Ativação Enzimática , Humanos , Cinética , Mutagênese Sítio-Dirigida , Nanoestruturas/química , Peptídeos/síntese química , Peptídeos/química , Fosforilação , Ligação Proteica , Proto-Oncogene Mas , Receptor Muscarínico M2/química , Receptores Adrenérgicos beta 2/química , Receptores de Vasopressinas/química , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/isolamento & purificação , Especificidade por Substrato , beta-Arrestina 1/química , beta-Arrestina 1/genética , Domínios de Homologia de src , Quinases da Família src/químicaRESUMO
Triple negative tumors are more aggressive than other breast cancer subtypes and there is a lack of specific therapeutic targets on them. Since muscarinic receptors have been linked to tumor progression, we investigated the effect of metronomic therapy employing a traditional anti-cancer drug, paclitaxel plus muscarinic agonists at low doses on this type of tumor. We observed that MDA-MB231 tumor cells express muscarinic receptors, while they are absent in the non-tumorigenic MCF-10A cell line, which was used as control. The addition of carbachol or arecaidine propargyl ester, a non-selective or a selective subtype 2 muscarinic receptor agonist respectively, plus paclitaxel reduces cell viability involving a down-regulation in the expression of ATP "binding cassette" G2 drug transporter and epidermal growth factor receptor. We also detected an inhibition of tumor cell migration and anti-angiogenic effects produced by those drug combinations in vitro and in vivo (in NUDE mice) respectively. Our findings provide substantial evidence about subtype 2 muscarinic receptors as therapeutic targets for the treatment of triple negative tumors.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Agonistas Colinérgicos/administração & dosagem , Paclitaxel/administração & dosagem , Receptor Muscarínico M2/metabolismo , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Administração Metronômica , Animais , Arecolina/administração & dosagem , Arecolina/análogos & derivados , Carbacol/administração & dosagem , Linhagem Celular Tumoral , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Regulação para Baixo/efeitos dos fármacos , Receptores ErbB/metabolismo , Feminino , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Humanos , Camundongos , Proteínas de Neoplasias/metabolismo , Neovascularização Patológica/tratamento farmacológico , Neovascularização Patológica/patologia , RNA Interferente Pequeno/metabolismo , Receptor Muscarínico M2/agonistas , Receptor Muscarínico M2/genética , Neoplasias de Mama Triplo Negativas/irrigação sanguínea , Neoplasias de Mama Triplo Negativas/patologia , Fator A de Crescimento do Endotélio Vascular/metabolismo , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Infection with Helicobacter pylori (H. pylori) is the main risk factor for gastric carcinogenesis. In this study, we investigated the expression, molecular functions, and downstream effectors of miR490-3p in gastric cancer. We used in vitro and in vivo models to investigate the role of H. pylori in regulating miR490-3p, DARPP-32-dependent functions, and therapeutic resistance. Human and mouse neoplastic gastric lesions demonstrated a negative correlation between DARPP-32 and miR490-3p expression (R = -0.58, P < 0.01). This was also detected following infection with H. pylori (R = -0.66, P < 0.01). Molecular assays confirmed DARPP-32 as a direct target of miR490-3p. CHRM2, the host gene of miR490-3p, was hypermethylated and downregulated in neoplastic gastric tissues (P < 0.05). H. pylori induced methylation and downregulation of CHRM2 and miR490-3p. Functionally, the reconstitution of miR490-3p sensitized cancer cells to gefitinib by inactivating DRAPP-32-dependent AKT and STAT3 pathways. Patients with low miR490-3p or high DARPP-32 expression had decreased overall survival (P < 0.05). Hypermethylation-mediated silencing of CHRM2 and miR490-3p by H. pylori increased DARPP-32 expression. Downregulation of miR490-3p in gastric cancer plays a role in gefitinib response by inducing DARPP-32-mediated activation of PI3K/AKT, STAT3 signaling pathways.
Assuntos
Fosfoproteína 32 Regulada por cAMP e Dopamina/fisiologia , Gefitinibe/uso terapêutico , Helicobacter pylori/patogenicidade , MicroRNAs/fisiologia , Neoplasias Gástricas/tratamento farmacológico , Animais , Linhagem Celular Tumoral , Metilação de DNA , Resistencia a Medicamentos Antineoplásicos , Infecções por Helicobacter/complicações , Humanos , Camundongos , Camundongos Endogâmicos C57BL , MicroRNAs/antagonistas & inibidores , Receptor Muscarínico M2/genética , Neoplasias Gástricas/genética , Neoplasias Gástricas/microbiologiaRESUMO
How G protein-coupled receptors (GPCRs) evoke specific biological outcomes while utilizing a limited array of G proteins and effectors is poorly understood, particularly in native cell systems. Here, we examined signaling evoked by muscarinic (M2R) and adenosine (A1R) receptor activation in the mouse sinoatrial node (SAN), the cardiac pacemaker. M2R and A1R activate a shared pool of cardiac G protein-gated inwardly rectifying K+ (GIRK) channels in SAN cells from adult mice, but A1R-GIRK responses are smaller and slower than M2R-GIRK responses. Recordings from mice lacking Regulator of G protein Signaling 6 (RGS6) revealed that RGS6 exerts a GPCR-dependent influence on GIRK-dependent signaling in SAN cells, suppressing M2R-GIRK coupling efficiency and kinetics and A1R-GIRK signaling amplitude. Fast kinetic bioluminescence resonance energy transfer assays in transfected HEK cells showed that RGS6 prefers Gαo over Gαi as a substrate for its catalytic activity and that M2R signals preferentially via Gαo, while A1R does not discriminate between inhibitory G protein isoforms. The impact of atrial/SAN-selective ablation of Gαo or Gαi2 was consistent with these findings. Gαi2 ablation had minimal impact on M2R-GIRK and A1R-GIRK signaling in SAN cells. In contrast, Gαo ablation decreased the amplitude and slowed the kinetics of M2R-GIRK responses, while enhancing the sensitivity and prolonging the deactivation rate of A1R-GIRK signaling. Collectively, our data show that differences in GPCR-G protein coupling preferences, and the Gαo substrate preference of RGS6, shape A1R- and M2R-GIRK signaling dynamics in mouse SAN cells.
Assuntos
Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Proteínas RGS/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Nó Sinoatrial/metabolismo , Potenciais de Ação/fisiologia , Animais , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/genética , Células HEK293 , Frequência Cardíaca/fisiologia , Humanos , Preparação de Coração Isolado , Camundongos , Camundongos Knockout , Cultura Primária de Células , Proteínas RGS/genética , Receptor A1 de Adenosina/metabolismo , Receptor Muscarínico M2/metabolismo , Transdução de Sinais/fisiologia , Nó Sinoatrial/citologiaRESUMO
A series of novel 1,4-dioxane analogues of the muscarinic acetylcholine receptor (mAChR) antagonist 2 was synthesized and studied for their affinity at M1-M5 mAChRs. The 6-cyclohexyl-6-phenyl derivative 3b, with a cis configuration between the CH2N+(CH3)3 chain in the 2-position and the cyclohexyl moiety in the 6-position, showed pKi values for mAChRs higher than those of 2 and a selectivity profile analogous to that of the clinically approved drug oxybutynin. The study of the enantiomers of 3b and the corresponding tertiary amine 33b revealed that the eutomers are (2S,6S)-(-)-3b and (2S,6S)-(-)-33b, respectively. Docking simulations on the M3 mAChR-resolved structure rationalized the experimental observations. The quaternary ammonium function, which should prevent the crossing of the blood-brain barrier, and the high M3/M2 selectivity, which might limit cardiovascular side effects, make 3b a valuable starting point for the design of novel antagonists potentially useful in peripheral diseases in which M3 receptors are involved.