Acetylcholinesterase in intestinal cell differentiation involves G2/M cell cycle arrest

Indirubin mediates adverse intestinal reactions in guinea pigs by downregulating the expression of AchE through AhR

Indirubin is the main component of the traditional Chinese medicine Indigo naturalis (IN), a potent agonist of aryl hydrocarbon receptors (AhRs). In China, IN is used to treat psoriasis and ulcerative colitis, and indirubin is used for the treatment of chronic myelogenous leukaemia. However, IN and indirubin have adverse reactions, such as abdominal pain, diarrhoea, and intussusception, and their specific mechanism is unclear.The purpose of our research was to determine the specific mechanism underlying the adverse effects of IN and indirubin. By tracking the modifications in guinea pigs after the intragastric administration of indirubin for 28 days.The results demonstrate that indirubin could accelerate bowel movements and decrease intestinal acetylcholinesterase (AchE) expression. Experiments with NCM460 cells revealed that indirubin significantly reduced the expression of AchE, and the AchE levels were increased after the silencing of AhR and re-exposure to indirubin.This study showed that the inhibition of AchE expression by indirubin plays a key role in the occurrence of adverse reactions to indirubin and that the underlying mechanism is related to AhR-mediated AchE downregulation.

Changes in the Acetylcholinesterase Enzymatic Activity in Tumor Development and Progression

Acetylcholinesterase is a well-known protein because of the relevance of its enzymatic activity in the hydrolysis of acetylcholine in nerve transmission. In addition to the catalytic action, it exerts non-catalytic functions; one is associated with apoptosis, in which acetylcholinesterase could significantly impact the survival and aggressiveness observed in cancer. The participation of AChE as part of the apoptosome could explain the role in tumors, since a lower AChE content would increase cell survival due to poor apoptosome assembly. Likewise, the high Ach content caused by the reduction in enzymatic activity could induce cell survival mediated by the overactivation of acetylcholine receptors (AChR) that activate anti-apoptotic pathways. On the other hand, in tumors in which high enzymatic activity has been observed, AChE could be playing a different role in the aggressiveness of cancer; in this review, we propose that AChE could have a pro-inflammatory role, since the high enzyme content would cause a decrease in ACh, which has also been shown to have anti-inflammatory properties, as discussed in this review. In this review, we analyze the changes that the enzyme could display in different tumors and consider the different levels of regulation that the acetylcholinesterase undergoes in the control of epigenetic changes in the mRNA expression and changes in the enzymatic activity and its molecular forms. We focused on explaining the relationship between acetylcholinesterase expression and its activity in the biology of various tumors. We present up-to-date knowledge regarding this fascinating enzyme that is positioned as a remarkable target for cancer treatment.

Muscarinic Receptors Associated with Cancer

Simple Summary

Recently, cancer research has described the presence of the cholinergic machinery, specifically muscarinic receptors, in a wide variety of cancers due to their activation and signaling pathways associated with tumor progression and metastasis, providing a wide overview of their contribution to different cancer formation and development for new antitumor targets. This review focused on determining the molecular signatures associated with muscarinic receptors in breast and other cancers and the need for pharmacological, molecular, biochemical, technological, and clinical approaches to improve new therapeutic targets.

Abstract

Cancer has been considered the pathology of the century and factors such as the environment may play an important etiological role. The ability of muscarinic agonists to stimulate growth and muscarinic receptor antagonists to inhibit tumor growth has been demonstrated for breast, melanoma, lung, gastric, colon, pancreatic, ovarian, prostate, and brain cancer. This work aimed to study the correlation between epidermal growth factor receptors and cholinergic muscarinic receptors, the survival differences adjusted by the stage clinical factor, and the association between gene expression and immune infiltration level in breast, lung, stomach, colon, liver, prostate, and glioblastoma human cancers. Thus, targeting cholinergic muscarinic receptors appears to be an attractive therapeutic alternative due to the complex signaling pathways involved.

Solar light induces expression of acetylcholinesterase in skin keratinocytes: Signalling mediated by activator protein 1 transcription factor

Acetylcholinesterase (AChE) hydrolyses acetylcholine to choline and acetate, playing an important role in terminating the neurotransmission in brain and muscle. Recently, the non-neuronal functions of AChE have been proposed in different tissues, in which there are various factors to regulate the expression of AChE. In mammalian skin, AChE was identified in melanocytes and keratinocytes. Our previous study has indicated that AChE in keratinocyte affects the process of solar light-induced skin pigmentation; however, the expression of AChE in keratinocytes in responding to sunlight remains unknown. Here, we provided several lines of evidence to support a notion that AChE could be upregulated at transcriptional and translational levels in keratinocytes when exposed to solar light. The light-mediated AChE expression was triggered by Ca²⁺, supported by an induction of Ca²⁺ ionophore A23187 and a blockage by Ca²⁺ chelator BAPTA-AM. In addition, this increase on AChE transcriptional expression was eliminated by mutagenesis on the activating protein 1 (AP1) site in ACHE gene. Hence, the solar light-induced AChE expression is mediated by Ca²⁺ signalling through AP1 site. This finding supports the role of solar light in affecting the cholinergic system in skin cells, and which may further influence the dermatological function.

Erythropoietin regulates the expression of dimeric form of acetylcholinesterase during differentiation of erythroblast

Acetylcholinesterase (AChE; EC 3.1.1.7) is known to hydrolyze acetylcholine at cholinergic synapses. In mammalian erythrocyte, AChE exists as a dimer (G₂ ) and is proposed to play role in erythropoiesis. To reveal the regulation of AChE during differentiation of erythroblast, erythroblast-like cells (TF-1) were induced to differentiate by application of erythropoietin (EPO). The expression of AChE was increased in parallel to the stages of differentiation. Application of EPO in cultured TF-1 cells induced transcriptional activity of ACHE gene, as well as its protein product. This EPO-induced event was in parallel with erythrocytic proteins, for example, α- and β-globins. The EPO-induced AChE expression was mediated by phosphorylations of Akt and GATA-1; because the application of Akt kinase inhibitor blocked the gene activation. Erythroid transcription factor also known as GATA-1, a downstream transcription factor of EPO signaling, was proposed here to account for regulation of AChE in TF-1 cell. A binding sequence of GATA-1 was identified in ACHE gene promoter, which was further confirmed by chromatin immunoprecipitation (ChIP) assay. Over-expression of GATA-1 in TF-1 cultures induced AChE expression, as well as activity of ACHE promoter tagged with luciferase gene (pAChE-Luc). The deletion of GATA-1 sequence on the ACHE promoter, pAChE_ΔGATA-1 -Luc, reduced the promoter activity during erythroblastic differentiation. On the contrary, the knock-down of AChE in TF-1 cultures could lead to a reduction in EPO-induced expression of erythrocytic proteins. These findings indicated specific regulation of AChE during maturation of erythroblast, which provided an insight into elucidating possible mechanisms in regulating erythropoiesis.

Acetylcholinesterase plays a non-neuronal, non-esterase role in organogenesis

Acetylcholinesterase (AChE) is crucial for degrading acetylcholine at cholinergic synapses. In vitro studies suggest that, in addition to its role in nervous system signaling, AChE can also modulate non-neuronal cell properties, although it remains controversial whether AChE functions in this capacity in vivo Here, we show that AChE plays an essential non-classical role in vertebrate gut morphogenesis. Exposure of Xenopus embryos to AChE-inhibiting chemicals results in severe defects in intestinal development. Tissue-targeted loss-of-function assays (via microinjection of antisense morpholino or CRISPR-Cas9) confirm that AChE is specifically required in the gut endoderm tissue, a non-neuronal cell population, where it mediates adhesion to fibronectin and regulates cell rearrangement events that drive gut lengthening and digestive epithelial morphogenesis. Notably, the classical esterase activity of AChE is dispensable for this activity. As AChE is deeply conserved, widely expressed outside of the nervous system, and the target of many environmental chemicals, these results have wide-reaching implications for development and toxicology.

Acetylcholinesterase is associated with a decrease in cell proliferation of hepatocellular carcinoma cells

Acetylcholinesterase (AChE), the enzyme that rapidly splits acetylcholine into acetate and choline, presents non-cholinergic functions through which may participate in the control of cell proliferation and apoptosis. These two features are relevant in cancer, particularly in hepatocellular carcinoma (HCC), a very aggressive liver tumor with high incidence and poor prognosis in advanced stages. Here we explored the relation between acetylcholinesterase and HCC growth by testing the influence of AChE on proliferation of Huh-7 and HepG2 cell lines, addressed in monolayer cultures, spheroid formation and human liver tumor samples. Results showed a clear relation in AChE expression and cell cycle progression, an effect which depended on cell confluence. Inhibition of AChE activity led to an increase in cell proliferation, which was associated with downregulation of p27 and cyclins. The fact that Huh-7 and HepG2 cell lines provided similar results lent weight to the relationship of AChE expression with cell cycle progression in hepatoma cell lines at least. Human liver tumor samples exhibited a decrease in AChE activity as compared with normal tissue. The evidence presented herein provides additional support for the proposed tumor suppressor role of AChE, which makes it a potential therapeutic target in therapies against hepatocellular carcinoma.

Role of acetylcholinesterase in lung cancer

Acetylcholinesterase (AChE) plays a key role in catalytic hydrolysis of cholinergic neurotransmitters. Intensive research has proven the involvement of this protein in novel functions, such as cell adhesion, differentiation, and proliferation. In addition, several recent studies have indicated that acetylcholinesterase is potentially a marker and regulator of apoptosis. Importantly, AChE is also a promising tumor suppressor. In this review, we briefly summarize the involvement of AChE in apoptosis and cancer, focusing on the role of AChE in lung cancer, as well as the therapeutic consideration of AChE for cancer therapy.

Deregulated proliferation and differentiation in brain tumors

Neurogenesis, the generation of new neurons, is deregulated in neural stem cell (NSC)- and progenitor-derived murine models of malignant medulloblastoma and glioma, the most common brain tumors of children and adults, respectively. Molecular characterization of human malignant brain tumors, and in particular brain tumor stem cells (BTSCs), has identified neurodevelopmental transcription factors, microRNAs, and epigenetic factors known to inhibit neuronal and glial differentiation. We are starting to understand how these factors are regulated by the major oncogenic drivers in malignant brain tumors. In this review, we will focus on the molecular switches that block normal neuronal differentiation and induce brain tumor formation. Genetic or pharmacological manipulation of these switches in BTSCs has been shown to restore the ability of tumor cells to differentiate. We will discuss potential brain tumor therapies that will promote differentiation in order to reduce treatment resistance, suppress tumor growth, and prevent recurrence in patients.

Acetylcholinesterase overexpression mediated by oncolytic adenovirus exhibited potent anti-tumor effect

Background

Acetylcholinesterase (AChE) mainly functions as an efficient terminator for acetylcholine signaling transmission. Here, we reported the effect of AChE on gastric cancer therapy.

Methods

The expression of AChE in gastric cancerous tissues and adjacent non-cancerous tissues was examined by immunohistochemistry. Gastric cancer cells were treated with AChE delivered by replication-deficient adenoviral vector (Ad.AChE) or oncolytic adenoviral vector (ZD55-AChE), respectively, followed by measurement of cell viability and apoptosis by MTT assay and apoptosis detection assays. In vivo, the tumor growth of gastric cancer xenografts in mice treated with Ad.AChE or ZD55-AChE (1 × 10⁹ PFU) were measured. In addition, the cell viability of gastric cancer stem cells treated with Ad.AChE or ZD55-AChE were evaluated by MTT assay.

Results

A positive correlation was found between higher level of AChE expression in gastric cancer patient samples and longer survival time of the patients. Ad.AChE and ZD55-AChE inhibited gastric cancer cell growth, and low dose of ZD55-AChE induced mitochondrial pathway of apoptosis in cells. ZD55-AChE repressed tumor growth in vivo, and the anti-tumor efficacy is greater than Ad.AChE. Moreover, ZD55-AChE suppressed the growth of gastric cancer stem cells.

Conclusion

ZD55-AChE represented potential therapeutic effect for human gastric cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2407-14-668) contains supplementary material, which is available to authorized users.

Quantification of the transcripts encoding different forms of AChE in various cell types: real-time PCR coupled with standards in revealing the copy number

Acetylcholinesterase (AChE) is encoded by a single gene, and the alternative splicing at the 3' end produces different isoforms, including tailed (AChET), read-through (AChER), and hydrophobic (AChEH). Different forms of this enzyme exist in different cell types. Each AChE form has been proposed to have unique function, and all of them could be found in same cell type. Thus, the splicing process of different AChE forms remains unclear. Here, we aimed to establish a quantification method in measuring the absolute amount of each AChE splicing variants within a cell type. By using real-time PCR coupled with standard curves of defined copy of AChE variants, the copies of AChET transcript per 100 ng of total RNA were 5.7 × 10(4) in PC12 (rat neuronal cell), 1.3 × 10(4) in Caco-2 (human intestinal cell), 0.67 × 10(4) in TF-1 (human erythropoietic precursor), 133.3 in SH-SY5Y (human neuronal cell), and 56.7 in human umbilical vein endothelial cells (human endothelial cells). The copies of AChEH in these cell types were 0.3 × 10(4), 3.3 × 10(4), 2.7 × 10(4), 133.3, and 46.7, respectively, and AChER were 0.07 × 10(4), 0.13 × 10(4), 890, 3.3, and 2.7, respectively. Furthermore, PC12 and TF-1 cells were chosen for the analysis of AChE splicing pattern during differentiation. The results demonstrated a selective increase in AChET mRNA but not AChER or AChEH mRNAs in PC12 upon nerve growth factor-induced neuronal differentiation. PC12 cells could therefore act as a good cell model for the study on alternative splicing mechanism and regulation of AChET.

A protocol for in situ enzyme assays to assess the differentiation of human intestinal Caco-2 cells

The Caco-2 cell line spontaneously differentiates into polarised enterocytes expressing high levels of brush border enzymes typical of small intestinal epithelial cells (peptidases, alkaline phosphatase, disaccharidases). The activities of these enzymes gradually increase after cell confluence reaching a plateau after 2-3 weeks of culture and can be used as reliable markers to evaluate differentiation of Caco-2 cells. We have developed a rapid in situ method on live cells to measure activities of alkaline phosphatase, alanyl amino peptidase and sucrase. The substrates were added to the apical compartment of confluent cells maintained for 8, 15 and 21 days on polycarbonate filter inserts and sampling was performed at time intervals. Alkaline phosphatase and alanyl aminopeptidase were assayed using as substrates p-Nitrophenyl phosphate and alanine-p-nitroanilide, respectively, and the yellow product detected spectrophotometrically at 405 nm. Sucrase activity was measured as the release of glucose from sucrose using a fluorimetric assay (Amplex® Red Glucose Assay Kit) in which H(2)O(2), produced by the coupled glucose oxidase/horseradish peroxidase reactions, oxidises the colourless reagent to red-fluorescent resorufin. All these assays are rapid and reproducible and can easily be adapted to robotised high throughput platforms.

Induction of a 55 kDa acetylcholinesterase protein during apoptosis and its negative regulation by the Akt pathway

Acetylcholinesterase (AChE) is emerging as an important contributor to apoptosis in various cell types. However, overexpression of AChE does not initiate apoptosis, and cells which express AChE at basal levels grow normally, suggesting that AChE may function differently between normal and apoptotic conditions. In this study, we determined that an AChE-derived protein (∼55 kDa) positively correlated with cellular apoptotic levels. The 55 kDa AChE protein was not a result of a novel splice variant of the AChE primary transcript. Instead, it was determined to be a cleaved fragment of the full-length 68 kDa AChE protein that could not be inhibited by cycloheximide (CHX) but could be suppressed by caspase inhibitors in apoptotic PC-12 cells. Furthermore, activation of the Akt cascade abolished the 55 kDa protein, and both AChE protein forms (68 and 55 kDa) accumulated in the nucleus during apoptosis. In a mouse model for ischemia/reperfusion (I/R)-induced acute renal failure, the 55 kDa AChE protein was detected in the impaired organs but not in the normal ones, and its levels correlated with the genotype of the mice. In summary, a 55 kDa AChE protein resulting from the cleavage of 68 kDa AChE is induced during apoptosis, and it is negatively regulated by the Akt pathway. This study suggests that an alternative form of AChE may play a role in apoptosis.