AChE deficiency or inhibition decreases apoptosis and p53 expression and protects renal function after ischemia/reperfusion

Two Fluorescent Probes for Recognition of Acetylcholinesterase: Design, Synthesis, and Comparative Evaluation

In this study, two "on-off" probes (BF2-cur-Ben and BF2-cur-But) recognizing acetylcholinesterase (AChE) were designed and synthesized. The obtained probes can achieve recognition of AChE with good selectivity and pH-independence with a linear range of 0.5~7 U/mL and 0.5~25 U/mL respectively. BF2-cur-Ben has a lower limit of detection (LOD) (0.031 U/mL), higher enzyme affinity (Km = 16 ± 1.6 μM), and higher inhibitor sensitivity. A responsive mechanism of the probes for AChE was proposed based on HPLC and mass spectra (MS) experiments, as well as calculations. In molecular simulation, BF2-cur-Ben forms more hydrogen bonds (seven, while BF2-cur-But has only four) and thus has a more stable enzyme affinity, which is mirrored by the results of the comparison of Km values. These two probes could enable recognition of intracellular AChE and probe BF2-cur-Ben has superior cell membrane penetration due to its higher log p value. These probes can monitor the overexpression of AChE during apoptosis of lung cancer cells. The ability of BF2-cur-Ben to monitor AChE in vivo was confirmed by a zebrafish experiment.

Donepezil halts acetic acid-induced experimental colitis in rats and its associated cognitive impairment through regulating inflammatory/oxidative/apoptotic cascades: An add-on to its anti-dementia activity

Ulcerative colitis (UC) is a persistent inflammatory bowel disease (IBD) that is regarded as a risk factor for cognitive impairment. Donepezil (DON), a centrally acting acetylcholinesterase inhibitor (AChEI), is approved for the management of Alzheimer's disease (AD). We aimed to scrutinize the impact of DON on acetic acid (AA)-induced UC in rats and to evaluate its ability to attenuate inflammatory response, oxidative strain, and apoptosis in this model and its associated cognitive deficits. Rats were categorized into: normal, DON, AA, and AA + DON groups. DON (5 mg/kg/day) was administered orally for 14 days either alone or beginning with the day of UC induction. Colitis was evoked by a single transrectal injection of 1 ml of 4 % acetic acid. Results revealed that DON significantly improved the behavioral abnormalities with the mitigation of inflammation, apoptosis, and histopathological changes in the hippocampi of the colitis group. Moreover, DON significantly alleviated the macroscopic and microscopic changes associated with colitis. Interestingly, DON inhibited pro-inflammatory cytokines via suppression of AA-induced activation of nuclear factor kappa-B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β) in the colon, along with serum IL-1β. DON inhibited colon lipid peroxidation, restored the antioxidants with a significant amelioration of the degree of neutrophil infiltration, and repressed colitis-induced matrix metalloproteinases-9 (MMP-9) production. Furthermore, DON decreased the Bax/Bcl-2 ratio and caspase-3 protein expressions. Eventually, in lipopolysaccharide (LPS)-treated RAW 264.7 macrophage cells, DON suppressed nitric oxide (NO) release, demonstrating the ability of DON to significantly curtail inflammation in immune cells. Taken together, DON ameliorated experimental colitis and its linked cognitive dysfunction, possibly via its antioxidant effect and modulation of pro-inflammatory cytokines and apoptosis. Thereby, DON could be a therapeutic nominee for UC and associated neurological disorders.

Protection of insect neurons by erythropoietin/CRLF3-mediated regulation of pro-apoptotic acetylcholinesterase

Cytokine receptor-like factor 3 (CRLF3) is a conserved but largely uncharacterized orphan cytokine receptor of eumetazoan animals. CRLF3-mediated neuroprotection in insects can be stimulated with human erythropoietin. To identify mechanisms of CRLF3-mediated neuroprotection we studied the expression and proapoptotic function of acetylcholinesterase in insect neurons. We exposed primary brain neurons from Tribolium castaneum to apoptogenic stimuli and dsRNA to interfere with acetylcholinesterase gene expression and compared survival and acetylcholinesterase expression in the presence or absence of the CRLF3 ligand erythropoietin. Hypoxia increased apoptotic cell death and expression of both acetylcholinesterase-coding genes ace-1 and ace-2. Both ace genes give rise to single transcripts in normal and apoptogenic conditions. Pharmacological inhibition of acetylcholinesterases and RNAi-mediated knockdown of either ace-1 or ace-2 expression prevented hypoxia-induced apoptosis. Activation of CRLF3 with protective concentrations of erythropoietin prevented the increased expression of acetylcholinesterase with larger impact on ace-1 than on ace-2. In contrast, high concentrations of erythropoietin that cause neuronal death induced ace-1 expression and hence promoted apoptosis. Our study confirms the general proapoptotic function of AChE, assigns a role of both ace-1 and ace-2 in the regulation of apoptotic death and identifies the erythropoietin/CRLF3-mediated prevention of enhanced acetylcholinesterase expression under apoptogenic conditions as neuroprotective mechanism.

Tacrine Derivatives in Neurological Disorders: Focus on Molecular Mechanisms and Neurotherapeutic Potential

Tacrine is a drug used in the treatment of Alzheimer's disease as a cognitive enhancer and inhibitor of the enzyme acetylcholinesterase (AChE). However, its clinical application has been restricted due to its poor therapeutic efficacy and high prevalence of detrimental effects. An attempt was made to understand the molecular mechanisms that underlie tacrine and its analogues influence over neurotherapeutic activity by focusing on modulation of neurogenesis, neuroinflammation, endoplasmic reticulum stress, apoptosis, and regulatory role in gene and protein expression, energy metabolism, Ca2+ homeostasis modulation, and osmotic regulation. Regardless of this, analogues of tacrine are considered as a model inhibitor of cholinesterase in the therapy of Alzheimer's disease. The variety both in structural make-up and biological functions of these substances is the main appeal for researchers' interest in them. A new paradigm for treating neurological diseases is presented in this review, which includes treatment strategies for Alzheimer's disease, as well as other neurological disorders like Parkinson's disease and the synthesis and biological properties of newly identified versatile tacrine analogues and hybrids. We have also shown that these analogues may have therapeutic promise in the treatment of neurological diseases in a variety of experimental systems.

Polystyrene nanoplastics induced cardiomyocyte apoptosis and myocardial inflammation in carp by promoting ROS production

Nanoplastics (NPs) existing in aquatic ecosystem is an emerging environmental pollutant, which has become a nagging serious environmental problem. Miniaturized plastic fragments with different diameters have different penetration capabilities to body tissues, and thus may have different toxicity to the target organs. However, the specific toxicological effects and mechanisms of NPs with different particle sizes on aquatic animal hearts are still unknown. To this end, carps were directly exposed to the aqueous environment of polystyrene NPs (1000 μg/L, PS-NPs) with three particle sizes (50 nm, 100 nm and 400 nm), respectively, for 28 days. H&E and TUNEL staining displayed that exposed to PS-NPs of three diameters all caused myocardial tissue inflammation and cardiomyocyte apoptosis in carps. Of note, at the same exposure concentration, the damage caused by PS-NPs with particle size of 50 nm was more serious than that of 100 nm and 400 nm. Further research found that, in carp hearts exposed to PS-NPs, the levels of carp innate immunity-related components TLR4 and NOX2 were significantly higher than those in controls and were negatively correlated with the exposed particle size. The content of ROS increased significantly, the activities of antioxidant enzymes (CAT, SOD1 and Gpx1) decreased, and MDA accumulated. In addition, as the particle size of PS-NPs decreased, Th1 cells gradually replaced Th2 cells to dominate, the Th1/Th2 balance was dysregulated, and the expression of apoptosis-inducing pathway IGFBP3/p53/ACHE-related genes was increased, markedly. Overall, our study results demonstrated that PS-NPs exposure caused oxidative stress, resulting in inflammation and apoptosis in carp heart, and the degree of damage was negatively correlated with the particle size of PS-NPs. Our work enriched the theoretical basis for NPs toxicological research and shed new light on the risk of NPs exposure.

Donepezil ameliorates oxygen‑glucose deprivation/reoxygenation‑induced cardiac microvascular endothelial cell dysfunction through PARP1/NF‑κB signaling

Ischemia/reperfusion (I/R) injury is a serious clinical condition characterized by high morbidity and mortality rates. Donepezil plays a neuroprotective role in I/R-associated diseases. The aim of the present study was to investigate the role and the potential mechanism of action of donepezil in I/R-induced myocardial microvascular endothelial cell dysfunction. An I/R model was simulated using oxygen-glucose deprivation/reoxygenation (OGD/R) injury in human cardiac microvascular endothelial cells (CMECs). Cell viability and lactate dehydrogenase release were examined following treatment with donepezil. Commercial kits were used to evaluate cell apoptosis, cell permeability and caspase-3 activity. The expression levels of apoptosis-associated proteins, as well as proteins found in tight junctions or involved in the poly(ADP-ribose) polymerase 1 (PARP1)/NF-κB pathway, were measured using western blotting. These parameters were also examined following PARP1 overexpression. The results demonstrated that donepezil increased cell viability and reduced toxicity in OGD/R-treated CMECs. The apoptotic rate, caspase-3 activity and protein expression levels of Bax and cleaved caspase-3 were significantly reduced following donepezil treatment, which was accompanied by Bcl-2 upregulation. Moreover, cell permeability was notably reduced, coupled with a marked increase in the expression of tight junction-associated proteins. The expression levels of proteins related to PARP1/NF-κB signaling were significantly downregulated in CMECs following donepezil treatment. However, the protective effects of donepezil on OGD/R-induced CMEC injury were reversed following PARP1 overexpression. In conclusion, donepezil suppressed OGD/R-induced CMEC dysfunction via PARP1/NF-κB signaling. This finding provided insight into the mechanism underlying myocardial I/R injury.

Bbc3 Loss Enhances Survival and Protein Clearance in Neurons Exposed to the Organophosphate Pesticide Chlorpyrifos

Exposure to environmental toxicants can increase the risk of developing age-related neurodegenerative disorders. Exposure to the widely used organophosphate pesticide chlorpyrifos (CPF) is associated with increased risk of developing Alzheimer's disease and Parkinson's disease, but the cellular mechanisms underlying CPF toxicity in neurons are not completely understood. We evaluated CPF toxicity in mouse primary cortical neuronal cultures, using RNA-sequencing to identify cellular pathways modulated by CPF. CPF exposure altered the expression of genes associated with intrinsic apoptosis, significantly elevating expression of the pro-apoptotic mediator Bbc3/Puma. Bbc3 loss attenuated CPF driven neurotoxicity, induction of other intrinsic apoptosis regulatory genes including Trp53 and Pmaip1 (encoding the NOXA protein), and cleavage of apoptosis executors caspase 3 and poly (ADP-ribose) polymerase (PARP). CPF exposure was associated with enhanced expression of endoplasmic reticulum stress-related genes and proteins and the accumulation of high molecular weight protein species in primary neuronal cultures. No evidence of alterations in the ubiquitin-proteosome system were observed, however, autophagy-related proteins were upregulated in CPF-treated Bbc3-/- neuronal cultures compared with identically exposed WT cultures. Elevated autophagy-related protein expression in Bbc3-/- neuronal cultures was associated with a reduction in CPF-induced high molecular weight alpha-synuclein and tau immunoreactive protein aggregates. Studies indicate that Bbc3-/- neuronal cultures enhance the endoplasmic reticulum stress response and upregulate protein clearance mechanisms as a component of resistance to CPF-mediated toxicity.

Acetylcholinesterase promotes apoptosis in insect neurons

Apoptosis plays a major role in development, tissue renewal and the progression of degenerative diseases. Studies on various types of mammalian cells reported a pro-apoptotic function of acetylcholinesterase (AChE), particularly in the formation of the apoptosome and the degradation of nuclear DNA. While three AChE splice variants are present in mammals, invertebrates typically express two ache genes that code for a synaptically located protein and a protein with non-synaptic functions respectively. In order to investigate a potential contribution of AChE to apoptosis in insects, we selected the migratory locust Locusta migratoria. We established primary neuronal cultures of locust brains and characterized apoptosis progression in vitro. Dying neurons displayed typical characteristics of apoptosis, including caspase-activation, nuclear condensation and DNA fragmentation visualized by TUNEL staining. Addition of the AChE inhibitors neostigmine and territrem B reduced apoptotic cell death under normal culture conditions. Moreover, both inhibitors completely suppressed hypoxia-induced neuronal cell death. Exposure of live animals to severe hypoxia moderately increased the expression of ace-1 in locust brains in vivo. Our results indicate a previously unreported role of AChE in insect apoptosis that parallels the pro-apoptotic role in mammalian cells. This similarity adds to the list of apoptotic mechanisms shared by mammals and insects, supporting the hypothesized existence of an ancient, complex apoptosis regulatory network present in common ancestors of vertebrates and insects.

Acetylcholinesterase and human cancers

The enzyme acetylcholinesterase (AChE) is a serine hydrolase whose primary function is to degrade acetylcholine (ACh) and terminate neurotransmission. Apart from its role in synaptic transmission, AChE has several "non-classical" functions in non-neuronal cells. AChE is involved in cellular growth, apoptosis, drug resistance pathways, response to stress signals and inflammation. The observation that the functional activity of AChE is altered in human tumors (relative to adjacent matched normal tissue) has raised several intriguing questions about its role in the pathophysiology of human cancers. Published reports show that AChE is a vital regulator of oncogenic signaling pathways involving proliferation, differentiation, cell-cell adhesion, migration, invasion and metastasis of primary tumors. The objective of this book chapter is to provide a comprehensive overview of the contributions of the AChE-signaling pathway in the growth of progression of human cancers. The AChE isoforms, AChE-T, AChE-R and AChE-S are robustly expressed in human cancer cell lines as well in human tumors (isolated from patients). Traditionally, AChE-modulators have been used in the clinic for treatment of neurodegenerative disorders. Emerging studies reveal that these drugs could be repurposed for the treatment of human cancers. The discovery of potent, selective AChE ligands will provide new knowledge about AChE-regulatory pathways in human cancers and foster the hope of novel therapies for this disease.

7,8-Dihydroxyflavone alleviated the high-fat diet and alcohol-induced memory impairment: behavioral, biochemical and molecular evidence

RATIONALE

Alcoholism and obesity impart a deleterious impact on human health and affects the quality of life. Chronic consumption of alcohol and western diet has been reported to cause memory deficits. 7,8-dihydroxyflavone (7,8-DHF), a TrkB agonist, comprises antioxidant and anti-inflammatory properties in treating various neurological disorders.

OBJECTIVES

The current study was aimed to determine the protective effect and molecular mechanism of 7,8-DHF against alcohol and high-fat diet (HFD)-induced memory deficits in rats.

METHODS

The adult male Wistar rats were given alcohol (3-15%) and HFD ad libitum for 12 weeks in different experimental groups. 7,8-DHF (5 mg/kg) was intraperitoneally injected daily for the last 4 weeks (9th-12th week).

RESULTS

The alcohol and HFD administration caused cognitive impairment as evaluated through the Morris water maze (MWM) test in alcohol, HFD, and alcohol + HFD-fed animals. The last 4-week treatment of 7,8-DHF (5 mg/kg; i.p.) attenuated alcohol and HFD-induced memory loss. 7,8-DHF treatment also restored the glutathione (GSH) level along with attenuation of nitrite, malondialdehyde content (markers of oxidative and nitrosative stress), and reduction of the acetylcholinesterase activity in the hippocampus of alcohol and HFD-fed animals. Furthermore, the administration of 7,8-DHF caused downregulation of NF-κB, iNOS, and caspase-3 and upregulation of Nrf2, HO-1, and BDNF mRNA level in rat hippocampus.

CONCLUSION

7,8-DHF administration conferred beneficial effects against alcohol and HFD-induced memory deficit via its unique antioxidant, anti-inflammatory, anti-apoptotic potential, along with the activation of TrkB/BDNF signaling pathway in the hippocampus.

Ameliorating effect of Citrus aurantium extracts and nobiletin on β‑amyloid (1‑42)‑induced memory impairment in mice

The aim of the present study was to evaluate the neuroprotective effect of Citrus aurantium extract (CAE) and nobiletin against amyloid β 1‑42 (Aβ 1‑42)‑induced spatial learning and memory impairment in mice. After injecting Aβ 1‑42 (5 µl/2.5 min, intracerebroventricular injection), amnesic mice were orally administered CAE and nobiletin for 28 days. Memory, spatial and cognitive ability were measured using passive avoidance and a Morris water maze task. Acetylcholinesterase (AchE) activity was investigated in the hippocampus and cortex using commercial kits and the analysis of Bax, Bcl‑2, and cleaved caspase‑3 protein expression by western blot assays was used to confirm the anti‑apoptotic mechanism of CAE and nobiletin. The present study confirmed impairments in learning and memory in the Aβ‑induced neurodegenerative mice with increased AchE activity in the brain. However, the daily administration of CAE and nobiletin reduced the spatial learning deficits and increased the AchE activity in the cortex and hippocampus. Furthermore, CAE and nobiletin significantly downregulated the Bax and cleaved caspase‑3 protein expression and upregulated the Bcl‑2 and Bcl‑2/Bax expression in the cortex and hippocampus of Aβ‑treated mice. These results suggest that CAE and nobiletin exert a neuroprotective effect by regulating anti‑apoptotic mechanisms, including reduced AchE activity in the cortex and hippocampus of the cognitive deficit mouse model.

Environmentally relevant concentrations of di(2-ethylhexyl)phthalate exposure alter larval growth and locomotion in medaka fish via multiple pathways

Di(2-ethylhexyl)phthalate (DEHP) is a commonly used plasticizer, with evidence of ubiquitous human exposure and widespread occurrence in the aquatic environment. It is an emerging environmental pollutant with regulatory priority; however, most studies have focused on the toxicity of DEHP related to endocrine disruption and reproduction in mammals. The ecotoxicological impact of phthalates (e.g., DEHP) on early life stages of fish under environmentally relevant concentrations of chronic exposure remains unclear. In this study, 7-day post-hatching fry of medaka fish (Oryzias latipes) underwent 21-day continuous exposure to DEHP solutions at 20, 100 and 200 μg/L to assess the effects on fish development and locomotion and related toxic mechanisms. Larval mortality was low with DEHP (20-200 μg/L) within 21 days, but such exposure significantly reduced fish body weight and length and altered swimming behavior. At 21 days, DEHP exposure resulted in specific patterns of larval locomotion (e.g., increased maximum velocity and absolute turn angle) and dose-dependently increased the mRNA expression of acetylcholinesterase (ache) but did not alter AChE activity. Transcriptional expression of antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase and peroxisome proliferation-activated receptor and retinoid X receptor genes was significantly suppressed with 21-day DEHP exposure (20-200 μg/L), with marginal alteration in reactive oxygen species levels and antioxidant activities within the dosing period. As well, DEHP altered the mRNA expression of p53-regulated apoptosis pathways, such as upregulated p53, p21 and bcl-2 and downregulated caspase-3 expression, with increased enzymatic activity of caspase-3 in larvae. Our results suggest that toxic mechanisms of waterborne DEHP altered fish growth and locomotion likely via a combined effect of oxidative stress, neurotoxicity and apoptosis pathways.

Huperzine A Provides Robust and Sustained Protection against Induced Seizures in Scn1a Mutant Mice

De novo loss-of-function mutations in the voltage-gated sodium channel (VGSC) SCN1A (encoding Na_v1.1) are the main cause of Dravet syndrome (DS), a catastrophic early-life encephalopathy associated with prolonged and recurrent early-life febrile seizures (FSs), refractory afebrile epilepsy, cognitive and behavioral deficits, and a 15–20% mortality rate. SCN1A mutations also lead to genetic epilepsy with febrile seizures plus (GEFS+), which is an inherited disorder characterized by early-life FSs and the development of a range of adult epilepsy subtypes. Current antiepileptic drugs often fail to protect against the severe seizures and behavioral and cognitive deficits found in patients with SCN1A mutations. To address the need for more efficacious treatments for SCN1A-derived epilepsies, we evaluated the therapeutic potential of Huperzine A, a naturally occurring reversible acetylcholinesterase inhibitor. In CF1 mice, Hup A (0.56 or 1 mg/kg) was found to confer protection against 6 Hz-, pentylenetetrazole (PTZ)-, and maximal electroshock (MES)-induced seizures. Robust protection against 6 Hz-, MES-, and hyperthermia-induced seizures was also achieved following Hup A administration in mouse models of DS (Scn1a^+/−) and GEFS+ (Scn1a^RH/+). Furthermore, Hup A-mediated seizure protection was sustained during 3 weeks of daily injections in Scn1a^RH/+ mutants. Finally, we determined that muscarinic and GABA_A receptors play a role in Hup A-mediated seizure protection. These findings indicate that Hup A might provide a novel therapeutic strategy for increasing seizure resistance in DS and GEFS+, and more broadly, in other forms of refractory epilepsy.

Cholinergic system and cell proliferation

The cholinergic system, comprising acetylcholine, the proteins responsible for acetylcholine synthesis and release, acetylcholine receptors and cholinesterases, is expressed by most human cell types. Acetylcholine is a neurotransmitter, but also a local signalling molecule which regulates basic cell functions, and cholinergic responses are involved in cell proliferation and apoptosis. So, activation of nicotinic and muscarinic receptors has a proliferative and anti-apoptotic effect in many cells. The content of choline acetyltransferase, acetylcholine receptors and cholinesterases is altered in many tumours, and cholinesterase content correlates with patient survival in some cancers. During apoptosis, acetylcholinesterase is induced and appears in the nuclei. Acetylcholinesterase participates in the regulation of cell proliferation and apoptosis through hydrolysis of acetylcholine and by other catalytic and non catalytic mechanisms, in a variant-specific manner. This review gathers information on the role of cholinergic system and specially acetylcholinesterase in cell proliferation and apoptosis.

Donepezil delays photoreceptor apoptosis induced by N-methyl-N-nitrosourea in mice

Retinitis pigmentosa (RP) is a group of inherited retinal degeneration diseases characterized by photoreceptor cell death that causes visual disturbances and eventual blindness. Intraperitoneal injection of N-methyl-N-nitrosourea (MNU) causes photoreceptor loss, and is used to create an animal model for investigating the mechanisms that cause retinal degeneration diseases. Donepezil is an acetylcholinesterase inhibitor that has a protective effect on retinal ganglion cells in vitro and in vivo, and it is understood that donepezil increases the expression of a heat shock protein 70 (Hsp70), which serves to protect neurons. Hsp70 functions as a chaperone molecule that protects cells from protein aggregation and assists in the refolding of denatured proteins. In the present study, the effects of donepezil on photoreceptor survival in mice was investigated. It was observed that donepezil upregulates the expression of Hsp70, to increase resistance to MNU-induced photoreceptor cell apoptosis by using its anti-apoptotic properties. In addition, the present study observed that Hsp70 promotes photoreceptor cell survival by upregulating the expression levels of B-cell lymphoma 2 (Bcl-2). In conclusion, the results of the present study indicate that donepezil has the potential to be used as a treatment for retinal degenerative diseases.

The protective role of tacrine and donepezil in the retina of acetylcholinesterase knockout mice

AIM

To determine the effect of different concentrations of the acetylcholinesterase (AChE) inhibitors tacrine and donepezil on retinal protection in AChE(+/-) mice (AChE knockout mice) of various ages.

METHODS

Cultured ARPE-19 cells were treated with hydrogen peroxide (H2O2) at concentrations of 0, 250, 500, 1000 and 2000 µmol/L and protein levels were measured using Western blot. Intraperitoneal injections of tacrine and donepezil (0.1 mg/mL, 0.2 mg/mL and 0.4 mg/mL) were respectively given to AChE(+/-) mice aged 2mo and 4mo and wild-type S129 mice for 7d; phosphate buffered saline (PBS) was administered to the control group. The mice were sacrificed after 30d by in vitro cardiac perfusion and retinal samples were taken. AChE-deficient mice were identified by polymerase chain reaction (PCR) analysis using specific genotyping protocols obtained from the Jackson Laboratory website. H&E staining, immunofluorescence and Western blot were performed to observe AChE protein expression changes in the retinal pigment epithelial (RPE) cell layer.

RESULTS

Different concentrations of H2O2 induced AChE expression during RPE cell apoptosis. AChE(+/-) mice retina were thinner than those in wild-type mice (P<0.05); the retinal structure was still intact at 2mo but became thinner with increasing age (P<0.05); furthermore, AChE(+/-) mice developed more slowly than wild-type mice (P<0.05). Increased concentrations of tacrine and donepezil did not significantly improve the protection of the retina function and morphology (P>0.05).

CONCLUSION

In vivo, tacrine and donepezil can inhibit the expression of AChE; the decrease of AChE expression in the retina is beneficial for the development of the retina.

Ischemia preconditioning protects rat submandibular glands from ischemia/reperfusion injuries

To investigate the effects of ischemia/reperfusion on rat submandibular glands without denervation and the possible protective effects of ischemia preconditioning on the glands that experienced ischemia/reperfusion, in-situ ischemia/reperfusion and ischemia preconditioning experimental models of submandibular glands of healthy male Wistar rats were conducted. For ischemia/reperfusion groups, the glands were subjected to 90 min of ischemia without denervation, followed by 1, 12, 24, or 72 h of reperfusion. Ischemia preconditioning was achieved by 3 min of ischemia following 3 min of reperfusion, performed three times before ischemia/reperfusion. Salivary secretion, histological changes, alterations of tight junctions, myeloperoxidase activity, cellular apoptosis, and reactive oxygen species levels were detected. In ischemia/reperfusion glands, rising acute-inflammation responses, reduced tight-junction width, and increased myeloperoxidase activity, reactive oxygen species levels, and apoptotic cell numbers were observed, along with secretory dysfunction, especially at 1 and 12 h post-reperfusion, which seemed to gradually return to normal by 72 h post-reperfusion. In contrast, ischemia preconditioning showed the potential to ameliorate the injury-stress responses caused by ischemia/reperfusion. Our study revealed that ischemia/reperfusion could cause a series of injury-stress responses and ultimately lead to hyposecretion, independently of the parasympathetic nerve supply, which might play an important role in the early-phase dysfunction of the transplanted glands. Ischemia preconditioning could protect the involved glands and improve ischemia/reperfusion-induced hyposecretion.

A novel role for synaptic acetylcholinesterase as an apoptotic deoxyribonuclease

In addition to terminating neurotransmission by hydrolyzing acetylcholine, synaptic acetylcholinesterase (AChES) has been found to have a pro-apoptotic role. However, the underlying mechanism has rarely been investigated. Here, we report a nuclear translocation-dependent role for AChES as an apoptotic deoxyribonuclease (DNase). AChES polypeptide binds to and cleaves naked DNA at physiological pH in a Ca(2+)-Mg(2+)-dependent manner. It also cleaves chromosomal DNA both in pre-fixed and in apoptotic cells. In the presence of a pan-caspase inhibitor, the cleavage still occurred after nuclear translocation of AChES, implying that AChES-DNase acts in a CAD- and EndoG-independent manner. AChE gene knockout impairs apoptotic DNA cleavage; this impairment is rescued by overexpression of the wild-type but not (aa 32-138)-deleted AChES. Furthermore, in comparison with the nuclear-localized wild-type AChES, (aa 32-138)-deleted AChES loses the capacity to initiate apoptosis. These observations confirm that AChES mediates apoptosis via its DNase activity.

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.

The protective effect of huperzine A against hepatic ischemia reperfusion injury in mice

BACKGROUND

Nowadays, hepatic ischemia reperfusion (HI/R) injury is regarded as a serious concern in clinical practices. Huperzine A (HupA) is an alkaloid isolated from the Chinese folk medicine huperzia serrate, which has possessed diverse pharmacological actions.

METHODS

A mouse model of HI/R was caused by clamping the hepatic artery, the hepatoportal vein, and the bile duct with a vascular clamp for 30 minutes followed by reperfusion for 6 hours under anesthesia. The sham group experienced the identical procedure without hepatic ischemia. The HupA group received an injection into the tail vein 5 minutes prior to HI/R at the doses of 167 and 500 μg/kg. The vehicle group was injected with physiological saline instead of HupA. The liver function was assessed by determinations of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Tissue levels of superoxide dismutase (SOD), catalase (CAT), malondiadehyde (MDA), and glutathione (GSH) were also measured spectrophotometrically. In addition, the activities of hepatic inflammatory mediators such as nuclear factor kappa B (NF-κB) p65, tumor necrosis factors-α (TNF-α, interleukin-1β (IL-1β) and IL-6 were also measured. Furthermore, the apoptotic damage was evaluated by measuring caspase-3 activity in hepatic tissues.

RESULTS

Treatment with HupA in mice at the doses of 167 and 500 μg/kg remarkably reduced serum ALT and AST activities in HupA-treated ischemic mice. Furthermore, HupA treatment could enhance the activities of hepatic tissue SOD, CAT, and GSH but decrease MDA tissue content. The activities of inflammatory cytokines including NF-κB p65, TNF-α, IL-1β and IL-6 were all decreased in ischemic mice treated with HupA. Colorimetric test results illustrated that a marked reduction of caspase-3 activity was found in the HupA-treated group compared with the vehicle group.

CONCLUSION

Our present data suggest that HupA has a protective role against HI/R injury of mice and antioxidative, anti-inflammatory, and antiapoptotic actions are involved in its protection.

Upregulation of Acetylcholinesterase Mediated by p53 Contributes to Cisplatin-Induced Apoptosis in Human Breast Cancer Cell

BACKGROUND

The expression of acetylcholinesterase (AChE) could be induced during apoptosis in various cell types. And reduced AChE expression either by siRNA could prevent apoptosis. However, the detailed mechanisms underlying the AChE regulation are largely unknown in human breast cancer cell.

MATERIAL AND METHODS

MCF-7 cells were cultured and treated by cisplatin in the absence or presence of p53 siRNA.

RESULTS

In this study, the regulation of AChE expression during apoptosis induced by cisplatin, a current used anticancer drug, was investigated in human breast cancer cell line MCF-7. Exposure of MCF-7 cells to cisplatin resulted in apoptosis in a time- and concentration-dependent manner. Meanwhile, the upregulated AChE and p53 were also observed during apoptosis. Silencing interfering RNA directed against p53 blocked the expression of AChE.

CONCLUSION

Taken together, these results suggested that AChE expression could be upregulated by the activation of p53 during apoptosis induced by cisplatin in MCF-7 cells.

Neuroprotective effects of bis(7)-tacrine in a rat model of pressure-induced retinal ischemia

The retinal ischemia-reperfusion model has been studied extensively and is an ideal animal model for studying clinical situations such as acute glaucoma and optic neuropathy. Our previous reports showed that bis(7)-tacrine had neuroprotective effects against glutamate-induced retinal ganglion cells damage through the drug's anti-NMDA receptor effects. Here, we investigated whether bis(7)-tacrine protects the retina from ischemic injury in a rat model. Retinal ischemia was induced by raising the intraocular pressure to 120 mmHg for 90 min. Rats received intraperitoneal injections of 0.2 mg/kg bis(7)-tacrine or saline at 30 min before ischemia, and then twice a day after retinal ischemia. Morphometric evaluation showed that bis(7)-tacrine dramatically reduced the retinal damage compared with the control group. Moreover, bis(7)-tacrine suppressed ischemia-induced reductions in a- and b-wave amplitudes of electroretinography. Protein levels of p53, the tumor suppressor gene known to induce apoptosis, were increased after ischemic injury, and treatment with bis(7)-tacrine reduced the expression of the protein. Our results suggest that bis(7)-tacrine has a neuroprotective effect against ischemic injury in the rat retina, possibly through the drug's anti-apoptotic effects. Bis(7)-tacrine may potentially be useful as a therapeutic drug in the management of ischemic retinal diseases.

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.

The role of microRNAs in the regulation of apoptosis in lung cancer and its application in cancer treatment

Lung cancer remains to be one of the most common and serious types of cancer worldwide. While treatment is available, the survival rate of this cancer is still critically low due to late stage diagnosis and high frequency of drug resistance, thus highlighting the pressing need for a greater understanding of the molecular mechanisms involved in lung carcinogenesis. Studies in the past years have evidenced that microRNAs (miRNAs) are critical players in the regulation of various biological functions, including apoptosis, which is a process frequently evaded in cancer progression. Recently, miRNAs were demonstrated to possess proapoptotic or antiapoptotic abilities through the targeting of oncogenes or tumor suppressor genes. This review examines the involvement of miRNAs in the apoptotic process of lung cancer and will also touch on the promising evidence supporting the role of miRNAs in regulating sensitivity to anticancer treatment.

Huperzine A attenuates hepatic ischemia reperfusion injury via anti-oxidative and anti-apoptotic pathways

Hepatic ischemia reperfusion (HI/R) injury may occur during liver transplantation and remains a serious concern in clinical practice. Huperzine A (HupA), an alkaloid isolated from the Chinese traditional medicine Huperzia serrata, has been demonstrated to possess anti‑oxidative and anti‑apoptotic properties. In the present study, a rat model of HI/R was established by clamping the hepatic artery, the hepatoportal vein and the bile duct with a vascular clamp for 30 min followed by reperfusion for 6 h under anesthesia. HupA was injected into the tail vein 5 min prior to the induction of HI/R at doses of 167 and 500 µg/kg. The histopathological assessment of the liver was performed using hematoxylin and eosin staining. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were assayed in the serum samples. The tissue levels of superoxide dismutase (SOD), catalase (CAT), malondiadehyde (MDA) and glutathione (GSH) were also measured spectrophotometrically. Furthermore, the protein expression of caspase‑3, Bcl‑2 and Bax in hepatic tissues was detected via western blot analysis. Treatment of Wistar rats with HupA at doses of 167 and 500 µg/kg markedly attenuated HI/R injury as observed histologically. In addition, the significant reductions of serum ALT and AST were observed in HupA‑treated ischemic rats. Furthermore, HupA treatment enhanced the activity of hepatic tissue SOD, CAT and GSH, but decreased the MDA tissue content. Western blot analysis revealed elevated levels of Bcl‑2 expression but decreased Bax and caspase‑3 tissue expression at the protein level in the HupA‑treated group. The present data suggest that HupA attenuates the HI/R injury of rats through its anti‑oxidative and anti‑apoptotic signaling pathways.

Qi-Dan Fang ameliorates adriamycin-induced nephrotic syndrome rat model by enhancing renal function and inhibiting podocyte injury

ETHNOPHARMACOLOGICAL RELEVANCE

Nephrotic syndrome (NS) is a clinical syndrome with a variety of causes, mainly characterized by heavy proteinuria. Podocyte injury plays a key role in proteinuria, one of the principal means for the control of NS is to prevent podocyte injury. Qi-Dan Fang consists of two of the most extensively applied herbal remedies among Traditional Chinese Medicine (TCM) (Radix Astragali Mongolici and Radix Salviae Miltiorrhizae, with a weight ratio of 5:1) which are specifically used for the treatment of various kidney diseases. In previous studies, we found that Qi-Dan Fang provides improvement to patients with adriamycin-induced nephrotic syndrome by alleviating proteinuria and serum lipid. The aim of this study is to study the efficiency of Qi-Dan Fang on NS model rat with renal dysfunction and podocyte injury, something which has not been carried out yet.

MATERIALS AND METHODS

The rats were divided into Normal, Model, Jin Gui Shen Qi Pill (4.12 g/kg), Qi-Dan Fang (3.09, 6.17 and 12.34 g/kg/d) groups, they were each given a single tail intravenous injection of Adriamycin (6.0 mg/kg) except for the Normal group and were orally administered dosages of Qi-Dian Fang and Jin Gui Shen Qi pills once daily for 7 weeks. Following the treatment, the content of cystation C (CysC), blood urea nitrogen (BUN), serum creatinine (Scr) were measured with an autobiochemical analyser. The pathomorphological changes to the glomeruli, the mRNA expressions of nephrin, podocin, CD2AP genes and p53, bax, bcl-2 proteins expressions were also carried out to probe the effects of Qi-Dan Fang.

RESULTS

(1) Qi-Dan Fang treatment raised the level of CysC in blood serum while lowering the content of BUN and Scr in the adriamycin-induced nephrotic syndrome rat model; (2) Long-term administration of Qi-Dan Fang was able to ameliorate pathomorphological change of glomeruli and repair the organization structure of Glomerulus; (3) Qi-Dan Fang could increase the mRNA expression of nephrin, podocin and CD2AP genes, down-regulate the expression of p53, bax proteins, while increased bcl-2 protein to protect the podocyte and restore Glomerular selective filtration function.

CONCLUSIONS

Results of our present studies reveal that Qi-Dan Fang is able to enhance renal function, inhibit podocyte injury to provide improvements to the Adriamycin-induced nephrotic syndrome.

Hsa-miR-132 regulates apoptosis in non-small cell lung cancer independent of acetylcholinesterase

MiR-132 is enriched in the central nerve system and is thought to be involved in neuronal development, maturation and function, and to be associated with several neurological disorders including Alzheimer's disease. In addition to its documented neuronal functions, an emerging role for miR-132 in tumorigenesis has been suggested. Recently, hsa-miR-132 was shown to be modulated in different tumor types. However, its role in non-small cell lung cancer (NSCLC) remains unclear. Here, we show that hsa-miR-132 can initiate apoptosis in NSCLC cells to dramatically attenuate tumor formation in nude mice independent of its effect on the proliferation/apoptosis-associated gene, acetylcholinesterase (AChE). Interestingly, hsa-miR-132 has no pro-apoptotic effect in normal pulmonary trachea epithelium. Taken together, these results suggest that hsa-miR-132 represses NSCLC growth by inducing apoptosis independent of AChE.

Synaptic acetylcholinesterase targeted by microRNA-212 functions as a tumor suppressor in non-small cell lung cancer

Acetylcholinesterase expression is modulated in various types of tumor, which suggests it is associated with tumor development; however, the mechanism of acetylcholinesterase gene regulation in tumors remains unclear. Here, we report that acetylcholinesterase is aberrantly expressed in non-small cell lung cancer and is an evolutionarily conserved functional target of miR-212. Acetylcholinesterase expression was negatively regulated by miR-212 in vitro and was inversely correlated with miR-212 expression in vivo. In addition, acetylcholinesterase levels were increased, and miR-212 levels decreased, in non-small cell lung cancer cells during cisplatin-induced apoptosis. We further determined that acetylcholinesterase acted as a pro-apoptotic gene in non-small cell lung cells; and attenuated the growth of xenografts in nude mice when upregulated. In contrast, elevated miR-212 levels preserved the protective effect of acetylcholinesterase silencing by RNA interference against cisplatin-induced apoptosis, whereas restoration of miR-212-resistant synaptic acetylcholinesterase expression inhibited the miR-212 anti-apoptotic function. The results demonstrated that miR-212 exerted an anti-apoptotic effect through direct repression of synaptic acetylcholinesterase expression in non-small cell lung cancer cells. Taken together, our study revealed that synaptic acetylcholinesterase may be a tumor suppressor and is modulated by miR-212 in non-small cell lung cancer.

Acetylcholinesterase deficiency decreases apoptosis in dopaminergic neurons in the neurotoxin model of Parkinson's disease

The apoptosis pathway has been proposed to be involved in causing neuronal cell death in the pathogenesis of Parkinson's disease. However, the details of this pathway are poorly understood. Previous research has shown increased acetylcholinesterase expression during apoptosis in various cell types, which suggests that acetylcholinesterase has a potential role in neuronal cell death. In this study, we found that acetylcholinesterase protein expression increased and caspase-3 was activated in PC12 cells treated with 1-methyl-4-phenylpyridinium. Furthermore, the genetic or pharmacological inhibition of acetylcholinesterase was shown to protect PC12 cells from MPP+ induced apoptotic cell death. To study the function of acetylcholinesterase as a mechanism of neuronal cell death in vivo, we subsequently established a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine Parkinson's disease mouse model utilizing acetylcholinesterase-deficient mice. Studies in these mice revealed reduced dopaminergic neuron loss and lower expression levels of apoptotic proteins in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated heterozygous mice compared to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated wild-type mice. We conclude that it is highly probable that acetylcholinesterase is involved in the pathogenesis of the neurotoxin model of Parkinson's disease via apoptosis. Specifically, a deficiency or inhibition of acetylcholinesterase can decrease apoptosis and protect dopaminergic neurons in the neurotoxin model of Parkinson's disease.

Lithium treatment induces proteasomal degradation of over-expressed acetylcholinesterase (AChE-S) and inhibit GSK3β

Lithium is one of the most widely used mood-stabilizing agents for the treatment of bipolar disorder. Lithium is also a potent inhibitor of glycogen synthase kinase-3β (GSK3β) activity, which is linked to Alzheimer's disease (AD). In experiments with cultured HEK293T cells, we show here that GSK3β stabilizes synaptic acetylcholinesterase (AChE-S), a critical component of AD development. Cells treated with lithium exhibited rapid proteasomal degradation of AChE-S. Furthermore treatment of the cells with MG132, an inhibitor of the 26S proteasome, prevented the destabilizing effect of lithium on AChE-S. Taken together, these findings suggest that regulation of AChE-S protein stability may be an important biological target of lithium therapy.

Acetylcholinesterase involvement in apoptosis

To date, more than 40 different types of cells from primary cultures or cell lines have shown AChE expression during apoptosis and after the induction apoptosis by different stimuli. It has been well-established that increased AChE expression or activity is detected in apoptotic cells after apoptotic stimuli in vitro and in vivo, and AChE could be therefore used as a marker of apoptosis. AChE is not an apoptosis initiator, but the cells in which AChE is overexpressed undergo apoptosis more easily than controls. Interestingly, cells with downregulated levels of AChE are not sensitive to apoptosis induction and AChE deficiency can protect against apoptosis. Some tumor cells do not express AChE, but when AChE is introduced into a tumor cell, the cells cease to proliferate and undergo apoptosis more readily. Therefore, AChE can be classified as a tumor suppressor gene. AChE plays a pivotal role in apoptosome formation, and silencing of the AChE gene prevents caspase-9 activation, with consequent decreased cell viability, nuclear condensation, and poly (adenosine diphosphate-ribose) polymerase cleavage. AChE is translocated into the nucleus, which may be an important event during apoptosis. Several questions still need to be addressed, and further studies that address the non-classical function of AChE in apoptosis are needed.

Induction of plasma acetylcholinesterase activity in mice challenged with organophosphorus poisons

The restoration of plasma acetylcholinesterase activity in mice following inhibition by organophosphorus pesticides and nerve agents has been attributed to synthesis of new enzyme. It is generally assumed that activity levels return to normal, are stable and do not exceed the normal level. We have observed over the past 10 years that recovery of acetylcholinesterase activity levels in mice treated with organophosphorus agents (OP) exceeds pretreatment levels and remains elevated for up to 2 months. The most dramatic case was in mice treated with tri-cresyl phosphate and tri-ortho-cresyl phosphate, where plasma acetylcholinesterase activity rebounded to a level 250% higher than the pretreatment activity. The present report summarizes our observations on plasma acetylcholinesterase activity in mice treated with chlorpyrifos, chlorpyrifos oxon, diazinon, tri-ortho-cresyl phosphate, tri-cresyl phosphate, tabun thiocholine, parathion, dichlorvos, and diisopropylfluorophosphate. We have developed a hypothesis to explain the excess acetylcholinesterase activity, based on published observations. We hypothesize that acetylcholinesterase activity is induced when cells undergo apoptosis and that consequently there is a rise in the level of plasma acetylcholinesterase.

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.