[Eserine, in Crooked House and Curtain]

Eserine, well-known as physostigmine, is classified as an alkaloid. It is a cholinesterase inhibitor and appears in Agatha Christie's novel entitled, Crooked House and Curtain: Poirot's Last Case. In clinical medicine, eserine was used as an ophthalmic treatment for glaucoma and considered as a treatment for myasthenia gravis, Alzheimer's disease, and hereditary cerebellar ataxias. Currently, it is used as a treatment for anticholinergic poisoning.

Participation of Modulating Rhythms of the Decasecond Range in Intersystem Correlation Interactions in Early Rat Ontogeny

On newborn non-narcotized 1-day-old (P1) and 16-day-old (P16) rats, a detailed analysis of intersystem somatovisceral interactions (ISI) mediated by decasecond (D1, 5-50 sec) range modulating rhythms was performed. Correlation interactions of the main body systems - cardiovascular, respiratory and somatomotor systems in norm and under conditions of changes in the level of cholinergic regulation were studied. Spectral correlation analysis was used to determine the participation of D1 range modulating rhythms in ISI. It was found that at P1, D1 range rhythms do not play a significant role in integrative processes. In P16 the activation of cholinergic structures, caused by the introduction of the acetylcholinesterase inhibitor physostigmine (eserine) leads to significant disturbances in the degree of correlation in the D1 range. Blockade of muscarinic and nicotinic cholinoreceptors does not alter the degree of correlation of systemic pairs in the slow-wave region (D1-low, 8-50 sec) of the D1 range. Under the influence on the cholinoreactive structures, the most significant changes in the degree of correlation in the ISI affect the somatorespiratory systemic pair. The results obtained indicate that the representation of the slow-wave components of D1 range modulating rhythms involved in the ISI increase during the first weeks of postnatal ontogeny. Changes in the level of cholinergic activation do not directly influence on ISI mediated by D1-low sub-band rhythms.

Ventral Tegmental Area M5 Muscarinic Receptors Mediate Effort-Choice Responding and Nucleus Accumbens Dopamine in a Sex-Specific Manner

Optimization of effort-related choices is impaired in depressive disorders. Acetylcholine (ACh) and dopamine (DA) are linked to depressive disorders, and modulation of ACh tone in the ventral tegmental area (VTA) affects mood-related behavioral responses in rats. However, it is unknown if VTA ACh mediates effort-choice behaviors. Using a task of effort-choice, rats can choose to lever press on a fixed-ratio 5 (FR5) schedule for a more-preferred food or consume freely available, less-preferred food. VTA administration of physostigmine (1 μg and 2 μg/side), a cholinesterase inhibitor, reduced FR5 responding for the more-preferred food while leaving consumption of the less-preferred food intact. VTA infusion of the M5 muscarinic receptor negative allosteric modulator VU6000181 (3 μM, 10 μM, 30 μM/side) did not affect lever pressing or chow consumption. However, VU6000181 (30 μM/side) coadministration with physostigmine (2 μg/side) attenuated physostigmine-induced decrease in lever pressing in female and male rats and significantly elevated lever pressing above vehicle baseline levels in male rats. In in vivo voltammetry experiments, VTA infusion of combined physostigmine and VU6000181 did not significantly alter evoked phasic DA release in the nucleus accumbens core (NAc) in female rats. In male rats, combined VTA infusion of physostigmine and VU6000181 increased phasic evoked DA release in the NAc compared with vehicle, physostigmine, or VU6000181 infusion alone. These data indicate a critical role and potential sex differences of VTA M5 receptors in mediating VTA cholinergic effects on effort choice behavior and regulation of DA release. SIGNIFICANCE STATEMENT: Effort-choice impairments are observed in depressive disorders, which are often treatment resistant to currently available thymoleptics. The role of ventral tegmental area (VTA) acetylcholine muscarinic M5 receptors, in a preclinical model of effort-choice behavior, is examined. Using the selective negative allosteric modulator of the M5 receptor VU6000181, we show the role of VTA M5 receptors on effort-choice and regulation of dopamine release in the nucleus accumbens core. This study supports M5 receptors as therapeutic targets for depression.

Pretreatment of rhesus monkeys with transdermal patches containing physostigmine and procyclidine: implications of the delivery system for the potential application against VX nerve agent intoxication in humans

Physostigmine (Phs) is a reversible inhibitor of acetylcholinesterase (AChE) that penetrates the blood-brain barrier (BBB) and could be used to protect the central nervous system (CNS) against the effects of nerve agents. For prophylactic effectiveness, long, steady, and adequate inhibition of AChE activity by Phs is needed to broadly protect against the CNS effects of nerve agents. Here, we evaluated the efficacy of transdermal patches containing Phs and procyclidine (PC) as prophylactic agents. Patches (25 cm²) containing 4.4 mg Phs and 17.8 mg PC had a protective ratio of approximately 78.6-fold in rhesus monkeys challenged with VX nerve agent and given an antidote. Physiologically based pharmacokinetic model in conjunction with an indirect pharmacodynamic (PBPK/PD) was developed for Phs and scaled to rhesus monkeys. The model was able to reproduce the concentration profile and inhibitory effect on AChE of Phs in monkeys, as evidenced by correlation coefficients of 0.994 and 0.992 for 25 cm² and 49 cm² patches, respectively (i.e., kinetic data), and 0.989 and 0.968 for 25 cm² and 49 cm² patches, respectively (i.e., dynamic data). By extending the monkey PBPK/ PD model to humans, the effective human dose was predicted to be five applications of a 25 cm² patch (i.e., 22 mg Phs), and two applications of a 49 cm² patch (i.e., 17.4 mg Phs). Therefore, given that patch application of Phs in rhesus monkeys has a prolonged effect (namely, AChE inhibition of 19.6% for the 25 cm² patch and 23.0% for the 49 cm² patch) for up to 216 h, patch formulation of Phs may provide similar protection against nerve agent intoxication in humans.

Dose-Dependent Heart Rhythm Disturbance Occurring in Response to the Activation of Choline-Reactive Structures in Early Rat Ontogeny

The effect of dose-dependent activation of cholinoreactive structures on the severity of sinus bradycardia occurring in some intact newborn rats during the first weeks after birth was analyzed in non-narcotized one-day-old (P1) and 16-day-old (P16) rats. The parameters of low-amplitude bradycardic oscillations of heart rhythm in norm and after administration of the acetylcholinesterase inhibitor physostigmine (eserine) in different doses (¹/₁₀₀, ¹/₁₀, and ³/₄LD₅₀) to rats were studied. The maximum increase in the power of low-amplitude brady-cardic oscillations was achieved during moderate activation of cholinoreactive structures after injection of eserine in a dose of ¹/₁₀LD₅₀. Further increase in acetylcholine level led to disappearance of the sinus rhythm and development of pathological bradycardia. The data obtained indicate the immaturity of the mechanisms of heart rhythm regulation in rats immediately after birth. During activation of cholinoreactive structures, the severity of bradycardia oscillations increases exponentially at P1 and has an inverse exponential character at P16, which indicates a high risk of cardiac rhythmogenesis disorders and dysrhythmia development in newborn rats under conditions of excessive enhancement of cholinergic activation.

Discovery of new acetylcholinesterase inhibitors for Alzheimer's disease: virtual screening and in vitro characterisation

For more than two decades, the development of potent acetylcholinesterase (AChE) inhibitors has been an ongoing task to treat dementia associated with Alzheimer's disease and improve the pharmacokinetic properties of existing drugs. In the present study, we used three docking-based virtual screening approaches to screen both ZINC15 and MolPort databases for synthetic analogs of physostigmine and donepezil, two highly potent AChE inhibitors. We characterised the in vitro inhibitory concentration of 11 compounds, ranging from 14 to 985 μM. The most potent of these compounds, S-I 26, showed a fivefold improved inhibitory concentration in comparison to rivastigmine. Moderate inhibitors carrying novel scaffolds were identified and could be improved for the development of new classes of AChE inhibitors.

Effects of Increased Central Cholinergic Activity on the Metabolic Challenge Induced by Submaximal Exercise in Rats: Adrenomedullary Secretion Influences

AIM

The aim of this study was to assess the influence of adrenomedullary secretion on the plasma glucose, lactate, and free fatty acids (FFAs) during running exercise in rats submitted to intracerebroventricular (i.c.v.) injection of physostigmine (PHY). PHY i.c.v. was used to activate the central cholinergic system.

METHODS

Wistar rats were divided into sham-saline (sham-SAL), sham-PHY, adrenal medullectomy-SAL, and ADM-PHY groups. The plasma concentrations of glucose, lactate, and FFAs were determined immediately before and after i.c.v. injection of 20 μL of SAL or PHY at rest and during running exercise on a treadmill.

RESULTS

The i.c.v. injection of PHY at rest increased plasma glucose in the sham group, but not in the ADM group. An increase in plasma glucose, lactate, and FFAs mobilization from adipose tissue was observed during physical exercise in the sham-SAL group; however, the increase in plasma glucose was greater with i.c.v. PHY. Moreover, the hyperglycemia induced by exercise and PHY in the ADM group were blunted by ADM, whereas FFA mobilization was unaffected.

CONCLUSION

These results indicate that there is a dual metabolic control by which activation of the central cholinergic pathway increases plasma glucose but not FFA during rest and exercise, and that this hyperglycemic response is dependent on adrenomedullary secretion.

A novel in vitro assay model developed to measure both extracellular and intracellular acetylcholine levels for screening cholinergic agents

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.

Pharmacological support to anti-arthritic prospective of physostigmine: a new approach

Rheumatoid arthritis (RA) is a slowly progressing inflammatory autoimmune disease. Several features are involved in the RA pathogenesis in addition to environmental and genetic factors. Previously it has been reported that acetyl cholinesterase (AChE) activity is enhanced in old age and may contribute in the progression of RA. The current experimental work was projected to assess the activity of physostigmine (a cholinesterase inhibitor) for treatment of RA. In vitro and in vivo approaches were used for such evaluation. However, enzyme linked immunosorbent assays (ELISA) was performed to determine the concentrations of Prostaglandins E2 (PGE2) and tumor necrosis factor-α in arthritic rats after treatment with physostigmine. Moreover, anti-oxidant assays were employed to calculate the level of super oxide dismutase (SOD) and catalase peroxidase (CAT) in tissue of treated animals. The results claimed the dose dependent protective and stabilizing effect of physostigmine on denaturation of albumin (egg and bovine serum) protein and human red blood cell membrane, respectively, through in vitro studies. Furthermore, the physostigmine (10 and 20 mg/kg) significantly (p < 0.001) reduced the swelling of paw after induction of arthritis with formaldehyde or complete Freund's adjuvant (CFA) as compared to arthritic control animals. Moreover, significant (p < 0.001) reduction in the levels of inflammatory markers (PGE2 and TNF-α) at doses of 10 and 20 mg/kg of physostigmine has been observed in ELISA test. Likewise, there was a prominent rise in levels of SOD and CAT in animals treated with physostigmine. These findings pharmacologically conclude the anti-arthritic effect of physostigmine.

Examining the role of muscarinic M5 receptors in VTA cholinergic modulation of depressive-like and anxiety-related behaviors in rats

Acetylcholine is implicated in mood disorders including depression and anxiety. Increased cholinergic tone in humans and rodents produces pro-depressive and anxiogenic-like effects. Cholinergic receptors in the ventral tegmental area (VTA) are known to mediate these responses in male rats, as measured by the sucrose preference test (SPT), elevated plus maze (EPM), and the forced swim test (FST). However, these effects have not been examined in females, and the VTA muscarinic receptor subtype(s) mediating the pro-depressive and anxiogenic-like behavioral effects of increased cholinergic tone are unknown. We first examined the behavioral effects of increased VTA cholinergic tone in male and female rats, and then determined whether VTA muscarinic M5 receptors were mediating these effects. VTA infusion of the acetylcholinesterase inhibitor physostigmine (0.5 μg, 1 μg and 2 μg/side) in males and females produced anhedonic-like, anxiogenic, pro-depressive-like responses on the SPT, EPM, and FST. In females, VTA administration of the muscarinic M5 selective negative allosteric modulator VU6000181 (0.68 ng, 2.3 ng, 6.8 ng/side for a 3 μM, 10 μM, 30 μM/side infusion) did not alter SPT, EPM nor FST behavior. However, in males intra-VTA infusion of VU6000181 alone reduced time spent immobile on the FST. Furthermore, co-infusion of VU6000181 with physostigmine, in male and female rats, attenuated the pro-depressive and anxiogenic-like behavioral responses induced by VTA physostigmine alone, in the SPT, EPM, and FST. Together, these data reveal a critical role of VTA M5 receptors in mediating the anhedonic, anxiogenic, and depressive-like behavioral effects of increased cholinergic tone in the VTA.

Low acetylcholine during early sleep is important for motor memory consolidation

The synaptic homeostasis theory of sleep proposes that low neurotransmitter activity in sleep optimizes memory consolidation. We tested this theory by asking whether increasing acetylcholine levels during early sleep would weaken motor memory consolidation. We trained separate groups of adult mice on the rotarod walking task and the single pellet reaching task, and after training, administered physostigmine, an acetylcholinesterase inhibitor, to increase cholinergic tone in subsequent sleep. Post-sleep testing showed that physostigmine impaired motor skill acquisition of both tasks. Home-cage video monitoring and electrophysiology revealed that physostigmine disrupted sleep structure, delayed non-rapid-eye-movement sleep onset, and reduced slow-wave power in the hippocampus and cortex. Additional experiments showed that: (1) the impaired performance associated with physostigmine was not due to its effects on sleep structure, as 1 h of sleep deprivation after training did not impair rotarod performance, (2) a reduction in cholinergic tone by inactivation of cholinergic neurons during early sleep did not affect rotarod performance, and (3) stimulating or blocking muscarinic and nicotinic acetylcholine receptors did not impair rotarod performance. Taken together, the experiments suggest that the increased slow wave activity and inactivation of both muscarinic and nicotinic receptors during early sleep due to reduced acetylcholine contribute to motor memory consolidation.

(-)-Phenserine and the prevention of pre-programmed cell death and neuroinflammation in mild traumatic brain injury and Alzheimer's disease challenged mice

Mild traumatic brain injury (mTBI) is a risk factor for neurodegenerative disorders, such as Alzheimer's disease (AD) and Parkinson's disease (PD). TBI-derived neuropathologies are promoted by inflammatory processes: chronic microgliosis and release of pro-inflammatory cytokines that further promote neuronal dysfunction and loss. Herein, we evaluated the effect on pre-programmed cell death/neuroinflammation/synaptic integrity and function of (-)-Phenserine tartrate (Phen), an agent originally developed for AD. This was studied at two clinically translatable doses (2.5 and 5.0 mg/kg, BID), in a weight drop (concussive) mTBI model in wild type (WT) and AD APP/PSEN1 transgenic mice. Phen mitigated mTBI-induced cognitive impairment, assessed by Novel Object Recognition and Y-maze behavioral paradigms, in WT mice. Phen fully abated mTBI-induced neurodegeneration, evaluated by counting Fluoro-Jade C-positive (FJC+) cells, in hippocampus and cortex of WT mice. In APP/PSEN1 mice, degenerating cell counts were consistently greater across all experimental groups vs. WT mice. mTBI elevated FJC+ cell counts vs. the APP/PSEN1 control (sham) group, and Phen similarly mitigated this. Anti-inflammatory effects on microglial activation (IBA1-immunoreactivity (IR)) and the pro-inflammatory cytokine TNF-α were evaluated. mTBI increased IBA1-IR and TNF-α/IBA1 colocalization vs. sham, both in WT and APP/PSEN1 mice. Phen decreased IBA1-IR throughout hippocampi and cortices of WT mice, and in cortices of AD mice. Phen, likewise, reduced levels of IBA1/TNF-α-IR colocalization volume across all areas in WT animals, with a similar trend in APP/PSEN1 mice. Actions on astrocyte activation by mTBI were followed by evaluating GFAP, and were similarly mitigated by Phen. Synaptic density was evaluated by quantifying PSD-95+ dendritic spines and Synaptophysin (Syn)-IR. Both were significantly reduced in mTBI vs. sham in both WT and APP/PSEN1 mice. Phen fully reversed the PSD-95+ spine loss in WT and Syn-IR decrease in both WT and APP/PSEN1 mice. To associate immunohistochemical changes in synaptic markers with function, hippocampal long term potentiation (LTP) was induced in WT mice. LTP was impaired by mTBI, and this impairment was mitigated by Phen. In synopsis, clinically translatable doses of Phen ameliorated mTBI-mediated pre-programmed cell death/neuroinflammation/synaptic dysfunction in WT mice, consistent with fully mitigating mTBI-induced cognitive impairments. Phen additionally demonstrated positive actions in the more pathologic brain microenvironment of AD mice, further supporting consideration of its repurposing as a treatment for mTBI.

Cholinergic rescue of neurocognitive insult following third-trimester equivalent alcohol exposure in rats

Neonatal ethanol exposure during the third trimester equivalent of human pregnancy in the rat significantly impairs hippocampal and prefrontal neurobehavioral functioning. Postnatal day [PD] 4-9 ethanol exposure in rats disrupts long-term context memory formation, resulting in abolished post-shock and retention test freezing in a variant of contextual fear conditioning called the Context Preexposure Facilitation Effect (CPFE). This behavioral impairment is accompanied by disrupted medial prefrontal, but not dorsal hippocampal expression of the immediate early genes (IEGs) c-Fos, Arc, Egr-1, and Npas4 (Heroux, Robinson-Drummer, Kawan, Rosen, & Stanton, 2019). The current experiment examined if systemic administration of the acetylcholinesterase inhibitor physostigmine (PHY) prior to context learning would rescue prefrontal IEG expression and freezing in the CPFE. From PD4-9, Long-Evans rats received oral intubation of ethanol (EtOH; 5.25 g/kg/day) or sham-intubation (SI). Rats received a systemic injection of saline (SAL) or PHY (0.01 mg/kg) prior to all three phases (Experiment 1) or just context exposure (Experiment 2) in the CPFE from PD31-33. A subset of rats were sacrificed 30 min after context learning to assay changes in IEG expression in the medial prefrontal cortex (mPFC), dorsal hippocampus (dHPC), and ventral hippocampus (vHPC). Administration of PHY prior to all three phases or just context learning rescued both post-shock and retention test freezing in the CPFE in EtOH rats without altering performance in SI rats. EtOH-SAL rats had significantly reduced mPFC but not dHPC expression of c-Fos, Arc, Egr-1, and Npas4. EtOH-PHY treatment rescued mPFC expression of c-Fos in ethanol-exposed rats and increased Arc and Npas4 regardless of dosing condition. While there was no effect of PHY on dHPC or vHPC expression of Arc, Egr-1, or Npas4, this treatment significantly boosted hippocampal expression of c-Fos regardless of ethanol treatment. These findings implicate impaired cholinergic and prefrontal function in cognitive deficits arising from 3rd-trimester equivalent alcohol exposure.

Effects of Neostigmine and Physostigmine on Activity of Na+,K+-ATPase in Various Subdivisions of Rat Brain

The effects of intramuscular administration of neostigmine and physostigmine on Na⁺,K⁺-ATPase activity in various cerebral subdivisions were examined in rats. In CNS and peripheral tissues, both agents rapidly and significantly reduced activity of cholinesterases by 30-50%. The development of intoxication did not change the marker indices of stress reaction. In the cerebral cortex, physostigmine increased Na⁺,K⁺-ATPase activity, whereas neostigmine suppressed it. In addition, neostigmine decreased activity of this enzyme in the cerebellum. In contrast, both agents produced no effects on Na⁺,K⁺-ATPase activity in the striatum. The data corroborate the view on functional interaction between Na⁺,K⁺-ATPase and nicotinic cholinoreceptors in rat cerebral cortex.

Hippocampal α7 nicotinic ACh receptors contribute to modulation of depression-like behaviour in C57BL/6J mice

BACKGROUND AND PURPOSE

Clinical studies have identified links between cholinergic signalling and depression in human subjects. Increased cholinergic signalling in hippocampus also increases behaviours related to anxiety and depression in mice, which can be reversed by ACh receptor antagonists.

EXPERIMENTAL APPROACH

As the α7 subunit of the nicotinic ACh receptor (nAChR) is highly expressed in hippocampus, we determined whether blocking α7 nAChRs could reverse the effects of increased ACh signalling in anxiety- and depression-related behaviours in mice.

KEY RESULTS

Administration of the α7 nAChR agonist GTS-21 had no effect in tail suspension or forced swim tests. Conversely, the α7 nAChR antagonist methyllycaconitine (MLA) induced significant antidepressant-like effects in male mice in these paradigms, consistent with previous studies, but this was not observed in female mice. MLA also decreased physostigmine-induced c-fos immunoreactivity (a marker of neuronal activity) in hippocampus. Local knockdown of α7 nAChRs in hippocampus had no effect on its own but decreased a subset of depression-like phenotypes induced by physostigmine in male mice. Few effects of α7 nAChR knockdown were observed in depression-like behaviors in female mice, possibly due to a limited response to physostigmine. There was no significant effect of hippocampal α7 nAChR knockdown on anxiety-like phenotypes in male mice. However, a modest increase in anxiety-like behavior was observed in female mice infused with a scrambled control vector in response to physostigmine administration, that was not seen after a7 nAChR knockdown in the hippocampus.

CONCLUSIONS AND IMPLICATIONS

These results suggest that ACh signalling through α7 nAChRs in the hippocampus contributes to regulation of a subset of depression-like behaviours when ACh is increased, as can occur under stressful conditions. These studies also provide evidence for sex differences that may be relevant for treatments of mood disorders based on cholinergic signalling.

LINKED ARTICLES

This article is part of a themed section on Nicotinic Acetylcholine Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.11/issuetoc.

The impact of bilateral vagotomy on the physostigmine-induced airway constriction in ferrets

Vagal innervations have a great role in the respiratory function and are the main route of signal transmission from respiratory neural centers into the trachea and others conducting airways. We have investigated the role of central mechanisms related to vagal neural pathways and the cholinergic outflow in tracheobronchial smooth muscle tone and lung mechanics parameters. Parameters of lung mechanics such as lung resistance (RL), dynamic compliance (Cdyn) and pressure in bypassed tracheal segment (Ptseg) were measured before and after vagotomy and asphyxia test. Before vagotomy (BV), the control measurements were obtained and physostigmine was administered systemically, in increasing dose 10, 40 and 100μg/kg body weight (bw) with 15min interval between doses. After vagotomy (AV), administration of physostigmine with the same doses as BV has been done and the asphyxia challenge was conducted as per study protocol. The values of Ptseg and RL after physostigmine administration, BV vs. AV, respectively, at maximal dose of 100μg/kg bw were 32.5±3.3cm H₂O, and 10.6±1.5cm H₂O (p<0.0001); 0.16±0.04cm H₂O/mL/s, and 0.067±0.006cm H₂O/mL/s AV (P<0.05). The Cydn values were affected after physostigmine administration only at the lowest dose of 10μg/kg bw, and BV was 0.75±0.05mL/cm H₂O vs. 0.53±0.04mL/cm H₂O AV (P<0.004). Cholinergic outflow produced increases in tracheal tone, lung resistance and a decrease in dynamic compliance before, but not after vagotomy. Our results show the high impact of central neuronal mechanism in parameters of lung mechanics and respiration. This study indicates that vagal nerves have a crucial role, in the transmission of impulses initiated from central nervous system, in regulating the respiration by contraction or relaxation of airway smooth muscle tone.

EXPRESSION AND EFFECTS OF MUTANT Bombyx mori ACETYLCHOLINESTRASE1 IN BmN CELLS

The main mechanism of toxicity of organophosphate (OP) and carbamate (CB) insecticides is their irreversible binding and inhibition of acetylcholinestrase (AChE), encoded by ace1 (acetylcholinestrase gene 1), leading to eventual death of insects. Mutations in AChE may significantly reduce insects susceptibility to these pesticides. Bombyx mori is an important beneficial insect, and no OP- or CB-resistant strains have been generated. In this study, wild-type ace1 (wace1) and mutant ace1 (mace1) were introduced into BmN cells, confirmed by screening and identification. The expression of wace1 and mace1 in the cells was confirmed by Western blot and their expression levels were about 21-fold higher than the endogenous ace1 level. The activities of AChE in wace1 and mace1 transgenic cells were 10.6 and 20.2% higher compared to control cells, respectively. mace1 transgenic cells had higher remaining activity than wace1 transgenic cells under the treatment of physostigmine (a reversible cholinesterase inhibitor) and phoxim (an OP acaricide). The results showed that ace1 transgene can significantly improve ace1 expression, and ace1 mutation at a specific site can reduce the sensitivity to AChE inhibitors. Our study provides a new direction for the exploration of the relationship between AChE mutations and drug resistance.

Ventral tegmental area muscarinic receptors modulate depression and anxiety-related behaviors in rats

Cholinergic and dopaminergic mechanisms within the mesolimbic dopamine system are suggested to play a role in the manifestation of depression and anxiety-related disorders. However, despite the fact that cholinergic mechanisms in the ventral tegmental area (VTA) highly regulate dopamine activity, the role of VTA cholinergic mechanisms in depression-related behaviors is relatively unknown. Here we sought to determine whether enhancing cholinergic tone in the VTA would alter depression and anxiety-related behavior in the forced swim test (FST), elevated plus maze (EPM) and sucrose preference test (SPT). Adult Sprague Dawley male rats received VTA infusion of the acetylcholinesterase inhibitor, physostigmine (0, 1, 2μg/side), immediately prior to the FST, EPM, or SPT. Physostigmine administration increased immobility time in the FST, decreased time spent on open arms in the EPM, and decreased sucrose preference. We also examined whether activation of VTA muscarinic receptors was sufficient to alter behavior in the FST and EPM. Similar to physostigmine, VTA infusion of the muscarinic receptor agonist, pilocarpine (0, 3, 30μg/side), increased immobility time in the FST and decreased time spent on open arms in the EPM. These data suggest that enhanced VTA cholinergic tone promotes pro-depressive and anxiogenic-like effects and demonstrate that specific activation of VTA muscarinic receptors is also sufficient to induce pro-depressive and anxiogenic responses. Together, these findings reveal a novel role of VTA cholinergic, and specifically muscarinic receptor, mechanisms in mediating responses to stress and anxiety.

[Anti-inflammatory effect of acetylcholine on lipopolysaccharide induced inflammatory response of alveolar macrophages]

OBJECTIVE

To observe the effect of acetylcholine (ACh) on lipopolysaccharide (LPS) induced inflammatory model of rat alveolar macrophages, and to observe the effect of the acetylcholinesterase inhibitor physostigmine (Phy) on the anti-inflammatory effect of ACh.

METHODS

The rat alveolar macrophages NR8383 were cultured in vitro, which were divided into five groups: blank control group, LPS group (stimulated with 1 mg/L LPS for 12 hours), LPS + ACh group (0.01, 0.1, 1, 10, 100 μmol/L of ACh were added for 5 minutes before LPS stimulation), LPS + Phy group (1 mmol/L Phy was added for 5 minutes before LPS stimulation), and LPS + ACh + Phy group (1 mmol/L Phy and 10 μmol/L ACh were added for 5 minutes before LPS stimulation). The supernatants were collected in each group, the enzyme-linked immunosorbent assay (ELISA) was used to assay the contents of tumor necrosis factor-α (TNF-α), interleukins (IL-1β, and IL-6). The activity of acetylcholine esterase (AChE ) in the supernatant was also determined.

RESULTS

(1) The contents of TNF-α (ng/L: 605.09 ± 57.13 vs. 34.07 ± 8.62), IL-1β (ng/L: 377.09 ± 28.55 vs. 32.33 ± 10.62) and IL-6 (ng/L: 558.04 ± 77.45 vs. 42.62 ± 11.21) in the LPS group were significantly higher than those in the blank control group (all P < 0.05). These results indicated that the inflammatory model of rat alveolar macrophages was constructed successfully. (2) ACh with the final concentrations of 0.01, 0.1, and 1 μmol/L had less influence on the production of TNF-α, IL-1β and IL-6 in the culture supernatants of alveolar macrophages stimulated with LPS compared with LPS group (all P > 0.05). Nevertheless, 10 μmol/L and 100 μmol/L ACh notably reduced the production of TNF-α (ng/L: 451.19 ± 30.67, 332.19 ± 32.19 vs. 604.96 ± 22.56), IL-1β (ng/L: 261.08 ± 24.78, 143.98 ± 28.39 vs. 367.06 ± 10.44) and IL-6 (ng/L: 342.75 ± 54.60, 235.48 ± 29.75 vs. 562.69 ± 63.34) in the culture supernatants compared with the LPS group (all P < 0.05). (3) The activity of AChE in the LPS group was significantly higher than that in the blank control group (kU/L: 5.21 ± 0.63 vs. 3.09 ± 0.10, P < 0.05). The activity of AChE was successfully inhibited by 1 mmol/L acetylcholinesterase inhibitor Phy pretreatment compared with that in the LPS group (1.51 ± 0.12 vs. 5.21 ± 0.63, P < 0.05). (4) The level of TNF-α (ng/L: 183.17 ± 35.44 vs. 451.19 ± 30.67), IL-1β (ng/L: 91.49 ± 12.27 vs. 261.08 ± 24.78) and IL-6 (ng/L: 108.17 ± 22.82 vs. 342.75 ± 54.60) in the culture supernatants of LPS + ACh + Phy group was significantly decreased as compared with LPS + ACh group (all P < 0.05).

CONCLUSIONS

ACh with the final concentrations of 10 μmol/L and 100 μmol/L can inhibit the LPS induced inflammatory reaction in alveolar macrophages. The acetylcholinesterase inhibitor Phy can reinforce the ACh-mediated anti-inflammatory effect on alveolar macrophages inflammatory model.

Modeling bipolar disorder in mice by increasing acetylcholine or dopamine: chronic lithium treats most, but not all features

RATIONALE

Bipolar disorder (BD) is a disabling and life-threatening disease characterized by states of depression and mania. New and efficacious treatments have not been forthcoming partly due to a lack of well-validated models representing both facets of BD.

OBJECTIVES

We hypothesized that cholinergic- and dopaminergic-pharmacological manipulations would model depression and mania respectively, each attenuated by lithium treatment.

METHODS

C57BL/6 J mice received the acetylcholinesterase inhibitor physostigmine or saline before testing for "behavioral despair" (immobility) in the tail suspension test (TST) and forced swim test (FST). Physostigmine effects on exploration and sensorimotor gating were assessed using the cross-species behavioral pattern monitor (BPM) and prepulse inhibition (PPI) paradigms. Other C57BL/6 J mice received chronic lithium drinking water (300, 600, or 1200 mg/l) before assessing their effects alone in the BPM or with physostigmine on FST performance. Another group was tested with acute GBR12909 (dopamine transporter inhibitor) and chronic lithium (1000 mg/l) in the BPM.

RESULTS

Physostigmine (0.03 mg/kg) increased immobility in the TST and FST without affecting activity, exploration, or PPI. Lithium (600 mg/l) resulted in low therapeutic serum concentrations and normalized the physostigmine-increased immobility in the FST. GBR12909 induced mania-like behavior in the BPM of which hyper-exploration was attenuated, though not reversed, after chronic lithium (1000 mg/ml).

CONCLUSIONS

Increased cholinergic levels induced depression-like behavior and hyperdopaminergia induced mania-like behavior in mice, while chronic lithium treated some, but not all, facets of these effects. These data support a cholinergic-monoaminergic mechanism for modeling BD aspects and provide a way to assess novel therapeutics.

Acetylcholinesterase in Biofouling Species: Characterization and Mode of Action of Cyanobacteria-Derived Antifouling Agents

Effective and ecofriendly antifouling (AF) compounds have been arising from naturally produced chemicals. The objective of this study is to use cyanobacteria-derived agents to investigate the role of acetylcholinesterase (AChE) activity as an effect and/or mode of action of promising AF compounds, since AChE inhibitors were found to inhibit invertebrate larval settlement. To pursue this objective, in vitro quantification of AChE activity under the effect of several cyanobacterial strain extracts as potential AF agents was performed along with in vivo AF (anti-settlement) screening tests. Pre-characterization of different cholinesterases (ChEs) forms present in selected tissues of important biofouling species was performed to confirm the predominance of AChE, and an in vitro AF test using pure AChE activity was developed. Eighteen cyanobacteria strains were tested as source of potential AF and AChE inhibitor agents. Results showed effectiveness in selecting promising eco-friendly AF agents, allowing the understanding of the AF biochemical mode of action induced by different compounds. This study also highlights the potential of cyanobacteria as source of AF agents towards invertebrate macrofouling species.

(-)-Phenserine attenuates soman-induced neuropathology

Organophosphorus (OP) nerve agents are deadly chemical weapons that pose an alarming threat to military and civilian populations. The irreversible inhibition of the critical cholinergic degradative enzyme acetylcholinesterase (AChE) by OP nerve agents leads to cholinergic crisis. Resulting excessive synaptic acetylcholine levels leads to status epilepticus that, in turn, results in brain damage. Current countermeasures are only modestly effective in protecting against OP-induced brain damage, supporting interest for evaluation of new ones. (-)-Phenserine is a reversible AChE inhibitor possessing neuroprotective and amyloid precursor protein lowering actions that reached Phase III clinical trials for Alzheimer's Disease where it exhibited a wide safety margin. This compound preferentially enters the CNS and has potential to impede soman binding to the active site of AChE to, thereby, serve in a protective capacity. Herein, we demonstrate that (-)-phenserine protects neurons against soman-induced neuronal cell death in rats when administered either as a pretreatment or post-treatment paradigm, improves motoric movement in soman-exposed animals and reduces mortality when given as a pretreatment. Gene expression analysis, undertaken to elucidate mechanism, showed that (-)-phenserine pretreatment increased select neuroprotective genes and reversed a Homer1 expression elevation induced by soman exposure. These studies suggest that (-)-phenserine warrants further evaluation as an OP nerve agent protective strategy.

Cholinesterase activity on Echinogammarus meridionalis (Pinkster) and Atyaephyra desmarestii (Millet): characterisation and in vivo effects of copper and zinc

Metals are released into freshwater ecosystems from natural and anthropogenic sources, compromising their structural and functional equilibrium. As early warning tools, cholinesterases (ChEs) are usually used to assess the effects of organophosphate and carbamate pesticides, but are also known to be inhibited by metals. The objectives of this work were to characterise the activity of ChE present in the amphipod Echinogammarus meridionalis and the shrimp Atyaephyra desmarestii and to evaluate the in vivo effects of the metals copper and zinc in their ChE activity. To achieve this, firstly the activity of ChE forms were characterised using different in vitro assays with substrates and selective inhibitors. Then, the in vivo effects of 48 h exposures to increasing concentrations of copper and zinc on ChE activity were determined. The ChE form present in both species was acetylcholinesterase (AChE) since both revealed preference for the acetylthiocholine iodide substrate, total inhibition with eserine, the inhibitor of ChEs, and with 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide, the specific inhibitor of AChE, and presented insensitivity to iso-OMPA, a specific inhibitor of butyrylcholinesterase. The activity of ChEs was inhibited by zinc exposures in the amphipod species, but was not affected by copper. Exposure to copper and zinc did not affect ChEs activity in the shrimp at the concentrations tested. This work is a relevant contribution as foundation for the use of AChE in freshwater crustaceans in further studies including biomonitoring campaigns in different contamination scenarios.

Inhibition of acetylcholinesterase modulates NMDA receptor antagonist mediated alterations in the developing brain

Exposure to N-methyl-d-aspartate (NMDA) receptor antagonists has been demonstrated to induce neurodegeneration in newborn rats. However, in clinical practice the use of NMDA receptor antagonists as anesthetics and sedatives cannot always be avoided. The present study investigated the effect of the indirect cholinergic agonist physostigmine on neurotrophin expression and the extracellular matrix during NMDA receptor antagonist induced injury to the immature rat brain. The aim was to investigate matrix metalloproteinase (MMP)-2 activity, as well as expression of tissue inhibitor of metalloproteinase (TIMP)-2 and brain-derived neurotrophic factor (BDNF) after co-administration of the non-competitive NMDA receptor antagonist MK801 (dizocilpine) and the acetylcholinesterase (AChE) inhibitor physostigmine. The AChE inhibitor physostigmine ameliorated the MK801-induced reduction of BDNF mRNA and protein levels, reduced MK801-triggered MMP-2 activity and prevented decreased TIMP-2 mRNA expression. Our results indicate that AChE inhibition may prevent newborn rats from MK801-mediated brain damage by enhancing neurotrophin-associated signaling pathways and by modulating the extracellular matrix.

Surface display and bioactivity of Bombyx mori acetylcholinesterase on Pichia pastoris

A Pichia pastoris (P. pastoris) cell surface display system of Bombyx mori acetylcholinesterase (BmAChE) was constructed and its bioactivity was studied. The modified Bombyx mori acetylcholinesterase gene (bmace) was fused with the anchor protein (AGα1) from Saccharomyces cerevisiae and transformed into P. pastoris strain GS115. The recombinant strain harboring the fusion gene bmace-AGα1 was induced to display BmAChE on the P. pastoris cell surface. Fluorescence microscopy and flow cytometry assays revealed that the BmAChE was successfully displayed on the cell surface of P. pastoris GS115. The enzyme activity of the displayed BmAChE was detected by the Ellman method at 787.7 U/g (wet cell weight). In addition, bioactivity of the displayed BmAChE was verified by inhibition tests conducted with eserine, and with carbamate and organophosphorus pesticides. The displayed BmAChE had an IC50 of 4.17×10(-8) M and was highly sensitive to eserine and five carbamate pesticides, as well as seven organophosphorus pesticides. Results suggest that the displayed BmAChE had good bioactivity.

Novel 5' untranslated region directed blockers of iron-regulatory protein-1 dependent amyloid precursor protein translation: implications for down syndrome and Alzheimer's disease

We reported that iron influx drives the translational expression of the neuronal amyloid precursor protein (APP), which has a role in iron efflux. This is via a classic release of repressor interaction of APP mRNA with iron-regulatory protein-1 (IRP1) whereas IRP2 controls the mRNAs encoding the L- and H-subunits of the iron storage protein, ferritin. Here, we identified thirteen potent APP translation blockers that acted selectively towards the uniquely configured iron-responsive element (IRE) RNA stem loop in the 5' untranslated region (UTR) of APP mRNA. These agents were 10-fold less inhibitory of 5'UTR sequences of the related prion protein (PrP) mRNA. Western blotting confirmed that the 'ninth' small molecule in the series selectively reduced neural APP production in SH-SY5Y cells at picomolar concentrations without affecting viability or the expression of α-synuclein and ferritin. APP blocker-9 (JTR-009), a benzimidazole, reduced the production of toxic Aβ in SH-SY5Y neuronal cells to a greater extent than other well tolerated APP 5'UTR-directed translation blockers, including posiphen, that were shown to limit amyloid burden in mouse models of Alzheimer's disease (AD). RNA binding assays demonstrated that JTR-009 operated by preventing IRP1 from binding to the IRE in APP mRNA, while maintaining IRP1 interaction with the H-ferritin IRE RNA stem loop. Thus, JTR-009 constitutively repressed translation driven by APP 5'UTR sequences. Calcein staining showed that JTR-009 did not indirectly change iron uptake in neuronal cells suggesting a direct interaction with the APP 5'UTR. These studies provide key data to develop small molecules that selectively reduce neural APP and Aβ production at 10-fold lower concentrations than related previously characterized translation blockers. Our data evidenced a novel therapeutic strategy of potential impact for people with trisomy of the APP gene on chromosome 21, which is a phenotype long associated with Down syndrome (DS) that can also cause familial Alzheimer's disease.

In vitro acetylcholinesterase activity of peptide derivatives isolated from two species of Leguminosae

CONTEXT

Cratylia mollis Martius ex Benth. and Cenostigma macrophyllum Tul. (Leguminosae) are both endemic Brazilian plants and they are used by the natives as medicinal plants, and the leaves of C. mollis are also employed as forage for cattle during the dry season of region.

OBJECTIVE

Isolation of the compounds responsible for the acetylcholinesterase (AChE) inhibition from the CHCl3 active extract.

MATERIALS AND METHODS

Two peptidic compounds were isolated by chromatographic techniques from the CHCl3 extract of the leaves of C. mollis and C. macrophyllum. They were identified by spectrometric data analysis (MS and NMR) and they were subjected to AChE inhibition employing Ellman's test.

RESULTS

The peptides were identified as N-benzoylphenylalaninoyl-phenlyalaninolacetate (aurentiamide acetate) (1) and N-benzoylphenylalaninyl-N-benzoylphenylalaninate (2). Both peptides 1 and 2 exhibit AChE inhibition, with IC50 values equal to 111.34 µM and 137.6 µM, respectively.

DISCUSSION AND CONCLUSION

Compound 1 (aurentiamide acetate) has rarely been isolated from the Leguminosae family, and N-benzoylphenylalaninyl-N-benzoylphenylalaninate (2) is a compound that has never previously been isolated from this family. Compound 1 is shown to be a potent inhibitor of AChE, with IC50 values similar to the physostigmine control (141.51 µM).

Acetylcholinesterase inhibitors reduce neuroinflammation and -degeneration in the cortex and hippocampus of a surgery stress rat model

Exogenous stress like tissue damage and pathogen invasion during surgical trauma could lead to a peripheral inflammatory response and induce neuroinflammation, which can result in postoperative cognitive dysfunction (POCD). The cholinergic anti-inflammatory pathway is a neurohumoral mechanism that plays a prominent role by suppressing the inflammatory response. Treatments with acetylcholinesterase inhibitors enhance cholinergic transmission and may therefore act as a potential approach to prevent neuroinflammation. In the presence or absence of acetylcholinesterase inhibitors, adult Wistar rats underwent surgery alone or were additionally treated with lipopolysaccharide (LPS). Physostigmine, which can overcome the blood-brain barrier or neostigmine acting only peripheral, served as acetylcholinesterase inhibitors. The expression of pro- and anti-inflammatory cytokines in the cortex, hippocampus, spleen and plasma was measured after 1 h, 24 h, 3 d and 7 d using Real-Time PCR, western blot analysis or cytometric bead array (CBA). Fluoro-Jade B staining of brain slices was employed to elucidate neurodegeneration. The activity of acetylcholinesterase was estimated using a spectrofluorometric method. Surgery accompanied by LPS-treatment led to increased IL-1beta gene and protein upregulation in the cortex and hippocampus but was significantly reduced by physostigmine and neostigmine. Furthermore, surgery in combination with LPS-treatment caused increased protein expression of IL-1, TNF-alpha and IL-10 in the spleen and plasma. Physostigmine and neostigmine significantly decreased the protein expression of IL-1 and TNF-alpha. Neuronal degeneration and the activity of acetylcholinesterase were elevated after surgery with LPS-treatment and reduced by physostigmine and neostigmine. Along with LPS-treatment, acetylcholinesterase inhibitors reduce the pro-inflammatory response as well as neurodegeneration after surgery in the cortex and hippocampus. This combination may represent a tool to break the pathogenesis of POCD.

Neurotrophic and neuroprotective actions of (-)- and (+)-phenserine, candidate drugs for Alzheimer's disease

Neuronal dysfunction and demise together with a reduction in neurogenesis are cardinal features of Alzheimer’s disease (AD) induced by a combination of oxidative stress, toxic amyloid-β peptide (Aβ) and a loss of trophic factor support. Amelioration of these was assessed with the Aβ lowering AD experimental drugs (+)-phenserine and (−)-phenserine in neuronal cultures, and actions in mice were evaluated with (+)-phenserine. Both experimental drugs together with the metabolite N1-norphenserine induced neurotrophic actions in human SH-SY5Y cells that were mediated by the protein kinase C (PKC) and extracellular signal–regulated kinases (ERK) pathways, were evident in cells expressing amyloid precursor protein Swedish mutation (APP_SWE), and retained in the presence of Aβ and oxidative stress challenge. (+)-Phenserine, together with its (−) enantiomer as well as its N1- and N8-norphenserine and N1,N8-bisnorphenserine metabolites, likewise provided neuroprotective activity against oxidative stress and glutamate toxicity via the PKC and ERK pathways. These neurotrophic and neuroprotective actions were evident in primary cultures of subventricular zone (SVZ) neural progenitor cells, whose neurosphere size and survival were augmented by (+)-phenserine. Translation of these effects in vivo was assessed in wild type and AD APPswe transgenic (Tg2576) mice by doublecortin (DCX) immunohistochemical analysis of neurogenesis in the SVZ, which was significantly elevated by 16 day systemic (+)-phenserine treatment, in the presence of a (+)-phenserine-induced elevation in brain- derived neurotrophic factor (BDNF).

Synthesis of the Alzheimer drug Posiphen into its primary metabolic products (+)-N1-norPosiphen, (+)-N8-norPosiphen and (+)-N1, N8-bisnorPosiphen, their inhibition of amyloid precursor protein, α-Synuclein synthesis, interleukin-1β release, and cholinergic action

A major pathological hallmark of Alzheimer disease (AD) is the appearance in the brain of senile plaques that are primarily composed of aggregated forms of β-amyloid peptide (Aβ) that derive from amyloid precursor protein (APP). Posiphen (1) tartrate is an experimental AD drug in current clinical trials that reduces Aβ levels by lowering the rate of APP synthesis without toxicity. To support the clinical development of Posiphen (1) and elucidate its efficacy, its three major metabolic products, (+)-N1-norPosiphen (15), (+)-N8-norPosiphen (17) and (+)-N1, N8-bisnorPosiphen (11), were required in high chemical and optical purity. The efficient transformation of Posiphen (1) into these metabolic products, 15, 17 and 11, is described. The biological activity of these metabolites together with Posiphen (1) and its enantiomer, the AD drug candidate (-)-phenserine (2), was assessed against APP,α-synuclein and classical cholinergic targets. All the compounds potently inhibited the generation of APP and α-synuclein in neuronal cultures. In contrast, metabolites 11 and 15, and (-)-phenserine (2) but not Posiphen (1) or 17, possessed acetyl cholinesterase inhibitory action and no compounds bound either nicotinic or muscarinic receptors. As Posiphen (1) lowered CSF markers of inflammation in a recent clinical trial, the actions of 1 and 2 on proinflammatory cytokine interleukin (IL)-1β release human peripheral blood mononuclear cells was evaluated, and found to be potently inhibited by both agents.

Differential inhibition of tumour cell-induced platelet aggregation by the nicotinate aspirin prodrug (ST0702) and aspirin

BACKGROUND AND PURPOSE

Tumour cell-induced platelet aggregation (TCIPA) facilitates cancer cell invasion, angiogenesis and the formation of metastatic foci. TCIPA can be modulated by pharmacological inhibitors of MMP-2 and ADP; however, the COX inhibitor aspirin did not prevent TCIPA. In this study, we have tested the pharmacological effects of a new group of isosorbide-based aspirin prodrugs on TCIPA.

EXPERIMENTAL APPROACH

TCIPA was induced in human platelets by mixing with human adenocarcinoma or fibrosarcoma cells under no flow and flow conditions. The release of gelatinases and P-selectin expression during TCIPA were studied by zymography and flow cytometry respectively.

KEY RESULTS

Tumour cells caused platelet aggregation. This aggregation resulted in the release of MMP-2 and a significant up-regulation of P-selectin on platelets, indicative of platelet activation. Pharmacological modulation of TCIPA revealed that ST0702, one of the aspirin prodrugs, down-regulated TCIPA while aspirin was ineffective. The deacetylated metabolite of ST0702, 5-nicotinate salicylate (ST0702 salicylate), down-regulated both ADP-stimulated platelet aggregation and TCIPA.

CONCLUSIONS AND IMPLICATIONS

Our results show that ST0702 was an effective inhibitor of TCIPA in vitro. Its deacetylated metabolite may contribute to the effects of ST0702 by inhibiting ADP-mediated TCIPA.

Acetylcholinesterase deficiency contributes to neuromuscular junction dysfunction in type 1 diabetic neuropathy

Diabetic neuropathy is associated with functional and morphological changes of the neuromuscular junction (NMJ) associated with muscle weakness. This study examines the effect of type 1 diabetes on NMJ function. Swiss Webster mice were made diabetic with three interdaily ip injections of streptozotocin (STZ). Mice were severely hyperglycemic within 7 days after the STZ treatment began. Whereas performance of mice on a rotating rod remained normal, the twitch tension response of the isolated extensor digitorum longus to nerve stimulation was reduced significantly at 4 wk after the onset of STZ-induced hyperglycemia. This mechanical alteration was associated with increased amplitude and prolonged duration of miniature end-plate currents (mEPCs). Prolongation of mEPCs was not due to expression of the embryonic acetylcholine receptor but to reduced muscle expression of acetylcholine esterase (AChE). Greater sensitivity of mEPC decay time to the selective butyrylcholinesterase (BChE) inhibitor PEC suggests that muscle attempts to compensate for reduced AChE levels by increasing expression of BChE. These alterations of AChE are attributed to STZ-induced hyperglycemia since similar mEPC prolongation and reduced AChE expression were found for db/db mice. The reduction of muscle end-plate AChE activity early during the onset of STZ-induced hyperglycemia may contribute to endplate pathology and subsequent muscle weakness during diabetes.

Pyridine alkaloids from Senna multijuga as acetylcholinesterase inhibitors

As part of an ongoing research project on Senna and Cassia species, five new pyridine alkaloids, namely, 12'-hydroxy-7'-multijuguinol (1), 12'-hydroxy-8'-multijuguinol (2), methyl multijuguinate (3), 7'-multijuguinol (4), and 8'-multijuguinol (5), were isolated from the leaves of Senna multijuga (syn. Cassiamultijuga). Their structures were elucidated on the basis of spectroscopic data analysis. Mass spectrometry was used for confirmation of the positions of the hydroxy groups in the side-chains of 1, 2, 4, and 5. All compounds exhibited weak in vitro acetylcholinesterase inhibitory activity as compared with the standard compound physostigmine.

Ibogaine and the inhibition of acetylcholinesterase

ETHNOPHARMACOLOGICAL RELEVANCE

Ibogaine is a psychoactive monoterpine indole alkaloid extracted from the root bark of Tabernanthe iboga Baill. that is used globally in medical and nonmedical settings to treat drug and alcohol addiction, and is of interest as an ethnopharmacological prototype for experimental investigation and pharmaceutical development. The question of whether ibogaine inhibits acetylcholinesterase (AChE) is of pharmacological and toxicological significance.

MATERIALS AND METHODS

AChE activity was evaluated utilizing reaction with Ellman's reagent with physostigmine as a control.

RESULTS

Ibogaine inhibited AChE with an IC(50) of 520±40 μM.

CONCLUSIONS

Ibogaine's inhibition of AChE is physiologically negligible, and does not appear to account for observations of functional effects in animals and humans that might otherwise suggest the possible involvement of pathways linked to muscarinic acetylcholine transmission.

Cholinesterase activities and sensitivity to pesticides in different tissues of silver European eel, Anguilla anguilla

Cholinesterase (ChE) activities were characterized in silver European eel, Anguilla anguilla, grown in the brackish lagoon of Comacchio (Italy). All specimens were harvested at the "lavoriero", a traditional eel trapping weir that captures eels while leaving internal waters at the onset of reproductive migration. To our knowledge, no investigation on ChE was reported in silver eels. Therefore a first characterization of enzyme activity in muscle, brain, liver and plasma of silver eel was carried out, in the presence of different substrates, selective inhibitors, and four pesticides representative of the carbamate and organophosphate classes. Brain and white skeletal muscle showed similar ChE activities, 5- and 10-fold higher than those detected in liver and plasma, respectively. Km values of 0.31 and 0.30 mM, and Vmax values of 40.28 and 35.47 nmol min(-1) mg protein(-1) were obtained in brain and muscle ChE, respectively. Acetycholinesterase was the predominant ChE form in all tissues, as concluded by comparing the effects of BW 284c51, iso-OMPA and eserine. ChE activities in brain and muscle were significantly inhibited by in vitro treatment with pesticides, with the following order of potency: carbofuran>carbaryl>chlorpyrifos≥diazinon.

Cholinesterase activity during embryonic development in the blood-feeding bug Triatoma patagonica

Triatoma patagonica Del Ponte (Hemiptera: Reduviidae), a vector of Chagas' disease, is widely distributed in Argentina and is found in sylvatic and peridomiciliary ecotopes, as well as occasionally in human dwellings after the chemical control of Triatoma infestans. Anti-cholinesteratic products can be applied in peridomiciliary areas and thus knowledge of cholinesterase activity during embryonic development in this species might contribute further information relevant to effective chemical control. Cholinesterase activity was characterized by reactions to eserine 10(-5) m, to increasing concentrations of substrate and to varying centrifugal speeds. Acetylcholinesterase activity was detected on day 4 and was significant from day 5. A reduction in cholinesterase activity towards acetylthiocholine (ATC) was observed on days 9 and 10 of development. Cholinesterase activity towards ATC and butyrylthiocholine (BTC) in homogenates of eggs was inhibited by eserine 10(-5) m. The shape of the curve indicating levels of inhibition at different concentrations of ATC was typical of acetylcholinesterase. Activity towards BTC did not appear to be inhibited by excess substrate, which parallels the behaviour of butyrylcholinesterases. Cholinesterase activity towards ATC was reduced in supernatant centrifuged at 15 000 g compared with supernatant centrifuged at 1100 g. The cholinesterase system that hydrolyzes mainly ATC seems to belong to the nervous system, as indicated by its behaviour towards the substrates assayed, its greater insolubility and the fact that it evolves parallel to the development of the nervous system. Knowledge of biochemical changes associated with the development and maturation of the nervous system during embryonic development would contribute to the better understanding of anti-cholinesteratic compounds with ovicidal action that might be used in control campaigns against vectors of Chagas' disease.

[Effect of acetylcholine and acetylcholinesterase on the activity of contractile vacuole of Amoeba proteus]

Acetylcholine (ACh, 1 microM) stimulates activity of the contractile vacuole of proteus. The effect of ACh is not mimicked by its analogs which are not hydrolyzed by acetylcholinesterase (AChE), i. e., carbacholine and 5-methylfurmethide. The effect of ACh is not sensitive to the blocking action of M-cholinolytics, atropine and mytolone, but is suppressed by N-cholinolytic, tubocurarine. The inhibitors of AChE, eserine (0.01 microM) and armine (0.1 microM), suppress the effect of ACh on amoeba contractile vacuole. ACh does not affect activation of contractile vacuole induced by arginine-vasopressin (1 microM), but it blocks such effect of opiate receptors agonist, dynorphin A1-13 (0.01 microM). This effect of ACh is also suppressed by the inhibitors of AChE. These results suggest that, in the above-described effects of ACh, AChE acts not as an antagonist, but rather as a synergist.

Pharmacological effects of Catharanthus roseus root alkaloids in acetylcholinesterase inhibition and cholinergic neurotransmission

The leaves of Catharanthus roseus constitute the only source of the well known indolomonoterpenic alkaloids vincristine and vinblastine. In this work we studied the biological potential of the roots, which are used in several countries as decocts or hot water extracts for the treatment of a number of conditions. The aqueous extract strongly inhibited acetylcholinesterase (AchE) in an in vitro microassay, an effect ascribable mainly to serpentine (IC(50) = 0.775 microM vs physostigmine IC(50) = 6.45 microM) as assessed with the pure compound. Pure alkaloids were tested for muscarinic and nicotinic antagonism using rat ex-vivo preparations, namely, ileum and diaphragm/phrenic-nerve, respectively. Serpentine competitively blocked muscarinic receptors with a pA(2) of 5.2, whereas the precursor ajmalicine up to 80 microM was undistinguishable from control, and catharanthine exhibited an unsurmountable muscarinic antagonism at greater than 10 microM concentrations. Nicotinic receptor mediated diaphragm contractions were fully inhibited by catharanthine (IC(50) = 59.6 microM) and ajmalicine (IC(50) = 72.3 microM), in a reversible but non-competitive manner, unlike the more potent nicotinic antagonist tubocurarine (IC(50) = 0.35 microM) whose competitive blockade was overcome by a physostigmine-induced increase in acetylcholine. Serpentine up to 100 microM did not change diaphragm contractions suggesting reduced affinity for neuromuscular nicotinic receptors. Despite strong in vitro AchE inhibition, serpentine failed to restore diaphragm contractions upon submaximal tubocurarine blockade, suggesting that poor tissue penetration may prevent serpentine from inhibiting AchE in deep neuromuscular synapses in the ex-vivo preparation. To our knowledge, the present study is the first to assess the effect of C. roseus root extracts, as well as of serpentine, ajmalicine and catharanthine on AchE. The results described herein suggest that the currently overlooked C. roseus roots may constitute a promising source of compounds with pharmaceutical interest. Moreover, given serpentine's potent in vitro AchE inhibitory activity and low cholinergic receptor affinity, it is conceivable that minor structural modifications may yield a potent and selective AchE inhibitor, potentially useful for the pharmacological management of conditions such as Alzheimer's disease and/or myasthenia gravis.

Increase of plasma insulin by racecadotril, an inhibitor of enkephalinase, in Wistar rats

Racecadotril is known as an inhibitor of enkephalinase. Increase of plasma insulin by racecadotril has been observed in rats while the mechanism of the action remains obscure. In the present study, intravenous injection of male Wistar rats with racecadotril significantly decreased blood glucose levels. However, this effect of racecadotril was not modified by naloxone at the dose sufficient to block opioid receptors. Thus, the blood glucose-lowering action of racecadotril might be through an endogenous opioid independent mechanism. Otherwise, we found that C-peptide content was also raised by racecadotril in parallel with the increase of insulin in Wistar rats. Thus, the blood glucose-lowering action of racecadotril was related to insulin secretion, but not through the inhibition of plasma insulin degradation. In addition, racecadotril showed no direct effect on insulin secretion in isolated islets or cultured HIT-T15 beta cells. The increase of plasma insulin and blood glucose-lowering action induced by racecadotril were reduced by pretreatment with atropine and enhanced by physotigmine. Direct inhibition of cholinesterase was not observed in brain homogenates treated with racecadotril. Moreover, actions of racecadotril were significantly reduced in rats receiving hemicholinium-3 at a sufficient dose to decrease endogenous acetylcholine. Activation of cholinergic tone is possibly involved in the blood glucose-lowering effect of racecadotril. Our results suggested that racecadotril increased insulin secretion to lower blood glucose mainly via regulation of parasympathetic tone in Wistar rats.

Scopolamine-induced learning impairment reversed by physostigmine in zebrafish

In this study, the effects of scopolamine, an acetylcholine muscarinic receptor antagonist, and physostigmine, an acetylcholinesterase inhibitor, on the learning ability and memory of zebrafish were evaluated using a passive avoidance response test. The zebrafish were trained to stay in a dark compartment to avoid a weight dropping into an acryl shuttle chamber with a central sliding door. The crossing time was increased significantly, from 30.7+/-40.8s to 179.3+/-27.3s in the training session and 179.9+/-28.0s in the test session carried out 2h later in the controls. When treatment with 200 microM scopolamine was administered for 1h prior to the training session, the crossing time did not increase. The scopolamine-induced learning deficit was ameliorated by pretreatment with 20 microM physostigmine for 1h prior to scopolamine treatment; the crossing time was similarly increased, as shown with the controls (60.9+/-11.5s, 130.9+/-27.5s, and 183.4+/-26.6s in the training session and 108.1+/-23.9s in the test session). When scopolamine treatment was administered after the training session, the crossing time in the test session was reduced significantly as compared to that noted in the third trial of the training session, which was also ameliorated by physostigmine pretreatment. These results show that scopolamine impairs both the acquisition of passive avoidance response and retention of the learned response, and that physostigmine rescues the amnesic effects of scopolamine in zebrafish.

Esterase patterns in species of the triatome bug Rhodnius

The aim of the present study was to analyse esterase patterns in three triatomine species of Rhodnius genus. Four loci, Est 1, Est 2, Est 3 and Est 4, were found. The corresponding enzymes were characterized as carboxylesterases (E.C. 3.1.1.1) or cholinesterases (E.C. 3.1.1.8) based on inhibitory experiments, using eserine sulphate, malathion, mercury chloride, p-chloromercuribenzoate (pCMB) and iodoacetamide. Low genetic variability was observed: Est 1, Est 2 and Est 3 were monomorphic in Rhodnius domesticus, Rhodnius robustus and Rhodnius neivai, whereas locus Est 4 was polymorphic in the first two species. The UPGMA analysis based on esterase genotypic frequencies indicated greater similarity between R. domesticus and R. robustus when compared with R. neivai. The present study expands our knowledge about genetic variability among triatomines and accords with the hypothesis that R. domesticus is a species derived from R. robustus.

Localization and properties of cholinesterases in the common prawn (Palaemon serratus): A kinetic-histochemical study

Due to the diversity in biochemical properties and tissue distribution of cholinesterase (ChE) enzymes, a characterization should be performed before they are used as biomarkers for monitoring pesticide contamination. In this study we investigate the distribution of ChEs and their kinetic properties in diverse tissues of the common prawn Palaemon serratus. The results concerning the histochemical localization of ChEs suggest that the highest amount of ChE activity occurs in prawn eyes, followed by the brain, gills, and digestive tract. Negligible staining was observed in the muscle. We describe the kinetic properties of ChEs in eyes, gills, and hepatopancreas, investigating their substrate preferences with different thiocholine esters and their sensitivity to inhibition with selective inhibitors. The results suggest that the studied enzymes are ChEs and not nonspecific esterases, due to their apparent affinity for choline esters, with a distinct preference for the substrate acetylthiocholine, and their high sensitivity to inhibition by eserine sulfate. P. serratus eyes can be considered the best tissue for recovery of ChE enzyme: this tissue is easy to isolate, it expresses high levels of ChE, and the enzyme shows properties of a vertebrate AChE.

Ontogeny of acylated ghrelin degradation in the rat

Ghrelin circulates as acylated (AG) and unacylated (or desacyl) ghrelin (UAG). We aimed at clarifying the effect of age and sex on plasma deacylation and degradation of AG in vivo and in vitro in the rat. In vivo, we compared AG and UAG concentrations following administration of 1 microg AG intraperitoneally in rat neonates during the first 3h of life. AG administration caused a 2-3 times increase in plasma AG concentrations contrasting with a approximately 1000 times increase in UAG concentrations suggesting rapid deacylation of AG into UAG. In vitro, we demonstrated that AG degradation was greater in the fetus (97% over 30 min) and decreased progressively to 57% in adult animals (P<0.001). Carboxylesterase and butyrylcholinesterase activities were determined during the fetal (day 21 of pregnancy) and postnatal period (days 1, 6, 13, 21 and 28) and in the adult rat and were found to increase with age (P<0.001). While inhibition of carboxylesterase and butyrylcholinesterase did not affect AG deacylation, serine protease inhibitors decreased AG degradation in the adult rat (from 59% to 23%) and, to a lesser extent, in the rat neonate (from 92% to 57%) by reducing both deacylation and degradation into non-UAG metabolites. Our data suggest that degradation of AG into UAG and non-UAG metabolites is much faster in the fetus and in the rat neonate compared to the adult. We speculate that this process allows for fine tuning of the physiological effects of both AG and UAG.

Cholinergic agonist physostigmine suppresses excessive superoxide anion radical generation in blood, oxidative stress, early inflammation, and endothelial injury in rats with forebrain ischemia/reperfusion

The cholinergic anti-inflammatory pathway is reportedly important in modulating the inflammatory response in local and systemic diseases, including ischemia/reperfusion pathophysiology. In this study, we investigated the effects of the cholinergic agonist, physostigmine, on jugular venous superoxide radical (O(2)(-)) generation, oxidative stress, early inflammation, and endothelial activation during forebrain ischemia/reperfusion (FBI/R) in rats. Fourteen male Wistar rat were allocated to the control group (n=7) or physostigmine group (n=7). The physostigmine group received 80 ng/g physostigmine intraperitoneally 24 h and 1 h before forebrain ischemia was established. The jugular venous O(2)(-) current was measured for 10 min during forebrain ischemia and for 120 min after reperfusion. The O(2)(-) current increased gradually during forebrain ischemia in both groups. The current increased markedly immediately after reperfusion in the control group but was significantly attenuated in the physostigmine group after reperfusion. Brain and plasma malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule 1 (ICAM1) were significantly attenuated in the physostigmine group compared with the control group, except for brain HMGB1. The amount of O(2)(-) generated during FBI/R correlated with malondialdehyde, HMGB1, and ICAM1 in both the brain and plasma. In conclusion, the cholinergic agonist physostigmine suppressed jugular venous O(2)(-) generation, oxidative stress, early inflammation, and endothelial activation in the brain and plasma in the acute phase of cerebral ischemia/reperfusion. Therefore, the suppression of O(2)(-) is a key mechanism of the cholinergic anti-inflammatory pathway in the pathophysiology of cerebral ischemia/reperfusion.

Cholinergic potentiation of the meal-related rise in ACTH and cortisol concentrations in men

The present study examined the influence of physostigmine, an acetylcholine esterase inhibitor, on the secretory activity of the hypothalamo-pituitary-adrenocortical (HPA)--axis under basal (experiment I) and stimulated (experiment II) conditions in young healthy men. In a third experiment, the effect of scopolamine, a muscarinic acetylcholine receptor antagonist, on HPA secretory activity after physiological stimulation was tested. The experiments started between 09.00 and 10.00 a.m.. After a resting period of 1.5 h, either physostigmine (0.0125 mg per kg body weight soluted in isotonic saline) or placebo (saline) was infused within 15 min. In experiment I subjects (n = 7) remained fasting while in experiment II (n = 18) a standardized lunch was offered after the infusion. Experiment III (n = 7) was designed as experiment II but instead of physostigmine, scopolamine or placebo (0.5 mg) was subcutaneously injected 105 min before the meal. Blood for the determination of ACTH and cortisol was drawn in regular intervals during the experiments. Physostigmine did not change basal ACTH and cortisol secretion per se, excluding activation of basal HPA secretion due to acetylcholineesterase inhibition and its non specific side effects. Meal intake stimulated ACTH and cortisol secretion which was significantly enhanced when physostigmine was administered (p < 0.05). Scopolamine did not influence the meal related ACTH and cortisol secretion. These findings demonstrate that cholinergic neurotransmission is able to increase ACTH and cortisol concentrations in humans. This effect seems to be complementary to other stimulatory neurotransmitter systems, and is functional during stimulated HPA secretory activity and not under basal conditions.

Phencyclidine-induced cognitive deficits in mice are ameliorated by subsequent subchronic administration of donepezil: role of sigma-1 receptors

This study was undertaken to examine the effects of two acetylcholinesterase inhibitors (donepezil and physostigmine) on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). In the novel object recognition test, PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were significantly improved by subsequent subchronic (14 days) administration of donepezil (1.0 mg/kg/day), but not donepezil (0.1 mg/kg/day). Furthermore, the effect of donepezil (1.0 mg/kg/day) on PCP-induced cognitive deficits was significantly antagonized by co-administration of the selective sigma-1 receptor antagonist NE-100 (1.0 mg/kg/day), suggesting the role of sigma-1 receptors in the active mechanisms of donepezil. In contrast, PCP-induced cognitive deficits were not improved by subsequent subchronic (14 days) administration of physostigmine (0.25 mg/kg/day). Moreover, repeated administration of PCP significantly caused the reduction of sigma-1 receptors in the hippocampus. The present study suggests that agonistic activity of donepezil at sigma-1 receptors plays a role in the active mechanisms of donepezil on PCP-induced cognitive deficits in mice. Therefore, it is likely that donepezil would be potential therapeutic drugs for the treatment of the cognitive deficits in schizophrenia.

Esterase polymorphism in the Adriatic sardine (Sardina pilchardus Walb.). 1. Electrophoretic and biochemical properties of the serum and tissue esterases

At least four zones of esterase activity designated I, II, III and IV were found after electrophoretic separation of sera and soluble extracts of sardine tissues on starch gel. Each zone consisted of one or more bands that were distinguishable from other zones by electrophoretic mobility, substrate specificity and sensitivity to various inhibitors. Polymorphism was noted in zones I, II and III, while zone IV consisted of a single band. A genetic interpretation of the polymorphism was given for zone I esterases in the tissue, which appears to be controlled by four codominant alleles. The zones designated I, II and IV in the sera and II, III and IV in the liver were characterized as carboxylesterases, zone II in the sera was the only one with cholinesterase activity, while zone I in the liver tissue was unclassifiable.

Genetic polymorphism of eserine resistant esterases in canine plasma

Six plasma eserine resistant esterase phenotypes were observed in a population of 1438 dogs consisting of 38 breeds. Analysis of parentage records of the dogs examined revealed that the phenotypic variation of eserine resistant esterases was controlled by 3 codominant alleles ESA, ESB and ESC at one autosomal locus. The gene frequency of ESB was high in most of the breeds examined. Allele ESC was only seen in 5 Japanese native breeds, Akita, Shikoku, Hokkaido, Shinshu-Shiba and Mino-Shiba, and in a Spitz dog. Allele ESA has a low frequency in Japanese breeds but a higher frequency in some of the European breeds tested.