Adaptive acetylcholinesterase splicing patterns attenuate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism in mice

Kaempferol counteracts toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in D. melanogaster: An implication of its mitoprotective activity

The current study aimed to investigate whether kaempferol (KMP), the major bioactive component of green leafy vegetables, could counteract the toxicity elicited by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in Drosophila melanogaster or not. First, we performed a dose-response curve, where adult wild-type flies were fed on diet-containing different concentrations of KMP throughout their lifespan. Afterward, flies were fed on a diet containing MPTP (500 μM) and KMP (20 and 40 μM) for 7 days. The MPTP- fed flies presented a higher mortality rate, lower emergence rate, locomotor deficits, and disruption in circadian rhythm when compared to the control. MPTP exposure induced severe oxidative stress, which was marked by reduction in thiol content, overproduction of reactive species, lipid and protein oxidation, and disruption of enzymes of antioxidant and neurotransmission pathways. MPTP also compromised the mitochondrial dynamics and respiration of flies, affecting the electron transport chain, oxidative phosphorylation, and fusion/fission processes. Besides extending per se the lifespan of flies, KMP counteracted the toxic effects of MPTP on the circadian cycle, survival, climbing, and hatching rates. KMP was also effective in restoring the activities of acetylcholinesterase (AChE) and monoamine oxidase (MAO) enzymes, as well as in normalizing the levels of all oxidant/antioxidant markers disrupted in MPTP-fed flies. Indeed, KMP reestablished the mitochondrial functionality in MPTP- fed flies, restoring the electron transport system linked to mitochondrial complex I and II, and rescuing the mRNA transcription of genes associated with mitochondrial fusion and fission, namely OPA-1 (Optic atrophy 1) and DRP-1 (Dynamin related protein 1). Our results showed the efficacy of KMP in hindering the toxicity induced by MPTP in D. melanogaster and suggest that the mitoprotective action of flavonoid may be boosting its anti-parkinsonism activity in the model. Besides, the study showed that wild-type strains of D. melanogaster proved to be reproducible in vivo model to mimic parkinsonian phenotypes through exposure to the neurotoxin MPTP.

The curative and mechanistic acumen of curcuminoids formulations against haloperidol induced Parkinson's disease animal model

Parkinson's disease (PD) is slowly developing neurodegenerative disorder associated with gradual decline in cerebration and laboriousness to perform routine piece of work. PD imposed a social burden on society through higher medical cost and by loss of social productivity in current era. The available treatment options are expensive and associated with serious adverse effect after long term use. Therefore, there is a critical clinical need to develop alternative pharmacotherapies from natural sources to prevent and cure the pathological hall marks of PD with minimal cost. Our study aimed to scrutinize the antiparkinsonian potential of curcuminoids-rich extract and its binary and ternary inclusion complexes. In healthy rats, 1 mg/kg haloperidol daily intraperitoneally, for 3 weeks was used to provoke Parkinsonism like symptoms except control group. Curcuminoids rich extract, binary and ternary inclusion complexes formulations 15-30 mg/kg, L-dopa and carbidopa (100 + 25 mg/kg) were orally administered on each day for 3 weeks. Biochemical, histopathological and RT-qPCR analyses were conducted after neurobehavioral observations. Findings of current study indicated that all curcuminoids formulations markedly mitigated the behavioral abnormalities, recovered the level of antioxidant enzymes, acetylcholinesterase inhibitory activity and neurotransmitters. Histological analysis revealed that curcuminoids supplements stabilized the neuronal loss, pigmentation and Lewy bodies' formation. The mRNA expressions of neuro-inflammatory and specific PD pathological biomarkers were downregulated by treatment with curcuminoids formulations. Therefore, it is suggested that these curcuminoids rich extract, binary and ternary supplements should be considered as promising therapeutic agents in development of modern anti-Parkinson's disease medications.

Acetylcholinesterase Inhibitors in the Treatment of Neurodegenerative Diseases and the Role of Acetylcholinesterase in their Pathogenesis

Acetylcholinesterase (AChE) plays an important role in the pathogenesis of neurodegenerative diseases by influencing the inflammatory response, apoptosis, oxidative stress and aggregation of pathological proteins. There is a search for new compounds that can prevent the occurrence of neurodegenerative diseases and slow down their course. The aim of this review is to present the role of AChE in the pathomechanism of neurodegenerative diseases. In addition, this review aims to reveal the benefits of using AChE inhibitors to treat these diseases. The selected new AChE inhibitors were also assessed in terms of their potential use in the described disease entities. Designing and searching for new drugs targeting AChE may in the future allow the discovery of therapies that will be effective in the treatment of neurodegenerative diseases.

Anti-Parkinson's Activity of Tribulus terrestris via Modulation of AChE, α-Synuclein, TNF-α, and IL-1β

Tribulus terrestris (T.T.) is a rich source of flavonoids and saponins, which have been reported to have neuroprotective and antioxidant potential. The current study was planned to investigate the anti-Parkinson's activity of T. terrestris methanol extract (TTME). It was hypothesized that TTME possessed antioxidant potential and can ameliorate Parkinson's disease (PD) via modulation of α-synuclein, acetylcholinesterase (AChE), TNF-α, and IL-1β. To test this hypothesis, in silico and in vivo studies were performed. The PD model in rats was prepared by giving haloperidol, 1 mg/kg, i.p. Rats were divided into six groups: control, disease control, standard, and treatment groups receiving TTME orally at 100, 300, and 1000 mg/kg dose levels for 21 days. Behavioral observations and biochemical analyses were done. The TTME modulatory effect on mRNA expression of α-synuclein, AChE, TNF-α, and interleukins in the brain homogenate was estimated by RT-PCR. Compounds detected in HPLC analysis disrupted the catalytic triad of AChE in in silico studies. Behavioral observations showed significant (p < 0.05) improvement in a reversal of catatonia, muscular strength, locomotor functions, stride length, and exploration in a dose-dependent manner (1000 >300 >100 mg/kg) of PD rats. Endogenous antioxidant enzyme levels CAT, SOD, GSH, and GPx were significantly restored at a high dose (p < 0.05) with a notable (p < 0.05) decrease in the MDA level in TTME-treated groups. TTME at a high dose significantly (p < 0.05) decreased the level of acetylcholinesterase. RT-PCR results are showing down-regulation in the mRNA expression levels of IL-1β, α -synuclein, TNF-α, and AChE in TTME-treated groups compared to the disease control group, indicating neuroprotection. It is concluded that TTME has potential to ameliorate the symptoms of Parkinson's disease.

Is Dysregulation of the HPA-Axis a Core Pathophysiology Mediating Co-Morbid Depression in Neurodegenerative Diseases?

There is increasing evidence of prodromal manifestation of neuropsychiatric symptoms in a variety of neurodegenerative diseases such as Parkinson's disease (PD) and Huntington's disease (HD). These affective symptoms may be observed many years before the core diagnostic symptoms of the neurological condition. It is becoming more apparent that depression is a significant modifying factor of the trajectory of disease progression and even treatment outcomes. It is therefore crucial that we understand the potential pathophysiologies related to the primary condition, which could contribute to the development of depression. The hypothalamic-pituitary-adrenal (HPA)-axis is a key neuroendocrine signaling system involved in physiological homeostasis and stress response. Disturbances of this system lead to severe hormonal imbalances, and the majority of such patients also present with behavioral deficits and/or mood disorders. Dysregulation of the HPA-axis is also strongly implicated in the pathology of major depressive disorder. Consistent with this, antidepressant drugs, such as the selective serotonin reuptake inhibitors have been shown to alter HPA-axis activity. In this review, we will summarize the current state of knowledge regarding HPA-axis pathology in Alzheimer's, PD and HD, differentiating between prodromal and later stages of disease progression when evidence is available. Both clinical and preclinical evidence will be examined, but we highlight animal model studies as being particularly useful for uncovering novel mechanisms of pathology related to co-morbid mood disorders. Finally, we purpose utilizing the preclinical evidence to better inform prospective, intervention studies.

Effect of monocrotophos, an organophosphorus insecticide, on the striatal dopaminergic system in a mouse model of Parkinson’s disease

Our earlier study had shown that low concentrations of monocrotophos (MCP) elicited dopaminergic features of Parkinson’s disease (PD) in the nematode Caenorhabditis elegans. In the present study, the effect of low doses of MCP on the striatal dopaminergic neurons was investigated using the mouse model system. MCP was initially screened for its ability to cause any neurobehavioral deficits and alterations in the dopaminergic system in Swiss albino mice, aged 8 weeks and weighing 25–30 g, with repeated doses at 0.3 and 0.6 mg/kg body weight (b.w.)/day for 7 days and 30 days. Mice were treated with four intraperitoneal injections for every 2 h with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at the dosage of 14 mg/kg b.w. MCP was administered to these mice at the above-mentioned doses for 7 days. Mice administered with MCP alone revealed a significant ( p < 0.05) reduction in the dopamine (DA) content at both 7 and 30 days and showed a significant ( p < 0.05) increase in neurobehavioral deficits. Interestingly, when MCP was administered for 7 days to MPTP-treated mice, further significant decrease in both DA content and increase in neurobehavioral deficits were apparent. The extent of reactive oxygen species and lipid peroxidation were markedly increased, while the ratio of reduced to oxidized glutathione levels were significantly decreased ( p < 0.05) in the treated mice as compared to the control. Significant histopathological alterations and a marked reduction in the number of tyrosine hydroxylase positive cells were evident in striatum of mice treated with higher doses of MCP. These changes were comparable to that seen in mice treated with MPTP and post-administered lower doses of MCP. Our findings suggest that MCP per se has the propensity to induce pathological changes in the dopaminergic neurons as well as augment the degeneration in a compromised nigrostriatal system such as that in PD.

DJ-1 interacts with and regulates paraoxonase-2, an enzyme critical for neuronal survival in response to oxidative stress

Loss-of-function mutations in DJ-1 (PARK7) gene account for about 1% of all familial Parkinson's disease (PD). While its physiological function(s) are not completely clear, DJ-1 protects neurons against oxidative stress in both in vitro and in vivo models of PD. The molecular mechanism(s) through which DJ-1 alleviates oxidative stress-mediated damage remains elusive. In this study, we identified Paraoxonase-2 (PON2) as an interacting target of DJ-1. PON2 activity is elevated in response to oxidative stress and DJ-1 is crucial for this response. Importantly, we showed that PON2 deficiency hypersensitizes neurons to oxidative stress induced by MPP⁺ (1-methyl-4-phenylpyridinium). Conversely, over-expression of PON2 protects neurons in this death paradigm. Interestingly, PON2 effectively rescues DJ-1 deficiency-mediated hypersensitivity to oxidative stress. Taken together, our data suggest a model by which DJ-1 exerts its antioxidant activities, at least partly through regulation of PON2.

Neuronal AChE splice variants and their non-hydrolytic functions: redefining a target of AChE inhibitors?

AChE enzymatic inhibition is a core focus of pharmacological intervention in Alzheimer's disease (AD). Yet, AChE has also been ascribed non-hydrolytic functions, which seem related to its appearance in various isoforms. Neuronal AChE presents as a tailed form (AChE-T) predominantly found on the neuronal synapse, and a facultatively expressed readthough form (AChE-R), which exerts short to medium-term protective effects. Notably, this latter form is also found in the periphery. While these non-hydrolytic functions of AChE are most controversially discussed, there is evidence for them being additional targets of AChE inhibitors. This review aims to provide clarification as to the role of these AChE splice variants and their interplay with other cholinergic parameters and their being targets of AChE inhibition: AChE-R is particularly involved in the mediation of (anti-)apoptotic events in cholinergic cells, involving adaptation of various cholinergic parameters and a time-dependent link to the expression of neuroprotective factors. The AChE-T C-terminus is central to AChE activity regulation, while isolated AChE-T C-terminal fragments mediate toxic effects via the α7 nicotinic acetylcholine receptor. There is direct evidence for roles of AChE-T and AChE-R in neurodegeneration and neuroprotection, with these roles involving AChE as a key modulator of the cholinergic system: in vivo data further encourages the use of AChE inhibitors in the treatment of neurodegenerative conditions such as AD since effects on both enzymatic activity and the enzyme's non-hydrolytic functions can be postulated. It also suggests that novel AChE inhibitors should enhance protective AChE-R, while avoiding the concomitant up-regulation of AChE-T.

Pathophysiological amyloid concentrations induce sustained upregulation of readthrough acetylcholinesterase mediating anti-apoptotic effects

Cholinergically differentiated SH-SY5Y neuroblastoma cells were treated with a pathophysiologically relevant, low (300 nM), and a high (3 μM) dose of amyloid beta 1-42 (Abeta) or 42-1 (revAbeta). At early (1 and 4h) and late (24h) time points, the pro- and anti-apoptotic factors--caspase-3 and p53, and B-cell lymphoma 2 protein (Bcl-2), respectively--were assessed together with lactate dehydrogenase (LDH) release as measure of cell viability and ATP levels as marker of mitochondrial activity. The low peptide dose significantly increased Bcl-2 and, time-delayed, caspase-3 and ATP levels, but barely impacted on LDH release, while the high concentration remarkably depressed Bcl-2 levels, depleted ATP and led to increased LDH release. We also monitored acetylcholinesterase (AChE) enzymatic activity and splice variant levels (tailed and readthrough AChE; AChE-T and AChE-R), and assessed choline acetyltransferase (ChAT) and high-affinity choline uptake (HACU). The low Abeta concentration drastically upregulated AChE-R and increased both ChAT and HACU, while the high dose caused cholinergic toxicity. We believe this study offers the first insight into the highly concentration-dependent effects of Abeta on cholinergic dynamics. In particular, it highlights the rescuing role of AChE-R as being, together with mitochondrial activity, involved in cholinergic adaptation to low doses of Abeta.

Deep brain stimulation induces rapidly reversible transcript changes in Parkinson's leucocytes

Subthalamic deep brain stimulation (DBS) reversibly modulates Parkinson's disease (PD) motor symptoms, providing an unusual opportunity to compare leucocyte transcripts in the same individuals before and after neurosurgery and 1 hr after stimulus cessation (ON- and OFF-stimulus). Here, we report DBS-induced reversibility and OFF-stimulus restoration in 12 of 16 molecular functions and 3 of 4 biological processes shown in exon microarrays to be differentially expressed between PD patients and controls, post-DBS from pre-DBS and OFF from ON states. Intriguingly, 6 of 18 inflammation and immune-related functions exhibited reversibility, and the extent of stimulus-induced changes correlated with the neurological DBS efficacy, suggesting mechanistic implications. A minimal list of 29 transcripts that changed in all three comparisons between states discriminated pre-surgery and OFF states from post-surgery and controls. Six of these transcripts were found to be able to distinguish between PD patients and both healthy controls and patients with other neurological diseases in a previously published whole blood 3’ array data study of early PD patients. Our findings support the future use of this approach for identifying targets for therapeutic intervention and assessing the efficacy of current and new treatments in this and other neurological diseases.

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.

Biosignatures for Parkinson's disease and atypical parkinsonian disorders patients

Diagnosis of Parkinson' disease (PD) carries a high misdiagnosis rate due to failure to recognize atypical parkinsonian disorders (APD). Usually by the time of diagnosis greater than 60% of the neurons in the substantia nigra are dead. Therefore, early detection would be beneficial so that therapeutic intervention may be initiated early in the disease process. We used splice variant-specific microarrays to identify mRNAs whose expression is altered in peripheral blood of early-stage PD patients compared to healthy and neurodegenerative disease controls. Quantitative polymerase chain reaction assays were used to validate splice variant transcripts in independent sample sets. Here we report a PD signature used to classify blinded samples with 90% sensitivity and 94% specificity and an APD signature that resulted in a diagnosis with 95% sensitivity and 94% specificity. This study provides the first discriminant functions with coherent diagnostic signatures for PD and APD. Analysis of the PD biomarkers identified a regulatory network with nodes centered on the transcription factors HNF4A and TNF, which have been implicated in insulin regulation.

Adaptive alternative splicing correlates with less environmental risk of parkinsonism

BACKGROUND/OBJECTIVE

Environmental exposure to anti-acetylcholinesterases (AChEs) aggravates the risk of Parkinsonism due to currently unclear mechanism(s). We explored the possibility that the brain's capacity to induce a widespread adaptive alternative splicing response to such exposure may be involved.

METHODS

Following exposure to the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), brain region transcriptome profiles were tested.

RESULTS

Changes in transcript profiles, alternative splicing patterns and splicing-related gene categories were identified. Engineered mice over-expressing the protective AChE-R splice variant showed less total changes but more splicing-related ones than hypersensitive AChE-S over-expressors with similarly increased hydrolytic activities. Following MPTP exposure, the substantia nigra and prefrontal cortex (PFC) of both strains showed a nuclear increase in the splicing factor ASF/SF2 protein. Furthermore, intravenous injection with highly purified recombinant human AChE-R changed transcript profiles in the striatum.

CONCLUSIONS

Our findings are compatible with the working hypothesis that inherited or acquired alternative splicing deficits may promote parkinsonism, and we propose adaptive alternative splicing as a strategy for attenuating its progression.

Pharmacogenetic regulation of acetylcholinesterase activity in Drosophila reveals the regulatory mechanisms of AChE inhibitors in synaptic plasticity

We conducted experiments in Drosophila to investigate the consequences of altered acetylcholinesterase (AChE) activity in the nervous system. In ace hypomorphic mutant larvae, the amount of ace mRNA and the activity of AChE both in vivo and in vitro were significantly reduced compared with those of controls. Reduced Ace in Drosophila larvae resulted in significant down-regulation of branch length and the number of boutons in Type 1 glutamatergic neuromuscular junctions (NMJs). These defects in ace hypomorphic mutant larvae were suppressed when Musca domestica AChE was transgenically expressed. Because AChE inhibitors are utilized for medications for Alzheimer's disease, we investigated whether pharmacological inhibition of AChE activity induced any synaptic defects. We found that controls exposed to a sublethal dose of DDVP phenocopied the synaptic structural defects of the ace hypomorphic mutant. These results suggest that down-regulation of AChE activity, regardless of whether it is due to genetic or pharmacological manipulations, results in altered synaptic architecture. Our study suggests that exposure to AChE inhibitors for 6-12 months may induce altered synaptic architectures in human brains with Alzheimer's diseases, similar to those reported here. These changes may underlie or contribute to the loss of efficacy of AChE inhibitors after prolonged treatment.

Drastic decrease in dopamine receptor levels in the striatum of acetylcholinesterase knock-out mouse

BACKGROUND

The acetylcholinesterase knock-out mouse lives to adulthood despite 60-fold elevated acetylcholine concentrations in the brain that are lethal to wild-type animals. Part of its mechanism of survival is a 50% decrease in muscarinic and nicotinic receptors and a 50% decrease in adrenoceptor levels.

HYPOTHESIS

The hypothesis was tested that the dopaminergic neuronal system had also adapted.

METHODS

Radioligand binding assays measured dopamine receptor level and binding affinity in the striatum. Immunohistochemistry of brain sections with specific antibodies visualized dopamine transporter. Effects on the intracellular compartment were measured as cAMP content, PI-phospholipase C activity.

RESULTS

Dopamine receptor levels were decreased 28-fold for the D(1)-like, and more than 37-fold for the D(2)-like receptors, though binding affinity was normal. Despite these huge changes in receptor levels, dopamine transporter levels were not affected. The intracellular compartment had normal levels of cAMP and PI-phospholipase C activity.

CONCLUSION

Survival of the acetylcholinesterase knock-out mouse could be linked to adaptation of many neuronal systems during development including the cholinergic, adrenergic and dopaminergic. These adaptations balance the overstimulation of cholinergic receptors caused by high acetylcholine concentrations and thus maintain homeostasis inside the cell, allowing the animal to live.