Up-regulation of GPR139 in the medial septum ameliorates cognitive impairment in two mouse models of Alzheimer's disease

G-protein coupled receptors (GPCRs) constitute the largest class of cell surface receptors and present prominent drug targets. GPR139 is an orphan GPCR detected in the septum of the brain. However, its roles in cognition are still unclear. Here we first established a mouse model of cognitive impairment by a single intracerebroventricular injection of aggregated amyloid-beta peptide 1-42 (Aβ1-42). RNA-sequencing data analysis showed that Aβ1-42 induced a significant decrease of GPR139 mRNA in the basal forebrain. Using GPR139 agonist JNJ-63533054 and behavioral tests, we found that GPR139 activation in the brain ameliorated Aβ1-42-induced cognitive impairment. Using western blot, TUNEL apoptosis and Golgi staining assays, we showed that GPR139 activation alleviated Aβ1-42-induced apoptosis and synaptotoxicity in the basal forebrain rather than prefrontal cortex and hippocampus. The further study identified that GPR139 was widely expressed in cholinergic neurons of the medial septum (MS). Using the overexpression virus and transgenic animal model, we showed that up-regulation of GPR139 in MS cholinergic neurons ameliorated cognitive impairment, apoptosis and synaptotoxicity in APP/PS1 transgenic mice. These findings reveal that GPR139 of MS cholinergic neurons could be a critical node in cognition and potentially provides insight into the pathogenesis of Alzheimer's disease.

Selective Medial Septum Lesions in Healthy Rats Induce Longitudinal Changes in Microstructure of Limbic Regions, Behavioral Alterations, and Increased Susceptibility to Status Epilepticus

Septo-hippocampal pathway, crucial for physiological functions and involved in epilepsy. Clinical monitoring during epileptogenesis is complicated. We aim to evaluate tissue changes after lesioning the medial septum (MS) of normal rats and assess how the depletion of specific neuronal populations alters the animals' behavior and susceptibility to establishing a pilocarpine-induced status epilepticus. Male Sprague-Dawley rats were injected into the MS with vehicle or saporins (to deplete GABAergic or cholinergic neurons; n = 16 per group). Thirty-two animals were used for diffusion tensor imaging (DTI); scanned before surgery and 14 and 49 days post-injection. Fractional anisotropy and apparent diffusion coefficient were evaluated in the fimbria, dorsal hippocampus, ventral hippocampus, dorso-medial thalamus, and amygdala. Between scans 2 and 3, animals were submitted to diverse behavioral tasks. Stainings were used to analyze tissue alterations. Twenty-four different animals received pilocarpine to evaluate the latency and severity of the status epilepticus 2 weeks after surgery. Additionally, eight different animals were only used to evaluate the neuronal damage inflicted on the MS 1 week after the molecular surgery. Progressive changes in DTI parameters in both white and gray matter structures of the four evaluated groups were observed. Behaviorally, the GAT1-saporin injection impacted spatial memory formation, while 192-IgG-saporin triggered anxiety-like behaviors. Histologically, the GABAergic toxin also induced aberrant mossy fiber sprouting, tissue damage, and neuronal death. Regarding the pilocarpine-induced status epilepticus, this agent provoked an increased mortality rate. Selective septo-hippocampal modulation impacts the integrity of limbic regions crucial for certain behavioral skills and could represent a precursor for epilepsy development.

The regulation of the pedunculopontine tegmental nucleus in sleep-wake states

The pedunculopontine tegmental nucleus (PPTg) plays a vital role in sleep/wake states. There are three main kinds of heterogeneous neurons involved: cholinergic, glutamatergic, and gamma-aminobutyric acidergic (GABAergic) neurons. However, the precise roles of cholinergic, glutamatergic and GABAergic PPTg cell groups in regulating sleep-wake are unknown. Recent work suggests that the cholinergic, glutamatergic, and GABAergic neurons of the PPTg may activate the main arousal-promoting nucleus, thus exerting their wakefulness effects. We review the related projection pathways and functions of various neurons of the PPTg, especially the mechanisms of the PPTg in sleep-wake, thus providing new perspectives for research of sleep-wake mechanisms.

Interictal spikes in Alzheimer's disease: Preclinical evidence for dominance of the dentate gyrus and cholinergic control by the medial septum

Interictal spikes (IIS) are a common type of abnormal electrical activity in Alzheimer's disease (AD) and preclinical models. The brain regions where IIS are largest are not known but are important because such data would suggest sites that contribute to IIS generation. Because hippocampus and cortex exhibit altered excitability in AD models, we asked which areas dominate the activity during IIS along the cortical-CA1-dentate gyrus (DG) dorso-ventral axis. Because medial septal (MS) cholinergic neurons are overactive when IIS typically occur, we also tested the novel hypothesis that silencing the MS cholinergic neurons selectively would reduce IIS. We used mice that simulate aspects of AD: Tg2576 mice, presenilin 2 (PS2) knockout mice and Ts65Dn mice. To selectively silence MS cholinergic neurons, Tg2576 mice were bred with choline-acetyltransferase (ChAT)-Cre mice and offspring were injected in the MS with AAV encoding inhibitory designer receptors exclusively activated by designer drugs (DREADDs). We recorded local field potentials along the cortical-CA1-DG axis using silicon probes during wakefulness, slow-wave sleep (SWS) and rapid eye movement (REM) sleep. We detected IIS in all transgenic or knockout mice but not age-matched controls. IIS were detectable throughout the cortical-CA1-DG axis and occurred primarily during REM sleep. In all 3 mouse lines, IIS amplitudes were significantly greater in the DG granule cell layer vs. CA1 pyramidal layer or overlying cortex. Current source density analysis showed robust and early current sources in the DG, and additional sources in CA1 and the cortex also. Selective chemogenetic silencing of MS cholinergic neurons significantly reduced IIS rate during REM sleep without affecting the overall duration, number of REM bouts, latency to REM sleep, or theta power during REM. Notably, two control interventions showed no effects. Consistent maximal amplitude and strong current sources of IIS in the DG suggest that the DG is remarkably active during IIS. In addition, selectively reducing MS cholinergic tone, at times when MS is hyperactive, could be a new strategy to reduce IIS in AD.

Insulin Preferentially Regulates the Activity of Parasympathetic Preganglionic Neurons over Sympathetic Preganglionic Neurons

BACKGRUOUND

Insulin is a peptide hormone that regulates post-prandial physiology, and it is well known that insulin controls homeostasis at least in part via the central nervous system. In particular, insulin alters the activity of neurons within the autonomic nervous system. However, currently available data are mostly from unidentified brainstem neurons of the dorsal motor nucleus of the vagus nerve (DMV).

METHODS

In this study, we used several genetically engineered mouse models to label distinct populations of neurons within the brainstem and the spinal cord for whole-cell patch clamp recordings and to assess several in vivo metabolic functions.

RESULTS

We first confirmed that insulin directly inhibited cholinergic (parasympathetic preganglionic) neurons in the DMV. We also found inhibitory effects of insulin on both the excitatory and inhibitory postsynaptic currents recorded in DMV cholinergic neurons. In addition, GABAergic neurons of the DMV and nucleus tractus solitarius were inhibited by insulin. However, insulin had no effects on the cholinergic sympathetic preganglionic neurons of the spinal cord. Finally, we obtained results suggesting that the insulininduced inhibition of parasympathetic preganglionic neurons may not play a critical role in the regulation of glucose homeostasis and gastrointestinal motility.

CONCLUSION

Our results demonstrate that insulin inhibits parasympathetic neuronal circuitry in the brainstem, while not affecting sympathetic neuronal activity in the spinal cord.

Upper brainstem cholinergic neurons project to ascending and descending circuits

BACKGROUND

Based on their anatomical location, rostral projections of nuclei are classified as ascending circuits, while caudal projections are classified as descending circuits. Upper brainstem neurons participate in complex information processing and specific sub-populations preferentially project to participating ascending or descending circuits. Cholinergic neurons in the upper brainstem have extensive collateralizations in both ascending and descending circuits; however, their single-cell projection patterns remain unclear because of the lack of comprehensive characterization of individual neurons.

RESULTS

By combining fluorescent micro-optical sectional tomography with sparse labeling, we acquired a high-resolution whole-brain dataset of pontine-tegmental cholinergic neurons (PTCNs) and reconstructed their detailed morphology using semi-automatic reconstruction methods. As the main source of acetylcholine in some subcortical areas, individual PTCNs had abundant axons with lengths up to 60 cm and 5000 terminals and innervated multiple brain regions from the spinal cord to the cortex in both hemispheres. Based on various collaterals in the ascending and descending circuits, individual PTCNs were grouped into four subtypes. The morphology of cholinergic neurons in the pedunculopontine nucleus was more divergent, whereas the laterodorsal tegmental nucleus neurons contained richer axonal branches and dendrites. In the ascending circuits, individual PTCNs innervated the thalamus in three different patterns and projected to the cortex via two separate pathways. Moreover, PTCNs targeting the ventral tegmental area and substantia nigra had abundant collaterals in the pontine reticular nuclei, and these two circuits contributed oppositely to locomotion.

CONCLUSIONS

Our results suggest that individual PTCNs have abundant axons, and most project to various collaterals in the ascending and descending circuits simultaneously. They target regions with multiple patterns, such as the thalamus and cortex. These results provide a detailed organizational characterization of cholinergic neurons to understand the connexional logic of the upper brainstem.

Plasminogen decreases Aβ42 and Tau deposition, and shows multi-beneficial effects on Alzheimer's disease in mice and humans

Alzheimer's disease (AD) is the most common neurodegenerative disorder in the world. The aggregation of both amyloid beta (Aβ) peptides extracellularly and Tau proteins intracellularly plays key roles in the pathological consequences of AD, which lead to cholinergic neurodegeneration and eventually death. Currently, there are no effective methods to stop the progression of AD. Using ex vivo, in vivo and clinical approaches, we investigated the functional effects of plasminogen on the widely used FAD, Aβ42 oligomer or Tau intracranial injection-induced AD mouse model and explored its therapeutic effects on patients with AD. The results show that intravenously injected plasminogen rapidly crosses the blood‒brain barrier (BBB); increases plasmin activity in the brain; colocalizes with and effectively promotes the clearance of Aβ42 peptide and Tau protein deposits ex vivo and in vivo; increases the choline acetyltransferase (ChAT) level and decreases the acetylcholinesterase (AChE) activity; and improves the memory functions. Clinically, when GMP-level plasminogen was administered to 6 AD patients for 1-2 weeks, their average scores on the Minimum Mental State Examination (MMSE), which is a standard scoring system used to measure the memory loss and cognitive deficits, were extremely significantly improved by 4.2 ± 2.23 points, e.g., an average increase from 15.5 ± 8.22 before treatment to 19.7 ± 7.09 after treatment. The preclinical study and pilot clinical study suggest that plasminogen is effective in treating AD and may be a promising drug candidate.

The impact of selective and non-selective medial septum stimulation on hippocampal neuronal oscillations: A study based on modeling and experiments

Alzheimer's disease (AD) is a neurodegenerative disorder with a rising socioeconomic impact on societies. The hippocampus (HPC), which plays an important role in AD, is affected in the early stages. The medial septum (MS) in the forebrain provides major cholinergic input to the HPC and has been shown to play a significant role in generating oscillations in hippocampal neurons. Cholinergic neurons in the basal forebrain are particularly vulnerable to neurodegeneration in AD. To better understand the role of MS neurons including the cholinergic, glutamatergic, and GABAergic subpopulations in generating the well-known brain rhythms in HPC including delta, theta, slow gamma, and fast gamma oscillations, we designed a detailed computational model of the septohippocampal pathway. We validated the results of our model, using electrophysiological recordings in HPC with and without stimulation of the cholinergic neurons in MS using designer receptors exclusively activated by designer drugs (DREADDs) in healthy male ChAT-cre rats. Then, we eliminated 75% of the MS cholinergic neurons in the model to simulate degeneration in AD. A series of selective and non-selective stimulations of the remaining MS neurons were performed to understand the dynamics of oscillation regulation in the HPC during the degenerated state. In this way, appropriate stimulation strategies able to normalize the aberrant oscillations are proposed. We found that selectively stimulating the remaining healthy cholinergic neurons was sufficient for network recovery and compare this to stimulating other subpopulations and a non-selective stimulation of all MS neurons. Our data provide valuable information for the development of new therapeutic strategies in AD and a tool to test and predict the outcome of potential theranostic manipulations.

A selective degeneration of cholinergic neurons mediated by NRADD in an Alzheimer's disease mouse model

Cholinergic neurons in the basal forebrain constitute a major source of cholinergic inputs to the forebrain, modulate diverse functions including sensory processing, memory and attention, and are vulnerable to Alzheimer's disease (AD). Recently, we classified cholinergic neurons into two distinct subpopulations; calbindin D28K-expressing (D28K+) versus D28K-lacking (D28K-) neurons. Yet, which of these two cholinergic subpopulations are selectively degenerated in AD and the molecular mechanisms underlying this selective degeneration remain unknown. Here, we reported a discovery that D28K+ neurons are selectively degenerated and this degeneration induces anxiety-like behaviors in the early stage of AD. Neuronal type specific deletion of NRADD effectively rescues D28K+ neuronal degeneration, whereas genetic introduction of exogenous NRADD causes D28K- neuronal loss. This gain- and loss-of-function study reveals a subtype specific degeneration of cholinergic neurons in the disease progression of AD and hence warrants a novel molecular target for AD therapy.

Resistance of Basal Forebrain Cholinergic Neurons to TDP-43 Proteinopathy in Primary Progressive Aphasia

Basal forebrain cholinergic neurons (BFCN) display accumulation of neurofibrillary tangles and degeneration in Alzheimer disease and are targets of therapeutic intervention. This study determined vulnerability of BFCN to accumulation of TDP-43 in primary progressive aphasia with TDP-43 proteinopathy (PPA-TDP). Brains from 16 PPA participants with pathologically confirmed TDP-43 proteinopathy, with available paraffin-embedded sections (Group 1), or systematically sampled frozen sections (Group 2), were studied. Immunohistochemistry was performed with an antibody against phosphorylated TDP-43. BFCN were identified by their magnocellular appearance in Nissl preparations. Presence of TDP-43 inclusions and preinclusions in BFCN was determined and quantitative analysis was performed in Group 2. In Group 1, BFCN were completely free of inclusions except for occasional dystrophic neurites. Sparse TDP-43 preinclusions with smooth or granular staining in BFCN were detected. In Group 2, extremely rare TDP-43 intranuclear inclusions were detected in 0.1% of BFCN per section, along with occasional dystrophic neurites. Although sparse, significantly more preinclusions (1.4% of BFCN) were present when compared with inclusions. No hemispheric differences were noted. Small neurons near BFCN contained more preinclusions compared with BFCN. Thus, BFCN in PPA-TDP are resistant to TDP-43 proteinopathy and degeneration, suggesting that cholinergic therapy is unlikely to be effective in this disorder.

Trihexyphenidyl increases delta activity in non-rapid eye movement sleep without impairing cognitive function in rodent models

Both human and rodent studies suggest the link between non-rapid eye movement (NREM) sleep and cognition. Recent study indicated that selective activation of cholinergic neurons in basal forebrain inhibits electroencephalogram (EEG) delta power and shortens NREM sleep. In the current study, we aimed to test the pharmacological effect of trihexyphenidyl (THP), a selective muscarinic M1 receptor antagonist, on EEG power spectra and sleep with or without the selective activation of basal forebrain cholinergic neurons. THP (1, 2, and 3 mg/kg) was administrated intraperitoneally in natural sleep phase. Basal forebrain cholinergic neurons expressing modified G protein-coupled muscarinic receptors (hM3Dq) were activated by intraperitoneal injection of clozapine-N-oxide in ChAT-IRES-Cre mice. EEG and electromyogram (EMG) signals were recorded in freely moving mice to analyze EEG power spectrum and sleep hypnogram. Y-maze and novel object recognition tests were used for testing cognition. THP 1 mg/kg significantly increased EEG delta power and facilitated NREM sleep in wildtype mice, while THP 3 mg/kg was required in ChAT-IRES-Cre mice treated with clozapine-N-oxide. THP with dosage up to 8 mg/kg did not induce cognitive impairments in wildtype mice. EEG delta power of NREM sleep is often used as an indicator of sleep depth or sleep quality, which tightly link with sleep-dependent cognition. Taken together, the data collected from rodents hinted that, THP could possibly be used as the NREM sleep facilitator in humans.

Cholinergic Senescence in the Ts65Dn Mouse Model for Down Syndrome

Down syndrome (DS) induces a variable phenotype including intellectual disabilities and early development of Alzheimer’s disease (AD). Moreover, individuals with DS display accelerated aging that affects diverse organs, among them the brain. The Ts65Dn mouse is the most widely used model to study DS. Progressive loss of cholinergic neurons is one of the hallmarks of AD present in DS and in the Ts65Dn model. In this study, we quantify the number of cholinergic neurons in control and Ts65Dn mice, observing a general reduction in their number with age but in particular, a greater loss in old Ts65Dn mice. Increased expression of the m1 muscarinic receptor in the hippocampus counteracts this loss. Cholinergic neurons in the Ts65Dn mice display overexpression of the early expression gene c-fos and an increase in the expression of β-galactosidase, a marker of senescence. A possible mechanism for senescence induction could be phosphorylation of the transcription factor FOXO1 and its retention in the cytoplasm, which we are able to confirm in the Ts65Dn model. In our study, using Ts65Dn mice, we observe increased cholinergic activity, which induces a process of early senescence that culminates in the loss of these neurons.

In vivo vesicular acetylcholine transporter density in human peripheral organs: an [18F]FEOBV PET/CT study

Background

The autonomic nervous system is frequently affected in some neurodegenerative diseases, including Parkinson’s disease and Dementia with Lewy bodies. In vivo imaging methods to visualize and quantify the peripheral cholinergic nervous system are lacking. By using [¹⁸F]FEOBV PET, we here describe the peripheral distribution of the specific cholinergic marker, vesicular acetylcholine transporters (VAChT), in human subjects. We included 15 healthy subjects aged 53–86 years for 70 min dynamic PET protocol of peripheral organs. We performed kinetic modelling of the adrenal gland, pancreas, myocardium, renal cortex, spleen, colon, and muscle using an image-derived input function from the aorta. A metabolite correction model was generated from venous blood samples. Three non-linear compartment models were tested. Additional time-activity curves from 6 to 70 min post injection were generated for prostate, thyroid, submandibular-, parotid-, and lacrimal glands.

Results

A one-tissue compartment model generated the most robust fits to the data. Total volume-of-distribution rank order was: adrenal gland > pancreas > myocardium > spleen > renal cortex > muscle > colon. We found significant linear correlations between total volumes-of-distribution and standard uptake values in most organs.

Conclusion

High [¹⁸F]FEOBV PET signal was found in structures with known cholinergic activity. We conclude that [¹⁸F]FEOBV PET is a valid tool for estimating VAChT density in human peripheral organs. Simple static images may replace kinetic modeling in some organs and significantly shorten scan duration.

Clinical Trial Registration Trial registration: NCT, NCT03554551. Registered 31 May 2018. https://clinicaltrials.gov/ct2/show/NCT03554551?term=NCT03554551&draw=2&rank=1.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-022-00889-9.

Cell-specific effects of Dyt1 knock-out on sensory processing, network-level connectivity, and motor deficits

DYT1 dystonia is a debilitating movement disorder characterized by repetitive, unintentional movements and postures. The disorder has been linked to mutation of the TOR1A/DYT1 gene encoding torsinA. Convergent evidence from studies in humans and animal models suggest that striatal medium spiny neurons and cholinergic neurons are important in DYT1 dystonia. What is not known is how torsinA dysfunction in these specific cell types contributes to the pathophysiology of DYT1 dystonia. In this study we sought to determine whether torsinA dysfunction in cholinergic neurons alone is sufficient to generate the sensorimotor dysfunction and brain changes associated with dystonia, or if torsinA dysfunction in a broader subset of cell types is needed. We generated two genetically modified mouse models, one with selective Dyt1 knock-out from dopamine-2 receptor expressing neurons (D2KO) and one where only cholinergic neurons are impacted (Ch2KO). We assessed motor deficits and performed in vivo 11.1 T functional MRI to assess sensory-evoked brain activation and connectivity, along with diffusion MRI to assess brain microstructure. We found that D2KO mice showed greater impairment than Ch2KO mice, including reduced sensory-evoked brain activity in key regions of the sensorimotor network, and altered functional connectivity of the striatum that correlated with motor deficits. These findings suggest that (1) the added impact of torsinA dysfunction in medium spiny and dopaminergic neurons of the basal ganglia generate more profound deficits than the dysfunction of cholinergic neurons alone, and (2) that sensory network impairments are linked to motor deficits in DYT1 dystonia.

The Organic Cation Transporter 2 Inhibitor Quinidine Modulates the Neuroprotective Effect of Nerve Growth Factor and Memantine on Cholinergic Neurons of the Basal Nucleus of Meynert in Organotypic Brain Slices

INTRODUCTION

Alzheimer's disease (AD) is a severe neurodegenerative disorder of the brain characterized by degeneration of cholinergic neurons which is directly linked to cognitive decline. Nerve growth factor (NGF) is the most potent protective factor for cholinergic neurons, additionally the NMDA antagonist memantine blocks glutamate-mediated excitotoxic activity. Quinidine is an inhibitor of organic cation transporter 2 (OCT2). OCT2 is located on cholinergic neurons and plays a role in presynaptic reuptake and recycling of acetylcholine in the brain. We hypothesize that quinidine can modulate the protective effects of NGF and memantine on cholinergic neurons in organotypic brain slices of the nucleus basalis of Meynert (nBM).

METHODS

Organotypic brain slices of nBM were incubated with 100 ng/mL NGF, 10 µM memantine, 10 µM quinidine, and combinations of these treatments for 2 weeks. Cholinergic neurons were immunohistochemically stained for choline acetyltransferase (ChAT).

RESULTS

Our data show that NGF as well as memantine counteracted the cell death of cholinergic nBM neurons. Quinidine alone had no toxic effect on cholinergic neurons but inhibited the protective effect of NGF and memantine when applied simultaneously.

DISCUSSION/CONCLUSION

Our data provide evidence that quinidine modulates the survival of cholinergic nBM neurons via OCT2.

The effects of astaxanthin treatment on a rat model of Alzheimer's disease

Alzheimer's disease (AD), a progressive neurodegenerative disorder characterized by memory loss and dementia, could be a consequence of the abnormalities of cortical milieu, such as oxidative stress, inflammation, and/or accompanied with the aggregation of β-amyloid. The majority of AD patients are sporadic, late-onset AD, which predominantly occurs over 65 years of age. Our results revealed that the ferrous amyloid buthionine (FAB)-infused sporadic AD-like model showed deficits in spatial learning and memory and with apparent loss of choline acetyltransferase (ChAT) expression in medial septal (MS) nucleus. In hippocampal CA1 region, the loss of pyramidal neurons was accompanied with cholinergic fiber loss and neuroinflammatory responses including glial reaction and enhanced expression of inducible nitric oxide synthase (iNOS). Surviving hippocampal CA1 pyramidal neurons showed the reduction of dendritic spines as well. Astaxanthin (ATX), a potent antioxidant, reported to improve the outcome of oxidative-stress-related diseases. The ATX treatment in FAB-infused rats decreased neuroinflammation and restored the ChAT + fibers in hippocampal CA1 region and the ChAT expression in MS nucleus. It also partly recovered the spine loss on hippocampal CA1 pyramidal neurons and ameliorated the behavioral deficits in AD-like rats. From these data, we believed that the ATX can be a potential option for slowing the progression of Alzheimer's disease.

Integrated phylogeny of the human brain and pathobiology of Alzheimer's disease: A unifying hypothesis

The disproportionate evolutionary expansion of the human cerebral cortex with reinforcement of cholinergic innervations warranted a major rise in the functional and metabolic load of the conserved basal forebrain (BF) cholinergic system. Given that acetylcholine (ACh) regulates properties of the microtubule-associated protein (MAP) tau and promotes non-amyloidogenic processing of amyloid precursor protein (APP), growing neocortex predicts higher demands for ACh, while the emerging role of BF cholinergic projections in Aβ clearance infers greater exposure of source neurons and their innervation fields to amyloid pathology. The higher exposure of evolutionary most recent cortical areas to the amyloid pathology of Alzheimer's disease (AD) with synaptic impairments and atrophy, therefore, might involve attenuated homeostatic effects of BF cholinergic projections, in addition to fall-outs of inherent processes of expanding association areas. This unifying model, thus, views amyloid pathology and loss of cholinergic cells as a quid pro quo of the allometric evolution of the human brain, which in combination with increase in life expectancy overwhelm the fine homeostatic balance and trigger the disease process.

Neural Circuits for Sleep-Wake Regulation

The neural mechanisms of sleep, a fundamental biological behavior from invertebrates to humans, have been a long-standing mystery and present an enormous challenge. Gradually, perspectives on the neurobiology of sleep have been more various with the technical innovations over the recent decades, and studies have now identified many specific neural circuits that selectively regulate the initiation and maintenance of wake, rapid eye movement (REM) sleep, and non-REM (NREM) sleep. The cholinergic system in basal forebrain (BF) that fire maximally during waking and REM sleep is one of the key neuromodulation systems related to waking and REM sleep. Here we outline the recent progress of the BF cholinergic system in sleep-wake cycle. The intricate local connectivity and multiple projections to other cortical and subcortical regions of the BF cholinergic system elaborately presented here form a conceptual framework for understanding the coordinating effects with the dissecting regions. This framework also provides evidences regarding the relationships between the general anesthesia and wakefulness/sleep cycle focusing on the neural circuitry of unconsciousness induced by anesthetic drugs.

Trans-Differentiation of Human Dental Pulp Stem Cells Into Cholinergic-Like Neurons Via Nerve Growth Factor

Introduction:

Cell therapy has been widely considered as a therapeutic approach for neurodegenerative diseases and nervous system damage. Cholinergic neurons as one of the most important neurons that play a significant role in controlling emotions, mobility, and autonomic systems. In this study, Human Dental Pulp Stem Cells (hDPSCs) were differentiated into the cholinergic neurons by β-mercaptoethanol in the preinduction phase and also by the nerve growth factor (NGF) in the induction phase.

Methods:

The hDPSCs were evaluated for CD73, CD31, CD34, and Oct-4. Concentration-time relationships for NGF were assessed by evaluating the viability rate of cells and the immune response to nestin, neurofilament 160, microtubule-associated protein-2, and choline acetyltransferase.

Results:

The hDPSCs had a negative response to CD34 and CD31. The optimal dose for the NGF was 50 ng/mL seven days after the induction when the highest percentage of expressing markers for the Cholinergic neurons (ChAT) was detected.

Conclusion:

The results of this study provided a method for producing cholinergic neurons by hDPSCs, which can be used in cytotherapy for degenerative diseases of the nervous system and also spinal cord injury.

Neuroimmune interactions and kidney disease

The autonomic nervous system plays critical roles in maintaining homeostasis in humans, directly regulating inflammation by altering the activity of the immune system. The cholinergic anti-inflammatory pathway is a well-studied neuroimmune interaction involving the vagus nerve. CD4-positive T cells expressing β2 adrenergic receptors and macrophages expressing the alpha 7 subunit of the nicotinic acetylcholine receptor in the spleen receive neurotransmitters such as norepinephrine and acetylcholine and are key mediators of the cholinergic anti-inflammatory pathway. Recent studies have demonstrated that vagus nerve stimulation, ultrasound, and restraint stress elicit protective effects against renal ischemia-reperfusion injury. These protective effects are induced primarily via activation of the cholinergic anti-inflammatory pathway. In addition to these immunological roles, nervous systems are directly related to homeostasis of renal physiology. Whole-kidney three-dimensional visualization using the tissue clearing technique CUBIC (clear, unobstructed brain/body imaging cocktails and computational analysis) has illustrated that renal sympathetic nerves are primarily distributed around arteries in the kidneys and denervated after ischemia-reperfusion injury. In contrast, artificial renal sympathetic denervation has a protective effect against kidney disease progression in murine models. Further studies are needed to elucidate how neural networks are involved in progression of kidney disease.

Comparative analysis of three different protocols for cholinergic neuron differentiation in vitro using mesenchymal stem cells from human dental pulp

A decrease in the activity of choline acetyltransferase, the enzyme responsible for acetylcholine synthesis in the cholinergic neurons cause neurological disorders involving a decline in cognitive abilities, such as Alzheimer's disease. Mesenchymal stem cells (MSCs) can be used as an efficient therapeutic agents due to their neuronal differentiation potential. Different source derived MSCs may have different differentiation potential under different inductions. Various in vitro protocols have been developed to differentiate MSCs into specific neurons but the comparative effect of different protocols utilizing same source derived MSCs, is not known. To address this issue, dental pulp derived MSCs (DPSCs) were differentiated into cholinergic neurons using three different protocols. In protocol I, DPSCs were pre-induced with serum-free ADMEM containing 1 mM of β-mercaptoethanol for 24 h and then incubated with 100 ng/ml nerve growth factor (NGF) for 6 days. Under protocol II, DPSCs were cultured in serum-free ADMEM containing 15 µg/ml of D609 (tricyclodecan-9-yl-xanthogenate) for 4 days. Under protocol III, the DPSCs were cultured in serum-free ADMEM containing 10 ng/ml of basic fibroblast growth factor (bFGF), 50 µM of forskolin, 250 ng/ml of sonic hedgehog (SHH), and 0.5 µM of retinoic acid (RA) for 7 days. The DPSCs were successfully trans-differentiated under all the protocols, exhibited neuron-like morphologies with upregulated cholinergic neuron-specific markers such as ChAT, HB9, ISL1, BETA-3, and MAP2 both at mRNA and protein levels in comparison to untreated cells. However, protocol III-induced cells showed the highest expression of the cholinergic markers and secreted the highest level of acetylcholine.

The Effect of Intrahippocampal Insulin Injection on Scopolamine-induced Spatial Memory Impairment and Extracellular Signal-regulated Kinases Alteration

Introduction

It is well documented that insulin has neuroprotective and neuromodulator effects and can protect against different models of memory loss. Furthermore, cholinergic activity plays a significant role in memory, and scopolamine-induced memory loss is widely used as an experimental model of dementia. The current study aimed at investigating the possible effects of insulin against scopolamine-induced memory impairment in Wistar rat and its underlying molecular mechanisms.

Methods

Accordingly, animals were bilaterally cannulated in CA1, hippocampus. Intrahippocampal administration of insulin 6 MU and 12 MU in CA1 per day was performed during first 6 days after surgery. During next four days, the animal's spatial learning and memory were assessed in Morris water maze test (three days of learning and one day of retention test). The animals received scopolamine (1 mg/kg) Intraperitoneally (IP) 30 minutes before the onset of behavioral tests in each day. In the last day, the hippocampi were dissected and the levels of MAPK (mitogen-activated protein kinases) and caspase-3 activation were analyzed by Western blot technique.

Results

The behavioral results showed that scopolamine impaired spatial learning and memory without activating casapase-3, P38, and JNK, but chronic pretreatment by both doses of insulin was unable to restore this spatial memory impairment. In addition, scopolamine significantly reduced Extracellular signal-Regulated Kinases (ERKs) activity and insulin was unable to restore this reduction. Results revealed that scopolamine-mediated memory loss was not associated with hippocampal damage.

Conclusion

Insulin as a neuroprotective agent cannot restore memory when there is no hippocampal damage. In addition, the neuromodulator effect of insulin is not potent enough to overwhelm scopolamine-mediated disruptions of synaptic neurotransmission.

Cholinergic Differentiation of Human Neuroblastoma SH-SY5Y Cell Line and Its Potential Use as an In vitro Model for Alzheimer's Disease Studies

Cholinergic transmission is critical to high-order brain functions such as memory, learning, and attention. Alzheimer's disease (AD) is characterized by cognitive decline associated with a specific degeneration of cholinergic neurons. No effective treatment to prevent or reverse the symptoms is known. Part of this might be due to the lack of in vitro models that effectively mimic the relevant features of AD. Here, we describe the characterization of an AD in vitro model using the SH-SY5Y cell line. Exponentially growing cells were maintained in DMEM/F12 medium and differentiation was triggered by the combination of retinoic acid (RA) and BDNF. Both acetylcholinesterase (AChE) and choline acetyltransferase (ChAT) enzymatic activities and immunocontent were determined. For mimicking tau and amyloid-β pathology, RA + BDNF-differentiated cells were challenged with okadaic acid (OA) or soluble oligomers of amyloid-β (AβOs) and neurotoxicity was evaluated. RA + BDNF-induced differentiation resulted in remarkable neuronal morphology alterations characterized by increased neurite density. Enhanced expression and enzymatic activities of cholinergic markers were observed compared to RA-differentiation only. Combination of sublethal doses of AβOs and OA resulted in decreased neurite densities, an in vitro marker of synaptopathy. Challenging RA + BDNF-differentiated SH-SY5Y cells with the combination of sublethal doses of OA and AβO, without causing considerable decrease of cell viability, provides an in vitro model which mimics the early-stage pathophysiology of cholinergic neurons affected by AD.

Differentiation of human glioblastoma U87 cells into cholinergic neuron

To facilitate research methodologies for investigating the role of cholinergic nerves in many diseases, establishing an in vitro cholinergic neuron model is necessary. In this study, we investigated whether human glioblastoma U87 cells could be differentiated into cholinergic neurons in vitro. Sodium butyrate was used as the differentiation agent. The differentiated cells established by inducing U87 cells with sodium butyrate were named D-U87 cells. Immunofluorescence was used to label the neuronal markers MAP2, NF-M, and ChAT and the glial marker GFAP in D-U87 cells. Flow cytometry was used to measure cell cycle distribution in D-U87 cells. PCR, protein chip, and western blot assays were used to measure the expression levels of muscarinic cholinergic receptor 1 (M1), M4, ChAT, SYP and Akt. ELISA was used to measure neurotransmitter levels. As a result, we found that sodium butyrate induced U87 cell differentiation into cells with neuronal characteristics and increased not only the expression levels of the cholinergic neuron-related proteins M1, M4, ChAT and SYP in D-U87 cells but also the acetylcholine neurotransmitters in D-U87 cells. Moreover, the Akt protein expression in D-U87 cells was increased compared with that in U87 cells. Finally, we found that M1, M4, ChAT and SYP protein expression and acetylcholine secretion levels were significantly decreased in D-U87 cells after treatment with the Akt inhibitor MK-2206. These results demonstrate that D-U87 cells exhibit cholinergic neuron characteristics and that sodium butyrate induced U87 cell differentiation into cholinergic neuron partially through Akt signaling.

Effects of diabetes mellitus on myenteric neuronal density and sodium channel expression in the rat ileum

Diabetes mellitus (DM) may lead to gastrointestinal motility disorders. Rodent models of DM indicate the presence of morpho-functional abnormalities of the enteric nervous system. Here, we evaluated whether experimental DM can cause changes in the excitatory cholinergic fibers, neuronal density, and voltage-gated sodium channel (Nav) expression in the myenteric plexus of the ileum. After streptozotocin-induced hyperglycemia in female rats progressed for eight weeks, triple immunofluorescence labeling experiments revealed that the neuronal density in DM rats was significantly lower than that in control. On average, the density of total neurons reduced by 52.2% (p = 0.0001), cholinergic neurons by 50.0% (p = 0.0068), and nitrergic neurons by 54.8% (p = 0.0042). The number of neurons per ganglionic area was also significantly reduced (to 28.2% of total neurons, p = 0.0002; 27.7% of cholinergic neurons, p = 0.0002, and 32.1% of nitrergic neurons, p = 0.0016). Furthermore, the density of the cholinergic fibers at the surface of the longitudinal muscle was significantly reduced (DM: 24 ± 3%; p = 0.003, control: 41 ± 2%); however, western-blot analysis did not indicate a reduction in the expression of choline acetyltransferase (ChAT) in the DM group. The Nav1.6 isoform was detected in different myenteric neurons of the ileum. RT-qPCR data did not suggest an alteration of transcripts for ChAT, neuronal nitric oxide synthase, Nav1.3, Nav1.6, or Nav1.7. Our data support the view that chronic DM leads to a reduction of excitatory cholinergic fibers and neuronal density. However, changes in sodium channel expression pattern, which could cause neuronal dysfunction, were not detected.

Direct conversion of mouse astrocytes into neural progenitor cells and specific lineages of neurons

Background

Cell replacement therapy has been envisioned as a promising treatment for neurodegenerative diseases. Due to the ethical concerns of ESCs-derived neural progenitor cells (NPCs) and tumorigenic potential of iPSCs, reprogramming of somatic cells directly into multipotent NPCs has emerged as a preferred approach for cell transplantation.

Methods

Mouse astrocytes were reprogrammed into NPCs by the overexpression of transcription factors (TFs) Foxg1, Sox2, and Brn2. The generation of subtypes of neurons was directed by the force expression of cell-type specific TFs Lhx8 or Foxa2/Lmx1a.

Results

Astrocyte-derived induced NPCs (AiNPCs) share high similarities, including the expression of NPC-specific genes, DNA methylation patterns, the ability to proliferate and differentiate, with the wild type NPCs. The AiNPCs are committed to the forebrain identity and predominantly differentiated into glutamatergic and GABAergic neuronal subtypes. Interestingly, additional overexpression of TFs Lhx8 and Foxa2/Lmx1a in AiNPCs promoted cholinergic and dopaminergic neuronal differentiation, respectively.

Conclusions

Our studies suggest that astrocytes can be converted into AiNPCs and lineage-committed AiNPCs can acquire differentiation potential of other lineages through forced expression of specific TFs. Understanding the impact of the TF sets on the reprogramming and differentiation into specific lineages of neurons will provide valuable strategies for astrocyte-based cell therapy in neurodegenerative diseases.

Alterations of functional circuitry in aging brain and the impact of mutated APP expression

Alzheimer's disease (AD) is a disease of aging that results in cognitive impairment, dementia, and death. Pathognomonic features of AD are amyloid plaques composed of proteolytic fragments of the amyloid precursor protein (APP) and neurofibrillary tangles composed of hyperphosphorylated tau protein. One type of familial AD occurs when mutant forms of APP are inherited. Both APP and tau are components of the microtubule-based axonal transport system, which prompts the hypothesis that axonal transport is disrupted in AD, and that such disruption impacts cognitive function. Transgenic mice expressing mutated forms of APP provide preclinical experimental systems to study AD. Here, we perform manganese-enhanced magnetic resonance imaging to study transport from hippocampus to forebrain in four cohorts of living mice: young and old wild-type and transgenic mice expressing a mutant APP with both Swedish and Indiana mutations (APPSwInd). We find that transport is decreased in normal aging and further altered in aged APPSwInd plaque-bearing mice. These findings support the hypothesis that transport deficits are a component of AD pathology and thus may contribute to cognitive deficits.

Acute Treatment with T-Type Calcium Channel Enhancer SAK3 Reduces Cognitive Impairments Caused by Methimazole-Induced Hypothyroidism Via Activation of Cholinergic Signaling

Hypothyroidism is a common disorder that is associated with psychological disturbances such as dementia, depression, and psychomotor disorders. We recently found that chronic treatment with the T-type calcium channel enhancer SAK3 prevents the cholinergic neurodegeneration induced by a single intraperitoneal (i.p.) injection of methimazole (MMI; 75 mg/kg), thereby improving cognition. Here, we evaluated the acute effect of SAK3 on cognitive impairments and its mechanism of action following the induction of hypothyroidism. Hypothyroidism was induced by 2 injections of MMI (75 mg/kg, i.p.) administered once per week. Four weeks after the final MMI treatment, MMI-treated mice showed reduced serum thyroxine (T4) levels and cognitive impairments without depression-like behaviors. Although acute SAK3 (1.0 mg/kg, p.o.) administration failed to ameliorate the decreased T4 levels and histochemical destruction of the glomerular structure, acute SAK3 (1.0 mg/kg, p.o.) administration significantly reduced cognitive impairments in MMI-treated mice. Importantly, the α7 nicotinic acetylcholine receptor (nAChR)-selective inhibitor methyllycaconitine (MLA; 12 mg/kg, i.p.) and T-type calcium channel-specific blocker NNC 55-0396 (25 mg/kg, i.p.) antagonized the acute effect of SAK3 on memory deficits in MMI-treated mice. We also confirmed that acute SAK3 administration does not rescue reduced olfactory marker protein or choline acetyltransferase immunoreactivity levels in the olfactory bulb or medial septum. Taken together, these results suggest that SAK3 has the ability to improve the cognitive decline caused by hypothyroidism directly through activation of nAChR signaling and T-type calcium channels.

Nerve growth factor released from collagen scaffolds protects axotomized cholinergic neurons of the basal nucleus of Meynert in organotypic brain slices

BACKGROUND

Alzheimeŕs disease is accompanied by cell death of cholinergic neurons, resulting in cognitive impairment and memory loss. Nerve growth factor (NGF) is the most potent protein to support survival of cholinergic neurons.

NEW METHOD

Organotypic brain slices of the basal nucleus of Meynert (nBM) are a valuable tool to study cell death of axotomized cholinergic neurons, as well as protective effects of NGF added into the medium. The aim of the present study is to use collagen scaffolds crosslinked with polyethyleneglycole and load with NGF to target delivery of NGF to organotypic nBM brain slices.

RESULTS

Collagen scaffolds (visualized by incorporating AlexaFluor 488 antibodies) slowly degraded when applied onto organotypic brain slices within 2 weeks in culture. GFAP reactive astrocytes and Iba1+ microglia became visible around the collagen scaffolds 7days after incubation, showing reactive gliosis. Cholinergic neurons of the nBM survived (201±21, n=8) when incubated with 100ng/ml NGF in the medium compared to NGF-free medium (69±12, n=7). Collagen scaffolds loaded with NGF (1ng/2μl scaffold) significantly rescued cholinergic cell death in the nBM brain slices (175±12, n=10), which was counteracted by an anti-NGF antibody (77±5, n=5).

COMPARISON WITH EXISTING METHODS

The combination of coronal brain slices with biomaterial is a novel and potent tool to selectively study neuroprotective effects.

CONCLUSIONS

Collagen scaffolds loaded with low amounts of a protein/drug of interest can be easily applied directly onto organotypic brain slices, allowing slow targeted release of a protective molecule. Such an approach is highly useful to optimize CollScaff for further in vivo applications.

The binding of botulinum neurotoxins to different peripheral neurons

Botulinum neurotoxins are the most potent toxins known. The double receptor binding modality represents one of the most significant properties of botulinum neurotoxins and largely accounts for their incredible potency and lethality. Despite the high affinity and the very specific binding, botulinum neurotoxins are versatile and multi-tasking toxins. Indeed they are able to act both at the somatic and at the autonomic nervous system. In spite of the preference for cholinergic nerve terminals botulinum neurotoxins have been shown to inhibit to some extent also the noradrenergic postganglionic sympathetic nerve terminals and the afferent nerve terminals of the sensory neurons inhibiting the release of neuropeptides and glutamate, which are responsible of nociception. Therefore, there is increasing evidence that the therapeutic effect in both motor and autonomic disorders is based on a complex mode of botulinum neurotoxin action modulating the activity of efferent as well as afferent nerve fibres.

Cholinergic neuron gene expression differences captured by translational profiling in a mouse model of Alzheimer's disease

Cholinergic neurotransmission is impaired in Alzheimer's disease (AD), and loss of basal forebrain cholinergic neurons is a key component of disease pathogenicity and symptomatology. To explore the molecular basis of this cholinergic dysfunction, we paired translating ribosome affinity purification (TRAP) with RNA sequencing (TRAP-Seq) to identify the actively translating mRNAs in anterior forebrain cholinergic neurons in the TgCRND8 mouse model of AD. Bioinformatic analyses revealed the downregulation of 67 of 71 known cholinergic-related transcripts, consistent with cholinergic neuron dysfunction in TgCRND8 mice, as well as transcripts related to oxidative phosphorylation, neurotrophins, and ribosomal processing. Upregulated transcripts included those related to axon guidance, glutamatergic synapses and kinase activity and included AD-risk genes Sorl1 and Ptk2b. In contrast, the total transcriptome of the anterior forebrain showed upregulation in cytokine signaling, microglia, and immune system pathways, including Trem2, Tyrobp, and Inpp5d. Hence, TRAP-Seq clearly distinguished the differential gene expression alterations occurring in cholinergic neurons of TgCRND8 mice compared with wild-type littermates, providing novel candidate pathways to explore for therapeutic development in AD.

The Lesion Analysis of Cholinergic Neurons in 5XFAD Mouse Model in the Three-Dimensional Level of Whole Brain

Cholinergic system is very important for many higher brain functions, including learning and memory. Cholinergic neurons, especially those in the basal forebrain, are specifically susceptible in some neurodegenerative diseases, such as in Alzheimer's disease (AD). Here, we studied the cholinergic system lesion effects of five familial AD mutations in 5XFAD mice, a transgenic mouse model of AD. Although the cholinergic system has been studied in this mouse model, the cholinergic deficits in AD mice have never been systematically mapped in a whole-brain three-dimensional (3D) reconstruction. Using the 3D reconstruction technology combined with immunohistochemistry (3D-IHC) and design-based stereology, we comprehensively compared the differences of the cholinergic neurons and fibers between the 5XFAD mice and C57BL/6 control mice at different age. Here, we found that the lesion of cholinergic fibers occurred earlier than the cholinergic neuron loss in 5XFAD mice. The cholinergic fiber lesions in the AD mice started sequentially in amygdala, cortex, hippocampus, and then basal forebrain. However, the basal forebrain was the first brain region observed with cholinergic neuron loss at the age of 9 months in 5XFAD mice, whereas such phenomenon first occurred at the age of 15 months in C57BL/6 control mice. Moreover, using 3D reconstruction to compare the lesion of cholinergic system of aged 5XFAD and C57BL/6 control mice, it is intuitive to notice the pathologic regions and severity of lesion. Therefore, the 3D-IHC provides detailed overview of the cholinergic neurons in the whole mouse brain, which will contribute to the study of the developing and pathologic mouse brain.

Cholinergic modulation of the immune system presents new approaches for treating inflammation

The nervous system and immune system have broad and overlapping distributions in the body, and interactions of these ubiquitous systems are central to the field of neuroimmunology. Over the past two decades, there has been explosive growth in our understanding of neuroanatomical, cellular, and molecular mechanisms that mediate central modulation of immune functions through the autonomic nervous system. A major catalyst for growth in this field was the discovery that vagal nerve stimulation (VNS) caused a prominent attenuation of the systemic inflammatory response evoked by endotoxin in experimental animals. This effect was mediated by acetylcholine (ACh) stimulation of nicotinic receptors on splenic macrophages. Hence, the circuit was dubbed the "cholinergic anti-inflammatory pathway". Subsequent work identified the α7 nicotinic ACh receptor (α7nAChR) as the crucial target for attenuation of pro-inflammatory cytokine release from macrophages and dendritic cells. Further investigation made the important discovery that cholinergic T cells within the spleen and not cholinergic nerve cells were the source of ACh that stimulated α7 receptors on splenic macrophages. Given the important role that inflammation plays in numerous disease processes, cholinergic anti-inflammatory mechanisms are under intensive investigation from a basic science perspective and in translational studies of animal models of diseases such as inflammatory bowel disease and rheumatoid arthritis. This basic work has already fostered several clinical trials examining the efficacy of VNS and cholinergic therapeutics in human inflammatory diseases. This review provides an overview of basic and translational aspects of the cholinergic anti-inflammatory response and relevant pharmacology of drugs acting at the α7nAChR.

Distribution of ASIC4 transcripts in the adult wild-type mouse brain

Acid-sensing ion channel 4 (ASIC4) belongs to the ASIC gene family of neuronal proton-gated cation channels, and is the least understood subtype among the members. Previous studies of ASIC4 expression in the mammalian central nervous system have shown that ASIC4 is abundantly expressed in the spinal cord and in various brain regions, such as the cerebral cortex, the hippocampus, and the cerebellum. However, the detailed distribution of ASIC4 transcripts in mammalian brains still remains to be elucidated. In the present study, radioactive in situ hybridization histochemistry with an ASIC4-specific cRNA probe was performed on wild-type mouse brains, followed by X-gal staining experiments with Asic4-lacZ reporter mice Asic4^{tm1a(KOMP)Mbp}. It was found that ASIC4 mRNAs were widely expressed throughout the wild-type brain, but preferentially concentrated in the olfactory bulb, the piriform cortex, the caudate putamen, the preoptic area, the paraventricular nucleus, the medial habenular nucleus, the pretectal area, the lateral geniculate nucleus, the amygdaloid complex, the superior colliculus, the interpeduncular nucleus, and the granule cell layer of the ventral hippocampus, and these results were in agreement with the X-gal-positive reactions observed in the mutant brain. In addition, X-gal staining combined with immunohistochemistry identified intense signals for ASIC4 transcriptional activity in most of the choline acetyltransferase (ChAT)-positive principal neurons located in the basal forebrain cholinergic nuclei. Our data provide useful information to speculate possible roles of ASIC4 in diverse brain functions.

Selective preservation of cholinergic MeCP2 rescues specific Rett-syndrome-like phenotypes in MeCP2stop mice

RTT is a neurodevelopmental disorder characterized by growth regression, motor dysfunction, stereotypic hand movements, and autism features. Typical Rett syndrome (RTT) is predominantly caused by mutations in X-linked MeCP2 gene which encodes methyl-CpG-binding protein 2 (MeCP2). The brain-abundant MeCP2 protein mainly functions as a transcriptional regulator for neurodevelopment-associated genes. Specific functions of MeCP2 in certain neuron types remain to be known. Although cholinergic system is an important modulating system in brain, how MeCP2 in cholinergic neurons contribute to RTT has not been clearly understood. Here we use a mouse model with selectively activated endogenous MeCP2 in cholinergic neurons in otherwise MeCP2^stop mice to determine the cholinergic MeCP2 effects on rescuing the RTT-like phenotypes. We found cholinergic MeCP2 preservation could reverse some aspects of the RTT-like phenotypes in mice including hypolocomotion and increased anxiety level, and delay the onset of underweight, instead of improving the hypersocial abnormality and the poor general conditions such as short lifespan, low brain weight, and increasing severity score. Our findings suggest that selective activation of cholinergic MeCP2 is sufficient to reverse the locomotor impairment and increased anxiety-like behaviors at least in early symptomatic stage, supporting future development of RTT therapies associated with cholinergic system.

Human presynaptic receptors

Presynaptic receptors are sites at which transmitters, locally formed mediators or hormones inhibit or facilitate the release of a given transmitter from its axon terminals. The interest in the identification of presynaptic receptors has faded in recent years and it may therefore be justified to give an overview of their occurrence in the autonomic and central nervous system; this review will focus on presynaptic receptors in human tissues. Autoreceptors are presynaptic receptors at which a given transmitter restrains its further release, though in some instances may also increase its release. Inhibitory autoreceptors represent a typical example of a negative feedback; they are tonically activated by the respective endogenous transmitter and/or are constitutively active. Autoreceptors also play a role under pathophysiological conditions, e.g. by limiting the massive noradrenaline release occurring during congestive heart failure. They can be used for therapeutic purposes; e.g., the α₂-adrenoceptor antagonist mirtazapine is used as an antidepressant and the inverse histamine H₃ receptor agonist pitolisant has been marketed as a new drug for the treatment of narcolepsy in 2016. Heteroreceptors are presynaptic receptors at which transmitters from adjacent neurons, locally formed mediators (e.g. endocannabinoids) or hormones (e.g. adrenaline) can inhibit or facilitate transmitter release; they may be subject to an endogenous tone. The constipating effect of the sympathetic nervous system or of the antihypertensive drug clonidine is related to the activation of inhibitory α₂-adrenoceptors on postganglionic parasympathetic neurons. Part of the stimulating effect of adrenaline on the sympathetic nervous system during stress is related to its facilitatory effect on noradrenaline release via β₂-adrenoceptors.

Neurotrophin-3 promotes proliferation and cholinergic neuronal differentiation of bone marrow- derived neural stem cells via notch signaling pathway

AIMS

Recently, the potential for neural stem cells (NSCs) to be used in the treatment of Alzheimer's disease (AD) has been reported; however, the therapeutic effects are modest by virtue of the low neural differentiation rate. In our study, we transfected bone marrow-derived NSCs (BM-NSCs) with Neurotrophin-3 (NT-3), a superactive neurotrophic factor that promotes neuronal survival, differentiation, and migration of neuronal cells, to investigate the effects of NT-3 gene overexpression on the proliferation and differentiation into cholinergic neuron of BM-NSCs in vitro and its possible molecular mechanism.

MAIN METHODS

BM-NSCs were generated from BM mesenchymal cells of adult C57BL/6 mice and cultured in vitro. After transfected with NT-3 gene, immunofluorescence and RT-PCR method were used to determine the ability of BM-NSCs on proliferation and differentiation into cholinergic neuron; Acetylcholine Assay Kit was used for acetylcholine (Ach). RT-PCR and WB analysis were used to characterize mRNA and protein level related to the Notch signaling pathway.

KEY FINDINGS

We found that NT-3 can promote the proliferation and differentiation of BM-NSCs into cholinergic neurons and elevate the levels of acetylcholine (ACh) in the supernatant. Furthermore, NT-3 gene overexpression increase the expression of Hes1, decreased the expression of Mash1 and Ngn1 during proliferation of BM-NSCs. Whereas, the expression of Hes1 was down-regulated, and Mash1 and Ngn1 expression were up-regulated during differentiation of BM-NSCs.

SIGNIFICANCE

Our findings support the prospect of using NT-3-transduced BM-NSCs in developing therapies for AD due to their equivalent therapeutic potential as subventricular zone-derived NSCs (SVZ-NSCs), greater accessibility, and autogenous attributes.

Common pitfalls of stem cell differentiation: a guide to improving protocols for neurodegenerative disease models and research

Induced pluripotent stem cells and embryonic stem cells have revolutionized cellular neuroscience, providing the opportunity to model neurological diseases and test potential therapeutics in a pre-clinical setting. The power of these models has been widely discussed, but the potential pitfalls of stem cell differentiation in this research are less well described. We have analyzed the literature that describes differentiation of human pluripotent stem cells into three neural cell types that are commonly used to study diseases, including forebrain cholinergic neurons for Alzheimer's disease, midbrain dopaminergic neurons for Parkinson's disease and cortical astrocytes for neurodegenerative and psychiatric disorders. Published protocols for differentiation vary widely in the reported efficiency of target cell generation. Additionally, characterization of the cells by expression profile and functionality differs between studies and is often insufficient, leading to highly variable protocol outcomes. We have synthesized this information into a simple methodology that can be followed when performing or assessing differentiation techniques. Finally we propose three considerations for future research, including the use of physiological O2 conditions, three-dimensional co-culture systems and microfluidics to control feeding cycles and growth factor gradients. Following these guidelines will help researchers to ensure that robust and meaningful data is generated, enabling the full potential of stem cell differentiation for disease modeling and regenerative medicine.

The positional identity of iPSC-derived neural progenitor cells along the anterior-posterior axis is controlled in a dosage-dependent manner by bFGF and EGF

Neural rosettes derived from human induced pluripotent stem cells (iPSCs) have been claimed to be a highly robust in vitro cellular model for biomedical application. They are able to propagate in vitro in the presence of mitogens, including basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF). However, these two mitogens are also involved in anterior-posterior patterning in a gradient dependent manner along the neural tube axis. Here, we compared the regional identity of neural rosette cells and specific neural subtypes of their progeny propagated with low and high concentrations of bFGF and EGF. We observed that low concentrations of bFGF and EGF in the culturing system were able to induce forebrain identity of the neural rosettes and promote subsequent cortical neuronal differentiation. On the contrary, high concentrations of these mitogens stimulate a mid-hindbrain fate of the neural rosettes, resulting in subsequent cholinergic neuron differentiation. Thus, our results indicate that different concentrations of bFGF and EGF supplemented during propagation of neural rosettes are involved in altering the identity of the resultant neural cells.

Induction of specific neuron types by overexpression of single transcription factors

Specific neuronal types derived from embryonic stem cells (ESCs) can facilitate mechanistic studies and potentially aid in regenerative medicine. Existing induction methods, however, mostly rely on the effects of the combined action of multiple added growth factors, which generally tend to result in mixed populations of neurons. Here, we report that overexpression of specific transcription factors (TFs) in ESCs can rather guide the differentiation of ESCs towards specific neuron lineages. Analysis of data on gene expression changes 2 d after induction of each of 185 TFs implicated candidate TFs for further ESC differentiation studies. Induction of 23 TFs (out of 49 TFs tested) for 6 d facilitated neural differentiation of ESCs as inferred from increased proportion of cells with neural progenitor marker PSA-NCAM. We identified early activation of the Notch signaling pathway as a common feature of most potent inducers of neural differentiation. The majority of neuron-like cells generated by induction of Ascl1, Smad7, Nr2f1, Dlx2, Dlx4, Nr2f2, Barhl2, and Lhx1 were GABA-positive and expressed other markers of GABAergic neurons. In the same way, we identified Lmx1a and Nr4a2 as inducers for neurons bearing dopaminergic markers and Isl1, Fezf2, and St18 for cholinergic motor neurons. A time-course experiment with induction of Ascl1 showed early upregulation of most neural-specific messenger RNA (mRNA) and microRNAs (miRNAs). Sets of Ascl1-induced mRNAs and miRNAs were enriched in Ascl1 targets. In further studies, enrichment of cells obtained with the induction of Ascl1, Smad7, and Nr2f1 using microbeads resulted in essentially pure population of neuron-like cells with expression profiles similar to neural tissues and expressed markers of GABAergic neurons. In summary, this study indicates that induction of transcription factors is a promising approach to generate cultures that show the transcription profiles characteristic of specific neural cell types.

Wogonin Attenuates Hippocampal Neuronal Loss and Cognitive Dysfunction in Trimethyltin-Intoxicated Rats

We examined whether wogonin (WO) improved hippocampal neuronal activity, behavioral alterations and cognitive impairment, in rats induced by administration of trimethyltin (TMT), an organotin compound that is neurotoxic to these animals. The ability of WO to improve cognitive efficacy in the TMT-induced neurodegenerative rats was investigated using a passive avoidance test, and the Morris water maze test, and using immunohistochemistry to detect components of the acetylcholinergic system, brain-derived neurotrophic factor (BDNF), and cAMP-response element-binding protein (CREB) expression. Rats injected with TMT showed impairments in learning and memory and daily administration of WO improved memory function, and reduced aggressive behavior. Administration of WO significantly alleviated the TMT-induced loss of cholinergic immunoreactivity and restored the hippocampal expression levels of BDNF and CREB proteins and their encoding mRNAs to normal levels. These findings suggest that WO might be useful as a new therapy for treatment of various neurodegenerative diseases.

Generation of Human Embryonic Stem Cell Line Expressing zsGreen in Cholinergic Neurons Using CRISPR/Cas9 System

Lineage specific human embryonic stem cell (hESC) reporter cell line is a versatile tool for biological studies on real time monitoring of differentiation, physiological and biochemical features of special cell types and pathological mechanism of disease. Here we report the generation of ChAT-zsGreen reporter hESC line that express zsGreen under the control of the choline acetyltransferase (ChAT) promoter using CRISPR (Clustered Regularly Interspersed Short Palindromic Repeats)/Cas9 system. We show that the ChAT-zsGreen hESC reporter cell lines retain the features of undifferentiated hESC. After cholinergic neuronal differentiation, cholinergic neurons were clearly labeled with green fluorescence protein (zsGreen). The ChAT-zsGreen reporter hESC lines are invaluable not only for the monitoring cholinergic neuronal differentiation but also for study physiological and biochemical hallmarks of cholinergic neurons.

Developmental alterations of the septohippocampal cholinergic projection in a lissencephalic mouse model

LIS1 is one of principal genes related with Type I lissencephaly, a severe human brain malformation characterized by abnormal neuronal migration in the cortex. The LIS1 gene encodes a brain-specific 45kDa non-catalytic subunit of platelet-activating factor (PAF) acetylhydrolase-1b (PAFAH1b), an enzyme that inactivates the PAF. We have studied the role of Lis1 using a Lis1/sLis1 murine model, which has deleted the first coding exon from Lis1 gene. Homozygous mice are not viable but heterozygous have shown a delayed corticogenesis and neuronal dysplasia, with enhanced cortical excitability. Lis1/sLis1 embryos also exhibited a delay of cortical innervation by the thalamocortical fibers. We have explored in Lis1/sLis1 mice anomalies in forebrain cholinergic neuron development, which migrate from pallium to subpallium, and functionally represent the main cholinergic input to the cerebral cortex, modulating cortical activity and facilitating attention, learning, and memory. We hypothesized that primary migration anomalies and/or disorganized cortex could affect cholinergic projections from the basal forebrain and septum in Lis1/sLis1 mouse. To accomplish our objective we have first studied basal forebrain neurons in Lis1/sLis1 mice during development, and described structural and hodological differences between wild-type and Lis1/sLis1 embryos. In addition, septohippocampal projections showed altered development in mutant embryos. Basal forebrain abnormalities could contribute to hippocampal excitability anomalies secondary to Lis1 mutations and may explain the cognitive symptoms associated to cortical displasia-related mental diseases and epileptogenic syndromes.

Development of non-catecholaminergic sympathetic neurons in para- and prevertebral ganglia of cats

Expression of vasoactive intestinal peptide (VIP), neuronal nitric oxide synthase (nNOS), choline acetyltransferase (ChAT) and calcitonin gene-related peptide (CGRP) in the sympathetic ganglia was investigated by immunohistochemistry in the superior cervical ganglion (SCG), stellate ganglion (SG) and celiac ganglion (CG) from cats of different ages (newborn, 10-day-old, 20-day-old, 30-day-old and 2-month-old). Non-catecholaminergic TH-negative VIP-immunoreactive (IR) and nNOS-IR sympathetic ganglionic neurons are present from the moment of birth. In all studied age groups, substantial populations of VIP-IR (up to 9.8%) and nNOS-IR cells (up to 8.3%) was found in the SG, with a much smaller population found in the SCG (<1%) and only few cells observed in the CG. The percentage of nNOS-IR and VIP-IR neurons in the CG and SCG did not significantly change during development. The proportion of nNOS-IR and VIP-IR neuron profiles in the SG increased in first 20 days of life from 2.3±0.15% to 8.3±0.56% and from 0.3±0.05% to 9.2±0.83%, respectively. In the SG, percentages of nNOS-IR sympathetic neurons colocalizing VIP increased in the first 20 days of life. ChAT-IR and CGRP-IR neurons were not observed in the sympathetic ganglia of newborn animals and did not appear until 10 days after birth. In the SG of newborn and 10-day-old kittens, the majority of NOS-IR neurons were calbindin (CB)-IR, whereas in the SCG and CG of cats of all age groups and in the SG of 30-day-old and older kittens, the vast majority of NOS-IR neurons lacked CB. We conclude that the development of various non-catecholaminergic neurons in different sympathetic ganglia has its own time dynamics and is concluded at the end of the second month of life.

Olfactory Deprivation Hastens Alzheimer-Like Pathologies in a Human Tau-Overexpressed Mouse Model via Activation of cdk5

Olfactory dysfunction is a recognized risk factor for the pathogenesis of Alzheimer's disease (AD), while the mechanisms are still not clear. Here, we applied bilateral olfactory bulbectomy (OBX), an olfactory deprivation surgery to cause permanent anosmia, in human tau-overexpressed mice (htau mice) to investigate changes of AD-like pathologies including aggregation of abnormally phosphorylated tau and cholinergic neuron loss. We found that tau phosphorylation in hippocampus was increased at Thr-205, Ser-214, Thr-231, and Ser-396 after OBX. OBX also increased the level of sarkosyl-insoluble Tau at those epitopes and accelerated accumulation of somatodendritic tau. Moreover, OBX resulted in the elevation of calpain activity accompanied by an increased expression of the cyclin-dependent kinase 5 (cdk5) neuronal activators, p35 and p25, in hippocampus. Furthermore, OBX induces the loss of the cholinergic neurons in medial septal. Administration of cdk5 pharmacological inhibitor roscovitine into lateral ventricles suppressed tau hyperphosphorylation and mislocalization and restored the cholinergic neuron loss. These findings suggest that olfactory deprivation by OBX hastens tau pathology and cholinergic system impairment in htau mice possibly via activation of cdk5.

Expression and possible role of IGF-IR in the mouse gastric myenteric plexus and smooth muscles

Insulin-like growth factor-I (IGF-I) and its receptor (IGF-IR) have tremendous trophic effects on the central, peripheral and enteric neurons. The loss of IGF-IR contributes to the development of diabetic gastroparesis. However, the nature and the function of the IGF-IR(+) cells in the gastric myenteric plexus remain unclear. In this study, anti-ChAT, anti-S100β or anti-c-KIT antibodies were used to co-label IGF-IR(+) cells and neurons, glial cells or interstitial cells of Cajal (ICCs), respectively. We also generated type 1 diabetic mice (DM) to explore the influence of impaired IGF-I/IGF-IR in the myenteric neurons. Results showed that IGF-IR was expressed in the epithelium, smooth muscles and myenteric plexi of the mouse stomach. Most of the IGF-IR(+) cells in the myenteric plexi were ChAT(+) cholinergic neurons, but not enteric glial cells and there were more IGF-IR(+) neurons and fibers in the gastric antrum than in the corpus. The IGF-IR(+)/ChAT(+) neurons and ICCs were closely juxtaposed, but distinctly distributed in the myenteric plexus, indicating a possible role for the IGF-IR(+)/ChAT(+) neurons in the mediation of gastric motility through ICCs. Moreover, the decrease of IGF-IR and cholinergic neurons in the myenteric plexi and smooth muscles of DM mice suggested that IGF-I/IGF-IR signaling might play a role in neuron survival and neurite outgrowth, as well as stem cell factor (SCF) production, which is required for the development of ICCs. Our results provide insights into the effects of IGF-I/IGF-IR signaling on the development of gastrointestinal motility disorders.

Platelet-derived nerve growth factor supports the survival of cholinergic neurons in organotypic rat brain slices

Platelets play a role in repair of vessels and contain different growth factors, including nerve growth factor (NGF). Since NGF is the most potent growth factor to support survival of cholinergic neurons, we aimed to study the effects of platelet-derived NGF on cholinergic neurons in organotypic brain slices. Brain slices of the nucleus basalis of Meynert (nBM) were cultured with or without NGF (10ng/ml) or platelet extracts (100μg/ml) or fresh platelets (10(8) platelets/ml). In order to enhance NGF in platelets recombinant NGF (100ng) was loaded into platelets using ultrasound (3h). Our data show that recombinant NGF markedly supports survival of cholinergic neurons. The addition of fresh platelets showed a tendency for enhancing cholinergic neuron numbers, while platelet extracts had no effects. Ultrasound was highly effective to load recombinant NGF into platelets. The addition of NGF-loaded platelets markedly enhanced cholinergic neuron numbers. In conclusion, our data provide evidence that NGF-derived platelets may counteract cell death of cholinergic neurons.

Familial Alzheimer’s disease modelling using induced pluripotent stem cell technology

Alzheimer’s disease (AD) is a progressive neurodegenerative disease in which patients exhibit gradual loss of memory that impairs their ability to learn or carry out daily tasks. Diagnosis of AD is difficult, particularly in early stages of the disease, and largely consists of cognitive assessments, with only one in four patients being correctly diagnosed. Development of novel therapeutics for the treatment of AD has proved to be a lengthy, costly and relatively unproductive process with attrition rates of > 90%. As a result, there are no cures for AD and few treatment options available for patients. Therefore, there is a pressing need for drug discovery platforms that can accurately and reproducibly mimic the AD phenotype and be amenable to high content screening applications. Here, we discuss the use of induced pluripotent stem cells (iPSCs), which can be derived from adult cells, as a method of recapitulation of AD phenotype in vitro. We assess their potential use in high content screening assays and the barriers that exist to realising their full potential in predictive efficacy, toxicology and disease modelling. At present, a number of limitations need to be addressed before the use of iPSC technology can be fully realised in AD therapeutic applications. However, whilst the use of AD-derived iPSCs in drug discovery remains a fledgling field, it is one with immense potential that is likely to reach fruition within the next few years.

A phase1 study of stereotactic gene delivery of AAV2-NGF for Alzheimer's disease

BACKGROUND

Nerve growth factor (NGF) is an endogenous neurotrophic-factor protein with the potential to restore function and to protect degenerating cholinergic neurons in Alzheimer's disease (AD), but safe and effective delivery has proved unsuccessful.

METHODS

Gene transfer, combined with stereotactic surgery, offers a potential means to solve the long-standing delivery obstacles. An open-label clinical trial evaluated the safety and tolerability, and initial efficacy of three ascending doses of the genetically engineered gene-therapy vector adeno-associated virus serotype 2 delivering NGF (AAV2-NGF [CERE-110]). Ten subjects with AD received bilateral AAV2-NGF stereotactically into the nucleus basalis of Meynert.

RESULTS

AAV2-NGF was safe and well-tolerated for 2 years. Positron emission tomographic imaging and neuropsychological testing showed no evidence of accelerated decline. Brain autopsy tissue confirmed long-term, targeted, gene-mediated NGF expression and bioactivity.

CONCLUSIONS

This trial provides important evidence that bilateral stereotactic administration of AAV2-NGF to the nucleus basalis of Meynert is feasible, well-tolerated, and able to produce long-term, biologically active NGF expression, supporting the initiation of an ongoing multicenter, double-blind, sham-surgery-controlled trial.

C-terminals in the mouse branchiomotor nuclei originate from the magnocellular reticular formation

Large cholinergic synaptic boutons called "C-terminals" contact motoneurons and regulate their excitability. C-terminals in the spinal somatic motor nuclei originate from cholinergic interneurons in laminae VII and X that express a transcription factor Pitx2. Cranial motor nuclei contain another type of motoneuron: branchiomotor neurons. Although branchiomotor neurons receive abundant C-terminal projections, the neural source of these C-terminals remains unknown. In the present study, we first examined whether cholinergic neurons express Pitx2 in the reticular formation of the adult mouse brainstem, as in the spinal cord. Although Pitx2-positive cholinergic neurons were observed in the magnocellular reticular formation and region around the central canal in the caudal medulla, none was present more rostrally in the brainstem tegmentum. We next explored the origin of C-terminals in the branchiomotor nuclei by using biotinylated dextran amine (BDA). BDA injections into the magnocellular reticular formation of the medulla and pons resulted in the labeling of numerous C-terminals in the branchiomotor nuclei: the ambiguous, facial, and trigeminal motor nuclei. Our results revealed that the origins of C-terminals in the branchiomotor nuclei are cholinergic neurons in the magnocellular reticular formation not only in the caudal medulla, but also at more rostral levels of the brainstem, which lacks Pitx2-positive neurons.