Neuroimaging features of cognitive impairments in schizophrenia and major depressive disorder

Cognitive dysfunctions are one of the key symptoms of schizophrenia (SZ) and major depressive disorder (MDD), which exist not only during the onset of diseases but also before the onset, even after the remission of psychiatric symptoms. With the development of neuroimaging techniques, these non-invasive approaches provide valuable insights into the underlying pathogenesis of psychiatric disorders and information of cognitive remediation interventions. This review synthesizes existing neuroimaging studies to examine domains of cognitive impairment, particularly processing speed, memory, attention, and executive function in SZ and MDD patients. First, white matter (WM) abnormalities are observed in processing speed deficits in both SZ and MDD, with distinct neuroimaging findings highlighting WM connectivity abnormalities in SZ and WM hyperintensity caused by small vessel disease in MDD. Additionally, the abnormal functions of prefrontal cortex and medial temporal lobe are found in both SZ and MDD patients during various memory tasks, while aberrant amygdala activity potentially contributes to a preference to negative memories in MDD. Furthermore, impaired large-scale networks including frontoparietal network, dorsal attention network, and ventral attention network are related to attention deficits, both in SZ and MDD patients. Finally, abnormal activity and volume of the dorsolateral prefrontal cortex (DLPFC) and abnormal functional connections between the DLPFC and the cerebellum are associated with executive dysfunction in both SZ and MDD. Despite these insights, longitudinal neuroimaging studies are lacking, impeding a comprehensive understanding of cognitive changes and the development of early intervention strategies for SZ and MDD. Addressing this gap is critical for advancing our knowledge and improving patient prognosis.

Affinity of Nicotinoids to a Model Nicotinic Acetylcholine Receptor (nAChR) Binding Pocket in the Human Brain

The binding affinity of nicotinoids to the binding residues of the α4β2 variant of the nicotinic acetylcholine receptor (nAChR) was identified as a strong predictor of the nicotinoid's addictive character. Using ab initio calculations for model binding pockets of increasing size composed of 3, 6, and 14 amino acids (3AA, 6AA, and 14AA) that are derived from the crystal structure, the differences in binding affinity of 6 nicotinoids, namely, nicotine (NIC), nornicotine (NOR), anabasine (ANB), anatabine (ANT), myosmine (MYO), and cotinine (COT) were correlated to their previously reported doses required for increases in intracranial self-stimulation (ICSS) thresholds, a metric for their addictive function. By employing the many-body decomposition, the differences in the binding affinities of the various nicotinoids could be attributed mainly to the proton exchange energy between the pyridine and non-pyridine rings of the nicotinoids and the interactions between them and a handful of proximal amino acids, namely Trp156, Trpβ57, Tyr100, and Tyr204. Interactions between the guest nicotinoid and the amino acids of the binding pocket were found to be mainly classical in nature, except for those between the nicotinoid and Trp156. The larger pockets were found to model binding structures more accurately and predicted the addictive character of all nicotinoids, while smaller models, which are more computationally feasible, would only predict the addictive character of nicotinoids that are similar to nicotine. The present study identifies the binding affinity of the guest nicotinoid to the host binding pocket as a strong descriptor of the nicotinoid's addiction potential, and as such it can be employed as a fast-screening technique for the potential addiction of nicotine analogs.

Allosteric Activation of α7 Nicotinic Acetylcholine Receptors by Novel 2-Arylamino-thiazole-5-carboxylic Acid Amide Derivatives for the Improvement of Cognitive Deficits in Mice

Enhancing α7 nAChR function serves as a therapeutic strategy for cognitive disorders. Here, we report the synthesis and evaluation of 2-arylamino-thiazole-5-carboxylic acid amide derivatives 6-9 that as positive allosteric modulators (PAMs) activate human α7 nAChR current expressed in Xenopus ooctyes. Among the 4-amino derivatives, a representative atypical type I PAM 6p exhibits potent activation of α7 current with an EC50 of 1.3 μM and the maximum activation effect on the current over 48-fold in the presence of acetylcholine (100 μM). The structure-activity relationship (SAR) analysis reveals that the 4-amino group is crucial for the allosteric activation of α7 currents by compound 6p as the substitution of 4-methyl group results in its conversion to compound 7b (EC50 = 2.1 μM; max effect: 58-fold) characterized as a typical type I PAM. Furthermore, both 6p and 7b are able to rescue auditory gating deficits in mouse schizophrenia-like model of acoustic startle prepulse inhibition.

Unraveling the molecular interactions between α7 nicotinic receptor and a RIC3 variant associated with backward speech

Recent work putatively linked a rare genetic variant of the chaperone Resistant to Inhibitors of acetylcholinesterase (RIC3) (NM_024557.4:c.262G > A, NP_078833.3:p.G88R) to a unique ability to speak backwards, a language skill that is associated with exceptional working memory capacity. RIC3 is important for the folding, maturation, and functional expression of α7 nicotinic acetylcholine receptors (nAChR). We compared and contrasted the effects of RIC3G88R on assembly, cell surface expression, and function of human α7 receptors using fluorescent protein tagged α7 nAChR and Förster resonance energy transfer (FRET) microscopy imaging in combination with functional assays and 125I-α-bungarotoxin binding. As expected, the wild-type RIC3 protein was found to increase both cell surface and functional expression of α7 receptors. In contrast, the variant form of RIC3 decreased both. FRET analysis showed that RICG88R increased the interactions between RIC3 and α7 protein in the endoplasmic reticulum. These results provide interesting and novel data to show that a RIC3 variant alters the interaction of RIC3 and α7, which translates to decreased cell surface and functional expression of α7 nAChR.

Imaging the Vesicular Acetylcholine Transporter in Schizophrenia: A Positron Emission Tomography Study Using [18F]-VAT

BACKGROUND

Despite longstanding interest in the central cholinergic system in schizophrenia (SCZ), cholinergic imaging studies with patients have been limited to receptors. Here, we conducted a proof-of-concept positron emission tomography study using [18F]-VAT, a new radiotracer that targets the vesicular acetylcholine transporter as a proxy measure of acetylcholine transmission capacity, in patients with SCZ and explored relationships of vesicular acetylcholine transporter with clinical symptoms and cognition.

METHODS

A total of 18 adult patients with SCZ or schizoaffective disorder (the SCZ group) and 14 healthy control participants underwent a positron emission tomography scan with [18F]-VAT. Distribution volume (VT) for [18F]-VAT was derived for each region of interest, and group differences in VT were assessed with 2-sample t tests. Functional significance was explored through correlations between VT and scores on the Positive and Negative Syndrome Scale and a computerized neurocognitive battery (PennCNB).

RESULTS

No group differences in [18F]-VAT VT were observed. However, within the SCZ group, psychosis symptom severity was positively associated with VT in multiple regions of interest, with the strongest effects in the hippocampus, thalamus, midbrain, cerebellum, and cortex. In addition, in the SCZ group, working memory performance was negatively associated with VT in the substantia innominata and several cortical regions of interest including the dorsolateral prefrontal cortex.

CONCLUSIONS

In this initial study, the severity of 2 important features of SCZ-psychosis and working memory deficit-was strongly associated with [18F]-VAT VT in several cortical and subcortical regions. These correlations provide preliminary evidence of cholinergic activity involvement in SCZ and, if replicated in larger samples, could lead to a more complete mechanistic understanding of psychosis and cognitive deficits in SCZ and the development of therapeutic targets.

Poor inhibitory control predicts sex-specific vulnerability to nicotine rewarding properties in mice

RATIONALE

The risk of becoming addicted to tobacco varies greatly from individual to individual, raising the possibility of behavioural biomarkers capable of predicting sensitivity to nicotine reward, a crucial step in the development of nicotine addiction. Amongst all of nicotine's pharmacological properties, one of central importance is the enhancement of cognitive performances, which depend on the balance between attentional processes and inhibitory control. However, whether the cognitive enhancement effects of nicotine are predictive of sensitivity to its rewarding properties is still unknown.

OBJECTIVE

Using male and female mice, we investigated whether the effects of nicotine on cognitive performances are predictive of sensitivity to the rewarding properties of nicotine and, if so, whether this relationship is sex dependent.

METHODS

Naïve male and female mice were first assessed for their performances in both baseline conditions and following nicotine injection (0.15 and 0.30 mg/kg) in a cued-Fixed Consecutive Number task (FCNcue) measuring both optimal (attention) and premature (inhibitory control) responding. Next, all mice underwent nicotine-induced conditioned place preference (CPP) in order to evaluate inter-individual differences in response to nicotine reward (0.30 mg/kg).

RESULTS

Results showed that males and females benefited from the effect of nicotine as a cognitive enhancer in the FCNcue task. However, only those males displaying poor inhibitory control, namely high-impulsive animals, subsequently displayed sensitivity to nicotine reward. In females, sensitivity to nicotine reward was independent of FCNcue performances, in both basal and nicotine conditions.

CONCLUSION

Thus, our study suggests that poor inhibitory control and its modulation by nicotine may be a behavioural biomarker for sensitivity to nicotine reward and consequent vulnerability to nicotine addiction in males but not females.

Early auditory processing dysfunction in schizophrenia: Mechanisms and implications

Schizophrenia is a major mental disorder that affects approximately 1% of the population worldwide. Cognitive deficits are a key feature of the disorder and a primary cause of long-term disability. Over the past decades, significant literature has accumulated demonstrating impairments in early auditory perceptual processes in schizophrenia. In this review, we first describe early auditory dysfunction in schizophrenia from both a behavioral and neurophysiological perspective and examine their interrelationship with both higher order cognitive constructs and social cognitive processes. Then, we provide insights into underlying pathological processes, especially in relationship to glutamatergic and N-methyl-D-aspartate receptor (NMDAR) dysfunction models. Finally, we discuss the utility of early auditory measures as both treatment targets for precision intervention and as translational biomarkers for etiological investigation. Altogether, this review points out the crucial role of early auditory deficits in the pathophysiology of schizophrenia, in addition to major implications for early intervention and auditory-targeted approaches.

Smoking status ameliorates cholinergic impairments in cortical inhibition in patients with schizophrenia

Rationale Modulation of cortical excitability, in particular inhibition, is impaired in patients with schizophrenia. Chronic nicotine consumption, which is prevalent in this group, has been shown to alter cortical excitability in healthy individuals and to increase inhibitory activity. Thus, beneficial effects of smoking on impaired cortical excitability in patients with schizophrenia have been proposed, though direct experimental evidence is still lacking.

OBJECTIVES

We aimed to explore the effect of chronic smoking on cortical excitability by comparing smoking and non-smoking patients with schizophrenia.

METHOD

Twenty-six smoking and 19 non-smoking patients diagnosed with schizophrenia were included. Transcranial magnetic stimulation (TMS) applied to the primary motor cortex served as experimental paradigm for measuring corticospinal and intracortical excitability as follows: Resting motor threshold (RMT) and the input/output curve (I/O curve) were obtained to assess corticospinal excitability. Intracortical excitability was explored using paired-pulse TMS techniques (intracortical facilitation (ICF), short-latency intracortical inhibition (SICI) and short-latency afferent inhibition (SAI)).

RESULTS

A significantly stronger inhibition in the cholinergically driven SAI protocol was observed in smokers compared to non-smokers. All other measures did not show significant differences between groups.

CONCLUSION

Our results suggest an increased inhibition within cholinergic circuits due to chronic nicotine consumption in schizophrenia. This increase may compensate impaired cholinergic neurotransmission and could explain the high rate of smokers in schizophrenia.

Do methylenetetrahydrofolate dehydrogenase, cyclohydrolase, and formyltetrahydrofolate synthetase 1 polymorphisms modify changes in intelligence of school-age children in areas of endemic fluorosis?

BACKGROUND

Excessive exposure to fluoride can reduce intelligence. Methylenetetrahydrofolate dehydrogenase, cyclohydrolase, and formyltetrahydrofolate synthetase 1 ( MTHFD1 ) polymorphisms have important roles in neurodevelopment. However, the association of MTHFD1 polymorphisms with children's intelligence changes in endemic fluorosis areas has been rarely explored.

METHODS

A cross-sectional study was conducted in four randomly selected primary schools in Tongxu County, Henan Province, from April to May in 2017. A total of 694 children aged 8 to 12 years were included in the study with the recruitment by the cluster sampling method. Urinary fluoride (UF) and urinary creatinine were separately determined using the fluoride ion-selective electrode and creatinine assay kit. Children were classified as the high fluoride group and control group according to the median of urinary creatinine-adjusted urinary fluoride (UF Cr ) level. Four loci of MTHFD1 were genotyped, and the Combined Raven's Test was used to evaluate children's intelligence quotient (IQ). Generalized linear model and multinomial logistic regression model were performed to analyze the associations between children's UF Cr level, MTHFD1 polymorphisms, and intelligence. The general linear model was used to explore the effects of gene-environment and gene-gene interaction on intelligence.

RESULTS

In the high fluoride group, children's IQ scores decreased by 2.502 when the UF Cr level increased by 1.0 mg/L (β = -2.502, 95% confidence interval [CI]:-4.411, -0.593), and the possibility for having "excellent" intelligence decreased by 46.3% (odds ratio = 0.537, 95% CI: 0.290, 0.994). Children with the GG genotype showed increased IQ scores than those with the AA genotype of rs11627387 locus in the high fluoride group ( P   <  0.05). Interactions between fluoride exposure and MTHFD1 polymorphisms on intelligence were observed (Pinteraction < 0.05).

CONCLUSION

Our findings suggest that excessive fluoride exposure may have adverse effects on children's intelligence, and changes in children's intelligence may be associated with the interaction between fluoride and MTHFD1 polymorphisms.

Marine Origin Ligands of Nicotinic Receptors: Low Molecular Compounds, Peptides and Proteins for Fundamental Research and Practical Applications

The purpose of our review is to briefly show what different compounds of marine origin, from low molecular weight ones to peptides and proteins, offer for understanding the structure and mechanism of action of nicotinic acetylcholine receptors (nAChRs) and for finding novel drugs to combat the diseases where nAChRs may be involved. The importance of the mentioned classes of ligands has changed with time; a protein from the marine snake venom was the first excellent tool to characterize the muscle-type nAChRs from the electric ray, while at present, muscle and α7 receptors are labeled with the radioactive or fluorescent derivatives prepared from α-bungarotoxin isolated from the many-banded krait. The most sophisticated instruments to distinguish muscle from neuronal nAChRs, and especially distinct subtypes within the latter, are α-conotoxins. Such information is crucial for fundamental studies on the nAChR revealing the properties of their orthosteric and allosteric binding sites and mechanisms of the channel opening and closure. Similar data are provided by low-molecular weight compounds of marine origin, but here the main purpose is drug design. In our review we tried to show what has been obtained in the last decade when the listed classes of compounds were used in the nAChR research, applying computer modeling, synthetic analogues and receptor mutants, X-ray and electron-microscopy analyses of complexes with the nAChRs, and their models which are acetylcholine-binding proteins and heterologously-expressed ligand-binding domains.

Chromosomal Microarray Analysis as First-Tier Genetic Test for Schizophrenia

Schizophrenia is a chronic, devastating mental disorder with complex genetic components. Given the advancements in the molecular genetic research of schizophrenia in recent years, there is still a lack of genetic tests that can be used in clinical settings. Chromosomal microarray analysis (CMA) has been used as first-tier genetic testing for congenital abnormalities, developmental delay, and autism spectrum disorders. This study attempted to gain some experience in applying chromosomal microarray analysis as a first-tier genetic test for patients with schizophrenia. We consecutively enrolled patients with schizophrenia spectrum disorder from a clinical setting and conducted genome-wide copy number variation (CNV) analysis using a chromosomal microarray platform. We followed the 2020 “Technical Standards for the interpretation and reporting of constitutional copy-number variants: a joint consensus recommendation of the American College of Medical Genetics and Genomics (ACMG) and the Clinical Genome Resource (ClinGen)” to interpret the clinical significance of CNVs detected from patients. We recruited a total of 60 patients (36 females and 24 males) into this study. We detected three pathogenic CNVs and one likely pathogenic CNV in four patients, respectively. The detection rate was 6.7% (4/60, 95% CI: 0.004–0.13), comparable with previous studies in the literature. Also, we detected thirteen CNVs classified as uncertain clinical significance in nine patients. Detecting these CNVs can help establish the molecular genetic diagnosis of schizophrenia patients and provide helpful information for genetic counseling and clinical management. Also, it can increase our understanding of the pathogenesis of schizophrenia. Hence, we suggest CMA is a valuable genetic tool and considered first-tier genetic testing for schizophrenia spectrum disorders in clinical settings.

Maternal corticosteroids and depression during gestation and decreased fetal heart rate variability

OBJECTIVE

Maternal depression during gestation is an adverse factor in fetal brain development that manifests in later childhood behavioral problems. Fetal heart rate variability (FHRV) mediated by parasympathetic input is a marker of gestational nervous system development. Biological mediators of adverse effects of maternal depression may involve the mother's corticosteroids; however, links between depression, corticosteroids, and early nervous system development remain inconclusive.

METHODS

Heart rate was recorded in 23 fetuses by transabdominal Doppler at 28-33 weeks gestation. The SD of interbeat intervals over 20 min assessed FHRV. Maternal depression ratings and hair concentrations of cortisol and cortisone were assayed. An auditory sensory gating paradigm assessed newborn development of cerebral inhibition. Parents rated their infant's temperament characteristics on the Infant Behavior Questionnaire-Revised Short Form (IBQ-R).

RESULTS

Maternal depression was associated with lower FHRV, especially for male fetuses, β = -0.633, P = 0.045. Maternal depression was associated with lower cortisol to total corticosteroids ratios, β = -0.519, P = 0.033. Lower cortisol ratios were associated with decreased FHRV, β = 0.485, P = 0.019. Decreased FHRV was associated with increased newborn sensory gating deficits, β = -0.992, P = 0.035, indicating poorer development of cerebral inhibition. Higher FHRV was related to increased infant IBQ-R self-regulatory behaviors, r = 0.454, P = 0.029.

CONCLUSION

Maternal depression is associated via corticosteroids with decreased development of nervous system control of fetal heart rate. Decreased FHRV indicates developmental alterations in gestation that correlate with altered brain function and subsequent regulatory challenges in early infancy.

Association Study of Polymorphisms in Neuronal Nicotinic Acetylcholine Receptor Subunit Genes With Schizophrenia in the Han Chinese Population

OBJECTIVE

To investigate the relation between nicotinic acetylcholine receptor subunit (nAChR) genes and schizophrenia, and the relation between tag single nucleotide polymorphism (rs1317286, rs1044396, rs6494212, rs16969968, and rs684513) and schizophrenia in Han Chinese people.

METHODS

The protein-protein interaction (PPI) network among nAChR protein and 350 proteins encoded by schizophrenia-related susceptibility genes was constructed through the String database to explore whether nAChR genes were associated with schizophrenia in these known databases. Then, five single nucleotide polymorphisms (SNPs) of CHRNA3 (rs1317286), CHRNA4 (rs1044396), CHRNA7 (rs6494212), and CHRNA5 (rs16969968, rs684513) were analyzed in a sample of 1,035 schizophrenic patients and 816 healthy controls. The interaction between the markers was analyzed using multifactor dimensionality reduction (MDR) software. Power analysis was performed using the Quanto program.

RESULTS

There are no significant differences in genotype or allele distribution were identified between the patients and controls (p>0.05). The haplotypes constructed by four markers rs1317286, rs6494212, rs16969968, and rs684513 were not associated with schizophrenia either. However, a significant association between models made of rs1317286, rs1044396, rs6494212, and rs684513 and schizophrenia was revealed in interaction analysis (p<0.05).

CONCLUSION

The nAChR protein may have effects on the development of schizophrenia through the interaction with proteins encoded by schizophrenia-related susceptibility genes, but no relation was found between selected polymorphisms and schizophrenia in the collected Han Chinese people. However, interaction analysis suggested four-SNP model has an important effect on schizophrenia.

Synthesis and Biological Evaluation of Novel Triazine Derivatives as Positive Allosteric Modulators of α7 Nicotinic Acetylcholine Receptors

Enhancing neuronal α7 nicotinic acetylcholine receptor (α7 nAChR) function can alleviate cognitive deficits. Here, we report the design, synthesis, and evaluation of N-(4-(trifluoromethoxy)phenyl)-1,3,5-triazin-2-amine derivatives 8-10 as a series of novel α7 nAChR positive allosteric modulators (PAMs). The representative compound 10e functions as a type I PAM with an EC50 of 3.0 μM and approximately 38-fold enhancement of α7 current in the presence of agonist acetylcholine (100 μM). It specifically enhances α7 current with high selectivity. Compound 10e shows good pharmacokinetic property in mice. Intraperitoneal injection of 10e (3 mg/kg) exhibits sufficient blood-brain barrier penetration in mice. Furthermore, 10e can also rescue the auditory gating deficit in mice with schizophrenia-like behavior. Molecular docking of 10e with homopentameric α7 nAChR reveals a new mode of action. These results support the potential of 10e for treatment for schizophrenia and Alzheimer's disease.

JWX-A0108, a positive allosteric modulator of α7 nAChR, attenuates cognitive deficits in APP/PS1 mice by suppressing NF-κB-mediated inflammation

Neuroinflammation plays an early and prominent role in the pathology of Alzheimer's disease (AD). Studies have shown that cholinergic lesion is a contributor for the pathophysiology of AD. The α7 nicotinic acetylcholine receptors (nAChRs), a subtype of nAChRs, are abundantly expressed in the brain regions related to cognition and memory, such as hippocampus and frontal cortex. The α7 nAChR is rapidly activated and desensitized by agonists. JWX-A0108 is a type I positive allosteric modulator (PAM) of α7 nAChR, which mainly enhances agonist-evoked peak currents. Here, we used the Morris Water Maze to evaluate the effect of JWX-A0108 on cognition and memory functions in APP/PS1 mice, and the mechanism related to anti-inflammatory effect. The results showed that JWX-A0108 could improve the learning and memory function of APP/PS1 transgenic mice in Morris water maze, decrease the expression of IL-1β, TNF-α, IL-6 in the brain and lower the phosphorylation level of IκBα (Ser32/36) and NF-κB p65 (Ser536), decrease the expression of Iba1, the microglia activation marker. Nissl staining showed that the CA3 and DG regions of hippocampus were damaged in APP/PS1 mice, which was improved by JWX-A0108. All of these effects of JWX-A0108 were reversed by MLA (α7 nAChR specific blocker). Taken together, the results reveal that JWX-A0108 improved the learning and memory function of APP/PS1 mice by enhancing the anti-inflammatory effect of the endogenous choline system through α7 nAChR, inhibited the activation of the NF-κB signaling pathway by inhibiting IκB phosphorylation, and ultimately inhibited inflammatory responses.

Nicotine Enhances Firing Activity of Layer 5 Pyramidal Neurons in the Medial Prefrontal Cortex through Inhibition of Kv7 Channels

Nicotine enhances attention, working memory and recognition. One of the brain regions associated with these effects of nicotine is the medial prefrontal cortex (mPFC). However, cellular mechanisms that induce the enhancing effects of nicotine remain unclear. To address this issue, we performed whole-cell patch-clamp recordings from mPFC layer 5 pyramidal neurons in slices of C57BL/6J mice. Shortly (approx. 2 min) after bath application of nicotine, the number of action potentials, which were elicited by depolarizing current injection, was increased, and this increase persisted for over 5 min. The effect of nicotine was blocked by the α4β2 nicotinic acetylcholine receptor (nAChR) antagonist dihydro-β-erythroidine, α7 nAChR antagonist methyllycaconitine, or intracellular perfusion with the Ca²⁺ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Additionally, the voltage-dependent potassium 7 (Kv7) channel blocker, 10,10-bis(4-pyridinylmethyl)-9(10H)-anthracenone dihydrochloride (XE-991), as well as nicotine, shortened the spike threshold latency and increased the spike numbers. By contrast, the Kv7 channel opener, retigabine reduced the number of firings, and the addition of nicotine did not increase the spike numbers. These results indicate that nicotine induces long-lasting enhancement of firing activity in mPFC layer 5 pyramidal neurons, which is mediated by the stimulation of the α4β2 and α7 nAChRs and subsequent increase in intracellular Ca²⁺ levels followed by the suppression of the Kv7 channels. The novel effect of nicotine might underlie the nicotine-induced enhancement of attention, working memory and recognition.

Genome-wide analyses of smoking behaviors in schizophrenia: Findings from the Psychiatric Genomics Consortium

While 17% of US adults use tobacco regularly, smoking rates among persons with schizophrenia are upwards of 60%. Research supports a shared etiological basis for smoking and schizophrenia, including findings from genome-wide association studies (GWAS). However, few studies have directly tested whether the same or distinct genetic variants also influence smoking behavior among schizophrenia cases. Using data from the Psychiatric Genomics Consortium (PGC) study of schizophrenia (35476 cases, 46839 controls), we estimated genetic correlations between these traits and tested whether polygenic risk scores (PRS) constructed from the results of smoking behaviors GWAS were associated with schizophrenia risk or smoking behaviors among schizophrenia cases. Results indicated significant genetic correlations of schizophrenia with smoking initiation (rg = 0.159; P = 5.05 × 10-10), cigarettes-smoked-per-day (rg = 0.094; P = 0.006), and age-of-onset of smoking (rg = 0.10; P = 0.009). Comparing smoking behaviors among schizophrenia cases to the general population, we observe positive genetic correlations for smoking initiation (rg = 0.624, P = 0.002) and cigarettes-smoked-per-day (rg = 0.689, P = 0.120). Similarly, TAG-based PRS for smoking initiation and cigarettes-smoked-per-day were significantly associated with smoking initiation (P = 3.49 × 10-5) and cigarettes-smoked-per-day (P = 0.007) among schizophrenia cases. We performed the first GWAS of smoking behavior among schizophrenia cases and identified a novel association with cigarettes-smoked-per-day upstream of the TMEM106B gene on chromosome 7p21.3 (rs148253479, P = 3.18 × 10-8, n = 3520). Results provide evidence of a partially shared genetic basis for schizophrenia and smoking behaviors. Additionally, genetic risk factors for smoking behaviors were largely shared across schizophrenia and non-schizophrenia populations. Future research should address mechanisms underlying these associations to aid both schizophrenia and smoking treatment and prevention efforts.

Repeated treatment with alpha 7 nicotinic acetylcholine receptor ligands enhances cognitive processes and stimulates Erk1/2 and Arc genes in rats

The α7 nicotinic acetylcholine receptor (α7 nAChR) is a potential target for the treatment of cognitive decline in patients with schizophrenia, Alzheimer's disease, and attention-deficit/hyperactivity disorder. Here we examined the promnesic activity of the α7 nAChR agonist (A582941), the type I (CCMI), and the type II (PNU120596) positive allosteric modulators (PAMs) in rats following single and repeated (once daily for seven days) treatment. To determine the neuronal mechanisms underlying the procognitive activity of the tested compounds, levels of the extracellular signal-regulated kinases (Erk1/2) and the activity-regulated cytoskeleton-associated protein (Arc) mRNAs were assessed in the frontal cortical and hippocampal brain regions. Using the novel object recognition test, we demonstrate that the lower doses of A582941 (0.1 mg/kg), CCMI (1 mg/kg), and PNU120596 (0.3 mg/kg) improved recognition memory after repeated but not single administration, suggesting a cumulative effect of repeated dosing. In contrast, the higher doses of A582941 (0.3 mg/kg), CCMI (3 mg/kg) and PNU120596 (1 mg/kg) demonstrated promnesic efficacy following both single and repeated administration. Subsequent in situ hybridization revealed that repeated treatment with A582941 and CCMI, but not PNU120596 enhanced mRNA expression of the Erk1/2 and Arc in the frontal cortex and hippocampus. Present data suggest that both the α7 nAChR agonist and PAMs exhibit procognitive effects after single and repeated administration. The increased level of the Erk1/2 and Arc genes is likely to be at least partially involved in this effect.

The ChAT-acetylcholine pathway promotes group 2 innate lymphoid cell responses and anti-helminth immunity

Group 2 innate lymphoid cells (ILC2s) reside in multiple tissues, including lymphoid organs and barrier surfaces, and secrete type 2 cytokines including interleukin-5 (IL-5), IL-9, and IL-13. These cells participate in multiple physiological processes including allergic inflammation, tissue repair, metabolic homeostasis, and host defense against helminth infections. Recent studies indicate that neurotransmitters and neuropeptides can play an important role in regulating ILC2 responses; however, the mechanisms that underlie these processes in vivo remain incompletely defined. Here, we identify that activated ILC2s up-regulate choline acetyltransferase (ChAT)-the enzyme responsible for the biosynthesis of acetylcholine (ACh)-after infection with the helminth parasite Nippostrongylus brasiliensis or treatment with alarmins or cytokines including IL-25, IL-33, and thymic stromal lymphopoietin (TSLP). ILC2s also express acetylcholine receptors (AChRs), and ACh administration promotes ILC2 cytokine production and elicits expulsion of helminth infection. In accordance with this, ChAT deficiency in ILC2s leads to defective ILC2 responses and impaired immunity against helminth infection. Together, these results reveal a previously unrecognized role of the ChAT-ACh pathway in promoting type 2 innate immunity to helminth infection.

Altered Effective Brain Connectivity During Habituation in First Episode Schizophrenia With Auditory Verbal Hallucinations: A Dichotic Listening EEG Study

Background: Habituation is considered to have protective and filtering mechanisms. The present study is aim to find the casual relationship and mechanisms of excitatory-inhibitory (E/I) dysfunctions in schizophrenia (SCZ) via habituation. Methods: A dichotic listening paradigm was performed with simultaneous EEG recording on 22 schizophrenia patients and 22 gender- and age-matched healthy controls. Source reconstruction and dynamic causal modeling (DCM) analysis were performed to estimate the effective connectivity and casual relationship between frontal and temporal regions before and after habituation. Results: The schizophrenia patients expressed later habituation onset (p < 0.01) and hyper-activity in both lateral frontal-temporal cortices than controls (p = 0.001). The patients also showed decreased top-down and bottom-up connectivity in bilateral frontal-temporal regions (p < 0.01). The contralateral frontal-frontal and temporal-temporal connectivity showed a left to right decreasing (p < 0.01) and right to left strengthening (p < 0.01). Conclusions: The results give causal evidence for E/I imbalance in schizophrenia during dichotic auditory processing. The altered effective connectivity in frontal-temporal circuit could represent the trait bio-marker of schizophrenia with auditory hallucinations.

The Role of Gamma Oscillations in the Pathophysiology of Substance Use Disorders

Substance use disorders (SUDs) are a major public health problem—with over 200 million people reporting drug use in 2016. Electroencephalography (EEG) is a powerful tool that can provide insights into the impact of SUDs on cognition. Specifically, modulated gamma activity may provide an index of the pathophysiology of SUDs. Thus, the purpose of this review was to investigate the impact of alcohol, tobacco, cannabis, cocaine, and amphetamine on gamma activity, among pre-clinical and clinical populations during acute and chronic exposure and withdrawal states. We searched multiple databases for key terms related to SUDs, EEG, and gamma and ensured rigorous methods by using a standardized review reporting tool. We included 30 studies in this review and found that all substances were associated with modulation of gamma activity, across states and in both preclinical and clinical populations. Gamma oscillations appeared to be differentially modulated in clinical versus preclinical populations and had the most complex relationship with alcohol, indicating that it may act differently than other substances. The findings of this review offer insights into the pathophysiology of SUDs, providing a potential window into novel treatments for SUDs via modulation of gamma activity.

Molecular, physiological and behavioral characterization of the heterozygous Df[h15q13]/+ mouse model associated with the human 15q13.3 microdeletion syndrome

The human 15q13.3 microdeletion syndrome (DS) is caused by a heterozygous microdeletion (MD) affecting six genes: FAN1; MTMR10; TRPM1; KLF13; OTUD7A; and CHRNA7. Carriers are at risk for intellectual disability, epilepsy, autism spectrum disorder, and schizophrenia. Here we used the Df[h15q13]/+ mouse model with an orthologous deletion to further characterize molecular, neurophysiological, and behavioral parameters that are relevant to the 15q13.3 DS. First, we verified the expression and distribution of the α7 nicotinic acetylcholine receptor (nAChR), a gene product of the CHRNA7, in cortical and subcortical areas. Results revealed similar mRNA distribution pattern in wildtype (WT) and heterozygous (Het) mice, with about half the number of α7 nAChR binding sites in mutants. Hippocampal recordings showed similar input/output responses of field excitatory post-synaptic potentials and theta-burst induced long-term potentiation in WT and Het mice. Het males exhibited impaired spatial learning acquisition in the Barnes Maze. Indicative of increased seizure susceptibility, Het mice developed secondary seizures after 6-Hz corneal stimulation, and had significantly increased sensitivity to the chemoconvulsant pentylenetetrazol resulting in increased spiking in hippocampal EEG recordings. Basal mRNA expression of brain derived neurotrophic factor and activity regulated immediate early genes (c-fos, Arc, Erg-1 and Npas4) during adolescence, a critical period of brain maturation, was unaffected by genotype. Thus, the MD did not show gross neuroanatomical, molecular, and neurophysiological abnormalities despite deficits in spatial learning and increased susceptibility to seizures. Altogether, our results verify the phenotypic profile of the heterozygous Df[h15q13]/+ mouse model and underscore its translational relevance for human 15q13.3 DS.

Maternal choline and respiratory coronavirus effects on fetal brain development

Prenatal COVID-19 infection is anticipated by the U.S. Centers for Disease Control to affect fetal development similarly to other common respiratory coronaviruses through effects of the maternal inflammatory response on the fetus and placenta. Plasma choline levels were measured at 16 weeks gestation in 43 mothers who had contracted common respiratory viruses during the first 6-16 weeks of pregnancy and 53 mothers who had not. When their infants reached 3 months of age, mothers completed the Infant Behavior Questionnaire-Revised (IBQ-R), which assesses their infants' level of activity (Surgency), their fearfulness and sadness (Negativity), and their ability to maintain attention and bond to their parents and caretakers (Regulation). Infants of mothers who had contracted a moderately severe respiratory virus infection and had higher gestational choline serum levels (≥7.5 mM consistent with U.S. Food and Drug Administration dietary recommendations) had significantly increased development of their ability to maintain attention and to bond with their parents (Regulation), compared to infants whose mothers had contracted an infection but had lower choline levels (<7.5 mM). For infants of mothers with choline levels ≥7.5 μM, there was no effect of viral infection on infant IBQ-R Regulation, compared to infants of mothers who were not infected. Higher choline levels obtained through diet or supplements may protect fetal development and support infant early behavioral development even if the mother contracts a viral infection in early gestation when the brain is first being formed.

Interaction of maternal choline levels and prenatal Marijuana's effects on the offspring

BACKGROUND

This study investigated whether higher maternal choline levels mitigate effects of marijuana on fetal brain development. Choline transported into the amniotic fluid from the mother activates α7-nicotinic acetylcholine receptors on fetal cerebro-cortical inhibitory neurons, whose development is impeded by cannabis blockade of their cannabinoid-1(CB1) receptors.

METHODS

Marijuana use was assessed during pregnancy from women who later brought their newborns for study. Mothers were informed about choline and other nutrients, but not specifically for marijuana use. Maternal serum choline was measured at 16 weeks gestation.

RESULTS

Marijuana use for the first 10 weeks gestation or more by 15% of mothers decreased newborns' inhibition of evoked potentials to repeated sounds (d' = 0.55, p < 0.05). This effect was ameliorated if women had higher gestational choline (rs = -0.50, p = 0.011). At 3 months of age, children whose mothers continued marijuana use through their 10th gestational week or more had poorer self-regulation (d' = -0.79, p < 0.05). This effect was also ameliorated if mothers had higher gestational choline (rs = 0.54, p = 0.013). Maternal choline levels correlated with the children's improved duration of attention, cuddliness, and bonding with parents.

CONCLUSIONS

Prenatal marijuana use adversely affects fetal brain development and subsequent behavioral self-regulation, a precursor to later, more serious problems in childhood. Stopping marijuana use before 10 weeks gestational age prevented these effects. Many mothers refuse to cease use because of familiarity with marijuana and belief in its safety. Higher maternal choline mitigates some of marijuana's adverse effects on the fetus.

Double blind, two dose, randomized, placebo-controlled, cross-over clinical trial of the positive allosteric modulator at the alpha7 nicotinic cholinergic receptor AVL-3288 in schizophrenia patients

Despite their theoretical rationale, nicotinic alpha-7 acetylcholine (nα₇) receptor agonists, have largely failed to demonstrate efficacy in placebo-controlled trials in schizophrenia. AVL-3288 is a nα₇ positive allosteric modulator (PAM), which is only active in the presence of the endogenous ligand (acetylcholine), and thus theoretically less likely to cause receptor desensitization. We evaluated the efficacy of AVL-3288 in a Phase 1b, randomized, double-blind, placebo-controlled, triple cross-over study. Twenty-four non-smoking, medicated, outpatients with schizophrenia or schizoaffective disorder and a Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) ≥62 were randomized. Each subject received 5 days of AVL-3288 (10, 30 mg) and placebo across three separate treatment weeks. The primary outcome measure was the RBANS total scale score, with auditory P50 evoked potential suppression the key target engagement biomarker. Secondary outcome measures include task-based fMRI (RISE task), mismatch negativity, the Scale for the Assessment of Negative Symptoms of Schizophrenia (SANS) and the Brief Psychiatric Rating Scale (BPRS). Twenty-four subjects were randomized and treated without any clinically significant treatment emergent adverse effects. Baseline RBANS (82 ± 17) and BPRS (41 ± 13) scores were consistent with moderate impairment. Primary outcomes were negative, with non-significant worsening for both active groups vs. placebo in the P50 and minimal between group changes on the RBANS. In conclusion, the results did not indicate efficacy of the compound, consistent with most prior results for the nα₇ target.

Meta-analysis of auditory P50 sensory gating in schizophrenia and bipolar disorder

The ability of the brain to reduce the amount of trivial or redundant sensory inputs is called gating function. Dysfunction of sensory gating may lead to cognitive fragmentation and poor real-world functioning. The auditory dual-click paradigm is a pertinent neurophysiological measure of sensory gating function. This meta-analysis aimed to examine the subcomponents of abnormal P50 waveforms in bipolar disorder and schizophrenia to assess P50 sensory gating deficits and examine effects of diagnoses, illness states (first-episode psychosis vs. schizophrenia, remission vs. episodes in bipolar disorder), and treatment status (medication-free vs. medicated). Literature search of PubMed between Jan 1st 1980 and March 31st 2019 identified 2091 records for schizophrenia, 362 for bipolar disorder. 115 studies in schizophrenia (4932 patients), 16 in bipolar disorder (975 patients) and 10 in first-degree relatives (848 subjects) met the inclusion criteria. P50 sensory gating ratio (S2/S1) and S1-S2 difference were significantly altered in schizophrenia, bipolar disorder and their first-degree relatives. First-episode psychosis did not differ from schizophrenia, however episodes altered P50 sensory gating in bipolar disorder. Medications improve P50 sensory gating alterations in schizophrenia significantly and at trend level in bipolar disorder. Future studies should examine longitudinal course of P50 sensory gating in schizophrenia and bipolar disorder.

The role of nicotinic cholinergic neurotransmission in delusional thinking

Delusions are a difficult-to-treat and intellectually fascinating aspect of many psychiatric illnesses. Although scientific progress on this complex topic has been challenging, some recent advances focus on dysfunction in neural circuits, specifically in those involving dopaminergic and glutamatergic neurotransmission. Here we review the role of cholinergic neurotransmission in delusions, with a focus on nicotinic receptors, which are known to play a part in some illnesses where these symptoms appear, including delirium, schizophrenia spectrum disorders, bipolar disorder, Parkinson, Huntington, and Alzheimer diseases. Beginning with what we know about the emergence of delusions in these illnesses, we advance a hypothesis of cholinergic disturbance in the dorsal striatum where nicotinic receptors are operative. Striosomes are proposed to play a central role in the formation of delusions. This hypothesis is consistent with our current knowledge about the mechanism of action of cholinergic drugs and with our abstract models of basic cognitive mechanisms at the molecular and circuit levels. We conclude by pointing out the need for further research both at the clinical and translational levels.

Prospects for improving future mental health of children through prenatal maternal micronutrient supplementation in China

Prenatal micronutrients in pregnant women's diets, including supplements, have an essential role in fetal brain development and may reduce the risk of mental disorders in offspring. Folic acid, vitamin D, omega-3 fatty acids, and choline have been investigated for this purpose. Folic acid supplementation throughout pregnancy has well-established positive effects. Vitamin D, administered to the mother before birth or to the newborn, has also been shown to reduce the risk of neurodevelopmental disorders. Omega-3 fatty acids during pregnancy have a more uncertain role, with recent trials questioning a beneficial effect on cognition and attention deficit disorder, despite positive effects on prematurity and neonatal wheezing prevention. Choline supplementation is associated with positive effects on cognition and behavior, including early behaviors associated with the development of autism and schizophrenia. There is no experience yet with COVID-19, but adverse effects on fetal brain development of most common coronaviruses are mitigated by higher choline levels. Maternal dietary supplementation of nutrients is a benign and inexpensive intervention in pregnancy to prevent life-long disability from mental illness. Use of dietary supplements in poorer, rural areas of China is below recommendations. Physicians, midwives, and public health officials in China can promote prenatal nutrient supplementation to reduce the future burden of mental illnesses that might be prevented before birth.

α7 nicotinic acetylcholine receptors as therapeutic targets in schizophrenia: Update on animal and clinical studies and strategies for the future

Schizophrenia is a devastating mental illness and its effective treatment is among the most challenging issues in psychiatry. The symptoms of schizophrenia are heterogeneous ranging from positive symptoms (e.g., delusions, hallucinations) to negative symptoms (e.g., anhedonia, social withdrawal) to cognitive dysfunction. Antipsychotics are effective at ameliorating positive symptoms in some patients; however, they are not reliably effective at improving the negative symptoms or cognitive impairments. The inability to address the cognitive impairments is a particular concern since they have the greatest long-term impact on functional outcomes. While decades of research have been devoted to the development of pro-cognitive agents for schizophrenia, to date, no drug has been approved for clinical use. Converging behavioral, neurobiological, and genetic evidence led to the identification of the α7-nicotinic acetylcholine receptor (α7-nAChR) as a therapeutic target several years ago and there is now extensive preclinical evidence that α7-nAChR ligands have pro-cognitive effects and other properties that should be beneficial to schizophrenia patients. However, like the other pro-cognitive strategies, no α7-nAChR ligand has been approved for clinical use in schizophrenia thus far. In this review, several topics are discussed that may impact the success of α7-nAChR ligands as pro-cognitive agents for schizophrenia including the translational value of the animal models used, clinical trial design limitations, confounding effects of polypharmacy, dose-effect relationships, and chronic versus intermittent dosing considerations. Determining the most optimal pharmacologic strategy at α7-nAChRs: agonist, positive allosteric modulator, or potentially even receptor antagonist is also discussed. article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

P50, N100, and P200 Auditory Sensory Gating Deficits in Schizophrenia Patients

BACKGROUND

Sensory gating describes neurological processes of filtering out redundant or unnecessary stimuli during information processing, and sensory gating deficits may contribute to the symptoms of schizophrenia. Among the three components of auditory event-related potentials reflecting sensory gating, P50 implies pre-attentional filtering of sensory information and N100/P200 reflects attention triggering and allocation processes. Although diminished P50 gating has been extensively documented in patients with schizophrenia, previous studies on N100 were inconclusive, and P200 has been rarely examined. This study aimed to investigate whether patients with schizophrenia have P50, N100, and P200 gating deficits compared with control subjects.

METHODS

Control subjects and clinically stable schizophrenia patients were recruited. The mid-latency auditory evoked responses, comprising P50, N100, and P200, were measured using the auditory-paired click paradigm without manipulation of attention. Sensory gating parameters included S1 amplitude, S2 amplitude, amplitude difference (S1-S2), and gating ratio (S2/S1). We also evaluated schizophrenia patients with PANSS to be correlated with sensory gating indices.

RESULTS

One hundred four patients and 102 control subjects were examined. Compared to the control group, schizophrenia patients had significant sensory gating deficits in P50, N100, and P200, reflected by larger gating ratios and smaller amplitude differences. Further analysis revealed that the S2 amplitude of P50 was larger, while the S1 amplitude of N100/P200 was smaller, in schizophrenia patients than in the controls. We found no correlations between sensory gating indices and schizophrenia positive or negative symptom clusters. However, we found a negative correlation between the P200 S2 amplitude and Bell's emotional discomfort factor/Wallwork's depressed factor.

CONCLUSION

Till date, this study has the largest sample size to analyze P50, N100, and P200 collectively by adopting the passive auditory paired-click paradigm without distractors. With covariates controlled for possible confounds, such as age, education, smoking amount and retained pairs, we found that schizophrenia patients had significant sensory gating deficits in P50-N100-P200. The schizophrenia patients had demonstrated a unique pattern of sensory gating deficits, including repetition suppression deficits in P50 and stimulus registration deficits in N100/200. These results suggest that sensory gating is a pervasive cognitive abnormality in schizophrenia patients that is not limited to the pre-attentive phase of information processing. Since P200 exhibited a large effect size and did not require additional time during recruitment, future studies of P50-N100-P200 collectively are highly recommended.

Activators of α7 nAChR as Potential Therapeutics for Cognitive Impairment

The α7 nicotinic acetylcholine receptor (nAChR) is a promising target for the treatment of cognitive deficits associated with psychiatric and neurological disorders, including schizophrenia and Alzheimer's disease (AD). Several α7 nAChR agonists and positive allosteric modulators (PAMs) have demonstrated procognitive effects in preclinical models and early clinical trials. However, despite intense research efforts in the pharmaceutical industry and academia, none of the α7 nAChR ligands has been approved for clinical use. This chapter will focus on the α7 nAChR ligands that have advanced to clinical studies and explore the reasons why these agents have not met with unequivocal clinical success.

Evidence-based guidelines for the pharmacological treatment of schizophrenia: Updated recommendations from the British Association for Psychopharmacology

These updated guidelines from the British Association for Psychopharmacology replace the original version published in 2011. They address the scope and targets of pharmacological treatment for schizophrenia. A consensus meeting was held in 2017, involving experts in schizophrenia and its treatment. They were asked to review key areas and consider the strength of the evidence on the risk-benefit balance of pharmacological interventions and the clinical implications, with an emphasis on meta-analyses, systematic reviews and randomised controlled trials where available, plus updates on current clinical practice. The guidelines cover the pharmacological management and treatment of schizophrenia across the various stages of the illness, including first-episode, relapse prevention, and illness that has proved refractory to standard treatment. It is hoped that the practice recommendations presented will support clinical decision making for practitioners, serve as a source of information for patients and carers, and inform quality improvement.

Alpha7 Nicotinic Receptors as Therapeutic Targets in Schizophrenia

While current treatments for schizophrenia often provide much relief for positive symptoms such as hallucinations, other symptoms, particularly cognitive deficits, persist and contribute to substantial suffering and reduced quality of life for patients. In searching for novel therapeutic avenues to treat cognitive deficits in schizophrenia, recent work is exploring nicotinic receptor neurobiology. Supported by a large body of evidence, with contributions from studies of smoking behaviors, genetics, receptor distribution and function, animal models and nicotinic effects on illness symptoms, the alpha7 nicotinic receptor has emerged as a potential therapeutic target. Despite promise in early clinical trials, however, no drug targeting nicotinic systems has succeeded in larger phase 3 trials. Following a brief review of nicotinic receptor biology and the evidence that has led to pursuit of alpha7 nicotinic agonism as a therapeutic strategy, this review will provide an update on the status of recent trials, discuss potential issues that may have contributed to negative outcomes, and point to new directions and promising advances in developing alpha7 nicotinic receptor-based treatment for cognitive symptoms in schizophrenia.

IMPLICATIONS

By examining alpha7 nicotinic receptor biology and recent efforts to target the receptor in clinical trials, it is hoped that investigators will be motivated to explore novel, promising directions focusing on the receptor as a strategy to treat cognitive symptoms in schizophrenia.

Precisely Timed Nicotinic Activation Drives SST Inhibition in Neocortical Circuits

Sleep, waking, locomotion, and attention are associated with cell-type-specific changes in neocortical activity. The effect of brain state on circuit output requires understanding of how neuromodulators influence specific neuronal classes and their synapses, with normal patterns of neuromodulator release from endogenous sources. We investigated the state-dependent modulation of a ubiquitous feedforward inhibitory motif in mouse sensory cortex, local pyramidal (Pyr) inputs onto somatostatin (SST)-expressing interneurons. Paired whole-cell recordings in acute brain slices and in vivo showed that Pyr-to-SST synapses are remarkably weak, with failure rates approaching 80%. Pharmacological screening revealed that cholinergic agonists uniquely enhance synaptic efficacy. Brief, optogenetically gated acetylcholine release dramatically enhanced Pyr-to-SST input, via nicotinic receptors and presynaptic PKA signaling. Importantly, endogenous acetylcholine release preferentially activated nicotinic, not muscarinic, receptors, thus differentiating drug effects from endogenous neurotransmission. Brain state- and synapse-specific unmasking of synapses may be a powerful way to functionally rewire cortical circuits dependent on behavioral demands.

An Exploratory Trial of Transdermal Nicotine for Aggression and Irritability in Adults with Autism Spectrum Disorder

Nicotinic acetylcholine receptors (nAChRs), particularly the α7 nAChR, are implicated in the pathophysiology of both autism spectrum disorder (ASD) and aggressive behavior. We explored the feasibility, tolerability, and preliminary efficacy of targeting nAChRs using transdermal nicotine to reduce aggressive symptoms in adults with ASD. Eight subjects were randomized in a double-blind crossover trial of 7 mg transdermal nicotine or placebo, each for 1 week. All participants tolerated nicotine treatment well. Five subjects contributed data to the primary outcome, Aberrant Behavior Checklist-Irritability (ABC-I) subscale change from baseline, which was improved by nicotine compared to placebo. Sleep ratings were also improved by nicotine and correlated with ABC-I improvement. These findings support further investigation of nAChR agonists for aggression and sleep in ASD.

Pharmacological characterization of JWX-A0108 as a novel type I positive allosteric modulator of α7 nAChR that can reverse acoustic gating deficits in a mouse prepulse inhibition model

The α7 nicotinic acetylcholine receptor (α7 nAChR) is a ligand-gated Ca²⁺-permeable homopentameric ion channel implicated in cognition and neuropsychiatric disorders. Pharmacological enhancement of α7 nAChR function has been suggested for improvement of cognitive deficits. In the present study, we characterized a thiazolyl heterocyclic derivative, 6-(2-chloro-6-methylphenyl)-2-((3-fluoro-4-methylphenyl)amino)thiazolo[4,5-d]pyrimidin-7(6H)-one (JWX-A0108), as a novel type I α7 nAChR positive allosteric modulator (PAM), and evaluated its ability to reverse auditory gating and spatial working memory deficits in mice. In Xenopus oocytes expressing human nAChR channels, application of JWX-A0108 selectively enhanced α7 nAChR-mediated inward current in the presence of the agonist ACh (EC₅₀ value = 4.35 ± 0.12 µM). In hippocampal slices, co-application of ACh and JWX-A0108 (10 µM for each) markedly increased both the frequency and amplitude of spontaneous inhibitory postsynaptic currents (sIPSCs) recorded in pyramidal neurons, but JWX-A0108 did not affect GABA-induced current in oocytes expressing human GABA_A receptor α1β3γ2 and α5β3γ2 subtypes. In mice with MK-801-induced deficits in auditory gating, administration of JWX-A0108 (1, 3, and 10 mg/kg, i.p.) dose-dependently attenuates MK-801-induced auditory gating deficits in five prepulse intensities (72, 76, 80, 84, and 88 dB). Furthermore, administration of JWX-A0108 (0.03, 0.1, or 0.3 mg/kg, i.p.) significantly reversed MK-801-induced impaired spatial working memory in mice. Our results demonstrate that JWX-A0108 is a novel type I PAM of α7 nAChR, which may be beneficial for improvement of cognitive deficits commonly found in neuropsychiatric disorders such as schizophrenia and Alzheimer's disease.

Nicotinic alpha-7 acetylcholine receptor deficiency exacerbates hepatic inflammation and fibrosis in a mouse model of non-alcoholic steatohepatitis

AIMS/INTRODUCTION

Non-alcoholic steatohepatitis (NASH), which occurs in association with insulin resistance and hepatic fat accumulation, is characterized by chronic liver injury and fibrosis. NASH onset and progression is closely related to hepatic inflammation, which is partly regulated by the vagus nerve through the α7 nicotinic acetylcholine receptor (α7nAchR). Hepatic α7nAchR action is impeded in obesity and insulin resistance. In the present study, using α7nAchR knockout (α7KO) mice, we elucidated the effect of α7nAchR deficiency on NASH-related inflammation and fibrosis.

MATERIALS AND METHODS

α7KO mice were fed an atherogenic high-fat diet (AD) for 32 weeks or methionine/choline-deficient diet (MCD) for 6 weeks, both of which induce NASH. Mice were then examined for the degree of NASH-related inflammation and fibrosis by hepatic gene expression analysis and Sirius red histological staining.

RESULTS

Hepatic triglyceride accumulation and elevated plasma transaminase levels were observed in both AD and MCD mice, but the plasma transaminase level increase was higher in α7KO mice than in control mice. α7KO mice fed an AD showed significant upregulation of the Col1a1 gene encoding alpha-1 type I collagen, which is involved in liver fibrosis, and the Ccl2 gene encoding C-C motif chemokine ligand 2, a pro-inflammatory chemokine; α7KO mice fed an MCD had significant upregulation of the Col1a1 gene and the Tnf gene, an inflammatory cytokine. Histological analysis showed that AD and MCD exacerbated liver fibrosis in α7KO mice.

CONCLUSIONS

The results of this study suggest that α7nAchR deficiency exacerbates hepatic inflammation and fibrosis in a diet-induced mouse model of NASH.

Selective attenuation of Ether-a-go-go related K+ currents by endogenous acetylcholine reduces spike-frequency adaptation and network correlation

Most neurons do not simply convert inputs into firing rates. Instead, moment-to-moment firing rates reflect interactions between synaptic inputs and intrinsic currents. Few studies investigated how intrinsic currents function together to modulate output discharges and which of the currents attenuated by synthetic cholinergic ligands are actually modulated by endogenous acetylcholine (ACh). In this study we optogenetically stimulated cholinergic fibers in rat neocortex and find that ACh enhances excitability by reducing Ether-à-go-go Related Gene (ERG) K⁺ current. We find ERG mediates the late phase of spike-frequency adaptation in pyramidal cells and is recruited later than both SK and M currents. Attenuation of ERG during coincident depolarization and ACh release leads to reduced late phase spike-frequency adaptation and persistent firing. In neuronal ensembles, attenuating ERG enhanced signal-to-noise ratios and reduced signal correlation, suggesting that these two hallmarks of cholinergic function in vivo may result from modulation of intrinsic properties.

Nicotine protects against manganese and iron-induced toxicity in SH-SY5Y cells: Implication for Parkinson's disease

Manganese (Mn) and iron (Fe) are trace elements that are essential for proper growth and physiological functions as both play critical role in a variety of enzymatic reactions. At high concentrations, however, they can be toxic and cause neurodegenerative disorders, particularly Parkinson-like syndromes. Nicotine, on the other hand, has been shown to have neuroprotective effects against various endogenous or exogenous toxins that selectively damage the dopaminergic cells. These cells include neuroblastoma-derived SH-SY5Y cells which express significant dopaminergic activity. However, practically no information on possible neuroprotective effects of nicotine against toxicity induced by trace elements is available. Therefore, in this study we investigated the effects of nicotine on toxicity induced by manganese or iron in these cells. Exposure of SH-SY5Y cells for 24 h to manganese (20 μM) or iron (20 μM) resulted in approximately 30% and 35% toxicity, respectively. Pretreatment with nicotine (1 μM) completely blocked the toxicities of Mn and Fe. The effects of nicotine, in turn, were blocked by selective nicotinic receptor antagonists. Thus, dihydro-beta erythroidine (DHBE), a selective alpha 4-beta 2 subtype antagonist and methyllycaconitine (MLA), a selective alpha7 antagonist, as well as mecamylamine, a non-selective nicotinic antagonist all dose-dependently blocked the protective effects of nicotine against both Mn and Fe. These findings provide further support for the potential utility of nicotine or nicotinic agonists in Parkinson's disease-like neurodegenerative disorders, including those that might be precipitated by trace elements, such as Fe and Mn. Moreover, both alpha4-beta2 and alpha7 nicotinic receptor subtypes appear to mediate the neuroprotective effects of nicotine against toxicity induced by these two trace metals.

Nicotinic Acetylcholine Receptor Ligands, Cognitive Function, and Preclinical Approaches to Drug Discovery

Interest in nicotinic acetylcholine receptor (nAChR) ligands as potential therapeutic agents for cognitive disorders began more than 30 years ago when it was first demonstrated that the tobacco alkaloid nicotine could improve cognitive function in nicotine-deprived smokers as well as nonsmokers. Numerous animal and human studies now indicate that nicotine and a variety of nAChR ligands have the potential to improve multiple domains of cognition including attention, spatial learning, working memory, recognition memory, and executive function. The purpose of this review is to (1) discuss several pharmacologic strategies that have been developed to enhance nAChR activity (eg, agonist, partial agonist, and positive allosteric modulator) and improve cognitive function, (2) provide a brief overview of some of the more common rodent behavioral tasks with established translational validity that have been used to evaluate nAChR ligands for effects on cognitive function, and (3) briefly discuss some of the topics of debate regarding the development of optimal therapeutic strategies using nAChR ligands. Because of their densities in the mammalian brain and the amount of literature available, the review primarily focuses on ligands of the high-affinity α4β2* nAChR ("*" indicates the possible presence of additional subunits in the complex) and the low-affinity α7 nAChR. The behavioral task discussion focuses on representative methods that have been designed to model specific domains of cognition that are relevant to human neuropsychiatric disorders and often evaluated in human clinical trials.

IMPLICATIONS

The preclinical literature continues to grow in support of the development of nAChR ligands for a variety of illnesses that affect humans. However, to date, no new nAChR ligand has been approved for any condition other than nicotine dependence. As discussed in this review, the studies conducted to date provide the impetus for continuing efforts to develop new nAChR strategies (ie, beyond simple agonist and partial agonist approaches) as well as to refine current behavioral strategies and create new animal models to address translational gaps in the drug discovery process.

Neurobiological Determinants of Tobacco Smoking in Schizophrenia

Purpose of review: To provide an overview of the underlying neurobiology of tobacco smoking in schizophrenia, and implications for treatment of this comorbidity. Recent findings: Explanations for heavy tobacco smoking in schizophrenia include pro-cognitive effects of nicotine, and remediation of the underlying pathophysiology of schizophrenia. Nicotine may ameliorate neurochemical deficits through nicotine acetylcholine receptors (nAChRs) located on the dopamine, glutamate, and GABA neurons. Neurophysiological indices including electroencephalography, electromyography, and smooth pursuit eye movement (SPEM) paradigms may be biomarkers for underlying neuronal imbalances that contribute to the specific risk of tobacco smoking initiation, maintenance, and difficulty quitting within schizophrenia. Moreover, several social factors including socioeconomic factors and permissive smoking culture in mental health facilities, may contribute to the smoking behaviors (initiation, maintenance, and inability to quit smoking) within this disorder. Summary: Tobacco smoking may alleviate specific symptoms associated with schizophrenia. Understanding the neurobiological underpinnings and psychosocial determinants of this comorbidity may better explain these potential beneficial effects, while also providing important insights into effective treatments for smoking cessation.

The α7 nicotinic acetylcholine receptors regulate hippocampal adult-neurogenesis in a sexually dimorphic fashion

Disruption in cholinergic signaling has been linked to many environmental and/or pathological conditions known to modify adult neurogenesis. The α7 nAChRs are in the family of cys-loop receptor channels which have been shown to be neuroprotective in adult neurons and are thought to be critical for survival and integration of immature neurons. However, in developing neurons, poor calcium buffering may cause α7 nAChR activation to be neurotoxic. To investigate whether the α7 nAChR regulates neurogenesis in the hippocampus, we used a combination of mouse genetics and imaging to quantify neural stem cell (NSC) densities located in the dentate gyrus of adult mice. In addition, we considered whether the loss of α7 nAChRs had functional consequences on a spatial discrimination task that is thought to rely on pattern separation mechanisms. We found that the loss of α7 nAChRs resulted in increased neurogenesis in male mice only, while female mice showed increased cell divisions and intermediate progenitors but no change in neurogenesis. Knocking out the α7 nAChR from nestin⁺ NSCs and their progeny showed signaling in these cells contributes to regulating neurogenesis. In addition, male, but not female, mice lacking α7 nAChRs performed significantly worse in the spatial discrimination task. This task was sexually dimorphic in wild-type mice, but not in the absence of α7 nAChRs. We conclude that α7 nAChRs regulate adult neurogenesis and impact spatial discrimination function in male, but not female mice, via a mechanism involving nestin⁺ NSCs and their progeny.

CHRNA7 copy number gains are enriched in adolescents with major depressive and anxiety disorders

OBJECTIVE

Neuronal nicotinic acetylcholine receptors (nAChRs), specifically the α7 nAChR encoded by the gene CHRNA7, have been implicated in behavior regulation in animal models. In humans, copy number variants (CNVs) of CHRNA7 are found in a range of neuropsychiatric disorders, including mood and anxiety disorders. Here, we aimed to determine the prevalence of CHRNA7 CNVs among adolescents and young adults with major depressive disorder (MDD) and anxiety disorders.

METHODS

Twelve to 21 year-old participants with MDD and/or anxiety disorders (34% males, mean ± std age: 18.9 ± 1.8 years) were assessed for CHRNA7 copy number state using droplet digital PCR (ddPCR) and genomic quantitative PCR (qPCR). Demographic, anthropometric, and clinical data, including the Beck Anxiety Index (BAI), Beck Depression Inventory (BDI), and the Inventory of Depressive Symptoms (IDS) were collected and compared across individuals with and without a CHRNA7 CNV.

RESULTS

Of 205 individuals, five (2.4%) were found to carry a CHRNA7 gain, significantly higher than the general population. No CHRNA7 deletions were identified. Clinically, the individuals carrying CHRNA7 duplications did not differ significantly from copy neutral individuals with MDD and/or anxiety disorders.

CONCLUSIONS

CHRNA7 gains are relatively prevalent among young individuals with MDD and anxiety disorders (odds ratio = 4.032) without apparent distinguishing clinical features. Future studies should examine the therapeutic potential of α7 nAChR targeting drugs to ameliorate depressive and anxiety disorders.

Genetic variation in CHRNA7 and CHRFAM7A is associated with nicotine dependence and response to varenicline treatment

The role of nicotinic acetylcholine receptors (nAChR) in nicotine dependence (ND) is well established; CHRNA7, encoding the α7 subunit, has a still uncertain role in ND, although it is implicated in a wide range of neuropsychiatric conditions. CHRFAM7A, a hybrid gene containing a partial duplication of CHRNA7, is possibly involved in modulating α7 nAChR function. The aim of this study was to investigate the role of CHRNA7 and CHRFAM7A genetic variants in ND and to test the hypothesis that α7 nAChR variation may modulate the efficacy of varenicline treatment in smoking cessation. We assessed CHRNA7 and CHRFAM7A copy number, CHRFAM7A exon 6 ∆2 bp polymorphism, and sequence variants in the CHRNA7 proximal promoter in an Italian sample of 408 treatment-seeking smokers. We conducted case-control and quantitative association analyses using two smoking measures (cigarettes per day, CPD, and Fagerström Test for Nicotine Dependence, FTND). Next, driven by the hypothesis that varenicline may exert some of its therapeutic effects through activation of α7 nAChRs, we restricted the analysis to a subgroup of 142 smokers who received varenicline treatment. The CHRNA7 promoter variant rs28531779 showed association with both smoking quantitative measures (FNTD p = 0.026, β = 0.89, 95% CI 0.11-1.67; CPD p = 0.006, β = 4.82 95% CI 1.42-8.22). Moreover, in the varenicline-treated subgroup we observed association of CHRFAM7A copy number with 6 months smoking abstinence (p = 0.035, OR = 3.18, 95% CI = 1.09-9.30). Thus, our study points to a possible role of genetic variation in CHRNA7 and CHRFAM7A in tobacco addiction mechanisms and response to varenicline treatment.

Molecular function of the novel α7β2 nicotinic receptor

The α7 nicotinic receptor is a promising drug target for neurological and inflammatory disorders. Although it is the homomeric member of the family, a novel α7β2 heteromeric receptor has been discovered. To decipher the functional contribution of the β2 subunit, we generated heteromeric receptors with fixed stoichiometry by two different approaches comprising concatenated and unlinked subunits. Receptors containing up to three β2 subunits are functional. As the number of β2 subunits increases in the pentameric arrangement, the durations of channel openings and activation episodes increase progressively probably due to decreased desensitization. The prolonged activation episodes conform the kinetic signature of α7β2 and may have an impact on neuronal excitability. For activation of α7β2 receptors, an α7/α7 binding-site interface is required, thus indicating that the three β2 subunits are located consecutively in the pentameric arrangement. α7-positive allosteric modulators (PAMs) are emerging as novel therapeutic drugs. The presence of β2 in the pentamer affects neither type II PAM potentiation nor activation by an allosteric agonist whereas it impairs type I PAM potentiation. This first single-channel study provides fundamental basis required to decipher the role and function of the novel α7β2 receptor and opens doors to develop selective therapeutic drugs.

Assessing the acute effects of CDP-choline on sensory gating in schizophrenia: A pilot study

Deficient sensory gating (SG) in schizophrenia is associated with functional outcome and offers a therapeutic target as it is linked to the altered function/expression of the α7 nicotinic acetylcholine receptors (nAChRs). This study analyzed the effects of citicoline (CDP-choline), a supplement with α7 nAChRs agonist properties, on SG in a sample of schizophrenia (SZ) patients. Using a randomized, placebo-controlled, double-blind design the dose-dependent (500 mg, 1000 mg, 2000 mg) and baseline-dependent (deficient versus normal suppressors) effects of CDP-choline on SG were examined using the P50 event-related potential (ERP) index of SG. Overall analysis failed to demonstrate treatment effects but CDP-choline improved SG (500 mg) in the deficient SZ subgroup by increasing suppression of the S2 P50 amplitude. These findings tentatively support α7 nAChR dysfunction in the expression of SG deficits and suggest further trials to assess the effects of sustained α7 nAChR activation on SG with low doses of CDP-choline.

Bidirectional Regulation of Aggression in Mice by Hippocampal Alpha-7 Nicotinic Acetylcholine Receptors

Humans with 15q13.3 microdeletion syndrome (15q13.3DS) are typically hemizygous for CHRNA7, the gene coding for the α7 nicotinic acetylcholine receptor (nAChR), and manifest a variable neuropsychiatric phenotype that frequently includes persistent aggression. In mice, nAChR activation by nicotine is anti-aggressive, or 'serenic,' an effect which requires α7 nAChRs and is recapitulated by GTS-21, an α7 nAChR partial agonist. Pharmacotherapies potentiating α7 nAChR signaling have also been shown to reduce aggression in human 15q13.3DS. These findings identify the α7 nAChR as an important regulator of aggressive behavior, but the underlying neurobiological substrates remain to be determined. We therefore investigated the brain regions and potential neural circuits in which α7 nAChRs regulate aggressive behavior in male mice. As in 15q13.3DS, mice heterozygous for Chrna7 were significantly more aggressive compared to wild-type controls in the resident-intruder test. We subsequently examined the hippocampus, where α7 nAChRs are highly expressed, particularly in GABAergic interneurons. Resident-intruder interactions strongly activated granule cells in the dentate gyrus (DG). In contrast, GTS-21, which reduces aggression in mice, reduced DG granule cell activity during resident-intruder interactions. Short hairpin RNA knockdown of Chrna7 in the DG enhanced baseline aggression and eliminated the serenic effects of both nicotine and GTS-21 on attack latency. These data further implicate α7 nAChRs in regulation of aggression, and demonstrate that hippocampal α7 nAChR signaling is necessary and sufficient to limit aggression. These findings suggest that nAChR-mediated regulation of hippocampal excitatory-inhibitory balance could be a promising therapeutic intervention for aggression arising in certain forms of neuropsychiatric disease.