Changes In Receptor Binding Research Articles

Isolated during adolescence: long-term impact on social behavior, pain sensitivity, and the oxytocin system in male and female rats

BackgroundAdolescent social isolation (ASI) has profound long-term effects on behavioral and neural development. Despite this, the specific long-term impact of ASI during different adolescent stages and across sexes remain underexplored.MethodsOur study addresses this gap by examining the effects of early- and late- adolescent social isolation on both male and female rats. Rats were either isolated (or group-housed) starting from PD 21 (early) or PD 42 (late) for three weeks and then rehoused into groups. In adulthood (PD 90), rats underwent a battery of tests: elevated plus-maze, open field, novel object recognition, social interaction and social recognition memory and hotplate tests. Finally, we analyzed oxytocin receptor binding in several regions in the brains of a second cohort of rats.ResultsBoth, male and female rats from the late adolescent social isolation (LASI) groups spent significantly less time interacting in the social interaction test. Additionally, we observed a general decrease in social recognition memory regardless of sex. Both male ASI groups demonstrated heightened thermal pain sensitivity, while the opposite was observed in early adolescent social isolation (EASI) female rats. In the brain, we observed changes in oxytocin receptor (OTR) binding in the paraventricular nucleus of the hypothalamus (PVN) and paraventricular nucleus of the thalamus (PVT) and central amygdala (CeA) with the largest changes in EASI and LASI female rats.ConclusionOur model demonstrates long-lasting alterations on behavior and oxytocin receptor binding levels following ASI providing insights into the long-term effects of ASI in a time- and sex-specific manner.

Structural Characterization of Human Bufavirus 1: Receptor Binding and Endosomal pH-Induced Changes.

Bufaviruses (BuV) are members of the Parvoviridae of the Protoparvovirus genus. They are non-enveloped, T = 1 icosahedral ssDNA viruses isolated from patients exhibiting acute diarrhea. The lack of treatment options and a limited understanding of their disease mechanisms require studying these viruses on a molecular and structural level. In the present study, we utilize glycan arrays and cell binding assays to demonstrate that BuV1 capsid binds terminal sialic acid (SIA) glycans. Furthermore, using cryo-electron microscopy (cryo-EM), SIA is shown to bind on the 2/5-fold wall of the capsid surface. Interestingly, the capsid residues stabilizing SIA binding are conserved in all human BuVs identified to date. Additionally, biophysical assays illustrate BuV1 capsid stabilization during endo-lysosomal (pH 7.4-pH 4) trafficking and capsid destabilization at pH 3 and less, which correspond to the pH of the stomach. Hence, we determined the cryo-EM structures of BuV1 capsids at pH 7.4, 4.0, and 2.6 to 2.8 Å, 3.2 Å, and 2.7 Å, respectively. These structures reveal capsid structural rearrangements during endo-lysosomal escape and provide a potential mechanism for this process. The structural insights gained from this study will add to the general knowledge of human pathogenic parvoviruses. Furthermore, the identification of the conserved SIA receptor binding site among BuVs provides a possible targetable surface-accessible pocket for the design of small molecules to be developed as anti-virals for these viruses.

APOE Christchurch enhances a disease-associated microglial response to plaque but suppresses response to tau pathology.

Apolipoprotein E ε4 (APOE4) is the strongest genetic risk factor for late-onset Alzheimer's disease (LOAD). A recent case report identified a rare variant in APOE, APOE3-R136S (Christchurch), proposed to confer resistance to autosomal dominant Alzheimer's Disease (AD). However, it remains unclear whether and how this variant exerts its protective effects. We introduced the R136S variant into mouse Apoe (ApoeCh) and investigated its effect on the development of AD-related pathology using the 5xFAD model of amyloidosis and the PS19 model of tauopathy. We used immunohistochemical and biochemical analysis along with single-cell spatial transcriptomics and proteomics to explore the impact of the ApoeCh variant on AD pathological development and the brain's response to plaques and tau. In 5xFAD mice, ApoeCh enhances a Disease-Associated Microglia (DAM) phenotype in microglia surrounding plaques, and reduces plaque load, dystrophic neurites, and plasma neurofilament light chain. By contrast, in PS19 mice, ApoeCh suppresses the microglial and astrocytic responses to tau-laden neurons and does not reduce tau accumulation or phosphorylation, but partially rescues tau-induced synaptic and myelin loss. We compared how microglia responses differ between the two mouse models to elucidate the distinct DAM signatures induced by ApoeCh. We identified upregulation of antigen presentation-related genes in the DAM response in a PS19 compared to a 5xFAD background, suggesting a differential response to amyloid versus tau pathology that is modulated by the presence of ApoeCh. These findings highlight the ability of the ApoeCh variant to modulate microglial responses based on the type of pathology, enhancing DAM reactivity in amyloid models and dampening neuroinflammation to promote protection in tau models. This suggests that the Christchurch variant's protective effects likely involve multiple mechanisms, including changes in receptor binding and microglial programming.

Altered Serotonin 1B Receptor Binding After Escitalopram for Depression Is Correlated With Treatment Effect.

Major depressive disorder (MDD) is commonly treated with selective serotonin reuptake inhibitors (SSRIs). SSRIs inhibit the serotonin transporter (5-HTT), but the downstream antidepressant mechanism of action of these drugs is poorly understood. The serotonin 1B (5-HT1B) receptor is functionally linked to 5-HTT and 5-HT1B receptor binding and 5-HT1B receptor mRNA is reduced in the raphe nuclei after SSRI administration in primates and rodents, respectively. The effect of SSRI treatment on 5-HT1B receptor binding in patients with MDD has not been examined previously. This positron emission tomography (PET) study aimed to quantify brain 5-HT1B receptor binding changes in vivo after SSRI treatment for MDD in relation to treatment effect. Eight unmedicated patients with moderate to severe MDD underwent PET with the 5-HT1B receptor radioligand [11C]AZ10419369 before and after 3 to 4 weeks of treatment with the SSRI escitalopram 10mg daily. Depression severity was assessed at time of PET and after 6 to 7 weeks of treatment with the Montgomery-Åsberg Depression Rating Scale. We observed a significant reduction in [11C]AZ10419369 binding in a dorsal brainstem (DBS) region containing the median and dorsal raphe nuclei after escitalopram treatment (P = .036). Change in DBS [11C]AZ10419369 binding correlated with Montgomery-Åsberg Depression Rating Scale reduction after 3-4 (r = 0.78, P = .021) and 6-7 (r = 0.94, P < .001) weeks' treatment. Our findings align with the previously reported reduction of 5-HT1B receptor binding in the raphe nuclei after SSRI administration and support future studies testing change in DBS 5-HT1B receptor binding as an SSRI treatment response marker.

Exploring the Specific Role of Iron Center in the Catalytic Activity of Human Serum Transferrin: CTAB-Induced Conformational Changes and Sequestration by Mixed Micelles.

Conformational changes play a seminal role in modulating the activity of proteins. This concept becomes all the more relevant in the context of metalloproteins, owing to the formation of specific conformation(s) induced by internal perturbations (like a change in pH, ligand binding, or receptor binding), which may carry out the binding and release of the metal ion/ions from the metal binding center of the protein. Herein, we investigated the conformational changes of an iron-binding protein, monoferric human serum transferrin (Fe-hTF), using several spectroscopic approaches. We could reversibly tune the cetyltrimethylammonium bromide (CTAB)-induced conformation of the protein, exploiting the concept of mixed micelles formed by three sequestrating agents: (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) hydrate (CHAPS) and two bile salts, namely, sodium cholate (NaC) and sodium deoxycholate (NaDC). The formation of mixed micelles between CTAB and these reagents (CHAPS/NaC/NaDC) results in the sequestration of CTAB molecules from the protein environment and aids the protein in reattaining its native-like structure. However, the guanidinium hydrochloride-induced denatured Fe-hTF did not acquire its native-like structure using these sequestrating agents, which substantiates the exclusive role of mixed micelles in the present study. Apart from this, we found that the conformation of transferrin (adopted in the presence of CTAB) displays pronounced esterase-like activity toward the para-nitrophenyl acetate (PNPA) substrate as compared to native transferrin. We also outlined the impact of the iron center and amino acids surrounding the iron center on the effective catalytic activity in the CTAB medium. We estimated ∼3 times higher specific catalytic efficiency for the iron-depleted Apo-hTF compared to the fully iron-saturated Fe2-hTF in the presence of CTAB.

Glucocorticoid receptor and PARP-1 genomic binding changes in response to corticosterone excess in mice

Glucocorticoid receptor and PARP-1 genomic binding changes in response to corticosterone excess in mice

Viral Capsid, Antibody, and Receptor Interactions: Experimental Analysis of the Antibody Escape Evolution of Canine Parvovirus.

Canine parvovirus (CPV) is a small nonenveloped single-stranded DNA virus that causes serious diseases in dogs worldwide. The original strain of the virus (CPV-2) emerged in dogs during the late 1970s due to a host range switch of a virus similar to the feline panleukopenia virus that infected another host. The virus that emerged in dogs had altered capsid receptor and antibody binding sites, with some changes affecting both functions. Further receptor and antibody binding changes arose when the virus became better adapted to dogs or to other hosts. Here, we used in vitro selection and deep sequencing to reveal how two antibodies with known interactions select for escape mutations in CPV. The antibodies bound two distinct epitopes, and one largely overlapped the host receptor binding site. We also generated mutated antibody variants with altered binding structures. Viruses were passaged with wild-type (WT) or mutated antibodies, and their genomes were deep sequenced during the selective process. A small number of mutations were detected only within the capsid protein gene during the first few passages of selection, and most sites remained polymorphic or were slow to go to fixation. Mutations arose both within and outside the antibody binding footprints on the capsids, and all avoided the transferrin receptor type 1 binding footprint. Many selected mutations matched those that have arisen in the natural evolution of the virus. The patterns observed reveal the mechanisms by which these variants have been selected in nature and provide a better understanding of the interactions between antibody and receptor selections. IMPORTANCE Antibodies protect animals against infection by many different viruses and other pathogens, and we are gaining new information about the epitopes that induce antibody responses against viruses and the structures of the bound antibodies. However, less is known about the processes of antibody selection and antigenic escape and the constraints that apply in this system. Here, we used an in vitro model system and deep genome sequencing to reveal the mutations that arose in the virus genome during selection by each of two monoclonal antibodies or their mutated variants. High-resolution structures of each of the Fab:capsid complexes revealed their binding interactions. The wild-type antibodies or their mutated variants allowed us to examine how changes in antibody structure influence the mutational selection patterns seen in the virus. The results shed light on the processes of antibody binding, neutralization escape, and receptor binding, and they likely have parallels for many other viruses.

Mu Opioid Receptor Dynamics in Healthy Volunteers with a History of Childhood Maltreatment.

Evidence suggests that adults with a history of childhood maltreatment, the experience of emotional or physical neglect and/or abuse within the family during childhood, have blunted reward and stress processing, and higher risk of depression. The mu opioid receptor rich nucleus accumbens and amygdala are critical to reward and stress processing respectively. We hypothesized that nucleus accumbens and amygdala mu opioid receptor densities and activity (change in receptor binding due to endogenous opioid release or receptor conformation change) were negatively associated with childhood maltreatment in healthy young adults.Maltreatment was assessed with the Childhood Trauma Questionnaire (CTQ). Healthy participants, n = 75 (52% female) completed [11C]carfentanil positron emission tomography imaging labeling mu opioid receptors. The relationship between CTQ score and binding potential (BPND, proportional to density of unoccupied receptors) was evaluated with a linear mixed effects model.No significant relationship was found between CTQ score and BPND (f = 3.28; df = 1, 73; p = 0.074) or change in BPND (activity) (t = 1.48; df = 198.3; p = 0.14).This is the first investigation of mu opioid receptors in those with childhood maltreatment. We did not identify a significant relationship between mu opioid receptor dynamics and severity of maltreatment in those without psychopathology. Because this cohort has a low CTQ score average, this may indicate that those with low severity of maltreatment may not have associated changes in mu opioid receptor dynamics. Future directions include evaluating a cohort with increased severity of childhood maltreatment.

Biophysical and structural characterizations of the effects of mutations on the structure-activity relationships of SARS-CoV-2 spike protein.

Mutations on the spike (S) protein of SARS-CoV-2 could induce structural changes that help increase viral transmissibility and enhance resistance to antibody neutralization. Here, we report a robust workflow to prepare recombinant S protein variants and its host receptor angiotensin-convert enzyme 2 (ACE2) by using a mammalian cell expression system. The functional states of the S protein variants are investigated by cryo-electron microscopy (cryo-EM) and negative staining electron microscopy (NSEM) to visualize their molecular structures in response to mutations, receptor binding, antibody binding, and environmental changes. The folding stabilities of the S protein variants can be deduced from morphological changes based on NSEM imaging analysis. Differential scanning calorimetry provides thermodynamic information to complement NSEM. Impacts of the mutations on host receptor binding and antibody neutralization are in vitro by kinetic binding analyses in addition to atomic insights gleaned from cryo-electron microscopy (cryo-EM). This experimental strategy is generally applicable to studying the molecular basis of host-pathogen interactions.

A positron emission tomography study of the serotonin1B receptor effect of electroconvulsive therapy for severe major depressive episodes

BackgroundElectroconvulsive therapy (ECT) is an effective treatment for depressive disorders, although its molecular mechanism of action is unknown. The serotonin 1B (5-HT1B) receptor is a potential target for treatment of depression and low 5-HT1B receptor binding in limbic regions has been reported in previous positron emission tomography (PET) studies of depression. MethodsThe objective of this longitudinal PET study was to examine the effect of ECT for depression on 5-HT1B receptor binding. Fifteen hospitalized patients with major depressive episodes were examined with PET and the 5-HT1B receptor selective radioligand [11C]AZ10419369, before and after ECT. Fifteen controls matched for age and sex were examined. Limbic regions with previously reported low 5-HT1B receptor binding in depression and a dorsal brain stem region were selected. ResultsThirteen patients completed the study according to protocol. Eleven out of thirteen patients responded to ECT. 5-HT1B receptor binding in hippocampus increased with 30 % after ECT (p=0.021). Using linear mixed effects modelling, we observed increases in 5-HT1B receptor binding following ECT with a moderate to large effect size, which did not differ significantly between regions. In an exploratory analysis, strong correlations between changes in 5-HT1B receptor binding and agitation scores on the Hamilton Depression Rating Scale after ECT were observed. LimitationsAlbeit representative of a PET study, the sample size is still small and there are potential confounding effects of medication. ConclusionsIncreased 5-HT1B receptor binding was observed following ECT for depression, corresponding to previous findings of increased 5-HT1B receptor binding in hippocampus after rapid acting ketamine for treatment resistant depression.

Lasting effects of a single psilocybin dose on resting-state functional connectivity in healthy individuals.

Background:Psilocybin is a psychedelic drug that has shown lasting positive effects on clinical symptoms and self-reported well-being following a single dose. There has been little research into the long-term effects of psilocybin on brain connectivity in humans.Aim:Evaluate changes in resting-state functional connectivity (RSFC) at 1 week and 3 months after one psilocybin dose in 10 healthy psychedelic-naïve volunteers and explore associations between change in RSFC and related measures.Methods:Participants received 0.2–0.3 mg/kg psilocybin in a controlled setting. Participants completed resting-state functional magnetic resonance imaging (fMRI) scans at baseline, 1-week and 3-month post-administration and [11C]Cimbi-36 PET scans at baseline and 1 week. We examined changes in within-network, between-network and region-to-region RSFC. We explored associations between changes in RSFC and psilocybin-induced phenomenology as well as changes in psychological measures and neocortex serotonin 2A receptor binding.Results:Psilocybin was well tolerated and produced positive changes in well-being. At 1 week only, executive control network (ECN) RSFC was significantly decreased (Cohen’s d = −1.73, pFWE = 0.010). We observed no other significant changes in RSFC at 1 week or 3 months, nor changes in region-to-region RSFC. Exploratory analyses indicated that decreased ECN RSFC at 1 week predicted increased mindfulness at 3 months (r = −0.65).Conclusions:These findings in a small cohort indicate that psilocybin affects ECN function within the psychedelic ‘afterglow’ period. Our findings implicate ECN modulation as mediating psilocybin-induced, long-lasting increases in mindfulness. Although our findings implicate a neural pathway mediating lasting psilocybin effects, it is notable that changes in neuroimaging measures at 3 months, when personality changes are observed, remain to be identified.

Anoxia at Birth Induces Behaviorally-Relevant Changes in alpha2-Noradrenergic Receptor Binding in the Adult Rat

Evidence suggests that Caesarean section birth in the rat, with or without an additional period of anoxia, results in long-term changes in brain catecholamine levels as well as reactivity to stress. The purpose of the present investigation was to determine whether Caesarean birth plus anoxia alters (alpha)2-noradrenergic receptor binding and sensitivity to the (alpha)2 receptor agonist, clonidine, in the Porsolt forced swim test. Sprague Dawley rat dams were decapitated and the uteruses were removed by Caesarean section. Pups were then delivered either immediately (Caesarean Only group), or were immersed in a saline bath for approximately 15 minutes (Caesarean plus Anoxia group) before delivery of the pups. A third group of animals born vaginally served as controls (Vaginally-born group). Four to five months postnatally, the expression of (alpha)2 receptors was measured by receptor autoradiography using [3H]-Rauwolscine binding. Receptor binding was increased in the area of the ventral hypothalamus and decreased in the CA1 region of the hippocampus in animals subjected to Caesarean plus Anoxia at birth. These animals also displayed a subsensitive response to the immobilizing effects of clonidine (100 micrograms/kg, i.p.) in the Porsolt forced swim test. Specifically these data show that Caesarean birth produces long-term changes in (alpha)2 receptor density and that, in animals subjected to Caesarean plus anoxia, these changes are reflected in a behavioral subsensitivity to the (alpha)2 agonist, clonidine. The findings reported here provide further experimental support for the hypothesis that birth complications may contribute to the pathophysiology of disorders such as schizophrenia that involve central catecholamine dysfunction.

Early life variations in temperature exposure affect the epigenetic regulation of the paraventricular nucleus in female rat pups.

Early life maternal care received has a profound effect on later-life behaviour in adult offspring, and previous studies have suggested epigenetic mechanisms are involved. Changes in thyroid hormone receptor signalling may be related to differences in maternal care received and DNA methylation modifications. We investigated the effects of variations in temperature exposure (a proxy of maternal contact) and licking-like tactile stimulation on these processes in week-old female rat pups. We assessed thyroid hormone receptor signalling by measuring circulating triiodothyronine and transcript abundance of thyroid hormone receptors and the thyroid hormone-responsive genes DNA methyltransferase 3a and oxytocin in the paraventricular nucleus of the hypothalamus. DNA methylation of the oxytocin promoter was assessed in relation to changes in thyroid hormone receptor binding. Repeated room temperature exposure was associated with a decrease in thyroid hormone receptor signalling measures relative to nest temperature exposure, while acute room temperature exposure was associated with an increase. Repeated room temperature exposure also increased thyroid hormone receptor binding and DNA methylation at the oxytocin promoter. These findings suggest that repeated room temperature exposure may affect DNA methylation levels as a consequence of alterations in thyroid hormone receptor signalling.

Bile Facilitates Human Norovirus Interactions with Diverse Histoblood Group Antigens, Compensating for Capsid Microvariation Observed in 2016-2017 GII.2 Strains.

Human norovirus (HuNoV) is the leading cause of global infectious acute gastroenteritis, causing ~20% of reported diarrheal episodes. Typically, GII.4 strains cause 50–70% of yearly outbreaks, and pandemic waves of disease approximately every 2–7 years due to rapid evolution. Importantly, GII.4 dominance is occasionally challenged by the sudden emergence of other GII strains, most recently by GII.2 strains which peaked in 2016–2017, dramatically increasing from 1% to 20% of total HuNoV outbreaks. To determine if viral capsid evolution may account for the sudden rise in GII.2 outbreaks, Virus Like Particles (VLPs) of two 2016–2017 GII.2 strains were compared by antigenic and histo blood group antigen (HBGA) binding profiles to the prototypic 1976 GII.2 Snow Mountain Virus (SMV) strain. Despite >50 years of GII.2 strain persistence in human populations, limited sequence diversity and antigenic differences were identified between strains. However, capsid microvariation did affect HBGA binding patterns, with contemporary strains demonstrating decreased avidity for type A saliva. Furthermore, bile salts increased GII.2 VLP avidity for HBGAs, but did not alter antigenicity. These data indicate that large changes in antigenicity or receptor binding are unlikely to explain GII.2 emergence, in contrast to the pandemic GII.4 strains, and indicate that host factors such as waning or remodeling of serum or mucosal immunity likely contributed to the surge in GII.2 prevalence.

The effect of 17β-estradiol on maternal immune activation-induced changes in prepulse inhibition and dopamine receptor and transporter binding in female rats

Maternal immune activation (MIA) during pregnancy is associated with an increased risk of development of schizophrenia in later life. 17β-estradiol treatment may improve schizophrenia symptoms, but little is known about its efficacy on MIA-induced psychosis-like behavioural deficits in animals. Therefore, in this study we used the poly(I:C) neurodevelopmental model of schizophrenia to examine whether MIA-induced psychosis-like behavioural and neurochemical changes can be attenuated by chronic treatment (2–6 weeks) with 17β-estradiol. Pregnant rats were treated with saline or the viral mimetic, poly(I:C), on gestational day 15 and adult female offspring were tested for changes in prepulse inhibition (PPI) and density of dopamine D1 and D2 receptors and dopamine transporters in the forebrain compared to control offspring. Poly(I:C)-treated offspring exhibited significantly disrupted PPI, an effect which was reversed by chronic treatment with 17β-estradiol. In control offspring, but not poly(I:C) offspring, PPI was significantly reduced by acute treatment with either the dopamine D1/D2 receptor agonist, apomorphine, or dopamine releaser, methamphetamine. 17β-estradiol restored the effect of apomorphine, but not methamphetamine, on PPI in poly(I:C) offspring. There was a strong trend for a dopamine D2 receptor binding density increase in the nucleus accumbens core region in poly(I:C) offspring, and this was reversed by chronic 17β-estradiol treatment. No changes were found in the nucleus accumbens shell, caudate putamen or frontal cortex or in the density of dopamine D1 receptors or transporters. These findings suggest that 17β-estradiol may improve some symptoms of schizophrenia, an effect that may be mediated by selective changes in dopamine D2 receptor density.

Visual stimuli induce serotonin release in occipital cortex: A simultaneous positron emission tomography/magnetic resonance imaging study.

Endogenous serotonin (5‐HT) release can be measured noninvasively using positron emission tomography (PET) imaging in combination with certain serotonergic radiotracers. This allows us to investigate effects of pharmacological and nonpharmacological interventions on brain 5‐HT levels in living humans. Here, we study the neural responses to a visual stimulus using simultaneous PET/MRI. In a cross‐over design, 11 healthy individuals were PET/MRI scanned with the 5‐HT1B receptor radioligand [11C]AZ10419369, which is sensitive to changes in endogenous 5‐HT. During the last part of the scan, participants either viewed autobiographical images with positive valence (n = 11) or kept their eyes closed (n = 7). The visual stimuli increased cerebral blood flow (CBF) in the occipital cortex, as measured with pseudo‐continuous arterial spin labeling. Simultaneously, we found decreased 5‐HT1B receptor binding in the occipital cortex (−3.6 ± 3.6%), indicating synaptic 5‐HT release. Using a linear regression model, we found that the change in 5‐HT1B receptor binding was significantly negatively associated with change in CBF in the occipital cortex (p = .004). For the first time, we here demonstrate how cerebral 5‐HT levels change in response to nonpharmacological stimuli in humans, as measured with PET. Our findings more directly support a link between 5‐HT signaling and visual processing and/or visual attention.

Neonatal Clonazepam Administration Induced Long-Lasting Changes in GABAA and GABAB Receptors.

Benzodiazepines (BZDs) are widely used in patients of all ages. Unlike adults, neonatal animals treated with BZDs exhibit a variety of behavioral deficits later in life; however, the mechanisms underlying these deficits are poorly understood. This study aims to examine whether administration of clonazepam (CZP; 1 mg/kg/day) in 7–11-day-old rats affects Gama aminobutyric acid (GABA)ergic receptors in both the short and long terms. Using RT-PCR and quantitative autoradiography, we examined the expression of the selected GABAA receptor subunits (α1, α2, α4, γ2, and δ) and the GABAB B2 subunit, and GABAA, benzodiazepine, and GABAB receptor binding 48 h, 1 week, and 2 months after treatment discontinuation. Within one week after CZP cessation, the expression of the α2 subunit was upregulated, whereas that of the δ subunit was downregulated in both the hippocampus and cortex. In the hippocampus, the α4 subunit was downregulated after the 2-month interval. Changes in receptor binding were highly dependent on the receptor type, the interval after treatment cessation, and the brain structure. GABAA receptor binding was increased in almost all of the brain structures after the 48-h interval. BZD-binding was decreased in many brain structures involved in the neuronal networks associated with emotional behavior, anxiety, and cognitive functions after the 2-month interval. Binding of the GABAB receptors changed depending on the interval and brain structure. Overall, the described changes may affect both synaptic development and functioning and may potentially cause behavioral impairment.

RELATIONSHIP BETWEEN CHOLINERGIC RECEPTOR BINDING AND ATTENTION IN COGNITIVE AGING USING POSITRON EMISSION TOMOGRAPHY AND THE STROOP

Introduction Cholinergic (Ach) neurotransmission has been associated with aspects of brain attention networks. Reductions in Ach are also thought to underlie cognitive symptoms in Alzheimer's Disease (AD). In a previous study using positron emission tomography (PET) imaging to measure nicotinic Ach receptor binding in vivo, our group found that Ach receptor binding was reduced in patients with AD relative to healthy controls. Reductions were observed in areas of the brain thought to mediate attention, including the anterior cingulate cortex/medial prefrontal cortex (ACC/mPFC) and insula. The Stroop is a neuropsychological measure used in research and clinical settings to assess attention and executive function. In a different study of AD patients, we found that performance on the Stroop was associated with metabolic activity in brain networks in the right hemisphere; the Stroop COLOR-WORD condition was associated with metabolic rate in the intraparietal sulcus (IPS), ACC/mPFC, and insula. In the present study, we sought to extend these findings by examining whether Ach binding was associated with performance on the Stroop prior to the onset of dementia. Methods The study included a combined group of healthy older adults or older adults with amnestic mild cognitive impairment (MCI). All participants completed the Stroop. The Stroop included three conditions: two simpler tasks requiring participants to name colors (COLOR) and read words (WORD) and a more complex task in which participants are required to name the color of ink used for a word that names a different color from the ink color (COLOR-WORD). Cholinergic (Ach) receptor binding was quantified using PET imaging, specifically 18F-2-FA PET (2FA), a radiotracer that binds to alpha4beta2 nicotinic receptor subunits. Scanning utilized a bolus plus infusion technique and measurement of nonmetabolized 2FA from plasma to calculate distribution volume (VT/fp) in PET Ach image voxels. Ach images were pre-processed using SPM12, which included motion correction, normalization to Montreal Neurological Institute (MNI) space using a co-registered T1 MRI image, and spatial smoothing of 8?mm full width at half maximum. First, a voxel-based analysis across the entire brain was used to measure the association between voxel VT/fp and performance on the Stroop COLOR-WORD test using a liberal statistical threshold (p Results Seventy-six participants were included in the sample, comprised of 43 healthy older adults and 33 patients with amnestic MCI (age: mean=73.1 (SD=7.7), MMSE: mean=28.3 (SD=2.1), 57 males and 19 females, education: mean=15.7?years (SD=2.5)). The combined group included 19 African-Americans, 48 Caucasians, 6 Hispanics, and 3?Asian/?Pacific Islanders. Performance on the COLOR task was associated with mean VT/fp in the ACC/mPFC (r=.23 p=.04), insula (r=.28, p=.02), and IPS (r=.23 p Conclusions Across the spectrum of cognitive aging, performance on the Stroop was associated with Ach binding in key brain regions involved in attention—the IPS, ACC/mPFC, and insula. These findings suggest that Ach binding, in part, mediates attentional processing. This appears true regardless of whether the task is simple, as in the COLOR and WORD conditions, or more complex, as in the COLOR-WORD condition. Thus, changes in Ach receptor binding may be an important factor in attentional deficits resulting from cognitive aging prior to onset of AD, and Ach neurotransmission could be a potential molecular target for novel pharmaceuticals to address these symptoms. This research was funded by: This work was supported by a VA Career Development grant awarded to Brandon C. Yarns, MD, MS, and VA Merit Review grants awarded to David L. Sultzer, MD, and Rebecca J. Melrose, PhD.

A single psilocybin dose is associated with long-term increased mindfulness, preceded by a proportional change in neocortical 5-HT2A receptor binding

A single dose of the serotonin 2A receptor (5-HT2AR) agonist psilocybin can have long-lasting beneficial effects on mood, personality, and potentially on mindfulness, but underlying mechanisms are unknown. Here, we for the first time conduct a study that assesses psilocybin effects on cerebral 5-HT2AR binding with [11C]Cimbi-36 positron emission tomography (PET) imaging and on personality and mindfulness. Ten healthy and psychedelic-naïve volunteers underwent PET neuroimaging of 5-HT2AR at baseline (BL) and one week (1W) after a single oral dose of psilocybin (0.2–0.3 mg/kg). Personality (NEO PI-R) and mindfulness (MAAS) questionnaires were completed at BL and at three-months follow-up (3M). Paired t-tests revealed statistically significant increases in personality Openness (puncorrected = 0.04, mean change [95%CI]: 4.2[0.4;∞]), which was hypothesized a priori to increase, and mindfulness (pFWER = 0.02, mean change [95%CI]: 0.5 [0.2;0.7]). Although 5-HT2AR binding at 1W versus BL was similar across individuals (puncorrected = 0.8, mean change [95%CI]: 0.007 [−0.04;0.06]), a post hoc linear regression analysis showed that change in mindfulness and 5-HT2AR correlated negatively (β [95%CI] = −5.0 [−9.0; −0.9], pFWER= 0.046). In conclusion, we confirm that psilocybin intake is associated with long-term increases in Openness and – as a novel finding – mindfulness, which may be a key element of psilocybin therapy. Cerebral 5-HT2AR binding did not change across individuals but the negative association between changes in 5-HT2AR binding and mindfulness suggests that individual change in 5-HT2AR levels after psilocybin is variable and represents a potential mechanism influencing long-term effects of psilocybin on mindfulness.

VULCAN integrates ChIP-seq with patient-derived co-expression networks to identify GRHL2 as a key co-regulator of ERa at enhancers in breast cancer

BackgroundVirtUaL ChIP-seq Analysis through Networks (VULCAN) infers regulatory interactions of transcription factors by overlaying networks generated from publicly available tumor expression data onto ChIP-seq data. We apply our method to dissect the regulation of estrogen receptor-alpha activation in breast cancer to identify potential co-regulators of the estrogen receptor’s transcriptional response.ResultsVULCAN analysis of estrogen receptor activation in breast cancer highlights the key components of the estrogen receptor complex alongside a novel interaction with GRHL2. We demonstrate that GRHL2 is recruited to a subset of estrogen receptor binding sites and regulates transcriptional output, as evidenced by changes in estrogen receptor-associated eRNA expression and stronger estrogen receptor binding at active enhancers after GRHL2 knockdown.ConclusionsOur findings provide new insight into the role of GRHL2 in regulating eRNA transcription as part of estrogen receptor signaling. These results demonstrate VULCAN, available from Bioconductor, as a powerful predictive tool.