Attenuation of oxytocin and serotonin 2A receptor signaling through novel heteroreceptor formation

The oxytocin receptor (OTR) and the 5-hydroxytryptamine 2A receptor (5-HTR2A) are expressed in similar brain regions modulating central pathways critical for social and cognition-related behaviors. Signaling crosstalk between their endogenous ligands, oxytocin (OT) and serotonin (5-hydroxytryptamine, 5-HT), highlights the complex interplay between these two neurotransmitter systems and may be indicative of the formation of heteroreceptor complexes with subsequent downstream signaling changes. In this study, we assess the possible formation of OTR-5HTR2A heteromers in living cells and the functional downstream consequences of this receptor–receptor interaction. First, we demonstrated the existence of a physical interaction between the OTR and 5-HTR2Ain vitro, using a flow cytometry-based FRET approach and confocal microscopy. Furthermore, we investigated the formation of this specific heteroreceptor complex ex vivo in the brain sections using the Proximity Ligation Assay (PLA). The OTR-5HTR2A heteroreceptor complexes were identified in limbic regions (including hippocampus, cingulate cortex, and nucleus accumbens), key regions associated with cognition and social-related behaviors. Next, functional cellular-based assays to assess the OTR-5HTR2A downstream signaling crosstalk showed a reduction in potency and efficacy of OT and OTR synthetic agonists, carbetocin and WAY267464, on OTR-mediated Gαq signaling. Similarly, the activation of 5-HTR2A by the endogenous agonist, 5-HT, also revealed attenuation in Gαq-mediated signaling. Finally, altered receptor trafficking within the cell was demonstrated, indicative of cotrafficking of the OTR/5-HTR2A pair. Overall, these results constitute a novel mechanism of specific interaction between the OT and 5-HT neurotransmitters via OTR-5HTR2A heteroreceptor formation and provide potential new therapeutic strategies in the treatment of social and cognition-related diseases

Molecular, biochemical and behavioural evidence for a novel oxytocin receptor and serotonin 2C receptor heterocomplex

The complexity of oxytocin-mediated functions is strongly associated with its modulatory effects on other neurotransmission systems, including the serotonin (5-hydroxytryptamine, 5-HT) system. Signalling between oxytocin (OT) and 5-HT has been demonstrated during neurodevelopment and in the regulation of specific emotion-based behaviours. It is suggested that crosstalk between neurotransmitters is driven by interaction between their specific receptors, particularly the oxytocin receptor (OTR) and the 5-hydroxytryptamine 2C receptor (5-HTR2C), but evidence for this and the downstream signalling consequences that follow are lacking. Considering the overlapping central expression profiles and shared involvement of OTR and 5-HTR2C in certain endocrine functions and behaviours, including eating behaviour, social interaction and locomotor activity, we investigated the existence of functionally active OTR/5-HTR2C heterocomplexes. Here, we demonstrate evidence for a potential physical interaction between OTR and 5-HTR2C in vitro in a cellular expression system using flow cytometry-based FRET (fcFRET). We could recapitulate this finding under endogenous expression levels of both receptors via in silico analysis of single cell transcriptomic data and ex vivo proximity ligation assay (PLA). Next, we show that co-expression of the OTR/5-HTR2C pair resulted in a significant depletion of OTR-mediated G alpha q-signalling and significant changes in receptor trafficking. Of note, attenuation of OTR-mediated downstream signalling was restored following pharmacological blockade of the 5-HTR2C. Finally, we demonstrated a functional relevance of this novel heterocomplex, in vivo, as 5-HTR2C antagonism increased OT-mediated hypoactivity in mice. Overall, we provide compelling evidence for the formation of functionally active OTR/5-HTR2C heterocomplexes, adding another level of complexity to OTR and 5-HTR2C signalling functionality.This article is part of the special issue on Neuropeptides

The microbiota-gut-brain axis

The importance of the gut-brain axis in maintaining homeostasis has long been appreciated. However, the past 15 yr have seen the emergence of the microbiota (the trillions of microorganisms within and on our bodies) as one of the key regulators of gut-brain function and has led to the appreciation of the importance of a distinct microbiota-gut-brain axis. This axis is gaining ever more traction in fields investigating the biological and physiological basis of psychiatric, neurodevelopmental, age-related, and neurodegenerative disorders. The microbiota and the brain communicate with each other via various routes including the immune system, tryptophan metabolism, the vagus nerve and the enteric nervous system, involving microbial metabolites such as short-chain fatty acids, branched chain amino acids, and peptidoglycans. Many factors can influence microbiota composition in early life, including infection, mode of birth delivery, use of antibiotic medications, the nature of nutritional provision, environmental stressors, and host genetics. At the other extreme of life, microbial diversity diminishes with aging. Stress, in particular, can significantly impact the microbiota-gut-brain axis at all stages of life. Much recent work has implicated the gut microbiota in many conditions including autism, anxiety, obesity, schizophrenia, Parkinson's disease, and Alzheimer's disease. Animal models have been paramount in linking the regulation of fundamental neural processes, such as neurogenesis and myelination, to microbiome activation of microglia. Moreover, translational human studies are ongoing and will greatly enhance the field. Future studies will focus on understanding the mechanisms underlying the microbiota-gut-brain axis and attempt to elucidate microbial-based intervention and therapeutic strategies for neuropsychiatric disorders

The Silencing of LGBTQ Older Adults' Identities through Ageing in Long-Term Care

This paper outlines how LGBTQ seniors often experience discrimination, prejudicial treatment, and often are forced to 'return to the closet' through the ageing process

Oxytocin receptor heteromerization-a novel convergence of central molecular signalling and G-protein coupled receptor crosstalk

G-protein coupled receptors (GPCR) are the largest family of cell membrane receptors, eliciting a multitude of effects. Due to their wide array of function, GPCRs have become widely studied, specifically within the pharmaceutical market; where over 30% of currently approved drugs target such GPCRs. It is now over three decades since the concept of a GPCR-GPCR interaction emerged, leading to the discovery of GPCR heterodimers which is the interaction of two different GPCRS, homodimers the interaction of two of the same GPCRS and high-order oligomers, the interaction of 3 or more GPCRs. Intriguingly these heterocomplex formations led to differential signalling of the GPCRs within these complexes compared to their monomer state. Such studies ushered in an exciting new field in GPCR research. Yet despite the large therapeutic effect produced from targeting GPCRs, the full ability of GPCR heterocomplex signalling remains largely unexplored. The oxytocin receptor (OTR), is one of the best studied central GPCRs located in multiple regions throughout the central nervous system and periphery. In addition to its ability to facilitate social behaviours it also known to impact multiple other interrelated behaviours such as food intake and mood. So, the question can be asked how such a well-studied receptor in its monomer state, with only one known endogenous ligand can elicit such a multitude of responses? Is it doing so in its monomer state or does it have the ability to form GPCR heterocomplexes subsequently altering its signalling ability? Therefore, this thesis focuses on the ability of the OTR to form a multitude of heterocomplexes which may impact its multifaceted signalling abilities. With a focus on the interplay between social behaviour, appetite and mood multiple GPCRs associated with such functions were screened for co-localisation with the OTR in HEK293A cells. Due to previous studies linking their signalling pathways and known co-expression in different brain regions associated with social behaviour, appetite and mood, a cellular screening platform was established to aid in the identification of an OTR heterocomplex with receptors such as the ghrelin 1a receptor (GHSR) (Chapter 2), glucagon like peptide 1 receptor (GLP-1r) (Chapter 3), serotonin 2a receptor (5-HT2A) (Chapter 4) and the serotonin 2c receptor (5-HT2C) (Chapter 5), receptors known too to signal in either social behaviour, food intake and mood. Chapter 1 will further expand on the current knowledge and impact of GPCR heterodimerization on GPCR signalling and where it stands as pharmacotherapeutic target. Moreover, introducing these receptors, there signalling abilities and central expression patterns, finally, finishing on the link between these receptors and how they may play a role in the intricate interplay between social behaviour, food intake and mood. An interplay possibly driven by such heterocomplex formations? Chapters 2 through 5 focuses on these heterocomplex formations, using a multitude of assays, including heterocomplex identification (co-localization and FRET, PLA) and functional assays (calcium mobilization, inositol monophosphate and ligand mediated trafficking, cyclic adenosine monophosphate) the ability of the OTR to form functional heterocomplexes was studied. Excitingly, data revealed the OTR to be a hub for GPCR heterocomplex formations, each leading to unique signalling pathways associated with these heterocomplex formation. Lastly, chapter 6 focuses on the current scientific knowledge of OTR heterodimerization and the impact of these dimer formations on such knowledge, moreover the possible impact these heterocomplexes may have in future therapeutics. In conclusion, this thesis highlights the ability of the OTR to heterodimerize with a number of other GPCRs, possibly implicating these heterodimer pairs in the ability of the OTR to regulate multiple behaviours. Thus, fully understanding the full extent of OTR heterocomplex signalling will aid in a better understanding of current therapies and may lead to the development of much needed novel, more potent and selective pharmacotherapies. An area which is already proving promising with the use of bivalent ligands

Gender and ethnic differences in smoking, drinking and illicit drug use among American 8th, 10th and 12th grade students, 1976–2000

Aims  This paper examines ethnic differences in licit and illicit drug use among American 8th, 10th and 12th grade students, with a particular focus on girls. Design  The study uses cross-sectional data from large, ethnically diverse, nationally representative samples of 8th, 10th and 12th grade girls. Setting  Data were collected through questionnaires administered in schools. Participants  A total of 40 416 8th grade girls and 37 977 8th grade boys, 35 451 10th grade girls and 33 188 10th grade boys, and 33 588 12th grade girls and 31 014 12th grade boys took part in the study. Findings  Across ethnic groups, drug use is highest among Native American girls and lowest among black and Asian American girls. Trend data suggest that there have been important changes in girls’ drug use over time and that girls’ and boys’ drug use patterns are converging. Conclusions  Drug use is widespread among American adolescent girls. Future research should examine further girls’ drug use and seek to identify whether risk and protective factors identified in past research, based on predominantly white samples, are also important predictors for drug use among non-white girls.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73026/1/j.1360-0443.2003.00282.x.pd

No association between perinatal mood disorders and hypertensive pregnancies

Mental health disorders such as anxiety and/or depression are the most common mental health disorders seen among reproductive aged women and can increase during pregnancy. Many sociodemographic risk factors have been associated with anxiety and/or depression in pregnancy, which can lead to adverse maternal and infant outcomes including the risk of a hypertensive pregnancy. The current study prospectively examined self-reported anxiety, depression and stress in pregnant women without a history of fetal loss or mood disorders beginning at 20–26 weeks. At each study visit, circulating immune factors associated with perinatal mood disorders were measured in blood samples that were collected. A total of 65 women were eligible for data analysis, 26 of which had hypertensive pregnancies. There was not a significant difference in self-reported depression, anxiety or stress between hypertensive disorders of pregnancy and normotensive women. Black women were more likely to have a hypertensive pregnancy and develop a perinatal mood disorder compared to non-black women. Both the inflammatory cytokines interleukin-17 and tumor necrosis factor-alpha were increased in patients with perinatal mood disorders. However, additional research is needed in a larger sample to truly understand the relationship between these factors along with the underlying etiologies and the associated outcomes