Dysregulation of brain olfactory and taste receptors in AD, PSP and CJD, and AD-related model

Taste impairment in patients with Parkinsonism

BACKGROUND

Taste impairment is a prevalent issue among individuals with idiopathic Parkinson's disease (iPD). However, understanding taste disorders among different Parkinsonism remains incomplete. Our objective was to assess the incidence and severity of taste responses to sweet, salty, sour, bitter, and umami substances in patients with iPD, progressive supranuclear palsy (PSP), and multiple system atrophy (MSA).

METHODS

Taste function was evaluated by assessing the intensity ratings of four concentrations of sweet, salty, sour, bitter, and umami in 221 healthy controls (HCs), 251 iPD patients, 156 PSP patients, and 60 MSA patients. The Kruskal-Wallis one-way analysis was employed to discern differences in taste function among groups. Logistic regression models were utilized to analyze the association between disease severity and taste function.

RESULTS

Participants with iPD, PSP, and MSA exhibited lower total taste scores (TTS) compared to HCs (P < 0.0001, P < 0.0001, and P = 0.0002, respectively). The TTS was significantly lower in iPD patients compared to PSP and MSA patients (P = 0.0024 and P = 0.0464, respectively), with no discernible difference between PSP and MSA patients (P = 0.9998). Furthermore, in patients with iPD, both disease severity and gastrointestinal function exhibited a significant negative correlation with the TTS. However, the taste test lacked the potency to reliably distinguish iPD from PSP and MSA.

CONCLUSIONS

These research findings suggest that taste impairment emerges as a phenotype of Parkinsonism, serving as a basis for differential diagnosis and guiding dietary adjustments for patients.

Comprehensive Transcriptomic Analysis Reveals Cell-Type-Specific Roles of Human Odorant Receptors in Glioblastoma and the Tumor Microenvironment

Odorant receptors (ORs), which constitute approximately 50% of all human G protein-coupled receptors, are increasingly recognized for their diverse roles beyond odor perception, including functions in various pathological conditions like brain diseases and cancers. However, the roles of ORs in glioblastoma (GBM), the most aggressive primary brain tumor with a median survival of only 15 months, remain largely unexplored. Here, we performed an integrated transcriptomic analysis combining The Cancer Genome Atlas RNA-seq and single-cell RNA sequencing data from GBM patients to uncover cell-type-specific roles of ORs within the tumor and its microenvironment. Our findings reveal that ORs display distinct expression patterns, with OR51E1 enriched in pericytes linked to vascular remodeling and angiogenesis, OR2B11 associated with tumor-associated macrophages supporting immunosuppressive phenotypes, and OR2L13 correlated with synaptic activity in recurrent tumors, potentially mediating treatment-induced neuronal adaptations. These results highlight ORs as potential therapeutic targets, offering new insights into their regulatory roles in GBM progression, immune modulation, and treatment resistance.

Aging is associated with a modality-specific decline in taste

Deficits in chemosensory processing are associated with healthy aging, as well as numerous neurodegenerative disorders, including Alzheimer's disease (AD). The fruit fly, Drosophila melanogaster, is a powerful model for studying chemosensation, aging, and aging-related pathologies, yet the effects of aging and neurodegeneration on taste function remain largely unexplored. Aging impaired response to sugars, but not medium-chain fatty acids that are sensed by a shared population of neurons. Selective expression of the human amyloid beta (Aβ) peptide phenocopied the effects of aging. Functional imaging of gustatory axon terminals revealed reduced response to sugar, but not fatty acids. Axonal innervation of the fly taste center was largely intact in aged flies; however, axonal innervation was reduced upon expression of Aβ. A comparison of transcript expression within the sugar-sensing taste neurons revealed age-related changes in 66 genes. Together, these findings suggest that different mechanisms underly taste deficits in aged and AD model flies.

The Olfactory Trail of Neurodegenerative Diseases

Alterations in olfactory functions are proposed as possible early biomarkers of neurodegenerative diseases. Parkinson's and Alzheimer's diseases manifest olfactory dysfunction as a symptom, which is worth mentioning. The alterations do not occur in all patients, but they can serve to rule out neurodegenerative pathologies that are not associated with small deficits. Several prevalent neurodegenerative conditions, including impaired smell, arise in the early stages of Parkinson's and Alzheimer's diseases, presenting an attractive prospect as a snitch for early diagnosis. This review covers the current knowledge on the link between olfactory deficits and Parkinson's and Alzheimer's diseases. The review also covers the emergence of olfactory receptors as actors in the pathophysiology of these diseases. Olfactory receptors are not exclusively expressed in olfactory sensory neurons. Olfactory receptors are widespread in the human body; they are expressed, among others, in the testicles, lungs, intestines, kidneys, skin, heart, and blood cells. Although information on these ectopically expressed olfactory receptors is limited, they appear to be involved in cell recognition, migration, proliferation, wound healing, apoptosis, and exocytosis. Regarding expression in non-chemosensory regions of the central nervous system (CNS), future research should address the role, in both the glia and neurons, of olfactory receptors. Here, we review the limited but relevant information on the altered expression of olfactory receptor genes in Parkinson's and Alzheimer's diseases. By unraveling how olfactory receptor activation is involved in neurodegeneration and identifying links between olfactory structures and neuronal death, valuable information could be gained for early diagnosis and intervention strategies in neurodegenerative diseases.

Olfactory Receptor OR2K2 Expression in Human Choroid Plexus as a Potential Marker in Early Sporadic Alzheimer's Disease

Epithelial cells comprising the choroid plexus (CP) form a crucial barrier between the blood and the cerebrospinal fluid, thereby assuming a central position in brain homeostasis and signaling. Mounting evidence suggests that the impairment of CP function may be a significant contributor to Alzheimer's disease (AD) pathogenesis. CP function relies on the expression of specific receptors, and the potential involvement of olfactory receptors (ORs) and taste receptors (TASRs) in chemical surveillance within the CP is being investigated. Previous studies have implicated ORs and TASRs in neurodegenerative disorders like AD, although the direct evidence of their expression in the human CP remains to be established. In this study, we conducted a transcriptomic analysis encompassing eleven ORs and TASRs in the CP, comparing samples from healthy age-matched controls to those from patients with AD spanning Braak stages I to VI. Among these receptors, a striking finding emerged-OR2K2 exhibited robust expression, with a statistically significant upregulation noted at Braak stage I. Surprisingly, at the protein level, OR2K2 showed a significant decrease in both Braak stage I and VI. Additionally, we identified CP epithelial cells as the source of OR2K2 expression, where it colocalized with autophagy markers LC3 and p62. We postulate that OR2K2 could be subjected to degradation by autophagy in the early stages of AD, triggering a compensatory mechanism that leads to increased OR2K2 mRNA transcription. This study uncovers a potential role for OR2K2 in AD pathogenesis, offering a novel perspective on the intricate dynamics at play in this neurodegenerative disorder.

Perspective: "Current understanding of NADs dynamics and mechanisms of Disease"

Chromatin architecture is essential for gene regulation, and multiple levels of the 3D chromatin organization exhibit dynamic changes during organismal development and cell differentiation. Heterochromatin, termed compartment B in Hi-C datasets, is a phase-separating gene-silencing form of chromatin, preferentially located at the two nuclear sites, nuclear (lamina-associate chromatin domains, LADs) and nucleoli (nucleoli-associated chromatin domains, NADs) peripheries. LADs and NADs contain both interchangeable and location-specific chromatin domains. Recent studies suggest striking dynamics in LADs and NADs during the differentiation of embryonic stem cells into neural progenitors and neurons. Here we discuss recent advances in understanding NADs changes during neuronal differentiation and future questions on how NADs integrity can contribute to healthy neurodevelopment and neurodevelopment diseases.

Aging is associated with a modality-specific decline in taste

Deficits in chemosensory processing are associated with healthy aging, as well as numerous neurodegenerative disorders, including Alzheimer's Disease (AD). In many cases, chemosensory deficits are harbingers of neurodegenerative disease, and understanding the mechanistic basis for these changes may provide insight into the fundamental dysfunction associated with aging and neurodegeneration. The fruit fly, Drosophila melanogaster , is a powerful model for studying chemosensation, aging, and aging-related pathologies, yet the effects of aging and neurodegeneration on chemosensation remain largely unexplored in this model, particularly with respect to taste. To determine whether the effects of aging on taste are conserved in flies, we compared the response of flies to different appetitive tastants. Aging impaired response to sugars, but not medium-chain fatty acids that are sensed by a shared population of neurons, revealing modality-specific deficits in taste. Selective expression of the human amyloid beta (Aβ) 1-42 peptide bearing the Arctic mutation (E693E) associated with early onset AD in the neurons that sense sugars and fatty acids phenocopies the effects of aging, suggesting that the age-related decline in response is localized to gustatory neurons. Functional imaging of gustatory axon terminals revealed reduced response to sugar, but not fatty acids. Axonal innervation of the fly taste center was largely intact in aged flies, suggesting that reduced sucrose response does not derive from neurodegeneration. Conversely, expression of the amyloid peptide in sweet-sensing taste neurons resulted in reduced innervation of the primary fly taste center. A comparison of transcript expression within the sugar-sensing taste neurons revealed age-related changes in 66 genes, including a reduction in odorant-binding protein class genes that are also expressed in taste sensilla. Together, these findings suggest that deficits in taste detection may result from signaling pathway-specific changes, while different mechanisms underly taste deficits in aged and AD model flies. Overall, this work provides a model to examine cellular deficits in neural function associated with aging and AD.

Bitter Phytochemicals as Novel Candidates for Skin Disease Treatment

Skin diseases represent a global healthcare challenge due to their rising incidence and substantial socio-economic burden. While biological, immunological, and targeted therapies have brought a revolution in improving quality of life and survival rates for certain dermatological conditions, there remains a stringent demand for new remedies. Nature has long served as an inspiration for drug development. Recent studies have identified bitter taste receptors (TAS2Rs) in both skin cell lines and human skin. Additionally, bitter natural compounds have shown promising benefits in addressing skin aging, wound healing, inflammatory skin conditions, and even skin cancer. Thus, TAS2Rs may represent a promising target in all these processes. In this review, we summarize evidence supporting the presence of TAS2Rs in the skin and emphasize their potential as drug targets for addressing skin aging, wound healing, inflammatory skin conditions, and skin carcinogenesis. To our knowledge, this is a pioneering work in connecting information on TAS2Rs expression in skin and skin cells with the impact of bitter phytochemicals on various beneficial effects related to skin disorders.

Human-derived air-liquid interface cultures decipher Alzheimer's disease-SARS-CoV-2 crosstalk in the olfactory mucosa

BACKGROUND

The neurological effects of the coronavirus disease of 2019 (COVID-19) raise concerns about potential long-term consequences, such as an increased risk of Alzheimer's disease (AD). Neuroinflammation and other AD-associated pathologies are also suggested to increase the risk of serious SARS-CoV-2 infection. Anosmia is a common neurological symptom reported in COVID-19 and in early AD. The olfactory mucosa (OM) is important for the perception of smell and a proposed site of viral entry to the brain. However, little is known about SARS-CoV-2 infection at the OM of individuals with AD.

METHODS

To address this gap, we established a 3D in vitro model of the OM from primary cells derived from cognitively healthy and AD individuals. We cultured the cells at the air-liquid interface (ALI) to study SARS-CoV-2 infection under controlled experimental conditions. Primary OM cells in ALI expressed angiotensin-converting enzyme 2 (ACE-2), neuropilin-1 (NRP-1), and several other known SARS-CoV-2 receptor and were highly vulnerable to infection. Infection was determined by secreted viral RNA content and confirmed with SARS-CoV-2 nucleocapsid protein (NP) in the infected cells by immunocytochemistry. Differential responses of healthy and AD individuals-derived OM cells to SARS-CoV-2 were determined by RNA sequencing.

RESULTS

Results indicate that cells derived from cognitively healthy donors and individuals with AD do not differ in susceptibility to infection with the wild-type SARS-CoV-2 virus. However, transcriptomic signatures in cells from individuals with AD are highly distinct. Specifically, the cells from AD patients that were infected with the virus showed increased levels of oxidative stress, desensitized inflammation and immune responses, and alterations to genes associated with olfaction. These results imply that individuals with AD may be at a greater risk of experiencing severe outcomes from the infection, potentially driven by pre-existing neuroinflammation.

CONCLUSIONS

The study sheds light on the interplay between AD pathology and SARS-CoV-2 infection. Altered transcriptomic signatures in AD cells may contribute to unique symptoms and a more severe disease course, with a notable involvement of neuroinflammation. Furthermore, the research emphasizes the need for targeted interventions to enhance outcomes for AD patients with viral infection. The study is crucial to better comprehend the relationship between AD, COVID-19, and anosmia. It highlights the importance of ongoing research to develop more effective treatments for those at high risk of severe SARS-CoV-2 infection.

Epigenetic silencing of OR and TAS2R genes expression in human orbitofrontal cortex at early stages of sporadic Alzheimer's disease

Modulation of brain olfactory (OR) and taste receptor (TASR) expression was recently reported in neurological diseases. However, there is still limited evidence of these genes' expression in the human brain and the transcriptional regulation mechanisms involved remain elusive. We explored the possible expression and regulation of selected OR and TASR in the human orbitofrontal cortex (OFC) of sporadic Alzheimer's disease (AD) and non-demented control specimens using quantitative real-time RT-PCR and ELISA. Global H3K9me3 amounts were measured on OFC total histone extracts, and H3K9me3 binding at each chemoreceptor locus was examined through native chromatin immunoprecipitation. To investigate the potential interactome of the repressive histone mark H3K9me3 in OFC specimens, native nuclear complex co-immunoprecipitation (Co-IP) was combined with reverse phase-liquid chromatography coupled to mass spectrometry analysis. Interaction between H3K9me3 and MeCP2 was validated by reciprocal Co-IP, and global MeCP2 levels were quantitated. We found that OR and TAS2R genes are expressed and markedly downregulated in OFC at early stages of sporadic AD, preceding the progressive reduction in their protein levels and the appearance of AD-associated neuropathology. The expression pattern did not follow disease progression suggesting transcriptional regulation through epigenetic mechanisms. We discovered an increase of OFC global H3K9me3 levels and a substantial enrichment of this repressive signature at ORs and TAS2Rs proximal promoter at early stages of AD, ultimately lost at advanced stages. We revealed the interaction between H3K9me3 and MeCP2 at early stages and found that MeCP2 protein is increased in sporadic AD. Findings suggest MeCP2 might be implicated in OR and TAS2R transcriptional regulation through interaction with H3K9me3, and as an early event, it may uncover a novel etiopathogenetic mechanism of sporadic AD.

Breeding honey bees (Apis mellifera L.) for low and high Varroa destructor population growth: Gene expression of bees performing grooming behavior

Introduction

Social organisms, including honey bees (Apis mellifera L.), have defense mechanisms to control the multiplication and transmission of parasites and pathogens within their colonies. Self-grooming, a mechanism of behavioral immunity, seems to contribute to restrain the population growth of the ectoparasitic mite Varroa destructor in honey bee colonies. Because V. destructor is the most damaging parasite of honey bees, breeding them for resistance against the mite is a high priority of the beekeeping industry.

Methods

A bidirectional breeding program to select honey bee colonies with low and high V. destructor population growth (LVG and HVG, respectively) was conducted. Having high and low lines of bees allowed the study of genetic mechanisms underlying self-grooming behavior between the extreme genotypes. Worker bees were classified into two categories: 'light groomers' and 'intense groomers'. The brains of bees from the different categories (LVG-intense, LVG-light, HVG-intense, and HVG-light) were used for gene expression and viral quantification analyses. Differentially expressed genes (DEGs) associated with the LVG and HVG lines were identified.

Results

Four odorant-binding proteins and a gustatory receptor were identified as differentially expressed genes. A functional enrichment analysis showed 19 enriched pathways from a list of 219 down-regulated DEGs in HVG bees, including the Kyoto Encyclopedia of Genes and Genomes (KEGG) term of oxidative phosphorylation. Additionally, bees from the LVG line showed lower levels of Apis rhabdovirus 1 and 2, Varroa destructor virus -1 (VDV-1/DWV-B), and Deformed wing virus-A (DWV-A) compared to bees of the HVG line. The difference in expression of odorant-binding protein genes and a gustatory receptor between bee lines suggests a possible link between them and the perception of irritants to trigger rapid self-grooming instances that require the activation of energy metabolic pathways.

Discussion

These results provide new insights on the molecular mechanisms involved in honey bee grooming behavior. Differences in viral levels in the brains of LVG and HVG bees showed the importance of investigating the pathogenicity and potential impacts of neurotropic viruses on behavioral immunity. The results of this study advance the understanding of a trait used for selective breeding, self-grooming, and the potential of using genomic assisted selection to improve breeding programs.

Impact of In Utero Folate Exposure on DNA Methylation and Its Potential Relevance for Later-Life Health-Evidence from Mouse Models Translated to Human Cohorts

SCOPE

Persistent DNA methylation changes may mediate effects of early-life exposures on later-life health. Human lifespan is challenging for prospective studies, therefore data from longitudinal studies are limited. Projecting data from mouse models of early-life exposure to human studies offers a tool to address this challenge.

METHODS AND RESULTS

C57BL/6J mice were fed low/normal folate diets before and during pregnancy and lactation. Genome-wide promoter methylation was measured in male offspring livers at 17.5 days gestation and 28 weeks. Eight promoters were concurrently hypermethylated by folate depletion in fetuses and adults (>1.10 fold-change; p < 0.05). Processes/pathways potentially influenced by global changes, and function of these eight genes, suggest neurocognitive effects. Human observational and randomized controlled trial data were interrogated for translation. Methylation at birth was inversely associated with maternal plasma folate in six genes (-1.15% to -0.16% per nmol L^-1 ; p < 0.05), while maternal folic acid supplementation was associated with differential methylation of four genes in adulthood. Three CpGs were persistently hypermethylated with lower maternal folate (p = 0.04).

CONCLUSION

Some persistent folate-induced methylation changes in mice are mirrored in humans. This demonstrates utility of mouse data in identifying human loci for interrogation as biomarkers of later-life health.

Odorant G protein-coupled receptors as potential therapeutic targets for adult diffuse gliomas: a systematic analysis and review

Odorant receptors (ORs) account for about 60% of all human G protein-coupled receptors (GPCRs). OR expression outside of the nose has functions distinct from odor perception, and may contribute to the pathogenesis of disorders including brain diseases and cancers. Glioma is the most common adult malignant brain tumor and requires novel therapeutic strategies to improve clinical outcomes. Here, we outlined the expression of brain ORs and investigated OR expression levels in glioma. Although most ORs were not ubiquitously expressed in gliomas, a subset of ORs displayed glioma subtype-specific expression. Moreover, through systematic survival analysis on OR genes, OR51E1 (mouse Olfr558) was identified as a potential biomarker of unfavorable overall survival, and OR2C1 (mouse Olfr15) was identified as a potential biomarker of favorable overall survival in isocitrate dehydrogenase (IDH) wild-type glioma. In addition to transcriptomic analysis, mutational profiles revealed that somatic mutations in OR genes were detected in > 60% of glioma samples. OR5D18 (mouse Olfr1155) was the most frequently mutated OR gene, and OR5AR1 (mouse Olfr1019) showed IDH wild-type-specific mutation. Based on this systematic analysis and review of the genomic and transcriptomic profiles of ORs in glioma, we suggest that ORs are potential biomarkers and therapeutic targets for glioma.

Cell-type specialization is encoded by specific chromatin topologies

The three-dimensional (3D) structure of chromatin is intrinsically associated with gene regulation and cell function1-3. Methods based on chromatin conformation capture have mapped chromatin structures in neuronal systems such as in vitro differentiated neurons, neurons isolated through fluorescence-activated cell sorting from cortical tissues pooled from different animals and from dissociated whole hippocampi4-6. However, changes in chromatin organization captured by imaging, such as the relocation of Bdnf away from the nuclear periphery after activation7, are invisible with such approaches8. Here we developed immunoGAM, an extension of genome architecture mapping (GAM)2,9, to map 3D chromatin topology genome-wide in specific brain cell types, without tissue disruption, from single animals. GAM is a ligation-free technology that maps genome topology by sequencing the DNA content from thin (about 220 nm) nuclear cryosections. Chromatin interactions are identified from the increased probability of co-segregation of contacting loci across a collection of nuclear slices. ImmunoGAM expands the scope of GAM to enable the selection of specific cell types using low cell numbers (approximately 1,000 cells) within a complex tissue and avoids tissue dissociation2,10. We report cell-type specialized 3D chromatin structures at multiple genomic scales that relate to patterns of gene expression. We discover extensive 'melting' of long genes when they are highly expressed and/or have high chromatin accessibility. The contacts most specific of neuron subtypes contain genes associated with specialized processes, such as addiction and synaptic plasticity, which harbour putative binding sites for neuronal transcription factors within accessible chromatin regions. Moreover, sensory receptor genes are preferentially found in heterochromatic compartments in brain cells, which establish strong contacts across tens of megabases. Our results demonstrate that highly specific chromatin conformations in brain cells are tightly related to gene regulation mechanisms and specialized functions.

An update on extra-oral bitter taste receptors

Bitter taste-sensing type 2 receptors (TAS2Rs or T2Rs), belonging to the subgroup of family A G-protein coupled receptors (GPCRs), are of crucial importance in the perception of bitterness. Although in the first instance, TAS2Rs were considered to be exclusively distributed in the apical microvilli of taste bud cells, numerous studies have detected these sensory receptor proteins in several extra-oral tissues, such as in pancreatic or ovarian tissues, as well as in their corresponding malignancies. Critical points of extra-oral TAS2Rs biology, such as their structure, roles, signaling transduction pathways, extensive mutational polymorphism, and molecular evolution, have been currently broadly studied. The TAS2R cascade, for instance, has been recently considered to be a pivotal modulator of a number of (patho)physiological processes, including adipogenesis or carcinogenesis. The latest advances in taste receptor biology further raise the possibility of utilizing TAS2Rs as a therapeutic target or as an informative index to predict treatment responses in various disorders. Thus, the focus of this review is to provide an update on the expression and molecular basis of TAS2Rs functions in distinct extra-oral tissues in health and disease. We shall also discuss the therapeutic potential of novel TAS2Rs targets, which are appealing due to their ligand selectivity, expression pattern, or pharmacological profiles.

Ectopic Odorant Receptor Responding to Flavor Compounds: Versatile Roles in Health and Disease

Prompted by the ground-breaking discovery of the rodent odorant receptor (OR) gene family within the olfactory epithelium nearly 30 years ago, followed by that of OR genes in cells of the mammalian germ line, and potentiated by the identification of ORs throughout the body, our appreciation for ORs as general chemoreceptors responding to odorant compounds in the regulation of physiological or pathophysiological processes continues to expand. Ectopic ORs are now activated by a diversity of flavor compounds and are involved in diverse physiological phenomena varying from adipogenesis to myogenesis to hepatic lipid accumulation to serotonin secretion. In this review, we outline the key biological functions of the ectopic ORs responding to flavor compounds and the underlying molecular mechanisms. We also discuss research opportunities for utilizing ectopic ORs as therapeutic strategies in the treatment of human disease as well as challenges to be overcome in the future. The recognition of the potent function, signaling pathway, and pharmacology of ectopic ORs in diverse tissues and cell types, coupled with the fact that they belong to G protein-coupled receptors, a highly druggable protein family, unequivocally highlight the potential of ectopic ORs responding to flavor compounds, especially food-derived odorant compounds, as a promising therapeutic strategy for various diseases.

Limbic Expression of mRNA Coding for Chemoreceptors in Human Brain-Lessons from Brain Atlases

Animals strongly rely on chemical senses to uncover the outside world and adjust their behaviour. Chemical signals are perceived by facial sensitive chemosensors that can be clustered into three families, namely the gustatory (TASR), olfactory (OR, TAAR) and pheromonal (VNR, FPR) receptors. Over recent decades, chemoreceptors were identified in non-facial parts of the body, including the brain. In order to map chemoreceptors within the encephalon, we performed a study based on four brain atlases. The transcript expression of selected members of the three chemoreceptor families and their canonical partners was analysed in major areas of healthy and demented human brains. Genes encoding all studied chemoreceptors are transcribed in the central nervous system, particularly in the limbic system. RNA of their canonical transduction partners (G proteins, ion channels) are also observed in all studied brain areas, reinforcing the suggestion that cerebral chemoreceptors are functional. In addition, we noticed that: (i) bitterness-associated receptors display an enriched expression, (ii) the brain is equipped to sense trace amines and pheromonal cues and (iii) chemoreceptor RNA expression varies with age, but not dementia or brain trauma. Extensive studies are now required to further understand how the brain makes sense of endogenous chemicals.

Amniotic fluid and urine metabolomic alterations associated with pregnant women with Down syndrome fetuses

BACKGROUND

Down syndrome (DS) is a chromosomal disorder caused by a third copy of all or part of chromosome 21. Clinical observations and preclinical studies both suggest that DS may be associated with significant metabolic and bioenergetic alterations. But the metabolic alterations in pregnant women carrying DS fetuses still remains unclear. In this study, we investigated the characteristic metabolomics and lipidomics changes during fetal development of DS.

METHODS

The AF and random urine specimens were selected from 20 pregnant women carrying DS fetuses and 20 pregnant women carrying healthy fetuses. The diagnosis of DS was screened according to chromosome karyotype analysis, and untargeted metabolomic and lipidomic analyses were performed.

RESULTS

Through the analyses of AF, 308 differential metabolites were selected between DS and controls. The metabolites with significant changes mainly involved lipid molecules, organic acids, nucleotides and carbon. Further analysis of lipidomics showed 64 differential metabolites, mainly involving glycerides, sphingolipids and glycerolipids. As for urine metabolomic and lipidomic analyses, there existed consistent metabolites with AF, but the number was much less.

CONCLUSIONS

Compared with the controls, carbon metabolism, amino acid metabolism, glyceride metabolism, sphingolipid metabolism and glycerophospholipid metabolism were significantly changed in DS cases. In addition, characterized biomarkers in AF and urine were screened for DS diagnosis, and these metabolites were mainly involved in energy metabolism and liver dysfunction. This finding may help improve the efficiency of prenatal screening for DS.

Association between Sour Taste SNP KCNJ2-rs236514, Diet Quality and Mild Cognitive Impairment in an Elderly Cohort

Differences in sour-taste thresholds have been identified in cognition-related diseases. Diet is a modulator of cognitive health, and taste perception influences dietary preferences and habits. Heritable genetics and polymorphisms in the KCNJ2 gene involved in the transduction of sour taste have been linked to variations in sour taste and non-gustatory functions. However, relationships between sour taste genetics, mild cognitive impairment, and diet quality are yet to be elucidated. This study investigated the associations between the presence of the KCNJ2-rs236514 variant (A) allele, diet quality indices, and mild cognitive impairment evaluated by the Mini-Mental State Examination (MMSE), in a secondary cross-sectional analysis of data from the Retirement Health & Lifestyle Study. Data from 524 elderly Australians (≥65y) were analyzed, using standard least squares regression and nominal logistic regression modeling, with demographic adjustments applied. Results showed that the presence of the KCNJ2-A allele is associated with increased proportions of participants scoring in the range indicative of mild or more severe cognitive impairment (MMSE score of ≤26) in the total cohort, and males. These associations remained statistically significant after adjusting for age, sex, and diet quality indices. The absence of association between the KCNJ2-A allele and cognitive impairment in women may be related to their higher diet quality scores in all indices. The potential link between sour taste genotype and cognitive impairment scores may be due to both oral and extra-oral functions of sour taste receptors. Further studies are required on the role and relationship of neurotransmitters, sour taste genotypes and sour taste receptors in the brain, and dietary implications, to identify potential risk groups or avenues for therapeutic or prophylactic interventions.

Human ectopic olfactory receptors and their food originated ligands: a review

Ectopic olfactory receptors (EORs) are expressed in non-nasal tissues of human body. They belong to the G-protein coupled receptor (GPCR) superfamily. EORs may not be capable of differentiating odorants as nasal olfactory receptors (ORs), but still can be triggered by odorants and are involved in different biological processes such as anti-inflammation, energy metabolism, apoptosis etc. Consumption of strong flavored foods like celery, oranges, onions, and spices, is a good aid to attenuate inflammation and boost our immune system. During the digestion of these foods in human digestive system and the metabolization by gut microbiota, the odorants closely interacting with EORs, may play important roles in various bio-functions like serotonin release, appetite regulation etc., and ultimately impact health and diseases. Thus, EORs could be a potential target linking the ligands from food and their bioactivities. There have been related studies in different research fields of medicine and physiology, but still no systematic food oriented review. Our review portrays that EORs could be a potential target for functional food development. In this review, we summarized the EORs found in human tissues, their impacts on health and disease, ligands interacting with EORs exerting specific biological effects, and the mechanisms involved.

Transcriptome Changes in the Alzheimer's Disease Middle Temporal Gyrus: Importance of RNA Metabolism and Mitochondria-Associated Membrane Genes

We used Illumina Human HT-12 v4 arrays to compare RNA expression of middle temporal gyrus (MTG; BA21) in Alzheimer's disease (AD = 97) and non-demented controls (ND = 98). A total of 938 transcripts were highly differentially expressed (adj p < 0.01; log2 FC ≥ |0.500|, with 411 overexpressed and 527 underexpressed in AD. Our results correlated with expression profiling in neurons from AD and ND obtained by laser capture microscopy in MTG from an independent dataset (log2 FC correlation: r = 0.504; p = 2.2e-16). Additionally, selected effects were validated by qPCR. ANOVA analysis yielded no difference between genders in response to AD, but some gender specific genes were detected (e.g., IL8 and AGRN in males, and HSPH1 and GRM1 in females). Several transcripts were associated with Braak staging (e.g., AEBP1 and DNALI1), antemortem MMSE (e.g., AEBP1 and GFAP), and tangle density (e.g., RNU1G2, and DNALI1). At the pathway level, we detected enrichment of synaptic vesicle processes and GABAergic transmission genes. Finally, applying the Weighted Correlation Network Analysis, we identified four expression modules enriched for neuronal and synaptic genes, mitochondria-associated membrane, chemical stimulus and olfactory receptor and non-coding RNA metabolism genes. Our results represent an extensive description of MTG mRNA profiling in a large sample of AD and ND. These data provide a list of genes associated with AD, and correlated to neurofibrillary tangles density. In addition, these data emphasize the importance of mitochondrial membranes and transcripts related to olfactory receptors in AD.

Pneumonia-induced endothelial amyloids reduce dendritic spine density in brain neurons

Pseudomonas aeruginosa pneumonia elicits endothelial cell release of cytotoxic amyloids that can be recovered from the bronchoalveolar lavage and cerebrospinal fluids of critically ill patients. Introduction of these cytotoxic amyloids into the lateral ventricle impairs learning and memory in mice. However, it is unclear whether the amyloids of lung origin (1) are neurotropic, and (2) cause structural remodeling of hippocampal dendrites. Thus, we used electrophysiological studies in brain slices and structural analysis of post-mortem tissues obtained from animals exposed to endothelium-derived amyloids to assess these issues. The amyloids were administered via three different routes, by intracerebroventricular, intratracheal, and intraperitoneal injections. Synaptic long-term potentiation was abolished following intracerebroventricular amyloid injection. Fluorescence dialysis or Golgi-impregnation labeling showed reduced dendritic spine density and destabilized spines of hippocampal pyramidal neurons 4 weeks after intracerebroventricular amyloid injection. In comparison, endothelial amyloids introduced to the airway caused the most prominent dendritic spine density reduction, yet intraperitoneal injection of these amyloids did not affect spine density. Our findings indicate that infection-elicited lung endothelial amyloids are neurotropic and reduce neuronal dendritic spine density in vivo. Amyloids applied into the trachea may either be disseminated through the circulation and cross the blood-brain barrier to access the brain, initiate feed-forward amyloid transmissibility among cells of the blood-brain barrier or access the brain in other ways. Nevertheless, lung-derived amyloids suppress hippocampal signaling and cause injury to neuronal structure.

Alzheimer's Disease: What Can We Learn From the Peripheral Olfactory System?

The sense of smell has been shown to deteriorate in patients with some neurodegenerative disorders. In Parkinson's disease (PD) and Alzheimer's disease (AD), decreased ability to smell is associated with early disease stages. Thus, olfactory neurons in the nose and olfactory bulb (OB) may provide a window into brain physiology and pathophysiology to address the pathogenesis of neurodegenerative diseases. Because nasal olfactory receptor neurons regenerate throughout life, the olfactory system offers a broad variety of cellular mechanisms that could be altered in AD, including odorant receptor expression, neurogenesis and neurodegeneration in the olfactory epithelium, axonal targeting to the OB, and synaptogenesis and neurogenesis in the OB. This review focuses on pathophysiological changes in the periphery of the olfactory system during the progression of AD in mice, highlighting how the olfactory epithelium and the OB are particularly sensitive to changes in proteins and enzymes involved in AD pathogenesis. Evidence reviewed here in the context of the emergence of other typical pathological changes in AD suggests that olfactory impairments could be used to understand the molecular mechanisms involved in the early phases of the pathology.

A pathogen-derived metabolite induces microglial activation via odorant receptors

Microglia (MG), the principal neuroimmune sentinels in the brain, continuously sense changes in their environment and respond to invading pathogens, toxins, and cellular debris, thereby affecting neuroinflammation. Microbial pathogens produce small metabolites that influence neuroinflammation, but the molecular mechanisms that determine whether pathogen-derived small metabolites affect microglial activation of neuroinflammation remain to be elucidated. We hypothesized that odorant receptors (ORs), the largest subfamily of G protein-coupled receptors, are involved in microglial activation by pathogen-derived small metabolites. We found that MG express high levels of two mouse ORs, Olfr110 and Olfr111, which recognize a pathogenic metabolite, 2-pentylfuran, secreted by Streptococcus pneumoniae. These interactions activate MG to engage in chemotaxis, cytokine production, phagocytosis, and reactive oxygen species generation. These effects were mediated through the G_αs -cyclic adenosine monophosphate-protein kinase A-extracellular signal-regulated kinase and G_βγ -phospholipase C-Ca²⁺ pathways. Taken together, our results reveal a novel interplay between the pathogen-derived metabolite and ORs, which has major implications for our understanding of microglial activation by pathogen recognition. DATABASE: Model data are available in the PMDB database under the accession number PM0082389.

Therapeutic potential of ectopic olfactory and taste receptors

Olfactory and taste receptors are expressed primarily in the nasal olfactory epithelium and gustatory taste bud cells, where they transmit real-time sensory signals to the brain. However, they are also expressed in multiple extra-nasal and extra-oral tissues, being implicated in diverse biological processes including sperm chemotaxis, muscle regeneration, bronchoconstriction and bronchodilatation, inflammation, appetite regulation and energy metabolism. Elucidation of the physiological roles of these ectopic receptors is revealing potential therapeutic and diagnostic applications in conditions including wounds, hair loss, asthma, obesity and cancers. This Review outlines current understanding of the diverse functions of ectopic olfactory and taste receptors and assesses their potential to be therapeutically exploited.

Bitter taste signaling mediated by Tas2r144 is down-regulated by 17β-estradiol and progesterone in the rat choroid plexus

The blood-cerebrospinal fluid barrier is constituted by choroid plexus epithelial cells (CPEC) that regulate molecular trafficking between the blood and the cerebrospinal fluid. We hypothesize that taste receptors expressed in CPEC monitor the composition of these body fluids in a sex hormone dependent way. Thus, we compared the expression of taste related genes in the choroid plexus of sham and ovariectomized female rats, and then studied the effect of 17β-estradiol and progesterone in their expression and function. We found that the bitter receptors Tas2r109, Tas2r144, and the taste-related genes Plcb2 and Trpm5 were down-regulated by ovarian hormones in vivo and ex vivo with functional implications. Knocking-down Tas2r144 with a specific siRNA in a CPEC line (Z310) effectively reduced the Ca²⁺ response to the bitter compound denatonium benzoate, in a similar manner to female sex hormones alone, suggesting that female sex hormones downregulated the responses of CPEC to chemical stimuli by reducing Tas2r144.

Dual binding mode of "bitter sugars" to their human bitter taste receptor target

The 25 human bitter taste receptors (hTAS2Rs) are responsible for detecting bitter molecules present in food, and they also play several physiological and pathological roles in extraoral compartments. Therefore, understanding their ligand specificity is important both for food research and for pharmacological applications. Here we provide a molecular insight into the exquisite molecular recognition of bitter β-glycopyranosides by one of the members of this receptor subclass, hTAS2R16. Most of its agonists have in common the presence of a β-glycopyranose unit along with an extremely structurally diverse aglycon moiety. This poses the question of how hTAS2R16 can recognize such a large number of "bitter sugars". By means of hybrid molecular mechanics/coarse grained molecular dynamics simulations, here we show that the three hTAS2R16 agonists salicin, arbutin and phenyl-β-D-glucopyranoside interact with the receptor through a previously unrecognized dual binding mode. Such mechanism may offer a seamless way to fit different aglycons inside the binding cavity, while maintaining the sugar bound, similar to the strategy used by several carbohydrate-binding lectins. Our prediction is validated a posteriori by comparison with mutagenesis data and also rationalizes a wealth of structure-activity relationship data. Therefore, our findings not only provide a deeper molecular characterization of the binding determinants for the three ligands studied here, but also give insights applicable to other hTAS2R16 agonists. Together with our results for other hTAS2Rs, this study paves the way to improve our overall understanding of the structural determinants of ligand specificity in bitter taste receptors.

Small-chain fatty acid activates astrocytic odorant receptor Olfr920

Odorant receptors are the largest subfamily of G protein-coupled receptors and were recently suggested to play critical roles in nonolfactory tissues. However, the expression and function of odorant receptors in astrocytes, the most abundant cells in the brain, are not well known. We demonstrate that Olfr920 is highly expressed and propose that it functions as a short-chain fatty acid sensor in primary cortical astrocytes. The short-chain fatty acid isobutyric acid (IBA) was identified via a luciferase assay as an Olfr920 ligand. We show that IBA activates the G_s protein-adenylyl cyclase-cAMP pathway via Olfr920 in primary cortical astrocytes by using cAMP and knockdown analyses. In addition, IBA reduces lipopolysaccharide-induced glial fibrillary acidic protein expression in reactive astrocytes. These results suggest that astrocytic Olfr920 is a potential novel target for increased reactive astrocytes.

Human Olfactory Receptors: Novel Cellular Functions Outside of the Nose

Olfactory receptors (ORs) are not exclusively expressed in the olfactory sensory neurons; they are also observed outside of the olfactory system in all other human tissues tested to date, including the testis, lung, intestine, skin, heart, and blood. Within these tissues, certain ORs have been determined to be exclusively expressed in only one tissue, whereas other ORs are more widely distributed in many different tissues throughout the human body. For most of the ectopically expressed ORs, limited data are available for their functional roles. They have been shown to be involved in the modulation of cell-cell recognition, migration, proliferation, the apoptotic cycle, exocytosis, and pathfinding processes. Additionally, there is a growing body of evidence that they have the potential to serve as diagnostic and therapeutic tools, as ORs are highly expressed in different cancer tissues. Interestingly, in addition to the canonical signaling pathways activated by ORs in olfactory sensory neurons, alternative pathways have been demonstrated in nonolfactory tissues. In this review, the existing data concerning the expression, as well as the physiological and pathophysiological functions, of ORs outside of the nose are highlighted to provide insights into future lines of research.

Olfactory, Taste, and Photo Sensory Receptors in Non-sensory Organs: It Just Makes Sense

Sensory receptors that detect and respond to light, taste, and smell primarily belong to the G-protein-coupled receptor (GPCR) superfamily. In addition to their established roles in the nose, tongue, and eyes, these sensory GPCRs have been found in many ‘non-sensory' organs where they respond to different physicochemical stimuli, initiating signaling cascades in these extrasensory systems. For example, taste receptors in the airway, and photoreceptors in vascular smooth muscle cells, both cause smooth muscle relaxation when activated. In addition, olfactory receptors are present within the vascular system, where they play roles in angiogenesis as well as in modulating vascular tone. By better understanding the physiological and pathophysiological roles of sensory receptors in non-sensory organs, novel therapeutic agents can be developed targeting these receptors, ultimately leading to treatments for pathological conditions and potential cures for various disease states.

Telmisartan Protects a Microglia Cell Line from LPS Injury Beyond AT1 Receptor Blockade or PPARγ Activation

The Angiotensin II Receptor Blocker (ARB) Telmisartan reduces inflammation through Angiotensin II AT1 receptor blockade and peroxisome proliferator-activated receptor gamma (PPARγ) activation. However, in a mouse microglia-like BV2 cell line, imitating primary microglia responses with high fidelity and devoid of AT1 receptor gene expression or PPARγ activation, Telmisartan reduced gene expression of pro-injury factors, enhanced that of anti-inflammatory genes, and prevented LPS-induced increase in inflammatory markers. Using global gene expression profiling and pathways analysis, we revealed that Telmisartan normalized the expression of hundreds of genes upregulated by LPS and linked with inflammation, apoptosis and neurodegenerative disorders, while downregulating the expression of genes associated with oncological, neurodegenerative and viral diseases. The PPARγ full agonist Pioglitazone had no neuroprotective effects. Surprisingly, the PPARγ antagonists GW9662 and T0070907 were neuroprotective and enhanced Telmisartan effects. GW9226 alone significantly reduced LPS toxic effects and enhanced Telmisartan neuroprotection, including downregulation of pro-inflammatory TLR2 gene expression. Telmisartan and GW9662 effects on LPS injury negatively correlated with pro-inflammatory factors and upstream regulators, including TLR2, and positively with known neuroprotective factors and upstream regulators. Gene Set Enrichment Analysis (GSEA) of the Telmisartan and GW9662 data revealed negative correlations with sets of genes associated with neurodegenerative and metabolic disorders and toxic treatments in cultured systems, while demonstrating positive correlations with gene sets associated with neuroprotection and kinase inhibition. Our results strongly suggest that novel neuroprotective effects of Telmisartan and GW9662, beyond AT1 receptor blockade or PPARγ activation, include downregulation of the TLR2 signaling pathway, findings that may have translational relevance.

Vertebrate Bitter Taste Receptors: Keys for Survival in Changing Environments

Research on bitter taste receptors has made enormous progress during recent years. Although in the early period after the discovery of this highly interesting receptor family special emphasis was placed on the deorphanization of mainly human bitter taste receptors, the research focus has shifted to sophisticated structure-function analyses, the discovery of small-molecule interactors, and the pharmacological profiling of nonhuman bitter taste receptors. These findings allowed novel perspectives on, for example, evolutionary and ecological questions that have arisen and that are discussed.

System-Wide Expression and Function of Olfactory Receptors in Mammals

Olfactory receptors (ORs) in mammals are generally considered to function as chemosensors in the olfactory organs of animals. They are membrane proteins that traverse the cytoplasmic membrane seven times and work generally by coupling to heterotrimeric G protein. The OR is a G protein‒coupled receptor that binds the guanine nucleotide-binding Gαolf subunit and the Gβγ dimer to recognize a wide spectrum of organic compounds in accordance with its cognate ligand. Mammalian ORs were originally identified from the olfactory epithelium of rat. However, it has been recently reported that the expression of ORs is not limited to the olfactory organ. In recent decades, they have been found to be expressed in diverse organs or tissues and even tumors in mammals. In this review, the expression and expected function of olfactory receptors that exist throughout an organism's system are discussed.

Sisyphus in Neverland

The study of life and living organisms and the way in which these interact and organize to form social communities have been central to my career. I have been fascinated by biology, neurology, and neuropathology, but also by history, sociology, and art. Certain current historical, political, and social events, some occurring proximally but others affecting people in apparently distant places, have had an impact on me. Epicurus, Seneca, and Camus shared their philosophical positions which I learned from. Many scientists from various disciplines have been exciting sources of knowledge as well. I have created a world of hypothesis and experiments but I have also got carried away by serendipity following unexpected observations. It has not been an easy path; errors and wanderings are not uncommon, and opponents close to home much more abundant than one might imagine. Ambition, imagination, resilience, and endurance have been useful in moving ahead in response to setbacks. In the end, I have enjoyed my dedication to science and I am grateful to have glimpsed beauty in it. These are brief memories of a Spanish neuropathologist born and raised in Barcelona, EU.

Regional and subtype-dependent miRNA signatures in sporadic Creutzfeldt-Jakob disease are accompanied by alterations in miRNA silencing machinery and biogenesis

Increasing evidence indicates that microRNAs (miRNAs) are contributing factors to neurodegeneration. Alterations in miRNA signatures have been reported in several neurodegenerative dementias, but data in prion diseases are restricted to ex vivo and animal models. The present study identified significant miRNA expression pattern alterations in the frontal cortex and cerebellum of sporadic Creutzfeldt-Jakob disease (sCJD) patients. These changes display a highly regional and disease subtype-dependent regulation that correlates with brain pathology. We demonstrate that selected miRNAs are enriched in sCJD isolated Argonaute(Ago)-binding complexes in disease, indicating their incorporation into RNA-induced silencing complexes, and further suggesting their contribution to disease-associated gene expression changes. Alterations in the miRNA-mRNA regulatory machinery and perturbed levels of miRNA biogenesis key components in sCJD brain samples reported here further implicate miRNAs in sCJD gene expression (de)regulation. We also show that a subset of sCJD-altered miRNAs are commonly changed in Alzheimer's disease, dementia with Lewy bodies and fatal familial insomnia, suggesting potential common mechanisms underlying these neurodegenerative processes. Additionally, we report no correlation between brain and cerebrospinal fluid (CSF) miRNA-profiles in sCJD, indicating that CSF-miRNA profiles do not faithfully mirror miRNA alterations detected in brain tissue of human prion diseases. Finally, utilizing a sCJD MM1 mouse model, we analyzed the miRNA deregulation patterns observed in sCJD in a temporal manner. While fourteen sCJD-related miRNAs were validated at clinical stages, only two of those were changed at early symptomatic phase, suggesting that the miRNAs altered in sCJD may contribute to later pathogenic processes. Altogether, the present work identifies alterations in the miRNA network, biogenesis and miRNA-mRNA silencing machinery in sCJD, whereby contributions to disease mechanisms deserve further investigation.

The Role of Food Antioxidants, Benefits of Functional Foods, and Influence of Feeding Habits on the Health of the Older Person: An Overview

This overview was directed towards understanding the relationship of brain functions with dietary choices mainly by older humans. This included food color, flavor, and aroma, as they relate to dietary sufficiency or the association of antioxidants with neurodegenerative diseases such as dementia and Alzheimer’s disease. Impairment of olfactory and gustatory function in relation to these diseases was also explored. The role of functional foods was considered as a potential treatment of dementia and Alzheimer’s disease through inhibition of acetylcholinesterase as well as similar treatments based on herbs, spices and antioxidants therein. The importance of antioxidants for maintaining the physiological functions of liver, kidney, digestive system, and prevention of cardiovascular diseases and cancer has also been highlighted. Detailed discussion was focused on health promotion of the older person through the frequency and patterns of dietary intake, and a human ecology framework to estimate adverse risk factors for health. Finally, the role of the food industry, mass media, and apps were explored for today’s new older person generation.

Network-Driven Proteogenomics Unveils an Aging-Related Imbalance in the Olfactory IκBα-NFκB p65 Complex Functionality in Tg2576 Alzheimer's Disease Mouse Model

Olfaction is often deregulated in Alzheimer’s disease (AD) patients, and is also impaired in transgenic Tg2576 AD mice, which overexpress the Swedish mutated form of human amyloid precursor protein (APP). However, little is known about the molecular mechanisms that accompany the neurodegeneration of olfactory structures in aged Tg2576 mice. For that, we have applied proteome- and transcriptome-wide approaches to probe molecular disturbances in the olfactory bulb (OB) dissected from aged Tg2576 mice (18 months of age) as compared to those of age matched wild-type (WT) littermates. Some over-represented biological functions were directly relevant to neuronal homeostasis and processes of learning, cognition, and behavior. In addition to the modulation of CAMP responsive element binding protein 1 (CREB1) and APP interactomes, an imbalance in the functionality of the IκBα-NFκB p65 complex was observed during the aging process in the OB of Tg2576 mice. At two months of age, the phosphorylated isoforms of olfactory IκBα and NFκB p65 were inversely regulated in transgenic mice. However, both phosphorylated proteins were increased at 6 months of age, while a specific drop in IκBα levels was detected in 18-month-old Tg2576 mice, suggesting a transient activation of NFκB in the OB of Tg2576 mice. Taken together, our data provide a metabolic map of olfactory alterations in aged Tg2576 mice, reflecting the progressive effect of APP overproduction and β-amyloid (Aβ) accumulation on the OB homeostasis in aged stages.

Bitter substances from plants used in traditional Chinese medicine exert biased activation of human bitter taste receptors

The number and variety of bitter compounds originating from plants are vast. Whereas some bitter chemicals are toxic and should not be ingested, other compounds exhibit health beneficial effects, which is manifest in the cross-cultural believe that the bitterness of medicine is correlated with the desired medicinal activity. The bitter taste receptors in the oral cavity serve as sensors for bitter compounds and, as they are expressed in numerous extraoral tissues throughout the body, may also be responsible for some physiological effects exerted by bitter compounds. Chinese herbal medicine uses bitter herbs since ancient times for the treatment of various diseases; however, the routes by which these herbs modify physiology are frequently not well understood. We therefore screened 26 bitter substances extracted from medical herbs for the activation of the 25 human bitter taste receptors. We identified six receptors activated by in total 17 different bitter compounds. Interestingly, we observed a bias in bitter taste receptor activation with 10 newly identified agonists for the broadly tuned receptor TAS2R46, seven agonists activating the TAS2R14 and two compounds activating narrowly tuned receptors, suggesting that these receptors play dominant roles in the evaluation and perhaps physiological activities of Chinese herbal medicines.

Agonist Binding to Chemosensory Receptors: A Systematic Bioinformatics Analysis

Human G-protein coupled receptors (hGPCRs) constitute a large and highly pharmaceutically relevant membrane receptor superfamily. About half of the hGPCRs' family members are chemosensory receptors, involved in bitter taste and olfaction, along with a variety of other physiological processes. Hence these receptors constitute promising targets for pharmaceutical intervention. Molecular modeling has been so far the most important tool to get insights on agonist binding and receptor activation. Here we investigate both aspects by bioinformatics-based predictions across all bitter taste and odorant receptors for which site-directed mutagenesis data are available. First, we observe that state-of-the-art homology modeling combined with previously used docking procedures turned out to reproduce only a limited fraction of ligand/receptor interactions inferred by experiments. This is most probably caused by the low sequence identity with available structural templates, which limits the accuracy of the protein model and in particular of the side-chains' orientations. Methods which transcend the limited sampling of the conformational space of docking may improve the predictions. As an example corroborating this, we review here multi-scale simulations from our lab and show that, for the three complexes studied so far, they significantly enhance the predictive power of the computational approach. Second, our bioinformatics analysis provides support to previous claims that several residues, including those at positions 1.50, 2.50, and 7.52, are involved in receptor activation.

Progressive modulation of the human olfactory bulb transcriptome during Alzheimer´s disease evolution: novel insights into the olfactory signaling across proteinopathies

Alzheimer´s disease (AD) is characterized by progressive dementia, initially presenting olfactory dysfunction. Despite the olfactory bulb (OB) is the first central structure of the olfactory pathway, we lack a complete molecular characterization of the transcriptional events that occurs in this olfactory area during AD progression. To address this gap in knowledge, we have assessed the genome-wide expression in postmortem OBs from subjects with varying degree of AD pathology. A stage-dependent deregulation of specific pathways was observed, revealing transmembrane transport, and neuroinflammation as part of the functional modules that are disrupted across AD grading. Potential drivers of neurodegeneration predicted by network-driven transcriptomics were monitored across different types of dementia, including progressive supranuclear palsy (PSP), mixed dementia, and frontotemporal lobar degeneration (FTLD). Epidermal growth factor receptor (EGFR) expression was significantly increased in the OB of AD and mixed dementia subjects. Moreover, a significant increment in the activation of signal transducer and activator of transcription 3 (STAT3) was exclusively detected in advanced AD stages, whereas total STAT3 levels were specifically overexpressed in mixed dementia. Furthermore, transcription factors deregulated in the OB of mixed dementia subjects such as cAMP Responsive Element Binding Protein 1 (CREB1) and AP-1 Transcription Factor Subunit (c-Jun) were not differentially modulated at olfactory level across AD grading. On the other hand, olfactory expression of this signal transducer panel was unchanged in PSP and FTLD subjects. Taken together, this study unveils cross-disease similarities and differences for specific signal transducers, providing mechanistic clues to the intriguing divergence of AD pathology across proteinopathies.

Dementia with Lewy Bodies: Molecular Pathology in the Frontal Cortex in Typical and Rapidly Progressive Forms

Objectives

The goal of this study was to assess mitochondrial function, energy, and purine metabolism, protein synthesis machinery from the nucleolus to the ribosome, inflammation, and expression of newly identified ectopic olfactory receptors (ORs) and taste receptors (TASRs) in the frontal cortex of typical cases of dementia with Lewy bodies (DLB) and cases with rapid clinical course (rpDLB: 2 years or less) compared with middle-aged non-affected individuals, in order to learn about the biochemical abnormalities underlying Lewy body pathology.

Methods

Real-time quantitative PCR, mitochondrial enzymatic assays, and analysis of β-amyloid, tau, and synuclein species were used.

Results

The main alterations in DLB and rpDLB, which are more marked in the rapidly progressive forms, include (i) deregulated expression of several mRNAs and proteins of mitochondrial subunits, and reduced activity of complexes I, II, III, and IV of the mitochondrial respiratory chain; (ii) reduced expression of selected molecules involved in energy metabolism and increased expression of enzymes involved in purine metabolism; (iii) abnormal expression of nucleolar proteins, rRNA18S, genes encoding ribosomal proteins, and initiation factors of the transcription at the ribosome; (iv) discrete inflammation; and (v) marked deregulation of brain ORs and TASRs, respectively. Severe mitochondrial dysfunction involving activity of four complexes, minimal inflammatory responses, and dramatic altered expression of ORs and TASRs discriminate DLB from Alzheimer’s disease. Altered solubility and aggregation of α-synuclein, increased β-amyloid bound to membranes, and absence of soluble tau oligomers are common in DLB and rpDLB. Low levels of soluble β-amyloid are found in DLB. However, increased soluble β-amyloid 1–40 and β-amyloid 1–42, and increased TNFα mRNA and protein expression, distinguish rpDLB.

Conclusion

Molecular alterations in frontal cortex in DLB involve key biochemical pathways such as mitochondria and energy metabolism, protein synthesis, purine metabolism, among others and are accompanied by discrete innate inflammatory response.

Copy Number Variations in Amyotrophic Lateral Sclerosis: Piecing the Mosaic Tiles Together through a Systems Biology Approach

Amyotrophic lateral sclerosis (ALS) is a devastating and still untreatable motor neuron disease. Despite the molecular mechanisms underlying ALS pathogenesis that are still far from being understood, several studies have suggested the importance of a genetic contribution in both familial and sporadic forms of the disease. In addition to single-nucleotide polymorphisms (SNPs), which account for only a limited number of ALS cases, a consistent number of common and rare copy number variations (CNVs) have been associated to ALS. Most of the CNV-based association studies use a traditional candidate-gene approach that is inadequate for uncovering the genetic architectures of complex traits like ALS. The emergent paradigm of “systems biology” may offer a new perspective to better interpret the wide spectrum of CNVs in ALS, enabling the characterization of the complex network of gene products underlying ALS pathogenesis. In this review, we will explore the landscape of CNVs in ALS, putting specific emphasis on the functional impact of common CNV regions and genes consistently associated with increased risk of developing disease. In addition, we will discuss the potential contribution of multiple rare CNVs in ALS pathogenesis, focusing our attention on the complex mechanisms by which these proteins might impact, individually or in combination, the genetic susceptibility of ALS. The comprehensive detection and functional characterization of common and rare candidate risk CNVs in ALS susceptibility may bring new pieces into the intricate mosaic of ALS pathogenesis, providing interesting and important implications for a more precise molecular biomarker-assisted diagnosis and more effective and personalized treatments.

Emerging Putative Associations between Non-Coding RNAs and Protein-Coding Genes in Neuropathic Pain: Added Value from Reusing Microarray Data

Regeneration of injured nerves is likely occurring in the peripheral nervous system, but not in the central nervous system. Although protein-coding gene expression has been assessed during nerve regeneration, little is currently known about the role of non-coding RNAs (ncRNAs). This leaves open questions about the potential effects of ncRNAs at transcriptome level. Due to the limited availability of human neuropathic pain (NP) data, we have identified the most comprehensive time-course gene expression profile referred to sciatic nerve (SN) injury and studied in a rat model using two neuronal tissues, namely dorsal root ganglion (DRG) and SN. We have developed a methodology to identify differentially expressed bioentities starting from microarray probes and repurposing them to annotate ncRNAs, while analyzing the expression profiles of protein-coding genes. The approach is designed to reuse microarray data and perform first profiling and then meta-analysis through three main steps. First, we used contextual analysis to identify what we considered putative or potential protein-coding targets for selected ncRNAs. Relevance was therefore assigned to differential expression of neighbor protein-coding genes, with neighborhood defined by a fixed genomic distance from long or antisense ncRNA loci, and of parental genes associated with pseudogenes. Second, connectivity among putative targets was used to build networks, in turn useful to conduct inference at interactomic scale. Last, network paths were annotated to assess relevance to NP. We found significant differential expression in long-intergenic ncRNAs (32 lincRNAs in SN and 8 in DRG), antisense RNA (31 asRNA in SN and 12 in DRG), and pseudogenes (456 in SN and 56 in DRG). In particular, contextual analysis centered on pseudogenes revealed some targets with known association to neurodegeneration and/or neurogenesis processes. While modules of the olfactory receptors were clearly identified in protein-protein interaction networks, other connectivity paths were identified between proteins already investigated in studies on disorders, such as Parkinson, Down syndrome, Huntington disease, and Alzheimer. Our findings suggest the importance of reusing gene expression data by meta-analysis approaches.

Sex differences between APPswePS1dE9 mice in A-beta accumulation and pancreatic islet function during the development of Alzheimer’s disease

The pathogenesis of Alzheimer’s disease (AD), a type of neurodegenerative disease characterized by learning and memory impairment, is often associated with pathological features, such as amyloid-beta (Aβ) accumulation and insulin resistance. The transgenic mouse, APPswePS1dE9 (APP/PS1), is one of the most commonly used animal models in pathogenesis studies of AD. The purpose of this study is to investigate the sex differences between APP/PS1 mice in the pathogenesis of AD. The impairment of glucose and insulin tolerance was found to develop earlier in male APP/PS1 mice than in females. Plasma insulin levels were significantly decreased in male APP/PS1 mice, while total cholesterol levels in male APP/PS1 mice were higher than those in females. Triglyceride levels in male mice in both the wild-type (WT) and APP/PS1 groups were higher than in their female littermates. Soluble and insoluble Aβ levels in female APP/PS1 mouse brains were higher than those in males. And the learning and memorizing abilities of female APP/PS1 mice were poorer than those of males. Our results concluded that there were sex differences in Aβ formation, pancreatic islet function and insulin sensitivity between male and female APP/PS1 mice during the pathogenesis of AD.

Olfactory Receptors in Non-Chemosensory Organs: The Nervous System in Health and Disease

Olfactory receptors (ORs) and down-stream functional signaling molecules adenylyl cyclase 3 (AC3), olfactory G protein α subunit (Gαolf), OR transporters receptor transporter proteins 1 and 2 (RTP1 and RTP2), receptor expression enhancing protein 1 (REEP1), and UDP-glucuronosyltransferases (UGTs) are expressed in neurons of the human and murine central nervous system (CNS). In vitro studies have shown that these receptors react to external stimuli and therefore are equipped to be functional. However, ORs are not directly related to the detection of odors. Several molecules delivered from the blood, cerebrospinal fluid, neighboring local neurons and glial cells, distant cells through the extracellular space, and the cells’ own self-regulating internal homeostasis can be postulated as possible ligands. Moreover, a single neuron outside the olfactory epithelium expresses more than one receptor, and the mechanism of transcriptional regulation may be different in olfactory epithelia and brain neurons. OR gene expression is altered in several neurodegenerative diseases including Parkinson’s disease (PD), Alzheimer’s disease (AD), progressive supranuclear palsy (PSP) and sporadic Creutzfeldt-Jakob disease (sCJD) subtypes MM1 and VV2 with disease-, region- and subtype-specific patterns. Altered gene expression is also observed in the prefrontal cortex in schizophrenia with a major but not total influence of chlorpromazine treatment. Preliminary parallel observations have also shown the presence of taste receptors (TASRs), mainly of the bitter taste family, in the mammalian brain, whose function is not related to taste. TASRs in brain are also abnormally regulated in neurodegenerative diseases. These seminal observations point to the need for further studies on ORs and TASRs chemoreceptors in the mammalian brain.

Comprehensive Analysis of Mouse Bitter Taste Receptors Reveals Different Molecular Receptive Ranges for Orthologous Receptors in Mice and Humans

One key to animal survival is the detection and avoidance of potentially harmful compounds by their bitter taste. Variable numbers of taste 2 receptor genes expressed in the gustatory end organs enable bony vertebrates (Euteleostomi) to recognize numerous bitter chemicals. It is believed that the receptive ranges of bitter taste receptor repertoires match the profiles of bitter chemicals that the species encounter in their diets. Human and mouse genomes contain pairs of orthologous bitter receptor genes that have been conserved throughout evolution. Moreover, expansions in both lineages generated species-specific sets of bitter taste receptor genes. It is assumed that the orthologous bitter taste receptor genes mediate the recognition of bitter toxins relevant for both species, whereas the lineage-specific receptors enable the detection of substances differently encountered by mice and humans. By challenging 34 mouse bitter taste receptors with 128 prototypical bitter substances in a heterologous expression system, we identified cognate compounds for 21 receptors, 19 of which were previously orphan receptors. We have demonstrated that mouse taste 2 receptors, like their human counterparts, vary greatly in their breadth of tuning, ranging from very broadly to extremely narrowly tuned receptors. However, when compared with humans, mice possess fewer broadly tuned receptors and an elevated number of narrowly tuned receptors, supporting the idea that a large receptor repertoire is the basis for the evolution of specialized receptors. Moreover, we have demonstrated that sequence-orthologous bitter taste receptors have distinct agonist profiles. Species-specific gene expansions have enabled further diversification of bitter substance recognition spectra.

Effects of postnatal alcohol exposure on hippocampal gene expression and learning in adult mice

Fetal alcohol syndrome (FAS) is a condition resulting from excessive drinking by pregnant women. Symptoms of FAS include abnormal facial features, stunted growth, intellectual deficits and attentional dysfunction. Many studies have investigated FAS, but its underlying mechanisms remain unknown. This study evaluated the relationship between alcohol exposure during the synaptogenesis period in postnatal mice and subsequent cognitive function in adult mice. We delivered two injections, separated by 2 h, of ethanol (3 g/kg, ethanol/saline, 20% v/v) to ICR mice on postnatal day 7. After 10 weeks, we conducted a behavioral test, sacrificed the animals, harvested brain tissue and analyzed hippocampal gene expression using a microarray. In ethanol-treated mice, there was a reduction in brain size and decreased neuronal cell number in the cortex, and also cognitive impairment. cDNA microarray results indicated that 1,548 genes showed a > 2-fold decrease in expression relative to control, whereas 974 genes showed a > 2-fold increase in expression relative to control. Many of these genes were related to signal transduction, synaptogenesis and cell membrane formation, which are highlighted in our findings.