The diversified function and potential therapy of ectopic olfactory receptors in non-olfactory tissues

Non-canonical olfactory pathway activation induces cell fusion of cervical cancer cells

Multinucleation occurs in various types of advanced cancers and contributes to their malignant characteristics, including anticancer drug resistance. Therefore, inhibiting multinucleation can improve cancer prognosis; however, the molecular mechanisms underlying multinucleation remain elusive. Here, we introduced a genetic mutation in cervical cancer cells to induce cell fusion-mediated multinucleation. The olfactory receptor OR1N2 was heterozygously mutated in these fused cells; the same OR1N2 mutation was detected in multinucleated cells from clinical cervical cancer specimens. The mutation-induced structural change in the OR1N2 protein activated protein kinase A (PKA), which, in turn, mediated the non-canonical olfactory pathway. PKA phosphorylated and activated furin protease, resulting in the cleavage of the fusogenic protein syncytin-1. Because this cleaved form of syncytin-1, processed by furin, participates in cell fusion, furin inhibitors could suppress multinucleation and reduce surviving cell numbers after anticancer drug treatment. The improved anticancer drug efficacy indicates a promising therapeutic approach for advanced cervical cancers.

Olfactory Receptors and Tumorigenesis: Implications for Diagnosis and Targeted Therapy

Olfactory receptors (ORs) are a class of G protein-coupled receptors (GPCR) widely distributed in olfactory sensory neurons and various non-olfactory tissues, serving significant physiological and pathological functions in the human body. Increasing evidence reveals the heightened expression of olfactory receptors in tumorous tissues and cells alongside normal tissues. Olfactory receptors have demonstrated influence over tumor cell proliferation and metastasis, establishing a close relationship with tumor initiation and progression. This review highlights the specific molecular actions and signaling pathways of olfactory receptors in the development of human tumors. The potential for precise tumor diagnosis and targeted therapy through therapeutic targeting of olfactory receptors as an adjunct anticancer treatment strategy is being considered.

Ecnomotopic olfactory receptors in metabolic regulation

Olfactory receptors are seven-transmembrane G-protein-coupled receptors on the cell surface. Over the past few decades, evidence has been mounting that olfactory receptors are not unique to the nose and that their ectopic existence plays an integral role in extranasal diseases. Coupled with the discovery of many natural or synthetic odor-compound ligands, new roles of ecnomotopic olfactory receptors regulating blood glucose, obesity, blood pressure, and other metabolism-related diseases are emerging. Many well-known scientific journals have called for attention to extranasal functions of ecnomotopic olfactory receptors. Thus, the prospect of ecnomotopic olfactory receptors in drug target research has been greatly underestimated. Here, we have provided an overview for the role of ecnomotopic olfactory receptors in metabolic diseases, focusing on their effects on various metabolic tissues, and discussed the possible molecular biological and pathophysiological mechanisms, which provide the basis for drug development and clinical application targeting the function of ecnomotopic olfactory receptors via literature machine learning and screening.

Genome-wide investigation of the OR gene family in Helicoverpa armigera and functional analysis of OR48 and OR75 in metamorphosis development

The cotton bollworm, Helicoverpa armigera, is a significant global agricultural pest, particularly detrimental during its larval feeding period. Insects' odorant receptors (ORs) are crucial for their crop-feeding activities, yet a comprehensive analysis of H. armigera ORs has been lacking, and the influence of hormones on ORs remain understudied. Herein, we conducted a genome-wide study and identified 81 ORs, categorized into 15 distinct groups. Analyses of protein motifs and gene structures revealed both conservation within groups and divergence among them. Comparative gene duplication analysis between H. armigera and Bombyx mori highlighted different duplication patterns. We further investigated subcellular localization and protein interactions within the odorant receptor family, providing valuable insights for future functional and interaction studies of ORs. Specifically, we identified that OR48 and OR75 were abundantly expressed during molting/metamorphosis and feeding stages, respectively. We demonstrated that 20E induced the upregulation of OR48 via EcR, while insulin upregulated OR75 expression through InR. Moreover, 20E induced the translocation of OR48 to the cell membrane, mediating its effects. Functional studies involving the knockdown of OR48 and OR75 revealed their roles in metamorphosis development, with OR48 knockdown resulting in delayed pupation and OR75 knockdown leading to premature pupation. OR48 can promote autophagy and apoptosis in fat body, while OR75 can significantly inhibit apoptosis and autophagy. These findings significantly contribute to our understanding of OR function in H. armigera and shed light on potential avenues for pest control strategies.

Immunologic features of nontuberculous mycobacterial pulmonary disease based on spatially resolved whole transcriptomics

BACKGROUND

The immunologic features of nontuberculous mycobacterial pulmonary disease (NTM-PD) are largely unclear. This study investigated the immunologic features of NTM-PD using digital spatial profiling techniques.

METHODS

Lung tissues obtained from six patients with NTM-PD between January 1, 2006, and December 31, 2020, at Seoul National University Hospital were subjected to RNA sequencing. Cores from the peribronchial areas were stained with CD3, CD68, and DNASyto13, and gene expression at the whole-transcriptome level was quantified using PCR amplification and Illumina sequencing. Lung tissues from six patients with bronchiectasis collected during the same period were used as controls. The RNA sequencing results were validated using immunohistochemistry (IHC) in another cohort (30 patients with NTM-PD and 15 patients with bronchiectasis).

RESULTS

NTM-PD exhibited distinct gene expression patterns in T cells and macrophages. Gene set enrichment analysis revealed that pathways related to antigen presentation and processing were upregulated in NTM-PD, particularly in macrophages. Macrophages were more prevalent and the expression of genes associated with the M1 phenotype (CD40 and CD80) was significantly elevated. Although macrophages were activated in the NTM-PD group T cell activity was unaltered. Notably, expression of the costimulatory molecule CD28 was decreased in NTM-PD. IHC analysis showed that T cells expressing Foxp3 or TIM-3, which facilitate the regulatory functions of T cells, were increased.

CONCLUSIONS

NTM-PD exhibits distinct immunologic signatures characterized by the activation of macrophages without T cell activation.

The Olfactory Receptor Olfr25 Mediates Sperm Dysfunction Induced by Low-Dose Bisphenol A through the CatSper-Ca2+ Signaling Pathway

Bisphenol A (BPA), a typical endocrine disruptor, is known to have various adverse effects on the male reproductive system. However, the toxic effects and mechanisms of low-dose BPA have not yet been fully explored. In this study, male Kunming mice were orally administered low-dose BPA (0.03, 0.3 and 3 mg/kg/d) for ten consecutive weeks. Pathological sections of testicular tissue showed no significant morphological differences after BPA exposure. An analysis of the functional parameters of sperm revealed that exposure to low-dose BPA significantly decreased sperm motility, chemotaxis, and the acrosome reaction. An in vitro BPA exposure model combined with an omics data analysis showed that the olfactory receptor-related pathway was significantly enriched after BPA treatment. Subsequent experiments verified the reduced mRNA level of a novel olfactory receptor gene, Olfr25, in vivo and in vitro exposure models. Meanwhile, exposure to low-dose BPA reduced the intracellular calcium ion concentration and the mRNA levels of pore-forming subunits of the CatSper channel in sperm. Importantly, the knockdown of Olfr25 inhibited calcium ion levels and CatSper subunit expression in GC-2 cells. Olfr25 overexpression attenuated the BPA-induced downregulation of CatSper subunit expression in GC-2 cells. These findings indicate that Olfr25 might participate in low-dose BPA-induced sperm dysfunction by affecting the CatSper-Ca2+ signaling pathway. This study reveals a new mechanism underlying the effects of low-dose BPA on sperm function and provides a reference for assessing the safety of low-dose BPA exposure.

NAD activates olfactory receptor 1386 to regulate type I interferon responses in Plasmodium yoelii YM infection

Olfactory receptors (Olfr) are G protein-coupled receptors that are normally expressed on olfactory sensory neurons to detect volatile chemicals or odorants. Interestingly, many Olfrs are also expressed in diverse tissues and function in cell-cell recognition, migration, and proliferation as well as immune responses and disease processes. Here, we showed that many Olfr genes were expressed in the mouse spleen, linked to Plasmodium yoelii genetic loci significantly, and/or had genome-wide patterns of LOD scores (GPLSs) similar to those of host Toll-like receptor genes. Expression of specific Olfr genes such as Olfr1386 in HEK293T cells significantly increased luciferase signals driven by IFN-β and NF-κB promoters, with elevated levels of phosphorylated TBK1, IRF3, P38, and JNK. Mice without Olfr1386 were generated using the CRISPR/Cas9 method, and the Olfr1386-/- mice showed significantly lower IFN-α/β levels and longer survival than wild-type (WT) littermates after infection with P. yoelii YM parasites. Inhibition of G protein signaling and P38 activity could affect cyclic AMP-responsive element promoter-driven luciferase signals and IFN-β mRNA levels in HEK293T cells expressing the Olfr1386 gene, respectively. Screening of malaria parasite metabolites identified nicotinamide adenine dinucleotide (NAD) as a potential ligand for Olfr1386, and NAD could stimulate IFN-β responses and phosphorylation of TBK1 and STAT1/2 in RAW264.7 cells. Additionally, parasite RNA (pRNA) could significantly increase Olfr1386 mRNA levels. This study links multiple Olfrs to host immune response pathways, identifies a candidate ligand for Olfr1386, and demonstrates the important roles of Olfr1386 in regulating type I interferon (IFN-I) responses during malaria parasite infections.

A family of olfactory receptors uniquely expanded in marsupial and monotreme genomes are expressed by a T cell subset also unique to marsupials and monotremes

Olfactory receptors (OR), expressed on olfactory neurons, mediate the sense of smell. Recently, OR have also been shown to be expressed in non-olfactory tissues, including cells of the immune system. An analysis of single-cell transcriptomes of splenocytes of the grey short-tailed opossum (Monodelphis domestica) found OR are expressed on a subset of T cells, the γμ T cells, that are unique to marsupials and monotremes. A majority of opossum γμ T cells transcriptomes contain OR family 14 transcripts, specifically, from the OR14C subfamily. Amongst the mammals, the OR14 gene family is expanded in the genomes of marsupials and monotremes, and rarer or absent in placental mammals. In summary, here we demonstrate the intriguing correlation that a family of OR genes, abundant in the genomes of marsupials and monotremes, are ectopically expressed in a particular subset of T cells unique to the marsupials and monotremes.

Localized Expression of Olfactory Receptor Genes in the Olfactory Organ of Common Minke Whales

Baleen whales (Mysticeti) possess the necessary anatomical structures and genetic elements for olfaction. Nevertheless, the olfactory receptor gene (OR) repertoire has undergone substantial degeneration in the cetacean lineage following the divergence of the Artiodactyla and Cetacea. The functionality of highly degenerated mysticete ORs within their olfactory epithelium remains unknown. In this study, we extracted total RNA from the nasal mucosae of common minke whales (Balaenoptera acutorostrata) to investigate ORs' localized expression. All three sections of the mucosae examined in the nasal chamber displayed comparable histological structure. However, the posterior portion of the frontoturbinal region exhibited notably high OR expression. Neither the olfactory bulb nor the external skin exhibited the expression of these genes. Although this species possesses four intact non-class-2 ORs, all the ORs expressed in the nasal mucosae belong to class-2, implying the loss of aversion to specific odorants. These anatomical and genomic analyses suggest that ORs are still responsible for olfaction within the nasal region of baleen whales, enabling them to detect desirable scents such as prey and potential mating partners.

Patent highlights August-September 2023

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

From odor to oncology: non-canonical odorant receptors in cancer

Odorant receptors, traditionally associated with olfaction as chemoreceptors, have been increasingly recognized for their presence and diverse functions in various non-nasal tissues throughout the body. Beyond their roles in sensory perception, emerging evidence suggests a compelling interplay between odorant receptors and cancer progression as well. Alongside the canonical GPCR odorant receptors, dysregulation of non-canonical odorant receptors such as trace amine-associated receptors (TAARs), formyl peptide receptors (FPRs), and membrane-spanning 4A family (MS4As) has been observed in various cancer types, suggesting their contributions to cancer progression. The roles of these non-canonical chemoreceptors in cancer are complex, with some receptors promoting tumorigenesis and others acting as tumor-suppressing factors upon activation, depending on the cancer type. These findings shed light on the potential of non-canonical odorant receptors as therapeutic targets and prognostic markers in cancer, inviting further exploration to unravel their precise mechanisms of action and implications in cancer biology. In this review, we provide a comprehensive overview of the intricate relationships between these chemoreceptors and various types of cancer, potentially paving the way for innovative odor-based therapeutics. Ultimately, this review discusses the potential development of novel therapeutic strategies targeting these non-canonical chemoreceptors.

Expression of olfactory receptor genes in non-olfactory tissues in the developing and adult zebrafish

Since the discovery of olfactory receptor (OR) genes, their expression in non-olfactory tissues have been reported in rodents and humans. For example, mouse OR23 (mOR23) is expressed in sperm and muscle cells and has been proposed to play a role in chemotaxis and muscle migration, respectively. In addition, mouse mesencephalic dopaminergic neurons express various ORs, which respond to corresponding ligands. As the OR genes comprise the largest multigene family of G protein-coupled receptors in vertebrates (over 400 genes in human and 1000 in rodents), it has been difficult to categorize the extent of their diverse expression in non-olfactory tissues making it challenging to ascertain their function. The zebrafish genome contains significantly fewer OR genes at around 140 genes, and their expression pattern can be easily analyzed by carrying out whole mount in situ hybridization (ISH) assay in larvae. In this study, we found that 31 out of 36 OR genes, including or104-2, or108-1, or111-1, or125-4, or128-1, or128-5, 133-4, or133-7, or137-3 are expressed in various tissues, including the trunk, pharynx, pancreas and brain in the larvae. In addition, some OR genes are expressed in distinct brain regions such as the hypothalamus and the habenula in a dynamic temporal pattern between larvae, juvenile and adult zebrafish. We further confirmed that OR genes are expressed in non-olfactory tissues by RT-PCR in larvae and adults. These results indicate tight regulation of OR gene expression in the brain in a spatial and temporal manner and that the expression of OR genes in non-olfactory tissues are conserved in vertebrates. This study provides a framework to start investigating the function of ORs in the zebrafish brain.

Activation of OR10A3 by Suberic Acid Promotes Collagen Synthesis in UVB-Irradiated Dermal Fibroblasts via the cAMP-Akt Pathway

In recent years, there has been a great deal of interest in the ectopic roles of olfactory receptors (ORs) throughout the human body. Especially, the ectopic function of OR in the skin is one of the most actively researched areas. Suberic acid, a scent compound, was hypothesized to increase collagen synthesis in the ultraviolet B (UVB)-irradiated human dermal fibroblasts (Hs68) through a specific olfactory receptor. Suberic acid ameliorated UVB-induced decreases in collagen production in Hs68 cells. Using in silico docking to predict the binding conformation and affinity of suberic acid to 15 ectopic ORs detectable in Hs68, several ORs were identified as promising candidates. The effect of suberic acid on collagen synthesis in UVB-exposed dermal fibroblasts was nullified only by a reduction in OR10A3 expression via specific siRNA. In addition, using the cells transiently expressing OR10A3, we demonstrated that suberic acid can activate OR10A3 by assessing the downstream effector cAMP response element (CRE) luciferase activity. We examined that the activation of OR10A3 by suberic acid subsequently stimulates collagen synthesis via the downstream cAMP-Akt pathway. The findings support OR10A3 as a promising target for anti-aging treatments of the skin.

Olfactory receptors in macrophages and inflammation

Olfactory receptors (ORs) that bind odorous ligands are the largest family of G-protein-coupled receptors. In the olfactory epithelium, approximately 400 and 1,100 members are expressed in humans and mice, respectively. Growing evidence suggests the extranasal functions of ORs. Here, we review OR expression and function in macrophages, specialized innate immune cells involved in the detection, phagocytosis, and destruction of cellular debris and pathogens as well as the initiation of inflammatory responses. RNA sequencing data in mice suggest that up to 580 ORs may be expressed in macrophages. Macrophage OR expression is increased after treatment with the Toll-like receptor 4 ligand lipopolysaccharide, which also induces the transcription of inflammasome components. Triggering human OR6A2 or its mouse orthologue Olfr2 with their cognate ligand octanal induces inflammasome assembly and the secretion of IL-1β, which exacerbates atherosclerosis. Octanal is positively correlated with blood lipids like low-density lipoprotein -cholesterol in humans. Another OR, Olfr78, is activated by lactate, which promotes the generation of tumor-associated macrophages that dampen the immune response and promote tumor progression. Olfactory receptors in macrophages are a rich source of untapped opportunity for modulating inflammation. It is not known which of the many ORs expressed in macrophages promote or modulate inflammation. Progress in this area also requires deorphanizing more ORs and determining the sources of their ligands.

Therapeutic and prognostic potential of GPCRs in prostate cancer from multi-omics landscape

Prostate cancer (PRAD) is a common and fatal malignancy. It is difficult to manage clinically due to drug resistance and poor prognosis, thus creating an urgent need for novel therapeutic targets and prognostic biomarkers. Although G protein-coupled receptors (GPCRs) have been most attractive for drug development, there have been lack of an exhaustive assessment on GPCRs in PRAD like their molecular features, prognostic and therapeutic values. To close this gap, we herein systematically investigate multi-omics profiling for GPCRs in the primary PRAD by analyzing somatic mutations, somatic copy-number alterations (SCNAs), DNA methylation and mRNA expression. GPCRs exhibit low expression levels and mutation frequencies while SCNAs are more prevalent. 46 and 255 disease-related GPCRs are identified by the mRNA expression and DNA methylation analysis, respectively, complementing information lack in the genome analysis. In addition, the genomic alterations do not exhibit an observable correlation with the GPCR expression, reflecting the complex regulatory processes from DNA to RNA. Conversely, a tight association is observed between the DNA methylation and mRNA expression. The virtual screening and molecular dynamics simulation further identify four potential drugs in repositioning to PRAD. The combination of 3 clinical characteristics and 26 GPCR molecular features revealed by the transcriptome and genome exhibit good performance in predicting progression-free survival in patients with the primary PRAD, providing candidates as new biomarkers. These observations from the multi-omics analysis on GPCRs provide new insights into the underlying mechanism of primary PRAD and potential of GPCRs in developing therapeutic strategies on PRAD.

Identification of New Toxicity Mechanisms in Drug-Induced Liver Injury through Systems Pharmacology

Among adverse drug reactions, drug-induced liver injury presents particular challenges because of its complexity, and the underlying mechanisms are still not completely characterized. Our knowledge of the topic is limited and based on the assumption that a drug acts on one molecular target. We have leveraged drug polypharmacology, i.e., the ability of a drug to bind multiple targets and thus perturb several biological processes, to develop a systems pharmacology platform that integrates all drug–target interactions. Our analysis sheds light on the molecular mechanisms of drugs involved in drug-induced liver injury and provides new hypotheses to study this phenomenon.

Ectopic odorant receptors responding to flavor compounds in skin health and disease: Current insights and future perspectives

Skin, the largest organ of human body, acts as a barrier to protect body from the external environment and is exposed to a myriad of flavor compounds, especially food- and plant essential oil-derived odorant compounds. Skin cells are known to express various chemosensory receptors, such as transient potential receptors, adenosine triphosphate receptors, taste receptors, and odorant receptors (ORs). We aim to provide a review of this rapidly developing field and discuss latest discoveries related to the skin ORs activated by flavor compounds, their impacts on skin health and disease, odorant ligands interacting with ORs exerting specific biological effects, and the mechanisms involved. ORs are recently found to be expressed in skin tissue and cells, such as keratinocytes, melanocytes, and fibroblasts. To date, several ectopic skin ORs responding to flavor compounds, are involved in different skin biological processes, such as wound healing, hair growth, melanin regulation, pressure stress, skin barrier function, atopic dermatitis, and psoriasis. The recognition of physiological role of skin ORs, combined with the fact that ORs belong to a highly druggable protein family (G protein-coupled receptors), underscores the potential of skin ORs responding to flavor compounds as a novel regulating strategy for skin health and disease.

Differential Expression and Bioinformatics Analysis of tRF/tiRNA in Endometriosis Patients

Background. Endometriosis (EMs) is a benign chronic condition that tends to recur in women of childbearing age, with an incidence of approximately 10%. It is a multifactorial disease for which the pathogenesis is currently unclear. This study is aimed at investigating the expression and clinical significance of tRNA-derived small RNA (tsRNA), a novel noncoding small RNA with potential regulatory functions, in endometriosis. Methods. The tRF/tiRNA expression profiles in endometrial tissues from three pairs of endometriosis patients and controls were detected by tRF&tiRNA PCR microarray technology and then verified by quantitative real-time polymerase chain reaction (qPCR). The target genes and target sites of TRF396, tiRNA-5030-GlnTTG-3, TRF308, and TRF320 were predicted by miRanda, and the network diagram of their interaction with miRNA was drawn. The impact of tRNA-derived fragments on the pathogenesis of endometriosis was analyzed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Results. Two upregulated and 19 downregulated tRNA-derived fragments were identified. The qRT-PCR results of 2 upregulated and 2 downregulated RNA-derived fragments were consistent with the RNA Seq data. The OR2B4 gene related to TRF396, the DGAT1 gene related to tiRNA-5030-GlnTTG-3, the KLF16 gene of TRF308, and the RNF213 gene of TRF320 had significant correlations. Gene Ontology and pathway analysis showed that the target genes of TRF396 and tiRNA-5030-GlnTTG-3 were mainly involved in the intrinsic components of the membrane and the overall composition of the membrane in cell components; molecular functions mainly involve olfactory conduction and G protein-coupled receptor activity. In the biological process, it was mainly involved in the detection of sensory stimuli. The target genes of TRF308 and TRF320 were mainly involved in the intracellular part; molecular functions are mainly related to DNA binding transcription factor activity and protein binding and mainly related to biological regulation of biological processes. Pathway analysis showed that the RAP1 signaling pathway and the AXON GUIDANCE signaling pathway may participate in the progression of endometriosis. Conclusion. The differential expression of tRF/tiRNA in endometriosis may be related to the pathogenesis of endometriosis. Furthermore, tRF/tiRNA may be a biomarker for the diagnosis and treatment of EMs in the future.

Association between Olfactory Receptors and Skin Physiology

Olfactory receptors are chemosensory receptors that detect odorants and function in the initial perception of a smell. Intriguingly, olfactory receptors are also expressed in cells other than olfaction sensory cells, an expression pattern termed ectopic expression. Ectopically expressed olfactory receptors have a distinct role depending on the type of tissues or cells in which they are expressed. This review introduces current research on the ectopic expression and function of olfactory receptors in skin and provides insight into directions for future research.

Genetic variants in eleven central and peripheral chemoreceptor genes in sudden infant death syndrome

BACKGROUND

Sudden infant death syndrome (SIDS) is still one of the leading causes of postnatal infant death in developed countries. The occurrence of SIDS is described by a multifactorial etiology that involves the respiratory control system including chemoreception. It is still unclear whether genetic variants in genes involved in respiratory chemoreception might play a role in SIDS.

METHODS

The exome data of 155 SIDS cases were screened for variants within 11 genes described in chemoreception. Pathogenicity of variants was assigned based on the assessment of variant types and in silico protein predictions according to the current recommendations of the American College of Medical Genetics and Genomics.

RESULTS

Potential pathogenic variants in genes encoding proteins involved in respiratory chemoreception could be identified in 5 (3%) SIDS cases. Two of the variants (R137S/A188S) were found in the KNCJ16 gene, which encodes for the potassium channel Kir5.1, presumably involved in central chemoreception. Electrophysiologic analysis of these KCNJ16 variants revealed a loss-of-function for the R137S variant but no obvious impairment for the A188S variant.

CONCLUSIONS

Genetic variants in genes involved in respiratory chemoreception may be a risk factor in a fraction of SIDS cases and may thereby contribute to the multifactorial etiology of SIDS.

IMPACT

What is the key message of your article? Gene variants encoding proteins involved in respiratory chemoreception may play a role in a minority of SIDS cases. What does it add to the existing literature? Although impaired respiratory chemoreception has been suggested as an important risk factor for SIDS, genetic variants in single genes seem to play a minor role. What is the impact? This study supports previous findings, which indicate that genetic variants in single genes involved in respiratory control do not have a dominant role in SIDS.

Are Multiple Chemosensory Systems Accountable for COVID-19 Outcome?

Chemosensory systems (olfaction, taste, trigeminus nerve, solitary chemoreceptor cells, neuroendocrine pulmonary cells, and carotid body, etc.) detect molecules outside or inside our body and may share common molecular markers. In addition to the impairment of taste and olfaction, the detection of the internal chemical environment may also be incapacitated by COVID-19. If this is the case, different consequences can be expected. (1) In some patients, hypoxia does not trigger distressing dyspnea ("silent" hypoxia): Long-term follow-up may determine whether silent hypoxia is related to malfunctioning of carotid body chemoreceptors. Moreover, taste/olfaction and oxygen chemoreceptors may be hit simultaneously: Testing olfaction, taste, and oxygen chemoreceptor functions in the early stages of COVID-19 allows one to unravel their connections and trace the recovery path. (2) Solitary chemosensory cells are also involved in the regulation of the innate mucosal immune response: If these cells are affected in some COVID-19 patients, the mucosal innate immune response would be dysregulated, opening one up to massive infection, thus explaining why COVID-19 has lethal consequences in some patients. Similar to taste and olfaction, oxygen chemosensory function can be easily tested with a non-invasive procedure in humans, while functional tests for solitary chemosensory or pulmonary neuroendocrine cells are not available, and autoptic investigation is required to ascertain their involvement.

Enterochromaffin Cells: Sentinels to Gut Microbiota in Hyperalgesia?

In recent years, increasing studies have been conducted on the mechanism of gut microbiota in neuropsychiatric diseases and non-neuropsychiatric diseases. The academic community has also recognized the existence of the microbiota-gut-brain axis. Chronic pain has always been an urgent difficulty for human beings, which often causes anxiety, depression, and other mental symptoms, seriously affecting people's quality of life. Hyperalgesia is one of the main adverse reactions of chronic pain. The mechanism of gut microbiota in hyperalgesia has been extensively studied, providing a new target for pain treatment. Enterochromaffin cells, as the chief sentinel for sensing gut microbiota and its metabolites, can play an important role in the interaction between the gut microbiota and hyperalgesia through paracrine or neural pathways. Therefore, this systematic review describes the role of gut microbiota in the pathological mechanism of hyperalgesia, learns about the role of enterochromaffin cell receptors and secretions in hyperalgesia, and provides a new strategy for pain treatment by targeting enterochromaffin cells through restoring disturbed gut microbiota or supplementing probiotics.

Dermal Olfactory Receptor OR51B5 Is Essential for Survival and Collagen Synthesis in Human Dermal Fibroblast (Hs68 Cells)

Skin dermis comprises extracellular matrix components, mainly collagen fibers. A decrease in collagen synthesis caused by several factors, including ultraviolet (UV) irradiation and stress, eventually causes extrinsic skin aging. Olfactory receptors (ORs) were initially considered to be specifically expressed in nasal tissue, but several ORs have been reported to be present in other tissues, and their biological roles have recently received increasing attention. In this study, we aimed to characterize the role of ORs in cell survival and collagen synthesis in dermal fibroblasts. We confirmed that UVB irradiation and dexamethasone exposure significantly decreased cell survival and collagen synthesis in Hs68 dermal fibroblasts. Moreover, we demonstrated that the mRNA expression of 10 ORs detectable in Hs68 cells was significantly downregulated in aged conditions compared with that in normal conditions. Thereafter, by individual knockdown of the 10 candidate ORs, we identified that only OR51B5 knockdown leads to a reduction of cell survival and collagen synthesis. OR51B5 knockdown decreased cAMP levels and dampened the downstream protein kinase A/cAMP-response element binding protein pathway, downregulating the survival- and collagen synthesis-related genes in the dermal fibroblasts. Therefore, OR51B5 may be an interesting candidate that plays a role in cell survival and collagen synthesis.

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.

The Olfactory Receptor Gene Product, OR5H2, Modulates Endometrial Cancer Cells Proliferation via Interaction with the IGF1 Signaling Pathway

Endometrial cancer is the most common gynecologic malignancy in Western countries. The insulin-like growth factor-1 (IGF1) axis has an important role in endometrial cancer biology and emerged as a promising therapeutic target in oncology. However, there is an urgent need to identify biomarkers that may help in patient stratification and prognosis. Laron syndrome (LS) is a type of dwarfism that results from the mutation of the growth hormone receptor (GHR) gene, leading to congenital IGF1 deficiency. While high circulating IGF1 is regarded as a risk factor in cancer, epidemiological studies have shown that LS patients are protected from cancer development. Recent genome-wide profilings conducted on LS-derived lymphoblastoid cells led to the identification of a series of genes whose over- or under-representation in this condition might be mechanistically linked to cancer protection. The olfactory receptor 5 subfamily H member 2 (OR5H2) was the top downregulated gene in LS, its expression level being 5.8-fold lower than in the control cells. In addition to their typical role in the olfactory epithelium, olfactory receptors (ORs) are expressed in multiple tissues and play non-classical roles in various pathologies, including cancer. The aim of our study was to investigate the regulation of OR5H2 gene expression by IGF1 in endometrial cancer. Data showed that IGF1 and insulin stimulate OR5H2 mRNA and the protein levels in uterine cancer cell lines expressing either a wild-type or a mutant p53. OR5H2 silencing led to IGF1R downregulation, with ensuing reductions in the downstream cytoplasmic mediators. In addition, OR5H2 knockdown reduced the proliferation rate and cell cycle progression. Analyses of olfr196 (the mouse orthologue of OR5H2) mRNA expression in animal models of GHR deficiency or GH overexpression corroborated the human data. In summary, OR5H2 emerged as a novel target for positive regulation by IGF1, with potential relevance in endometrial cancer.

DNA Methylation and Blood Pressure Phenotypes: A Review of the Literature

Genetic studies of DNA have been unable to explain a significant portion of the variance of the estimated heritability of blood pressure (BP). Epigenetic mechanisms, particularly DNA methylation, have helped explain additional biological processes linked to BP phenotypes and diseases. Candidate gene methylation studies and genome-wide methylation studies of BP have highlighted impactful cytosine-phosphate-guanine (CpG) markers across different ethnicities. Furthermore, many of these BP-related CpG sites are also linked to metabolism-related phenotypes. Integrating epigenome-wide association study data with other layers of molecular data such as genotype data (from single nucleotide polymorphism arrays or sequencing), other epigenetic data, and/or transcriptome data can provide additional information about the significance and complexity of these relationships. Recent data suggest that epigenetic changes can be consequences rather than causes of BP variation. Finally, these data can give insight into downstream effects of long-standing high BP (due to target organ damage (TOD)). The current review provides a literature overview of epigenetic modifications in BP and TOD. Recent studies strongly support the importance of epigenetic modifications, such as DNA methylation, in BP and TOD for relevant biological insights, reliable biomarkers, and possible future therapeutics.

UV-Irradiation- and Inflammation-Induced Skin Barrier Dysfunction Is Associated with the Expression of Olfactory Receptor Genes in Human Keratinocytes

Olfactory receptors (ORs) have diverse physiological roles in various cell types, beyond their function as odorant sensors in the olfactory epithelium. These previous findings have suggested that ORs could be diagnostic markers and promising therapeutic targets in several pathological conditions. In the current study, we sought to characterize the changes in the expression of ORs in the HaCaT human keratinocytes cell line exposed to ultraviolet (UV) light or inflammation, well-recognized stimulus for skin barrier disruption. We confirmed that major olfactory signaling components, including ORs, GNAL, Ric8b, and adenylate cyclase type 3, are highly expressed in HaCaT cells. We have also demonstrated that the 12 ectopic ORs detectable in HaCaT cells are more highly expressed in UV-irradiated or inflamed conditions than in normal conditions. We further assessed the specific OR-mediated biological responses of HaCaT cells in the presence of known odorant ligands of ORs and observed that specific ligand-activated ORs downregulate skin barrier genes in HaCaT cells. This study shows the potential of OR as a marker for skin barrier abnormalities. Further research is needed to explore how OR is implicated in the development and progression of barrier dysfunction.

The mutational landscape of human olfactory G protein-coupled receptors

BACKGROUND

Olfactory receptors (ORs) constitute a large family of sensory proteins that enable us to recognize a wide range of chemical volatiles in the environment. By contrast to the extensive information about human olfactory thresholds for thousands of odorants, studies of the genetic influence on olfaction are limited to a few examples. To annotate on a broad scale the impact of mutations at the structural level, here we analyzed a compendium of 119,069 natural variants in human ORs collected from the public domain.

RESULTS

OR mutations were categorized depending on their genomic and protein contexts, as well as their frequency of occurrence in several human populations. Functional interpretation of the natural changes was estimated from the increasing knowledge of the structure and function of the G protein-coupled receptor (GPCR) family, to which ORs belong. Our analysis reveals an extraordinary diversity of natural variations in the olfactory gene repertoire between individuals and populations, with a significant number of changes occurring at the structurally conserved regions. A particular attention is paid to mutations in positions linked to the conserved GPCR activation mechanism that could imply phenotypic variation in the olfactory perception. An interactive web application (hORMdb, Human Olfactory Receptor Mutation Database) was developed for the management and visualization of this mutational dataset.

CONCLUSION

We performed topological annotations and population analysis of natural variants of human olfactory receptors and provide an interactive application to explore human OR mutation data. We envisage that the utility of this information will increase as the amount of available pharmacological data for these receptors grow. This effort, together with ongoing research in the study of genetic changes in other sensory receptors could shape an emerging sensegenomics field of knowledge, which should be considered by food and cosmetic consumer product manufacturers for the benefit of the general population.

Differences in taste and smell perception between type 2 diabetes mellitus patients and healthy controls

BACKGROUND AND AIMS

The senses of taste and smell are essential determinants of food choice, which in turn may contribute to the development of chronic diseases, including diabetes. Although past studies have evaluated the relationship between type 2 diabetes mellitus (DM2) and senses disorders, this relationship remains controversial. In this study, we evaluated taste and smell perception in DM2 patients and healthy controls (HC). Moreover, we analyzed the association of chemosensory impairments with anthropometric and clinical outcomes (e.g. Body Mass Index (BMI), Fasting blood glucose (FBG), drugs, cardiovascular diseases (CVD), and hypertension) in DM2 patients.

METHODS AND RESULTS

The study included 94 DM2 patients and 244 HC. Taste recognition for 6-n-propylthiouracil (PROP), quinine, citric acid, sucrose, and sodium chloride (NaCl) compounds was assessed using a filter paper method, while smell recognition of 12 odorants was performed using a Sniffin' sticks test. We found that a higher percentage of DM2 patients showed identification impairment in salt taste (22% vs. 5%, p-value<0.0009) and smell recognition (55% vs. 27%, p-value = 0.03) compared to HC. We also observed that 65% of hypertensive DM2 subjects presented smell identification impairment compared to 18% of non-hypertensive patients (p-value = 0.019). Finally, patients with impairments in both taste and smell showed elevated FBG compared to patients without impairment (149.6 vs.124.3 mg/dL, p-value = 0.04).

CONCLUSION

The prevalence of taste and smell identification impairments was higher in DM2 patients compared to HC, and a possible relationship with glycemic levels emerged.

Alterations of 5-hydroxymethylcytosines in circulating cell-free DNA reflect retinopathy in type 2 diabetes

Diabetic retinopathy (DR) is a common microvascular complication that may cause severe visual impairment and blindness in patients with type 2 diabetes mellitus (T2DM). Early detection of DR will expand the range of potential treatment options and enable better control of disease progression. Epigenetic dysregulation has been implicated in the pathogenesis of microvascular complications in patients with T2DM. We sought to explore the diagnostic value of 5-hydroxymethylcytosines (5hmC) in circulating cell-free DNA (cfDNA) for DR, taking advantage of a highly sensitive technique, the 5hmC-Seal. The genome-wide 5hmC profiles in cfDNA samples from 35 patients diagnosed with DR and 35 age-, gender-, diabetic duration-matched T2DM controls were obtained using the 5hmC-Seal, followed by a case-control analysis and external validation. The genomic distribution of 5hmC in cfDNA from patients with DR reflected potential gene regulatory relevance, showing co-localization with histone modification marks for active expression (e.g., H3K4me1). A three-gene signature (MESP1, LY6G6D, LINC01556) associated with DR was detected using the elastic net regularization on the multivariable logistic regression model, showing high accuracy to distinguish patients with DR from T2DM controls (AUC [area under curve] = 91.4%; 95% CI [confidence interval], 84.3- 98.5%), achieving a sensitivity of 88.6% and a specificity of 91.4%. In an external testing set, the 5hmC model detected 5 out of 6 DR patients and predicted 7 out of 8 non-DR patients with other microvascular complications. Circulating cfDNA from patients with DR contained 5hmC information that could be exploited for DR detection. As a novel non-invasive approach, the 5hmC-Seal holds the promise to be an integrated part of patient care and surveillance tool for T2DM patients.

Copy number variant analysis and expression profiling of the olfactory receptor-rich 11q11 region in obesity predisposition

Genome-wide copy number surveys associated chromosome 11q11 with obesity. As this is an olfactory receptor-rich region, we hypothesize that genetic variation in olfactory receptor genes might be implicated in the pathogenesis of obesity. Multiplex Amplicon Quantification analysis was applied to screen for copy number variants at chromosome 11q11 in 627 patients with obesity and 330 healthy-weight individuals. A ± 80 kb deletion with an internally 1.3 kb retained segment was identified, covering the three olfactory receptor genes OR4C11, OR4P4, and OR4S2. A significant increase in copy number loss(es) was perceived in our patient cohort (MAF = 27%; p = 0.02). Gene expression profiling in metabolic relevant tissues was performed to evaluate the functional impact of the obesity susceptible locus. All three 11q11 genes were present in visceral and subcutaneous adipose tissue while no expression was perceived in the liver. These results support the 'metabolic system' hypothesis and imply that gene disruption of OR4C11, OR4P4, and OR4S2 will negatively influence energy metabolism, ultimately leading to fat accumulation and obesity. Our study thus demonstrates a role for structural variation within olfactory receptor-rich regions in complex diseases and defines the 11q11 deletion as a risk factor for obesity.

COVID-19-Related Anosmia: The Olfactory Pathway Hypothesis and Early Intervention

Anosmia is a well-described symptom of Corona Virus Disease 2019 (COVID-19). Several respiratory viruses are able to cause post-viral olfactory dysfunction, suggesting a sensorineural damage. Since the olfactory bulb is considered an immunological organ contributing to prevent the invasion of viruses, it could have a role in host defense. The inflammatory products locally released in COVID-19, leading to a local damage and causing olfactory loss, simultaneously may interfere with the viral spread into the central nervous system. In this context, olfactory receptors could play a role as an alternative way of SARS-CoV-2 entry into cells locally, in the central nervous system, and systemically. Differences in olfactory bulb due to sex and age may contribute to clarify the different susceptibility to infection and understand the role of age in transmission and disease severity. Finally, evaluation of the degree of functional impairment (grading), central/peripheral anosmia (localization), and the temporal course (evolution) may be useful tools to counteract COVID-19.

Associations between high blood pressure and DNA methylation

Background

High blood pressure is a major risk factor for cardiovascular disease and is influenced by both environmental and genetic factors. Epigenetic processes including DNA methylation potentially mediate the relationship between genetic factors, the environment and cardiovascular disease. Despite an increased risk of hypertension and cardiovascular disease in individuals of South Asians compared to Europeans, it is not clear whether associations between blood pressure and DNA methylation differ between these groups.

Methods

We performed an epigenome-wide association study and differentially methylated region (DMR) analysis to identify DNA methylation sites and regions that were associated with systolic blood pressure, diastolic blood pressure and hypertension. We analyzed samples from 364 European and 348 South Asian men (first generation migrants to the UK) from the Southall And Brent REvisited cohort, measuring DNA methylation from blood using the Illumina Infinium^® HumanMethylation450 BeadChip.

Results

One CpG site was found to be associated with DBP in trans-ancestry analyses (i.e. both ethnic groups combined), while in Europeans alone seven CpG sites were associated with DBP. No associations were identified between DNA methylation and either SBP or hypertension. Comparison of effect sizes between South Asian and European EWAS for DBP, SBP and hypertension revealed little concordance between analyses. DMR analysis identified several regions with known relationships with CVD and its risk factors.

Conclusion

This study identified differentially methylated sites and regions associated with blood pressure and revealed ethnic differences in these associations. These findings may point to molecular pathways which may explain the elevated cardiovascular disease risk experienced by those of South Asian ancestry when compared to Europeans.

Beta-caryophyllene enhances wound healing through multiple routes

Beta-caryophyllene is an odoriferous bicyclic sesquiterpene found in various herbs and spices. Recently, it was found that beta-caryophyllene is a ligand of the cannabinoid receptor 2 (CB2). Activation of CB2 will decrease pain, a major signal for inflammatory responses. We hypothesized that beta-caryophyllene can affect wound healing by decreasing inflammation. Here we show that cutaneous wounds of mice treated with beta-caryophyllene had enhanced re-epithelialization. The treated tissue showed increased cell proliferation and cells treated with beta-caryophyllene showed enhanced cell migration, suggesting that the higher re-epithelialization is due to enhanced cell proliferation and cell migration. The treated tissues also had up-regulated gene expression for hair follicle bulge stem cells. Olfactory receptors were not involved in the enhanced wound healing. Transient Receptor Potential channel genes were up-regulated in the injured skin exposed to beta-caryophyllene. Interestingly, there were sex differences in the impact of beta- caryophyllene as only the injured skin of female mice had enhanced re-epithelialization after exposure to beta-caryophyllene. Our study suggests that chemical compounds included in essential oils have the capability to improve wound healing, an effect generated by synergetic impacts of multiple pathways.

Genome Wide Meta-Analysis identifies common genetic signatures shared by heart function and Alzheimer's disease

Echocardiography has become an indispensable tool for the study of heart performance, improving the monitoring of individuals with cardiac diseases. Diverse genetic factors associated with echocardiographic measures have been previously reported. The impact of several apoptotic genes in heart development identified in experimental models prompted us to assess their potential association with human cardiac function. This study aimed at investigating the possible association of variants of apoptotic genes with echocardiographic traits and to identify new genetic markers associated with cardiac function. Genome wide data from different studies were obtained from public repositories. After quality control and imputation, a meta-analysis of individual association study results was performed. Our results confirmed the role of caspases and other apoptosis related genes with cardiac phenotypes. Moreover, enrichment analysis showed an over-representation of genes, including some apoptotic regulators, associated with Alzheimer's disease. We further explored this unexpected observation which was confirmed by genetic correlation analyses. Our findings show the association of apoptotic gene variants with echocardiographic indicators of heart function and reveal a novel potential genetic link between echocardiographic measures in healthy populations and cognitive decline later on in life. These findings may have important implications for preventative strategies combating Alzheimer's disease.

Transcriptional profiling identifies strain-specific effects of caloric restriction and opposite responses in human and mouse white adipose tissue

Caloric restriction (CR) has been extensively studied in rodents as an intervention to improve lifespan and healthspan. However, effects of CR can be strain- and species-specific. This study used publically available microarray data to analyze expression responses to CR in males from 7 mouse strains (C57BL/6J, BALB/c, C3H, 129, CBA, DBA, B6C3F1) and 4 tissues (epididymal white adipose tissue (eWAT), muscle, heart, cortex). In each tissue, the largest number of strain-specific CR responses was identified with respect to the C57BL/6 strain. In heart and cortex, CR responses in C57BL/6 mice were negatively correlated with responses in other strains. Strain-specific CR responses involved genes associated with olfactory receptors (Olfr1184, Olfr910) and insulin/IGF-1 signaling (Igf1, Irs2). In each strain, CR responses in eWAT were negatively correlated with those in human subcutaneous WAT (scWAT). In human scWAT, CR increased expression of genes associated with stem cell maintenance and vascularization. However, orthologous genes linked to these processes were down-regulated in mouse. These results identify strain-specific CR responses limiting generalization across mouse strains. Differential CR responses in mouse versus human WAT may be due to differences in the depots examined and/or the presence of “thrifty genes” in humans that resist adipose breakdown despite caloric deficit.

Mammalian Taste Cells Express Functional Olfactory Receptors

The peripheral taste and olfactory systems in mammals are separate and independent sensory systems. In the current model of chemosensation, gustatory, and olfactory receptors are genetically divergent families expressed in anatomically distinct locations that project to disparate downstream targets. Although information from the 2 sensory systems merges to form the perception of flavor, the first cross talk is thought to occur centrally, in the insular cortex. Recent studies have shown that gustatory and olfactory receptors are expressed throughout the body and serve as chemical sensors in multiple tissues. Olfactory receptor cDNA has been detected in the tongue, yet the presence of physiologically functional olfactory receptors in taste cells has not yet been demonstrated. Here we report that olfactory receptors are functionally expressed in taste papillae. We found expression of olfactory receptors in the taste papillae of green fluorescent protein-expressing transgenic mice and, using immunocytochemistry and real-time quantitative polymerase chain reaction experiments, the presence of olfactory signal transduction molecules and olfactory receptors in cultured human fungiform taste papilla (HBO) cells. Both HBO cells and mouse taste papilla cells responded to odorants. Knockdown of adenylyl cyclase mRNA by specific small inhibitory RNA and pharmacological block of adenylyl cyclase eliminated these responses, leading us to hypothesize that the gustatory system may receive olfactory information in the periphery. These results provide the first direct evidence of the presence of functional olfactory receptors in mammalian taste cells. Our results also demonstrate that the initial integration of gustatory and olfactory information may occur as early as the taste receptor cells.

Characterizing novel olfactory receptors expressed in the murine renal cortex

The kidney uses specialized G protein-coupled receptors, including olfactory receptors (ORs), to act as sensors of molecules and metabolites. In the present study, we cloned and studied seven renal ORs, which we previously found to be expressed in the murine renal cortex. As most ORs are orphan receptors, our goal was to identify ligands for these ORs in the hope that this will guide future research into their functional roles. We identified novel ligands for two ORs: Olfr558 and Olfr90. For Olfr558, we confirmed activation by previously reported ligands and identified 16 additional carboxylic acids that activated this OR. The strongest activation of Olfr558 was produced by butyric, cyclobutanecarboxylic, isovaleric, 2-methylvaleric, 3-methylvaleric, 4-methylvaleric, and valeric acids. The primary in vivo source of both butyric and isovaleric acids is gut microbial metabolism. We also identified 14 novel ligands that activated Olfr90, the strongest of which were 2-methyl-4-propyl-1,3-oxathiane, 1-octen-3-ol, 2-octanol, and 3-octanol. Interestingly, 8 of these 14 ligands are of fungal origin. We also investigated the tissue distribution of these receptors and found that they are each found in a subset of "nonsensory" tissues. Finally, we examined the putative human orthologs of Olfr558 and Olfr90 and found that the human ortholog of Olfr558 (OR51E1) has a similar ligand profile, indicating that the role of this OR is likely evolutionarily conserved. In summary, we examined seven novel renal ORs and identified new ligands for Olfr558 and Olfr90, which imply that both of these receptors serve to detect metabolites produced by microorganisms.

Beyond the Flavour: The Potential Druggability of Chemosensory G Protein-Coupled Receptors

G protein-coupled receptors (GPCRs) belong to the largest class of drug targets. Approximately half of the members of the human GPCR superfamily are chemosensory receptors, including odorant receptors (ORs), trace amine-associated receptors (TAARs), bitter taste receptors (TAS2Rs), sweet and umami taste receptors (TAS1Rs). Interestingly, these chemosensory GPCRs (csGPCRs) are expressed in several tissues of the body where they are supposed to play a role in biological functions other than chemosensation. Despite their abundance and physiological/pathological relevance, the druggability of csGPCRs has been suggested but not fully characterized. Here, we aim to explore the potential of targeting csGPCRs to treat diseases by reviewing the current knowledge of csGPCRs expressed throughout the body and by analysing the chemical space and the drug-likeness of flavour molecules.

Expression and function of the ectopic olfactory receptor OR10G7 in patients with atopic dermatitis

BACKGROUND

Ectopic olfactory receptors (ORs) are found in the skin, but their expression and biological function in normal skin and skin form patients with atopic dermatitis (AD) are unknown.

OBJECTIVES

We sought to characterize the expression of ORs in the skin and assess OR-mediated biological responses of primary human keratinocytes in the presence of odorant ligands.

METHODS

OR expression was examined by using whole-transcriptome sequencing of skin tape strips collected from patients with AD and healthy control (HC) subjects. OR10G7 and filaggrin 1 (FLG-1) expression was analyzed by using RT-PCR and immunostaining in skin biopsy specimens and primary human keratinocytes from patients with AD and HC subjects. ATP and cyclic AMP production by control and OR10G7 small interfering RNA-transfected keratinocytes in response to odorant stimulation with acetophenone and eugenol was assessed.

RESULTS

A total of 381 OR gene transcripts were detected in the skin samples, with the greatest OR expression detected in the skin tape strips corresponding to the upper granular layer of the skin. OR10G7 expression was significantly increased in skin biopsy specimens from patients with AD compared with those from HC subjects (P = .01) and inversely correlated with FLG-1 expression (P = .009). OR10G7 expression was greatest in undifferentiated keratinocytes from patients with AD and was downregulated with progressive differentiation. Primary human keratinocytes produced ATP, an essential neurotransmitter in sensory pathways, in response to acetophenone and eugenol, odorants previously identified as potential ligands for this receptor. This response was abolished in OR10G7 small interfering RNA-transfected keratinocytes.

CONCLUSIONS

OR10G7 is expressed at significantly greater levels in undifferentiated keratinocytes from patients with AD compared with HC subjects. OR10G7 is likely involved in transmission of skin-induced chemosensory responses to odorant stimulation, which might modulate differential nociceptive responses in AD skin.

Gene expression profiling in adipose tissue of Sprague Dawley rats identifies olfactory receptor 984 as a potential obesity treatment target

The aim of the study was to identify and functionally characterize novel candidate gene/s involved in the development of resistance to diet-induced obesity in rats. In a high-fat-diet (HFD) study of rats, we found subgroups which either developed resistance to HFD-induced obesity (DR) or showed an obesity-prone phenotype (DIO). Gene expression analysis in 10 samples (5 DIO vs 5 DR) was performed. The most promising gene, OR6C3 (orthologous with rat Olr984 and mouse Olfr788) was measured by qRT-PCR in paired samples of human visceral (Vis) and subcutaneous (SC) adipose tissue (AT) (n = 225) and in sub-fractions of adipocytes and cells of stromal vascular fraction. Gene expression analyses showed Olr984 with significantly reduced mRNA expression in DR rats. In the Vis AT of human samples we found an up-regulation of OR6C3 compared to SC AT, independent of gender, glucose tolerance or type 2 diabetes. We observed significantly lower levels of SC AT OR6C3 mRNA in subjects with obesity compared to those with normal-weight or overweight. OR6C3 is more expressed in SVF than in adipocytes. Olr984 could be a novel candidate gene related to diet-induced obesity in rats. Variation in human AT mRNA expression is related to obesity parameters and glucose homeostasis and linked to the regulatory role of insulin on the Olr984.

The essence of appetite: does olfactory receptor variation play a role?

Olfactory receptors are G-protein-coupled chemoreceptors expressed on millions of olfactory sensory neurons within the nasal cavity. These receptors detect environmental odorants and signal the brain regarding the location of feed, potential mates, and the presence of possible threats (e.g., predators or chemical toxins). Olfactory receptors also are present in organs outside of the nasal cavity where they bind to molecules such as nutrients and metabolites from the animal's internal environment to elicit physiological responses, including changes in gut motility, ventilation rate, and cellular migration. Recent evidence supports an additional role of olfactory receptors in the regulation of appetite in humans and rodents. In particular, genetic variation among individuals in specific odorant receptor genes has been linked to differences in their feeding behaviors, food choices, and the regulation of energy balance. This review provides a general overview of the olfactory receptors of vertebrates and their genetic variability and provides supporting evidence for a physiological role of olfactory receptors in appetite regulation of livestock. Basic research on olfactory receptors of livestock and their ligands should facilitate the development of novel odorant receptor agonists and identification of specific olfactory receptor variants that may be developed to enhance animal production efficiency.

Clonal Heterogeneity Reflected by PI3K-AKT-mTOR Signaling in Human Acute Myeloid Leukemia Cells and Its Association with Adverse Prognosis

Clonal heterogeneity detected by karyotyping is a biomarker associated with adverse prognosis in acute myeloid leukemia (AML). Constitutive activation of the phosphatidylinositol-3-kinase-Akt-mechanistic target of rapamycin (PI3K-Akt-mTOR) pathway is present in AML cells, and this pathway integrates signaling from several upstream receptors/mediators. We suggest that this pathway reflects biologically important clonal heterogeneity. We investigated constitutive PI3K-Akt-mTOR pathway activation in primary human AML cells derived from 114 patients, together with 18 pathway mediators. The cohort included patients with normal karyotype or single karyotype abnormalities and with an expected heterogeneity of molecular genetic abnormalities. Clonal heterogeneity reflected as pathway mediator heterogeneity was detected for 49 patients. Global gene expression profiles of AML cell populations with and without clonal heterogeneity differed with regard to expression of ectopic olfactory receptors (a subset of G-protein coupled receptors) and proteins involved in G-protein coupled receptor signaling. Finally, the presence of clonal heterogeneity was associated with adverse prognosis for patients receiving intensive antileukemic treatment. The clonal heterogeneity as reflected in the activation status of selected mediators in the PI3K-Akt-mTOR pathway was associated with a different gene expression profile and had an independent prognostic impact. Biological heterogeneity reflected in the intracellular signaling status should be further investigated as a prognostic biomarker in human AML.

Liver clear cell foci and viral infection are associated with non-cirrhotic, non-fibrolamellar hepatocellular carcinoma in young patients from South America

We previously described a divergent clinical and molecular presentation of hepatocellular carcinoma (HCC) in Peru. The present study aimed to further characterize the tissue features associated with this singular nosological form of HCC in order to gain insight into the natural history of the disease. We performed an exploratory analysis of the histology of both tumor and non-tumor liver (NTL) tissues from 50 Peruvian HCC patients, and compared with that of 75 individuals with non-HCC liver tumor or benign liver lesions as a baseline for NTL features. We complemented this approach with a transcriptome analysis in a subset of NTL tissue samples and also performed an ultra-sensitive hepatitis B virus (HBV) detection in liver tissues of the patients. Overall, results highlighted the low rate of liver parenchymal alterations in a young patient cohort (median age: 40 years old), despite a strong prevalence of underlying HBV infection (c. 67%). Withal, liver clear cell foci of cellular alteration were genuinely associated with HCC and appended to some changes in immune and G protein-coupled receptor gene expression ontologies. Our findings confirm the occurrence of a particular setting of HCC in South America, a region where the pathophysiology of liver cancer remains largely unexplored.

Olfactory Receptors as Biomarkers in Human Breast Carcinoma Tissues

Olfactory receptors (ORs) are known to be expressed in a variety of human tissues and act on different physiological processes, such as cell migration, proliferation, or secretion and have been found to function as biomarkers for carcinoma tissues of prostate, lung, and small intestine. In this study, we analyzed the OR expression profiles of several different carcinoma tissues, with a focus on breast cancer. The expression of OR2B6 was detectable in breast carcinoma tissues; here, transcripts of OR2B6 were detected in 73% of all breast carcinoma cell lines and in over 80% of all of the breast carcinoma tissues analyzed. Interestingly, there was no expression of OR2B6 observed in healthy tissues. Immunohistochemical staining of OR2B6 in breast carcinoma tissues revealed a distinct staining pattern of carcinoma cells. Furthermore, we detected a fusion transcript containing part of the coding exon of OR2B6 as a part of a splice variant of the histone HIST1H2BO transcript. In addition, in cancer tissues and cell lines derived from lung, pancreas, and brain, OR expression patterns were compared to that of corresponding healthy tissues. The number of ORs detected in lung carcinoma tissues was significantly reduced in comparison to the surrounding healthy tissues. In pancreatic carcinoma tissues, OR4C6 was considerably more highly expressed in comparison to the respective healthy tissues. We detected OR2B6 as a potential biomarker for breast carcinoma tissues.