Nasal oxidative stress mediating the effects of colder temperature exposure on pediatric asthma symptoms.

BACKGROUND: Colder temperature exposure is a known trigger for pediatric asthma exacerbation. The induction of oxidative stress is a known pathophysiologic pathway for asthma exacerbation. However, the role of oxidative stress in linking colder temperature exposure and worsened pediatric asthma symptoms is poorly understood. METHODS: In a panel study involving 43 children with asthma, aged 5-13 years old, each child was visited 4 times with a 2-week interval. At each visit, nasal fluid, urine, and saliva samples were obtained and measured for biomarkers of oxidative stress in the nasal cavity (nasal malondialdehyde [MDA]), the circulatory system (urinary MDA), and the oral cavity (salivary MDA). Childhood Asthma-Control Test (CACT) was used to assess asthma symptoms. RESULTS: When ambient daily-average temperature ranged from 7 to 18 °C, a 2 °C decrement in personal temperature exposures were significantly associated with higher nasal MDA and urinary MDA concentrations by 47-77% and 6-14%, respectively. We estimated that, of the decrease in child-reported CACT scores (indicating worsened asthma symptoms and asthma control) associated with colder temperature exposure, 14-57% were mediated by nasal MDA. CONCLUSION: These results suggest a plausible pathway that colder temperature exposure worsens pediatric asthma symptoms partly via inducing nasal oxidative stress. IMPACT: The role of oxidative stress in linking colder temperature exposure and worsened asthma symptoms is still poorly understood. Lower temperature exposure in a colder season was associated with higher nasal and systemic oxidative stress in children with asthma. Nasal MDA, a biomarker of nasal oxidative stress, mediated the associations between colder temperature exposures and pediatric asthma symptoms. The results firstly suggest a plausible pathway that colder temperature exposure worsens pediatric asthma symptoms partly via inducing oxidative stress in the nasal cavity.

Enhanced Stability and Solidification of Volatile Eugenol by Cyclodextrin-Metal Organic Framework for Nasal Powder Delivery.

Eugenol (Eug) holds potential as a treatment for bacterial rhinosinusitis by nasal powder drug delivery. To stabilization and solidification of volatile Eug, herein, nasal inhalable γ-cyclodextrin metal-organic framework (γ-CD-MOF) was investigated as a carrier by gas-solid adsorption method. The results showed that the particle size of Eug loaded by γ-CD-MOF (Eug@γ-CD-MOF) distributed in the range of 10-150 µm well. In comparison to γ-CD and ß-CD-MOF, γ-CD-MOF has higher thermal stability to Eug. And the intermolecular interactions between Eug and the carriers were verified by characterizations and molecular docking. Based on the bionic human nasal cavity model, Eug@γ-CD-MOF had a high deposition distribution (90.07 ± 1.58%). Compared with free Eug, the retention time Eug@γ-CD-MOF in the nasal cavity was prolonged from 5 min to 60 min. In addition, the cell viability showed that Eug@γ-CD-MOF (Eug content range 3.125-200 µg/mL) was non-cytotoxic. And the encapsulation of γ-CD-MOF could not reduce the bacteriostatic effect of Eug. Therefore, the biocompatible γ-CD-MOF could be a potential and valuable carrier for nasal drug delivery to realize solidification and nasal therapeutic effects of volatile oils.

The Effect of Surgical Procedure in the Nasal Cavity on the Passive Avoidance Conditioning and the Hypothalamic Level of Monoamines in Rats.

A rat biological model of septoplasty was used to study the effect of surgery on passive avoidance conditioning (PAC). Septoplasty was shown to increase anxiety and to reduce exploratory activity in rodents during PAC. A neurochemical analysis of the hypothalamus was carried out immediately after the end of the experiment and showed an increase in norepinephrine (NE) metabolism after septoplasty. The finding was tentatively associated with activation of the hypothalamic-pituitary-adrenal axis.

Molecular Evidence for Olfactory Neuroblastoma as a Tumor of Malignant Globose Basal Cells.

Olfactory neuroblastoma (ONB, esthesioneuroblastoma) is a sinonasal cancer with an underdeveloped diagnostic toolkit, and is the subject of many incidents of tumor misclassification throughout the literature. Despite its name, connections between the cancer and normal cells of the olfactory epithelium have not been systematically explored and markers of olfactory epithelial cell types are not deployed in clinical practice. Here, we utilize an integrated human-mouse single-cell atlas of the nasal mucosa, including the olfactory epithelium, to identify transcriptomic programs that link ONB to a specific population of stem/progenitor cells known as olfactory epithelial globose basal cells (GBCs). Expression of a GBC transcription factor NEUROD1 distinguishes both low- and high-grade ONB from sinonasal undifferentiated carcinoma, a potential histologic mimic with a distinctly unfavorable prognosis. Furthermore, we identify a reproducible subpopulation of highly proliferative ONB cells expressing the GBC stemness marker EZH2, suggesting that EZH2 inhibition may play a role in the targeted treatment of ONB. Finally, we study the cellular states comprising ONB parenchyma using single-cell transcriptomics and identify evidence of a conserved GBC transcriptional regulatory circuit that governs divergent neuronal-versus-sustentacular differentiation. These results link ONB to a specific cell type for the first time and identify conserved developmental pathways within ONB that inform diagnostic, prognostic, and mechanistic investigation.

Prognostic significance of PD-1, CTLA-4, CD4, and CD8 expression in olfactory neuroblastoma.

There are limited data regarding immune surveillance mechanisms in olfactory neuroblastoma. We investigated the expression of programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), CD4, and CD8 in olfactory neuroblastoma to identify potential therapeutic targets. Immunohistochemistry was used to detect PD-1 and CTLA-4 and measure the numbers of CD4+ and CD8+ T cells in 56 patients with olfactory neuroblastoma. The relationships between these molecules in tumor microenvironment, clinicopathological features, and survival were analyzed. The prevalence of PD-1 in Kadish C stage was 24.14%, significantly greater than in Kadish A and B stage. CD4+ T-cell and CD8+ T-cell levels correlated with higher Hyams histological grade and Kadish stage. In addition, PD-1 was related positively with CTLA-4, CD4+ T cells, and CD8+ T cells in olfactory neuroblastoma. Univariate survival analysis showed that higher PD-1 positivity, CD8+ T cells, and Hyams grade correlated with worse clinical outcome. Multivariate analysis showed that the expression of PD-1 was an independent parameter for poor prognosis. In conclusion, olfactory neuroblastoma with PD-1 expression had more aggressive clinicopathological features and worse prognosis. PD-1 may potentially predict the outcome of olfactory neuroblastoma patients.

A systems genomics approach uncovers molecular associates of RSV severity.

Respiratory syncytial virus (RSV) infection results in millions of hospitalizations and thousands of deaths each year. Variations in the adaptive and innate immune response appear to be associated with RSV severity. To investigate the host response to RSV infection in infants, we performed a systems-level study of RSV pathophysiology, incorporating high-throughput measurements of the peripheral innate and adaptive immune systems and the airway epithelium and microbiota. We implemented a novel multi-omic data integration method based on multilayered principal component analysis, penalized regression, and feature weight back-propagation, which enabled us to identify cellular pathways associated with RSV severity. In both airway and immune cells, we found an association between RSV severity and activation of pathways controlling Th17 and acute phase response signaling, as well as inhibition of B cell receptor signaling. Dysregulation of both the humoral and mucosal response to RSV may play a critical role in determining illness severity.

The prognostic value of S-100 protein and Ki-67 index in olfactory neuroblastoma.

OBJECTIVE: To evaluate the prognostic value of S-100 protein and Ki-67 labeling index in olfactory neuroblastomas. METHODS: A retrospective study was conducted on a cohort of 85 patients with olfactory neuroblastomas. The immunohistochemical expression of S-100 and Ki-67 was assessed, and the predictive value of S-100 and Ki-67 was further evaluated. The optimal cutoff value of Ki-67 labeling index was determined using time-dependent receiver operating characteristic curve analysis. Overall survival and progression-free survival were assessed using the Kaplan-Meier method. RESULTS: A cut-off Ki-67 labeling index value of 67.5% was determined for prognosis in patients with olfactory neuroblastomas. There was a significant correlation between Ki-67 expression and cervical lymph node metastasis (P = 0.049). Compared with S-100 (+), S-100 (-) was associated with a higher rate of lymph node metastasis and a higher level of Ki-67 (P = 0.007, < 0.001, respectively), as well as an advanced Kadish stage (P = 0.037). Survival analyses showed that patients with S-100 (+) had better 5-year overall survival than those with S-100 (-) (P = 0.028), and patients with both S-100 (+) and Ki-67 (<67.5%) had superior 5-year overall survival compared with all the other patients (P = 0.0225). CONCLUSION: Our findings suggest that S-100 combined with Ki-67 labeling index are reliable prognostic factors in patients with olfactory neuroblastomas.

Prognostic value of microvessel density and its correlation with clinicopathological features in human olfactory neuroblastoma.

Although angiogenesis plays an important role in tumor growth and invasion, its role in the progression of olfactory neuroblastoma (ONB) has rarely been published. The aim of the present research was to analyze the prognostic role of microvessel density (MVD) in ONB and its association with clinicopathological parameters. 70 ONB cases were assessed for immunohistochemical expression of CD31, CD34, CD105, VEGF, and VEGFR2. The expression of CD105-MVD was negatively associated with histological grade and tumor Kadish stage, and its expression was positively correlated with the expression of VEGF/VEGFR2. Low expression of CD105-MVD and high tumor histological grade were strongly associated with poor survival. Thus, CD105-MVD was demonstrated to be a valuable independent prognostic indicator for ONB. MVD is expected to be useful as an important marker to distinguish tumor histological grade.

[IgG4-related disease in nasal cavity and paranasal sinuses: a clinicopathological analysis of ten cases].

Objective: To study clinicopathological features and differential diagnosis of IgG4-related diseases (IgG4-RD) in nasal cavity and paranasal sinuses. Methods: A retrospective analysis was performed in patients presenting initially with rhinosinusitis or a nasal mass, who also underwent nasal mucosa biopsy in Beijing Tongren Hospital Affiliated to Capital Medical University, from March 2016 to March 2021. According to the latest international classification diagnostic criteria of IgG4-RD published by the American Society of Rheumatology (ACR)/European Association for Rheumatology (EULAR) in 2019, 10 cases of nasal cavity and paranasal sinuses IgG4-RD were diagnosed and included in the study. The clinical features, histopathology and immunohistochemical expression of IgG and IgG4 were analyzed. Results: Among the 10 patients, five patients were male and five female. The age ranged from 30 to 71 years (median 52.7 years). Nasal polyp/nasal masses were seen in six cases, and lacrimal gland swelling was found in four cases. The serum IgG and IgG4 level was increased in four cases. Microscopically, all 10 cases showed intense lymphoplasmocytic infiltration and varying degrees of fibrosis in nasal or sinus mucosa, while four cases showed occlusive vasculitis. The number of IgG4 positive plasma cells in nasal mucosa was more than 10/high power field (HPF), with a mean of 67/HPF. The number of IgG4 positive plasma cells in the cases with severe fibrosis was significantly lower than in those without. The ratio of IgG4+/IgG+plasma cells was higher than 40% in six cases. Conclusions: IgG4-RD in nasal cavity and paranasal sinuses is a local manifestation of a systemic disease, while nasal cavity and paranasal sinuses are rarely involved by IgG4-RD. The diagnosis is based on clinical symptoms, imaging, IgG4-related serology and histopathologic scores. Histopathology has a core diagnostic value. IgG4 serology and imaging have important diagnostic values in the cases without biopsy.

Tropism of SARS-CoV-2, SARS-CoV, and Influenza Virus in Canine Tissue Explants.

BACKGROUND: Human spillovers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to dogs and the emergence of a highly contagious avian-origin H3N2 canine influenza virus have raised concerns on the role of dogs in the spread of SARS-CoV-2 and their susceptibility to existing human and avian influenza viruses, which might result in further reassortment. METHODS: We systematically studied the replication kinetics of SARS-CoV-2, SARS-CoV, influenza A viruses of H1, H3, H5, H7, and H9 subtypes, and influenza B viruses of Yamagata-like and Victoria-like lineages in ex vivo canine nasal cavity, soft palate, trachea, and lung tissue explant cultures and examined ACE2 and sialic acid (SA) receptor distribution in these tissues. RESULTS: There was limited productive replication of SARS-CoV-2 in canine nasal cavity and SARS-CoV in canine nasal cavity, soft palate, and lung, with unexpectedly high ACE2 levels in canine nasal cavity and soft palate. Canine tissues were susceptible to a wide range of human and avian influenza viruses, which matched with the abundance of both human and avian SA receptors. CONCLUSIONS: Existence of suitable receptors and tropism for the same tissue foster virus adaptation and reassortment. Continuous surveillance in dog populations should be conducted given the many chances for spillover during outbreaks.

Morphology of GNAT3-immunoreactive chemosensory cells in the nasal cavity and pharynx of the rat.

Solitary chemosensory cells and chemosensory cell clusters are distributed in the pharynx and larynx. In the present study, the morphology and reflexogenic function of solitary chemosensory cells and chemosensory cell clusters in the nasal cavity and pharynx were examined using immunofluorescence for GNAT3 and electrophysiology. In the nasal cavity, GNAT3-immunoreactive solitary chemosensory cells were widely distributed in the nasal mucosa, particularly in the cranial region near the nostrils. Solitary chemosensory cells were also observed in the nasopharynx. Solitary chemosensory cells in the nasopharyngeal cavity were barrel like or slender in shape with long lateral processes within the epithelial layer to attach surrounding ciliated epithelial cells. Chemosensory cell clusters containing GNAT3-immunoreactive cells were also detected in the pharynx. GNAT3-immunoreactive cells gathered with SNAP25-immunoreactive cells in chemosensory clusters. GNAT3-immunoreactive chemosensory cells were in close contact with a few SP- or CGRP-immunoreactive nerve endings. In the pharynx, GNAT3-immunoreactive chemosensory cells were also attached to P2X3-immunoreactive nerve endings. Physiologically, the perfusion of 10 mM quinine hydrochloride (QHCl) solution induced ventilatory depression. The QHCl-induced reflex was diminished by bilateral section of the glossopharyngeal nerve, suggesting autonomic reflex were evoked by chemosensory cells in pharynx but not in nasal mucosa. The present results indicate that complex shape of nasopharyngeal solitary chemosensory cells may contribute to intercellular communication, and pharyngeal chemosensory cells may play a role in respiratory depression.

Olfactory Deprivation and Enrichment: An Identity of Opposites?

The effects of deprivation and enrichment on the electroolfactogram of mice were studied through the paradigms of unilateral naris occlusion and odor induction, respectively. Deprivation was shown to cause an increase in electroolfactogram amplitudes after 7 days. We also show that unilateral naris occlusion is not detrimental to the gross anatomical appearance or electroolfactogram of either the ipsilateral or contralateral olfactory epithelium even after year-long survival periods, consistent with our previous assumptions. Turning to induction, the increase in olfactory responses after a period of odor enrichment, could not be shown in CD-1 outbred mice for any odorant tried. However, consistent with classical studies, it was evident in C57BL/6J inbred mice, which are initially insensitive to isovaleric acid. As is the case for deprivation, enriching C57BL/6J mice with isovaleric acid causes an increase in their electroolfactogram response to this odorant over time. In several experiments on C57BL/6J mice, the odorant specificity, onset timing, recovery timing, and magnitude of the induction effect were studied. Considered together, the current findings and previous work from the laboratory support the counterintuitive conclusion that both compensatory plasticity in response to deprivation and induction in response to odor enrichment are caused by the same underlying homeostatic mechanism, the purpose of which is to preserve sensory information flow no matter the odorant milieu. This hypothesis, the detailed evidence supporting it, and speculations concerning human odor induction are discussed.

Overcoming the challenges of developing an intranasal diazepam rescue therapy for the treatment of seizure clusters.

Seizure clusters must be treated quickly and effectively to prevent progression to prolonged seizures and status epilepticus. Rescue therapy for seizure clusters has focused on the use of benzodiazepines. Although intravenous benzodiazepine administration is the primary route in hospitals and emergency departments, seizure clusters typically occur in out-of-hospital settings, where a more portable product that can be easily administered by nonmedical caregivers is needed. Thus, other methods of administration have been examined, including rectal, intranasal, intramuscular, and buccal routes. Following US Food and Drug Administration (FDA) approval in 1997, rectal diazepam became the mainstay of out-of-hospital treatment for seizure clusters in the United States. However, social acceptability and consistent bioavailability present limitations. Intranasal formulations have potential advantages for rescue therapies, including ease of administration and faster onset of action. A midazolam nasal spray was approved by the FDA in 2019 for patients aged 12 years or older. In early 2020, the FDA approved a diazepam nasal spray for patients aged 6 years or older, which has a different formulation than the midazolam nasal product and enhances aspects of bioavailability. Benzodiazepines, including diazepam, present significant challenges in developing a suitable intranasal formulation. Diazepam nasal spray contains dodecyl maltoside (DDM) as an absorption enhancer and vitamin E to increase solubility in an easy-to-use portable device. In a Phase 1 study, absolute bioavailability of the diazepam nasal spray was 97% compared with intravenous diazepam. Subsequently, the nasal spray demonstrated less variability in bioavailability than rectal gel (percentage of geometric coefficient of variation of area under the curve = 42%-66% for diazepam nasal spray compared with 87%-172% for rectal gel). The diazepam nasal spray safety profile is consistent with that expected for rectal diazepam, with low rates of nasal discomfort (≤6%). To further improve the efficacy of rescue therapy, investigation of novel intranasal benzodiazepine formulations is underway.

Assessment of respiratory and systemic toxicity of Benzalkonium chloride following a 14-day inhalation study in rats.

BACKGROUND: Although biocides at low concentrations have been used to control pests, they can be more harmful than industrial chemicals as humans are directly and frequently exposed to such biocides. Benzalkonium chloride (BAC or BKC) is a non-toxic substance used to control pests. Recently, BAC has been increasingly used as a component in humidifier disinfectants in Korea, raising a serious health concern. Moreover, it poses significant health hazards to workers handling the chemical because of direct exposure. In the present study, we aimed to evaluate the respiratory toxicity of BAC due to its inhalation at exposure concentrations of 0.8 (T1 group), 4 (T2 group) and 20 (T3 group) mg/m3. RESULTS: In our previous study on the acute inhalational toxicity of BAC, bleeding from the nasal cavity was observed in all the rats after exposure to 50 mg/m3 BAC. Therefore, in this study, 20 mg/m3 was set as the highest exposure concentration, followed by 4 and 0.8 mg/m3 as the medium and low concentrations for 6 h/day and 14 days, respectively. After exposure, recovery periods of 2 and 4 weeks were provided. Additionally, alveolar lavage fluid was analyzed in males of the BAC-exposed groups at the end of exposure and 2 weeks after exposure to evaluate oxidative damage. In the T3 group exposed to BAC, deep breathing, hoarseness, and nasal discharge were observed along with a decline in feed intake and body weight, and nasal discharge was also observed in the T1 and T2 groups. ROS/RNS, IL-1ß, IL-6, and MIP-2 levels decreased in a concentration-dependent manner in the bronchoalveolar lavage fluid. Histopathological examination showed cellular changes in the nasal cavity and the lungs of the TI, T2, and T3 groups. CONCLUSIONS: As a result, it was confirmed that the target organs in the respiratory system were the nasal cavity and the lungs. The adverse effects were evaluated as reversible responses to oxidative damage. Furthermore, the no observed adverse effect level was found to be less than 0.8 mg/m3 and the lowest benchmark dose was 0.0031 mg/m3. Accordingly, the derived no-effect level of BAC was calculated as 0.000062 mg/m3.

Nose-to-Brain Delivery.

The global prevalence of neurologic disorders is rising, and yet we are still unable to deliver most drug molecules, in therapeutic quantities, to the brain. The blood brain barrier consists of a tight layer of endothelial cells surrounded by astrocyte foot processes, and these anatomic features constitute a significant barrier to drug transport from the blood to the brain. One way to bypass the blood brain barrier and thus treat diseases of the brain is to use the nasal route of administration and deposit drugs at the olfactory region of the nares, from where they travel to the brain via mechanisms that are still not clearly understood, with travel across nerve fibers and travel via a perivascular pathway both being hypothesized. The nose-to-brain route has been demonstrated repeatedly in preclinical models, with both solution and particulate formulations. The nose-to-brain route has also been demonstrated in human studies with solution and particle formulations. The entry of device manufacturers into the arena will enable the benefits of this delivery route to become translated into approved products. The key factors that determine the efficacy of delivery via this route include the following: delivery to the olfactory area of the nares as opposed to the respiratory region, a longer retention time at the nasal mucosal surface, penetration enhancement of the active through the nasal epithelia, and a reduction in drug metabolism in the nasal cavity. Indications where nose-to-brain products are likely to emerge first include the following: neurodegeneration, post-traumatic stress disorder, pain, and glioblastoma.

Intranasal Coadministration of a Diazepam Prodrug with a Converting Enzyme Results in Rapid Absorption of Diazepam in Rats.

Intranasal administration is an attractive route for systemic delivery of small, lipophilic drugs because they are rapidly absorbed through the nasal mucosa into systemic circulation. However, the low solubility of lipophilic drugs often precludes aqueous nasal spray formulations. A unique approach to circumvent solubility issues involves coadministration of a hydrophilic prodrug with an exogenous converting enzyme. This strategy not only addresses poor solubility but also leads to an increase in the chemical activity gradient driving drug absorption. Herein, we report plasma and brain concentrations in rats following coadministration of a hydrophilic diazepam prodrug, avizafone, with the converting enzyme human aminopeptidase B Single doses of avizafone equivalent to diazepam at 0.500, 1.00, and 1.50 mg/kg were administered intranasally, resulting in 77.8% ± 6.0%, 112% ± 10%, and 114% ± 7% bioavailability; maximum plasma concentrations 71.5 ± 9.3, 388 ± 31, and 355 ± 187 ng/ml; and times to peak plasma concentration 5, 8, and 5 minutes for each dose level, respectively. Both diazepam and a transient intermediate were absorbed. Enzyme kinetics incorporated into a physiologically based pharmacokinetic model enabled estimation of the first-order absorption rate constants: 0.0689 ± 0.0080 minutes-1 for diazepam and 0.122 ± 0.022 minutes-1 for the intermediate. Our results demonstrate that diazepam, which is practically insoluble, can be delivered intranasally with rapid and complete absorption by coadministering avizafone with aminopeptidase B. Furthermore, even faster rates of absorption might be attained simply by increasing the enzyme concentration, potentially supplanting intravenous diazepam or lorazepam or intramuscular midazolam in the treatment of seizure emergencies.

Axonal Transport Enables Neuron-to-Neuron Propagation of Human Coronavirus OC43.

Human coronaviruses (HCoVs) are recognized respiratory pathogens for which accumulating evidence indicates that in vulnerable patients the infection can cause more severe pathologies. HCoVs are not always confined to the upper respiratory tract and can invade the central nervous system (CNS) under still unclear circumstances. HCoV-induced neuropathologies in humans are difficult to diagnose early enough to allow therapeutic interventions. Making use of our already described animal model of HCoV neuropathogenesis, we describe the route of neuropropagation from the nasal cavity to the olfactory bulb and piriform cortex and then the brain stem. We identified neuron-to-neuron propagation as one underlying mode of virus spreading in cell culture. Our data demonstrate that both passive diffusion of released viral particles and axonal transport are valid propagation strategies used by the virus. We describe for the first time the presence along axons of viral platforms whose static dynamism is reminiscent of viral assembly sites. We further reveal that HCoV OC43 modes of propagation can be modulated by selected HCoV OC43 proteins and axonal transport. Our work, therefore, identifies processes that may govern the severity and nature of HCoV OC43 neuropathogenesis and will make possible the development of therapeutic strategies to prevent occurrences.IMPORTANCE Coronaviruses may invade the CNS, disseminate, and participate in the induction of neurological diseases. Their neuropathogenicity is being increasingly recognized in humans, and the presence and persistence of human coronaviruses (HCoV) in human brains have been proposed to cause long-term sequelae. Using our mouse model relying on natural susceptibility to HCoV OC43 and neuronal cell cultures, we have defined the most relevant path taken by HCoV OC43 to access and spread to and within the CNS toward the brain stem and spinal cord and studied in cell culture the underlying modes of intercellular propagation to better understand its neuropathogenesis. Our data suggest that axonal transport governs HCoV OC43 egress in the CNS, leading to the exacerbation of neuropathogenesis. Exploiting knowledge on neuroinvasion and dissemination will enhance our ability to control viral infection within the CNS, as it will shed light on underlying mechanisms of neuropathogenesis and uncover potential druggable molecular virus-host interfaces.

Tissue-Dependent Expression of Bitter Receptor TAS2R38 mRNA.

TAS2R38 is a human bitter receptor gene with a common but inactive allele; people homozygous for the inactive form cannot perceive low concentrations of certain bitter compounds. The frequency of the inactive and active forms of this receptor is nearly equal in many human populations, and heterozygotes with 1 copy of the active form and 1 copy of the inactive form have the most common diplotype. However, even though they have the same genotype, heterozygotes differ markedly in their perception of bitterness, perhaps in part because of differences in TAS2R38 mRNA expression. Other tissues express this receptor too, including the nasal sinuses, where it contributes to pathogen defense. We, therefore, wondered whether heterozygous people had a similar wide range of TAS2R38 mRNA in sinonasal tissue and whether those with higher TAS2R38 mRNA expression in taste tissue were similarly high expressers in nasal tissue. To that end, we measured gene expression by quantitative PCR in taste and sinonasal tissue and found that expression abundance in one tissue was not related to the other. We confirmed the independence of expression in other tissue pairs expressing TAS2R38 mRNA, such as pancreas and small intestine, using autopsy data from the Genotype-Tissue Expression project (although people with high expression of TAS2R38 mRNA in colon also tended to have higher expression in the small intestine). Thus, taste tissue TAS2R38 mRNA expression among heterozygotes is unlikely to predict expression in other tissues, perhaps reflecting tissue-dependent function, and hence regulation, of this protein.

Expression of Bitter Taste Receptors and Solitary Chemosensory Cell Markers in the Human Sinonasal Cavity.

Some bitter taste receptors (TAS2R gene products) are expressed in the human sinonasal cavity and may function to detect airborne irritants. The expression of all 25 human bitter taste receptors and their location within the upper airway is not yet clear. The aim of this study is to characterize the presence and distribution of TAS2R transcripts and solitary chemosensory cells (SCCs) in different locations of the human sinonasal cavity. Biopsies were obtained from human subjects at up to 4 different sinonasal anatomic sites. PCR, microarray, and qRT-PCR were used to examine gene transcript expression. The 25 human bitter taste receptors as well as the sweet/umami receptor subunit, TAS1R3, and canonical taste signaling effectors are expressed in sinonasal tissue. All 25 human bitter taste receptors are expressed in the human upper airway, and expression of these gene products was higher in the ethmoid sinus than nasal cavity locations. Fluorescent in situ hybridization demonstrates that epithelial TRPM5 and TAS2R38 are expressed in a rare cell population compared with multiciliated cells, and at times, consistent with SCC morphology. Secondary analysis of published human sinus single-cell RNAseq data did not uncover TAS2R or canonical taste transduction transcripts in multiciliated cells. These findings indicate that the sinus has higher expression of SCC markers than the nasal cavity in chronic rhinosinusitis patients, comprising a rare cell type. Biopsies obtained from the ethmoid sinus may serve as the best location for study of human upper airway taste receptors and SCCs.

Metabolism of Odorant Molecules in Human Nasal/Oral Cavity Affects the Odorant Perception.

In this study, we examined the mode of metabolism of food odorant molecules in the human nasal/oral cavity in vitro and in vivo. We selected 4 odorants, 2-furfurylthiol (2-FT), hexanal, benzyl acetate, and methyl raspberry ketone, which are potentially important for designing food flavors. In vitro metabolic assays of odorants with saliva/nasal mucus analyzed by gas chromatography mass spectrometry revealed that human saliva and nasal mucus exhibit the following 3 enzymatic activities: (i) methylation of 2-FT into furfuryl methylsulfide (FMS); (ii) reduction of hexanal into hexanol; and (iii) hydrolysis of benzyl acetate into benzyl alcohol. However, (iv) demethylation of methyl raspberry ketone was not observed. Real-time in vivo analysis using proton transfer reaction-mass spectrometry demonstrated that the application of 2-FT and hexanal through 3 different pathways via the nostril or through the mouth generated the metabolites FMS and hexanol within a few seconds. The concentration of FMS and hexanol in the exhaled air was above the perception threshold. A cross-adaptation study based on the activation pattern of human odorant receptors suggested that this metabolism affects odor perception. These results suggest that some odorants in food are metabolized in the human nasal mucus/saliva, and the resulting metabolites are perceived as part of the odor quality of the substrates. Our results help improve the understanding of the mechanism of food odor perception and may enable improved design and development of foods in relation to odor.