RESUMO
Toxic puffers accumulate tetrodotoxin (TTX), a well-known neurotoxin, by feeding on TTX-bearing organisms and using it to defend themselves from predators. Our previous studies have demonstrated that toxic puffers are attracted to 5,6,11-trideoxytetrodotoxin (TDT), a nontoxic TTX analog that is simultaneously accumulated with TTX in toxic puffers and their prey. In addition, activity labeling using immunohistochemistry targeting neuronal activity marker suggests that TDT activates crypt olfactory sensory neurons (OSN) of the green spotted puffer. However, it remains to be determined whether individual crypt OSNs can physiologically respond to TDT. By employing electroporation to express GCaMP6s in OSNs, we successfully identified a distinct group of oval OSNs that exhibited a specific calcium response when exposed to TDT in green spotted puffers. These oval OSNs showed no response to amino acids (AAs), which serve as food odor cues for teleosts. Furthermore, oval morphology and surface positioning of TDT-sensitive OSNs in the olfactory epithelium closely resemble that of crypt OSNs. These findings further substantiate that TDT is specifically detected by crypt OSNs in green spotted puffer. The TDT odor may act as a chemoattractant for finding conspecific toxic puffers and for feeding TTX-bearing organisms for effective toxification.
Assuntos
Odorantes , Neurônios Receptores Olfatórios , Tetraodontiformes , Tetrodotoxina , Animais , Tetrodotoxina/farmacologia , Neurônios Receptores Olfatórios/efeitos dos fármacos , Neurônios Receptores Olfatórios/metabolismo , Odorantes/análise , Cálcio/metabolismoRESUMO
Tsetse flies transmit trypanosomes-parasites that cause devastating diseases in humans and livestock-across much of sub-Saharan Africa. Chemical communication through volatile pheromones is common among insects; however, it remains unknown if and how such chemical communication occurs in tsetse flies. We identified methyl palmitoleate (MPO), methyl oleate, and methyl palmitate as compounds that are produced by the tsetse fly Glossina morsitans and elicit strong behavioral responses. MPO evoked a behavioral response in male-but not virgin female-G. morsitans. G. morsitans males mounted females of another species, Glossina fuscipes, when they were treated with MPO. We further identified a subpopulation of olfactory neurons in G. morsitans that increase their firing rate in response to MPO and showed that infecting flies with African trypanosomes alters the flies' chemical profile and mating behavior. The identification of volatile attractants in tsetse flies may be useful for reducing disease spread.
Assuntos
Ácidos Graxos Voláteis , Neurônios Receptores Olfatórios , Atrativos Sexuais , Moscas Tsé-Tsé , Animais , Feminino , Masculino , Atrativos Sexuais/farmacologia , Atrativos Sexuais/fisiologia , Trypanosoma , Moscas Tsé-Tsé/parasitologia , Moscas Tsé-Tsé/fisiologia , Neurônios Receptores Olfatórios/efeitos dos fármacos , Neurônios Receptores Olfatórios/fisiologia , Ácidos Graxos Voláteis/farmacologia , Ácidos Graxos Voláteis/fisiologiaRESUMO
Functional characterization of mammalian olfactory receptors (ORs) remains a major challenge to ultimately understanding the olfactory code. Here, we compare the responses of the mouse Olfr73 ectopically expressed in olfactory sensory neurons using AAV gene delivery in vivo and expressed in vitro in cell culture. The response dynamics and concentration-dependence of agonists for the ectopically expressed Olfr73 were similar to those reported for the endogenous Olfr73, however the antagonism previously reported between its cognate agonist and several antagonists was not replicated in vivo. Expressing the OR in vitro reproduced the antagonism reported for short odor pulses, but not for prolonged odor exposure. Our findings suggest that both the cellular environment and the stimulus dynamics shape the functionality of Olfr73 and argue that characterizing ORs in 'native' conditions, rather than in vitro, provides a more relevant understanding of ligand-OR interactions.
Assuntos
Proteínas dos Microfilamentos/metabolismo , Odorantes/análise , Mucosa Olfatória/metabolismo , Neurônios Receptores Olfatórios/metabolismo , Receptores Odorantes/metabolismo , Animais , Cálcio/metabolismo , AMP Cíclico , Dependovirus/genética , Feminino , Ligantes , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Proteínas dos Microfilamentos/agonistas , Proteínas dos Microfilamentos/antagonistas & inibidores , Proteínas dos Microfilamentos/genética , Mucosa Olfatória/efeitos dos fármacos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores Odorantes/agonistas , Receptores Odorantes/antagonistas & inibidores , Receptores Odorantes/genéticaRESUMO
Although praying mantises rely mainly on vision for predatory behaviours, olfaction also plays a critical role in feeding and mating behaviours. However, the receptive processes underlying olfactory signals remain unclear. Here, we identified olfactory sensory neurons (OSNs) that are highly tuned to detect aldehydes in the mantis Tenodera aridifolia. In extracellular recordings from OSNs in basiconic sensilla on the antennae, we observed three different spike shapes, indicating that at least three OSNs are housed in a single basiconic sensillum. Unexpectedly, one of the three OSNs exhibited strong excitatory responses to a set of aldehydes. Based on the similarities of the response spectra to 15 different aldehydes, the aldehyde-specific OSNs were classified into three classes: B, S, and M. Class B broadly responded to most aldehydes used as stimulants; class S responded to short-chain aldehydes (C3-C7); and class M responded to middle-length chain aldehydes (C6-C9). Thus, aldehyde molecules can be finely discriminated based on the activity patterns of a population of OSNs. Because many insects emit aldehydes for pheromonal communication, mantises might use aldehydes as olfactory cues for locating prey habitat.
Assuntos
Aldeídos/farmacologia , Mantódeos/fisiologia , Neurônios Receptores Olfatórios/efeitos dos fármacos , Animais , Fenômenos Eletrofisiológicos/efeitos dos fármacos , Feminino , Masculino , Mantódeos/efeitos dos fármacos , Neurônios Receptores Olfatórios/fisiologia , Sensilas/efeitos dos fármacos , Sensilas/fisiologia , OlfatoRESUMO
Olfactory dysfunctions, including hyposmia and anosmia, affect ~100 million people around the world and the underlying causes are not fully understood. Degeneration of olfactory sensory neurons and incapacity of globose basal cells to generate olfactory sensory neurons are found in elder people and patients with smell disorders. Thus, olfactory stem cell may function as a promising tool to replace inactivated globose basal cells and to generate sensory neurons. Methods: We established clonal expansion of cells from the murine olfactory epithelium as well as colony growth from human olfactory mucosa using Matrigel-based three-dimensional system. These colonies were characterized by immunostaining against olfactory epithelium cellular markers and by calcium imaging of responses to odors. Chemical addition was optimized to promote Lgr5 expression, colony growth and sensory neuron generation, tested by quantitative PCR and immunostaining against progenitor and neuronal markers. The differential transcriptomes in multiple signaling pathways between colonies under different base media and chemical cocktails were determined by RNA-Seq. Results: In defined culture media, we found that VPA and CHIR99021 induced the highest Lgr5 expression level, while LY411575 resulted in the most abundant yield of OMP+ mature sensory neurons in murine colonies. Different base culture media with drug cocktails led to apparent morphological alteration from filled to cystic appearance, accompanied with massive transcriptional changes in multiple signaling pathways. Generation of sensory neurons in human colonies was affected through TGF-ß signaling, while Lgr5 expression and cell proliferation was regulated by VPA. Conclusion: Our findings suggest that targeting expansion of olfactory epithelium/mucosa colonies in vitro potentially results in discovery of new source to cell replacement-based therapy against smell loss.
Assuntos
Alanina/análogos & derivados , Azepinas/farmacologia , Neurogênese , Mucosa Olfatória/citologia , Neurônios Receptores Olfatórios/citologia , Piridinas/farmacologia , Pirimidinas/farmacologia , Receptores Acoplados a Proteínas G/metabolismo , Células-Tronco/citologia , Alanina/farmacologia , Animais , Diferenciação Celular , Proliferação de Células , Feminino , Humanos , Masculino , Camundongos , Mucosa Olfatória/efeitos dos fármacos , Mucosa Olfatória/metabolismo , Neurônios Receptores Olfatórios/efeitos dos fármacos , Neurônios Receptores Olfatórios/metabolismo , Receptores Acoplados a Proteínas G/genética , Células-Tronco/efeitos dos fármacos , Células-Tronco/metabolismoRESUMO
Odor landscapes contain complex blends of molecules that each activate unique, overlapping populations of olfactory sensory neurons (OSNs). Despite the presence of hundreds of OSN subtypes in many animals, the overlapping nature of odor inputs may lead to saturation of neural responses at the early stages of stimulus encoding. Information loss due to saturation could be mitigated by normalizing mechanisms such as antagonism at the level of receptor-ligand interactions, whose existence and prevalence remains uncertain. By imaging OSN axon terminals in olfactory bulb glomeruli as well as OSN cell bodies within the olfactory epithelium in freely breathing mice, we find widespread antagonistic interactions in binary odor mixtures. In complex mixtures of up to 12 odorants, antagonistic interactions are stronger and more prevalent with increasing mixture complexity. Therefore, antagonism is a common feature of odor mixture encoding in OSNs and helps in normalizing activity to reduce saturation and increase information transfer.
Assuntos
Misturas Complexas/farmacologia , Odorantes , Percepção Olfatória/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Olfato/fisiologia , Animais , Antagonismo de Drogas , Feminino , Ligantes , Masculino , Camundongos , Microscopia de Fluorescência por Excitação Multifotônica , Bulbo Olfatório/citologia , Bulbo Olfatório/diagnóstico por imagem , Bulbo Olfatório/fisiologia , Mucosa Olfatória/citologia , Mucosa Olfatória/efeitos dos fármacos , Mucosa Olfatória/metabolismo , Percepção Olfatória/efeitos dos fármacos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Terminações Pré-Sinápticas/fisiologia , Receptores Odorantes/metabolismo , Respiração , Olfato/efeitos dos fármacosRESUMO
Glioblastoma multiforme (GBM) is described as an invasive astrocytic tumor in adults. Despite current standard treatment approaches, the outcome of GBM remains unfavorable. The downregulation of connexin 43 (Cx43) expression is one of the molecular transformations in GBM cells. The Cx43 levels and subsequently gap junctional intercellular communication (GJIC) have an important role in the efficient transfer of cytotoxic drugs to whole tumor cells. As shown in our previous study, the stimulation of the ß2-adrenergic receptor (ß2-AR) leads to the modulation of Cx43 expression level in the GBM cell line. Here we further examine the effect of clenbuterol hydrochloride as a selective ß2-AR agonist on the Cx43 expression in human GBM-derived astrocyte cells and human olfactory ensheathing cells (OECs) as a potent vector for future gene therapy. In this experiment, first we established a primary culture of astrocytes from GBM samples and verified the purity using immunocytofluorescent staining. Western blot analysis was performed to evaluate the Cx43 protein level. Our western blot findings reveal that clenbuterol hydrochloride upregulates the Cx43 protein level in both primary human astrocyte cells and human OECs. Conversely, ICI 118551 as a ß2-AR antagonist inhibits these effects. Moreover, clenbuterol hydrochloride increases the Cx43 expression in primary human astrocyte cells and OECs co-culture systems, and ICI 118551 reverses these effects. To confirm the western blot results, immunocytofluorescent staining was performed to evaluate the ß2-AR agonist effect on Cx43 expression. Our immunocytofluorescent results supported western blot analysis in primary human astrocyte cells and the OECs co-culture system. The results of this study suggest that the activation of ß2-AR with regard to Cx43 protein levels enhancement in GBM cells and OECs might be a promising approach for GBM treatment in the future.
Assuntos
Agonistas de Receptores Adrenérgicos beta 2/farmacologia , Neoplasias Encefálicas/metabolismo , Clembuterol/farmacologia , Conexina 43/genética , Glioblastoma/metabolismo , Antagonistas de Receptores Adrenérgicos beta 2/farmacologia , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Células Cultivadas , Conexina 43/metabolismo , Humanos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Neurônios Receptores Olfatórios/metabolismo , Propanolaminas/farmacologia , Células Tumorais Cultivadas , Regulação para CimaRESUMO
The cellular and molecular basis of metaplasia and declining neurogenesis in the aging olfactory epithelium (OE) remains unknown. The horizontal basal cell (HBC) is a dormant tissue-specific stem cell presumed to only be forced into self-renewal and differentiation by injury. Here we analyze male and female mice and show that HBCs also are activated with increasing age as well as non-cell-autonomously by increased expression of the retinoic acid-degrading enzyme CYP26B1. Activating stimuli induce HBCs throughout OE to acquire a rounded morphology and express IP3R3, which is an inositol-1,4,5-trisphosphate receptor constitutively expressed in stem cells of the adjacent respiratory epithelium. Odor/air stimulates CYP26B1 expression in olfactory sensory neurons mainly located in the dorsomedial OE, which is spatially inverse to ventrolateral constitutive expression of the retinoic acid-synthesizing enzyme (RALDH1) in supporting cells. In ventrolateral OE, HBCs express low p63 levels and preferentially differentiate instead of self-renewing when activated. When activated by chronic CYP26B1 expression, repeated injury, or old age, ventrolateral HBCs diminish in number and generate a novel type of metaplastic respiratory cell that is RALDH- and secretes a mucin-like mucus barrier protein (FcγBP). Conversely, in the dorsomedial OE, CYP26B1 inhibits injury-induced and age-related replacement of RALDH- supporting cells with RALDH1+ ciliated respiratory cells. Collectively, these results support the concept that inositol-1,4,5-trisphosphate type 3 receptor signaling in HBCs, together with altered retinoic acid metabolism within the niche, promote HBC lineage commitment toward two types of respiratory cells that will maintain epithelial barrier function once the capacity to regenerate OE cells ceases.SIGNIFICANCE STATEMENT Little is known about signals that activate dormant stem cells to self-renew and regenerate odor-detecting neurons and other olfactory cell types after loss due to injury, infection, or toxin exposure in the nose. It is also unknown why the stem cells do not prevent age-dependent decline of odor-detecting neurons. We show that (1) stem cells are kept inactive by the vitamin A derivative retinoic acid, which is synthesized and degraded locally by olfactory cells; (2) old age as well as repeated injuries activate the stem cells and exhaust their potential to produce olfactory cells; and (3) exhausted stem cells alter the local retinoic acid metabolism and maintain the epithelial tissue barrier by generating airway cells instead of olfactory cells.
Assuntos
Envelhecimento/metabolismo , Isotretinoína/farmacologia , Células-Tronco Neurais/metabolismo , Neurônios Receptores Olfatórios/metabolismo , Ácido Retinoico 4 Hidroxilase/metabolismo , Animais , Feminino , Masculino , Metaplasia/metabolismo , Camundongos , Células-Tronco Neurais/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Neurogênese/fisiologia , Mucosa Olfatória/efeitos dos fármacos , Mucosa Olfatória/metabolismo , Neurônios Receptores Olfatórios/efeitos dos fármacosRESUMO
Most natural odors are complex mixtures of volatile components, competing to bind odorant receptors (ORs) expressed in olfactory sensory neurons (OSNs) of the nose. To date, surprisingly little is known about how OR antagonism shapes neuronal representations in the detection layer of the olfactory system. Here, we investigated its prevalence, the degree to which it disrupts OR ensemble activity, and its conservation across phylogenetically related ORs. Calcium imaging microscopy of dissociated OSNs revealed significant inhibition, often complete attenuation, of responses to indole-a commonly occurring volatile associated with both floral and fecal odors-by a set of 36 tested odorants. To confirm an OR mechanism for the observed inhibition, we performed single-cell transcriptomics on OSNs exhibiting specific response profiles to a diagnostic panel of odorants and identified three paralogous receptors-Olfr740, Olfr741, and Olfr743-which, when tested in vitro, recapitulated OSN responses. We screened ten ORs from the Olfr740 gene family with â¼800 perfumery-related odorants spanning a range of chemical scaffolds and functional groups. Over half of these compounds (430) antagonized at least one of the ten ORs. OR activity fitted a mathematical model of competitive receptor binding and suggests normalization of OSN ensemble responses to odorant mixtures is the rule rather than the exception. In summary, we observed OR antagonism occurred frequently and in a combinatorial manner. Thus, extensive receptor-mediated computation of mixture information appears to occur in the olfactory epithelium prior to transmission of odor information to the olfactory bulb.
Assuntos
Odorantes/análise , Percepção Olfatória/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Receptores Odorantes/antagonistas & inibidores , Transcriptoma , Animais , Perfilação da Expressão Gênica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Análise de Célula ÚnicaRESUMO
Schizophrenia (SCZ) has been associated with serotonergic and endocannabinoid systems dysregulation, but difficulty in obtaining in vivo neurological tissue has limited its exploration. We investigated CB1R-5-HT2AR heteromer expression and functionality via intracellular pERK and cAMP quantification in olfactory neuroepithelium (ON) cells of SCZ patients non-cannabis users (SCZ/nc), and evaluated whether cannabis modulated these parameters in patients using cannabis (SCZ/c). Results were compared vs healthy controls non-cannabis users (HC/nc) and healthy controls cannabis users (HC/c). Further, antipsychotic effects on heteromer signaling were tested in vitro in HC/nc and HC/c. Results indicated that heteromer expression was enhanced in both SCZ groups vs HC/nc. Additionally, pooling all 4 groups together, heteromer expression correlated with worse attentional performance and more neurological soft signs (NSS), indicating that these changes may be useful markers for neurocognitive impairment. Remarkably, the previously reported signaling properties of CB1R-5-HT2AR heteromers in ON cells were absent, specifically in SCZ/nc treated with clozapine. These findings were mimicked in cells from HC/nc exposed to clozapine, suggesting a major role of this antipsychotic in altering the quaternary structure of the CB1R-5-HT2AR heteromer in SCZ/nc patients. In contrast, cells from SCZ/c showed enhanced heteromer functionality similar to HC/c. Our data highlight a molecular marker of the interaction between antipsychotic medication and cannabis use in SCZ with relevance for future studies evaluating its association with specific neuropsychiatric alterations.
Assuntos
Antipsicóticos/farmacologia , Agonistas de Receptores de Canabinoides/farmacologia , Dronabinol/farmacologia , Uso da Maconha , Células Neuroepiteliais , Neurônios Receptores Olfatórios , Receptor CB1 de Canabinoide , Receptor 5-HT2A de Serotonina , Esquizofrenia/metabolismo , Adulto , Agonistas de Receptores de Canabinoides/sangue , Células Cultivadas , Clozapina/farmacologia , Estudos Transversais , Dronabinol/sangue , Feminino , Humanos , Masculino , Células Neuroepiteliais/efeitos dos fármacos , Células Neuroepiteliais/metabolismo , Neurônios Receptores Olfatórios/efeitos dos fármacos , Neurônios Receptores Olfatórios/metabolismo , Receptor CB1 de Canabinoide/efeitos dos fármacos , Receptor CB1 de Canabinoide/metabolismo , Receptor 5-HT2A de Serotonina/efeitos dos fármacos , Receptor 5-HT2A de Serotonina/metabolismo , Adulto JovemRESUMO
Mate finding in most moths is based on male perception of a female-emitted pheromone whose species specificity resides in component chemistry and proportions. Components are individually detected by specialized olfactory receptor neurons (ORNs) projecting into the macroglomerular complex (MGC) of the male brain. We asked how robust ratio recognition is when challenged by a plant volatile background. To test this, we investigated the perception of the pheromone blend in Agrotis ipsilon, a moth species whose females produce a blend of Z7-dodecenyl acetate (Z7-12:Ac), Z9-tetradecenyl acetate (Z9-14:Ac), and Z11-hexadecenyl acetate in a 4:1:4 ratio optimally attractive for males. First, we recorded the responses of specialist ORNs for Z7 and Z9 and showed that heptanal, a flower volatile, activated Z7 but not Z9 neurons. Then, we recorded intracellularly the responses of MGC neurons to various ratios and showed that heptanal altered ratio responses of pheromone-sensitive neurons. Finally, we analyzed the behavior of males in a wind tunnel and showed that their innate preference for the 4:1:4 blend was shifted in the presence of heptanal. Pheromone ratio recognition may thus be altered by background odorants. Therefore, the olfactory environment might be a selective force for the evolution of pheromone communication systems.
Assuntos
Aldeídos/farmacologia , Flores/química , Mariposas/efeitos dos fármacos , Odorantes/análise , Neurônios Receptores Olfatórios/efeitos dos fármacos , Atrativos Sexuais/farmacologia , Animais , Feminino , Masculino , Mariposas/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Percepção , OlfatoRESUMO
The perception of odors relies on combinatorial codes consisting of odorant receptor (OR) response patterns to encode odor identity. Modulation of these patterns by odorant interactions at ORs potentially explains several olfactory phenomena: mixture suppression, unpredictable sensory outcomes, and the perception of odorant mixtures as unique objects. We determined OR response patterns to 4 odorants and 3 binary mixtures in vivo in mice, identifying 30 responsive ORs. These patterns typically had a few strongly responsive ORs and a greater number of weakly responsive ORs. ORs responsive to an odorant were often unrelated sequences distributed across several OR subfamilies. Mixture responses predicted pharmacological interactions between odorants, which were tested in vitro by heterologous expression of ORs in cultured cells, providing independent evidence confirming odorant agonists for 13 ORs and identifying both suppressive and additive effects. This included 11 instances of antagonism of ORs by an odorant, 1 instance of additive responses to a binary mixture, 1 instance of suppression of a strong agonist by a weak agonist, and the discovery of an inverse agonist for an OR. Interactions between odorants at ORs are common even when the odorants are not known to interact perceptually in humans, and in some cases interactions at mouse ORs correlate with the ability of humans to perceive an odorant in a mixture.
Assuntos
Odorantes , Neurônios Receptores Olfatórios/metabolismo , Receptores Odorantes/metabolismo , Olfato , Aldeídos/farmacologia , Animais , Células Cultivadas , Feminino , Lactonas/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Neurônios Receptores Olfatórios/efeitos dos fármacos , Pentanóis/farmacologia , Receptores Odorantes/agonistas , Receptores Odorantes/antagonistas & inibidoresRESUMO
Adult neurogenesis, analogous to early development, is comprised of several, often concomitant, processes including proliferation, differentiation, and formation of synaptic connections. However, due to continual, asynchronous turn-over, newly-born adult olfactory sensory neurons (OSNs) must integrate into existing circuitry. Additionally, OSNs express high levels of cellular prion protein (PrPC), particularly in the axon, which implies a role in this cell type. The cellular prion has been shown to be important for proper adult OSN neurogenesis primarily by stabilizing mature olfactory neurons within this circuitry. However, the role of PrPC on each specific adult neurogenic processes remains to be investigated in detail. To tease out the subtle effects of prion protein expression level, a large population of regenerating neurons must be investigated. The thyroid drug methimazole (MTZ) causes nearly complete OSN loss in rodents and is used as a model of acute olfactory injury, providing a mechanism to induce synchronized OSN regeneration. This study investigated the effect of PrPC on adult neurogenesis after acute nasotoxic injury. Altered PrPC levels affected olfactory sensory epithelial (OSE) regeneration, cell proliferation, and differentiation. Attempts to investigate the role of PrPC level on axon regeneration did not support previous studies, and glomerular targeting did not recover to vehicle-treated levels, even by 20 weeks. Together, these studies demonstrate that the cellular prion protein is critical for regeneration of neurons, whereby increased PrPC levels promote early neurogenesis, and that lack of PrPC delays the regeneration of this tissue after acute injury.
Assuntos
Regeneração Nervosa/fisiologia , Neurônios Receptores Olfatórios/patologia , Proteínas Priônicas/metabolismo , Doença Aguda , Animais , Axônios/efeitos dos fármacos , Axônios/metabolismo , Diferenciação Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Feminino , Masculino , Metimazol/toxicidade , Camundongos Transgênicos , Regeneração Nervosa/efeitos dos fármacos , Neurogênese/efeitos dos fármacos , Mucosa Olfatória/efeitos dos fármacos , Mucosa Olfatória/patologia , Neurônios Receptores Olfatórios/efeitos dos fármacosRESUMO
Olfactory sensory neurons (OSNs) of the vertebrate olfactory epithelium (OE) undergo continuous turnover but also regenerate efficiently when the OE is acutely damaged by traumatic injury. Two distinct pools of neuronal stem/progenitor cells, the globose (GBCs), and horizontal basal cells (HBCs) have been shown to selectively contribute to intrinsic OSN turnover and damage-induced OE regeneration, respectively. For both types of progenitors, their rate of cell divisions and OSN production must match the actual loss of cells to maintain or to re-establish sensory function. However, signals that communicate between neurons or glia cells of the OE and resident neurogenic progenitors remain largely elusive. Here, we investigate the effect of purinergic signaling on cell proliferation and OSN neurogenesis in the zebrafish OE. Purine stimulation elicits transient Ca2+ signals in OSNs and distinct non-neuronal cell populations, which are located exclusively in the basal OE and stain positive for the neuronal stem cell marker Sox2. The more apical population of Sox2-positive cells comprises evenly distributed glia-like sustentacular cells (SCs) and spatially restricted GBC-like cells, whereas the more basal population expresses the HBC markers keratin 5 and tumor protein 63 and lines the entire sensory OE. Importantly, exogenous purine stimulation promotes P2 receptor-dependent mitotic activity and OSN generation from sites where GBCs are located but not from HBCs. We hypothesize that purine compounds released from dying OSNs modulate GBC progenitor cell cycling in a dose-dependent manner that is proportional to the number of dying OSNs and, thereby, ensures a constant pool of sensory neurons over time.
Assuntos
Cálcio/metabolismo , Células-Tronco Neurais/efeitos dos fármacos , Neurogênese , Mucosa Olfatória/efeitos dos fármacos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Purinas/farmacologia , Receptores Purinérgicos/metabolismo , Animais , Diferenciação Celular , Proliferação de Células , Células-Tronco Neurais/metabolismo , Mucosa Olfatória/metabolismo , Neurônios Receptores Olfatórios/metabolismo , Fatores de Transcrição SOXB1/metabolismo , Transdução de Sinais , Peixe-ZebraRESUMO
The olfactory epithelium (OE) is the peripheral organ for the sense of smell, housing primary sensory neurons that project axons from the nose to the brain. Due to the presence of a basal stem cell niche, the adult mammalian OE is a dynamic tissue capable of replacing neurons following their loss. Nonetheless, certain conditions, such as blunt head trauma, can result in persistent olfactory loss, thought to be due to shearing of olfactory nerve filaments at the skull base, degeneration, and failures in proper regeneration/reinnervation. The identification of new treatment strategies aimed at preventing degeneration of olfactory neurons is, therefore, needed. In considering potential therapies, we have focused on N-acetylcysteine (NAC), a glutathione substrate shown to be neuroprotective, with a record of safe clinical use. Here, we have tested the use of NAC in an animal model of olfactory degeneration. Administered acutely, we found that NAC (100 mg/kg, twice daily) resulted in a reduction of olfactory neuronal loss from the OE of the nose following surgical ablation of the olfactory bulb. At 1 week postlesion, we identified 54 ± 8.1 mature neurons per 0.5 mm epithelium in NAC-treated animals vs. 28 ± 4.2 in vehicle-treated controls (P = 0.02). Furthermore, in an olfactory cell culture model, we have identified significant alterations in the expression of several genes involved in oxidative stress pathways following NAC exposure. Our results provide evidence supporting the potential therapeutic utility for NAC acutely following head trauma-induced olfactory loss. Anat Rec, 303:626-633, 2020. © 2019 American Association for Anatomy.
Assuntos
Acetilcisteína/uso terapêutico , Degeneração Neural/tratamento farmacológico , Fármacos Neuroprotetores/uso terapêutico , Mucosa Olfatória/efeitos dos fármacos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Acetilcisteína/farmacologia , Animais , Sobrevivência Celular/efeitos dos fármacos , Camundongos , Degeneração Neural/patologia , Fármacos Neuroprotetores/farmacologia , Bulbo Olfatório/lesões , Mucosa Olfatória/patologia , Neurônios Receptores Olfatórios/patologiaRESUMO
Odorant molecules stimulate olfactory receptor neurons, and axons of these neurons project into the main olfactory bulb where they synapse onto mitral and tufted cells. These project to the primary olfactory cortex including the anterior olfactory nucleus (AON), the piriform cortex, amygdala, and the entorhinal cortex. The properties of mitral cells have been investigated extensively, but how odor information is processed in subsequent brain regions is less well known. In the present study, we recorded the electrical activity of AON neurons in anesthetized rats. Most AON cells fired in bursts of 2-10 spikes separated by very short intervals (<20 ms), in a period linked to the respiratory rhythm. Simultaneous recordings from adjacent neurons revealed that the rhythms of adjacent cells, while locked to the same underlying rhythm, showed marked differences in phase. We studied the responses of AON cells to brief high-frequency stimulation of the lateral olfactory tract, mimicking brief activation of mitral cells by odor. In different cells, such stimuli evoked transient or sustained bursts during stimulation or, more commonly, post-stimulation bursts after inhibition during stimulation. This suggests that, in AON cells, phase shifts occur as a result of post-inhibitory rebound firing, following inhibition by mitral cell input, and we discuss how this supports processing of odor information in the olfactory pathway. Cells were tested for their responsiveness to a social odor (the bedding of a strange male) among other simple and complex odors tested. In total, 11 cells responded strongly and repeatedly to bedding odor, and these responses were diverse, including excitation (transient or sustained), inhibition, and activation after odor presentation, indicating that AON neurons respond not only to the type of complex odor but also to temporal features of odor application.
Assuntos
Odorantes , Bulbo Olfatório/fisiologia , Córtex Olfatório/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Potenciais de Ação/efeitos dos fármacos , Potenciais de Ação/fisiologia , Animais , Estimulação Elétrica/métodos , Masculino , Bulbo Olfatório/efeitos dos fármacos , Córtex Olfatório/efeitos dos fármacos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Ratos , Ratos Sprague-DawleyRESUMO
Sensory cortices process stimuli in manners essential for perception. Very little is known regarding interactions between olfactory cortices. The piriform "primary" olfactory cortex, especially its anterior division (aPCX), extends dense association fibers into the ventral striatum's olfactory tubercle (OT), yet whether this corticostriatal pathway is capable of shaping OT activity, including odor-evoked activity, is unknown. Further unresolved is the synaptic circuitry and the spatial localization of OT-innervating PCX neurons. Here we build upon standing literature to provide some answers to these questions through studies in mice of both sexes. First, we recorded the activity of OT neurons in awake mice while optically stimulating principal neurons in the aPCX and/or their association fibers in the OT while the mice were delivered odors. This uncovered evidence that PCX input indeed influences OT unit activity. We then used patch-clamp recordings and viral tracing to determine the connectivity of aPCX neurons upon OT neurons expressing dopamine receptor types D1 or D2, two prominent cell populations in the OT. These investigations uncovered that both populations of neurons receive monosynaptic inputs from aPCX glutamatergic neurons. Interestingly, this input originates largely from the ventrocaudal aPCX. These results shed light on some of the basic physiological properties of this pathway and the cell-types involved and provide a foundation for future studies to identify, among other things, whether this pathway has implications for perception.SIGNIFICANCE STATEMENT Sensory cortices interact to process stimuli in manners considered essential for perception. Very little is known regarding interactions between olfactory cortices. The present study sheds light on some of the basic physiological properties of a particular intercortical pathway in the olfactory system and provides a foundation for future studies to identify, among other things, whether this pathway has implications for perception.
Assuntos
Ácido Glutâmico/metabolismo , Neurônios Receptores Olfatórios/metabolismo , Tubérculo Olfatório/metabolismo , Córtex Piriforme/metabolismo , Receptores de Dopamina D1/biossíntese , Receptores de Dopamina D2/biossíntese , Animais , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Odorantes , Neurônios Receptores Olfatórios/efeitos dos fármacos , Tubérculo Olfatório/efeitos dos fármacos , Córtex Piriforme/efeitos dos fármacos , Receptores de Dopamina D1/genética , Receptores de Dopamina D2/genética , Olfato/fisiologiaRESUMO
Olfactory dysfunction significantly impedes the life quality of patients. Neuropeptide Y (NPY) is not only a neurotrophic factor in the rodent olfactory system but also an orexigenic peptide that regulates feeding behavior. NPY increases the olfactory receptor neurons (ORNs) responsivity during starvation; however, whether NPY can promote differentiation of human ORNs remains unexplored. This study investigates the effect of NPY on the differentiation of human olfactory neuroepithelial cells in vitro. Human olfactory neuroepithelium explants were cultured on tissue culture polystyrene dishes for 21â¯days. Then, cells were cultured with or without NPY at the concentration of 0.5â¯ng/mâ for 7â¯days. The effects of treatment were assessed by phase contrast microscopy, immunocytochemistry and western blot analysis. The further mechanism was evaluated with NPY Y1 receptor-selected antagonist BIBP3226. NPY-treated olfactory neuroepithelial cells exhibited thin bipolar shape, low circularity, low spread area, and long processes. The expression levels of Ascl1, ßIII tubulin, GAP43 and OMP were significantly higher in NPY-treated cells than in controls (pâ¯<â¯0.05). NPY-treated olfactory neuroepithelial cells expressed more components of signal transduction apparatuses, Golf and ADCY3, than those without NPY treatment. Western blot analysis also further confirmed these findings (pâ¯<â¯0.05). Additionally, the expression levels of Ascl1, ßIII2 tubulin, GAP43, OMP, ADCY3, and Golf in BIBP3226â¯+â¯NPY and controls were comparable (pâ¯>â¯0.05). NPY not only increases expressions of protein markers of human olfactory neuronal progenitor cells, but also promotes differentiation of ORN and enhances formation of components of olfactory-specific signal transduction pathway through Y1 receptors.
Assuntos
Diferenciação Celular/efeitos dos fármacos , Neuropeptídeo Y/farmacologia , Mucosa Olfatória/efeitos dos fármacos , Neurônios Receptores Olfatórios/efeitos dos fármacos , Receptores de Neuropeptídeo Y/antagonistas & inibidores , Arginina/análogos & derivados , Arginina/farmacologia , Células Cultivadas , Humanos , Mucosa Olfatória/citologia , Neurônios Receptores Olfatórios/citologia , Transdução de Sinais/efeitos dos fármacosRESUMO
In order to understand how olfactory stimuli are encoded and processed in the brain, it is important to build a computational model for olfactory receptor neurons (ORNs). Here, we present a simple and reliable mathematical model of a moth ORN generating spikes. The model incorporates a simplified description of the chemical kinetics leading to olfactory receptor activation and action potential generation. We show that an adaptive spike threshold regulated by prior spike history is an effective mechanism for reproducing the typical phasic-tonic time course of ORN responses. Our model reproduces the response dynamics of individual neurons to a fluctuating stimulus that approximates odorant fluctuations in nature. The parameters of the spike threshold are essential for reproducing the response heterogeneity in ORNs. The model provides a valuable tool for efficient simulations of olfactory circuits.
Assuntos
Potenciais de Ação/fisiologia , Adaptação Fisiológica , Mariposas/fisiologia , Neurônios Receptores Olfatórios/fisiologia , Atrativos Sexuais/farmacologia , Animais , Fenômenos Eletrofisiológicos , Masculino , Modelos Biológicos , Neurônios Receptores Olfatórios/efeitos dos fármacosRESUMO
OBJECTIVE: This study aimed to investigate the effect of the p38 mitogen-activated protein kinase (p38MAPK) signaling pathway on olfactory mucosa function and apoptosis of olfactory sensory neurons (OSNs) in an allergic rhinitis (AR) mouse model. METHOD: Fifty-five BALB/c mice were used to establish AR models by ovalbumin, and their olfactory function was confirmed by the buried food pellet test. Then, 28 mice with hyposmia were selected. SB203580, a p38MAPK inhibitor, and normal saline (NS) were injected into mice with olfactory defects. The olfactory function, apoptosis of OSNs in olfactory mucosa, and the expression of the olfaction marker protein (OMP), p38MAPK, and p-p38MAPK were detected after the intervention. RESULT: SB203580 treatment significantly upregulated OMP expression and significantly improved the olfactory function of AR mice by reducing the percentage of apoptotic OSNs. In addition, SB203580 attenuated the activation of the p38MAPK signaling pathway. CONCLUSION: SB203580 protected olfactory function in an AR mouse model. This protective effect may be associated with the antiapoptotic effects of SB203580 via the p38MAPK signaling pathway.