The smelling of Hedione results in sex-differentiated human brain activity

lncRNA lnc-POP1-1 upregulated by VN1R5 promotes cisplatin resistance in head and neck squamous cell carcinoma through interaction with MCM5

Cisplatin resistance is a major therapeutic challenge in advanced head and neck squamous cell carcinoma (HNSCC). Here, we aimed to investigate the key signaling pathway for cisplatin resistance in HNSCC cells. Vomeronasal type-1 receptor 5 (VN1R5) was identified as a cisplatin resistance-related protein and was highly expressed in cisplatin-resistant HNSCC cells and tissues. The long noncoding RNA (lncRNA) lnc-POP1-1 was confirmed to be a downstream target induced by VN1R5. VN1R5 transcriptionally regulated lnc-POP1-1 expression by activating the specificity protein 1 (Sp1) transcription factor via the cyclic AMP (cAMP)/protein kinase A (PKA) pathway. VN1R5 promoted cisplatin resistance in HNSCC cells in a lnc-POP1-1-dependent manner. Mechanistically, lnc-POP1-1 bound to the minichromosome maintenance deficient 5 (MCM5) protein directly and decelerated MCM5 degradation by inhibiting ubiquitination of the MCM5 protein, which facilitated the repair of DNA damage caused by cisplatin. In summary, we identified the cisplatin resistance-related protein VN1R5 and its downstream target lnc-POP1-1. Upon upregulation by VN1R5, lnc-POP1-1 promotes DNA repair in HNSCC cells through interaction with MCM5 and deceleration of its degradation.

Effects of the odorant Hedione on the human stress response

Olfactory cues can affect subjective and autonomic manifestations of the human stress response, but evidence of altered endocrine stress reactivity is inconclusive. In the present study, we investigated effects of the odorant Hedione on the human stress response. We exposed 56 women in their follicular phases to a stressor in a room scented with Hedione or no odor. Subjective stress was captured via repeated self-report measurements and the assessment of anticipatory appraisal. As physiological markers of stress, we assessed blood pressure, salivary cortisol and alpha-amylase. The odorant enhanced the cortisol and cardiovascular stress response while leaving subjective stress unaffected. Our results provide evidence for a modulation of the human response to acute psychosocial stress by Hedione. A potential mechanism underlying this effect is Hedione targeting the hypothalamus via binding to the VN1R1 receptor, which is expressed on the human nasal mucosa.

Sex Differences in Odor Hedonic Perception: An Overview

Odor hedonic evaluation (pleasant/unpleasant) is considered as the first and one of the most prominent dimension in odor perception. While sex differences in human olfaction have been extensively explored, gender effect in hedonic perception appears to be less considered. However, a number of studies have included comparisons between men and women, using different types of measurements (psychophysical, psychophysiological,…). This overview presents experimental works with non-specific and body odors separately presented as well as experimental studies comparing healthy participants vs patients with psychiatric disorders. Contrary to sensitivity, identification or discrimination, the overall literature tends to prove that no so clear differences occur in odor hedonic judgment between men and women. On the whole, gender effect appears more marked for body than non-specific odors and is almost never reported in psychiatric diseases. These findings are discussed in relation to the processes classically implied in pleasantness rating and emotional processes.

Odours as context cues of emotional memories - The role of semantic relatedness

Odours constitute effective context cues, facilitating memory retrieval. Identifying factors which modulate the effectiveness of olfactory context cues can advance the understanding of processes underlying this effect. We hypothesized that the interplay of subjective stress and semantic relatedness between the odour and the learning material would modulate the effectiveness of an olfactory context cue. We further explored the effect of the odorant Hedione, which is a ligand for a putative human pheromone receptor (VN1R1). To this end, 120 participants watched a video of a stressful episode in which visual objects were present, that were either manipulated in the video (central objects) or not (peripheral objects). Participants rated their subjective stress afterwards. After 24 h, recognition and spatial memory of the objects in the video were tested. Ambient during encoding and recall was an odour related to the episode, an unrelated odour, Hedione or no odour. As a result, we observed a narrowing of recognition memory with increased subjective stress elicited by the video - but only if a semantically related odour was ambient. Moreover, higher subjective stress predicted enhanced spatial memory in the no odour condition, but not in presence of a semantically related or unrelated odour. When exposed to Hedione, higher subjective stress predicted impaired recognition and spatial memory of peripheral objects. Our findings stress the importance of considering semantic relatedness between the olfactory context and the encoded episode when applying odours as context cues for emotional or stressful memories.

The De-Scent of Sexuality: Did Loss of a Pheromone Signaling Protein Permit the Evolution of Same-Sex Sexual Behavior in Primates?

Primate same-sex sexual behavior (SSSB) is rarely observed in strepsirrhine species, and only somewhat more common in platyrrhines, but is observed in nearly all catarrhine species, including humans, suggesting the common catarrhine ancestor as the origin of routine SSSB. In mice, disruption of the transient receptor potential cation channel 2 (TRPC2) gene, which is crucial for transducing chemosensory signals from pheromones in the vomeronasal organ, greatly increased the likelihood of SSSB. We note that catarrhine primates share a common deleterious mutation in this gene, indicating that the protein was dysfunctional in the common catarrhine ancestral primate approximately 25 mya (million years ago). We hypothesize that the loss of this protein for processing pheromonal signals in males and females made SSSB more likely in a primate ancestral species by effectively lifting a pheromonally mediated barrier to SSSB and that this was an important precursor to the evolution of such behavior in humans. Additional comparisons between SSSB and the functional status of the TRPC2 gene or related proteins across primate species could lend support to or falsify this hypothesis. Our current research indicates that loss of TRPC2 function in developing mice leads to the loss or attenuation of sexually dimorphisms in the adult brain, which may help us to understand the biological underpinnings of SSSB. Our hypothesis offers an ultimate evolutionary explanation for SSSB in humans.

Prior exposure to Hedione, a model of pheromone, does not affect female ratings of male facial attractiveness or likeability

The existence of pheromones in humans is controversial, partly because of definitional difficulties and partly because of the question of possible chemical substances. The synthetic compound Methyl dihydrojasmonate (Hedione) is potent to bind to vomeronasal-type 1 receptors (VN1R1s) and activate limbic areas of the brain in a sex-specific manner. However, one of the most important definitional points for a human pheromone effect has not yet been investigated, i.e., whether smelling Hedione, a model of pheromone, has a behavioral effect. We tested in females whether Hedione leads to altered perception of male social stimuli. Each of the included women were sensitive to Hedione and were tested around the time of ovulation in three consecutive sessions, during each they were exposed to either Hedione or Phenylethyl alcohol or Odorless air. We measured the speed of male face recognition (implicit priming task) and collected ratings of facial attractiveness and likeability of men (explicit task). Only about half of the women tested were sensitive to Hedione. Those women did not show any effect of Hedione exposure in the implicit priming task and moderate, but non-significant effects in the explicit task. We therefore assume that Hedione is not a potent model of pheromone in humans and this observation may be due to the fact that the artificially produced substance is not suited for signaling the proximity of other humans. Furthermore, the high rate of Hedione-specific anosmia leads to the hypothesis that a substantial proportion of individuals has a poor V1NR1 receptor expression.

Brain Responses to Food Odors Associated With BMI Change at 2-Year Follow-Up

The understanding of food cue associated neural activations that predict future weight variability may guide the design of effective prevention programs and treatments for overeating and obesity. The current study investigated the association between brain response to different food odors with varied energy density and individual changes of body mass index (BMI) over 2 years. Twenty-five participants received high-fat (chocolate and peanut), low-fat (bread and peach) food odors, and a nonfood odor (rose) while the brain activation was measured using functional magnetic resonance imaging (fMRI). BMIs were calculated with participant’s self-reported body weight and height collected at the time of the fMRI scan and again at 2 years later. Regression analyses revealed significant negative correlations between BMI increase over 2 years and brain activation of the bilateral precuneus and the right posterior cingulate cortex (PCC) in response to high-fat vs. low-fat food odors. Also, brain activation of the right supplementary motor area (SMA) in response to food vs. non-food odor was negatively correlated to subsequent BMI increase over 2 years. Taken together, the current findings suggest that individual differences in neural responsivity to (high calorie) food odors in brain regions of the default mode and motor control network serve as a neural marker for future BMI change.

Single-cell analysis of olfactory neurogenesis and differentiation in adult humans

The presence of active neurogenic niches in adult humans is controversial. We focused attention to the human olfactory neuroepithelium, an extracranial site supplying input to the olfactory bulbs of the brain. Using single-cell RNA sequencing analyzing 28,726 cells, we identified neural stem cell and neural progenitor cell pools and neurons. Additionally, we detailed the expression of 140 olfactory receptors. These data from the olfactory neuroepithelium niche provide evidence that neuron production may continue for decades in humans.

Hedione Reduces Subjective Vicarious Stress

Observing another person in a stressful situation can cause a full-blown physiological stress response in the observer, which is referred to as empathic stress. One way through which stress-related information might be transmitted between individuals under conditions of empathic stress is chemosensory communication. In the present study, we investigated whether the odorant Hedione, as a potential chemosignal, affects the empathic stress response at a physiological and psychological level. For this purpose, two experiments were designed, each testing one group of participants in an odor-free room and a second group in a room scented with Hedione. In Experiment 1, 60 participants (25 males) watched a video of an unknown female participant in the Trier Social Stress Test (TSST). In Experiment 2, 37 free-cycling females watched a live video of a male participant in the TSST. Observers’ psychological and physiological stress response was captured via repeated measurements of salivary cortisol, alpha-amylase, and self-report ratings. Empathy with the stressed participants was assessed on the dimensions of personal distress and empathic concern of the Emotional Response Scale (ERS). Our results show no substantial physiological stress response in the observers and no effect of Hedione on physiological stress measures. Further, in Experiment 1, there was no subjective stress elicited by the video and no effect of Hedione. In Experiment 2, the observation was perceived as stressful and Hedione reduced subjective vicarious stress. The subjective stress response was associated with the Observers’ direct personal distress, but not with their empathic concern for the target in both experiments. Based on the findings presented above, we conclude that under conditions of empathic stress, Hedione alleviates subjectively perceived stress felt when observing another person being stressed, while leaving empathic concern for the target unaffected. In this regard, future research is warranted to clarify the underlying mechanisms of this effect.

[Modern studies of the role of the vomeronasal system in the perception of pheromones and their impact on social and sexual behavior]

The vomeronasal system (VNS) provides regulation of a wide range of autonomic and affective functions, behavioral reactions in response to the specific chemical stimuli pheromones secreted by mammals, including humans. The results of experimental studies confirming the existence of VNS and explaining the basic mechanisms of its functioning are presented. The results of studies of healthy volunteers, explaining the effect of pheromones on a number of functions of the human body, are considered.

Sex differences in main olfactory system pathways involved in psychosexual function

We summarize literature from animal and human studies assessing sex differences in the ability of the main olfactory system to detect and process sex-specific olfactory signals ("pheromones") that control the expression of psychosexual functions in males and females. A case is made in non primate mammals for an obligatory role of pheromonal signaling via the main olfactory system (in addition to the vomeronasal-accessory olfactory system) in mate recognition and sexual arousal, with male-specific as well as female-specific pheromones subserving these functions in the opposite sex. Although the case for an obligatory role of pheromones in mate recognition and mating among old world primates, including humans, is weaker, we review the current literature assessing the role of putative human pheromones (eg, AND, EST, "copulin"), detected by the main olfactory system, in promoting mate choice and mating in men and women. Based on animal studies, we hypothesize that sexually dimorphic effects of putative human pheromones are mediated via main olfactory inputs to the medial amygdala which, in turn, transmits olfactory information to sites in the hypothalamus that regulate reproduction.

The characterization of flavored hookahs aroma profile and in response to heating as analyzed via headspace solid-phase microextraction (SPME) and chemometrics

Flavors profiling in flavored hookah tobacco is an issue of increasing scrutiny for the health sector owing to its adverse effects on humans, especially being heated to produce smoke. This study aims at tackling the components involved in the flavored hookah tobacco from a chemical and biological point of view. Detecting individual flavor compounds, within a complex hookah tobacco matrix was accomplished using headspace solid phase microextraction (SPME). A total of 114 volatiles were identified in 13 flavored hookah tobacco products, with esters amounting for the major component up to 40%. Whereas oxygenated monoterpenes presented another major volatile class, contributing up to 23%, including (E)-anethole. Superheating flavored hookah tobacco at 190 °C resulted in the release of a mixture of phenol derivatives and polycyclic aromatic compounds that are indicative of coal tar, a major component produced during hookah tobacco usage with potential health hazards. This study provides the first comprehensive volatile profile of hookah tobacco products from different origins identifying chemical components involved in flavors. It is expected to serve as informative grounds for the better understanding of hookah tobacco production and usage. The information presented is also expected to raise awareness on the health risks of hookah tobacco smoking.

Potential therapeutic effects of odorants through their ectopic receptors in pigmented cells

Several olfactory receptors (ORs) have been characterized outside the olfactory neuroepithelium in neuronal and non-neuronal tissues, where they were implicated in the recognition of diverse chemical signals. ORs have been found to regulate melanogenesis in skin melanocytes, and OR expression has been found in the human brain nigrostriatal dopaminergic neurons, where production of melanin occurs as neuromelanin and can change with age; OR expression is downregulated in Parkinson's disease. Therefore, we propose several odorants as new functional ligands to ORs expressed in non-olfactory pigmented cells as dopaminergic neurons and melanocytes, where, by acting on cAMP-induced melanin production, they could help to counteract melanogenic and neurodegenerative dysfunctions, including melanoma and Parkinson's disease.

Exposure to Hedione Increases Reciprocity in Humans

Cooperation among unrelated humans is frequently regarded as a defining feature in the evolutionary success of our species. Whereas, much research has addressed the strategic and cognitive mechanisms that underlie cooperation, investigations into chemosensory processes have received very limited research attention. To bridge that gap, we build on recent research that has identified the chemically synthesized odorant Hedione (HED) as a ligand for the putative human pheromone receptor (VN1R1) expressed in the olfactory mucosa, and hypothesize that exposure to HED may increase reciprocity. Applying behavioral economics paradigms, the present research shows that exposure to the ligand causes differentiated behavioral effects in reciprocal punishments (Study 1) as well as rewards (Study 2), two types of behaviors that are frequently regarded as essential for the development and maintenance of cooperation.

A missense polymorphism in the putative pheromone receptor gene VN1R1 is associated with sociosexual behavior

Pheromones regulate social and reproductive behavior in most mammalian species. These effects are mediated by the vomeronasal and main olfactory systems. Effects of putative pheromones on human neuroendocrine activity, brain activity and attractiveness ratings suggest that humans may communicate via similar chemosignaling. Here we studied two samples of younger and older individuals, respectively, with respect to one nonsynonymous polymorphism in the gene encoding the human vomeronasal type-1 receptor 1, VN1R1, and one nonsynonymous polymorphism in the gene encoding the olfactory receptor OR7D4. Participants in both samples had self-reported their sociosexual behavior using the sociosexual orientation inventory, including questions regarding lifetime number of one-night stands, number of partners last year and expected number of partners the coming 5 years. In women, there was a significant association between the VN1R1 polymorphism and sociosexual behavior in both samples, driven specifically by the question regarding one-night stands. Our results support the hypothesis that human social interaction is modulated by communication via chemosignaling.

Odorants could elicit repair processes in melanized neuronal and skin cells

The expression of ectopic olfactory receptors (ORs) in melanized cells, such as the human brain nigrostriatal dopaminergic neurons and skin melanocytes, is here pointed out. ORs are recognized to regulate skin melanogenesis, whereas OR expression in the dopaminergic neurons, characterized by accumulation of pigment neuromelanin, is downregulated in Parkinson's disease. Furthermore, the correlation between the pigmentation process and the dopamine pathway through α-synuclein expression is also highlighted. Purposely, these ORs are suggested as therapeutic target for neurodegenerative diseases related to the pigmentation disorders. Based on this evidence, a possible way of turning odorants into drugs, acting on three specific olfactory receptors, OR51E2, OR2AT4 and VN1R1, is thus introduced. Various odorous molecules are shown to interact with these ORs and their therapeutic potential against melanogenic and neurodegenerative dysfunctions, including melanoma and Parkinson's disease, is suggested. Finally, a direct functional link between olfactory and endocrine systems in human brain through VN1R1 is proposed, helping to counteract female susceptibility to Parkinson's disease in quiescent life.

Advances of Molecular Imaging for Monitoring the Anatomical and Functional Architecture of the Olfactory System

The olfactory system of organisms serves as a genetically and anatomically model for studying how sensory input can be translated into behavior output. Some neurologic diseases are considered to be related to olfactory disturbance, especially Alzheimer's disease, Parkinson's disease, multiple sclerosis, and so forth. However, it is still unclear how the olfactory system affects disease generation processes and olfaction delivery processes. Molecular imaging, a modern multidisciplinary technology, can provide valid tools for the early detection and characterization of diseases, evaluation of treatment, and study of biological processes in living subjects, since molecular imaging applies specific molecular probes as a novel approach to produce special data to study biological processes in cellular and subcellular levels. Recently, molecular imaging plays a key role in studying the activation of olfactory system, thus it could help to prevent or delay some diseases. Herein, we present a comprehensive review on the research progress of the imaging probes for visualizing olfactory system, which is classified on different imaging modalities, including PET, MRI, and optical imaging. Additionally, the probes' design, sensing mechanism, and biological application are discussed. Finally, we provide an outlook for future studies in this field.

Human amygdala activations during nasal chemoreception

This review serves as a comprehensive discussion of chemosensory stimulation of the amygdala in healthy humans. Following an introduction of the neuroanatomy of chemosensory processing in primary and secondary olfactory structures, functional resonance magnetic imaging and positron imaging tomography studies are systematically categorized based on valence of stimuli, stimulus concentration, and paradigm-dependent amygdala activation. The amygdala shows patterns of lateralization due to stimulus valence. Main findings include pleasant odors being associated with bilateral or left amygdala activation, and unpleasant odors being associated with activation of the right amygdala, suggesting a crucial role of the right amygdala in evolutionary preservation. Potentially threatening social stimuli, however, might be processed apart from the olfactory system and tend to activate the left amygdala. Amygdala response to chemosensory stimuli correlated with simultaneous activation in the orbitofrontal cortex (OFC), piriform cortex (PC), and insula, suggesting a close-knit network of these areas during stimulus processing.