Mika Shirasu

The scent of disease: volatile organic compounds of the human body related to disease and disorder

Hundreds of volatile organic compounds (VOCs) are emitted from the human body, and the components of VOCs usually reflect the metabolic condition of an individual. Therefore, contracting an infectious or metabolic disease often results in a change in body odour. Recent progresses in analytical techniques allow rapid analyses of VOCs derived from breath, blood, skin and urine. Disease-specific VOCs can be used as diagnostic olfactory biomarkers of infectious diseases, metabolic diseases, genetic disorders and other kinds of diseases. Elucidation of pathophysiological mechanisms underlying production of disease-specific VOCs may provide novel insights into therapeutic approaches for treatments for various diseases. This review summarizes the current knowledge on chemical and clinical aspects of body-derived VOCs, and provides a brief outlook at the future of olfactory diagnosis.

Dimethyl trisulfide as a characteristic odor associated with fungating cancer wounds.

Some advanced cancer patients suffer from pungent sulfury malodor. To determine the chemical identity of the odorant, we performed gas chromatography-mass spectrometry-olfactometry analysis of volatiles from fungating cancer wounds. We identified the source of the characteristic smell as dimethyl trisulfide, a compound that is known to be emitted from some vegetables and microorganisms. Controlling the production of dimethyl trisulfide should improve quality of life of patients.

Olfactory Receptor and Neural Pathway Responsible for Highly Selective Sensing of Musk Odors

Musk odorants are used widely in cosmetic industries because of their fascinating animalic scent. However, how this aroma is perceived in the mammalian olfactory system remains a great mystery. Here, we show that muscone, one musk odor secreted by various animals from stink glands, activates a few glomeruli clustered in a neuroanatomically unique anteromedial olfactory bulb. The muscone-responsive glomeruli are highly specific to macrocyclic ketones; interestingly, other synthetic musk odorants with nitro or polycyclic moieties or ester bonds activate distinct but nearby glomeruli. Anterodorsal bulbar lesions cause muscone anosmia, suggesting that this region is involved in muscone perception. Finally, we identified the mouse olfactory receptor, MOR215-1, that was a specific muscone receptor expressed by neurons innervating the muscone-responsive anteromedial glomeruli and also the human muscone receptor, OR5AN1. The current study documents the olfactory neural pathway in mice that senses and transmits musk signals from receptor to brain.

Decreased olfactory mucus secretion and nasal abnormality in mice lacking type 2 and type 3 IP3 receptors

Although nasal mucus is thought to play important roles in the mammalian olfactory system, the mechanisms of secretion of it and its physiological roles are poorly understood. Here we show that type 2 and type 3 IP3 receptors (IP3R2 and IP3R3) play critical roles in olfactory mucus secretion. Histological studies showed that IP3R2 and IP3R3 are predominantly expressed in two types of nasal glands, the anterior glands of the nasal septum and the lateral nasal glands (LNG), which contain mucosal proteins secreted to the main olfactory epithelium. We therefore examined LNG acinar cells, and found that acetylcholine‐mediated calcium responses and fluid‐ and protein‐ secretion in the acinar cells were markedly decreased in IP3R2–R3 double‐knockout (KO) mice. We also found nasal inflammation and a decrease in olfactory capacity in IP3R2–R3 KO mice. Despite intact signal transduction in the olfactory epithelium, IP3R2–R3 KO mice exhibited elevated threshold sensitivity to odorants on in vivo imaging of olfactory glomerular responses and behavioral tests. Our findings suggest that IP3R2 and IP3R3 mediate nasal mucus secretion, which is important for the maintenance of nasal tissue as well as the perception of odors.

Chemical Identity of a Rotting Animal-Like Odor Emitted from the Inflorescence of the Titan Arum (Amorphophallus titanum)

The titan arum, Amorphophallus titanum, is a flowering plant with the largest inflorescence in the world. The flower emits a unique rotting animal-like odor that attracts insects for pollination. To determine the chemical identity of this characteristic odor, we performed gas chromatography-mass spectrometry-olfactometry analysis of volatiles derived from the inflorescence. The main odorant causing the smell during the flower-opening phase was identified as dimethyl trisulfide, a compound with a sulfury odor that has been found to be emitted from some vegetables, microorganisms, and cancerous wounds.

Objective Display and Discrimination of Floral Odors from Amorphophallus titanum, Bloomed on Different Dates and at Different Locations, Using an Electronic Nose

As olfactory perceptions vary from person to person, it is difficult to describe smells objectively. In contrast, electronic noses also detect smells with their sensors, but in addition describe those using electronic signals. Here we showed a virtual connection method between a human nose perceptions and electronic nose responses with the smell of standard gases. In this method, Amorphophallus titanum flowers, which emit a strong carrion smell, could objectively be described using an electronic nose, in a way resembling the skill of sommeliers. We could describe the flower smell to be close to that of a mixture of methyl mercaptan and propionic acid, by calculation of the dilution index from electronic resistances. In other words, the smell resembled that of “decayed cabbage, garlic and pungent sour” with possible descriptors. Additionally, we compared the smells of flowers which bloomed on different dates and at different locations and showed the similarity of odor intensities visually, in standard gas categories. We anticipate our assay to be a starting point for a perceptive connection between our noses and electronic noses.

Ligand Specificity and Evolution of Mammalian Musk Odor Receptors: Effect of Single Receptor Deletion on Odor Detection

Musk odors have been used widely for fragrance and medicine for >2000 years because of their fascinating scent and physiological effects. Therefore, fragrance manufacturers have been eager to develop high-quality musk compounds that are safe and easily synthesized. We recently identified muscone-responsive olfactory receptors (ORs) MOR215-1 and OR5AN1 in mice and humans, respectively (Shirasu et al., 2014). In this study, we identified musk ORs that are evolutionarily closely related to MOR215-1 or OR5AN1 in various primates and investigated structure–activity relationships for various musk odorants and related compounds. We found that each species has one or two functional musk ORs that exhibit specific ligand spectra to musk compounds. Some of them, including the human OR5AN1, responded to nitro musks with chemical properties distinct from muscone. The ligand specificity of OR5AN1 reflects the perception of musk odors in humans. Genetic deletion of MOR215-1 in mice resulted in drastic reduction of sensitivity to muscone, suggesting that MOR215-1 plays a critical role in muscone perception. Therefore, the current study reveals a clear link between the identified OR and muscone perception. Moreover, the strategy established for screening ligands for the muscone OR may facilitate the development of novel and commercially useful musk odors. SIGNIFICANCE STATEMENT The long-sought musk odor receptor family in mammals was discovered and found to be well conserved and narrowly tuned to musk odors. In mice, deletion of the most sensitive musk receptor resulted in drastic reduction in sensitivity to muscone, demonstrating a strong link between receptor and odor perception. In humans, we found one musk receptor that recognized both macrocyclic and nitro musks that had distinct chemical structures. The structure–activity relationships were in a good agreement with human sensory perception and therefore may be used to develop novel musk aroma in fragrance fields. Finally, identification of a natural ligand(s) for musk receptors in mammals other than musk deer would reveal an evolutionarily pivotal role in each species in the future.

Child Odors and Parenting: A Survey Examination of the Role of Odor in Child-Rearing

Parental caregiving is critical for the survival of our young and continuation of our species. In humans, visual and auditory signals from offspring have been shown to be potent facilitators of parenting. However, whether odors emitted by our young also influence human parenting remains unclear. To explore this, we conducted a series of questionnaire surveys targeting parents with children under 6 years old. First, we collected episodes on experiencing odors/sniffing various parts of a child’s body (n = 507). The prevalence of experiencing events described in those episodes was examined in a separate survey (n = 384). Based on those results, the Child Odor in Parenting scale (COPs) was developed, and subsequently used in the main survey (n = 888). We found COPs to have adequate content validity, concurrent validity, and reliability. Responses to the COPs demonstrated that parents, especially mothers with infants, are aware of odors from their offspring, and actively seek them in daily child-rearing. The factor structure and content of the COPs items indicated that child odors have both affective and instrumental roles. Affective experiences induce loving feeling and affectionate sniffing, while instrumental experiences pertain to specific hygienic needs. The head was the most frequent source of affective experiences, and the child’s bottom of instrumental. Each was experienced by more than 90% of the mothers with a child below 1 year of age. Affective experiences significantly declined as the child grew older, possibly associated with the decline of physical proximity between parents and child. This age-related decline was not prominent for instrumental experiences, except for the bottom, which significantly declined after 3 years of age. The present findings suggest that child odors play roles in human parenting, and that their nature and significance change during the course of a child’s development.

Dimethyl Trisulfide as a Characteristic Odor Associated with Fungating Breast Cancer Wounds.

Background: Some advanced cancer patients suffer from unpleasant odor from their fungating wounds. The fungating wounds have been reported to occur in about 5% of patients with cancer. These wounds are usually superinfected with bacteria, and therefore, the infected area tends to emit malodor. However, the odorant(s) causing the malodor has not been revealed. Here we aim to determine the chemical identity of the cancer wound-derived odor(s). Results: We examined three female patients with breast cancer (B1; stage IV, B2; stage IIIB, B3; stage IV) and two male patients with head and neck cancer (H1; stage III, H2; stage IVA). First, we evaluated the intensity and quality of body odors emitted from the fungating wounds of patients. All of them had a similar pungent sulfury odor. In addition to the sulfury odor, B1and B2 had a cheese-like odor and B3, H1 and H2 had a rotten fish odor. Next, we analyzed the malodor emitted from the wounds of each patient. Sterile gauze pads were placed on fungating wounds of the patients for 6-12h. The head-space volatiles of pads were extracted onto SPME fibers for 2h. The compounds on the SPME fibers were then analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) that enabled us to examine mass spectra and odor qualities of individual GC-separated odorants simultaneously. GC-MS-O analysis and evaluation of body odors were performed by three persons. As a result, the sulfury odor, which was the same as the odor we identified in body odors of all patients, came out at the retention time (RT) of 19.46min. Cheese-like odors in B1 and B2 patients came out at RT=24.01min, 25.47min and 26.08min. The structure of dimethyl trisulfide (DMTS) was predicted by the mass spectrum of the peak around 19.5min. The mass spectrum and the RT of authentic DMTS were identical to those of the peak compound, demonstrating that the sulfury odor at 19.46min was DMTS. Comparing the odor quality and intensity of various concentrations of DMTS solutions and cancer samples, we conclude that DMTS is emitted from the cancer wounds at the level significant enough to make ones feel uncomfortable. We also identified the structure of compounds with cheese-like odors: isobutyric acid for the cheese odor (24.01min), butyric acid for the cheese and vomit odor (25.47min), and isovaleric acid for the cheese and feet odor (26.08min). Discussion: We identified DMTS as the main odorant that caused the severe malodor in some advanced cancer patients. DMTS has been found in volatiles emitted from vegetables such as cooked onion. DMTS is also reported to be produced by aerobes such as Pseudomonas aeruginosa that reside in leg ulcers. Thus, although the source of DMTS found in the fungating cancer wounds in this study remains to be elucidated, DMTS may be a product of infected bacteria in fungating wounds. To improve the QOL of patients, the development of the way to prevent or reduce the DMTS odor is awaited. Indeed, almost all patients with fungating wounds are suffering from this malodor. Our results provide new insights into the better strategies toward the treatment of malodor in cancer patients. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5042.