Yoshinori Masuo

It is difficult to evaluate the pre-symptomatic state of mental disorders and prevent its onset. Since stress could be a trigger of mental disorders, it may be helpful to identify stress-responsive biomarkers (stress markers) for the evaluation of stress levels. We have so far performed omics analyses of the rat brain and peripheral blood after various kinds of stress and have found numerous factors that respond to stress. In this study, we investigated the effects of relatively moderate stress on these factors in the rat to identify stress marker candidates. Adult male Wistar rats underwent water immersion stress for 12 h, 24 h, or 48 h. Stress caused weight loss and elevated serum corticosterone levels, and alterations regarded as anxiety and/or fear-like behaviors. Reverse-transcription PCR and Western blot analyses revealed significant alterations in the expressions of hippocampal genes and proteins by the stress for no longer than 24 h, such as mitogen-activated protein kinase phosphatase 1 (MKP-1), CCAAT/enhancer-binding protein delta (CEBPD), small ubiquitin-like modifier proteins 1/sentrin-specific peptidase 5 (SENP5), matrix metalloproteinase-8 (MMP-8), kinase suppressor of Ras 1 (KSR1), and MKP-1, MMP-8, nerve growth factor receptor (NGFR). Similar alterations were observed in three genes (MKP-1, CEBPD, MMP-8) in the peripheral blood. The present results strongly suggest that these factors may serve as stress markers. The correlation of these factors in the blood and brain may enable the evaluation of stress-induced changes in the brain by blood analysis, which will contribute to preventing the onset of mental disorders.

(1) Sesame oil aroma has stress-relieving properties, but there is little information on its effective use and active ingredients. (2) Methods: ICR male mice were housed under water-immersion stress for 24 h. Then, the scent of sesame oil or a typical ingredient was inhaled to the stress groups for 30, 60, or 90 min. We investigated the effects of sesame oil aroma on mice behavior and the expression of the dual specificity phosphatase 1 (DUSP1) gene, a candidate stress marker gene in the brain. (3) Results: In an elevated plus-maze test, the rate of entering into the open arm of a maze and the staying time were increased to a maximum after 60 min of inhalation, but these effects decreased 90 min after inhalation. As for the single component, anxiolytic effects were observed in the 2,5-dimethylpyrazine and 2-methoxy phenol group, but the effect was weakened in the furfuryl mercaptan group. The expression levels of DUSP1 in the hippocampus and striatum were significantly decreased in 2,5-dimethylpyrazine and 2-methoxy phenol groups. (4) Conclusions: We clarified the active ingredients and optimal concentrations of sesame oil for its sedative effect. In particular, 2,5-dimethylpyrazine and 2-methoxy phenol significantly suppressed the stress-induced changes in the expression of DUSP1, which are strong anti-stress agents. Our results suggest that these molecules may be powerful anti-stress agents.

The stress response in the brain is not fully understood, although stress is one of the risk factors for developing mental disorders. On the other hand, the stimulation of the olfactory system can influence stress levels, and a certain smell has been empirically known to have a stress-suppressing effect, indeed. In this review, we first outline what stress is and previous studies on stress-responsive biomarkers (stress markers) in the brain. Subsequently, we confirm the olfactory system and review previous studies on the relationship between smell and stress response by species, such as humans, rats, and mice. Numerous studies demonstrated the stress-suppressing effects of aroma. There are also investigations showing the effects of odor that induce stress in experimental animals. In addition, we introduce recent studies on the effects of aroma of coffee beans and essential oils, such as lavender, cypress, α-pinene, and thyme linalool on the behavior and the expression of stress marker candidates in the brain. The transfer of volatile components into the brain is also discussed while using the results of thyme linalool as an example. These studies may provide a good opportunity to connect chemical research at the molecular level with neuropharmacological approaches in the future.

(1) Background: Sesame has been popular as a healthy food since ancient times, and effects of the aroma component of roasted sesame are also expected. However, little research has been reported on its scent; (2) Methods: Jcl:ICR male mice were housed under water immersion stress for 24 h. Then, the scent of saline or sesame oil was inhaled to stress groups for 90 min. We investigated the effects of sesame oil aroma on the behavior and brains of mice; (3) Results: In an elevated plus maze test, the rate of entering to open arm and the staying time were decreased by the stress. These decrements were significantly enhanced by sesame oil aroma. Stress had a tendency to increase the serum corticosterone concentration, which was slightly decreased by the aroma. Expression of Kruppel-like factor-4 (Klf-4) and Dual-specificity phosphatase-1 (Dusp-1) in the striatum were increased by water immersion stress, and the level of Klf-4 and Dusp-1 in the striatum and hippocampus were significantly attenuated by sesame oil aroma (4) Conclusions: The present results strongly suggest that the odor component of sesame oil may have stress suppressing effects. Moreover, Klf-4 and Dusp-1 may be sensitive stress-responsive biomarkers.

DNA microarray unravels rapid changes in transcriptome of MK-801 treated rat brain

Essential oils are mainly administered by inhalation. Administration by inhalation is considered to occur through two pathways, neurological transfer and pharmacological transfer. However, the relationship between the two routes is not clear. To clarify this relationship, we administered α‐pinene, which has an anxiolytic‐like effect, to mice. Emotional behavior and accumulation and expression of relevant mRNAs in the brain (brain‐derived neurotrophic factor (BDNF); tyrosine hydroxylase (TH)) were examined following inhaled administration of α‐pinene (10 μL/L air for 60 or 90 min). To evaluate the anxiolytic‐like effect, the elevated plus maze (EPM) test was used. Inhalation of α‐pinene for 60 min produced a significant increase in the total distance traveled in the EPM test compared with control (water). The concentration of α‐pinene in the brain after 60 min of inhalation was significantly increased compared with that after 90 min of inhalation. The expression of BDNF mRNA in the olfactory bulb and in the hippocampus was almost the same after 60 min of inhalation compared to that after 90 min of inhalation. The expression of TH mRNA in the midbrain after 60 min of inhalation was significantly increased compared with that of the control. Thus, an increase in α‐pinene in the brain induces an increase in TH mRNA expression and increases locomotor activity. The anxiolytic‐like effect may be related to both neurological transfer and pharmacological transfer. Copyright © 2014 John Wiley & Sons, Ltd.

The vulnerability of developing brains to environmental chemicals has been reported. Here, we examined the temporal effects of bisphenol A on dopaminergic neurons. Exposure of 5-day-old rats to bisphenol A caused hyperactivity in juveniles, after which spontaneous motor activity leveled off at 8 weeks of age, when apoptotic cell death was still observed along with the loss of tyrosine hydroxylase immunoreactivity. Accumulation of α-synuclein, a pathological marker of neurodegeneration, was also detectable in the substantia nigra, but not in the cerebral cortex. In adult rats, acute toxicity following microinjection of bisphenol A (20 μg) caused degeneration of dopaminergic neurons, similar to that following administration of 6-hydroxydopamine (15 μg). Chronic exposure of adult rats to bisphenol A (3 mg/kg/day for 28 days) caused neurodegeneration in the substantia nigra. However, behavioral effects were not seen after either acute or chronic exposure of adult rats to bisphenol A. Thus, the sensitivity of the central nervous system to bisphenol A was shown to be different at different life stages, confirming the greater vulnerability of the developing central nervous system.

Various effects have been reported in the literature for the essential oil from Chamaecyparis obtusa (EOCO), such as antibacterial and antifungal activity. In this study, we examined the effect of EOCO on emotional behavior and stress-induced biomarkers. Male ICR mice, aged 5 weeks at the start of each experiment, were individually housed in cages for 1 week. After placing each mouse in a glass container and exposing it to EOCO for 90 min, we then investigated the influence on emotional behavior using the elevated-plus maze (EPM) test, which is one of the evaluation methods for anxiolytic-like behavior. Significant anxiolytic-like effects were observed for the 7.0 mg/L air EOCO (PP<0.05). These results indicate that EOCO has both anxiolytic-like and stress mitigation effects.