Kazufumi Yoshihara

Critical role of gut microbiota in the production of biologically active, free catecholamines in the gut lumen of mice

There is increasing interest in the bidirectional communication between the mammalian host and prokaryotic cells. Catecholamines (CA), candidate molecules for such communication, are presumed to play an important role in the gut lumen; however, available evidence is limited because of the lack of actual data about luminal CA. This study evaluated luminal CA levels in the gastrointestinal tract and elucidated the involvement of gut microbiota in the generation of luminal CA by comparing the findings among specific pathogen-free mice (SPF-M), germ-free mice (GF-M), and gnotobiotic mice. Substantial levels of free dopamine and norepinephrine were identified in the gut lumen of SPF-M. The free CA levels in the gut lumen were lower in GF-M than in SPF-M. The majority of CA was a biologically active, free form in SPF-M, whereas it was a biologically inactive, conjugated form in GF-M. The association of GF-M with either Clostridium species or SPF fecal flora, both of which have abundant β-glucuronidase activity, resulted in the drastic elevation of free CA. The inoculation of E. coli strain into GF-M induced a substantial amount of free CA, but the inoculation of its mutant strain deficient in the β-glucuronidase gene did not. The intraluminal administration of DA increased colonic water absorption in an in vivo ligated loop model of SPF-M, thus suggesting that luminal DA plays a role as a proabsorptive modulator of water transport in the colon. These results indicate that gut microbiota play a critical role in the generation of free CA in the gut lumen.

IL-15 Regulates CD8+ T Cell Contraction during Primary Infection

During the course of acute infection with an intracellular pathogen, Ag-specific T cells proliferate in the expansion phase, and then most of the T cells die by apoptosis in the following contraction phase, but the few that survive become memory cells and persist for a long period of time. Although IL-15 is known to play an important role in long-term maintenance of memory CD8+ T cells, the potential roles of IL-15 in CD8+ T cell contraction are not known. Using an adoptive transfer system of OT-I cells expressing OVA257–264/Kb-specific TCR into control, IL-15 knockout (KO) and IL-15 transgenic (Tg) mice followed by challenge with recombinant Listeria monocytogenes expressing OVA, we found that the survival of CD44+CD62L−CD127− effector OT-I cells during the contraction phase is critically dependent on IL-15. In correlation with the expression level of Bcl-2 in OT-I cells, the number of OT-I cells was markedly reduced in IL-15 KO mice but remained at a high level in IL-15 Tg mice during the contraction phase, compared with control mice. In vivo administration of rIL-15 during the contraction phase in IL-15 KO mice inhibited the contraction of effector OT-I cells accompanied by up-regulation of Bcl-2 expression. Furthermore, enforced expression of Bcl-2 protected the majority of effector OT-I cells from death in IL-15 KO mice after infection. These results suggest that IL-15 plays a critical role in protecting effector CD8+ T cells from apoptosis during the contraction phase following a microbial infection via inducing antiapoptotic molecules.

Role of interleukin 15 in colitis induced by dextran sulphate sodium in mice

Background and aims: Interleukin (IL)-15 is a member of the IL-2 family, stimulating dendritic cells, natural killer (NK) cells, NK T cells and memory CD8+ T cells. IL-15 levels were elevated in the intestinal mucosa of inflammatory bowel diseases. Here we investigated the involvement of IL-15 in the pathogenesis of acute and chronic dextran sulphate sodium (DSS) induced colitis. Methods: IL-15 knockout (KO) mice and control C57BL/6 mice were used to induce colitis with DSS in their drinking water. Survival rate, clinical activity of diseases, extent of tissue damage, leucocyte population, and cytokine production of lamina propria (LP) cells of the large intestines were assessed. Results: IL-15 KO mice exhibited resistance to DSS induced acute colitis, as reflected by lower lethality, weight loss, clinical scores, and histological scores compared with those in control mice (p<0.05). The proportions of CD44high CD8+ T cells and NK cells in LP cells and levels of interferon (IFN)-γ, tumour necrosis factor (TNF)-α, and IL-12p40 in culture supernatants of LP cells were reduced in IL-15 KO mice (p<0.05). In vivo depletion of CD8+ T cells and NK cells decreased levels of IFN-γ, TNF-α, and IL-12p40 in culture supernatants of LP cells in C57BL/6 mice (p<0.01). In chronic colitis, weight loss and clinical scores were improved and levels of IFN-γ, TNF-α, and IL-12p40 in culture supernatants of LP cells were also reduced in IL-15 KO mice (p<0.05). Conclusions: IL-15 plays an important role in the pathogenesis of both acute and chronic colitis induced by DSS in mice.

Profile of mood states and stress-related biochemical indices in long-term yoga practitioners

BackgroundPrevious studies have shown the short-term or intermediate-term practice of yoga to be useful for ameliorating several mental disorders and psychosomatic disorders. However, little is known about the long-term influences of yoga on the mental state or stress-related biochemical indices. If yoga training has a stress-reduction effect and also improves an individuals mental states for a long time, long-term yoga practitioners may have a better mental state and lower stress-related biochemical indices in comparison to non-experienced participants. This study simultaneously examined the differences in mental states and urinary stress-related biochemical indices between long-term yoga practitioners and non-experienced participants.MethodsThe participants were 38 healthy females with more than 2 years of experience with yoga (long-term yoga group) and 37 age-matched healthy females who had not participated in yoga (control group). Their mental states were assessed using the Profile of Mood States (POMS) questionnaire. The level of cortisol, 8-hydroxydeoxyguanosine (8-OHdG) and biopyrrin in urine were used as stress-related biochemical indices.ResultsThe average self-rated mental disturbance, tension-anxiety, anger-hostility, and fatigue scores of the long-term yoga group were lower than those of the control group. There was a trend toward a higher vigor score in the long-term yoga group than that in the control group. There were no significant differences in the scores for depression and confusion in the POMS between the two groups. The urine 8-OHdG concentration showed a trend toward to being lower in the long-term yoga group in comparison to the control group. There were no significant differences in the levels of urine biopyrrin or cortisol.ConclusionsThe present findings suggest that long-term yoga training can reduce the scores related to mental health indicators such as self-rated anxiety, anger, and fatigue.

Effect of 12 weeks of yoga training on the somatization, psychological symptoms, and stress-related biomarkers of healthy women

BackgroundPrevious studies have shown that the practice of yoga reduces perceived stress and negative feelings and that it improves psychological symptoms. Our previous study also suggested that long-term yoga training improves stress-related psychological symptoms such as anxiety and anger. However, little is known about the beneficial effects of yoga practice on somatization, the most common stress-related physical symptoms, and stress-related biomarkers. We performed a prospective, single arm study to examine the beneficial effects of 12 weeks of yoga training on somatization, psychological symptoms, and stress-related biomarkers.MethodsWe recruited healthy women who had no experience with yoga. The data of 24 participants who were followed during 12 weeks of yoga training were analyzed. Somatization and psychological symptoms were assessed before and after 12 weeks of yoga training using the Profile of Mood State (POMS) and the Symptom Checklist-90-Revised (SCL-90-R) questionnaires. Urinary 8-hydroxydeoxyguanosine (8-OHdG), biopyrrin, and cortisol levels were measured as stress-related biomarkers. The Wilcoxon signed-rank test was used to compare the stress-related biomarkers and the scores of questionnaires before and after 12 weeks of yoga training.ResultsAfter 12 weeks of yoga training, all negative subscale scores (tension-anxiety, depression, anger-hostility, fatigue, and confusion) from the POMS and somatization, anxiety, depression, and hostility from the SCL-90-R were significantly decreased compared with those before starting yoga training. Contrary to our expectation, the urinary 8-OHdG concentration after 12 weeks of yoga training showed a significant increase compared with that before starting yoga training. No significant changes were observed in the levels of urinary biopyrrin and cortisol after the 12 weeks of yoga training.ConclusionsYoga training has the potential to reduce the somatization score and the scores related to mental health indicators, such as anxiety, depression, anger, and fatigue. The present findings suggest that yoga can improve somatization and mental health status and has implications for the prevention of psychosomatic symptoms in healthy women.Trial registrationUniversity Hospital Medical Information Network (UMIN CTR) UMIN000007868.

The hepatic vagus nerve attenuates Fas-induced apoptosis in the mouse liver via α7 nicotinic acetylcholine receptor

BACKGROUND & AIMS Although accumulating evidence has recently shown that the efferent vagus nerve attenuates systemic inflammation, it remains unclear whether or not the vagus nerve can affect Fas-induced liver apoptosis. We investigated the effect of the vagus nerve by using a selective hepatic vagotomy. METHODS We assessed the mortality and apoptosis in Fas-induced fulminant hepatitis in sham-operated and vagotomized male C57BL/6 mice. To determine how the nerve influences hepatocyte apoptosis, hepatitis was preceded by pretreatment with nicotine; PNU-282987, an alpha7 nicotinic acetylcholine receptor (AChR) agonist; liposome-encapsulated dichloromethylene diphosphonate (lipo-Cl(2)MDP), a macrophage eliminator; and Mn (III) tetrakis (4-benzoic acid) porphyrin chloride (MnTBAP), an oxidative inhibitor. RESULTS Mortality in the vagotomized mice was significantly higher than that in the sham-operated mice following intravenous administration with the anti-Fas antibody Jo-2. This result was also supported by the data from both terminal deoxynucleotidyl-transferase mediated dUTP nick-end labeling and caspase-3 assay, in which vagotomized livers showed a significant elevation in the number of apoptotic hepatocytes and increased caspase-3 activity following Jo-2 treatment compared with the sham-operated livers. Supplementation with nicotine and PNU-282987 dose dependently inhibited this detrimental effect of the vagotomy. Moreover, the vagotomy-triggered exacerbation of Fas-induced hepatitis was completely blocked by lipo-Cl(2)MDP. Similarly, pretreatment with MnTBAP also completely suppressed the vagotomy-triggered exacerbation. CONCLUSIONS The hepatic vagus nerve appears to play an important role in attenuating Fas-induced hepatocyte apoptosis through alpha7 nicotinic AChR, perhaps by causing the Kupffer cells to reduce their generation of an excessive amount of reactive oxygen species.

IL‐15 exacerbates collagen‐induced arthritis with an enhanced CD4+ T cell response to produce IL‐17

IL‐15 is thought to be involved in the pathogenesis of rheumatoid arthritis (RA). We found that IL‐15 plays an important role in the development of murine collagen‐induced arthritis (CIA). The incidence and severity of CIA were slightly decreased in IL‐15 KO mice but were increased in IL‐15 Tg mice compared with wild‐type (WT) mice. The levels of type II collagen (CII)‐specific IL‐17 production were significantly increased in IL‐15 Tg mice compared with WT mice with CIA. Expression of IL‐23R was up‐regulated in CD4+ T cells in IL‐15 Tg mice but down‐regulated in IL‐15 KO mice compared with WT mice. In correlation with the expression levels of IL‐23R, IL‐17 production by CD4+ T cells in response to exogenous IL‐23 was increased in IL‐15 Tg mice compared with WT mice. Furthermore, exogenous IL‐15 synergized with IL‐23 to induce CII‐specific IL‐17 production by CD4+ T cells in vitro. Taken together, these results indicate that IL‐15 plays an important role in the progression of CIA through increasing antigen‐specific IL‐17 production by CD4+ T cells.

Neural substrates of shared attention as social memory: A hyperscanning functional magnetic resonance imaging study

During a dyadic social interaction, two individuals can share visual attention through gaze, directed to each other (mutual gaze) or to a third person or an object (joint attention). Shared attention is fundamental to dyadic face-to-face interaction, but how attention is shared, retained, and neutrally represented in a pair-specific manner has not been well studied. Here, we conducted a two-day hyperscanning functional magnetic resonance imaging study in which pairs of participants performed a real-time mutual gaze task followed by a joint attention task on the first day, and mutual gaze tasks several days later. The joint attention task enhanced eye-blink synchronization, which is believed to be a behavioral index of shared attention. When the same participant pairs underwent mutual gaze without joint attention on the second day, enhanced eye-blink synchronization persisted, and this was positively correlated with inter-individual neural synchronization within the right inferior frontal gyrus. Neural synchronization was also positively correlated with enhanced eye-blink synchronization during the previous joint attention task session. Consistent with the Hebbian association hypothesis, the right inferior frontal gyrus had been activated both by initiating and responding to joint attention. These results indicate that shared attention is represented and retained by pair-specific neural synchronization that cannot be reduced to the individual level.

Pyrogenic cytokines did not mediate a stress interview-induced hyperthermic response in a patient with psychogenic fever: a case report.

Objective: To investigate if pyrogenic cytokines mediated psychological stress-induced hyperthermic response in a patient with psychogenic fever. Despite many case reports on psychogenic fever, the mechanism responsible for how psychological stress increases core body temperature (Tc) in humans is not yet known. Case Presentation: A 13-year-old girl with fever (>38°C) of unknown causes was referred to our department because psychogenic fever was suspected. To determine if the fever was actually induced by psychological stress, we conducted a 60-minute stress interview. Her baseline oral temperature was 36.60°C and it began to increase immediately after commencement of the interview, reaching a maximum of 37.42°C 20 minutes after the end of the interview. The plasma level of prostaglandin E2 and the serum interleukin-6 level were increased 90 minutes after the interview. Serum levels of interleukin-1α, interleukin-1β, and macrophage inflammatory protein-1α were all less than their minimum detectable level throughout the observation period. We also measured the patients thermal preference by immersing her hands in warm (40°C) and cold (20°C) water. Her preference changed from cold to warm only during the increasing phase of oral temperature. Conclusions: This case report shows that a stress interview actually increased Tc in a patient with psychogenic fever. This study suggests that, although pyrogenic cytokines are not involved, the stress interview-induced increase in Tc was an active hyperthermia under the control of the brain, as is infection-induced fever. BP = blood pressure; HR = heart rate; IL = interleukin; MIP-1α = macrophage inflammatory protein-1α; Tc = core temperature; PGE2 = prostaglandin E2; SIH = stress-induced hyperthermia.

Structural and functional associations of the rostral anterior cingulate cortex with subjective happiness.

Happiness is one of the most fundamental human goals, which has led researchers to examine the source of individual happiness. Happiness has usually been discussed regarding two aspects (a temporary positive emotion and a trait-like long-term sense of being happy) that are interrelated; for example, individuals with a high level of trait-like subjective happiness tend to rate events as more pleasant. In this study, we hypothesized that the interaction between the two aspects of happiness could be explained by the interaction between structure and function in certain brain regions. Thus, we first assessed the association between gray matter density (GMD) of healthy participants and trait-like subjective happiness using voxel-based morphometry (VBM). Further, to assess the association between the GMD and brain function, we conducted functional magnetic resonance imaging (MRI) using the task of positive emotion induction (imagination of several emotional life events). VBM indicated that the subjective happiness was positively correlated with the GMD of the rostral anterior cingulate cortex (rACC). Functional MRI demonstrated that experimentally induced temporal happy feelings were positively correlated with subjective happiness level and rACC activity. The rACC response to positive events was also positively correlated with its GMD. These results provide convergent structural and functional evidence that the rACC is related to happiness and suggest that the interaction between structure and function in the rACC may explain the trait-state interaction in happiness.