Hiroaki Hori

Interface between hypothalamic-pituitary-adrenal axis and brain-derived neurotrophic factor in depression.

Although the pathophysiology of depressive disorder remains elusive, two hypothetical frameworks seem to be promising: the involvement of hypothalamic pituitary‐adrenal (HPA) axis abnormalities and brain‐derived neurotrophic factor (BDNF) in the pathogenesis and in the mechanism of action of antidepressant treatments. In this review, we focused on research based on these two frameworks in relation to depression and related conditions and tried to formulate an integrated theory of the disorder. Hormonal challenge tests, such as the dexamethasone/corticotropin‐releasing hormone test, have revealed elevated HPA activity (hypercortisolism) in at least a portion of patients with depression, although growing evidence has suggested that abnormally low HPA axis (hypocortisolism) has also been implicated in a variety of stress‐related conditions. Several lines of evidence from postmortem studies, animal studies, blood levels, and genetic studies have suggested that BDNF is involved in the pathogenesis of depression and in the mechanism of action of biological treatments for depression. Considerable evidence has suggested that stress reduces the expression of BDNF and that antidepressant treatments increase it. Moreover, the glucocorticoid receptor interacts with the specific receptor of BDNF, TrkB, and excessive glucocorticoid interferes with BDNF signaling. Altered BDNF function is involved in the structural changes and possibly impaired neurogenesis in the brain of depressed patients. Based on these findings, an integrated schema of the pathological and recovery processes of depression is illustrated.

Increased cerebrospinal fluid interleukin-6 levels in patients with schizophrenia and those with major depressive disorder

Elevated peripheral levels of interleukin-6 (IL-6) are common findings in schizophrenia and depression. However, previous studies that measured cerebrospinal fluid (CSF) IL-6 levels in these disorders reported controversial results. The present study examined whether CSF IL-6 levels are altered in patients with schizophrenia and those with depression. Lumbar punctures were performed in 32 patients with schizophrenia, 30 with major depressive disorder (MDD), and 35 healthy controls. Serum samples were simultaneously collected from all subjects in the patient groups and from 32 of the control group. CSF and serum IL-6 levels were determined by enzyme-linked immunosorbent assay. Both the patients with schizophrenia and MDD had significantly higher CSF IL-6 levels compared to the controls (schizophrenia: P = 0.0027; MDD: P = 0.012). IL-6 levels were significantly higher in the CSF than in the serum. No significant correlation was observed between CSF and serum IL-6 levels. The present findings suggest that IL-6 of central origin is associated with the pathophysiology of schizophrenia and MDD, although confounding effect of smoking status can not be entirely excluded.

Negative correlation between cerebrospinal fluid oxytocin levels and negative symptoms of male patients with schizophrenia

BACKGROUNDnAccumulating evidence indicates that oxytocin plays an important role in social interactions. Previous studies also suggest altered oxytocin function in patients with schizophrenia and depression. However, few studies have examined the central oxytocin levels in these disorders.nnnMETHODSnCerebrospinal fluid (CSF) oxytocin levels were measured by ELISA in male participants consisting of 27 patients with schizophrenia, 17 with major depressive disorder (MDD), and 21 healthy controls.nnnRESULTSnCSF oxytocin levels of patients with schizophrenia or MDD did not differ significantly with healthy controls. The antidepressant dose or the Hamilton depression rating scale score did not significantly correlate with the oxytocin levels in MDD patients. CSF oxytocin levels in schizophrenic patients significantly negatively correlated with second generation antipsychotic dose (r=-0.49, P=0.010) but not with first generation antipsychotic dose (r=-0.13, P=0.50). A significant correlation was observed between oxytocin levels and negative subscale of PANSS (r=-0.38, P=0.050). This correlation remained significant even after controlling for second generation antipsychotic dose (r=-0.47, P=0.016).nnnCONCLUSIONSnWe obtained no evidence of altered CSF oxytocin levels in patients with schizophrenia or those with MDD. However, lower oxytocin levels may be related to higher second generation antipsychotic dose and more severe negative symptoms in schizophrenia.

Attitudes toward schizophrenia in the general population, psychiatric staff, physicians, and psychiatrists: A web-based survey in Japan

Little is known about possible differences in the attitudes toward schizophrenia between the general public and various healthcare professionals. After screening for the study enrollment, 197 subjects in the general population, 100 psychiatric staff (other than psychiatrists), 112 physicians (other than psychiatrists) and 36 psychiatrists were enrolled in a web-based survey using an Internet-based questionnaire format. To assess subjects attitudes toward schizophrenia, we used a 13-item questionnaire created by Uçok et al. (2006), to which five items were added. These 18 items were subjected to exploratory factor analysis, which yielded three factors classified as stigma, underestimation of patients abilities, and skepticism regarding treatment. These factors were compared between the four groups using analysis of covariance (ANCOVA), controlling for potential confounders. The ANCOVA for the stigma factor showed that psychiatrists scored significantly lower than the other three groups. The ANCOVA for the underestimation of patients abilities factor revealed that psychiatric staff scored significantly lower than the general population. The present results indicated that attitudes toward schizophrenia consist of at least three separable factors. Psychiatrists had the least negative attitudes toward schizophrenia, which was followed by the psychiatric staff, and attitudes of the general population and of physicians were equally stigmatizing.

Functional interactions between steroid hormones and neurotrophin BDNF

Brain-derived neurotrophic factor (BDNF), a critical neurotrophin, regulates many neuronal aspects including cell differentiation, cell survival, neurotransmission, and synaptic plasticity in the central nervous system (CNS). Though BDNF has two types of receptors, high affinity tropomyosin-related kinase (Trk)B and low affinity p75 receptors, BDNF positively exerts its biological effects on neurons via activation of TrkB and of resultant intracellular signaling cascades including mitogen-activated protein kinase/extracellular signal-regulated protein kinase, phospholipase Cγ, and phosphoinositide 3-kinase pathways. Notably, it is possible that alteration in the expression and/or function of BDNF in the CNS is involved in the pathophysiology of various brain diseases such as stroke, Parkinsons disease, Alzheimers disease, and mental disorders. On the other hand, glucocorticoids, stress-induced steroid hormones, also putatively contribute to the pathophysiology of depression. Interestingly, in addition to the reduction in BDNF levels due to increased glucocorticoid exposure, current reports demonstrate possible interactions between glucocorticoids and BDNF-mediated neuronal functions. Other steroid hormones, such as estrogen, are involved in not only sexual differentiation in the brain, but also numerous neuronal events including cell survival and synaptic plasticity. Furthermore, it is well known that estrogen plays a role in the pathophysiology of Parkinsons disease, Alzheimers disease, and mental illness, while serving to regulate BDNF expression and/or function. Here, we present a broad overview of the current knowledge concerning the association between BDNF expression/function and steroid hormones (glucocorticoids and estrogen).

Relationships between psychological distress, coping styles, and HPA axis reactivity in healthy adults

Psychological distress and coping styles have been suggested to relate to altered function in the hypothalamic-pituitary-adrenal (HPA) axis, although there remains much to be understood about their relationships. High and low cortisol levels (or reactivity) both represent HPA axis dysfunction, with accumulated evidence suggesting that they are linked to different types of psychopathology. The dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test has been extensively used to identify HPA axis abnormalities in various psychiatric conditions including mood disorders; however, the possible associations of psychological distress and coping styles with HPA axis function have not been well documented using this test. Here, we examined the relationships of HPA axis reactivity as measured by the DEX/CRH test with subjectively perceived psychological distress and coping styles, both of which were assessed with self-report questionnaires, in 121 healthy volunteers. Subjects were divided into three groups by the cortisol suppression pattern, namely the incomplete-suppressors (DST-Cortisolxa0≥xa05xa0μg/dL or DEX/CRH-Cortisolxa0≥xa05xa0μg/dL), moderate-suppressors (DST-Cortisolxa0<xa05xa0μg/dL and 1xa0μg/dLxa0≤xa0DEX/CRH -Cortisolxa0<xa05xa0μg/dL), and enhanced-suppressors (DST-Cortisolxa0<xa05xa0μg/dL and DEX/CRH-Cortisolxa0<xa01xa0μg/dL). The enhanced-suppressors showed significantly higher scores in obsessive-compulsive, interpersonal sensitivity and anxiety symptoms and significantly more frequent use of avoidant coping strategy, compared to the other two groups. These results point to the important role of enhanced suppression of cortisol, or blunted cortisol reactivity, in non-clinical psychopathology such as avoidant coping strategy and greater psychological distress.

Poor sleep is associated with exaggerated cortisol response to the combined dexamethasone/CRH test in a non-clinical population

Although sleep disturbance has been shown to be associated with psychological distress and the hypothalamic-pituitary-adrenal (HPA) axis function, the simultaneous relationship between sleep, distress and HPA axis function is less clear. Here we examined the relationship between sleep quality as assessed with the Pittsburgh Sleep Quality Index, psychological distress as assessed with the Hopkins Symptom Checklist, and cortisol responses to the dexamethasone (DEX)/corticotropin-releasing hormone (CRH) test in 139 non-clinical volunteers. Poor sleep was significantly correlated with greater cortisol response to the combined DEX/CRH challenge, but not with the cortisol level just before CRH challenge. When subjects were divided into three groups based on the suppression pattern of cortisol (i.e., incomplete-, moderate-, and enhanced-suppressors), poor sleep was significantly associated with the incomplete suppression in women while no significant association was found between sleep and the enhanced suppression. The association between poor sleep and exaggerated cortisol response to the CRH challenge became more clear in the regression analysis where the confounding effect of psychological distress was taken into consideration. These results indicate that poor sleep would be associated with exaggerated cortisol reactivity. The observed association of poor sleep with reactive cortisol indices to the CRH challenge, but not with the cortisol level after DEX administration alone, might add to the well-established evidence demonstrating the role of CRH in the regulation of sleep. Our findings further suggest that the mediation model would work better than the bivariate approach in investigating the relationship between sleep, distress and HPA axis reactivity.

Association between the functional polymorphism (C3435T) of the gene encoding P-glycoprotein (ABCB1) and major depressive disorder in the Japanese population.

Human P-glycoprotein (P-gp), which is encoded by ABCB1 (ATP-binding cassette, sub-family B member 1), is expressed in the blood brain barrier and protects the brain from many kinds of drugs and toxins including glucocorticoids by acting as an efflux pump. We examined whether functional polymorphisms of ABCB1 give susceptibility to major depressive disorder (MDD). The five functional single nucleotide polymorphisms (SNPs), A-41G (rs2188524), T-129C (rs3213619), C1236T (Gly412Gly: rs1128503), G2677A/T (Ala893Ser/Thr: rs2032582), and C3435T (Ile1145Ile: rs1045642) were genotyped in 631 MDD patients and 1100 controls in the Japanese population. A tri-allelic SNP, G2677A/T, was genotyped by pyrosequencing and the remaining SNPs were genotyped by the TaqMan 5-exonuclease allelic discrimination assay. The minor T3435 allele was significantly increased in MDD patients than in the controls (χ(2)xa0=xa04.5, dfxa0=xa01, pxa0=xa00.034, odds ratio [OR] 1.16, 95% confidential interval [CI] 1.01-1.34). Homozygotes for the T3435 allele was significantly more common in patients than in the controls (χ(2)xa0=xa07.5, dfxa0=xa01, pxa0=xa00.0062, OR 1.43, 95%CI 1.11-1.85). With respect to the other 4 SNPs, there was no significant difference in genotype or allele distribution. In the haplotype-based analysis, the proportion of individuals with the TT1236-TT3435 haploid genotype was significantly increased in patients than in controls (χ(2)xa0=xa08.5, dfxa0=xa01, p = 0.0037, OR 1.50, 95%CI 1.14-1.98). Our results suggest that the T3435 allele or carrying two copies of this allele confers susceptibility to MDD in the Japanese population.

A genetic variation in the dysbindin gene (DTNBP1) is associated with memory performance in healthy controls

Schizophrenia is a common psychiatric disorder characterized by disturbances of cognition, emotion and social functioning. There are few studies investigating a possible genetic basis for the underlying mechanism of cognitive dysfunctions. A genetic variation in the dysbindin gene (DTNBP1: dystrobrevin binding protein 1), a susceptibility gene for schizophrenia, has been reported to be associated with general cognitive ability and cognitive decline in patients with schizophrenia. Although profound disturbances of memory performance are observed in schizophrenia, only one study has reported a relationship between this gene and spatial working memory in a Caucasian population. We examined a possible association between a protective haplotype of DTNBP1 for developing schizophrenia and memory performance measured by the Wechsler Memory Scale-Revised (WMS-R) and the Wechsler Adult Intelligence Scale-Revised (WAIS-R) in 165 healthy volunteers and 70 patients with schizophrenia in a Japanese population. Healthy controls that carry the protective haplotype showed higher performance in several memory domains measured by the WMS-R than those who did not. Genotype effect on memory performance was not observed in patients with schizophrenia. This haplotype did not affect IQ and its sub-scores as measured by the Wechsler Adult Intelligence Scale-Revised in both groups. These data suggest that DTNBP1 may have impact on parts of memory functions.

Effects of the CACNA1C risk allele on neurocognition in patients with schizophrenia and healthy individuals

Recent genetic association studies have identified the A-allele of rs1006737 within CACNA1C as a risk factor for schizophrenia as well as mood disorders. Some evidence suggests that this polymorphism plays a role in cognitive function both in schizophrenia patients and healthy individuals; however, the precise nature of this association remains unclear. Here we investigated the possible association of this polymorphism with a wide range of neurocognitive functions in schizophrenia patients and in healthy subjects. Schizophrenia patients exhibited significantly poorer performance on all the cognitive domains as compared to healthy controls. In patients, A-allele carriers demonstrated significantly worse logical memory performance than the G-allele homozygotes. In controls, no significant association was observed between the genotype and any of the cognitive domains examined. These results add to the literature suggesting that rs1006737 may be associated with schizophrenia through its detrimental effect on endophenotypic traits.