Eszter Molnár

New Evidence for the Association of the Serotonin Transporter Gene (SLC6A4) Haplotypes, Threatening Life Events, and Depressive Phenotype

BACKGROUND Since the first report of the significant gene-environment interaction (G x E) in depression published by Caspi et al., the literature is considerably contradictory in this field. To clarify this question, we analyzed the interaction between the serotonin transporter gene (SLC6A4) and threatening life events (TLE) on Zung Self-Rating Depression Score (ZSDS). METHODS Five markers tagging the whole SLC6A4 gene (5-HTTLPR and 4 single nucleotide polymorphisms: rs2020942, rs140700, rs3798908, rs1042173) were genotyped in 567 nonclinical individuals. Generalized linear models were used to analyze single marker associations, and likelihood ratio tests and score tests were used for haplotype analysis. RESULTS Haplotype analysis revealed a significant global effect of haplotypes on ZSDS score in high TLE subgroup (p = .008). Besides the 5-HTTLPR, rs140700 tagging the middle region of the gene had significant effects. Subjects carrying the A allele of rs140700 scored lower on ZSDS independently of 5-HTTLPR carrier status. Explained variances for depressive phenotype were 1%, 4%, and 6% when 5-HTTLPR, 5-HTTLPR x TLE and 5-HTTLPR x rs140700 x TLE were included in the model, respectively. CONCLUSIONS Our results demonstrate heterogeneity of individuals carrying S alleles of 5-HTTLPR in association with high TLE providing possible explanation for the inconsistency of previous studies. In addition to the promoter, the middle region of the SLC6A4 gene carries the G x G x E interaction for mood, and this new model provided a higher explained variance. We report the first evidence for the significant effects of haplotypes of the SLC6A4 gene and threatening life events on depressive phenotype.

Significant association between the C(-1019)G functional polymorphism of the HTR1A gene and impulsivity.

Serotonin‐1A (5‐HT1A) receptors are known to play a role in impulsivity‐related behavior. The C(−1019)G functional polymorphism (rs6295) has been suggested to regulate the 5‐HT1A receptor gene (HTR1A) expression in presynaptic raphe neurons, namely, increased receptor concentration and reduced neuronal firing could be associated with the G allele. Previous studies indicate that this polymorphism is associated with aggression, suicide, and several psychiatric disorders, yet its association with impulsivity has rarely been investigated. We studied the relationship between impulsivity and the C(−1019)G polymorphism of the HTR1A in a population sample of 725 volunteers using the Impulsiveness subscale (IVE‐I) of the Eysenck Impulsiveness, Venturesomeness, and Empathy scale and also the Barratt Impulsiveness Scale (BIS‐11). Data were analyzed using analysis of variance with age and gender as covariates and Tukeys HSD post‐hoc test. Post‐hoc analysis revealed that the study had 0.958 power to detect 0.15 effect size. Significant differences between the C(−1019)G genotype groups (GG vs. GC vs. CC) were found. Subjects carrying GG genotype showed significantly higher impulsiveness scores compared to GC or CC carriers for the IVE‐I scale (P = 0.014), for the Motor (P = 0.021), Cognitive Impulsiveness (P = 0.002), and for the BIS total score (P = 0.008) but not for the Nonplanning Impulsiveness (P = 0.520) subscale of the BIS‐11. Our results suggest the involvement of the HTR1A in the continuum phenotype of impulsivity.

Decrease in REM latency and changes in sleep quality parallel serotonergic damage and recovery after MDMA: a longitudinal study over 180 days

The recreational drug ecstasy [3,4-methylenedioxymethamphetamine (MDMA)], has been found to selectively damage brain serotonin neurons in experimental animals, and probably in human MDMA users, but detailed morphometric analyses and parallel functional measures during damage and recovery are missing. Since there is evidence that serotonin regulates sleep, we have compared serotonergic markers parallel with detailed analysis of sleep patterns at three time-points within 180 d after a single dose of 15 mg/kg MDMA in male Dark Agouti rats. At 7 d and 21 d after MDMA treatment, significant(30-40%), widespread reductions in serotonin transporter (5-HTT) density were detected in the cerebral cortex, hippocampus, most parts of the hypothalamus, and some of the brainstem nuclei. With the exception of the hippocampus, general recovery was observed in the brain 180 d after treatment. Transient increases followed by decreases were detected in 5-HTT mRNA expression of dorsal and median raphe nuclei at 7 d and 21 d after the treatment. Significant reductions in rapid eye movement (REM) sleep latency, increases in delta power spectra in non-rapid eye movement sleep and increased fragmentation of sleep were also detected, but all these alterations disappeared by the 180th day. The present data provide evidence for long-term, albeit, except for the hippocampus, transient changes in the terminal and cellular regions of the serotonergic system after this drug. Reduced REM latency and increased sleep fragmentation are the most characteristic alterations of sleep consistently described in depression using EEG sleep polygraphy.

Small platform sleep deprivation selectively increases the average duration of rapid eye movement sleep episodes during sleep rebound

The single platform-on-water (flower pot) method is extensively used for depriving rapid eye movement sleep (REMS). Detailed comparison of sleep-wake architecture, recorded during the rebound period after spending three days on either a small or large platform, could separate the effects of REMS deficit from other stress factors caused by the procedure. A further aim of the study was to find the most characteristic REMS parameter of the rebound originating from REMS deficit. Rats were kept on a small or large platform for 72 h. Their fronto-parietal electroencephalogram, electromyogram and motility were recorded during the 24 h rebound at the beginning of the passive phase. A similar period of a home cage group was also recorded. The most typical differences between the two rebound groups were the increased cumulative time and longer average duration of REMS episodes without significant change in the number of these episodes of the small platform animals during the passive phase. Results obtained by cosinor analysis were in accordance with the findings above. Since we did not find any difference in the average duration of REMS episodes comparing the large platform rebound group and the home cage group, we concluded that the increased mean duration of REMS episodes is a selective marker for the rebound caused by small platform sleep deprivation, while other changes in sleep architecture may be the consequence of stress and also some sleep deficit.

Histamine as a potential autocrine regulator of melanoma.

Malignant tumor cells express autocrine and paracrine growth factors that can block immune effectiveness and facilitate the acquisition of partial or complete growth autonomy. Recently histamine (Hi) was proved to have an important role as a mediator in normal and malignant cell proliferation. We have reported that Hi behaves as an autocrine growth factor in an experimental mammary carcinoma and in pancreatic carcinoma cells [1, 2]. Human melanoma cells contain high HDC activity and mRNA expression [3, 4]. In this work, we thus investigated the possible role of Hi in the regulation of melanoma growth.

Interaction of 5-HTTLPR genotype and unipolar major depression in the emergence of aggressive/hostile traits

OBJECTIVE The 5-HTTLPR polymorphism has been associated both with depression and aggression/hostility. The multidirectional association between depression, aggression and the s allele may be important, since all these phenomena are related to suicidal behavior. Our aim was to investigate the association between 5-HTTLPR and aggressive/hostile traits in depressed patients and controls. METHODS 137 depressive and 118 control women completed the Buss-Durkee Hostility Inventory and were genotyped for 5-HTTLPR. BDHI scores in the different groups were investigated by Generalized Linear Model Analysis. Association between dependent and independent variables in the model was tested by the likelihood ratio Chi-square statistic. RESULTS Diagnosis and genotype showed a significant association with several aggressive/hostile traits. Interaction of the two main effects was also significant in case of several subscales. Post hoc analyses indicated a significant association between BDHI subscales and s allele only in the depressed group. LIMITATION Only women were studied and since gender differences are present both in aggressive behavior and putatively in the behavioral effects of 5-HTTLPR genotype, our findings pertain only to females. CONCLUSION Our results indicate a robust relationship between aggression/hostility and 5-HTTLPR genotype, but this association is more marked in the presence of depression. The presence of the s allele thus not only contributes to a higher risk of depression, but in depressives also leads to higher aggression/hostility. Our results have important implications for suicide research, since the s allele is associated with violent suicide, and this association may be mediated through the emergence of increased aggression/hostility in depressed patients carrying the s allele.

Seasonality and winter-type seasonal depression are associated with the rs731779 polymorphism of the serotonin-2A receptor gene

Seasonal Affective Disorder (SAD), seasonality and increased sensitivity to the fluctuation of seasons in biological and psychological parameters can manifest to varying degrees across a normal population. The serotonin-2A (5-HT2A) receptor gene has long been suggested as a candidate for the genetic basis of this phenomenon. We hypothesized that functional sequence variation in this gene could contribute to seasonality and the development of winter- and/or summer-type seasonal depression. Seasonality was measured by the self-rating Global Seasonality Score (GSS) of the Seasonal Pattern Assessment Questionnaire, and SAD by the Seasonal Health Questionnaire (SHQ). We analysed associations between GSS or SAD scores and 5-HTR2A receptor gene polymorphisms rs731779, rs985934 and rs6311, in 609 individuals. People carrying the GG genotype of rs731779 were six times more likely to manifest winter or summer SAD compared to GT or TT genotypes (OR = 6.47), and the chance of having winter-type SAD was almost nine-fold (OR = 8.7) with the GG genotype. GG subjects of rs731779 also scored significantly higher on the GSS scale compared to carriers of the T allele. In the haplotype analysis subjects carrying the G allele of rs731779 scored higher on the GSS scale, while the presence of the T allele leads to lower scores. These results suggest that variations in the 5-HTR2A gene play a significant role in the development of seasonality and especially in winter-type SAD. The fact that the above polymorphism showed association not only with clinical SAD but also seasonality symptoms in a general population provides evidence for the spectrum nature of this connection.

Association between the activation of MCH and orexin immunorective neurons and REM sleep architecture during REM rebound after a three day long REM deprivation

Rapid eye movement (REM) sleep rebound following REM deprivation using the platform-on-water method is characterized by increased time spent in REM sleep and activation of melanin-concentrating hormone (MCH) expressing neurons. Orexinergic neurons discharge reciprocally to MCH-ergic neurons across the sleep-wake cycle. However, the relation between REM architecture and the aforementioned neuropeptides remained unclear. MCH-ergic neurons can be divided into two subpopulations regarding their cocaine- and amphetamine-regulated transcript (CART) immunoreactivity, and among them the activation of CART-immunoreactive subpopulation is higher during the REM rebound. However, the possible role of stress in this association has not been elucidated. Our aims were to analyze the relationship between the architecture of REM rebound and the activation of hypothalamic MCH-ergic and orexinergic neurons. We also intended to separate the effect of stress and REM deprivation on the subsequent activation of subpopulations of MCH-ergic neurons. In order to detect neuronal activity, we performed MCH/cFos and orexin/cFos double immunohistochemistry on home cage, sleep deprived and sleep-rebound rats using the platform-on-water method with small and large (stress control) platforms. Furthermore, REM architecture was analyzed and a triple MCH/CART/cFos immunohistochemistry was also performed on the rebound groups in the same animals. We found that the activity of MCH- and orexin-immunoreactive neurons during REM rebound was positively and negatively correlated with the number of REM bouts, respectively. A negative reciprocal correlation was also found between the activation of MCH- and orexin-immunoreactive neurons during REM rebound. Furthermore, difference between the activation of CART-immunoreactive (CART-IR) and non-CART-immunoreactive MCH-ergic neuron subpopulations was found only after selective REM deprivation, it was absent in the large platform (stress control) rebound group. These results support the role of CART-IR subpopulation of MCH-ergic neurons and the inverse relationship of MCH and orexin in the regulation of REM sleep after REM sleep deprivation.

Acute SSRI-induced anxiogenic and brain metabolic effects are attenuated 6 months after initial MDMA-induced depletion

To assess the functional state of the serotonergic system, the acute behavioural and brain metabolic effect of SSRI antidepressants were studied during the recovery period after MDMA-induced neuronal damage. The effects of the SSRI fluoxetine and the serotonin receptor agonist meta-chloro-phenylpiperazine (m-CPP) were investigated in the social interaction test in Dark Agouti rats, 6 months after treatment with a single dose of MDMA (15 or 30 mg kg(-1), i.p.). At earlier time points these doses of MDMA have been shown to cause 30-60% loss in axonal densities in several brain regions. Densities of the serotonergic axons were assessed using serotonin-transporter and tryptophan-hydroxylase immunohistochemistry. In a parallel group of animals, brain function was examined following an acute challenge with either fluoxetine or citalopram, using 2-deoxyglucose autoradiographic imaging. Six months after MDMA treatment the densities of serotonergic axons were decreased in only a few brain areas including hippocampus and thalamus. Basal anxiety was unaltered in MDMA-treated animals. However, the acute anxiogenic effects of fluoxetine, but not m-CPP, were attenuated in animals pretreated with MDMA. The metabolic response to both citalopram and fluoxetine was normal in most of the brain areas examined with the exception of ventromedial thalamus and hippocampal sub-fields where the response was attenuated. These data provide evidence that 6 months after MDMA-induced damage serotonergic axons show recovery in most brain areas, but serotonergic functions to challenges with SSRIs including anxiety and aggression remain altered.

Genetic variants in the catechol-o-methyltransferase gene are associated with impulsivity and executive function: Relevance for major depression†‡

The catechol‐o‐methyltransferase (COMT) gene has been extensively investigated in depression with somewhat contradictory results but the role of impulsivity, as a possible intermediate phenotype in this disorder, has not been considered yet. In our study, four tagging SNPs in the COMT gene (rs933271, rs740603, rs4680, rs4646316) were genotyped in two independent population cohorts: Manchester (n = 1267) and Budapest (n = 942). First, we investigated the association between COMT genotypes, impulsivity, neuroticism and depression using haplotype trend regression, and constructed a model using structural equation modeling to investigate the interaction between these factors. Secondly, we tested the effect of executive function on this model in a smaller interviewed sample (n = 207). Our results demonstrated that COMT haplotypes were significantly associated with impulsivity in the combined cohort, showing the same direction of effects in both populations. The COMT effect on depressive symptoms (in subjects without history of depression) and on executive function (interviewed sample) showed the opposite pattern to impulsivity. Structural equation models demonstrated that COMT and impulsivity acted, both together (through neuroticism) and independently, to increase the risk of depression. In addition, better executive function also operated as a risk factor for depression, possibly though reduced ability to flexibly disengage negative emotions. In conclusion, variations in the COMT gene exert complex effects on susceptibility to depression involving various intermediate phenotypes, such as impulsivity and executive function. These findings emphasise that modeling of disease pathways at phenotypic level are valuable for identifying genetic risk factors.