Increased levels of 5HT2A receptor mRNA expression in peripheral blood mononuclear cells of patients with major depression: correlations with severity and duration of illness

Neutrophil-to-lymphocyte ratio as a predictive biomarker for early diagnosis of depression: A narrative review

Depression is a mood disorder that causes persistent feelings of sadness, hopelessness, loss of interest, and decreased energy. Early diagnosis of depression can improve its negative impacts and be effective in its treatment. Previous studies have indicated that inflammation plays an important role in the initiation and development of depression, hence, various inflammatory biomarkers have been investigated for early diagnosis of depression, the most popular of which are blood biomarkers. The Neutrophil to lymphocyte ratio (NLR) may be more informative in the early diagnosis of depression than other widely used markers, such as other leukocyte characteristics or interleukins. Considering the importance of early diagnosis of depression and the role of NLR in early diagnosis of depression, our paper reviews the literature on NLR as a diagnostic biomarker of depression, which may be effective in its treatment. Various studies have shown that elevated NLR is associated with depression, suggesting that NLR may be a valuable, reproducible, easily accessible, and cost-effective method for the evaluation of depression and it may be used in outpatient clinic settings. Closer follow-up can be performed for these patients who have higher NLR levels. However, it seems that further studies on larger samples, taking into account important confounding factors, and assessing them together with other inflammatory markers are necessary to draw some conclusive statements.

Antidepressant Potential of a Functionalized 3-Selanyl Benzo[b]Furan Compound in Mice: Focus on the Serotonergic System

The present study investigated the antidepressant-like potential of a functionalized 3-selanyl benzo[b]furan (SeBZF) in male Swiss mice. To evaluate possible antidepressant-like actions, the compounds SeBZF1-5 (50 mg/kg, intragastric, i.g., route) were acutely screened in the tail suspension tests (TSTs). The compound 3-((4-methoxyphenyl)selanyl)-2-phenylbenzofuran (SeBZF3) was then selected. Dose-response and time-response curves revealed that SeBFZ3 exerts antidepressant-like effects in the TST (5-50 mg/kg) and forced swimming test (FST; 50 mg/kg). Additional tests demonstrated that pretreatment with receptor antagonists WAY100635 (5-HT_1A; 0.1 mg/kg, subcutaneous route), ketanserin (5-HT_2A/C; 1 mg/kg, intraperitoneal, i.p.), or ondansetron (5-HT₃; 1 mg/kg, i.p.) blocked the SeBZF3 antidepressant-like effects (50 mg/kg) in the TST. In addition, the coadministration of subeffective doses of SeBZF3 (1 mg/kg, i.g.) and fluoxetine (a selective serotonin reuptake inhibitor; 5 mg/kg, i.p.) produced synergistic action. A high dose of SeBZF3 (300 mg/kg) did not produce oral acute toxicity. The present results provide evidence for the antidepressant-like action of SeBZF3 and its relative safety, as well as predict the possible interactions with the serotonergic system, aiding in the development of novel options to alleviate psychiatric disabilities.

Potential biomarkers of addiction identified by real-time PCR in human peripheral blood lymphocytes: a narrative review

Addiction-related neurobiological factors could be considered as potential biomarkers. The concentration of peripheral biomarkers in tissues like blood lymphocytes may mirror their brain levels. This review is focused on the mRNA expression of potential addiction biomarkers in human peripheral blood lymphocytes (PBLs). PubMed, EMBASE, Web of Science, Scopus and Google Scholar were searched using the keywords 'addiction', 'biomarker', 'peripheral blood lymphocyte', 'gene expression' and 'real-time PCR'. The results showed the alterations in the regulation of genes such as dopamine receptors, opioid receptors, NMDA receptors, cannabinoid receptors, α-synuclein, DYN, MAO-A, FosB and orexin-A as PBLs biomarkers in addiction stages. Such variations could also be found during abstinence and relapse. PBLs biomarkers may help in drug development and have clinical implications.

Gene expression studies in Depression development and treatment: an overview of the underlying molecular mechanisms and biological processes to identify biomarkers

A combination of different risk factors, such as genetic, environmental and psychological factors, together with immune system, stress response, brain neuroplasticity and the regulation of neurotransmitters, is thought to lead to the development of major depressive disorder (MDD). A growing number of studies have tried to investigate the underlying mechanisms of MDD by analysing the expression levels of genes involved in such biological processes. These studies have shown that MDD is not just a brain disorder, but also a body disorder, and this is mainly due to the interplay between the periphery and the Central Nervous System (CNS). To this purpose, most of the studies conducted so far have mainly dedicated to the analysis of the gene expression levels using postmortem brain tissue as well as peripheral blood samples of MDD patients. In this paper, we reviewed the current literature on candidate gene expression alterations and the few existing transcriptomics studies in MDD focusing on inflammation, neuroplasticity, neurotransmitters and stress-related genes. Moreover, we focused our attention on studies, which have investigated mRNA levels as biomarkers to predict therapy outcomes. This is important as many patients do not respond to antidepressant medication or could experience adverse side effects, leading to the interruption of treatment. Unfortunately, the right choice of antidepressant for each individual still remains largely a matter of taking an educated guess.

Association of blood lead level with neurobehavior and neurotransmitter expressions in Indian children

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BLL had a significant direct correlation with abnormal neurobehavior.

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Serum serotonin levels were significantly lower in children with high blood lead levels (BLL).

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Serum serotonin and dopamine receptor expression were upregulated in children with high BLL.

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Serum serotonin levels had significant negative association with adverse neurobehavior.

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Dopamine receptor expression had significant positive association with adverse neurobehavior.

Present study aimed to assess the alterations in neurotransmitter expression and its association with Blood Lead Level (BLL) and neurobehavioral pattern in children. 72 school going children were recruited. Blood lead levels were determined by Atomic Absorption Spectrophotometer. Neurobehavioral state was assessed by means of population specific scale i.e. CPMS (Childhood Psychopathological measurement Schedule). Serum serotonin and dopamine were estimated by ELISA, receptor and transporter gene expressions were assessed by quantitative real time PCR. Significant positive correlation was observed between Total CPMS score (i.e. adverse neurobehaviour) and BLL. Further, serum serotonin levels and dopamine receptor expression showed a negative and positive association with BLL, respectively. In similarity, serum serotonin levels showed a negative correlation and dopamine receptor expression had a significant positive correlation with total CPMS score. Environmental exposure to Lead (Pb) may result in significant alterations in the neurotransmitter levels which may be associated with neurobehavioral changes in the children exposed to Pb.

In Silico Study Examining New Phenylpropanoids Targets with Antidepressant Activity

BACKGROUND

Natural products, such as phenylpropanoids, which are found in essential oils derived from aromatic plants, have been explored during non-clinical psychopharmacology studies, to discover new molecules with relevant pharmacological activities in the central nervous system, especially antidepressant and anxiolytic activities. Major depressive disorder is a highly debilitating psychiatric disorder and is considered to be a disabling public health problem, worldwide, as a primary factor associated with suicide. Current clinically administered antidepressants have late-onset therapeutic actions, are associated with several side effects, and clinical studies have reported that some patients do not respond well to treatment or reach complete remission.

OBJECTIVE

To review important new targets for antidepressant activity and to select phenylpropanoids with antidepressant activity, using Molegro Virtual Docker and Ossis Data Warris, and to verify substances with more promising antidepressant activity.

RESULTS AND CONCLUSION

An in silico molecular modeling study, based on homology, was conducted to determine the three-dimensional structure of the 5-hydroxytryptamine 2A receptor (5- HT2AR), then molecular docking studies were performed and the predisposition for cytotoxicity risk among identified molecules was examined. A model for 5-HT2AR homology, with satisfactory results, was obtained indicating the good stereochemical quality of the model. The phenylpropanoid 4-allyl-2,6-dimethoxyphenol showed the lowest binding energy for 5-HT2AR, with results relevant to the L-arginine/nitric oxide (NO)/cGMP pathway, and showed no toxicity within the parameters of mutagenicity, carcinogenicity, reproductive system toxicity, and skin-tissue irritability, when evaluated in silico; therefore, this molecule can be considered promising for the investigation of antidepressant activity.

Pivotal mental states

This paper introduces a new construct, the 'pivotal mental state', which is defined as a hyper-plastic state aiding rapid and deep learning that can mediate psychological transformation. We believe this new construct bears relevance to a broad range of psychological and psychiatric phenomena. We argue that pivotal mental states serve an important evolutionary function, that is, to aid psychological transformation when actual or perceived environmental pressures demand this. We cite evidence that chronic stress and neurotic traits are primers for a pivotal mental state, whereas acute stress can be a trigger. Inspired by research with serotonin 2A receptor agonist psychedelics, we highlight how activity at this particular receptor can robustly and reliably induce pivotal mental states, but we argue that the capacity for pivotal mental states is an inherent property of the human brain itself. Moreover, we hypothesize that serotonergic psychedelics hijack a system that has evolved to mediate rapid and deep learning when its need is sensed. We cite a breadth of evidences linking stress via a variety of inducers, with an upregulated serotonin 2A receptor system (e.g. upregulated availability of and/or binding to the receptor) and acute stress with 5-HT release, which we argue can activate this primed system to induce a pivotal mental state. The pivotal mental state model is multi-level, linking a specific molecular gateway (increased serotonin 2A receptor signaling) with the inception of a hyper-plastic brain and mind state, enhanced rate of associative learning and the potential mediation of a psychological transformation.

Gene-Based Association Analysis Suggests Association of HTR2A With Antidepressant Treatment Response in Depressed Patients

The serotonin [5-hydroxytryptamine (5-HT)] system has been implicated in the pathogenesis of major depressive disorder (MDD). Among the 5-HT receptor subtypes, 5-HT2 is one of the major pharmacological therapeutic targets for MDD. There have been inconsistent findings in previous pharmacogenetic studies investigating the antidepressant therapeutic response using one or several 5-HT2A (HTR2A) genetic polymorphisms. By using gene-based association analysis, we hope to identify genetic variants of HTR2A which are related to MDD susceptibility and its antidepressant therapeutic response. 288 HTR2A single nucleotide polymorphisms in MDD susceptibility have been investigated through a case–control (455 MDD patients and 2, 998 healthy controls) study, as well as in antidepressant efficacy (n = 455) in our current research. The 21-item Hamilton Rating Scale for Depression was used to evaluate measures of antidepressant therapeutic efficacy. From two MDD groups in the antidepressant therapeutic response, by using gene-based analyses, we have identified 14 polymorphisms as suggestive markers for therapeutic response (13 for remission and 1 for response) in both meta- and mega-analyses. All of these HTR2A reported polymorphisms did not reach statistical significance in the case–control association study. This current investigation supported the link between HTR2A variants and antidepressant therapeutic response in MDD but not with MDD susceptibility.

mRNA Levels of MAOA and 5-HT 2 A Receptor in Patients With Pathological Internet Use: Correlations With Comorbid Symptoms

Objective: Uncontrolled internet use may lead to the emergence of pathological internet use (PIU). PIU has become a global public health concern that can cause a range of psychotic symptoms, including anxiety, depression, and impulse control disorder. To date, we know very little about the principal biological factors related to PIU. Monoamine oxidase type A (MAOA) and serotonin (5-HT) 5-HT_2A receptor (5-HT_2AR) play critical roles in the development of behavioural and drug addictions. Thus, the aim of this study was to measure the relative expression of mRNA of MAOA and 5-HT_2AR in peripheral blood mononuclear cells (PBMCs) of patients with PIU and to determine the correlations between these biological indicators and the comorbid symptoms of patients with PIU. Methods: In this study, the mRNA of MAOA and 5-HT_2AR was detected using real-time PCR in PBMCs of the patients with PIU (n = 24) and healthy controls (HCs, n = 25). The relationship between the mRNA levels of MAOA and 5-HT_2AR and clinical symptoms in patients with PIU was further investigated. Results: MAOA mRNA in PBMCs was significantly upregulated in patients with PIU compared with that in HCs. mRNA levels of 5-HT_2AR were not found to differ significantly between HCs and patients with PIU. Correlation analyses further revealed a significant positive correlation between the relative expression of MAOA mRNA in PBMCs of patients with PIU and the Young's Internet Addiction Test and Self-Rating Depression Scale scores. Conclusion: The present study revealed upregulated expression of MAOA mRNA in patients with PIU and an association between the expression of MAOA mRNA and clinical symptoms of PIU, suggesting that the neurobiological changes may be similar between PIU and substance addiction. Additionally, this study demonstrated a potential association between comorbid symptoms and mRNA levels of MAOA.

Evaluation of the relationship between the gene expression level of orexin-1 receptor in the rat blood and prefrontal cortex, novelty-seeking, and proneness to methamphetamine dependence: A candidate biomarker

BACKGROUND

previous studies have suggested that methamphetamine (METH) abuse may affect orexin regulation. However, the data regarding the relationship between the current level of orexin and the vulnerability to METH abuse are minimal. Here, we have investigated the correlation between the gene expression level of the orexin-1 receptor (OX1R) in the rat prefrontal cortex (PFC) and blood lymphocytes and susceptibility to METH dependence and its impact on novelty-seeking behavior.

METHODS

male Wistar rats were first examined for novelty-seeking behavior by the novel object recognition test, and the expression level of OX1R in their blood lymphocytes was evaluated by real-time PCR. Then, the susceptibility to METH abuse was investigated by voluntary METH oral consumption test. According to the amounts of METH consumption, the animals were divided into two groups of METH preferring and non-preferring. Half of the rats in each group were sacrificed, and the level of OX1R in their blood lymphocytes and PFC tissue was measured. The other half were sacrificed for the same reason after two weeks of drug abstinence.

RESULTS

The indexes of novelty-seeking behavior were significantly higher in the METH- preferring group compared to the non-preferring animals. Furthermore, the expression level of OX1R in the blood lymphocytes and PFC in the preferring group was considerably higher than the non-preferring group.

CONCLUSION

Up-regulation of the mRNA expression level of OX1R in the lymphocytes and PFC may predict vulnerability to the METH consumption and novelty-seeking, which may serve as a potential biomarker for METH abuse.

Gene expression of serotonergic markers in peripheral blood mononuclear cells of patients with late-onset Alzheimer's disease

Serotonin or 5-hydroxytryptamine (5-HT) is primarily involved in the regulation of learning and memory. Pathological changes in metabolism or functional imbalance of 5-HT has been associated with Alzheimer's disease (AD). The hypothesis tested is that in peripheral blood, markers of the serotonergic pathway can be used as a diagnostic tool for AD. The current study measured the relative expression of 5-HT receptors (5-HTR2A and 5-HTR3A) as well as the 5-HT catalytic enzyme, Monoamine oxidase A (MAO-A) mRNA in Peripheral Blood Mononuclear Cells (PBMCs) of patients with late-onset Alzheimer's disease (LOAD) and age-matched controls. 5-HTR2A, 5-HTR3A, and MAO-A mRNA expressions were examined in PBMCs of 30 patients with LOAD and 30 control individuals. Real-time quantitative PCR was used to measure mRNA expression. The dementia status of patients in this study was assessed using a Mini-Mental State Examination (MMSE). Mean data of relative mRNA expression of 5-HTR2A, 5-HTR3A and MAO-A were significantly lower in PBMCs of patients with LOAD compared with controls. Based on the down-regulation of serotonergic markers in PBMCs, our findings may be another claim to the systemic nature of LOAD. The role of peripheral serotonergic downregulation, in the pathogenesis of AD, needs to be further studied. Given the extremely convenient access to PBMCs, these molecular events may represent more complete dimensions of AD neuropathophysiology or possibly lead to a new direction in studies focused on blood-based markers.

Gene expression in peripheral blood in treatment-free major depression

BACKGROUND

Peripheral gene expression of several molecular pathways has been studied in major depressive disorder (MDD) with promising results. We sought to investigate some of these genes in a treatment-free Latino sample of Mexican descent.

MATERIAL AND METHODS

The sample consisted of 50 MDD treatment-free cases and 50 sex and age-matched controls. Gene expression of candidate genes of neuroplasticity (BDNF, p11, and VGF), inflammation (IL1A, IL1B, IL4, IL6, IL7, IL8, IL10, MIF, and TNFA), the canonical Wnt signaling pathway (TCF7L2, APC, and GSK3B), and mTOR, was compared in cases and controls. RNA was obtained from blood samples. We used bivariate analyses to compare subjects versus control mean mRNA quantification of target genes and lineal regression modelling to test for effects of age and body mass index on gene expression.

RESULTS

Most subjects were female (66%) with a mean age of 26.7 (SD 7.9) years. Only GSK3B was differentially expressed between cases and controls at a statistically significant level (p = 0.048). TCF7L-2 showed the highest number of correlations with MDD-related traits, yet these were modest in size.

DISCUSSION

GSK3B encodes a moderator of the canonical Wnt signaling pathway. It has a role in neuroplasticity, neuroprotection, depression, and other psychiatric phenotypes. We found that adding population diversity has the potential to elicit distinct peripheral gene expression markers in MDD and MDD-related traits. However, our results should only be considered as hypothesis-generating research that merits further replication in larger cohorts of similar ancestry.

Associations Among Monoamine Neurotransmitter Pathways, Personality Traits, and Major Depressive Disorder

Major depressive disorder (MDD) is a complex psychiatric disease requiring multidisciplinary approaches to identify specific risk factors and establish more efficacious treatment strategies. Although the etiology and pathophysiology of MDD are not clear until these days, it is acknowledged that they are almost certainly multifactorial and comprehensive. Monoamine neurotransmitter system dysfunction and specific personality traits are independent risk factors for depression and suicide. These factors also demonstrate complex interactions that influence MDD pathogenesis and symptom expression. In this review, we assess these relationships with the aim of providing a reference for the development of precision medicine.

Evaluation of dynorphin and kappa-opioid receptor level in the human blood lymphocytes and plasma: Possible role as a biomarker in severe opioid use disorder

BACKGROUND

The dynorphin (DYN)/kappa opioid receptor (KOR) system plays an important role in the development of addiction, and dysregulation of this system could lead to abnormal activity in the reward pathway. It has been reported that the expression state of the neurotransmitters and their receptors in the brain is reflected in peripheral blood lymphocytes (PBLs).

METHODS

We have evaluated the PBLs and plasma samples of four groups: 1) subjects with severe opioid use disorder (SOD), 2) methadone-maintenance treated (MMT) individuals, 3) long-term abstinent subjects having former SOD, and 4) healthy control subjects (n = 20 in each group). The mRNA expression level of preprodynorphin (pPDYN) and KOR in PBLs has been evaluated by real-time PCR. Peptide expression of PDYN in PBLs has been studied by western blot, and DYN concentration in plasma has been measured by ELISA.

RESULTS

The relative expression level of the pPDYN mRNA and PDYN peptide in PBLs were significantly up-regulated in SOD, MMT, and abstinent groups compared to control subjects. No significant difference was found in the plasma DYN concentration between study groups. The expression level of the KOR mRNA in PBLs was significantly decreased in all three study groups compared to the control subjects.

CONCLUSION

the expression changes in the DYN/KOR system after chronic exposure to opioids, including methadone, seems to be stable and does not return to normal levels even after 12 months abstinence. These long-time and permanent changes in PBLs may serve as a biomarker and footprint of SOD development in the periphery.

A cross-talk between blood-cell neuroplasticity-related genes and environmental enrichment in working dogs

This study aims to identify a panel of blood-cell neuroplasticity-related genes expressed following environmental enrichment stimulation (EE). The Drug detection (DD) training course was an excellent model for the study of EE in the working dog. This research is divided into two experimental trials. In the First Trial, we identified a panel of blood-cell neuroplasticity related-genes associated with DD ability acquired during the training course. In the Second Trial, we assessed the EE additional factor complementary feeding effect on blood-cell neuroplasticity gene expressions. In the First and Second Trials, at different time points of the DD test, blood samples were collected, and NGF, BDNF, VEGFA, IGF1, EGR1, NGFR, and ICE2 blood-cell neuroplasticity related-genes were analyzed. As noted in the First Trial, the DD test in working dogs induced the transient up-regulation of VEGFA, NGF, NGFR, BDNF, and IGF, immediately after the DD test, suggesting the existence of gene regulations. On the contrary, the Second Trial, with feeding implementation, showed an absence of mRNA up-regulation after the DD test. We suppose that complementary feeding alters the systemic metabolism, which, in turn, changes neuroplasticity-related gene blood-cell mRNA. These findings suggested that, in working dogs, there is a cross-talk between blood-cell neuroplasticity-related genes and environmental enrichment. These outcomes could be used to improve future treatments in sensory implementation.

FCPR16, a novel phosphodiesterase 4 inhibitor, produces an antidepressant-like effect in mice exposed to chronic unpredictable mild stress

The canonical phosphodiesterase 4 (PDE4) inhibitors produce antidepressant-like effects in a variety of animal models. However, severe side effects, particularly vomiting and nausea, limit their clinical application. FCPR16 is a novel PDE4 inhibitor with less vomiting potential. However, whether it will exert an antidepressant-like effect remains unclear. Here, we aimed to evaluate the effect of FCPR16 in mice subjected to chronic unpredictable mild stress (CUMS). Our results showed that FCPR16 produced antidepressant-like effects in multiple behavioral tests, including a forced swimming test, tail suspension test, sucrose preference test and novelty suppression feeding test. Simultaneously, data indicated that FCPR16 enhanced the levels of several proteins, including cAMP, brain derived neurotrophic factor, exchange protein directly activated by cAMP 2 (EPAC-2), synapsin1, postsynaptic density protein 95, phosphorylated cAMP response element binding protein and extracellular regulated protein kinases 1/2, which were downregulated by CUMS in both the cerebral cortex and hippocampus. The number of DCX⁺ cells in the hippocampus of CUMS mice was increased after FCPR16 treatment. Moreover, treatment with FCPR16 resulted in decreased expression of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β) and increased expression of anti-inflammatory cytokines (IL-10) in mice challenged with CUMS. Consistently, the mRNA levels of microglial M1 markers (iNOS and TNF-α) were downregulated, while M2 markers (Arginase 1 and CD206) were upregulated in CUMS-exposed mice after FCPR16 treatment. Immunofluorescence analysis showed that FCPR16 inhibited the activation of microglial cells and increased the number of CD206⁺ in CUMS-exposed mice. Collectively, these results suggested that FCPR16 is a potential compound with effects against depressive-like behaviors, and the antidepressant-like effect of FCPR16 is possibly mediated through activation of the cAMP-mediated signaling pathways and inhibition of neuroinflammation in both the cerebral cortex and hippocampus.

GRP Receptor Regulates Depression Behavior via Interaction With 5-HT2a Receptor

OBJECTIVE

Accumulating evidences indicate that gastrin-releasing peptide receptor (GRPR) may contribute to the pathophysiology of depression. However, the mechanism of the involvement of GRPR in the progression of depression remains unclear. Here, we showed the extent to which stress and antidepressant treatment impact GRPR expression, and explored the interactions between 5-HT2a receptor (5-HT2aR) and GRPR at the cellular level.

METHODS

The rat depression models were created with chronic unpredictable mild stress (CUMS). Then, these rats were treated with fluoxetine for 4 weeks after CUMS. We measured body weight and performed behavioral tests to determine the effects of stress and fluoxetine on depressive-like behaviors. Real-time PCR and western blotting were used to measure the mRNA and protein expression levels of GRPR in the hypothalamus. Then, Flag-tagged protein (pcmv-Flag-5HT2aR) and Myc-tagged protein (pcmv-Myc-GRPR) expression vectors were constructed, identified, and transfected into human embryo kidney 293 (HEK293) cells. The interaction between 5-HT2aR and GRPR was detected by coimmunoprecipitation and double-label immunofluorescence.

RESULTS

The rats subjected to 4 weeks of CUMS showed depressive-like behaviors, including decreased body weight, sucrose preference, and distance traveled, rearing frequency and velocity in the open field test and increased immobility time in the forced swimming test. Fluoxetine treatment reversed CUMS-induced depressive-like behavior. The mRNA and protein expression of GRPR in the hypothalamus was significantly increased after 4 weeks CUMS exposure, and treatment with fluoxetine reversed these changes. Coimmunoprecipitation showed that 5-HT2aR and GRPR combine with each other in vitro. Immunofluorescence revealed that the 5-HT2aR and GRPR were colocalization in both the cell membrane and cytoplasm.

CONCLUSION

Our study enhances the understanding of the involvement of GRPR in depression. This study also provides in vitro experimental evidence of the interaction between 5-HT2aR and GRPR, which may play an important role in the pathogenesis of depression.

The Interaction of TPH2 and 5-HT2A Polymorphisms on Major Depressive Disorder Susceptibility in a Chinese Han Population: A Case-Control Study

Purpose: TPH2 and 5-HT2A appear to play vital roles in the homeostatic regulation of serotonin levels in the brain, their genetic variations may lead to impaired homeostatic regulation of serotonin resulting in abnormal levels of serotonin in the brain, thus predisposing individuals to MDD. However, research studies have yet to confirm which gene-gene interaction effect between TPH2 and 5-HT2A polymorphisms results in increased susceptibility to MDD. Methods: A total of 565 participants, consisting of 278 MDD patients and 287 healthy controls from the Chinese Han population, were recruited for the present study. Six single nucleotide polymorphisms (SNPs) of TPH2/5-HT2A were selected to assess their interaction by use of a generalized multifactor dimensionality reduction method. Results: A-allele carriers of rs11178997 and rs120074175 were more likely to suffer from MDD than T-allele carriers of rs11178997, or G-allele carriers of rs120074175. The interaction between TPH2 (rs120074175, rs11178997) and 5-HT2A (rs7997012) was considered as the best multi-locus model upon the MDD susceptibility. Conclusions: Our data identified an important effect of TPH2 genetic variants (rs11178997 and rs120074175) upon the risk of MDD, and suggested that the interaction of TPH2/5-HT2A polymorphism variants confer a greater susceptibility to MDD in Chinese Han population.

Decreased serum magnesium levels in depression: a systematic review and meta-analysis

BACKGROUND

Magnesium (Mg²⁺), an endogenous N-methyl-D-aspartate receptor antagonist, has received increased attention recently because of its role in the pathophysiology of and treatment response in depression. However, whether Mg²⁺ level is decreased in depression is not firmly established. We aimed to conduct a systematic review and meta-analysis to help making consensus for the association between Mg²⁺ levels and depression.

METHODS

A systematic search was conducted in the electronic database resources PubMed and Embase. After a careful selection of relevant studies, a meta-analysis using the random effects model was conducted in each measuring source, such as serum, plasma, and cerebrospinal fluid (CSF).

RESULTS

A total of 18 studies were included in this study. Among 11 studies that measured Mg²⁺ in the serum, Mg²⁺ level was lower in patients with depression than in controls (weighted mean difference  = -.088, 95% confidence interval  = -.164 to -.012). In the sensitivity analysis by removing studies one by one, 2 out of the 11 studies obliterated such significant differences. There were no significant differences in the Mg²⁺ levels in the studies for plasma and CSF.

CONCLUSIONS

Despite some evidence supporting an association between decreased Mg²⁺ levels and depression from studies with serum, the results of our meta-analysis urge to use caution when associating Mg²⁺ levels and depression. Future studies are needed to establish a consensus for the role of low Mg²⁺ levels in depression.

Stress exposure and psychopathology alter methylation of the serotonin receptor 2A (HTR2A) gene in preschoolers

Serotonin signaling pathways play a key role in brain development, stress reactivity, and mental health. Epigenetic alterations in the serotonin system may underlie the effect of early life stress on psychopathology. The current study examined methylation of the serotonin receptor 2A (HTR2A) gene in a sample of 228 children including 119 with child welfare documentation of moderate to severe maltreatment within the last 6 months. Child protection records, semistructured interviews in the home, and parent reports were used to assess child stress exposure, psychiatric symptoms, and behavior. The HTR2A genotype and methylation of HTR2A were measured at two CpG sites (-1420 and -1224) from saliva DNA. HTR2A genotype was associated with HTR2A methylation at both CpG sites. HTR2A genotype also moderated associations of contextual stress exposure and HTR2A methylation at site -1420. Contextual stress was positively associated with -1420 methylation among A homozygotes, but negatively associated with -1420 methylation among G homozygotes. Posttraumatic stress disorder and major depressive disorder symptoms were negatively associated with methylation at -1420, but positively associated with methylation at -1224. Results support the view that the serotonin system is sensitive to stress exposure and psychopathology, and HTR2A methylation may be a mechanism by which early adversity is biologically encoded.

Expression of NMDA receptor subunits in human blood lymphocytes: A peripheral biomarker in online computer game addiction

Background and aims Repeated performance of some behaviors such as playing computer games could result in addiction. The NMDA receptor is critically involved in the development of behavioral and drug addictions. It has been claimed that the expression level of neurotransmitter receptors in the brain may be reflected in peripheral blood lymphocytes (PBLs). Methods Here, using a real-time PCR method, we have investigated the mRNA expression of GluN2A, GluN2D, GluN3A, and GluN3B subunits of the NMDA receptor in PBLs of male online computer game addicts (n = 25) in comparison with normal subjects (n = 26). Results Expression levels of GluN2A, GluN2D, and GluN3B subunits were not statistically different between game addicts and the control group. However, the mRNA expression of the GluN3A subunit was downregulated in PBLs of game addicts. Discussion and conclusions Transcriptional levels of GluN2A and GluN2D subunits in online computer game addicts are similar to our previously reported data of opioid addiction and are not different from the control group. However, unlike our earlier finding of drug addiction, the mRNA expression levels of GluN3A and GluN3B subunits in PBLs of game addicts are reduced and unchanged, respectively, compared with control subjects. It seems that the downregulated state of the GluN3A subunit of NMDA receptor in online computer game addicts is a finding that deserves more studies in the future to see whether it can serve as a peripheral biomarker in addiction studies, where the researcher wants to rule out the confusing effects of abused drugs.

PET radioligands for the dopamine D1-receptor: Application in psychiatric disorders

The dopamine (DA) system is considered to be centrally involved in the pathophysiology of several major psychiatric disorders. Using positron emission tomography (PET), aberrations in dopamine D2/D3-receptors (D2-R) levels and uptake of the DA precursor FDOPA have been shown for schizophrenia, substance abuse and depression. Radioligands for the dopamine D1-receptor (D1-R) have been available for more than three decades, however this receptor subtype has received much less attention in psychiatry research. Here, studies investigating D1-R in psychiatric patients in comparison to healthy control subjects are summarized. Although small sample sizes, medication effects and heterogeneous methods of quantification limit the conclusions that can be drawn, the data is suggestive of higher levels of cortical D1-R in drug naïve patients with psychosis, and lower D1-R in patients with affective disorders. Data sharing and reanalysis using harmonized methodology are important next steps towards clarifying the role of D1-R in these disorders.