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

The role of serotonin in depression-A historical roundup and future directions

Depression is one of the most common psychiatric disorders worldwide, affecting approximately 280 million people, with probably much higher unrecorded cases. Depression is associated with symptoms such as anhedonia, feelings of hopelessness, sleep disturbances, and even suicidal thoughts. Tragically, more than 700 000 people commit suicide each year. Although depression has been studied for many decades, the exact mechanisms that lead to depression are still unknown, and available treatments only help a fraction of patients. In the late 1960s, the serotonin hypothesis was published, suggesting that serotonin is the key player in depressive disorders. However, this hypothesis is being increasingly doubted as there is evidence for the influence of other neurotransmitters, such as noradrenaline, glutamate, and dopamine, as well as larger systemic causes such as altered activity in the limbic network or inflammatory processes. In this narrative review, we aim to contribute to the ongoing debate on the involvement of serotonin in depression. We will review the evolution of antidepressant treatments, systemic research on depression over the years, and future research applications that will help to bridge the gap between systemic research and neurotransmitter dynamics using biosensors. These new tools in combination with systemic applications, will in the future provide a deeper understanding of the serotonergic dynamics in depression.

Neuroimaging Genomics a Predictor of Major Depressive Disorder (MDD)

Depression is a complex psychiatric disorder influenced by various genetic and environmental factors. Strong evidence has established the contribution of genetic factors in depression through twin studies and the heritability rate for depression has been reported to be 37%. Genetic studies have identified genetic variations associated with an increased risk of developing depression. Imaging genetics is an integrated approach where imaging measures are combined with genetic information to explore how specific genetic variants contribute to brain abnormalities. Neuroimaging studies allow us to examine both structural and functional abnormalities in individuals with depression. This review has been designed to study the correlation of the significant genetic variants with different regions of neural activity, connectivity, and structural alteration in the brain as detected by imaging techniques to understand the scope of biomarkers in depression. This might help in developing novel therapeutic interventions targeting specific genetic pathways or brain circuits and the underlying pathophysiology of depression based on this integrated approach can be established at length.

Influence of TPH2 and HTR1A polymorphisms on lifelong premature ejaculation risk among the chinese Han population

BACKGROUND

Lifelong premature ejaculation (LPE) is one of the most common ejaculatory dysfunctions in men. The serotonin (5-HT) synthesis rate-limiting enzyme (TPH2) and receptor (HTR1A) in the 5-HT regulatory system may play a key role in the pathogenesis of LPE. However, there are few studies on the effects of TPH2 and HTR1A polymorphisms on LPE risk. We speculated that TPH2 and HTR1A polymorphisms may affect the occurrence and development of LPE in the Chinese Han population.

METHODS

In this study, 91 patients with LPE and 362 normal controls aged 18 to 64 years were enrolled in the male urology department of Hainan General Hospital in China from January 2016 to December 2018. The SNPs in HTR1A and TPH2, which are related to 5-HT regulation, were selected as indexes to genotype the collected blood samples of participants. Logistic regression was used to analyze the correlation between SNPs of HTR1A and TPH2 with LPE susceptibility, as well as the relationship with leptin, 5-HT and folic acid levels.

RESULTS

The results revealed that HTR1A-rs6295 increased LPE risk in recessive model. Rs11178996 in TPH2 significantly reduced susceptibility to LPE in allelic (odds ratio (OR) = 0.68, 95% confidence interval (95% CI) = 0.49-0.96, p = 0.027), codominant (OR = 0.58, 95% CI = 0.35-0.98, p = 0.040), dominant (OR = 0.58, 95% CI = 0.36-0.92, p = 0.020), and additive (OR = 0.71, 95% CI = 0.52-0.98, p = 0.039) models. G_rs11179041T_rs10879352 could reduce the risk of LPE (OR = 0.44, 95% CI = 0.22-0.90, p = 0.024) by haplotype analysis.

CONCLUSION

HTR1A-rs6295 and TPH2-rs11178996 are associated with LPE risk in the Chinese Han population based on the finding of this study.

5-Fluorouracil reduces the fibrotic scar via inhibiting matrix metalloproteinase 9 and stabilizing microtubules after spinal cord injury

AIMS

Fibrotic scars composed of a dense extracellular matrix are the major obstacles for axonal regeneration. Previous studies have reported that antitumor drugs promote neurofunctional recovery.

METHODS

We investigated the effects of 5-fluorouracil (5-FU), a classical antitumor drug with a high therapeutic index, on fibrotic scar formation, axonal regeneration, and functional recovery after spinal cord injury (SCI).

RESULTS

5-FU administration after hemisection SCI improved hind limb sensorimotor function of the ipsilateral hind paws. 5-FU application also significantly reduced the fibrotic scar formation labeled with aggrecan and fibronectin-positive components, Iba1⁺ /CD11b⁺ macrophages/microglia, vimentin, chondroitin sulfate proteoglycan 4 (NG2/CSPG4), and platelet-derived growth factor receptor beta (PDGFRβ)⁺ pericytes. Moreover, 5-FU treatment promoted stromal cells apoptosis and inhibited fibroblast proliferation and migration by abrogating the polarity of these cells and reducing matrix metalloproteinase 9 expression and promoted axonal growth of spinal neurons via the neuron-specific protein doublecortin-like kinase 1 (DCLK1). Therefore, 5-FU administration impedes the formation of fibrotic scars and promotes axonal regeneration to further restore sensorimotor function after SCI.

Serotonin Receptor and Transporter Endocytosis Is an Important Factor in the Cellular Basis of Depression and Anxiety

Depression and anxiety are common, debilitating psychiatric conditions affecting millions of people throughout the world. Current treatments revolve around selective serotonin reuptake inhibitors (SSRIs), yet these drugs are only moderately effective at relieving depression. Moreover, up to 30% of sufferers are SSRI non-responders. Endocytosis, the process by which plasma membrane and extracellular constituents are internalized into the cell, plays a central role in the regulation of serotonin (5-hydroxytryptophan, 5-HT) signaling, SSRI function and depression and anxiety pathogenesis. Despite their therapeutic potential, surprisingly little is known about the endocytosis of the serotonin receptors (5-HT receptors) or the serotonin transporter (SERT). A subset of 5-HT receptors are endocytosed by clathrin-mediated endocytosis following serotonin binding, while for the majority of 5-HT receptors the endocytic regulation is not known. SERT internalizes serotonin from the extracellular space into the cell to limit the availability of serotonin for receptor binding and signaling. Endocytosis of SERT reduces serotonin uptake, facilitating serotonin signaling. SSRIs predominantly inhibit SERT, preventing serotonin uptake to enhance 5-HT receptor signaling, while hallucinogenic compounds directly activate specific 5-HT receptors, altering their interaction with endocytic adaptor proteins to induce alternate signaling outcomes. Further, multiple polymorphisms and transcriptional/proteomic alterations have been linked to depression, anxiety, and SSRI non-response. In this review, we detail the endocytic regulation of 5-HT receptors and SERT and outline how SSRIs and hallucinogenic compounds modulate serotonin signaling through endocytosis. Finally, we will examine the deregulated proteomes in depression and anxiety and link these with 5-HT receptor and SERT endocytosis. Ultimately, in attempting to integrate the current studies on the cellular biology of depression and anxiety, we propose that endocytosis is an important factor in the cellular basis of depression and anxiety. We will highlight how a thorough understanding 5-HT receptor and SERT endocytosis is integral to understanding the biological basis of depression and anxiety, and to facilitate the development of a next generation of specific, efficacious antidepressant treatments.

A Systematic Review of Candidate Genes for Major Depression

Background and Objectives: The aim of this systematic review was to analyse which candidate genes were examined in genetic association studies and their association with major depressive disorder (MDD). Materials and Methods: We searched PUBMED for relevant studies published between 1 July 2012 and 31 March 2019, using combinations of keywords: “major depressive disorder” OR “major depression” AND “gene candidate”, “major depressive disorder” OR “major depression” AND “polymorphism”. Synthesis focused on assessing the likelihood of bias and investigating factors that may explain differences between the results of studies. For selected gene list after literature overview, functional enrichment analysis and gene ontology term enrichment analysis were conducted. Results: 141 studies were included in the qualitative review of gene association studies focusing on MDD. 86 studies declared significant results (p < 0.05) for 172 SNPs in 85 genes. The 13 SNPs associations were confirmed by at least two studies. The 18 genetic polymorphism associations were confirmed in both the previous and this systematic analysis by at least one study. The majority of the studies (68.79 %) did not use or describe power analysis, which may have had an impact over the significance of their results. Almost a third of studies (N = 54) were conducted in Chinese Han population. Conclusion: Unfortunately, there is still insufficient data on the links between genes and depression. Despite the reported genetic associations, most studies were lacking in statistical power analysis, research samples were small, and most gene polymorphisms have been confirmed in only one study. Further genetic research with larger research samples is needed to discern whether the relationship is random or causal. Summations: This systematic review had summarized all reported genetic associations and has highlighted the genetic associations that have been replicated. Limitations: Unfortunately, most gene polymorphisms have been confirmed only once, so further studies are warranted for replicating these genetic associations. In addition, most studies included a small number of MDD cases that could be indicative for false positive. Considering that polymorphism loci and associations with MDD is also vastly dependent on interpersonal variation, extensive studies of gene interaction pathways could provide more answers to the complexity of MDD.

Meta-analysis of association between TPH2 single nucleotide poiymorphism and depression

Tryptophan hydroxylase 2 (TPH2) plays a crucial role in the human brain. Although the association between the TPH2 gene and depression has been suggested in previous meta-analyses, studies based on Chinese subjects are often neglected. Therefore, we included some previous studies based on Chinese subjects to explore the relationship between TPH2 polymorphisms and depression via conducting an extensive meta-analysis. We reviewed 40 research papers that included data on TPH2 gene single nucleotide polymorphisms (SNPs) from 5766 patients with depression and 5988 healthy subjects. The analysis showed an association between polymorphisms in the TPH2 gene and depression, and some results were significant in 24 studies that included Chinese Han study participants. The results of our meta-analysis showed that rs4570625, rs17110747, rs120074175, rs4290270, rs120074175, and rs4290270 may be significantly associated with depression, and that rs11178997 (A/A genotype) may be a significant risk factor for depression in the Chinese subjects. Based on the results of this study, biological experiments should be performed in the future to explore how different SNPs affect depression.

Application of antidepressants in depression: A systematic review and meta-analysis

BACKGROUND

The type and quantities of antidepressants are increasing, but the efficacy and safety of first-line and emerging drugs vary between studies. In this article, we estimated the efficacy and safety of first-line and emerging antidepressants (anti-inflammatory drugs and ketamine).

METHOD

ystematic search of EMBASE, ERIC, MEDLINE, psycARTICLES, and psycINFO without language restriction for studies on the depression, depressive symptoms, antidepressants, fluoxetine (Prozac), paroxetine, escitalopram, sertraline, fluvoxamine, venlafaxine, duloxetine, NSAIDs, anti-cytokine drugs or pioglitazone published before May 1st, 2019. Information on study characteristics, depression or depressive symptoms, antidepressants and the descriptive statistics (including efficacy and safety of antidepressants) was extracted independently by 2 investigators. Estimates were pooled using random-effects meta-analysis. Differences by study-level characteristics were estimated using stratified meta-analysis and meta-regression. The response and remission of antidepressants were used as clinical evaluation indicators, and the evaluation criteria were clinical depression scales. OR value of antidepressants as assessed by meta-analysis.

RESULTS

The literature search retrieved 5529 potentially relevant articles of which 49 studies were finally included. We compared the efficacy of antidepressants (seven first-line antidepressants (fluoxetine, paroxetine, escitalopram, sertraline, fluvoxamine, venlafaxine, duloxetine), there kinds of anti-inflammatory drugs(NASIDs, cytokine-inhibitor, pioglitazone) and ketamine) by comparing the OR values.

CONCLUSION

The three drugs with the highest OR value in response were NASID (OR = 3.62(1.58, 8.32)), venlafaxin (OR = 3.50(1.83, 6.70)) and ketamine (OR = 3.28(1.89, 5.68)), while the highest OR value in remission were NASID (OR = 3.17(1.60, 6.29)), ketamine (OR = 2.99(1.58, 5.67)) and venlafaxin (OR = 2.55(1.72, 3.78)). Through reading the literature, we found 69 SNPs associated with depression. Major depression was a debilitating disorder that could ultimately lead to enormous societal and economical challenge [1]. The number of person which affected by depression was up to 16% of the population worldwide. More than 300 million individuals were estimated to suffer depression these days [1,2]. Therefore, it is apparent that safety and effective treatments for depression are necessary. In the 1930 s, the first drug for schizophrenia was discovered. This finding was a landmark for the emerging of biological psychiatry. In the 1950 s, pharmacologists had stumbled upon the antidepressant effect of imipramine. Since then, every 30 years, the use of antidepressants had made a pulsatile leap. Selective serotonin reuptake inhibitors (SSRIs) are the most widely-prescribed psychiatric drugs for the treatment of depression. However, the efficacy was variable and incomplete: 60%-70% of the patients do not experience remission, while 30%-40% do not show a significant response [3,4]. Nevertheless, SSRIs, SNRIs (selective serotonin-norepinephrine reuptake inhibitors, which can block norepinephrine at the same time) and NaSSAs (norepinephrine and selective serotonin receptor agonist), constituted the first-line clinical drugs. Nearly 30 years after the outbreak of SSRIs, antidepressants have ushered in a new chapter. It has been found that anti-inflammatory drugs could also have the small and moderate antidepressant effect and it's widely discussed [5]. More than 40 anti-inflammatory drugs have been certificated to have antidepressant effects in preclinical and clinical studies [6]. The antidepressant that has been approved for use recently is ketamine. There is no comprehensive comparison of the efficacy of all these drugs. In this review, we tried to estimate the efficacy and safety of first-line antidepressants, anti-inflammatory drugs and ketamine. On the other hand, with the development of GWAS, SNPs related to depression have been reported, and the corresponding mechanisms have been elaborated, respectively. However, patients with these SNPs have not been treated with individualized drugs according to the mechanisms. We hope to push this process forward through the summary of this article.

METHODS

Search Strategy and Study Eligibility.

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.