Differential expression of prostaglandin D2 synthase (PTGDS) in patients with attention deficit-hyperactivity disorder and bipolar disorder

Human transcriptome array analysis and diffusion tensor imaging in attention-deficit/hyperactivity disorder

The mRNA markers identified using microarray assay and diffusion tensor magnetic resonance imaging (DTI) were applied to elucidate the pathophysiology of attention-deficit hyperactivity disorder (ADHD). First, we obtained total RNA from leukocytes from three children with ADHD and three healthy controls for analysis with microarray assays. Subsequently, we applied real-time quantitative polymerase chain reaction (qRT‒PCR) assays to validate the differential expression of 7 genes (COX7B, CYCS, TFAM, UTP14A, ZNF280C, IFT57 and NDUFB5) between 130 ADHD patients and 70 controls, and we built an ADHD prediction model based on the ΔCt values of aforementioned seven genes (AUROC = 0.98). Finally, in a validation group (28 patients with ADHD and 27 healthy controls), mRNA expression of the above seven genes also significantly differentiated ADHD patients from controls (AUROC value = 0.91). The DTI analysis showed increased fractional anisotropy (FA) of the forceps minor, superior corona radiata, posterior corona radiata and anterior corona radiata in ADHD patients. Moreover, the FA of the right superior corona radiata tract was positively correlated with ΔCt levels of the COX7B gene and the IFT57 gene. The results shed a new light on a genetic profile of ADHD that may help in deciphering the white matter microstructural features in disease pathogenesis.

Transcriptomic risk scores for attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is a highly heritable neurodevelopmental disorder. We performed a transcriptome-wide association study (TWAS) using the latest genome-wide association study (GWAS) meta-analysis, in 38,691 individuals with ADHD and 186,843 controls, and 14 gene-expression reference panels across multiple brain tissues and whole blood. Based on TWAS results, we selected subsets of genes and constructed transcriptomic risk scores (TRSs) for the disorder in peripheral blood mononuclear cells of individuals with ADHD and controls. We found evidence of association between ADHD and TRSs constructed using expression profiles from multiple brain areas, with individuals with ADHD carrying a higher burden of TRSs than controls. TRSs were uncorrelated with the polygenic risk score (PRS) for ADHD and, in combination with PRS, improved significantly the proportion of variance explained over the PRS-only model. These results support the complementary predictive potential of genetic and transcriptomic profiles in blood and underscore the potential utility of gene expression for risk prediction and deeper insight in molecular mechanisms underlying ADHD.

Novel non-stimulants rescue hyperactive phenotype in an adgrl3.1 mutant zebrafish model of ADHD

ADHD is a highly prevalent neurodevelopmental disorder. The first-line therapeutic for ADHD, methylphenidate, can cause serious side effects including weight loss, insomnia, and hypertension. Therefore, the development of non-stimulant-based therapeutics has been prioritized. However, many of these also cause other effects, most notably somnolence. Here, we have used a uniquely powerful genetic model and unbiased drug screen to identify novel ADHD non-stimulant therapeutics. We first found that adgrl3.1 null (adgrl3.1^-/-) zebrafish larvae showed a robust hyperactive phenotype. Although the hyperactivity was rescued by three ADHD non-stimulant therapeutics, all interfered significantly with sleep. Second, we used wild-type zebrafish larvae to characterize a simple behavioral phenotype generated by atomoxetine and screened the 1200 compound Prestwick Chemical Library® for a matching behavioral profile resulting in 67 hits. These hits were re-assayed in the adgrl3.1^-/-. Using the previously identified non-stimulants as a positive control, we identified four compounds that matched the effect of atomoxetine: aceclofenac, amlodipine, doxazosin, and moxonidine. We additionally demonstrated cognitive effects of moxonidine in mice using a T-maze spontaneous alternation task. Moxonidine, has high affinity for imidazoline 1 receptors. We, therefore, assayed a pure imidazoline 1 agonist, LNP599, which generated an effect closely matching other non-stimulant ADHD therapeutics suggesting a role for this receptor system in ADHD. In summary, we introduce a genetic model of ADHD in zebrafish and identify five putative therapeutics. The findings offer a novel tool for understanding the neural circuits of ADHD, suggest a novel mechanism for its etiology, and identify novel therapeutics.

Comprehensive analysis of omics data identifies relevant gene networks for Attention-Deficit/Hyperactivity Disorder (ADHD)

Attention-deficit/hyperactivity disorder (ADHD) is a highly prevalent neurodevelopmental disorder that results from the interaction of both genetic and environmental risk factors. Genome-wide association studies have started to identify multiple genetic risk loci associated with ADHD, however, the exact causal genes and biological mechanisms remain largely unknown. We performed a multi-step analysis to identify and characterize modules of co-expressed genes associated with ADHD using data from peripheral blood mononuclear cells of 270 ADHD cases and 279 controls. We identified seven ADHD-associated modules of co-expressed genes, some of them enriched in both genetic and epigenetic signatures for ADHD and in biological pathways relevant for psychiatric disorders, such as the regulation of gene expression, epigenetics and immune system. In addition, for some of the modules, we found evidence of potential regulatory mechanisms, including microRNAs and common genetic variants. In conclusion, our results point to promising genes and pathways for ADHD, supporting the use of peripheral blood to assess gene expression signatures in psychiatric disorders. Furthermore, they highlight that the combination of multi-omics signals provides deeper and broader insights into the biological mechanisms underlying ADHD.

Identification of Hypothalamic Long Noncoding RNAs Associated with Hypertension and the Behavior/Neurological Phenotype of Hypertensive ISIAH Rats

Long noncoding RNAs (lncRNAs) play an important role in the control of many physiological and pathophysiological processes, including the development of hypertension and other cardiovascular diseases. Nonetheless, the understanding of the regulatory function of many lncRNAs is still incomplete. This work is a continuation of our earlier study on the sequencing of hypothalamic transcriptomes of hypertensive ISIAH rats and control normotensive WAG rats. It aims to identify lncRNAs that may be involved in the formation of the hypertensive state and the associated behavioral features of ISIAH rats. Interstrain differences in the expression of seven lncRNAs were validated by quantitative PCR. Differential hypothalamic expression of lncRNAs LOC100910237 and RGD1562890 between hypertensive and normotensive rats was shown for the first time. Expression of four lncRNAs (Snhg4, LOC100910237, RGD1562890, and Tnxa-ps1) correlated with transcription levels of many hypothalamic genes differentially expressed between ISIAH and WAG rats (DEGs), including genes associated with the behavior/neurological phenotype and hypertension. After functional annotation of these DEGs, it was concluded that lncRNAs Snhg4, LOC100910237, RGD1562890, and Tnxa-ps1 may be involved in the hypothalamic processes related to immune-system functioning and in the response to various exogenous and endogenous factors, including hormonal stimuli. Based on the functional enrichment analysis of the networks, an association of lncRNAs LOC100910237 and Tnxa-ps1 with retinol metabolism and an association of lncRNAs RGD1562890 and Tnxa-ps1 with type 1 diabetes mellitus are proposed for the first time. Based on a discussion, it is hypothesized that previously functionally uncharacterized lncRNA LOC100910237 is implicated in the regulation of hypothalamic processes associated with dopaminergic synaptic signaling, which may contribute to the formation of the behavioral/neurological phenotype and hypertensive state of ISIAH rats.

Extralysosomal cathepsin B in central nervous system: Mechanisms and therapeutic implications

Cathepsin B (CatB) is a typical cysteine lysosomal protease involved in a variety of physiologic and pathological processes. It is expressed in most cell types and is primarily localized within subcellular endosomal and lysosomal compartments. Emerging scientific evidence indicates that lysosomal leaked CatB is involved in mitochondrial stress, inflammasome activation, and nuclear senescence, but without the acidic environment. CatB is also secreted as a myokine, which is involved in muscle‐brain cross talk and neuronal dendritic remodeling. Lysosomal‐leaked and cellular‐secreted CatB functions are dependent on its enzymatic activity at a neutral pH. In the present review, we summarize the available experimental evidence that mechanistically links extralysosomal CatB to physiological and pathological functions in central nervous system, and their potential for use in therapeutic approaches.

Are Mannan-binding Lectine Serin Protease-2 and Alpha-1-microglobulin and Bukinin Precursor the Potential Biomarkers of Manic Episode? A Study via Urinary Proetomic Analysis

Objective

Investigating the molecular basis of bipolar disorder (BD) is crucial in terms of developing effective treatment strategies as well as objective laboratory-based diagnostic tools for the disease.

Methods

We examined the urine samples of BD patients both in manic episode and after remission and compared their urinary protein profiles with the controls. Twelve patients and twelve controls (C group) included to the study. Urinary samples of patients were first collected during manic episode (M group) and then after remission (R group). Two-dimensional gel electrophoresis (2-DE) coupled to MALDI-TOF/TOF massspectrometry approach and Western blot analysis were used.

Results

Alphα-1-microglobulin and bukinin precursor (AMBP), Mannan-binding lectine serin protease-2 (MASP-2), and Ig gamma-1-chain displayed significant increases in their abundance in the urine protein pool of M group in comparison to the C and R groups. Alpha-1B glycoprotein and prostaglandin-H2 D-isomerase (PGD2) levels were significantly higher in the urine protein pool of the M and R groups in comparison to the C group. Annexin A1 was downregulated significantly in the urine protein pool of the M group in comparison to the C group.

Conclusion

Intensities of MASP-2 and AMBP proteins discriminated manic episode from remission period and healthy controls indicating that these proteins may be candidate biomarkers for manic episode. The decrease in Annexin A1 and increase in Ig gamma-1 chain levels appeared to be associated with “Manic Episode” while the increase in PGD2 and alpha-1B glycoprotein levels appeared to be associated with “Bipolar Disorder”.

Peripheral biomarkers of attention-deficit hyperactivity disorder: Current status and future perspective

Attention-deficit hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, characterized by a persistent pattern of inattention, hyperactivity, and impulsivity. Since the diagnosis of ADHD is defined by operational diagnostic criteria consisting of several clinical symptoms, a number of heterogeneous mechanisms have been considered to be implicated in its pathophysiology. Although no clinically reliable biomarkers are available for the diagnosis of ADHD, several plausible candidate biomarkers have been proposed based on recent advances in biochemistry and molecular biology. This review article summarizes potential peripheral biomarkers associated with ADHD, mainly from recently published case-control studies. These include 1) biochemical markers: neurotransmitters and their receptors, neurotrophic factors, serum electrolytes, and inflammation markers; 2) genetic and epigenetic markers: microRNA, mRNA expression, and peripheral DNA methylation; 3) physiological markers: eye movement and electroencephalography. It also discusses the limitations and future directions of these potential biomarkers for application in clinical practice.

Integrating genomics and transcriptomics: Towards deciphering ADHD

Attention-deficit/hyperactivity disorder (ADHD) is a highly heritable condition that represents the most common neurodevelopmental disorder in childhood, persisting into adulthood in around 40-65% of the cases. ADHD is characterised by age-inappropriate symptoms of inattention, impulsivity, and hyperactivity. Mounting evidence points towards ADHD having a strong genetic component and the first genome-wide significant findings have recently been reported. However, the functional characterization of variants unravelled by genome-wide association studies (GWAS) is challenging. Likewise, gene expression profiling studies have also been undertaken and novel integrative approaches combining genomic and transcriptomic data are starting to be conducted, which offers an exciting way that might provide a more informative insight towards the genetic architecture of ADHD. In this review, we summarised current knowledge on genomics, transcriptomics and integrative approaches in ADHD, focusing on GWAS and GWAS meta-analyses (GWAS-MA)- as genomics analyses- microarray and RNA-seq- as transcriptomics analyses-, and studies integrating genomics and transcriptomics data. In addition, current strengths and limitations of such approaches are discussed and further research avenues are proposed in order to face unsolved issues. Although important progress has been made, there is still a long way ahead to elucidate the biological mechanisms of ADHD, which eventually may lead to more personalized approaches in the future. Large- scale research efforts and new technological and statistical approaches are envisaged as important means towards deciphering ADHD in the upcoming years.

The Role of Cathepsins in Memory Functions and the Pathophysiology of Psychiatric Disorders

Cathepsins are proteases with functions in cellular homeostasis, lysosomal degradation and autophagy. Their role in the development of neurodegenerative diseases has been extensively studied. It is well established that impairment of proper cathepsin function plays a crucial role in the pathophysiology of neurodegenerative diseases, and in recent years a role for cathepsins in mental disorders has emerged given the involvement of cathepsins in memory function, hyperactivity, and in depression- and anxiety-like behavior. Here we review putative cathepsin functions with a special focus on their role in the pathophysiology of psychiatric diseases. Specifically, cathepsins are crucial for maintaining cellular homeostasis, particularly as part of the autophagy machinery of neural strategies underlying acute stress response. Disruption of cathepsin functions can lead to psychiatric diseases such as major depressive disease (MDD), bipolar disorder, and schizophrenia. Specifically, cathepsins can be excreted via a process called secretory autophagy. Thereby, they are able to regulate extracellular factors such as brain-derived neurotrophic factor and perlecan c-terminal fragment LG3 providing maintenance of neuronal homeostasis and mediating neuronal plasticity in response to acute stress or trauma. In addition, impairment of proper cathepsin function can result in impaired synaptic transmission by compromised recycling and biogenesis of synaptic vesicles. Taken together, further investigations on cathepsin functions and stress response, neuroplasticity, and synaptic transmission will be of great interest in understanding the pathophysiology of psychiatric disorders.

Update on the human and mouse lipocalin (LCN) gene family, including evidence the mouse Mup cluster is result of an "evolutionary bloom"

Lipocalins (LCNs) are members of a family of evolutionarily conserved genes present in all kingdoms of life. There are 19 LCN-like genes in the human genome, and 45 Lcn-like genes in the mouse genome, which include 22 major urinary protein (Mup) genes. The Mup genes, plus 29 of 30 Mup-ps pseudogenes, are all located together on chromosome (Chr) 4; evidence points to an “evolutionary bloom” that resulted in this Mup cluster in mouse, syntenic to the human Chr 9q32 locus at which a single MUPP pseudogene is located. LCNs play important roles in physiological processes by binding and transporting small hydrophobic molecules —such as steroid hormones, odorants, retinoids, and lipids—in plasma and other body fluids. LCNs are extensively used in clinical practice as biochemical markers. LCN-like proteins (18–40 kDa) have the characteristic eight β-strands creating a barrel structure that houses the binding-site; LCNs are synthesized in the liver as well as various secretory tissues. In rodents, MUPs are involved in communication of information in urine-derived scent marks, serving as signatures of individual identity, or as kairomones (to elicit fear behavior). MUPs also participate in regulation of glucose and lipid metabolism via a mechanism not well understood. Although much has been learned about LCNs and MUPs in recent years, more research is necessary to allow better understanding of their physiological functions, as well as their involvement in clinical disorders.

Functional Analogy in Human Metabolism: Enzymes with Different Biological Roles or Functional Redundancy?

Since enzymes catalyze almost all chemical reactions that occur in living organisms, it is crucial that genes encoding such activities are correctly identified and functionally characterized. Several studies suggest that the fraction of enzymatic activities in which multiple events of independent origin have taken place during evolution is substantial. However, this topic is still poorly explored, and a comprehensive investigation of the occurrence, distribution, and implications of these events has not been done so far. Fundamental questions, such as how analogous enzymes originate, why so many events of independent origin have apparently occurred during evolution, and what are the reasons for the coexistence in the same organism of distinct enzymatic forms catalyzing the same reaction, remain unanswered. Also, several isofunctional enzymes are still not recognized as nonhomologous, even with substantial evidence indicating different evolutionary histories. In this work, we begin to investigate the biological significance of the cooccurrence of nonhomologous isofunctional enzymes in human metabolism, characterizing functional analogous enzymes identified in metabolic pathways annotated in the human genome. Our hypothesis is that the coexistence of multiple enzymatic forms might not be interpreted as functional redundancy. Instead, these enzymatic forms may be implicated in distinct (and probably relevant) biological roles.

Proteomic Analysis of the Peri-Infarct Area after Human Umbilical Cord Mesenchymal Stem Cell Transplantation in Experimental Stroke

Among various therapeutic approaches for stroke, treatment with human umbilical cord mesenchymal stem cells (hUC-MSCs) has acquired some promising results. However, the underlying mechanisms remain unclear. We analyzed the protein expression spectrum of the cortical peri-infarction region after ischemic stroke followed by treatment with hUC-MSCs, and found 16 proteins expressed differentially between groups treated with or without hUC-MSCs. These proteins were further determined by Gene Ontology term analysis and network with CD200-CD200R1, CCL21-CXCR3 and transcription factors. Three of them: Abca13, Grb2 and Ptgds were verified by qPCR and ELISA. We found the protein level of Abca13 and the mRNA level of Grb2 consistent with results from the proteomic analysis. Finally, the function of these proteins was described and the potential proteins that deserve to be further studied was also highlighted. Our data may provide possible underlying mechanisms for the treatment of stroke using hUC-MSCs.

The role of the NG2 proteoglycan in OPC and CNS network function

In the normal mammalian CNS, the NG2 proteoglycan is expressed by oligodendrocyte precursor cells (OPC) but not by any other neural cell-type. NG2 is a type-1 membrane protein, exerting multiple roles in the CNS including intracellular signaling within the OPC, with effects on migration, cytoskeleton interaction and target gene regulation. It has been recently shown that the extracellular region of NG2, in addition to an adhesive function, acts as a soluble ECM component with the capacity to alter defined neuronal network properties. This region of NG2 is thus endowed with neuromodulatory properties. In order to generate biologically active fragments yielding these properties, the sequential cleavage of the NG2 protein by α- and γ-secretases occurs. The basal level of constitutive cleavage is stimulated by neuronal network activity. This processing leads to 4 major NG2 fragments which all have been associated with distinct biological functions. Here we summarize these functions, focusing on recent discoveries and their implications for the CNS. This article is part of a Special Issue entitled SI:NG2-glia(Invited only).

Lack of CUL4B leads to increased abundance of GFAP-positive cells that is mediated by PTGDS in mouse brain

Astrocytes are the most abundant cell type in the mammalian brain and are important for the functions of the central nervous system. Glial fibrillary acidic protein (GFAP) is regarded as a hallmark of mature astrocytes, though some GFPA-positive cells may act as neural stem cells. Missense heterozygous mutations in GFAP cause Alexander disease that manifests leukodystrophy and intellectual disability. Here, we show that CUL4B, a scaffold protein that assembles E3 ubiquitin ligase, represses the expression of GFAP in neural progenitor cells (NPCs) during brain development. Lack of Cul4b in NPCs in cultures led to increased generation of astrocytes, marked by GFAP and S100β. The GFAP+ cells were also found to be more abundant in the brains of nervous system-specific Cul4b knockout mice in vivo. Moreover, we demonstrated that the increased generation of GFAP+ cells from Cul4b-null NPCs was mediated by an upregulation of prostaglandin D2 synthase PTGDS. We showed that the increased GFAP expression can be attenuated by pharmacological inhibition of the PTGDS enzymatic activity or by shRNA-mediated knockdown of Ptgds. Importantly, exogenously added PTGDS could promote the generation of GFAP+ cells from wild-type NPCs. We further observed that Ptgds is targeted and repressed by the CUL4B/PRC2 complex. Together, our results demonstrate CUL4B as a negative regulator of GFAP expression during neural development.

Reduced mRNA expression of PTGDS in peripheral blood mononuclear cells of rapid-cycling bipolar disorder patients compared with healthy control subjects

BACKGROUND

Disturbances related to the arachidonic acid cascade and prostaglandin metabolism may be involved in the pathophysiology of bipolar disorder, as supported by a recent genome-wide association study meta-analysis; however, evidence from clinical studies on a transcriptional level is lacking. Two enzymes in the arachidonic acid cascade are the prostaglandin D synthase (PTGDS), which catalyzes the conversion of prostaglandin H2 to prostaglandin D2 (PGD2), and the aldo-keto reductase family 1 member C3 (AKR1C3), which catalyzes the reduction of PGD2. We aimed to test the hypothesis that mRNA expression of PTGDS and AKR1C3 is deregulated in rapid-cycling disorder patients in a euthymic or current affective state compared with healthy control subjects, and that expression alters with affective states.

METHODS

PTGDS and AKR1C3 mRNA expression in peripheral blood mononuclear cells was measured in 37 rapid-cycling bipolar disorder patients and 40 age- and gender-matched healthy control subjects using reverse transcription quantitative real-time polymerase chain reaction. Repeated measurements of PTGDS and AKR1C3 mRNA expression were obtained in various affective states during 6-12 months and compared with repeated measurements in healthy control subjects.

RESULTS

Adjusted for age and gender, PTGDS mRNA expression was down-regulated in rapid-cycling bipolar disorder patients in a euthymic, depressive, and manic/hypomanic state compared with healthy control subjects. No difference in PTGDS mRNA expression was observed between affective states. AKR1C3 mRNA expression did not differ between bipolar disorder patients in any affective state or in comparison with healthy control subjects.

CONCLUSIONS

The results suggest a role for aberrantly-regulated PTGDS mRNA expression in rapid-cycling bipolar disorder. The sample size was limited; replication of the findings in larger, independent samples is warranted to further explore the role of the arachidonic acid cascade and prostaglandin metabolism as a potential therapeutic target in bipolar disorder.

A role for prostaglandins in rapid cycling suggested by episode-specific gene expression shifts in peripheral blood mononuclear cells: a preliminary report

OBJECTIVES

Over 12% of patients with bipolar disorder exhibit rapid cycling. The underlying biological mechanisms of this extreme form of bipolar disease are still unknown. This study aimed at replicating and extending findings of our previously published case report, where an involvement of prostaglandin synthesis-related genes in rapid cycling was first proposed.

METHODS

Psychopathological follow-up of the reported case was performed under cessation of celecoxib treatment. In a prospective observational study, patients with bipolar disorder (n = 47; of these, four had rapid cycling) or with monopolar depression (n = 97) were recruited over a period of three years. Repeated psychopathology measurements were conducted using standard instruments. Peripheral blood mononuclear cells (PBMC) were obtained during as many consecutive episodes as possible and processed for mRNA isolation and quantitative real-time reverse transcriptase polymerase chain reaction for prostaglandin D2 synthase (PTGDS), aldo-ketoreductase family 1, member C3 (AKR1C3), cyclooxygenase-2 (PAN means all splice variants) (COX2PAN ), prostaglandin-endoperoxide synthase 2 (PTGS2), and purinergic receptor P2X, ligand-gated ion channel 7 (P2RX7).

RESULTS

The follow-up of our original case of a patient with rapid cycling who had shown impressive psychopathological improvement under celecoxib revealed complete loss of this effect upon discontinuation of the COX2 inhibitor. Episode-specific gene expression measurements in PBMC of four newly recruited rapid cycling patients confirmed the higher expression of PTGDS in depressive compared to manic phases. Additionally, higher relative expression of PTGS2/COX2PAN was found. No comparable alterations were observable in samples available from the remaining 43 patients with bipolar disorder and the 97 monopolar depressed patients, emphasizing the advantages of the rapid cycling condition with its rapid and frequent shifts for identification of gene expression changes.

CONCLUSIONS

This study supports a role for prostaglandins in rapid cycling and advocates the cyclooxygenase cascade as a treatment target in this condition.