Striatal neurodevelopment is dysregulated in purine metabolism deficiency and impacts DARPP-32, BDNF/TrkB expression and signaling: new insights on the molecular and cellular basis of Lesch-Nyhan Syndrome

Naringin corrects renal failure related to Lesch-Nyhan disease in a rat model via NOS-cAMP-PKA and BDNF/TrkB pathways

This study explored the effect of naringin (NAR) on HGPRT1 deficiency and hyperuricemia through NOS-cAMP-PKA and BDNF/TrkB signaling pathways induced by caffeine (CAF) and KBrO3 in a rat model. Sixty-three adult male albino rats were randomly assigned into nine (n = 7) groups. Group I: control animals, Group II was treated with 100 mg/kg KBrO3 , Group III was treated with 250 mg/kg CAF, Group IV was treated with 100 mg/kg KBrO3  + 250 mg/kg CAF, Group V was administered with 100 mg/kg KBrO3  + 100 mg/kg haloperidol, Group VI was administered with 100 mg/kg KBrO3  + 50 mg/kg NAR, Group VII was administered with 500 mg/kg CAF + 50 mg/kg NAR, and Group VIII was administered with 100 mg/kg KBrO3  + 250 mg/kg CAF + 50 mg/kg NAR. Finally, group IX was treated with 50 mg/kg NAR. The exposure of rats to KBrO3 and CAF for 21 days induced renal dysfunction linked with Lesch-Nyhan disease. NAR obliterated renal dysfunction linked with Lesch-Nyhan disease by decreasing uric acid, renal malondialdehyde level, inhibiting the activities of arginase, and phosphodiesterase-51 (PDE-51) with corresponding upregulation of brain derived-neurotrophic factor and its receptor (BDNF-TrkB), Bcl11b, HGPRT1, and DARPP-32. Additionally, renal failure related to Lesch-Nyhan disease was remarkably corrected by NAR as shown by the reduced activities of AChE and enzymes of ATP hydrolysis (ATPase, AMPase, and ADA) with affiliated increase in the NO level. This study therefore validates NAR as nontoxic and effective chemotherapy against kidney-related Lesch-Nyhan disease by mitigating effects of toxic food additives and enzymes of ATP-hydrolysis via NOS-cAMP-PKA and BDNF/TrkB signaling pathways.

Neurodevelopmental exposome: The effect of in utero co-exposure to heavy metals and phthalates on child neurodevelopment

In this study, the exposome paradigm has been applied on a mother-child cohort adopting an optimised untargeted metabolomics approach for human urine followed by advanced bioinformatics analysis. Exposome-wide association algorithms were used to draw links between in utero co-exposure to metals and phthalates, metabolic pathways deregulation, and clinically observed phenotypes of neurodevelopmental disorders such as problems in linguistic, motor development and cognitive capacity. Children (n = 148) were tested at the first and second year of their life using the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III). Their mothers had been exposed to metals and phthalates during the pregnancy, according to human biomonitoring results from previously performed studies. Untargeted metabolomics analysis of biobanked urine samples from the mothers was performed using a combination of the high throughput analytical methods liquid chromatography-high resolution mass spectrometry (LC-HRMS) and nuclear magnetic resonance (NMR). Most perturbed metabolic pathways from co-exposure heavy metals and phthalates were pathways related to the tricarboxylic acid cycle (TCA cycle) and oxidative phosphorylation, indicating the possibility of disruption of mitochondrial respiration. Overproduction of reactive oxygen species (ROS); the presence of glutathione peroxidase 3 (GPx3) during pregnancy and presence of glutathione peroxidase 1 (GPx1) in the umbilical cord were linked to verbal development problems. Another finding of the study is that in real life, adverse outcomes occur as a combination of environmental and social factors, all of them acting synergistically towards the deployment of an observed phenotype. Finally, the two-steps association process (exposure to pathways and pathways to adverse outcomes) was able to (a) provide associations that are not evident by directly associating exposure to outcomes and (b) provides additional insides on the mechanisms of environmental disease.

ASCL1-regulated DARPP-32 and t-DARPP stimulate small cell lung cancer growth and neuroendocrine tumour cell proliferation

Background

Small cell lung cancer (SCLC) is the most aggressive form of lung cancer, and new molecular insights are necessary for prognostic and therapeutic advances.

Methods

Dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) and its N-terminally truncated splice variant, t-DARPP, were stably overexpressed or ablated in human DMS-53 and H1048 SCLC cells. Functional assays and immunoblotting were used to assess how DARPP-32 isoforms regulate SCLC cell growth, proliferation, and apoptosis. DARPP-32-modulated SCLC cells were orthotopically injected into the lungs of SCID mice to evaluate how DARPP-32 and t-DARPP regulate neuroendocrine tumour growth. Immunostaining for DARPP-32 proteins was performed in SCLC patient-derived specimens. Bioinformatics analysis and subsequent transcription assays were used to determine the mechanistic basis of DARPP-32-regulated SCLC growth.

Results

We demonstrate in mice that DARPP-32 and t-DARPP promote SCLC growth through increased Akt/Erk-mediated proliferation and anti-apoptotic signalling. DARPP-32 isoforms are overexpressed in SCLC patient-derived tumour tissue, but undetectable in physiologically normal lung. Achaete-scute homologue 1 (ASCL1) transcriptionally activates DARPP-32 isoforms in human SCLC cells.

Conclusions

We reveal new regulatory mechanisms of SCLC oncogenesis that suggest DARPP-32 isoforms may represent a negative prognostic indicator for SCLC and serve as a potential target for the development of new therapies.

PDE10A mutations help to unwrap the neurobiology of hyperkinetic disorders

The dual-specific cAMP/cGMP phosphodiesterase PDE10A is exclusively localised to regions of the brain and specific cell types that control crucial brain circuits and behaviours. The downside to this expression pattern is that PDE10A is also positioned to be a key player in pathology when its function is perturbed. The last decade of research has seen a clear role emerge for PDE10A inhibition in modifying behaviours in animal models of psychosis and Huntington's disease. Unfortunately, this has not translated to the human diseases as expected. More recently, a series of families with hyperkinetic movement disorders have been identified with mutations altering the PDE10A protein sequence. As these mutations have been analysed and characterised in other model systems, we are beginning to learn more about PDE10A function and perhaps catch a glimpse into how PDE10A activity could be modified for therapeutic benefit.

Emerging Role of Purine Metabolizing Enzymes in Brain Function and Tumors

The growing evidence of the involvement of purine compounds in signaling, of nucleotide imbalance in tumorigenesis, the discovery of purinosome and its regulation, cast new light on purine metabolism, indicating that well known biochemical pathways may still surprise. Adenosine deaminase is important not only to preserve functionality of immune system but also to ensure a correct development and function of central nervous system, probably because its activity regulates the extracellular concentration of adenosine and therefore its function in brain. A lot of work has been done on extracellular 5′-nucleotidase and its involvement in the purinergic signaling, but also intracellular nucleotidases, which regulate the purine nucleotide homeostasis, play unexpected roles, not only in tumorigenesis but also in brain function. Hypoxanthine guanine phosphoribosyl transferase (HPRT) appears to have a role in the purinosome formation and, therefore, in the regulation of purine synthesis rate during cell cycle with implications in brain development and tumors. The final product of purine catabolism, uric acid, also plays a recently highlighted novel role. In this review, we discuss the molecular mechanisms underlying the pathological manifestations of purine dysmetabolisms, focusing on the newly described/hypothesized roles of cytosolic 5′-nucleotidase II, adenosine kinase, adenosine deaminase, HPRT, and xanthine oxidase.

MiR-132 regulated olfactory bulb proteins linked to olfactory learning in greater short-nosed fruit bat Cynopterus sphinx

Earlier, we showed that micro RNA-132 (miR-132) regulate the immediate early genes (IEGs) in the olfactory bulb (OB) of fruit bat Cynopterus sphinx during olfactory learning. This study was designed to examine whether the miR-132 regulate other proteins in OB during olfactory learning. To test this, miR-132 anti-sense oligodeoxynucleotide (AS-ODN) was delivered to the OB and then trained to novel odor. The 2-dimensional gel electrophoresis analysis showed that inhibition of miR-132 altered olfactory training induced expression of 321 proteins. Further, liquid chromatography-mass spectrometry (LC-MS/MS) analysis reveals the identity of differently expressed proteins such as phosphoribosyl transferase domain containing protein (PRTFDC 1), Sorting nexin-8 (SNX8), Creatine kinase B-type (CKB) and Annexin A11 (ANX A11). Among them PRTFDC 1 showing 189 matching peptides with highest sequence coverage (67.0%) and protein-protein interaction analysis showed that PRTFDC 1 is a homolog of hypoxanthine phosphoribosyltransferase-1 (HPRT-1). Subsequent immunohistochemical analysis (IHC) showed that inhibition of miR-132 down-regulated HPRT expression in OB of C. sphinx. In addition, western blot analysis depicts that HPRT, serotonin transporter (SERT), N-methyl-d-asparate (NMDA) receptors (2A,B) were down-regulated, but not altered in OB of non-sense oligodeoxynucleotide (NS-ODN) infused groups. These analyses suggest that miR-132 regulates the process of olfactory learning and memory formation through SERT and NMDA receptors signalling, which is possibly associated with the PRTFDC1-HPRT interaction.

Aicar effect in early neuronal development

The neurological manifestations of Lesch-Nyhan disease (LND) have been attributed to the effect of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency on nervous system development. An increase has been reported in the levels of 5-aminoimidazole-4-carboxamide-1-β-D-ribotide (AICAR) and its triphosphate form ZTP in the red blood cells of patients with LND. AICAR accumulation in the brain has been hypothesized as the cause of some of the neurological symptoms of patients with LND. In this study, we examined the effect of AICAR on the differentiation of neurons in the well-established human NTERA-2 cl.D1 (NT2/D1) embryonic carcinoma neurogenesis model. NT2/D1 cells were differentiated along neuroectodermal lineages after exposure to 10-µM retinoic acid (RA), with or without the addition of 25-µM AICAR to the culture medium. The effect of AICAR on RA differentiation were examined through changes in the expression of genes essential to neuronal differentiation, as well as genes from the Wnt/β-catenin, transforming growth factor beta (TGFβ) and sonic hedgehog (SHH) pathways. Results: RA-induced differentiation in the NT2/D1 cells significantly increased the expression of MAP2, NRG1, NRP1, NRP2, NEUROG1 and EN1 genes (genes linked to neural differentiation) compared with undifferentiated NT2/D1 cells. We found that AICAR increased the expression of the SHH gene and the WNT2 and WNT7B genes but did not influence the expression of genes whose overexpression characterize early neurodevelopmental processes. Conclusion: The relevance of the AICAR related changes in the SHH and Wnt/β-catenin pathway genes expression in the physiopathology of LND warrants further exploration.

The interrelationship of metabolic syndrome and neurodegenerative diseases with focus on brain-derived neurotrophic factor (BDNF): Kill two birds with one stone

The brain-derived neurotrophic factor (BDNF) is involved in metabolic syndrome (MetS) and neurodegenerative diseases (NDD) like Alzheimer's disease, Huntington's disease, Parkinson's disease and depression. If one factor plays an essential role in the pathogenesis of two diseases, it can be concluded that there might be a common root in these two diseases, as well. This review was aimed to highlight the crucial roles of BDNF in the pathogenesis of MetS and NDD and to introduce sole prophylactic or therapeutic applications, BDNF gene therapy and BDFN administration, in controlling MetS and NDD.

The involvement of DARPP-32 in the pathophysiology of schizophrenia

Schizophrenia is one of the most devastating heterogeneous psychiatric disorders. The dopamine hypothesis is the longest standing pathoetiologic theory of schizophrenia based on neurochemical evidences of elevated brain striatal dopamine synthesis capacity and increased dopamine release in response to stress. Dopamine and cyclic AMP-regulated phosphoprotein of relative molecular mass 32,000 (DARPP-32) is a cytosolic protein highly enriched in the medium spiny neurons of the neostriatum, considered as the most important integrator between the cortical input and the basal ganglia, and associated with motor control. Accumulating evidences has indicated the involvement of DARPP-32 in the development of schizophrenia; i. DARPP-32 phosphorylation is regulated by several neurotransmitters, including dopamine and glutamate, neurotransmitters implicated in schizophrenia pathogenesis; ii. decrease of both total and phosphorylated DARPP-32 in the prefrontal cortex are observed in schizophrenic animal models; iii. postmortem brain studies indicated decreased expression of DARPP-32 protein in the superior temporal gyrus and dorsolateral prefrontal cortex in patients with schizophrenia; iv. DARPP-32 phosphorylation is increased upon therapy with antipsychotic drugs, such as haloperidol and risperidone which improve behavioral performance in experimental animal models and patients; v. Genetic analysis of the gene coding for DARPP-32 propose an association with schizophrenia. Cumulatively, these findings implicate DARPP-32 protein in schizophrenia and propose it as a potential therapeutic target. Here, we summarize the possible roles of DARPP-32 during the development of schizophrenia and make some recommendations for future research. We propose that DARPP-32 and its interacting proteins may serve as potential therapeutic targets in the treatment of schizophrenia.

A review of the implication of hypoxanthine excess in the physiopathology of Lesch-Nyhan disease

Lesch-Nyhan disease is caused by HGprt deficiency, however, the mechanism by which enzyme deficiency leads to the severe neurological manifestations is still unknown. We hypothesized that hypoxanthine excess leads, directly or indirectly, through its action in adenosine transport, to aberrations in neuronal development. We found that hypoxanthine diminishes adenosine transport and enhances stimulation of adenosine receptors. These effects cause an imbalance between adenosine, dopamine, and serotonin receptors in HGprt deficient cells, and cells differentiated with hypoxanthine showed an increase in dopamine, adenosine and serotonin receptors expression. Hypoxanthine deregulates early neuronal differentiation increasing WNT4 and EN1 gene expression.

Hypoxanthine deregulates genes involved in early neuronal development. Implications in Lesch-Nyhan disease pathogenesis

Neurological manifestations in Lesch-Nyhan disease (LND) are attributed to the effect of hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency on the nervous system development. HPRT deficiency causes the excretion of increased amounts of hypoxanthine into the extracellular medium and we hypothesized that HPRT deficiency related to hypoxanthine excess may then lead, directly or indirectly, to transcriptional aberrations in a variety of genes essential for the function and development of striatal progenitor cells. We have examined the effect of hypoxanthine excess on the differentiation of neurons in the well-established human NTERA-2 cl.D1 (NT2/D1) embryonic carcinoma neurogenesis model. NT2/D1 cells differentiate along neuroectodermal lineages after exposure to retinoic acid (RA). Hypoxanthine effects on RA-differentiation were examined by the changes on the expression of various transcription factor genes essential to neuronal differentiation and by the changes in tyrosine hydroxylase (TH), dopamine, adenosine and serotonin receptors (DRD, ADORA, HTR). We report that hypoxanthine excess deregulate WNT4, from Wnt/β-catenin pathway, and engrailed homeobox 1 gene and increased TH and dopamine DRD1, adenosine ADORA2A and serotonin HTR7 receptors, whose over expression characterize early neuro-developmental processes.

MicroRNAs: tools of mechanistic insights and biological therapeutics discovery for the rare neurogenetic syndrome Lesch-Nyhan disease (LND)

MicroRNAs (miRNAs) are small regulatory RNAs that modulate the translation of mRNA. They have emerged over the past few years as indispensable entities in the transcriptional regulation of genes. Their discovery has added additional layers of complexity to regulatory networks that control cellular homeostasis. Also, their dysregulated pattern of expression is now well demonstrated in myriad diseases and pathogenic processes. In the current review, we highlight the role of miRNAs in Lesch-Nyhan disease (LND), a rare neurogenetic syndrome caused by mutations in the purine metabolic gene encoding the hypoxanthine-guanine phosphoribosyltransferase (HPRT) enzyme. We describe how experimental and biocomputational approaches have helped to unravel genetic and signaling pathways that provide mechanistic understanding of some of the molecular and cellular basis of this ill-defined neurogenetic disorder. Through miRNA-based target predictions, we have identified signaling pathways that may be of significance in guiding biological therapeutic discovery for this incurable neurological disorder. We also propose a model to explain how a gene such as HPRT, mostly known for its housekeeping metabolic functions, can have pleiotropic effects on disparate genes and signal transduction pathways. Our hypothetical model suggests that HPRT mRNA transcripts may be acting as competitive endogenous RNAs (ceRNAs) intertwined in multiregulatory cross talk between key neural transcripts and miRNAs. Overall, this approach of using miRNA-based genomic approaches to elucidate the molecular and cellular basis of LND and guide biological target identification might be applicable to other ill-defined rare inborn-error metabolic diseases.