Alfredo Bellon

One-carbon metabolism and schizophrenia: current challenges and future directions

Schizophrenia is a heterogeneous disease generally considered to result from a combination of heritable and environmental factors. Although its pathophysiology has not been fully determined, biological studies support the involvement of several possible components including altered DNA methylation, abnormal glutamatergic transmission, altered mitochondrial function, folate deficiency and high maternal homocysteine levels. Although these factors have been explored separately, they all involve one-carbon (C1) metabolism. Furthermore, C1 metabolism is well positioned to integrate gene-environment interactions by influencing epigenetic regulation. Here, we discuss the potential roles of C1 metabolism in the pathophysiology of schizophrenia. Understanding the contribution of these mechanisms could yield new therapeutic approaches aiming to counteract disease onset or progression.

Melatonin induces neuritogenesis at early stages in N1E-115 cells through actin rearrangements via activation of protein kinase C and Rho-associated kinase

Abstract:  Melatonin increases neurite formation in N1E‐115 cells through microtubule enlargement elicited by calmodulin antagonism and vimentin intermediate filament reorganization caused by protein kinase C (PKC) activation. Microfilament rearrangement is also a necessary process in growth cone formation during neurite outgrowth. In this work, we studied the effect of melatonin on microfilament rearrangements present at early stages of neurite formation and the possible participation of PKC and the Rho‐associated kinase (ROCK), which is a downstream kinase in the PKC signaling pathway. The results showed that 1 nm melatonin increased both the number of cells with filopodia and with long neurites. Similar results were obtained with the PKC activator phorbol 12‐myristate 13‐acetate (PMA). Both melatonin and PMA increased the quantity of filamentous actin. In contrast, the PKC inhibitor bisindolylmaleimide abolished microfilament organization elicited by either melatonin or PMA, while the Rho inhibitor C3, or the ROCK inhibitor Y27632, abolished the bipolar neurite morphology of N1E‐115 cells. Instead, these inhibitors prompted neurite ramification. ROCK activity measured in whole cell extracts and in N1E‐115 cells was increased in the presence of melatonin and PMA. The results indicate that melatonin increases the number of cells with immature neurites and suggest that these neurites can be susceptible to differentiation by incoming extracellular signals. Data also indicate that PKC and ROCK are involved at initial stages of neurite formation in the mechanism by which melatonin recruits cells for later differentiation.

Searching for New Options for Treating Insomnia: Are Melatonin and Ramelteon Beneficial?

Insomnia is one of the most common complaints faced in clinical practice. The limited pharmacological options available make the treatment of this complaint a challenge. All of the available benzodiazepines and non-benzodiazepine hypnotics have the potential to induce addiction, cause withdrawal symptoms, or trigger rebound insomnia. Further, the evidence supporting the utility of commonly prescribed options such as antidepressants and antipsychotics is limited. Melatonin is a hormone that has been associated with soporific effects. Based on this premise, a melatonin receptor agonist was created. Ramelteon was approved by the Food and Drug Administration in 2005 and is the only medication indicated for the long-term treatment of insomnia. A critical review with a clinical perspective of randomized, placebo-controlled clinical trials was conducted to determine the efficacy of melatonin and ramelteon for the treatment of insomnia. Based on this review, it appears that more placebo-controlled trials are indicated before valid judgments concerning the efficacy of both melatonin and ramelteon can be made. In the meantime, there is some support for the use of melatonin for the treatment of insomnia, and findings concerning ramelteon also appear promising. Nevertheless, clinicians who prescribe melatonin or ramelteon should be cautious and carefully monitor both potential benefits and adverse effects, since data on melatonin are based on studies with multiple limitations and only three controlled trials have been done with ramelteon.

Association of Disrupted in Schizophrenia 1 (DISC1) missense variants with ultra-resistant schizophrenia.

Three common missense variants of the Disrupted in Schizophrenia 1 (DISC1) gene, rs3738401 (Q264R), rs6675281 (L607F) and rs821616 (S704C), have been variably associated with the risk of schizophrenia. In a case–control study, we examine whether these gene variants are associated with schizophrenia and ultra-resistant schizophrenia (URS) in a population of French Caucasian patients. The URS phenotype is characterized according to stringent criteria as patients who experience no clinical, social and/or occupational remission in spite of treatment with clozapine and at least two periods of treatment with distinct conventional or atypical antipsychotic drugs. We find a significant association between DISC1 missense variants and URS. The association with rs3738401 remains significant after appropriate correction for multiple testing. These results suggest that the DISC1 rs3738401 missense variant is statistically linked with ultra-resistance to antipsychotic treatment.

Neuropathological and Reelin Deficiencies in the Hippocampal Formation of Rats Exposed to MAM; Differences and Similarities with Schizophrenia

Background Adult rats exposed to methylazoxymethanol (MAM) at embryonic day 17 (E17) consistently display behavioral characteristics similar to that observed in patients with schizophrenia and replicate neuropathological findings from the prefrontal cortex of psychotic individuals. However, a systematic neuropathological analysis of the hippocampal formation and the thalamus in these rats is lacking. It is also unclear if reelin, a protein consistently associated with schizophrenia and potentially involved in the mechanism of action of MAM, participates in the neuropathological effects of this compound. Therefore, a thorough assessment including cytoarchitectural and neuromorphometric measurements of eleven brain regions was conducted. Numbers of reelin positive cells and reelin expression and methylation levels were also studied. Principal Findings Compared to untreated rats, MAM-exposed animals showed a reduction in the volume of entorhinal cortex, hippocampus and mediodorsal thalamus associated with decreased neuronal soma. The entorhinal cortex also showed laminar disorganization and neuronal clusters. Reelin methylation in the hippocampus was decreased whereas reelin positive neurons and reelin expression were unchanged. Conclusions Our results indicate that E17-MAM exposure reproduces findings from the hippocampal formation and the mediodorsal thalamus of patients with schizophrenia while providing little support for reelins involvement. Moreover, these results strongly suggest MAM-treated animals have a diminished neuropil, which likely arises from abnormal neurite formation; this supports a recently proposed pathophysiological hypothesis for schizophrenia.

Seizures associated with levofloxacin: case presentation and literature review

PurposeWe present a case of a patient who developed seizures shortly after initiating treatment with levofloxacin and to discuss the potential drug-drug interactions related to the inhibition of cytochrome P450 (CYP) 1A2 in this case, as well as in other cases, of levofloxacin-induced seizures.MethodsSeveral biomedical databases were searched including MEDLINE, Cochrane and Ovid. The main search terms utilized were case report and levofloxacin. The search was limited to studies published in English.ResultsSix cases of levofloxacin-induced seizures have been reported in the literature. Drug-drug interactions related to the inhibition of CYP1A2 by levofloxacin are likely involved in the clinical outcome of these cases.ConclusionsClinicians are exhorted to pay close attention when initiating levofloxacin therapy in patients taking medications with epileptogenic properties that are CYP1A2 substrates.

Factoring neurotrophins into a neurite-based pathophysiological model of schizophrenia

Neurotrophins are growth factors that, through variations in concentration and changes in receptor expression, regulate the formation of axons and dendrites during development and throughout adult life. Here we review these growth factors, particularly in the context of schizophrenia, a psychiatric disorder characterized by neurodevelopmental abnormalities. We first discuss emerging information derived from physiologically relevant organotypic cultures and in vivo studies regarding the effects of neurotrophins on the neuronal structure including pruning and GABAergic neurons. We then review postmortem studies of neurotrophin levels and their receptors in brains of individuals with schizophrenia, and compare them with what is known about neurotrophin effects on neuronal structure. This comparison indicates that only some neuropathological defects encountered in patients with schizophrenia can be explained by the single action of neurotrophins on dendrites and axons. However, we propose that a number of inconsistent findings and apparently unrelated results in the schizophrenia field can be reconciled if neurons are considered structurally plastic cells capable of extending and retracting dendrites and axons throughout life.

Association of an UCP4 (SLC25A27) haplotype with ultra-resistant schizophrenia.

AIMS Neuronal uncoupling proteins are involved in the regulation of reactive oxygen species production and intracellular calcium homeostasis, and thus, play a neuroprotective role. In order to explore the potential consequences of neuronal uncoupling proteins variants we examined their association in a sample of Caucasian patients suffering from schizophrenia and phenotyped them according to antipsychotic response. MATERIALS & METHODS Using a case-control design, we compared the frequencies of 15 genetic variants spanning UCP2, UCP4 and UCP5 in 106 French Caucasian patients suffering from schizophrenia and 127 healthy controls. In addition, patients with schizophrenia who responded to antipsychotic treatment were compared with patients with ultra-resistant schizophrenia (URS). This latter population presented no clinical, social and/or occupational remission despite at least two periods of treatment with conventional or atypical antipsychotic drugs and also with clozapine. RESULTS There were no differences in the distribution of the respective alleles between URS and responding patients. However, one haplotype spanning UCP4 was found to be significantly under-represented in URS patients. This relationship remained significant after multiple testing corrections. CONCLUSION Although our sample is of limited size and not representative of schizophrenia as a whole, the association found between the URS group and the UCP4 haplotype is noteworthy as it may influence treatment outcome in schizophrenia.

Associating schizophrenia, long non-coding RNAs and neurostructural dynamics.

Several lines of evidence indicate that schizophrenia has a strong genetic component. But the exact nature and functional role of this genetic component in the pathophysiology of this mental illness remains a mystery. Long non-coding RNAs (lncRNAs) are a recently discovered family of molecules that regulate gene transcription through a variety of means. Consequently, lncRNAs could help us bring together apparent unrelated findings in schizophrenia; namely, genomic deficiencies on one side and neuroimaging, as well as postmortem results on the other. In fact, the most consistent finding in schizophrenia is decreased brain size together with enlarged ventricles. This anomaly appears to originate from shorter and less ramified dendrites and axons. But a decrease in neuronal arborizations cannot explain the complex pathophysiology of this psychotic disorder; however, dynamic changes in neuronal structure present throughout life could. It is well recognized that the structure of developing neurons is extremely plastic. This structural plasticity was thought to stop with brain development. However, breakthrough discoveries have shown that neuronal structure retains some degree of plasticity throughout life. What the neuroscientific field is still trying to understand is how these dynamic changes are regulated and lncRNAs represent promising candidates to fill this knowledge gap. Here, we present evidence that associates specific lncRNAs with schizophrenia. We then discuss the potential role of lncRNAs in neurostructural dynamics. Finally, we explain how dynamic neurostructural modifications present throughout life could, in theory, reconcile apparent unrelated findings in schizophrenia.

Transdifferentiation of Human Circulating Monocytes Into Neuronal-Like Cells in 20 Days and Without Reprograming

Despite progress, our understanding of psychiatric and neurological illnesses remains poor, at least in part due to the inability to access neurons directly from patients. Currently, there are in vitro models available but significant work remains, including the search for a less invasive, inexpensive and rapid method to obtain neuronal-like cells with the capacity to deliver reproducible results. Here, we present a new protocol to transdifferentiate human circulating monocytes into neuronal-like cells in 20 days and without the need for viral insertion or reprograming. We have thoroughly characterized these monocyte-derived-neuronal-like cells (MDNCs) through various approaches including immunofluorescence (IF), flow cytometry, qRT-PCR, single cell mRNA sequencing, electrophysiology and pharmacological techniques. These MDNCs resembled human neurons early in development, expressed a variety of neuroprogenitor and neuronal genes as well as several neuroprogenitor and neuronal proteins and also presented electrical activity. In addition, when these neuronal-like cells were exposed to either dopamine or colchicine, they responded similarly to neurons by retracting their neuronal arborizations. More importantly, MDNCs exhibited reproducible differentiation rates, arborizations and expression of dopamine 1 receptors (DR1) on separate sequential samples from the same individual. Differentiation efficiency measured by cell morphology was on average 11.9 ± 1.4% (mean, SEM, n = 38,819 cells from 15 donors). To provide context and help researchers decide which in vitro model of neuronal development is best suited to address their scientific question,we compared our results with those of other in vitro models currently available and exposed advantages and disadvantages of each paradigm.