A role for picomolar concentrations of pregnenolone sulfate in synaptic activity-dependent Ca2+ signaling and CREB activation

Potential plasma biomarker panels identification for the diagnosis of first-episode schizophrenia and monitoring antipsychotic monotherapy with the use of metabolomics analyses

Schizophrenia (SCZ) is a severe mental disorder. Using liquid chromatography mass spectrometry, we performed comprehensive metabolomics analyses of plasma samples from healthy controls (HC) and first episode SCZ patients before and after an acute period of medication. Ten lipid metabolites and 27 soluble small molecules were identified as potential biomarkers associated with the diagnosis and treatment of SCZ. These metabolites were significantly reduced in SCZ, and lipids and sulfate were significantly increased after treatment. Of the metabolites identified, four showed significant correlations with the Positive and Negative Syndrome Scale total scores. A biomarker panel composed of alpha-dimorphecolic, Phosphatidylcholine (PC) (16:0/18:1(11Z)), 1-methylnicotinamide, Phosphatidylethanolamine (PE) (20:2(11Z,14Z)/18:2(9Z,12Z)), sulfate, and L-tryptophan was selected to distinguish SCZ from HC; this provided the maximum classification performance with an AUC of 0.972. A biomarker panel including C16 sphinganine, gamma-linolenic acid, linoleic acid, PC(16:0/18:1(11Z)), PE(20:2(11Z,14Z)/18:2(9Z,12Z)), and sulfate, was selected for discrimination between SCZ before and after medication, and produced the optimal classification performance with an AUC of 0.905. Disturbances in lipid metabolism, sulfation modification, tryptophan metabolism, anti-inflammatory and antioxidant systems, and unsaturated fatty acids metabolism, were identified in SCZ. Our findings could facilitate the development of objective diagnostic or drug treatment monitoring tools for schizophrenia.

A neuroactive steroid with a therapeutically interesting constellation of actions at GABAA and NMDA receptors

Neuroactive steroids are an ascendant class of treatment for neuropsychiatric illness. Effects on ligand-gated neurotransmitter receptors appear to be a major mechanism of action. Here we describe a neuroactive steroid with a unique constellation of receptor actions. MQ-221 is a sulfated, 3β-hydroxy neurosteroid analogue that inhibits NMDAR function but also potentiates GABAAR function, thereby exhibiting unusual but potentially clinically desirable effects. Although the compound also exhibited features of other sulfated steroids, namely activation-dependent inhibition of GABAAR function, net potentiation dominated under physiological conditions. Potentiation of GABAAR function was distinct from the mechanism governing potentiation by anesthetic neurosteroids. Inhibition of NMDAR function showed weaker channel activation dependence than pregnanolone sulfate (3α5βPS). MQ-221 was unique among four stereoisomers explored in the pattern of effects at GABAA and NMDARs. Taken together, MQ-221 may represent a new class of compound with unique psychoactive effects and beneficial prospects for treating neuropsychiatric disorders.

Pregnenolone Inhibits Osteoclast Differentiation and Protects Against Lipopolysaccharide-Induced Inflammatory Bone Destruction and Ovariectomy-Induced Bone Loss

Osteolytic bone disease is characterized by excessive osteoclast bone resorption leading to increased skeletal fragility and fracture risk. Multinucleated osteoclasts formed through the fusion of mononuclear precursors are the principle cell capable of bone resorption. Pregnenolone (Preg) is the grand precursor of most if not all steroid hormones and have been suggested to be a novel anti-osteoporotic agent. However, the effects of Preg on osteoclast biology and function has yet to be shown. Here we examined the effect of Preg on receptor activator of nuclear factor kappa B ligand (RANKL)-induced osteoclast formation and bone resorption in vitro, and potential therapeutic application in inflammatory bone destruction and bone loss in vivo. Our in vitro cellular assays demonstrated that Preg can inhibit the formation of TRAP^+ve osteoclast formation as well as mature osteoclast bone resorption in a dose-dependent manner. The expression of osteoclast marker genes CTSK, TRAP, DC-STAMP, ATP6V0d2, and NFATc1 were markedly attenuated. Biochemical analyses of RANKL-induced signaling pathways showed that Preg inhibited the early activation of extracellular regulated protein kinases (ERK) mitogen-activated protein kinase (MAPK) and nuclear factor-κB, which consequently impaired the downstream induction of c-Fos and NFATc1. Using reactive oxygen species (ROS) detection assays, we found that Preg exhibits anti-oxidant properties inhibiting the generation of intracellular ROS following RANKL stimulation. Consistent with these in vitro results, we confirmed that Preg protected mice against local Lipopolysaccharide (LPS)-induced inflammatory bone destruction in vivo by suppressing osteoclast formation. Furthermore, we did not find any observable effect of Preg on osteoblastogenesis and mineralization in vitro. Finally Preg was administered to ovariectomy (OVX)-induced bone loss and demonstrated that Preg prevented systemic OVX-induced osteoporosis. Collectively, our observations provide strong evidence for the use of Preg as anti-osteoclastogenic and anti-resorptive agent for the potential treatment of osteolytic bone conditions.

Neurosteroid Actions in Memory and Neurologic/Neuropsychiatric Disorders

Memory dysfunction is a symptomatic feature of many neurologic and neuropsychiatric disorders; however, the basic underlying mechanisms of memory and altered states of circuitry function associated with disorders of memory remain a vast unexplored territory. The initial discovery of endogenous neurosteroids triggered a quest to elucidate their role as neuromodulators in normal and diseased brain function. In this review, based on the perspective of our own research, the advances leading to the discovery of positive and negative neurosteroid allosteric modulators of GABA type-A (GABA_A), NMDA, and non-NMDA type glutamate receptors are brought together in a historical and conceptual framework. We extend the analysis toward a state-of-the art view of how neurosteroid modulation of neural circuitry function may affect memory and memory deficits. By aggregating the results from multiple laboratories using both animal models for disease and human clinical research on neuropsychiatric and age-related neurodegenerative disorders, elements of a circuitry level view begins to emerge. Lastly, the effects of both endogenously active and exogenously administered neurosteroids on neural networks across the life span of women and men point to a possible underlying pharmacological connectome by which these neuromodulators might act to modulate memory across diverse altered states of mind.

Neurosteroids: non-genomic pathways in neuroplasticity and involvement in neurological diseases

Neurosteroids are neuroactive brain-born steroids. They can act through non-genomic and/or through genomic pathways. Genomic pathways are largely described for steroid hormones: the binding to nuclear receptors leads to transcription regulation. Pregnenolone, Dehydroepiandrosterone, their respective sulfate esters and Allopregnanolone have no corresponding nuclear receptor identified so far whereas some of their non-genomic targets have been identified. Neuroplasticity is the capacity that neuronal networks have to change their structure and function in response to biological and/or environmental signals; it is regulated by several mechanisms, including those that involve neurosteroids. In this review, after a description of their biosynthesis, the effects of Pregnenolone, Dehydroepiandrosterone, their respective sulfate esters and Allopregnanolone on their targets will be exposed. We then shall highlight that neurosteroids, by acting on these targets, can regulate neurogenesis, structural and functional plasticity. Finally, we will discuss the therapeutic potential of neurosteroids in the pathophysiology of neurological diseases in which alterations of neuroplasticity are associated with changes in neurosteroid levels.

Combined administration of levetiracetam and valproic acid attenuates age-related hyperactivity of CA3 place cells, reduces place field area, and increases spatial information content in aged rat hippocampus

Learning and memory deficits associated with age-related mild cognitive impairment have long been attributed to impaired processing within the hippocampus. Hyperactivity within the hippocampal CA3 region that is associated with aging is mediated in part by a loss of functional inhibitory interneurons and thought to underlie impaired performance in spatial memory tasks, including the abnormal tendency in aged animals to pattern complete spatial representations. Here, we asked whether the spatial firing patterns of simultaneously recorded CA3 and CA1 neurons in young and aged rats could be manipulated pharmacologically to selectively reduce CA3 hyperactivity and thus, according to hypothesis, the associated abnormality in spatial representations. We used chronically implanted high-density tetrodes to record the spatial firing properties of CA3 and CA1 units during animal exploration for food in familiar and novel environments. Aged CA3 place cells have higher firing rates, larger place fields, less spatial information content, and respond less to a change from a familiar to a novel environment than young CA3 cells. We also find that the combination of levetiracetam (LEV) + valproic acid (VPA), previously shown to act as a cognitive enhancer in tests of spatial memory, attenuate CA3 place cell firing rates, reduce place field area, and increase spatial information content in aged but not young adult rats. This is consistent with drug enhancing the specificity of neuronal firing with respect to spatial location. Contrary to expectation, however, LEV + VPA reduces place cell discrimination between novel and familiar environments, i.e., spatial correlations increase, independent of age even though drug enhances performance in cognitive tasks. The results demonstrate that spatial information content, or the number of bits of information encoded per action potential, may be the key correlate for enhancement of spatial memory by LEV + VPA.

Effects of glutamate positive modulators on cognitive deficits in schizophrenia: a systematic review and meta-analysis of double-blind randomized controlled trials

Hypofunction of N-methyl-d-aspartate (NMDA) receptors has been proposed to have an important role in the cognitive impairments observed in schizophrenia. Although glutamate modulators may be effective in reversing such difficult-to-treat conditions, the results of individual studies thus far have been inconsistent. We conducted a systematic review and meta-analysis to examine whether glutamate positive modulators have beneficial effects on cognitive functions in patients with schizophrenia. A literature search was conducted to identify double-blind randomized placebo-controlled trials in schizophrenia or related disorders, using Embase, Medline, and PsycINFO (last search: February 2015). The effects of glutamate positive modulators on cognitive deficits were evaluated for overall cognitive function and eight cognitive domains by calculating standardized mean differences (SMDs) between active drugs and placebo added to antipsychotics. Seventeen studies (N=1391) were included. Glutamate positive modulators were not superior to placebo in terms of overall cognitive function (SMD=0.08, 95% confidence interval=-0.06 to 0.23) (11 studies, n=858) nor each of eight cognitive domains (SMDs=-0.03 to 0.11) (n=367-940) in this population. Subgroup analyses by diagnosis (schizophrenia only studies), concomitant antipsychotics, or pathway of drugs to enhance the glutamatergic neurotransmission (glycine allosteric site of NMDA receptors or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors) suggested no procognitive effect of glutamate positive modulators. Further, no effect was found in individual compounds on cognition. In conclusion, glutamate positive modulators may not be effective in reversing overall cognitive impairments in patients with schizophrenia as adjunctive therapies.

New steps forward in the neuroactive steroid field

Evidence accumulated in recent years suggests that the systemic treatment with neuroactive steroids, or the pharmacological modulation of its production by brain cells, represent therapeutic options to promote neuroprotection. However, new findings, which are reviewed in this paper, suggest that the factors to be considered for the design of possible therapies based on neuroactive steroids are more complex than previously thought. Thus, although as recently reported, the nervous system regulates neuroactive steroid synthesis and metabolism in adaptation to modifications in peripheral steroidogenesis, the neuroactive steroid levels in the brain do not fully reflect its levels in plasma. Even, in some cases, neuroactive steroid level modifications occurring in the nervous tissues, under physiological and pathological conditions, are in the opposite direction than in the periphery. This suggests that the systemic treatment with these molecules may have unexpected outcomes on neural steroid levels. In addition, the multiple metabolic pathways and signaling mechanisms of neuroactive steroids, which may change from one brain region to another, together with the existence of regional and sex differences in its neural levels are additional sources of complexity that should be clarified. This complexity in the levels and actions of these molecules may explain why in some cases these molecules have detrimental rather than beneficial actions for the nervous system. This article is part of a Special Issue entitled 'Steroid Perspectives'.