Allosteric modulation of the NMDA receptor by neurosteroids in rat brain and the impact of long term morphine administration

Cognitive Alterations in Addictive Disorders: A Translational Approach

The cognitive decline in people with substance use disorders is well known and can be found during both the dependence and drug abstinence phases. At the clinical level, cognitive decline impairs the response to addiction treatment and increases dropout rates. It can be irreversible, even after the end of drug abuse consumption. Improving our understanding of the molecular and cellular alterations associated with cognitive decline could be essential to developing specific therapeutic strategies for its treatment. Developing animal models to simulate drug abuse-induced learning and memory alterations is critical to continue exploring this clinical situation. The main aim of this review is to summarize the most recent evidence on cognitive impairment and the associated biological markers in patients addicted to some of the most consumed drugs of abuse and in animal models simulating this clinical situation. The available information suggests the need to develop more studies to further explore the molecular alterations associated with cognitive impairment, with the ultimate goal of developing new potential therapeutic strategies.

Sulphated dehydroepiandrosterone serum levels are reduced in women with alcohol use disorder and correlate negatively with craving: A sex-separated cross-sectional and longitudinal study

Previous studies have established a role of sex hormones in alcohol use disorder (AUD).Only few clinical investigations with low numbers of patients with AUD have focused on the sulphated form of dehydroepiandrosterone (DHEA-S), despite its function as a neuromodulating sex steroid on receptors in the central nervous system (γ-aminobutyric acid type A, N-methyl-D-aspartate, sigma-1 receptors). DHEA-S serum levels were compared between 200 inpatients with AUD (44% women) admitted for withdrawal treatment and 240 healthy controls (45% women) and analysed longitudinally in patients from early abstinence (baseline) to a median of 5 days later. We also correlated DHEA-S levels with craving, liver enzyme activities, and prospective alcohol-related readmissions during a 24-month follow-up. DHEA-S concentrations were lower in female patients than in female healthy controls during baseline (70%) and decreased from baseline to follow-up in the female and male patients groups (down to: women, 92%; men, 76%). Baseline DHEA-S concentrations correlated with the total and obsessive subscales of the Obsessive-Compulsive Drinking Scale and with maximum visual analogue scale craving scores in female patients (Rho ≤ -0.240) and gamma-glutamyl transferase activity in female (Rho = -0.292) and male (Rho = -0.391) patients. DHEA-S did not significantly predict outcome. We found interactions with smoking behaviour and age. This is the first study based on large cohorts of inpatients with AUD undergoing a qualified detoxification treatment to provide sex-separated evidence for associations of DHEA-S serum concentrations with AUD and related phenotypes. The results stimulate further investigations whether DHEA-S directly influences alcohol craving building a basis to develop sex-sensitive prevention and treatment strategies.

Dehydroepiandrosterone (DHEA) and its Sulphate (DHEAS) in Alzheimer's Disease

BACKGROUND

Neurosteroids Dehydroepiandrosterone (DHEA) and Dehydroepiandrosterone Sulphate (DHEAS) are involved in many important brain functions, including neuronal plasticity and survival, cognition and behavior, demonstrating preventive and therapeutic potential in different neuropsychiatric and neurodegenerative disorders, including Alzheimer's disease.

OBJECTIVE

The aim of the article was to provide a comprehensive overview of the literature on the involvement of DHEA and DHEAS in Alzheimer's disease.

METHODS

PubMed and MEDLINE databases were searched for relevant literature. The articles were selected considering their titles and abstracts. In the selected full texts, lists of references were searched manually for additional articles.

RESULTS

We performed a systematic review of the studies investigating the role of DHEA and DHEAS in various in vitro and animal models, as well as in patients with Alzheimer's disease, and provided a comprehensive discussion on their potential preventive and therapeutic applications.

CONCLUSION

Despite mixed results, the findings of various preclinical studies are generally supportive of the involvement of DHEA and DHEAS in the pathophysiology of Alzheimer's disease, showing some promise for potential benefits of these neurosteroids in the prevention and treatment. However, so far small clinical trials brought little evidence to support their therapy in AD. Therefore, large-scale human studies are needed to elucidate the specific effects of DHEA and DHEAS and their mechanisms of action, prior to their applications in clinical practice.

The neuroprotective effect of NeuroAid on morphine-induced amnesia with respect to the expression of TFAM, PGC-1α, ΔfosB and CART genes in the hippocampus of male Wistar rats

Morphine is a natural alkaloid which derived from the opium poppy Papaver somniferum. Many studies have reported the effect of morphine on learning, memory and gene expression. CART (cocaine-amphetamine regulated transcript)is an important neuropeptide which has a critical role in physiological processes including drug dependence and antioxidant activity. ΔfosB is a transcription factor which modulates synaptic plasticity and affects learning and memory. TFAM (the mitochondrial transcription factor A) and PGC-1α (Peroxisome proliferator-activated receptor γ coactivator-1α) are critically involved in mitochondrial biogenesis and antioxidant pathways. NeuroAid is a Chinese medicine that induces neuroprotective and anti-apoptotic effects. In this research, we aimed to investigate the effect of NeuroAid on morphine-induced amnesia with respect to the expression of TFAM, PGC-1α, ΔfosB and CART in the rat's hippocampus. In this study, Morphine sulfate (at increasing doses), Naloxone hydrochloride (2.5 mg/kg) and NeuroAid (2.5 mg/kg) were administered intraperitoneal and real-time PCR reactions were done to assess gene expression. The results showed, morphine impaired memory of step-through passive avoidance, while NeuroAid had no effect. NeuroAid attenuated (but not reversed) morphine-induced memory impairment in morphine-addicted rats. Morphine increased the expression of PGC-1α and decreased the expression of CART. However, NeuroAid increased the expression of TFAM, PGC-1α, ΔfosB and CART. NeuroAid restored the effect of morphine on the expression of CART and PGC-1α. In conclusion, morphine impaired memory of step-through passive avoidance and NeuroAid attenuated this effect. The effect of NeuroAid on morphine-induced memory impairment/gene expression may be related to its anti-apoptotic and neuroprotective effects.

Involvement of the N/OFQ-NOP system in rat morphine antinociceptive tolerance: Are astrocytes the crossroad?

The development of tolerance to the antinociceptive effect is a main problem associated with the repeated administration of opioids. The progressively higher doses required to relieve pain reduce safety and exacerbate the side effects of classical opioid receptor agonists like morphine. Nociceptin/orphanin FQ (N/OFQ) and its NOP receptor constitute the fourth endogenous opioid system that is involved in the control of broad spectrum of biological functions, including pain transmission. Aim of this work was to evaluate the relevance of the N/OFQ-NOP system in morphine antinociceptive action and in the development of morphine tolerance in the rat. Continuous spinal intrathecal infusion of morphine (1-3 nmol/h) evoked analgesic effects for 5 days in wild type animals. The same doses infused in NOP(-/-) rats showed a lower analgesic efficacy, while the onset of tolerance was delayed to day 9. N/OFQ (1-3 nmol/h), continuously infused in NOP(+/+) animals, showed an analgesic profile similar to morphine. Immunohistochemical analysis of the dorsal horn of the spinal cord of morphine tolerant NOP(+/+) rats showed an increased number of Iba1- and GFAP-positive cells (microglia and astrocytes, respectively). Interestingly, microglia but not astrocyte activation was observed in NOP(-/-) morphine tolerant rat. A selective activation of astrocytes was observed in the dorsal horn of wild type N/OFQ tolerant rats. The antinociceptive effect of morphine partially depends by the N/OFQ-NOP system that participates in the development of morphine tolerance. In particular, NOP receptors are involved in morphine-induced astrocyte activation, and N/OFQ per se increases astrocyte density.

Blocking ATP-sensitive potassium channel alleviates morphine tolerance by inhibiting HSP70-TLR4-NLRP3-mediated neuroinflammation

BACKGROUND

Long-term use of morphine induces analgesic tolerance, which limits its clinical efficacy. Evidence indicated morphine-evoked neuroinflammation mediated by toll-like receptor 4 (TLR4) - NOD-like receptor protein 3 (NLRP3) inflammasome was important for morphine tolerance. In our study, we investigated whether other existing alternative pathways caused morphine-induced activation of TLR4 in microglia. We focused on heat shock protein 70 (HSP70), a damage-associated molecular pattern (DAMP), which was released from various cells upon stimulations under the control of K_ATP channel and bound with TLR4-inducing inflammation. Glibenclamide, a classic K_ATP channel blocker, can improve neuroinflammation by inhibiting the activation of NLRP3 inflammasome. Our present study investigated the effect and possible mechanism of glibenclamide in improving morphine tolerance via its specific inhibition on the release of HSP70 and activation of NLRP3 inflammasome induced by morphine.

METHODS

CD-1 mice were used for tail-flick test to evaluate morphine tolerance. The microglial cell line BV-2 and neural cell line SH-SY5Y were used to investigate the pharmacological effects and the mechanism of glibenclamide on morphine-induced neuroinflammation. The activation of microglia was accessed by immunofluorescence staining. Neuroinflammation-related cytokines were measured by western blot and real-time PCR. The level of HSP70 and related signaling pathway were evaluated by western blot and immunofluorescence staining.

RESULTS

Morphine induced the release of HSP70 from neurons. The released HSP70 activated microglia and triggered TLR4-mediated inflammatory response, leading to the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) p65 and the activation of NLRP3 inflammasome. Moreover, anti-HSP70 neutralizing antibody partly attenuated chronic morphine tolerance. The secretion of HSP70 was under the control of MOR/AKT/K_ATP/ERK signal pathway. Glibenclamide as a classic K_ATP channel blocker markedly inhibited the release of HSP70 induced by morphine and suppressed HSP70-TLR4-NLRP3 inflammasome-mediated neuroinflammation, which consequently attenuated morphine tolerance.

CONCLUSIONS

Our study indicated that morphine-induced extracellular HSP70 was an alternative way for the activation of TLR4-NLRP3 in analgesic tolerance. The release of HSP70 was regulated by MOR/AKT/K_ATP/ERK pathway. Our study suggested a promising target, K_ATP channel and a new leading compound, glibenclamide, for treating morphine tolerance.

Exploring the neural mechanisms of finasteride: a proteomic analysis in the nucleus accumbens

The enzyme 5α-reductase (5αR) catalyzes the conversion of progesterone and testosterone into neuroactive steroids implicated in a wide array of behavioral functions. The prototypical 5αR inhibitor, finasteride (FIN), is clinically approved for the treatment of androgenic alopecia and benign prostatic hyperplasia. Recent evidence has shown that FIN, albeit generally well tolerated, can induce untoward psychological effects in a subset of patients; furthermore, this drug may have therapeutic efficacy for a number of different neuropsychiatric conditions, ranging from Tourette syndrome to schizophrenia. In rat models of these conditions, FIN has been shown to block the effects of dopamine receptors in the nucleus accumbens (NAcc), a key terminal of the dopamine mesolimbic system. The biological underpinnings of these effects, however, remain mostly elusive. To elucidate the neurochemical networks that may be responsible for the behavioral effects of FIN, we evaluated the proteomic profile of the NAcc following acute (100mg/kg, IP) and subchronic (7 days; 100mg/kg/day, IP) treatment with this drug, in comparison with vehicle treatment (n=5/group). Two-dimensional electrophoresis (2-DE) analysis coupled to mass spectrometry revealed significant changes in the expression of nine proteins (CRMP2, PSMD1, STX18, KCNC3, CYP255, GABRP, GABT, PRPS1, CYP2B3), which were further analyzed by ontological classification (PANTHER). These results point to a number of novel potential chemical targets of FIN, and may help elucidate the underpinnings of FIN's behavioral effects and therapeutic potential for neuropsychiatric disorders.

Agmatine Prevents Adaptation of the Hippocampal Glutamate System in Chronic Morphine-Treated Rats

Chronic exposure to opioids induces adaptation of glutamate neurotransmission, which plays a crucial role in addiction. Our previous studies revealed that agmatine attenuates opioid addiction and prevents the adaptation of glutamate neurotransmission in the nucleus accumbens of chronic morphine-treated rats. The hippocampus is important for drug addiction; however, whether adaptation of glutamate neurotransmission is modulated by agmatine in the hippocampus remains unknown. Here, we found that continuous pretreatment of rats with ascending doses of morphine for 5 days resulted in an increase in the hippocampal extracellular glutamate level induced by naloxone (2 mg/kg, i.p.) precipitation. Agmatine (20 mg/kg, s.c.) administered concurrently with morphine for 5 days attenuated the elevation of extracellular glutamate levels induced by naloxone precipitation. Furthermore, in the hippocampal synaptosome model, agmatine decreased the release and increased the uptake of glutamate in synaptosomes from chronic morphine-treated rats, which might contribute to the reduced elevation of glutamate levels induced by agmatine. We also found that expression of the hippocampal NR2B subunit, rather than the NR1 subunit, of N-methyl-D-aspartate receptors (NMDARs) was down-regulated after chronic morphine treatment, and agmatine inhibited this reduction. Taken together, agmatine prevented the adaptation of the hippocampal glutamate system caused by chronic exposure to morphine, including modulating extracellular glutamate concentration and NMDAR expression, which might be one of the mechanisms underlying the attenuation of opioid addiction by agmatine.

Procyanidins alleviates morphine tolerance by inhibiting activation of NLRP3 inflammasome in microglia

Background

The development of antinociceptive tolerance following repetitive administration of opioid analgesics significantly hinders their clinical use. Evidence has accumulated indicating that microglia within the spinal cord plays a critical role in morphine tolerance. The inhibitor of microglia is effective to attenuate the tolerance; however, the mechanism is not fully understood. Our present study investigated the effects and possible mechanism of a natural product procyanidins in improving morphine tolerance via its specific inhibition on NOD-like receptor protein3 (NLRP3) inflammasome in microglia.

Methods

CD-1 mice were used for tail-flick test to evaluate the degree of pain. The microglial cell line BV-2 was used to investigate the effects and the mechanism of procyanidins. Reactive oxygen species (ROS) produced from BV-2 cells was evaluated by flow cytometry. Cell signaling was measured by western blot assay and immunofluorescence assay.

Results

Co-administration of procyanidins with morphine potentiated its antinociception effect and attenuated the development of acute and chronic morphine tolerance. Procyanidins also inhibited morphine-induced increase of interleukin-1β and activation of NOD-like receptor protein3 (NLRP3) inflammasome. Furthermore, procyanidins decreased the phosphorylation of p38 mitogen-activated protein kinase, inhibited the translocation of nuclear factor-κB (NF-κB), and suppressed the level of reactive oxygen species in microglia.

Conclusions

Procyanidins suppresses morphine-induced activation of NLRP3 inflammasome and inflammatory responses in microglia, and thus resulting in significant attenuation of morphine antinociceptive tolerance.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0520-z) contains supplementary material, which is available to authorized users.

Dehydroepiandrosterone, its metabolites and ion channels

This review is focused on the physiological and pathophysiological relevance of steroids influencing the activities of the central and peripheral nervous systems with regard to their concentrations in body fluids and tissues in various stages of human life like the fetal development or pregnancy. The data summarized in this review shows that DHEA and its unconjugated and sulfated metabolites are physiologically and pathophysiologically relevant in modulating numerous ion channels and participate in vital functions of the human organism. DHEA and its unconjugated and sulfated metabolites including 5α/β-reduced androstane steroids participate in various physiological and pathophysiological processes like the management of GnRH cyclic release, regulation of glandular and neurotransmitter secretions, maintenance of glucose homeostasis on one hand and insulin insensitivity on the other hand, control of skeletal muscle and smooth muscle activities including vasoregulation, promotion of tolerance to ischemia and other neuroprotective effects. In respect of prevalence of steroid sulfates over unconjugated steroids in the periphery and the opposite situation in the CNS, the sulfated androgens and androgen metabolites reach relevance in peripheral organs. The unconjugated androgens and estrogens are relevant in periphery and so much the more in the CNS due to higher concentrations of most unconjugated steroids in the CNS tissues than in circulation and peripheral organs. This article is part of a Special Issue entitled "Essential role of DHEA".

Pregnenolone sulfate as a modulator of synaptic plasticity

RATIONALE

The neurosteroid pregnenolone sulfate (PregS) acts as a cognitive enhancer and modulator of neurotransmission, yet aligning its pharmacological and physiological effects with reliable measurements of endogenous local concentrations and pharmacological and therapeutic targets has remained elusive for over 20 years.

OBJECTIVES

New basic and clinical research concerning neurosteroid modulation of the central nervous system (CNS) function has emerged over the past 5 years, including important data involving pregnenolone and various neurosteroid precursors of PregS that point to a need for a critical status update.

RESULTS

Highly specific actions of PregS affecting excitatory N-methyl-D-aspartate receptor (NMDAR)-mediated synaptic transmission and the pharmacological effects of PregS on various receptors and ion channels are discussed. The discovery of a high potency (nanomolar) signal transduction pathway for PregS-induced NMDAR trafficking to the cell surface via a Ca(2+)- and G protein-coupled receptor (GPCR)-dependent mechanism and a potent (EC50 ~ 2 pM) direct enhancement of intracellular Ca(2+) levels is discussed in terms of its agonist effects on long-term potentiation (LTP) and memory. Lastly, preclinical and clinical studies assessing the promnestic effects of PregS and pregnenolone toward cognitive dysfunction in schizophrenia, and altered serum levels in epilepsy and alcohol dependence, are reviewed.

CONCLUSIONS

PregS is present in human and rodent brain at physiologically relevant concentrations and meets most of the criteria for an endogenous neurotransmitter/neuromodulator. PregS likely plays a significant role in modulation of glutamatergic excitatory synaptic transmission underlying learning and memory, yet the molecular target(s) for its action awaits identification.

Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement

Despite the high prevalence of performance-enhancing drug (PED) use, media attention has focused almost entirely on PED use by elite athletes to illicitly gain a competitive advantage in sports, and not on the health risks of PEDs. There is a widespread misperception that PED use is safe or that adverse effects are manageable. In reality, the vast majority of PED users are not athletes but rather nonathlete weightlifters, and the adverse health effects of PED use are greatly underappreciated. This scientific statement synthesizes available information on the medical consequences of PED use, identifies gaps in knowledge, and aims to focus the attention of the medical community and policymakers on PED use as an important public health problem. PED users frequently consume highly supraphysiologic doses of PEDs, combine them with other PEDs and/or other classical drugs of abuse, and display additional associated risk factors. PED use has been linked to an increased risk of death and a wide variety of cardiovascular, psychiatric, metabolic, endocrine, neurologic, infectious, hepatic, renal, and musculoskeletal disorders. Because randomized trials cannot ethically duplicate the large doses of PEDs and the many factors associated with PED use, we need observational studies to collect valid outcome data on the health risks associated with PEDs. In addition, we need studies regarding the prevalence of PED use, the mechanisms by which PEDs exert their adverse health effects, and the interactive effects of PEDs with sports injuries and other high-risk behaviors. We also need randomized trials to assess therapeutic interventions for treating the adverse effects of PEDs, such as the anabolic-androgen steroid withdrawal syndrome. Finally, we need to raise public awareness of the serious health consequences of PEDs.

Dopamine D3 receptor-regulated NR2B subunits of N-methyl-d-aspartate receptors in the nucleus accumbens involves in morphine-induced locomotor activity

AIMS

Dopamine and glutamate receptors are densely expressed in the nucleus accumbens (NAc). Active interactions between these receptors contribute to the development of neuropsychiatric diseases, such as drug addiction and relapse. However, the molecular mechanisms underlying these interactions remain unclear.

METHODS

This study established a mouse model of intermittent morphine-induced mouse behavioral sensitization model. Western blot and electrophysiological recording methods were performed to directly identify the affective components of morphine behavioral sensitization.

RESULTS

Interval morphine administration could cause significant locomotor sensitization. Hyperlocomotion and behavioral locomotor sensitization were significantly suppressed when ifenprodil (5 mg/kg), a selective NR2B subunit-containing N-methyl-d-aspartate (NMDA) receptor antagonist, or nafadotride (25 μg/kg), a dopamine D3 receptor (D3R)-preferring antagonist, was coadministered with morphine. Western blot analysis showed that morphine behavioral sensitization induced a region-specific increase in phosphorylation of NR2B (pNR2B) and total levels of NR2B (NR2B) expression in the NAc. Systemically administered nafadotride attenuated behavioral locomotor sensitization induced by morphine and significantly reversed the overexpression of pNR2B and NR2B subunit-containing NMDA receptor in the NAc. NMDA receptor-mediated excitatory postsynaptic currents in the NAc were also significantly reduced by nafadotride.

CONCLUSIONS

These findings suggest that D3Rs are involved in morphine-induced behavioral locomotor sensitization in mice by regulating the NR2B subunits of NMDA receptors in the NAc.

Pregnenolone sulfate: from steroid metabolite to TRP channel ligand

Pregnenolone sulfate is a steroid metabolite with a plethora of actions and functions. As a neurosteroid, pregnenolone sulfate modulates a variety of ion channels, transporters, and enzymes. Interestingly, as a sulfated steroid, pregnenolone sulfate is not the final- or waste-product of pregnenolone being sulfated via a phase II metabolism reaction and renally excreted, as one would presume from the pharmacology textbook knowledge. Pregnenolone sulfate is also the source and thereby the starting point for subsequent steroid synthesis pathways. Most recently, pregnenolone sulfate has been functionally “upgraded” from modulator of ion channels to an activating ion channel ligand. This review will focus on molecular aspects of the neurosteroid, pregnenolone sulfate, its metabolism, concentrations in serum and tissues and last not least will summarize the functional data.

Endogenous opiates and behavior: 2010

This paper is the thirty-third consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2010 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).

Regulation of neuronal ferritin heavy chain, a new player in opiate-induced chemokine dysfunction

The heavy chain subunit of ferritin (FHC), a ubiquitous protein best known for its iron-sequestering activity as part of the ferritin complex, has recently been described as a novel inhibitor of signaling through the chemokine receptor CXCR4. Levels of FHC as well as its effects on CXCR4 activation increase in cortical neurons exposed to mu-opioid receptor agonists such as morphine, an effect likely specific to neurons. Major actions of CXCR4 signaling in the mature brain include a promotion of neurogenesis, activation of pro-survival signals, and modulation of excitotoxic pathways; thus, FHC up-regulation may contribute to the neuronal dysfunction often associated with opiate drug abuse. This review summarizes our knowledge of neuronal CXCR4 function, its regulation by opiates and the role of FHC in this process, and known mechanisms controlling FHC production. We speculate on the mechanism involved in FHC regulation by opiates and offer FHC as a new target in opioid-induced neuropathology.