Changes of protein expression profiles in the amygdala during the process of morphine-induced conditioned place preference in rats

The ubiquitin-proteasome system and learning-dependent synaptic plasticity - A 10 year update

Over 25 years ago, a seminal paper demonstrated that the ubiquitin-proteasome system (UPS) was involved in activity-dependent synaptic plasticity. Interest in this topic began to expand around 2008 following another seminal paper showing that UPS-mediated protein degradation controlled the "destabilization" of memories following retrieval, though we remained with only a basic understanding of how the UPS regulated activity- and learning-dependent synaptic plasticity. However, over the last 10 years there has been an explosion of papers on this topic that has significantly changed our understanding of how ubiquitin-proteasome signaling regulates synaptic plasticity and memory formation. Importantly, we now know that the UPS controls much more than protein degradation, is involved in plasticity underlying drugs of abuse and that there are significant sex differences in how ubiquitin-proteasome signaling is used for memory storage processes. Here, we aim to provide a critical 10-year update on the role of ubiquitin-proteasome signaling in synaptic plasticity and memory formation, including updated cellular models of how ubiquitin-proteasome activity could be regulating learning-dependent synaptic plasticity in the brain.

Impact of Opioids on Cellular Metabolism: Implications for Metabolic Pathways Involved in Cancer

Opioid utilization for pain management is prevalent among cancer patients. There is significant evidence describing the many effects of opioids on cancer development. Despite the pivotal role of metabolic reprogramming in facilitating cancer growth and metastasis, the specific impact of opioids on crucial oncogenic metabolic pathways remains inadequately investigated. This review provides an understanding of the current research on opioid-mediated changes to cellular metabolic pathways crucial for oncogenesis, including glycolysis, the tricarboxylic acid cycle, glutaminolysis, and oxidative phosphorylation (OXPHOS). The existing literature suggests that opioids affect energy production pathways via increasing intracellular glucose levels, increasing the production of lactic acid, and reducing ATP levels through impediment of OXPHOS. Opioids modulate pathways involved in redox balance which may allow cancer cells to overcome ROS-mediated apoptotic signaling. The majority of studies have been conducted in healthy tissue with a predominant focus on neuronal cells. To comprehensively understand the impact of opioids on metabolic pathways critical to cancer progression, research must extend beyond healthy tissue and encompass patient-derived cancer tissue, allowing for a better understanding in the context of the metabolic reprogramming already undergone by cancer cells. The current literature is limited by a lack of direct experimentation exploring opioid-induced changes to cancer metabolism as they relate to tumor growth and patient outcome.

Astroglial correlates of neuropsychiatric disease: From astrocytopathy to astrogliosis

Complex roles for astrocytes in health and disease continue to emerge, highlighting this class of cells as integral to function and dysfunction of the nervous system. In particular, escalating evidence strongly implicates a range of changes in astrocyte structure and function associated with neuropsychiatric diseases including major depressive disorder, schizophrenia, and addiction. These changes can range from astrocytopathy, degeneration, and loss of function, to astrogliosis and hypertrophy, and can be either adaptive or maladaptive. Evidence from the literature indicates a myriad of changes observed in astrocytes from both human postmortem studies as well as preclinical animal models, including changes in expression of glial fibrillary protein, as well as changes in astrocyte morphology and astrocyte-mediated regulation of synaptic function. In this review, we seek to provide a comprehensive assessment of these findings and consequently evidence for common themes regarding adaptations in astrocytes associated with neuropsychiatric disease. While results are mixed across conditions and models, general findings indicate decreased astrocyte cellular features and gene expression in depression, chronic stress and anxiety, but increased inflammation in schizophrenia. Changes also vary widely in response to different drugs of abuse, with evidence reflective of features of astrocytopathy to astrogliosis, varying across drug classes, route of administration and length of withdrawal.

Proteomic Data in Morphine Addiction Versus Real Protein Activity: Metabolic Enzymes

Drug dependence is an escalating problem worldwide and many efforts are being made to understand the molecular basis of addiction. The morphine model is widely used in these investigations. To date, at least 29 studies exploring the influence of morphine on mammals' proteomes have been published. Among various proteins indicated as up- or down-regulated, the expression changes of enzymes engaged in energy metabolism pathways have often been confirmed. To verify whether proteomics-indicated alterations in enzyme levels reflect changes in their activity, four enzymes: PK, MDH, Complex I, and Complex V were investigated in morphine addiction and abstinence models. After analyses of the rat brain mitochondria fraction in the model of morphine dependence, we found that one of the investigated enzymes (pyruvate kinase) showed statistically significant differences observed between morphine, control, and abstinence groups. J. Cell. Biochem. 118: 4323-4330, 2017. © 2017 Wiley Periodicals, Inc.

Bidirectional Modulation of Extinction of Drug Seeking by Deep Brain Stimulation of the Ventral Striatum

BACKGROUND

Recent research in humans and rodents has explored the use of deep brain stimulation (DBS) of the ventral capsule/ventral striatum (VS) as a possible treatment for drug addiction. However, the optimum electrode placement and optimum DBS parameters have not been thoroughly studied. Here we varied stimulation sites and frequencies to determine whether DBS of the VS could facilitate the extinction of morphine-induced conditioned place preference in rats.

METHODS

Rats were implanted with DBS electrodes in the dorsal or ventral subregions of the VS and trained to the morphine conditioned place preference. Subsequently, rats received extinction sessions over 9 days, combined with 60 min of either high- (130 Hz) or low- (20 Hz) frequency DBS. To study circuit-wide activations after DBS of the VS, c-fos immunohistochemistry was performed in regions involved in the extinction of drug-seeking behaviors.

RESULTS

High-frequency DBS of the dorsal-VS impaired both extinction training and extinction memory, whereas high-frequency DBS of the ventral-VS had no effect. In contrast, low-frequency DBS of the dorsal-VS strengthened extinction memory when tested 2 or 9 days after the cessation of stimulation. Both DBS frequencies increased c-fos expression in the infralimbic prefrontal cortex, but only low-frequency DBS increased c-fos expression in the basal amygdala and the medial portion of the central amygdala.

CONCLUSIONS

Our results suggest that low-frequency (rather than high-frequency) DBS of the dorsal-VS strengthens extinction memory and may be a potential adjunct for extinction-based therapies for treatment-refractory opioid addiction.

The potential biomarkers of drug addiction: proteomic and metabolomics challenges

Drug addiction places a significant burden on society and individuals. Proteomics and metabolomics approaches pave the road for searching potential biomarkers to assist the diagnosis and treatment. This review summarized putative drug addiction-related biomarkers in proteomics and metabolomics studies and discussed challenges and prospects in future studies. Alterations of several hundred proteins and metabolites were reported when exposure to abused drug, which enriched in energy metabolism, oxidative stress response, protein modification and degradation, synaptic function and neurotrasmission, etc. Hsp70, peroxiredoxin-6 and α- and β-synuclein, as well as n-methylserotonin and purine metabolites, were promising as potential biomarker for drug addiction.

Cocaine and ethanol target 26S proteasome activity and gene expression in neuroblastoma cells

BACKGROUND

Ethanol and cocaine are widely abused drugs triggering long-lasting changes in neuronal circuits and synaptic transmission through the regulation of enzyme activity and gene expression. Compelling evidence indicates that the ubiquitin-proteasome system plays a role in the molecular changes induced by addictive substances, impacting on several mechanisms implicated in abuse. The goal of these studies was to evaluate the effects of cocaine or ethanol on proteasome activity in neuroblastoma cells. Moreover, the gene expression of specific subunits was assessed.

METHODS

Chymotrypsin-like activity was measured after 2 h, 24 h, and 48 h exposure to 5 μM cocaine or 40 mM ethanol. Proteasome subunit transcripts were evaluated by qPCR at the same time-points.

RESULTS

Treatments modified proteasome function in opposite directions, since cocaine increased and ethanol reduced chymotrypsin-like activity. Interestingly, we observed gene expression alterations induced by these drugs. In the core particle, the β1 and α5 subunits were mainly up-regulated by cocaine, whereas α6 transcripts were mostly decreased. β2 and β5 did not change. Similarly, ethanol exposure generally increased β1 and α5 mRNAs. Moreover, the β2 subunit was significantly up-regulated by ethanol only. The β5 and α6 subunits were not altered. In the regulatory particle, Rpt3 was increased by cocaine exposure, whereas it was reduced by ethanol. No significant Rpn9 alterations were observed.

CONCLUSIONS

These findings support the notion that addictive substances regulate proteasome function, contributing to the dysregulations related to drug abuse since the availability of adequate subunit amounts is necessary for proper complex assembly and function.

GluR2-3Y Inhibits the Acquisition and Reinstatement of Morphine-Induced Conditioned Place Preference in Rats

Accumulating evidence indicates that α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) are involved in the relapse to abused drugs. However, the role of AMPARs containing the GluR2 subunit in opiate addiction is still unclear. GluR2-3Y, an interfering peptide, prevents the endocytosis of AMPARs containing the GluR2 subunit. In this study, we explored the effect of intravenous injection of GluR2-3Y on the acquisition, expression, and reinstatement of morphine-induced conditioned place preference (mCPP) in rats. We found that infusion of GluR2-3Y (1.5 nmol/g) one hour before morphine during the conditioning phase inhibited the acquisition of mCPP, while an identical injection one hour before the post-conditioning test had no influence on the expression of mCPP. Injection of GluR2-3Y (1.5 nmol/g) after mCPP extinction blocked the morphine-induced reinstatement of mCPP. Our results strongly support the hypothesis that inhibition of AMPAR endocytosis provides a new target for the treatment of opiate addiction.

Influences of Morphine on the Spontaneous and Evoked Excitatory Postsynaptic Currents in Lateral Amygdala of Rats

Acute morphine exposure induces antinociceptive activity, but the underlying mechanisms in the central nervous system are unclear. Using whole-cell patch clamp recordings, we explore the role of morphine in the modulation of excitatory synaptic transmission in lateral amygdala neurons of rats. The results demonstrate that perfusion of 10 μM of morphine to the lateral amygdala inhibits the discharge frequency significantly. We further find that there are no significant influences of morphine on the amplitude of spontaneous excitatory postsynaptic currents (sEPSCs). Interestingly, morphine shows no marked influence on the evoked excitatory postsynaptic currents (eEPSCs) in the lateral amygdala neurons. These results indicate that acute morphine treatment plays an important role in the modulation on the excitatory synaptic transmission in lateral amygdala neurons of rats.

Acupuncture activates signal transduction pathways related to brain-tissue restoration after ischemic injury

A middle cerebral artery occlusion-model was established in rats using the improved thread embolism method. Rats were treated with acupuncture at either Dazhui (DU14), Renzhong (DU26), Baihui (DU20), or a non-meridian point. Detection with protein-chip technology showed that the level of protein phosphorylation in both groups was upregulated or downregulated depending on the signaling pathway compared with the model group that did not receive acupuncture. Analysis of proteins showing downregulated phosphorylation revealed that five signaling pathways were activated in the acupuncture-treatment group, while only two were activated in the acupuncture- control group. In contrast, analysis of proteins showing upregulated phosphorylation revealed only one pathway was activated in the acupuncture-treatment group, whereas four pathways were activated in the acupuncture-control group. Furthermore, the number of activated proteins in the acupuncture-treatment group was not only higher than the acupuncture-control group, but unlike the acupuncture-control group, the majority of activated proteins were key proteins in the signaling pathways. Our findings indicate that acupuncture at specific points can activate multiple signaling pathways to promote the restoration of brain tissue following ischemic injury, and that this is based on a combination of effects resulting from multiple pathways, targets, and means.

Roles of the ubiquitin proteasome system in the effects of drugs of abuse

Because of its ability to regulate the abundance of selected proteins the ubiquitin proteasome system (UPS) plays an important role in neuronal and synaptic plasticity. As a result various stages of learning and memory depend on UPS activity. Drug addiction, another phenomenon that relies on neuroplasticity, shares molecular substrates with memory processes. However, the necessity of proteasome-dependent protein degradation for the development of addiction has been poorly studied. Here we first review evidences from the literature that drugs of abuse regulate the expression and activity of the UPS system in the brain. We then provide a list of proteins which have been shown to be targeted to the proteasome following drug treatment and could thus be involved in neuronal adaptations underlying behaviors associated with drug use and abuse. Finally we describe the few studies that addressed the need for UPS-dependent protein degradation in animal models of addiction-related behaviors.

Chronic morphine treatment induces over-expression of HSP70 in mice striatum related with abnormal ubiquitin-proteasome degradation

BACKGROUND

It has been shown that opioid dependence-related neuronal plasticity may rely not only on protein synthesis, but also on protein degradation, mainly mediated by ubiquitin-proteasome system (UPS). The aim of the present study was to determine the effect of morphine on the regulation of protein degradation in the brain and to determine which proteins are involved in the underlying mechanism.

METHODS

Mice were given chronic morphine administration and the state of morphine dependence was confirmed by induction of naloxone-precipitated withdrawal jumping. The level of ubiquitinated proteins in the striatum and spinal cord of morphine-dependent mice was detected by Western blotting. One of the abnormal-ubiquitinated proteins in mice striatum was identified by electrospray ionization quadrupole time-of-flight tandem mass spectrometry and the result was further confirmed by Western blotting and immunofluorescence method.

RESULTS

We found that the expression of some ubiquitinated proteins was clearly decreased in the striatum of morphine-depnendent mice, but not in the spinal cord. And we identified a ubiquitinated protein (>79 kDa) decreased in the striatum as heat shock cognate 70 protein, one member of the 70 kDa family of heat shock proteins (HSP70). Moreover, we confirmed the level of HSP70 protein was significantly increased in mice striatum.

CONCLUSIONS

These data strongly suggest morphine-induced HSP70 overexpression in the striatum is closely related with its abnormal degradation by UPS and it seems to be an important mechanism associated with morphine dependence.

Applying mass spectrometry-based qualitative proteomics to human amygdaloid complex

The amygdaloid complex is a key brain structure involved in the expression of behaviors and emotions such as learning, fear, and anxiety. Brain diseases including depression, epilepsy, autism, schizophrenia, and Alzheimer's disease, have been associated with amygdala dysfunction. For several decades, neuroanatomical, neurophysiological, volumetric, and cognitive approaches have been the gold standard techniques employed to characterize the amygdala functionality. However, little attention has been focused specifically on the molecular composition of the human amygdala from the perspective of proteomics. We have performed a global proteome analysis employing protein and peptide fractionation methods followed by nano-liquid chromatography tandem mass spectrometry (nanoLC-MS/MS), detecting expression of at least 1820 protein species in human amygdala, corresponding to 1814 proteins which represent a nine-fold increase in proteome coverage with respect to previous proteomic profiling of the rat amygdala. Gene ontology analysis were used to determine biological process represented in human amygdala highlighting molecule transport, nucleotide binding, and oxidoreductase and GTPase activities. Bioinformatic analyses have revealed that nearly 4% of identified proteins have been previously associated to neurodegenerative syndromes, and 26% of amygdaloid proteins were also found to be present in cerebrospinal fluid (CSF). In particular, a subset of amygdaloid proteins was mainly involved in axon guidance, synaptic vesicle release, L1CAM interactome, and signaling pathways transduced by NGF and NCAM1. Taken together, our data contributes to the repertoire of the human brain proteome, serving as a reference library to provide basic information for understanding the neurobiology of the human amygdala.

An integrated quantitative proteomics and systems biology approach to explore synaptic protein profile changes during morphine exposure

Morphine is a classic analgesic for the treatment of chronic pain. However, its repeated use is known to produce tolerance, physical dependence, and addiction; these properties limit its long-term therapeutic use and this has led to a quest for therapeutics without these unwanted side effects. Understanding the molecular changes in response to long-term use of morphine is likely to aid in the development of novel therapeutics for the treatment of pain. Studies examining the effects of chronic morphine administration have reported alterations in gene expression, synapse morphology, and synaptic transmission implying changes in synaptic protein profile. To fully understand the changes in protein profiles, proteomic techniques have been used. Studies using two-dimensional gel electrophoresis of various brain regions combined with mass spectrometry have found alterations in the levels of a number of proteins. However, neither the changes in brain regions relevant to morphine effects nor changes in the abundance of synaptic proteins have been clearly delineated. Recent studies employing subcellular fractionation to isolate the striatal synapse, combined with quantitative proteomics and graph theory-inspired network analyses, have begun to quantify morphine-regulated changes in synaptic proteins and facilitate the generation of networks that could serve as targets for the development of novel therapeutics for the treatment of chronic pain. Thus, an integrated quantitative proteomics and systems biology approach can be useful to identify novel targets for the treatment of pain and other disorders of the brain.

Endogenous opiates and behavior: 2011

This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 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).

Repeated paired-testing impairs extinction of morphine-induced conditioned place preference dependent on the inter-test interval in rats

Using exposure to morphine- and saline-paired sides alternatively as the extinction training procedure, we find that post-retrieval extinction training enhances or hinders the extinction of morphine-induced conditioned place preference (CPP) dependent on the retrieval-extinction training intervals. Here, we examine the influence of post-retrieval extinction training with repeated paired testing on extinction of morphine-induced CPP of rats. Our results demonstrate that paired-testing with a 10-min inter-test interval does not influence the extinction of CPP, while post-retrieval extinction training blocks the extinction of CPP with a 3-h retrieval-extinction interval. These results strongly indicate that the interval between exposure trials influences the outcome of exposure therapy in addiction treatment.

Proteomic analysis of the nucleus accumbens in rhesus monkeys of morphine dependence and withdrawal intervention

It has been known that the reinforcing effects and long-term consequences of morphine are closely associated with nucleus accumbens (NAc) in the brain, a key region of the mesolimbic dopamine pathway. However, the proteins involved in neuroadaptive processes and withdrawal symptom in primates of morphine dependence have not been well explored. In the present study, we performed proteomes in the NAc of rhesus monkeys of morphine dependence and withdrawal intervention with clonidine or methadone. Two-dimensional electrophoresis was used to compare changes in cytosolic protein abundance in the NAc. We found a total of 46 proteins differentially expressed, which were further identified by mass spectrometry analysis. The identified proteins can be classified into 6 classes: metabolism and mitochondrial function, synaptic transmission, cytoskeletal proteins, oxidative stress, signal transduction and protein synthesis and degradation. Importantly, we discovered 14 proteins were significantly but similarly altered after withdrawal therapy with clonidine or methadone, revealing potential pharmacological strategies or targets for the treatment of morphine addiction. Our study provides a comprehensive understanding of the neuropathophysiology associated with morphine addiction and withdrawal therapy in primate, which is helpful for the development of opiate withdrawal pharmacotherapies.