Dissociative role for dorsal hippocampus in mediating heroin self-administration and relapse through CDK5 and RhoB signaling revealed by proteomic analysis

The Impact of Heroin Self-Administration and Environmental Enrichment on Ventral Tegmental CRF1 Receptor Expression

BACKGROUND

There is a strong link between chronic stress and vulnerability to drug abuse and addiction. Corticotropin releasing factor (CRF) is central to the stress response that contributes to continuation and relapse to heroin abuse. Chronic heroin exposure can exacerbate CRF production, leading to dysregulation of the midbrain CRF-dopamine-glutamate interaction.

METHODS

Here we investigated the role of midbrain CRF1 receptors in heroin self-administration and assessed neuroplasticity in CRF1 receptor expression in key opioid addiction brain regions.

RESULTS

Infusions of antalarmin (a CRF1 receptor antagonist) into the ventral tegmental area (VTA) dose dependently reduced heroin self-administration in rats but had no impact on food reinforcement or locomotor activity in rats. Using RNAscope in situ hybridization, we found that heroin, but not saline, self-administration upregulated CRF1 receptor mRNA in the VTA, particularly on dopamine neurons. AMPA GluR1 and dopamine reuptake transporter mRNA in VTA neurons were not affected by heroin. The western-blot assay showed that CRF1 receptors were upregulated in the VTA and nucleus accumbens. No significant changes in CRF1 protein expression were detected in the prefrontal cortex, insula, dorsal hippocampus, and substantia nigra. In addition, we found that 15 days of environmental enrichment implemented after heroin self-administration does not reverse upregulation of VTA CRF1 receptor mRNA but it downregulates dopamine transporter mRNA.

CONCLUSIONS

Overall, these data suggest that heroin self-administration requires stimulation of VTA CRF1 receptors and upregulates their expression in brain regions involved in reinforcement. Such long-lasting neuroadaptations may contribute to continuation of drug use and relapse due to stress exposure and are not easily reversed by EE exposure.

The Cdk5 inhibitor β-butyrolactone impairs reconsolidation of heroin-associated memory in the rat basolateral amygdala

The persistence of maladaptive heroin-associated memory, which is triggered by drug-related stimuli that remind the individual of the drug's pleasurable and rewarding effects, can impede abstinence efforts. Cyclin-dependent kinase 5 (Cdk5), a neuronal serine/threonine protein kinase that plays a role in multiple neuronal functions, has been demonstrated to be involved in drug addiction and learning and memory. Here, we aimed to investigate the role of cdk5 activity in the basolateral amygdala (BLA) in relapse to heroin seeking, using a self-administration rat model. Male rats underwent 10 days of heroin self-administration training, during which an active nose poke resulted in an intravenous infusion of heroin that was accompanied by a cue. The rats then underwent nose poke extinction for 10 days, followed by subsequent tests of heroin-seeking behaviour. We found that intra-BLA infusion of β-butyrolactone (100 ng/side), a Cdk5 inhibitor, administered 5 min after reactivation, led to a subsequent decrease in heroin-seeking behaviour. Further experiments demonstrated that the effects of β-butyrolactone are dependent on reactivated memories, temporal-specific and long-lasting on relapse of heroin-associated memory. Results provide suggestive evidence that the activity of Cdk5 in BLA is critical for heroin-associated memory and that the specific inhibitor, β-butyrolactone, may hold potential as a substance for the treatment of heroin abuse.

The potential therapeutic roles of Rho GTPases in substance dependence

Rho GTPases family are considered to be molecular switches that regulate various cellular processes, including cytoskeleton remodeling, cell polarity, synaptic development and maintenance. Accumulating evidence shows that Rho GTPases are involved in neuronal development and brain diseases, including substance dependence. However, the functions of Rho GTPases in substance dependence are divergent and cerebral nuclei-dependent. Thereby, comprehensive integration of their roles and correlated mechanisms are urgently needed. In this review, the molecular functions and regulatory mechanisms of Rho GTPases and their regulators such as GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs) in substance dependence have been reviewed, and this is of great significance for understanding their spatiotemporal roles in addictions induced by different addictive substances and in different stages of substance dependence.

A vicious cycle of neuropathological, cognitive and behavioural sequelae of repeated opioid overdose

In the midst of an escalating U.S. opioid crisis, the immediate focus of public health interventions is on fatal overdose prevention. Few studies, however, have sought to examine the long-term health consequences of exposure to repeated nonfatal opioid overdose. We reviewed recent literature to examine three corresponding downstream health outcomes of repeated overdose: a) neurodegenerative processes; b) cognition and memory; and c) overdose risk behaviours. We found a remarkable congruency among available biochemical and cognitive data on how nonfatal overdose precipitates various pathological feedforward and feedback loops that affect people who use opioids for years to come. We found however that downstream behavioural implications of neurodegenerative and cognitive sequelae are less studied despite being most proximal to an overdose. Findings point to a vicious cycle of nonfatal overdose leading to neurodegeneration - closely resembling Alzheimer Disease - that results in cognitive decline that in turn leads to potentially reduced adherence to safe drug use behaviours. The collected evidence not only brings into the focus the long-term health consequences of nonfatal overdose from the perspectives of biology, neuroscience, and public health, but also creates new cross-disciplinary context and awareness in the research and public health community that should benefit people at risk.

Ube2b-dependent degradation of DNMT3a relieves a transcriptional brake on opiate-induced synaptic and behavioral plasticity

Compelling evidence suggests that synaptic structural plasticity, driven by remodeling of the actin cytoskeleton, underlies addictive drugs-induced long-lasting behavioral plasticity. However, the signaling mechanisms leading to actin cytoskeleton remodeling remain poorly defined. DNA methylation is a critical mechanism used to control activity-dependent gene expression essential for long-lasting synaptic plasticity. Here, we provide evidence that DNA methyltransferase DNMT3a is degraded by the E2 ubiquitin-conjugating enzyme Ube2b-mediated ubiquitination in dorsal hippocampus (DH) of rats that repeatedly self-administrated heroin. DNMT3a degradation leads to demethylation in CaMKK1 gene promotor, thereby facilitating CaMKK1 expression and consequent activation of its downstream target CaMKIα, an essential regulator of spinogenesis. CaMKK1/CaMKIα signaling regulates actin cytoskeleton remodeling in the DH and behavioral plasticity by activation of Rac1 via acting Rac guanine-nucleotide-exchange factor βPIX. These data suggest that Ube2b-dependent degradation of DNMT3a relieves a transcriptional brake on CaMKK1 gene and thus activates CaMKK1/CaMKIα/βPIX/Rac1 cascade, leading to drug use-induced actin polymerization and behavior plasticity.

Prolonged Withdrawal From Escalated Oxycodone Is Associated With Increased Expression of Glutamate Receptors in the Rat Hippocampus

People suffering from opioid use disorder (OUD) exhibit cognitive dysfunctions. Here, we investigated potential changes in the expression of glutamate receptors in rat hippocampi at 2 h and 31 days after the last session of oxycodone self-administration (SA). RNA extracted from the hippocampus was used in quantitative polymerase chain reaction analyses. Rats, given long-access (9 h per day) to oxycodone (LgA), took significantly more drug than rats exposed to short-access (3 h per day) (ShA). In addition, LgA rats could be further divided into higher oxycodone taking (LgA-H) or lower oxycodone taking (LgA-L) groups, based on a cut-off of 50 infusions per day. LgA rats, but not ShA, rats exhibited incubation of oxycodone craving. In addition, LgA rats showed increased mRNA expression of GluA1-3 and GluN2a-c subunits as well as Grm3, Grm5, Grm6, and Grm8 subtypes of glutamate receptors after 31 days but not after 2 h of stopping the SA experiment. Changes in GluA1-3, Grm6, and Grm8 mRNA levels also correlated with increased lever pressing (incubation) after long periods of withdrawal from oxycodone. More studies are needed to elucidate the molecular mechanisms involved in altering the expression of these receptors during withdrawal from oxycodone and/or incubation of drug seeking.

Does a hypoxic injury from a non-fatal overdose lead to an Alzheimer Disease?

Long term consequence of non-fatal overdose in people who use opioids are not well understood. The intermittent exposure to non-fatal overdose leads to a tauopathy that is often accompanied by abrogated neuroprotective response, abnormal amyloid processing and other pathologies. The scope and limitations of available literature are discussed including neuropathologies associated with opioid and overdose exposures, contributing comorbidities and proteinopathies. Contrasting postmortem data of overdose victims with animal models of opioid neuropathologies and hypoxic injury paints a picture distinct from other proteinopathies as well as effects of moderate opioid exposure. Furthermore the reported biochemical changes and potential targets for therapeutic intervention were mapped pointing to underlying imbalance between tau kinases and phosphatases that is characteristic of Alzheimer Disease.

DNMT3a in the hippocampal CA1 is crucial in the acquisition of morphine self-administration in rats

Drug-reinforced excessive operant responding is one fundamental feature of long-lasting addiction-like behaviors and relapse in animals. However, the transcriptional regulatory mechanisms responsible for the persistent drug-specific (not natural rewards) operant behavior are not entirely clear. In this study, we demonstrate a key role for one of the de novo DNA methyltransferase, DNMT3a, in the acquisition of morphine self-administration (SA) in rats. The expression of DNMT3a in the hippocampal CA1 region but not in the nucleus accumbens shell was significantly up-regulated after 1- and 7-day morphine SA (0.3 mg/kg/infusion) but not after the yoked morphine injection. On the other hand, saccharin SA did not affect the expression of DNMT3a or DNMT3b. DNMT inhibitor 5-aza-2-deoxycytidine (5-aza) microinjected into the hippocampal CA1 significantly attenuated the acquisition of morphine SA. Knockdown of DNMT3a also impaired the ability to acquire the morphine SA. Overall, these findings suggest that DNMT3a in the hippocampus plays an important role in the acquisition of morphine SA and may be a valid target to prevent the development of morphine addiction.

Endogenous opiates and behavior: 2017

This paper is the fortieth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2017 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Systemic Administration of the Cyclin-Dependent Kinase Inhibitor (S)-CR8 Selectively Reduces Escalated Ethanol Intake in Dependent Rats

BACKGROUND

Chronic exposure to ethanol (EtOH) and other drugs of abuse can alter the expression and activity of cyclin-dependent kinase 5 (CDK5) and its cofactor p35, but the functional implication of CDK5 signaling in the regulation of EtOH-related behaviors remains unknown. In the present study, we sought to determine whether CDK5 activity plays a role in the escalation of EtOH self-administration triggered by dependence.

METHODS

We tested the effect of systemically administered (S)-CR8, a nonselective CDK inhibitor, on operant responding for EtOH or saccharin, a highly palatable reinforcer, in adult male Wistar rats. Half of the rats were made EtOH-dependent via chronic intermittent EtOH inhalation (CIE). We then sought to identify a possible neuroanatomical locus for the behavioral effect of (S)-CR8 by quantifying protein levels of CDK5 and p35 in subregions of the extended amygdala and prefrontal cortex from EtOH-naïve, nondependent, and dependent rats at the expected time of EtOH self-administration. We also analyzed the phosphorylation of 4 CDK5 substrates and of the CDK substrate consensus motif.

RESULTS

(S)-CR8 dose-dependently reduced EtOH self-administration in dependent rats. It had no effect on water or saccharin self-administration, nor in nondependent rats. The abundance of CDK5 or p35 was not altered in any of the brain regions analyzed. In the bed nucleus of the stria terminalis, CDK5 abundance was negatively correlated with intoxication levels during EtOH vapor exposure but there was no effect of dependence on the phosphorylation ratio of CDK5 substrates. In contrast, EtOH dependence increased the phosphorylation of low-molecular-weight CDK substrates in the basolateral amygdala (BLA).

CONCLUSIONS

The selective effect of (S)-CR8 on excessive EtOH intake has potential therapeutic value for the treatment of alcohol use disorders. Our data do not support the hypothesis that this effect would be mediated by the inhibition of up-regulated CDK5 activity in the extended amygdala nor prefrontal cortex. However, increased activity of CDKs other than CDK5 in the BLA may contribute to excessive EtOH consumption in alcohol dependence. Other (S)-CR8 targets may also be implicated.

Proteomic analysis of male rat nucleus accumbens, dorsal hippocampus and amygdala on conditioned place aversion induced by morphine withdrawal

Addiction is characterized by compulsive drug seeking and taking behavior, which is thought to result from persistent neuroadaptations, encoded by changes of gene expression. We previously demonstrated that the changes in synaptic plasticity were required for the formation of aversive memories associated with morphine withdrawal. However, the proteins involved in synaptic plasticity and aversive memory formation have not been well explored. In the present study, we employed a two-dimensional gel electrophoresis (2-DE)-based proteomic technique to detect the changes of protein expression in the nucleus accumbens, amygdala and dorsal hippocampus of the rats that had developed conditioned morphine withdrawal. We found that twenty-three proteins were significantly altered in the amygdala and dorsal hippocampus after conditioned morphine withdrawal. These proteins can be classified into multiple categories, such as energy metabolism, signal transduction, synaptic transmission, cytoskeletal proteins, chaperones, and protein metabolism according to their biological functions. Eight proteins related to synaptic plasticity were further confirmed by western blot analysis. It is very likely that these identified proteins may contribute to conditioned morphine withdrawal-induced neural plasticity and aversive memory formation. Thus, our work will help understand the potential mechanism associated with generation of drug withdrawal memories.

Reversible SAHH inhibitor protects against glomerulonephritis in lupus-prone mice by downregulating renal α-actinin-4 expression and stabilizing integrin-cytoskeleton linkage

BACKGROUND

Glomerulonephritis is one of the major complications and causes of death in systemic lupus erythematosus (SLE) and is characterized by glomerulosclerosis, interstitial fibrosis, and tubular atrophy, along with severe persistent proteinuria. DZ2002 is a reversible S-adenosyl-L-homocysteine hydrolase (SAHH) inhibitor with potent therapeutic activity against lupus nephritis in mice. However, the molecular events underlying the renal protective effects of DZ2002 remained unclear. This study is designed to uncover the molecular mechanisms of DZ2002 on glomerulonephritis of lupus-prone mice.

METHODS

We conducted a twice-daily treatment of DZ2002 on the lupus-prone NZB/WF1 mice, and the progression of lupus nephritis and alteration of renal function were monitored. The LC-MS-based label-free quantitative (LFQ) proteomic approach was applied to analyze the kidney tissue samples from the normal C57BL/6 mice and the NZB/WF1 mice treated with DZ2002 or vehicle. KEGG pathway enrichment and direct protein-protein interaction (PPI) network analyses were used to map the pathways in which the significantly changed proteins (SCPs) are involved. The selected proteins from proteomic analysis were validated by Western blot analysis and immunohistochemistry in the kidney tissues.

RESULTS

The twice-daily regimen of DZ2002 administration significantly ameliorated the lupus nephritis and improved the renal function in NZB/WF1 mice. A total of 3275 proteins were quantified, of which 253 proteins were significantly changed across normal C57BL/6 mice and the NZB/WF1 mice treated with DZ2002 or vehicle. Pathway analysis revealed that 13 SCPs were involved in tight junction and focal adhesion process. Further protein expression validation demonstrated that DZ2002-treated NZB/WF1 mice exhibited downregulation of α-actinin-4 and integrin-linked kinase (ILK), as well as the restoration of β1-integrin activation in the kidney tissues compared with the vehicle-treated ones.

CONCLUSIONS

Our study demonstrated the first evidence for the molecular mechanism of SAHH inhibitor on glomerulonephritis in SLE via the modulation of α-actinin-4 expression and focal adhesion-associated signaling proteins in the kidney.

From Synapse to Function: A Perspective on the Role of Neuroproteomics in Elucidating Mechanisms of Drug Addiction

Drug addiction is a complex disorder driven by dysregulation in molecular signaling across several different brain regions. Limited therapeutic options currently exist for treating drug addiction and related psychiatric disorders in clinical populations, largely due to our incomplete understanding of the molecular pathways that influence addiction pathology. Recent work provides strong evidence that addiction-related behaviors emerge from the convergence of many subtle changes in molecular signaling networks that include neuropeptides (neuropeptidome), protein-protein interactions (interactome) and post-translational modifications such as protein phosphorylation (phosphoproteome). Advancements in mass spectrometry methodology are well positioned to identify these novel molecular underpinnings of addiction and further translate these findings into druggable targets for therapeutic development. In this review, we provide a general perspective of the utility of novel mass spectrometry-based approaches for addressing critical questions in addiction neuroscience, highlighting recent innovative studies that exemplify how functional assessments of the neuroproteome can provide insight into the mechanisms of drug addiction.

Andrographolide Sulfonate Attenuates Acute Lung Injury by Reducing Expression of Myeloperoxidase and Neutrophil-Derived Proteases in Mice

Andrographolide sulfonate (Andro-S), a sulfonation derivative of andrographolide, is known to be effective in treating inflammation-related diseases, while the underlying mechanisms and global protein alterations in response to Andro-S remain unknown. This study aimed to investigate the pharmacological effects and potential targets of Andro-S in a murine model of acute lung injury (ALI). ALI was induced by aerosolized lipopolysaccharide (LPS) exposure before treatment with Andro-S. Inflammatory state of each treatment group was determined by histological analysis and quantification of inflammatory markers. Differentially expressed proteins in lung tissues were identified by an iTRAQ-based quantitative proteomic approach and further confirmed by immunohistochemistry analysis. Administration of Andro-S alleviated LPS-induced histological changes in the lung and reduced the expression of inflammatory markers in serum, bronchoalveolar fluid and lung tissues. Proteomic analysis identified 31 differentially expressed proteins from a total of 2,234 quantified proteins in the lung. According to bioinformatics analysis, neutrophil elastase (ELANE), cathepsin G (CTSG) and myeloperoxidase (MPO), three neutrophil-derived proteases related to immune system process and defense responses to fungi were chosen as potential targets of Andro-S. Further immunohistochemistry analysis confirmed the inhibitory effects of Andro-S on LPS-induced ELANE, CTSG and MPO up-regulation. These results indicate that Andro-S suppressed the severity of LPS-induced ALI, possibly by attenuating the expression of and neutrophil-derived proteases.

Effect of Sirtuin-1 on Synaptic Plasticity in Nucleus Accumbens in a Rat Model of Heroin Addiction

BACKGROUND Synaptic plasticity plays an important role in the process of addiction. This study investigated the relationship between synaptic plasticity and changes in addictive behavior and examined the expression of synaptic plasticity-associated proteins and genes in the nucleus accumbens (NAc) region in different rat models. MATERIAL AND METHODS Heroin addiction, SIRT1-overexpression, and SIRT1-silenced rat models were established. Polymerase chain reaction gene chip technology, immunohistochemistry, Western blotting, and transmission electron microscopy were used to detect changes in synaptic plasticity-related gene and protein expression, and changes in the ultrastructure of synapses, in the NAc. RESULTS Naloxone withdrawal symptoms appeared in the SIRT1-overexpression group. In the SIRT1-silenced group the symptoms were reduced. Immunohistochemistry and Western blotting results showed that FOXO1 expression decreased in the heroin addiction (HA) group but increased in the SIRT1-silenced group (p<0.05). The expression of Cdk5, Nf-κB, PSD95, and Syn was enhanced in the HA group (p<0.05) and further increased in the SIRT1-overexpression group but were reduced in the SIRT1-silenced group (p<0.05). The number of synapses increased in the HA group (p<0.05) along with mitochondrial swelling in the presynaptic membrane and obscuring of the synaptic cleft. CONCLUSIONS SIRT1 and other synaptic plasticity-related genes in NAc are involved in the regulation of heroin addiction. SIRT1 overexpression can increase behavioral sensitization in the NAc of rats, and SIRT1 silencing might ease withdrawal symptoms and reduce conditioned place preferences.

Quantitative Proteomic Study Reveals Up-Regulation of cAMP Signaling Pathway-Related Proteins in Mild Traumatic Brain Injury

Traumatic brain injury (TBI), as a neurological injury, becomes a leading cause of disability and mortality due to lacking effective therapy. About 75% of TBI is mild traumatic brain injury (mTBI). However, the complex molecular mechanisms underlying mTBI pathophysiology remains to be elucidated. In this study, iTRAQ-based quantitative proteomic approach was employed to measure temporal-global proteome changes of rat brain tissues from different time points (1 day, 7 day and 6 months) post single mTBI (smTBI) and repetitive mTBI (rmTBI). A total of 5169 proteins were identified, of which, 237 proteins were significantly changed between control rats and mTBI model rats. Fuzzy c-means (FCM) clustering analysis classified these 237 proteins into six clusters according to their temporal pattern of protein abundance. Functional bioinformatics analysis and protein-protein interaction (PPI) network mapping of these FCM clusters showed that phosphodiesterase 10A (Pde10a) and guanine nucleotide-binding protein G (olf) subunit alpha (Gnal) were the node proteins in the cAMP signaling pathway. Other biological processes, such as cell adhesion, autophagy, myelination, microtubule depolymerization and brain development, were also over-represented in FCM clusters. Further Western Blot experiments confirmed that Pde10a and Gnal were acutely up-regulated in severity-dependent manner by mTBI, but these two proteins could not be down-regulated to basal level at the time point of 6 months post repetitive mTBI. Our study demonstrated that different severity of mTBI cause significant temporal profiling change at the proteomic level and pointed out the cAMP signaling pathway-related proteins, Pde10a and Gnal, may play important roles in the pathogenesis and recovery of mTBI.