Alterations in the levels of heterotrimeric G protein subunits induced by psychostimulants, opiates, barbiturates, and ethanol: Implications for drug dependence, tolerance, and withdrawal

Differential regulation of G protein-coupled receptor-associated proteins in the caudate and the putamen of cynomolgus macaques following chronic ethanol drinking

The dorsal striatum is composed of the caudate nucleus and the putamen in human and non-human primates. These two regions receive different cortical projections and are functionally distinct. The caudate is involved in the control of goal-directed behaviors, while the putamen is implicated in habit learning and formation. Previous reports indicate that ethanol differentially influences neurotransmission in these two regions. Because neurotransmitters primarily signal through G protein-coupled receptors (GPCRs) to modulate neuronal activity, the present study aimed to determine whether ethanol had a region-dependent impact on the expression of proteins that are involved in the trafficking and function of GPCRs, including G protein subunits and their effectors, protein kinases, and elements of the cytoskeleton. Western blotting was performed to examine protein levels in the caudate and the putamen of male cynomolgus macaques that self-administered ethanol for 1 year under free access conditions, along with control animals that self-administered an isocaloric sweetened solution under identical operant conditions. Among the 18 proteins studied, we found that the levels of one protein (PKCβ) were increased, and 13 proteins (Gαi1/3, Gαi2, Gαo, Gβ1γ, PKCα, PKCε, CaMKII, GSK3β, β-actin, cofilin, α-tubulin, and tubulin polymerization promoting protein) were reduced in the caudate of alcohol-drinking macaques. However, ethanol did not alter the expression of any proteins examined in the putamen. These observations underscore the unique vulnerability of the caudate nucleus to changes in protein expression induced by chronic ethanol exposure. Whether these alterations are associated with ethanol-induced dysregulation of GPCR function and neurotransmission warrants future investigation.

GPCRs Are Optimal Regulators of Complex Biological Systems and Orchestrate the Interface between Health and Disease

GPCRs arguably represent the most effective current therapeutic targets for a plethora of diseases. GPCRs also possess a pivotal role in the regulation of the physiological balance between healthy and pathological conditions; thus, their importance in systems biology cannot be underestimated. The molecular diversity of GPCR signaling systems is likely to be closely associated with disease-associated changes in organismal tissue complexity and compartmentalization, thus enabling a nuanced GPCR-based capacity to interdict multiple disease pathomechanisms at a systemic level. GPCRs have been long considered as controllers of communication between tissues and cells. This communication involves the ligand-mediated control of cell surface receptors that then direct their stimuli to impact cell physiology. Given the tremendous success of GPCRs as therapeutic targets, considerable focus has been placed on the ability of these therapeutics to modulate diseases by acting at cell surface receptors. In the past decade, however, attention has focused upon how stable multiprotein GPCR superstructures, termed receptorsomes, both at the cell surface membrane and in the intracellular domain dictate and condition long-term GPCR activities associated with the regulation of protein expression patterns, cellular stress responses and DNA integrity management. The ability of these receptorsomes (often in the absence of typical cell surface ligands) to control complex cellular activities implicates them as key controllers of the functional balance between health and disease. A greater understanding of this function of GPCRs is likely to significantly augment our ability to further employ these proteins in a multitude of diseases.

Involvement of GRK2 in modulating nalfurafine-induced reduction of excessive alcohol drinking in mice

Though it is well known that G protein-coupled receptor kinase 2 [GRK2] is involved in regulation of mu opioid receptor [MOR] desensitization and morphine-related behaviors, the potential role of GRK2 in regulation of kappa opioid receptor [KOR] functions in vivo has not been established yet. A couple of recent studies have found that GRK2 activity desensitizes KOR functions via decreasing G protein-coupled signaling with sensitizing arrestin-coupled signaling. Nalfurafine, a G protein-biased KOR full agonist, produces an inhibitory effect on alcohol intake in mice, with fewer side effects (sedation, aversion, or anxiety/depression-like behaviors). Using RNA sequencing (RNA-seq) analysis, we first identified that nuclear transcript level of grk2 [adrbk1] (but not other grks) was significantly up-regulated in mouse nucleus accumbens shell (NAcs) after chronic excessive alcohol drinking, suggesting alcohol specifically increased NAcs grk2 expression. We then tested whether selective GRK2/3 inhibitor CMPD101 could alter alcohol intake and found that CMPD101 alone had no effect on alcohol drinking. Therefore, we hypothesized that the grk2 increase in the NAcs could modulate the nalfurafine effect on alcohol intake via interacting with the G protein-mediated KOR signaling. Nalfurafine decreased alcohol drinking in a dose-related manner, and pretreatment with CMPD101 enhanced the reduction in alcohol intake induced by nalfurafine, indicating an involvement of GRK2/3 blockade in modulating G protein-biased KOR agonism of nalfurafine. Together, our study provides initial evidence relevant to the transcriptional change of grk2 gene in the NAc shell after excessive alcohol drinking. Pharmacological GRK2/3 blockade enhanced nalfurafine's efficacy, suggesting a GRK2/3-mediated mechanism, probably through the G protein-mediated KOR signaling.

Continuous High Frequency Deep Brain Stimulation of the Rat Anterior Insula Attenuates the Relapse Post Withdrawal and Strengthens the Extinction of Morphine Seeking

Deep brain stimulation (DBS) modulates the neuronal activity in specific brain circuits and has been recently considered as a promising intervention for refractory addiction. The insula cortex is the hub of interoception and is known to be involved in different aspects of substance use disorder. In the present study, we investigate the effects of continuous high frequency DBS in the anterior insula (AI) on drug-seeking behaviors and examined the molecular mechanisms of DBS action in morphine-addicted rats. Sprague-Dawley rats were trained to the morphine-conditioned place preference (CPP, day 1-8) followed by bilaterally implanted with DBS electrodes in the AI (Day 10) and recovery (Day 10-15). Continuous high-frequency (HF) -DBS (130 Hz, 150 μA, 90 μs) was applied during withdrawal (Day 16-30) or extinction sessions. CPP tests were conducted on days 16, 30, 40 during withdrawal session and several rats were used for proteomic analysis on day 30. Following the complete extinction, morphine-CPP was reinstated by a priming dose of morphine infusion (2 mg/kg). The open field and novel objective recognition tests were also performed to evaluate the DBS side effect on the locomotion and recognition memory. Continuous HF-DBS in the AI attenuated the expression of morphine-CPP post-withdrawal (Day 30), but morphine addictive behavior relapsed 10 days after the cessation of DBS (Day 40). Continuous HF-DBS reduced the period to full extinction of morphine-CPP and blocked morphine priming-induced recurrence of morphine addiction. HF-DBS in the AI had no obvious effect on the locomotor activity and novel objective recognition and did not cause anxiety-like behavior. In addition, our proteomic analysis identified eight morphine-regulated proteins in the AI and their expression levels were reversely changed by HF-DBS. Continuous HF-DBS in the bilateral anterior insula prevents the relapse of morphine place preference after withdrawal, facilitates its extinction, blocks the reinstatement induced by morphine priming and reverses the expression of morphine-regulated proteins. Our findings suggest that manipulation of insular activity by DBS could be a potential intervention to treat substance use disorder, although future research is warranted.

[Endomorphins: structure, localization, immunoregulatory activity]

Endomorphins – endogenous tetrapeptides with the highest affinity for the µ-opioid receptor. Currently, two tetrapeptides that differ in one amino acid residue have been isolated and characterized. The structure of endomorphins differs from the structure of members of three main families of opioid peptides: endorphins, enkephalins, and dynorphins, which contain the same N-terminal sequence. In the central nervous system, endomorphins are distributed everywhere, where they are primarily responsible for antinociception. Distribution of endomorphins in the immune system, similar to that of other opioid peptides, has allowed to suggest their active participation in the processes of immune regulation. This review summarizes modern views on the structure of endomorphins, their localization, possible intracellular mechanisms of signal transmission and their effects on the processes of activation, proliferation and differentiation of cells of innate and adaptive immunity. Endomorphins actively modulate the functions of the cells of the immune system. Peptides predominantly suppress adaptive immunity reactions. There effects on the functions of innate immunity cells (granulocytes, macrophages, monocytes, dendritic cells) depending on the conditions and can have either an inhibitory or stimulating orientation. Thus, endomorphins can be promising compounds that can effectively regulate both nociceptive signals and processes in the immune system.

G-protein αq gene expression plays a role in alcohol tolerance in Drosophila melanogaster

Ethanol is a psychoactive substance causing both short- and long-term behavioural changes in humans and animal models. We have used the fruit fly Drosophila melanogaster to investigate the effect of ethanol exposure on the expression of the Gαq protein subunit. Repetitive exposure to ethanol causes a reduction in sensitivity (tolerance) to ethanol, which we have measured as the time for 50% of a set of flies to become sedated after exposure to ethanol (ST50). We demonstrate that the same treatment that induces an increase in ST50 over consecutive days (tolerance) also causes a decrease in Gαq protein subunit expression at both the messenger RNA and protein level. To identify whether there may be a causal relationship between these two outcomes, we have developed strains of flies in which Gαq messenger RNA expression is suppressed in a time- and tissue-specific manner. In these flies, the sensitivity to ethanol and the development of tolerance are altered. This work further supports the value of Drosophila as a model to dissect the molecular mechanisms of the behavioural response to alcohol and identifies G proteins as potentially important regulatory targets for alcohol use disorders.

Metabolism and Pharmacokinetics of Phytochemicals in the Human Body

Background:

Phytochemicals are obtained from various plants and used for the treatment of diseases as both traditional and modern medicines. Poor bioavailability of phytochemicals is a major concern in applying phytochemicals as a therapeutic agent. It is, therefore, necessary to understand the metabolism and pharmacokinetics of phytochemicals for its implication as a therapeutic agent.

Methods:

Articles on the metabolism of phytochemicals from the PubMed database. The articles were classified into the digestion, absorption, metabolism, excretion, toxicity, and bioavailability of phytochemicals and the effect of gut microbiota on the metabolism of phytochemicals.

Results:

The metabolism of each phytochemical is largely dependent on the individual's digestive ability, membrane transporters, metabolizing enzymes and gut microbiota. Further, the form of the phytochemical and genetic make-up of the individual greatly influences the metabolism of phytochemicals.

Conclusion:

The metabolism of phytochemicals is mostly depended on the form of phytochemicals and individualspecific variations in the metabolism of phytochemicals. Understanding the metabolism and pharmacokinetics of phytochemicals might help in applying plant-based medicines for the treatment of various diseases.

The influence of adolescent nicotine exposure on ethanol intake and brain gene expression

Nicotine and alcohol are often co-abused. Adolescence is a vulnerable period for the initiation of both nicotine and alcohol use, which can lead to subsequent neurodevelopmental and behavioral alterations. It is possible that during this vulnerable period, use of one drug leads to neurobiological alterations that affect subsequent consumption of the other drug. The aim of the present study was to determine the effect of nicotine exposure during adolescence on ethanol intake, and the effect of these substances on brain gene expression. Forty-three adolescent female C57BL/6J mice were assigned to four groups. In the first phase of the experiment, adolescent mice (PND 36-41 days) were exposed to three bottles filled with water or nicotine (200 μg/ml) for 22 h a day and a single bottle of water 2 h a day for six days. In the second phase (PND 42-45 days), the 4-day Drinking-in-the-Dark paradigm consisting of access to 20% v/v ethanol or water for 2h or 4h (the last day) was overlaid during the time when the mice did not have nicotine available. Ethanol consumption (g/kg) and blood ethanol concentrations (BEC, mg %) were measured on the final day and whole brains including the cerebellum, were dissected for RNA sequencing. Differentially expressed genes (DEG) were detected with CuffDiff and gene networks were built using WGCNA. Prior nicotine exposure increased ethanol consumption and resulting BEC. Significant DEG and biological pathways found in the group exposed to both nicotine and ethanol included genes important in stress-related neuropeptide signaling, hypothalamic-pituitary-adrenal (HPA) axis activity, glutamate release, GABA signaling, and dopamine release. These results replicate our earlier findings that nicotine exposure during adolescence increases ethanol consumption and extends this work by examining gene expression differences which could mediate these behavioral effects.

N-Docosahexaenoylethanolamine ameliorates ethanol-induced impairment of neural stem cell neurogenic differentiation

Previous studies demonstrated that prenatal exposure to ethanol interferes with embryonic and fetal development, and causes abnormal neurodevelopment. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid highly enriched in the brain, was shown to be essential for proper brain development and function. Recently, we found that N-docosahexenoyethanolamine (synaptamide), an endogenous metabolite of DHA, is a potent PKA-dependent neurogenic factor for neural stem cell (NSC) differentiation. In this study, we demonstrate that ethanol at pharmacologically relevant concentrations downregulates cAMP signaling in NSC and impairs neurogenic differentiation. In contrast, synaptamide reverses ethanol-impaired NSC neurogenic differentiation through counter-acting on the cAMP production system. NSC exposure to ethanol (25-50 mM) for 4 days dose-dependently decreased the number of Tuj-1 positive neurons and PKA/CREB phosphorylation with a concomitant reduction of cellular cAMP. Ethanol-induced cAMP reduction was accompanied by the inhibition of G-protein activation and expression of adenylyl cyclase (AC) 7 and AC8, as well as PDE4 upregulation. In contrast to ethanol, synaptamide increased cAMP production, GTPγS binding, and expression of AC7 and AC8 isoforms in a cAMP-dependent manner, offsetting the ethanol-induced impairment in neurogenic differentiation. These results indicate that synaptamide can reduce ethanol-induced impairment of neuronal differentiation by counter-affecting shared targets in G-protein coupled receptor (GPCR)/cAMP signaling. The synaptamide-mediated mechanism observed in this study may offer a possible avenue for ameliorating the adverse impact of fetal alcohol exposure on neurodevelopment.

Acute morphine alters GABAergic transmission in the central amygdala during naloxone-precipitated morphine withdrawal: role of cyclic AMP

The central amygdala (CeA) plays an important role in opioid addiction. Therefore, we examined the effects of naloxone-precipitated morphine withdrawal (WD) on GABAergic transmission in rat CeA neurons using whole-cell recordings with naloxone in the bath. The basal frequency of miniature inhibitory postsynaptic currents (mIPSCs) increased in CeA neurons from WD compared to placebo rats. Acute morphine (10 μ M) had mixed effects (≥20% change from baseline) on mIPSCs in placebo and WD rats. In most CeA neurons (64%) from placebo rats, morphine significantly decreased mIPSC frequency and amplitude. In 32% of placebo neurons, morphine significantly increased mIPSC amplitudes but had no effect on mIPSC frequency. In WD rats, acute morphine significantly increased mIPSC frequency but had no effect on mIPSC amplitude in 41% of CeA neurons. In 45% of cells, acute morphine significantly decreased mIPSC frequency and amplitude. Pre-treatment with the cyclic AMP inhibitor (R)-adenosine, cyclic 3',5'-(hydrogenphosphorothioate) triethylammonium (RP), prevented acute morphine-induced potentiation of mIPSCs. Pre-treatment of slices with the Gi/o G-protein subunit inhibitor pertussis toxin (PTX) did not prevent the acute morphine-induced enhancement or inhibition of mIPSCs. PTX and RP decreased basal mIPSC frequencies and amplitudes only in WD rats. The results suggest that inhibition of GABAergic transmission in the CeA by acute morphine is mediated by PTX-insensitive mechanisms, although PTX-sensitive mechanisms cannot be ruled out for non-morphine responsive cells; by contrast, potentiation of GABAergic transmission is mediated by activated cAMP signaling that also mediates the increased basal GABAergic transmission in WD rats. Our data indicate that during the acute phase of WD, the CeA opioid and GABAergic systems undergo neuroadaptative changes conditioned by a previous chronic morphine exposure and dependence.

Coordinated dynamic gene expression changes in the central nucleus of the amygdala during alcohol withdrawal

BACKGROUND

Chronic alcohol use causes widespread changes in the cellular biology of the amygdala's central nucleus (CeA), a GABAergic center that integrates autonomic physiology with the emotional aspects of motivation and learning. While alcohol-induced neurochemical changes play a role in dependence and drinking behavior, little is known about the CeA's dynamic changes during withdrawal, a period of emotional and physiologic disturbance.

METHODS

We used a qRT-PCR platform to measure 139 transcripts in 92 rat CeA samples from control (N = 33), chronically alcohol exposed (N = 26), and withdrawn rats (t = 4, 8, 18, 32, and 48 hours; N = 5, 10, 7, 6, 5). This focused transcript set allowed us to identify significant dynamic expression patterns during the first 48 hours of withdrawal and propose potential regulatory mechanisms.

RESULTS

Chronic alcohol exposure causes a limited number of small magnitude expression changes. In contrast, withdrawal results in a greater number of large changes within 4 hours of removal of the alcohol diet. Sixty-five of the 139 measured transcripts (47%) showed differential regulation during withdrawal. Over the 48-hour period, dynamic changes in the expression of γ-aminobutyric acid type A (GABA(A) ), ionotropic glutamate and neuropeptide system-related G-protein-coupled receptor subunits, and the Ras/Raf signaling pathway were seen as well as downstream transcription factors (TFs) and epigenetic regulators. Four temporally correlated gene clusters were identified with shared functional roles including NMDA receptors, MAPKKK and chemokine signaling cascades, and mediators of long-term potentiation, among others. Cluster promoter regions shared overrepresented binding sites for multiple TFs including Cebp, Usf-1, Smad3, Ap-2, and c-Ets, suggesting a potential regulatory role.

CONCLUSIONS

During alcohol withdrawal, the CeA experiences rapid changes in mRNA expression of these functionally related transcripts that were not predicted by measurement during chronic exposure. This study provides new insight into dynamic expression changes during alcohol withdrawal and suggests novel regulatory relationships that potentially impact the aspects of emotional modulation.

Endogenous opioid peptides in regulation of innate immunity cell functions

Endogenous opioid peptides comprise a group of bioregulatory factors involved in regulation of functional activity of various physiological systems of an organism. One of most important functions of endogenous opioids is their involvement in the interaction between cells of the nervous and immune systems. Summary data on the effects of opioid peptides on regulation of functions of innate immunity cells are presented.

Genome-wide gene expression analysis identifies K-ras as a regulator of alcohol intake

Adaptations in the anterior cingulate cortex (ACC) have been implicated in alcohol and drug addiction. To identify genes that may contribute to excessive drinking, here we performed microarray analyses in laser microdissected rat ACC after a single or repeated administration of an intoxicating dose of alcohol (3 g/kg). Expression of the small G protein K-ras was differentially regulated following both single and repeated alcohol administration. We also observed that voluntary alcohol intake in K-ras heterozygous null mice (K-ras(+/-)) did not increase after withdrawal from repeated cycles of intermittent ethanol vapor exposure, unlike in their wild-type littermates. To identify K-ras regulated pathways, we then profiled gene expression in the ACC of K-ras(+/-), heterozygous null mice for the K-ras negative regulator Nf1 (Nf1(+/-)) and wild-type mice following repeated administration of an intoxicating dose of alcohol. Pathway analysis showed that alcohol differentially affected various pathways in a K-ras dependent manner - some of which previously shown to be regulated by alcohol - including the insulin/PI3K pathway, the NF-kappaB, the phosphodiesterases (PDEs) pathway, the Jak/Stat and the adipokine signaling pathways. Altogether, the data implicate K-ras-regulated pathways in the regulation of excessive alcohol drinking after a history of dependence.

Poly(lactide-co-glycolide) nanoparticle assembly for highly efficient delivery of potent therapeutic agents from medical devices

Controlled delivery of therapeutic agents from medical devices can improve their safety and effectiveness in vivo, by ameliorating the surrounding tissue responses and thus maintaining the functional integrity of the devices. Previously, we presented a new method for providing simultaneous controlled delivery from medical devices, by surface assembly of biodegradable polymer nanoparticles (NPs) encapsulating fluorescent dyes. Here, we continue our investigation with NPs loaded with therapeutic agents, dexamethasone (DEX) or plasmid DNA, and evaluated the bioactivity of the released molecules with macrophage cells associated with inflammation. Over a period of one week, NPs encapsulating DEX released 24.9+/-0.8ng from the probe surface and was successful at suppressing macrophage cell growth by 40+/-10%. This percentage of suppression corresponded to approximately 100% drug delivery efficiency, in comparison with the unencapsulated drug. DNA NP coatings, in contrast, released approximately 1ng of plasmid DNA and were effective at transfecting macrophage cells to express the luciferase gene at 300+/-200 relative luminescence/mg total protein. This amount of luciferase activity corresponded to 100% gene delivery efficiency. Thus, NP coatings were capable of providing continuous release of bioactive agents in sufficient quantities to induce relevant biological effects in cell culture studies. These coatings also remained intact, even after 14 days of incubation with phosphate buffered saline. Although the maximum loading for NP coatings is inherently lower than the more established matrix coating, our study suggests that the NP coatings are a more versatile and efficient approach toward drug delivery or gene delivery from a medical device surface and are perhaps best suited for continuous release of highly potent therapeutic agents.