PPARγ agonism attenuates cocaine cue reactivity

Promising immunomodulators for management of substance and alcohol use disorders

INTRODUCTION

The neuroimmune system has emerged as a novel target for the treatment of substance use disorders (SUDs), with immunomodulation producing encouraging therapeutic benefits in both preclinical and clinical settings.

AREAS COVERED

In this review, we describe the mechanism of action and immune response to methamphetamine, opioids, cocaine, and alcohol. We then discuss off-label use of immunomodulators as adjunctive therapeutics in the treatment of neuropsychiatric disorders, demonstrating their potential efficacy in affective and behavioral disorders. We then discuss in detail the mechanism of action and recent findings regarding the use of ibudilast, minocycline, probenecid, dexmedetomidine, pioglitazone, and cannabidiol to treat (SUDs). These immunomodulators are currently being investigated in clinical trials described herein, specifically for their potential to decrease substance use, withdrawal severity, central and peripheral inflammation, comorbid neuropsychiatric disorder symptomology, as well as their ability to improve cognitive outcomes.

EXPERT OPINION

We argue that although mixed, findings from recent preclinical and clinical studies underscore the potential benefit of immunomodulation in the treatment of the behavioral, cognitive, and inflammatory processes that underlie compulsive substance use.

Neuroimmune modulators as novel pharmacotherapies for substance use disorders

One promising avenue of research is the use of neuroimmune modulators to treat substance use disorders (SUDs). Neuroimmune modulators target the interactions between the nervous system and immune system, which have been found to play a crucial role in the development and maintenance of SUDs. Multiple classes of substances produce alterations to neuroimmune signaling and peripheral immune function, including alcohol, opioids, and psychostimulants Preclinical studies have shown that neuroimmune modulators can reduce drug-seeking behavior and prevent relapse in animal models of SUDs. Additionally, early-phase clinical trials have demonstrated the safety and feasibility of using neuroimmune modulators as a treatment for SUDs in humans. These therapeutics can be used as stand-alone treatments or as adjunctive. This review summarizes the current state of the field and provides future directions with a specific focus on personalized medicine.

Ghrelin receptor antagonist JMV2959 blunts cocaine and oxycodone drug-seeking, but not self-administration, in male rats

The drug overdose crisis has spawned serious health consequences, including the increased incidence of substance use disorders (SUDs), conditions manifested by escalating medical and psychological impairments. While medication management is a key adjunct in SUD treatment, this crisis has crystallized the need to develop additional therapeutics to facilitate extended recovery from SUDs. The "hunger hormone" ghrelin acts by binding to the growth hormone secretagogue receptor 1α (GHS1αR) to control homeostatic and hedonic aspects of food intake and has been implicated in the mechanisms underlying SUDs. Preclinical studies indicate that GHS1αR antagonists and inverse agonists suppress reward-related signaling associated with cocaine and opioids. In the present study, we found that the GHS1αR antagonist JMV2959 was efficacious to suppress both cue-reinforced cocaine and oxycodone drug-seeking, but not cocaine or oxycodone self-administration in male Sprague-Dawley rats. These data suggest a role of the ghrelin-GHS1αR axis in mediating overlapping reward-related aspects of cocaine and oxycodone and premises the possibility that a GHS1αR antagonist may be a valuable therapeutic strategy for relapse vulnerability in SUDs.

Sustained drug delivery strategies for treatment of common substance use disorders: Promises and challenges

Substance use disorders (SUDs) are a leading cause of death and other ill health effects in the United States and other countries in the world. Several approaches ranging from detoxification, behavioral therapy, and the use of antagonists or drugs with counter effects are currently being applied for its management. Amongst these, drug therapy is the mainstay for some drug abuse incidences, as is in place specifically for opioid abuse or alcohol dependence. The severity of the havocs observed with the SUDs has triggered constant interest in the discovery and development of novel medications as well as suitable or most appropriate methods for the delivery of these agents. The chronic need of such drugs in users warrants the need for their prolonged or sustained systemic availability. Further, the need to improve patient tolerance to medication, limit invasive drug use and overall treatment outcome are pertinent considerations for embracing sustained release designs for medications used in managing SUDs. This review aims to provide an overview on up-to-date advances made with regards to sustained delivery systems for the drugs for treatment of different types of SUDs such as opioid, alcohol, tobacco, cocaine, and cannabis use disorders. The clinical relevance, promises and the limitations of deployed sustained release approaches along with future opportunities are discussed.

Cannabidiol and substance use disorder: Dream or reality

BACKGROUND

Cannabidiol (CBD) is one of the major constituents of Cannabis sativa L. that lacks psychotomimetic and rewarding properties and inhibits the rewarding and reinforcing effects of addictive drugs such as cocaine, methamphetamine (METH), and morphine. Additionally, CBD's safety profile and therapeutic potential are currently evaluated in several medical conditions, including pain, depression, movement disorders, epilepsy, multiple sclerosis, Alzheimer's disease, ischemia, and substance use disorder. There is no effective treatment for substance use disorders such as addiction, and this review aims to describe preclinical and clinical investigations into the effects of CBD in various models of opioid, psychostimulant, cannabis, alcohol, and nicotine abuse. Furthermore, the possible mechanisms underlying the therapeutic potential of CBD on drug abuse disorders are reviewed.

METHODS

The current review considers and summarizes the preclinical and clinical investigations into CBD's effects in various models of drug abuse include opioids, psychostimulants, cannabis, alcohol, and nicotine.

RESULTS

Several preclinical and clinical studies have proposed that CBD may be a reliable agent to inhibit the reinforcing and rewarding impact of drugs.

CONCLUSIONS

While the currently available evidence converges to suggest that CBD could effectively reduce the rewarding and reinforcing effects of addictive drugs, more preclinical and clinical studies are needed before CBD can be added to the therapeutic arsenal for treating addiction.

Targeting white matter neuroprotection as a relapse prevention strategy for treatment of cocaine use disorder: Design of a mechanism-focused randomized clinical trial

Cocaine use continues to be a significant public health problem with limited treatment options and no approved pharmacotherapies. Cognitive-behavioral therapy (CBT) remains the mainstay treatment for preventing relapse, however, people with chronic cocaine use display cognitive impairments that are associated with poor response to CBT. Emerging evidence in animal and human studies suggests that the peroxisome proliferator-activated receptor-gamma (PPAR- γ) agonist, pioglitazone, improves white matter integrity that is essential for cognitive function. This project will determine whether adjunctive use of pioglitazone enhances the effect of CBT in preventing relapse during the early phase of recovery from cocaine use disorder. This paper describes the design of a mechanism-focused phase 2 randomized clinical trial that aims first to evaluate the effects of pioglitazone on targeted mechanisms related to white matter integrity, cognitive function, and cocaine craving; and second, to evaluate the extent to which improvements on target mechanisms predict CBT response. Positive results will support pioglitazone as a potential cognitive enhancing agent to advance to later stage medication development research.

Repurposing Peroxisome Proliferator-Activated Receptor Agonists in Neurological and Psychiatric Disorders

Common pathophysiological mechanisms have emerged for different neurological and neuropsychiatric conditions. In particular, mechanisms of oxidative stress, immuno-inflammation, and altered metabolic pathways converge and cause neuronal and non-neuronal maladaptative phenomena, which underlie multifaceted brain disorders. The peroxisome proliferator-activated receptors (PPARs) are nuclear receptors modulating, among others, anti-inflammatory and neuroprotective genes in diverse tissues. Both endogenous and synthetic PPAR agonists are approved treatments for metabolic and systemic disorders, such as diabetes, fatty liver disease, and dyslipidemia(s), showing high tolerability and safety profiles. Considering that some PPAR-acting drugs permeate through the blood-brain barrier, the possibility to extend their scope from the periphery to central nervous system has gained interest in recent years. Here, we review preclinical and clinical evidence that PPARs possibly exert a neuroprotective role, thereby providing a rationale for repurposing PPAR-targeting drugs to counteract several diseases affecting the central nervous system.

Reduced alcohol use in patients prescribed pioglitazone

BACKGROUND AND OBJECTIVES

Alcohol use disorder (AUD) is common and causes significant morbidity and mortality. Currently approved medications are moderately effective. Novel medications are needed to address AUD. Preliminary data suggests pioglitazone may reduce alcohol use.

METHODS

Veterans seen at the Minneapolis VA Health Care System, who were prescribed pioglitazone for diabetes between October 1, 2015 and September 30, 2016, were identified using a national VA database (N = 49). Further chart review was performed to identify all Alcohol Use Disorder Identification Test-Consumption (AUDIT-C) scores prior to starting pioglitazone. Hierarchical Linear models were used to compare all AUDIT-C scores on and off pioglitazone and compare the change in AUDIT-C scores over time before and during pioglitazone was prescribed. AUDIT-C scores were nested within subject with fixed effects for pioglitazone and random intercept and slope for time.

RESULTS

Forty-nine patients were prescribed pioglitazone and had AUDIT-C scores of 3 or more. The estimated mean AUDIT-C score prior to receiving pioglitazone was 3.98 (95% confidence interval [CI]: 3.51-4.44) and this was reduced to 2.89 (95% CI: 2.46-3.32), reflecting a significant change F(1, 323) = 43.3, p < .001 in the score. The primary reduction occurred within the first year of the pioglitazone prescription. This effect remained significant after controlling for age.

CONCLUSION AND SCIENTIFIC SIGNIFICANCE

This is the first study of pioglitazone used in a clinical sample focused on alcohol use outcome. The data show that pioglitazone may reduce alcohol use in patients with heavy drinking. Clinical trials of pioglitazone are warranted in patients with AUD.

Beta-caryophyllene inhibits cocaine addiction-related behavior by activation of PPARα and PPARγ: repurposing a FDA-approved food additive for cocaine use disorder

Cocaine abuse continues to be a serious health problem worldwide. Despite intense research, there is still no FDA-approved medication to treat cocaine use disorder (CUD). In this report, we explored the potential utility of beta-caryophyllene (BCP), an FDA-approved food additive for the treatment of CUD. We found that BCP, when administered intraperitoneally or intragastrically, dose-dependently attenuated cocaine self-administration, cocaine-conditioned place preference, and cocaine-primed reinstatement of drug seeking in rats. In contrast, BCP failed to alter food self-administration or cocaine-induced hyperactivity. It also failed to maintain self-administration in a drug substitution test, suggesting that BCP has no abuse potential. BCP was previously reported to be a selective CB2 receptor agonist. Unexpectedly, pharmacological blockade or genetic deletion of CB1, CB2, or GPR55 receptors in gene-knockout mice failed to alter BCP's action against cocaine self-administration, suggesting the involvement of non-CB1, non-CB2, and non-GPR55 receptor mechanisms. Furthermore, pharmacological blockade of μ opioid receptor or Toll-like receptors complex failed to alter, while blockade of peroxisome proliferator-activated receptors (PPARα, PPARγ) reversed BCP-induced reduction in cocaine self-administration, suggesting the involvement of PPARα and PPARγ in BCP's action. Finally, we used electrical and optogenetic intracranial self-stimulation (eICSS, oICSS) paradigms to study the underlying neural substrate mechanisms. We found that BCP is more effective in attenuation of cocaine-enhanced oICSS than eICSS, the former driven by optical activation of midbrain dopamine neurons in DAT-cre mice. These findings indicate that BCP may be useful for the treatment of CUD, likely by stimulation of PPARα and PPARγ in the mesolimbic system.

Andrographis paniculata and Its Main Bioactive Ingredient Andrographolide Decrease Alcohol Drinking and Seeking in Rats Through Activation of Nuclear PPARγ Pathway

BACKGROUND AND AIMS

Andrographis paniculata is an annual herbaceous plant which belongs to the Acanthaceae family. Extracts from this plant have shown hepatoprotective, anti-inflammatory and antidiabetic properties, at least in part, through activation of the nuclear receptor Peroxisome Proliferator-Activated Receptor-gamma (PPAR γ). Recent evidence has demonstrated that activation of PPARγ reduces alcohol drinking and seeking in Marchigian Sardinian (msP) alcohol-preferring rats.

METHODS

The present study evaluated whether A. paniculata reduces alcohol drinking and relapse in msP rats by activating PPARγ.

RESULTS

Oral administration of an A. paniculata dried extract (0, 15, 150 mg/kg) lowered voluntary alcohol consumption in a dose-dependent manner and achieved ~65% reduction at the dose of 450 mg/kg. Water and food consumption were not affected by the treatment. Administration of Andrographolide (5 and 10 mg/kg), the main active component of A. paniculata, also reduced alcohol drinking. This effect was suppressed by the selective PPARγ antagonist GW9662. Subsequently, we showed that oral administration of A. paniculata (0, 150, 450 mg/kg) prevented yohimbine- but not cues-induced reinstatement of alcohol seeking.

CONCLUSIONS

Results point to A. paniculata-mediated PPARγactivation as a possible therapeutic strategy to treat alcohol use disorder.

Further evidence for the involvement of the PPARγ system on alcohol intake and sensitivity in rodents

RATIONALE

Peroxisome Proliferator Activator receptors (PPARs) are intracellular receptors that function as transcription factors, which regulate specific metabolic and inflammatory processes. PPARs are broadly distributed in the body and are also expressed in the central nervous system, especially in areas involved in addiction-related behavioral responses. Recent studies support a role of PPARs in alcoholism and pioglitazone: a PPARγ agonist used for treatment of type 2 diabetes showed efficacy in reducing alcohol drinking, stress-induced relapse, and alcohol withdrawal syndrome in rats.

OBJECTIVES AND METHODS

In the current work, we tested the pharmacological effects of pioglitazone on binge-like alcohol consumption using an intermittent two-bottle choice paradigm in Wistar rats and on the "drinking in the dark" (DID) model in mice with selective deletion of PPARγ in neurons.

RESULTS

Our data show that repeated administration of pioglitazone (10, 30 mg/kg) reduces high voluntary alcohol consumption in Wistar rats. Pre-treatment with the selective PPARγ antagonist GW9662 (5 mg/kg) completely prevented the effect of pioglitazone, demonstrating that its action is specifically mediated by activation of PPARγ. In line with this result, repeated administration of pioglitazone (30 mg/kg) attenuated binge alcohol consumption in PPARγ^(+/+) mice. Whereas in PPARγ^(-/-) mice, which exhibit reduced alcohol consumption, pioglitazone had no effect. Of note, PPARγ^(-/-) mice exhibited lower patterns of alcohol drinking without showing difference in sucrose (control) intake. Interestingly, PPARγ^(-/-) mice displayed a higher sensitivity to the sedative and ataxic effect of alcohol compared with their wild-type counterpart.

CONCLUSIONS

Collectively, these data suggest that PPARγ agonists, and specifically pioglitazone, could be potential therapeutics for the treatment of binge alcohol drinking.

Cocaine-mediated circadian reprogramming in the striatum through dopamine D2R and PPARγ activation

Substance abuse disorders are linked to alteration of circadian rhythms, although the molecular and neuronal pathways implicated have not been fully elucidated. Addictive drugs, such as cocaine, induce a rapid increase of dopamine levels in the brain. Here, we show that acute administration of cocaine triggers reprogramming in circadian gene expression in the striatum, an area involved in psychomotor and rewarding effects of drugs. This process involves the activation of peroxisome protein activator receptor gamma (PPARγ), a nuclear receptor involved in inflammatory responses. PPARγ reprogramming is altered in mice with cell-specific ablation of the dopamine D2 receptor (D2R) in the striatal medium spiny neurons (MSNs) (iMSN-D2RKO). Administration of a specific PPARγ agonist in iMSN-D2RKO mice elicits substantial rescue of cocaine-dependent control of circadian genes. These findings have potential implications for development of strategies to treat substance abuse disorders.

Drugs of abuse have been shown to perturb circadian rhythms. Here, the authors show in mice that cocaine exposure modulates circadian gene expression in the striatum through a previously unappreciated pathway that involves dopamine D2 receptors and the nuclear receptor PPARγ.

Potential of Glial Cell Modulators in the Management of Substance Use Disorders

The pervasive and devastating nature of substance use disorders underlies the need for the continued development of novel pharmacotherapies. We now know that glia play a much greater role in neuronal processes than once believed.  The various types of glial cells (e.g., astrocytes, microglial, oligodendrocytes) participate in numerous functions that are crucial to healthy central nervous system function. Drugs of abuse have been shown to interact with glia in ways that directly contribute to the pharmacodynamic effects responsible for their abuse potential. Through their effect upon glia, drugs of abuse also alter brain function resulting in behavioral changes associated with substance use disorders. Therefore, drug-induced changes in glia and inflammation within the central nervous system (neuroinflammation) have been investigated to treat various aspects of drug abuse and dependence. This article presents a brief overview of the effects of each of the major classes of addictive drugs on glia. Next, the paper reviews the pre-clinical and clinical studies assessing the effects that glial modulators have on abuse-related behavioral effects, such as pleasure, withdrawal, and motivation. There is a strong body of pre-clinical literature demonstrating the general effectiveness of several glia-modulating drugs in models of reward and relapse. Clinical studies have also yielded promising results, though not as robust. There is still much to disentangle regarding the integration between addictive drugs and glial cells. Improved understanding of the relationship between glia and the pathophysiology of drug abuse should allow for more precise exploration in the development and testing of glial-directed treatments for substance use disorders.

Therapeutic Potential of Peroxisome Proliferator-Activated Receptor (PPAR) Agonists in Substance Use Disorders: A Synthesis of Preclinical and Human Evidence

Targeting peroxisome proliferator-activated receptors (PPARs) has received increasing interest as a potential strategy to treat substance use disorders due to the localization of PPARs in addiction-related brain regions and the ability of PPAR ligands to modulate dopamine neurotransmission. Robust evidence from animal models suggests that agonists at both the PPAR-α and PPAR-γ isoforms can reduce both positive and negative reinforcing properties of ethanol, nicotine, opioids, and possibly psychostimulants. A reduction in the voluntary consumption of ethanol following treatment with PPAR agonists seems to be the most consistent finding. However, the human evidence is limited in scope and has so far been less promising. There have been no published human trials of PPAR agonists for treatment of alcohol use disorder, despite the compelling preclinical evidence. Two trials of PPAR-α agonists as potential smoking cessation drugs found no effect on nicotine-related outcomes. The PPAR-γ agonist pioglitazone showed some promise in reducing heroin, nicotine, and cocaine craving in two human laboratory studies and one pilot trial, yet other outcomes were unaffected. Potential explanations for the discordance between the animal and human evidence, such as the potency and selectivity of PPAR ligands and sex-related variability in PPAR physiology, are discussed.

Activation of PPARγ Attenuates the Expression of Physical and Affective Nicotine Withdrawal Symptoms through Mechanisms Involving Amygdala and Hippocampus Neurotransmission

An isoform of peroxisome proliferator-activated receptors (PPARs), PPARγ, is the receptor for the thiazolidinedione class of anti-diabetic medications including pioglitazone. Neuroanatomical data indicate PPARγ localization in brain areas involved in drug addiction. Preclinical and clinical data have shown that pioglitazone reduces alcohol and opioid self-administration, relapse to drug seeking, and plays a role in emotional responses. Here, we investigated the behavioral effect of PPARγ manipulation on nicotine withdrawal in male Wistar rats and in male mice with neuron-specific PPARγ deletion (PPARγ^(-/-)) and their littermate wild-type (PPARγ^(+/+)) controls. Real-time quantitative RT-PCR and RNAscope in situ hybridization assays were used for assessing the levels of expression and cell-type localization of PPARγ during nicotine withdrawal. Brain site-specific microinjections of the PPARγ agonist pioglitazone were performed to explore the role of this system on nicotine withdrawal at a neurocircuitry level. Results showed that activation of PPARγ by pioglitazone abolished the expression of somatic and affective nicotine withdrawal signs in rats and in (PPARγ^(+/+)) mice. This effect was blocked by the PPARγ antagonist GW9662. During early withdrawal and protracted abstinence, the expression of PPARγ increased in GABAergic and glutamatergic cells of the amygdala and hippocampus, respectively. Hippocampal microinjections of pioglitazone reduced the expression of the physical signs of withdrawal, whereas excessive anxiety associated with protracted abstinence was prevented by pioglitazone microinjection into the amygdala. Our results demonstrate the implication of the neuronal PPARγ in nicotine withdrawal and indicates that activation of PPARγ may offer an interesting strategy for smoking cessation.SIGNIFICANCE STATEMENT Smoking cessation leads the occurrence of physical and affective withdrawal symptoms representing a major burden to quit tobacco use. Here, we show that activation of PPARγ prevents the expression of both somatic and affective signs of nicotine withdrawal. At molecular levels results show that PPARγ expression increases in GABAergic cells in the hippocampus and in GABA- and glutamate-positive cells in the basolateral amygdala. Hippocampal microinjections of pioglitazone reduce the insurgence of the physical withdrawal signs, whereas anxiety linked to protracted abstinence is attenuated by pioglitazone injected into the amygdala. Our results demonstrate the implication of neuronal PPARγ in nicotine withdrawal and suggest that PPARγ agonism may represent a promising treatment to aid smoking cessation.

Neuroimmune signaling in alcohol use disorder

Alcohol use disorder (AUD) is a widespread disease with limited treatment options. Targeting the neuroimmune system is a new avenue for developing or repurposing effective pharmacotherapies. Alcohol modulates innate immune signaling in different cell types in the brain by altering gene expression and the molecular pathways that regulate neuroinflammation. Chronic alcohol abuse may cause an imbalance in neuroimmune function, resulting in prolonged perturbations in brain function. Likewise, manipulating the neuroimmune system may change alcohol-related behaviors. Psychiatric disorders that are comorbid with AUD, such as post-traumatic stress disorder, major depressive disorder, and other substance use disorders, may also have underlying neuroimmune mechanisms; current evidence suggests that convergent immune pathways may be involved in AUD and in these comorbid disorders. In this review, we provide an overview of major neuroimmune cell-types and pathways involved in mediating alcohol behaviors, discuss potential mechanisms of alcohol-induced neuroimmune activation, and present recent clinical evidence for candidate immune-related drugs to treat AUD.

Assessment of pioglitazone and proinflammatory cytokines during buprenorphine taper in patients with opioid use disorder

BACKGROUND

Preliminary evidence suggested that the PPARγ agonist pioglitazone reduces opioid-withdrawal symptoms, possibly by inhibiting increases in proinflammatory cytokines.

METHODS

A randomized, placebo-controlled clinical trial was conducted utilizing two different study designs (entirely outpatient, and a combination of inpatient and outpatient) to evaluate the safety and efficacy of pioglitazone as an adjunct medication for people with opioid physical dependence undergoing a buprenorphine taper. Participants were stabilized on buprenorphine/naloxone (sublingual, up to 16/4 mg/day), then randomized to receive oral pioglitazone (up to 45 mg/day) or placebo before, during, and after buprenorphine taper. Outcome measures included the Subjective Opiate Withdrawal Scale (SOWS) and Clinical Opiate Withdrawal Scale, use of rescue medications to alleviate opioid withdrawal symptoms, and opioid-positive urine specimens. Cerebrospinal fluid (CSF) and plasma were collected during the taper in a subset of participants for measurement of proinflammatory cytokines.

RESULTS

The clinical trial was prematurely terminated due to slow enrollment; 40 participants per group were required for adequate statistical power to test study hypotheses. Twenty-four participants enrolled; 17 received at least one dose of study medication (6 pioglitazone, 11 placebo). SOWS scores were higher in the pioglitazone arm than in the placebo arm after adjusting for use of rescue medications; participants in the pioglitazone arm needed more rescue medications than the placebo arm during the post-taper phase. SOWS scores were positively correlated with monocyte chemoattractant protein-1 (MCP-1) in CSF (r = 0.70, p = 0.038) and plasma (r = 0.77, p = 0.015). Participants having higher levels of plasma MCP-1 reported higher SOWS, most notably after the buprenorphine taper ended.

CONCLUSIONS

Results from this study provide no evidence that pioglitazone reduces opioid withdrawal symptoms during buprenorphine taper. High correlations between MCP-1 and opioid withdrawal symptoms support a role of proinflammatory processes in opioid withdrawal.

TRIAL REGISTRATION

clinicaltrials.gov identifier: NCT01517165.

A Protocol for Measuring Cue Reactivity in a Rat Model of Cocaine Use Disorder

Cocaine use disorder (CUD) follows a trajectory of repetitive self-administration during which previously neutral stimuli gain incentive value. Cue reactivity, the sensitivity to cues previously linked with the drug-taking experience, plays a prominent role in human craving during abstinence. Cue reactivity can be assessed as the attentional orientation toward drug-associated cues that is measurable as appetitive approach behavior in both preclinical and human studies. Herein describes an assessment of cue reactivity in rats trained to self-administer cocaine. Cocaine self-administration is paired with the presentation of discrete cues that act as conditioned reinforcers (i.e., house light, stimulus light, infusion pump sounds). Following a period of abstinence, lever presses in the cocaine self-administration context accompanied by the discrete cues previously paired with cocaine infusion are measured as cue reactivity. This model is useful to explore neurobiological mechanisms underlying cue reactivity processes as well as to assess pharmacotherapies to suppress cue reactivity and therefore, modify relapse vulnerability. Advantages of the model include its translational relevance, and its face and predictive validities. The primary limitation of the model is that the cue reactivity task can only be performed infrequently and must only be used in short duration (e.g., 1 hour), otherwise rats will begin to extinguish the pairing of the discrete cues with the cocaine stimulus. The model is extendable to any positively reinforcing stimulus paired with discrete cues; though particularly applicable to drugs of abuse, this model may hold future applications in fields such as obesity, where palatable food rewards can act as positively reinforcing stimuli.

Design, Synthesis, and Characterization of 4-Undecylpiperidine-2-carboxamides as Positive Allosteric Modulators of the Serotonin (5-HT) 5-HT2C Receptor

An impaired signaling capacity of the serotonin (5-HT) 5-HT_2C receptor (5-HT_2CR) has been implicated in the neurobehavioral processes that promote relapse vulnerability in cocaine use disorder (CUD). Restoration of the diminished 5-HT_2CR signaling through positive allosteric modulation presents a novel therapeutic approach. Several new molecules with the 4-alkylpiperidine-2-carboxamide scaffold were designed, synthesized, and pharmacologically evaluated, leading to the discovery of selective 5-HT_2CR positive allosteric modulators (PAMs). Compound 16 (CYD-1-79) potentiated 5-HT-evoked intracellular calcium release in cells stably expressing the human 5-HT_2CR but not the 5-HT_2AR cells. A topographically distinct allosteric site was identified based on the newly solved 5-HT_2CR structure. Compound 16 modulated 5-HT_2CR-mediated spontaneous ambulation, partially substituted for the training dose of the 5-HT_2CR agonist WAY163909, synergized with a low dose of WAY163909 to substitute fully for the stimulus effects of WAY163909, and attenuated relapse vulnerability as assessed in a rodent self-administration model, indicating its therapeutic promise for CUD.

Pioglitazone, a PPARγ agonist, reduces nicotine craving in humans, with marginal effects on abuse potential

Possibly through their actions upon glia, peroxisome proliferator-activated receptor agonists (PPAR) have been shown to alter the abuse potential of addictive drugs in several preclinical models. The current study extends this research into the human laboratory as the first clinical study into the effects of the PPAR gamma agonist, pioglitazone, on the abuse potential of nicotine. Heavy smokers were recruited for this 3-week study. Upon admission, participants were randomized to either active (45mg, n=14) or placebo (0mg, n=13) PIO maintenance conditions for the duration of the study. After 5-7days of stabilization on a 7mg nicotine patch, participants began laboratory testing. On the 1st-4th test days, participants could self-administer cigarettes or receive money by making verbal choices for either option. On the 5th day, participants were administered 10 puffs of their usual brand of cigarette in the morning and later chose between smoking and money by making finger presses on a computer mouse in a progressive ratio self-administration task. Later on the 5th day participants also underwent a smoking cue exposure session. The 8th-11th test days were identical to the 1st-4th test days with the exception that during one of the test weeks de-nicotinized cigarettes were available, and during the other nicotinized cigarettes were available. Nicotinized cigarettes were always administered on the 5th and 12th days. On some measures PIO increased indicators of abuse potential, though this effect was typically not statistically significant. However, PIO did significantly reduce measures of craving.

Glial and neuroinflammatory targets for treating substance use disorders

BACKGROUND

The plenary session at the 2016 Behavior, Biology and Chemistry: Translational Research in Addiction Conference focused on glia as potential players in the development, persistence and treatment of substance use disorders. Glia partake in various functions that are important for healthy brain activity. Drugs of abuse alter glial cell activity producing several perturbations in brain function that are thought to contribute to behavioral changes associated with substance use disorders. Consequently, drug-induced changes in glia-driven processes in the brain represent potential targets for pharmacotherapeutics treating substance use disorders.

METHODS

Four speakers presented preclinical and clinical research illustrating the effects that glial modulators have on abuse-related behavioral effects of psychostimulants and opioids. This review highlights some of these findings and expands its focus to include other research focused on drug-induced glia abnormalities and glia-focused treatment approaches in substance use disorders.

RESULTS

Preclinical findings show that drugs of abuse induce neuroinflammatory signals and disrupt glutamate homeostasis through their interaction with microglia and astrocytes. Preclinical and clinical studies testing the effects of glial modulators show general effectiveness in reducing behaviors associated with substance use disorders.

CONCLUSIONS

The contribution of drug-induced glial activity continues to emerge as an intriguing target for substance use disorder treatments. Clinical investigations of glial modulators have yielded promising results on substance use measures and indicate that they are generally safe and well-tolerated. However, results have not been entirely positive and more questions remain for continued exploration in the development and testing of glial-directed treatments for substance use disorders.

PPAR-gamma agonist pioglitazone modifies craving intensity and brain white matter integrity in patients with primary cocaine use disorder: a double-blind randomized controlled pilot trial

BACKGROUND AND AIMS

Pioglitazone (PIO), a potent agonist of PPAR-gamma, is a promising candidate treatment for cocaine use disorder (CUD). We tested the effects of PIO on targeted mechanisms relevant to CUD: cocaine craving and brain white matter (WM) integrity. Feasibility, medication compliance and tolerability were evaluated.

DESIGN

Two-arm double-blind randomized controlled proof-of-concept pilot trial of PIO or placebo (PLC).

SETTING

Single-site out-patient treatment research clinic in Houston, TX, USA.

PARTICIPANTS

Thirty treatment-seeking adults, 18 to 60 years old, with CUD. Eighteen participants (8 = PIO; 10 = PLC) completed diffusion tensor imaging (DTI) of WM integrity at pre-/post-treatment.

INTERVENTION

Study medication was dispensed at thrice weekly visits along with once-weekly cognitive behavioral therapy for 12 weeks.

MEASUREMENTS

Measures of target engagement mechanisms of interest included cocaine craving assessed by the Brief Substance Craving Scale (BSCS), the Obsessive Compulsive Drug Use Scale (OCDUS), a visual analog scale (VAS) and change in WM integrity. Feasibility measures included number completing treatment, medication compliance (riboflavin detection) and tolerability (side effects, serious adverse events).

FINDINGS

Target engagement change in mechanisms of interest, defined as a ≥ 0.75 Bayesian posterior probability of an interaction existing favoring PIO over PLC, was demonstrated on measures of craving (BSCS, VAS) and WM integrity indexed by fractional anisotropy (FA) values. Outcomes indicated greater decrease in craving and greater increase in FA values in the PIO group. Feasibility was demonstrated by high completion rates among those starting treatment (21/26 = 80%) and medication compliance (≥ 80%). There were no reported serious adverse events for PIO.

CONCLUSIONS

Compared with placebo, patients receiving pioglitazone show a higher likelihood of reduced cocaine craving and improved brain white matter integrity as a function of time in treatment. Pioglitazone shows good feasibility as a treatment for cocaine use disorder.

PPARgamma agonists rescue increased phosphorylation of FGF14 at S226 in the Tg2576 mouse model of Alzheimer's disease

BACKGROUND

Cognitive impairment in humans with Alzheimer's disease (AD) and in animal models of Aβ-pathology can be ameliorated by treatments with the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARγ) agonists, such as rosiglitazone (RSG). Previously, we demonstrated that in the Tg2576 animal model of AD, RSG treatment rescued cognitive deficits and reduced aberrant activity of granule neurons in the dentate gyrus (DG), an area critical for memory formation.

METHODS

We used a combination of mass spectrometry, confocal imaging, electrophysiology and split-luciferase assay and in vitro phosphorylation and Ingenuity Pathway Analysis.

RESULTS

Using an unbiased, quantitative nano-LC-MS/MS screening, we searched for potential molecular targets of the RSG-dependent rescue of DG granule neurons. We found that S226 phosphorylation of fibroblast growth factor 14 (FGF14), an accessory protein of the voltage-gated Na⁺ (Nav) channels required for neuronal firing, was reduced in Tg2576 mice upon treatment with RSG. Using confocal microscopy, we confirmed that the Tg2576 condition decreased PanNav channels at the AIS of the DG, and that RSG treatment of Tg2576 mice reversed the reduction in PanNav channels. Analysis from previously published data sets identified correlative changes in action potential kinetics in RSG-treated T2576 compared to untreated and wildtype controls. In vitro phosphorylation and mass spectrometry confirmed that the multifunctional kinase GSK-3β, a downstream target of insulin signaling highly implicated in AD, phosphorylated FGF14 at S226. Assembly of the FGF14:Nav1.6 channel complex and functional regulation of Nav1.6-mediated currents by FGF14 was impaired by a phosphosilent S226A mutation. Bioinformatics pathway analysis of mass spectrometry and biochemistry data revealed a highly interconnected network encompassing PPARγ, FGF14, SCN8A (Nav 1.6), and the kinases GSK-3 β, casein kinase 2β, and ERK1/2.

CONCLUSIONS

These results identify FGF14 as a potential PPARγ-sensitive target controlling Aβ-induced dysfunctions of neuronal activity in the DG underlying memory loss in early AD.