The Naturally Occurring Compound Garcinia Indica Selectively Impairs the Reconsolidation of a Cocaine-Associated Memory

Natural products as the therapeutic strategies for addiction

World Drug Report 2023 concluded that 296 million people abused drugs, 39.5 million became addiction and 494,000 died as a direct or indirect result of addiction. Addiction has become a growing problem that affects individuals, their families, societies, countries and even the world. However, treatment for addiction is only limited to some developed countries because of the high cost, difficult implementation, and time consuming. Therefore, there is an urgent need to develop a low-cost, effective drug for the development of addiction treatment in more countries, which is essential for the stability and sustainable development of the world. In this review, it provided an overview of the abuse of common addictive drugs, related disorders, and current therapeutic regimen worldwide, and summarized the mechanisms of drug addiction as reward circuits, neuroadaptation and plasticity, cognitive decision-making, genetics, and environment. According to their chemical structure, 43 natural products and 5 herbal combinations with potential to treat addiction were classified, and their sources, pharmacological effects and clinical trials were introduced. It was also found that mitragine, ibogine, L-tetrahydropalmatine and crocin had greater potential for anti-addiction.

Regulation of histone acetylation by garcinol blocks the reconsolidation of heroin-associated memory

Drug-associated long-term memories underlie substance use disorders, including heroin use disorder (HUD), which are difficult to eliminate through existing therapies. Addictive memories may become unstable when reexposed to drug-related cues and need to be stabilized again through protein resynthesis. Studies have shown the involvement of histone acetylation in the formation and reconsolidation of long-term drug-associated memory. However, it remains unknown whether and how histone acetyltransferases (HAT), the essential regulators of histone acetylation, contribute to the reconsolidation of heroin-associated memories. Herein, we investigated the function of HAT in the reconsolidation concerning heroin-conditioned memory by using a rat self-administration model. Systemic administration of the HAT inhibitor garcinol inhibited cue and heroin-priming induced reinstatement of heroin seeking, indicating the treatment potential of garcinol for relapse prevention.

Garcinia kola: a critical review on chemistry and pharmacology of an important West African medicinal plant

Garcinia kola Heckel (Clusiaceae) is a tree indigenous to West and Central Africa. All plant parts, but especially the seeds, are of value in local folklore medicine. Garcinia kola is used in treatment of numerous diseases, including gastric disorders, bronchial diseases, fever, malaria and is used to induce a stimulating and aphrodisiac effect. The plant is now attracting considerable interest as a possible source of pharmaceutically important drugs. Several different classes of compounds such as biflavonoids, benzophenones, benzofurans, benzopyran, vitamin E derivatives, xanthones, and phytosterols, have been isolated from G. kola, of which many appears to be found only in this species, such as garcinianin (found in seeds and roots), kolanone (fruit pulp, seeds, roots), gakolanone (stem bark), garcinoic acid, garcinal (both in seeds), garcifuran A and B, and garcipyran (all in roots). They showed a wide range of pharmacological activities (e.g. analgesic, anticancer, antidiabetic, anti-inflammatory, antimalarial, antimicrobial, hepatoprotective and neuroprotective effects), though this has only been confirmed in animal models. Kolaviron is the most studied compound and is perceived by many studies as the active principle of G. kola. However, its research is associated with significant flaws (e.g. too high doses tested, inappropriate positive control). Garcinol has been tested under better conditions and is perhaps showing more promising results and should attract deeper research interest (especially in the area of anticancer, antimicrobial, and neuroprotective activity). Human clinical trials and mechanism-of-action studies must be carried out to verify whether any of the compounds present in G. kola may be used as a lead in the drug development.

Molecular and functional characterization of an evolutionarily conserved CREB-binding protein in the Lymnaea CNS

In eukaryotes, CREB-binding protein (CBP), a coactivator of CREB, functions both as a platform for recruiting other components of the transcriptional machinery and as a histone acetyltransferase (HAT) that alters chromatin structure. We previously showed that the transcriptional activity of cAMP-responsive element binding protein (CREB) plays a crucial role in neuronal plasticity in the pond snail Lymnaea stagnalis. However, there is no information on the molecular structure and HAT activity of CBP in the Lymnaea central nervous system (CNS), hindering an investigation of its postulated role in long-term memory (LTM). Here, we characterize the Lymnaea CBP (LymCBP) gene and identify a conserved domain of LymCBP as a functional HAT. Like CBPs of other species, LymCBP possesses functional domains, such as the KIX domain, which is essential for interaction with CREB and was shown to regulate LTM. In-situ hybridization showed that the staining patterns of LymCBP mRNA in CNS are very similar to those of Lymnaea CREB1. A particularly strong LymCBP mRNA signal was observed in the cerebral giant cell (CGC), an identified extrinsic modulatory interneuron of the feeding circuit, the key to both appetitive and aversive LTM for taste. Biochemical experiments using the recombinant protein of the LymCBP HAT domain showed that its enzymatic activity was blocked by classical HAT inhibitors. Preincubation of the CNS with such inhibitors blocked cAMP-induced synaptic facilitation between the CGC and an identified follower motoneuron of the feeding system. Taken together, our findings suggest a role for the HAT activity of LymCBP in synaptic plasticity in the feeding circuitry.

Ca2+-permeable AMPA receptors set the threshold for retrieval of drug memories

Frequent relapse prevents the successful treatment of substance use disorders and is triggered in part by retrieval of drug-associated memories. Drug-conditioned behaviours in rodents are reinstated upon drug memory retrieval following re-exposure to cues previously associated with the drug, or the drug itself. Therapies based on mechanistic insights from rodent studies have focused on amnesic procedures of cue-drug associations but with so far limited success. Conversely, more recent studies propose that inhibiting drug memory retrieval offers improved anti-relapse efficacy. However, mechanisms of memory retrieval are poorly understood. Here, we used a conditioned place preference (CPP) procedure in mice to investigate the cellular and molecular underpinnings of drug-induced memory retrieval. After extinction training of CPP, Ca²⁺-permeable AMPA receptors (CP-AMPARs) accumulated at drug-generated silent synapses of nucleus accumbens (NAc) medium spiny neurons. The NAc CP-AMPARs regulated the retrieval mechanism of drug memories after extinction. Specifically, we used different priming doses of cocaine, fentanyl, or a cue associated with drug exposure to reinstate CPP, providing different memory retrieval conditions. Although both high and low doses of these two drugs induced CPP reinstatement, compromising CP-AMPAR accumulation impaired CPP reinstatement, induced by low doses of each drug or the cue. This threshold effect was mediated by NAc CP-AMPARs as region specific knock-down of PSD-95 prevented low-dose cocaine-induced retrieval selectively. These results demonstrate the NAc as a brain region and CP-AMPARs as key synaptic substrates that govern the threshold for drug-induced retrieval and behavioural expression of drug memories.

Possible Mechanisms Underlying the Effects of Glucagon-Like Peptide-1 Receptor Agonist on Cocaine Use Disorder

Cocaine use disorder (CUD) is a major public health challenge with a high relapse rate and lack of effective pharmacotherapies; therefore, there is a substantial need to identify novel medications to treat this epidemic. Since the advent of glucagon-like peptide-1 (GLP-1) receptors (GLP-1Rs) agonists (GLP-1RAs), their potential has been extensively explored and expanded. In this review, we first summarized the biological effects of GLP-1, GLP-1Rs, and GLP-1RAs. Subsequently, the recent literature examining the behavioral effects and the possible pharmacological mechanisms of GLP-1RAs on CUD was reviewed. Increasing preclinical evidence suggests that GLP-1RAs are promising in regulating dopamine release, dopamine transporter (DAT) surface expression and function, mesolimbic reward system and GABAergic neurons, and maladaptive behaviors in animal models of self-administration and conditioned place preference. In addition, the emerging role of GLP-1RAs in inhibiting inflammatory cytokines was reported. These findings indicate that GLP-1RAs perform essential functions in the modulation of cocaine-seeking and cocaine-taking behaviors likely through multifaceted mechanisms. Although the current preclinical evidence provides convincing evidence to support GLP-1RA as a promising pharmacotherapy for CUD, other questions concerning clinical availability, impact and specific mechanisms remain to be addressed in further studies.

Glucagon-Like Peptide-1 Agonist Exendin-4 Facilitates the Extinction of Cocaine-Induced Condition Place Preference

Accumulating studies suggest that the glucagon-like peptide-1 receptor agonist exendin-4 (Ex4) and toll-like receptor 4 (TLR4) play a pivotal role in the maladaptive behavior of cocaine. However, few studies have assessed whether Ex4 can facilitate the extinction of drug-associated behavior and attenuate the reinstatement of cocaine-induced condition place preference (CPP) in mice. The main objective of the present study was to evaluate Ex4's ability to regulate the extinction and reinstatement of cocaine-induced CPP. C57BL/6 mice were conditioned to either cocaine (20 mg/kg) or an equivalent volume of saline to establish a cocaine-mediated CPP paradigm. To investigate the potential effects of Ex4 on extinction, animals received an intraperitoneal injection of Ex4 either immediately or 6 h after each extinction or only on the test day. The persistence of extinction was measured using the reinstatement paradigm evoked by 10 mg/kg of cocaine. To explore the possible impacts of Ex4 and neuroinflammation on cocaine, the expression levels of TLR4 within the hippocampus was detected using western blotting. As a result, we found that systemic administration of Ex4 immediately after each extinction training, instead of 6 h after each extinction and on the day of extinction test, was capable of facilitating extinction in the confined or non-confined CPP extinction paradigms and blocking the cocaine-primed reinstatement of cocaine-induced CPP. Additionally, we also observed that Ex4 was competent to alleviate TLR4 signaling that has been up-regulated by cocaine. Altogether, our findings indicated that the combination of Ex4 with daily extinction training was sufficient to facilitate extinction of the conditioned behavior, attenuate reinstatement of cocaine-induced CPP and inhibit TLR4 signaling. Thus, Ex4 deserves further investigation as a potential intervention for the treatment of cocaine use disorder.

Effects of Glucagon-Like Peptide-1 Receptor Agonist Exendin-4 on the Reinstatement of Cocaine-Mediated Conditioned Place Preference in Mice

A high percentage of relapse to compulsive cocaine-taking and cocaine-seeking behaviors following abstinence constitutes a major obstacle to the clinical treatment of cocaine addiction. Thus, there is a substantial need to develop effective pharmacotherapies for the prevention of cocaine relapse. The reinstatement paradigm is known as the most commonly used animal model to study relapse in abstinent human addicts. The primary aim of this study is to investigate the potential effects of systemic administration of glucagon-like peptide-1 receptor agonist (GLP-1RA) exendin-4 (Ex4) on the cocaine- and stress-triggered reinstatement of cocaine-induced conditioned place preference (CPP) in male C57BL/6J mice. The biased CPP paradigm was induced by alternating administration of saline and cocaine (20 mg/kg), followed by extinction training and then reinstatement by either a cocaine prime (10 mg/kg) or exposure to swimming on the reinstatement test day. To examine the effects of Ex4 on the reinstatement, Ex4 was systemically administered 1 h after the daily extinction session. Additionally, we also explored the associated molecular basis of the behavioral effects of Ex4. The expression of nuclear factor κβ (NF-κβ) in the nucleus accumbens (NAc) was detected using Western blotting. As a result, all animals that were treated with cocaine during the conditioning period successfully acquired CPP, and their CPP response was extinguished after 8 extinction sessions. Furthermore, the animals that were exposed to cocaine or swimming on the reinstatement day showed a significant reinstatement of CPP. Interestingly, systemic pretreatment with Ex4 was sufficient to attenuate cocaine- and stress-primed reinstatement of cocaine-induced CPP. Additionally, the expression of NF-κβ, which was upregulated by cocaine, was normalized by Ex4 in the cocaine-experienced mice. Altogether, our study reveals the novel effect of Ex4 on the reinstatement of cocaine-induced CPP and suggests that GLP-1R agonists appear to be highly promising drugs in the treatment of cocaine use disorder.

Epigenetic Mechanisms in Drug Relapse

A growing body of evidence from the past 15 years implicates epigenetic mechanisms in the behavioral effects of addictive drugs. The main focus of these studies has been epigenetic mechanisms of psychomotor sensitization and drug reinforcement, as assessed by the conditioned place preference and drug self-administration procedures. Some of these studies have documented long-lasting changes in the expression of epigenetic enzymes and molecules that persist for weeks after the last drug exposure. These observations have inspired more recent investigations on the epigenetic mechanisms of relapse to drug seeking after prolonged abstinence. Here, we review studies that have examined epigenetic mechanisms (e.g., histone modifications, chromatin remodeler-associated modifications, and DNA methylation) that contribute to relapse to cocaine, amphetamine, methamphetamine, morphine, heroin, nicotine, or alcohol seeking, as assessed in rodent models. We first provide a brief overview of studies that have examined persistent epigenetic changes in the brain after prolonged abstinence from noncontingent drug exposure or drug self-administration. Next, we review studies on the effect of either systemic or brain site-specific epigenetic manipulations on the reinstatement of drug-conditioned place preference after extinction of the learned preference, the reinstatement of drug seeking after operant drug self-administration and extinction of the drug-reinforced responding, and the incubation of drug craving (the time-dependent increase in drug seeking after cessation of drug self-administration). We conclude by discussing the implications of these studies for understanding mechanisms contributing to persistent relapse vulnerability after prolonged abstinence. We also discuss the implications of these results for translational research on the potential use of systemically administered epigenetic enzyme inhibitors for relapse prevention in human drug users.

Molecular and circuit mechanisms regulating cocaine memory

Risk of relapse is a major challenge in the treatment of substance use disorders. Several types of learning and memory mechanisms are involved in substance use and have implications for relapse. Associative memories form between the effects of drugs and the surrounding environmental stimuli, and exposure to these stimuli during abstinence causes stress and triggers drug craving, which can lead to relapse. Understanding the neural underpinnings of how these associations are formed and maintained will inform future advances in treatment practices. A large body of research has expanded our knowledge of how associative memories are acquired and consolidated, how they are updated through reactivation and reconsolidation, and how competing extinction memories are formed. This review will focus on the vast literature examining the mechanisms of cocaine Pavlovian associative memories with an emphasis on the molecular memory mechanisms and circuits involved in the consolidation, reconsolidation, and extinction of these memories. Additional research elucidating the specific signaling pathways, mechanisms of synaptic plasticity, and epigenetic regulation of gene expression in the circuits involved in associative learning will reveal more distinctions between consolidation, reconsolidation, and extinction learning that can be applied to the treatment of substance use disorders.

The Efficacy of Lidocaine in Disrupting Cocaine Cue-Induced Memory Reconsolidation

RATIONAL

Cue-induced craving memories, linked to drug-seeking behaviors, require key molecular processes for memory reconsolidation. Lidocaine, a sodium channel blocker, inhibits NMDA receptor activation and suppresses nitric oxide and ERK production. These processes are required for memory re-consolidation; inhibiting them may reduce cue-related craving memories in cocaine dependent subjects.

OBJECTIVES

To assess the efficacy of lidocaine in decreasing cue-induced cocaine craving and cocaine use.

METHODS

Treatment-seeking cocaine-dependent participants (n = 33, 25 men) were recruited. Personalized craving and relaxation scripts were developed. Participants were then randomly assigned in a double-blind design to either receive intravenous lidocaine immediately following a cocaine craving script (lidocaine/craving), saline following a craving script (saline/craving), or lidocaine following a relaxation script (lidocaine/relax). One week following the infusion, cue-induced craving was assessed in the same paradigm without an infusion. Cocaine use and craving were assessed for 4 weeks following infusion.

RESULTS

The administration of lidocaine during craving induction (lidocaine/craving) did not decrease cue-induced craving during craving reactivation one week later or craving and cocaine use over the 4-week follow-up period compared to the saline/craving group. There were no significant differences in craving and cocaine use between the lidocaine/relax and saline/craving groups.

CONCLUSION

Lidocaine administered following craving induction did not decrease subsequent cue-induced craving or cocaine use. Blocking the reconsolidation of craving-related memories with pharmacological agents remains an important area of investigation.

Can cocaine-induced neuroinflammation explain maladaptive cocaine-associated memories?

Persistent and intrusive memories define a number of psychiatric disorders, including posttraumatic stress disorder and substance use disorder. In the latter, memory for drug-paired cues plays a critical role in sustaining compulsive drug use as these are potent triggers of relapse. As with many drugs, cocaine-cue associated memory is strengthened across presentations as cues become reliable predictors of drug availability. Recently, the targeting of cocaine-associated memory through disruption of the reconsolidation process has emerged as a potential therapeutic strategy; reconsolidation reflects the active process by which memory is re-stabilized after retrieval. In addition, a separate line of work reveals that neuroinflammatory markers, regulated by cocaine intake, play a role in memory processes. Our review brings these two literatures together by summarizing recent findings on cocaine-associated reconsolidation and cocaine-induced neuroinflammation. We discuss the interactions between reconsolidation processes and neuroinflammation following cocaine use, concluding with a new perspective on treatment to decrease risk of relapse to cocaine use.

Regulation of Garcinol on Histone Acetylation in the Amygdala and on the Reconsolidation of a Cocaine-Associated Memory

Exposure to drug-related cues often disrupts abstinence from cocaine use by triggering memories of drug effects, leading to craving and possible relapse. One prospective method of treatment is weakening cocaine-associated memories via impairment of memory reconsolidation. Previous experiments have shown that systemic injection of the amnestic agent garcinol impairs the reconsolidation of cocaine-cue memories in a temporally constrained, cue-specific, and persistent manner. Here, we investigated garcinol’s effect on cocaine-cue memory reconsolidation when administered to the lateral nucleus of the amygdala (LA), as well as its epigenetic activity following systemic garcinol administration and also when given in conjunction with trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor. Rats received 12 days of cocaine self-administration training during which time an active lever press resulted in an i.v. cocaine infusion that was concurrently paired with the presentation of a light/tone cue. After 8 days of lever extinction, rats received a memory reactivation session followed by a cue-induced reinstatement test. Intra-LA garcinol following memory reactivation significantly impaired reconsolidation only if the memory was reactivated. Additional studies revealed a significant reduction in histone H3 K27 acetylation and reduced expression of the immediate-early genes Arc and Egr-1 in the LA. When administered alone, TSA enhanced the reinstatement of a cocaine-cue memory, an effect that was prevented when garcinol was concurrently administered. These data indicate the LA is a key structure responsive to garcinol, suggest that one of garcinol’s mechanisms of action is through the reduction of memory-related gene expression in the LA, implicate changes in histone acetylation in memory reconsolidation, and support garcinol as a potential therapeutic tool for sustaining abstinence.

Chemical and Biological Aspects of Garcinol and Isogarcinol: Recent Developments

The natural polyisoprenylated benzophenone derivatives garcinol and isogarcinol are secondary plant metabolites isolated from various Garcinia species including Garcinia indica. This review takes stock of the recent chemical and biological research into these interesting natural compounds over the last five years. New biological sources and chemical syntheses are discussed followed by new insights into the activity of garcinol and isogarcinol against cancer, pathogenic bacteria, parasite infections and various inflammatory diseases.

Reconsolidation blockade for the treatment of addiction: challenges, new targets, and opportunities

Addiction is a chronic, relapsing disorder. The progression to pathological drug-seeking is thought to be driven by maladaptive learning processes which store and maintain associative memory, linking drug highs with cues and actions in the environment. These memories can encode Pavlovian associations which link predictive stimuli (e.g., people, places, and paraphernalia) with a hedonic drug high, as well as instrumental learning about the actions required to obtain drug-associated incentives. Learned memories are not permanent however, and much recent interest has been generated in exploiting the process of reconsolidation to erase or significantly weaken maladaptive memories to treat several mental health disorders, including addictions. Normally reconsolidation serves to update and maintain the adaptive relevance of memories, however administration of amnestic agents within the critical "reconsolidation window" can weaken or even erase maladaptive memories. Here we discuss recent advances in the field, including ongoing efforts to translate preclinical reconsolidation research in animal models into clinical practice.

Research Progress of Polycyclic Polyprenylated Acylphloroglucinols

Polycyclic polyprenylated acylphloroglucinols (PPAPs) are a class of hybrid natural products sharing the mevalonate/methylerythritol phosphate and polyketide biosynthetic pathways and showing considerable structure and bioactivity diversity. This review discusses the progress of research into the chemistry and biological activity of 421 natural PPAPs in the past 11 years as well as in-depth studies of biological activities and total synthesis of some PPAPs isolated before 2006. We created an online database of all PPAPs known to date at http://www.chem.uky.edu/research/grossman/PPAPs . Two subclasses of biosynthetically related metabolites, spirocyclic PPAPs with octahydrospiro[cyclohexan-1,5'-indene]-2,4,6-trione core and complicated PPAPs produced by intramolecular [4 + 2] cycloadditions of MPAPs, are brought into the PPAP family. Some PPAPs' relative or absolute configurations are reassigned or critically discussed, and the confusing trivial names in PPAPs investigations are clarified. Pharmacologic studies have revealed a new molecular mechanism whereby hyperforin and its derivatives regulate neurotransmitter levels by activating TRPC6 as well as the antitumor mechanism of garcinol and its analogues. The antineoplastic potential of some type B PPAPs such as oblongifolin C and guttiferone K has increased significantly. As a result of the recent appearances of innovative synthetic methods and strategies, the total syntheses of 22 natural PPAPs including hyperforin, garcinol, and plukenetione A have been accomplished.

Garcinol Blocks the Reconsolidation of Multiple Cocaine-Paired Cues after a Single Cocaine-Reactivation Session

Manipulations of memory reconsolidation can interfere with the ability of a drug-paired cue to drive drug-seeking behavior. However, the typical reconsolidation paradigm that reactivates the memory through the presentation of the cue (conditioned stimulus (CS)) only interferes with the memory of the reactivated CS while leaving other drug-paired CSs intact and able to continue driving drug-seeking behavior. Here, we used a novel unconditioned-stimulus (US) reactivation paradigm to interfere with the ability of multiple cues to drive drug-seeking behavior after just one reactivation and treatment session. Rats were trained to self-administer cocaine, during which time each active lever press resulted in an i.v. cocaine infusion paired with one of two cues that alternated within each session. The drug memory was later reactivated with either i.v. or i.p. cocaine presentation in the absence of any cue. The histone acetyltransferase (HAT) inhibitor garcinol or vehicle was injected following US reactivation to impair reconsolidation. Rats were later tested on cue-induced reinstatement to both cues. Garcinol administered after either i.v. or i.p. cocaine reactivation significantly decreased cue-induced reinstatement to both cues, indicative of reconsolidation impairment. In addition, garcinol administered in the absence of reconsolidation or at a 6 h delay when the memory should be restabilized had no effect on reinstatement, further suggesting that garcinol's effects on reinstatement are through reconsolidation-based mechanisms. Our results demonstrate that a US-reactivation paradigm may be preferable to traditional CS-reactivation paradigms for treating disorders that involve multiple CS-US associations and support investigations of garcinol as a therapeutic pharmacological agent.

Reconsolidation and psychopathology: Moving towards reconsolidation-based treatments

Interfering with memory reconsolidation has valuable potential to be used as a treatment for maladaptive memories and psychiatric disorders. Numerous studies suggest that reconsolidation-based therapies may benefit psychiatric populations, but much remains unanswered. After reviewing the literature in clinical and healthy human populations, we discuss some of the major limitations to reconsolidation studies and clinical application. Finally, we provide recommendations for developing improved reconsolidation-based treatments, namely exploiting known boundary conditions and focusing on a novel unconditioned stimulus-retrieval paradigm.