Pitolisant and intravenous cocaine self-administration in mice

The role of heterodimers formed by histamine H3 receptors and dopamine D1 receptors on the methamphetamine-induced conditioned place preference

RATIONALE

The rewarding effect of Methamphetamine (METH) is commonly believed to play an important role in METH use disorder. The altered expression of dopamine D1 receptor (D1R) has been suggested to be essential to the the rewarding effect of METH. Notably, D1R could interact with histamine H3 receptors (H3R) by forming a H3R-D1R heteromer (H3R-D1R).

OBJECTIVES

This study was designed to specifically investigate the involvement of H3R-D1R in the rewarding effect of METH.

METHODS

C57BL/6 mice were treated with intraperitoneal injections of a selective H3R antagonist (Thioperamide, THIO; 20mg/kg), an H1R antagonist (Pyrilamine, PYRI; 10mg/kg), or microinjections of cytomegalovirus (CMV)-transmembrane domain 5 (TM5) into the nucleus accumbens (NAc). The animal model of Conditioned Place Preference (CPP) was applied to determine the impact of H3R-D1R on the rewarding effect of METH.

RESULTS

METH resulted in a significant preference for the drug-associated chamber, in conjunction with increased H3R and decreased D1R expression in both NAc and the ventral tegmental area (VTA). THIO significantly attenuated the rewarding effect of METH, accompanied by decreased H3R and increased D1R expression. In contrast, pyrilamine failed to produce the similar effects. Moreover, the inhibitory effect of THIO on METH-induced CPP was reversed by SKF38393, a D1R agonist. Furthermore, SCH23390, a D1R antagonist, counteracted the ameliorative effect of SKF38393 on THIO. Co-immunoprecipitation (CO-IP) experiments further demonstrated the specific interaction between H3R and D1R in METH CPP mice. The rewarding effect of METH was also significantly blocked by the interruption of CMV-transmembrane domain 5 (TM5), but not CMV-transmembrane domain 7 (TM7) in NAc.

CONCLUSION

These results suggest that modulating the activity of H3R-D1R complex holds promise for regulating METH use disorder and serves as a potential drug target for its treatment.

Neuroprotective effect of histamine H3 receptor blockade on methamphetamine-induced cognitive impairment in mice

OBJECTIVE

Methamphetamine (METH) exposure is commonly believed to result in cognitive impairment. Histamine H3 receptor (H3R) antagonists reportedly have potential applications for treating cognitive impairment accompanied by various neuropsychiatric disorders. The present study aimed to investigate the effect of H3R blockade by Thioperamide (THIO) on METH-induced cognitive impairment and the underlying mechanism.

METHODS

In Experiment 1, C57BL/6 mice received daily injections of saline or 5 mg/kg METH for 5 consecutive days. The Novel Object Recognition (NOR) and Morris water maze (MWM) tasks were used to assess cognitive functions of mice. H3R protein expression and apoptosis were subsequently measured in the hippocampus. In Experiment 2, HT22 cells were first treated with ddH₂O or 3 mM METH. The cell survival rate and H3R protein level were subsequently assessed. In Experiment 3, the animals were first treated with saline or 20 mg/kg THIO for 7 days, followed by co-administration of either saline or 5 mg/kg METH for an additional 5 days. The remaining experiments were carried out in the same manner as Experiment 1. In Experiment 4, HT22 cells were pretreated with either ddH₂O or 5 mM THIO for 2 h, followed by ddH₂O or 3 mM METH treatment for an additional 12 h. The remaining experiments were carried out in the same manner as Experiment 2. In Experiment 5, the changes in MEK1/2, p-MEK1/2, ERK1/2 and p-ERK1/2 protein levels were examined in the hippocampus of all mice from Experiment 3 and HT22 cells from Experiment 4.

RESULTS

METH-treated mice showed significantly worsened NOR and MWM performance, along with markably hippocampal apoptosis. A significantly lower cell survival rate was observed in METH-treated HT22 cells. Increased levels of H3R protein were found in both METH-treated mice and HT22 cells. THIO significantly improved METH-induced cognitive impairment in mice and toxicity in HT22 cells. METH significantly increased the level of p-MEK1/2 and p-ERK1/2 proteins in the hippocampus of mice and HT22 cells, which was reversed by THIO pretreatment.

CONCLUSION

Our findings reveal that H3R blockade by THIO yields a neuroprotective effect against METH-induced cognitive impairment in mice and toxicity in HT22 cells via the raf-MEK-ERK signaling pathway.

Establishment of multi-stage intravenous self-administration paradigms in mice

Genetically tractable animal models provide needed strategies to resolve the biological basis of drug addiction. Intravenous self-administration (IVSA) is the gold standard for modeling psychostimulant and opioid addiction in animals, but technical limitations have precluded the widespread use of IVSA in mice. Here, we describe IVSA paradigms for mice that capture the multi-stage nature of the disorder and permit predictive modeling. In these paradigms, C57BL/6J mice with long-standing indwelling jugular catheters engaged in cocaine- or remifentanil-associated lever responding that was fixed ratio-dependent, dose-dependent, extinguished by withholding the drug, and reinstated by the presentation of drug-paired cues. The application of multivariate analysis suggested that drug taking in both paradigms was a function of two latent variables we termed incentive motivation and discriminative control. Machine learning revealed that vulnerability to drug seeking and relapse were predicted by a mouse's a priori response to novelty, sensitivity to drug-induced locomotion, and drug-taking behavior. The application of these behavioral and statistical-analysis approaches to genetically-engineered mice will facilitate the identification of neural circuits driving addiction susceptibility and relapse and focused therapeutic development.

Therapeutic Potential of Histamine H3 Receptors in Substance Use Disorders

Substance use disorders are a leading cause of morbidity and mortality, and available pharmacological treatments are of modest efficacy. Histamine is a biogenic amine with four types of receptors. The histamine H₃ receptor (H₃R) is an autoreceptor and also an heteroreceptor. H₃Rs are highly expressed in the basal ganglia, hippocampus and cortex, and regulate a number of neurotransmitters including acetylcholine, norepinephrine, GABA and dopamine. Its function and localization suggest that the H₃R may be relevant to a number of psychiatric disorders and could represent a potential therapeutic target for substance use disorders. The purpose of the present review is to summarize preclinical studies investigating the effects of H₃R agonists and antagonists on animal models of alcohol, nicotine and psychostimulant use. At present, the effects of H₃R antagonists such as thioperamide, pitolisant or ciproxifan have been investigated in drug-induced locomotion, conditioned place preference, drug self-administration, reinstatement, sensitization and drug discrimination. For alcohol and nicotine, the effects of H₃R ligands on two-bottle choice and memory tasks, respectively, have also been investigated. The results of these studies are inconsistent. For alcohol, H₃R antagonists generally decreased the reward-related properties of ethanol, which suggests that H₃R antagonists may be effective as a treatment option for alcohol use disorder. However, the effects of H₃R antagonists on nicotine and psychostimulant motivation and reward are less clear. H₃R antagonists potentiated the abuse-related properties of nicotine, but only a handful of studies have been conducted. For psychostimulants, evidence is mixed and suggests that more research is needed to establish whether H₃R antagonists are a viable therapeutic option. The fact that different drugs of abuse have different brain targets may explain the differential effects of H₃R ligands.

Towards Modeling Anhedonia and Its Treatment in Zebrafish

Mood disorders, especially depression, are a major cause of human disability. The loss of pleasure (anhedonia) is a common, severely debilitating symptom of clinical depression. Experimental animal models are widely used to better understand depression pathogenesis and to develop novel antidepressant therapies. In rodents, various experimental models of anhedonia have already been developed and extensively validated. Complementing rodent studies, the zebrafish (Danio rerio) is emerging as a powerful model organism to assess pathobiological mechanisms of affective disorders, including depression. Here, we critically discuss the potential of zebrafish for modeling anhedonia and studying its molecular mechanisms and translational implications.

Histamine-4 Receptor: Emerging Target for the Treatment of Neurological Diseases

A major challenge in the field of the biogenic amine histamine is the search for new-generation histamine receptor specific drugs. Daniel Bovet and Sir James Black received their Nobel Prizes for Medicine for their work on histamine-1 receptor (H₁R) and H₂R antagonists to treat allergies and gastrointestinal disorders. The first H₃R-targeting drug to reach the market was approved for the treatment of the neurological disorder narcolepsy in 2018. The antagonists for the most recently identified histamine receptor, H₄R, are currently under clinical evaluation for their potential therapeutic effects on inflammatory diseases such as atopic dermatitis and pruritus. In this chapter, we propose that H₄R antagonists are endowed with prominent anti-inflammatory and immune effects, including in the brain. To substantiate this proposition, we combine data from transcriptional analyses of postmortem human neurodegenerative disease brain samples, human genome-wide association studies (GWAS), and translational animal model studies. The results prompt us to suggest the potential involvement of the H₄R in various neurodegenerative diseases and how manipulating the H₄R may create new therapeutic opportunities in central nervous system diseases.

Histamine H3 receptor gene variants associated with drug abuse in patients with cocaine use disorder

BACKGROUND

Preclinical work revealed significant interactions between ligands of the histamine H₃ receptor and different drugs of abuse. In the case of psychostimulants, the results reported are somewhat controversial and human data are still scarce, despite the fact that an inverse agonist of the H₃ receptor (pitolisant) has reached the market after approval for the treatment of narcolepsy.

AIMS

We have studied associations between histamine H₃ receptor gene variants and cocaine use disorder to increase the knowledge of the possible involvement of histamine H₃ receptor in drug abuse.

METHODS

Seven single nucleotide polymorphisms of the histamine H3 receptor gene were genotyped by using a multiplexing assay in 248 samples of subjects with cocaine use disorder and 500 randomized samples of subjects representative of the Spanish population.

RESULTS

The study of the epidemiological information associated to the samples revealed that subjects with cocaine use disorder broadly abused alcohol, tobacco and cannabinoids. Two single nucleotide polymorphisms (rs3787430 and rs74627870) were found significantly associated with the occurrence of addiction and one more (rs13042865) was specifically related to the severity of cocaine dependence within drug abusers.

CONCLUSIONS

The associations found in this study further extend the hypothesis that histamine H₃ receptor function could be relevant in drug abuse in general and cocaine addiction in particular.

Pitolisant to Treat Excessive Daytime Sleepiness and Cataplexy in Adults with Narcolepsy: Rationale and Clinical Utility

Narcolepsy is a sleep disorder marked by chronic, debilitating excessive daytime sleepiness and can be associated with cataplexy, sleep paralysis and sleep-related hallucinations. Pharmacological therapy for narcolepsy primarily aims to increase wakefulness and reduce cataplexy attacks. Pitolisant is a first-in-class agent utilizing histamine to improve wakefulness by acting as an antagonist/inverse agonist of the presynaptic histamine 3 receptor. This review summarizes the clinical efficacy, safety and tolerability of pitolisant in treating the symptoms of narcolepsy. Randomized and observational studies demonstrate pitolisant to be effective in treating both hypersomnolence and cataplexy while generally being well tolerated at prescribed doses. The most common adverse reactions include headache, insomnia and nausea.

Pitolisant: A Review in Narcolepsy with or without Cataplexy

Pitolisant (Wakix^®), an orally available, first-in-class antagonist/inverse agonist of the histamine 3 receptor, is approved in the EU (as of March 2016) for the treatment of narcolepsy with or without cataplexy in adults and in the USA (as of August 2019) for the treatment of excessive daytime sleepiness (EDS) in adults with narcolepsy. Pitolisant was demonstrated to have minimal risk of abuse in preclinical and clinical studies, and is the only anti-narcoleptic drug not scheduled as a controlled substance in the USA. The totality of evidence from pivotal and supportive phase III trials suggests that pitolisant administered at up to the recommended maximum dose of 36 mg once daily reduces EDS and cataplexy in adults with narcolepsy relative to placebo. Noninferiority of pitolisant to modafinil in the management of EDS was not demonstrated. Pitolisant was generally well tolerated in clinical trials. Consistent with its mechanism of action, the most common treatment-emergent adverse events included headache, insomnia and anxiety. With minimal abuse potential and offering the convenience of oral, once-daily administration, pitolisant extends the range of approved treatment options available to adult patients with narcolepsy with or without cataplexy.