The histidine triad nucleotide binding 1 protein is involved in nicotine reward and physical nicotine withdrawal in mice

HINT1 Inhibitors as Selective Modulators of MOR-NMDAR Cross-Regulation and Non-Opioid Analgesia

Human histidine triad nucleotide-binding protein 1 (HINT1) has recently become a protein of interest due to its involvement in several CNS processes, including neuroplasticity and the development of several neuropsychiatric disorders. Crucially, HINT1 behaves as a mediator for cross-regulation of the mu-opioid receptor (MOR) and N-methyl-d-aspartate receptor (NMDAR). Active site inhibition of HINT1 using small-molecule inhibitors has been demonstrated to have a significant impact on this cross-regulatory relationship in vivo. Herein, we describe the development of a series of ethenoadenosine HINT1 inhibitors to further evaluate the effect of HINT1 inhibition on morphine's blockade of NMDA-evoked behaviors, the development of acute endomorphin-2 tolerance, and analgesia. X-ray crystallographic analysis and HINT1 binding experiments demonstrate that modifications to the inhibitor nucleobase greatly impact the inhibitor binding interactions with HINT1. Our results reveal a complex structure-activity relationship for HINT1 inhibitors, in which minor modifications to the ethenoadenosine scaffold resulted in dramatic changes to their activity in these assays modeling MOR-NMDAR interaction. Specifically, we observed the ability of HINT1 inhibitors to selectively affect individual pathways of MOR-NMDAR crosstalk. Furthermore, we observed that a carbamate ethenoadenosine inhibitor of HINT1 can induce analgesia while not affecting opioid tolerance. Additionally, although past studies have indicated that the loss of HINT1 expression can result in the downregulation of p53, we have shown that the inhibition of HINT1 has no effect on either the expression of HINT1 or p53. These studies highlight the critical role of HINT1 in MOR-NMDAR crosstalk and demonstrate the intriguing potential of using HINT1 active-site inhibitors as tools to probe its role in these biochemical pathways and its potential as a novel pain target.

HINT1 Gene Polymorphisms, Smoking Behaviour, and Personality Traits: A Haplotype Case-Control Study

The factors influencing the development and maintenance of nicotine dependence are numerous and complex. Recent studies indicate that smokers exhibit distinct genetic predispositions to nicotine dependence. We aimed to analyse (1) the association between rs2551038 and cigarette smoking, (2) the association of between the rs3864236-rs2526303-rs2551038 haplotype and cigarette smoking, and (3) the personality traits measured by the NEO Five-Factor Inventory in cigarette users and never-smokers. No significant differences were present in the frequency of rs2551038 genotypes and alleles in the studied cigarette users compared to the control group. Cigarette users, compared to the control group, had higher scores on the NEO-FFI Extraversion scale (p = 0.0011), and lower scores were obtained by the cigarette users for the NEO-FFI Openness (p = 0.0060), Agreeability (p ≤ 0.000), and Conscientiousness (p ≤ 0.000) scales. There was a significant positive Pearson's linear correlation between the age and the Fagestrom test (r = 0.346; p < 0.0001) and the NEO-FFI Openness scale (r = 0.180; p < 0.0001) in the group of cigarette users. We observed significant linkage disequilibrium between rs2526303 and rs3864236 (D' = 0.3581; p < 2.2204 × 10-16) and between rs2526303 and rs2551038 (D' = 0.9993; p < 2.2204 × 10-16) in the tested sample. The sex-stratified haplotype analysis revealed that in the group of male never-smokers, the GTC haplotype was significantly more frequent than in the group of cigarette users (38% vs. 22%; p = 0.0039). The presented study reveals significant differences in personality trait scores between cases and controls. Moreover, the sex-stratified analysis showed significant differences in haplotype distribution. These results underscore the interplay between genetic predisposition, sex, and personality in nicotine-using individuals.

The Many Faces of Histidine Triad Nucleotide Binding Protein 1 (HINT1)

The histidine triad nucleotide binding protein 1 (HINT1) is a nucleoside phosphoramidase that has garnered interest due to its widespread expression and participation in a broad range of biological processes. Herein, we discuss the role of HINT1 as a regulator of several CNS functions, tumor suppressor, and mast cell activator via its interactions with multiple G-protein-coupled receptors and transcription factors. Importantly, altered HINT1 expression and mutation are connected to the progression of multiple disease states, including several neuropsychiatric disorders, peripheral neuropathy, and tumorigenesis. Additionally, due to its involvement in the activation of several clinically used phosphoramidate prodrugs, tremendous efforts have been made to better understand the interactions behind nucleoside binding and phosphoramidate hydrolysis by HINT1. We detail the substrate specificity and catalytic mechanism of HINT1 hydrolysis, while highlighting the structural biology behind these efforts. The aim of this review is to summarize the multitude of biological and pharmacological functions in which HINT1 participates while addressing the areas of need for future research.

Association of the rs3864283 Polymorphism Located in the HINT1 Gene with Cigarette Use and Personality Traits

Nicotine is the major reinforcing component of tobacco and it is believed that the pharmacological effects of nicotine motivate the initiation and maintenance of a smoking habit. HINT1 appears to play a role in the modulation of the effects of drug abuse. Hence, the aim of this study was the analysis of the association between the rs3864283 polymorphism of the HINT1 gene and cigarette use; the analysis of personality traits assessed by the means of the NEO-FFI Inventory; the analysis of anxiety measured by the STAI questionnaire; and the analysis of the interactions between the rs3864283 and both personality traits and anxiety. The study group consisted of 522 volunteers. Of these, 371 were cigarette users and 151 were never-smokers. The genomic DNA was isolated from venous blood using standard procedures. The results of both inventories, i.e., NEO-FFI and STAI., were reported as the sten scores. Genotyping was conducted with the real-time PCR method. Statistically significant differences were found in the frequency of rs3864283 genotypes and alleles in the tested sample of Cigarette Users when compared to the control group. The Cigarette Users compared to the control group obtained higher scores in the assessment of NEO-FFI extraversion scale, and significantly lower results were obtained for the NEO-FFI openness scale, the agreeableness scale, and the conscientiousness scale. There was a statistically significant effect of rs3864283 genotype interaction and Cigarette Use or not using (control group) on the extraversion scale. There was also a statistically significant effect of Cigarette Users or the control group on the extraversion scale score. The results obtained in the presented study indicated a significant association between the HINT1 rs3864283 variant and smoking status. Moreover, this is the first study incorporating genetic association of above-mentioned polymorphic site with interaction analysis of personality traits and anxiety. Overall, the results of this study suggest that HINT1 is an important genetic component associated with nicotine usage mechanisms.

The role of HINT1 protein in morphine addiction: An animal model-based study

Drug addiction is a recurrent, chronic brain disease. The existing treatment methods have limitations, such as poor adherence and inability to completely avoid relapse. Histidine triad nucleotide-binding protein 1 (HINT1) is involved in many neuropsychiatric diseases, such as schizophrenia, pain, and drug dependence. Studies have confirmed that there is a genetic link between HINT1 and addictions such as nicotine and cocaine. However, there is no research on the role of HINT1 protein in morphine addiction at home and abroad. Thus, we designed this project by constructing different types of morphine addiction animal models, including conditioned place preference and behavioral sensitization. We comprehensively examined the participation of HINT1 protein in key brain regions associated with addiction, including prefrontal cortex, nucleus accumbens, corpus striatum, and hippocampus, in different stages of different models. In addition, we used HINT1 knockout mice to establish the above models and physical dependence model to investigate the effect of HINT1 protein deletion on morphine addiction-related behaviors. We found that HINT1 has varying degrees of involvement in different stages of multiple addictive animal models. The absence of HINT1 can attenuate morphine-mediated addictive behavior to a certain extent and can alleviate the withdrawal symptoms of morphine.

The role of HINT1 in methamphetamine-induced behavioral sensitization

BACKGROUND

Drug addiction is a chronically relapsing disorder in humans yet the underlying mechanism remained unclear. Recent studies suggested that histidine triad nucleotide binding protein1 (HINT1) may play significant roles in diverse neuropsychiatric diseases including drug addiction.

METHODS

In the current study, we used different batches of mice to establish different stages of methamphetamine (METH)-induced behavioral sensitization (BS) to explore the dynamic changes throughout the process of addiction in different brain regions, including the prefrontal cortex (PFC), nucleus accumbens (NAc), caudate putamen (CPu), and hippocampus (Hip). In addition, we used HINT1 knockout (KO) mice to investigate the effect of HINT1 protein deletion on METH-induced BS.

RESULTS

We found that in PFC of the METH group mice, the HINT1 expression level initially increased after development phase, and then dropped to the normal level during expression phase. However, there was no statistical difference in the HINT1 expression level in the other three encephalic regions (NAc, CPu, and Hip). The absence of HINT1 could promote METH-mediated addictive behavior to a certain extent, while the significant difference between genotypes only occurred in the development phase.

CONCLUSIONS

Using the new technique, hip fractures were correctly predicted in 78% of cases compared with 36% when using the T-score. The accuracy of the prediction was not greatly reduced when using SSM and SAM (78% and 74% correct, respectively). Various geometric and BMD distribution traits were identified in the fractured and non-fractured groups.

Emerging role and therapeutic implication of Wnt signaling pathways in liver fibrosis

Activation of hepatic stellate cells (HSCs) is a pivotal cellular event in liver fibrosis. Therefore, improving our understanding of the molecular pathways that are involved in these processes is essential to generate new therapies for liver fibrosis. Greater knowledge of the role of the Wnt signaling pathway in liver fibrosis could improve understanding of the liver fibrosis pathogenesis. The aim of this review is to describe the present knowledge about the Wnt signaling pathway, which significantly participates in liver fibrosis and HSC activation, and look ahead on new perspectives of Wnt signaling pathway research. Moreover, we will discuss the different interactions with Wnt signaling pathway-regulated liver fibrosis. The Wnt signaling pathway modulates several important aspects of function, including cell proliferation, activation and differentiation. Targeting the Wnt signaling pathway can be a promising direction in liver fibrosis treatment. We discuss new perspectives of Wnt signaling pathway activation in liver fibrosis. For example, antagonist to Wnt and Wnt ligands could inhibit liver fibrosis by regulating Wnt/β-catenin signaling pathway. These findings identify the Wnt signaling pathway as a potentially important for therapeutic targets in liver fibrosis. Future studies are needed in order to find safer and more effective Wnt-based drugs.

Switch-on fluorescent/FRET probes to study human histidine triad nucleotide binding protein 1 (hHint1), a novel target for opioid tolerance and neuropathic pain

Histidine Triad Nucleotide Binding Protein 1 (Hint1) has emerged to be an important post-synaptic protein associated with a variety of central nervous system disorders such as pain, addiction, and schizophrenia. Recently, inhibition of histidine nucleotide binding protein 1 (Hint1) with a small nucleoside inhibitor has shown promise as a new therapeutic strategy for the treatment of neuropathic pain. Herein, we describe the first rationally designed small molecule switch-on probes with dual fluorescence and FRET properties to study Hint1. Two non-natural fluorescent nucleosides with a fluorescent lifetime of 20 and 25 ns were each coupled through a linker to the indole ring, i.e. probes 7 and 8. Both probes were found to be water soluble and quenched intramolecularly via photoinduced electron transfer (PET) resulting in minimal background fluorescence. Upon incubating with Hint1, compound 7 and 8 exhibited a 40- and 16-fold increase in the fluorescence intensity compared to the control. Compounds 7 and 8 bind Hint1 with a dissociation constant of 0.121 ± 0.02 and 2.2 ± 0.36 μM, respectively. We demonstrate that probe 8 exhibits a switch-on FRET property with an active site tryptophan residue (W123). We show the utility of probes in performing quantitative ligand displacement studies, as well as in selective detection of Hint1 in the cell lysates. These probes should be useful for studying the dynamics of the active site, as well as for the development of fluorescence lifetime based high throughput screening assay to identify novel inhibitors for Hint1 in future.

Endocannabinoid control of glutamate NMDA receptors: the therapeutic potential and consequences of dysfunction

Glutamate is probably the most important excitatory neurotransmitter in the brain. The glutamate N-methyl-D-aspartate receptor (NMDAR) is a calcium-gated channel that coordinates with G protein-coupled receptors (GPCRs) to establish the efficiency of the synaptic transmission. Cross-regulation between these receptors requires the concerted activity of the histidine triad nucleotide-binding protein 1 (HINT1) and of the sigma receptor type 1 (σ1R). Essential brain functions like learning, memory formation and consolidation, mood and behavioral responses to exogenous stimuli depend on the activity of NMDARs. In this biological context, endocannabinoids are released to retain NMDAR activity within physiological limits. The efficacy of such control depends on HINT1/σ1R assisting in the physical coupling between cannabinoid type 1 receptors (CB1Rs) and NMDARs to dampen their activity. Subsequently, the calcium-regulated HINT1/σ1R protein tandem uncouples CB1Rs to prevent NMDAR hypofunction. Thus, early recruitment or a disproportionate cannabinoid induced response can bring about excess dampening of NMDAR activity, impeding its adequate integration with GPCR signaling. Alternatively, this control circuit can apparently be overridden in situations where bursts of NMDAR overactivity provoke convulsive syndromes. In this review we will discuss the possible relevance of the HINT1/σ1R tandem and its use by endocannabinoids to diminish NMDAR activity and their implications in psychosis/schizophrenia, as well as in NMDAR-mediated convulsive episodes.

HINT1 in Neuropsychiatric Diseases: A Potential Neuroplastic Mediator

Although many studies have investigated the functions of histidine triad nucleotide-binding protein 1 (HINT1), its roles in neurobiological processes remain to be fully elucidated. As a member of the histidine triad (HIT) enzyme superfamily, HINT1 is distributed in almost every organ and has both enzymatic and nonenzymatic activity. Accumulating clinical and preclinical evidence suggests that HINT1 may play an important role as a neuroplastic mediator in neuropsychiatric diseases, such as schizophrenia, inherited peripheral neuropathies, mood disorders, and drug addiction. Though our knowledge of HINT1 is limited, it is believed that further research on the neuropathological functions of HINT1 would eventually benefit patients with neuropsychiatric and even psychosomatic diseases.

Design, Synthesis, and Characterization of Sulfamide and Sulfamate Nucleotidomimetic Inhibitors of hHint1

Hint1 has recently emerged to be an important target of interest due to its involvement in the regulation of a broad range of CNS functions including opioid signaling, tolerance, neuropathic pain, and nicotine dependence. A series of inhibitors were rationally designed, synthesized, and tested for their inhibitory activity against hHint1 using isothermal titration calorimetry (ITC). The studies resulted in the development of the first small-molecule inhibitors of hHint1 with submicromolar binding affinities. A combination of thermodynamic and high-resolution X-ray crystallographic studies provides an insight into the biomolecular recognition of ligands by hHint1. These novel inhibitors have potential utility as molecular probes to better understand the role and function of hHint1 in the CNS.

The ON:OFF switch, σ1R-HINT1 protein, controls GPCR-NMDA receptor cross-regulation: implications in neurological disorders

In the brain, the histidine triad nucleotide-binding protein 1 (HINT1) and sigma 1 receptors (σ1Rs) coordinate the activity of certain G-protein coupled receptors (GPCRs) with that of glutamate N-methyl-D-aspartate receptors (NMDARs). To determine the role of HINT1-σ1R in the plasticity of GPCR-NMDAR interactions, substances acting at MOR, cannabinoid CB1 receptor, NMDAR and σ1R were injected into mice, and their effects were evaluated through in vivo, ex vivo, and in vitro assays. It was observed that HINT1 protein binds to GPCRs and NMDAR NR1 subunits in a calcium-independent manner, whereas σ1R binding to these proteins increases in the presence of calcium. In this scenario, σ1R agonists keep HINT1 at the GPCR and stimulate GPCR-NMDAR interaction, whereas σ1R antagonists transfer HINT1 to NR1 subunits and disengage both receptors. This regulation is lost in σ1R-/- mice, where HINT1 proteins mostly associate with NMDARs, and GPCRs are physically and functionally disconnected from NMDARs. In HINT1-/- mice, ischemia produces low NMDAR-mediated brain damage, suggesting that several different GPCRs enhance glutamate excitotoxicity via HINT1-σ1R. Thus, several GPCRs associate with NMDARs by a dynamic process under the physiological control of HINT1 proteins and σ1Rs. The NMDAR-HINT1-σ1R complex deserves attention because it offers new therapeutic opportunities.