Multispectroscopic and Theoretical Investigation on the Binding Interaction of a Neurodegenerative Drug, Lobeline with Human Serum Albumin: Perturbation in Protein Conformation and Hydrophobic-Hydrophilic Surface.

Lobeline (LOB), a naturally occurring alkaloid, has a broad spectrum of pharmacological activities and therapeutic potential, including applications in central nervous system disorders, drug misuse, multidrug resistance, smoking cessation, depression, and epilepsy. LOB represents a promising compound for developing treatments in various medical fields. However, despite extensive pharmacological profiling, the biophysical interaction between the LOB and proteins remains largely unexplored. In the current article, a range of complementary photophysical and cheminformatics methodologies were applied to study the interaction mechanism between LOB and the carrier protein HSA. Steady-state fluorescence and fluorescence lifetime experiments confirmed the static-quenching mechanisms in the HSA-LOB system. "K" (binding constant) of the HSA-LOB system was determined to be 105 M-1, with a single preferable binding site in HSA. The forces governing the HSA-LOB stable complex were analyzed by thermodynamic parameters and electrostatic contribution. The research also investigated how various metal ions affect complex binding. Site-specific binding studies depict Site I as probable binding in HSA by LOB. We conducted synchronous fluorescence, 3D fluorescence, and circular dichroism studies to explore the structural alteration occurring in the microenvironment of amino acids. To understand the robustness of the HSA-LOB complex, we used theoretical approaches, including molecular docking and MD simulations, and analyzed the principal component analysis and free energy landscape. These comprehensive studies of the structural features of biomolecules in ligand binding are of paramount importance for designing targeted drugs and delivery systems.

Unveiling the molecular basis of lobeline's allosteric regulation of NMDAR: insights from molecular modeling.

Neurological and psychiatric disorders contribute significantly to the global disease burden, adversely affecting the quality of life for both patients and their families. Impaired glutamatergic signaling is considered to be a major cause for most of the neurological and psychiatric disorders. Glutamate receptors are over activated in excitotoxic conditions, leading to dysregulation of Ca2+ homeostasis, triggering the production of free radicals and oxidative stress, mitochondrial dysfunction and eventually cell death. Excitotoxicity primarily results from the overactivity of NMDARs, a subtype of ionotropic glutamate receptors, due to their pronounced Ca2+ permeability and conductance characteristics. NMDAR antagonists are suggested to have therapeutic use as they can prevent excitotoxicity. Our previous studies demonstrated lobeline, an alkaloid, exerts neuroprotective action in excitotoxic conditions by blocking NMDAR. However, the atomic level interactions of lobeline with NMDAR was not characterized yet. Structural comparison of lobeline with a known NMDAR antagonist ifenprodil, followed by molecular docking and dynamics simulations revealed that lobeline could bind to the ifenprodil binding site i.e., in the heterodimer interface of GluN1-GluN2B subunits and exert ifenprodil like activities. By in silico structure guided modifications on lobeline and subsequent free energy calculations, we propose putative NMDAR antagonists derived from lobeline.

Lobeline: A multifunctional alkaloid modulates cholinergic and glutamatergic activities.

Developing drugs for Alzheimer's disease (AD) is an extremely challenging task due to its devastating pathology. Previous studies have indicated that natural compounds play a crucial role as lead molecules in the development of drugs. Even though, there are remarkable technological advancements in the isolation and synthesis of natural compounds, the targets for many of them are still unknown. In the present study, lobeline, a piperidine alkaloid has been identified as a cholinesterase inhibitor through chemical similarity assisted target fishing method. The structural similarities between lobeline and donepezil, a known acetylcholinesterase (AChE) inhibitor encouraged us to hypothesize that lobeline may also exhibit AChE inhibitory properties. It was further confirmed by in silico, in vitro and biophysical studies that lobeline could inhibit cholinesterase. The binding profiles indicated that lobeline has a higher affinity for AChE than BChE. Since excitotoxicity is one of the major pathological events associated with AD progression, we also investigated the neuroprotective potential of lobeline against glutamate mediated excitotoxicity in rat primary cortical neurons. The cell based NMDA receptor (NMDAR) assay with lobeline suggested that neuroprotective potential of lobeline is mediated through the blockade of NMDAR activity.

Quick nic: novel smokeless nicotine products and pediatric trends.

PURPOSE OF REVIEW: The development and marketing of smokeless nicotine products in recent years have become increasingly popular among adolescents. In addition to well known conventional inhaled nicotine products, noninhaled products, such as nicotine toothpicks, orbs, lozenges, strips, and more, have dangerously captivated a new youth audience. Although smokeless nicotine products may seem to be less threatening than conventional inhaled nicotine products, there are significant risks associated with the use of these products, including addiction and severe health issues. The purpose of this review is to provide up-to-date information about alternative nicotine products currently on the market that may appeal to youth, and the dangers of nicotine use for pediatric populations. RECENT FINDINGS: Smokeless nicotine products appeal to minors with their varying flavors and discrete packaging. These products may lead to nicotine toxicity as well as severe health problems, such as cancer, issues with reproduction, and heart attacks. Nicotine is extremely dangerous for young children; in fact, using nicotine products before the age of 18 years can lead to addiction and is linked to an increased likelihood of experimenting with stronger nicotine products or illicit drugs. The development of inconspicuous nicotine packaging has led to increasing concerns for accidental nicotine exposure and overdose in youth. SUMMARY: Greater knowledge regarding current nicotine products on the market, specifically smokeless nicotine products, will help clinicians be more aware of the dangers associated with these products. Clinicians will be better able to provide their patients and families with proper guidance to avoid nicotine addiction, further drug use, and detrimental health issues. Caregivers and medical professionals must recognize novel and inconspicuous nicotine products commonly used among youth, understand the signs of nicotine abuse and dependence, and take measures to address possible nicotine-related health risks.

2,6-Disubstituted Piperidine Alkaloids with Neuroprotective Activity from Hippobroma longiflora.

Three new alkaloids, hipporidine A (1: ), hipporidine B (2: ), and (-)-lobeline N-oxide (3: ), were discovered from the whole plant of Hippobroma longiflora together with five known compounds (4: -8: ). Their 2,6-disubstituted piperidine structures were established based on the HRESIMS, NMR (COSY, HMBC, HSQC, NOESY), and UV spectroscopic data. Hipporidines A (1: ) and B (2: ) possess a rare 1,3-oxazinane moiety. Compound 3: is the N-oxide derivative of (-)-lobeline (6: ). Moreover, the absolute configuration of norlobeline (5: ) was established by single-crystal X-ray diffraction analysis. Three major secondary metabolites (6: -8: ) were evaluated for their neuroprotective effect against paclitaxel-induced neurotoxicity. Consequently, pretreatment with compound 8: at a concentration of 1.0 µM displayed significant attenuation on paclitaxel-damaged neurite outgrowth of dorsal root ganglion neurons without interfering with the cytotoxicity of paclitaxel on cervical cancer SiHa cells.

Overall and cause-specific mortality rates among men and women with high exposure to indoor air pollution from the use of smoky and smokeless coal: a cohort study in Xuanwei, China.

OBJECTIVES: Never-smoking women in Xuanwei (XW), China, have some of the highest lung cancer rates in the country. This has been attributed to the combustion of smoky coal used for indoor cooking and heating. The aim of this study was to evaluate the spectrum of cause-specific mortality in this unique population, including among those who use smokeless coal, considered 'cleaner' coal in XW, as this has not been well-characterised. DESIGN: Cohort study. SETTING: XW, a rural region of China where residents routinely burn coal for indoor cooking and heating. PARTICIPANTS: Age-adjusted, cause-specific mortality rates between 1976 and 2011 were calculated and compared among lifetime smoky and smokeless coal users in a cohort of 42 420 men and women from XW. Mortality rates for XW women were compared with those for a cohort of predominately never-smoking women in Shanghai. RESULTS: Mortality in smoky coal users was driven by cancer (41%), with lung cancer accounting for 88% of cancer deaths. In contrast, cardiovascular disease (CVD) accounted for 32% of deaths among smokeless coal users, with 7% of deaths from cancer. Total cancer mortality was four times higher among smoky coal users relative to smokeless coal users, particularly for lung cancer (standardised rate ratio (SRR)=17.6). Smokeless coal users had higher mortality rates of CVD (SRR=2.9) and pneumonia (SRR=2.5) compared with smoky coal users. These patterns were similar in men and women, even though XW women rarely smoked cigarettes. Women in XW, regardless of coal type used, had over a threefold higher rate of overall mortality, and most cause-specific outcomes were elevated compared with women in Shanghai. CONCLUSIONS: Cause-specific mortality burden differs in XW based on the lifetime use of different coal types. These observations provide evidence that eliminating all coal use for indoor cooking and heating is an important next step in improving public health particularly in developing countries.

From cis-Lobeline to trans-Lobeline: Study on the Pharmacodynamics and Isomerization Factors.

Lobeline is an alkaloid derived from the leaves of an Indian tobacco plant (Lobelia inflata), which has been prepared by chemical synthesis. It is classified as a partial nicotinic agonist and has a long history of therapeutic usage ranging from emetic and respiratory stimulant to tobacco smoking cessation agent. The presence of both cis and trans isomers in lobeline is well known, and many studies on the relationship between the structure and pharmacological activity of lobeline and its analogs have been reported. However, it is a remarkable fact that no studies have reported the differences in pharmacological activities between the two isomers. In this article, we found that different degrees of isomerization of lobeline injection have significant differences in respiratory excitatory effects in pentobarbital sodium anesthetized rats. Compared with cis-lobeline injections, the respiratory excitatory effect was significantly reduced by 50.2% after administration of injections which contained 36.9% trans-lobeline. The study on the influencing factors of isomerization between two isomers shown that this isomerization was a one-way isomerism and only converted from cis to trans, where temperature was the catalytic factor and pH was the key factor. This study reports a new discovery. Despite the widespread use of ventilators, first-aid medicines such as nikethamide and lobeline has retired to second line, but as a nonselective antagonist with high affinity for a4b2 and a3b2 nicotinic acetylcholine receptors (nAChRs). In recent years, lobeline has shown great promise as a therapeutic drug for mental addiction and nervous system disorders, such as depression, Alzheimer disease and Parkinson disease. Therefore, we suggest that the differences between two isomers should be concerned in subsequent research papers and applications.

New smokeless moxibustion for knee osteoarthritis: A study protocol for a multicenter, single-blind, randomized controlled trial.

INTRODUCTION: Knee osteoarthritis (KOA) is a chronic inflammatory disease with high morbidity and disability. As the aging and obese population increase, so will the medical services for this disease. The purpose of this study is to compare the clinical efficacy of herbal activated carbon smokeless moxibustion and traditional moxibustion in the treatment of KOA and to determine the clinical efficacy of herbal activated carbon smokeless moxibustion in the treatment of KOA. METHODS/DESIGN: This is a multicenter, two parallel-group, single-blind, randomized controlled trial. Eighty-eight subjects with KOA (Kellgren Lawrence grade II or III) will be recruited and randomly treated with smokeless moxibustion or traditional moxibustion in the ratio of 1:1. The smokeless moxibustion group will use plant herbal activated carbon smokeless moxa cone. The traditional moxibustion group will be treated with pure moxa cone. Subjects in both groups will receive treatment at the affected knee(s) at the acupuncture point ST35, EX-LE2, and EX-LE4. Subjects in both groups will receive 3 sessions per week of moxibustion for 4 weeks. The primary outcome are changes in the Western Ontario and McMaster Universities Osteoarthritis Index pain scores from baseline to week 24. Secondary outcomes include visual analog scale, 50 yards fast walking time, short-form heath survey 36, overall clinical efficacy evaluation, self-assessment of safety, treatment credibility and expectancy, and cytokines related to osteoarthritis in serum. DISCUSSION: This randomized single-blind controlled trial takes traditional moxibustion as the control group to provide strict evidence for the clinical efficacy and safety of herbal activated carbon smokeless moxibustion in the treatment of KOA.

The use of an intermittent schedule of reinforcement to evaluate detection dogs' generalization from smokeless-powder.

Odor generalization is essential for detection dogs. Regardless of its importance, limited research is available on detection dog odor generalization. The objectives of this study were (1) evaluate the use of an intermittent schedule of reinforcement to assess generalization in dogs and (2) evaluate olfactory generalization from a single exemplar of smokeless powder (SP). Dogs (N = 5) were trained to detect SP in an automated olfactometer under an intermittent schedule of reinforcement where only 60% of correct responses were reinforced. After training, eight non-reinforced probe trials were inserted within a session. A total of 15 testing odors were evaluated across 15 consecutive sessions (one odor/session). Six of the testing odors were control and the remaining testing odors were objects indirectly exposed to SP, objects that contained or were directly exposed to SP, single-base SP and diphenylamine (the main volatile present in the headspace of SP). Dogs' response rate to all testing odors except for the cotton gauzes and t-shirt cloths exposed to the headspace of SP, the simulated IED, and Getxent tubes exposed to direct contact with SP were statistically lower than their response rate of actual SP. The response rate to SP was not different across all 15 testing sessions suggesting that the intermittent schedule of reinforcement, maintained dog motivation and performance. Data show that the outlined method is a good approach to study generalization in detection dogs. These results also highlight dog generalization to SP varieties and associated odors.

Rapid and straight forward mass spectrometric determination of nitrocellulose in smokeless powder by DART-Q-ToF-MS/MS.

Smokeless powders (SPs) are a group of low-explosives primarily used as propellant in various munitions and are frequently employed as explosive charges in bombings and terrorist attacks. However, the reliable determination of nitrocellulose (NC), one of the main components of SP remains an analytical challenge, especially in post-blast residues. While highly desirable because of its selectivity, the mass spectrometric (MS) detection of NC is hindered by its polymeric nature and broadly distributed molecular weight, as well as its poor ionizability in many common MS ion-sources. Direct Analysis in Real Time (DART) - MS allows for the rapid and simple analysis of samples and poses a means of circumventing the problems associated with detection of NC. Analytes in DART readily form adducts, which enables the straight-forward detection of nitrate esters such as glucose trinitrate and cellobiose hexanitrate, the respective monomeric and dimeric subunit of NC, and obviates the need for prior derivatization. Therefore, this method is well suited to rapidly and reliably determine the presence of NC in bulk, as well as consumed SP, as could be shown in this proof-of-concept study for a set of three single-base SPs.

Characterization and comparison of smokeless powders by on-line two-dimensional liquid chromatography.

Smokeless powders (SPs) are one of the most commonly used propellants for ammunition but can also be abused as energetic material in improvised explosive devices (IEDs) such as pipe bombs. After a shooting or explosion, unburnt or partially burnt particulates may be observed which can be used for forensic investigation. SPs comprise mainly nitrocellulose (NC) and additives. Therefore, the characterization of both NC and the additives is of significant forensic importance. Typically, the identification, classification, and chemical profiling of smokeless powders are based exclusively on the analysis of the additives. In this study, information regarding the NC base component was combined with the chemical analysis of the additives using two-dimensional liquid chromatography (2D-LC). The system combines size-exclusion chromatography (SEC) and reversed-phase liquid chromatography (RPLC) in an on-line heart-cut 2D-LC configuration. In the first dimension, the NC is characterized by its molecular-weight distribution (MWD) while being separated from the additives. The additives are then transferred to the second-dimension separation using a novel analyte-transfer system. In the second dimension, the additives are separated to obtain a detailed profile of the low-molecular-mass compounds in the SP. With this approach, the MWD of the NC and the composition of the additives in SP have been obtained within an hour. A discrimination power of 90.53% was obtained when studying exclusively the NC MWD, and 99.47% for the additive profile. This novel combination enables detailed forensic comparison of intact SPs. Additionally, no extensive sample preparation is required, making the developed method less labor intensive.

[Acupuncture combined with smokeless or smoky moxibustion for regulating immune function of experimental chronic rhinosinusitis mice].

OBJECTIVE: To observe the therapeutic effect of moxa fume in the treatment of chronic rhinosinusitis（CRS） and the effect of acupuncture plus smokeless moxibustion or smoky moxibustion on the expression of thymic stromal lymphopoietin (TSLP) and pituitary adenylate cyclase activating polypeptide (PACAP) proteins in the sinus mucosal tissue in CRS mice. METHODS: Sixty male C57BL/6J mice were randomly divided into 6 groups, namely normal control, sham operation, CRS model, medication, acupuncture plus smokeless moxibustion (Acu+smokeless Moxi) and acupuncture plus smoky moxibustion (Acu+smoky Moxi) groups, with 20 mice in each group. The CRS model was established by inserting a piece of polyporous sponge filled with streptococcus pneumoniae into the maxillary sinus after operation. The mice in the sham operation group received skin incision after opening the maxillary sinus. Mice of the medication group received gavage of clarithromycin 0.103 g·kg-1·d-1 for 21 days. For mice of the Acu+smokeless Moxi and Acu +smoky Moxi groups, manual acupuncture stimulation was applied to bilateral "Zusanli" (ST36), "Shenshu" (BL23) and "Hegu" (LI4) with the needles retained for 30 min, once every other day, and on the following day, moxibustion was applied to "Guanyuan" (CV4) and "Shenque" (BL23) for 20 min, once every other day. The treatment was given for 21 days. Mice of the normal, sham operation and model groups received gavage of normal saline (200 µL/d) for 21 days. Histopathological changes of the nasal mucosa were observed after H.E. staining, the TSLP and PACAP contents and expression were determined by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry, separately. RESULTS: At the end of the treatment, mice of the model group still had symptoms of nasal obstruction and runny nose, but those of the 3 treatment groups were obviously relieved in the nasal symptoms. H.E. staining showed an obvious chronic inflammatory reaction in the sinus mucosa, uneven distribution of the mucosal epithelium and necrotic and exfoliated epithelial cells, hyperplasia of fibrous tissue in the submucosa, etc. in the model group, which were relatively milder in the medication, Acu+smokeless Moxi and Acu+smoky Moxi groups, while no obvious inflammation was found in the normal group and sham operation group. In comparison with the normal group, no significant changes were found in the expression levels of PACAP and TSLP in the sham operation group (P>0.05). The expression level of PACAP was significantly lower (P<0.05) and that of TSLP significantly higher in the model group than in the normal and sham operatin groups (P<0.05). Compared with the model group, no significant changes were found in the expression of PACAP in the medication, Acu+smokeless Moxi and Acu+smoky Moxi groups (P>0.05), and the expression of TSLP was further obviously increased in the Acu+smokeless Moxi group (P<0.01), but obviously decreased in the Acu+smoky Moxi group (P<0.01). CONCLUSION: Acupuncture combined with smoky moxibustion can down-regulate the expression of TSLP protein in the nasal sinus mucosa in CRS mice, which maybe contribute to its effect in reducing the inflammatory reaction and nasal symptoms.

J receptor activity in idiopathic pulmonary hypertension and its expected change in the presence of pulmonary bed vasodilators.

Juxtapulmonary receptors (J) lying in the lung parenchyma are stimulated naturally by any condition that produces interstitial oedema, transient increases in interstitial volume and pressure or raised pulmonary capillary pressure. There is no information available about the level of their stimulation in patients with idiopathic pulmonary hypertension (IPH) who have high levels of pulmonary artery systolic pressures. The aim of the present study therefore was to find the level of these receptors activity in these patients at their prevailing pulmonary artery systolic pressures. This was done by the established method of determining the dose of i.v. lobeline that gives rise to threshold levels of sensations in the upper chest areas and accelerates respiration. In IPH patients it was found to be as high as 31.6 ± 5.6 µg/kg i.e., twice as much as that known for healthy individuals which is 15 µg/kg. This shows an enhanced stimulation of J receptors in IPH patients. Expectedly when pulmonary artery systolic pressure falls with pulmonary bed vasodilator medication given to IPH patients, a reduction in the natural stimulus of J receptors would also occur leading to a fall in their activity and hence that of the quantum of their reflexes of respiratory acceleration and inhibition of exercise. This finding provides the first insight of a neural mechanism that could be influenced to produce its effects when pulmonary artery systolic pressure falls by pulmonary vasodilator medication.

Smoke or smokeless moxibustion treatment for breech presentation: A three-arm pilot trial.

AIMS: We conducted a pilot trial to compare the effects of smoke and smokeless moxibustion with a control as a possible supplement to external cephalic version (ECV) for converting breech to cephalic presentation and increasing adherence to cephalic position, and to assess their effects on the well-being of the mother and child. METHODS: We used a quasi-experimental design with 3 arms: a smoke moxibustion (SM) (n = 20) and smokeless moxibustion (SLM) (n = 20) groups (20-min acupoint BL67 stimulation once or twice daily for 10-14 days), and a control group (n = 20). The participants had singleton breech presentations between 33 and 35 gestation weeks. The primary outcome was cephalic presentation at the conclusion of intervention. The secondary outcomes were cephalic presentation at birth and effects on mother and child well-being. RESULTS: At the conclusion of intervention, cephalic presentation was higher in the SLM (60.0%) than the control groups (25.0%), Relative Risk 2.40, 95% Confidence Interval [1.04-5.56]; there was no significant difference for SM. At birth, there were no significant differences in cephalic presentation or well-being. CONCLUSION: SLM treatment showed an increasing trend towards cephalic presentation at the conclusion of intervention. Although significant differences were not observed at birth possibly due to the small samples and non-randomization, moxibustion was safe, and not associated with perinatal morbidity and mortality. A randomized controlled trial with a larger sample is warranted to ascertain SLM treatment as a possible ECV supplement for converting and increasing adherence to cephalic position.

Infiltration properties of n-alkanes in mesoporous biochar: The capacity of smokeless support for stability and energy storage.

Biochar, also named biocarbon, is a solid particulate material produced from the thermal decomposition of biomass at moderate temperatures. It has progressively become the topic of scientific interest in energy storage and conversion applications due to its affordability, environment friendliness, and structural tunability. In this study, biochar (obtained 600 °C pyrolysis) was introduced as phase change materials (PCMs) support. Three different n-alkanes (such as dodecane, tetradecane, and octadecane) are used as PCMs. The PCMs were infiltrated in the biochar network via the vacuum impregnation method. Among the biochar/n-alkane composites, one from octadecane exhibited a high latent heat storage capacity of 91.5 kJ/kg, 15.7 % and 25.9 % higher than that of dodecane and tetradecane-based composites, respectively. The molecular length of the PCMs and intermolecular interaction between the functional groups play an imperative role. The infiltration ratio of PCM in the biochar reached 50.1 % with improved thermal stability and chemical compatibility. This is attributed to the favorable morphological and structural properties (e.g., large BET surface area and mesopore structure) of the biochar that resides the n-alkanes found in the nanosized chain length. Hence, this report will lay a foundation for the application of biochars in thermal energy management systems.

Chemical Profiling of Lobelia chinensis with High-Performance Liquid Chromatography/Quadrupole Time-of-Flight Mass Spectrometry (HPLC/Q-TOF MS) Reveals Absence of Lobeline in the Herb.

Lobelia chinensis is a kind of herbal medicine widely distributed and used in Asia. The chemical components of this herb, however, have not been well studied until now. Lobeline, as an essential and famous bioactive compound in Lobelia genus, has been assumed to be present in L. chinensis. In order to ascertain its presence and, more importantly, proper use of this herb, chemical profiling this herb with highly sensitive and high-resolution analytical mass spectrometry was applied. In this study, high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC/Q-TOF MS) method was employed to systematically profile the chemical constituents of L. chinensis for the first time. Comparative chemical profiling study of L. chinensis and Lobelia inflata was also conducted to provide evidence whether lobeline is present or not. Piperidine alkaloids except for lobeline, alkaloid-lignan hybrids, flavonoids, polyacetylenes, nonanedioic acid, and some new phytochemicals were successfully identified in L. chinensis simultaneously. Comparing to the chemical profiles of L. inflata, lobeline was found to be absent in L. chinensis. All of the secondary metabolites in L. chinensis were determined with the HPLC/Q-TOF MS method. The absence of lobeline in L. chinensis was confirmed after this extensive study.

Mannich-type Reactions of Cyclic Nitrones: Effective Methods for the Enantioselective Synthesis of Piperidine-containing Alkaloids.

Even though there are dozens of biologically active 2-substituted and 2,6-disubstituted piperidines, only a limited number of approaches exist for their synthesis. Herein is described two Mannich-type additions to nitrones, one using ß-ketoacids under catalyst-free conditions and another using methyl ketones in the presence of chiral thioureas, which can generate a broad array of such 2-substituted materials, as well as other ring variants, in the form of ß-N-hydroxy-aminoketones. Both processes have broad scope, with the latter providing products with high enantioselectivity (up to 98 %). The combination of these methods, along with other critical steps, has enabled 8-step total syntheses of the 2,6-disubstituted piperidine alkaloids (-)-lobeline and (-)-sedinone.

New Scaffold for Lead Compounds to Treat Methamphetamine Use Disorders.

Despite increased methamphetamine use worldwide, pharmacotherapies are not available to treat methamphetamine use disorder. The vesicular monoamine transporter-2 (VMAT2) is an important pharmacological target for discovery of treatments for methamphetamine use disorder. VMAT2 inhibition by the natural product, lobeline, reduced methamphetamine-evoked dopamine release, methamphetamine-induced hyperlocomotion, and methamphetamine self-administration in rats. Compared to lobeline, lobelane exhibited improved affinity and selectivity for VMAT2 over nicotinic acetylcholine receptors. Lobelane inhibited neurochemical and behavioral effects of methamphetamine, but tolerance developed to its behavioral efficacy in reducing methamphetamine self-administration, preventing further development. The lobelane analog, R-N-(1,2-dihydroxypropyl)-2,6-cis-di-(4-methoxyphenethyl)piperidine hydrochloride (GZ-793A), potently and selectively inhibited VMAT2 function and reduced neurochemical and behavioral effects of methamphetamine. However, GZ-793A exhibited potential to induce ventricular arrhythmias interacting with human-ether-a-go-go (hERG) channels. Herein, a new lead, R-3-(4-methoxyphenyl)-N-(1-phenylpropan-2-yl)propan-1-amine (GZ-11610), from the novel scaffold (N-alkyl(1-methyl-2-phenylethyl)amine) was evaluated as a VMAT2 inhibitor and potential therapeutic for methamphetamine use disorder. GZ-11610 was 290-fold selective for VMAT2 over dopamine transporters, suggesting that it may lack abuse liability. GZ-11610 was 640- to 3500-fold selective for VMAT2 over serotonin transporters and nicotinic acetylcholine receptors. GZ-11610 exhibited > 1000-fold selectivity for VMAT2 over hERG, representing a robust improvement relative to our previous VMAT2 inhibitors. GZ-11610 (3-30 mg/kg, s.c. or 56-300 mg/kg, oral) reduced methamphetamine-induced hyperactivity in methamphetamine-sensitized rats. Thus, GZ-11610 is a potent and selective inhibitor of VMAT2, may have low abuse liability and low cardiotoxicity, and after oral administration is effective and specific in inhibiting the locomotor stimulant effects of methamphetamine, suggesting further investigation as a potential therapeutic for methamphetamine use disorder.

Varenicline and GZ-793A differentially decrease methamphetamine self-administration under a multiple schedule of reinforcement in rats.

Methamphetamine is a potent psychostimulant with high abuse rates. Currently, there is no Food and Drug Administration-approved pharmacotherapy for methamphetamine addiction. Ideally, a pharmacotherapy should selectively decrease methamphetamine self-administration without affecting responding for other reinforcers. One way to test this is with the use of a multiple schedule of reinforcement, in which drug and food are available in alternating components within a session. The present study evaluated GZ-793A, a vesicular monoamine transporter-2 inhibitor, and varenicline, a partial agonist at α4ß2 and full agonist at α7 nicotinic acetylcholine receptors, for their ability to decrease methamphetamine and food self-administration using a multiple schedule of reinforcement. Male Sprague-Dawley rats self-administered methamphetamine (0.03 mg/kg/intravenous infusion) and food pellets under a multiple schedule of reinforcement. GZ-793A or varenicline was administered before multiple schedule sessions. GZ-793A (5 and 20 mg/kg) significantly decreased methamphetamine intake compared with saline and did not alter food-maintained responding. In contrast, varenicline decreased methamphetamine intake less specifically across time. The results suggest that vesicular monoamine transporter-2 inhibition may be a viable pharmacological target for the treatment of methamphetamine-use disorders.