Human monoamine oxidase is inhibited by tobacco smoke: beta-carboline alkaloids act as potent and reversible inhibitors

Neurobiological research on N,N-dimethyltryptamine (DMT) and its potentiation by monoamine oxidase (MAO) inhibition: from ayahuasca to synthetic combinations of DMT and MAO inhibitors

The potent hallucinogen N,N-dimethyltryptamine (DMT) has garnered significant interest in recent years due to its profound effects on consciousness and its therapeutic psychopotential. DMT is an integral (but not exclusive) psychoactive alkaloid in the Amazonian plant-based brew ayahuasca, in which admixture of several β-carboline monoamine oxidase A (MAO-A) inhibitors potentiate the activity of oral DMT, while possibly contributing in other respects to the complex psychopharmacology of ayahuasca. Irrespective of the route of administration, DMT alters perception, mood, and cognition, presumably through agonism at serotonin (5-HT) 1A/2A/2C receptors in brain, with additional actions at other receptor types possibly contributing to its overall psychoactive effects. Due to rapid first pass metabolism, DMT is nearly inactive orally, but co-administration with β-carbolines or synthetic MAO-A inhibitors (MAOIs) greatly increase its bioavailability and duration of action. The synergistic effects of DMT and MAOIs in ayahuasca or synthetic formulations may promote neuroplasticity, which presumably underlies their promising therapeutic efficacy in clinical trials for neuropsychiatric disorders, including depression, addiction, and post-traumatic stress disorder. Advances in neuroimaging techniques are elucidating the neural correlates of DMT-induced altered states of consciousness, revealing alterations in brain activity, functional connectivity, and network dynamics. In this comprehensive narrative review, we present a synthesis of current knowledge on the pharmacology and neuroscience of DMT, β-carbolines, and ayahuasca, which should inform future research aiming to harness their full therapeutic potential.

Formation, Identification, and Occurrence of the Furan-Containing β-Carboline Flazin Derived from l-Tryptophan and Carbohydrates

β-Carbolines (βCs) are bioactive indole alkaloids found in foods and in vivo. This work describes the identification, formation, and occurrence in foods of the βC with a furan moiety flazin (1-[5-(hydroxymethyl)furan-2-yl]-9H-pyrido[3,4-b]indole-3-carboxylic acid). Flazin was formed by the reaction of l-tryptophan with 3-deoxyglucosone but not with 5-hydroxymethylfurfural. Its formation was favored in acidic conditions and heating (70-110 °C). The proposed mechanism of formation occurs through the formation of intermediates 3,4-dihydro-β-carboline-3-carboxylic acid (imines), followed by the oxidation to C═O in the carbohydrate chain and aromatization to βC ring with subsequent dehydration steps and cyclization to afford the furan moiety. Flazin is generated in the reactions of tryptophan with carbohydrates. Its formation from fructose was higher than from glucose, whereas sucrose gave flazin under acidic conditions and heating owing to hydrolysis. Flazin was identified in foods by HPLC-MS, and its content was determined by HPLC-fluorescence. It occurred in numerous processed foods, such as tomato products, including crushed tomato puree, fried tomato, ketchup, tomato juices, and jams, but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onions, and honey. Their concentrations ranged from not detected to 22.3 μg/mL, with the highest mean levels found in tomato concentrate (13.9 μg/g) and soy sauce (9.4 μg/mL). Flazin was formed during the heating process, as shown in fresh tomato juice and crushed tomatoes. These results indicate that flazin is widely present in foods and is daily uptaken in the diet.

Discovery of indole analogues from Periplaneta americana extract and their activities on cell proliferation and recovery of ulcerative colitis in mice

Background: As an important medicinal insect, Periplaneta americana (PA) has been applied for the treatment of wounds, burns, and ulcers with fewer side effects and a reduced recurrence rate, which provides great potential for developing new drugs based on its active constituents. Materials and methods: The main chromatographic peaks determined by high performance liquid chromatography (HPLC) in the PA concentrated ethanol-extract liquid (PACEL) were separated, purified, and identified by semi-preparative LC, mass spectrum, and 1H NMR spectroscopic analysis. The biological activities of the identified compounds were investigated by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method based on in vitro human skin fibroblasts (HSF) and in vivo experiments based on dextran sulfate sodium (DSS)-induced ulcerative colitis (UC) mouse model. Furthermore, RT-qPCR of six genes related to inflammation or intestinal epithelial cell proliferation was employed to investigate the molecular mechanism of the indole analogues recovering UC in mice. Results: Five indole analogues were purified and identified from PACEL, including tryptophan (Trp), tryptamine (pa01), 1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa02), (1S, 3S)-1-methyl-1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa03), and (1R, 3S)-1-methyl-1,2,3,4-tetrahydrogen-β-carboline-3-carboxylic acid (pa04), among which the pa02 and pa04 were reported in PA for the first time. In vitro and in vivo experiments showed that PACEL, Trp, and pa02 had promoting HSF proliferation activity and intragastric administration of them could alleviate symptoms of weight loss and colon length shortening in the UC mice. Although recovery activity of the compound pa01 on the colon length was not as obvious as other compounds, it showed anti-inflammatory activity in histological analysis. In addition, The RT-qPCR results indicated that the three indole analogues could alleviate DSS-induced intestinal inflammation in mice by inhibiting pro-inflammatory cytokines (MMP7, IL1α) and down-regulating BMP8B expression. Conclusion: This study reported the isolation, purification, structure identification, and biological activity of the active indole analogues in PACEL. It was found for the first time that the PA extract contained many indole analogues and Trp, which exhibited good proliferation activity on HSF fibroblasts as well as anti-UC activity in mice. These indole analogues probably are important components related to the pharmacological activity in PA.

Identification, Formation, and Occurrence of Perlolyrine: A β-Carboline Alkaloid with a Furan Moiety in Foods

β-Carbolines are naturally occurring bioactive alkaloids found in foods and in vivo. This research reports the identification, characterization, mechanism of formation, and occurrence of perlolyrine (1-(5-(hydroxymethyl)furan-2-yl)-9H-pyrido[3,4-b]indole), a β-carboline with a furan moiety. Perlolyrine did not arise from l-tryptophan and hydroxymethylfurfural but from the reaction of l-tryptophan with 3-deoxyglucosone, an intermediate of carbohydrate degradation. The mechanism of formation occurs through 3,4-dihydro-β-carboline-3-carboxylic acid intermediates (imines), followed by the oxidation of C1'-OH to ketoimine and oxidative decarboxylation at C-3, along with dehydration and cyclization to afford the β-carboline with a furan moiety. The formation of perlolyrine was favored in acidic conditions and temperatures in the range of 70-110 °C. Perlolyrine occurred in the reactions of tryptophan with carbohydrates. The formation rate from fructose was much higher than from glucose. Sucrose also gave perlolyrine under acidic conditions and heating. Perlolyrine was identified in many foods by HPLC-MS and analyzed by HPLC-fluorescence. It occurred in many processed foods such as tomato products including tomato puree, fried tomato, ketchups, tomato juices, and jams but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onion, and honey. The concentrations ranged from an undetected amount to 3.5 μg/g with the highest average levels found in tomato concentrate (1.9 μg/g) and soy sauce (1.5 μg/mL). The results show that perlolyrine formed during the heating process of foods. It is concluded that perlolyrine is widely present in foods and it is daily ingested in the diet.

β-Carboline Alkaloids in Soy Sauce and Inhibition of Monoamine Oxidase (MAO)

Monoamine oxidase (MAO) oxidizes neurotransmitters and xenobiotic amines, including vasopressor and neurotoxic amines such as the MPTP neurotoxin. Its inhibitors are useful as antidepressants and neuroprotectants. This work shows that diluted soy sauce (1/3) and soy sauce extracts inhibited human MAO-A and -B isozymes in vitro, which were measured with a chromatographic assay to avoid interferences, and it suggests the presence of MAO inhibitors. Chromatographic and spectrometric studies showed the occurrence of the β-carboline alkaloids harman and norharman in soy sauce extracts inhibiting MAO-A. Harman was isolated from soy sauce, and it was a potent and competitive inhibitor of MAO-A (0.4 µM, 44 % inhibition). The concentrations of harman and norharman were determined in commercial soy sauces, reaching 243 and 52 μg/L, respectively. Subsequently, the alkaloids 1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (THCA) and 1-methyl-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (MTCA) were identified and analyzed in soy sauces reaching concentrations of 69 and 448 mg/L, respectively. The results show that MTCA was a precursor of harman under oxidative and heating conditions, and soy sauces increased the amount of harman under those conditions. This work shows that soy sauce contains bioactive β-carbolines and constitutes a dietary source of MAO-A and -B inhibitors.

Current development of β-carboline derived potential antimalarial scaffolds

β-Carboline alkaloids are an eminent class of nitrogen-based natural alkaloids and therapeutic molecules which exert various pharmacological activities through diverse mechanisms. A lot of attention has recently been directed towards this moiety in order to develop effective antimalarial drugs. "Malaria", an acute febrile illness caused by diverse Plasmodium parasites, is a continuing and escalating problem that devastates economically less developed countries by significantly increased morbidity and mortality rates. The mounting parasite resistance towards the antimalarial drugs and augmenting the 'habitat of the insect vector' are creating a catastrophe, indicating an urgent need for new efficacious therapeutics to combat this tropical disease. This article comprehensively encapsulates the clinical and preclinical antimalarial scaffolds comprising β-carboline moiety in their structure. Herein, various classes of natural and semi-synthetic analogues of β-carbolines reported in the last decade (2011-2021) have been extensively studied and illustrated. This review will help the readers to develop an insight into the β-carboline based antimalarials and molecular mechanisms lying behind their mode of action, which is anticipated to be beneficial for the future development of new β-carboline based therapeutics.

Assay of MAO Inhibition by Chromatographic Techniques (HPLC/HPLC-MS)

Monoamine oxidase (MAO) enzymes (MAO A and B) catalyze the oxidative deamination of biogenic amines, neurotransmitters, and xenobiotic amines and contribute to the regulation of the content of these active substances in mammalian organisms. The oxidation of biogenic amines by MAO produces hydrogen peroxide (H₂O₂) and aldehydes that represent risk factors for oxidative injury. The inhibitors of MAO are useful as antidepressants and neuroprotective agents. Usually, the assays of MAO determine amine deamination products or measure the H₂O₂ released by using direct spectrophotometric or fluorimetric methods. Direct methods are more prone to interferences and can afford inaccurate results. Those limitations can be avoided by using chromatographic techniques. This work describes a chromatographic method to assay MAO A and MAO B activity by using kynuramine as a nonselective substrate and the subsequent analysis of 4-hydroxyquinoline by RP-HPLC-DAD-fluorescence and mass spectrometry (MS). Alternatively, the assay uses the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxin as a substrate of MAO that is oxidized (bioactivated) to neurotoxic pyridinium cations which are analyzed by HPLC. These methods are applied to assess the inhibition of MAO by bioactive β-carboline alkaloids occurring in foods, plants, and biological systems.

Computational Insights into β-Carboline Inhibition of Monoamine Oxidase A

Monoamine oxidases (MAOs) are an important group of enzymes involved in the degradation of neurotransmitters and their imbalanced mode of action may lead to the development of various neuropsychiatric or neurodegenerative disorders. In this work, we report the results of an in-depth computational study in which we performed a static and a dynamic analysis of a series of substituted β-carboline natural products, found mainly in roasted coffee and tobacco smoke, that bind to the active site of the MAO-A isoform. By applying molecular docking in conjunction with structure-based pharmacophores and molecular dynamics simulations coupled with dynamic pharmacophores, we extensively investigated the geometric aspects of MAO-A binding. To gain insight into the energetics of binding, we used the linear interaction energy (LIE) method and determined the key anchors that allow productive β-carboline binding to MAO-A. The results presented herein could be applied in the rational structure-based design and optimization of β-carbolines towards preclinical candidates that would target the MAO-A enzyme and would be applicable especially in the treatment of mental disorders such as depression.

A review of monoamine oxidase (MAO) inhibitors in tobacco or tobacco smoke

Tobacco smoking is reputed to be the most difficult addiction of all to give up, and nicotine has been noted as the major addictive agent in tobacco smoke. However, research shows that nicotine addiction is due to more than nicotine alone. One hypothesis is that monoamine oxidase (MAO) inhibition from non-nicotinic components in, or derived from, tobacco smoke contributes to nicotine addiction. Harman and norharman, have been recognised as major and potent MAO inhibitors in tobacco smoke, but these two inhibitors together comprise perhaps less than 10% of the total MAO A inhibitory activity in cigarette smoke suggesting other unidentified components may make significant contributions to total inhibitory activity. Therefore, we reviewed an index of the chemical components of tobacco and tobacco smoke and identified those known to be MAO inhibitors. Amongst these inhibitors, phenols and phenolic acids with MAO inhibitory activity are commonly reversible and selective MAO A inhibitors, whereas trans,trans-farnesol, 2-methyl-1,4-naphthoquinone (menadione), 1,4-naphthoquinone, scopoletin, and diosmetin with MAO inhibitory activity are reversible and selective MAO B inhibitors. The compound, 1,4-benzoquinone is an irreversible MAO A inhibitor and to the best of our knowledge, this is the first irreversible MAO A inhibitor to be reported in tobacco smoke. MAO inhibitors have been used clinically to treat depression, anxiety, and Parkinson's disease. The MAO inhibitors identified from tobacco and tobacco smoke and summarized in this review, are potential pharmacological candidates to be investigated further. This review will enhance our knowledge of the way tobacco smoke affects MAO activity in smokers and will also be important in helping to understand nicotine addiction.

Monoamine oxidase inhibition in cigarette smokers: From preclinical studies to tobacco product regulation

Monoamine oxidase (MAO) activity is reduced in cigarette smokers and this may promote the reinforcing actions of nicotine, thereby enhancing the addictive properties of cigarettes. At present, it is unclear how cigarette smoking leads to MAO inhibition, but preclinical studies in rodents show that MAO inhibition increases nicotine self-administration, especially at low doses of nicotine. This effect of MAO inhibition develops slowly, likely due to plasticity of brain monoamine systems; studies relying on acute MAO inhibition are unlikely to replicate what happens with smoking. Given that MAO inhibition may reduce the threshold level at which nicotine becomes reinforcing, it is important to consider this in the context of very low nicotine content (VLNC) cigarettes and potential tobacco product regulation. It is also important to consider how this interaction between MAO inhibition and the reinforcing actions of nicotine may be modified in populations that are particularly vulnerable to nicotine dependence. In the context of these issues, we show that the MAO-inhibiting action of cigarette smoke extract (CSE) is similar in VLNC cigarettes and cigarettes with a standard nicotine content. In addition, we present evidence that in a rodent model of schizophrenia the effect of MAO inhibition to enhance nicotine self-administration is absent, and speculate how this may relate to brain serotonin systems. These issues are relevant to the MAO-inhibiting effect of cigarette smoking and its implications to tobacco product regulation.

Roles of selected non-P450 human oxidoreductase enzymes in protective and toxic effects of chemicals: review and compilation of reactions

This is an overview of the metabolic reactions of drugs, natural products, physiological compounds, and other (general) chemicals catalyzed by flavin monooxygenase (FMO), monoamine oxidase (MAO), NAD(P)H quinone oxidoreductase (NQO), and molybdenum hydroxylase enzymes (aldehyde oxidase (AOX) and xanthine oxidoreductase (XOR)), including roles as substrates, inducers, and inhibitors of the enzymes. The metabolism and bioactivation of selected examples of each group (i.e., drugs, "general chemicals," natural products, and physiological compounds) are discussed. We identified a higher fraction of bioactivation reactions for FMO enzymes compared to other enzymes, predominately involving drugs and general chemicals. With MAO enzymes, physiological compounds predominate as substrates, and some products lead to unwanted side effects or illness. AOX and XOR enzymes are molybdenum hydroxylases that catalyze the oxidation of various heteroaromatic rings and aldehydes and the reduction of a number of different functional groups. While neither of these two enzymes contributes substantially to the metabolism of currently marketed drugs, AOX has become a frequently encountered route of metabolism among drug discovery programs in the past 10-15 years. XOR has even less of a role in the metabolism of clinical drugs and preclinical drug candidates than AOX, likely due to narrower substrate specificity.

Formation, Characterization, and Occurrence of β-Carboline Alkaloids Derived from α-Dicarbonyl Compounds and l-Tryptophan

β-Carbolines (βCs) are naturally occurring bioactive alkaloids, whereas α-dicarbonyl compounds are reactive substances generated in foods and in vivo. In this work, l-tryptophan reacted with α-dicarbonyl compounds affording new β-carbolines. Glyoxal afforded 1-hydroxymethyl-β-carboline (HME-βC) and its 3-carboxylic acid, and methylglyoxal afforded 1-(1-hydroxyethyl)-β-carboline (HET-βC) and its 3-carboxylic acid. 3-Deoxyglucosone afforded 1-(1,3,4,5-tetrahydroxypent-1-yl)-β-carboline isomers (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-β-carboline (2), and 1-(1,5-dihydroxypent-3-en-1-yl)-β-carboline (3). The formation of these βCs increased under acidic conditions and with increasing temperature. A mechanism is proposed explaining the conversion of a carbonyl into a hydroxy group based on tautomerism and cyclization to the dihydro-βC-3-COOH intermediates, which were isolated and gave the βCs. These α-dicarbonyl-derived βCs occurred in model reactions of l-tryptophan with fructose or glucose incubated under heating and can be considered as advanced glycation end products (AGEs). They were also present in foods and formed during heating processes. HET-βC appeared in processed foods, reaching up to 309 ng/g, with the highest amount found in dried tomato, fried onion, toasted bread, and Manuka honey. HME-βC was only detected in some foods with lower amounts than HET-βC. HET-βC appeared in foods as a racemic mixture of enantiomers suggesting the same mechanism of formation as the synthetized product. α-Dicarbonyl-derived βCs (HET-βC, HME-βC, and 1a/b-3) occur in foods and food processing and, therefore, they are ingested during diet.

Harmane Potentiates Nicotine Reinforcement Through MAO-A Inhibition at the Dose Related to Cigarette Smoking

Nicotine is the primary addictive component in cigarette smoke, and dopamine release induced by nicotine is considered a significant cause of persistent smoking and nicotine dependence. However, the effects of nicotine replacement therapy on smoking cessation were less effective than expected, suggesting that other non-nicotine constituents may potentiate the reinforcing effects of nicotine. Harmane is a potent, selective monoamine oxidase A (MAO-A) inhibitor found in cigarette smoke, but showed no effect on nicotine self-administration in previous studies, possibly due to the surprisingly high doses used. In the present study, we found that harmane potentiated nicotine self-administration on the fixed ration schedule at the dose related to human cigarette smoking by the synergistic effects in up-regulating genes in addiction-related pathways, and the effect was reduced at doses 10 times higher or lower than the smoking-related dose. The smoking-related dose of harmane also enhanced the increase of locomotor activity induced by nicotine, accompanied by increased dopamine basal level and dopamine release in the nucleus accumbens through MAO-A inhibition. Our findings provided new evidence for the important role of non-nicotine ingredients of tobacco products in smoking addiction.

Cigarette Smoke Extract, but Not Electronic Cigarette Aerosol Extract, Inhibits Monoamine Oxidase in vitro and Produces Greater Acute Aversive/Anhedonic Effects Than Nicotine Alone on Intracranial Self-Stimulation in Rats

Conventional tobacco cigarettes appear to have greater abuse liability than non-combusted products such as electronic cigarettes (ECs) and nicotine replacement therapy (NRT). This may be due to the higher levels of behaviorally active non-nicotine constituents [e.g., monoamine oxidase (MAO) inhibitors such as β-carbolines] in cigarette smoke (CS) compared to non-combusted products. To evaluate this hypothesis, the current studies compared the relative abuse liability of CS and EC aerosol extracts containing nicotine and a range of non-nicotine constituents to that of nicotine alone (NRT analog) using intracranial self-stimulation (ICSS) in rats. Effects of formulations on brain MAO activity in vitro and ex vivo were also studied to evaluate the potential role of MAO inhibition in the ICSS study. CS extract contained higher levels of several behaviorally active non-nicotine constituents (e.g., the β-carbolines norharmane and harmane) than EC extract. Nicotine alone reduced ICSS thresholds at a moderate nicotine dose, suggesting a reinforcement-enhancing effect that may promote abuse liability, and elevated ICSS thresholds at a high nicotine dose, suggesting an aversive/anhedonic effect that may limit abuse liability. CS extract elevated ICSS thresholds to a greater degree than nicotine alone at high nicotine doses. Effects of EC extract on ICSS did not differ from those of nicotine alone. Finally, CS extract significantly inhibited MAO-A and MAO-B activity in vitro, whereas EC extract and nicotine alone did not. None of the formulations inhibited MAO measured ex vivo. These findings indicate greater acute aversive/anhedonic effects for CS extract compared to nicotine alone, suggesting lower abuse liability. Although confirmation of our findings using other dosing regimens, preclinical addiction models, and tobacco product extracts is needed, these findings suggest that the centrally-mediated effects of MAO inhibitors and other non-nicotine constituents may not account for the greater abuse liability of cigarettes compared to non-combusted products. Nonetheless, identifying the specific constituent(s) mediating the effects of CS extracts in this study could help clarify mechanisms mediating tobacco addiction and inform FDA product standards.

Biologically Active Compounds Present in Tobacco Smoke: Potential Interactions Between Smoking and Mental Health

Tobacco dependence remains one of the major preventable causes of premature morbidity and mortality worldwide. There are well over 8,000 compounds present in tobacco and tobacco smoke, but we do not know what effect, if any, many of them have on smokers. Major interest has been on nicotine, as well as on toxic and carcinogenic effects and several major and minor components of tobacco smoke responsible for the negative health effects of smoking have been elucidated. Smokers themselves report a variety of positive effects from smoking, including effects on depression, anxiety and mental acuity. Smoking has also been shown to have protective effects in Parkinson’s Disease. Are the subjective reports of a positive effect of smoking due to nicotine, of some other components of tobacco smoke, or are they a manifestation of the relief from nicotine withdrawal symptoms that smoking provides? This mini-review summarises what is currently known about the components of tobacco smoke with potential to have positive effects on smokers.

Monoamine Oxidase Inhibition by Plant-Derived β-Carbolines; Implications for the Psychopharmacology of Tobacco and Ayahuasca

The monoamine oxidases (MAOs) are flavin-containing amine oxidoreductases responsible for metabolism of many biogenic amine molecules in the brain and peripheral tissues. Whereas serotonin is the preferred substrate of MAO-A, phenylethylamine is metabolized by MAO-B, and dopamine and tyramine are nearly ambivalent with respect to the two isozymes. β-Carboline alkaloids such as harmine, harman(e), and norharman(e) are MAO inhibitors present in many plant materials, including foodstuffs, medicinal plants, and intoxicants, notably in tobacco (Nicotiana spp.) and in Banisteriopsis caapi, a vine used in the Amazonian ayahuasca brew. The β-carbolines present in B. caapi may have effects on neurogenesis and intrinsic antidepressant properties, in addition to potentiating the bioavailability of the hallucinogen N,N-dimethyltryptamine (DMT), which is often present in admixture plants of ayahuasca such as Psychotria viridis. Tobacco also contains physiologically relevant concentrations of β-carbolines, which potentially contribute to its psychopharmacology. However, in both cases, the threshold of MAO inhibition sufficient to interact with biogenic amine neurotransmission remains to be established. An important class of antidepressant medications provoke a complete and irreversible inhibition of MAO-A/B, and such complete inhibition is almost unattainable with reversible and competitive inhibitors such as β-carbolines. However, the preclinical and clinical observations with synthetic MAO inhibitors present a background for obtaining a better understanding of the polypharmacologies of tobacco and ayahuasca. Furthermore, MAO inhibitors of diverse structures are present in a wide variety of medicinal plants, but their pharmacological relevance in many instances remains to be established.

Development and Clinical Application of Positron Emission Tomography Imaging Agents for Monoamine Oxidase B

Monoamine oxidase B (MAO-B) is a high-density protein in the brain mainly found on outer mitochondrial membranes, primarily in astroglia, but additionally in serotonergic neurons and in the substantia nigra in the midbrain. It is an enzyme that participates in the oxidative metabolism of important monoamines including dopamine, norepinephrine, benzylamine, and phenylethylamine. Elevated MAO-B density may be associated with astrogliosis and inhibiting MAO-B may reduce astrogliosis. MAO-B density is elevated in postmortem sampling of pathology for many neuropsychiatric diseases including Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and alcohol use disorder. Initial development of positron emission tomography (PET) imaging agents focused on analogs of [¹¹C]L-deprenyl, with the most commonly applied being the deuterium substituted [¹¹C]L-deprenyl-D2. This latter radiotracer was modeled with an irreversible trapping compartment reflecting its irreversible binding to MAO-B. Subsequently, [¹¹C]SL25.1188, a reversible binding MAO-B radioligand with outstanding properties including high specific binding and excellent reversibility was developed. [¹¹C]SL25.1188 PET was applied to discover a substantive elevation of MAO-B binding in the prefrontal cortex in major depressive disorder (MDD) with an effect size of more than 1.5. Longer duration of MDD was associated with greater MAO-B binding throughout most gray matter regions in the brain, suggesting progressive astrogliosis. Important applications of [¹¹C]L-deprenyl-D2 PET are detecting a 40% loss in radiotracer accumulation in cigarette smokers, and substantial occupancy of novel therapeutics like EVT301 and sembragiline. Given the number of diseases with elevations of MAO-B density and astrogliosis, and the advance of [¹¹C]SL25.1188, clinical applications of MAO-B imaging are still at an early stage.

Toward the Allelopathy of Peganum sp. and Related Chemical Constituents in Agriculture

The genus Peganum constitutes one of the perennial groups of plants of semi-arid regions across the world. It produces diverse classes of metabolites with claimed valuable pharmacological applications. Despite the key chemical and biological properties of the genus, its allelopathy or that of one of its species has not been reviewed yet. Thus, the present survey aims to report the agricultural applications of extracts, fractions, and compounds from the genus Peganum. This work was based on the available literature related to both the Peganum genus and agriculture, which were generated from available high-impact scientific engines. The plants in this genus contain a large group of secondary metabolites including phenolic compounds, terpenes, and N-containing compounds. Alkaloids, as the main components of the extracts from plants in the genus, were identified as the major active principles. The toxicity of Peganum isolates against plants and related pest organisms was also reviewed. Extract preparations from species of Peganum were listed among insecticidal and herbicidal allelochemicals used for crop protection. The review also tried to contextualize natural products in agriculture. Peganum plant extracts and fractions have showed significant potential in weed and crops management, soil health, and biopesticide production.

Harmol alleviates dimethylhydrazine induced colon cancer by downregulating Bcl2/IL-6/TNF-α expression in association with p53 mediated apoptosis

Objectives: Colorectal cancer is the world’s third most prevalent cancer. Herbal drugs are increasingly being used to treat a variety of disorders, including cancer, due to the severe adverse effects. Harmol, natural molecule containing β-carboline alkaloids, has aroused the interest of researchers due to its diverse biological functions, including anticancer properties. Methods: In this study, the chemotherapeutic effects of harmol have been investigated on HT-29 colon cancer cell line and a rat model of colon cancer. In the in vitro study the cytotoxicity assay, DAPI analysis and the flow cytometric analysis was performed to assess the anticancer efficacy of harmol in HT-29 cell. The colorectal cancer was developed in male Wistar rats through the administration of DMH followed by treatment with DSS. The rats were treated with harmol (100, 200 and 400 mg/kg) for 18 weeks. At the end of therapy, the colon tissues were assessed for ACF, in vivo antioxidant activity, histopathology, immunohistochemistry, immunofluorescence analysis and apoptosis assay. Results: The in vitro data suggested that the harmol therapy would significantly increase the percentage of early apoptosis in HT-29 cells through halting of G0/G1 phase. Furthermore, inhibition of ACF development with improved colonic abrasion and morphological features in colonic mucosal region were noted. Harmol treatment also increased the levels of antioxidants and p53 and downregulated Bcl2, IL-6 and TNF-α expression. Conclusion: These outcomes signify that harmol successfully recover colorectal carcinoma by reprogramming the p53, Bcl2, IL-6 and TNF-α pathway in rats.

Smoking and suicidal ideation among college students: Smoking expectancies as potential moderators

Objective: In the present study, we sought to establish a link between suicidal ideation (SI) and smoking in college students, determine whether psychopathology accounted for the association, and determine whether smoking expectancies were moderators. Participants: Participants (N = 607) were identified as nonsmokers, exsmokers, infrequent smokers, or daily smokers. Methods: Participants were assessed for smoking patterns, smoking expectancies, psychopathology, SI, and past suicide attempts. Results: Daily smokers had the highest level of SI. There was a dose-response relationship between smoking and SI, such that the higher the daily smoking rate, the greater the SI, even when controlling for depression, alcohol use, and drug use. Trend-level results indicated that at lower smoking rates, elevated smoking-related negative affect reduction (NAR) expectancies were associated with lower SI, while elevated NAR expectancies in combination with higher smoking rates were associated with greater SI. Conclusion: Smoking cessation programs for college students should screen for SI.

Rodent models for nicotine withdrawal

BACKGROUND

Animal models are critical to improve our understanding of the neuronal mechanisms underlying nicotine withdrawal. Nicotine dependence in rodents can be established by repeated nicotine injections, chronic nicotine infusion via osmotic minipumps, oral nicotine intake, tobacco smoke exposure, nicotine vapor exposure, and e-cigarette aerosol exposure. The time course of nicotine withdrawal symptoms associated with these methods has not been reviewed in the literature.

AIM

The goal of this review is to discuss nicotine withdrawal symptoms associated with the cessation of nicotine, tobacco smoke, nicotine vapor, and e-cigarette aerosol exposure in rats and mice. Furthermore, age and sex differences in nicotine withdrawal symptoms are reviewed.

RESULTS

Cessation of nicotine, tobacco smoke, nicotine vapor, and e-cigarette aerosol exposure leads to nicotine withdrawal symptoms such as somatic withdrawal signs, changes in locomotor activity, anxiety- and depressive-like behavior, learning and memory deficits, attention deficits, hyperalgesia, and dysphoria. These withdrawal symptoms are most pronounced within the first week after cessation of nicotine exposure. Anxiety- and depressive-like behavior, and deficits in learning and memory may persist for several months. Adolescent (4-6 weeks old) rats and mice display fewer nicotine withdrawal symptoms than adults (>8 weeks old). In adult rats and mice, females show fewer nicotine withdrawal symptoms than males. The smoking cessation drugs bupropion and varenicline reduce nicotine withdrawal symptoms in rodents.

CONCLUSION

The nicotine withdrawal symptoms that are observed in rodents are similar to those observed in humans. Tobacco smoke and e-cigarette aerosol contain chemicals and added flavors that enhance the reinforcing properties of nicotine. Therefore, more valid animal models of tobacco and e-cigarette use need to be developed by using tobacco smoke and e-cigarette aerosol exposure methods to induce dependence.

Xenobiotic transport and metabolism in the human brain

Organisms have metabolic pathways responsible for eliminating endogenous and exogenous toxicants. Generally, we associate the liver par excellence as the organ in charge of detoxifying the body; however, this process occurs in all tissues, including the brain. Due to the presence of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB), the Central Nervous System (CNS) is considered a partially isolated organ, but similar to other organs, the CNS possess xenobiotic transporters and metabolic pathways associated with the elimination of xenobiotic agents. In this review, we describe the different systems related to the detoxification of xenobiotics in the CNS, providing examples in which their association with neurodegenerative processes is suspected. The CNS detoxifying systems include carrier-mediated, active efflux and receptor-mediated transport, and detoxifying systems that include phase I and phase II enzymes, as well as those enzymes in charge of neutralizing compounds such as electrophilic agents, reactive oxygen species (ROS), and free radicals, which are products of the bioactivation of xenobiotics. Moreover, we discuss the differential expression of these systems in different regions of the CNS, showing the different detoxifying needs and the composition of each region in terms of the cell type, neurotransmitter content, and the accumulation of xenobiotics and/or reactive compounds.

Design and synthesis of β-carboline derivatives with nitrogen mustard moieties against breast cancer

To discover the promising antitumor agents, a series of β-carboline derivatives with nitrogen mustard moieties were designed and synthesized. Most target derivatives showed antiproliferative activity against MCF-7 and MDA-MB-231 cells. Among them, (1-methyl-9H-pyrido[3,4-b]indol-3-yl)methyl (S)-3-(4-(bis(2-chloroethyl)amino)phenyl)-2-formamidopropanoate possessed the most potent antiproliferative activity with IC₅₀ values of 1.79 μM and 4.96 μM, respectively, which were significantly higher than that of the parent compounds, and the efficacy was comparable to that of the positive control doxorubicin. More importantly, it showed weak cytotoxicity against human normal breast cell line MCF-10A (IC₅₀ > 20 μM), exhibiting certain selectivity. Subsequently, further mechanism exploration indicated that it induced G2/M phase cell cycle arrest and apoptosis in MDA-MB-231 cells. The DCFH-DA fluorescent probe assay and comet assay showed that this compound could cause intracellular ROS accumulation and DNA damage. In addition, it exerted potent inhibitory effect on the migration, invasion and adhesion of MDA-MB-231 cells in vitro. In short, (1-methyl-9H-pyrido[3,4-b]indol-3-yl)methyl (S)-3-(4-(bis(2-chloroethyl)amino)phenyl)-2-formamidopropanoate was considered as a promising compound for anti-breast cancer.

Identification of harmine and β-carboline analogs from a high-throughput screen of an approved drug collection; profiling as differential inhibitors of DYRK1A and monoamine oxidase A and for in vitro and in vivo anti-cancer studies

DYRK1A (dual-specificity tyrosine phosphorylation-regulated kinase 1a) is highly expressed in glioma, an aggressive brain tumor, and has been proposed as a therapeutic target for cancer. In the current study, we have used an optimized and validated time-resolved fluorescence energy transfer (TR-FRET)-based DYRK1A assay for high-throughput screening (HTS) in 384-well format. A small-scale screen of the FDA-approved Prestwick drug collection identified the β-carboline, harmine, and four related analogs as DYRK1A inhibitors. Hits were confirmed by dose response and in an orthogonal DYRK1A assay. Harmine's potential therapeutic use has been hampered by its off-target activity for monoamine oxidase A (MAO-A) which impacts multiple nervous system targets. Selectivity profiling of harmine and a broader collection of analogs allowed us to map some divergent SAR (structure-activity relationships) for the DYRK1A and MAO-A activities. The panel of harmine analogs had varying activities in vitro in glioblastoma (GBM) cell lines when tested for anti-proliferative effects using a high content imaging assay. In particular, of the identified analogs, harmol was found to have the best selectivity for DYRK1A over MAO-A and, when tested in a glioma tumor xenograft model, harmol demonstrated a better therapeutic window compared to harmine.

Occurrence, Formation from d-Fructose and 3-Deoxyglucosone, and Activity of the Carbohydrate-Derived β-Carbolines in Foods

β-Carbolines are naturally occurring bioactive alkaloids. In this work, carbohydrate-derived β-carbolines (βCs), 1-(1,3,4,5-tetrahydroxypent-1-yl)-β-carboline isomers (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-β-carboline (2), 1-(1,5-dihydroxypent-3-en-1-yl)-β-carboline (3), and 1-(1,2,3,4,5-pentahydroxypent-1-yl)-β-carboline (4) were identified and analyzed in commercial foods. The concentrations of βCs 1-4 in foods ranged from undetectable to 11.4 μg/g levels, suggesting their intake in the diet. Processed foods contained higher amounts than fresh or unprocessed foods, and the highest content was found in processed tomato and fruit products, sauces, and baked foods. βCs 1-3 were formed in foods during heating, and 1a/b were the main compounds. The formation of carbohydrate-derived βCs was studied in model reactions of tryptophan and carbohydrates. They formed in reactions of tryptophan with glucose under acidic conditions at temperatures higher than 80 °C. The formation of 1a/b was favored, but 2-3 increased at high temperatures. Noticeably, the βCs 1-3 formed in the reactions of tryptophan with fructose or sucrose, and the formation from fructose was much higher than from glucose. Thus, fructose was the main carbohydrate involved in the formation of 1-3, whereas sucrose gave these βCs after acid hydrolysis. It is shown for the first time that the mechanism of formation of βCs 1-3 occurs from the sugar intermediate 3-deoxyglucosone that reacts with tryptophan affording these carbohydrate-derived βCs. A mechanism of reaction to give βCs 1-3 is proposed that relies on the tautomerism (keto-enediol or enamine-imine) of intermediates involved in the reaction. Carbohydrate βCs 1-4 were assessed as inhibitors of monoamine oxidase (MAO), as antioxidants, and for their interaction with DNA. They were not good inhibitors of MAO-A or -B, were poor antioxidants, and did not appreciably interact with DNA.

Effects of Natural Monoamine Oxidase Inhibitors on Anxiety-Like Behavior in Zebrafish

Monoamine oxidases (MAO) are a valuable class of mitochondrial enzymes with a critical role in neuromodulation. In this study, we investigated the effect of natural MAO inhibitors on novel environment-induced anxiety by using the zebrafish novel tank test (NTT). Because zebrafish spend more time at the bottom of the tank when they are anxious, anxiolytic compounds increase the time zebrafish spend at the top of the tank and vice versa. Using this paradigm, we found that harmane, norharmane, and 1,2,3,4-tetrahydroisoquinoline (TIQ) induce anxiolytic-like effects in zebrafish, causing them to spend more time at the top of the test tank and less time at the bottom. 2,3,6-trimethyl-1,4-naphtoquinone (TMN) induced an interesting mix of both anxiolytic- and anxiogenic-like effects during the first and second halves of the test, respectively. TIQ was unique in having no observable effect on general movement. Similarly, a reference MAO inhibitor clorgyline—but not pargyline—increased the time spent at the top in a concentration-dependent manner. We also demonstrated that the brain bioavailability of these compounds are high based on the ex vivo bioavailability assay and in silico prediction models, which support the notion that the observed effects on anxiety-like behavior in zebrafish were most likely due to the direct effect of these compounds in the brain. This study is the first investigation to demonstrate the anxiolytic-like effects of MAO inhibitors on novel environment-induced anxiety in zebrafish.

Monoamine Oxidase A Inhibits Lung Adenocarcinoma Cell Proliferation by Abrogating Aerobic Glycolysis

Lung adenocarcinoma (LUAD) accounts for ~30% of all lung cancers and is one of the causes of cancer-related death worldwide. As the role of monoamine oxidase A (MAOA) in LUAD remains unclear, in this study, we examine how MAOA affects LUAD cell proliferation. Analyses of both public data and our data reveal that the expression of MAOA is downregulated in LUAD compared with non-tumor tissue. In addition, the expression of MAOA in tumors correlates with clinicopathologic features, and the expression of MAOA serves as an independent biomarker in LUAD. In addition, the overexpression of MAOA inhibits LUAD cell proliferation by inducing G1 arrest in vitro. Further mechanistic studies show that MAOA abrogates aerobic glycolysis in LUAD cells by decreasing hexokinase 2 (HK2). Finally, the expression of HK2 shows a negative correlation with MAOA in LUAD, and high HK2 predicts poor clinical outcome. In conclusion, our findings indicate that MAOA functions as a tumor suppressor in LUAD. Our results indicate that the MAOA/HK2 axis could be potential targets in LUAD therapy.

β-Carbolines as potential anticancer agents

β-Carbolines are indole alkaloids having a tricyclic pyrido[3,4-b]indole ring in their structure. Since the isolation of first β-carboline from Peganum harmala in 1841, the isolation and synthesis of various β-carboline derivatives surged in the following centuries. β-Carboline derivatives due to their widespread availability from natural sources, structural flexibility, quick reactivity and interaction with varied anticancer targets such as DNA (intercalation, groove binding, etc.), enzymes (GPX4, topoisomerases, kinases, etc.) and proteins (tubulin, ABCG2/BRCP1, etc.) have established themselves as promising lead compounds for the synthesis of various anticancer active agents. The current review covers the synthesis and isolation, anticancer activity, mechanism of action and SAR of various β-carboline containing molecules, its derivatives and congeners.

β-Carboline as a Privileged Scaffold for Multitarget Strategies in Alzheimer's Disease Therapy

The natural β-carboline alkaloids display similarities with neurotransmitters that can be favorably exploited to design bioactive and bioavailable drugs for Alzheimer's disease (AD) therapy. Several AD targets are currently and intensively being investigated, divided in different hypotheses: mainly the cholinergic, the amyloid β (Aβ), and the Tau hypotheses. To date, only symptomatic treatments are available involving acetylcholinesterase and NMDA inhibitors. On the basis of plethoric single-target structure-activity relationship studies, the β-carboline scaffold was identified as a powerful tool for fostering activity and molecular interactions with a wide range of AD-related targets. This knowledge can undoubtedly be used to design multitarget-directed ligands, a highly relevant strategy preferred in the context of multifactorial pathology with intricate etiology such as AD. In this review, we first individually discuss the AD targets of the β-carbolines, and then we focus on the multitarget strategies dedicated to the deliberate design of new efficient scaffolds.

A review on β-carboline alkaloids and their distribution in foodstuffs: A class of potential functional components or not?

Pharmacologically active β-carboline alkaloids (βCs) such as harman, norharman and some others are naturally present in plants and occur in many foodstuffs. They have a lot of pharmacological properties, including antitumor, antioxidant, anti-inflammatory and antimicrobial effects, and possess the potential for treating Alzheimer's disease, Parkinson's disease, depression and other central nervous system diseases. Dietary intake is proven to be an important source of βCs. Therefore, it is important to know the amounts of βCs that can be gotten from daily diets. This review summarizes the pharmacological activities, toxicology and formation of βCs, and gives collective information on contents of βCs in different foodstuffs.

Solid-Contact Potentiometric Sensors Based on Main-Tailored Bio-Mimics for Trace Detection of Harmine Hallucinogen in Urine Specimens

All-solid-state potentiometric sensors have attracted great attention over other types of potentiometric sensors due to their outstanding properties such as enhanced portability, simplicity of handling, affordability and flexibility. Herein, a novel solid-contact ion-selective electrode (SC-ISE) based on poly(3,4-ethylenedioxythiophene) (PEDOT) as the ion-to-electron transducer was designed and characterized for rapid detection of harmine. The harmine-sensing membrane was based on the use of synthesized imprinted bio-mimics as a selective material for this recognition. The imprinted receptors were synthesized using acrylamide (AA) and ethylene glycol dimethacrylate (EGDMA) as functional monomer and cross-linker, respectively. The polymerization process was carried out at 70 °C in the presence of dibenzoyl peroxide (DBO) as an initiator. The sensing membrane in addition to the solid-contact layer was applied to a glassy-carbon disc as an electronic conductor. All performance characteristics of the presented electrode in terms of linearity, detection limit, pH range, response time and selectivity were evaluated. The sensor revealed a wide linearity over the range 2.0 × 10⁻⁷–1.0 × 10⁻² M, with a detection limit of 0.02 µg/mL and a sensitivity slope of 59.2 ± 0.8 mV/hamine concentration decade. A 40 mM Britton–Robinson (BR) buffer solution at pH of 6 was used for all harmine measurements. The electrode showed good selectivity towards harmine over other common interfering ions, and maintained a stable electrochemical response over two weeks. After applying the validation requirements, the proposed method revealed good performance characteristics. Method precision, accuracy, bias, trueness, repeatability, reproducibility, and uncertainty were also evaluated. These analytical capabilities support the fast and direct assessment of harmine in different urine specimens. The analytical results were compared with the standard liquid chromatographic method. The results obtained demonstrated that PEDOT/PSS was a promising solid-contact ion-to-electron transducer material in the development of harmine-ISE. The electrodes manifested enhanced stability and low cost, which provides a wide number of potential applications for pharmaceutical and forensic analysis.

Harmaline potentiates morphine-induced antinociception via affecting the ventral hippocampal GABA-A receptors in mice

Morphine is one of the most effective medications for treatment of pain, but its side effects limit its use. Therefore, identification of new strategies that can enhance morphine-induced antinociception and/or reduce its side effects will help to develop therapeutic approaches for pain relief. Considering antinociceptive efficacy of harmaline and also highlighted the important role of GABA-A receptors in the pain perception, this research aimed to determine whether the ventral hippocampal (vHip) GABA-A receptors are involved in the possible harmaline-induced enhancement of morphine antinociception. To achieve this, vHip regions of adult male mice were bilaterally cannulated and pain sensitivity was measured in a tail-flick apparatus. Intraperitoneally administration of morphine (0, 2, 4 and 6 mg/kg) or harmaline (0, 1.25, 5 and 10 mg/kg) increased the percentage of maximal possible effect (%MPE) and induced antinociception. Interestingly, co-administration of sub-effective doses of harmaline (5 mg/kg) and morphine (2 mg/kg) induced antinociception. Intra-vHip microinjection of muscimol (0, 200 and 300 ng/mice), a GABA-A receptor agonist, enhanced the anti-nociceptive effects of harmaline (2.5 mg/kg)+morphine (2 mg/kg) combination. Microinjection of the same doses of muscimol into the vHip by itself did not alter tail-flick latency. Intra-vHip microinjection of bicuculline (100 ng/mouse), a GABA-A receptor antagonist, did not cause a significant change in MPE%. Bicuculline (60 and 100 ng/mouse, intra-vHip) was administered with the harmaline (5 mg/kg)+morphine (2 mg/kg), and inhibited the potentiating effect of harmaline on morphine response. These findings favor the notion that GABAergic mechanisms in the vHip facilitate harmaline-induced potentiation of morphine response in the tail-flick test in part through GABA-A receptors. These findings shall provide insights and strategies into the development of pain suppressing drugs.

Neuroinflammation in psychiatric disorders: PET imaging and promising new targets

Neuroinflammation is a multifaceted physiological and pathophysiological response of the brain to injury and disease. Given imaging findings of 18 kDa translocator protein (TSPO) and the development of radioligands for other inflammatory targets, PET imaging of neuroinflammation is at a particularly promising stage. This Review critically evaluates PET imaging results of inflammation in psychiatric disorders, including major depressive disorder, schizophrenia and psychosis disorders, substance use, and obsessive-compulsive disorder. We also consider promising new targets that can be measured in the brain, such as monoamine oxidase B, cyclooxygenase-1 and cyclooxygenase-2, colony stimulating factor 1 receptor, and the purinergic P2X7 receptor. Thus far, the most compelling TSPO imaging results have arguably been found in major depressive disorder, for which consistent increases have been observed, and in schizophrenia and psychosis, for which patients show reduced TSPO levels. This pattern highlights the importance of validating brain biomarkers of neuroinflammation for each condition separately before moving on to patient stratification and treatment monitoring trials.

β-Carbolines found in cigarette smoke elevate intracranial self-stimulation thresholds in rats

Identifying novel constituents that contribute to tobacco addiction is essential for developing more effective treatments and informing FDA regulation of tobacco products. While preclinical data indicate that monoamine oxidase (MAO) inhibitors can have abuse liability or potentiate the addiction-related effects of nicotine, most of these studies have used clinical MAO inhibitors (e.g., tranylcypromine) that are not present in cigarette smoke. The primary goal of this study was to evaluate the abuse potential of the β-carbolines harmane, norharmane, and harmine - MAO inhibitors that are found in cigarette smoke - in an intracranial self-simulation (ICSS) model in rats. A secondary goal was to evaluate the ability of norharmane to influence nicotine's acute effects on ICSS. None of the β-carbolines lowered ICSS thresholds at any dose studied when administered alone, suggesting a lack of abuse liability. Rather, all three β-carbolines produced dose-dependent elevations in ICSS thresholds, indicating aversive/anhedonic effects. Harmane and harmine also elevated ICSS response latencies, suggesting a disruption of motor function, albeit with reduced potency compared to their ICSS threshold-elevating effects. Norharmane (2.5 mg/kg) modestly attenuated the effects of nicotine on ICSS thresholds. Our findings indicate that these β-carbolines produced only aversive/anhedonic effects in an ICSS model when administered alone, and that norharmane unexpectedly attenuated nicotines acute effects on ICSS. Future work evaluating the addiction-related effects of nicotine combined with these and other MAO inhibitors present in smoke may be useful for understanding the role of MAO inhibition in tobacco addiction and informing FDA tobacco regulation.

"Tobacco Is the Chief Medicinal Plant in My Work": Therapeutic Uses of Tobacco in Peruvian Amazonian Medicine Exemplified by the Work of a Maestro Tabaquero

Introduction

Harmful usage of tobacco is a public health problem of global concern and, in many countries, the main risk factor for non-communicable diseases. Yet, in the Peruvian Amazon, the geographical region believed to be tobacco’s historical birthplace, this plant is associated with a strikingly different usage and repute: Tobacco (especially Nicotiana rustica L.) in this area is described as a potent medicinal plant, used topically or via ingestion to treat a variety of health conditions. The goal of this transdisciplinary field study was to investigate clinical applications of the tobacco plant as per Amazonian medicine exemplified in the practice of a reputed Maestro Tabaquero, an Amazonian traditional healer whose medical specialization focuses on tobacco-based treatments.

Methods

Using a transdisciplinary clinical approach, we conducted in-depth interviews with the tabaquero applying the systematizing expert interview method, in order to map modes of preparation and administration, indications, contraindications, effects, risks, adverse effects, and systemic aspects of tobacco-based remedies.

Results

The informant’s descriptions revealed refined knowledge on this plant’s therapeutic properties and scope, safety profile, and application techniques. The main indications mentioned included “problems of the mind,” of the respiratory system, parasitic illnesses (intestinal/skin), gout, and Amazonian epistemic conditions described as spiritual-energetic in nature. A liquid remedy taken orally was his most commonly used preparation, with acute/sub-acute effects involving a pronounced psychoactive component (altered state of consciousness) and physiological response (emesis, nausea). A skilled tabaquero that knows how to dose, administer, and intervene in case of adverse effects was considered imperative for safe treatment delivery.

Conclusions

To our knowledge, this is the first study employing a transdisciplinary clinical approach to examine therapeutic applications of tobacco by an Amazonian tabaquero. Our findings significantly contribute to the growing research literature on Amazonian medicine and emergent psychedelic-assisted therapies and could, in the long-term, open new treatment avenues in several domains. Forthcoming studies should assess toxicity/safety and clinical outcomes of patients receiving Amazonian tobacco-based treatment.

REM sleep loss-induced elevated noradrenaline could predispose an individual to psychosomatic disorders: a review focused on proposal for prediction, prevention, and personalized treatment

Historically and traditionally, it is known that sleep helps in maintaining healthy living. Its duration varies not only among individuals but also in the same individual depending on circumstances, suggesting it is a dynamic and personalized physiological process. It has been divided into rapid eye movement sleep (REMS) and non-REMS (NREMS). The former is unique that adult humans spend the least time in this stage, when although one is physically asleep, the brain behaves as if awake, the dream state. As NREMS is a pre-requisite for appearance of REMS, the latter can be considered a predictive readout of sleep quality and health. It plays a protective role against oxidative, stressful, and psychopathological insults. Several modern lifestyle activities compromise quality and quantity of sleep (including REMS) affecting fundamental physiological and psychopathosomatic processes in a personalized manner. REMS loss-induced elevated brain noradrenaline (NA) causes many associated symptoms, which are ameliorated by preventing NA action. Therefore, we propose that awareness about personalized sleep hygiene (including REMS) and maintaining optimum brain NA level should be of paramount significance for leading physical and mental well-being as well as healthy living. As sleep is a dynamic, multifactorial, homeostatically regulated process, for healthy living, we recommend addressing and treating sleep dysfunctions in a personalized manner by the health professionals, caregivers, family, and other supporting members in the society. We also recommend that maintaining sleep profile, optimum level of NA, and/or prevention of elevation of NA or its action in the brain must be seriously considered for ameliorating lifestyle and REMS disturbance-associated dysfunctions.

Differences in mechanisms underlying reinstatement of cigarette smoke extract- and nicotine-seeking behavior in rats

Despite extensive research, current therapies for smoking cessation are largely ineffective at maintaining abstinence for more than a year. Whereas most preclinical studies use nicotine alone, the goal of the present study was to evaluate whether inclusion of non-nicotine tobacco constituents provides better face validity for the development of new pharmacological therapies for smoking cessation. Here, we trained adult male rats to self-administer nicotine alone or cigarette smoke extract (CSE), which contains nicotine and other aqueous constituents of cigarette smoke. After stable self-administration behavior was established, animals underwent extinction training followed by drug and cue primed reinstatement testing. We show that animals that self-administered CSE had significant reinstatement in all drug and drug + cue stimulus conditions whereas animals that self-administered nicotine only showed significant reinstatement in the drug + cue conditions. AT-1001, an α3β4 nicotinic acetylcholine receptor (nAChR) functional antagonist, attenuated drug + cue-primed reinstatement of both CSE- and nicotine-seeking behavior. However, AT-1001 was less potent in blocking drug-primed reinstatement in animals that had self-administered CSE than in those that had self-administered nicotine alone. This was the case even when nicotine was used to prime reinstatement in animals that had self-administered CSE, suggesting that prior CSE exposure had altered the functional role of α3β4-containing nAChRs in drug-seeking behavior. These findings confirm the importance of non-nicotine tobacco constituents and α3β4* nAChRs in cue- and nicotine-primed craving. They also suggest that tests using CSE may be more valid models to study tobacco dependence than use of nicotine alone.

Comparison of monoamine oxidase inhibition by cigarettes and modified risk tobacco products

The adverse effects of cigarette smoking are well documented, and the two main strategies for reducing smoking prevalence are prevention of smoking initiation and promotion of smoking cessation. More recently, a third and complementary avenue, tobacco harm reduction has emerged, which is aimed to reduce the burden of smoking-related diseases. This has been enabled by the development of novel products such as electronic cigarettes (e-cigarettes) and heated tobacco products, designed to deliver nicotine with significantly reduced levels of the toxicants that are emitted by cigarettes. Several potential modified risk tobacco products (pMRTP) have been reported to emit significantly less toxicants than cigarettes and significantly reduce toxicant exposure in smokers who switch completely to such products. These are two prerequisites for pMRTPs to reduce harm and the risk of smoking-related disease. However, concerns remain regarding the addictive nature of these products. Smoking addiction is a complex phenomenon involving multiple pharmacological and non-pharmacological factors. Although the main pharmacological substance associated with smoking addiction is nicotine, accumulating evidence suggests that nicotine mostly acts as a primary reinforcer and that other factors are involved in establishing smoking addiction. Inhibition of monoamine oxidases (MAO)-mammalian flavoenzymes with a central role in neurotransmitter metabolism-has also been suggested to be involved in this process. Therefore, we aimed to comparatively investigate the ability of several types of pMRTPs and cigarette smoke (3R4F) to inhibit MAO activity. The results showed that the heated tobacco product Tobacco Heating System (THS) 2.2 and the MESH 1.1 e-cigarette possessed no MAO inhibitory activity while 3R4F significantly inhibits the levels of MAO activity (3R4F MAO-A and B; > 2 μM nicotine). Snus products have similar inhibition profiles as 3R4F but for larger nicotine concentrations (snus MAO-A; ∼68-fold, snus MAO-B; ∼23-fold higher compared to 3R4F). These observations were confirmed by analytical datasets of potential MAO inhibitors emitted by these products. In conclusion, we have demonstrated that specific pMRTPs, namely THS 2.2 and MESH 1.1, have a significantly lower MAO-inhibitory activity than 3R4F. These findings provide a basis for further investigation of the role of MAO inhibitors in cigarette addiction as well as the implications of the findings for abuse liability of pMRTPs in comparison with cigarettes.

Dysregulation of the Tryptophan Pathway Evidences Gender Differences in COPD

Increased activity of indoleamine 2,3-dioxygenase (IDO) and tryptophan hydroxylase (TPH) have been reported in individuals with chronic obstructive pulmonary disease (COPD). We therefore investigated the effect of gender stratification upon the observed levels of tryptophan metabolites in COPD. Tryptophan, serotonin, kynurenine, and kynurenic acid were quantified in serum of never-smokers (n = 39), smokers (n = 40), COPD smokers (n = 27), and COPD ex-smokers (n = 11) by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). The individual metabolite associations with lung function, blood, and bronchoalveolar lavage (BAL) immune-cell composition, as well as chemokine and cytokine levels, were investigated. Stratification by gender and smoking status revealed that the observed alterations in kynurenine and kynurenic acid, and to a lesser extent serotonin, were prominent in males, irrespective of COPD status (kynurenine p = 0.005, kynurenic acid p = 0.009, and serotonin p = 0.02). Inferred serum IDO activity and kynurenine levels decreased in smokers relative to never-smokers (p = 0.005 and p = 0.004, respectively). In contrast, inferred tryptophan hydroxylase (TPH) activity and serotonin levels showed an increase with smoking that reached significance with COPD (p = 0.01 and p = 0.01, respectively). Serum IDO activity correlated with blood CXC chemokine ligand 9 (CXCL9, p = 0.0009, r = 0.93) and chemokine (C-C motif) ligand 4 (CCL4.(p = 0.04, r = 0.73) in female COPD smokers. Conversely, serum serotonin levels correlated with BAL CD4+ T-cells (%) (p = 0.001, r = 0.92) and CD8+ T-cells (%) (p = 0.002, r = -0.90) in female COPD smokers, but not in male COPD smokers (p = 0.1, r = 0.46 and p = 0.1, r = -0.50, respectively). IDO- and TPH-mediated tryptophan metabolites showed gender-based associations in COPD, which were primarily driven by smoking status.

The effect of CA1 dopaminergic system on amnesia induced by harmane in mice

In the present study, the effects of bilateral injections of dopaminergic drugs into the hippocampal CA1 regions (intra-CA1) on harmane-induced amnesia were examined in mice. We used a single-trial step-down inhibitory avoidance task for the assessment of memory acquisition in adult male mice. Our data indicated that pre-training intra-peritoneal (i.p.) administration of harmane (12 mg/kg) impaired memory acquisition. Moreover, intra-CA1 administration of dopamine D1 receptor agonist, SKF38393 (0.25 µg/mouse), dopamine D1 receptor antagonist, SCH23390 (0.25 µg/mouse), dopamine D2 receptor agonist, quinpirole (0.125 and 0.25 µg/mouse) and dopamine D2 receptor antagonist, sulpiride (0.2 and 0.4 µg/mouse) decreased the learning of a single-trial inhibitory avoidance task. Furthermore, pre-training intra-CA1 injection of sub-threshold doses of SKF38393 (0.0625 µg/mouse) or sulpiride (0.1 µg/mouse) increased pre-training harmane (4 and 8 mg/kg, i.p.)-induced amnesia. On the other hand, pre-training intra-CA1 injection of a sub-threshold dose of SCH23390 (0.0625 µg/mouse) reversed amnesia induced by an effective dose of harmane (12 mg/kg; i.p.). In addition, Pre-training intra-CA1 injection of quinpirole (0.0625 µg/mouse) had no effect on memory impairment induced by harmane. These findings indicate the involvement of CA1 dopaminergic system on harmane-induced impairment of memory acquisition.

Neuroprotective effects of anthocyanins and its major component cyanidin-3-O-glucoside (C3G) in the central nervous system: An outlined review

Anthocyanins, a class of water soluble flavonoids extracted from plants like berries and soybean seed, have been shown to display obvious anti-oxidative, anti-inflammatory, and anti-apoptotic activities. They are recommended as a supplementation for prevention and/or treatment of disorders ranging from cardiovascular disease, metabolic syndrome, and cancer. In the central nervous system (CNS), anthocyanins and its major component cyanidin-3-O-glucoside (C3G) have been reported to produce preventive and/or therapeutic activities in a wide range of disorders, such as cerebral ischemia, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and glioblastoma. Both anthocyanins and C3G can also affect some important processes in aging, including neuronal apoptosis and death as well as learning and memory impairment. Further, the anthocyanins and C3G have been shown to prevent neuro-toxicities induced by different toxic factors, such as lipopolysaccharide, hydrogen peroxide, ethanol, kainic acid, acrolein, glutamate, and scopolamine. Mechanistic studies have shown that inhibition of oxidative stress and neuroinflammation are two critical mechanisms by which anthocyanins and C3G produce protective effects in CNS disorder prevention and/or treatment. Other mechanisms, including suppression of c-Jun N-terminal kinase (JNK) activation, amelioration of cellular degeneration, activation of the brain-derived neurotrophic factor (BDNF) signaling, and restoration of Ca²⁺ and Zn²⁺ homeostasis, may also mediate the neuroprotective effects of anthocyanins and C3G. In this review, we summarize the pharmacological effects of anthocyanins and C3G in CNS disorders as well as their possible mechanisms, aiming to get a clear insight into the role of anthocyanins in the CNS.

Pre-clinical investigations of β-carboline alkaloids as antidepressant agents: A systematic review

Depressive disorders remain a current public health problem whose prevalence has increased in the past decades. In the constant search for new therapeutic alternatives, β-carboline alkaloids have been identified as good candidates for new antidepressant drugs. In this systematic review, we summarized all pre-clinical investigations involving the use of natural or semisynthetic β-carboline in depression models. A literature search was conducted in August 2018, using PubMed, Scopus and Science Direct databases. All reports were carefully analyzed, and data extraction was conducted through standardized forms. Methodological quality assessment of in vivo studies was also performed. The entire systematic review was performed according to PRISMA statement. From a total of 373 articles, 26 met all inclusion criteria. In vitro and in vivo studies have evaluated a wide variety of β-carbolines through enzymatic and binding assays, and acute or chronic animal models. Most of the in vivo and in vitro studies is concentrated on two molecules: harman and harmine. They have been investigated in several animal models and some mechanisms of action have been proposed for their antidepressant activity. In general, β-carbolines modulate 5-HT and GABA systems, promote neurogenesis, induce neuroendocrine response and restore astrocytic function, being effective when administrated acutely or chronically in different animal models, including chronic mild stress protocols. In short, β-carbolines are multi-target antidepressant compounds and may be useful in the treatment of depressive disorders.

Wastewater-based epidemiology in low Human Development Index states: bias in consumption monitoring of illicit drugs

Wastewater-based epidemiology is a promising approach worldwide, and its application is currently being developed in non-advanced economies. This technology, based on known toxicokinetic data initially used to detect illicit drugs in well-managed and maintained local sewer networks, has been extended to assess other products such as pesticides, alcohol, flame retardants, nicotine, and other substances. This technology is also used in countries with non-advanced economies. The present review aims to support future wastewater-based epidemiology in such countries by providing toxicokinetic data for locally used narcotic drugs that are expected or known to be emerging in developed countries, outlining the excretion differences due to human polymorphism, and summarising the practical obstacles due to the coverage, maintenance efficiency, or type of local sewage network.Case study feedback from Martinique is presented as an example; the Martinique field study complies with the Organisation for Economic Co-operation and Development standards for health issues, but not with regard to population and urban dynamics.

CuBr2-Catalyzed Mild Oxidation of 3,4-Dihydro-β-Carbolines and Application in Total Synthesis of 6-Hydroxymetatacarboline D

A green chemical method for the conversion of 3,4-dihydro-β-carbolines to β-carbolines has been developed using air as the oxidant. With 15 mol % CuBr₂ as the catalyst, 3,4-dihydro-β-carbolines could be efficiently oxidized to β-carbolines in dimethyl sulfoxide at room temperature in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (or Et₃N). By applying this method, the first total synthesis of 6-hydroxymetatacarboline D was performed through 12 steps in 22% overall yield starting from l-5-hydroxy-tryptophan.

Privileged scaffolds as MAO inhibitors: Retrospect and prospects

This review aims to be a comprehensive, authoritative, critical, and readable review of general interest to the medicinal chemistry community because it focuses on the pharmacological, chemical, structural and computational aspects of diverse chemical categories as monoamine oxidase inhibitors (MAOIs). Monoamine oxidases (MAOs), namely MAO-A and MAO-B represent an enormously valuable class of neuronal enzymes embodying neurobiological origin and functions, serving as potential therapeutic target in neuronal pharmacotherapy, and hence we have coined the term "Neurozymes" which is being introduced for the first time ever. Nowadays, therapeutic attention on MAOIs engrosses two imperative categories; MAO-A inhibitors, in certain mental disorders such as depression and anxiety, and MAO-B inhibitors, in neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). The use of MAOIs declined due to some potential side effects, food and drug interactions, and introduction of other classes of drugs. However, curiosity in MAOIs is reviving and the recent developments of new generation of highly selective and reversible MAOIs, have renewed the therapeutic prospective of these compounds. The initial section of the review emphasizes on the detailed classification, structural and binding characteristics, therapeutic potential, current status and future challenges of the privileged pharmacophores. However, the chemical prospective of privileged scaffolds such as; aliphatic and aromatic amines, amides, hydrazines, azoles, diazoles, tetrazoles, indoles, azines, diazines, xanthenes, tricyclics, benzopyrones, and more interestingly natural products, along with their conclusive SARs have been discussed in the later segment of review. The last segment of the article encompasses some patents granted in the field of MAOIs, in a simplistic way.

Effects of Vernonia cinerea Compounds on Drug-metabolizing Cytochrome P450s in Human Liver Microsomes

Vernonia cinerea has been widely used in traditional medicines for various diseases and shown to aid in smoking abstinence and has anticancer properties. V. cinerea bioactive compounds, including flavonoids and hirsutinolide-type sesquiterpene lactones, have shown an inhibition effect on the nicotine-metabolizing cytochrome P450 2A6 (CYP2A6) enzyme and hirsutinolides reported suppressing cancer growth. In this study, V. cinerea ethanol extract and its bioactive compounds, including four flavonoids and four hirsutinolides, were investigated for an inhibitory effect on human liver microsomal CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, and 3A4 using cocktail inhibition assays combined with LC-MS/MS analysis. Among tested flavonoids, chrysoeriol was more potent in inhibition on CYP2A6 and CYP1A2 than other liver CYPs, with better binding efficiency toward CYP2A6 than CYP1A2 (K_i values in competitive mode of 1.93 ± 0.05 versus 3.39 ± 0.21 μM, respectively). Hirsutinolides were prominent inhibitors of CYP2A6 and CYP2D6, with IC₅₀ values of 12-23 and 15-41 μM, respectively. These hirsutinolides demonstrated time-dependent inhibition, an indication of mechanism-based inactivation, toward CYP2A6. Quantitative prediction of microsomal metabolism of these flavonoids and hirsutinolides, including half-lives and hepatic clearance rate, was examined. These findings may have implications for further in vivo studies of V. cinerea. Copyright © 2017 John Wiley & Sons, Ltd.