2-Phenylethylamine, a constituent of chocolate and wine, causes mitochondrial complex-I inhibition, generation of hydroxyl radicals and depletion of striatal biogenic amines leading to psycho-motor dysfunctions in Balb/c mice

Modulating autism spectrum disorder pathophysiology using a trace amine-focused approach: targeting the gut

Autism spectrum disorder (ASD) affects approximately 1% of the population directly, but also a much higher proportion (family and caregivers) indirectly. Although ASD is characterized by high prevalence of anxiety and poor gastrointestinal health, current treatment strategies are mainly focused on neurological symptomatic treatment, with little to no attention to gut health. Furthermore, many psychiatric drugs used for management of secondary neurological symptoms, are known to exacerbate gut health issues and neurological dysregulation across the gut-brain axis.Trace amines are neurotransmitter-like substances synthesized endogenously in the human brain - in trace amounts - but also in high abundance by the microbiome. Emerging evidence suggests dysregulation of the trace amine system in ASD. Since trace aminergic signalling is central to regulatory system homeostasis, we hypothesize targeting this system in the ASD context. Given the various sources of trace amines, we suggest that normalization of functional dysbiosis in terms of trace aminergic signalling - rather than microbial compositional dysbiosis - should be a focus in medicines development. In addition, a holistic consideration including also other factors at play in determining trace aminergic signalling outcome - such as receptor binding, enzymatic role players, etc. - is required to fully elucidate and therapeutically modify the pathophysiology of regulatory systems implicated in ASD.This review firstly provides a brief overview of trace amine dysregulation in ASD for context. Secondly, we formulate our hypothesis on how this may therapeutically address symptomology, with consideration of cellular and molecular mechanism interplay across the gut-brain axis. Finally, we provide a critical assessment of advances in therapeutics development and drug re-purposing, gaps in knowledge and priorities for medicines development going forward.

Transition metal ions and neurotransmitters: coordination chemistry and implications for neurodegeneration

Neurodegeneration is characterized by a disturbance in neurotransmitter-mediated signaling pathways. Recent studies have highlighted the significant role of transition metal ions, including Cu(i/ii), Zn(ii), and Fe(ii/iii), in neurotransmission, thereby making the coordination chemistry of neurotransmitters a growing field of interest in understanding signal dysfunction. This review outlines the physiological functions of transition metal ions and neurotransmitters, with the metal-binding properties of small molecule-based neurotransmitters and neuropeptides. Additionally, we discuss the structural and conformational changes of neurotransmitters induced by redox-active metal ions, such as Cu(i/ii) and Fe(ii/iii), and briefly describe the outcomes arising from their oxidation, polymerization, and aggregation. These observations have important implications for neurodegeneration and emphasize the need for further research to develop potential therapeutic strategies.

Phenethylamine in chlorella alleviates high-fat diet-induced mouse liver damage by regulating generation of methylglyoxal

This study examined the effects of oral administration of water extract of chlorella (WEC) (100 mg/kg bodyweight) and phenethylamine (10 μg/kg bodyweight) on high-fat diet (HFD)-induced liver damage in mice. Phenethylamine significantly mitigated HFD-induced lipid oxidation (generation of malondialdehyde) and liver damage without markedly decreasing hepatic lipid accumulation. WEC exerted similar effects although with decreased efficacy. In addition, WEC and phenethylamine decreased the methylglyoxal levels and increased the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) protein levels in the liver. Methylglyoxal is generated from substrates of GAPDH, dihydroxyacetone phosphate and glyceraldehyde 3-phosphate. These facts indicate that methylglyoxal triggers oxidation of accumulated lipid, which generates malondialdehyde and consequently induces liver damage. Suppression of generation of toxic aldehydes by WEC and phenethylamine was also confirmed by maintaining hepatic cysteine, highly reactive to aldehydes. Thus, trace amounts of phenethylamine alleviate HFD-induced liver damage by regulating methylglyoxal via increase of GAPDH.

Foods with Potential Prooxidant and Antioxidant Effects Involved in Parkinson's Disease

Oxidative stress plays a fundamental role in the pathogenesis of Parkinson's disease (PD). Oxidative stress appears to be responsible for the gradual dysfunction that manifests via numerous cellular pathways throughout PD progression. This review will describe the prooxidant effect of excessive consumption of processed food. Processed meat can affect health due to its high sodium content, advanced lipid oxidation end-products, cholesterol, and free fatty acids. During cooking, lipids can react with proteins to form advanced end-products of lipid oxidation. Excessive consumption of different types of carbohydrates is a risk factor for PD. The antioxidant effects of some foods in the regular diet provide an inconclusive interpretation of the environment's mechanisms with the modulation of oxidation stress-induced PD. Some antioxidant molecules are known whose primary mechanism is the neuroprotective effect. The melatonin mechanism consists of neutralizing reactive oxygen species (ROS) and inducing antioxidant enzyme's expression and activity. N-acetylcysteine protects against the development of PD by restoring levels of brain glutathione. The balanced administration of vitamin B3, ascorbic acid, vitamin D and the intake of caffeine every day seem beneficial for brain health in PD. Excessive chocolate intake could have adverse effects in PD patients. The findings reported to date do not provide clear benefits for a possible efficient therapeutic intervention by consuming the nutrients that are consumed regularly.

The biogenic amine tryptamine, unlike β-phenylethylamine, shows in vitro cytotoxicity at concentrations that have been found in foods

β-phenylethylamine and tryptamine are biogenic amines (BA) often found in foods. In general, BA are assumed to be toxic and their accumulation in food is not recommended. However, present knowledge regarding the toxicity of β-phenylethylamine and tryptamine is limited; more information is needed if qualitative and quantitative risk assessments of foods are to be successfully conducted. This study describes a real-time analysis of β-phenylethylamine and tryptamine toxicity on a human intestinal epithelial cell line. Both BA caused cell necrosis and apoptosis, although the former was the main mode of action of β-phenylethylamine, and the latter the main mode of action of tryptamine. Only tryptamine was cytotoxic at concentrations found in BA-rich foods. The results presented in this work may contribute to establish legal limits for β-phenylethylamine and tryptamine in food.

Photodelivery of β-phenylethylamines

Photodelivery of amino neurotransmitters.

NQO1: A target for the treatment of cancer and neurological diseases, and a model to understand loss of function disease mechanisms

NAD(P)H quinone oxidoreductase 1 (NQO1) is a multi-functional protein that catalyses the reduction of quinones (and other molecules), thus playing roles in xenobiotic detoxification and redox balance, and also has roles in stabilising apoptosis regulators such as p53. The structure and enzymology of NQO1 is well-characterised, showing a substituted enzyme mechanism in which NAD(P)H binds first and reduces an FAD cofactor in the active site, assisted by a charge relay system involving Tyr-155 and His-161. Protein dynamics play important role in physio-pathological aspects of this protein. NQO1 is a good target to treat cancer due to its overexpression in cancer cells. A polymorphic form of NQO1 (p.P187S) is associated with increased cancer risk and certain neurological disorders (such as multiple sclerosis and Alzheimer´s disease), possibly due to its roles in the antioxidant defence. p.P187S has greatly reduced FAD affinity and stability, due to destabilization of the flavin binding site and the C-terminal domain, which leading to reduced activity and enhanced degradation. Suppressor mutations partially restore the activity of p.P187S by local stabilization of these regions, and showing long-range allosteric communication within the protein. Consequently, the correction of NQO1 misfolding by pharmacological chaperones is a viable strategy, which may be useful to treat cancer and some neurological conditions, targeting structural spots linked to specific disease-mechanisms. Thus, NQO1 emerges as a good model to investigate loss of function mechanisms in genetic diseases as well as to improve strategies to discriminate between neutral and pathogenic variants in genome-wide sequencing studies.

Structural features of monohydrated 2-(4-fluorophenyl)ethylamine: a combined spectroscopic and computational study

A jet-cooled singly hydrated 2-(4-fluorophenyl)ethylamine (4-FPEA-H₂O) cluster has been studied by ionization-loss stimulated Raman spectroscopy of the 4-FPEA photofragment and density functional calculations of the parent. Comparison of the measured spectrum of the photofragment to computed scaled harmonic Raman spectra of different conformers of the 4-FPEA-H₂O cluster, at the M06-2X/6-311++G(d,p) level of theory, allowed determination of the calculated spectrum that best fits the experimental one. The correlation between them was further supported by the stability of the cluster, as revealed from the calculated energies of the fully optimized geometries of the possible different clusters in the ground electronic state. The corresponding structure consists of a water molecule, which is hydrogen-bonded to the nitrogen lone pair of the folded ethylamino side chain in the most stable gauche conformer of 4-FPEA. The presence of the hydrogen bond and other bonding and non-bonding interactions was also tested by atoms in molecules and noncovalent interaction analyses. The former approach showed no critical points in electron density, while the latter revealed regional topologies of reduced density gradients, indicating the formation of this hydrogen-bond and other attractive and repulsive interactions. The monohydration of 4-FPEA provides an insight into the intra- and inter-molecular interactions that play a role in stabilizing the cluster.

A highly reproducible mice model of chronic kidney disease: Evidences of behavioural abnormalities and blood-brain barrier disruption

AIMS

In the present study, a novel mice model of chronic kidney disease (CKD) was developed, and psycho-motor behavioural abnormalities, blood-brain barrier (BBB) integrity and brain histology were studied.

MAIN METHODS

Swiss albino female mice were given high adenine diet (0.3% w/w mixed with feed) for 4weeks. Serum urea and creatinine levels and renal histological studies were performed to validate the model. Psycho-motor behavioural abnormalities and neurological severity were studied. BBB integrity was assessed using Evans blue extravasation method. Nissl staining was performed to see possible morphological aberrations in brain.

KEY FINDINGS

There was a significant increase in serum urea and creatinine levels in mice given high adenine diet, and the mice had abnormal kidney morphology. Deposition of adenine and 2,8-dihydroxyadenine crystals, and increased collagen deposits in the renal tissues were found, which validate induction of CKD in the mice. Motor behavioural abnormalities, depression-like and anxiolytic behaviour and increase in neurological severity were prevalent in mice with CKD. Evans Blue dye extravasation was found to occur in the brain, which signifies disruption of BBB. However, Nissl staining did not reveal any morphological aberration in brain tissue.

SIGNIFICANCE

The present study puts forward a highly reproducible mice model of CKD validated with serum parameters and renal histopathological changes. The mice showed psycho-motor behavioural abnormalities and BBB disruption. It is a convenient model to study the disease pathology, and understanding the associated disorders, and their therapeutic interventions.

The emerging roles of human trace amines and human trace amine-associated receptors (hTAARs) in central nervous system

Human trace amines (TAs) are endogenous compounds, previously almost ignored in human pathology for many reasons (difficulty of their measurement in biological fluids, unknown receptors for elusive amines), are now considered to play a significant role in synaptic transmission within the central nervous system (CNS) acting as neuromodulators. The recent discovery of a novel family of G-protein-coupled receptors (GPCRs) that includes individual members that are highly specific for TAs indicates a potential role for TAs as vertebrate neurotransmitters or neuromodulators, although the majority of these GPCRs so far have not been demonstrated to be activated by TAs. Human trace amine receptors (including TAAR1 TAAR2 TAAR5 TAAR6 TAAR8 TAAR9) are expressed in the brain and play significant physiological and neuropathological roles by activation of trace amines. We herein discuss the recent findings that provide insights into the functional roles of human trace amines (including P-Octopamine, β phenylethylamine, Tryptamine, Tyramine, Synephrine, 3-Iodothyronamine, 3-Methoxytyramine, N-Methyltyramine, N-Methylphenethylamine) in brain. Furthermore, we discuss the known functions of human trace amine receptors in brain.

Nimodipine, an L-type calcium channel blocker attenuates mitochondrial dysfunctions to protect against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinsonism in mice

Parkinson's disease (PD), the most common progressive neurodegenerative movement disorder, results from loss of dopaminergic neurons of substantia nigra pars compacta. These neurons exhibit Cav1.3 channel-dependent pacemaking activity. Epidemiological studies suggest reduced risk for PD in population under long-term antihypertensive therapy with L-type calcium channel antagonists. These prompted us to investigate nimodipine, an L-type calcium channel blocker for neuroprotective effect in cellular and animal models of PD. Nimodipine (0.1-10 μM) significantly attenuated 1-methyl-4-phenyl pyridinium ion-induced loss in mitochondrial morphology, mitochondrial membrane potential and increases in intracellular calcium levels in SH-SY5Y neuroblastoma cell line as measured respectively employing Mitotracker green staining, TMRM, and Fura-2 fluorescence, but only a feeble neuroprotective effect was observed in MTT assay. Nimodipine dose-dependently reduced 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian syndromes (akinesia and catalepsy) and loss in swimming ability in Balb/c mice. It attenuated MPTP-induced loss of dopaminergic tyrosine hydroxylase positive neurons in substantia nigra, improved mitochondrial oxygen consumption and inhibited reactive oxygen species production in the striatal mitochondria measured using dichlorodihydrofluorescein fluorescence, but failed to block striatal dopamine depletion. These results point to an involvement of L-type calcium channels in MPTP-induced dopaminergic neuronal death in experimental parkinsonism and more importantly provide evidences for nimodipine to improve mitochondrial integrity and function.

Chronic exposure of homocysteine in mice contributes to dopamine loss by enhancing oxidative stress in nigrostriatum and produces behavioral phenotypes of Parkinson's disease

Increased homocysteine (Hcy) level has been implicated as an independent risk factor for various neurological disorders, including Parkinson’s disease (PD). Hcy has been reported to cause dopaminergic neuronal loss in rodents and causes the behavioral abnormalities. This study is an attempt to investigate molecular mechanisms underlying Hcy-induced dopaminergic neurotoxicity after its chronic systemic administration. Male Swiss albino mice were injected with different doses of Hcy (100 and 250 mg/kg; intraperitoneal) for 60 days. Animals subjected to higher doses of Hcy, but not the lower dose, produces motor behavioral abnormalities with significant dopamine depletion in the striatum. Significant inhibition of mitochondrial complex-I activity in nigra with enhanced activity of antioxidant enzymes in the nigrostriatum have highlighted the involvement of Hcy-induced oxidative stress. While, chronic exposure to Hcy neither significantly alters the nigrostriatal glutathione level nor it causes any visible change in tyrosine hydroxylase-immunoreactivity of dopaminergic neurons. The finding set us to hypothesize that the mild oxidative stress due to prolonged Hcy exposure to mice is conducive to striatal dopamine depletion leading to behavioral abnormalities similar to that observed in PD.

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Chronic intraperitoneal Hcy injection causes parkinsonian like motor abnormalities.

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Hcy injection caused complex-I inhibition in nigra and striatal dopamine depletion.

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Hcy injection caused enhanced activity of antioxidant enzymes in nigrostriatum.

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Hcy-induced mild oxidative stress is not sufficient to alter GSH and TH.

The cytotoxicity of the α1-adrenoceptor antagonist prazosin is linked to an endocytotic mechanism equivalent to transport-P

Since the α1-adrenergic antagonist prazosin (PRZ) was introduced into medicine as a treatment for hypertension and benign prostate hyperplasia, several studies have shown that PRZ induces apoptosis in various cell types and interferes with endocytotic trafficking. Because PRZ is also able to induce apoptosis in malignant cells, its cytotoxicity is a focus of interest in cancer research. Besides inducing apoptosis, PRZ was shown to serve as a substrate for an amine uptake mechanism originally discovered in neurones called transport-P. In line with our hypothesis that transport-P is an endocytotic mechanism also present in non-neuronal tissue and linked to the cytotoxicity of PRZ, we tested the uptake of QAPB, a fluorescent derivative of PRZ, in cancer cell lines in the presence of inhibitors of transport-P and endocytosis. Early endosomes and lysosomes were visualised by expression of RAB5-RFP and LAMP1-RFP, respectively; growth and viability of cells in the presence of PRZ and uptake inhibitors were also tested. Cancer cells showed co-localisation of QAPB with RAB5 and LAMP1 positive vesicles as well as tubulation of lysosomes. The uptake of QAPB was sensitive to transport-P inhibitors bafilomycin A1 (inhibits v-ATPase) and the antidepressant desipramine. Endocytosis inhibitors pitstop(®) 2 (general inhibitor of endocytosis), dynasore (dynamin inhibitor) and methyl-β-cyclodextrin (cholesterol chelator) inhibited the uptake of QAPB. Bafilomycin A1 and methyl-β-cyclodextrin but not desipramine were able to preserve growth and viability of cells in the presence of PRZ. In summary, we confirmed the hypothesis that the cellular uptake of QAPB/PRZ represents an endocytotic mechanism equivalent to transport-P. Endocytosis of QAPB/PRZ depends on a proton gradient, dynamin and cholesterol, and results in reorganisation of the LAMP1 positive endolysosomal system. Finally, the link seen between the cellular uptake of PRZ and cell death implies a still unknown pro-apoptotic membrane protein with affinity towards PRZ.

Heterobimetallic metallation studies of N,N-dimethylphenylethylamine (DMPEA): benzylic C–H bond cleavage/dimethylamino capture or intact DMPEA complex

The cleave and capture capacity of various bimetallic amido–alkyl mixtures is illustrated through reaction with the deprotonation sensitiveN,N-dimethylphenylethylamine.

β-phenethylamine--a phenylalanine derivative in brain--contributes to oxidative stress by inhibiting mitochondrial complexes and DT-diaphorase: an in silico study

AIM

Till date, the mode of action of β-PEA on neurons is not well illustrated. We tested the hypothesis that β-PEA has the ability to cause oxidative stress by inhibiting the antioxidant enzyme DT-diaphorase and mitochondrial complexes (Complex-I and complex-III).

METHODS

Using molecular docking as a tool, we here studied and compared the inhibitory capacity of β-PEA on DT-diaphorase and mitochondrial complexes. Three-dimensional structures of mitochondrial complexes and DT-diaphorase and their ligands were downloaded from the respective data banks, and free energy of binding (docking scores) were determined.

RESULTS

The present finding demonstrated for the first time that β-PEA potentiates reactive oxygen species generation by inhibiting the antioxidant enzyme DT-diaphorase, in addition to the mitochondrial complex-I and complex-III.

CONCLUSION

As lowering of cellular antioxidant molecules is evident in many neurodegenerative disorders, β-PEA-induced lowering of DT-diaphorase activity may have the capability to cause neurodegeneration, which may be potentiated by its ability to inhibit mitochondrial complexes. Thus, β-PEA-due to its cumulative actions-may be more potent in causing neurodegeneration as compared to other endogenous neurotoxins.

Contribution of β-phenethylamine, a component of chocolate and wine, to dopaminergic neurodegeneration: implications for the pathogenesis of Parkinson's disease

While the cause of dopaminergic neuronal cell death in Parkinson's disease (PD) is not yet understood, many endogenous molecules have been implicated in its pathogenesis. β-phenethylamine (β-PEA), a component of various food items including chocolate and wine, is an endogenous molecule produced from phenylalanine in the brain. It has been reported recently that long-term administration of β-PEA in rodents causes neurochemical and behavioral alterations similar to that produced by parkinsonian neurotoxins. The toxicity of β-PEA has been linked to the production of hydroxyl radical ((·)OH) and the generation of oxidative stress in dopaminergic areas of the brain, and this may be mediated by inhibition of mitochondrial complex-I. Another significant observation is that administration of β-PEA to rodents reduces striatal dopamine content and induces movement disorders similar to those of parkinsonian rodents. However, no reports are available on the extent of dopaminergic neuronal cell death after administration of β-PEA. Based on the literature, we set out to establish β-PEA as an endogenous molecule that potentially contributes to the progressive development of PD. The sequence of molecular events that could be responsible for dopaminergic neuronal cell death in PD by consumption of β-PEA-containing foods is proposed here. Thus, long-term over-consumption of food items containing β-PEA could be a neurological risk factor having significant pathological consequences.

Monoamine oxidases in development

Monoamine oxidases (MAOs) are flavoproteins of the outer mitochondrial membrane that catalyze the oxidative deamination of biogenic and xenobiotic amines. In mammals there are two isoforms (MAO-A and MAO-B) that can be distinguished on the basis of their substrate specificity and their sensitivity towards specific inhibitors. Both isoforms are expressed in most tissues, but their expression in the central nervous system and their ability to metabolize monoaminergic neurotransmitters have focused MAO research on the functionality of the mature brain. MAO activities have been related to neurodegenerative diseases as well as to neurological and psychiatric disorders. More recently evidence has been accumulating indicating that MAO isoforms are expressed not only in adult mammals, but also before birth, and that defective MAO expression induces developmental abnormalities in particular of the brain. This review is aimed at summarizing and critically evaluating the new findings on the developmental functions of MAO isoforms during embryogenesis.