Radical Scavenging and Antioxidant Capacity of Serotonin

Metabolic Engineering of a Serotonin Overproducing Saccharomyces cerevisiae Strain

The EU Green Deal prioritises the transformation of the chemical industry to a more environmentally sustainable model. This involves using microorganisms, such as Saccharomyces cerevisiae, to produce molecules more sustainably through biotechnological approaches. In this study, we demonstrate an example of serotonin production using S. cerevisiae as a cell factory, along with its optimisation and upscaling. To achieve this, we introduced two heterologous genes, the combination of tryptophan decarboxylase from Clostridium sporogenes (CsTDC) and tryptamine 5-hydroxylase from Oryza sativa (OsT5H), to complete the serotonin biosynthetic pathway using L-tryptophan (L-TRP) as a precursor. By modifying ARO4 to a feedback-resistant version (ARO4*), the flux of the shikimate pathway was significantly increased and serotonin production was achieved at levels up to 120 mg/L directly from the glucose source. After a medium optimisation, a final concentration of 80 g/L glucose and 300 mg/L of nitrogen resulted in better conditions for increasing serotonin titres. Using this medium in a 1 L bioreactor fermentation resulted in approximately 250 mg/L of serotonin. A targeted metabolomic study of the bioreactor growth medium identified potential bottlenecks in the serotonin-overproducing strain and future targets for increasing its titre. We have constructed a strain of S. cerevisiae that represents the first steps towards feasible industrial production of serotonin using a sustainable and environmentally friendly approach, paving the way for the development of similar biotechnological strategies in the future.

Comparison of Protective Effects of Antidepressants Mediated by Serotonin Receptor in Aβ-Oligomer-Induced Neurotoxicity

Amyloid β-peptide (Aβ) synthesis and deposition are the primary factors underlying the pathophysiology of Alzheimer's disease (AD). Aβ oligomer (Aβo) exerts its neurotoxic effects by inducing oxidative stress and lesions by adhering to cellular membranes. Though several antidepressants have been investigated as neuroprotective agents in AD, a detailed comparison of their neuroprotection against Aβo-induced neurotoxicity is lacking. Here, we aimed to elucidate the neuroprotective effects of clinically prescribed selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and noradrenergic and specific serotonergic antidepressants at the cellular level and establish the underlying mechanisms for their potential clinical applications. Therefore, we compared the neuroprotective effects of three antidepressants, fluoxetine (Flx), duloxetine (Dlx), and mirtazapine (Mir), by their ability to prevent oxidative stress-induced cell damage, using SH-SY5Y cells, by evaluating cell viability, generation of reactive oxygen species (ROS) and mitochondrial ROS, and peroxidation of cell membrane phospholipids. These antidepressants exhibited potent antioxidant activity (Dlx > Mir > Flx) and improved cell viability. Furthermore, pretreatment with a 5-hydroxytryptamine 1A (5-HT1A) antagonist suppressed their effects, suggesting that the 5-HT1A receptor is involved in the antioxidant mechanism of the antidepressants' neuroprotection. These findings suggest the beneficial effects of antidepressant treatment in AD through the prevention of Aβ-induced oxidative stress.

Phytochemical analysis and antioxidant potential of Mondia whitei and Guibourtia tessmannii against H2O2-induced cytotoxicity in PC3 cells

The management of oxidative stress-related disorders has garnered significant interest, particularly in the exploration of medicinal plants possessing potent antioxidant activities. This study was undertaken to evaluate the antioxidant activity of Mondia whitei (MW) and Guibourtia tessmannii (GT) against H2O2-induced cytotoxicity in PC3 cells. The phytochemical composition of MW and GT was determined by GC-MS analysis. Total phenolic (TP) and total flavonoid (TF) contents were quantified by Folin Ciocalteu and AlCl3 methods, respectively. The antioxidant potential of the extracts was determined using the DPPH and ABTS+ radicals scavenging method, as well as cupric and ferric reducing capacity assay. Moreover, all phytocompounds were docked against acetylcholinesterase (AChE) and glutathione S-transferase (GST) using ArgusLab, and results were analyzed using the BIOVIA Discovery Studio Visualizer 2021 client. MW and GT comprised 20 and 22 compounds, respectively. GT exhibited higher TP and TF contents (210.70 ± 12.7; 12.61 ± 1.3 GAE/g DW) compared to MW (132.59 ± 12.59; 5.53 ± 1.3 mg of GAE/g DW). Both MW and GT demonstrated substantial antioxidant activity, with GT proving to be more effective in preventing H2O2-induced cytotoxicity. For instance, MW and GT significantly (p < .001) increased the DPPH, ABTS+, and cupric activity, compared with the H2O2 group. All compounds identified in MW and GT exhibited a strong binding affinity against AChE and GST. Drug likeness and toxicity of all phytocompounds were under the acceptable norms of Lipinski's rule. In conclusion, these plants could be effective candidates for the management/treatment of oxidative stress-related disorders.

Ndufs4 KO mice: A model to study comorbid mood disorders associated with mitochondrial dysfunction

The Ndufs4 knockout (KO) mouse is a validated and robust preclinical model of mitochondrial diseases (specifically Leigh syndrome), that displays a narrow window of relative phenotypical normality, despite its inherent mitochondrial complex I dysfunction and severe phenotype. Preclinical observations related to psychiatric comorbidities that arise in patients with mitochondrial diseases and indeed in Leigh syndrome are, however, yet to be investigated in this model. Strengthening this narrative is the fact that major depression and bipolar disorder are known to present with deficits in mitochondrial function. We therefore screened the behavioural profile of male and female Ndufs4 KO mice (relative to heterozygous; HET and wildtype; WT mice) between postnatal days 28 and 35 for locomotor, depressive- and anxiety-like alterations and linked it with selected brain biomarkers, viz. serotonin, kynurenine, and redox status in brain areas relevant to psychiatric pathologies (i.e., prefrontal cortex, hippocampus, and striatum). The Ndufs4 KO mice initially displayed depressive-like behaviour in the tail suspension test on PND31 but not on PND35 in the forced swim test. In the mirror box test, increased risk resilience was observed. Serotonin levels of KO mice, compared to HET controls, were increased on PND36, together with increased tryptophan to serotonin and kynurenine turnover. Kynurenine to kynurenic acid turnover was however decreased, while reduced versus oxidized glutathione ratio (GSH/GSSG) was increased. When considering the comorbid psychiatric traits of patients with mitochondrial disorders, this work elaborates on the neuropsychiatric profile of the Ndufs KO mouse. Secondly, despite locomotor differences, Ndufs4 KO mice present with a behavioural profile not unlike rodent models of bipolar disorder, namely variable mood states and risk-taking behaviour. The model may elucidate the bio-energetic mechanisms underlying mood disorders, especially in the presence of mitochondrial disease. Studies are however required to further validate the model's translational relevance.

Oral Treatment with Plant-Derived Exosomes Restores Redox Balance in H2O2-Treated Mice

Plant-derived exosomes (PDEs) are receiving much attention as a natural source of antioxidants. Previous research has shown that PDEs contain a series of bioactives and that their content varies depending on the fruit or vegetable source. It has also been shown that fruits and vegetables derived from organic agriculture produce more exosomes, are safer, free of toxic substances, and contain more bioactives. The aim of this study was to investigate the ability of orally administered mixes of PDE (Exocomplex^®) to restore the physiological conditions of mice treated for two weeks with hydrogen peroxide (H₂O₂), compared with mice left untreated after the period of H₂O₂ administration and mice that received only water during the experimental period. The results showed that Exocomplex^® had a high antioxidant capacity and contained a series of bioactives, including Catalase, Glutathione (GSH), Superoxide Dismutase (SOD), Ascorbic Acid, Melatonin, Phenolic compounds, and ATP. The oral administration of Exocomplex^® to the H₂O₂-treated mice re-established redox balance with reduced serum levels of both reactive oxygen species (ROS) and malondialdehyde (MDA), but also a general recovery of the homeostatic condition at the organ level, supporting the future use of PDE for health care.

Potentiating the Benefits of Melatonin through Chemical Functionalization: Possible Impact on Multifactorial Neurodegenerative Disorders

Although melatonin is an astonishing molecule, it is possible that chemistry will help in the discovery of new compounds derived from it that may exceed our expectations regarding antioxidant protection and perhaps even neuroprotection. This review briefly summarizes the significant amount of data gathered to date regarding the multiple health benefits of melatonin and related compounds. This review also highlights some of the most recent directions in the discovery of multifunctional pharmaceuticals intended to act as one-molecule multiple-target drugs with potential use in multifactorial diseases, including neurodegenerative disorders. Herein, we discuss the beneficial activities of melatonin derivatives reported to date, in addition to computational strategies to rationally design new derivatives by functionalization of the melatonin molecular framework. It is hoped that this review will promote more investigations on the subject from both experimental and theoretical perspectives.

Escitalopram Targets Oxidative Stress, Caspase-3, BDNF and MeCP2 in the Hippocampus and Frontal Cortex of a Rat Model of Depression Induced by Chronic Unpredictable Mild Stress

In recent years, escitalopram (ESC) has been suggested to have different mechanisms of action beyond its well known selective serotonin reuptake inhibition. The aim of this study is to investigate the effects of escitalopram on oxidative stress, apoptosis, brain-derived neurotrophic factor (BDNF), Methyl-CpG-binding protein 2 (MeCP2), and oligodendrocytes number in the brain of chronic unpredictable mild stress-induced depressed rats. The animals were randomised in four groups (8 in each group): control, stress, stress + ESC 5 and stress + ESC 5/10. ESC was administered for 42 days in a fixed dose (5 mg/kg b.w.) or in an up-titration regimen (21 days ESC 5 mg/kg b.w. then 21 days ESC 10 mg/kg b.w.). Sucrose preference test (SPT) and elevated plus maze (EPM) were also performed. ESC improved the percentage of sucrose preference, locomotion and anxiety. ESC5/10 reduced the oxidative damage in the hippocampus and improved the antioxidant defence in the hippocampus and frontal lobe. ESC5/10 lowered caspase 3 activity in the hippocampus. Escitalopram had a modulatory effect on BDNF and the number of oligodendrocytes in the hippocampus and frontal lobe and also improved the MeCP2 expressions. The results confirm the multiple pathways implicated in the pathogenesis of depression and suggest that escitalopram exerts an antidepressant effect via different intricate mechanisms.

Nutritional, Medicinal, and Cosmetic Value of Bioactive Compounds in Button Mushroom (Agaricus bisporus): A Review

Fungi are vital to numerous industrial and household processes, especially producing cheeses, beer, wine, and bread, and they are accountable for breaking down organic matter. The remarkable medicinal and nutritional values of the mushrooms have increased their consumption. Agaricus bisporus belongs to the Agaricaceae family, and it is a top-ranked cultivated mushroom that is well known for its edibility. A. bisporus is rich in nutrients such as carbohydrates, amino acids, fats, and minerals and has potential anticancer, antioxidant, anti-obesity, and anti-inflammation properties. The bioactive compounds extracted from this mushroom can be used for the treatment of several common human diseases including cancer, bacterial and fungal infections, diabetes, heart disorder, and skin problems. A. bisporus has opened new horizons for the world to explore mushrooms as far as their culinary and medicinal values are concerned. In recent years, tyrosinase and ergothioneine have been extracted from this mushroom, which has made this mushroom worth considering more for nutritional and medicinal purposes. To emphasize various aspects of A. bisporus, a comprehensive review highlighting the nutritional, medicinal, and cosmetic values and finding out the research gaps is presented. In this way, it would be possible to improve the quality and quantity of bioactive compounds in A. bisporus, ultimately contributing to the discovery of new drugs and the responsible mechanisms. In the present review, we summarize the latest advancements regarding the nutritional, pharmaceutical, and cosmetic properties of A. bisporus. Moreover, research gaps with future research directions are also discussed.

The therapeutic potential of diet on immune-related diseases: based on the regulation on tryptophan metabolism

Tryptophan (TRP), as an essential amino acid, plays crucial roles in maintaining immune homeostasis due to its complex metabolism pathway, including the microbial metabolism, 5-hydroxytryptamine and kynurenine pathways (KP). Metabolites from these pathways can act antioxidant and endogenous ligand of aryl hydrocarbon receptor (including microbiota metabolites: indole, indole aldehyde, indole acetic acid, indole acrylic acid, indole lactate, indole pyruvate acid, indole propionic acid, skatole, tryptamine, and indoxyl sulfate; and KP metabolites: kynurenine, kynurenic acid, 3-hydroxyanthranilic acid, xanthurenic acid, and cinnabarinic acid) for regulating immune response. In immune-related diseases, the production of pro-inflammatory cytokine activates indoleamine-2,3-dioxygenase, a rate-limiting enzyme of KP, leading to abnormal TRP metabolism in vivo. Many recent studies found that TRP metabolism could be regulated by diet, and the diet regulation on TRP metabolism could therapy related diseases. Accordingly, this review provides a critical overview of the relationships among diet, TRP metabolism and immunity with the aim to seek a treatment opportunity for immune-related diseases.

Gut dysbiosis and serotonin: intestinal 5-HT as a ubiquitous membrane permeability regulator in host tissues, organs, and the brain

The microbiota and microbiome and disruption of the gut-brain axis were linked to various metabolic, immunological, physiological, neurodevelopmental, and neuropsychiatric diseases. After a brief review of the relevant literature, we present our hypothesis that intestinal serotonin, produced by intestinal enterochromaffin cells, picked up and stored by circulating platelets, participates and has an important role in the regulation of membrane permeability in the intestine, brain, and other organs. In addition, intestinal serotonin may act as a hormone-like continuous regulatory signal for the whole body, including the brain. This regulatory signal function is mediated by platelets and is primarily dependent on and reflects the intestine’s actual health condition. This hypothesis may partially explain why gut dysbiosis could be linked to various human pathological conditions as well as neurodevelopmental and neuropsychiatric disorders.

Fluoxetine scaffold to design tandem molecular antioxidants and green catalysts

Fluoxetine finds application in the treatment of depression and mood disorders. This selective serotonin-reuptake inhibitor (SSRI) also contrasts oxidative stress by direct ROS scavenging, modulation of the endogenous antioxidant defense system, and/or enhancement of the serotonin antioxidant capacity. We synthesised some fluoxetine analogues incorporating a selenium nucleus, thus expanding its antioxidant potential by enabling a hydroperoxides-inactivating, glutathione peroxidase (GPx)-like activity. Radical scavenging and peroxidatic activity were combined in a water-soluble, drug-like, tandem antioxidant molecule. Selenofluoxetine derivatives were reacted with H₂O₂ in water, and the mechanistic details of the reaction were unravelled combining nuclear magnetic resonance (NMR), electrospray ionisation-mass spectrometry (ESI-MS) and quantum chemistry calculations. The observed oxidation–elimination process led to the formation of seleninic acid and cinnamylamine in a trans-selective manner. This mechanism is likely to be extended to other substrates for the preparation of unsaturated cinnamylamines.

We modified fluoxetine by incorporating a selenium nucleus enabling a hydroperoxide-inactivating, glutathione peroxidase (GPx)-like activity and paving the way for its use as green catalyst.

Major Depressive Disorder and Oxidative Stress: In Silico Investigation of Fluoxetine Activity against ROS

Major depressive disorder is a psychiatric disease having approximately a 20% lifetime prevalence in adults in the United States (U.S.), as reported by Hasin et al. in JAMA Psichiatry 2018 75, 336–346. Symptoms include low mood, anhedonia, decreased energy, alteration in appetite and weight, irritability, sleep disturbances, and cognitive deficits. Comorbidity is frequent, and patients show decreased social functioning and a high mortality rate. Environmental and genetic factors favor the development of depression, but the mechanisms by which stress negatively impacts on the brain are still not fully understood. Several recent works, mainly published during the last five years, aim at investigating the correlation between treatment with fluoxetine, a non-tricyclic antidepressant drug, and the amelioration of oxidative stress. In this work, the antioxidant activity of fluoxetine was investigated using a computational protocol based on the density functional theory approach. Particularly, the scavenging of five radicals (HO•, HOO•, CH3OO•, CH2=CHOO•, and CH3O•) was considered, focusing on hydrogen atom transfer (HAT) and radical adduct formation (RAF) mechanisms. Thermodynamic as well as kinetic aspects are discussed, and, for completeness, two metabolites of fluoxetine and serotonin, whose extracellular concentration is enhanced by fluoxetine, are included in our analysis. Indeed, fluoxetine may act as a radical scavenger, and exhibits selectivity for HO• and CH3O•, but is inefficient toward peroxyl radicals. In contrast, the radical scavenging efficiency of serotonin, which has been demonstrated in vitro, is significant, and this supports the idea of an indirect antioxidant efficiency of fluoxetine.

Antioxidant and Membrane Binding Properties of Serotonin Protect Lipids from Oxidation

Serotonin (5-hydroxytryptamine, 5-HT) is a well-known neurotransmitter that is involved in a growing number of functions in peripheral tissues. Recent studies have shown nonpharmacological functions of 5-HT linked to its chemical properties. Indeed, it was reported that 5-HT may, on the one hand, bind lipid membranes and, on the other hand, protect red blood cells through a mechanism independent of its specific receptors. To better understand these underevaluated properties of 5-HT, we combined biochemical, biophysical, and molecular dynamics simulations approaches to characterize, at the molecular level, the antioxidant capacity of 5-HT and its interaction with lipid membranes. To do so, 5-HT was added to red blood cells and lipid membranes bearing different degrees of unsaturation. Our results demonstrate that 5-HT acts as a potent antioxidant and binds with a superior affinity to lipids with unsaturation on both alkyl chains. We show that 5-HT locates at the hydrophobic-hydrophilic interface, below the glycerol group. This interfacial location is stabilized by hydrogen bonds between the 5-HT hydroxyl group and lipid headgroups and allows 5-HT to intercept reactive oxygen species, preventing membrane oxidation. Experimental and molecular dynamics simulations using membrane enriched with oxidized lipids converge to further reveal that 5-HT contributes to the termination of lipid peroxidation by direct interaction with active groups of these lipids and could also contribute to limit the production of new radicals. Taken together, our results identify 5-HT as a potent inhibitor of lipid peroxidation and offer a different perspective on the role of this pleiotropic molecule.

Phenolic Melatonin-Related Compounds: Their Role as Chemical Protectors against Oxidative Stress

There is currently no doubt about the serious threat that oxidative stress (OS) poses to human health. Therefore, a crucial strategy to maintain a good health status is to identify molecules capable of offering protection against OS through chemical routes. Based on the known efficiency of the phenolic and melatonin (MLT) families of compounds as antioxidants, it is logical to assume that phenolic MLT-related compounds should be (at least) equally efficient. Unfortunately, they have been less investigated than phenols, MLT and its non-phenolic metabolites in this context. The evidence reviewed here strongly suggests that MLT phenolic derivatives can act as both primary and secondary antioxidants, exerting their protection through diverse chemical routes. They all seem to be better free radical scavengers than MLT and Trolox, while some of them also surpass ascorbic acid and resveratrol. However, there are still many aspects that deserve further investigations for this kind of compounds.

Synthesis and determination of some biological activities of novel 2,4-dinitrophenyl derivatives

The antioxidant and radical scavenging activities of the synthesized compounds 3, 5, and 6 were determined by various in vitro assays such as 2,2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid radical (ABTS(·+) ) scavenging, ferric ion (Fe(3+) ) reducing power and ferrous ion (Fe(2+) ) chelating activities. Moreover, these activities were compared to those of standard antioxidants such as butylated hydroxyanisole, butylated hydroxytoluene, and trolox. The results showed that the new compounds (3, 5, and 6) had potential antioxidant activity. Besides, inhibition of the two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II with some nitrobenzene compounds was investigated. Compounds 1-6 showed Ki values in the range of 4.88-193.4 µM and 5.295-54.75 µM for hCA I and hCA II, respectively.

Fe(3+)-Fe(2+) transformation method: an important antioxidant assay

If we look at the multitude of varied and interesting reaction that constitute biochemistry and bioorganic chemistry, it is possible to classify a great many as either oxidation or reduction reactions. The reducing agent transfers electrons to another substance and is thus it oxidized. And, because it gives electrons, it is also called an electron donor. Electron donors can also form charge transfer complexes with electron acceptors. Reductants in biochemistry are very diverse. For example ferric ions (Fe(3+)) are good reducing agents. Also, different bioanalytical reduction methods are available such as Fe(3+)-ferrous ions (Fe(2+)) reduction method, ferric reducing antioxidant power reducing assay. In this section, Fe(3+)-Fe(2+) transformation will be discussed. Recently there has been growing interest in research into the role of plant-derived antioxidants in food and human health. The beneficial influence of many foodstuffs and beverages including fruits, vegetables, tea, coffee, and cacao on human health has been recently recognized to originate from their antioxidant activity. For this purpose, the most commonly method used in vitro determination of reducing capacity of pure food constituents or plant extracts is Fe(3+) reducing ability. This commonly used reducing power method is reviewed and presented in this study. Also, the general chemistry underlying this assay was clarified. Hence, this overview provides a basis and rationale for developing standardized antioxidant capacity methods for the food, nutraceutical, and dietary supplement industries. In addition, the most important advantages of this method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of Fe(3+)-Fe(2+) transformation assay are outlined and critically discussed.