Quercetin can act either as an inhibitor or an inducer of the mitochondrial permeability transition pore: A demonstration of the ambivalent redox character of polyphenols

Pro-Oxidant Influence of Quercetin Supplementation in Saccharomyces cerevisiae

How could quercetin exert a pro-survival phenotype (antioxidant) and simultaneously be toxic for eukaryotic cells? The redox capacity of quercetin may explain its antioxidant and toxic effects, based on the idea that quercetin impairs the electron transport chain, affecting ATP production and forming quercetin-derived free radicals. Herein, we provide evidence that quercetin supplementation: (1) depolarizes the mitochondrial membrane and augments the ADP/ATP ratio; (2) increases superoxide anion cellular levels; (3) changes the cellular response to H2O2 challenge associated with the antioxidant cellular response; and (4) sensitizes the cellular response to lipoperoxidation challenge. These events suggest that the quercetin pro-oxidant effect is related to mitochondrial respiration dysfunction and could induce cellular antioxidant response.

Phytochemicals Modulate Biosynthesis and Function of Serotonin, Dopamine, and Norepinephrine for Treatment of Monoamine Neurotransmission-Related Psychiatric Diseases

Serotonin (5-HT), dopamine (DA), and norepinephrine (NE) are key monoamine neurotransmitters regulating behaviors, mood, and cognition. 5-HT affects early brain development, and its dysfunction induces brain vulnerability to stress, raising the risk of depression, anxiety, and autism in adulthood. These neurotransmitters are synthesized from tryptophan and tyrosine via hydroxylation and decarboxylation, and are metabolized by monoamine oxidase (MAO). This review aims to summarize the current findings on the role of dietary phytochemicals in modulating monoamine neurotransmitter biosynthesis, metabolism, and function, with an emphasis on their potential therapeutic applications in neuropsychiatric disorders. Phytochemicals exert antioxidant, neurotrophic, and neurohormonal activities, regulate gene expression, and induce epigenetic modifications. Phytoestrogens activate the estrogen receptors or estrogen-responsive elements of the promoter of target genes, enhance transcription of tryptophan hydroxylase and tyrosine hydroxylase, while inhibiting that of MAO. These compounds also influence the interaction between genetic and environmental factors, potentially reversing dysregulated neurotransmission and the brain architecture associated with neuropsychiatric conditions. Despite promising preclinical findings, clinical applications of phytochemicals remain challenging. Advances in nanotechnology and targeted delivery systems offer potential solutions to enhance clinical efficacy. This review discusses mechanisms, challenges, and strategies, underscoring the need for further research to advance phytochemical-based interventions for neuropsychiatric diseases.

Functional activity and morphology of isolated rat cardiac mitochondria under calcium overload. Effect of naringin

The function of mitochondria as a regulator of myocyte calcium homeostasis has been extensively discussed. The aim of the present work was further clarification of the details of modulation of the functional activity of rat cardiac mitochondria by exogenous Ca2+ ions either in the absence or in the presence of the plant flavonoid naringin. Low free Ca2+ concentrations (40-250 nM) effectively inhibited the respiratory activity of heart mitochondria, remaining unaffected the efficacy of oxygen consumption. In the presence of high exogenous Ca2+ ion concentrations (Ca2+ free was 550 µM), we observed a dramatic increase in mitochondrial heterogeneity in size and electron density, which was related to calcium-induced opening of the mitochondrial permeability transition pores (MPTP) and membrane depolarization (Ca2+free ions were from 150 to 750 µM). Naringin partially prevented Ca2+-induced cardiac mitochondrial morphological transformations (200 µM) and dose-dependently inhibited the respiratory activity of mitochondria (10-75 µM) in the absence or in the presence of calcium ions. Our data suggest that naringin (75 µM) promoted membrane potential dissipation, diminishing the potential-dependent accumulation of calcium ions by mitochondria and inhibiting calcium-induced MPTP formation. The modulating effect of the flavonoid on Ca2+-induced mitochondria alterations may be attributed to the weak-acidic nature of the flavonoid and its protonophoric/ionophoric properties. Our results show that the sensitivity of rat heart mitochondria to Ca2+ ions was much lower in the case of MPTP opening and much higher in the case of respiration inhibition as compared to liver mitochondria.

Constitutive Plasma Membrane Turnover in T-REx293 cells via Ordered Membrane Domain Endocytosis under Mitochondrial Control

Clathrin/dynamin-independent endocytosis of ordered plasma membrane domains (ordered membrane domain endocytosis, OMDE) can become massive in response to cytoplasmic Ca elevations, G protein activation by non-hydrolyzable GTP analogs, and enhanced oxidative metabolism. In patch-clamped murine bone marrow macrophages (BMMs), cytoplasmic succinate and pyruvate, but not β-hydroxybutyrate, induce OMDE of 75% of the plasma membrane within 2 min. The responses require palmitoylation of membrane proteins, being decreased by 70% in BMMs lacking the acyltransferase, DHHC5, by treatment with carnitine to shift long-chain acyl groups from cytoplasmic to mitochondrial acyl-CoAs, by bromopalmitate/albumin complexes to block DHHCs, and by the mitochondria-specific cyclosporin, NIM811, to block permeability transition pores that may release mitochondrial coenzyme A into the cytoplasm. Using T-REx293 cells, OMDE amounts to 40% with succinate, pyruvate, or GTPγS, and it is inhibited by actin cytoskeleton disruption. Pyruvate-induced OMDE is blocked by the hydrophobic antioxidant, edaravone, which prevents permeability transition pore openings. Using fluorescent 3kD dextrans to monitor endocytosis, OMDE appears to be constitutively active in T-REx293 cells but not in BMMs. After 1 h without substrates or bicarbonate, pyruvate and hydroxybutyrate inhibit constitutive OMDE, as expected for a shift of CoA from long-chain acyl-CoAs to other CoA metabolites. In the presence of bicarbonate, pyruvate strongly enhances OMDE, which is then blocked by β-hydroxybutyrate, bromopalmitate/albumin complexes, cyclosporines, or edaravone. After pyruvate responses, T-REx293 cells grow normally with no evidence for apoptosis. Fatty acid-free albumin (15 μM) inhibits basal OMDE in T-REx293 cells, as do cyclosporines, carnitine, and RhoA blockade. Surprisingly, OMDE in the absence of substrates and bicarbonate is not inhibited by siRNA knockdown of the acyltransferases, DHHC5 or DHHC2, which are required for activated OMDE in patch clamp experiments. We verify biochemically that small CoA metabolites decrease long-chain acyl-CoAs. We verify also that palmitoylations of many PM-associated proteins decrease and increase when OMDE is inhibited and stimulated, respectively, by different metabolites. STED microscopy reveals that vesicles formed during constitutive OMDE in T-REX293 cells have 90 to 130 nm diameters. In summary, OMDE is likely a major G-protein-dependent endocytic mechanism that can be constitutively active in some cell types, albeit not BMMs. OMDE depends on different DHHC acyltransferases in different circumstances and can be limited by local supplies of fatty acids, CoA, and long-chain acyl-CoAs.

A Comparative Analysis of Neuroprotective Properties of Taxifolin and Its Water-Soluble Form in Ischemia of Cerebral Cortical Cells of the Mouse

Cerebral ischemia, and, as a result, insult, attacks up to 15 million people yearly in the world. In this connection, the development of effective preventive programs and methods of therapy has become one of the most urgent problems in modern angiology and pharmacology. The cytoprotective action of taxifolin (TAX) in ischemia is well known, but its limitations are also known due to its poor solubility and low capacity to pass through the hematoencephalic barrier. Molecular mechanisms underlying the protective effect of TAX in complex systems such as the brain remain poorly understood. It is known that the main cell types of the brain are neurons, astrocytes, and microglia, which regulate the activity of each other through neuroglial interactions. In this work, a comparative study of cytoprotective mechanisms of the effect of TAX and its new water-soluble form aqua taxifolin (aqTAX) was performed on cultured brain cells under ischemia-like conditions (oxygen-glucose deprivation (OGD)) followed by the reoxygenation of the culture medium. The concentration dependences of the protective effects of both taxifolin forms were determined using fluorescence microscopy, PCR analysis, and vitality tests. It was found that TAX began to effectively inhibit necrosis and the late stages of apoptosis in the concentration range of 30-100 µg/mL, with aqTAX in the range of 10-30 µg/mL. At the level of gene expression, aqTAX affected a larger number of genes than TAX; enhanced the basic and OGD/R-induced expression of genes encoding ROS-scavenging proteins with a higher efficiency, as well as anti-inflammatory and antiapoptotic proteins; and lowered the level of excitatory glutamate receptors. As a result, aqTAX significantly inhibited the OGD-induced increase in the Ca²⁺ levels in the cytosol ([Ca²⁺]_i) in neurons and astrocytes under ischemic conditions. After a 40 min preincubation of cells with aqTAX under hypoxic conditions, these Ca²⁺ signals were completely inhibited, resulting in an almost complete suppression of necrotic death of cerebral cortical cells, which was not observed with the use of classical TAX.

Effect of Quercetin on mitoBKCa Channel and Mitochondrial Function in Human Bronchial Epithelial Cells Exposed to Particulate Matter

Particulate matter (PM) exposure increases reactive oxygen species (ROS) levels. It can lead to inflammatory responses and damage of the mitochondria thus inducing cell death. Recently, it has been shown that potassium channels (mitoK) located in the inner mitochondrial membrane are involved in cytoprotection, and one of the mechanisms involves ROS. To verify the cytoprotective role of mitoBKCa, we performed a series of experiments using a patch-clamp, transepithelial electrical resistance assessment (TEER), mitochondrial respiration measurements, fluorescence methods for the ROS level and mitochondrial membrane potential assessment, and cell viability measurements. In the human bronchial epithelial cell model (16HBE14σ), PM < 4 μm in diameter (SRM-PM4.0) was used. We observed that PM decreased TEER of HBE cell monolayers. The effect was partially abolished by quercetin, a mitoBKCa opener. Consequently, quercetin decreased the mitochondrial membrane potential and increased mitochondrial respiration. The reduction of PM-induced ROS level occurs both on cellular and mitochondrial level. Additionally, quercetin restores HBE cell viability after PM administration. The incubation of cells with PM substantially reduced the mitochondrial function. Isorhamnetin had no effect on TEER, the mitoBKCa activity, respiratory rate, or mitochondrial membrane potential. Obtained results indicate that PM has an adverse effect on HBE cells at the cellular and mitochondrial level. Quercetin is able to limit the deleterious effect of PM on barrier function of airway epithelial cells. We show that the effect in HBE cells involves mitoBKCa channel-activation. However, quercetin’s mechanism of action is not exclusively determined by modulation of the channel activity.

Therapeutic Potential of Quercetin-Loaded Nanoemulsion against Experimental Visceral Leishmaniasis: In Vitro/Ex Vivo Studies and Mechanistic Insights

Visceral leishmaniasis (VL) is one of the most fatal and neglected tropical diseases caused by Leishmania donovani (L. donovani). The applications of currently available chemotherapy (amphotericin B, miltefosine, and others) in VL treatment have been limited due to their poor bioavailability, unfavorable toxicity profile, and prolonged parenteral dosing. Quercetin (QT), a potent natural antioxidant, is a prominent target when conducting investigations on alternative therapies against L. donovani infections. However, the therapeutic applications of QT have been restricted due to its low solubility and bioavailability. In the present study, we developed and evaluated the antileishmanial activity (ALA) of quercetin-loaded nanoemulsion (QTNE) against L. donovani clinical strains. In vitro anti-promastigote assay results demonstrated that QTNE (IC₅₀ 6.6 μM, 48 h) significantly inhibited the growth of parasites more efficiently than the pure QT suspension in a dose- and time-dependent manner. Results of the anti-amastigote assay revealed that the infected macrophages (%) of QTNE were significantly more than those of the pure QT suspension at all concentrations (6.6, 26.4, and 52.8 μM; p < 0.05, p < 0.01 compared to the control). Moreover, the results of in vitro and ex vivo studies assisted in determining the mechanistic insights associated with the ALA of QTNE. The overall findings suggested that QTNE exhibited potential ALA by enhancing the intracellular ROS and nitric oxide levels, inducing distortion of membrane integrity and phosphatidylserine release (AV/PI), rupturing the parasite DNA (late apoptosis/necrosis process), and upregulating the immunomodulatory effects (IFN-γ and IL-10 levels). Additionally, QTNE showed superior biocompatibility against all of the treated healthy cells (PBMCs, PECs, and BMCs) as compared to the control. In conclusion, QTNE acts as a potential antileishmanial agent targeting both promastigote and intracellular amastigote forms of L. donovani, which thus opens a new avenue for the use of QTNE in VL therapy.

Activation of TLR-pathway to induce host Th1 immune respons eagainst visceral leishmaniasis: Involvement of galactosylated-flavonoids

Immunotherapeutic strategies against visceral leishmaniasis (VL) are pertinent because of the emergence of resistance against existing chemotherapy, coupled with their toxicity and high costs. Various bioactive components with potential immunomodulatory activity, such as alkaloids, terpenes, saponins, flavonoids obtained primarily from medicinal plants, have been screened against different disease models. Reports suggested that glycans containing terminal β-galactose can skew host immune response towards Th1 by engaging TLRs. In this study, two synthesized terminal galactose-containing flavones, Quercetin 3-d-galactoside (Q-gal) and Kaempferol 3-O-d-galactoside (K-gal), are profiled in terms of inducing host protective Th1 response in both in vitro & in vivo animal models of experimental VL individually against antimony-resistant & antimony-susceptible Leishmania donovani. Further, we explored that both Q-gal and K-gal induce TLR4 mediated Th1 response to encounter VL. Molecular docking analysis also suggested strong interaction with TLR4 for both the galactosides, with a slightly better binding potential towards Q-gal. Treatment with both Q-gal and K-gal showed significant antileishmanial efficacy. Each considerably diminished the liver and splenic parasite burden 60 days after post-infection (>90% in AG83 infected mice and >87% in GE1F8R infected mice) when administered at a 5 mg/kg/day body-weight dose for ten consecutive days. However, the treatments failed to clear the parasites in the TLR4 deficient C3H/HeJ mice. Treatment with these compounds favors the elevation of TLR4 dependent host protective Th1 cytokines and suppression of disease-promoting IL-10. Q-gal and K-gal also triggered sufficient ROS generation in macrophages to kill intracellular parasites directly.

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Galactosilated flavonoids treatment clears in-vivo drug-resistant Leishmania donovani infection.

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Quercetin 3-d-galactoside (Q-gal) & Kaempferol 3-O-d-galactoside (K-gal) induce host TLR4 pathway.

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These flavonoids up-regulate Th1 cytokines and suppress the disease-promoting IL-10.

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TLR4 deficient C3H/HeJ mice are unresponsive towards Q-gal and K-gal treatment.

Antioxidant Potential and Inhibition of Mitochondrial Permeability Transition Pore by Myricetin Reduces Aluminium Phosphide-Induced Cytotoxicity and Mitochondrial Impairments

Oxidative stress and mitochondrial dysfunction are involved in the mechanisms of cardiac toxicity induced by aluminum phosphide (AlP). AlP-induced cardiotoxicity leads to cardiomyocyte death, cardiomyopathy, cardiac dysfunction, and eventually severe heart failure and death. Importantly, protecting cardiomyocytes from death resulting from AlP is vital for improving survival. It has been reported that flavonoids such as myricetin (Myr) act as modifiers of mitochondrial function and prevent mitochondrial damage resulting from many insults and subsequent cell dysfunction. In this study, the ameliorative effect of Myr, as an important antioxidant and mitochondrial protective agent, was investigated in cardiomyocytes and mitochondria isolated from rat heart against AlP-induced toxicity, oxidative stress, and mitochondrial dysfunction. Treatment of AlP (20 μg/ml) significantly increased cytotoxicity; reduced glutathione (GSH) depletion, cellular reactive oxygen species (ROS) formation, malondialdehyde (MDA) level, ATP depletion, caspase-3 activation, mitochondrial membrane potential (ΔΨm) collapse, and lysosomal dysfunction; and decreased the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in intact cardiomyocytes. Also, treatment of AlP (20 μg/ml) significantly increased mitochondrial dysfunction and swelling in isolated mitochondria. Myr (80 µM) appeared to ameliorate AlP-induced cytotoxicity in isolated cardiomyocytes; significantly lessened the AlP-stimulated intracellular ROS and MDA production and depletion of GSH; and increased the activities of SOD, CAT, and GSH-Px. Furthermore, Myr (40 and 80 µM) lowered AlP-induced lysosomal/mitochondrial dysfunction, ATP depletion, and caspase-3 activation. In the light of these findings, we concluded that Myr through antioxidant potential and inhibition of mitochondrial permeability transition (MPT) pore exerted an ameliorative role in AlP-induced toxicity in isolated cardiomyocytes and mitochondria, and it would be valuable to examine its in vivo effects.

Disease-modifying treatment of Parkinson's disease by phytochemicals: targeting multiple pathogenic factors

Parkinson's disease is characterized by typical motor symptoms, loss of dopamine neurons in the substantia nigra, and accumulation of Lewy body composed of mutated α-synuclein. However, now it is considered as a generalized disease with multiple pathological features. Present available treatments can ameliorate symptoms at least for a while, but only a few therapies could delay progressive neurodegeneration of dopamine neurons. Lewy body accumulates in peripheral tissues many years before motor dysfunction becomes manifest, suggesting that disease-modifying therapy should start earlier during the premotor stage. Long-termed regulation of lifestyle, diet and supplement of nutraceuticals may be possible ways for the disease-modification. Diet can reduce the incidence of Parkinson's disease and phytochemicals, major bioactive ingredients of herbs and plant food, modulate multiple pathogenic factors and exert neuroprotective effects in preclinical studies. This review presents mechanisms underlying neuroprotection of phytochemicals against neuronal cell death and α-synuclein toxicity in Parkinson's disease. Phytochemicals are antioxidants, maintain mitochondrial function and homeostasis, prevent intrinsic apoptosis and neuroinflammation, activate cellular signal pathways to induce anti-apoptotic and pro-survival genes, such as Bcl-2 protein family and neurotrophic factors, and promote cleavage of damaged mitochondria and α-synuclein aggregates. Phytochemicals prevent α-synuclein oligomerization and aggregation, and dissolve preformed α-synuclein aggregates. Novel neuroprotective agents are expected to develop based on the scaffold of phytochemicals permeable across the blood-brain-barrier, to increase the bioavailability, ameliorate brain dysfunction and prevent neurodegeneration.

Synthesis and Testing of Novel Isomeric Mitochondriotropic Derivatives of Resveratrol and Quercetin

Resveratrol and quercetin are among the most studied plant polyphenols, and have many health-promoting actions. Strategies to accumulate them into mitochondria may be of therapeutic relevance, since these compounds are redox active and are well known to impact mitochondria and mitochondrial proteins. We report here the procedures to synthesize mitochondria-targeted resveratrol and quercetin derivatives; the synthetic strategies reported are however expected to be adaptable to other polyphenols with similar reactivity at the phenolic hydroxyls. Mitochondrial targeting can be achieved by conjugation with triphenylphosphonium , a lipophilic cation; this was linked via a butyl spacer forming an ether bond with one of the phenolic oxygens. The first step toward the synthesis of all mitochondriotropic derivatives described in this work is the production of a regiospecific -(4-O-chlorobutyl) derivative. Triphenylphosphonium (P⁺Ph₃I^-) is then introduced through two consecutive nucleophilic substitution steps: -Cl → -I → -P⁺Ph₃I^-. Pure mono-substituted chlorobutyl regioisomers are obtained by purification from the reaction mixture in the case of resveratrol , while specific protection strategies are required for quercetin to favor alkylation of one specific hydroxyl.Functionalization of the remaining hydroxyls can be exploited to modulate the physicochemical properties of the derivatives (i.e., water solubility, affinity for cell membranes); we report here synthetic protocols to obtain acetylated and methylated analogs.A brief description of some methods to assess the accumulation of the derivatives in mitochondria is also given; the proposed techniques are the use of a TPP ⁺-selective electrode (with isolated rat liver mitochondria ) and fluorescence microscopy (with cultured cells).

Quercetin-Loaded Luminescent Hydroxyapatite Nanoparticles for Theranostic Application in Monolayer and Spheroid Cultures of Cervical Cancer Cell Line In Vitro

Nanoscale materials have been explored as better alternatives to conventional therapeutic agents in cancer theranostics in the recent period due to efficacy in overcoming biological, biomedical, and biophysical barriers. Analysis on the ability of copper nanocluster (CuNC)-doped hydroxyapatite nanoparticles (Cu-HXNPs) as suitable nanocarriers for anticell proliferative application was carried out. Having high adsorption capacity, the Cu-HXNPs could be loaded with the anticancer drug quercetin, which is a polyphenolic flavonoid compound, and were used as nanocarriers to be applied on HeLa (cancer cells) and HEK-293 (normal cells). The drug release profile was found to be pH-dependent, where maximum release of quercetin from quercetin-loaded Cu-HXNPs was observed in acidic pH as compared to physiological pH. The Cu-HXNPs could release quercetin, which could effectively decline proliferation of cancer cells via generation of reactive oxygen species. Moreover, the released quercetin significantly altered the cell cycle pattern and triggered the cells to undergo apoptosis. Additionally, the efficacy of Cu-HXNPs as a nanocarrier to release quercetin on 3D spheroids of HeLa had been checked, which demonstrated significant reduction in the viability of 3D spheroids. The luminescent CuNCs used for doping HXNPs endowed the nanocarrier with the imaging property, which was an excellent feature in confirming their uptake by the cells. Thus, the study suggested Cu-HXNPs to be a beneficial nanocarrier for both bioimaging and therapeutic purpose in the field of cancer theranostics.

Stigmasterol isolated from the chloroform fraction of Adenopus breviflorus Benth fruit induces mitochondrial-dependent apoptosis in rat liver

OBJECTIVES

Decoction of Adenopus breviflorus fruit is used in folkloric medicine for treating dysmenorrhea and gonorrhea. Phytochemicals from A. breviflorus may be potent in inducing mitochondrial-dependent apoptosis via the opening of the mitochondrial permeability transition (MPT) pore. Therefore, this study investigated the in vitro effects of stigmasterol isolated from the chloroform fraction of A. breviflorus (CFAB) and also the increasing concentration of CFAB on the opening of rat liver mitochondrial permeability transition (MPT) pore.

METHODS

Fractionation of CFAB on column chromatography yielded a needle-like crystal which structure was elucidated by standard spectroscopic techniques. The effects of stigmasterol and CFAB on MPT pore opening were assayed spectrophotometrically. Also, the effect of CFAB on mitochondrial ATPase (mATPase) activity and cytochrome c (Cyt c) release were determined.

RESULTS

Stigmasterol isolated from CFAB induced MPT pore opening significantly (p<0.05) when compared with the control. Similarly, CFAB significantly (p<0.05) induced MPT pore opening in rat liver mitochondria in a concentration-dependent manner in the presence and absence of the triggering agent - calcium ion. Furthermore, the increasing concentration of CFAB significantly (p<0.05) stimulated mitochondrial ATPase (mATPase) activity and Cyt c release in a concentration-dependent manner.

CONCLUSIONS

The study showed that stigmasterol isolated from the chloroform fraction of A. breviflorus is a potent inducer of mitochondrial-dependent apoptosis. Also, the study further revealed that CFAB possesses potent bioactive compounds which can induce the mitochondrial-dependent apoptosis through the opening of the mitochondrial permeability transition pore, activation of mitochondrial ATPase (mATPase) activity and cytochrome c release.

Antioxidants in smokers

Cigarette smoke (CS) is likely the most common preventable cause of human morbidity and mortality worldwide. Consequently, inexpensive interventional strategies for preventing CS-related diseases would positively impact health systems. Inhaled CS is a powerful inflammatory stimulus and produces a shift in the normal balance between antioxidants and oxidants, inducing oxidative stress in both the respiratory system and throughout the body. This enduring and systemic pro-oxidative state within the body is reflected by increased levels of oxidative stress and inflammation biomarkers seen in smokers. Smokers might benefit from consuming antioxidant supplements, or a diet rich in fruit and vegetables, which can reduce the CS-related oxidative stress. This review provides an overview of the plasma profile of antioxidants observable in smokers and examines the heterogeneous literature to elucidate and discuss the effectiveness of interventional strategies based on antioxidant supplements or an antioxidant-rich diet to improve the health of smokers. An antioxidant-rich diet can provide an easy-to-implement and cost-effective preventative strategy to reduce the risk of CS-related diseases, thus being one of the simplest ways for smokers to stay in good health for as long as possible. The health benefits attributable to the intake of antioxidants have been observed predominantly when these have been consumed within their natural food matrices in an optimal antioxidant-rich diet, while these preventive effects are rarely achieved with the intake of individual antioxidants, even at high doses.

Interactions between free and bound antioxidants under different conditions in food systems

This review aimed to give comprehensive information about the interactions between free and bound antioxidants naturally found in different food matrices. In this context, firstly, the free and bound antioxidant terms are defined; their place in the daily diet, the path they follow in the body and their characteristics are explained. Factors affecting the interactions have been revealed as a result of the compilation of studies conducted until today, related to bound and free antioxidant interactions. Accordingly, it was observed that many factors such as reaction environment, concentration, pH, chemical structure, source and antioxidant/prooxidant nature of the compounds were effective on interactions. It has been emphasized that the interactions between free and bound antioxidants have a dynamic balance that can easily change under the influence of various factors, which in turn needs the interactions to be handled specifically for each case.

Pomegranate juice rescues developmental, neurobehavioral and biochemical disorders in aluminum chloride-treated male mice

PURPOSE

Aluminum (Al) is a harmful metal to organisms and is capable of entering the human body in multiple ways, such as through drinking, breathing, deodorant use, and vaccination. This study examined the prospective toxicity of Al and the protective attributes of pomegranate juice (PJ) on neurobehavioral and biochemical parameters of male mice.

METHODS

Six groups of male mice were treated for 35 days with 20 % PJ (group II), 40 % PJ (group III), 400 mg/kg Al (group IV), Al + 20 % PJ (group V), Al + 40 % PJ (group VI) or tap water (control, group I). Behavioral assessments were conducted for learning and memory evaluations at the end of experiment. In addition, the forebrain was isolated for biochemical analysis.

RESULTS

The exposure of male mice to Al decreased learning and memory retention in the shuttle box, Morris water-maze and T-Maze tests. Biochemical analysis revealed significant depletions in neurotransmitters including DA, 5-HT and AChE and oxidative proteins including GSH, GST, CAT and SOD and increased TBARES levels in Al-treated mice compared to untreated mice. Pomegranate juice provided protection against these effects after Al exposure by ameliorating learning and memory retention and oxidative state in a dose-independent manner.

CONCLUSION

Our data demonstrated that Al exposure caused behavioral and biochemical disorders. Pomegranate juice in lower dose has beneficial properties for health and can be used as a source of antioxidants to reduce the toxicity of Al and other substances.

Physiological evidence of mitochondrial permeability transition pore opening caused by lipid deposition leading to hepatic steatosis in db/db mice

Mitochondrial permeability transition pore (mPTP) is an important regulator in cell apoptosis and necrosis. However, its role in hepatic steatosis, especially its electrophysiological properties transformation remains elusive. Herein, using diabetes mice, we investigated the role of mPTP in hepatic steatosis triggered by diabetes and the mechanisms involved. We found that hepatic steatosis altered mitochondrial morphology, generating mega mitochondria, mitochondria swelling, calcein fluorescence quenching and mitochondrial membrane potential depolarization. At the same time, we confirmed an augmented mPTP opening with patch clamping in liver mitoplasts in db/db mice and a similar transformation with arachidonic acid (AA) simulating liquid deposition. We also found mPTP opening was significantly attenuated in wt mice after removing mitochondrial matrix, while that in db/db mice remained active. In addition, we observed that AA could directly activate mPTP in inside-out mode, independent of matrix calcium. In conclusion, we for the first time provided a physiological evidence of mPTP opening in lipid deposition, which could be directly induced by AA without Ca²⁺ and can be inhibited by cyclosporine A. As a result, it led to mitochondria morphology and function transformation. This might provide insights into potential therapeutic target for future treatment of mitochondrial liver disease.

Regulation of Mitochondrial Quality Control by Natural Drugs in the Treatment of Cardiovascular Diseases: Potential and Advantages

Mitochondria are double-membraned cellular organelles that provide the required energy and metabolic intermediates to cardiomyocytes. Mitochondrial respiratory chain defects, structure abnormalities, and DNA mutations can affect the normal function of cardiomyocytes, causing an imbalance in intracellular calcium ion homeostasis, production of reactive oxygen species, and apoptosis. Mitochondrial quality control (MQC) is an important process that maintains mitochondrial homeostasis in cardiomyocytes and involves multi-level regulatory mechanisms, such as mitophagy, mitochondrial fission and fusion, mitochondrial energy metabolism, mitochondrial antioxidant system, and mitochondrial respiratory chain. Furthermore, MQC plays a role in the pathological mechanisms of various cardiovascular diseases (CVDs). In recent years, the regulatory effects of natural plants, drugs, and active ingredients on MQC in the context of CVDs have received significant attention. Effective active ingredients in natural drugs can influence the production of energy-supplying substances in the mitochondria, interfere with the expression of genes associated with mitochondrial energy requirements, and regulate various mechanisms of MQC modulation. Thus, these ingredients have therapeutic effects against CVDs. This review provides useful information about novel treatment options for CVDs and development of novel drugs targeting MQC.

Blueberry Consumption Challenges Hepatic Mitochondrial Bioenergetics and Elicits Transcriptomics Reprogramming in Healthy Wistar Rats

An emergent trend of blueberries’ (BB) “prophylactic” consumption, due to their phytochemicals’ richness and well-known health-promoting claims, is widely scaled-up. However, the benefits arising from BB indiscriminate intake remains puzzling based on incongruent preclinical and human data. To provide a more in-depth elucidation and support towards a healthier and safer consumption, we conducted a translation-minded experimental study in healthy Wistar rats that consumed BB in a juice form (25 g/kg body weight (BW)/day; 14 weeks’ protocol). Particular attention was paid to the physiological adaptations succeeding in the gut and liver tissues regarding the acknowledged BB-induced metabolic benefits. Systemically, BB boosted serum antioxidant activity and repressed the circulating levels of 3-hydroxybutyrate (3-HB) ketone bodies and 3-HB/acetoacetate ratio. Moreover, BB elicited increased fecal succinic acid levels without major changes on gut microbiota (GM) composition and gut ultra-structural organization. Remarkably, an accentuated hepatic mitochondrial bioenergetic challenge, ensuing metabolic transcriptomic reprogramming along with a concerted anti-inflammatory pre-conditioning, was clearly detected upon long-term consumption of BB phytochemicals. Altogether, the results disclosed herein portray a quiescent mitochondrial-related metabolomics and hint for a unified adaptive response to this nutritional challenge. The beneficial or noxious consequences arising from this dietary trend should be carefully interpreted and necessarily claims future research.

Role of flavonoids against adriamycin toxicity

Doxorubicin (DOX), or adriamycin, is an anthracycline antineoplastic drug widely used in the chemotherapy of a large variety of cancers due to its potency and action spectrum. However, its use is limited by the toxicity on healthy cells and its acute and chronic side effects. One of the developed strategies to attenuate DOX toxicity is the combined therapy with bioactive compounds such as flavonoids. This review embraces the role of flavonoids on DOX treatment side effects. Protective properties of some flavonoidss against DOX toxicity have been investigated and observed mainly in heart but also in liver, kidney, brain, testis or bone marrow. Protective mechanisms involve reduction of oxidative stress by decrease of ROS levels and/or increase antioxidant defenses and interferences with autophagy, apoptosis and inflammation. Studies in cancer cells have reported that the anticancer activity of DOX was not compromised by the flavonoids. Moreover, some of them increased DOX efficiency as anti-cancer drug even in multidrug resistant cells.

Flavonoids modulate liposomal membrane structure, regulate mitochondrial membrane permeability and prevent erythrocyte oxidative damage

In the present work, we investigated the interaction of flavonoids (quercetin, naringenin and catechin) with cellular and artificial membranes. The flavonoids considerably inhibited membrane lipid peroxidation in rat erythrocytes treated with tert-butyl hydroperoxide (700 μM), and the IC₅₀ values for prevention of this process were equal to 9.7 ± 0.8 μM, 8.8 ± 0.7 μM, and 37.8 ± 4.4 μM in the case of quercetin, catechin and naringenin, respectively, and slightly decreased glutathione oxidation. In isolated rat liver mitochondria, quercetin, catechin and naringenin (10-50 μM) dose-dependently increased the sensitivity to Ca²⁺ ions - induced mitochondrial permeability transition. Using the probes TMA-DPH and DPH we showed that quercetin rather than catechin and naringenin strongly decreased the microfluidity of the 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomal membrane bilayer at different depths. On the contrary, using the probe Laurdan we observed that naringenin transfer the bilayer to a more ordered state, whereas quercetin dose-dependently decreased the order of lipid molecule packing and increased hydration in the region of polar head groups. The incorporation of the flavonoids, quercetin and naringenin and not catechin, into the liposomes induced an increase in the zeta potential of the membrane and enlarged the area of the bilayer as well as lowered the temperature and the enthalpy of the membrane phase transition. The effects of the flavonoids were connected with modification of membrane fluidity, packing, stability, electrokinetic properties, size and permeability, prevention of oxidative stress, which depended on the nature of the flavonoid molecule and the nature of the membrane.

Exploring the multimodal role of phytochemicals in the modulation of cellular signaling pathways to combat age-related neurodegeneration

Neurodegeneration is the progressive loss of neuronal structures and functions that lead to copious disorders like Alzheimer's (AD), Parkinson's (PD), Huntington's (HD), amyotrophic lateral sclerosis (ALS), and other less recurring diseases. Aging is the prime culprit for most neurodegenerative events. Moreover, the shared pathogenic factors of many neurodegenerative processes are inflammatory responses and oxidative stress (OS). Unfortunately, it is very complicated to treat neurodegeneration and there is no effective remedy. The rapid progression of the neurodegenerative diseases that exacerbate the burden and the concurrent absence of effective treatment strategies force the researchers to investigate more therapeutic approaches that ultimately target the causative factors of the neurodegeneration. Phytochemicals have great potential to exert their neuroprotective effects by targeting various mechanisms, such as OS, neuroinflammation, abnormal protein aggregation, neurotrophic factor deficiency, disruption in mitochondrial function, and apoptosis. Therefore, this review represents the molecular mechanisms of neuroprotection by multifunctional phytochemicals to combat age-linked neurodegenerative disorders.

Targeting Mitochondrial Calcium Uptake with the Natural Flavonol Kaempferol, to Promote Metabolism/Secretion Coupling in Pancreatic β-cells

Pancreatic β-cells secrete insulin to lower blood glucose, following a meal. Maintenance of β-cell function is essential to preventing type 2 diabetes. In pancreatic β-cells, mitochondrial matrix calcium is an activating signal for insulin secretion. Recently, the molecular identity of the mitochondrial calcium uniporter (MCU), the transporter that mediates mitochondrial calcium uptake, was revealed. Its role in pancreatic β-cell signal transduction modulation was clarified, opening new perspectives for intervention. Here, we investigated the effects of a mitochondrial Ca²⁺-targeted nutritional intervention strategy on metabolism/secretion coupling, in a model of pancreatic insulin-secreting cells (INS-1E). Acute treatment of INS-1E cells with the natural plant flavonoid and MCU activator kaempferol, at a low micromolar range, increased mitochondrial calcium rise during glucose stimulation, without affecting the expression level of the MCU and with no cytotoxicity. Enhanced mitochondrial calcium rises potentiated glucose-induced insulin secretion. Conversely, the MCU inhibitor mitoxantrone inhibited mitochondrial Ca²⁺ uptake and prevented both glucose-induced insulin secretion and kaempferol-potentiated effects. The kaempferol-dependent potentiation of insulin secretion was finally validated in a model of a standardized pancreatic human islet. We conclude that the plant product kaempferol activates metabolism/secretion coupling in insulin-secreting cells by modulating mitochondrial calcium uptake.

Hypoxia induces an increase in intestinal permeability and pulmonary arterial pressures in neonatal Holstein calves despite feeding the flavonoid rutin

The purposes of this study were to determine whether the naturally occurring flavonoid quercetin, as its glucorhamnoside rutin, reduces intestinal permeability and susceptibility to hypoxia-induced pulmonary hypertension in neonatal Holstein calves. A 2 × 2 between-subjects factorial design was conducted using Holstein steers (n = 16). Factors included oxygen level (simulated altitude of 4,572 m vs. 975 m) and quercetin supplementation as its glucorhamnoside rutin (4 g of quercetin per day vs. 0 g per day). Two days after arrival (d 0 of study) the calves were blocked by body mass into treatment groups, and treatments were initiated. Pulmonary arterial pressure, echocardiography, and serum concentrations of orally administered lactulose (0.45 g/kg) and mannitol (0.15 g/kg) were measured on d 12, 13, and 14, respectively. Calves were euthanized on d 15 and pulmonary tissues collected for semiquantitative scoring of histological lesions. Data were analyzed using linear regression, generalized estimating equations, and 2-sample proportion tests. Hypoxia, but not rutin, was found to be associated with intestinal permeability. The lactulose-mannitol ratio was 0.54 ± 0.13 (standard error) in hypoxic calves and 0.02 ± 0.13 in normoxic controls. Hypoxia increased mean pulmonary arterial pressure. Calves fed rutin under hypoxic conditions tended to have a lower mean pulmonary arterial pressure (59 ± 7 mmHg) than control calves (80 ± 7 mmHg) but similar pressures under normoxic conditions. Paradoxically, however, a greater proportion of calves fed rutin had histological evidence of pulmonary arteriolar medial hypertrophy and adventitial hyperplasia than did controls. In conclusion, the findings of this study indicate that hypoxia increased intestinal permeability in neonatal calves. The flavonoid quercetin, as its glucorhamnoside rutin, had no protective effect on intestinal permeability, and, although it tended to reduce the severity of hypoxia-induced pulmonary hypertension, a greater proportion of calves fed rutin had histological lesions consistent with pulmonary arteriolar remodeling.

Dietary Polyphenols and Mitochondrial Function: Role in Health and Disease

Mitochondria are cytoplasmic double-membraned organelles that are involved in a myriad of key cellular regulatory processes. The loss of mitochondrial function is related to the pathogenesis of several human diseases. Over the last decades, an increasing number of studies have shown that dietary polyphenols can regulate mitochondrial redox status, and in some cases, prevent or delay disease progression. This paper aims to review the role of four dietary polyphenols - resveratrol, curcumin, epigallocatechin-3-gallate nd quercetin - in molecular pathways regulated by mitochondria and their potential impact on human health. Cumulative evidence showed that the aforementioned polyphenols improve mitochondrial functions in different in vitro and in vivo experiments. The mechanisms underlying the polyphenols' beneficial effects include, among others, the attenuation of oxidative stress, the regulation of mitochondrial metabolism and biogenesis and the modulation of cell-death signaling cascades, among other mitochondrial-independent effects. The understanding of the chemicalbiological interactions of dietary polyphenols, namely with mitochondria, may have a huge impact on the treatment of mitochondrial dysfunction-related disorders.

Mitochondria in Neuroprotection by Phytochemicals: Bioactive Polyphenols Modulate Mitochondrial Apoptosis System, Function and Structure

In aging and neurodegenerative diseases, loss of distinct type of neurons characterizes disease-specific pathological and clinical features, and mitochondria play a pivotal role in neuronal survival and death. Mitochondria are now considered as the organelle to modulate cellular signal pathways and functions, not only to produce energy and reactive oxygen species. Oxidative stress, deficit of neurotrophic factors, and multiple other factors impair mitochondrial function and induce cell death. Multi-functional plant polyphenols, major groups of phytochemicals, are proposed as one of most promising mitochondria-targeting medicine to preserve the activity and structure of mitochondria and neurons. Polyphenols can scavenge reactive oxygen and nitrogen species and activate redox-responsible transcription factors to regulate expression of genes, coding antioxidants, anti-apoptotic Bcl-2 protein family, and pro-survival neurotrophic factors. In mitochondria, polyphenols can directly regulate the mitochondrial apoptosis system either in preventing or promoting way. Polyphenols also modulate mitochondrial biogenesis, dynamics (fission and fusion), and autophagic degradation to keep the quality and number. This review presents the role of polyphenols in regulation of mitochondrial redox state, death signal system, and homeostasis. The dualistic redox properties of polyphenols are associated with controversial regulation of mitochondrial apoptosis system involved in the neuroprotective and anti-carcinogenic functions. Mitochondria-targeted phytochemical derivatives were synthesized based on the phenolic structure to develop a novel series of neuroprotective and anticancer compounds, which promote the bioavailability and effectiveness. Phytochemicals have shown the multiple beneficial effects in mitochondria, but further investigation is required for the clinical application.

Endogenous and Exogenous Modulation of Nrf2 Mediated Oxidative Stress Response in Bovine Granulosa Cells: Potential Implication for Ovarian Function

Nrf2 is a redox sensitive transcription factor regulating the expression of antioxidant genes as defense mechanism against various stressors. The aim of this study is to investigate the potential role of noncoding miRNAs as endogenous and quercetin as exogenous regulators of Nrf2 pathway in bovine granulosa cells. For this cultured granulosa cells were used for modulation of miRNAs (miR-28, 153 and miR-708) targeting the bovine Nrf2 and supplementation of quercentin to investigate the regulatory mechanisms of the Nrf2 antioxidant system. Moreover, cultured cells were treated with hydrogen peroxide to induce oxidative stress in those cells. Our results showed that, oxidative stress activated the expression of Nrf2 as a defense mechanism, while suppressing the expression of those miRNAs. Overexpression of those miRNAs resulted in downregulation of Nrf2 expression resulted in higher ROS accumulation, reduced mitochondrial activity and cellular proliferation. Quercetin supplementation showed its protective role against oxidative stress induced by H₂O₂ by inducing the expression of antioxidant enzymes. In conclusion, this study highlighted the involvement of miR-153, miR-28 and miR-708 in regulatory network of Nrf2 mediated antioxidant system in bovine granulosa cells function. Furthermore, quercetin at a low dose played a protective role in bovine granulosa cells against oxidative stress damage.

Neuroprotection of multifunctional phytochemicals as novel therapeutic strategy for neurodegenerative disorders: antiapoptotic and antiamyloidogenic activities by modulation of cellular signal pathways

In neurodegenerative disorders, including Alzheimer's and Parkinson's disease, neuroprotection by diet and natural bioactive compounds has been proposed to prevent the onset and progress of neurodegeneration by modification of pathogenic factors. Plant food-derived phytochemicals protect neurons via targeting oxidative stress, mitochondrial dysfunction, neurotrophic factor deficit, apoptosis and abnormal protein accumulation. This review presents the molecular mechanism of neuroprotection by phytochemicals: direct regulation of mitochondrial apoptotic machinery, modification of cellular signal pathways, induction of antiapoptotic Bcl-2 protein family and prosurvival neurotrophic factors, such as brain- and glial cell line-derived neurotrophic factor, and prevention of protein aggregation. Multitargeted neuroprotective agents are under development based on the structure of blood–brain barrier-permeable phytochemicals to ameliorate brain dysfunction and prevent neurodegeneration.

Quercetin manipulates the expression of genes involved in the reactive oxygen species (ROS) process in chicken heterophils

Chicken heterophils generate reactive oxygen species (ROS) molecules to defend against invading pathogens. The present study examined effects of quercetin on chicken heterophils. Heterophils were stimulated with PBS, 50 µM quercetin (QH), PMA or Escherichia coli (EC) and the resulting intracellular ROS molecules were determined. Flow cytometry results showed that cells stimulated with QH, PMA and EC had a higher ROS production. Increases in intracellular ROS molecules were identified in all treatment groups by fluorescence microscopy. Determination of the ability of quercetin to manipulate mRNA expression of ROS subunits was assessed using real-time RT-PCR. Quercetin and other stimulants up-regulated the majority of genes involved in ROS production: CYBB (NOX2), NCF1 (p47^phox), NCF2 (p67^phox), NOX1 and RAC2. The antioxidant property of QH was explored by measuring mRNA expression of CAT and SOD1. The data indicate increased levels of CAT with all treatments; however, only QH attenuated the expression of the SOD1 gene. To further investigate the effects of ROS-driven inflammation or cell death, IL6, CASP8 and MCL1 genes were preferentially tested. The inflammatory gene (IL6) was profoundly down-regulated in the QH- and PMA-treated groups while EC induced a strikingly high IL6 expression level. Investigation of the known apoptotic (CASP8) and anti-apoptotic (MCL1) genes found down-regulation of CASP8 in the QH- and PMA-treated groups which were contradicted to the MCL1 gene. In conclusion, quercetin can enhance ROS production by regulating the expression of genes involved in ROS production as well as in subsequent processes.

Neurotrophic function of phytochemicals for neuroprotection in aging and neurodegenerative disorders: modulation of intracellular signaling and gene expression

Bioactive compounds in food and beverages have been reported to promote health and prevent age-associated decline in cognitive, motor and sensory activities, and emotional function. Phytochemicals, a ubiquitous class of plant secondary metabolites, protect neuronal cells by interaction with cellular activities, in addition to the antioxidant and anti-inflammatory function. In aging and age-associated neurodegenerative disorders, phytochemicals protect neuronal cells by neurotrophic factor-mimic activity, in addition to suppression of apoptosis signaling in mitochondria. This review presents the cellular mechanisms underlying anti-apoptotic function and neurotrophic function of phytochemicals in the brain. Phytochemicals bind to receptors of neurotrophic factors, and also receptors for γ-aminobutyric acid, acetylcholine, serotonin, and glutamate and estrogen, and activate downstream signal pathways. Phytochemicals also directly intervene intracellular signaling molecules to modify the brain function. Finally, phytochemicals enhance the endogenous biosynthesis of genes coding anti-apoptotic Bcl-2 and neurotrophic factors, such as brain-derived and glial cell line-derived neurotrophic factor. The gene induction may play a major role in the neuroprotective function of dietary compounds shown by epidemiological studies. Quantitative measurement of neurotrophic factors induced by phytochemicals in the serum, cerebrospinal fluid, and other clinical samples is proposed as a surrogate assay method to evaluate the neuroprotective potency. Development of novel neuroprotective compounds is expected among compounds chemically synthesized from the brain-permeable basic structure of phytochemicals.

Linking lipid peroxidation and neuropsychiatric disorders: focus on 4-hydroxy-2-nonenal

4-hydroxy-2-nonenal (HNE) is considered to be a strong marker of oxidative stress; the interaction between HNE and cellular proteins leads to the formation of HNE-protein adducts able to alter cellular homeostasis and cause the development of a pathological state. By virtue of its high lipid concentration, oxygen utilization, and the presence of metal ions participating to redox reactions, the brain is highly susceptible to the formation of free radicals and HNE-related compounds. A variety of neuropsychiatric disorders have been associated with elevations of HNE concentration. For example, increased levels of HNE were found in the cortex of bipolar and schizophrenic patients, while HNE plasma concentrations resulted high in patients with major depression. On the same line, high brain concentrations of HNE were found associated with Huntington's inclusions. The incidence of high HNE levels is relevant also in the brain and cerebrospinal fluid of patients suffering from Parkinson's disease. Intriguingly, in this case the increase of HNE was associated with an accumulation of iron in the substantia nigra, a brain region highly affected by the pathology. In the present review we recapitulate the findings supporting the role of HNE in the pathogenesis of different neuropsychiatric disorders to highlight the pathogenic mechanisms ascribed to HNE accumulation. The aim of this review is to offer novel perspectives both for the understanding of etiopathogenetic mechanisms that remain still unclear and for the identification of new useful biological markers. We conclude suggesting that targeting HNE-driven cellular processes may represent a new more efficacious therapeutical intervention.

Nutrigenomics in cancer: Revisiting the effects of natural compounds

Nutrigenomics effects have an important role in the manipulation of dietary components for human benefit, particularly in cancer prevention or treatment. The impact of dietary components, including phytochemicals, is largely studied by nutrigenomics, looking at the gene expression and molecular mechanisms interacting with bioactive compounds and nutrients, based on new 'omics' technologies. The high number of preclinical studies proves the relevant role of nutrigenomics in cancer management. By deciphering the network of nutrient-gene connections associated with cancer, relevant data will be transposed as therapeutic interventions for this devastating pathology and for fulfilling the concept of personalized nutrition. All these are presented under the nutrigenomics canopy for a better comprehension of the relation between ingested phytochemicals and chemoprevention or chemotherapy. The profits from the nutrigenomics progress, with a particular focus on the coding and noncoding genes related to the exposure of natural compounds need to be validated. A precise attention receives the evaluation of the role of natural compounds in tandem with conventional therapy using genomic approaches, with emphasis on the capacity to inhibit drug resistance mechanisms. All these relevant nutrigenomics aspects are summarized in the present review paper. It is concluded that further nutrigenomics studies are required to improve our understanding related to the complex mechanisms of action of the natural compounds and for their appropriate application as gears in cancer therapy.

Quercetin, a natural product supplement, impairs mitochondrial bioenergetics and locomotor behavior in larval zebrafish (Danio rerio)

Quercetin is a natural product that is sold as a supplement in health food stores. While there are reported benefits for this flavonoid as a dietary supplement due to antioxidant properties, the full scope of its biological interactions has not been fully addressed. To learn more about the mechanisms of action related to quercetin, we exposed zebrafish (Danio rerio) embryos to 1 and 10μg/L quercetin for 96h starting at 3h post fertilization. Quercetin up to 10μg/L did not induce significant mortality in developing fish, but did increase prevalence of an upward-curved dorsal plane in hatched larvae. To determine whether this developmental defect was potentially related to mitochondrial bioenergetics during development, we measured oxygen consumption rate in whole embryos following a 24-hour exposure to quercetin. Basal mitochondrial and ATP-linked respiration were decreased at 1 and 10μg/L quercetin, and maximal respiration was decreased at 10μg/L quercetin, suggesting that quercetin impairs mitochondrial bioenergetics. This is proposed to be related to the deformities observed during development. Due to the fact that ATP production was affected by quercetin, larval behaviors related to locomotion were investigated, as well as transcriptional responses of six myogenesis transcripts. Quercetin at 10μg/L significantly reduced the swimming velocity of zebrafish larvae. The expression levels of both myostatin A (mstna) and myogenic differentiation (myoD) were also altered by quercetin. Mstna, an inhibitory factor for myogenesis, was significantly increased at 1μg/L quercetin exposure, while myoD, a stimulatory factor for myogenesis, was significantly increased at 10μg/L quercetin exposure. There were no changes in transcripts related to apoptosis (bcl2, bax, casp3, casp7), but we did observe a decrease in mRNA levels for catalase (cat) in fish exposed to each dose, supporting an oxidative stress response. Our data support the hypothesis that quercetin may affect locomotion and induce deformities in zebrafish larvae by diminishing ATP production and by altering the expression of transcripts related to muscle formation and activity.

Diet and hair loss: effects of nutrient deficiency and supplement use

Patients presenting with hair loss should be screened by medical history, dietary history and physical exam for risk factors for nutrient deficiency. If warranted, laboratory studies may be performed. In patients with no risk factors, further laboratory evaluation searching for nutritional deficiencies is not warranted. For patients with nutritional deficiencies, it is clear that those deficiencies should be corrected. Further research is required to determine whether any benefit exists for nutrient supplementation in the absence of documented deficiency. At this time, patients must be informed that such research is lacking and that in fact some supplements carry the risk of worsening hair loss or the risk of toxicity.

Exogenous antioxidants--Double-edged swords in cellular redox state: Health beneficial effects at physiologic doses versus deleterious effects at high doses

The balance between oxidation and antioxidation is believed to be critical in maintaining healthy biological systems. Under physiological conditions, the human antioxidative defense system including e.g., superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH) and others, allows the elimination of excess reactive oxygen species (ROS) including, among others superoxide anions (O₂^.-), hydroxyl radicals (OH.), alkoxyl radicals (RO.) and peroxyradicals (ROO.). However, our endogenous antioxidant defense systems are incomplete without exogenous originating reducing compounds such as vitamin C, vitamin E, carotenoids and polyphenols, playing an essential role in many antioxidant mechanisms in living organisms. Therefore, there is continuous demand for exogenous antioxidants in order to prevent oxidative stress, representing a disequilibrium redox state in favor of oxidation. However, high doses of isolated compounds may be toxic, owing to prooxidative effects at high concentrations or their potential to react with beneficial concentrations of ROS normally present at physiological conditions that are required for optimal cellular functioning. This review aims to examine the double-edged effects of dietary originating antioxidants with a focus on the most abundant compounds, especially polyphenols, vitamin C, vitamin E and carotenoids. Different approaches to enrich our body with exogenous antioxidants such as via synthetic antioxidants, diets rich in fruits and vegetables and taking supplements will be reviewed and experimental and epidemiological evidences discussed, highlighting that antioxidants at physiological doses are generally safe, exhibiting interesting health beneficial effects.

Preparation and antioxidant/pro-oxidant activities of 3-monosubstituted 5-hydroxyoxindole derivatives

Antioxidant treatments have been expected to be a novel therapeutics for various oxidative stress-mediated disorders. Our previous study revealed that 5-hydroxyoxindole and its 3-phenacyl-3-hydroxy derivatives showed excellent antioxidant activities such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and lipid-peroxidation inhibitory activity. However, the DPPH radical scavenging activity of the 3,3-disubstituted derivatives was lower than that of the original 5-hydroxyoxindole. In the present study, we synthesized novel 3-monosubstituted 5-hydroxyoxindole derivatives that exhibited stronger DPPH radical scavenging activities and lipid peroxidation-inhibitory activities than the 3,3-disubstituted 5-hydroxyoxindoles. Moreover, the 3-monosubstituted 5-hydroxyoxindole derivatives showed neither an iron-mediated pro-oxidant effect nor a remarkable cytotoxicity against HL-60 cell lines except some of the highly lipophilic compounds. These results indicate that 3-monosubstituted 5-hydroxyoxindoles can be used as a promising antioxidant scaffold for drug discovery.

The mitochondrial permeability transition pore in AD 2016: An update

Over the past 30years the mitochondrial permeability transition - the permeabilization of the inner mitochondrial membrane due to the opening of a wide pore - has progressed from being considered a curious artifact induced in isolated mitochondria by Ca(2+) and phosphate to a key cell-death-inducing process in several major pathologies. Its relevance is by now universally acknowledged and a pharmacology targeting the phenomenon is being developed. The molecular nature of the pore remains to this day uncertain, but progress has recently been made with the identification of the FOF1 ATP synthase as the probable proteic substrate. Researchers sharing this conviction are however divided into two camps: these believing that only the ATP synthase dimers or oligomers can form the pore, presumably in the contact region between monomers, and those who consider that the ring-forming c subunits in the FO sector actually constitute the walls of the pore. The latest development is the emergence of a new candidate: Spastic Paraplegia 7 (SPG7), a mitochondrial AAA-type membrane protease which forms a 6-stave barrel. This review summarizes recent developments of research on the pathophysiological relevance and on the molecular nature of the mitochondrial permeability transition pore. This article is part of a Special Issue entitled: Mitochondrial Channels edited by Pierre Sonveaux, Pierre Maechler and Jean-Claude Martinou.

Phytochemicals prevent mitochondrial membrane permeabilization and protect SH-SY5Y cells against apoptosis induced by PK11195, a ligand for outer membrane translocator protein

Epidemiological studies present the beneficial effects of dietary habits on prevention of aging-associated decline of brain function. Phytochemicals, the second metabolites of food, protect neuronal cells from cell death in cellular models of neurodegenerative disorders, and the neuroprotective activity has been ascribed to the anti-oxidant and anti-inflammatory functions. In this paper, the cellular mechanism of neuroprotection by phytochemicals was investigated, using the cellular model of mitochondrial apoptosis induced by PK11195, a ligand of outer membrane translocator protein, in SH-SY5Y cells. PK11195 induced mitochondrial membrane permeabilization with rapid transit production of superoxide (superoxide flashes) and calcium release from mitochondria, and activated apoptosis signal pathway. Study on the structure-activity relationship of astaxanthin, ferulic acid derivatives, and sesame lignans revealed that these phytochemicals inhibited mitochondrial membrane permeabilization and protected cells from apoptosis. Ferulic acid derivatives and sesame lignans inhibited or enhanced the mitochondrial pore formation and cell death by PK11195 according to their amphiphilic properties, not directly depending on the antioxidant activity. Regulation of pore formation at mitochondrial membrane is discussed as a novel mechanism behind neuroprotective activity of phytochemicals in aging and age-associated neurodegenerative disorders, and also behind dual functions of phytochemicals in neuronal and cancer cells.

Selected polyphenols potentiate the apoptotic efficacy of glycolytic inhibitors in human acute myeloid leukemia cell lines. Regulation by protein kinase activities

Background

The glycolysis inhibitor 2-deoxy-d-glucose (2-DG) is a safe, potentially useful anti-tumour drug, but its efficacy is normally low when used alone. Recent studies indicated that 2-DG stimulates the PI3K/Akt and MEK/ERK defensive pathways, which limits the apoptotic efficacy in tumour cell lines. We hypothesized that co-treatment with selected polyphenols could improve 2-DG-provoked apoptosis by preventing defensive kinase activation.

Methods

Cell proliferation was measured by cell counting or the MTT assay. Cell cycle, apoptosis and necrosis were determined by propidium iodide staining and/or annexin V labeling followed by flow cytometry. Mitochondria pore transition and depolarization were determined by calcein-ATM or rhodamine 123 labeling followed flow cytometry. Intracellular reactive oxygen species and GSH were determined by dichlorodihydrofluorescein diacetate or monochlorobimane labeling followed by flow cytometry or fluorimetry. Expression and phosphorylation of protein kinases were analyzed by the Western blot.

Results

(i) 2-DG-provoked apoptosis was greatly potentiated by co-treatment with the sub-lethal concentrations of the flavonoid quercetin in human HL60 acute myeloblastic leukemia cells. Allowing for quantitative differences, apoptosis potentiation was also obtained using NB4 promyelocytic and THP-1 promonocytic cells, using curcumin or genistein instead of quercetin, and using lonidamine instead of 2-DG, but not when 2-DG was substituted by incubation in glucose-free medium. (ii) Quercetin and 2-DG rapidly elicited the opening of mitochondria pore transition, which preceded the trigger of apoptosis. (iii) Treatments did not affect GSH levels, and caused disparate effects on reactive oxygen species generation, which did not match the changes in lethality. (iv) 2-DG and lonidamine stimulated defensive Akt and ERK phosphorylation/activation, while glucose starvation was ineffective. Polyphenols prevented the stimulation of Akt phosphorylation, and in some cases also ERK phosphorylation. In addition, quercetin and 2-DG stimulated GSK-3α,β phosphorylation/inactivation, although with different isoform specificity. The use of pharmacologic inhibitors confirmed the importance of these kinase modifications for apoptosis.

Conclusions

The present in vitro observations suggest that co-treatment with low concentrations of selected polyphenols might represent a manner of improving the poor anti-tumour efficacy of some glycolytic inhibitors, and that apoptosis potentiation may be at least in part explained by the regulation of defensive protein kinase activities.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-016-0345-y) contains supplementary material, which is available to authorized users.

Quercetin Impacts Expression of Metabolism- and Obesity-Associated Genes in SGBS Adipocytes

Obesity is characterized by the rapid expansion of visceral adipose tissue, resulting in a hypoxic environment in adipose tissue which leads to a profound change of gene expression in adipocytes. As a consequence, there is a dysregulation of metabolism and adipokine secretion in adipose tissue leading to the development of systemic inflammation and finally resulting in the onset of metabolic diseases. The flavonoid quercetin as well as other secondary plant metabolites also referred to as phytochemicals have anti-oxidant, anti-inflammatory, and anti-diabetic effects known to be protective in view of obesity-related-diseases. Nevertheless, its underlying molecular mechanism is still obscure and thus the focus of this study was to explore the influence of quercetin on human SGBS (Simpson Golabi Behmel Syndrome) adipocytes’ gene expression. We revealed for the first time that quercetin significantly changed expression of adipokine (Angptl4, adipsin, irisin and PAI-1) and glycolysis-involved (ENO2, PFKP and PFKFB4) genes, and that this effect not only antagonized but in part even overcompensated the effect mediated by hypoxia in adipocytes. Thus, these results are explained by the recently proposed hypothesis that the protective effect of quercetin is not solely due to its free radical-scavenging activity but also to a direct effect on mitochondrial processes, and they demonstrate that quercetin might have the potential to counteract the development of obesity-associated complications.

Quercetin and the mitochondria: A mechanistic view

Quercetin is an important flavonoid that is ubiquitously present in the diet in a variety of fruits and vegetables. It has been traditionally viewed as a potent antioxidant and anti-inflammatory molecule. However, recent studies have suggested that quercetin may exert its beneficial effects independent of its free radical-scavenging properties. Attention has been placed on the effect of quercetin on an array of mitochondrial processes. Quercetin is now recognized as a phytochemical that can modulate pathways associated with mitochondrial biogenesis, mitochondrial membrane potential, oxidative respiration and ATP anabolism, intra-mitochondrial redox status, and subsequently, mitochondria-induced apoptosis. The present review evaluates recent evidence on the ability of quercetin to interact with the abovementioned pathways, and critically analyses how, such interactions can exert protection against mitochondrial damage in response to toxicity induced by several exogenously and endogenously-produced cellular stressors, and oxidative stress in particular.