Polyphenols and mitochondria: an update on their increasingly emerging ROS-scavenging independent actions

Flavonoids modulate AMPK/PGC-1α and interconnected pathways toward potential neuroprotective activities

As progressive, chronic, incurable and common reasons for disability and death, neurodegenerative diseases (NDDs) are significant threats to human health. Besides, the increasing prevalence of neuronal gradual degeneration and death during NDDs has made them a global concern. Since yet, no effective treatment has been developed to combat multiple dysregulated pathways/mediators and related complications in NDDs. Therefore, there is an urgent need to create influential and multi-target factors to combat neuronal damages. Accordingly, the plant kingdom has drawn a bright future. Among natural entities, flavonoids are considered a rich source of drug discovery and development with potential biological and medicinal activities. Growing studies have reported multiple dysregulated pathways in NDDs, which among those mediator AMP-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) play critical roles. In this line, critical role of flavonoids in the upregulation of AMPK/PGC-1α pathway seems to pave the road in the treatment of Alzheimer's disease (AD), Parkinson's disease (PD), aging, central nervous system (brain/spinal cord) damages, stroke, and other NDDs. In the present study, the regulatory role of flavonoids in managing various NDDs has been shown to pass through AMPK/PGC-1α signaling pathway.

Protective effects of naringin on valproic acid-induced hepatotoxicity in rats

Valproic acid (VPA) is mainly prescribed to treat epilepsy. VPA has been reported to be associated with many adverse effects, including hepatotoxicity. Naringin (NRG) is a natural, therapeutically active flavanone glycoside with anti-inflammatory, anti-apoptotic, and antioxidant. The current study was therefore designed to investigate the protective effect of NRG against the VPA-induced experimental hepatotoxicity model. For this purpose, 24 Wistar albino rats were randomly divided into three groups as control (Vehicle), VPA (500 mg/kg), and NRG + VPA (100 mg/kg NRG + 500 mg/kg VPA) groups. The agents were administered via oral gavage for 14 days. Blood and liver tissue samples were taken on the end of the experiment. Biochemical analyzes were performed on the blood and liver samples. Also, malondialdehyde (MDA), superoxide dismutase (SOD) enzyme, glutathione (GSH) content, catalase (CAT) enzyme levels were examined in the liver tissue samples. Histopathological changes (hydropic degeneration and congestion) in the VPA group were increased significantly when compared to the control group (p < 0.05). We also found a decrease in enzymes of serum liver function in the VPA group. However, NRG has been shown not to prevent histopathological changes in the VPA group. According to our results with this experiment protocol, NRG could not exert sufficient protection against VPA-induced hepatotoxicity.

Paving Plant-Food-Derived Bioactives as Effective Therapeutic Agents in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, where social and communication deficits and repetitive behaviors are present. Plant-derived bioactives have shown promising results in the treatment of autism. In this sense, this review is aimed at providing a careful view on the use of plant-derived bioactive molecules for the treatment of autism. Among the plethora of bioactives, curcumin, luteolin, and resveratrol have revealed excellent neuroprotective effects and can be effectively used in the treatment of neuropsychological disorders. However, the number of clinical trials is limited, and none of them have been approved for the treatment of autism or autism-related disorder. Further clinical studies are needed to effectively assess the real potential of such bioactive molecules.

Bridging the Gap Between Nature and Antioxidant Setbacks: Delivering Gallic Acid to Mitochondria

Research on mitochondria-targeted active molecules became a hot topic in the past decade. Development of mitochondria permeability transition pore (mPTP )-targeting agents with clinical applications is needed not only because of the importance of the target in several diseases but also due to the fact that the current developed molecules have shown poor clinical success. In fact, only a reduced percentage reach mitochondria , effectively preventing pathological mPTP opening. The mitochondrial-targeting strategies should be a promising solution to increase the selectivity of compounds to the mPTP , reducing also their potential side effects. Chemical conjugation of bioactive molecules with a lipophilic cation such as the triphenylphosphonium (TPP ⁺) has been established as a robust strategy to specifically target mitochondria . Phytochemicals such as hydroxybenzoic acids are normal constituents of the human diet. These molecules display beneficial healthy effects, ranging from antioxidant action through diverse mechanisms to modulation of mitochondrial-related apoptotic system, although their therapeutic application is limited due to pharmacokinetic drawbacks. Accordingly, the development of a new antioxidant based on the dietary benzoic acid-gallic acid -is described as well as the demonstration of its mitochondriotropic characteristics.

A. Mohamed I, Wang Z, Khatab A, Sherif A, Ahmad H, Khan MN, Hassan HM, Elrewainy IM, Kuai J, Zhou G, Wang B. Antioxidative and Metabolic Contribution to Salinity Stress Responses in Two Rapeseed Cultivars during the Early Seedling Stage

Measuring metabolite patterns and antioxidant ability is vital to understanding the physiological and molecular responses of plants under salinity. A morphological analysis of five rapeseed cultivars showed that Yangyou 9 and Zhongshuang 11 were the most salt-tolerant and -sensitive, respectively. In Yangyou 9, the reactive oxygen species (ROS) level and malondialdehyde (MDA) content were minimized by the activation of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) for scavenging of over-accumulated ROS under salinity stress. Furthermore, Yangyou 9 showed a significantly higher positive correlation with photosynthetic pigments, osmolyte accumulation, and an adjusted Na⁺/K⁺ ratio to improve salt tolerance compared to Zhongshuang 11. Out of 332 compounds identified in the metabolic profile, 225 metabolites were filtrated according to p < 0.05, and 47 metabolites responded to salt stress within tolerant and sensitive cultivars during the studied time, whereas 16 and 9 metabolic compounds accumulated during 12 and 24 h, respectively, in Yangyou 9 after being sown in salt treatment, including fatty acids, amino acids, and flavonoids. These metabolites are relevant to metabolic pathways (amino acid, sucrose, flavonoid metabolism, and tricarboxylic acid cycle (TCA), which accumulated as a response to salinity stress. Thus, Yangyou 9, as a tolerant cultivar, showed improved antioxidant enzyme activity and higher metabolite accumulation, which enhances its tolerance against salinity. This work aids in elucidating the essential cellular metabolic changes in response to salt stress in rapeseed cultivars during seed germination. Meanwhile, the identified metabolites can act as biomarkers to characterize plant performance in breeding programs under salt stress. This comprehensive study of the metabolomics and antioxidant activities of Brassica napus L. during the early seedling stage is of great reference value for plant breeders to develop salt-tolerant rapeseed cultivars.

Taurisolo®, a Grape Pomace Polyphenol Nutraceutical Reducing the Levels of Serum Biomarkers Associated With Atherosclerosis

Trimethylamine-N-oxide (TMAO) is a gut microbiota-derived metabolite recognized as strongly related to cardiovascular diseases (CVD), mainly increasing the risk of atherosclerosis development. Currently, no pharmacological approaches have been licensed for reduction of TMAO serum levels and conventional anti-atherosclerosis treatments only target the traditional risk factors, and the cardiovascular risk (CVR) still persist. This underlines the need to find novel targeted strategies for management of atherosclerosis. In this study we tested the ability of a novel nutraceutical formulation based on grape pomace polyphenols (Taurisolo®) in reducing both the serum levels of TMAO and oxidative stress-related biomarkers in humans (n = 213). After chronic treatment with Taurisolo® we observed significantly reduced levels of TMAO (−49.78 and −75.80%, after 4-week and 8-week treatment, respectively), oxidized LDL (oxLDL; −43.12 and −65.05%, after 4-week and 8-week treatment, respectively), and reactive oxygen species (D-ROMs; −34.37 and −49.68%, after 4-week and 8-week treatment, respectively). On the other hand, no significant changes were observed in control group. Such promising, the results observed allow indicating Taurisolo® as an effective nutraceutical strategy for prevention of atherosclerosis.

Clinical Trial Registration: This study is listed on the ISRCTN registry with ID ISRCTN10794277 (doi: 10.1186/ISRCTN10794277).

Advances in the role of silence information regulator family in pathological pregnancy

Aberrant maternal inflammation and oxidative stress are the two main mechanisms of pathological pregnancy. The silence information regulator (sirtuin) family is a highly conserved family of nicotinamide adenine dinucleotide (NAD)-dependent deacylases. By regulating the post-translational modification of proteins, sirtuin is involved in various biological processes including oxidative stress and inflammation. Nowadays, emerging evidence indicates that sirtuin may be closely related to the occurrence and development of pathological pregnancy. The down-regulation of sirtuin can cause spontaneous preterm delivery by promoting uterine contraction and rupture of fetal membranes, cause gestational diabetes mellitus through promoting oxidative stress and affecting the activity of key enzymes in glucose metabolism, cause preeclampsia by reducing the proliferation and invasion ability of trophoblasts, cause intrahepatic cholestasis of pregnancy by promoting the production of bile acids and T helper 1 cell (Th1) cytokines, and cause intrauterine growth restriction through inducing mitochondrial dysfunction. Moreover, the expression and activation of sirtuin can be modulated through dietary interventions, thus sirtuin is expected to become a new target for the prevention and treatment of pregnancy complications. This article reviews the role of the sirtuin family in the occurrence and development of pathological pregnancy and its influence on the development of the offspring.

Ex Vivo Study on the Antioxidant Activity of a Winemaking By-Product Polyphenolic Extract (Taurisolo®) on Human Neutrophils

Oxidative stress (OxS) has been linked to several chronic diseases and is recognized to have both major causes and consequences. The use of antioxidant-based nutraceuticals has been licensed as an optimal tool for management of OxS-related diseases. Currently, great interest is focused on the valorization of agri-food by-products as a source of bioactive compounds, including polyphenols. In this sense, we evaluated the efficacy of a novel nutraceutical formulation based on polyphenolic extract from Aglianico cultivar grape pomace (registered as Taurisolo^®). In particular, we tested both native and in vitro gastrointestinal digested forms. The two extracts have been used to treat ex vivo neutrophils from subjects with metabolic syndrome, reporting a marked antioxidant activity of Taurisolo^®, as shown by its ability to significantly reduce both the levels of reactive oxygen species (ROS) and the activities of catalase and myeloperoxidase in the cell medium after stimulation of neutrophils with phorbol 12-myristate 13-acetate (PMA). Interestingly, we observed an increase in intracellular enzymatic activities in PMA-treated cells, suggesting that Taurisolo^® polyphenols might be able to activate nuclear factors, up-regulating the expression of this target antioxidant gene. In addition, Taurisolo^® reversed the increase in malondialdehyde induced by PMA; reduced the expression of pro-inflammatory genes such as cyclooxygenase 2 (COX-2), tumor necrosis factor alpha (TNFα) and myeloperoxidase (MPO); and induced the expression of the anti-inflammatory cytokine IL-10. Overall, these results suggest the efficacy of Taurisolo^® in contrasting the OxS at blood level, providing evidence for its therapeutic potential in the management of OxS-related pathological conditions in humans.

The Neuroprotective Effect of Tea Polyphenols on the Regulation of Intestinal Flora

Tea polyphenols (TPs) are the general compounds of natural polyhydroxyphenols extracted in tea. Although a large number of studies have shown that TPs have obvious neuroprotective and neuro repair effects, they are limited due to the low bioavailability in vivo. However, TPs can act indirectly on the central nervous system by affecting the “microflora–gut–brain axis”, in which the microbiota and its composition represent a factor that determines brain health. Bidirectional communication between the intestinal microflora and the brain (microbe–gut–brain axis) occurs through a variety of pathways, including the vagus nerve, immune system, neuroendocrine pathways, and bacteria-derived metabolites. This axis has been shown to influence neurotransmission and behavior, which is usually associated with neuropsychiatric disorders. In this review, we discuss that TPs and their metabolites may provide benefits by restoring the imbalance of intestinal microbiota and that TPs are metabolized by intestinal flora, to provide a new idea for TPs to play a neuroprotective role by regulating intestinal flora.

Phenolic acid metabolites of polyphenols act as inductors for hormesis in C. elegans

INTRODUCTION

Aging represents a major risk factors for metabolic diseases, such as diabetes, obesity, or neurodegeneration. Polyphenols and their metabolites, especially simple phenolic acids, gained growing attention as a preventive strategy against age-related, non-communicable diseases, due to their hormetic potential. Using Caenorhabditis elegans (C. elegans) we investigate the effect of protocatechuic, gallic, and vanillic acid on mitochondrial function, health parameters, and the induction of potential hormetic pathways.

METHODS

Lifespan, heat-stress resistance and chemotaxis of C. elegans strain P X 627, a specific model for aging, were assessed in 2-day and 10-day old nematodes. Mitochondrial membrane potential (ΔΨm) and ATP generation were measured. mRNA expression levels of longevity and energy metabolism-related genes were determined using qRT-PCR.

RESULTS

All phenolic acids were able to significantly increase the nematodes lifespan, heat-stress resistance and chemotaxis at micromolar concentrations. While ΔΨm was only affected by age, vanillic acid (VA) significantly decreased ATP concentrations in aged nematodes. Longevity pathways, were activated by all phenolic acids, while VA also induced glycolytic activity and response to cold.

CONCLUSION

While life- and health span parameters are positively affected by the investigated phenolic acids, the concentrations applied were unable to affect mitochondrial performance. Therefore we suggest a hormetic mode of action, especially by activation of the sirtuin-pathway.

Grape Polyphenols Attenuate Diet-Induced Obesity and Hepatic Steatosis in Mice in Association With Reduced Butyrate and Increased Markers of Intestinal Carbohydrate Oxidation

A Western Diet (WD) low in fiber but high in fats and sugars contributes to obesity and non-alcoholic fatty liver disease (NAFLD). Supplementation with grape polyphenols (GPs) rich in B-type proanthocyanidins (PACs) can attenuate symptoms of cardiometabolic disease and alter the gut microbiota and its metabolites. We hypothesized that GP-mediated metabolic improvements would correlate with altered microbial metabolites such as short chain fatty acids (SCFAs). To more closely mimic a WD, C57BL/6J male mice were fed a low-fiber diet high in sucrose and butterfat along with 20% sucrose water to represent sugary beverages. This WD was supplemented with 1% GPs (WD-GP) to investigate the impact of GPs on energy balance, SCFA profile, and intestinal metabolism. Compared to WD-fed mice, the WD-GP group had higher lean mass along with lower fat mass, body weight, and hepatic steatosis despite consuming more calories from sucrose water. Indirect and direct calorimetry revealed that reduced adiposity in GP-supplemented mice was likely due to their greater energy expenditure, which resulted in lower energy efficiency compared to WD-fed mice. GP-supplemented mice had higher abundance of Akkermansia muciniphila, a gut microbe reported to increase energy expenditure. Short chain fatty acid measurements in colon content revealed that GP-supplemented mice had lower concentrations of butyrate, a major energy substrate of the distal intestine, and reduced valerate, a putrefactive SCFA. GP-supplementation also resulted in a lower acetate:propionate ratio suggesting reduced hepatic lipogenesis. Considering the higher sucrose consumption and reduced butyrate levels in GP-supplemented mice, we hypothesized that enterocytes would metabolize glucose and fructose as a replacement energy source. Ileal mRNA levels of glucose transporter-2 (GLUT2, SLC2A2) were increased indicating higher glucose and fructose uptake. Expression of ketohexokinase (KHK) was increased in ileum tissue suggesting increased fructolysis. A GP-induced increase in intestinal carbohydrate oxidation was supported by: (1) increased gene expression of duodenal pyruvate dehydrogenase (PDH), (2) a decreased ratio of lactate dehydrogenase a (LDHa): LDHb in jejunum and colon tissues, and (3) decreased duodenal and colonic lactate concentrations. These data indicate that GPs protect against WD-induced obesity and hepatic steatosis by diminishing portal delivery of lipogenic butyrate and sugars due to their increased intestinal utilization.

Flavonoids and cellular stress: a complex interplay affecting human health

Flavonoid consumption has beneficial effects on human health, however, clinical evidence remains often inconclusive due to high interindividual variability. Although this high interindividual variability has been consistently observed in flavonoid research, the potential underlying reasons are still poorly studied. Especially the knowledge on the impact of health status on flavonoid responsiveness is limited and merits more investigation. Here, we aim to highlight the bidirectional interplay between flavonoids and cellular stress. First, the state-of-the-art concerning inflammatory stress and mitochondrial dysfunction is reviewed and a comprehensive overview of recent in vitro studies investigating the impact of flavonoids on cellular stress, induced by tumor necrosis factor α, lipopolysaccharide and mitochondrial stressors, is given. Second, we critically discuss the influence of cellular stress on flavonoid uptake, accumulation, metabolism and cell responses, which has, to our knowledge, never been extensively reviewed before. Next, we advocate the innovative insight that stratification of the general population based on health status can reveal subpopulations that benefit more from flavonoid consumption. Finally, suggestions are given for the development of future cell models that simulate the physiological micro-environment, including interindividual variability, since more mechanistic research is needed to establish scientific-based personalized food recommendations for specific subpopulations.

N-acetylcysteine is more effective than ellagic acid in preventing acrolein induced dysfunction in mitochondria isolated from rat liver

Acrolein, a common environmental, food, and water pollutant, has been linked to the pathology of several diseases. This toxic substance is an unsaturated aldehyde and a major component of cigarette smoke and also produced during the processing of fat-containing foods. This study aimed to evaluate the protective effect of ellagic acid and N-acetylcysteine (NAC) in acrolein-induced toxicity in mitochondria isolated from the rat liver. The mitochondria were exposed to different concentrations of acrolein for 40 min, then functionality was assessed. Contact with acrolein rapidly and remarkably depleted the intracellular glutathione and antioxidant capacity, because of increased ROS production and lipid peroxidation which may lead to the cell death. Mitochondria were then pre-exposed to different concentrations of ellagic acid, NAC, and IC₅₀ concentration of acrolein. Consistent with the results, acrolein decreased GSH content and increased ROS level and lipid peroxidation, which led to ATP depletion and mitochondrial dysfunction. While ellagic acid has been able to reduce ROS and therefore the permeability of the mitochondrial membrane potential (MMP), presumably via its antioxidant properties, we've not detected its favorable effect on GSH and ATP restoration and also on mitochondrial complex II function. However, NAC strongly decreased ROS, lipid peroxidation and MMP and improved GSH content and complex II activity. These results showed that ellagic acid while reported to possess some cellular protective properties, did not prevent mitochondria from being affected by acrolein during this in vitro study. PRACTICAL APPLICATIONS: Ellagic acid is found in fruits, vegetables, and nuts which are revealed to possess strong antioxidant and protective properties. Mitochondrial dysfunction has been implicated in the pathogenesis of some chronic diseases including cancer, diabetes, liver disease, and neurodegenerative disorders, and presumably, ellagic acid by its mitochondrial protective effects can be helpful in these chronic conditions. Acrolein is an α,β-unsaturated aldehyde that can be produced during cooking at high temperature. By increasing the ROS level and lipid peroxidation and depleting the glutathione content, acrolein induces cellular damage and mitochondrial toxicity. This toxicant is taken into account as a carcinogen and mutagen. In this study, the protective effect of ellagic acid in comparison with N-acetylcysteine has been investigated during the toxicity of acrolein in the rat liver mitochondria to look for evidence of whether it is useful or not through this insult.

Maternal polyphenol intake impairs cerebellar redox homeostasis in newborn rats

INTRODUCTION

Polyphenols are compounds found in plants that have been extensively studied due to the health benefits of its consumption in adulthood. Meanwhile, recent evidence suggests that polyphenol consumption during pregnancy may not be safe for the fetus.

OBJECTIVE

The goal of this study was to evaluate the effect of naringenin supplementation during pregnancy on brain redox homeostasis and mitochondrial activity of the newborn rat.

METHODS

Adult female Wistar rats were divided into two groups: (1) vehicle (1 mL/Kg p.o.) or (2) naringenin (50 mg/Kg p.o.). Naringenin was administered once a day during pregnancy. The offspring were euthanized on postnatal day 7, as well the dams, and brain regions were dissected.

RESULTS

The offspring cerebellum was the most affected region, presenting increased activity of the mitochondrial electron transport system, allied to increased reactive species levels, lipid peroxidation, and glutathione concentration. The nitric oxide levels suffered structure-dependent alteration, with decreased levels in the pups' cerebellum and increased in the hippocampus. The offspring parietal cortex was not affected, as well as the parameters evaluated in the dams' brains.

CONCLUSION

Maternal consumption of naringenin alters offspring cerebellar redox homeostasis, which could be related to adverse effects on the motor and cognitive development in the descendants.

Micellar Nanocarriers of Hydroxytyrosol Are Protective against Parkinson's Related Oxidative Stress in an In Vitro hCMEC/D3-SH-SY5Y Co-Culture System

Hydroxytyrosol (HT) is a natural phenolic antioxidant which has neuroprotective effects in models of Parkinson’s disease (PD). Due to issues such as rapid metabolism, HT is unlikely to reach the brain at therapeutic concentrations required for a clinical effect. We have previously developed micellar nanocarriers from Pluronic F68^® (P68) and dequalinium (DQA) which have suitable characteristics for brain delivery of antioxidants and iron chelators. The aim of this study was to utilise the P68 + DQA nanocarriers for HT alone, or in combination with the iron chelator deferoxamine (DFO), and assess their physical characteristics and ability to pass the blood–brain barrier and protect against rotenone in a cellular hCMEC/D3-SH-SY5Y co-culture system. Both HT and HT + DFO formulations were less than 170 nm in size and demonstrated high encapsulation efficiencies (up to 97%). P68 + DQA nanoformulation enhanced the mean blood–brain barrier (BBB) passage of HT by 50% (p < 0.0001, n = 6). This resulted in increased protection against rotenone induced cytotoxicity and oxidative stress by up to 12% and 9%, respectively, compared to the corresponding free drug treatments (p < 0.01, n = 6). This study demonstrates for the first time the incorporation of HT and HT + DFO into P68 + DQA nanocarriers and successful delivery of these nanocarriers across a BBB model to protect against PD-related oxidative stress. These nanocarriers warrant further investigation to evaluate whether this enhanced neuroprotection is exhibited in in vivo PD models.

One Week of CDAHFD Induces Steatohepatitis and Mitochondrial Dysfunction with Oxidative Stress in Liver

The prevalence of nonalcoholic fatty liver disease (NAFLD) has been rapidly increasing worldwide. A choline-deficient, L-amino acid-defined, high-fat diet (CDAHFD) has been used to create a mouse model of nonalcoholic steatohepatitis (NASH). There are some reports on the effects on mice of being fed a CDAHFD for long periods of 1 to 3 months. However, the effect of this diet over a short period is unknown. Therefore, we examined the effect of 1-week CDAHFD feeding on the mouse liver. Feeding a CDAHFD diet for only 1-week induced lipid droplet deposition in the liver with increasing activity of liver-derived enzymes in the plasma. On the other hand, it did not induce fibrosis or cirrhosis. Additionally, it was demonstrated that CDAHFD significantly impaired mitochondrial respiration with severe oxidative stress to the liver, which is associated with a decreasing mitochondrial DNA copy number and complex proteins. In the gene expression analysis of the liver, inflammatory and oxidative stress markers were significantly increased by CDAHFD. These results demonstrated that 1 week of feeding CDAHFD to mice induces steatohepatitis with mitochondrial dysfunction and severe oxidative stress, without fibrosis, which can partially mimic the early stage of NASH in humans.

Regulation of Cytochrome c Oxidase by Natural Compounds Resveratrol, (-)-Epicatechin, and Betaine

Numerous naturally occurring molecules have been studied for their beneficial health effects. Many compounds have received considerable attention for their potential medical uses. Among them, several substances have been found to improve mitochondrial function. This review focuses on resveratrol, (–)-epicatechin, and betaine and summarizes the published data pertaining to their effects on cytochrome c oxidase (COX) which is the terminal enzyme of the mitochondrial electron transport chain and is considered to play an important role in the regulation of mitochondrial respiration. In a variety of experimental model systems, these compounds have been shown to improve mitochondrial biogenesis in addition to increased COX amount and/or its enzymatic activity. Given that they are inexpensive, safe in a wide range of concentrations, and effectively improve mitochondrial and COX function, these compounds could be attractive enough for possible therapeutic or health improvement strategies.

Intracellular quercetin accumulation and its impact on mitochondrial dysfunction in intestinal Caco-2 cells

PURPOSE

Flavonoid bioavailability and bioactivity is associated with interindividual variability, which is partially due to differences in health status. Previously, it was demonstrated that cellular stress, especially mitochondrial stress, increases intracellular quercetin uptake and this is associated with beneficial health effects. Here, the impact of quercetin on mitochondrial dysfunction, induced by stressors targeting different sites of the electron transport chain, is investigated. The influence of the mitochondrial stress on quercetin uptake and subcellular location is studied and the accumulated quercetin metabolites in intestinal Caco-2 cells and mitochondria are characterized.

PRINCIPAL RESULTS

It was observed that quercetin counteracted (i) the carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP)-induced decrease in maximum oxygen consumption, (ii) the valinomycin-, oligomycin- and FCCP-induced reactive oxygen species production and (iii) the valinomycin-induced disruption of mitochondrial membrane potential. Using confocal microscopy, it was found that upon mitochondrial stress, the intracellular quercetin accumulation increased and was partially located in the mitochondria. Finally, it was demonstrated that quercetin was present as O-methyl, O-methylglucuronide and O-methylsulfate conjugates in the cell lysate and mitochondria-enriched fraction.

MAJOR CONCLUSIONS

This study shows that quercetin can partially restore, especially FCCP-induced, mitochondrial dysfunction and this protective effect was linked with an intracellular quercetin accumulation in the mitochondria of intestinal cells.

Novel arylidene malonate derivative, KM-34, showed neuroprotective effects on in vitro and in vivo models of ischemia/reperfusion

Cerebral ischemia constitutes the most frequent type of cerebrovascular disease. The reduction of blood supply to the brain initiates the ischemic cascade starting from ionic imbalance to subsequent glutamate excitotoxicity, neuroinflammation and oxidative stress, eventually causing neuronal death. Previously, the authors have demonstrated the in vitro cytoprotective and antioxidant effects of a new arylidene malonate derivative, KM-34, against oxidizing agents like hydrogen peroxide, glutamate or Fe3+/ascorbate. Here, we examined for the first time the neuroprotective effect of KM-34 on ischemia/reperfusion models. In vitro, treatment with 10 and 50 μM KM-34 reduced the cellular death (propidium iodide incorporation) induced by oxygen glucose deprivation (OGD) in rat organotypic hippocampal slices cultures. In vivo, stroke was induced in male Wistar rats through middle cerebral artery occlusion (MCAO), followed by 23 h of reperfusion. KM-34 was orally administered 105 min after MCAO onset. We noticed that 1 mg/kg KM-34 reduced infarct volume and neurological score, and increased the latency to fall in the Hanging Wire test compared to vehicle-treated ischemic animals. While ischemic and sham-operated groups showed similar horizontal locomotor activity, vertical counts decreased after MCAO, suggesting that vertical movements are more sensitive to the ischemic injury. Treatment with KM-34 also alleviated the mitochondrial impairment (ROS generation, swelling and membrane potential dissipation) induced by transient MCAO but not significant alterations were found in oxidative stress parameters. Overall, the study provides preclinical evidences confirming the neuroprotective effects of a novel synthetic molecule and paved the way for future investigations regarding its therapeutic potential against brain ischemia/reperfusion injury.

From winery by-product to healthy product: bioavailability, redox signaling and oxidative stress modulation by wine pomace product

The wine pomace is the main winery by-products that suppose an economic and environmental problem and their use as a functional ingredient are being increasingly recognized as a good and inexpensive source of bioactive compounds. In this sense, it is known the potential health properties of wine pomace products in the prevention of disorders associated with oxidative stress and inflammation such as endothelial dysfunction, hypertension, hyperglycemia, diabetes, obesity. Those effects are due to the bioactive compounds of wine pomace and the mechanisms concern especially modulation of antioxidant/prooxidant activity, improvement of nitric oxide bioavailability, reduction of pro-inflammatory cytokines and modulation of antioxidant/inflammatory signal pathways. This review mainly summarizes the mechanisms of wine pomace products as modulators of oxidative status involved in cell pathologies as well as their potential therapeutic use for cardiovascular diseases. For this purpose, the review provides an overview of the findings related to the wine pomace bioactive compounds profile, their bioavailability and the action mechanisms for maintaining the redox cell balance involved in health benefits. The review suggests an important role for wine pomace product in cardiovascular diseases prevention and their regular food intake may attenuate the development and progression of comorbidities associated with cardiovascular diseases.

Heat Stress in Broiler Chickens and the Effect of Dietary Polyphenols, with Special Reference to Willow (Salix spp.) Bark Supplements-A Review

Over the last decade, there has been a growing interest in the use of a wide range of phytoadditives to counteract the harmful effects of heat stress in poultry. Willow (Salix spp.) is a tree with a long history. Among various forms, willow bark is an important natural source of salicin, β-O-glucoside of saligenin, but also of polyphenols (flavonoids and condensed tannins) with antioxidant, antimicrobial, and anti-inflammatory activity. In light of this, the current review presents some literature data aiming to: (1) describe the relationship between heat stress and oxidative stress in broilers, (2) present or summarize literature data on the chemical composition of Salix species, (3) summarize the mechanisms of action of willow bark in heat-stressed broilers, and (4) present different biological effects of the extract of Salix species in different experimental models.

Flavonoids and Polyphenolic Compounds as Potential Talented Agents for the Treatment of Alzheimer's Disease and their Antioxidant Activities

Aging is a normal human cycle and the most important risk factor for neurodegenerative diseases. Alternations in cells due to aging contribute to loss of the nutrient-sensing, cell function, increased oxidative stress, loss of the homeostasis cell, genomic instability, the build-up of malfunctioning proteins, weakened cellular defenses, and a telomere split. Disturbance of these essential cellular processes in neuronal cells can lead to life threats including Alzheimer's disease (AD), Huntington's disease (HD), Lewy's disease, etc. The most common cause of death in the elderly population is AD. Specific therapeutic molecules were created to alleviate AD's social, economic, and health burden. In clinical practice, almost every chemical compound was found to relieve symptoms only in palliative treatment. The reason behind these perfect medicines is that the current medicines are not effective in targeting the cause of this disease. In this paper, we explored the potential role of flavonoid and polyphenolic compounds, which could be the most effective preventative anti-Alzheimer's strategy.

The gut-brain connection in the pathogenicity of Parkinson disease: Putative role of autophagy

Parkinson disease (PD) is a progressive movement functionality disorder resulting in tremor and inability to execute voluntary functions combined with the preponderant non-motor disturbances encompassing constipation and gastrointestinal irritation. Despite continued research, the pathogenesis of PD is not yet clear. The available class of drugs for effective symptomatic management of PD includes a combination of levodopa and carbidopa. In recent past, the link between gut with PD has been explored. According to recent preclinical evidence, pathogens such as virus or bacterium may initiate entry into the gut via the nasal cavity that may aggravate lewy pathology in the gut that eventually propagates and progresses towards the brain via the vagus nerve resulting in the prodromal non-motor symptoms. Additionally, experimental evidence also suggests that alpha-synuclein misfolding commences at a very early stage in the gut and is transported via the vagus nerve prior to seeding PD pathology in the brain. However, this progression and resultant deterioration of the neurones can effectively be altered by an autophagy inducer, Trehalose, although the mechanism behind it is still enigmatic. Hence, this review will mainly focus on analysing the basic components of the gut that might be responsible for aggravating lewy pathology, the mediator(s) responsible for transmission of PD pathology from gut to brain and the important role of trehalose in ameliorating gut dysbiosis related PD complications that would eventually pave the way for therapeutic management of PD.

Acute administration of the olive constituent, oleuropein, combined with ischemic postconditioning increases myocardial protection by modulating oxidative defense

Oleuropein, one of the main polyphenolic constituents of olive, is cardioprotective against ischemia reperfusion injury (IRI). We aimed to assess the cardioprotection afforded by acute administration of oleuropein and to evaluate the underlying mechanism. Importantly, since antioxidant therapies have yielded inconclusive results in attenuating IRI-induced damage on top of conditioning strategies, we investigated whether oleuropein could enhance or imbed the cardioprotective manifestation of ischemic postconditioning (PostC). Oleuropein, given during ischemia as a single intravenous bolus dose reduced the infarct size compared to the control group both in rabbits and mice subjected to myocardial IRI. None of the inhibitors of the cardioprotective pathways, l-NAME, wortmannin and AG490, influence its infarct size limiting effects. Combined oleuropein and PostC cause further limitation of infarct size in comparison with PostC alone in both animal models. Oleuropein did not inhibit the calcium induced mitochondrial permeability transition pore opening in isolated mitochondria and did not increase cGMP production. To provide further insights to the different cardioprotective mechanism of oleuropein, we sought to characterize its anti-inflammatory potential in vivo. Oleuropein, PostC and their combination reduce inflammatory monocytes infiltration into the heart and the circulating monocyte cell population. Oleuropein's mechanism of action involves a direct protective effect on cardiomyocytes since it significantly increased their viability following simulated IRI as compared to non-treated cells. Οleuropein confers additive cardioprotection on top of PostC, via increasing the expression of the transcription factor Nrf-2 and its downstream targets in vivo. In conclusion, acute oleuropein administration during ischemia in combination with PostC provides robust and synergistic cardioprotection in experimental models of IRI by inducing antioxidant defense genes through Nrf-2 axis and independently of the classic cardioprotective signaling pathways (RISK, cGMP/PKG, SAFE).

Prospective Role of Polyphenolic Compounds in the Treatment of Neurodegenerative Diseases

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Aging is an important stage of the human life cycle and the primary risk factor for neurodegenerative diseases (ND). The aging process contributes to modifications in cells, which may lead to a lack of nutrient signaling, disrupted cellular activity, increased oxidative pressure, cell homeostasis depletion, genomic instability, misfolded protein aggregation, impaired cellular protection, and telomere reduction. The neuropathologies found in Alzheimer's disease (AD) and Parkinson's disease (PD) are internally and extrinsically compound environmental stressors which may be partially alleviated by using different phytochemicals. The new therapies for ND are restricted as they are primarily targeted at final disease progression, including behavioral shifts, neurological disorders, proteinopathies, and neuronal failure. This review presents the role of phytochemicals-related polyphenolic compounds as an accompanying therapy model to avoid neuropathologies linked to AD, PD and to simultaneously enhance two stochastic stressors, namely inflammation and oxidative stress, promoting their disease pathologies. Therefore, this approach represents a prophylactic way to target risk factors that rely on their action against ND that does not occur through current pharmacological agents over the life of a person.

Artemisia annua L. Polyphenol-Induced Cell Death Is ROS-Independently Enhanced by Inhibition of JNK in HCT116 Colorectal Cancer Cells

c-Jun N-terminal kinase (JNK) is activated by chemotherapeutic reagents including natural plant polyphenols, and cell fate is determined by activated phospho-JNK as survival or death depending on stimuli and cell types. The purpose of this study was to elucidate the role of JNK on the anticancer effects of the Korean plant Artemisia annua L. (pKAL) polyphenols in p53 wild-type HCT116 human colorectal cancer cells. Cell morphology, protein expression levels, apoptosis/necrosis, reactive oxygen species (ROS), acidic vesicles, and granularity/DNA content were analyzed by phase-contrast microscopy; Western blot; and flow cytometry of annexin V/propidium iodide (PI)-, dichlorofluorescein (DCF)-, acridine orange (AO)-, and side scatter pulse height (SSC-H)/DNA content (PI)-stained cells. The results showed that pKAL induced morphological changes and necrosis or late apoptosis, which were associated with loss of plasma membrane/Golgi integrity, increased acidic vesicles and intracellular granularity, and decreased DNA content through downregulation of protein kinase B (Akt)/β-catenin/cyclophilin A/Golgi matrix protein 130 (GM130) and upregulation of phosphorylation of H2AX at Ser-139 (γ-H2AX)/p53/p21/Bak cleavage/phospho-JNK/p62/microtubule-associated protein 1 light chain 3B (LC3B)-I. Moreover, JNK inhibition by SP600125 enhanced ROS-independently pKAL-induced cell death through downregulation of p62 and upregulation of p53/p21/Bak cleavage despite a reduced state of DNA damage marker γ-H2AX. These findings indicate that phospho-JNK activated by pKAL inhibits p53-dependent cell death signaling and enhances DNA damage signaling, but cell fate is determined by phospho-JNK as survival rather than death in p53 wild-type HCT116 cells.

Antiproliferative Activity on Human Colon Adenocarcinoma Cells and In Vitro Antioxidant Effect of Anthocyanin-Rich Extracts from Peels of Species of the Myrtaceae Family

There is a significant indication of the beneficial health effects of fruit rich diets. Fruits of native plant species have noticeably different phytochemicals and bioactive effects. The aim of this work was to characterize and compare the constituents of jabuticaba (Myrciaria jaboticaba, MJ), jamun-berry (Syzygium cumini, SC), and malay-apple (Syzygium malaccense, SM) extracts and their influence on antioxidant activity in vitro and antiproliferative effects on human colon adenocarcinoma cells. According to the results, dried peel powders (DP) have a high anthocyanin content, phenolic compounds, and antioxidant activity when compared to freeze dried extracts (FD). M. jaboticaba dried peel powder extract had a higher total anthocyanin and phenolic compounds content (802.90 ± 1.93 and 2152.92 ± 43.95 mg/100 g, respectively). A reduction in cell viability of HT-29 cells after treatment with M. jaboticaba extracts (DP-MJ and FD-MJ) was observed via MTT assay. Flow cytometry showed that the treatment with the anthocyanin-rich extracts from MJ, SC, and SM had an inhibitory impact on cell development due to G₂/M arrest and caused a rise in apoptotic cells in relation to the control group. The findings of this study highlight the potential of peel powders from Myrtaceae fruits as an important source of natural antioxidants and a protective effect against colon adenocarcinoma.

Antioxidants in Fish Sperm and the Potential Role of Melatonin

In recent years, the effects of novel antioxidants have played an important role in the research focusing on fish cell protection. As food demand grows, aquaculture production becomes more intensive, and fish are more exposed to oxidative stress conditions, like high densities, temperature shifting, frequent fish handling and samplings, and prophylactic or disease treatments, which expose fish to a different environment. Particularly in reproduction, germ cells lose antioxidant capacity with spermatogenesis, as spermatozoa are more prone to oxidative stress. Antioxidants have been used in a variety of fish physiological problems including in reproduction and in the establishment of cryopreservation protocols. From the most used antioxidants to natural plant food and herbs, and endogenously produced antioxidants, like melatonin, a review of the literature available in terms of their effects on the protection of fish spermatozoa is presented here in a classified structure. Several direct and indirect approaches to improve gamete quality using antioxidants administration are mentioned (through feed supplementation or by adding in cryopreservation media), as well as factors affecting the efficiency of these molecules and their mechanisms of action. Special attention is given to the unclear melatonin pathway and its potential scavenger activity to prevent and counteract oxidative stress damage on fish spermatozoa.

Anti-Tumor Activity of Hypericum perforatum L. and Hyperforin through Modulation of Inflammatory Signaling, ROS Generation and Proton Dynamics

In this paper we review the mechanisms of the antitumor effects of Hypericum perforatum L. (St. John's wort, SJW) and its main active component hyperforin (HPF). SJW extract is commonly employed as antidepressant due to its ability to inhibit monoamine neurotransmitters re-uptake. Moreover, further biological properties make this vegetal extract very suitable for both prevention and treatment of several diseases, including cancer. Regular use of SJW reduces colorectal cancer risk in humans and prevents genotoxic effects of carcinogens in animal models. In established cancer, SJW and HPF can still exert therapeutic effects by their ability to downregulate inflammatory mediators and inhibit pro-survival kinases, angiogenic factors and extracellular matrix proteases, thereby counteracting tumor growth and spread. Remarkably, the mechanisms of action of SJW and HPF include their ability to decrease ROS production and restore pH imbalance in tumor cells. The SJW component HPF, due to its high lipophilicity and mild acidity, accumulates in membranes and acts as a protonophore that hinders inner mitochondrial membrane hyperpolarization, inhibiting mitochondrial ROS generation and consequently tumor cell proliferation. At the plasma membrane level, HPF prevents cytosol alkalization and extracellular acidification by allowing protons to re-enter the cells. These effects can revert or at least attenuate cancer cell phenotype, contributing to hamper proliferation, neo-angiogenesis and metastatic dissemination. Furthermore, several studies report that in tumor cells SJW and HPF, mainly at high concentrations, induce the mitochondrial apoptosis pathway, likely by collapsing the mitochondrial membrane potential. Based on these mechanisms, we highlight the SJW/HPF remarkable potentiality in cancer prevention and treatment.

Potential Therapeutic Role of Phytochemicals to Mitigate Mitochondrial Dysfunctions in Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by a decline in cognitive function and neuronal damage. Although the precise pathobiology of AD remains elusive, accumulating evidence suggests that mitochondrial dysfunction is one of the underlying causes of AD. Mutations in mitochondrial or nuclear DNA that encode mitochondrial components may cause mitochondrial dysfunction. In particular, the dysfunction of electron transport chain complexes, along with the interactions of mitochondrial pathological proteins are associated with mitochondrial dysfunction in AD. Mitochondrial dysfunction causes an imbalance in the production of reactive oxygen species, leading to oxidative stress (OS) and vice versa. Neuroinflammation is another potential contributory factor that induces mitochondrial dysfunction. Phytochemicals or other natural compounds have the potential to scavenge oxygen free radicals and enhance cellular antioxidant defense systems, thereby protecting against OS-mediated cellular damage. Phytochemicals can also modulate other cellular processes, including autophagy and mitochondrial biogenesis. Therefore, pharmacological intervention via neuroprotective phytochemicals can be a potential strategy to combat mitochondrial dysfunction as well as AD. This review focuses on the role of phytochemicals in mitigating mitochondrial dysfunction in the pathogenesis of AD.

The effect of dietary (poly)phenols on exercise-induced physiological adaptations: A systematic review and meta-analysis of human intervention trials

We performed a systematic review and meta-analysis to determine whether (poly)phenol supplementation augments the physiological adaptations to exercise training. Eligible studies administered a (poly)phenol supplement alongside ≥2 weeks of supervised exercise in adult humans. After screening, 22 studies were included in the analysis. Isoflavones and green tea (poly)phenols were administered most frequently. Quality assessments suggested most studies were free from bias. (Poly)phenols had no effect on training-induced adaptations in muscle strength, peak power output, and V̇O_2max, but enhanced exercise capacity (SMD: 0.67, 95% CI: 0.25 to 1.09, p < 0.01). (Poly)phenols had no overall effect on fat loss (SMD: 0.10, 95% CI: -0.10 to 0.29; p = 0.97) or lean mass gains (SMD: 0.06, 95% CI: -0.18 to 0.30, p = 0.62) but sub-analysis suggested that isoflavones increased lean mass (SMD: 0.25, 95 CI%: -0.00 to 0.50, p = 0.05). Resveratrol impaired adaptations in two studies, although this was a non-statistically significant finding (SMD: -0.54, 95% CI: -1.15 to 0.07, p = 0.08). Our results suggest that isoflavones may augment aspects of the adaptive response to exercise training, while resveratrol may compromise training adaptations. More high-quality research is needed to resolve the effects of (poly)phenols on exercise training adaptations.

Verbascoside Protects Pancreatic β-Cells against ER-Stress

Substantial epidemiological evidence indicates that a diet rich in polyphenols protects against developing type 2 diabetes. The phenylethanoid glycoside verbascoside/acteoside, a widespread polyphenolic plant compound, has several biological properties including strong antioxidant, anti-inflammatory and neuroprotective activities. The aim of this research was to test the possible effects of verbascoside on pancreatic β-cells, a target never tested before. Mouse and human β-cells were incubated with verbascoside (0.8-16 µM) for up to five days and a combination of biochemical and imaging techniques were used to assess the β-cell survival and function under normal or endoplasmic reticulum (ER)-stress inducing conditions. We found a dose-dependent protective effect of verbascoside against oxidative stress in clonal and human β-cells. Mechanistic studies revealed that the polyphenol protects β-cells against ER-stress mediated dysfunctions, modulating the activation of the protein kinase RNA-like endoplasmic reticulum kinase (PERK) branch of the unfolded protein response and promoting mitochondrial dynamics. As a result, increased viability, mitochondrial function and insulin content were detected in these cells. These studies provide the evidence that verbascoside boosts the ability of β-cells to cope with ER-stress, an important contributor of β-cell dysfunction and failure in diabetic conditions and support the therapeutic potential of verbascoside in diabetes.

Flavonoids mitigate neurodegeneration in aged Caenorhabditis elegans by mitochondrial uncoupling

Dietary supplementation of flavonoids has been shown to reduce the severity of neurodegenerative disorders such as dementia, Parkinson's disease, and Alzheimer's disease by their antioxidant effects. However, their low bioavailabilityin vivo raises the question of how much their antioxidant capacity actually contributes to the mitigating effects. The physicochemical properties of flavonoids suggest they could function as mitochondrial uncouplers. Moreover, mitochondrial uncoupling alleviated neurodegeneration in Caenorhabditis elegans during aging in previous research. Therefore, we investigated whether various flavonoids (fisetin, quercetin, apigenin, chrysin, catechin, and naringenin) could reduce neuronal defects by mitochondrial uncoupling in C. elegans. Both neuronal defects and mitochondrial membrane potential were reduced in aged worms in nearly all of the flavonoid treatments suggesting that flavonoids may reduce neurodegeneration in C. elegans. However, there was no significant reduction of neuronal defects in mitophagy-deficient pink-1/pdr-1 double mutants under flavonoid treatments. These results suggest that flavonoids could function as mitochondrial uncouplers to mitigate neurodegeneration in aged C. elegans, possibly via a PINK1/Parkin mitophagy process.

Mitochondrial Protection and Anti-inflammatory Effects Induced by Emodin in the Human Neuroblastoma SH-SY5Y Cells Exposed to Hydrogen Peroxide: Involvement of the AMPK/Nrf2 Signaling Pathway

Emodin (EM; 1,3,8-trihydroxy-6-methylanthracene-9,10-dione; C₁₅H₁₀O₅) is an anthraquinone and exerts cytoprotective effects, as observed in both in vitro and in vivo experimental models. Mitochondrial dysfunction induced by reactive species plays a central role in the onset and progression of different human diseases. Thus, we have tested here whether a pretreatment (for 4 h) with EM (at 40 µM) would be able to promote mitochondrial protection in the human neuroblastoma SH-SY5Y cells exposed to the pro-oxidant agent hydrogen peroxide (H₂O₂). We found that the pretreatment with EM suppressed the effects of H₂O₂ on the activity of the mitochondrial complexes I and V, as well as on the production of adenosine triphosphate (ATP) and on the mitochondrial membrane potential (MMP). EM also prevented the H₂O₂-induced collapse in the tricarboxylic acid cycle (TCA) function. An anti-inflammatory role for EM was also observed in this experimental model, since this anthraquinone decreased the secretion of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) by the H₂O₂-challenged cells. Inhibition of the adenosine monophosphate-activated protein kinase (AMPK) or silencing of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) abolished the protection induced by EM in the H₂O₂-treated cells. Therefore, EM prevented the H₂O₂-induced mitochondrial dysfunction and pro-inflammatory state in the SH-SY5Y cells by an AMPK/Nrf2-dependent manner.

Nanoformulations to Enhance the Bioavailability and Physiological Functions of Polyphenols

Polyphenols are micronutrients that are widely present in human daily diets. Numerous studies have demonstrated their potential as antioxidants and anti-inflammatory agents, and for cancer prevention, heart protection and the treatment of neurodegenerative diseases. However, due to their vulnerability to environmental conditions and low bioavailability, their application in the food and medical fields is greatly limited. Nanoformulations, as excellent drug delivery systems, can overcome these limitations and maximize the pharmacological effects of polyphenols. In this review, we summarize the biological activities of polyphenols, together with systems for their delivery, including phospholipid complexes, lipid-based nanoparticles, protein-based nanoparticles, niosomes, polymers, micelles, emulsions and metal nanoparticles. The application of polyphenol nanoparticles in food and medicine is also discussed. Although loading into nanoparticles solves the main limitation to application of polyphenolic compounds, there are some concerns about their toxicological safety after entry into the human body. It is therefore necessary to conduct toxicity studies and residue analysis on the carrier.

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.

Flavonoids and Mitochondria: Activation of Cytoprotective Pathways?

A large number of diverse mechanisms that lead to cytoprotection have been described to date. Perhaps, not surprisingly, the role of mitochondria in these phenomena is notable. In addition to being metabolic centers, due to their role in cell catabolism, ATP synthesis, and biosynthesis these organelles are triggers and/or end-effectors of a large number of signaling pathways. Their role in the regulation of the intrinsic apoptotic pathway, calcium homeostasis, and reactive oxygen species signaling is well documented. In this review, we aim to characterize the prospects of influencing cytoprotective mitochondrial signaling routes by natural substances of plant origin, namely, flavonoids (e.g., flavanones, flavones, flavonols, flavan-3-ols, anthocyanidins, and isoflavones). Flavonoids are a family of widely distributed plant secondary metabolites known for their beneficial effects on human health and are widely applied in traditional medicine. Their pharmacological characteristics include antioxidative, anticarcinogenic, anti-inflammatory, antibacterial, and antidiabetic properties. Here, we focus on presenting mitochondria-mediated cytoprotection against various insults. Thus, the role of flavonoids as antioxidants and modulators of antioxidant cellular response, apoptosis, mitochondrial biogenesis, autophagy, and fission and fusion is reported. Finally, an emerging field of flavonoid-mediated changes in the activity of mitochondrial ion channels and their role in cytoprotection is outlined.

Grape Polyphenols Ameliorate Muscle Decline Reducing Oxidative Stress and Oxidative Damage in Aged Rats

A large number of studies have demonstrated the implication of oxidative stress (OxS) in the pathogenesis of ageing-related muscle decline and atrophy. The key mechanism is related to the OxS-induced production of free radicals, with the consequent increase in oxidative damage, resulting in affected muscle quality and strength. The present study aimed to evaluate the efficacy of a grape polyphenol-based nutraceutical formulation (Taurisolo^®) in reducing the OxS in muscle of aged rats. A group of 16 aged (20 months) rats were orally administered with Taurisolo^® (n = 8; 100 mg/kg Taurisolo^®) or placebo (n = 8; 50 mg/kg maltodextrin); an additional group of eight young (three months) rats were also treated with placebo. All the treatments were orally administered for 30 days. The activities of antioxidant enzymes, the levels of malondialdehyde (MDA) and nitrotyrosine (N-Tyr) and the expression of OxS- and inflammation-related genes were evaluated on the gastrocnemius muscle. In muscle samples of the treated-group, increased activity of antioxidant enzymes, reduced MDA and N-Tyr levels and increased expression of antioxidant and anti-inflammatory genes were observed in respect to the placebo. Data herein presented suggest that the chronic treatment with Taurisolo^® significantly reduces oxidative damage and improves muscle performance in aged rats.

Green tea polyphenols boost gut-microbiota-dependent mitochondrial TCA and urea cycles in Sprague-Dawley rats

Green tea polyphenols (GTPs) were found to boost mammal energy conversion by modulating gut-microbial community structure, gene orthologs and metabolic pathways. Here we examined the metabolites present in the gut-microbiota-dependent mitochondrial tricarboxylic acid (TCA) cycle and urea cycle using hydrophilic interaction liquid chromatography (HILIC)-heated electrospray ionization (HESI)-tandem liquid chromatogram mass spectrometry (LC-MS). Six groups (n=12) of Sprague-Dawley rats (6-mo, ~250 g) were administered with water containing 0%, 0.5%, and 1.5% GTPs (wt/vol or g/dL). Gut-content samples were collected at 3- and 6-mo. Untargeted metabolomics detected 2177 features, with 91 features demonstrating significant dose- and time-dependencies on the GTPs treatment. Targeted metabolomics analysis revealed remarkable changes of 39 metabolites in the mitochondrial TCA cycle and urea cycle, including argininosuccunic acid (0.9-fold vs control), dihydrouracil (1.14-fold vs control), fumaric acid (1.19-fold vs control), malic acid (2.17-fold vs control), citrulline (1.86-fold vs control), and succinic acid (0.4-fold vs control). The untargeted metabolomics data were mined using bioinformatics approaches, such as analysis of variance-simultaneous component analysis (ASCA), enrichment pathway analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway mapping analysis. The results of 16S rRNA survey, metagenomics analysis, and metabolomics analysis were extrapolated and integrated using databases of Integrated Microbial Genomes and Microbiomes (IMG/M) and KEGG. Our analysis demonstrates that GTPs enhance energy conversion by boosting mitochondrial TCA cycle and urea cycle of gut-microbiota in rats. This metabolic modulation is achieved by enriching many gene orthologs, following the increase of beneficial microbials in families C. Ruminococcaceae, C. Lachnospiraceae and B. Bacteroidaceae.

Bioactive Polyphenols and Neuromodulation: Molecular Mechanisms in Neurodegeneration

The interest in dietary polyphenols in recent years has greatly increased due to their antioxidant bioactivity with preventive properties against chronic diseases. Polyphenols, by modulating different cellular functions, play an important role in neuroprotection and are able to neutralize the effects of oxidative stress, inflammation, and apoptosis. Interestingly, all these mechanisms are involved in neurodegeneration. Although polyphenols display differences in their effectiveness due to interindividual variability, recent studies indicated that bioactive polyphenols in food and beverages promote health and prevent age-related cognitive decline. Polyphenols have a poor bioavailability and their digestion by gut microbiota produces active metabolites. In fact, dietary bioactive polyphenols need to be modified by microbiota present in the intestine before being absorbed, and to exert health preventive effects by interacting with cellular signalling pathways. This literature review includes an evaluation of the literature in English up to December 2019 in PubMed and Web of Science databases. A total of 307 studies, consisting of research reports, review articles and articles were examined and 146 were included. The review highlights the role of bioactive polyphenols in neurodegeneration, with a particular emphasis on the cellular and molecular mechanisms that are modulated by polyphenols involved in protection from oxidative stress and apoptosis prevention.

Interaction Between Neurogenic Stimuli and the Gene Network Controlling the Activation of Stem Cells of the Adult Neurogenic Niches, in Physiological and Pathological Conditions

In the adult mammalian brain new neurons are continuously generated throughout life in two niches, the dentate gyrus of the hippocampus and the subventricular zone. This process, called adult neurogenesis, starts from stem cells, which are activated and enter the cell cycle. The proliferative capability of stem cells progressively decreases during aging. The population of stem cells is generally quiescent, and it is not clear whether the potential for stem cells to expand is limited, or whether they can expand and then return to quiescence, remaining available for further activation. Certain conditions may deregulate stem cells quiescence and self-renewal. In fact we discuss the possibility of activation of stem cells by neurogenic stimuli as a function of the intensity of the stimulus (i.e., whether this is physiological or pathological), and of the deregulation of the system (i.e., whether the model is aged or carrying genetic mutations in the gene network controlling quiescence). It appears that when the system is aged and/or carrying mutations of quiescence-maintaining genes, preservation of the quiescent state of stem cells is more critical and stem cells can be activated by a neurogenic stimulus which is ineffective in normal conditions. Moreover, when a neurogenic stimulus is in itself a cause of brain damage (e.g., kainic acid treatment) the activation of stem cells occurs bypassing any inhibitory control. Plausibly, with strong neurogenic stimuli, such as kainic acid injected into the dentate gyrus, the self-renewal capacity of stem cells may undergo rapid exhaustion. However, the self-renewal capability of stem cells persists when normal stimuli are elicited in the presence of a mutation of one of the quiescence-maintaining genes, such as p16Ink4a, p21Cip1 or Btg1. In this case, stem cells become promptly activated by a neurogenic stimulus even during aging. This indicates that stem cells retain a high proliferative capability and plasticity, and suggests that stem cells are protected against the response to stimulus and are resilient to exhaustion. It will be interesting to assess at which functional degree of deregulation of the quiescence-maintaining system, stem cells will remain responsive to repeated neurogenic stimuli without undergoing exhaustion of their pool.

Selenium ameliorates cadmium-induced mouse leydig TM3 cell apoptosis via inhibiting the ROS/JNK /c-jun signaling pathway

Despite the well-known acknowledgement of both the toxicity of cadmium (Cd) and the ameliorative effect of selenium (Se), the mechanism of the protective effect of selenium on cadmium-induced Mouse Leydig (TM3) cell apoptosis remains unknown. In this study, we hypothesized that the reactive oxygen species (ROS)-mediated c-jun N-terminal kinase (JNK) signaling pathway is involved in anti-apoptosis of selenium against cadmium in TM3 cells. We found that exposure to cadmium caused evident cytotoxicity, in which cell viability was inhibited, followed by inducement of apoptosis. Moreover, the level of ROS generation was elevated, leading to the phosphorylation of JNK. In addition, following cadmium exposure, the nuclear transcription factor c-jun was significantly activated, which led to increased expression of downstream gene c-jun, resulting in downstream activation of the apoptosis-related protein Caspase3 and upregulation of Cleaved-PARP, as well as inhibition of the anti-apoptosis protein Bcl-2. However, pretreatment with selenium remarkably suppressed cadmium-induced TM3 cell apoptosis. Furthermore, the level of ROS declined, and the JNK signaling pathway was blocked. Following this, the gene expression of c-jun decreased while Bcl-2 increased, which was consistent with the effects on proteins, that Caspase3 activity and Cleaved-PARP were inhibited while Bcl-2 level was restored. In order to explain the relationship between molecules of the signaling pathway, N-acetyl-L-cysteine (NAC), the ROS inhibitor, and JNK1/2 siRNA were administered, which further indicated the mediatory role of the ROS/JNK/c-jun signaling pathway in regulating anti-apoptosis of selenium against cadmium-induced TM3 cell apoptosis.

From sunscreens to medicines: Can a dissipation hypothesis explain the beneficial aspects of many plant compounds?

Medicine has utilised plant‐based treatments for millennia, but precisely how they work is unclear. One approach is to use a thermodynamic viewpoint that life arose by dissipating geothermal and/or solar potential. Hence, the ability to dissipate energy to maintain homeostasis is a fundamental principle in all life, which can be viewed as an accretion system where layers of complexity have built upon core abiotic molecules. Many of these compounds are chromophoric and are now involved in multiple pathways. Plants have further evolved a plethora of chromophoric compounds that can not only act as sunscreens and redox modifiers, but also have now become integrated into a generalised stress adaptive system. This could be an extension of the dissipative process. In animals, many of these compounds are hormetic, modulating mitochondria and calcium signalling. They can also display anti‐pathogen effects. They could therefore modulate bioenergetics across all life due to the conserved electron transport chain and proton gradient. In this review paper, we focus on well‐described medicinal compounds, such as salicylic acid and cannabidiol and suggest, at least in animals, their activity reflects their evolved function in plants in relation to stress adaptation, which itself evolved to maintain dissipative homeostasis.

Protective effects of anthocyanins against brain ischemic damage

Anthocyanins are considered as bioactive components of plant-based diets that provide protection against ischemic cardiovascular pathologies by mechanisms dependent on their antioxidant and reductive capacities. However, it is not clear whether similar anthocyanin-mediated mechanisms can provide protection against ischemia-induced brain mitochondrial injury and cell death. In this study, we compared effects of three cyanidin-3-glycosides - glucoside (Cy3G), galactoside (Cy3Gal) and rutinoside (Cy3R), with pelargonxidin-3-glucoside (Pg3G) and found that at 10-20 μM concentrations they have no direct effect on respiratory functions of mitochondria isolated from normal or ischemia-damaged rat brain slices. However, intravenous injection of Cy3Gal and Cy3G (0,025 mg/kg or 0,05 mg/kg what matches 10 μM or 20 μM respectively) but not Cy3R in rats protected against ischemia-induced caspase activation and necrotic cell death, and reduced infarct size in cerebral cortex and cerebellum. These effects correlated with cytochrome c reducing capacity of cyanidin-3-glycosides. In contrast, intravenous injection of 0,025 mg/kg Pg3G which has the lowest cytochrome c reducing capacity among investigated anthocyanins, had no effect on ischemia-induced caspase activation and necrosis but reduced brain infarct size whereas intravenous injection of 0,05 mg/kg of Pg3G slightly promoted necrosis in the brain. Our data suggest that reductive rather than antioxidant capacities of anthocyanins may be important components in providing protection against ischemic brain damage.

Mitochondrial reactive oxygen species: the effects of mitochondrial ascorbic acid vs untargeted and mitochondria-targeted antioxidants

PREMISE

Mitochondria represent critical sites for reactive oxygen species (ROS) production, which dependent on concentration is responsible for the regulation of both physiological and pathological processes.

PURPOSE

Antioxidants in mitochondria regulate the redox balance, prevent mitochondrial damage and dysfunction and maintain a physiological ROS-dependent signaling. The aim of the present review is to provide critical elements for addressing this issue in the context of various pharmacological approaches using antioxidants targeted or non-targeted to mitochondria. Furthermore, this review focuses on the mitochondrial antioxidant effects of ascorbic acid (AA), providing clues on the complexities associated with the cellular uptake and subcellular distribution of the vitamin.

CONCLUSIONS

Antioxidants that are not specifically targeted to mitochondria fail to accumulate in significant amounts in critical sites of mitochondrial ROS production and may eventually interfere with the ensuing physiological signaling. Mitochondria-targeted antioxidants are more effective, but are expected to interfere with the mitochondrial ROS-dependent physiologic signaling. AA promotes multiple beneficial effects in mitochondria. The complex regulation of vitamin C uptake in these organelles likely contributes to its versatile antioxidant response, thereby providing a central role to the vitamin for adequate control of mitochondrial dysfunction associated with increased mitochondrial ROS production.

Molybdenum and cadmium co-induce oxidative stress and apoptosis through mitochondria-mediated pathway in duck renal tubular epithelial cells

High doses of molybdenum (Mo) and cadmium (Cd) cause adverse reactions on animals, but the joint toxic effects of Mo and Cd on duck renal tubular epithelial cells are not fully illustrated. To investigate the combined effects of Mo and Cd on oxidative stress and mitochondrial apoptosis in primary duck renal tubular epithelial cells, the cells were either treated with (NH₄)₆Mo₇O₂₄·4H₂O (480, 960 μM Mo), 3CdSO₄·8H₂O (2.5, 5.0 μM Cd) or combination of Mo and Cd for 12 h, and then the joint cytotoxicity was evaluated. The results demonstrated that Mo or/and Cd exposure could induce release of intracellular lactate dehydrogenase, reactive oxygen species generation, acidification, increase levels of malondialdehyde and [Ca²⁺]i, decrease levels of glutathione, glutathione peroxidase, catalase, superoxide dismutase, total antioxidant capacity, Na⁺/K⁺-ATPase, Ca²⁺-ATPase, and mitochondrial membrane potential; upregulate mRNA levels of Caspase-3, Bak-1, Bax, and cytochrome C, inhibit Bcl-2 mRNA level, and induce cell apoptosis in a dose-dependent manner. Furthermore, the changes of these indicators in co-treated groups were more remarkable. The results indicated that exposure to Mo or/and Cd could induce oxidative stress and apoptosis via the mitochondrial pathway in duck renal tubular epithelial cells and the two metals may have a synergistic effect.