Protection by apple peel polyphenols against indometacin-induced oxidative stress, mitochondrial damage and cytotoxicity in Caco-2 cells

Investigating the impact of Psidium guajava leaf hydroalcoholic extract in improving glutamatergic toxicity-induced oxidative stress in Danio rerio larvae

Glutamate is one of the predominant excitatory neurotransmitters released from the central nervous system; however, at high concentrations, this substance may induce excitotoxicity. This phenomenon is involved in numerous neuropathologies. At present, clinically available pharmacotherapeutic agents to counteract glutamatergic excitotoxicity are not completely effective; therefore, research to develop novel compounds is necessary. In this study, the main objective was to determine the pharmacotherapeutic potential of the hydroalcoholic extract of Psidium guajava (PG) in a model of oxidative stress-induced by exposure to glutamate utilizing Danio rerio larvae (zebrafish) as a model. Data showed that treatment with glutamate produced a significant increase in oxidative stress, chromatin damage, apoptosis, and locomotor dysfunction. All these effects were attenuated by pre-treatment with the classical antioxidant N-acetylcysteine (NAC). Treatment with PG inhibited oxidative stress responsible for cellular damage induced by glutamate. However, exposure to PG failed to prevent glutamate-initiated locomotor damage. Our findings suggest that under conditions of oxidative stress, PG can be considered as a promising candidate for treatment of glutamatergic excitotoxicity and consequent neurodegenerative diseases.

A preliminary therapeutic study of the effects of molecular hydrogen on intestinal dysbiosis and small intestinal injury in high-fat diet-loaded senescence-accelerated mice

OBJECTIVES

Aging and excessive fat intake may additively induce dysbiosis of the gut microbiota and intestinal inflammatory damage. Here, we analyzed microbiota dysbiosis and intestinal injury in high-fat diet-loaded senescence-accelerated mice (SAMP8). Additionally, we examined whether treatment with molecular hydrogen could improve the intestinal environment.

METHODS

SAMP8 and SAMR1 (control) mice were first fed a normal diet (ND) or high-fat diet (HFD) for 10 wk (n = 10 each group). Subsequently, HFD was supplemented with a placebo jelly or hydrogen-rich jelly (HRJ) for 4 wk. After treatment, isolated small intestinal tissues were used for hematoxylin and eosin staining, immunofluorescence staining, and thiobarbituric acid reactive substances (TBARS) assay. Furthermore, we analyzed alterations in the microbiota composition in cecal feces using 16S rRNA gene analysis for microbiota profiling. Statistical analyses were performed using unpaired Student's t tests or one-way analysis of variance and Tukey's post hoc test for multiple comparisons.

RESULT

HFD feeding reduced the expression of caudal-related homeobox transcription factor 2 (CDX2) and 5-bromo-2'-deoxyuridine (BrdU) and enhanced malondialdehyde (MDA) levels in the small intestine of SAMP8. HRJ treatment improved the reduction in CDX2 and BrdU and enhanced MDA levels. We performed a sequence analysis of the gut microbiota at the genus level and identified 283 different bacterial genera from the 30 samples analyzed in the study. Among them, Parvibacter positively correlated with both HFD intake and aging, whereas 10 bacteria, including Anaerofustis, Anaerosporobacter, Butyricicoccus, and Ruminococcus were negatively correlated with both HFD and aging. HRJ treatment increased Lactinobactor and decreased Akkermansia, Gracilibacter, and Marvinbryantia abundance.

CONCLUSION

Our findings suggest that treatment with molecular hydrogen may affect microbiota profiling and suppress intestinal injury in HFD-loaded SAMP8.

Gastroprotective Role of Fruit Extracts in Gastric Damage Induced by Non-Steroidal Anti-Inflammatory Drugs: A Systematic Review

The aim of this study was to systematically review the scientific literature, with Preferred Reporting Items of Systematic Reviews and Meta-analyses (PRISMA) guidelines, of the articles found in the past 11 years on the gastroprotective role of fruit extracts in gastric ulcers induced by non-steroidal anti-inflammatory drugs (NSAIDs). Scientific articles published between 2010 and 2020 were included in this systematic review, including in vitro and in vivo models, to define the gastroprotective role of fruit extracts. Studies were selected by Rayyan using PubMed, Web of Science, Scopus, and Science Direct databases. The keywords for the search strategy were: "gastric injury," "gastric ulcer," "fruit," "indomethacin," and "aspirin." Twenty-two articles with animal models of gastric ulcers were included. The NSAIDs used were aspirin and indomethacin. To know the damage caused by these, the ulceration index and biomarkers, such as aggressive/defensive factors involved in the gastric ulceration process, were measured. Most studies have shown that fruit extracts have antiulcer activity, with the most abundant metabolites being flavonoids, followed by terpenes and alkaloids. Possible antiulcer activities such as antioxidant, cytoprotective, gastric acid antisecretory, anti-inflammatory, or angiogenesis stimulant were declared, manifested mainly as a reduction of lipid peroxidation products, an increase in antioxidant enzymes and prostaglandins, and by the formation of a protective film through protein precipitation in the ulcer area. This systematic review demonstrates the importance of fruit extracts as gastric protectors.

Oxidation of Quercetin and Kaempferol Markedly Amplifies Their Antioxidant, Cytoprotective, and Anti-Inflammatory Properties

The contention that flavonoids' oxidation would necessarily lead to a loss of their antioxidant properties was recently challenged by the demonstration that quercetin oxidation leads to the formation of 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (Que-BZF), a metabolite whose antioxidant potency was notably higher than that of its precursor. Here, we compared and expanded the former observation to that of the quercetin analogue kaempferol. Oxidation of kaempferol led to the formation of a mixture of metabolites that included the 2-(4-hydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (Kae-BZF). Following the chromatographic isolation of Kae-BZF from such a mixture, its antioxidant, mitochondria- and cell-protecting, and NF-kB-inhibiting effects were assessed, and compared with those of Que-BZF, in Caco-2 cells exposed to indomethacin as a source of ROS. The concentrations of Que-BZF (100 nm) and Kae-BZF (1 nm) needed to attain their maximal protection effects were 50- and 5000-fold lower than those of their respective precursors. The former differences in concentrations were also seen when the abilities of Que-BZF and Kae-BZF to inhibit the indomethacin-induced activation of NF-kB were compared. These data not only reveal that the oxidative conversion of quercetin and kaempferol into their respective 2-benzoyl-2-hydroxy-3(2H)-benzofuranones (BZF) results in a considerable amplification of their original antioxidant properties, but also that the in the case of kaempferol, such amplification is 100-fold greater than that of quercetin.

Revisiting the Oxidation of Flavonoids: Loss, Conservation or Enhancement of Their Antioxidant Properties

Flavonoids display a broad range of health-promoting bioactivities. Among these, their capacity to act as antioxidants has remained most prominent. The canonical reactive oxygen species (ROS)-scavenging mode of the antioxidant action of flavonoids relies on the high susceptibility of their phenolic moieties to undergo oxidation. As a consequence, upon reaction with ROS, the antioxidant capacity of flavonoids is severely compromised. Other phenol-compromising reactions, such as those involved in the biotransformation of flavonoids, can also markedly affect their antioxidant properties. In recent years, however, increasing evidence has indicated that, at least for some flavonoids, the oxidation of such residues can in fact markedly enhance their original antioxidant properties. In such apparent paradoxical cases, the antioxidant activity arises from the pro-oxidant and/or electrophilic character of some of their oxidation-derived metabolites and is exerted by activating the Nrf2–Keap1 pathway, which upregulates the cell’s endogenous antioxidant capacity, and/or, by preventing the activation of the pro-oxidant and pro-inflammatory NF-κB pathway. This review focuses on the effects that the oxidative and/or non-oxidative modification of the phenolic groups of flavonoids may have on the ability of the resulting metabolites to promote direct and/or indirect antioxidant actions. Considering the case of a metabolite resulting from the oxidation of quercetin, we offer a comprehensive description of the evidence that increasingly supports the concept that, in the case of certain flavonoids, the oxidation of phenolics emerges as a mechanism that markedly amplifies their original antioxidant properties. An overlooked topic of great phytomedicine potential is thus unraveled.

Bioactive extracts from brewer's spent grain

In this study, antioxidant-rich extracts from brewer's spent grain (BSG) extracted by solid-to-liquid extraction using different solvents water and ethanol and their mixtures at two ratios (80% ethanol : water (v/v) and 60% ethanol : water (v/v)) were characterized. Nutritional composition was evaluated for the extracts and for the solid residues obtained after extraction. Additionally, the extracts were analyzed for the total phenolic content and individual phenolic compounds and related biological properties including antioxidant capacity (ABTS; ORAC and DNA protection), antihypertensive capacity, antibacterial activity and antibiofilm capacity. Safety was also demonstrated through genotoxicity and cytotoxicity tests. The results obtained showed that while all the extracts exhibited high antioxidant capacity (except ethanolic extract), the highest values were obtained for the 60% ethanol : water extract. The identification of phenolic compounds using HPLC showed that catechin and vanillin were the main compounds identified with the highest concentration being obtained for 60% ethanol : water extraction. In the biological activity assays, water and hydroethanolic extracts were multifunctional (antioxidant and antihypertensive capacity, antibacterial and antibiofilm activity), and the 80% ethanol : water presented better results in some assays. All were non-genotoxic, but the cytotoxicity was dependent on the extract concentration, with complete safe application for all up to 1 mg mL-1. Therefore, this study shows the potential of a viable green solvent based and low cost extraction recovery method of bioactive compounds from brewer's spent grain.

Galangin and Kaempferol Alleviate the Indomethacin-Caused Cytotoxicity and Barrier Loss in Rat Intestinal Epithelial (IEC-6) Cells Via Mediating JNK/Src Activation

Nonsteroidal anti-inflammatory drugs (NSAIDs) like indomethacin and others are widely used in clinics, but they have the potential to cause severe gastrointestinal damage including intestinal barrier dysfunction. Thus, two flavonols galangin and kaempferol with or without heat treatment (100 °C, 30 min) were assessed for their effect on indomethacin-damaged rat intestine epithelial (IEC-6) cells. In total, the cell exposure of 300 μmol/L indomethacin for 24 h caused cell toxicity efficiently, resulting in decreased cell viability, enhanced lactate dehydrogenase (LDH) release or reactive oxygen species (ROS) production, and obvious barrier loss. Meanwhile, pretreatment of the cells with these flavonols for 24 and 48 h before the indomethacin exposure could alleviate cytotoxicity and especially barrier loss, resulting in increased cell viability and transepithelial resistance, decreased LDH release, ROS production, and paracellular permeability, together with the promoted expression of three tight junction proteins zonula occluden-1, occludin, and claudin-1. Moreover, the intracellular Ca2+ concentration and expression levels of p-JNK and p-Src arisen from the indomethacin damage were also reduced by the flavonols, suggesting an inhibited calcium-mediated JNK/Src activation. Consistently, galangin showed higher activity than kaempferol to the cells, while the heated flavonols were less efficient than the unheated counterparts. It is thus highlighted that the two flavonols could alleviate indomethacin cytotoxicity and combat against the indomethacin-induced barrier loss in IEC-6 cells, but heat treatment of the flavonols would weaken the two beneficial functions.

Effects of prolonged cold-ischemia on autophagy in the graft lung in a rat orthotopic lung transplantation model

INTRODUCTION

Ischemia-reperfusion (I/R) injury causes present challenges in the field of graft transplantation which is also a major contributor to early graft dysfunction or failure after organ transplantation. The study focuses on the effects of prolonged cold-ischemia (CI) on the autophagic activity in the graft lung in a rat orthotopic lung transplantation model.

MATERIAL AND METHODS

Donor lungs were preserved under CI conditions for different periods. An orthotopic lung transplantation model was developed, and the lung tissues from donor lungs subjected to CI preservation and reperfusion were harvested. We evaluated the effects of different CI periods on autophagy, reactive oxygen species (ROS) and glucose consumption. Additionally, the mechanism by which prolonged CI affected autophagy was investigated through determination of the molecules related to the mTOR pathway after treatment with 3-Methyladenine (3-MA), rapamycin and an adenosine triphosphate (ATP) synthase inhibitor oligomycin (OM).

RESULTS

Prolonged CI led to increased activities of key glycolytic enzymes, glucose consumption and lactic acid production. Autophagy, ROS and glucose consumption were induced in the graft lung after I/R, which reached peak levels after 6 h and was gradually decreased. Most importantly, the perfusion treatment of 3-MA or OM decreased ROS level and autophagy, but increased the extent of mTOR phosphorylation, while the perfusion treatment of rapamycin induced ROS and autophagy.

CONCLUSION

Taken together, autophagy mediated by a prolonged CI preservation affects the glucose consumption and ROS production in the graft lung via the mTOR signaling pathway.

Quercetin Oxidation Metabolite Present in Onion Peel Protects Caco-2 Cells against the Oxidative Stress, NF-kB Activation, and Loss of Epithelial Barrier Function Induced by NSAIDs

The potential of 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (BZF), a quercetin oxidation metabolite, and that of a BZF-rich onion peel aqueous extract (OAE) to protect Caco-2 monolayers against the oxidative stress (OS) and an increased permeability (IP) induced by five nonsteroidal anti-inflammatory drugs (NSAIDs) (indomethacin, diclofenac, piroxicam, ibuprofen, and metamizole) were investigated. Under identical OS conditions, the NSAIDs substantially differed in their ability to induce an IP and/or NF-kB activation. The OAE (100 nM BZF) protected in identical magnitude (84-86%) against OS but in a highly dissimilar manner against the IP (18-73%). While all NSAIDs activated NF-kB, the OAE prevented only that induced by indomethacin. Results reveal that the IP has no direct relationship with the OS and that with the exception of indomethacin, the prevention of NSAIDs-induced OS and/or NF-kB activation plays no fundamental role in the IP-protecting effect of OAE. These results warrant the in vivo evaluation of OAE against indomethacin-induced loss of intestinal barrier function.

The Microbiota-Derived Metabolite of Quercetin, 3,4-Dihydroxyphenylacetic Acid Prevents Malignant Transformation and Mitochondrial Dysfunction Induced by Hemin in Colon Cancer and Normal Colon Epithelia Cell Lines

Meat diet plays a pivotal role in colorectal cancer (CRC). Hemin, a metabolite of myoglobin, produced after meat intake, has been involved in CRC initiation. The compound, 3,4-dihydroxyphenylacetic acid (3,4HPAA) is a scarcely studied microbiota-derived metabolite of the flavonoid quercetin (QUE), which exert antioxidant properties. The aim of this study was to determine the protective effect of 3,4HPAA against malignant transformation (increased cell proliferation, decreased apoptosis, DNA oxidative damage and augmented reactive oxidative species (ROS) levels) and mitochondrial dysfunction induced by hemin in normal colon epithelial cells and colon cancer cells. The effect of 3,4HPAA was assessed in comparison to its precursor, QUE and to a known CRC protective agent, sulforaphane (SFN). The results showed that both, tumor and normal cells, exposed to hemin, presented increased cell proliferation, decreased caspase 3 activity and cytochrome c release, as well as augmented production of intracellular and mitochondrial ROS. In addition, hemin decreased the mitochondrial membrane potential (MMP) and the activity of complexes I and II of the electron transport chain. These effects of hemin were prevented by the action of 3,4HPAA. The metabolite showed to be more active than QUE and slightly less active than SFN. In conclusion, 3,4HPAA administration could represent a promising strategy for preventing malignant transformation and mitochondrial dysfunction in colon epithelia induced by hemin.

Biotechnological re-cycling of apple by-products: A reservoir model to produce a dietary supplement fortified with biogenic phenolic compounds

This study is an example of apple by-products (AP) recycling through a designed fermentation by selected autochthonous Lactobacillus plantarum AFI5 and Lactobacillus fabifermentans ALI6 used singly or as binary cultures with the selected Saccharomyces cerevisiae AYI7. Compared to Raw-, Unstarted- and Chemically Acidified-AP, Fermented-AP promoted the highest levels of total and insoluble dietary fibers, DPPH scavenging capacity, and free phenolics. The binary culture of L. plantarum AFI5 and S. cerevisiae AYI7 had the best effect on the bioavailability phenolic compounds as resulted by the LC-MS/MS validated method. The accumulation of phenolic acids derivatives highlighted the microbial metabolism during AP fermentation. Bio-converted phenolics were likely responsible for the increased DPPH scavenging capacity. The potential health-promoting effects of Fermented-AP were highlighted using Caco-2 cells. With variations among single and binary cultures, fermented-AP counteracted the inflammatory processes and the effects of oxidative stress in Caco-2 cells, and preserved the integrity of tight junctions.

From old to new - Repurposing drugs to target mitochondrial energy metabolism in cancer

Although we have entered the era of personalized medicine and tailored therapies, drugs that target a large variety of cancers regardless of individual patient differences would be a major advance nonetheless. This review article summarizes current concepts and therapeutic opportunities in the area of targeting aerobic mitochondrial energy metabolism in cancer. Old drugs previously used for diseases other than cancer, such as antibiotics and antidiabetics, have the potential to inhibit the growth of various tumor entities. Many drugs are reported to influence mitochondrial metabolism. However, here we consider only those drugs which predominantly inhibit oxidative phosphorylation.

Low nanomolar concentrations of a quercetin oxidation product, which naturally occurs in onion peel, protect cells against oxidative damage

The occurrence of the quercetin oxidation metabolite 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone (BZF), whose antioxidant potency is notably higher than the antioxidant potency of quercetin, was investigated in twenty quercetin-rich plant foods. BZF was identified (HPLC-DAD-ESI-MS/MS) only in the dry outer scales of onions and shallots. Aqueous extracts of onions (OAE) and shallots (SAE) were evaluated for their antioxidant and cytoprotective properties. OAE, whose potency did not differ from SAE, protected ROS-exposed Caco2 cells against oxidative (78%) and cellular (90%) damage at a 3 µg/L concentration (corresponding to 0.03 nM of BZF). After chromatographic resolution of OAE, the BZF peak accounted fully and exclusively for its antioxidant effect. The antioxidant effects of OAE and of a pure BZF were described by two perfectly overlapping curves whose concentration-dependence was within the 3 × 10^-4 to 10² nM BZF range. Such unprecedented low concentrations place BZF-containing plants on the frontier of the search for novel sources of antioxidants.

Psidium guajava bioactive product chemical analysis and heavy metal toxicity reduction

The present study had as its objective to verify the Psidium guajava var. Pomifera L. chelating, antioxidant and cytoprotective effects against mercury and aluminum. The ethanolic extract, tannic and flavonoid fractions were subjected to LC-MS analysis. The Ferric Reducing Antioxidant Power (FRAP) and ferric ion reduction demonstrated a present antioxidant activity. The fungicidal and bactericidal activity of these metals were established. After determining the sub-allelopathic doses, germination tests using Lactuca sativa were performed. Quercetin and its derivatives were the main compounds identified in the extract and the fractions. Mercury chloride significantly reduced the bactericidal effect of the flavonoid fraction (p < 0.001). None of the fractions were cytoprotective against mercury or aluminum in the fungal model assays. Using a sub-allelopathic concentration (64 μg/mL), the ethanolic extract, flavonoid and tannic fractions were found to be cytoprotective against aluminum for radicles, however only the tannic fraction was cytoprotective for caulicles. These data suggest that natural P. guajava products are promising cytoprotective compound sources. This activity may be related to the antioxidant effect of secondary metabolites, mainly flavonoids. Our results point to a potential for environmental intervention product and technique development aimed at mitigating contamination by toxic metals such as mercury and aluminum.

Determination of potential oxidative damage, hepatotoxicity, and cytogenotoxicity in male Wistar rats: Role of indomethacin

The present study demonstrated the indomethacin (INDO) induced oxidative stress, hepatotoxicity, and genotoxicity in male Wistar rats. Animals were orally administrated INDO at doses of 0.302 and 0.605 (mg/kg b.w.) for 2 weeks. Reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and lipid peroxidation (LPO) activities/levels were measured in the liver, kidney, and brain tissues. The aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP) activities, total bilirubin (TBIL) levels, and histopathological changes were determined in the liver tissues. Micronucleus frequency (micronucleus test) and DNA damage (comet assay) tests were performed in the bone marrow cells and leukocytes, respectively. Results show that INDO treatment decreased the GSH, SOD, and CAT levels/activities and increased the LPO, ALT, AST, ALP, and TBIL activities/levels. INDO induced significant hepatic injury and micronucleus and DNA damage. Thus, the current investigations confirm the oxidative stress, hepatotoxic, and genotoxic properties of INDO in the male Wistar rats.

Quercetin Oxidation Paradoxically Enhances its Antioxidant and Cytoprotective Properties

Quercetin oxidation is generally believed to ultimately result in the loss of its antioxidant properties. To test this assertion, quercetin oxidation was induced, and after each of its major metabolites was identified and isolated by HPLC-DAD-ESI-MS/MS, the antioxidant (dichlorodihydrofluorescein oxidation-inhibiting) and cytoprotective (LDH leakage-preventing) properties were evaluated in Hs68 and Caco2 cells exposed to indomethacin. Compared to quercetin, the whole mixture of metabolites (Q_OX) displayed a 20-fold greater potency. After resolution of Q_OX into 12 major peaks, only one (peak 8), identified as 2,5,7,3',4'-pentahydroxy-3,4-flavandione or its 2-(3,4-dihydroxybenzoyl)-2,4,6-trihydroxy-3(2H)-benzofuranone tautomer, could account for the antioxidant and cytoprotective effects afforded Q_OX. Peak 8 exerted such effects at a 50 nM concentration, revealing a potency 200-fold higher than that of quercetin. The effects of peak 8 were seen regardless of whether it was added to the cells 40 min before or simultaneously with the oxygen-reactive species-generating agent, suggesting an intracellular ability to trigger early antioxidant responses. Thus, the present study is the first to reveal that in regard to the intracellular actions of quercetin, attention should be extended toward some of its oxidation products.

Uric acid ameliorates indomethacin-induced enteropathy in mice through its antioxidant activity

BACKGROUND AND AIM

Uric acid is excreted from blood into the intestinal lumen, yet the roles of uric acid in intestinal diseases remain to be elucidated. The study aimed to determine whether uric acid could reduce end points associated with nonsteroidal anti-inflammatory drug (NSAID)-induced enteropathy.

METHODS

A mouse model of NSAID-induced enteropathy was generated by administering indomethacin intraperitoneally to 8-week-old male C57BL/6 mice, and then vehicle or uric acid was administered orally. A group of mice treated with indomethacin was also concurrently administered inosinic acid, a uric acid precursor, and potassium oxonate, an inhibitor of uric acid metabolism, intraperitoneally. For in vitro analysis, Caco-2 cells treated with indomethacin were incubated in the presence or absence of uric acid.

RESULTS

Oral administration of uric acid ameliorated NSAID-induced enteropathy in mice even though serum uric acid levels did not increase. Intraperitoneal administration of inosinic acid and potassium oxonate significantly elevated serum uric acid levels and ameliorated NSAID-induced enteropathy in mice. Both oral uric acid treatment and intraperitoneal treatment with inosinic acid and potassium oxonate significantly decreased lipid peroxidation in the ileum of mice with NSAID-induced enteropathy. Treatment with uric acid protected Caco-2 cells from indomethacin-induced oxidative stress, lipid peroxidation, and cytotoxicity.

CONCLUSIONS

Uric acid within the intestinal lumen and in serum had a protective effect against NSAID-induced enteropathy in mice, through its antioxidant activity. Uric acid could be a promising therapeutic target for NSAID-induced enteropathy.

Effects of flavonoids on intestinal inflammation, barrier integrity and changes in gut microbiota during diet-induced obesity

Diet-induced obesity is associated with low-grade inflammation, which, in most cases, leads to the development of metabolic disorders, primarily insulin resistance and type 2 diabetes. Although prior studies have implicated the adipose tissue as being primarily responsible for obesity-associated inflammation, the latest discoveries have correlated impairments in intestinal immune homeostasis and the mucosal barrier with increased activation of the inflammatory pathways and the development of insulin resistance. Therefore, it is essential to define the mechanisms underlying the obesity-associated gut alterations to develop therapies to prevent and treat obesity and its associated diseases. Flavonoids appear to be promising candidates among the natural preventive treatments that have been identified to date. They have been shown to protect against several diseases, including CVD and various cancers. Furthermore, they have clear anti-inflammatory properties, which have primarily been evaluated in non-intestinal models. At present, a growing body of evidence suggests that flavonoids could exert a protective role against obesity-associated pathologies by modulating inflammatory-related cellular events in the intestine and/or the composition of the microbiota populations. The present paper will review the literature to date that has described the protective effects of flavonoids on intestinal inflammation, barrier integrity and gut microbiota in studies conducted using in vivo and in vitro models.

Effect of biologically active substances present in water extracts of white mustard and coriander on antioxidant status and lipid peroxidation of mouse C2C12 skeletal muscle cells

Coriander and white mustard, an annual plants originated in the Mediterranean region, have been cultivated and used as spices for a long time. Recent studies have shown that they may constitute a potential source of phenolic compounds. The aim of this study was to evaluate the content of polyphenols in coriander and white mustard water extracts and to investigate their antioxidant activity in C2C12 mouse skeletal muscle cells, which serve as a good model of cells with intensive metabolism. HPLC analysis showed that polyphenols were able to permeate from the water extracts of studied plants into the undifferentiated myoblasts as well as myocytes undergoing differentiation, increasing the concentration of reduced glutathione and upregulating glutathione reductase and peroxidase activity. White mustard and coriander extracts also decreased the levels of oxysterols and sum of tiobarbituric acid reactive substances (TBARS) in both: myoblasts and differentiating myocytes, demonstrating protective effect on cell membranes. The obtained results indicate that polyphenols synthesized by both herbs may have beneficial effects on muscle tissue.

Cranberry flavonoids prevent toxic rat liver mitochondrial damage in vivo and scavenge free radicals in vitro

The present study was undertaken for further elucidation of the mechanisms of flavonoid biological activity, focusing on the antioxidative and protective effects of cranberry flavonoids in free radical-generating systems and those on mitochondrial ultrastructure during carbon tetrachloride-induced rat intoxication. Treatment of rats with cranberry flavonoids (7 mg/kg) during chronic carbon tetrachloride-induced intoxication led to prevention of mitochondrial damage, including fragmentation, rupture and local loss of the outer mitochondrial membrane. In radical-generating systems, cranberry flavonoids effectively scavenged nitric oxide (IC50  = 4.4 ± 0.4 µg/ml), superoxide anion radicals (IC50  = 2.8 ± 0.3 µg/ml) and hydroxyl radicals (IC50  = 53 ± 4 µg/ml). The IC50 for reduction of 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH) was 2.2 ± 0.3 µg/ml. Flavonoids prevented to some extent lipid peroxidation in liposomal membranes and glutathione oxidation in erythrocytes treated with UV irradiation or organic hydroperoxides as well as decreased the rigidity of the outer leaflet of the liposomal membranes. The hepatoprotective potential of cranberry flavonoids could be due to specific prevention of rat liver mitochondrial damage. The mitochondria-addressed effects of flavonoids might be related both to radical-scavenging properties and modulation of various mitochondrial events.

Apples: content of phenolic compounds vs. variety, part of apple and cultivation model, extraction of phenolic compounds, biological properties

Apples are among the most popular fruits in the world. They are rich in phenolic compounds, pectin, sugar, macro- and microelements. Applying different extraction techniques it is possible to isolate a particular group of compounds or individual chemicals and then test their biological properties. Many reports point to the antioxidant, antimicrobial, anticancer and many other beneficial effects of apple components that may have potential applications in food, pharmaceutical and cosmetic industries. This paper summarizes and compiles information about apple phenolic compounds, their biological properties with particular emphasis on health-related aspects. The data are reviewed with regard to different apple varieties, part of apple, cultivation model and methods of extraction.

Effects of methanolic extract form Fuzhuan brick-tea on hydrogen peroxide-induced oxidative stress in human intestinal epithelial adenocarcinoma Caco-2 cells

The present study investigated the protective effect of methanolic extract from Fuzhuan brick‑tea (FME) on hydrogen peroxide (H2O2)‑induced oxidative stress in the human intestinal epithelial adenocarcinoma cell line Caco‑2. Caco‑2 cells were pretreated with different concentrations (50, 100 and 200 µg/ml) of FME for 2 h and then exposed to H2O2 (1 mM) for 6 h. FME did not exhibit a significant cytotoxic effect and increased the cell viability following H2O2 treatment by decreasing lipid peroxidation in Caco‑2 cells. To investigate the protective effect of FME on H2O2‑induced oxidative stress in Caco‑2 cells, the levels of intracellular glutathione (GSH) and the activity of the endogenous antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH‑px) and glutathione S‑transferase (GST), were determined. FME significantly increased the level of GSH and the activity of antioxidant enzymes. The results from the present study demonstrated that FME has a protective effect on H2O2‑induced oxidative damage in Caco‑2 cells through the inhibition of lipid peroxidation and the increase in the activity of antioxidant enzymes. In addition, FME reduced the H2O2‑induced expression of interleukin‑8 at both the mRNA and protein levels in Caco‑2 cells.

Nonsteroidal anti-inflammatory drug induces proinflammatory damage in gastric mucosa through NF-κB activation and neutrophil infiltration: anti-inflammatory role of heme oxygenase-1 against nonsteroidal anti-inflammatory drug

Nonsteroidal anti-inflammatory drug (NSAID)-induced mitochondrial oxidative stress (MOS) is an important prostaglandin (PG)-independent pathway of the induction of gastric mucosal injury. However, the molecular mechanism behind MOS-mediated gastric pathology is still obscure. In various pathological conditions of tissue injury oxidative stress is often linked with inflammation. Here we report that MOS induced by indomethacin (an NSAID) induces gastric mucosal inflammation leading to proinflammatory damage. Indomethacin, time dependently stimulated the expression of proinflammatory molecules such as intercellular adhesion molecule 1(ICAM-1), vascular cell adhesion molecule 1(VCAM-1), interleukin1β (IL-1β), and monocyte chemotactic protein-1 (MCP-1) in gastric mucosa in parallel with the increase of neutrophil infiltration and injury of gastric mucosa in rat. Western immunoblotting and confocal microscopic studies revealed that indomethacin induced nuclear translocation of nuclear factor kappa-B (NF-κB) in gastric mucosal cells, which resulted in proinflammatory signaling. The prevention of MOS by antioxidant tryptamine-gallic acid hybrid (SEGA) inhibited indomethacin-induced expression of ICAM-1, VCAM-1, IL-1β, and MCP-1. SEGA also prevented indomethacin-induced NF-κB activation and neutrophil infiltration as documented by chromatin immunoprecipitation studies and neutrophil migration assay, respectively. Heme oxygenase-1 (HO-1), a cytoprotective enzyme associated with tissue repair mechanisms is stimulated in response to oxidative stress. We have investigated the role of HO-1 against MOS and MOS-mediated inflammation in recovering from gastropathy. Indomethacin stimulated the expression of HO-1 and indomethacin-stimulated HO-1 expression was reduced by SEGA, an antioxidant, which could prevent MOS. Thus, the data suggested that the induction of HO-1 was a protective response against MOS developed by indomethacin. Moreover, the induction of HO-1 by cobalt protoporphyrin inhibited inflammation and chemical silencing of HO-1 by zinc protoporphyrin aggravated the inflammation by indomethacin. Thus, NSAID by promoting MOS-induced proinflammatory response damaged gastric mucosa and HO-1 protected NSAID-induced gastric mucosal damage by preventing NF-κB activation and proinflammatory activity.

Modulation of oxidative stress by proanthocyanidin in H2O2-exposed human diploid fibroblast cells

Proanthocyanidin (a persimmon-peel extract) is known to have potent antioxidative effects, but its protective action specifically against cellular damage has not been fully explored. In this work, we investigated the protective property of proanthocyanidin against cellular oxidative stress with an experimental model, H2O2-exposed human diploid fibroblasts (HDFs). To investigate the proposed underlying beneficial actions of proanthocyanidin as to cellular injury induced by H2O2, several major biochemical parameters were determined, including estimation of total reactive species (RS) generation, antioxidant enzyme activities, reduced glutathione (GSH)/oxidized glulathione (GSSG) ratio, and mitochondrial membrane potential. The results indicate that proanthocyanidin reduced total RS generation while enhancing the activities of catalase and glutathione reductase and the GSH/GSSG ratio. Additionally, proanthocyanidin was found to protect against mitochondrial membrane damage in HDFs treated H2O2. Based on these results, we conclude that proanthocyanidin has strong protective effects against cellular damage to several key cellular functions by suppressing oxidative stress in H2O2-treated HDFs.

Polyphenols protect the epithelial barrier function of Caco-2 cells exposed to indomethacin through the modulation of occludin and zonula occludens-1 expression

The aim of this study was to determine the protective effect of quercetin, epigallocatechingallate, resveratrol, and rutin against the disruption of epithelial integrity induced by indomethacin in Caco-2 cell monolayers. Indomethacin decreased the transepithelial electrical resistance and increased the permeability of the monolayers to fluorescein-dextran. These alterations were abolished by all the tested polyphenols but rutin, with quercetin being the most efficient. The protective effect of quercetin was associated with its capacity to inhibit the redistribution of ZO-1 protein induced in the tight junction by indomethacin or rotenone, a mitochondrial complex-I inhibitor, and to prevent the decrease of ZO-1 and occludin expression induced by indomethacin. The fact that the antioxidant polyphenols assayed in this study differ in their protective capacity against the epithelial damage induced by indomethacin suggests that this damage is due to the ability of this agent to induce not only oxidative stress but also mitochondrial dysfunction.

Inhibition of mitochondrial complex I by various non-steroidal anti-inflammatory drugs and its protection by quercetin via a coenzyme Q-like action

Mitochondrial dysfunction plays a major role in the development of oxidative stress and cytotoxicity induced by non-steroidal anti-inflammatory drugs (NSAIDs). A major objective of the present study was to investigate whether in vitro the NSAIDs, aspirin, indomethacin, diclofenac, piroxicam and ibuprofen, which feature different chemical structures, are able to inhibit mitochondrial complex I. All NSAIDs were effective inhibitors when added both, directly to mitochondria isolated from rat duodenum epithelium (50 μM) or to Caco-2 cells (250 μM). In the former system, complex I inhibition was concentration-dependent and susceptible to competition and reversion by the addition of coenzyme Q (32.5-520 μM). Based on reports suggesting a potential gastro-protective activity of quercetin, the ability of this flavonoid to protect isolated mitochondria against NSAIDs-induced complex I inhibition was evaluated. Low micromolar concentrations of quercetin (1-20 μM) protected against such inhibition, in a concentration dependent manner. In the case of aspirin, quercetin (5 μM) increased the IC50 by 10-fold. In addition, the present study shows that quercetin (5-10 μM) can behave as a "coenzyme Q-mimetic" molecule, allowing a normal electron flow along the whole electron transporting chain (complexes I, II, III and IV). The exposed findings reveal that complex I inhibition is a common deleterious effect of NSAIDs at the mitochondrial level, and that such effect is, for all tested agents, susceptible to be prevented by quercetin. Data provided here supports the contention that the protective action of quercetin resides on its, here for first time-shown, ability to behave as a coenzyme Q-like molecule.

Mitochondrial pharmacology: electron transport chain bypass as strategies to treat mitochondrial dysfunction

Mitochondrial dysfunction (primary or secondary) is detrimental to intermediary metabolism. Therapeutic strategies to treat/prevent mitochondrial dysfunction could be valuable for managing metabolic and age-related disorders. Here, we review strategies proposed to treat mitochondrial impairment. We then concentrate on redox-active agents, with mild-redox potential, who shuttle electrons among specific cytosolic or mitochondrial redox-centers. We propose that specific redox agents with mild redox potential (-0.1 V; 0.1 V) improve mitochondrial function because they can readily donate or accept electrons in biological systems, thus they enhance metabolic activity and prevent reactive oxygen species (ROS) production. These agents are likely to lack toxic effects because they lack the risk of inhibiting electron transfer in redox centers. This is different from redox agents with strong negative (-0.4 V; -0.2 V) or positive (0.2 V; 0.4 V) redox potentials who alter the redox status of redox-centers (i.e., become permanently reduced or oxidized). This view has been demonstrated by testing the effect of several redox active agents on cellular senescence. Methylene blue (MB, redox potential ≅10 mV) appears to readily cycle between the oxidized and reduced forms using specific mitochondrial and cytosolic redox centers. MB is most effective in delaying cell senescence and enhancing mitochondrial function in vivo and in vitro. Mild-redox agents can alter the biochemical activity of specific mitochondrial components, which then in response alters the expression of nuclear and mitochondrial genes. We present the concept of mitochondrial electron-carrier bypass as a potential result of mild-redox agents, a method to prevent ROS production, improve mitochondrial function, and delay cellular aging. Thus, mild-redox agents may prevent/delay mitochondria-driven disorders.

Differential protective effects of quercetin, resveratrol, rutin and epigallocatechin gallate against mitochondrial dysfunction induced by indomethacin in Caco-2 cells

The beneficial effects of dietary polyphenols on health are due not only to their antioxidant properties but also to their antibacterial, anti-inflammatory and/or anti-tumoral activities. It has recently been proposed that protection of mitochondrial function (which is altered in several diseases such as Alzheimer, Parkinson, obesity and diabetes) by these compounds, may be important in explaining the beneficial effects of polyphenols on health. The aim of this study was to evaluate the protective effects of dietary polyphenols quercetin, rutin, resveratrol and epigallocatechin gallate against the alterations of mitochondrial function induced by indomethacin (INDO) in intestinal epithelial Caco-2 cells, and to address the mechanism involved in such damaging effect by INDO, which generates oxidative stress. INDO concentration dependently decreases cellular ATP levels and mitochondrial membrane potential in Caco-2 cells after 20min of incubation. INDO also inhibits the activity of mitochondrial complex I and causes accumulation of NADH; leading to overproduction of mitochondrial O(2)()(-), since it is prevented by pyruvate. Quercetin (0.01mg/ml), resveratrol (0.1mg/ml) and rutin (1mg/ml) protected Caco-2 cells against INDO-induced mitochondrial dysfunction, while no protection was observed with epigallocatechin gallate. Quercetin was the most efficient in protecting against mitochondrial dysfunction; this could be due to its ability to enter cells and accumulate in mitochondria. Additionally its structural similarity with rotenone could favor its binding to the ubiquinone site of complex I, protecting it from inhibitors such as INDO or rotenone. These findings suggest a possible new protective role for dietary polyphenols for mitochondria, complementary of their antioxidant property. This new role might expand the preventive and/or therapeutic use of PPs in conditions involving mitochondrial dysfunction and associated with increased oxidative stress at the cellular or tissue levels.

Apple peel polyphenol extract protects against indomethacin-induced damage in Caco-2 cells by preventing mitochondrial complex I inhibition

The aim of this work was to investigate the role of mitochondrial dysfunction in the development of oxidative stress and cytotoxicity induced by indomethacin and to evaluate the potential of an apple peel polyphenol extract (APPE) in protecting against these events. Indomethacin induced, time-dependently, mitochondrial and oxidative perturbations which led to cell losses. An inhibition of complex I activity, shown for first time here, which resulted in a concomitant drop in cellular ATP and an increment in mitochondrial superoxide production, was observed after 10 min of exposure. These early cytotoxicity-triggering events were followed by an increase in the intracellular production of superoxide (20 min), an elevation in the activity of xanthine oxidase which led to an increased lipid peroxidation (30 min), and a decline in cell viability which manifested after 40 min. These events were selectively prevented using allopurinol, tempol and APPE (a standardized apple peel polyphenol extract). While the oxidative and cell lytic effects of indomethacin were equally prevented by the three agents, only APPE protected against complex I inhibition and its downstream oxidative consequences. Since tempol (a SOD mimetic) prevented the elevation in xanthine oxidase activity, and allopurinol (a xanthine oxidase inhibitor) totally abolished the increment in lipid peroxidation and loss of cell viability, it appears that a superoxide-dependent increase in xanthine oxidase activity is critical to trigger cytotoxicity. Thus, preventing the early increment in superoxide formation that, as a result of inhibiting complex I, takes place within mitochondria would be key toward protecting the cells against the oxidative and cytolytic effects of indomethacin. The ability of APPE in preventing the inhibition of complex I and the subsequent superoxide-dependent increase in XO activity warrants further studies to evaluate the mechanism involves in the protecting effect of APPE against the indomethacin-associated adverse effects in vivo.

Apple peel polyphenols protect against gastrointestinal mucosa alterations induced by indomethacin in rats

The stability of an apple peel polyphenol extract (APPE) with powerful antioxidant activity was evaluated under acidic conditions in vitro, and its protective effect against gastrointestinal damage was investigated in rats treated with indomethacin. The antioxidant activity of APPE remained stable at pH 2.0 for 4 h. In rats treated with indomethacin (40 mg/kg ig), the previous administration of APPE protected the gastric, intestinal, and colonic mucosa from oxidative stress by preventing increased malondialdehyde concentrations and decreasing the GSH/GSSG ratio. APPE also displayed anti-inflammatory effects by preventing neutrophil infiltration in the mucosa, as evidenced by the lower myeloperoxidase activity. These protective effects of APPE resulted in the prevention of macro- and microscopic damage and of barrier dysfunction along the gastrointestinal tract of the indomethacin-treated animals. This study supports the concept that apple peel polyphenols may be useful in the prevention and/or treatment of nonsteroidal anti-inflammatory drug-associated side effects.

Effects of diphenyl diselenide on lipid profile and hepatic oxidative stress parameters in ovariectomized female rats

Objectives

Ovarian hormone decline after menopause is linked to many pathophysiological reactions. Female rats submitted to ovariectomy are employed as a model of post-menopausal condition. This study investigated the effects of diphenyl diselenide (PhSe)2 on body weight gain, intra-abdominal fat deposition, plasma lipid profile and hepatic oxidative stress in ovariectomized rats.

Methods

Female adult Wistar rats were ovariectomized (OVX rats) or sham-operated and divided into four groups: (i) sham-operated, (ii) (PhSe)2, (iii) OVX and (iv) OVX + (PhSe)2. (PhSe)2 (5 mg/kg; 5 ml/kg, p.o.) was administered once a day for 30 days to groups (ii) and (iv). After that, rats were anaesthetized for blood sample gathering and submitted to euthanasia.

Key findings

(PhSe)2 (5 mg/kg) was effective in preventing the rise in body weight gain and intra-abdominal fat deposition induced in OVX rats. Although (PhSe)2 was not effective in avoiding the increase in plasma total cholesterol and non-HDL levels induced in OVX rats, (PhSe)2 reduced plasma triglycerides and augmented HDL levels in OVX rats. (PhSe)2 also increased hepatic ascorbic acid levels, reduced glutathione content, glutathione S-transferase activity and restored catalase activity in liver of OVX rats.

Conclusions

These findings suggest that (PhSe)2 could be a promising alternative to minimize menopause related symptoms.

Anti-inflammatory effect of Rhus verniviflua Stokes by suppression of iNOS-mediated Akt and ERK pathways: in-vitro and in-vivo studies

OBJECTIVES

Rhus verniciflua Stokes (RVS), which has valuable medicinal properties, has for many years been prescribed for inflammation in east Asian medicine. Recent studies suggest that RVS has potent antioxidative, antitumor and anti-inflammatory properties.

METHODS

In this study, the anti-inflammatory effects of RVS in vitro and in vivo were investigated. The ethanol extract from RVS was partitioned with different solvents in order of increasing polarity.

KEY FINDINGS

Among the various extracts, the n-butanol extract displayed the most potent activity against nitric oxide and reactive oxygen species. The n-butanol extract also significantly regulates expression of nitric oxide synthase, which inhibits nitric oxide production at the transcriptional level in activated macrophages. Immunoblot analysis also showed that n-butanol extract suppresses the phosphorylation of extracellular signal-regulated kinase and Akt, suggesting that nitric oxide synthase suppression might be mediated via the extracellular signal-regulated kinase and Akt signaling pathways. This study also investigated whether n-butanol exerts an anti-inflammatory effect in an animal model. n-butanol extract significantly reduces carrageenan-induced mouse paw edema at 5 h.

CONCLUSIONS

These results suggest that RVS could be a promising candidate agent for inflammation prevention and combination therapy with anti-inflammatory drugs.

Neuroprotective properties of Spanish red wine and its isolated polyphenols on astrocytes

The neuroprotective effect of Merlot red wine and its isolated polyphenols was evaluated in an oxidative stress model induced by Fenton reaction and hydrogen peroxide in the human astrocytoma U373 MG cell line. Compared with cells treated only with oxidative stress inductors, the pre-incubation with Merlot red wine for 24h caused a significant increase in cell viability for all concentrations assayed. The most abundant polyphenols found in Merlot red wine were the flavonoids catechin (37.8mg/l), epicatechin (52.3mg/l), quercetin (5.89mg/l) and procyanidins (15.2mg/l), the hydroxybenzoic acid gallic acid (16.7mg/l), and the phenolic alcohol tyrosol (31.4mg/l). The potential protective role of these polyphenols when isolated was then assessed in treated Fenton reaction U373 MG cells. Polyphenols decreased reactive oxygen species generation and increased the activity and the protein expression of the antioxidant enzymes catalase, superoxide dismutase, glutathione reductase and glutathione peroxidase. Of the polyphenols, quercetin and procyanidins showed the highest neuroprotective effect.