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

Phenolic Compounds from Apples: From Natural Fruits to the Beneficial Effects in the Digestive System

Conditions in the gastrointestinal tract and microbial metabolism lead to biotransformation of parent, native phenolic compounds from apples into different chemical forms. The aim of this work was to review current knowledge about the forms of phenolic compounds from apples in the gastrointestinal tract and to connect it to their potential beneficial effects, including the mitigation of health problems of the digestive tract. Phenolic compounds from apples are found in the gastrointestinal tract in a variety of forms: native (flavan-3-ols, phenolic acids, flavonols, dihydrochalcones, and anthocyanins), degradation products, various metabolites, and catabolites. Native forms can show beneficial effects in the stomach and small intestine and during the beginning phase of digestion in the colon. Different products of degradation and phase II metabolites can be found in the small intestine and colon, while catabolites might be important for bioactivities in the colon. Most studies connect beneficial effects for different described health problems to the whole apple or to the amount of all phenolic compounds from apples. This expresses the influence of all native polyphenols from apples on beneficial effects. However, further studies of the peculiar compounds resulting from native phenols and their effects on the various parts of the digestive tract could provide a better understanding of the specific derivatives with bioactivity in humans.

Role of Flavonoids in Modulation of Mitochondria Dynamics during Oxidative Stress

BACKGROUND

Flavonoids are a widespread category of naturally occurring polyphenols distinguished by the flavan nucleus in plant-based foods and beverages, known for their various health benefits. Studies have suggested that consuming 150-500 mg of flavonoids daily is beneficial for health. Recent studies suggest that flavonoids are involved in maintaining mitochondrial activity and preventing impairment of mitochondrial dynamics by oxidative stress.

OBJECTIVE

This review emphasized the significance of studying the impact of flavonoids on mitochondrial dynamics, oxidative stress, and inflammatory response.

METHODS

This review analysed and summarised the findings related to the impact of flavonoids on mitochondria from publicly available search engines namely Pubmed, Scopus, and Web of Science.

DESCRIPTION

Any disruption in mitochondrial dynamics can contribute to cellular dysfunction and diseases, including cancer, cardiac conditions, and neurodegeneration. Flavonoids have been shown to modulate mitochondrial dynamics by regulating protein expression involved in fission and fusion events. Furthermore, flavonoids exhibit potent antioxidant properties by lowering the production of ROS and boosting the performance of antioxidant enzymes. Persistent inflammation is a characteristic of many different disorders. This is because flavonoids also alter the inflammatory response by controlling the expression of numerous cytokines and chemokines involved in the inflammatory process. Flavonoids exhibit an impressive array of significant health effects, making them an effective therapeutic agent for managing various disorders. Further this review summarised available mechanisms underlying flavonoids' actions on mitochondrial dynamics and oxidative stress to recognize the optimal dose and duration of flavonoid intake for therapeutic purposes.

CONCLUSION

This review may provide a solid foundation for developing targeted therapeutic interventions utilizing flavonoids, ultimately benefiting individuals afflicted with various disorders.

The Oxidative Stress and Nervous Distress Connection in Gastrointestinal Disorders

Oxidative stress is increasingly recognized as a central player in a range of gastrointestinal (GI) disorders, as well as complications stemming from therapeutic interventions. This article presents an overview of the mechanisms of oxidative stress in GI conditions and highlights a link between oxidative insult and disruption to the enteric nervous system (ENS), which controls GI functions. The dysfunction of the ENS is characteristic of a spectrum of disorders, including neurointestinal diseases and conditions such as inflammatory bowel disease (IBD), diabetic gastroparesis, and chemotherapy-induced GI side effects. Neurons in the ENS, while essential for normal gut function, appear particularly vulnerable to oxidative damage. Mechanistically, oxidative stress in enteric neurons can result from intrinsic nitrosative injury, mitochondrial dysfunction, or inflammation-related pathways. Although antioxidant-based therapies have shown limited efficacy, recognizing the multifaceted role of oxidative stress in GI diseases offers a promising avenue for future interventions. This comprehensive review summarizes the literature to date implicating oxidative stress as a critical player in the pathophysiology of GI disorders, with a focus on its role in ENS injury and dysfunction, and highlights opportunities for the development of targeted therapeutics for these diseases.

Honokiol, an inducer of sirtuin-3, protects against non-steroidal anti-inflammatory drug-induced gastric mucosal mitochondrial pathology, apoptosis and inflammatory tissue injury

BACKGROUND AND PURPOSE

Mitochondrial oxidative stress, inflammation and apoptosis primarily underlie gastric mucosal injury caused by the widely used non-steroidal anti-inflammatory drugs (NSAIDs). Alternative gastroprotective strategies are therefore needed. Sirtuin-3 pivotally maintains mitochondrial structural integrity and metabolism while preventing oxidative stress; however, its relevance to gastric injury was never explored. Here, we have investigated whether and how sirtuin-3 stimulation by the phytochemical, honokiol, could rescue NSAID-induced gastric injury.

EXPERIMENTAL APPROACH

Gastric injury in rats induced by indomethacin was used to assess the effects of honokiol. Next-generation sequencing-based transcriptomics followed by functional validation identified the gastroprotective function of sirtuin-3. Flow cytometry, immunoblotting, qRT-PCR and immunohistochemistry were used measure effects on oxidative stress, mitochondrial dynamics, electron transport chain function, and markers of inflammation and apoptosis. Sirtuin-3 deacetylase activity was also estimated and gastric luminal pH was measured.

KEY RESULTS

Indomethacin down-regulated sirtuin-3 to induce oxidative stress, mitochondrial hyperacetylation, 8-oxoguanine DNA glycosylase 1 depletion, mitochondrial DNA damage, respiratory chain defect and mitochondrial fragmentation leading to severe mucosal injury. Indomethacin dose-dependently inhibited sirtuin-3 deacetylase activity. Honokiol prevented mitochondrial oxidative damage and inflammatory tissue injury by attenuating indomethacin-induced depletion of both sirtuin-3 and its transcriptional regulators PGC1α and ERRα. Honokiol also accelerated gastric wound healing but did not alter gastric acid secretion, unlike lansoprazole.

CONCLUSIONS AND IMPLICATIONS

Sirtuin-3 stimulation by honokiol prevented and reversed NSAID-induced gastric injury through maintaining mitochondrial integrity. Honokiol did not affect gastric acid secretion. Sirtuin-3 stimulation by honokiol may be utilized as a mitochondria-based, acid-independent novel gastroprotective strategy against NSAIDs.

Thinned young apple polyphenols may prevent neuronal apoptosis by up-regulating 5-hydroxymethylcytosine in the cerebral cortex of high-fat diet-induced diabetic mice

Apple polyphenols exert neuroprotective effects by improving the mitochondrial tricarboxylic acid (TCA) cycle function, but the details of their mechanisms are still not fully understood. TCA cycle metabolites regulate the level of 5-hydroxymethylcytosine (5hmC) by affecting the ten-eleven translocation (TET) enzyme activity. Therefore, we hypothesized that thinned young apple polyphenols (TYAPs) inhibit neuronal apoptosis by up-regulating the level of 5hmC in the cerebral cortex of high-fat diet-induced diabetic mice. C57BL/6J mice were randomly divided into 5 groups (n = 10 each group): the control (CON) group, the high-fat diet (HFD, negative control) group, the lovastatin (LOV, positive drug control) group, the resveratrol (RES, positive polyphenol control) group and the TYAP group during an eight-week intervention. The presented results verified that in the HFD group, the level of 5hmC and the expression of TET2 in the cerebral cortex were significantly lower, and the ratio of (succinic acid + fumaric acid)/α-ketoglutarate and the neuronal apoptosis rate were significantly higher than those in the CON group. However, TYAP intervention effectively restored the level of 5hmC through up-regulating the expression and activity of TET2, so as to improve diabetes symptoms and prevent diabetes-induced neuronal apoptosis.

The potential of probiotics in the amelioration of hyperuricemia

Hyperuricemia is a common disease caused by metabolic disorders or the excessive intake of high-purine foods. Persistent hyperuricemia in extreme cases induces gout, and asymptomatic hyperuricemia is probably linked to other metabolic diseases, such as hypertension. The typical damage caused by asymptomatic hyperuricemia includes inflammation, oxidative stress and gut dysbiosis. Probiotics have broad potential applications as food additives, not as drug therapies, in the amelioration of hyperuricemia. In this review, we describe novel methods for potential hyperuricemia amelioration with probiotics. The pathways through which probiotics may ameliorate hyperuricemia are discussed, including the decrease in uric acid production through purine assimilation and XOD (xanthine oxidase) inhibition as well as enhanced excretion of uric acid production by promoting ABCG2 (ATP binding cassette subfamily G member 2) activity, respectively. Three possible probiotic-related therapeutic pathways for alleviating the syndrome of hyperuricemia are also summarized. The first mechanism is to alleviate the oxidation and inflammation induced by hyperuricemia through the inhibition of NLRP3 inflammasome, the second is to restore damaged intestinal epithelium barriers and prevent gut microbiota dysbiosis, and the third is to enhance the innate immune system by increasing the secretion of immunoglobulin A (sIgA) to resist the stimulus by hyperuricemia. We propose that future research should focus on superior strain resource isolation and insight into the cause-effect mechanisms of probiotics for hyperuricemia amelioration. The safety and effects of the application of probiotics in clinical use also need verification.

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.

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.

Transport, metabolism and remedial potential of functional food extracts (FFEs) in Caco-2 cells monolayer: A review

Caco-2, a human intestinal carcinoma cell line, has been used to test the absorption and transport mechanism of functional foods and drugs across the intestinal epithelium in order to study their antioxidant, anticancer and anti-inflammatory activities. Caco-2 cells represent the morphological and functional characteristics of small intestinal cells and capable of expressing brush borders, tight junctions, intestinal efflux and uptake transporters which regulate permeation of drugs and functional food extracts from intestinal lumen to systemic circulation. The integrity of the Caco-2 monolayer is controlled by establishing the TEER between 200 and 1000 O per cm². FFEs affect intestinal permeability by adjusting the tight junction proteins between the cells in order to maintain the epithelial barrier function. Because of the side effects of medicines, there is an increased interest in functional food extracts (FFEs) as drug substitutes. Functional foods undergo intricate transport processes and biotransformation after oral administration. Metabolism and transport studies of FFEs in Caco-2 cells are very important for determining their bioavailability. Functional foods and their constituents produce anti-proliferative and anti-cancer effects through apoptosis, cell cycle arrest and inhibition of various signal transduction pathways across Caco-2 cell lines. The current review has summarized the anti-inflammation, anticancer, antioxidant and cholesterol lowering potential of FFEs using Caco-2 cells through reducing local inflammatory signals, production of ROS and lipid accumulation. The transport, bioavailability, metabolism, mechanisms of actions, cellular pathways adopted by FFEs across Caco-2 cell lines are predominantly affected by their molecular weight, structures and physicochemical properties. These studies are beneficial for investigating the different mechanisms of action of FFEs in the human body.

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.

Natural polyphenols prevent indomethacin-induced and diclofenac-induced Caco-2 cell death by reducing endoplasmic reticulum stress regardless of their direct reactive oxygen species scavenging capacity

Objectives

Indomethacin (INDO) and diclofenac (DIC) can induce intestinal cell death through induction of oxidative stress-mediated ER stress and mitochondrial dysfunction. This study investigated the cytoprotective potential of 11 polyphenols, namely caffeic acid (CAF), curcumin (CUR), epigallocatechin gallate (EGCG), gallic acid (GAL), hypophyllanthin (HYPO), naringenin (NAR), phyllanthin (PHY), piperine (PIP), quercetin (QUE), rutin (RUT) and silymarin (SLY) against these two NSAIDs in Caco-2 cells.

Methods

Reactive oxygen species (ROS) production was determined with fluorescence spectroscopy using specific probes (DHE, DCFH-DA, HPF). Cell viability and mitochondrial function were assessed by MTT and TMRE assays. The mRNA levels of Bax, Bcl-2 and CHOP proteins were determined by quantitative real-time polymerase chain reaction technique.

Key findings

All test polyphenols reduced NSAIDs-mediated ROS production. Only EGCG, QUE and RUT protected INDO-/DIC-induced cell death. These three polyphenols suppressed Bax/Bcl-2 mRNA ratio, CHOP up-regulation and MMP disruption in NSAIDs-treated cells. CAF and NAR prevented cytotoxicity from INDO, but not DIC. The cytoprotective effect of NAR, but not CAF, involved alteration of Bax/Bcl-2 mRNA ratio or MMP disruption, but not CHOP transcription.

Conclusion

The cytoprotective activity of polyphenols against NSAIDs-induced toxicity stemmed from either suppression of CHOP-related ER and mitochondria stresses or other CHOP-independent pathways, but not from the intrinsic ROS scavenging capacity.

Crosstalk between mitochondrial metabolism and oxidoreductive homeostasis: a new perspective for understanding the effects of bioactive dietary compounds

Mitochondria play an important role in a number of fundamental cellular processes, including energy production, biosynthetic pathways and cellular oxidoreductive homeostasis (redox status), and their dysfunction can lead to numerous pathophysiological consequences. As the biochemical mechanisms orchestrating mitochondrial metabolism and redox homeostasis are functionally linked, mitochondria have been identified as a potential therapeutic target. Consequently, considerable effort has been made to evaluate the efficacy of natural compounds that modulate mitochondrial function. Molecules produced by plants (for example, polyphenols and isothiocyanates) have been shown to modulate mitochondrial metabolism/biogenesis and redox status; however, despite the existence of a functional link, few studies have considered the combined efficacy of these mitochondrial functions. The present review provides a complete overview of the molecular pathways involved in modulating mitochondrial metabolism/biogenesis and redox status. Crosstalk between these critical mechanisms is also discussed, whilst major data from the literature regarding their antioxidant abilities are described and critically analysed. We also provide a summary of recent evidence regarding the ability of several plant-derived compounds to target these mitochondrial functions. An in-depth understanding of the functional link between mitochondrial metabolism/biogenesis and redox status could facilitate the analysis of the biological effects of natural compounds as well as the development of new therapeutic approaches.

Indomethacin impairs mitochondrial dynamics by activating the PKCζ-p38-DRP1 pathway and inducing apoptosis in gastric cancer and normal mucosal cells

The subcellular mechanism by which nonsteroidal anti-inflammatory drugs (NSAIDs) induce apoptosis in gastric cancer and normal mucosal cells is elusive because of the diverse cyclooxygenase-independent effects of these drugs. Using human gastric carcinoma cells (AGSs) and a rat gastric injury model, here we report that the NSAID indomethacin activates the protein kinase Cζ (PKCζ)-p38 MAPK (p38)-dynamin-related protein 1 (DRP1) pathway and thereby disrupts the physiological balance of mitochondrial dynamics by promoting mitochondrial hyper-fission and dysfunction leading to apoptosis. Notably, DRP1 knockdown or SB203580-induced p38 inhibition reduced indomethacin-induced damage to AGSs. Indomethacin impaired mitochondrial dynamics by promoting fissogenic activation and mitochondrial recruitment of DRP1 and down-regulating fusogenic optic atrophy 1 (OPA1) and mitofusins in rat gastric mucosa. Consistent with OPA1 maintaining cristae architecture, its down-regulation resulted in EM-detectable cristae deformity. Deregulated mitochondrial dynamics resulting in defective mitochondria were evident from enhanced Parkin expression and mitochondrial proteome ubiquitination. Indomethacin ultimately induced mitochondrial metabolic and bioenergetic crises in the rat stomach, indicated by compromised fatty acid oxidation, reduced complex I- associated electron transport chain activity, and ATP depletion. Interestingly, Mdivi-1, a fission-preventing mito-protective drug, reversed indomethacin-induced DRP1 phosphorylation on Ser-616, mitochondrial proteome ubiquitination, and mitochondrial metabolic crisis. Mdivi-1 also prevented indomethacin-induced mitochondrial macromolecular damage, caspase activation, mucosal inflammation, and gastric mucosal injury. Our results identify mitochondrial hyper-fission as a critical and common subcellular event triggered by indomethacin that promotes apoptosis in both gastric cancer and normal mucosal cells, thereby contributing to mucosal injury.

Mitochondrial ATP Depletion Disrupts Caco-2 Monolayer Integrity and Internalizes Claudin 7

Objective:In vivo studies suggest that intestinal barrier integrity is dependent on mitochondrial ATP production. Here, we aim to provide mechanistic support, using an in vitro model mimicking the oxidative in vivo situation. Methods: Human Caco-2 cells were cultured for 10 days in culture flasks or for 14 days on transwell inserts in either glucose-containing or galactose-containing medium. Mitochondria were visualized and cellular respiration and levels of oxidative phosphorylation (OXPHOS) proteins were determined. Mitochondrial ATP depletion was induced using CCCP, rotenone, or piericidin A (PA). Monolayer permeability was assessed using transepithelial electrical resistance (TEER) and fluorescein flux. Gene expression and cellular distribution of tight junction proteins were analyzed. Results: Caco-2 cells cultured in galactose-containing, but not in glucose-containing, medium showed increased mitochondrial connectivity, oxygen consumption rates and levels of OXPHOS proteins. Inhibition of mitochondrial ATP production using CCCP, rotenone or PA resulted in a dose-dependent increase in Caco-2 monolayer permeability. In-depth studies with PA showed a six fold decrease in cellular ATP and revealed increased gene expression of tight junction proteins (TJP) 1 and 2, occludin, and claudin 1, but decreased gene expression of claudin 2 and 7. Of these, claudin 7 was clearly redistributed from the cellular membrane into the cytoplasm, while the others were not (TJP1, occludin) or slightly (claudin 2, actin) affected. In vivo studies suggest that intestinal barrier integrity is dependent on mitochondrial ATP production. Here, we aim to provide mechanistic support, using an in vitro model mimicking the oxidative in vivo situation. Conclusions: Well-functioning mitochondria are essential for maintaining cellular energy status and monolayer integrity of galactose grown Caco-2 cells. Energy depletion-induced Caco-2 monolayer permeability may be facilitated by changes in the distribution of claudin 7.

Apple peel polyphenols: a key player in the prevention and treatment of experimental inflammatory bowel disease

Diets rich in fruits and vegetables may reduce oxidative stress (OxS) and inflammation via several mechanisms. These beneficial effects may be due to their high polyphenol content. The aims of the present study are to evaluate the preventive and therapeutic aspects of polyphenols in dried apple peel powder (DAPP) on intestinal inflammation while elucidating the underlying mechanisms and clinical benefits. Induction of intestinal inflammation in mice was performed by oral administration of the inflammatory agent dextran sulfate sodium (DSS) at 2.5% for 10 days. Physiological and supraphysiological doses of DAPP (200 and 400 mg/kg/day respectively) were administered by gavage for 10 days pre- and post-DSS treatment. DSS-mediated inflammation caused weight loss, shortening of the colon, dystrophic detachment of the epithelium, and infiltration of mono- and poly-morphonuclear cells in the colon. DSS induced an increase in lipid peroxidation, a down-regulation of antioxidant enzymes, an augmented expression of myeloperoxidase (MPO) and cyclooxygenase-2 (COX-2), an elevated production of prostaglandin E2 (PGE2) and a shift in mucosa-associated microbial composition. However, DAPP normalized most of these abnormalities in preventive or therapeutic situations in addition to lowering inflammatory cytokines while stimulating antioxidant transcription factors and modulating other potential healing pathways. The supraphysiological dose of DAPP in therapeutic situations also improved mitochondrial dysfunction. Relative abundance of Peptostreptococcaceae and Enterobacteriaceae bacteria was slightly decreased in DAPP-treated mice. In conclusion, DAPP exhibits powerful antioxidant and anti-inflammatory action in the intestine and is associated with the regulation of cellular signalling pathways and changes in microbiota composition. Evaluation of preventive and therapeutic effects of DAPP may be clinically feasible in individuals with intestinal inflammatory bowel diseases.

Selective scavenging of intra-mitochondrial superoxide corrects diclofenac-induced mitochondrial dysfunction and gastric injury: A novel gastroprotective mechanism independent of gastric acid suppression

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to treat multiple inflammatory diseases and pain but severe gastric mucosal damage is the worst outcome of NSAID-therapy. Here we report that mitoTEMPO, a mitochondrially targeted superoxide (O₂^-) scavenger protected as well as healed gastric injury induced by diclofenac (DCF), the most commonly used NSAID. Common existing therapy against gastric injury involves suppression of gastric acid secretion by proton pump inhibitors and histamine H₂ receptor antagonists; however, dyspepsia, vitamin B12 deficiency and gastric microfloral dysbalance are the major drawbacks of acid suppression. Interestingly, mitoTEMPO did not inhibit gastric acid secretion but offered gastroprotection by preventing DCF-induced generation of O₂^- due to mitochondrial respiratory chain failure and by preventing mitochondrial oxidative stress (MOS)-mediated mitopathology. MitoTEMPO even restored DCF-stimulated reduced fatty acid oxidation, mitochondrial depolarization and bioenergetic crisis in gastric mucosa. MitoTEMPO also prevented the activation of mitochondrial pathway of apoptosis and MOS-mediated proinflammatory signaling through NF-κB by DCF. Furthermore, mitoTEMPO when administered in rats with preformed gastric lesions expedited the healing of gastric injury and the healed stomach exhibited its normal physiology as evident from gastric acid and pepsin secretions under basal or stimulated conditions. Thus, in contrast to the existing antiulcer drugs, mitochondrially targeted O₂^- scavengers like mitoTEMPO may represent a novel class of gastroprotective molecules that does not affect gastric acid secretion and may be used in combination with DCF, keeping its anti-inflammatory action intact, while reducing its gastrodamaging effects.

Deleterious Effect of p-Cresol on Human Colonic Epithelial Cells Prevented by Proanthocyanidin-Containing Polyphenol Extracts from Fruits and Proanthocyanidin Bacterial Metabolites

The protective effect of proanthocyanidin-containing polyphenol extracts from apples, avocados, cranberries, grapes, or proanthocyanidin microbial metabolites was evaluated in colonic epithelial cells exposed to p-cresol, a deleterious compound produced by the colonic microbiota from l-tyrosine. In HT29 Glc(-/+) cells, p-cresol significantly increased LDH leakage and decreased ATP contents, whereas in Caco-2 cell monolayers, it significantly decreased the transepithelial electrical resistance and increased the paracellular transport of FITC-dextran. The alterations induced by p-cresol in HT29 Glc(-/+) cells were prevented by the extracts from cranberries and avocados, whereas they became worse by extracts from apples and grapes. The proanthocyanidin bacterial metabolites decreased LDH leakage, ameliorating cell viability without improving intracellular ATP. All of the polyphenol extracts and proanthocyanidin bacterial metabolites prevented the p-cresol-induced alterations of barrier function. These results suggest that proanthocyanidin-containing polyphenol extracts and proanthocyanidin metabolites likely contribute to the protection of the colonic mucosa against the deleterious effects of p-cresol.

Mechanism-based pharmacokinetic-pharmacodynamic modeling of salvianolic acid A effects on plasma xanthine oxidase activity and uric acid levels in acute myocardial infarction rats

1. Salvianolic acid A (SalA) was found to attenuate plasma uric acid (UA) concentration and xanthine oxidase (XO) activity in acute myocardial infraction (AMI) rats, which was characterized with developed mechanism-based pharmacokinetic-pharmacodynamic (PK-PD) model. 2. AMI was induced in rats by coronary artery ligation. Surviving AMI rats received a single intravenous dose of 5 mg/kg of SalA and normal saline. The plasma SalA concentrations were determined by HPLC-MS/MS method. The plasma UA concentrations were determined by HPLC method and plasma XO activity were measured spectrophotometrically. An integrated mathematical model characterized the relationship between plasma UA and SalA. 3. Pharmacokinetics was described using two-compartment model for SalA with linear metabolic process. In post-AMI rats, XO activity and UA concentrations were increased, while SalA dosing palliated this increase. These effects were well captured by using two series of transduction models, simulating the delay of inhibition on XO driven by SalA and UA elevation resulted from the multiple factors, respectively. 4. The effect was well described by the developed PK-PD model, indicating that SalA can exert cardiovascular protective effects by decreasing elevated plasma UA levels induced by AMI.

Chlorogenic acid decreased intestinal permeability and ameliorated intestinal injury in rats via amelioration of mitochondrial respiratory chain dysfunction

Chlorogenic acid (CGA), an abundant polyphenol compound in plants, exhibits anti-oxidant effects. The protective effect of CGA in the rat intestine with endotoxin infusion was evaluated. CGA administration ameliorated endotoxin-induced intestinal injury, and decreased the ratio of lactulose/mannitol, the ileum pathological grade, the myeloperoxidase activity in the ileum, and the malondialdehyde content in the ileum and in ileum mitochondria. The small intestine weight, activities of alkaline phosphatase and superoxide dismutase in the ileum, and β-nicotinamide adenine dinucleotide reduce form (NADH) dehydrogenase and succinate dehydrogenase activities in ileum mitochondria were increased. Intestinal permeability was positively correlated with intestinal mitochondrial injury indicated as the level of malondialdehyde in ileum mitochondria, and negatively correlated with NADH dehydrogenase activity. Dietary administration of CGA protected against increased intestinal permeability caused by endotoxin infusion. The protective effect of CGA was probably associated with a decrease in mitochondrial lipid peroxidation levels and an increase in NADH dehydrogenase activity.

Accumulation of Flavonols over Hydroxycinnamic Acids Favors Oxidative Damage Protection under Abiotic Stress

Efficient detoxification of reactive oxygen species (ROS) is thought to play a key role in enhancing the tolerance of plants to abiotic stresses. Although multiple pathways, enzymes, and antioxidants are present in plants, their exact roles during different stress responses remain unclear. Here, we report on the characterization of the different antioxidant mechanisms of tomato plants subjected to heat stress, salinity stress, or a combination of both stresses. All the treatments applied induced an increase of oxidative stress, with the salinity treatment being the most aggressive, resulting in plants with the lowest biomass, and the highest levels of H2O2 accumulation, lipid peroxidation, and protein oxidation. However, the results obtained from the transcript expression study and enzymatic activities related to the ascorbate-glutathione pathway did not fully explain the differences in the oxidative damage observed between salinity and the combination of salinity and heat. An exhaustive metabolomics study revealed the differential accumulation of phenolic compounds depending on the type of abiotic stress applied. An analysis at gene and enzyme levels of the phenylpropanoid metabolism concluded that under conditions where flavonols accumulated to a greater degree as compared to hydroxycinnamic acids, the oxidative damage was lower, highlighting the importance of flavonols as powerful antioxidants, and their role in abiotic stress tolerance.

NSAIDs and Cardiovascular Diseases: Role of Reactive Oxygen Species

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs worldwide. NSAIDs are used for a variety of conditions including pain, rheumatoid arthritis, and musculoskeletal disorders. The beneficial effects of NSAIDs in reducing or relieving pain are well established, and other benefits such as reducing inflammation and anticancer effects are also documented. The undesirable side effects of NSAIDs include ulcers, internal bleeding, kidney failure, and increased risk of heart attack and stroke. Some of these side effects may be due to the oxidative stress induced by NSAIDs in different tissues. NSAIDs have been shown to induce reactive oxygen species (ROS) in different cell types including cardiac and cardiovascular related cells. Increases in ROS result in increased levels of oxidized proteins which alters key intracellular signaling pathways. One of these key pathways is apoptosis which causes cell death when significantly activated. This review discusses the relationship between NSAIDs and cardiovascular diseases (CVD) and the role of NSAID-induced ROS in CVD.

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

Polyphenols, ubiquitously present in fruits and vegetables, have been traditionally viewed as antioxidant molecules. Such contention emerged, mainly from their well established in vitro ability to scavenge free radicals and other reactive oxygen species (ROS). During the last decade, however, increasing evidence has emerged supporting the ability of certain polyphenols to also exert numerous ROS-scavenging independent actions. Although the latter can comprise the whole cell, particular attention has been placed on the ability of polyphenols to act, whether favorably or not, on a myriad of mitochondrial processes. Thus, some particular polyphenols are now recognized as molecules capable of modulating pathways that define mitochondrial biogenesis (i.e., inducing sirtuins), mitochondrial membrane potential (i.e., mitochondrial permeability transition pore opening and uncoupling effects), mitochondrial electron transport chain and ATP synthesis (i.e., modulating complexes I to V activity), intra-mitochondrial oxidative status (i.e., inhibiting/inducing ROS formation/removal enzymes), and ultimately mitochondrially-triggered cell death (i.e., modulating intrinsic-apoptosis). The present review describes recent evidence on the ability of some polyphenols to modulate each of the formerly mentioned pathways, and discusses on how, by acting on such mitochondrial processes, polyphenols may afford protection against those mitochondrial damaging events that appear to be key in the cellular toxicity induced by various xenobiotics as well as that seen during the development of several ROS-related diseases.

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.

The role of polyphenols in the modulation of sirtuins and other pathways involved in Alzheimer's disease

Alzheimer's disease (AD) is characterised by extracellular amyloid deposits, neurofibrillary tangles, synaptic loss, inflammation and extensive oxidative stress. Polyphenols, which include resveratrol, epigallocatechin gallate and curcumin, have gained considerable interest for their ability to reduce these hallmarks of disease and their potential to slow down cognitive decline. Although their antioxidant and free radical scavenging properties are well established, more recently polyphenols have been shown to produce other important effects including anti-amyloidogenic activity, cell signalling modulation, effects on telomere length and modulation of the sirtuin proteins. Brain accessible polyphenols with multiple effects on pathways involved in neurodegeneration and ageing may therefore prove efficacious in the treatment of age-related diseases such as AD, although the evidence for this so far is limited. This review aims to explore the known effects of polyphenols from various natural and synthetic sources on brain ageing and neurodegeneration, and to examine their multiple mechanisms of action, with an emphasis on the role that the sirtuin pathway may play and the implications this may have for the treatment of AD.

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.

Indomethacin-induced translocation of bacteria across enteric epithelia is reactive oxygen species-dependent and reduced by vitamin C

The enteric epithelium must absorb nutrients and water and act as a barrier to the entry of luminal material into the body; this barrier function is a key component of innate immunity. Nonsteroidal anti-inflammatory drug (NSAID)-induced enteropathy occurs via inhibition of prostaglandin synthesis and perturbed epithelial mitochondrial activity. Here, the direct effect of NSAIDs [indomethacin, piroxicam (cyclooxygenase 1 and 2 inhibitors), and SC-560 (a cyclooxygenase 1 inhibitor)] on the barrier function of human T84 epithelial cell line monolayers was assessed by transepithelial electrical resistance (TER) and internalization and translocation of a commensal Escherichia coli. Exposure to E. coli in the presence and absence of drugs for 16 h reduced TER; however, monolayers cotreated with E. coli and indomethacin, but not piroxicam or SC-560, displayed significant increases in internalization and translocation of the bacteria. This was accompanied by increased reactive oxygen species (ROS) production, which was also increased in epithelia treated with E. coli only. Colocalization revealed upregulation of superoxide synthesis by mitochondria in epithelia treated with E. coli + indomethacin. Addition of antioxidants (vitamin C or a green tea polyphenol, epigallocathechin gallate) quenched the ROS and prevented the increase in E. coli internalization and translocation evoked by indomethacin, but not the drop in TER. Evidence of increased apoptosis was not observed in this model. The data implicate epithelial-derived ROS in indomethacin-induced barrier dysfunction and show that a portion of the bacteria likely cross the epithelium via a transcellular pathway. We speculate that addition of antioxidants as dietary supplements to NSAID treatment regimens would reduce the magnitude of decreased barrier function, specifically the transepithelial passage of bacteria.

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.