Effects of kaempferol and myricetin on inducible nitric oxide synthase expression and nitric oxide production in rats

Myricetin inhibits pseudorabies virus infection through direct inactivation and activating host antiviral defense

Myricetin, a polyhydroxyflavone compound, is one of the main ingredients of various human foods and therefore also known as dietary flavonoids. Due to the continuous emergence of resistant strains of herpesviruses, novel control measures are required. In the present study, myricetin exhibited potent antiviral activity against pseudorabies virus (PRV), a model organism of herpesvirus. The suppression rate could reach up to 96.4% at a concentration of 500 μM in cells, and the 50% inhibitory concentration (IC₅₀) was 42.69 μM. Moreover, the inhibitory activity was not attenuated by the increased amount of infective dose, and a significant reduction of intracellular PRV virions was observed by indirect immunofluorescence. A mode of action study indicated that myricetin could directly inactivate the virus in vitro, leading to inhibition of viral adsorption, penetration and replication in cells. In addition to direct killing effect, myricetin could also activate host antiviral defense through regulation of apoptosis-related gene expressions (Bcl-2, Bcl-xl, Bax), NF-κB and MAPK signaling pathways and cytokine gene expressions (IL-1α, IL-1β, IL-6, c-Jun, STAT1, c-Fos, and c-Myc). In PRV-infected mouse model, myricetin could enhance the survival rate by 40% at 5 days post infection, and viral loads in kidney, liver, lung, spleen, and brain were significantly decreased. The pathological changes caused by PRV infection were improved by myricetin treatment. The gene expressions of inflammatory factors (MCP-1, G-CSF, IL-1α, IL-1β, and IL-6) and apoptotic factors (Bcl-xl, Bcl-2, and Bax) were regulated by myricetin in PRV-infected mice. The present findings suggest that myricetin can effectively inhibit PRV infection and become a candidate for development of new anti-herpesvirus drugs.

Mangiferin exert protective effects on joints of adjuvant-induced arthritis rats by regulating the MAPKs/NF-κB pathway of fibroblast-like synoviocytes

BACKGROUND

Mangiferin (MF) is a bioactive ingredient predominantly isolated from the mango tree, that has been reported to have antioxidant, anti-inflammatory, and immunomodulatory effects. This study was aimed to investigate the protective effect of MF on the joints of arthritic rats and explore the underlying mechanisms of this function.

METHODS

Adjuvant-induced arthritis (AA) rat model was established and clinical severity of AA was evaluated by arthritis index, paw edema, plasma, and synovium homogenate parameters. The severity of joint destruction was assessed by radiological and histopathological. Immunohistochemical analysis was employed to detect the protein expression of MMP-3, MMP-13 in synovium and cartilage tissues. The vitro effects of MF on proliferation, migration, apoptosis, and production of inflammatory mediators in RA- FLSs were determined by the CCK8 assay, transwell assay, flow cytometry, and real-time PCR, respectively.

RESULTS

The results demonstrated that MF treatment significantly alleviated arthritis index, paw swelling and decreased the secretion of inflammatory cytokines in plasma and synovium. Meanwhile, MF inhibited synovial inflammation, pannus formation, and bone erosion in AA rats. It also ameliorated the oxidative stress state of arthritic rats via modulating the level of MDA, SOD, CAT, GSH, NO. In addition, MF effectively attenuated the destructive behavior of RA-FLSs by inhibiting proliferation, migration, and secretion of inflammatory mediators, and promoting apoptosis. The further mechanistic analysis demonstrated that MF might exert an antiarthritic effect via inhibiting the pathway of MAPKs (ERK2 and p38) and NF-κ B.

CONCLUSION

Taken together, our results demonstrated that MF would be a promising anti-arthritic agent candidate for further research.

Going "Green" in the Prevention and Management of Atherothrombotic Diseases: The Role of Dietary Polyphenols

During the 20th century processed and ready-to-eat foods became routinely consumed resulting in a sharp rise of fat, salt, and sugar intake in people's diets. Currently, the global incidence of obesity, raised blood lipids, hypertension, and diabetes in an increasingly aged population contributes to the rise of atherothrombotic events and cardiovascular diseases (CVD) mortality. Drug-based therapies are valuable strategies to tackle and help manage the socio-economic impact of atherothrombotic disorders though not without adverse side effects. The inclusion of fresh fruits and vegetables rich in flavonoids to human diets, as recommended by WHO offers a valuable nutritional strategy, alternative to drug-based therapies, to be explored in the prevention and management of atherothrombotic diseases at early stages. Though polyphenols are mostly associated to color and taste in foods, food flavonoids are emerging as modulators of cholesterol biosynthesis, appetite and food intake, blood pressure, platelet function, clot formation, and anti-inflammatory signaling, supporting the health-promoting effects of polyphenol-rich diets in mitigating the impact of risk factors in atherothrombotic disorders and CVD events. Here we overview the current knowledge on the effect of polyphenols particularly of flavonoid intake on the atherothrombotic risk factors and discuss the caveats and challenges involved with current experimental cell-based designs.

Myricetin protects natural killer cells from arsenite induced DNA damage by attenuating oxidative stress and retaining poly(ADP-Ribose) polymerase 1 activity

Environmental exposure to arsenite (As⁺³) is known to induce immunotoxicity. Natural killer (NK) cells are innate lymphoid cells act as professional killers of tumor cells. Our previous report indicated that 500 ppb As⁺³ drinking water exposure induced significant DNA damage in the NK cells of C57BL/6 mice. Myricetin is a plant-derived flavonoid known as a strong antioxidant. In this study, daily administration of myricetin at 20 mg/kg was found to alleviate the cell population decrease and DNA damage in the NK cells of BALB/c mice exposed to 500 and 1000 ppb As⁺³ via drinking water. Oxidative stress and poly(ADP-ribose) polymerase 1 (PARP-1) inhibition were induced by As⁺³ at 1 and 2 μM in isolated mouse NK cells in vitro, which were attenuated by 20 μM myricetin. The mitigatory effect of myricetin on the PARP-1 inhibition in NK cells treated with As⁺³ was also found to be the result of its prevention of the zinc loss induced by As⁺³ on PARP-1. Collectively, these results demonstrated, for the first time, that myricetin could protect NK cells from As⁺³ induced DNA through attenuating oxidative stress and retaining PARP-1 activity, indicating that myricetin may be utilized for the prevention of the immunotoxicity induced by As⁺³ in NK cells.

Probing the chemoprevention potential of the antidepressant fluoxetine combined with epigallocatechin gallate or kaempferol in rats with induced early stage colon carcinogenesis

The enhanced chemopreventive action against 1,2 Dimethylhydrazine (DMH)-induced preneoplastic lesion in rats could be achieved via simultaneous administration of the antidepressant fluoxetine (FLX) with two natural polyphenolic compounds viz., kaempferol (KMP) and/or epigallocatechin-gallate (EGCG). The obtained results revealed that single FLX pre-treatment possess a significant apoptotic effect by increasing the activity of serum and colon tissue caspase 3. It also attenuated the DMH driven increase in, colon tissue MDA, NO, PCNA and COX-2 expression as well as serum and colon tissue β-catenin, with a decrease in the multiplicity of ACF and number of MPLs. The combination of FLX with either KMP or EGCG improved the antioxidant, anti-inflammatory and antiproliferating activities but with higher apoptotic activity in case of KMP. Eventually, histopathological assessment of colon tissues exposed that while sole pre-treatment can improve DMH-induced hyperplasia with only moderate inflammatory infiltration, tissues from the combined pre-treatment regimens groups exhibited almost a normal colonic architecture with slight submucosal edema. The study proved that single FLX administration prior to DMH exerts a chemopreventive effect and that the investigated combined pre-treatment regimens demonstrated more potent chemopreventive and antiproliferative actions.

Myricetin Abrogates Cisplatin-Induced Oxidative Stress, Inflammatory Response, and Goblet Cell Disintegration in Colon of Wistar Rats

Cisplatin [cis-diamminedichloroplatinum II] is an extensively prescribed drug in cancer chemotherapy; it is also useful for the treatment of diverse types of malignancies. Conversely, cisplatin is associated with a range of side effects such as nephrotoxicity, hepatotoxicity, gastrointestinal toxicity, and so on. Myricetin (3,5,7-trihydroxy-2-(3,4,5-trihydroxyphenyl)-4chromenone) is a very common natural flavonoid found in fruits, tea, and plants. It has been found to have high-value pharmacological properties and strong health benefits. To examine the role of myricetin in colon toxicity induced by cisplatin, we conducted a concurrent prophylactic study in experimental animals that were treated orally with myricetin for 14 days at two doses—25 and 50 mg/kg of body weight. On the 14th day, a single intraperitoneal injection of cisplatin (7.5 mg/kg body weight) was administered in all groups except control. The effects of myricetin in cisplatin-induced toxicity in the colon were assessed in terms of antioxidant status, phase-II detoxification enzymes, the level of inflammatory markers, and goblet cell disintegration. Myricetin was found to restore the level of all the antioxidant enzymes analyzed in the study. In addition, the compound ameliorated cisplatin-induced lipid peroxidation, increase in xanthine oxidase activity, and phase-II detoxifying enzyme activity. Myricetin also attenuated deteriorative effects induced by cisplatin by regulating the level of molecular markers of inflammation (NF-κB, Nrf-2, IL-6, and TNF-α), restoring Nrf-2 levels, and controlling goblet cell disintegration. The current study reinforces the conclusion that myricetin exerts protection in colon toxicity via up-regulation of inflammatory markers, improving anti-oxidant status, and protecting tissue damage.

Biotransformation of Myricetin: A Novel Metabolic Pathway to Produce Aminated Products in Mice

SCOPE

In this study, whether amination is a novel metabolic pathway of myricetin, one of the major dietary flavonoids found in fruits, vegetables, and tea, and whether the aminated metabolite of myricetin remains bioactive, are investigated.

METHODS AND RESULTS

It is found that myricetin with a vic-trihydroxyl group on the B ring can chemically react with ammonia via the formation of myricetin quinone to generate the aminated product in vitro. As expected, the amination occurs on position 4´ of the B-ring of myricetin. The structure of this new product is confirmed by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography-mass spectrometry and is named 4´-NH₂ -myricetin. Using the synthetic 4´-NH₂ -myricetin as a standard, the presence of this compound is searched for in fecal samples collected from myricetin-treated mice using LC-MS, and 4´-NH₂ -myricetin is confirmed as the metabolite of myricetin in mice for the first time. Furthermore, two metabolites of myricetin, the mono-methylated myricetin and the microbial-derived metabolite 3,4,5-trihydroxyphenylacetic acid, are confirmed to be aminated in vivo based on LC-MS data analysis. After administration of different doses of myricetin through oral gavage, the amination of myricetin shows a dose-dependent response in feces. A similar trend is observed for the amination of the mono-methylated myricetin, but not for the microbial-derived metabolite 3,4,5-trihydroxyphenylacetic acid. In plasma, the trend of a dose-dependent response for the amination of myricetin and its mono methylated metabolite is observed, and the plasma concentration of the aminated 3,4,5-trihydroxyphenylacetic acid at 200 mg kg^-1 dose is significantly higher than those at the 100 and 400 mg kg^-1 doses. Interestingly, it is observed that the aminated myricetin retains the anti-inflammatory activity of myricetin.

CONCLUSION

This result demonstrates that amination is a novel biotransformation mechanism of myricetin to produce aminated metabolites.

Chemopreventive effect of sulindac in combination with epigallocatechin gallate or kaempferol against 1,2-dimethyl hydrazine-induced preneoplastic lesions in rats: A Comparative Study

A systematic investigation of the chemopreventive effect of sulindac (SL) in combination with either epigallocatechin gallate (EGCG) or kaempferol similar (KMP) has been carried out 1,2-dimethyl hydrazine-treated rats (DMH). Those SL combinations with KMP and EGCG have enhanced the SL activity producing greater antioxidant, anti-inflammatory, antiproliferating, and apoptotic activities in both combinations than SL alone. The chemopreventive effects of SL with both EGCG and KMP were demonstrated by a decrease in thiobaribituric acid reactive substances level, tissue nitric oxide (NO), serum, and tissue β-catenin as well as a reduction in the multiplicity of aberrant crypt foci (ACF) with alleviation in the dysplastic changes that resulted from DMH administration. Down-regulation of proliferating cell nuclear antigen (PCNA) and cyclooxygenase-2 (COX-2) were also confirmed by immunohistochemical staining. The current study paves the way for the use of sulindac combination with kaempferol or EGCG as potential chemopreventive agents against colon cancer with more effect in combination with EGCG.

Myricetin: A Dietary Molecule with Diverse Biological Activities

Myricetin is a common plant-derived flavonoid and is well recognised for its nutraceuticals value. It is one of the key ingredients of various foods and beverages. The compound exhibits a wide range of activities that include strong anti-oxidant, anticancer, antidiabetic and anti-inflammatory activities. It displays several activities that are related to the central nervous system and numerous studies have suggested that the compound may be beneficial to protect against diseases such as Parkinson's and Alzheimer's. The use of myricetin as a preserving agent to extend the shelf life of foods containing oils and fats is attributed to the compound's ability to protect lipids against oxidation. A detailed search of existing literature revealed that there is currently no comprehensive review available on this important molecule. Hence, the present work includes the history, synthesis, pharmaceutical applications and toxicity studies of myricetin. This report also highlights structure-activity relationships and mechanisms of action for various biological activities.

Anti-cancer Effect and Underlying Mechanism(s) of Kaempferol, a Phytoestrogen, on the Regulation of Apoptosis in Diverse Cancer Cell Models

Phytoestrogens exist in edible compounds commonly found in fruits or plants. For long times, phytoestrogens have been used for therapeutic treatments against human diseases, and they can be promising ingredients for future pharmacological industries. Kaempferol is a yellow compound found in grapes, broccoli and yellow fruits, which is one of flavonoid as phytoestrogens. Kaempferol has been suggested to have an antioxidant and anti-inflammatory effect. In past decades, many studies have been performed to examine anti-toxicological role(s) of kaempferol against human cancers. It has been shown that kaempferol may be involved in the regulations of cell cycle, metastasis, angiogenesis and apoptosis in various cancer cell types. Among them, there have been a few of the studies to examine a relationship between kaempferol and apoptosis. Thus, in this review, we highlight the effect(s) of kaempferol on the regulation of apoptosis in diverse cancer cell models. This could be a forecast in regard to use of kaempferol as promising treatment against human diseases.

Myricetin protects against cytokine-induced cell death in RIN-m5f β cells

Cytokine-induced cell death is recognized as a major cause of progressive β-cell loss. Tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interferon γ (IFN-γ) in combination trigger a series of events that lead to β-cell death. In the past few decades, the use of myricetin as an anti-inflammatory and cytoprotective agent has gained much attention. The present study focused on the protective roles of myricetin against cytokine-induced cell death in insulin-secreting RIN-m5f β cells. The results showed that myricetin (especially at concentrations of 10 μM and 20 μM) increased cell viability and decreased cell apoptosis induced by the cytokine mixture of TNF-α (10 ng/mL), IL-1β (5 ng/mL), and IFN-γ (1000 IU/mL) for 3 days. Moreover, the cytokines increased the total and p65 subunit levels of nuclear factor κB, decreased inhibitor κB α levels, stimulated the accumulation of nitric oxide, increased cytochrome c release from mitochondria, and induced reactive oxygen species generation; myricetin (especially at the concentration of 20 μM) abolished all of these parameters. These results suggest that myricetin might have therapeutic value for preventing β-cell death.

Modulation of the oxidative stress and inflammatory cytokine response by thymoquinone in the collagen induced arthritis in Wistar rats

Thymoquinone (TQ) is the major active compound derived from Nigella sativa. Our aim of this work was to evaluate the antioxidant and antiarthritic activity of TQ in Wistar rat by collagen induced arthritis (CIA). TQ was administered at a dose of 5mgkg(-1) body weight once daily for 21days. The effects of treatment in the rats were assessed by biochemical (articular elastase, MPO, LPO, GSH, catalase, SOD and NO), inflammatory mediators (IL-1β, IL-6, TNF-α, IL-10, IFN-γ and PGE(2)) and histological studies in joints. TQ was effective in bringing significant changes on all the parameters (articular elastase, MPO, LPO, GSH, catalase, SOD and NO) studied. Oral administration of TQ resulted in significantly reduced the levels of pro-inflammatory mediators (IL-1β, IL-6, TNF-α, IFN-γ and PGE(2)) and increased level of IL-10. The protective effects of TQ against RA were also evident from the decrease in arthritis scoring and bone histology. In conclusion, the fact that TQ abolished a number of factors known to be involved in RA pathogenesis indicates that the administration of thymoquinone may have potential value in the treatment of inflammatory disease.

Herbal medicinal products target defined biochemical and molecular mediators of inflammatory autoimmune arthritis

Rheumatoid arthritis (RA) is a chronic debilitating disease characterized by synovial inflammation, damage to cartilage and bone, and deformities of the joints. Several drugs possessing anti-inflammatory and immunomodulatory properties are being used in the conventional (allopathic) system of medicine to treat RA. However, the long-term use of these drugs is associated with harmful side effects. Therefore, newer drugs with low or no toxicity for the treatment of RA are actively being sought. Interestingly, several herbs demonstrate anti-inflammatory and anti-arthritic activity. In this review, we describe the role of the major biochemical and molecular mediators in the pathogenesis of RA, and highlight the sites of action of herbal medicinal products that have anti-arthritic activity. With the rapidly increasing use of CAM products by patients with RA and other inflammation-related disorders, our review presents timely information validating the scientific rationale for the use of natural therapeutic products.

Effects of Lycopene, Indole-3-Carbinol, and Luteolin on Nitric Oxide Production and iNOS Expression are Organ-Specific in Rats

Natural compounds are known to modify NO content in tissues; however, the biological activity of polyphenol-rich food often does not correspond to the effects of individual polyphenols on NO synthase activity. The aim of this study was to see how natural compounds luteolin, indole-3-carbinol, and lycopene modify NO production in rat tissues and change the expression of the iNOS gene and protein. Indole-3-carbinol produced multiple effects on the NO level; it significantly decreased NO concentration in blood, lungs, and skeletal muscles and increased it in the liver. Indole-3-carbinol enhanced lipopolyssaccharide (LPS)-induced NO production in all rat organs. It decreased iNOS gene expression in the brain cortex of animals that did not receive LPS and up-regulated it in the LPS-treated animals. Lycopene increased the iNOS gene transcription rate in the brain cortex of LPS-treated animals. Luteolin did not modify NO production in any organ of LPS-untreated rats, nor did it affect gene expression in the liver. In the brain it slightly decreased iNOS gene expression. Luteolin decreased NO production in the blood of LPS-treated animals and the number of iNOS-positive cells in these animals. Our results suggest that changes in tissue NO levels caused by natural compounds cannot be predicted from their effect on NOS expression or activity obtained in model systems. This stresses the importance of direct measurements of NO and NOS expression in animal tissues.