Effect of naturally occurring phenolic acids on the expression of glutathione S-transferase isozymes in the rat

Oil-mediated oxidative-stress responses in a keystone zooplanktonic species, Calanus finmarchicus

The copepod Calanus finmarchicus is an ecologically important species in the North Atlantic, Norwegian and Barents seas. Accidental or continuous petroleum pollution from oil and gas production in these seas may pose a significant threat to this low trophic level keystone species. Responses related to oxidative stress, protein damage and lipid peroxidation were investigated in C. finmarchicus exposed to a water-accommodated fraction (WAF) of a naphthenic North Atlantic crude oil. The exposure concentration corresponded to 50% of the 96 h LC₅₀, and samples were obtained at 0, 24, 48, 72 and 96 h after exposure initiation. Gene expressions (superoxide dismutase, catalase, glutathione S-transferase, glutathione synthetase, heat shock protein 70 and 90, ubiquitin and cytochrome P-450 330A1), enzyme activities (superoxide dismutase, catalase, glutathione S-transferase) and concentrations of total glutathione and malondialdehyde were analyzed. Gene expression analyses showed no differences between controls and the exposed animals, however significantly higher glutathione S-transferase activity and malondialdehyde concentrations were found in the exposed group, suggests lipid peroxidation as main toxic effect.

Tannic acid is a gastroprotective that regulates inflammation and oxidative stress

This study investigated the gastroprotective effect of TA against gastric ulcer in mice, and its possible mechanisms of action. The effects were investigated in a model of ethanol and ethanol/HCl induced ulcers, and physical barrier test. Quantification of oxidative stress mediators and inflammatory cytokines in gastric tissue was performed. The involvement of sulfhydryl compounds (-SH), nitric oxide (NO), prostaglandin E₂ (PGE₂), potassium channels (K ⁺_ATP) and opioid receptors in gastroprotection were investigated. Oral treatment with TA at a dose of 50 mg/kg resulted in 97.96% and 94.20% (reduction in gastric injury) of gastroprotection, against injuries caused by ethanol and ethanol/HCL, respectively, in addition to having a systematic effect. TA promotes increased levels of superoxide dismutase (SOD), catalase (CAT) and reduced glutathione (GSH), as well as reduced levels of malondialdehyde (MDA) reaction to thiobarbituric acid and myeloperoxidase (MPO). In addition, there was reduction in levels of tumor necrosis factor alpha (TNF-α) and interleukins (IL) IL-1β and IL-6 and increased IL-10. The gastroprotective activity of TA involved K ⁺_ATP channels and the production of -SH, NO and PGE_2, demonstrating multiple mechanisms of action. The results of the present study suggest that TA may be a gastroprotective agent counteracting oxidative and inflammatory stress.

Inhibitory Effect of Thai Purple Rice Husk Extract on Chemically Induced Carcinogenesis in Rats

This study investigated the cancer chemopreventive effects of an acidic methanol extract of purple rice husk on chemically induced carcinogenesis in rats. This purple rice husk extract (PRHE) had high polyphenol contents. Vanillic acid was a major phenolic compound in PRHE. Three major anthocyanins found in PRHE were malvidin-3-glucoside, peonidin-3-glucoside and cyanidin-3-glucoside. PRHE was not toxic and clastogenic in rats. The LD50 of PRHE was greater than 2000 mg kg-1 body weight (BW). The oral administration of 300 or 1000 mg kg-1 BW of PRHE for 28 days significantly decreased the number of micronucleated hepatocytes in diethylnitrosamine-initiated rats. The inhibitory mechanisms were associated with the reduction of cytochrome P450 2E1 expression and induction of some detoxifying enzymes in the liver. In addition, treatment with 500 mg kg-1 BW of PRHE for eight weeks did not induce preneoplastic lesions in the liver and colon. It significantly inhibited hepatic glutathione-S-transferase positive foci formation induced by diethylnitrosamine and 1,2-dimethylhydrazine by suppression of hepatocyte proliferation and induction of apoptosis. In conclusion, PRHE did not present toxicity, clastogenicity or carcinogenicity in rats. It exhibited cancer chemopreventive properties against chemically induced early stages rat hepatocarcinogenesis. Anthocyanins and vanillic acid might be candidate anticarcinogenic compounds in purple rice husk.

Anticlastogenicity and Anticarcinogenicity of Purple Rice Extract in Rats

Oryza sativa L. var. indica cv. Kum Doi Saket is a pigmented rice variety grown in northern Thailand. Our previous study found that the methanol extract of purple rice seed had the highest level of antimutagenicity in a Salmonella mutation assay. The present study was designed to evaluate its in vivo anticlastogenic and anticarcinogenic potentials. The purple rice extract had no acute toxicity on rats. The oral administration of 1,000 mg/kg body weight (bw) of the extract for 28 days did not increase the number of micronucleated hepatocytes. Interestingly, it significantly reduced the amount of micronucleus formation in the liver of diethylnitrosamine (DEN)-treated rats. The inhibitory mechanism involved the induction of hepatic glutathione S-transferase (GST) activity. In addition, oral administration of 500 mg/kg bw extract for 10 weeks significantly decreased the number of hepatic GST placental form positive foci, but did not modulate the number of colonic aberrant crypt foci in DEN- and dimethylhydrazine-initiated rats. In conclusion, the methanol extract of purple rice seed showed no toxicity, clastogenicity, or carcinogenicity in laboratory rats. It did display chemopreventive activity against the early stages of rat hepatocarcinogenesis.

The activation of the Nrf2/ARE pathway in HepG2 hepatoma cells by phytochemicals and subsequent modulation of phase II and antioxidant enzyme expression

Previous studies have shown that naturally occurring phytochemicals, indole-3-carbinol, phenethyl isothiocyanate, protocatechuic acid, and tannic acid increased the activity and protein level of hepatic phase II enzymes in animal models. In order to further explore the mechanism of this activity, we investigated the effect of these compounds on the activation of nuclear factor erythroid-2-related factor 2 (Nrf2)-regulated transcription in human hepatocellular carcinoma HepG2 cells. Treatment with all the tested compounds resulted in the translocation from the cytosol and nuclear accumulation of active phosphorylated Nrf2. Furthermore, phenethyl isothiocyanate and indole-3-carbinol increased the transcript and protein levels of GSTA, GSTP, GSTM, GSTT, and NQO1. On the other hand, protocatechuic and tannic acids enhanced only the expression of GSTA, GSTM, and GSTT. The expression of genes encoding antioxidant enzymes CAT, SOD, GR, and GPx was increased after the treatment with all the tested phytochemicals. These results indicate that isothiocyanates/indoles and protocatechuic and tannic acids induce phase II and antioxidant gene expression in HepG2 cells through the Nrf2-Keap1-ARE signaling pathway. Moreover, the results of this study confirmed that the degradation products of glucosinolates are more effective inducers of phase II and antioxidant enzymes than protocatechuic and tannic acids.

Impact of tannic acid on blood pressure, oxidative stress and urinary parameters in L-NNA-induced hypertensive rats

Hypertension is a major health problem with increasing prevalence around the world. Tannic acid is water-soluble polyphenol that is present in tea, green tea, coffee, red wine, nuts, fruits and many plant foods. It has been reported to serve as an antioxidant or a pro-oxidant depending on the type of cells and its concentration. The purpose of our study was to evaluate the effect of tannic acid on systolic blood pressure, oxidative stress and some urinary parameters in the rat model of essential hypertension. Blood pressures of all rats were measured using the tail-cuff method. The nitric oxide synthase inhibitor N (omega)-nitro-L-arginine was administered orally at a dose of 0.5 g/l/day for 15 days to rats in order to create an animal model of hypertension. Tannic acid was intraperitoneally injected at a dose of 50 mg/kg for 15 days. Superoxide dismutase, catalase activity and the concentration of malondialdehyde (MDA) were determined in blood plasma and homogenates of heart, liver and kidney. In order to evaluate renal functions, urine pH, urine volume, urine creatine, uric acid, and urea nitrogen values were measured. Compared with the hypertension group, a decrease in MDA concentrations of heart tissue (p < 0.01), urea nitrogen values (p < 0.01) and urine volumes (p < 0.001) were established in hypertension + tannic acid group. There was also a decrease in blood pressure values (20th and 30th days) of this group, but there was no a statistical difference according to hypertension group. The findings of our research show the effect of tannic acid in lowering blood pressure in hypertensive rats.

Evaluation of the effect of beetroot juice on DMBA-induced damage in liver and mammary gland of female Sprague-Dawley rats

Red beetroot contains a specific class of antioxidants collectively named betalains, which have been shown to have anticarcinogenic and anti-inflamatory potential. We investigated the effect of beetroot juice on the hepatic and mammary gland carcinogen metabolizing enzymes, DNA damage and liver injury, altered by 7,12-dimethylbenz[a]anthracene (DMBA). In the liver, pretreatment with beetroot juice significantly decreased levels and activities of the majority of tested biochemical parameters, elevated by DMBA. Feeding with beetroot juice decreased the activities of CYP1A1 and 1A2 and increased phase II enzymes. The activities of all enzymes tested were enhanced in the animals treated with DMBA alone and in combination with beetroot juice. The most significant changes in the level of the enzymes tested were observed for

NAD(P)H

quinone oxidoreductase-1. In mammary gland, beetroot juice induced the level of glutathione S-transferase pi, enzyme involved in active metabolites of DMBA detoxification. The final effects of beetroot juice are tissue specific and depend on the class of carcinogen.

Processing and storage effect on berry polyphenols: challenges and implications for bioactive properties

Anthocyanins and tannins in blueberries, blackberries and black raspberries are susceptible to degradation during processing, with juices showing the greatest losses due to physical removal of skins and seeds. Anthocyanins and procyanidins are also degraded in processed products stored at ambient temperature with losses accompanied by increased polymeric pigments (PPs). Using chokeberry as a model, formation of PPs occurred in both pasteurized and aged juices and pasteurized juice contained a greater proportion of low molecular weight PPs than aged juice, while aged juice contained a greater proportion of higher molecular PPs. Formation of PP accounts for some of the losses of anthocyanins and procyanidins during processing and storage, but the complete fate of anthocyanins remains unclear. In this review we highlight the steps in processing where significant losses of polyphenols occur, and discuss potential mechanisms responsible for losses, methods to mitigate losses, and implications on bioactive properties.

Beetroot juice protects against N-nitrosodiethylamine-induced liver injury in rats

Red beetroot, a common ingredient of diet, is a rich source of a specific class of antioxidants, betalains. Our previous studies have shown the protective role of beetroot juice against carcinogen induced oxidative stress in rats. The aim of this study was to examine the effect of long term feeding (28 days) with beetroot juice on phase I and phase II enzymes, DNA damage and liver injury induced by hepatocarcinogenic N-nitrosodiethylamine (NDEA). Long term feeding with beetroot juice decreased the activities of enzymatic markers of cytochrome P450, CYP1A1/1A2 and CYP2E1. NDEA treatment also reduced the activities of these enzymes, but increased the activity of CYP2B. Moreover, combined treatment with beetroot juice and NDEA enhanced significantly CYP2B only. Modulation of P450 enzyme activities was accompanied by changes in the relevant proteins levels. Increased level and activity of NQO1 was the most significant change among phase II enzymes. Beetroot juice reduced the DNA damage increased as the result of NDEA treatment, as well as the biomarkers of liver injury. Collectively, these results confirm the protective effect of beetroot juice against oxidative damage shown in our previous studies and indicate that metabolic alterations induced by beetroot feeding may protect against liver damage.

In vitro and in vivo toxicological evaluation of extract and fractions from Baccharis trimera with anti-inflammatory activity

ETHNOPHARMACOLOGICAL RELEVANCE

Baccharis trimera (Less) DC. (Asteraceae), popularly known in Brazil as "carqueja", have been used in folk medicine to treat gastrointestinal, hepatic and renal diseases, and inflammatory processes as rheumatism.

AIM OF THE STUDY

To evaluate the in vitro and in vivo toxicological effects of anti-inflammatory Baccharis trimera aqueous extract and fractions.

MATERIALS AND METHODS

Aqueous extract of Baccharis trimera (AEBt) was produced by infusion in boiling water. After lyophylization AEBt was extracted with 80% ethanol, originating the ethanolic supernatant fraction (EFBt) and the aqueous sediment fraction (AFBt). Anti-inflammatory properties of AEBt, EFBt or AFBt (3, 30 or 300 μg/kg b.w.) were evaluated by the carrageenan-induced mouse paw edema using indomethacin (10mg/kg) as positive control. The growth of rat hepatoma cells (HTC) and human embryo kidney epithelial cells (HEK) was determined by protein staining assay. Cytotoxicity was assayed by the tetrazolium salt (MTT) reduction. Cyclosporin was used as reference cytotoxic drug for spleen cells and doxorubicin for HTC and HEK cells. For in vivo toxicological evaluation SW male mice were daily and oral (gavage) treated with extract/fractions at 4.2mg/kg or 42 mg/kg during 15 days. After treatment liver or kidney cells were submitted to comet assay to determine the DNA damage index, and the glutathione S-transferase activity was assayed towards ETHA (class Pi) and CDNB (several classes). Mutagenicity was evaluated by the Ames test using Salmonella typhimurium strains TA97, TA98, TA100, and TA102.

RESULTS

The anti-inflammatory effects of EFBt were higher than those of AEBt or AFBt. Mice treatment (3-300 μg/kg) with AFBt reduced the paw edema (3h) at lower levels (29.2-37.3%; P<0.01), than those observed for AEBt (44.7-54.2%; P<0.001), EFBt (49.3-58.2%; P<0.001) or indomethacin (64.6%, P<0.001, 10mg/kg). The growth of kidney cells (HEK) was inhibited by AEBt (IC(50) 182.6 μg/ml), EFBt (IC(50) 78.1 μg/ml) and AFBt (IC(50) 86.2 μg/ml), with lower effects on HTC hepatic cell (IC(50) 308.8 μg/ml, 396.5 μg/ml and 167.9 μg/ml, respectively). As evaluated by MTT test, AFBt exhibited cytotoxicity for HEK cells (IC(50) 372.5 μg/ml), but none for HTC ones; by the way, AFBt stimulated spleen cells (EC(50) 2.2 μg/ml) while cyclosporine, a cytotoxic reference drug inhibited them with IC(50) of 0.42 μg/ml; the IC(50) for doxorubicin for HEK and HTC cells was 0.28 μg/ml and 14.4 μg/ml, respectively, at 96h. No mutagenic potential was observed. Mice treatment with AEBt or AFBt at 42 mg/kg for 15 days altered the kidney relative weight, but not at 4.2mg/kg. Baccharis trimera did not change liver, spleen or popliteal lymph node relative weight. DNA damage index of kidney cells was observed on mice treated with AEBt/AFBt, but not on animals treated with EFBt, while DNA lesions were detected on liver cells only after AFBt treatment. The general activities of hepatic GST and Pi GST were reduced by EFBt and AFBt treatment, respectively.

CONCLUSIONS

Baccharis trimera did not show mutagenicity, inhibited the GST activity, a hepatic detoxification enzyme, and induced in vivo (genotoxicity) and in vitro toxicological effects to kidney cells.

Route of administration determines the anxiolytic activity of the flavonols kaempferol, quercetin and myricetin--are they prodrugs?

Several in vivo and in vitro studies have confirmed that flavonols are metabolized by the intestinal microflora to their corresponding hydroxyphenylacetic acids. In this article, a comparison of the anxiolytic activity of the flavonols kaempferol, quercetin and myricetin in the elevated plus maze after oral (po) and intraperitoneal (ip) administration to mice in a dose range of 0.1 to 2.0 mg/kg is presented. In addition, their corresponding metabolites p-hydroxyphenylacetic acid (p-HPAA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were tested after intraperitoneal administration. Anxiolytic activity was detected for kaempferol and quercetin only after oral administration. No anxiolytic effects were observed when kaempferol and quercetin were given via the intraperitoneal administration route. The corresponding hydroxyphenylacetic metabolites p-HPAA and DOPAC showed anxiolytic effects after intraperitoneal application. In order to further test the hypothesis that flavonoids are possible prodrugs which require activation by intestinal bacteria, gut sterilization was performed using pretreatment with the antibiotic enrofloxacin (7.5 mg/day, po, for 4 days). After antibiotic treatment, the anxiolytic effect of kaempferol and quercetin disappeared, whereas it was still present for the positive control diazepam. Our results support the hypothesis that flavonoids act as prodrugs which are transformed into their active hydroxyphenylacetic acid metabolites by intestinal microflora.

Protective effect of acetyl-l-carnitine and α-lipoic acid against the acute toxicity of diepoxybutane to human lymphocytes

The biotransformation and oxidative stress may contribute to 1,2:3,4-diepoxybutane (DEB)-induced toxicity to human lymphocytes of Fanconi Anemia (FA) patients. Thus, the identification of putative inhibitors of bioactivation, as well as the determination of the protective role of oxidant defenses, on DEB-induced toxicity, can help to understand what is failing in FA cells. In the present work we studied the contribution of several biochemical pathways for DEB-induced acute toxicity in human lymphocyte suspensions, by using inhibitors of epoxide hydrolases, inhibitors of protective enzymes as glutathione S-transferase and catalase, the depletion of glutathione (GSH), and the inhibition of protein synthesis; and a variety of putative protective compounds, including antioxidants, and mitochondrial protective agents. The present study reports two novel findings: (i) it was clearly evidenced, for the first time, that the acute exposure of freshly isolated human lymphocytes to DEB results in severe GSH depletion and loss of ATP, followed by cell death; (ii) acetyl-l-carnitine elicits a significant protective effect on DEB induced toxicity, which was potentiated by α-lipoic acid. Collectively, these findings contribute to increase our knowledge of DEB-induce toxicity and will be very useful when applied in studies with lymphocytes from FA patients, in order to find out a protective agent against spontaneous and DEB-induced chromosome instability.

Subchronic effects of cyanobacterial cells on the transcription of antioxidant enzyme genes in tilapia (Oreochromis niloticus)

The increasing occurrence of toxic cyanobacterial blooms in eutrophic water bodies is nowadays of worldwide concern due to their ability to produce toxins such as microcystins (MCs). These cyanobacterial toxins have been shown to affect aquatic organisms such as fish, resulting in oxidative stress. Among the antioxidant enzymes, glutathione peroxidase (GPx) and soluble glutathione-S-transferases (sGST) play an important role in the detoxification of MCs. In the present work tilapia (Oreochromis niloticus) were orally exposed to cyanobacterial cells containing MCs and non-containing MCs for 21 days. The activity and relative mRNA expression by real-time PCR of both enzymes and the GST protein abundance by Western blot analysis were evaluated in liver and kidney. Also the induction of lipid peroxidation (LPO) was assayed. MCs containing cyanobacterial cells induced an increase of LPO products in both organs, and MCs containing and MCs non-containing cyanobacterial cells altered the activity, gene expression and protein abundance of the enzymes, indicating the importance of GPx and sGST in MCs detoxification. Moreover, liver, the main organ involved in biodegradation and biotransformation, experienced an adaptative response to the toxic insult. These results show for the first time that the subchronic exposure to cyanobacterial cells causes changes in antioxidant and detoxification enzymes and that GPx and GST gene expression are good markers of these alterations in tilapia.

Chokeberry (Aronia melanocarpa) juice modulates 7,12-dimethylbenz[a]anthracene induced hepatic but not mammary gland phase I and II enzymes in female rats

Chokeberry is a rich source of procyanidins known to have several types of biological activity including anticarcinogenic potential in experimental models. In this study we examined the effect of chokeberry juice on the hepatic and mammary gland carcinogen metabolizing enzyme expression altered by the polycyclic aromatic hydrocarbon, 7,12-dimethylbenz[a]anthracene (DMBA). Sprague-Dawley rats were gavaged with chokeberry juice (8 ml/kg b.w.) for 28 consecutive days. DMBA was administered i.p. on the 27th and the 28th days. Pretreatment with chokeberry juice reduced the activity of CYP1A1 and increased that of CYP2B involved in metabolic activation/detoxication of DMBA in rat liver, as well as expression and activity of phase II enzymes. Chokeberry juice had no effect on these parameters in the mammary gland and DMBA induced DNA damage in rat blood cells. These results together with our earlier observations indicate that metabolic alterations induced by chokeberry feeding are tissue specific and depend on the class of carcinogen.

Modulation of rat hepatic and kidney phase II enzymes by cabbage juices: comparison with the effects of indole-3-carbinol and phenethyl isothiocyanate

The effect of raw cabbage and sauerkraut juices on the expression and activity of phase II enzymes, glutathione S-transferase (GST) and NAD(P)H:quinone oxidoreductase 1 (NQO1), in the rat liver and kidney was compared with that of two commercially available products of glucosinolate degradation: indole-3-carbinol (I3C) and phenethyl isothiocyanate (PEITC). Male Wistar rats were treated by oral administration with cabbage juices, I3C or PEITC for 4, 10 and 30 d. The results showed that juices, particularly sauerkraut juice as with I3C and PEITC, significantly increased GST and NQO1 activities in the rat liver. The only exception was the 30 d time point of feeding with raw cabbage juice. Cabbage juices, I3C and PEITC affected the hepatic GST μ to the greatest extent and GST α to a lesser extent. The results of the present study also showed that the treatment of rats with juices and compounds tested caused the translocation of the NF-E2-related transcription factor (Nrf2) active subunit from the cytosol to the nucleus, providing an argument for the involvement of this transcription factor in the induction of GST and NQO1. In contrast to the liver, cabbage juices affected only the renal GST θ, while treatment with I3C and PEITC significantly increased the activity of NQO1. Thus, the results of the present study indicate that induction of the key detoxifying enzymes by cabbage juices, particularly sauerkraut, may be responsible for their chemopreventive activity demonstrated by epidemiological studies and in animal models. However, the final effects might be organ or tissue dependent.

Urinary excretion of phenolic acids in rats fed cranberry

Dietary flavonoids can be converted into phenolic acids by colonic microflora. Phenolic acids can then be absorbed into the circulation and may contribute to the health-promoting effects of the parent compounds. Phenolic acids can be further metabolized in other tissues via methylation and conjugation with glucuronide or sulfate. The objectives of this study were to identify and quantify the urinary excretion of 19 phenolic acids and their conjugates in rats fed three levels of a concentrated cranberry powder (3.3, 6.6, and 33 mg/kg of diet). The basic diet used was AIN93G diet containing very low amounts of any polyphenolic compounds. Of the phenolic acids studied, the amounts excreted varied by 4 orders of magnitude, with hippuric acid being excreted in the highest quantities. Amounts of 4-hydroxyphenylacetic acid (4HPAA), 3-hydroxyphenylacetic acid (3HPAA), 3-hydroxyphenylpropionic acid (3HPPA), and 4-hydroxycinnamic acid (4HCA) excreted were in the range of 18-33 microg/mg creatinine in animals fed the highest level of cranberry powder, whereas phenylacetic acid (PAA), gallic acid (GA), 3,4-dihydroxyphenylacetic acid (34HPAA), 3,4-dihydroxybenzoic acid (34HBA), 3,4-dihydroxycinnamic acid (34HCA), and 4-hydroxy-3-methoxycinnamic acid (FA) were excreted in the urine in concentrations of 0.1-2 microg/mg creatinine. As the amount of cranberry in the diet was increased, the amount of 4HPAA excreted decreased but the percentage of conjugated 4HPAA excreted increased (from 57 to 91%). For other phenolic acids analyzed, the percentage excreted in the conjugated form was approximately constant across levels of cranberry in the diet and ranged from 65 to 100% for the individual phenolic acids. Studies of bioactivity and health effects need to consider more than just the compound(s) in the food, because they can be metabolized to other lower molecular weight compounds, which in turn may also be methylated or conjugated in some form that may affect the perceived health effects.

Effect of Chokeberry (Aronia melanocarpa) juice on the metabolic activation and detoxication of carcinogenic N-nitrosodiethylamine in rat liver

Chokeberry is a rich source of polyphenols, which may counteract the action of chemical carcinogens. The aim of this study was to examine the effect of chokeberry juice alone or in combination with N-nitrosodiethylamine (NDEA) on phase I and phase II enzymes and DNA damage in rat liver. The forced feeding with chokeberry juice alone decreased the activities of enzymatic markers of cytochrome P450, CYP1A1 and 1A2. NDEA treatment also decreased the activity of CYP2E1 but enhanced the activity of CYP2B. Pretreatment with chokeberry juice further reduced the activity of these enzymes. Modulation of P450 enzyme activities was accompanied by the changes in the relevant proteins levels. Phase II enzymes were increased in all groups of animals tested. Chokeberry juice augmented DNA damage and aggravated the effect of NDEA. These results indicate that chokeberry may protect against liver damage; however, in combination with chemical carcinogens it might enhance their effect.