Protective Effects of Tea Melanin against 2,3,7,8-Tetrachlorodibenzo-p-dioxin-Induced Toxicity: Antioxidant Activity and Aryl Hydrocarbon Receptor Suppressive Effect

Electrolytic stimulation in aid of poly(β-L-malic acid) production by Aureobasidium melanogenum ipe-1

Poly (β-L-malic acid) (PMLA) is attracting industrial interest for its potential application in medicine and other industries. In this study, electrolytic stimulation assisted PMLA production was developed. Firstly, it was found that the pentavalent nitrogen source (i.e., NO₃^-) was more suitable for PMLA production. Secondly, a usual single-chamber bioelectric-fermentation system (BES) cannot improve PMLA production, which can only promote cell growth. Then, a new single-chamber BES with an external circulation was developed, where the PMLA metabolism was further intensified. Finally, the integration of NO₃^- addition and electrolytic stimulation mode (c) showed a positive synergy on the PMLA production. Compared to the case without NO₃^- addition and electrolytic stimulation, the PMLA production was increased by 22.9 % using the integrated process. Moreover, compared to the case without the electrolytic stimulation mode (c), it was revealed that the different genes involved in 12 metabolic subsystems using the integrated process, where 31 and 177 genes were up-regulated and down-regulated, respectively. The up-regulated genes were mainly participated in melanin metabolic process, catalase activity, and oxidoreductase activity. Hence, the integration of electrolytic stimulation represents a novel approach to improve PMLA production.

Downstream processing and structural confirmation of pullulan - A comprehensive review

Pullulan is a microbial polymer, commercially produced from Aureobasidium pullulans. Downstream processing of pullulan involves a multi-stage process which should be efficient, safe and reproducible. In liquid-liquid separations, firstly cell free extract is separated. Cell biomass can be separated after fermentation either by centrifugation or filtration. Due to practically insolubility of pullulan in organic solvents, ethanol and isopropanol are the most commonly used organic solvents for its recovery. Pullulan can also be purified by chromatographic techniques, but these are not cost effective for the purification of pullulan. Efficient aqueous two-phase system can be used for the purification of pullulan. The current review describes the methods and perspectives used for solid-liquid separation, liquid-liquid separations and finishing steps for the recovery of pullulan. Techniques used to determine the structural attributes of pullulan have also been highlighted.

Intermediate Thermoresistance in Black Yeast Asexual Cells Variably Increases with Culture Age, Promoting Survival and Spoilage in Thermally Processed Shelf-Stable Foods

ABSTRACT

Black yeasts are a functional group that has caused spoilage in cold-filled and hot-filled beverages, as well as other water activity-controlled food products. We established quantitative thermoresistance parameters for the inactivation of 12 Aureobasidium and Exophiala isolates through isothermal experiments and a challenge study. Culture age (2 versus 28 days) variably affected the thermoresisitance among the black yeast strains. Variation in thermoresistance exists within each genus, but the two most resistant strains were the Exophiala isolates. The two most heat-resistant isolates were Exophiala phaeomuriformis FSL-E2-0572, with a D60-value of 7.69 ± 0.63 min in 28-day culture and Exophiala dermatitidis YB-734, with a D60-value of 16.32 ± 2.13 min in 28-day culture. Although these thermoresistance levels were, in some cases, greater than those for conidia and vegetative cells from other common food spoilage fungi, they were much more sensitive than the ascospores of heat-resistant molds most associated with spoilage of hot-filled products. However, given that black yeasts have caused spoilage in hot-filled products, we hypothesized that this intermediate degree of thermoresistance may support survival following introduction during active cooling before package seals have formed. A challenge study was performed in an acidic (apple cider) and water activity-controlled (maple syrup) product to evaluate survival. When apple cider was hot filled at 82°C, black yeast counts were reduced by 4.1 log CFU/mL 24 h after the heat treatment, but the survivors increased up to 6.7 log CFU/mL after 2 weeks. In comparison, the counts were below the detection limit after both 24 h and 14 days of shelf life in both products when filled at the boiling points. This suggests that ensuring water microbial quality in cooling tunnels and nozzle sanitation may be essential in mitigating the introduction of these fungi.

HIGHLIGHTS

Pharmacological Properties of Melanin and its Function in Health

The biological pigment melanin is present in most of the biological systems. It manifests a host of biological and pharmacological properties. Its role as a molecule with special properties and functions affecting general health, including photoprotective and immunological action, are well recognized. Its antioxidant, anti-inflammatory, immunomodulatory, radioprotective, hepatic, gastrointestinal and hypoglycaemic benefits have only recently been recognized and studied. It is also associated with certain disorders of the nervous system. In this MiniReview, we consider the steadily increasing literature on the bioavailability and functional activity of melanin. Published literature shows that melanin may play a number of possible pharmacological effects such as protective, stimulatory, diagnostic and curative roles in human health. In this MiniReview, possible health roles and pharmacological effects are considered.

An alternative anionic bio-sustainable anti-fungal agent: Investigation of its mode of action on the fungal cell membrane

The potential of a lactylate (the sodium caproyl lactylate or C10 lactylate), a typical food grade emulsifier, as an anionic environmental friendly anti-fungal additive was tested in growth medium and formulated in a protective coating for exterior wood. Different laboratory growth tests on the blue stain fungus Aureobasidium pullulans were performed and its interactions on a model fungal cell membrane were studied. Promising short term anti-fungal effects in growth tests were observed, although significant but less dramatic effects took place in coating test on wood panels. Scanning electron microscope analysis shows clear differences in the amount of fungal slime on the mycelium of Aureobasidium pullulans when the fungus was exposed of C10 lactylate. This could indicate an effect on the pullulan and melanin production by the fungus. Moreover, the interaction studies on model fungal cell membranes show that C10 lactylate affects the phospholipid bilayer in a similar manner to other negative charged detergents.

Hepatoprotective and antioxidant effects of dietary Glycyrrhiza polysaccharide against TCDD-induced hepatic injury and RT-PCR quantification of AHR2, ARNT2, CYP1A mRNA in Jian Carp (Cyprinus carpio var. Jian)

To evaluate the protective effects of Glycyrrhiza polysaccharide (GPS) against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced hepatotoxicity in Jian carp, the fish were fed diets containing GPS at doses of 0.1, 0.5 and 1.0g/kg for 60days before an intraperitoneal injection of 0.6μg/kg TCDD at a volume of 0.05mL/10g body weight. At 72hr post-injection, blood and liver samples were taken for biochemical analysis and the fish liver samples were used for the preparation of pathological slices. The results showed that increases in alanine aminotransferase (GPT), aspartate aminotransferase (GOT), lactate dehydrogenase (LDH), and alkaline phosphatase (AKP) in serum induced by TCDD were significantly inhibited by pre-treatment with 1.0g/kg GPS. Following the 1.0g/kg GPS pre-treatment, total protein (TP), albumin (Alb), catalase (CAT), glutathione peroxidase (GPx), total antioxidant capacity (T-AOC) and superoxide dismutase (SOD) activities in liver tissue increased significantly, malondialdehyde (MDA) formation (P<0.05 or P<0.01) was significantly inhibited, and the expression of cytochrome P4501A (CYP1A), aryl hydrocarbon receptor 2 (AHR2) and aryl hydrocarbon receptor nuclear translocator 2 (ARNT2) mRNA (P<0.05) was significantly enhanced. Histological observations on fish liver were obtained by preparing paraffin tissue sections via HE staining, and the results showed that histological changes were obviously reduced by 0.5 and 1.0g/kg GPS. GPS significantly reduced liver tissue damage caused by TCDD. Overall, these results proved the hepatoprotective effect of GPS in protecting against fish liver injury induced by TCDD, and supported the use of GPS (1.0g/kg) as a hepatoprotective and antioxidant agent in fish.

2,3,7,8-TCDD-mediated toxicity in peripheral blood mononuclear cells is alleviated by the antioxidants present in Gelidiella acerosa: an in vitro study

Seaweeds have been used as a source of traditional medicine worldwide for the treatment of various ailments, mainly due to their ability to quench the free radicals. The present study aims at evaluating the protective effect of methanolic extract of Gelidiella acerosa, an edible red seaweed against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced toxicity in peripheral blood mononuclear cells (PBMC). For evaluating the protective effect of G. acerosa, PBMC were divided into four groups: vehicle control, TCDD (10 nM), TCDD + G. acerosa (300 μg/ml), and G. acerosa alone treated. Scavenging of intracellular reactive oxygen species (ROS) induced by TCDD was assessed by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) method. Alterations at macromolecular level were quantified through lipid peroxidation (LPO) level, protein carbonyl content (PCC) level, and comet assay. The cellular morphology upon TCDD toxicity and G. acerosa treatment was obtained by light microscopy and histopathological studies. The chemical composition present in the methanolic extract of G. acerosa was determined by gas chromatography-mass spectrometry (GC-MS) analysis. The results reveal that 10 nM TCDD caused significant (P < 0.05) reduction in cell viability (94.10 ± 0.99), and treatment with 300 μg/ml extract increased the cell viability (99.24 ± 0.69). TCDD treatment resulted in a significant increase in the production of ROS, LPO (114 ± 0.09), and PCC (15.13 ± 1.53) compared to the control, whereas co-treatment with G. acerosa significantly (P < 0.05) mitigated the effects. Further, G. acerosa significantly (P < 0.05) prevented TCDD-induced genotoxicity and cell damage. GC-MS analysis showed the presence of n-hexadecanoic acid (retention time (RT) 13.15), cholesterol (RT 28.80), α-D-glucopyranose, 4-O-α-D-galactopyranosyl (RT 20.01), and azulene (RT 4.20). The findings suggest that G. acerosa has a strong protective ability against TCDD-induced cytotoxicity, oxidative stress, and DNA damage.

A direct comparison of methods used to measure oxidized glutathione in biological samples: 2-vinylpyridine and N-ethylmaleimide

The ratio of glutathione disulfide (GSSG) to reduced glutathione (GSH) in biological samples is a frequently used parameter of oxidative stress. As a result, many methods are developed to measure GSSG. The most popular and convenient of these relies on enzymatic cycling following the chemical masking of GSH in the sample using 2-vinylpyridine (2VP). However, 2VP is a slow reactant and its use may result in artificially high GSSG values due to oxidation of the sample over time. Fast-reacting reagents such as N-ethylmaleimide (NEM) may provide more accurate results. We performed a direct comparison of methods using 2VP and NEM. With 2VP, the percentage of total glutathione (GSH+GSSG) in the oxidized form was significantly higher in all tested tissues (kidney, lung and liver) compared to the same procedure performed using NEM. We conclude that NEM, when coupled with a simple solid-phase extraction procedure, is more accurate for the determination of GSSG. We also tested the effects of various handling and storage conditions on GSSG. A detailed description and a discussion of other methods are also included.

Ameliorative effects of docosahexaenoic acid on the toxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured rat hepatocytes

The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant toxicant that mediates carcinogenic effects associated with oxidative DNA damage. Docosahexaenoic acid (DHA) with antioxidant functions has many biochemical, cellular, and physiological functions for cells. The present study assessed, for the first time, the ameliorative effect of DHA in alleviating the toxicity of TCDD on primary cultured rat hepatocytes (HEPs). In vitro, isolated HEPs were incubated with TCDD (5 and 10 μM) in the presence and absence of DHA (5, 10, and 20 μM) for 48 h. The cell viability was detected by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay and lactate dehydrogenase (LDH) release. DNA damage was analyzed by liver micronucleus assay and 8-oxo-2-deoxyguanosine (8-OH-dG) level. In addition, total antioxidant capacity (TAC) and total oxidative stress (TOS) were assessed to determine the oxidative injury in HEPs. The results of MTT and LDH assays showed that TCDD decreased cell viability but not DHA. On the basis of increasing treatment concentrations, the dioxin caused significant increases of micronucleated HEPs and 8-OH-dG as compared to control culture. TCDD also led to significant increases in TOS content. On the contrary, in cultures treated with DHA, the level of TAC was significantly increased during treatment in a concentration-dependent fashion. DHA showed therapeutic potential against TCDD-mediated cell viability and DNA damages. As conclusion, this study provides the first evidence that DHA has protective effects against TCDD toxicity on primary cultured rat hepatocytes.

The protective role of antioxidants in the defence against ROS/RNS-mediated environmental pollution

Overproduction of reactive oxygen and nitrogen species can result from exposure to environmental pollutants, such as ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons, and many other compounds present in the environment. It appears that increased oxidative/nitrosative stress is often neglected mechanism by which environmental pollutants affect human health. Oxidation of and oxidative damage to cellular components and biomolecules have been suggested to be involved in the aetiology of several chronic diseases, including cancer, cardiovascular disease, cataracts, age-related macular degeneration, and aging. Several studies have demonstrated that the human body can alleviate oxidative stress using exogenous antioxidants. However, not all dietary antioxidant supplements display protective effects, for example, β-carotene for lung cancer prevention in smokers or tocopherols for photooxidative stress. In this review, we explore the increases in oxidative stress caused by exposure to environmental pollutants and the protective effects of antioxidants.

Ameliorative effect of lycopene against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced rat liver microsomal toxicity

The objective of the current study was to investigate the potential oxidative damage of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in hepatic microsomal fractions in vitro and to further elucidate the potential modulatory effect of lycopene. Rat liver microsomes were divided into four groups. Group I served as a control and is incubated with vehicle (toluene). Groups II and IV were incubated with 20 µM lycopene for 1 h before further incubating; groups III and IV with 15 nM of TCDD for further 1 h. Hydrogen peroxide (H2O2) production, lipid peroxidation (LPO), protein carbonyl content and activities of uridine 5′-diphospho-glucuronyltransferase (UDPGT) and P450 were significantly increased. Moreover, the activity of antioxidant enzymes superoxide dismutase, glutathione peroxidase, catalse, glutathione- S-transferase and glutathione reductase as well as the microsomal thiol content were significantly decreased. Incubation with lycopene (group IV) maintained near normal activities of the enzymes, normalized thiol and carbonyl content and significantly reduced LPO and H2O2 production. In conclusion, the findings of the study indicate that TCDD induces a significant oxidative stress in liver microsomes as manifested by increased LPO, H2O2 production, protein carbonyl content and activities of UDPGT and P450 and decreased antioxidant enzymes activities and thiol content. By the reversal of biochemical and oxidative markers toward normalcy, the protective role of lycopene is illuminated in rat liver microsomal toxicity.

Sulforaphane inhibits CYP1A1 activity and promotes genotoxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in vitro

Increasing environmental pollution by carcinogens such as some of persistent organic pollutants (POPs) has prompted growing interest in searching for chemopreventive compounds which are readily obtainable. Sulforaphane (SFN) is isolated from cruciferous vegetables and has the potentials to reduce carcinogenesis through various pathways. In this study, we studied the effects of SFN on CYP1A1 activity and genotoxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The results showed that SFN inhibited TCDD-induced CYP1A1 activity in H4IIE cells by directly inhibiting CYP1A1 activity, probably through binding to aryl hydrocarbon receptor and/or CYP1A1 revealed by molecular docking. However, SFN promoted TCDD-induced DNA damage in yeast cells and reduced the viability of initiated yeast cells. Besides, it is surprising that SFN also failed to reduce genotoxicity induced by other genotoxic reagents which possess different mechanisms to lead to DNA damage. Currently, it is difficult to predict whether SFN has the potentials to reduce the risk of TCDD based on the conflicting observations in the study. Therefore, further studies should be urgent to reveal the function and mechanism of SFN in the stress of such POPs on human health.

Ameliorative effect of supplementation with L-glutamine on oxidative stress, DNA damage, cell viability and hepatotoxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in rat hepatocyte cultures

The most potent of the dioxins, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is a persistent and ubiquitous environmental contaminant. And the health impact of exposure to TCDD is of great concern to the general public. Recent data indicate that L-glutamine (Gln) has antioxidant properties and may influence hepatotoxicity. The objective of the present study was undertaken to explore the effectiveness of Gln in alleviating the hepatotoxicity of TCDD on primary cultured rat hepatocytes. Gln (0.5, 1 and 2 mM) was added to cultures alone or simultaneously with TCDD (0.005 and 0.01 mM). The hepatocytes were treated with TCDD and Gln for 48 h. Then cell viability was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC), total glutathione (TGSH) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by liver micronucleus assay (MN) and 8-oxo-2-deoxyguanosine (8-OH-dG). The results of MTT and LDH assays showed that TCDD decreased cell viability but not L-glutamine. TCDD also increased TOS level in rat hepatocytes and significantly decreased TAC and TGSH levels. On the basis of increasing doses, the dioxin in a dose-dependent manner caused significant increases of micronucleated hepatocytes (MNHEPs) and 8-OH-dG as compared to control culture. Whereas, in cultures exposured with Gln alone, TOS levels were not changed and TAC and TGSH together were significantly increased in dose-dependent fashion. The presence of Gln with TCDD modulated the hepatotoxic effects of TCDD on primary hepatocytes cultures. Noteworthy, Gln has a protective effect against TCDD-mediated DNA damages. As conclusion, we reported here an increased potential therapeutic significance of L-glutamine in TCDD-mediated hepatic injury for the first time.

The effect of laurel leaf extract against toxicity induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin in cultured rat hepatocytes

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a very toxic environmental pollutant that raises great public concern about its impact on human health. Recent studies indicate that laurel leaf extract exhibits antioxidant properties that can counter the toxic effects of certain compounds in the liver. The aim of this study was to assess how effective LE is against the toxicity of TCDD in a primary culture of rat hepatocytes. The extract (50 mg L(-1), 100 mg L(-1), and 200 mg L(-1)) was added to cultures alone or with TCDD (1.61 mg L(-1) and 3.22 mg L(-1)) for 48 hours. Cell viability was measured using the [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and the lactate dehydrogenase (LDH) cytotoxicity assay, while oxidative damage was assessed by measuring total antioxidant capacity (TAC) and total oxidative stress (TOS). DNA damage was also analysed using the micronucleus (MN) assay of the cultured hepatocytes. TCDD alone lowered, and laurel extract had no effect on cell viability. TCDD also increased TOS and significantly decreased TAC. It significantly increased the frequency of micronucleated hepatocytes in a dose-dependent manner. In cultures exposed to LE alone, TOS did not change and TAC significantly increased in a dose-dependent manner. Added to TCDD, laurel countered its toxic effects and showed protective effects against TCDD-mediated DNA damage. This points to the therapeutic potential of laurel against TCDD toxicity in the liver.

Propolis alleviates 2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced histological changes, oxidative stress and DNA damage in rat liver

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) induces hepatic damage. Propolis exhibits antioxidant properties and several studies suggest that supplementations with antioxidants can influence hepatotoxicity. Therefore, the aim of the current study was to explore the effectiveness of propolis in alleviating the toxicity of TCDD in the liver of rats. Animals were divided into six groups, namely, TCDD (0.75 and 8 µg/kg body weight (bw)), propolis (50 mg/kg bw), TCDD (0.75 and 8 µg) plus propolis (50 mg/kg bw), and control, respectively. Rats were intraperitoneally administered with their respective doses daily for 21 days. In rats that received a high dose of TCDD, the antioxidant enzymes were significantly decreased and the serious pathological findings were established. Also, the rate of hepatocyte micronucleus (HMN) was increased after treating with TCDD. The reactions of enzymes in control and low-dose group were weak. The frequencies of HMN and liver histology were similar to both the groups. The presence of propolis with TCDD alleviated its pathological effects in hepatic tissue. Propolis also prevented the suppression of antioxidant enzymes in the livers of animals exposed to TCDD and displayed a strong protective effect against HMN. It can be concluded that propolis has beneficial influences and was able to antagonize TCDD toxicity in the liver.

Beneficial effect of astaxanthin on 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced liver injury in rats

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) represents a potential health risk and hepatotoxicity. Astaxanthin (ASTA) exhibits antioxidant properties and can influence hepatotoxicity. Therefore, the present study was carried out for using ASTA against hepatotoxicity induced by TCDD in the liver of rats. Animals were treated intraperitoneally daily with TCDD (8 µg/kg body weight (b.w.)), ASTA (12.5 mg/kg b.w. and 25 mg/kg b.w.) and TCDD plus ASTA (12.5 and 25 mg/kg b.w.) for 21 days. TCDD significantly decreased the activities of antioxidant enzymes and resulted in serious pathological findings. Moreover, the rate of micronucleus (MN) in hepatocytes increased after treating with TCDD. The activities of enzymes, frequencies of MNs and liver histology in lower dosage group of ASTA remained unchanged compared with the control group. In rats treated with ASTA, at higher dosage alone, the MNs remained unchanged and the activities of antioxidant enzymes significantly increased. The presence of ASTA (except for lower dose) with TCDD alleviated its pathological effects in hepatic tissue. ASTA also prevented the suppression of antioxidant enzymes in the livers of animals exposed to TCDD and displayed a strong protective effect against MNs. Thus, the present findings might provide new insight into the development of therapeutic and preventive approaches of TCDD toxicity.

Modulatory effect of l-glutamine on 2,3,7,8 tetrachlorodibenzo-p-dioxin-induced liver injury in rats

The aim of this study was to explore the effectiveness of l-glutamine (Gln) in alleviating the toxicity of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in liver of rats. Rats were intraperitoneally administered Gln and TCDD doses daily for 21 days. In the liver of rats, the biochemical tests, pathological examination and micronucleus (MN) test were performed. TCDD significantly decreased the activities of antioxidant enzymes and serious pathological findings. Moreover, the rate of MNs in hepatocytes increased after treatment with dioxin. In rats treated with Gln alone, the MNs remained unchanged, but the ratio of glutathione (GSH) and the activity of glutathione peroxidase (GSH-Px) were significantly increased. Gln also prevented the suppression of GSH-Px (except for superoxide dismutase and catalase) and GSH in the livers of animals exposed to TCDD and displayed a strong protective effect against MNs. Thus, our findings for Gln might provide new insight into the development of therapeutic and preventive approaches in TCDD toxicity.

Ameliorative effect of docosahexaenoic acid on 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced histological changes, oxidative stress, and DNA damage in rat liver

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is an environmental contaminant that leads to the development of hepatotoxicity. Docosahexaenoic acid (DHA) has been proposed to counteract oxidative stress and improve antioxidant status, and several studies suggest that supplementations with antioxidants can influence hepatotoxicity. The aim of the current study was to explore the role of DHA in modulating the toxicity of TCDD in the liver of Sprague-Dawley rats. Animals were assigned to four groups (n = 5): control (only dimethyl sulfoxide (DMSO)), 8 μg/kg body weight (b.w.) TCDD in DMSO solution; 250 mg/kg b.w. DHA and TCDD plus DHA; respectively. Rats were intraperitoneally administered their respective doses daily for 21 days. On day 21, the animals were killed, and then biochemical tests, pathological examination, and micronucleus (MN) assay were performed in the liver. Our results showed that the activities of antioxidant enzymes were significantly decreased and serious pathological findings were established in rats that received TCDD. Beside the rate of MNs in hepatocytes was increased after the treatment with dioxin. In rats treated with DHA alone, MNs were not changed and the activities of antioxidant enzymes were significantly increased. The presence of DHA with TCDD alleviated its pathological effects in hepatic tissue. DHA also prevented the suppression of antioxidant enzymes in the livers of animals exposed to TCDD and displayed a strong protective effect against MNs. It can be concluded that DHA has beneficial influences and could be able to antagonize TCDD toxicity in liver.

Eicosapentaenoic acid protects against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced hepatic toxicity in cultured rat hepatocytes

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent and ubiquitous environmental contaminant. The health impact of TCDD exposure is of great concern to the general public. Recent reports have implied that eicosapentaenoic acid (EPA) might be a potential chemopreventive agent and influence hepatotoxicity. The aim of the current study was to explore the effectiveness of EPA in alleviating the toxicity of TCDD on primary cultured rat hepatocytes. EPA (5, 10 and 20 μM) was added to cultures alone or simultaneously with TCDD (5 and 10 μM). Rat hepatocytes were treated with TCDD and EPA for 48 h, and then cytotoxicity was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by liver micronucleus assay (LMN) and 8-oxo-2-deoxyguanosine (8-OH-dG). The results of MTT and LDH assays showed that TCDD but not EPA decreased cell viability. TCDD also increased TOS level and significantly decreased TAC level in rat hepatocytes in a clear dose dependent manner. On the basis of increasing doses, the dioxin caused significant increases of micronucleated hepatocytes (MNHEPs) and 8-OH-dG as compared to control culture. Whereas, in cultures treated with EPA alone, TOS level did not change and the level of TAC significantly increased. The presence of EPA with TCDD minimized the toxic effects of the dioxin on primary hepatocytes cultures. Noteworthy, EPA has a protective effect against TCDD-mediated DNA damages.

Propolis protects against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced toxicity in rat hepatocytes

The present experiment was undertaken to determine the effectiveness of propolis in alleviating the toxicity of TCDD on cultured primary rat hepatocytes. Propolis (25, 50 and 100 μM) was added to plain culture or simultaneously with TCDD (5 and 10 μM). The hepatocytes were treated with TCDD and propolis for 48 h. Then cell viability was detected by [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyltetrazolium bromide] (MTT) assay and lactate dehydrogenase (LDH) release, while total antioxidant capacity (TAC) and total oxidative stress (TOS) levels were determined to evaluate the oxidative injury. The DNA damage was also analyzed by liver micronucleus assay (LMN) and 8-oxo-2-deoxyguanosine (8-OH-dG). The results of MTT and LDH assays showed that TCDD decreased cell viability. TCDD also increased TOS level and decreased TAC level in rat hepatocytes. On the basis of increasing doses, the TCDD caused significant increases of micronucleated hepatocytes (MNHEPs) and 8-OH-dG levels as compared to control culture. In cultures treated with propolis alone, cell viability and TOS level were not affected, while the level of TAC was significantly increased in dose-dependent fashion. The presence of propolis with TCDD modulated its toxic effects on primary hepatocytes cultures. Noteworthy, propolis has a protective effect against TCDD-mediated DNA damages.

Hydroxytyrosol, the phenolic compound of olive oil protects human PBMC against oxidative stress and DNA damage mediated by 2,3,7,8-TCDD

The protective effect of hydroxytyrosol (HT), a strong antioxidant compound from extra virgin olive oil, against TCDD induced toxicity was investigated in human peripheral blood mononuclear cells (PBMC). PBMC (1 × 10(6)cellsmL(-1)) were divided into four groups and were incubated in a CO(2) incubator (5% CO(2)) for 12h with vehicle, TCDD (10 nM), TCDD+HT (10 nM+100 μM) and HT alone (100 μM) respectively. To clarify the role of HT against TCDD induced cytotoxicity, oxidative stress and the levels of antioxidant enzymes were assessed. Incubation of PBMC with TCDD significantly decreased cell viability, catalase (CAT) and glutathione peroxidase (GPx) and increased the levels of superoxide dismutase (SOD), glutathione reductase (GR) and oxidative stress markers such as lipid peroxidation products (LPO), protein carbonyl content (PCC) and reactive oxygen species (ROS). Whereas, HT had an effective antioxidant property as observed by the increased cell viability, normalization of antioxidant enzymes and decreased levels of LPO, PCC and ROS in PBMC co-treated with HT and TCDD. Apoptosis detection and comet assay results shows that HT, by acting as an antioxidant, prevents the damage to DNA induced by TCDD. In addition light microscopic and histopathological observations revealed that the cells are apoptotic and degenerated during TCDD treatment, whereas cells showed intact morphology during co-treatment with HT. On the whole, the results reveal that HT exerts a promising antioxidant potential in protecting the PBMC against TCDD induced oxidative stress, which might be due to the presence of catechol moiety in its structure.

Antioxidative effects of curcumin, β-myrcene and 1,8-cineole against 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced oxidative stress in rats liver

The aim of this study was to investigate the effectiveness of curcumin, β-myrcene (myrcene) and 1,8-cineole (cineole) on antioxidant defense system in rats given a persistent environmental pollutant (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Rats (n = 112) were divided randomly into 8 equal groups. One group was kept as control and given corn oil as carrier. TCDD was orally administered at the dose of 2 μg/kg/week. Curcumin, myrcene and cineole were orally administered at the doses of 100 mg/kg/day, 200 mg/kg/day and 100 mg/kg/ day, respectively, by gavages dissolved in corn oil with and without TCDD. The liver samples were taken from half of all rats on day 30 and from the remaining half on day 60 for the determination of thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), catalase (CAT), glutathione peroxidase (GSH-Px) and CuZn-SOD levels by spectrophotometric method. The results indicated that although TCDD significantly (p ≤ 0.01) increased formation of TBARS, it caused a significant decline in the levels of GSH, CAT, GSH-Px and CuZn-SOD in rats. In contrast, curcumin, myrcene and cineole significantly increased GSH, CAT, GSH-Px and CuZn-SOD levels but decreased formation of TBARS. Additionally, the antioxidative effects of curcumin, myrcene and cineole were increased at day 60 compared to day 30. In the TCDD groups given curcumin, myrcene and cineole, oxidative stress decreased by time. In conclusion, curcumin, myrcene and cineole showed antioxidant activity and eliminated TCDD-induced oxidative stress in rats in a time-dependent manner.

Suppressive effect of Siraitia grosvenorii extract on dicyclanil-promoted hepatocellular proliferative lesions in male mice

Dicyclanil (DC) generates reactive oxygen species (ROS) due to Cyp1a1 induction, and DNA damage caused by oxidative stress is probably involved in hepatocarcinogenesis in mice. To clarify the modifying effect of the Siraitia grosvenorii extract (SGE), which has antioxidative properties, we employed a 2-stage liver carcinogenesis model in partially hepatectomized male ICR mice. Mice maintained on diet containing DC at a concentration of 1,500 ppm for 9 weeks after a single intraperitoneal injection of diethylnitrosamine (DEN) at a dose of 30 mg/kg and they were given water containing 2,500 ppm of SGE for 11 weeks including 2 weeks as pre-administration on DC. SGE inhibited the induction of gamma-glutamyltranspeptidase-positive hepatocytes, lipid peroxidation, and gene expression of Cyp1a1, all of which were caused by DC. To examine whether SGE indirectly inhibits Cyp1a1 expression induced by inhibition of aryl hydrocarbon receptor (Ahr)-mediated signal transduction caused by DC, mice with high (C57BL/6J mice) and low affinities (DBA/2J mice) to Ahr were given DC-containing diet and/or SGE-containing tap water for 2 weeks. Cyp1a1 gene expression was significantly lower in C57BL/6J mice administered DC + SGE than in C57BL/6J mice administered DC alone; there was no difference in the Cyp1a1 expression between DBA/2J mice administered DC + SGE and DC alone. These results suggest that SGE suppresses the induction of Cyp1a1, leading to inhibition of ROS generation and consequently inhibited hepatocarcinogenesis, probably due to suppression of Ahr activity.

Effects of melanin on the accumulation of exopolysaccharides by Aureobasidium pullulans grown on nitrate

Aureobasidium pullulans produced pullulan and melanin when grown in medium containing low nitrate levels. With high nitrate concentrations, however, this fungus produced a mixture of exopolysaccharides (EPS) without melanin synthesis. At 0.78 g l(-1) N as nitrate, where no melanin synthesis occurred, maximum EPS yields reached 6.92 g l(-1) and then decreased to the final yield of 2.36 g l(-1). Following melanin addition (0.1 g l(-1)), yields reached 7.02 g l(-1) at 48 h and fell to a final yield of 5.21 g l(-1). The EPS produced in high nitrate medium contained both pullulan and (1-->3)-beta-glucan, but only pullulan was produced with melanin-supplementation. With melanin addition a doubling of (1-->3)-beta-glucanase activity was observed in high nitrate medium compared to that without supplementation. On the other hand amylolytic activities disappeared in medium with melanin production or addition. Culture filtrates sustained a higher reducing capacity (RC) when melanin was present. Low RC appeared to reduce (1-->3)-beta-glucanase activity and increase amylolytic activities. Thus, higher RC appears to inhibit production/activity of amylose-degrading enzymes capable of degrading pullulan, and stimulates (1-->3)-beta-glucanase synthesis/activity, leading to a preferential accumulation of pullulan.