Query: Counteracting the Effects of Dioxins Through Diet

Relevant passages:
You AhR what you eat: linking diet and immunity. <=SEP=> The aryl hydrocarbon receptor (AhR) is responsible for the toxic effects of environmental pollutants such as dioxin, but little is known about its normal physiological functions. Li et al. (2011) now show that specific dietary compounds present in cruciferous vegetables act through the AhR to promote intestinal immune function, revealing AhR as a critical link between diet and immunity. Copyright © 2011 Elsevier Inc. All rights reserved.

Camel urine inhibits the cytochrome P450 1a1 gene expression through an AhR-dependent mechanism in Hepa 1c1c7 cell line. <=SEP=> AIM OF THE STUDY: Drinking camel urine has been used traditionally to treat numerous cases of cancer yet, the exact mechanism was not investigated. Therefore, we examined the ability of three different camel urines (virgin, lactating, and pregnant source) to modulate a well-known cancer-activating enzyme, the cytochrome P450 1a1 (Cyp1a1) in murine hepatoma Hepa 1c1c7 cell line. MATERIALS AND METHODS: The effect of different camel urines, compared to bovine urines, on Cyp1a1 mRNA was determined using real-time polymerase chain reaction. Cyp1a1 protein and catalytic activity levels were determined using Western blot analysis and 7-ethoxyresorufin as a substrate, respectively. The role of aryl hydrocarbon receptor (AhR)-dependent mechanism was determined using electrophoretic mobility shift assay (EMSA) and the AhR-dependent luciferase reporter gene. RESULTS: All types of camel, but not bovine, urines differentially inhibited the induction of Cyp1a1 gene expression by TCDD, the most potent Cyp1a1 inducer and known carcinogenic chemical. Importantly, virgin camel urine showed the highest degree of inhibition at the activity level, followed by lactating and pregnant camel urines. Furthermore, we have shown that virgin camel urine significantly inhibited the TCDD-mediated induction of Cyp1a1 at the mRNA and protein expression levels. Mechanistically, the ability of virgin camel urine to inhibit Cyp1a1 was strongly correlated with its ability to inhibit AhR-dependent luciferase activity and DNA binding as determined by EMSA, suggesting that AhR-dependent mechanism is involved. CONCLUSIONS: The present work provides the first evidence that camel urine but not that of bovine inhibits the TCDD-mediated toxic effect by inhibiting the expression of Cyp1a1, at both transcriptional and post-transcriptional levels through an AhR-dependent mechanism. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

The aryl hydrocarbon receptor and its xenobiotic ligands: a fundamental trigger for cardiovascular diseases. <=SEP=> This review reconsiders a major cause of cardiovascular diseases, tobacco smoking, as the activation of the Aryl hydrocarbon Receptor (AhR), also known as the dioxin receptor, by aryl hydrocarbons from the tar fraction of tobacco in various organs of the cardiovascular domain. This concept sheds new light on well-known albeit controversial epidemiological concepts such as the Mediterranean diet and the French paradox. We also review the discovery that resveratrol, a natural AhR antagonist, may be of interest in the prevention and treatment of cardiovascular diseases.

Flavones and flavonols at dietary levels inhibit a transformation of aryl hydrocarbon receptor induced by dioxin. <=SEP=> Dioxins invade the body mainly through the diet, and produce toxicity through the transformation of aryl hydrocarbon receptor (AhR). An inhibitor of the transformation should therefore protect against the toxicity and ideally be part of the diet. We examined flavonoids ubiquitously expressed in plant foods as one of the best candidates, and found that the subclasses flavones and flavonols suppressed antagonistically the transformation of AhR induced by 1 nM of 2,3,7,8-tetrachlorodibenzo-p-dioxin, without exhibiting agonistic effects that transform AhR. The antagonistic IC(50) values ranged from 0.14 to 10 microM, close to the physiological levels in human.

Biology and function of the aryl hydrocarbon receptor: report of an international and interdisciplinary conference. <=SEP=> The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor present in many cells. The AhR links environmental chemical stimuli with adaptive responses, such as detoxification, cellular homoeostasis or immune responses. Furthermore, novel roles of AhR in physiological and genetic functions are being discovered. This is a report of a recent meeting in Düsseldorf. The meeting highlighted that AhR research has moved from its focus on toxic effects of dioxins and other environmental pollutants to its biological roles. For instance, it was recently discovered that AhR-responsive elements in retrotransposons contribute to the functional structure of the genome. Other exciting new reports concerned the way plant-derived compounds in our diet are necessary for a fully functioning immune system of the gut. Also, human brain tumours use the AhR system to gain growth advantages. Other aspects covered were neurotoxicology, the circadian rhythm, or the breadth of the adaptive and innate immune system (hematopoietic stem cells, dendritic cells, T cells, mast cells). Finally, the meeting dealt with the discovery of new xenobiotic and natural ligands and their use in translational medicine, or cancer biology and AhR.

An update on the dietary ligands of the AhR. <=SEP=> BACKGROUND: Halogenated aromatic hydrocarbons including dioxins and non-halogenated polycyclic aromatic hydrocarbons are ligands of an aryl hydrocarbon receptor (AhR) and stimulate its transformation. Exposure to these environmental contaminants occurs mainly through diet. Recent articles demonstrated that certain food factors regulate the AhR transformation and expression of downstream drug-metabolizing enzymes. OBJECTIVE: To explain the actions of these food factors on the AhR transformation, as the mechanisms underlying are not fully understood. METHODS: This review introduces recent articles that have demonstrated the molecular mechanisms by which food factors regulate the AhR transformation and downstream drug-metabolizing enzymes. RESULTS/CONCLUSION: The role of classical ligands including dioxins as agonists of the receptor is well documented. As to the food factors, they act as antagonists because they basically suppress the AhR transformation by different mechanisms. Moreover, the fate and metabolism of food factors are important to understand their mechanisms.

Antimutagens and anticarcinogens: a survey of putative interceptor molecules. <=SEP=> In this review recent publications are cited for a number of antimutagens. The molecules surveyed are potential or proven "desmutagens" or "interceptors." These are biologically prevalent or synthetic molecules that are most often small metabolites proficient in binding to, or reacting with, mutagenic chemicals and free radicals. Many of this class of "blocking agents" are "soft" and "hard" nucleophiles with consequently varying abilities to react with particular classes of electrophiles, the major classes of direct-acting mutagens. Although they serve as a first line of defense against mutagens and carcinogens, many interceptor molecules are under-investigated with regard to their spectra of activity and their possible relevance to prophylaxis or treatment of human disease states.

Effects of chlorophyll and chlorophyllin on low-dose aflatoxin B(1) pharmacokinetics in human volunteers. <=SEP=> Chlorophyll (Chla) and chlorophyllin (CHL) were shown previously to reduce carcinogen bioavailability, biomarker damage, and tumorigenicity in trout and rats. These findings were partially extended to humans, where CHL reduced excretion of aflatoxin B(1) (AFB(1))-DNA repair products in Chinese unavoidably exposed to dietary AFB(1). However, neither AFB(1) pharmacokinetics nor Chla effects were examined. We conducted an unblinded crossover study to establish AFB(1) pharmacokinetic parameters among four human volunteers, and to explore possible effects of CHL or Chla cotreatment in three of those volunteers. For protocol 1, fasted subjects received an Institutional Review Board-approved dose of 14C-AFB(1) (30 ng, 5 nCi) by capsule with 100 mL water, followed by normal eating and drinking after 2 hours. Blood and cumulative urine samples were collected over 72 hours, and 14C- AFB(1) equivalents were determined by accelerator mass spectrometry. Protocols 2 and 3 were similar except capsules also contained 150 mg of purified Chla or CHL, respectively. Protocols were repeated thrice for each volunteer. The study revealed rapid human AFB(1) uptake (plasma k(a), 5.05 + or - 1.10 h(-1); T(max), 1.0 hour) and urinary elimination (95% complete by 24 hours) kinetics. Chla and CHL treatment each significantly impeded AFB(1) absorption and reduced Cmax and AUCs (plasma and urine) in one or more subjects. These initial results provide AFB(1) pharmacokinetic parameters previously unavailable for humans, and suggest that Chla or CHL co-consumption may limit the bioavailability of ingested aflatoxin in humans, as they do in animal models.

Molecular pathways for cancer chemoprevention by dietary phytochemicals. <=SEP=> Interest in dietary phytochemicals for potential cancer chemoprevention has increased substantially. Screening dietary compounds for chemopreventive activity however, requires a systematic and wide-ranging approach to encompass the complexity of carcinogenesis. We present some of the molecular pathways that underpin the broad biological processes involved in carcinogenesis. Oxidative stress, inflammation, and the evasion of apoptosis are important biological mechanisms by which carcinogenesis occurs. Subsequently, antioxidant, anti-inflammatory, and pro-apoptotic activity represent important activities for preventing, suppressing, or reversing the development of carcinogenesis. Ultimately, these mechanisms of action may provide a useful basis for screening novel phytochemicals for chemopreventive activity. In this review, we identify the important molecular processes that may be targeted in routine screenings of dietary phytochemicals to ultimately select the most effective potential candidates for cancer chemoprevention.

Natural compounds in the human diet and their ability to bind mutagens prevents DNA-mutagen intercalation. <=SEP=> Human diet may contain many mutagenic or carcinogenic aromatic compounds as well as some beneficial physiologically active dietary components, especially plant food phytochemicals, which act as mutagenesis or carcinogenesis inhibitors. This study compared the binding properties of natural compounds in the human diet (caffeine, theophylline, theobromine, and resveratrol) with a water-soluble derivative of chlorophyll to bind to acridine orange, a known mutagen. An analysis was conducted to determine which substances were effective binding agents and may thus be useful in prevention of chemical-induced mutagenesis and carcinogenesis. Data indicated that in order to bind 50% of the mutagen in a complex, less than twice the concentration of chlorophyllin was needed, the resveratrol concentration was 20-fold higher, while a 1000-fold or even 10,000-fold excess of xanthines were required to bind acridine orange.

Impact of adopting a vegan diet or an olestra supplementation on plasma organochlorine concentrations: results from two pilot studies. <=SEP=> The aim of these studies was to evaluate the potential of some nutritional approaches to prevent or reduce the body load of organochlorines (OC) in humans. Study 1 compared plasma OC concentrations between vegans and omnivores while study 2 verified if the dietary fat substitute olestra could prevent the increase in OC concentrations that is generally observed in response to a weight-reducing programme. In study 1, nine vegans and fifteen omnivores were recruited and the concentrations of twenty-six OC (beta-hexachlorocyclohexane (beta-HCH), p, p'-dichlorodiphenyldichloroethane (p, p'-DDE), p, p'-dichlorodiphenyltrichloroethane (p, p'-DDT), hexachlorobenzene, mirex, aldrin, alpha-chlordane, gamma-chlordane, oxychlordane, cis-nonachlor, trans-nonachlor, polychlorinated biphenyl (PCB) nos. 28, 52, 99, 101, 105, 118, 128, 138, 153, 156, 170, 180, 183 and 187, and aroclor 1260) were determined. In study 2, the concentrations of these twenty-six OC were measured before and after weight loss over 3 months in thirty-seven obese men assigned to one of the following treatments: standard group (33 % fat diet; n 13), fat-reduced group (25 % fat diet; n 14) or fat-substituted group (1/3 of dietary lipids substituted by olestra; n 10). In study 1, plasma concentrations of five OC compounds (aroclor 1260 and PCB 99, PCB 138, PCB 153 and PCB 180) were significantly lower in vegans compared with omnivores. In study 2, beta-HCH was the only OC which decreased in the fat-substituted group while increasing in the other two groups (P = 0.045). In conclusion, there was a trend toward lesser contamination in vegans than in omnivores, and olestra had a favourable influence on beta-HCH but did not prevent plasma hyperconcentration of the other OC during ongoing weight loss.

Nowhere to hide: Chemical toxicants and the unborn child. <=SEP=> Contemporary reproductive aged women and their offspring are facing an unprecedented onslaught of toxicant exposures from myriad sources in their day-to-day life. Public health recommendations regarding optimal diet and nutrition in pregnancy must incorporate several considerations including safety of available foodstuffs, cultural practices and lifestyle issues. Gestational consumption of contaminated seafood remains a potential source of toxicant exposure, including mercury, for the developing child. Health care professionals responsible for the care of women and their developing children need to become apprised of: a) risks associated with toxicant bioaccumulation in pregnancy; b) ongoing information emerging in the important field of reproductive toxicology; and c) strategies within the clinical setting to facilitate nutritional sufficiency and precautionary avoidance of adverse exposure among young women.

Evaluation of background exposures of Americans to dioxin-like compounds in the 1990s and the 2000s. <=SEP=> The US Environmental Protection Agency's 2004 Dioxin Reassessment included a characterization of background exposures to dioxin-like compounds, including an estimate of an average background intake dose and an average background body burden. These quantities were derived from data generated in the mid-1990s. Studies conducted in the 2000s were gathered in an attempt to update the estimates generated by the Reassessment. While these studies suggest declines in the average background dose and body burden, a precise quantification of this decline, much less a conclusion that a decline has indeed occurred, cannot be made because of the inconsistency of study design and data sources, and the treatment of non-detects in the generation of congener average concentrations. The average background intake of the Reassessment was 61.0 pg TEQ/day, and using more current data, the average background intake was 40.6 pg TEQ/day. The average body burden from the surveys in the mid-1990s was 22.9 pg TEQ/g lipid weight (pg/g lwt). More recent blood concentration data, from NHANES 2001/2, suggest an adult average at 21.7 pg/g TEQ lwt. These TEQ values include the 17 dioxin and furan congeners and 3 coplanar PCBs, and were generated substituting ND=(1/2)DL or ND=DL/sq rt (2). Results are provided for ND=0 and analyses conducted to evaluate the impacts of this substitution. A more detailed examination of beef and pork data from similarly designed national statistical surveys show that declines in pork are statistically significant while the beef concentrations appeared to have remained constant between the time periods.

Egg consumption and the risk of cancer: a multisite case-control study in Uruguay. <=SEP=> BACKGROUND: Previous studies have suggested that egg consumption may increase the risk of colorectal cancer and some other cancers. However, the evidence is still limited. To further explore the association between egg intake and cancer risk we conducted a case-control study of 11 cancer sites in Uruguay between 1996 and 2004, including 3,539 cancer cases and 2,032 hospital controls. RESULTS: In the multivariable model with adjustment for age, sex (when applicable), residence, education, income, interviewer, smoking, alcohol intake, intake of fruits and vegetables, grains, dairy products, fatty foods, meat, energy intake and BMI, there was a significant increase in the odds of cancers of the oral cavity and pharynx (OR= 2.02, 95% CI: 1.19-3.44), upper aerodigestive tract (OR= 1.67, 95% CI: 1.17-2.37), colorectum (OR= 1.64, 95% CI: 1.02-2.63), lung (OR= 1.59, 95% CI: 1.10-2.29), breast (OR= 2.86, 95% CI: 1.66-4.92), prostate (OR= 1.89, 95% CI: 1.15-3.10), bladder (OR= 2.23, 95% CI: 1.30-3.83) and all cancer sites combined (OR= 1.71, 95% CI: 1.35-2.17) with a high vs low egg intake. CONCLUSIONS: We found an association between higher intake of eggs and increased risk of several cancers. Further prospective studies of these associations are warranted.