The link between bracken fern and stomach cancer: milk

Food-Borne Chemical Carcinogens and the Evidence for Human Cancer Risk

Commonly consumed foods and beverages can contain chemicals with reported carcinogenic activity in rodent models. Moreover, exposures to some of these substances have been associated with increased cancer risks in humans. Food-borne carcinogens span a range of chemical classes and can arise from natural or anthropogenic sources, as well as form endogenously. Important considerations include the mechanism(s) of action (MoA), their relevance to human biology, and the level of exposure in diet. The MoAs of carcinogens have been classified as either DNA-reactive (genotoxic), involving covalent reaction with nuclear DNA, or epigenetic, involving molecular and cellular effects other than DNA reactivity. Carcinogens are generally present in food at low levels, resulting in low daily intakes, although there are some exceptions. Carcinogens of the DNA-reactive type produce effects at lower dosages than epigenetic carcinogens. Several food-related DNA-reactive carcinogens, including aflatoxins, aristolochic acid, benzene, benzo[a]pyrene and ethylene oxide, are recognized by the International Agency for Research on Cancer (IARC) as causes of human cancer. Of the epigenetic type, the only carcinogen considered to be associated with increased cancer in humans, although not from low-level food exposure, is dioxin (TCDD). Thus, DNA-reactive carcinogens in food represent a much greater risk than epigenetic carcinogens.

Ptaquiloside, the major carcinogen of bracken fern, in the pooled raw milk of healthy sheep and goats: an underestimated, global concern of food safety

Bracken fern (Pteridium aquilinum) is a worldwide plant containing toxic substances, which represent an important chemical hazard for animals, including humans. Ptaquiloside, 1, a norsesquiterpenoid glucoside, is the major carcinogen of bracken detected in the food chain, particularly in the milk from farm animals. To date, ptaquiloside has been shown in the milk of cows feeding on a diet containing bracken fern. This is the first study that shows the systematic detection of ptaquiloside, 1, and reports its direct quantitation in pooled raw milk of healthy sheep and goats grazing on bracken. Ptaquiloside, 1, was detected by a sensitive method based on the chemical conversion of ptaquiloside, 1, into bromopterosine, 4, following gas chromatography-mass spectrometry (GC-MS) analysis. The presence of ptaquiloside, 1, possibly carcinogenic to humans, in the milk of healthy animals is an unknown potential health risk, thus representing a harmful and potential global concern of food safety.

Perfil de propriedades rurais com pastos invadidos por Pteridium arachnoideum na região norte de Mato Grosso e prevalência de hematúria enzoótica bovina

Descreve-se o perfil de 40 propriedades rurais com pastagens invadidas por Pteridium arachnoideum na região norte de Mato Grosso, bem como a prevalência de hematúria enzoótica bovina (HEB) em bovinos de leite e corte nessa região. A HEB foi observada em 15/40 propriedades com prevalências variando entre 0,8 e 16,6%. Aspectos relacionados à implantação das pastagens e manejos utilizados foram discutidos. A maior parte das propriedades que apresentaram HEB possuíam pastagens altamente invadidas pela planta, enquanto que a maioria das propriedades que nunca apresentaram animais acometidos por HEB possuíam pastos com áreas invadidas abaixo de 10%. O desmatamento e a utilização de queimada foram fatores determinantes na invasão de piquetes por P. arachnoidem.

The environmental and human effects of ptaquiloside-induced enzootic bovine hematuria: a tumorous disease of cattle

In this review, we address the major aspects of enzootic bovine hematuria and have placed special emphasis on describing the etiology, human health implications, and advanced molecular diagnosis of the disease.Enzootic bovine hematuria (EBH) is a bovine disease characterized by the intermittent presence of blood in the urine and is caused by malignant lesions in the urinary bladder. This incurable disease is a serious malady in several countries across many continents. Accurate early-stage diagnosis of the disease is possible by applying advanced molecular techniques, e.g., detection of genetic mutations in the urine of cows from endemic areas. Use of such diagnostic approaches may help create an effective therapy against the disease.There is a consensus that EBH is caused primarily by animals consuming bracken fern (P. aquilinum) as they graze. The putative carcinogen in bracken is ptaquiloside(PT), a glycoside. However, other bracken constituents like quercetin, isoquercetin,ptesculentoside, caudatoside, astragalin, and tannins may also be carcinogenic.Studies are needed to identify the role of other metabolites in inducing urinary bladder carcinogenesis.The bovine papilloma virus is also thought to be an associated etiology in causing EBH in cattle. There is growing alarm that these fern toxins and their metabolites reach and contaminate the soil and water environment and that the carcinogen (PT)is transmitted via cow's milk to the human food chain, where it may now pose a threat to human health. An increased incidence of gastric and esophageal cancer has been recorded in humans consuming bracken ferns, and among those living for long periods in areas infested with bracken ferns.Although preliminary therapeutic vaccine trials with inactivated BPV-2 against EBH have been performed, further work is needed to standardize and validate vaccine doses for animals.

Glycophenotypic alterations induced by Pteridium aquilinum in mice gastric mucosa: synergistic effect with Helicobacter pylori infection

The bracken fern Pteridium aquilinum is a plant known to be carcinogenic to animals. Epidemiological studies have shown an association between bracken fern exposure and gastric cancer development in humans. The biological effects of exposure to this plant within the gastric carcinogenesis process are not fully understood. In the present work, effects in the gastric mucosa of mice treated with Pteridium aquilinum were evaluated, as well as molecular mechanisms underlying the synergistic role with Helicobacter pylori infection. Our results showed that exposure to Pteridium aquilinum induces histomorphological modifications including increased expression of acidic glycoconjugates in the gastric mucosa. The transcriptome analysis of gastric mucosa showed that upon exposure to Pteridium aquilinum several glycosyltransferase genes were differently expressed, including Galntl4, C1galt1 and St3gal2, that are mainly involved in the biosynthesis of simple mucin-type carbohydrate antigens. Concomitant treatment with Pteridium aquilinum and infection with Helicobacter pylori also resulted in differently expressed glycosyltransferase genes underlying the biosynthesis of terminal sialylated Lewis antigens, including Sialyl-Lewis^x. These results disclose the molecular basis for the altered pattern of glycan structures observed in the mice gastric mucosa. The gene transcription alterations and the induced glycophenotypic changes observed in the gastric mucosa contribute for the understanding of the molecular mechanisms underlying the role of Pteridium aquilinum in the gastric carcinogenesis process.

A new facile synthesis of d₄-pterosin B and d₄-bromopterosin, deuterated analogues of ptaquiloside

Ptaquiloside (Pta) is a potent carcinogen present in bracken fern and in soil matrices, that can potentially leach to the aquatic environment. More recently its presence in the milk of different farm animals has been reported. Pterosin B (Ptb) and bromopterosin (BrPt) represent the most convenient analogues in the detection of ptaquiloside by mass spectrometry. Pterosin sesquiterpenes are also involved in many patented biomedical protocols. In this work we introduce a new and convenient approach to the synthesis in three steps and more than 80% yield of d₄-pterosin B (d₄-Ptb) and d₄-bromopterosin (d₄-BrPt), useful as internal standards in the quantification of ptaquiloside.

Pteridium aquilinum and its ptaquiloside toxin induce DNA damage response in gastric epithelial cells, a link with gastric carcinogenesis

The multifactorial origin of gastric cancer encompasses environmental factors mainly associated with diet. Pteridium aquilinum-bracken fern-is the only higher plant known to cause cancer in animals. Its carcinogenic toxin, ptaquiloside, has been identified in milk of cows and groundwater. Humans can be directly exposed by consumption of the plant, contaminated water or milk, and spore inhalation. Epidemiological studies have shown an association between bracken exposure and gastric cancer. In the present work, the genotoxicity of P. aquilinum and ptaquiloside, including DNA damaging effects and DNA damage response, was characterized in human gastric epithelial cells and in a mouse model. In vitro, the highest doses of P. aquilinum extracts (40 mg/ml) and ptaquiloside (60 μg/ml) decreased cell viability and induced apoptosis. γH2AX and P53-binding protein 1 analysis indicated induction of DNA strand breaks in treated cells. P53 level also increased after exposure, associated with ATR-Chk1 signaling pathway activation. The involvement of ptaquiloside in the DNA damage activity of P. aquilinum was confirmed by deregulation of the expression of a panel of genes related to DNA damage signaling pathways and DNA repair, in response to purified ptaquiloside. Oral administration of P. aquilinum extracts to mice increased gastric cell proliferation and led to frameshift events in intron 2 of the P53 gene. Our data demonstrate the direct DNA damaging and mutagenic effects of P. aquilinum. These results are in agreement with the carcinogenic properties attributed to this fern and its ptaquiloside toxin and support their role in promoting gastric carcinogenesis.

Risk factors for esophageal and gastric cancers in Shanxi Province, China: a case-control study

OBJECTIVE

Smoking and alcohol consumption explain little of the risk for upper-gastrointestinal (UGI) cancer in China, where over half of all cases in the world occur.

METHODS

We evaluated questionnaire-based risk factors for UGI cancers in a case-control study from Shanxi Province, China, including 600 esophageal squamous cell carcinomas (ESCCs), 599 gastric cardia adenocarcinomas (GCAs), 316 gastric noncardia adenocarcinomas (GNCAs), and 1514 age- and gender-matched controls.

RESULTS

Ever smoking and ever use of any alcohol were not associated with risk of UGI cancer; only modest associations were observed between ESCC risk and highest cumulative smoking exposure, as well as GNCA risk and beer drinking. While several associations were noted for socioeconomic and some dietary variables with one or two UGI cancers, the strongest and most consistent relations for all three individual UGI cancers were observed for consumption of scalding hot foods (risk increased 150-219% for daily vs. never users) and fresh vegetables and fruits (risk decreased 48-70% for vegetables and 46-68% for fruits, respectively, for high vs. low quartiles).

CONCLUSION

This study confirms the minor role of tobacco and alcohol in UGI cancers in this region, and highlights thermal damage as a leading etiologic factor.

Impact of lactose containing foods and the genetics of lactase on diseases: an analytical review of population data

Dairy foods (DFs) contain complex ingredients that could affect different diseases. The control of lactose digestion phenotypically divides populations into those who can [lactase persistent (LP)] and those who cannot [lactase nonpersistent (LNP)] assimilate lactose. LNP subjects, however, can adapt to lactose intolerance through intestinal bacteria. The DF/LNP status interactions may function as disease risk modifiers. We evaluated the relationship between DF and LNP with colorectal, breast, prostate, ovarian, lung, and stomach cancer and inflammatory bowel diseases (IBD; Crohn's disease and ulcerative colitis). Yearly per capita DF consumption, LNP national prevalence, cancer mortality, and incidence of IBD were obtained from several sources. A negative binomial regression model was used to derive incremental risks. There were statistically significant (P <or= 0.05) increases in risk for colorectal and prostate cancer and ulcerative colitis with DFs and a statistically significant decreased risk for stomach cancer. There were trends (P<0.1) for lung and ovarian cancers and Crohn's disease. As LNP prevalence increased, stomach cancer risk increased, whereas risks of all other conditions decreased (P<0.01). In 3 cancers (prostate, ovarian, and breast), meta-analyses of case-based studies support ecological data. In colorectal cancer, on the contrary, meta-analyses of case-based studies suggest protection. The possible importance of distinguishing LNP/LP status in studies is discussed.

Ptaquiloside, the major toxin of bracken, and related terpene glycosides: chemistry, biology and ecology

Bracken (Pteridium spp.) is a ubiquitous fern which has been described as one of the five most common plants on the earth. The toxic effects of bracken on livestock have been recorded since the end of the 19th century, and extensive and intensive investigations for the bracken toxin(s) led to the isolation of ptaquiloside in 1983 as the major, but unstable, toxin of bracken. This review concentrates mainly on the results of the scientific investigations into ptaquiloside, and cites 133 references.

Sorption, degradation and mobility of ptaquiloside, a carcinogenic Bracken (Pteridium sp.) constituent, in the soil environment

Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glucoside produced by Bracken in amounts up to at least 500 mg m(-2). The toxin is transferred from Bracken to the underlying soil from where it may leach to surface and groundwater's impairing the quality of drinking water. The objectives of the present study were to characterize the solubility, degradation and retention of PTA in soils in order to evaluate the risk for groundwater contamination. PTA was isolated from Bracken. The logarithmic octanol-water and ethyl acetate-water partitioning coefficients for PTA were -0.63 and -0.88, respectively, in agreement with the high water solubility of the compound. PTA hydrolysed rapidly in aqueous solution at pH 4 or lower, but was stable above pH 4. Incubation of PTA with 10 different soils at 25 degrees C showed three different first order degradation patterns: (i) rapid degradation observed for acid sandy soils with half life's ranging between 8 and 30 h decreasing with the soil content of organic matter, (ii) slow degradation in less acid sandy soils with half-lives of several days, and (iii) fast initial degradation with a concurrent solid phase-water partitioning reaction observed for non-acid, mostly clayey soils. The presence of clay silicates appears to retard the degradation of PTA, possibly through sorption. Degradation at 4 degrees C was generally of type (iii) and degradation rates were up to 800 times lower than at 25 degrees C. Sorption isotherms for the same set of soils were almost linear and generally showed very low sorption affinity with distribution coefficients in the range 0.01-0.22 l kg(-1) at a solution concentration of 1 mg l(-1) except for the most acid soil; Freundlich affinity coefficients increased linearly with clay and organic matter contents. Negligible sorption was also observed in column studies where PTA and a non-sorbing tracer showed almost coincident break-through. Leaching of PTA to the aqueous environment will be most extensive on sandy soils, having pH >4 and poor in organic matter which are exposed to high precipitation rates during cold seasons.

Occurrence of the carcinogenic Bracken constituent ptaquiloside in fronds, topsoils and organic soil layers in Denmark

Bracken (Pteridium aquilinum (L.) Kuhn) is a common fern found on all continents except Antarctica. It is under suspicion of causing cancer among people who utilizes it as food. The main carcinogenic compound is thought to be the water-soluble compound ptaquiloside. Ptaquiloside-uptake may occur not only through food, but also via drinking water as ptaquiloside might leach from plant material. The purpose of the study was to identify environmental parameters that correlate with the ptaquiloside-content in fronds, and to quantify the amount of ptaquiloside in the soil environment. The ptaquiloside-content in fronds, Oi/Oe-, and Oa/A-horizons was quantified at end of the growth season at 20 sites in Denmark. The fronds had ptaquiloside-contents between 108 and 3795 microgg(-1). The Oi/Oe-horizons had contents between 0.09 and 7.70 microgg(-1), while Oa/A-horizons had contents between 0.01 and 0.09 microgg(-1). The ptaquiloside-content in the standing biomass, which could be transferred to the soil by the end of the growing season, ranged between 10 and 260 mgm(-2), with nine sites having ptaquiloside loads over 100 mgm(-2). The carbon-content in the O-horizon, the precipitation, the amount of Bracken-litter, the turnover rate and the size of Bracken-stands determined the ptaquiloside-content in the soil materials while the content in fronds was found to be a function of the frond-height and the light-exposure in the ecosystem.

Distribution of the carcinogenic terpene ptaquiloside in bracken fronds, rhizomes (Pteridium aquilinum), and litter in Denmark

The distribution of ptaquiloside (PTA) was studied in four Danish bracken populations in order to evaluate the transfer of PTA from ferns to soil. Populations showed statistically significant differences in PTA contents of fronds and rhizomes despite large in-site variations. The highest concentrations were encountered in fronds with concentrations ranging between 213 and 2145 microg/g, while rhizomes had concentrations between 11 and 902 microg/g. PTA was present in soil materials in amounts of 0.22-8.49 microg/g but apparently with no correlation with PTA contents of fronds or rhizomes. Laboratory tests showed that water could leach PTA from bracken fronds, which is in support of the high soil contents observed at sites exposed to heavy showers just before sampling. The observed soil contents correspond to estimated soil solution concentrations of 200-8500 microg/liter, demonstrating a substantial risk of PTA contamination of surface water and groundwater.