Analysis of aflatoxin B1 in human tissues with high-pressure liquid chromatography

Upregulation of miR-34a-5p antagonizes AFB1-induced genotoxicity in F344 rat liver

Aflatoxin B1 (AFB1) is a well-known human hepatotoxicant and genotoxicant. Recent studies demonstrated that aberrant miRNA expression patterns were correlated with the cellular and genetic lesions induced by chemicals. To explore the role of miRNAs in AFB1-induced hepatotoxicity and genotoxicity, we examined alterations in miRNA expression patterns in F334 rat livers after exposure to 100 μg/kg or 200 μg/kg AFB1 for 28 days. Using high-throughput sequencing, we discovered that rno-miR-34a-5p, rno-miR-200b-3p, and rno-miR-429 were up-regulated and that rno-miR-130a-3p was down-regulated in liver tissue from rats that received 200 μg/kg of AFB1; this finding was validated by real-time PCR. AFB1 treatment resulted in the upregulation of rno-miR-34a-5p and rno-miR-200b-3p in the rat H-4-II-E cell line similar to our in vivo observations. Moreover, rno-miR-34a-5p was transcriptionally elevated via p53 activation after AFB1 exposure. Upregulation of rno-miR-34a-5p suppressed the expression of the cell cycle-related genes CCND1, CCNE2 and MET and led to cell cycle arrest in the G0-G1 phase. The CBMN assay indicated that inhibition of rno-miR-34a-5p and p53 expression aggravated the DNA damage induced by AFB1, which might be associated with shortening of the DNA damage repair period. Circulating miR-34a-5p in rat sera preceded a significant increase in ALT activity and other miRNAs in the 100 μg/kg AFB1 group. These observations demonstrated that rno-miR-34a-5p responded sensitively to AFB1 exposure and facilitated p53 repair of DNA damage by impacting the cell cycle. Thus, circulating rno-miR-34a-5p may be a sensitive indicator for the induction of hepatic genotoxicity by AFB1 in rats.

Serum aflatoxin levels of the healthy adult population living in the north and south regions of Turkey

OBJECTIVE

To determine the serum concentrations of aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1) and aflatoxin G2 (AFG2) in the healthy adult population living in both the Black Sea and Mediterranean regions of Turkey and to investigate the regional, seasonal and gender variability in aflatoxins (AF) exposure in these regions.

DESIGN

Serum AFB1, AFB2, AFG1 and AFG2 concentrations were analysed by HPLC. Settings In total, four hundred and eighty-four serum samples were analysed.

SUBJECTS

Four hundred and eighty-four healthy adult volunteers living in rural areas of the Black Sea and Mediterranean regions of Turkey were studied.

RESULTS

The mean serum concentration of total AF in the Black Sea region was 1·33 ppb (min-max 0·15-3·38 ppb) and 0·90 ppb (min-max 0·18-2·48 ppb) for summer and winter, respectively. In the Mediterranean region, the mean serum concentration of total AF was determined as 0·55 ppb (range 0·04-1·72 ppb) for summer and 0·45 ppb (range 0·12-1·43 ppb) for winter. The total AF concentrations in serum samples were statistically higher in summer compared with winter for the two regions. The differences between the regions were statistically significant concerning all samples, with higher total AF concentrations in the Black Sea region.

CONCLUSIONS

The overall results suggest that the Turkish population living in these two regions is continuously exposed to AF, particularly in the summer, and that mycotoxin contamination in food should be monitored routinely for food safety and human health.

Human exposure to mycotoxins in Egypt

This investigation examined the exposure of Egyptian infants to Aflatoxin M1 (AfM1) and of lactating mothers to Aflatoxin B1, using AfM1 in human milk as a biomarker for exposure to AfB1. The presence of ochratoxin A (OA) in human milk was also investigated to determine the levels of infants exposure to OA from human milk. The results indicated that AfM1 was found in 66 (55 %) of 120 human milk samples with a mean of 0.3 ± 0.53 ng/mL (range 0.02 to 2.09 ng/mL). OA was found in 43 (35.8 %) of 120 human milk samples with a mean of 21.1 ± 13.7 ng/mL (range 5.07 to 45.01 ng/mL), which will cause a daily intake of OA from human milk exceeding the suggested tolerable dose of 5 ng/kg-1 of OA body weight. On the other side AfM1 was found in 25 % of blood samples (5 out of 20 samples), at a mean of 1.18 ng/mL, but it was detected only in one urine sample (1 out of 20 samples). OA was detected only in 2 out of 13 blood samples (15.4 %) with an average 3.67 ng/mL. Whereas OA was not detected in all analyzed urine samples.

Aflatoxicosis in turkey poults is prevented by treatment of naturally contaminated corn with ozone generated by electrolysis

Previous studies have demonstrated that a novel source of ozone gas (O3) maybe used to chemically degrade numerous mycotoxins, including aflatoxin (AF) B1. Subsequent in vitro analyses demonstrated detoxification of AFB1, suggesting a potential method of remediate AF-contaminated grain. The objective of this study was to evaluate the capability of electrochemically produced ozone to degrade AFB1 in naturally contaminated whole kernel corn and confirm detoxification in turkey poults. Corn was procured from the southern coastal areas of Texas and HPLC revealed 1,220 +/- 73.3 ppb AFB1. Control and contaminated corn were treated for 92 h with O3 at 200 mg/min in 30 kg batches; greater than 95% reduction of AFB1 in contaminated corn was achieved. One-day-old female turkey poults were fed 1) control corn, 2) control corn + O3, 3) AFB1 corn, or 4) AFB1 corn + O3 mixed in rations (46% by wt.) and consumed ad libitum for 3 wk. When compared with controls, turkeys fed AFB1 corn had reduced body weight gain and relative liver weight, whereas turkeys fed control corn + O3 or AFB1 corn + O3 did not differ from controls. Furthermore, alterations in the majority of relative organ weight, liver discoloration, serum enzyme activity, hematological parameters, and blood chemistry caused by AFB1 were eliminated (no difference from controls) by treatment with O3. These data demonstrate that treatment of contaminated corn with electrochemically produced O3 provided protection against AFB1 in young turkey poults. It is important to note that treatment of control corn with O3 did not alter the performance of the turkey poults.

Oxidative degradation and detoxification of mycotoxins using a novel source of ozone

Practical methods to degrade mycotoxins using ozone gas (O3) have been limited due to low O3 production capabilities of conventional systems and their associated costs. Recent advances in electrochemistry (i.e. proton-exchange membrane and electrolysis technologies) have made available a novel and continuous source of O3 gas up to 20% by weight. It is possible that the rapid delivery of high concentrations of O3 will result in mycotoxin degradation in contaminated grains--with minimal destruction of nutrients. The major objectives of this study were to investigate the degradation and detoxification of common mycotoxins in the presence of high concentrations of O3. In this study, aqueous equimolar (32 microM) solutions of aflatoxins B1 (AfB1), B2 (AfB2), G1 (AfG1), G2 (AfG2), cyclopiazonic acid (CPA), fumonisin B1 (FB1), ochratoxin A (OA), patulin, secalonic acid D (SAD) and zearalenone (ZEN) were treated with 2, 10 and/or 20 weight% O3 over a period of 5.0 min and analysed by HPLC. Results indicated that AfB1 and AfG1 were rapidly degraded using 2% O3, while AfB2 and AfG2 were more resistant to oxidation and required higher levels of O3 (20%) for rapid degradation. In other studies, patulin, CPA, OA, SAD and ZEN were degraded at 15 sec, with no by-products detectable by HPLC. Additionally, the toxicity of these compounds (measured by a mycotoxin-sensitive bioassay) was significantly decreased following treatment with O3 for 15 sec. In another study, FB1 (following reaction with O3) was rapidly degraded at 15 sec, with the formation of new products. One of these appeared to be a 3-keto derivative of FB1. Importantly, degradation of FB1 did not correlate with detoxification, since FB1 solutions treated with O3 were still positive in two bioassay systems.

Effect of peanut tannin extracts on growth of Aspergillus parasiticus and aflatoxin production

Twenty-three peanut (Arachis hypogaea L.) genotypes were evaluated for kernel resistance to Aspergillus parasiticus Spear. colonization and aflatoxin contamination when incubated under high relative humidity. Also, tannin-containing extracts from kernel coats (testae) and cotyledons of these genotypes were prepared and tested for their effect on A. parasiticus growth and aflatoxin production in vitro. The lowest degree of colonization, less than 30%, was noted in kernels from the genotypes, Toalson x UF 73-4022 (selections TX-798731 and TX-798736), A72118, SN 55-437, PI337409, and Florunner. Genotypes with low levels of colonization also had the lowest aflatoxin contamination. The coefficient of correlation between infection frequency and aflatoxin contamination was 0.66. Higher levels of tannins were detected in the testae (23.9-97.2 mg g tissue) compared to the cotyledons (0.17-0.82 mg g tissue). Some of the methanol-extracted and water-soluble tannin extracts from testae and cotyledons, when incorporated in yeast extract sucrose liquid medium (100 mg l), significantly inhibited A. parasiticus growth and reduced the levels of aflatoxin produced. There was no overall correlation between the peanut genotypes and the influence of tannin extracts on A parasiticus growth and aflatoxin production. However, correlations were higher for specific genotypes. For example, the coefficient of correlation between the ability of tannin extracts from testae of genotypes PI337409 and TX-798736 to inhibit aflatoxin production was 0.93 and 0.85 respectively.

Aflatoxin B1 formamidopyrimidine adducts in human hepatocarcinogenesis: a preliminary report

The presence of aflatoxin-B1-formamidopyrimidine, a persistent aflatoxin-deoxyribonucleic acid (DNA) adduct, was investigated in vivo by immunohistochemical analysis in 14 paired hepatocellular carcinoma and nontumorous human liver tissue sections using a monoclonal anti-aflatoxin-B1-formamidopyrimidine antibody. Nuclear and cytoplasmic accumulations of adducts were found in 4 of 14 nontumorous specimens but in none of 14 tumorous tissues and in none of three normal control livers. In vitro adduct formation and cellular DNA was investigated with a modified DNA immunoblot assay. These studies revealed (a) no significant difference in the amount of adduct formed by DNA samples with or without integrated hepatitis B virus DNA, (b) no difference in the amount of adduct formed with DNA from either tumorous or nontumorous tissues from a given individual, and (c) remarkable and reproducible differences in the capacity of DNA from different individuals to form in vitro adducts. Our DNA immunoblot assay will facilitate further studies on the molecular role of aflatoxin-B1-form-amidopyrimidine adducts in human hepatocarcinogenesis.

An ELISA method for the rapid and simple determination of aflatoxin in human serum

A rapid, simple method for the determination of aflatoxin in human serum using anti-aflatoxin antisera in an indirect, double antibody microtitration plate enzyme-linked immunosorbent assay (ELISA) is described. Direct assay of serum necessitated the availability of a large sample volume, due to the presence of 'non-specific' interference. Addition of methanol to sera removed the interference enabling the analysis to be performed on small volumes (0.5 ml) of serum. The sensitivity of the assay is 20 pg ml-1. Total assay time, including sample preparation, is 4.5 h. No aflatoxin was found in any of the UK samples analysed.

Analysis of UK sera for aflatoxin by enzyme-linked immunosorbent assay

1. Aflatoxins are toxic, carcinogenic secondary fungal metabolites produced by certain moulds that commonly infest foods. Measurement of aflatoxins in human serum would give a direct measurement of exposure. 2. Twenty-seven serum samples from UK blood donors were found to contain aflatoxin levels not greater than 64 pmol/l (20 pg/ml) by an enzyme-linked immunosorbent assay. 3. These findings may indicate that present UK guideline tolerances for aflatoxin in imported food are effective in limiting human exposure to toxic aflatoxins in the UK diet, though further work would be needed to confirm this. In particular, sub-populations suspected of being at higher risk may need special considerations.

Characterization of the aflatoxin B1-binding site of rat albumin

A fluorescence-enhancement method was used to investigate the non-covalent interaction between aflatoxin B1 and rat albumin. Solvent-induced shifts in the emission spectrum of aflatoxin B1 provided evidence that the aflatoxin B1-binding site of rat albumin is a highly nonpolar environment. A dissociation constant of 20 microM was determined at 20 degrees C. The possibility that aflatoxin B1 binds one of the three major drug sites of albumin was investigated by ligand-displacement experiments. Mechanisms whereby marker ligands displace aflatoxin B1 were further investigated by comparing the experimental binding parameters with those derived theoretically, assuming competitive binding. The results indicate that: aflatoxin B1 and phenylbutazone compete for a common high-affinity site on rat albumin; high-affinity binding of aflatoxin B1 and site-II marker ligands takes place independently; aflatoxin B1 does not compete with either cholate or warfarin for the same high-affinity site, but the simultaneous binding of warfarin or cholate negatively modulates the binding of aflatoxin B1 to albumin. Fluorescence energy-transfer studies show that the lone tryptophan residue, Trp-214, is not associated with the aflatoxin B1-binding site.

Aflatoxins and kwashiorkor: clinical studies in Sudanese children

Aflatoxin analysis of blood and urine by high performance liquid chromatography in 584 Sudanese children is reported. The results in 404 malnourished children comprising 141 kwashiorkor, 111 marasmic kwashiorkor and 152 with marasmus are compared with 180 age-matched controls and correlated with clinical findings. The aflatoxin detection rate and mean concentration were higher in serum of children with kwashiorkor than the other groups. The difference between the detection rate in kwashiorkor and controls was significant (p less than 0.05). The aflatoxin detection rate in urine was highest in the marasmic kwashiorkor group and the mean concentration was higher in the marasmic kwashiorkor and marasmic groups than in the kwashiorkor and control groups. There were important differences in the detection of certain aflatoxins between the groups. Aflatoxicol was detected in the sera of 16 (11.6%) kwashiorkor, in six (6.1%) marasmic kwashiorkor, but in none of the controls and only once in marasmus. These differences are highly significant (p less than 0.0001). The ratio of AFB1 to AFM1 was higher in the sera and urines of kwashiorkors than in controls, suggesting that the normal transformation of AFB1 to AFM1 may be impaired in kwashiorkor with consequent increase in transformation of AFB1 to aflatoxicol. The study therefore provides evidence of differences in the metabolism of aflatoxins in children with kwashiorkor compared with children with other forms of malnutrition and normally nourished children and confirms the association between aflatoxins and kwashiorkor contained in a preliminary report on this work.

Reye syndrome

Reye syndrome has emerged as the quintessential example of an acute metabolic encephalopathy with an annual incidence ranging from 0.3 to 6.0 cases per 100,000 children. The general management has become standardized, and the mortality has declined to approximately 10 per cent. The role of aspirin in the etiopathogenesis remains controversial.