Article

Skin Absorption as a Route of Exposure for Aflatoxin and Trichothecenes

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Abstract

Airborne occurrence of mycotoxins in agricultural and residential environments has generated concern that these toxins may be absorbed via the skin and respiratory tract. This paper summarizes information available on the in vivo and in vitro cutaneous permeability of several mycotoxins (aflatoxin, T-2 toxin [T-2], diacetoxyscirpenol, and verrucarin A). Published data is used to calculate the dose absorbed during cutaneous exposure to fungal toxins in hypothetical agricultural and research laboratory environments. These estimated doses of T-2 (0.004 and 0.041 μg/kg, respectively) were 25,000 and 2,439 times less than a reported oral dose (100 μg T-2/kg/day) which caused immunosuppression in monkeys. In general, exposure of human skin to aflatoxin and trichothecenes results in slow absorption. The risk of systemic toxicity resulting from dermal exposure increases in the presence of high toxin concentrations, occlusion, and vehicles which enhance penetration.

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... The ethanolic-water mixture was chosen as solvent, not only for solubility reasons, but also as a reasonable worst case model formulation seen "penetration enhancers" like ethanol are most probably also present in real-life. Caution must also be taken when cleaning skin surfaces exposed to mycotoxins, as certain decontaminating solvents and excessive skin rubbing may enhance skin absorption (Kemppainen, 1988). EtOH/H 2 O mixtures have penetration promoting effects by extraction of the lipids and changing the skin's protein conformation (Artusi et al., 2004). ...
... In our study, a K p of 2.11 × 10 −4 cm/h was found. Factors like the skin thickness and formulation could be the reason for these different observations (Kemppainen, 1988). Literature data of T-2 are more consistent with our findings. ...
... For DAS and VCA, about 50% and 80% was metabolized in skin, respectively (Kemppainen et al., 1987a). T-2 toxin has been metabolized extensively (up to 90%), with HT-2 toxin as the major metabolite (80%) in human skin, followed by T-2 tetraol, T-2 triol, which all are less toxic than T-2 toxin itself (Kemppainen, 1988;Kemppainen et al., 1987b). Moreover, 3 -hydroxy-T-2, 3 -hydroxy-HT-2, 3 -hydroxy-T-2 triol, and actyl-T-2 toxin, were tentatively identified in human skin (Wu et al., 2010). ...
... This is important because the skin is the major interface between the body and surrounding environment, and there is a chance that the skin of grain handling workers as well as of domestic animals is exposed to mycotoxins [10][11][12] . Concerning this point, it has been shown that such mycotoxins as aflatoxin B1 (AFB1) [13][14][15] and T-2 toxin 14,16,17 readily penetrate through human and animal skin and cause systemic toxic effects in their respective organs and also in the brain 18 . Recently, Boonen et al. examined the transdermal kinetics of seven kinds of mycotoxins, AFB1, OTA, FB1, citrinin (CTN), zearalenone (ZEN) and T-2 toxin, using human skin in an in vitro Franz diffusion cell setup 19 , and they reported that except for FB1, all mycotoxins penetrate through the skin and that OTA shows the highest penetration 19 . ...
... This is important because the skin is the major interface between the body and surrounding environment, and there is a chance that the skin of grain handling workers as well as of domestic animals is exposed to mycotoxins [10][11][12] . Concerning this point, it has been shown that such mycotoxins as aflatoxin B1 (AFB1) [13][14][15] and T-2 toxin 14,16,17 readily penetrate through human and animal skin and cause systemic toxic effects in their respective organs and also in the brain 18 . Recently, Boonen et al. examined the transdermal kinetics of seven kinds of mycotoxins, AFB1, OTA, FB1, citrinin (CTN), zearalenone (ZEN) and T-2 toxin, using human skin in an in vitro Franz diffusion cell setup 19 , and they reported that except for FB1, all mycotoxins penetrate through the skin and that OTA shows the highest penetration 19 . ...
Article
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Among the many mycotoxins, T-2 toxin, citrinin (CTN), patulin (PAT), aflatoxin B1 (AFB1) and ochratoxin A (OTA) are known to have the potential to induce dermal toxicity and/or tumorigenesis in rodent models. T-2 toxin, CTN, PAT and OTA induce apoptosis in mouse or rat skin. PAT, AFB1 and OTA have tumor initiating properties, and OTA is also a tumor promoter in mouse skin. This paper reviews the molecular mechanisms of dermal toxicity and tumorigenesis induced in rodent models by these mycotoxins especially from the viewpoint of oxidative stress-mediated pathways.
... Earlier studies have reported that mycotoxins can penetrate through human and animal skin causing toxicological manifestations in their target organs [19,20,34,35]. Since skin penetration potential of DON has not been assessed earlier, it was observed that DON has skin penetration potential but permeates with a low rate through mice skin. ...
... Since skin penetration potential of DON has not been assessed earlier, it was observed that DON has skin penetration potential but permeates with a low rate through mice skin. The skin permeation potential of DON even in low amounts cannot be neglected as the risk of systemic toxicity after dermal exposure might increase with an increase in toxin concentrations, repeated exposure rates and vehicles which can enhance penetration potential of the mycotoxins [35]. This was evident in the previous study where twentyfour weeks of topical application of DON led to enlargement in Peyer's patches in mouse intestine which is the target organ for DON [22]. ...
Article
Exposure to mycotoxins is mostly by ingestion but also occurs by the dermal and inhalation routes. The present study for the first time demonstrated that mycotoxin Deoxynivalenol (DON), permeates through Swiss albino mice skin, which demands awareness of health risks in people who are dermally exposed to mycotoxins especially agricultural farmers. Despite the widespread contamination of DON in food commodities studies to alleviate DON's toxicity are sparsely reported. Thus effective measures to combat mycotoxins associated toxicity remains an imperative aspect to be considered from the angle of dermal exposure. Topical application of Celecoxib (1–2 mg), followed by DON (100 μμg) application on the dorsal side of mice, resulted in substantial decrease in DON-induced (i) edema, hyperplasia, cell proliferation (ii) inhibition of cytokine and prostaglandin-E2 levels (iii) phosphorylation of ERK1/2, JNK, p38, MAPKKs, CREB, P90-RSK (iv) downregulation of c-Jun, c- Fos, phospho-NF-kB and their downstream target proteins cyclin D1 and COX-2. Using Ro-31-8220 (Protein-Kinase-C inhibitor), it was observed PKC was responsible for DON induced upregulation of COX-2 and iNOS proteins. Treatment of Celecoxib decreased DON-induced translocation of Protein Kinase C isozymes (α,ε,γ), demonstrating the role of PKC in DON-mediated biochemical and molecular alterations responsible for its dermal toxicity. The present findings indicate that topical application of celecoxib is effective in the management of inflammatory skin disorders induced by foodborne fungal toxin DON. The skin permeation potential of Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor NSAID, was also assessed, and the results indicated that the permeation was relatively lower as compared to the oral mode of administration. Hence topical use of celecoxib may be preferred over oral dosing because of lower systemic absorption and to avoid the unwanted side effects. This study provides a prospect for exploring the clinical efficacy of topically applied COX-2 inhibitors for the management of inflammatory skin disorders induced by foodborne fungal toxins.
... 6,7 However, other exposure routes include inhalation and direct contact through the skin or the mucosa. [18][19][20] Continuous long-term exposure to AFs in low quantities, either via occupational inhalation or dietary consumption, are both linked to adverse health outcomes. [21][22][23] Both routes of exposure have been associated with mucous membrane irritation, nausea, immune suppression, acute and chronic liver illnesses, and carcinogenesis. ...
... Even though the role of dermal contact for the total AFB 1 internal dose is still unclear, two studies have shown than the skin is permeable to AFB 1 . 18,19 The skin as an exposure route can have a significant role if the workers are involved in intense physical work and are sweating. 39 Dermal absorption is prevalent where workers do not wear personal protective clothing and are in direct contact with contaminated products. ...
Article
Aflatoxins [AFs] are secondary metabolites of the fungus species Aspergillus spp. Both animal and epidemiological studies provided sufficient evidence on the carcinogenic, immuno-toxic, mutagenic, and genotoxic potential of AFs. While inges-tion is the main route of exposure for AFs through consumption of contaminated food products, agricultural workers and personnel who handle AF-contaminated grains are also at higher risk of exposure via inhalation. The main objective of the review is to provide a comprehensive overview of past scientific studies on occupational exposure to AFs, high-risk occupations, and disease outcomes. A search of peer-reviewed articles was done on PubMed and Web of Science Databases. A total of 164 papers was identified and 61 journal articles were selected for further review. High risk occupations include animal husbandry and processing of grain cereals and/or animal feed. Primary liver cancer and respiratory cancers were the most reported as a result of occupational exposure to AFs. For future studies, improved study designs, better characterization of AFs exposure in an occupational setting, and use of biomarkers are recommended in order to promote better understanding of occupational exposure to AFs and the resulting disease burden among workers.
... Ochratoxin A immunotoxicity can increase the risk of infectious diseases and accounts for economic loss to the poultry sector. Although the oral route of OTA exposure is frequently employed in studies to evaluate the effects on the immune system, this is not an exclusive route of contamination; humans and animals may also be contaminated through skin absorption [18,19]. To date, there are no data on birds, but an in vitro human skin model demonstrated higher diffusion of OTA compared to other mycotoxins (AFB1, FB1, CIT, ZEA, and T-2) [20]. ...
... Although the skin absorption route is an important route of low molecular weight chemicals [24], it is often overlooked in relation to mycotoxins, which also present small molecular weight [19]. Mycotoxins are able to penetrate through human skin [18,20,25] and OTA is a mycotoxin that demonstrates high ability to diffuse through human skin [20]. ...
Article
Full-text available
Ochratoxin A (OTA), an immunosuppressive mycotoxin, can increase the risk of many infectious diseases and contribute to economic losses to the poultry industry. The immunosuppressive effect has mainly been investigated through oral exposure; however, birds may also be contaminated through skin absorption. The present study investigated the influence of OTA exposure on the defense system of broiler chicks through the subcutaneous route and including low doses. Groups of broiler chicks (Cobb), 05 days old, were exposed to subcutaneous inoculation of OTA at concentrations of 0.1; 0.5; 0.9; 1.3; and 1.7 mg OTA/kg body weight. The size of the lymphoid organs, circulating immune cells, and total IgY and IgA levels were evaluated 21 days post inoculation. Subcutaneous OTA exposure decreased the weight of the thymus, spleen, and bursa of Fabricius, and leukocytopenia (p < 0.05) was detected in chicks of the OTA treated groups. In a dose-dependent way, decreased levels of circulating lymphocytes and heterophils (p < 0.05), and increased levels of monocytes (p < 0.05) were detected. Decreased IgY and IgA serum concentrations were noted in the OTA treated groups (p < 0.05). In conclusion, subcutaneous OTA exposure induces immunosuppression even at low levels.
... [12][13][14] Mycotoxins on the fungal spores are easily absorbed by the airways, intestinal lining, and skin. 15 The word mycotoxin is derived from "myco" meaning fungus and "toxin" meaning naturally produced poison. Fungi probably developed toxins to serve as a chemical defense against insects, microorganisms, nematodes, grazing animals, and humans. ...
Article
Full-text available
Disease associated with exposure to mycotoxins is known as the "Great Masquerader" of the 21st century because of its complex natural history involving different tissues and resembling different diseases at each stage in its evolution. It can present with a variety of nonspecific clinical signs and symptoms such as rash, conjunctivitis, epistaxis, apnea, cough, wheezing, nausea, and vomiting. Some cases of vomiting illness, bone marrow failure, acute pulmonary hemorrhage, and recurrent apnea and/or "pneumonia" are associated with exposure to mycotoxins. Familiarity with the symptoms of exposure to the major classes of mycotoxins enables the clinician to ask pertinent questions about possible fungal exposures and to remove the infant or child from the source of exposure, which could be contaminated food(s), clothing and furniture, or the indoor air of the home. Failure to prevent recurrent exposure often results in recurrent illness. A variety of other conditions, including hepatocellular and esophageal cancer and neural tube defects, are associated with consumption of foods contaminated with mycotoxins. Awareness of the short- and long-term consequences of exposures to these natural toxins helps pediatricians to serve as better advocates for children and families.
... Se ha reportado que la aflatoxina B 1 se absorbe lentamente por piel, aunque esta absorción se ve afectada por la concentración, el solvente, la solubilidad y la diferencia de especie. 42 Al administrar AFB 1 a ratones moteados se observó una fuerte y persistente acumulación no sólo en el hígado, sino también en tejidos pigmentados. No se conoce la implicación biológica que pueda tener esta acumulación, pero una unión preferencial de la AFB 1 a la melanina podría indicar un potencial de este compuesto para la inducción de melanomas. ...
Article
Full-text available
En México se ha detectado la presencia AFB1 en humanos: como mutación en el gene p53 en hepatocarcinomas de pacientes de Monterrey, Nuevo León, México, en 1996 y como aducto AFB1-lisina en suero de pacientes del Instituto Mexicano del Seguro Social de Matamoros, Tamaulipas, México, en 2003. La aflatoxina B1 ha sido clasificada por la Agencia Internacional para Investigación en Cáncer como un agente carcinogénico para humanos. Este compuesto es un contaminante natural encontrado en alimentos y es sintetizado por Aspergillus flavus y/o A. parasiticus cuando estos hongos crecen en diversos productos alimenticios. Considerando el riesgo que este compuesto representa para los seres humanos, en el presente artículo se revisa y analiza, a nivel molecular, su capacidad carcinogénica, mutagénica y tóxica y se ilustra su relación causal con hepatocarcinomas en humanos. Se destaca que la capacidad carcinogénica y mutagénica están determinadas por la AFB1-formamidopirimidina, la cual causa errores en las transcripciones del ADN. Los resultados ilustran que la población mexicana está consumiendo alimentos con bajas concentraciones de AFB1. La toxicidad es consecuencia de la acción carcinogénica en el hígado.
... This is an important aspect from the point of view of developing countries including India where manual labor is employed during pre-and postharvest stages of agriculture, thus indicating a probable cause of exposure through dermal route. Earlier studies have shown that mycotoxins like aflatoxin-B1 (AFB1) and trichothecenes (T-2 Toxin) readily penetrates through human skin and causes systemic toxic effects in their respective target organs (Kemppainen et al., 1987(Kemppainen et al., , 1988. In this regard, our prior studies have revealed that dermal exposure to AFB1 and patulin resulted in toxicological injury in skin (Rastogi et al., 2006;Saxena et al., 2009). ...
Article
The mycotoxin, citrinin (CTN), is a contaminant of various food and feed materials. Several in vivo and in vitro studies have demonstrated that CTN has broad toxicity spectra; however, dermal toxicity is not known. In the present investigation, dermal exposure to CTN was undertaken to study oxidative stress, DNA damage, cell cycle arrest, and apoptosis in mouse skin. A single topical application of CTN caused significant change in oxidative stress markers, such as lipid peroxidation, protein carbonyl content, glutathione (GSH) content, and antioxidant enzymes in a dose-dependent (25-100 μg/mouse) and time-dependent (12-72 h) manner. Single topical application of CTN (50 μg/mouse) for 12-72 h caused significant enhancement in (1) reactive oxygen species (ROS); (2) cell cycle arrest at the G0/G1 phase (30-71%) and G2/M phase (56-65%) along with the induction of apoptosis (3.6-27%); (3) expression of p53, p21/waf1; (4) Bax/Bcl₂ ratio and cytochome c release; and (5) activities of caspase 9 (22-46%) and 3 (42-54%) as well as increased poly(ADP-ribose) polymerase cleavage. It was also observed that pretreatment with bio-antioxidants viz butylated hydroxyanisole (55 μmol/100 μl), quercetin (10 μmol/100 μl), or α-tocopherol (40 μmol/100 μl) resulted in decreases of ROS generation, arrest in the G0/G1 phase of the cell cycle, and apoptosis. These data confirm the involvement of ROS in apoptosis and suggest that these bio-antioxidants may be useful in the prevention of CTN-induced dermal toxicity.
... [101][102][103][104] Studies on aflatoxin contamination by dermal contact are few; however, it has been shown that AFB 1 can penetrate the outermost layer of the skin, and although absorption is slow, a high concentration can generate a possible health risk for people who are in contact with contaminated material. [105][106][107] Rastogi, et al. [108] verified in a model study with mice that dermal contact with AFB 1 promotes tumor formation; in addition, AFB 1 metabolites in the skin can be transported to the liver through the blood. Finally, they indicated that prolonged exposure to this aflatoxin can lead to liver carcinogenesis. ...
Article
Aflatoxins generate great concern worldwide regarding their impact on health; they are associated with liver cancer and have an economic impact on agricultural products, as they lead to rejection of food products due to noncompliance with quality standards and affect the health of consumers. Aflatoxins are commonly found in the three most important cereals in the world, namely, maize, rice, and wheat; moreover, they have been reported in different areas of the world (Africa, America, Asia, and Europe). A higher occurrence of aflatoxins is associated with areas with high humidity and temperatures, which favor the growth of toxigenic fungi such as Aspergillus flavus and Aspergillus parasiticus. Few studies have focused on the presence of aflatoxins in cereals; therefore, the objective of this article is to review the occurrence of aflatoxins worldwide with an emphasis on maize, wheat and rice, as well as the economic impact, health effects, and main decontamination methods to reduce aflatoxins. Different aflatoxin control strategies have been reported for cereals, including physical, chemical, and biological methods, with results ranging from a 14% reduction to complete elimination, depending on the decontamination strategy used, food, concentration, and type of aflatoxins.
... Se ha reportado que la aflatoxina B 1 se absorbe lentamente por piel, aunque esta absorción se ve afectada por la concentración, el solvente, la solubilidad y la diferencia de especie. 42 Al administrar AFB 1 a ratones moteados se observó una fuerte y persistente acumulación no sólo en el hígado, sino también en tejidos pigmentados. No se conoce la implicación biológica que pueda tener esta acumulación, pero una unión preferencial de la AFB 1 a la melanina podría indicar un potencial de este compuesto para la inducción de melanomas. ...
Article
Full-text available
The presence of AFB1 in human beings was detected in Mexico in 1996 both as a mutation of the gene p53 in hepatocellular carcinomas in Monterrey, Mexico, and as the adduct AFB1-lysine in serum from patients in Matamoros, Mexico in 2003. Aflatoxin B1 has been classified as a carcinogenic agent to humans by the International Agency for Research on Cancer. The compound is a natural contaminant produced by Aspergillus flavus and/or A. parasiticus when these fungi grow on different food products. At the molecular level, this review covers the carcinogenic, mutagenic and toxic properties of these mycotoxins and their risk to humans. It also gives insight into the causal relationship between aflatoxins and hepatocellular carcinoma. Information is provided about AFB1-formamidopyrimidine, which is a determinant of the carcinogenic and mutagenic capabilities. The results suggest that the Mexican population ingests food containing low amounts of AFB1. Analyses is presented of AFB1 toxicity, which is a consequence of the carcinogenic activity in liver cells.
... Exhaust ventilation and the use of masks are some of the most common measures applied. Additionally, previous studies have shown, as mentioned already, that skin is permeable to AFB1 and other mycotoxins (Kemppainen et al., 1988;Boonen et al., 2012) and this exposure route can have a significant role in some occupational settings, particularly if the workers are sweating due to tasks involving high metabolic rates or if they use short clothes. In this case is important to protect skin and to follow strict hygienic procedures after work. ...
Chapter
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This chapter presents an overview of current chemometric tools utilized for the evaluation of several mycotoxins often found in foodstuff, such as cereals, peanuts, pistachio nuts and condiments. Mycotoxins are compounds produced as a result of the secondary metabolism of fungus, such as Aspergillus, Fusarium and Pénicillium. Because of their harmful effect in animals and humans, their levels in food are strictly controlled. Discussions are focused on the analysis of first and second-order data generated through several techniques such as near infrared spectroscopy, fluorescence spectroscopy and high performance liquid chromatography with diode array detector. This review manuscript describes the algorithms frequently used to model this type of data, including Partial Least Squares (PLS) regression, Parallel Factor Analysis (PARAFAC) and Multivariate Curve Resolution Alternating Least Squares (MCR-ALS). These multivariate calibration methods allow the quantification of multiple analytes in complex food samples with the application of minimum pre-treatment techniques. Another important chemometric tool commented in this review is the Response Surface Method (RSM), commonly applied in the optimization of experimental procedures and chemical measurements. This chapter discusses the different strategies implemented for the analysis of a wide spectrum of mycotoxins, as well as their advantages and disadvantages.
... The importance of dermal contact for the total AFB1 internal dose is still unclear as it is impossible to estimate what is the real contribution of this exposure route. Previous studies have shown that skin is permeable to AFB1 and other mycotoxins (Kemppainen et al., 1988;Boonen et al., 2012). This exposure route can have a significant role if the workers are sweating due to tasks involving high metabolic rates or if they use short clothes. ...
Article
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Aflatoxin B1 (AFB1) is considered by different International Agencies as a genotoxic and potent hepatocarcinogen. However, despite the fact that the fungi producing this compound are detected in some work environments, AFB1 is rarely monitored in occupational settings. The aim of the present investigation was to assess exposure to AFB1 of workers from one Portuguese waste company located in the outskirt of Lisbon. Occupational exposure assessment to AFB1 was done with a biomarker of internal dose that measures AFB1 in the serum by enzyme-linked immunosorbent assay. Forty-one workers from the waste company were enrolled in this study (26 from sorting; 9 from composting; 6 from incineration). A control group (n = 30) was also considered in order to know the AFB1 background levels for the Portuguese population. All the workers showed detectable levels of AFB1 with values ranging from 2.5ng ml−1 to 25.9ng ml−1 with a median value of 9.9±5.4ng ml−1. All of the controls showed values below the method’s detection limit. Results obtained showed much higher (8-fold higher) values when compared with other Portuguese settings already studied, such as poultry and swine production. Besides this mycotoxin, other mycotoxins are probably present in this occupational setting and this aspect should be taken into consideration for the risk assessment process due to possible synergistic reactions. The data obtained suggests that exposure to AFB1 occurs in a waste management setting and claims attention for the need of appliance of preventive and protective safety measures.
Article
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This statement describes molds, their toxic properties, and their potential for causing toxic respiratory problems in infants. Guidelines for pediatricians are given to help reduce exposures to mold in homes of infants. This is a rapidly evolving area and more research is ongoing.
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T-2 toxin is the most toxic among mycotoxins and poses a potential health hazard for both humans and animals. At high doses, T-2 toxin can cause shock-like syndrome that can result in death. We evaluated the effect of time course and route of exposure on hepatic oxidative damage in mice and it is only such study so far to compare the effects of dermal and subcutaneous exposure of T-2 toxin. Mice were exposed to 1 LD50 of T-2 toxin either by percutaneous (5.94 mg/kg body weight) or subcutaneous (1.54 mg/kg body weight) route and sacrificed at 0, 1, 3, and 7 days postexposure. Analysis of a number of serum biochemical variables, antioxidant enzymes activity, gene and protein expression by immunoblot assay showed time and route dependent effects of T-2 induced hepatic oxidative damage. Time dependent increase in protein carbonyl content and protein oxidation was seen in serum and liver. Results of our study may provide possible mechanism for developing medical countermeasures against T-2 toxin. © 2013 Wiley Periodicals, Inc. Environ Toxicol, 2013.
Chapter
Book Description: Exposure to certain types of mycotoxins, the bioactive secondary metabolites of filamentous fungi, significantly impact the animal industry as well as human health. The contamination of food with mycotoxins is a worldwide problem in animal production and direct consequences are the reducing of food intake and production. In this book, the authors increase the public awareness of the implications of certain types of mycotoxins exposure to promote the health of livestock as well as the general public; an analysis of trichothecens (TCEs), a large group of mycotoxins, and their impact on lifestock health and production are also examined, as well as the occurrence of mycotoxins in animal products such as goat milk. Different strategies implemented for the analysis of a wide spectrum of mycotoxins, as well as their advantages and disadvantages are provided by the authors. In the next few chapters, the occurrence of mycotoxins in cereals and cereal products and in particular, their toxic properties are looked at; a discussion on deoxynivalenol (DON) and related 8-ketotrichothecene mycotoxins, which are extensively distributed in cereal-based foods and feed stuffs worldwide are reviewed; potential toxigenic fungi from diverse habitats are identified with special emphasis on the methods as well as on the genetic markers employed; the importance of performing exposure assessments to Aflatoxin B and some of the most important aspects to consider in the risk assessment process, including the simultaneous presence of other mycotoxins and the challenge of choosing the most suitable method to perform exposure assessment are analyzed; and finally, a review of the occurrence of dietary mycotoxins in Africa as well as the advances in analytical methods of mycotoxin extraction and detection over the last decade is provided.
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Chapter
Fungi are distributed worldwide, as they can grow on a wide range of substrates and under various conditions. Fungi not only play an important role in most ecosystems, but they have a direct impact on society due to production of secondary metabolites. From a big array of fungal secondary metabolites, some compounds are beneficial for the society (e.g. antibiotics), and others (e.g. mycotoxins) represent a threat to human and animal health and cause economic losses. This chapter provides an overview of fungal secondary metabolites with emphasis on one of the most important groups, mycotoxins. The different classes of these metabolites are discussed. Due to an enormous diversity in chemical structures, biosynthetic origins and biological effects, only exemplary classifications are provided, which, however, form a complete and clear picture of similarities and differences between the metabolites. Furthermore, their impact on human and animal health is described. The different routes of human and animal exposure (ingestion, inhalation, dermal route) to mycotoxins are also presented and supported by occurrence data.
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Although quality of life studies suggest that allergic rhinitis has a substantial impact on work impairment, national survey estimates of the magnitude of this impairment have varied widely. Retrospective recall bias is likely to be a major cause of this variability. This study used a nationally representative daily diary sample to obtain prospective data that improve on previous estimates of the work impairment because of allergic rhinitis. The MacArthur Foundation National Survey of Daily Experience is a daily diary survey that included a nationally representative subsample of 739 employed people, each of whom provided daily reports on work performance for 1 randomly assigned week of the calendar year. National Allergy Bureau monitoring station data were merged with the survey data to study the association of time-space variation in pollen/mold exposure with impaired daily work quality and quantity. National Allergy Bureau pollen/mold counts are significantly related to work impairments only among respondents with self-reported allergic rhinitis. The average estimated monthly salary-equivalent work impairment costs associated with pollen/mold exposure for each allergy sufferer is between $109 and $156, with an annualized national projection of between $5.4 billion and $7.7 billion. The extent to which these costs can be recovered by increasing the proportion of allergy sufferers who are successfully treated remains unknown and can only be evaluated definitively in effectiveness trials.
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An extensive body of data demonstrates that diverse groups of mycotoxins can alter the structure and function of the nervous system in a variety of ways with notable human health consequences. Myconeurotoxicity refers to any adverse effects of exposure to mycotoxins or byproducts of primary and secondary mold metabolism, including volatile organic compounds (VOCs) on the structural or functional integrity of the developing or adult nervous system. Neuromycotoxic effects may involve a spectrum of biochemical, morphological, behavioral, and physiological abnormalities whose onset can vary from immediate to delayed action, following exposure to a mycotoxin, and whose duration may be transient or persistent and result in disability, while some may have life-threatening consequences. Myconeurotoxicity may result from effects of the mycotoxins acting directly on the elements of the nervous system or acting on other biological systems, which then adversely affect the nervous system. This paper reviews the application, effectiveness, and limitations of the electrophysiological diagnosis of myconeurotoxic effects of chronic environmental exposure to mycotoxins. The systemic targets of mycotoxic effects were reviewed for greater understanding as to why different neurophysiological test techniques have different levels of outcomes. Thus, nerve conduction velocity, sensory, motor, and evoked potentials, electroencephalographic techniques were evaluated using previously published papers and our clinical experience. Although, neuromycotoxic disorders can be established using clinical electrophysiological diagnosis, there is always the possibility of false positive and false negative results in some patients, which may be due to a multi-factorial etiopathogenesis of neuromycotoxicity. Detection of nervous system toxicity and other measures of toxicity could be achieved using a combination of these neurodiagnostic techniques.
Article
Full-text available
The use of in vitro preparations of human skin to study percutaneous absorption is widespread. Yet, up to the present time, little has been done to systematically validate this model and demonstrate the extent to which it mimicks in vivo absorption. In this study, the permeability of 12 organic compounds has been evaluated in excised skin and the results compared to those obtained previously by others in living man. With special emphasis being given here to duplicating in vivo conditions, it was possible to demonstrate an excellent qualitative agreement between the two methods. In all cases, the absorption pattern determined in vitro rather precisely paralleled the pattern which was obtained in vivo. Quantitative agreement between the two sets of data was less than perfect, although the in vitro method adequately distinguished compounds of low permeability from those of high permeability and ranked then in approximately the same order found in vivo. This systematic comparison of in vitro with in vivo data was clearly shown how accurately in vitro absorption studies can reflect the living state.
Article
Full-text available
The purpose of this study was to determine if aflatoxin B1 (AFB1) could penetrate through isolated human epidermis (stratum corneum plus viable epidermis). [14C]AFB1 (7.5-9.3 micrograms) was applied to the stratum corneum of epidermal disks mounted in Teflon diffusion cells. [14C]AFB1 penetrated chemically unaltered through the isolated epidermis. Chloroform-extractable radioactivity accounted for 82.5 +/- 3.7% of the total penetrating radioactivity in the receptor fluid of the diffusion cells. The rate of penetration was very slow when experiments were conducted under nonoccluded conditions, but was approximately 40 times greater under conditions of occlusion. The maximum velocity of penetration was 0.63 +/- 0.71 and 27.31 +/- 10.15 pmol/h under conditions of exposure to ambient conditions and occlusion, respectively. Penetration after 46 h was less than 0.05% and 3.41% of the applied dose under nonoccluded and occluded conditions, respectively. Total recovery expressed as a percentage of the applied radioactivity was 98.6 +/- 6.4%.
Article
T-2 toxin at 0 (6 pigs) or 15 mg/kg (8 pigs) in 0.75 ml of dimethyl sulfoxide was topically applied to 9- to 10-week-old, male castrated, specific-pathogen-free derived pigs which were immunized subcutaneously with sheep red blood cells (SRBC) on Days 0 and 21. Whole blood and serum samples were taken periodically for clinical pathologic and immunologic evaluations. The pigs were observed daily and weighed weekly; their rectal temperatures were measured periodically. The T-2-treated pigs displayed anorexia, lethargy, posterior weakness and paresis, persistent high fever, and reduced body weight gain. Prominent neutrophilia, decreased serum glucose, albumin, and alkaline phosphatase activity, and increased serum globulin were seen in the T-2-treated group. The responses of enriched peripheral blood mononuclear cells to mitogens concanavalin A, phytohemagglutinin, and pokeweed mitogen of the T-2-treated group were significantly lower than those of the control group both at early (3 to 5 days) and late (20 to 28 days) postdosing intervals. No significant effects were noted in the hemagglutination titer to SRBC. Thus, in addition to the severe local dermal injury reported previously, topical exposure of swine to a sublethal dose of T-2 toxin, 15 mg/kg, can cause significant systemic effects on parameters such as body weight gain, rectal temperature, hematology, serum biochemistry, and cellular immune response.
Article
• This study determines the percutaneous absorption of hydrocortisone when applied as a single dose or on a repetitive basis. Application was to the shaved ventral forearm of the rhesus monkey, an animal model in which some relevance to man has been shown. Absorption was quantified by measuring14C in aliquots of urine over five days. There was no substantial difference in total absorption when 13.3 μg/sq cm was applied as a single dose or when the 13.3 μg/sq cm was applied three times, totaling 40 μg/sq cm. However, when 40 μg/sq cm was applied as a single dose, absorption was substantially increased over 13.3 μg/sq cm applied either once or three times. Additionally, when the skin was washed between applications to remove previously applied material in the three application experiment, there was a statistically significant increase over not washing the skin. The clinical importance of these results to man will await appropriate clinical studies. (Arch Dermatol 113:620-622, 1977)
Article
Synopsis--Tests for PERCUTANEOUS ABSORPTION are needed principally for substances that are toxic or biologically active or which accumulate in body tissues. The most sensitive SPECIES for percutaneous absorption tests are the rabbit and the guinea-pig. The technique most widely applicable is the measurement by ANALYTICAL or ISOTOPE techniques of the rate of DISAPPEARANCE of a test substance from the site of its topical application. Urine examination or measurement of blood levels may be useful in certain circumstances. IN VITRO measurements are often useful as a guide to the planning of IN VIVO tests. The principal barrier against percutaneous absorption is the STRATUM CORNEUM. Water and water-soluble substances traverse this layer with difficulty while LIPID-SOLUBLE substances do so with less difficulty. Substances that are soluble in both water and lipids (amphipathic) penetrate readily. Vehicles may retard or enhance percutaneous absorption in relation to their water-lipid solubility. They may also enhance absorption by increasing the permeability of the stratum corneum. In the case of OINTMENTS, partition of the test substances between vehicle and stratum corneum is often an important factor influencing absorption. Temperature and pH of the test preparations are additional factors that influence absorption.
Article
A heavy infestation of Stachybotrys atra in a house in suburban Chicago has caused chronic health problems for the members of the household. Extracts of the S. atra contaminated household material proved toxic to animals; from these extracts were isolated several highly toxic macrocyclic trichothecenes. After the contaminated duct work, insulation and building material had been replaced, the members of the household no longer complained of illnesses suggestive of trichothecene toxicosis.
Article
IN 1944 we obtained a culture of a Metarrhizium sp. from the United States Department of Agriculture, which had been described by Great-house, Klemme and Barker1 as an active decomposer of cellulose, particularly suitable for in vitro assessment of textile preservative treatments. This fungus was afterwards described by Pope2 as a new species, M. glutinosum. Our organism agrees with Pope's description. We have found that this mould, when grown on a variety of synthetic media, produces fungistatic culture filtrates. From cultures of this mould on Raulin Thorn medium, supplemented by 0.01 per cent `Difco' yeast extract, we have isolated a substance for which we propose the name `glutinosin', in yields of the order of 15 mgm. per litre of culture filtrate.
Article
Discs of abdominal skin (obtained from humans and hybrid monkeys at autopsy) were mounted on diffusion cells. The epidermal surfaces were dosed with [3H]T-2 dissolved in dimethyl sulfoxide (DMSO). The rate of [3H]T-2 penetration (expressed as ng/cm2/hr) through human skin was 0.38 ± 0.10 and 3.85 ± 0.96 ( confidence limit) when dosed with 74 and 582 ng/cm2, respectively. [3H]T-2 penetrated through monkey skin at the rate of 0.37 ± 0.14, 0.80 ± 0.43, 4.13 ± 1.71, and 6.55 ± 3.45 when dosed with 70, 155, 555 and 1063 ng/cm2, respectively. Analysis of the receptor fluid bathing human skin revealed 15% of the radioactivity was associated with T-2, 71% with HT-2 toxin (HT-2), and 6.3% with an unknown metabolite more polar than HT-2. The radioactivity in the receptor fluid bathing monkey skin was associated with T-2 (87%) and HT-2 (1.0%). The results are consistent with the hypothesis that metabolism of T-2 occurred during penetration through the excised skin and did not occur in the receptor fluid due to enzymes leaching out of the skin. These findings indicate that excised monkey skin is a good model for T-2 penetration through human skin when DMSO is the vehicle, but that dermal metabolism of T-2 is different in these two species.
Article
An in vitro apparatus was developed to determine the evaporation and percutaneous penetration of radiolabeled chemicals applied to pig skin. The dermal side of the skin was mounted on a penetration cell. Appearance of radioactivity in the fluid flowing past the dermal side of the skin indicated percutaneous penetration. An evaporation manifold, with replaceable vapor traps, was mounted on the stratum corneum side of the skin. Using the model, the influence of a number of factors (storage conditions, flow rate and composition of fluid in the penetration cell, and temperature and humidity of air flowing through the evaporation manifold) on the disposition of chemicals on the skin was determined. The percutaneous penetration and evaporation of N,N-diethyl-m-toluamide were determined on skin samples immediately after excision and after a freezing period of 1 to 6 weeks at -80°C. Progressively greater percutaneous penetration values were associated with samples which had the greater storage times. Thereafter, only fresh skin was used. When the penetration cell flow was increased from 5 to 10 ml/hr of Tyrodes solution, or when porcine serum was substituted for Tyrodes solution as the fluid flowing through the penetration cell, no significant difference was found in total percutaneous penetration of several control compounds. However, total percutaneous penetration of N,N-diethyl-m-toluamide more than doubled when the air temperature was increased from 20 to 32°C, whereas total evaporation decreased. Increasing the humidity of air flowing through the evaporation manifold enhanced the percutaneous penetration of polar organic compounds but had little effect of the percutaneous penetration of highly lipid soluble organic compounds. Using the model under standardized conditions, the percutaneous penetration of 10 control compounds (N,N-diethyl-m-toluamide, benzoic acid, caffeine, three steroids, and four insecticides) were found to correlate with the corresponding published values for man (r = 0.77, p = 0.05). The skin disposition of the nerve agent analog (diisopropylfluorophosphate, DFP) and simulant (diethyl malonate) was determined using the model. When applied to the skin at a dose of 0.1 mg/cm2, DFP and diethyl malonate were lost from the skin surface mainly by evaporation. Skin penetration was limited due to loss by evaporation.
Article
The etiology of the classical turkey "X" disease syndrome is reappraised based on original reports in conjunction with current information. The clinical signs described in those original reports cannot be totally explained as being typical for aflatoxicosis. The unexplained effects of the disease can be resolved by the proposed presence of the mycotoxin cyclopiazonic acid which is frequently produced byAspergillus flavus along with the aflatoxins.
Article
Sodium hypochlorite solution which has been in use for a long time as a reagent to treat laboratory wastes and equipment contaminated with aflatoxin B1, has been shown by TLC, HPLC and mass spectrometry to lead to the formation of products which include its carcinogenic 2,3-dichloro derivative. A modification to the method of decontamination using sodium hypochlorite, based on the instability of the 2,3-dichloro derivative in the presence of acetone, is suggested.
Article
LARGE numbers of turkey poults1 and ducklings2 died on British farms in 1960 as a result of consuming groundnut (Arachis hypogaea) meal imported from Brazil. Afterwards, outbreaks of disease associated with the feeding of Brazilian groundnut meal were reported in cattle3, pigs4, and sheep (Buxton, J. C., personal communication). More recently it has been shown that some samples of groundnut products from a number of other producing countries are toxic to animals5.
Article
Application of aflatoxins in chloroform solution on the depilated skin of rabbits produced characteristic lesions of the epidermis.Low levels of B-toxins resulted in the formation of intra-epidermal vesicles. With intermediate levels of toxins, confluent bullae filled with leukocytic exudate were produced and with high levels, necrosis of epidermis and hair follicles gradually supervened.Application of G1-toxin produced epidermal necrosis in a similar dose as a mixture of B1 and B2 aflatoxins.It is suggested that occupational dermatoses may occur in handlers of groundnuts or other grain contaminated with toxin-producing Aspergillus flavus.
Article
Many hyphomyceteous fungi have been found to produce closely related toxic metabolites which form the class of compounds called scirpenes. The structures of those compounds are reviewed and current studies on their biological activity and possible implication in moldy corn poisoning are discussed.
Article
The absorption of two hydrophobic compounds through rat skin was measured by in vivo and in vitro techniques. The permeation of the fragrance ingredients 3-phenyl-2-propenyl 2-aminobenzoate (I) and 1-(3-ethyl-5,6,7,8-tetrahydro-5,5,8,8-tetramethyl-2-naphthalenyl)ethanone (II) was measured from a petrolatum and an acetone vehicle. Increases in permeation of 8-fold (I) and 95-fold (II) were observed when the compounds were tested in vivo under conditions similar to in vitro procedures. The apparent inability of the compounds to freely enter the diffusion cell receptor fluid was partially reversed by replacing normal saline with other fluids: rabbit serum, 3% bovine serum albumin, organic solvents, and dilutions of four nonionic surfactants. The effect of the receptor fluids on the integrity of the skin barrier was assessed by measuring the permeability of control compounds (cortisone, urea, and water). A 6% solution of polyethylene glycol 20 oleyl ether was the receptor fluid of choice. Without apparent damage to the skin, 61% (petrolatum vehicle) or 73% (acetone vehicle) of the in vivo absorption of I was obtained. With II, only 32% of the in vivo absorption was achieved (petrolatum vehicle). Even when the surfactant solution is used, significant differences may still remain between in vivo and in vitro results.
Article
An in vitro apparatus was developed to determine the evaporation and percutaneous penetration of radiolabeled chemicals applied to pig skin. The dermal side of the skin was mounted on a penetration cell. Appearance of radioactivity in the fluid flowing past the dermal side of the skin indicated percutaneous penetration. An evaporation manifold, with replaceable vapor traps, was mounted on the stratum corneum side of the skin. Using the model, the influence of a number of factors (storage conditions, flow rate and composition of fluid in the penetration cell, and temperature and humidity of air flowing through the evaporation manifold) on the disposition of chemicals on the skin was determined. The percutaneous penetration and evaporation of N,N-diethyl-m-toluamide were determined on skin samples immediately after excision and after a freezing period of 1 to 6 weeks at −80°C. Progressively greater percutaneous penetration values were associated with samples which had the greater storage times. Thereafter, only fresh skin was used. When the penetration cell flow was increased from 5 to 10 ml/hr of Tyrodes solution, or when porcine serum was substituted for Tyrodes solution as the fluid flowing through the penetration cell, no significant difference was found in total percutaneous penetration of several control compounds. However, total percutaneous penetration of N,N-diethyl-m-toluamide more than doubled when the air temperature was increased from 20 to 32°C, whereas total evaporation decreased. Increasing the humidity of air flowing through the evaporation manifold enhanced the percutaneous penetration of polar organic compounds but had little effect of the percutaneous penetration of highly lipid soluble organic compounds. Using the model under standardized conditions, the percutaneous penetration of 10 control compounds (N,N-diethyl-m-toluamide, benzoic acid, caffeine, three steroids, and four insecticides) were found to correlate with the corresponding published values for man (r = 0.77, p = 0.05). The skin disposition of the nerve agent analog (diisopropylfluorophosphate, DFP) and simulant (diethyl malonate) was determined using the model. When applied to the skin at a dose of 0.1 mg/cm2, DFP and diethyl malonate were lost from the skin surface mainly by evaporation. Skin penetration was limited due to loss by evaporation.
Article
T-2 toxin at 0 (6 pigs) or 15 mg/kg (8 pigs) in 0.75 ml of dimethyl sulfoxide was topically applied to 9- to 10-week-old, male castrated, specific-pathogen-free derived pigs which were immunized subcutaneously with sheep red blood cells (SRBC) on Days 0 and 21. Whole blood and serum samples were taken periodically for clinical pathologic and immunologic evaluations. The pigs were observed daily and weighed weekly; their rectal temperatures were measured periodically. The T-2-treated pigs displayed anorexia, lethargy, posterior weakness and paresis, persistent high fever, and reduced body weight gain. Prominent neutrophilia, decreased serum glucose, albumin, and alkaline phosphatase activity, and increased serum globulin were seen in the T-2-treated group. The responses of enriched peripheral blood mononuclear cells to mitogens concanavalin A, phytohemagglutinin, and pokeweed mitogen of the T-2-treated group were significantly lower than those of the control group both at early (3 to 5 days) and late (20 to 28 days) postdosing intervals. No significant effects were noted in the hemagglutination titer to SRBC. Thus, in addition to the severe local dermal injury reported previously, topical exposure of swine to a sublethal dose of T-2 toxin, 15 mg/kg, can cause significant systemic effects on parameters such as body weight gain, rectal temperature, hematology, serum biochemistry, and cellular immune response.
Article
A microsomal fraction, prepared from mouse skin, catalyzed the hydroxylation of benzpyrene and aniline and the deethylation of 7-ethoxycoumarin. Contamination of the preparation by cytochrome oxidase and cytochrome P-420 was determined by spectral analysis. The enzyme activities studied in mouse skin (Swiss-Webster CD-1) did not respond to topical application of 3-MC. Twenty-four hours after topical application of TCDD to mice, microsomes from skin had 50% greater benzpyrene hydroxylase and 7-ethoxycoumarin deethylase activity, and 4- to 8-fold greater activity of these enzymes was seen after 72 hr. Increases in cytochrome P-450 content of skin microsomes could be demonstrated 24 and 72 hr after topical TCDD treatment of mice. Cholate treatment (solubilization) of skin microsomes, followed by centrifugation, removed the contaminating cytochrome oxidase. Quantitative and qualitative analyses of cytochrome P-450 difference spectra were made from the solubilized preparations.
Article
This study determines the percutaneous absorption of hydrocortisone when applied as a single dose or on a repetitive basis. Application was to the shaved ventral forearm of the rhesus monkey, an animal model in which some relevance to man has been shown. Absorption was quantified by measuring 14C in aliquots of urine over five days. There was no substantial difference in total absorption when 13.3 microng/sq cm was applied as a single dose or when the 13.3 microng/sq cm was applied three times, totaling 40 microng/sq cm. However, when 40 microng/sq cm was applied as a single dose, absorption was substantially increased over 13.3 microng/sq cm applied either once or three times. Additionally, when the skin was washed between applications to remove previously applied material in the three application experiment, there was a statistically significant increase over not washing the skin. The clinical importance of these results to man will await appropriate clinical studies.
Article
The cutaneous responses to irritation by two trichothecene mycotoxins, T-2 toxin and diacetoxyscirpenol (DAS), were examined in rats and rabbits. Sequential gross and histopathological observations on cutaneous lesions produced by low doses of T-2 toxin revealed a non-specific acute dermal inflammatory reaction, characterized by hyperaemia, oedema and neutrophil exudation, with variable degrees of necrosis of the epidermis. Reactions increased in intensity until 48 hr, after which the inflammatory response rapidly diminished. Inflammatory reactions to T-2 toxin were histologically similar to reactions to croton oil. Lesions developed similarly in each species, but the intensity of reactions to a given dose was higher in rabbits than in rats. Wide variation in the intensity of reactions among either rabbits or rats prevented an accurate prediction of dose on the basis of a quantitative scoring of inflammation. A reliable assay technique was designed in which concentrations of solutions of T-2 toxin (2 μl in volume) were estimated directly by assessing the intensity of reaction relative to reactions to a graded series of standard solutions of T-2 toxin applied to the same rat. By this simple and sensitive procedure, concentrations of T-2 toxin in the range of 5–60μg/ml could be measured accurately and precisely. Measurements obtained were independent of the degree of sensitivity of test animals.
Article
Male and female Mongolian gerbils failed to show observable pathological responses in the liver to topically applied AFB1 and DMF indicating that percutaneous absorption of AFB1 is absent in this species. In males, some responses in weight changes were attributed, proportionally, to increased doses of DMF. Unexplained and currently under investigation is the possibility that AFB1 may have reduced the response of some animals to DMF. This response may relate in some way to the modification of absorption of DMF in the gerbil since AFB1 is known to have an influence on cell membranes.
Article
The metabolism of aflatoxin B1 in vitro was examined in rat liver microsomal preparations. 2. H.p.l.c. (high-performance liquid-chromatographic) systems were used. A silica column was used to separate non-polar metabolites. A system utilizing a reversed-phase column which separates both poar and non-polar metabolites was also developed. 3. The principal metabolites of aflatoxin B1 found were aflatoxin M1, aflatoxin Q1 and a compound which co-chromatographed with a degradation product of aflatoxin B1 2,3-dihydrodiol. 4. The time course of metabolism of aflatoxin B1 by microsomal preparations isolated from control and phenobarbitone-pretreated rats was examined. The rate and extent of metabolism was greater with microsomal preparations from the latter. The formation of aflatoxin Q1 was enhanced 4--5-fold by phenobarbitone pretreatment, whereas the production of aflatoxin M1 was only increased 1--2-fold. The formation of the degradation product of aflatoxin B1 2,3-dihydrodiol was increased 4--5-fold by the pretreatment with phenobarbitone. 5. The microsomal metabolism of aflatoxins M1, P1 and Q1 was examined. Aflatoxin M1 apparently underwent very limited microsomal metabolism to more polar compounds. Aflatoxin P1 was not metabolized. The situation with aflatoxin Q1 was complicated in that it was metabolized in the absence of NADPH to an unidentified metabolite. Aflatoxin B1 appeared as a metabolite of aflatoxin Q1 only when NADPH was present, and the formation of more polar metabolites was also then observed.
Article
Mouse skin exhibits relatively high aryl hydrocarbon hydroxylase (AHH) activity when measured under optimal conditions. The enzyme is unequally distributed in the cutaneous layers with the highest concentration in the epidermis. Subcellularly, it is localized in the microsomal fraction. As much as two-thirds of the enzymatic activity was destroyed when harsh homogenization techniques were used during tissue preparation. Incorporation of the reduced pyridine nucleotide NADH into an incubation mixture containing NADPH increased epidermal AHH activity by one-third. When methods that maximize activity were employed, the AHH activities of skin of C57BL/6 inbred mice and of ICR Swiss random-bred mice were 5 to 10 times as active as lung tissue and about one-tenth as active as liver.
Article
Cutaneous application in rats of two widely used microscope immersion oils known to contain the environmental pollutant chemicals, polychlorinated biphenyls, was evaluated. After skin application of 1 or 10 μl of these oils, significant increases in liver weight, microsomal protein, cytochrome P-450 and in the metabolism of ethylmorphine and benzo(a)pyrene resulted. Cutaneously treated sites also showed large increases in benzo(a)pyrene hydroxylation. Immersion oil treatment resulted in the induction of hepatic cytochrome P-448 and caused spectral changes in the hemoprotein analogous to those produced by polycyclic hydrocarbons, such as 3-methylcholanthrene. A single cutaneous application resulted in significant enhancement of the same parameters; this response reached a maximum at 2 days and lasted at least 10 days with each immersion oil tested. The data presented show that extremely small exposures of the skin to microscopic immersion oils lead to marked induction of hepatic and cutaneous drug-metabolizing enzymes.
Article
The cytochrome P-450 content of primary hepatocyte cultures was maintained at levels close to those found by using a defined medium containing testosterone, thyroxine, hydrocortisone, estradiol, glucagon, insulin, linoleic acid and oleic acid. Using these cultures, [14C]aflatoxin B1, a potent liver carcinogen, was metabolized primarily to water-soluble metabolites. In agreement with results, aflatoxin M1 was the only nonpolar metabolite detected. In addition, a significant portion of radioactivity was covalently bound to cell constituents. These results suggest that primary hepatocyte cultures may be a good model of the liver for studying the metabolism and mechanism of action of toxic chemicals.
Article
T-2 toxin, HT-2 toxin, Diacetoxyscirpenol (DAS), Roridin A, Verrucarin A and 3-Acetyl-deoxynivalenol (3-AcDON) were dissolved in dimethyl sulfoxide and applied topically to mice. For a mortality study, groups of 10–20 male mice received either 5, 10, 20, 30 or 40 mg toxin/kg BW. Further, mixtures of trichothecenes were applied, e. g.: T-2 toxin + DAS + 3-AcDON; T-2 toxin + DAS; T-2 toxin + 3-AcDON; DAS + 3-AcDON. Animals were observed until death or until day 14 after application, and the mortality rates were established. To study progressive morphological changes, groups of 20 male mice received 40 mg/kg BW of the individual toxins listed above, and mice were killed at 6, 12, 18 or 24 hrs after application.
Article
The fate and distribution of T-2 were examined in 6 guinea pigs. T-2 (1.2 micrograms/cm2), in methanol or DMSO, was painted onto the shaved backs of guinea pigs, a screen barrier was applied, urine and feces were collected daily and the guinea pigs were killed after 48 hr. Disks of skin (lateral to the in vivo site of application) were excised from the guinea pigs and used for in vitro penetration studies with static diffusion cells. Skin excised from 6 additional guinea pigs was used for penetration studies with flow-through diffusion cells. For in vitro studies, T-2 dissolved in methanol or DMSO was applied to the epidermal surfaces and the appearance of penetrant in receptor fluid bathing the dermal surfaces was monitored for 48 hr. Metabolism of T-2 was measured by using thin layer radiochromatography to identify metabolites. In the in vivo study, mean cutaneous absorption (n = 3) after 48 hr (expressed as per cent dose) was 22.5 and 51.9 for the methanol and DMSO groups, respectively. In vitro cutaneous penetration for static diffusion cells was 3.9 and 38.4 for the methanol and DMSO groups. For flow-through diffusion cells, mean penetration (n = 9) was 14.6 and 42.6 for the methanol and DMSO groups. Urinary metabolites of T-2 were T-2 triol, 3' OH-HT-2, T-2 tetraol, the glucuronide conjugate of HT-2 and several more polar metabolites. The main metabolite of T-2 in the receptor fluid bathing the dermal surfaces of excised skin was HT-2.
Article
The purpose of this research was to determine which species of laboratory animal provided the best approximation of in vitro percutaneous penetration and metabolism of T-2 in humans. The [3H]T-2 which penetrated discs of skin after 48 hr (expressed as per cent of dose, 581 ng/cm2) was 1.0, 1.4, 2.8 and 9.7% for the human, rabbit, guinea pig and rat when the vehicle was methanol. The penetration was 29.2, 19.6, 51.9 and 52.6% for the human, rabbit, guinea pig and rat when the vehicle was DMSO. When 2 concentrations were compared, 79 ng/cm2 and 581 ng/cm2 (the vehicle was methanol), the higher dose caused a significant (P less than 0.05) increase in the per cent of dose which penetrated human and guinea pig skin. Metabolism was extensive in the human, rabbit, and rat, with the main metabolite being HT-2 toxin. Previous studies comparing human to monkey indicated penetration in these 2 species was different when methanol was the vehicle. This study indicates that the rabbit provides the best approximation of human skin, both in terms of penetration kinetics and metabolic activity.
Article
The purpose of this research was to determine the rate of cutaneous penetration and metabolism of [3H]diacetoxyscirpenol (DAS) and [3H]verrucarin A (VCA) and compare these values to previously determined values for [3H]T-2 toxin (T-2), to compare the cutaneous penetration and metabolism of DAS in human and guinea-pig skin, and to compare the effects of dose and of two vehicles, methanol and dimethylsulphoxide (DMSO), on penetration rates. DAS or VCA was applied to the epidermal surface of excised skin, and the receptor fluid bathing the dermal surface was sampled periodically for 48 hr. Whether the applied dose (581 ng/cm2) was dissolved in methanol or DMSO, the rate of penetration through human skin was lower for VCA than for DAS or T-2, the rates for the two latter compounds being similar at this dose. Metabolism of DAS occurred during penetration through excised human skin and did not occur in the receptor fluid as a result of enzymes leaching out of the skin. VCA appeared to be metabolized by human skin, but this conclusion is tentative because of the relative instability of this compound. DAS penetrated significantly (P less than 0.05) faster through excised guinea-pig skin than through human skin. Metabolism of DAS was greater in human skin than in guinea-pig skin. When compared with methanol, DMSO increased the penetration of DAS and VCA by factors of between 7 and 52. At the low dose (79 ng/cm2) DAS penetrated human and guinea-pig skin significantly (P less than 0.05) faster than T-2 using either vehicle.
Article
The penetration and distribution of T-2 toxin in excised human abdominal skin has been determined for a dose range of 1.0-2.6 micrograms/cm2 skin using an ethanol vehicle and a saline receptor solution. In all cases the overall percentage penetration of T-2 after 48 h was low, the greatest amounts of toxin being present in the stratum corneum with less in the epidermis and relatively little in the dermis. Vehicle: skin partition coefficients support this finding. Neither penetration nor distribution were changed by a rabbit serum receptor solution. Electron micrographs showed that at 1.8 micrograms/cm2 and above the contents of the intercellular space are leached out to leave the integument as a porous membrane. The distribution of T-2 within the skin after 48 h would suggest that for doses up to 2.6 micrograms/cm2 the irritative and inflammatory effects on the skin would be of more immediate concern than would systemic toxicity.
Article
Evaluation of Monkey Skin as a Model for in Vitro Percutaneous Penetration and Metabolism of [3H]T-2 Toxin in Human Skin. KEMPPAINEN, B.W., RILEY, R.T., PACE, J.G., HOERR, F.J., AND JOYAVE, J. (1986). Fundam. Appl. Toxicol. 7, 367–375. Discs of abdominal skin (obtained from humans and hybrid monkeys at autopsy) were mounted on diffusion cells. The epidermal surfaces were dosed with [3H]T-2 dissolved in dimethyl sulfoxide (DMSO). The rate of [3H]T-2 penetration (expressed as ng/cm2/hr) through human skin was 0.38±0.10 and 3.85±0.96 (x±95percnt; confidence limit) when dosed with 74 and 582 ng/cm2, respectively. [3H]T-2 penetrated through monkey skin at the rate of 0.37±0.14, 0.80±0.43, 4.13±1.71, and 6.55±3.45 when dosed with 70, 155, 555 and 1063 ng/cm2, respectively. Analysis of the receptor fluid bathing human skin revealed 15% of the radioactivity was associated with T-2, 71% with HT-2 toxin (HT-2), and 6.3% with an unknown metabolite more polar than HT-2. The radioactivity in the receptor fluid bathing monkey skin was associated with T-2 (87%) and HT-2 (1.0%). The results are consistent with the hypothesis that metabolism of T-2 occurred during penetration through the excised skin and did not occur in the receptor fluid due to enzymes leaching out of the skin. These findings indicate that excised monkey skin is a good model for T-2 penetration through human skin when DMSO is the vehicle, but that dermal metabolism of T-2 is different in these two species.
Sodium hypochlorite was used to suppress diacetoxyscirpenol cutaneous toxicity; mice skin can be decontaminated with "Eau de Javel" (1 p. 100 free chlorine) if application is performed less than 15 min. after contact with toxin.
Article
Percutaneous absorption of chemicals is generally considered a diffusional process, with the rate-limiting barrier being the nonviable stratum corneum. Because viable skin possesses enzyme activities, including those involved in the metabolism of xenobiotics, the extent to which cutaneous metabolism may influence the percutaneous fate of topically applied chemicals in the skin was examined in mammalian skin maintained as short-term organ cultures. Skin samples from mouse, rat, rabbit, guinea pig, marmoset, and man were examined. The results from studies with benzo[a]pyrene (BP) and testosterone showed that, in all species, metabolic viability was a major factor involved in the in vitro skin permeation of surface-applied chemicals. Permeation was accompanied by extensive cutaneous "first pass" metabolism; both parent compounds and a full spectrum of metabolites were found in the receptor fluid from viable skin preparations. However, in previously frozen nonviable skin preparations, essentially only unchanged parent compounds were detected in the receptor fluid. Permeation of BP and testosterone was highest in mouse skin, and significant species variations in the metabolite profiles were observed. Studies with mouse skin also demonstrated that induction of cutaneous drug-metabolizing enzymes can result in a two- to threefold increase in the in vitro permeation of topical BP, and a significant reduction in permeation was observed when KCN was added to the perfusion medium. These results indicate that diffusional and metabolic processes are intimately involved in the percutaneous fate of surface-applied chemicals. The relative importance of these processes is dependent upon the physicochemical properties of the compounds and the metabolic capabilities of the skin toward the compounds in question. Furthermore, these findings suggest that meaningful in vitro studies on skin absorption should consider both diffusion and cutaneous biotransformation of the applied compound.
Article
Penetration of [3H]T-2 toxin through excised human and monkey skin stored at -60 degrees C was faster than through human and monkey skin stored at 4 degrees C, respectively. The permeability of refrigerated human skin was 34% of the permeability of refrigerated monkey skin. Increasing the concentration of [3H]T-2 toxin applied to the refrigerated monkey skin increased the amount of [3H]T-2 toxin penetrating the skin and enhanced the efficiency of penetration. Metabolites of [3H]T-2 toxin were identified in the receptor fluid bathing the dermal side of the excised human and monkey skin.
Article
Skin may play an important role in the detoxification of certain substances during their passage into the body. The degree of hydrolysis of diisopropyl fluorophosphate, DFP, in skin suspensions and during penetration through isolated epidermis and full-thickness skin from humans was investigated in vitro. When isolated sheets of epidermis were used, 11% of the penetrated amount of DFP was hydrolyzed whereas 46% was hydrolyzed during penetration through full-thickness skin. A comparison is made between the degree of hydrolysis during penetration as obtained from direct measurements and that calculated from kinetic data of the enzyme (Kappm and Vappmax), the half-life of DFP, the skin concentration, and the lag time. The concentration of DFP in the skin was not measured, but the concentration of DFP equivalents (DFP and metabolites formed during penetration) was determined at different times. At steady state, the amount of DFP equivalents in the skin corresponded to the amount that had penetrated into the skin during the lag time. This indicates that the penetration rate corresponded to the uptake via the skin and that no diffusion barrier existed between the skin and the receptor medium. It was also found that the concentration in the skin was proportional to the penetration rate, thus indicating that the enzymatic degree of hydrolysis depends upon the penetration rate.
A rabbit bioassay test has been developed which can be used for screening large numbers of field samples of corn for T-2 and other toxins. Two μl each of the control solutions, 0.005–0.12 μg standards, and about 12 samples in ethyl acetate were applied simultaneously to the closely clipped skin of a 2–3 kg young rabbit. The skin reactions were read at 24, 48, and 72 hr. The prominent features of the reactions were erythema, edema, and necrosis. The T-2 toxin equivalences of the samples were estimated by the degree of the skin reactions caused by the standards. The method is reliable to at least 0.01 μg/test or 50 ppb. Graded response to the toxin is dependent upon the use of sensitive animals and properly diluted samples and standards. Rabbits were more sensitive than weanling rats or young guinea pigs, and the method showed better reproducibility with rabbits. Citrinin and zearalenone (F-2) showed negative skin reactions when applied at a level of 20 μg/skin site. They also showed poor skin reactions when administered by intradermal injection into rabbit skin. However, all 3 mycotoxins showed distinct skin reactions in guinea pigs by the intradermal route. The test was as sensitive as the topical test using rabbits with T-2 toxin. The prominent feature of the skin reaction was induration.
Article
Aflatoxin, dissolved in dimethylsulfoxide or acetone, was applied to the shaved skin between the shoulder blades of rats. Half of the rats were anesthetized. No aflatoxin was found in the internal organs of anesthetized rats at 20 or 130 min after skin application. Aflatoxin was found on the paws and in the stomach, liver, and kidney of conscious rats indicating that aflatoxin is ingested after being removed from the skin by the paws during grooming. Larger quantities of aflatoxin were ingested when it was applied dissolved in dimethylsulfoxide than in acetone presumably because dimethylsulfoxide is less volatile and, therefore, easier to remove during grooming. There was no evidence of percutaneous absorption. These findings explain how aflatoxin which is applied to rat skin produces hepatic lesions.
Article
Under normal conditions the stratum corneum in vivo is very much less hydrated than the excised tissue routinely used in laboratory permeability experiments. As a consequence, certain quantitative predictions of skin permeability based on laboratory experiments are not applicable to many cases of clinical and practical interest. In this study a modified in vitro permeability technique was used which permitted the hydration of the stratum corneum to be maintained very close to its natural state. Penetrant molecules were applied by adding a few microliters of acetone solution to the stratum corneum surface. The acetone quickly evaporated leaving a residue of solid penetrant. The time course of penetration of the solid material through the epidermis was observed as a function of applied dose, mild hydration, and solvent contact time. Remarkably steady, uniform penetration persisting over several weeks was observed. Generally, the penetration rates were similar to those observed in vivo and increased in a similar manner upon occlusion. Diffusion through the stratum corneum rather than sorption of the solid at the surface appears to be rate limiting.
Article
A modified rat skin test based on dermatitic properties of trichothecenes is described which is quick, convenient, and sensitive to 0.05 mug of T-2 toxin.
Article
Zusammenfassung Nachweis der Absorption von Aflatoxin B1 durch die Rattenhaut. Die toxische Leberwirkung nach der Hautbepinselung entsprach den von anderen Autoren gefundenen Verhältnissen bei peroraler oder intraperitonealer Verabreichung.
Article
The extent to which cutaneous metabolism may be involved in the penetration and fate of topically applied xenobiotics was examined by metabolically viable and structurally intact mouse skin in organ culture. Evidence that skin penetration of certain chemicals is coupled to cutaneous metabolism was based upon observations utilizing [14C]benzo[a]pyrene (BP). As judged by the recovery of radioactivity in the culture medium 24 hr after in vitro topical application of [14C]BP to the skin from both control and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced C3H mice, skin penetration of BP was higher in the induced tissue. All classes of metabolites of BP were found in the culture medium; water-soluble metabolites predominated and negligible amounts of unmetabolized BP were found. As shown by enzymatic hydrolysis of the medium, TCDD induction resulted in shifting the cutaneous metabolism of BP toward the synthesis of more water-soluble conjugates. Differences in the degree of covalent binding of BP, via diol epoxide intermediates to epidermal DNA, from control and induced tissues were observed. These differences may reflect a change in the pathways of metabolism as a consequence of TCDD induction. These results indicated that topically applied BP is metabolized by the skin during its passage through the skin; and the degree of percutaneous penetration and disposition of BP was dependent upon the metabolic status of the tissue. This suggests that cutaneous metabolism may play an important role in the translocation and subsequent physiological disposition of topically applied BP.