Elsevier

Toxicology

Volume 301, Issues 1–3, 15 November 2012, Pages 21-32
Toxicology

Human skin penetration of selected model mycotoxins

https://doi.org/10.1016/j.tox.2012.06.012Get rights and content

Abstract

Dermal exposure data for mycotoxins are very scarce and fragmentary, despite their widespread skin contact and hazard toxicity. In this study, the transdermal kinetics of aflatoxin B1 (AFB1), ochratoxin A (OTA), fumonisin B1 (FB1), citrinin (CIT), zearalenone (ZEA) and T-2 toxin (T-2) were quantitatively evaluated, using human skin in an in vitro Franz diffusion cell set-up. All mycotoxins penetrated through the skin, except for FB1, which showed concentrations in the receptor fluid below the LoD, resulting in a Kp < 3.24 × 10−6 cm/h. OTA showed the highest permeation (Kp = 8.20 × 10−4 cm/h), followed by CIT (Kp = 4.67 × 10−4 cm/h). AFB1 and ZEA showed lower permeability rates (Kp = 2.11 and 2.33 × 10−4 cm/h, respectively). T-2 was found to have the lowest permeability (Kp = 6.07 × 10−5 cm/h). From literature-based mycotoxin-concentrations, dermal contact surface, exposure time and apparent Kp's obtained in this study, the daily dermal exposure (DDE) in two industrial and one residential scenario was estimated. Dermal exposure to the DNA-reactive genotoxic carcinogenic AFB1 can lead to a health risk for agricultural workers which are exposed to a mycotoxin contaminated solution in a worst case situation. For all the other investigated mycotoxins, no significant health risk is calculated after dermal contact in neither agricultural nor residential environments.

Highlights

Transdermal permeability coefficients are obtained for seven selected mycotoxins. ► Dermal exposure to specific mycotoxins like aflatoxin B1 can pose health risks. ► It is strongly recommended to limit the dermal exposure of mycotoxins.

Introduction

Mycotoxins are secondary metabolites produced by fungi (Braese et al., 2009). The worldwide contamination of these ubiquitous natural products in food, feed and environment, including indoor surfaces and particles, form a health risk for animals as well as humans (Zain, 2011). Over 400 mycotoxins are identified, but there are indications that thousands of mycotoxins exist (Nielsen and Smedsgaard, 2003). Very often, more than one mycotoxin is found on the contaminated substrate. The question arises to what extent these mycotoxins form a health risk (Creppy, 2002, Hussein and Brasel, 2001, Muro-Cacho et al., 2004, Peraica et al., 1999). Absorption of mycotoxins often occurs by ingestion of contaminated food, but can also be via inhalation or dermal exposure to air and dust containing mycotoxins. However, there are many uncertainties about the toxin fraction absorbed and hence, about the true impact of mycotoxin exposure via the different routes. Mayer et al. (2007) identified the research need of exposure assessment to mycotoxins. The health risk of mycotoxins was generally assessed via the oral route. Recently, the inhalation route is also gaining scientific interest (Halstensen, 2008, Hardin et al., 2009, Soroka et al., 2008, Tangni and Pussemier, 2007, Terr, 2009). The skin however, is almost unexplored as exposure route. Although the skin forms a natural barrier for exogenous compounds, the low molecular weight mycotoxins are lipid soluble, possessing appropriate properties for occupational as well as accidental skin penetration. Compared to the amount of identified mycotoxins and their health risk, to date, skin permeability data of mycotoxins is nevertheless quite limited but highly wanted (Degen, 2011). Supplementary Table S1 gives a literature overview of the skin related mycotoxin research. Anno end 2011, about 50, mostly fragmentary studies, have evaluated the (trans)dermal behaviour and resulted effects of less than 20 mycotoxins, mainly AFB1 and T-2 toxin. The majority of these studies, about 70%, describe in vivo animal methods, frequently using rats, mice, pigs and rabbits. Half of the remaining studies have also applied in vitro animal skin models and very often, quantitative kinetics are lacking. Therefore, in this study, the transdermal kinetics of mycotoxins were quantitatively evaluated using excised human skin in an in vitro Franz diffusion cell (FDC) set-up.

Model mycotoxins were selected based upon their toxicity, co-occurrence and toxicological interactions (Table 1). In most countries, aflatoxins (AF), ochratoxins (OT), fumonisins (F), deoxynivalenol (DON), zearalenone (ZEA), and patulin (PAT) are subjected to governmental regulation (Reddy et al., 2010). Aflatoxin B1 (AFB1), ochratoxin A (OTA) and fumonisin B1 (FB1) are proven to be the most toxic aflatoxin, ochratoxin and fumonisin, respectively. The International Agency for Research on Cancer (IARC) indicates that these mycotoxins are proven to be human carcinogen (AFB1) or probable carcinogens (OTA and FB1). Moreover, synergetic, additive and antagonistic interactions between pairs of these mycotoxins are observed at several target levels (Grenier and Oswald, 2011). Another regulated mycotoxin, the resorcyl lactone ZEA, shows no direct skin effect after topical application, yet ingestion results in exudative-necrotic inflammation of the skin (Juhasz et al., 2001, Vanyi et al., 1995). In addition, its interaction with OTA's nephrotoxic effects has been documented (Grenier and Oswald, 2011). The trichothecene T-2 toxin exhibits local as well as systemic effects after dermal absorption up to lethality (see Supplementary Table S1). Moreover, the co-occurrence with AFB1 (Coulombe, 1993) and interaction with other selected model mycotoxins (AFB1, OTA, and FB1) was reported (Grenier and Oswald, 2011). Therefore, T-2 toxin was included in our model set. Even though CIT is currently not regulated and is considered to be not carcinogenic to humans, its co-occurrence with OTA (Flajs et al., 2011, Flajs and Peraica, 2009, Pfohl-Leszkowicz and Manderville, 2007) and toxicological interactions with AFB1 and OTA (Grenier and Oswald, 2011) underpin our motivation to include this mycotoxin in the transdermal study as representative of the citrinin type. Moreover, very recently, one study reports the in vivo apoptosis in mouse skin via the intrinsic mitochondrial pathway (Kumar et al., 2011), indicating the relevance of CIT in dermal exposure framework.

Section snippets

Chemicals and reagents

Six investigated mycotoxins (aflatoxin B1 (AFB1), ochratoxin A (OTA), fumonisin B1 (FB1), citrinin (CIT), zearalenone (ZEA) and T-2 toxin (T2)) (≥98.95% by HPLC) were supplied by Fermentek Ltd. (Jerusalem, Israel). LC–MS gradient grade methanol (MeOH) and acetonitrile (ACN) were purchased from Biosolve (Valkenswaard, The Netherlands). Ultrapure water (H2O) was produced by a Milli-Q Gradient System (Millipore, Brussels, Belgium) or an Arium 611 purification system (Sartorius, Göttingen,

Franz diffusion cell experiments using human skin

For the first time it is shown that, beside T-2 toxin, also AFB1, OTA, CIT and ZEA permeate the human skin when applied in 70/30 (V/V) EtOH/H2O. Only FB1 could not be detected in the receptor fluid samples (concentration below detection limit of 10 ng/mL). All other mycotoxins confirmed the steady-state principle: after 24 h, only 0.04–2.66% of the dose applied, was cumulatively found in the receptor chamber. Fig. 1 shows the individual plots of the cumulative amounts of the mycotoxins (ng) versus

Discussion

For the first time, quantitative transdermal parameters were obtained using human skin which is the golden standard. Although different research results are indicative for penetration into skin (Albarenque and Doi, 2005, Albarenque et al., 1999, Antony et al., 2002, Bhavanishankar et al., 1988, Blaylock et al., 1993, Bunner et al., 1988, Dimitri and Gabal, 1996, Hsia et al., 2004, Konoshima et al., 1999, Kumar et al., 2011, Lambert et al., 1995, Liu et al., 1999, Rea et al., 2003, Reboux, 2006,

Conclusions

For the first time, quantitative skin permeability data of six selected mycotoxins were obtained by an in vitro FDC infinite dose approach using dermatomed split-thickness human skin. Based on hazard characterization of the selected mycotoxin, risk assessment revealed that a cancer health risk is present after dermal exposure to AFB1, but not to OTA. Moreover, non-cancer related health effects are not expected after dermal exposure to FB1, CIT, ZEA and T-2 toxin. However, seen extremely toxic

Conflict of interest

The authors declare that they have no conflict of interest.

Acknowledgements

This research is funded by the “Institute for the Promotion of Innovation through Science and Technology in Flanders (IWT-Vlaanderen)” (No. 091257 to Jente Boonen). The authors would like to thank Nathalie Roche for the provision of the human skin and Bram Baert for the technical assistance.

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