**1. Introduction**

Mycotoxins represent one of the most important categories of biologically produced natural toxins with potential e ffects on human and animal health. The worldwide contamination by these natural products of food, feed, and environment, represents a health risk for animals and humans [1].

Several *Fusarium* species produce toxic substances of considerable concern to livestock and poultry producers. The mycotoxins beauvericin (BEA) and zearalenone (ZEN) and their derivatives (α-zearalenol ( α-ZEL), β-zearalenol (β-ZEL), zeranol, taleranol, and zearalanone) can be produced by several *Fusarium* species (mainly *Fusarium graminearum*, but also *Fusarium culmorum*, *Fusarium cerealis*, *Fusarium equiseti*, and *Fusarium semitectum*) that grow on crops in temperate and warm-climate zones [2]. These fungi are present in almost all continents, can grow under poor storage conditions, and mainly contaminate cereal grains, such as maize, wheat, oats, soybeans, and their derived food products [3,4].

It has been proved that ZEN and α-ZEL bind to human estrogen receptors and elicit permanent reproductive tract alterations, and consequently, chronical exposure to ZEN present contaminated food can be a cause of female reproductive changes as a result of its powerful estrogenic activity [5–8]. It has been also reported that ZEN induces genotoxic e ffects by induction of DNA adducts, DNA fragmentation, and apoptosis [9,10]. As reported by Dong et al. (2010) [5], metabolic conversion of ZEN mycotoxin to α-ZEL and β-ZEL was found in almost all tissues and occurred more e fficiently to α-ZEL than to β-ZEL; these mycotoxins are endocrine disruptors which affect steroid hormones such as progesterone [7]. In 2016, EFSA (European food Safety Authorities) indicated that there is a high uncertainty associated with the exposure to ZEN and its modified forms and so that it would rather overestimate than underestimate any risk associated with exposure to modified ZEN [8]. Also, recent studies have indicated that ZEN is immunotoxic [4,11,12] and cytotoxic in various cell lines by inhibiting cell proliferation and increasing ROS (reactive oxygen species) generation [13–15].

On the other hand, BEA causes cytotoxic effects by reducing cell proliferation in a timeand concentration-dependent manner [16,17]. Moreover, it can increase ROS generation and lipid peroxidation and produces oxidative stress and depletion of antioxidant cellular mechanisms [14,18,19].

Neurotoxicological testing is mainly based on experimental animal models, but several cell lines and tissue culture models have been developed to study the mechanism of neurotoxicity. In general, cells of human origin are attractive alternatives to animal models for the exploration of toxicity to humans. Nonetheless, there are few studies about the e ffect of mycotoxins at the neuronal level [6,20–22].

Regarding the important role of the food industry in human health, studying the impact of mycotoxins and their combinations in feed and food commodities has gained attention over the last few years, due to the ability of most *Fusarium* spp. to simultaneously produce di fferent mycotoxins [23–25]. Hence, EFSA has recently published a draft guidance document where a harmonized risk assessment methodology for combined exposure to multiple chemicals in all relevant areas is described [26].

Due to the importance of dietetic exposure to various mycotoxins and their impacts on human's health, there is an increasing concern about the hazard of co-occurrence of mycotoxins produced by *Fusarium* and of co-exposure to them through diet. Many studies have been conducted on the toxicity of individual mycotoxins; however, few studies have been dedicated to the toxicological interaction of mycotoxins when present in double and triple combinations on di fferent cell lines [16–18,27–29].

The objective of the present study was to investigate the cytotoxicological interactions between α-ZEL, β-ZEL, and BEA mycotoxins in human neuroblastoma SH-SY5Y cells, via the MTT assay. The e ffects of combinations of two and three mycotoxins were evaluated by isobologram analysis [30] to determine whether their interaction was synergistic, additive, or antagonistic, as well as to understand how mycotoxins can act at the cellular level.
