The Emerging Mycotoxin 2-Amino-14, 16-Dimethyloctadecan-3-ol (AOD) Alters Transcriptional Regulation and Sphingolipid Metabolism and Undergoes N-Acylation by HepG2 Cells

2-Amino-14,16-dimethyloctadecan-3-ol (AOD) is commonly found in foods contaminated with Fusarium avenaceum, particularly cereals or fruits, and is structurally related to Fusarium mycotoxins (fumonisins) and mammalian sphingoid bases, especially 1-deoxysphinganine (m18:0): therefore, it might enter systemic circulation and tissues upon dietary intake. Knowledge about what happens when cells are exposed to AOD is limited, but it has been reported to be cytotoxic and to induce vacuolization in HepG2 cells. We also found that AOD is cytotoxic for HepG2 cells, but even at a concentration where cell viability remained above 85% (5 &mu:M), it altered 24 differentially expressed genes based on RNA sequencing-based transcriptomic profiling. Among these genes, 13 were shared with cells treated with m18:0. These overlapping differentially expressed genes were primarily enriched in activated stress response pathways of cells, including the upregulation of specific genes in the hypoxia-inducible factor 1&alpha: (HIF-1&alpha:) signaling pathway, such as hexokinase 1 (HK1) and egl-9 family hypoxia-inducible factor 3 (EGLN3), the activation of key components in the p53 signaling pathway, and the induction of cellular senescence-associated transcriptional programs involving serpin family E member 1 (SERPINE1). Transcriptional analysis of genes related to sphingolipid metabolism showed that treatment with AOD increased the mRNA expression of ceramide synthase 4 (CerS4), sphingosine-1-phosphate phosphatase 1 (SGPP1), and UDP-glucosylceramide glucosyltransferase (UGCG), while decreasing the expression of dihydroceramide desaturase 1 (DEGS1) and fatty acid desaturase 3 (FADS3), a pattern of gene expression changes that mirrored the alterations observed with m18:0 treatment. Lipidomic analyses revealed that AOD significantly perturbed the sphingolipid composition of HepG2 cells, specifically increasing hexosylceramide content while decreasing ceramide and sphingomyelin levels. Moreover, AOD was found to undergo intracellular metabolism to N-acyl-AODs, perhaps by ceramide synthase(s), since this acylation was inhibited by fumonisin B1 (FB1). These findings demonstrate that AOD or possibly its N-acyl metabolites can alter cellular sphingolipid metabolism and affect the expression of genes involved in cell stress. These new insights call for more studies of the impact of this food contaminant on cells and the implications for human health.