An altered gene expression profile in tyramine-exposed intestinal cell cultures supports the genotoxicity of this biogenic amine at dietary concentrations

Abstract

Tyramine, histamine and putrescine are the most commonly detected and most abundant biogenic amines (BA) in food. The consumption of food with high concentrations of these BA is discouraged by the main food safety agencies, but legal limits have only been set for histamine. The present work reports a transcriptomic investigation of the oncogenic potential of the above-mentioned BA, as assessed in the HT29 human intestinal epithelial cell line. Tyramine had a greater effect on the expression of genes involved in tumorigenesis than did histamine or putrescine. Since some of the genes that showed altered expression in tyramine-exposed cells are involved in DNA damage and repair, the effect of this BA on the expression of other genes involved in the DNA damage response was investigated. The results suggest that tyramine might be genotoxic for intestinal cells at concentrations easily found in BA-rich food. Moreover, a role in promoting intestinal cancer cannot be excluded.

Figure 1

Gene expression analysis of cancer pathways in tyramine-treated HT29 cells compared to untreated cells. (A) Volcano plot representation of tyramine-exposed HT29 cell cultures vs. untreated control cultures. The horizontal black line represents the threshold of statistical significance (p = 0.05). The vertical dotted black lines represent a fold change cut-off of ≥4. (B) Genes showing a statistically significant fold change (≥4) are shown. See also Supplementary Table 1S. Tma: tyramine.

Figure 2

Gene expression analysis of DNA damage-signalling pathways in tyramine-exposed HT29 cells compared to untreated cells. (A) Volcano plot representation of tyramine-exposed HT29 cultures vs. untreated control cultures. The horizontal black line represents the threshold of statistical significance (p = 0.05). The vertical dotted black lines represent a fold change cut-off of ≥4. (B) Genes showing a statistically significant fold change (≥4) are shown. See also Supplementary Table 2S. Tma: tyramine.

Figure 3

Real time qPCR gene expression analysis of differently expressed genes – (A) BBC3, (B) CPT2, (C) GADD45A, (D) GADD45G, (E) PPP1R15A and (F) DDIT3 - in tyramine-exposed HT29 cells compared to control cultures. Cell cultures were exposed to one of six tyramine concentrations (0, 0.91, 1.82, 3.65, 7.29 or 14.58 mM) for 6 h. Data were normalized against the total RNA content using GAPDH as a reference gene. The data represent the mean of two biological replicates (each in duplicate). Vertical bars represent standard deviations. *p < 0.05, **p < 0.001 compared to control cultures.