| Summary: | Since the ingredients of soft drinks are generally hidden and protected by law, unknown substances may affect cell proliferation and the function of the gastrointestinal epithelial cells. Concerns have been expressed regarding the toxicity of caramel coloring used in soft drinks. The present study examined the potential toxicity of 2-acetyl-4(5)-tetrahydroxy butylimidazole (THI), a byproduct of caramel coloring III, and its effects on three types of gastrointestinal cells (HGC-27, IEC-6, and Caco-2 cells). The inhibition of cell proliferation was stronger by Caramel III containing THI than by Caramel I or IV without THI. However, the inhibition of cell proliferation was not observed under THI exposure conditions, suggesting that THI does not act as a failure factor. On the other hand, since THI increased trans-epithelial electrical resistance (TEER), an indicator of epithelial physical barrier function, it may exert enhancing effects on tight junctions, a representative physical barrier. No cytotoxicity against gastrointestinal epithelial cells was observed, even under THI exposure conditions at concentrations that were markedly higher than those obtained from the ingestion of beverages. Conversely, TEER was elevated by the exposure to high THI concentrations, and was suggested to enhance epithelial cell barrier function. Since THI appears to act on absorption-regulating factors, further studies are needed, including methods for the application of THI.
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