The Microbiota-Derived Metabolite of Quercetin, 3,4-Dihydroxyphenylacetic Acid Prevents Malignant Transformation and Mitochondrial Dysfunction Induced by Hemin in Colon Cancer and Normal Colon Epithelia Cell Lines

Meat diet plays a pivotal role in colorectal cancer (CRC). Hemin, a metabolite of myoglobin, produced after meat intake, has been involved in CRC initiation. The compound, 3,4-dihydroxyphenylacetic acid (3,4HPAA) is a scarcely studied microbiota-derived metabolite of the flavonoid quercetin (QUE), which exert antioxidant properties. The aim of this study was to determine the protective effect of 3,4HPAA against malignant transformation (increased cell proliferation, decreased apoptosis, DNA oxidative damage and augmented reactive oxidative species (ROS) levels) and mitochondrial dysfunction induced by hemin in normal colon epithelial cells and colon cancer cells. The effect of 3,4HPAA was assessed in comparison to its precursor, QUE and to a known CRC protective agent, sulforaphane (SFN). The results showed that both, tumor and normal cells, exposed to hemin, presented increased cell proliferation, decreased caspase 3 activity and cytochrome c release, as well as augmented production of intracellular and mitochondrial ROS. In addition, hemin decreased the mitochondrial membrane potential (MMP) and the activity of complexes I and II of the electron transport chain. These effects of hemin were prevented by the action of 3,4HPAA. The metabolite showed to be more active than QUE and slightly less active than SFN. In conclusion, 3,4HPAA administration could represent a promising strategy for preventing malignant transformation and mitochondrial dysfunction in colon epithelia induced by hemin.