Human β-Defensin-2 Induction in Human Foreskin Keratinocyte by Synergetic Stimulation with Foods and Escherichia Coli

摘要

We established a real-time quantitative RT-PCR assay that permits rapid and sensitive screening of foods that increase the human β-defensin-2 (hBD-2) mRNA level in human foreskin keratinocyte (HFK) cells. The range of hBD-2 mRNA concentrations suitable for the assay was between 8 × 10⁻¹¹ M (39-cycle amplification) and 8 × 10⁻¹⁸ M (13-cycle amplification) as calibrated with standard hBD-2 cDNA. With this assay system, it was found that the stimulation of HFK cells by the addition of yeast powder at 5 g l⁻¹ to the culture medium resulted in about 40 times increase in hBD-2 mRNA level, though stimulation with Escherichia coli attained the same level of induction. The active component of yeast was insoluble in water. Simultaneous co-stimulation of HFK cells with E. coli and grains, such as amaranth, millet, soybean and sesame, boosted hBD-2 mRNA induction significantly (6.1, 2.5, 3.3, and 3.3 times, respectively) above the level attained with E. coli alone. The results of successive fractionations of amaranth grain powder by ether extraction and amylase digestion showed that the boosting activity of amaranth grain resided in its insoluble fraction. Significant boosting of hBD-2 mRNA induction in epithelial cells with foods opens a new possibility of developing functional foods that can protect the human body against microbial infection at the oral cavity, skin, and respiratory tract among others.