Mechanisms Underlying Food Functionality via Molecular Chaperones: Chemical Training Hypothesis

AKIRA MURAKAMI* AND KOHTA OHNISHI

Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Kyoto, Japan.

ABSTRACT

Most physiologically functional food factors are derived from plants. Although those chemicals exhibit versatile bioactivities, their mechanisms of action are not fully understood. It is important to indicate that phytochemicals, but not plant nutrients, xenobiotics in humans and thus induce expressions of self-defense molecules, including anti-oxidative and xenobiotic function as metabolizing enzymes via the Keap1/Nrf2 system. In addition, recent reports have shown that several phytochemicals are capable of up-regulating the activities of molecular chaperones such as heat shock proteins (HSPs) and proteasomes. For example, sulforaphane, a sulfur-containing phytochemical present in cruciferous plants, was recently reported to induce HSP27 expression and increase proteasome activity. On the other hand, accumulating evidence shows that some toxins exert health beneficial effects under non-toxic doses, a phenomenon termed hormesis. Importantly, those beneficial effects are abrogated or disappear when given in high doses. Collectively, chronic exposure to phytochemicals, i.e., ‘chemical training’, may increase self-defense mechanisms, thereby contributing to health promotion and disease prevention.

Key words: phytochemical, molecular chaperone, heat shock protein, stress adaptation.