The application of DNA micro-arrays (gene arrays) to the study of herbal medicines.

DNA micro-arrays (gene arrays) have become a popular and useful tool with which to study the effects of various agents and treatments on gene expression in cells and tissues. In theory one can simultaneously evaluate, in a single experiment, changes in gene expression (at the level of transcription) of the entire genome of the organism under study. Consequently these techniques have been used by many investigators interested in cancer research, differentiation and development, toxicology, and the effects of pharmaceuticals on cells and animals. In addition, recent studies have shown the capacity of the technique for revealing the importance of genes not previously implicated in a given response. However, relatively few attempts have been made so far to evaluate herbal medicines, although the potential to answer a number of relevant questions is there. In this review we first discuss the fundamental principles of the gene array technology, focusing on the individual steps in the process and their problems and pitfalls, and we discuss the analysis and interpretation of the data, the discipline of bio-informatics, without which meaningful evaluation of gene expression changes would be impossible. We next analyze specific studies, which utilized gene array technology, aimed at evaluating the effects of certain herbal medicine formulas and bioactive ingredients in animal tissues and in cell cultures. We also include a brief description of our own evaluation of Echinacea, which we have been studying for several years, to indicate possible mechanisms of action of this herbal, and also to illustrate how the techniques, especially the bio-informatics, continue to evolve. We believe, on the basis of experience acquired by us and other investigators to date, that the technology of gene array analysis can make significant contributions to understanding how herbal medicines work, and therefore can validate their applications in medicine.