Using Transcription Factor Based Assays to Study Herbal Products

Transcription factors bind to specific DNA sequences in the vicinity of genes and are the major regulators of gene expression. The activity of these factors is controlled by the various signal transduction mechanisms and second messenger systems used by the cell to coordinate and respond to signals from the extracellular environment, including hormones and the local tissue environment. Because of this, transcription factors can be used to indirectly monitor the activity of many cellular components, such as the status of membrane receptor-hormone interactions, the biochemical transformations accompanying the relay of this binding event to a cytoplasmic signal, or the multitude of protein targets used to coordinate this signal to various cellular compartments. By monitoring the activity of several transcription factors, one can gain an overall impression of the state of various signal transduction systems and other targets. Therefore, monitoring transcription factors’ activities is useful for determining the influence that a particular herb or herbal component may have on a cell. The easiest way to detect changes in transcription factor activity is through luciferase reporter gene technology. These plasmid constructs can contain either the complex promoter region of a gene or binding sites for a particular transcription factor. Comparing activity profiles of herbs or herbal components to specific transcription factors can provide an index of specificity, in addition to determining potential mechanisms of action. The particular transcription factor binding sites comprising the battery are chosen based on the type of activity an herb exhibits and/or upon a well-established therapeutic target of the disorder. The same criteria determine the cell type or types used for the assays. Results and examples of the utilization of this technology over the past several years at the National Center for the Development of Natural Products (NCNPR) will be presented from the therapeutic areas of inflammation and immunomodulation.