Scientists in pharmaceutical companies utilize various Bioactivity Screening Programs to identify novel synthetic chemical compounds that might prove effective in treating various diseases such as cancer, cardiovascular, arthritis or other inflammatory diseases. Such screening always starts with looking at the effect of a given compound on some biological response in cultured human or animal cells. For example a compound being studied for anti-cancer activities, might be tested on cancer cells in culture for its ability to halt cell proliferation or, alternatively, to trigger the cancer cell to undergo apoptosis (cell death). For dermatology applications, a chemical compound candidate might be tested for its ability to block the production of PGE-2 in human fibroblasts treated with ultraviolet radiation.
In studies conducted several years ago in the Department of Biochemistry and Molecular Biologyat the University of Oklahoma Health, scientists tested the ability of a variety of natural antioxidant compounds, such as curcumin, resveratrol, quercetin, gallic acid, vitamin C, retinol, and EGCG (from green tea) to inhibit either the production of or action of a variety of inflammatory markers (cytokines) produced by skin and immune cells and which are known to be important in the development of various inflammatory skin problems, such as psoriasis and atopic dermatitis. A typical cutaneous inflammatory response and the key cytokines and adhesion molecules expressed during this reaction are illustrated below.
The inflammatory reaction begins with an initial insult to the skin, which results in the release of inflammatory cytokines by keratinocytes and fibroblasts. These cytokines then stimulate endothelial cells to express adhesion molecules, which aid in the attachment and transmigration of immune cells into the area of inflammation. Once the immune cells have entered the area of insult, the inflammatory response is perpetuated until the insult and damage caused is resolved. The inhibition of the expression of one or more of these cytokines or adhesion molecules during an inflammatory response can result in a reduction or inhibition of inflammation.
Depending on the laboratory doing the work, the screening of a candidate molecule’s ability to reduce the production of these key inflammatory markers may be based on the following assays:
- The effect of a candidate compound on the production of inflammatory cytokines and adhesion molecules produced by keratinocytes, fibroblasts and monocytes (ELISA) is usually assessed first.
- The effect of the candidate on the gene expression of key inflammatory cytokines in keratinocytes, fibroblasts and monocytes (RT-PCR) is determined.
- The ability of the compound to alter the gene expression of key adhesion molecules produced by endothelial cells is determined using RT-PCR technology.
- The effect of a drug candidate on the production of other important inflammatory cytokines is determined by use of Antibody Arrays.
This anti-inflammatory screening strategy is illustrated below.
By carrying out this type of rigorous analysis for anti-inflammatory effects of natural compounds, it is possible to identify those botanically based antioxidants which have benefticial anti-inflammtory activities. This type of screening is being used by many research laboratories with excellent success in identifying safe and gentle naturally occurring antioxidants that are widely distributed in foods and which have beneficial health properties. In fact, the increasing amount of published reports discussing which fruits and vegatables to eat to improve health and reduce the risk of disease, is largely based on results from this type of screening. The various inflammatory processes that one particular natural antioxidant compound, TH-211, can inhibit, either directly (blue X) or indirectly (red X) are shown below.
Interestingly, this particular compound, discovered at the University of Oklahoma, is not only an antioxidant, but an approved food flavoring additive that has been used in foods worldwide for over 50 years.