Biosensor for Measuring Stress in Cells
Reactive oxygen compounds, including the well-known "free radicals", have an oxidation effect and, thereby, damage cells. However, at low levels, they also regulate key life processes. Scientists at the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) have developed a highly sensitive biological measuring system for determining the oxidation state of living cells in real time. It is the first system that enables researchers to directly observe oxidation state variations accompanying biological processes. The biosensor can also be used for studying the oxidation effect of food constituents and pharmaceutical substances. These results have been published in Nature Methods by a group of researchers headed by Dr. Tobias Dick.
Human cancer cells with biosensor show different fluorescence before (left) and after (right) the development of "Oxidative stress"
© dkfz.de
Cancer, nervous system disorders such as Parkinson’s disease, cardiovascular disorders and old age have one thing in common: Both in afflicted tissue and in aging cells, scientists have observed oxidative changes in important biomolecules. These are caused by reactive oxygen molecules, including the notorious "free radicals" that are formed as a by-product of cellular respiration and attack cellular proteins, nucleic and fatty acids.
Today, reactive oxygen molecules are no longer regarded by and large as culprits, since it has turned out that they are also involved in regulating major life processes such as growth and cell death. The right balance between oxidation and the reverse reaction, reduction, makes the difference between health and disease. "Oxidative stress" arises when this balance shifts towards oxidation-promoting processes.
So far, it has hardly been possible for scientists to measure the level of oxidation and, thus, the stress status of living cells. This will now be feasible thanks to a highly sensitive biomarker presented in the journal Nature Methods by Dr. Tobias Dick and co-workers of the German Cancer Research Center, jointly with colleagues from the University of Heidelberg.
The biosensor specifically measures the oxidation state of glutathione. This is an important protection molecule that captures a large portion of reactive oxygen molecules within a cell by oxidation. If much of a cell’s glutathione is present in an oxidized state, this is an important indicator of the cell’s overall oxidation level. The investigators equipped test cells with a fluorescent protein that reacts to changes in oxidation level by releasing light signals. Since the fluorescent protein on its own is not sensitive enough, it was coupled with an enzyme called glutaredoxin. This enzyme "measures" the oxidation state of glutathione and transmits the value to the fluorescent protein.
The stress biosensor developed by Dick and colleagues measures the slightest changes in the oxidation state of glutathione without destroying the cell. Even more relevant, however, is its precise time resolution, as Tobias Dick explains: "In order to measure short-term variations of oxidation state, the systems needs to react instantly and dynamically. This is guaranteed with our biosensor, which works down to the scale of seconds." The measuring system allows researchers to determine those short-term variations that occur when reactive oxygen compounds are released as signaling molecules. However, the biosensor is equally suitable for use in pharmaceutical research, for example, to determine the effect of new substances or plant food constituents on oxidative processes and, thus, on the stress status of cells.
Marcus Gutscher, Anne-Laure Pauleau, Laurent Marty, Thorsten Brach, Guido H. Wabnitz, Yvonne Samstag, Andreas J. Meyer and Tobias P. Dick: Real-time imaging of the intracellular glutathione redox potential. Nature Methods 2008, DOI: 10.1038/nmeth.1212
With more than 3,000 employees, the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) is Germany’s largest biomedical research institute. DKFZ scientists identify cancer risk factors, investigate how cancer progresses and develop new cancer prevention strategies. They are also developing new methods to diagnose tumors more precisely and treat cancer patients more successfully. The DKFZ's Cancer Information Service (KID) provides patients, interested citizens and experts with individual answers to questions relating to cancer.
To transfer promising approaches from cancer research to the clinic and thus improve the prognosis of cancer patients, the DKFZ cooperates with excellent research institutions and university hospitals throughout Germany:
The DKFZ is 90 percent financed by the Federal Ministry of Education and Research and 10 percent by the state of Baden-Württemberg. The DKFZ is a member of the Helmholtz Association of German Research Centers.
