Press and Public Relations

Biosensor for Measuring Stress in Cells

No. 29 | 16/05/2008 | by (Koh)

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

The German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) with its more than 3,000 employees is the largest biomedical research institute in Germany. At DKFZ, more than 1,000 scientists investigate how cancer develops, identify cancer risk factors and endeavor to find new strategies to prevent people from getting cancer. They develop novel approaches to make tumor diagnosis more precise and treatment of cancer patients more successful. The staff of the Cancer Information Service (KID) offers information about the widespread disease of cancer for patients, their families, and the general public. Jointly with Heidelberg University Hospital, DKFZ has established the National Center for Tumor Diseases (NCT) Heidelberg, where promising approaches from cancer research are translated into the clinic. In the German Consortium for Translational Cancer Research (DKTK), one of six German Centers for Health Research, DKFZ maintains translational centers at seven university partnering sites. Combining excellent university hospitals with high-profile research at a Helmholtz Center is an important contribution to improving the chances of cancer patients. DKFZ is a member of the Helmholtz Association of National Research Centers, with ninety percent of its funding coming from the German Federal Ministry of Education and Research and the remaining ten percent from the State of Baden-Württemberg.

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