Researchers at the University of Chicago have found that extracts from the Chinese herb Scutellaria baicalensis, contain powerful antioxidants that can significantly reduce cellular damage due to free radicals-highly reactive compounds that are generated during metabolism and which contribute to the normal wear and tear of the cell. A rapid buildup of free radicals in cells may be an underlying cause of death in cardiac arrest patients who quickly regain a pulse.
"Restoring the regular heart beat in cardiac arrest patients does not mean the patient is out of the woods," says Terry Vanden Hoek, MD, assistant professor of emergency medicine, and one of the authors of the paper to appear in the October issue of the Journal of Molecular and Cellular Cardiology. "Despite return of a pulse, most of these patients still die within minutes to hours."
Scientists think this is because during cardiac arrest, when oxygen and energy are cut off from the cells, wastes build up and become trapped. Once blood flow is restored, the cells switch into overdrive to rid themselves of accumulated toxic compounds. In this revved up state, cells produce an explosion of free radicals which can cause permanent cellular damage.
Antioxidants like vitamin C and E work by binding to free radicals and preventing them from doing damage to the cells. But vitamins C and E are slow to penetrate the cell membrane.
Vanden Hoek and his colleagues found out about baicalensis from Chun-Su Yuan, MD, Ph.D., assistant professor of anesthesia & critical care and clinical pharmacology at the University of Chicago with an interest in traditional Chinese medicine. Yuan noticed that extracts from baicalensis contained high concentrations of antioxidants whose molecular shape allowed them to slip quickly into cells. The roots of the plant (known as Huang-Quin in Chinese and wogon in Japanese) have been used for more than 1,000 years to treat allergic and inflammatory diseases.
The researchers tested the effect of the extract on chicken cardiomyocetes (heart cells) in a petri dish that simulates blood flow using liquid medium containing dissolved oxygen and sugars. They simulated the conditions of cardiac arrest by halting the flow of oxygen and sugar through the medium for one hour. A fluorescent marker was used to label free radicals.
During the simulation, a gradual build up of fluorescent marker appeared in the cells. But when the oxygen and sugar were reintroduced into the liquid (simulating the restoration of a pulse) a burst of fluorescence was observed, reflecting a rapid increase in the production of free radicals. In the following hours, the cells never regained their natural ability to beat rhythmically.
In experiments where baicalensis extract was added to the perfusion fluid along with the oxygen and sugar, the cells eventually began to contract rythmically again. "Even though the cells that got the extract never beat entirely normally again, they did regain their ability to contract which is a really great start," says Vanden Hoek.
"Though this extract is far from human trials, this paves the way for developing new therapies for cardiac arrest as well as other diseases where oxygen flow is blocked and then restored such as in a stroke," Vanden Hoek explains.
Other researchers on the paper included Zuo-Hui Shao,MD; Chang-Quing Li, MD; Lance Becker, MD, Paul T. Schumacker, Ph.D., from the department of Emergency Medicine and Pulmonary/Critical Care and the Emergency Resuscitation Research Center (ERRC) at the University of Chicago; Ji A. Wu and Anoja S. Attele from the Department of Anesthesiology and Critical Care and the Committee on Clinical Pharmacology at the University of Chicago.
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