Green tea has received increasing attention for its potentially beneficial effects for cardiovascular health. Recent studies have suggested that the major organic antioxidant compound in green tea, EGCG, increases cardiac contractility, but the molecular mechanisms responsible for this effect are unclear.
Björn Knollmann, M.D., Ph.D., professor of Medicine and Pharmacology, and colleagues report in the November issue of Molecular Pharmacology that EGCG increases the calcium available for contraction, which increases the force of contraction, by modulating the function of calcium-handling proteins. They demonstrate that EGCG increases calcium loading into the sarcoplasmic reticulum (SR, the cell’s internal calcium storage area), activates SR calcium release channels (ryanodine receptors) and inhibits proteins that pump calcium out of the cell (sodium-calcium exchangers).
These newly recognized EGCG actions occur at concentrations that are relevant for human consumption of green tea and may provide a novel therapeutic strategy for improving contractile function in heart failure. The authors caution, however, that EGCG could increase the risk for abnormal heart rhythms.
This research was supported by grants from the National Heart, Lung, and Blood Institute (HL088635, HL071670) and the National Institute of Environmental Health Sciences (ES004699) of the National Institutes of Health, and from the American Heart Association.