A study from the University of California, Irvine reveals that compounds in both green and black tea relax blood vessels by triggering ion channel proteins in the blood vessel wall. The discovery helps explain the antihypertensive properties of tea and could cause the design of new blood pressure-lowering medications.
Released in Cellular Physiology and Biochemistry, the discovery was made by the laboratory of Geoffrey Abbott, PhD, a professor in the Department of Physiology and Biophysics in the UCI School of Medicine. Kaitlyn Redford, a graduate student in the Abbott Lab, was first author of this study titled, “KCNQ5 potassium channel activation underlies vasodilation by tea.”
Results from the research revealed that two catechin-type flavonoid chemicals (epicatechin gallate and epigallocatechin-3-gallate) found in tea, each trigger a certain type of ion channel protein called KCNQ5, allowing potassium ions to diffuse out of cells to reduce cellular excitability. As KCNQ5 is found in the smooth muscle that lines blood vessels, its stimulation by tea catechins was also predicted to relax blood vessels – a prediction confirmed by collaborators in the University of Copenhagen.
“We found by using computer modeling and mutagenesis studies that specific catechins bind to the foot of the voltage sensor, which is the part of KCNQ5 that allows the channel to open in response to cellular excitation. This binding allows the channel to open much more easily and earlier in the cellular excitation process,” explained Abbott.
As many as one third of the world’s adult population have hypertension, and this condition is regarded as the number one modifiable risk factor for international cardiovascular disease and premature mortality, new methods for treating hypertension possess enormous potential to improve global public health. Prior studies demonstrated that consumption of green or black tea can decrease blood pressure by a small but constant quantity, and catechins were previously found to contribute to this property. Identification of KCNQ5 as a novel target for the hypertensive properties of tea catechins may ease medicinal chemistry for enhanced efficacy or effectiveness.
Along with its function in controlling blood vessels tone, KCNQ5 is expressed in a variety of areas of the brain, where it regulates electrical activity and signaling between neurons. Pathogenic KCNQ5 gene variations exist that impair its station work and in doing so cause epileptic encephalopathy, a developmental disorder that is seriously debilitating and triggers frequent seizures. Since catechins can cross the blood-brain barrier, discovery of their capacity to trigger KCNQ5 might recommend a potential mechanism to fix broken KCNQ5 channels to ameliorate brain excitability ailments stemming from their dysfunction.
Tea has been generated and consumed for more than 4,000 years and upwards of two billion cups of tea are now consumed daily worldwide, second only to water in terms of the quantity consumed by people worldwide. The three generally consumed caffeinated teas (green, oolong, and black) are all produced from the leaves of the evergreen species Camellia sinensis, the differences arising from other degrees of fermentation during tea creation.
Black tea is commonly mixed with milk before it’s consumed in countries including the United Kingdom and the United States. The researchers in the current research found that when black tea has been applied to blood vessels cells comprising the KCNQ5 channel, the addition of milk prevented the beneficial KCNQ5-activating effects of tea. But, according to Abbott, “We don’t believe this means one needs to avoid milk when drinking tea to take advantage of the beneficial properties of tea. We are confident that the environment in the human stomach will separate the catechins from the proteins and other molecules in milk that would otherwise block catechins’ beneficial effects.”
This theory is borne out by other studies demonstrating antihypertensive blood vessels advantages of tea regardless of milk co-consumption. The team also discovered that using mass spectrometry, that warming green tea to 37 degrees Celsius (95 degrees Fahrenheit) alters its chemical makeup in a manner that leaves it more effective at triggering KCNQ5.
“Regardless of whether tea is consumed iced or hot, this temperature is achieved after tea is drunk, as human body temperature is about 37 degrees Celsius,” explained Abbott. “Thus, simply by drinking tea we activate its beneficial, antihypertensive properties.”
Related Journal Article: https://www.cellphysiolbiochem.com/Articles/000337/