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A new study from the University of California, Irvine shows that chemicals in both black and green tea relax blood vessels by activating ion channel proteins in the blood vessel wall. The discovery helps explain the antihypertensive properties of tea and could lead to the design of new blood pressure-lowering medications.
Released in Cellular Physiology and Biochemistry, the discovery was made by the lab of Geoffrey Abbott, PhD, a professor in the Department of Physiology and Biophysics at the UCI School of Medicine.
Results from the research revealed that two catechin-type flavonoid compounds (epicatechin gallate and epigallocatechin-3-gallate) found in tea, each trigger a specific type of ion channel protein called KCNQ5, allowing potassium ions to diffuse out of cells to reduce cellular excitability. As KCNQ5 is located in the smooth muscle that lines blood vessels, its activation by tea catechins was also predicted to relax blood vessels – a prediction confirmed by collaborators at 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.”
Geoffrey Abbott, PhD, Professor, Department of Physiology and Biophysics, UCI School of Medicine
As many as one third of the world’s adult population have hypertension, and this condition is thought of as the number one modifiable risk factor for global cardiovascular disease and premature mortality, new approaches to treating hypertension have 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 consistent amount, 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 facilitate medicinal chemistry optimization for improved potency or efficacy.
In addition to its role in controlling vascular tone, KCNQ5 is expressed in various parts of the brain, where it regulates electrical activity and signaling between neurons. Pathogenic KCNQ5 gene variants exist which impair its channel function and in doing so cause epileptic encephalopathy, a developmental disorder that’s seriously debilitating and causes frequent seizures. Since catechins can cross the blood-brain barrier, discovery of their ability to activate KCNQ5 might recommend a future mechanism to fix broken KCNQ5 channels to ameliorate brain excitability disorders stemming from their dysfunction.
Tea has been produced and consumed for more than 4,000 years and upwards of 2 billion cups of tea are currently drunk each day worldwide, second only to water concerning the volume consumed by people globally.
Black tea is usually mixed with milk before it is consumed in countries including the United Kingdom and the USA. The researchers in the present study found that when black tea has been directly applied to cells containing the KCNQ5 channel, the addition of milk avoided the beneficial KCNQ5-activating effects of tea. However, according to Abbott,”We do not think this means one wants to prevent milk when drinking tea to take advantage of the beneficial properties of tea. We’re confident that the environment in the human gut will separate the catechins in the proteins and other molecules in milk which would otherwise block catechins’ beneficial effects.”
This theory is borne out by other research showing antihypertensive benefits of tea irrespective of milk co-consumption. The team also discovered, using mass spectrometry, that warming green tea to 35 degrees Celsius changes its chemical makeup in a manner that renders it more effective at activating KCNQ5.
“Regardless of if tea is consumed iced or warm, 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 valuable, antihypertensive properties.”
University of California – Irvine
Redford, K.E., et al. (2021) KCNQ5 Potassium Channel Activation Underlies Vasodilation by Tea. Cellular Physiology and Biochemistry. doi.org/10.33594/000000337.