Researchers have found that the skin may play an important role in blood pressure regulation.
By studying mice, researchers from the United Kingdom and Sweden found that the skin responds to levels of oxygen in the environment, which influences blood pressure levels.
Study co-author Prof. Randall Johnson, of the Department of Physiology, Development and Neuroscience at the University of Cambridge in the U.K., and colleagues recently reported their findings in the journal eLife.
The condition arises when blood pushes against the wall of the arteries with too much force. This can damage the lining of the arteries, which, in turn, increases the risk of heart attack, stroke, and heart disease.
Being overweight, not partaking in physical activity, and eating a poor diet are major risk factors for high blood pressure, but according to Prof. Johnson and team, many hypertension cases arise with no known cause.
"Most research in this area," says Prof. Johnson, "tends to look at the role played by organs such as the brain, heart and kidneys, and so we know very little about what role other tissue and organs play."
According to the researchers, previous studies have shown that blood flow to a tissue rises when it is starved of oxygen, and that this is down to the presence of a family of proteins known as HIF.
For their study, Prof. Johnson and his colleagues set out to determine how oxygen starvation affects blood flow in the skin, and whether or not this influences blood pressure.
The skin, hypoxia, and blood pressure
To reach their findings, the team experimented with mice that were genetically engineered to lack various HIF proteins in the skin.
The mice were then exposed to low oxygen levels, or hypoxia. Their skin temperature, blood pressure, and heart rate were monitored in response to these conditions, and then they were compared with those of healthy rodents.
The team was interested to find that, compared with healthy mice, rodents that lacked either the HIF-1-alpha or HIF-2-alpha proteins in their skin showed an altered response to low oxygen levels.
More specifically, the mice lacking HIF-1-alpha or HIF-2-alpha experienced a significant rise in skin temperature, heart rate, and blood pressure, and their physical activity levels declined.
The study also revealed some interesting findings regarding the body's response to low oxygen in healthy mice. The researchers found that blood pressure and heart rate began to rise in the healthy rodents within 10 minutes of hypoxia, before falling to below normal levels for up to 36 hours.
By 48 hours after exposure to low-oxygen conditions, the blood pressure and heart rate of the healthy rodents returned to normal.
The scientists note that a lack of HIF proteins, as well as other proteins associated with hypoxia, in the skin affected the point at which heart rate and blood pressure started to rise, as well as how long they were increased.
Insight into the causes of hypertension
First study author Dr. Andrew Cowburn, also from the University of Cambridge, says that the team's findings indicate that the skin's response to low oxygen levels may have a significant influence on the cardiovascular system.
"Low oxygen levels — whether temporary or sustained — are common and can be related to our natural environment or to factors such as smoking and obesity. We hope that our study will help us better understand how the body's response to such conditions may increase our risk of — or even cause — hypertension."
Dr. Andrew Cowburn
Given that the skin is the body's largest organ, Prof. Johnson notes that perhaps its role in blood pressure regulation should not come as a surprise.
"But this suggests to us that we may need to take a look at other organs and tissues in the body and see how they, too, are implicated," he concludes.