Diseases of the heart and blood vessels are linked with high blood pressure.
The causes of most cases of high blood pressure are unknown, but it is often accompanied by the reduced flow of blood through small vessels in the skin and other parts of the body that are a long way from the heart.
It is not clear why this change happens or why it tends to get worse over time in people with high blood pressure that has not been treated.
Previous studies have shown that when a tissue is starved of oxygen — as can happen in areas of high altitude, or in response to pollution, smoking or obesity, for example — blood flow to that tissue will increase. In such situations, this increase in blood flow is controlled in part by the HIF (hypoxia-inducible factor) family of proteins.
To investigate what role the skin plays in the flow of blood through small vessels, Dr Cowburn and his colleagues from the University of Cambridge and the Karolinska Institute in Sweden exposed mutant mice that cannot produce certain HIF proteins specifically in the skin to low-oxygen conditions.
“Nine of ten cases of high blood pressure appear to occur spontaneously, with no known cause,” said study senior author Professor Randall Johnson, from the University of Cambridge.
“Most research in these areas 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.”
“Our study was set up to understand the feedback loop between skin and the cardiovascular system. By working with mice, we were able to manipulate key genes involved in this loop.”
The team found that in mice lacking one of two proteins in the skin (HIF-1α or HIF-2α), the response to low levels of oxygen changed compared to normal mice and that this affected their heart rate, blood pressure, skin temperature and general levels of activity.
Mice lacking specific proteins controlled by the HIFs also responded in a similar way.
The authors also demonstrated that the way normal healthy mice respond to oxygen starvation is more complex than previously thought.
Blood pressure and heart rate rise up during the first ten minutes. This is followed by a period of up to 36 hours where blood pressure and heart rate decrease below normal levels. By around 48 hours after exposure to low levels of oxygen, blood pressure and heart rate recover, returning to normal levels.
Loss of the HIF proteins or other proteins involved in the response to oxygen starvation specifically in the skin affect when this process starts and how long it takes.
“These findings suggest that our skin’s response to low levels of oxygen may have substantial effects on the how the heart pumps blood around the body,” Dr Cowburn said.
“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.”
Source: Sci News