Extracted form: www.news-medical.net
Skin plays a surprising role in helping regulate blood pressure and heart rate, according to scientists at the University of Cambridge and the Karolinska Institute, Sweden. While this discovery was made in mice, the researchers believe it is likely to be true also in humans.
In a study published in the open access journal eLife, the researchers show that skin – our largest organ, typically covering two square meters in humans – helps regulate blood pressure and heart rate in response to changes in the amount of oxygen available in the environment.
High blood pressure is associated with cardiovascular disease, such as heart attack and stroke. For the vast majority of cases of high blood pressure, there is no known cause. The condition is often associated with reduced flow of blood through small blood vessels in the skin and other parts of the body, a symptom which can get progressively worse if the hypertension is not treated.
Previous research has 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’ family of proteins.
To investigate what role the skin plays in the flow of blood through small vessels, a team of researchers from Cambridge and Sweden exposed mice to low-oxygen conditions. These mice had been genetically modified so that they are unable to produce certain HIF proteins in the skin.
“Nine of ten cases of high blood pressure appear to occur spontaneously, with no known cause,” says Professor Randall Johnson from the Department of Physiology, Development and Neuroscience at the University of Cambridge. “Most research in this 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 researchers 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.
In addition, the researchers showed that even the response of normal, healthy mice to oxygen starvation was more complex than previously thought. In the first ten minutes, blood pressure and heart rate rise, and 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 levels had returned to normal.
Loss of the HIF proteins or other proteins involved in the response to oxygen starvation in the skin, was found to dramatically change 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,” adds first author Dr Andrew Cowburn, also from Cambridge. “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.”
Professor Johnson adds: “Given that skin is the largest organ in our body, it perhaps shouldn’t be too surprising that it plays a role in regulation such a fundamental mechanism as blood pressure. 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.”
科學家證實－皮膚扮演著調節血壓及心律的角色
新聞來源：www.news-medical.net
英國劍橋大學 (University of Cambridge)及瑞典卡羅林斯卡學院 (Karolinska Institute, Sweden)的科學家表示，皮膚在調節血壓及心率上扮演意想不到的角色。雖然這項結果主要在老鼠身上發現，學者認為該結論可能也適用於人類。
學者在開放式取用期刊⟪eLife⟫中發表的研究中指出，皮膚這個佔人體表面約兩平方公尺的最大器官，可以根據環境中的供氧變化調整人體血壓及心率。
高血壓與心血管疾病如心肌梗塞、中風有關，然而大部分高血壓的成因至今仍是未知，僅推測其和皮膚及身體各處微小血管的血流減少有關，且症狀可能因缺乏治療而逐漸惡化。
根據之前的研究顯示，在缺氧誘導因子 (HIF proteins) 調控下，當身體處於高海拔環境或在毒害、菸害、肥胖等因素中造成的組織缺氧，會導致流往該組織的血流增加。
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劍橋大學和瑞典的研究團隊將經過基因修改以後、皮膚無法表現缺氧誘導因子的小鼠置於低氧環境中，以釐清皮膚對於微小血管血流調控的角色。
劍橋大學生理暨神經科學學院 (Department of Physiology, Development and Neuroscience at the University of Cambridge) Randall Johnson教授表示：「十分之九的高血壓是自發性的，沒有人知道原因。而大部分這方面的研究著重於大腦、心臟和腎臟等扮演的角色，我們對於其他器官的作用了解甚少。」
「我們的研究目的是為了了解皮膚和心血管循環系統之間的回饋機制。藉由小鼠基因的操作，我們得以找到操控這個迴路中的關鍵基因。」
研究發現缺乏其中之一 HIF protein (HIF-1α 及 HIF-2α)的小鼠在低氧環境中的反應，無論是心率、血壓，體表溫度或整體活動力，都和正常小鼠有顯著差異。缺乏由HIF所調控之下游蛋白的小鼠，也有類似表現。
另外，健康正常小鼠在缺氧環境下的反應也較預期複雜。在最初十分鐘，血壓及心率上升，接下來的36小時，兩者皆降低至正常值以下，直到48小時後回到正常值。
而缺乏HIF或其他相關的蛋白的小鼠在缺氧環境下的起始反應和反應持續時間都有相當顯著的變化。
「這些發現顯示皮膚在低氧環境下的反應可能對體內血液的運輸有實質上的影響，」Andrew Cowburn博士補充道。「暫時性或持續性的低氧都很常見，除了自然環境之外，也可能和抽菸及肥胖等因素有關。我們希望藉由這項研究更加了解身體在面對這些環境時的反應是否會增加高血壓的風險或直接導致高血壓。」
Johnson教授提到：「既然皮膚是身體最大的器官，它在血壓調節這樣的基礎機制上扮演重要角色或許不是件值得驚訝的事，但這也提醒我們應該試著了解其他器官或組織和血壓調節之間的關聯。」