The scientists said that hypertension, which can lead to heart attacks, strokes and kidney damage, is an inflammatory vascular disease of the brain rather than the heart, as previously thought.
They discovered that a protein located in the brain, JAM-1, trapped white blood cells, which can then cause inflammation and obstruct blood flow, leading to poor oxygen supply to the brain.
The associate medical director of the British Heart Foundation, Professor Jeremy Pearson, said: "This exciting study is important because it suggests there are unexpected causes of high blood pressure related to blood supply to the brain.
"It therefore opens up the possibility of new ways to treat this common, but often poorly managed condition."
More than 600 million people worldwide are thought to suffer from hypertension.