Bursting the bubble
31 August 2006
Known as the ‘silent killer’, high blood pressure – or hypertension – is one of the world’s biggest killers, affecting one in three of us.
Once hypertension is established it will eventually lead to a number of serious and disabling illnesses such as stroke, kidney disease, heart attacks and angina. Despite extensive research, we still do not know what causes hypertension in 95% of suffers.
Worryingly, more than two thirds of people taking anti-hypertensive medication continue to have a blood pressure reading above the normal limit. This has prompted new investigations by a group of researchers at the Bristol Heart Institute into how the body regulates blood pressure and what can be done to control it in conditions of hypertension.
Whilst obesity, diet, lack of exercise, genetic (hereditary) factors and emotional stress may all contribute to the development of hypertension, recent evidence indicates that excessive nerve activity from the brain may also be a potential cause.
You don't feel hypertension, so why worry about it?
In healthy people, blood pressure is regulated by nervous activity that originates from specific regions of the hind brain, or brainstem. Its function is to accelerate the heart beat and narrow the arteries, thereby increasing arterial pressure during conditions of exercise and stress, for example. However, this activity becomes greatly exaggerated in people with hypertension. Interestingly, this nervous activity appears to be raised before high blood pressure fully develops, indicating that it may be a causative mechanism.
Researchers in the Bristol Heart Institute have identified genetic differences in the brainstem of hypertensive subjects, when compared to those with normal blood pressure. What’s more, they have been able to show that some of these genes can cause hypertension when they are activated in the brainstem.
Many of these genes are associated with the cells that line the blood vessels supplying the brainstem and cause an inflammatory response. This has led to the emergence of the novel concept that the diffusion of molecules from these genetically altered and inflamed blood vessels directly affects the activity of brain cells that normally regulate blood pressure. These molecules are highly reactive and potentially damaging to brain cell function and appear to cause hypertension. This is an exciting new finding as now the blood vessels within the brainstem provide a novel target for treating with new drugs and possibly gene therapy strategies.
The idea would be to reduce the production of inflammatory related molecules to rescue normal brain cell function. These findings may provide a much-needed and more powerful way to bring blood pressure back down to normal, safe levels.