Adrenaline and your heart

Heart muscle cells derived from stem cells

Judy O’Sullivan talks to Professor Sian Harding about her BHF-funded research looking at the complex effects of adrenaline on the heart.

Have you heard of people showing almost superhuman powers to combat or flee a dangerous situation?

When a sudden disaster such as an earthquake strikes, there are often reports of parents somehow rescuing their children by lifting heavy objects that, under normal circumstances, they wouldn’t have been able to budge.

This is known as the ‘fight or flight’ response, where the body experiences a rapid increase in energy in extreme situations.

While the majority of us are lucky enough not to have experienced an earthquake, we will all have felt an adrenaline rush during moments of great anger or excitement at some point in our lives. Most of the time, the release of adrenaline is protective – or at least harmless – but this is not always the case.

More than 570,000 people in the UK live with a condition called chronic heart failure

More than 570,000 people in the UK live with a condition called chronic heart failure, which is when the heart muscle is permanently damaged. This is usually as a result of a heart attack and it means that the heart doesn’t work as efficiently.

We know that the body releases adrenaline to try to make the inefficient heart work harder, and cardiologists had thought that this would protect the damaged heart. However, thanks to medical research, we now know that adrenaline, in these circumstances, actually causes further damage.

We also know that there are specific sites on the cells of major organs, including the heart, called beta receptors, which respond to the adrenaline when it is released, by increasing the heart rate. Making the inefficient heart work harder can be dangerous so, to block this response, scientists developed a type of drug called beta blockers. As there are several types of beta receptor, there are also several types of beta blocker to act on them.

Many of you may be familiar with beta blockers, as it is standard medical practice to advise patients with heart failure to take them to protect their hearts from the effects of adrenaline.

Sian Harding's research into Takotsubo cardiomyopathy

Sian Harding, Professor of Cardiac Pharmacology at Imperial College London, is researching "broken heart syndrome" and what it can tell us about chronic heart failure.

Motivations

I am interested in chronic heart failure, but have recently been intrigued by a rarer condition called Takotsubo syndrome, which is a sudden and temporary bulging of the heart muscle that causes acute and short-term heart failure.

Takotsubo syndrome happens in times of extreme emotional distress such as bereavement, which is why it’s also known as broken heart syndrome.

Of course, people all over the world are affected by bereavement on a regular basis, but the majority of us do not experience such an extreme reaction as Takotsubo syndrome, so I would like to understand why it happens to some people and not others.

Approximately 3,000 people in the UK each year suffer from the condition and it is most common in post-menopausal women.

I would also like to find out why the majority of people who have this condition make such a good recovery, despite their heart having been exposed to large doses of adrenaline.

My research

My theory is that in Takotsubo syndrome (short-term heart failure), one type of beta receptor switches its behaviour to being protective and reduces the stimulation of the heart, which is why people make a good recovery. My team and I want to study this change of behaviour because, if we are able to understand it in Takotsubo syndrome, it might lead to the development of a drug that would kick-start the protective mechanism in chronic heart failure.

We hope that beta blockers will help guide drug development for patients with chronic heart failure

We want to examine the interaction between adrenaline and beta receptors in human cells, so we are using stem cells. Stem cells are the body’s master cells or building blocks – when babies develop in the womb, some of their stem cells become brain cells, some become heart cells and so on. Scientific research has made it possible for us to turn skin cells into stem cells and then into heart muscle cells, so that is what we are working on now.

Because we have cells from lots of people, we can look at different genetic backgrounds, as well as examine the ways heart muscle cells behave when they have been damaged. We are also looking at the different types of beta receptor and their response to the beta blockers.

What it means for patients

We hope that a better understanding of beta receptors and their interaction with beta blockers will help guide drug development for patients with chronic heart failure. It may be that some of the beta blockers already have the properties needed, or we may need to make new ones.

Beta blockers

  • Beta blockers work by blocking the effect of hormones such as adrenaline on the heart.
  • They are commonly prescribed to people with heart failure or angina, or following a heart attack.
  • They are used to treat high blood pressure alongside another drug.
  • They can also be used in the short term for people whose heart rate is disturbed because of emotional stress.

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