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The healing power of light

Light makes us flourish – in this respect we humans are just like a rose or an azalea. Light can also be used to treat people who are ill. In Leiden, Sylvestre Bonnet and Esther Habers are working – each in their own discipline – on new applications of light in a clinical context.

This article previously appeared in Leidraad, Leiden University’s free alumni magazine.

Psychologist Esther Habers: light therapy for rheumatoid arthritis

‘People with rheumatoid arthritis often suffer from extreme fatigue. There are good drugs nowadays for many patients, but the fatigue remains. Sleep and rest don’t help. These people are tired when they get up in the morning and tired when they go to bed at night. Cognitive behavioural therapy is sometimes used and can help somewhat.

‘For our research, we are approaching this problem from a new perspective: we are researching what light can do for this group. Patients with rheumatoid arthritis often go to bed early and generally wake up really early too. Their biological clock seems to be set too early; this may be related to their exhaustion.

Hormone melatonin

‘With our 24-hour clock, the hormone melatonin plays an important role as a transmitter substance. When it becomes dark, the body starts to produce melatonin. There are indications that people with rheumatoid arthritis start producing melatonin too early in the evening. We are now researching whether light therapy can delay this melatonin production.

‘We are using a set of glasses that emit bright light. Test subjects will wear these for half an hour every evening for a period of four weeks. We hope that their melatonin production will kick into action later in the evening. They will therefore be exposed to bright light between 20:00 and 21:00. The body will then think it’s still day.

Measuring melatonin levels

‘Before the four weeks begin, we will measure the test subjects’ melatonin levels during an evening and a night, and we will repeat this afterwards. The results will show whether light therapy has worked. That would be great because this therapy is really easy to use. The glasses that we are using are available in the shops. I expect to have the results of the research later this year. This research has made me appreciate how important light is and how it affects all the processes in the body. I now try to go outside every day, regardless of how busy I am.’

Chemist Sylvestre Bonnet: light-activated chemotherapy

‘Light is magic. Imagine bringing light into contact with a certain substance and this causing a chemical reaction. It is precisely this aspect that I am using in my research into photodynamic therapy, or light-activated chemotherapy in cancer. This therapy has already been in use for some time in hospitals. It works as follows: the patient is administered a medicine that can only be activated by light. By shining a laser on the tumour, the medicine starts to work – but only in the tumour itself, not in other parts of the body.

Laser light

‘The laser light can be in different colours and at different intensities. Blue light mainly works superficially and is thus suited for skin cancer, for instance. The current photodynamic therapy doesn’t work on some tumours because their blood supply is low and they are thus oxygen poor. Oxygen is an essential part of the chemical reaction.

Complicated search

‘I was awarded a Vici grant at the start of the year to look with my team for molecules that can be used in photodynamic therapy with oxygen-poor or hypoxic tumours. That’s a complicated search because the molecule has to be able to absorb and react to light. We use ruthenium, a toxic metal, and are now concentrating on tumours in the brain, liver, head and neck region, skin and eyes.

The Vici project will take five years; it is fundamental scientific research. Applied research is also important to this topic. I therefore hope that we will be able to find an industrial partner or a network of companies and form a partnership with a hospital. You can find an excellent molecule, but that isn’t enough to make it available for patients. It also has to be tested in a clinical environment. If we manage to find a partner, the new drug could even be on the market in ten years’ time.’

Read Leidraad alumni magazine

Read the latest Leidraad online [in Dutch]. 

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