Scientists in Sweden have discovered certain peptides kill off the yeast Malassezia sympodialis which can trigger skin disorders such as atopic eczema, seborrhoeic eczema, and dandruff, without harming healthy skin cells. While further work is needed to clarify the underlying mechanisms, they hope their discovery will lead to a new treatment for these debilitating skin conditions.

The study is the work of Tina Holm and her colleagues at Stockholm University and Karolinska Institute, and was published online in the journal Letters in Applied Microbiology on 21 November.

Holm told the press:

“Many questions remain to be solved before these peptides can be used in humans. However, the appealing combination of being toxic to the yeast at low concentrations whilst sparing human cells makes them very promising as antifungal agents. We hope that these peptides in the future can be used to ease the symptoms of patients suffering from atopic eczema and significantly increase their quality of life.”

Atopic eczema is a mild to severe inflammation of the skin characterized by dry, itchy and flaky skin that usually starts in early childhood and is prone to flare-ups. It is not uncommon: for instance in the UK about 20% of children have the condition. Altough it usually clears up by the time most children reach their teens, about 7% of adults will continue to suffer for the rest of their lives.

Furthermore, atopic eczema is on the increase, and while we don’t know what causes it or how to cure it, we do know that one of the triggers is the yeast M. sympodialis, one of the most common skin yeasts in both healthy people and those suffering from eczema. Usually our skin barrier stops the yeast from causing infection: but in people with eczema, the barrier is often more fragile or even broken, so it allows the yeast to cause infection and make the condition worse.

For their study, Holm and colleagues investigated the ability of 21 different antimicrobial peptides and cell-penetrating peptides to inhibit the growth of M. sympodialis.

Peptides are like mini-proteins, they are made from the same building blocks, but are much shorter in length.

Antimicrobial peptides (AMPs) are natural antibiotics that kill many different types of microorganisms, including certain yeasts, bacteria, fungi and viruses. Cell-penetrating peptides (CPPs) are often investigated by drug companies looking for new ways to deliver drugs because they are able to cross cell membranes, although it is not clear how they do this.

The researchers added the peptides to separate colonies of M. sympodialis on glass plates to assess their antifungal activity. They also treated human skin cells or keratinocytes with the peptides to assess any potential damage.

They found that 6 (five CPPs and one AMP) of the 21 peptides successfully killed the yeast without damaging the membranes of the keratinocytes.

The researchers concluded that:

“To our knowledge, this is the first time peptides have been identified as antifungal agents against M. sympodialis. Further studies to elucidate the mechanism are warranted.”

Written by Catharine Paddock PhD