16 Oct 2014

Chlorine Bleach in the Airways

From Our Changing World, 9:34 pm on 16 October 2014

By Ruth Beran

A painting by Fernand Léger called Starfish (L'Etoile de mer)

Starfish (L'Etoile de mer) by Fernand Léger Photo: Artists Rights Society (ARS), New York / ADAGP, Paris

Starfish is a painting by Fernand Léger which is part of the Guggenheim Collection.

Professor Tony Kettle from the University of Otago, Christchurch has a print of it on the wall of his office, and he can see processes in it that Léger probably never imagined.

“In the centre of the picture we have what I see as a white blood cell,” says Tony.

This white blood cell has a big black entity inside it.

“And that I see as a bacterium being eaten by the white cell,” says Tony.

White blood cells travel throughout the body when we get an infection. Their role is to hunt down pathogenic bacteria, and ingest them into a tiny space called a phagasome. The white blood cells then trap the bacteria and kill them.

“One way of killing them is with this green here, we call them granules, inside the white cell,” says Tony.

The green colour is an enzyme called myeloperoxidase, the same colour you get in green snot.

“So the white cells dump the myeloperoxidase onto the bacteria, and then the myeloperoxidase does an amazing thing,” says Tony. “It actually oxidises chloride common salt to chlorine bleach, and the chlorine bleach kills the bacteria trapped inside that cell.”

This is a normal process in the body, but in a number of diseases the neutrophils can’t get hold of the bacteria. In cystic fibrosis, for example, children get mucus in their airways, an environment conducive for bacteria.

“The neutrophils come in to get the bacteria but they get trapped in the mucus,” says Tony. “So they can’t actually eat the bacteria and they get frustrated and in the process they release chlorine bleach into the airways.”

“The chlorine bleach doesn’t kill the bugs it actually starts to destroy the healthy tissue in the lungs and breaks it down,” he says.

Over time, this chlorine bleach destroys the elasticity of the lungs and leads to lung failure in children with cystic fibrosis.

A picture of Tony Kettle

Tony Kettle Photo: University of Otago, Christchurch

Tony and his team are trying to understand how neutrophils normally kill bacteria, and also how the neutrophils die and are cleared by macrophages.

“We’re looking at trying to find compounds that will actually prevent this green enzyme myeloperoxidase from producing chlorine bleach in cystic fibrosis hopefully, but also in a number of other inflammatory diseases,” says Tony.

Cystic fibrosis affects approximately 500 New Zealanders. It is the most common life-threatening genetic disorder in this country, with one in every 5000 babies born with the disease. Bubbles Week is New Zealand’s national awareness week for cystic fibrosis and runs from 13 to 19 October. Blowing bubbles is a fun form of chest physiotherapy for children with cystic fibrosis, but it is hoped that it the future research like Tony Kettle’s work will lead to new drugs being developed to treat the condition.