The crucial role of lipids in atopic eczema

October 9, 2012 § Leave a comment

(1) The outermost layer of the epidermis, the stratum corneum, has dead cells embedded in a lipid matrix, known as the brick-and-mortar structure. (2) The intercellular lipids are arranged in layers (lamellae) (3), with two phases. The lamellar phases either have a repeat distance of 6 nm (the short periodicity phase) or 13 nm (the long periodicity phase). There are three possible arrangements of the lipids. Image from the Journal of Lipid Research, DOI:10.1194/jlr.P030338

Dry skin, blisters and inflammation are some of the uncomfortable and irritating symptoms of atopic eczema (also known as atopic dermatitis).  In a recent paper in the Journal of Lipid Research, scientists have worked out what role lipids play in the disease.

The prevalence of the disorder has been rising, especially in children, says Joke Bouwstra at Leiden University in The Netherlands. Although it is not a life-threatening disease, she says, the condition “has a large impact on the quality of life of children and their families.”

Skin acts as a first line of defense in our bodies, forming a barrier against environmental assaults. Any disruption reduces skin’s ability to act as a protective barrier.

Loss-of-function mutations in a gene for an epitheliad barrier protein called filaggrin has been known to be a risk factor for developing atopic eczema. Besides filaggrin, lipids in the skin are thought to play an important role in the skin’s barrier function. But, says Bouwstra, there isn’t much known about the role of lipids in atopic eczema.

So she and her colleagues undertook a detailed analysis of ceramides, a class of lipids that are critical for the skin’s barrier properties. The investigators recruited healthy people and patients with atopic eczema.

“We wanted to study whether changes in lipid properties also correlated with filaggrin mutations,” says Bouwstra, so they also profiled all subjects to see what filaggrin mutations they did and did not carry. The investigators analyzed how much water the controls and patients lost through their skin, a measure of how well the skin was working as a barrier. The investigators also studied skin samples collected from the study participants by liquid chromatography and mass spectrometry to get detailed information about the types of ceramides.

The investigators found that patients with atopic eczema had more short-chain ceramides in their skin than their control counterparts. They also found that the lipid organization was different in the patients with the disease. “Lipid chain length and lipid organization both correlate with the impaired skin barrier function and the severity of the disease,” says Bouwstra.

Bouwstra says that the data seem to suggest that normalizing the ceramide composition is important for fixing the skin of atopic eczema patients. “After repairing the skin barrier, the penetration of allergens and irritants may be reduced, which may result in a reduction of the inflammation,” she says.

Bouwtra’s group is now working on what causes changes in ceramide biosynthesis in atopic eczema patients and hope that the work may reveal ways to treat the disease.

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