A certain hormone works in tandem with vitamin D to control how skin cells produce a natural microbe-fighting agent, and can compensate for a lack of vitamin D, scientists have found.
The new results help explain something that has confused researchers for a long time: although it is known that vitamin D plays a role in the immune defense, there are very few clinical trials that show that taking supplemental vitamin D helps prevent infection.
The work was led by Richard Gallo, a professor of medicine and pediatrics and chief of the Division of Dermatology at the University of California, San Diego. It was published this week in the journal Science Translational Medicine.
The skin makes natural antimicrobial compounds (protein fragments called peptides) to kill unwanted bacteria, fungi, and viruses. Eczema patients produce these compounds at lower levels than normal; psoriasis patients, at higher levels. Vitamin D initiates production of cathelicidin, a broad-spectrum antimicrobial.
Gallo and colleagues showed that human skin cells produce parathyroid hormone (PTH) when treated with a bacterial compound known to trigger the immune system. The same cells, stimulated with vitamin D, manufactured copies of the receptor for PTH. And the skin cells produce far more cathelicidin when they are treated with parathyroid hormone and vitamin D than with either compound alone.
The results suggest a model in which, in humans, vitamin D can stimulate cathelicidin production by itself—but PTH is doing so by a parallel pathway, which vitamin D can amplify.
The scientists also showed that PTH helps reduce the severity and extent of Streptococcus skin infections in mice—but it does so much more strongly in normal mice, compared to mice genetically engineered to be unable to convert vitamin D to its active form. (Apparently it is very difficult to make a mouse deficient in vitamin D.)
What this means for eczema patients is not clear yet. The research gets us further toward understanding how vitamin D and other factors participate in the skin’s immune response. If I were a doctor, it would make me hesitant to recommend that patients with normal vitamin D levels should take supplements.
That's interesting; my derm had suggested that my eczema wouldn't be anywhere near as bad if I lived somewhere sunny - but he'd said that as suppressing immune behaviour; I hadn't been aware of eczema not producing as much of the natural antibiotic. It would be kind of interesting to know why the levels were lower with Eczema and how it was linked to any of the other reasons that the rest of eczema seems to be triggered by.
ReplyDeleteMutations in the filaggrin gene could reduce the amount of filaggrin breakdown products, some of which are known to make the skin more acidic and less hospitable to pathogenic bacteria. I can't immediately think of a reason for the shortage of antimicrobial peptides in eczematous skin though.
ReplyDeleteI've known about the "sun is good for eczema" idea for a long time. But I haven't personally found it true. My vague understanding of the theory is that UV somehow suppresses proliferation of skin cells--that would apply more to psoriasis than eczema though. I'll watch for research on how sunlight might interact with the immune response (besides producing vitamin D).
FYI there was an article in JACI this week about the connection between UV, vitamin D, and the immune system. http://www.jacionline.org/article/S0091-6749%2812%2900402-2/abstract
ReplyDeleteWe were staying out of the sun, but taking vitamin d in Australia. Now that we are in San Fran and it's cooler out, we are not wearing sunscreen, out in the sun all the time, and still taking Vitamin D in a Nordic Naturals Fish oil capsule with D-- using Cerave, drinking Kangen water, and wearing Dermasilk pajamas-- and our eczema has been gone for several months-- and it was severe. I do think the sun combined with it not being insanely hot in San Fran has made a big difference.??
ReplyDeleteThe climate here is about all you could wish for if you have eczema--mostly sunny, reasonable temperatures in a narrow range (I used to think in Celsius but have unfortunately converted to Fahrenheit when it comes to weather--it's usually 50-70F year round) and a quasi-desert countryside without huge amounts of pollen. Plus stress levels are a little lower, unless you are in a traffic jam or hunting for an apartment. It's a good place to be!
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