Lung airway cells activate vitamin D and increase immun...( Vitamin D is essential to good heal...)

Vitamin D is essential to good health but needs to be activated to function properly in the human body. Until recently, this activation was thought to happen primarily in the kidneys, but a new University of Iowa study finds that the activation step can also occur in lung airway cells.

The study also links the vitamin D locally produced in the lung airway cells to activation of two genes that help fight infection. The study results appear in the Nov. 15 issue of the Journal of Immunology, now online.

In addition to contributing to calcium absorption and bone health, vitamin D is increasingly recognized for its beneficial effects on the immune system. Vitamin D deficiency has been recently linked to increased risk of some infections, autoimmune diseases such as multiple sclerosis and type 1 diabetes, and some cancers.

"The more scientists have been studying vitamin D, the more we learn about new roles it plays in the human body," said the study's lead author Sif Hansdottir, M.D., fellow in internal medicine in the University of Iowa Carver College of Medicine. "The active form of vitamin D is known to affect the expression of more than 200 genes, so we were interested both in the possible lung-specific production of active vitamin D and in vitamin D-dependent production of proteins that fight infections."

The first step in vitamin D activation takes place in the liver, where an enzyme called 25-hydroxylase converts vitamin D into a "storage" form. The next step takes place typically in the kidneys, but in recent years, tissue and organs such as skin, intestines, breast and prostate have been found also to express the enzyme that completes vitamin D conversion.

The University of Iowa team, based in the laboratory of Gary Hunninghake, M.D., professor of internal medicine and the study's senior author, used cells from deceased human donors to demonstrate that the presence of the enzyme 1 alpha-hydroxylase in
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