Vitamin D is activated in the lungs to fight infection

The November 15, 2008 issue of the Journal of Immunology reports that vitamin D, believed to be activated primarily by the kidneys, is also converted to its active form in lung tissue. This activation is essential for the utilization of the vitamin in the body.

"The more scientists have been studying vitamin D, the more we learn about new roles it plays in the human body," stated lead author Sif Hansdottir, MD, of 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."

By studying human lung tissue samples, Dr Hansdottir and his colleagues found that an enzyme called 1 alpha-hydroxylase helps convert vitamin D stored in the lungs' airway cells into the active form of the vitamin. "When we put the storage form of vitamin D on the lung airway cells, we saw them convert it to the active form," Dr Hansdottir explained. "The next step was to investigate whether this active form could affect the expression of genes."

The team found that activated vitamin D increased the expression of a gene that controls the production of cathelicidin, which destroys bacteria, as well as the gene CD14 which produces a protein that assists cells in their recognition of potentially threatening pathogens.

"Vitamin D not only increases proteins involved in bacterial killing but also can dampen inflammation," Dr Hansdottir added. "Controlling inflammation through vitamin D is good because too much inflammation can cause problems such as sepsis and seems to contribute to autoimmune disease."

—D Dye