"When we put the storage form of vitamin D on the lung airway cells, we saw them convert it to the active form," Hansdottir said. "The next step was to investigate whether this active form could affect the expression of genes."
The team then showed that vitamin D activated by airway cells affects two genes involved in immune defense. One gene expresses a protein called cathelicidin that can kill bacteria. The second gene, called CD14, produces a protein that helps cells recognize different kinds of pathogens that could be a threat.
"Vitamin D converted by the kidneys circulates in the bloodstream, but vitamin D converted by other organs appears to stay within those organs and protect them from infection," Hansdottir said. "We were able to see this happen in cells lining the trachea and main bronchi."
The team also found that when lung airway cells are infected by a virus, they express more of the enzyme that activates vitamin D. Hansdottir said the team is very interested in pursuing studies on the role of viral infections in vitamin D production and subsequent effects on lung infections.
"Vitamin D not only increases proteins involved in bacterial killing but also can dampen inflammation," Hansdottir said. "Controlling inflammation through vitamin D is good because too much inflammation can cause problems such as sepsis and seems to contribute to autoimmune disease."
Hansdottir noted that vitamin D insufficiencies and deficiencies (which are more severe) are fairly common, particularly for people living in northern latitudes. While vitamin D can be generated through sun exposure, such exposure is generally not recommended as a remedy because of skin cancer risks. Instead, supplements can be used.
The American Academy of Pediatrics recently recommended that the vitamin D dosage for children be increased to 400 IU (inte
|Contact: Becky Soglin|
University of Iowa