Vitamin D may protect ocular surface against infection, inflammation

Research has shown that it lowers the production of pro-inflammatory cytokines.

Issue: September 2016

Cell-based research indicates that vitamin D may prevent infection and inflammation on the ocular surface, but clinical studies are needed to further understand its role, according to Rose Y. Reins, PhD, and Alison M. McDermott, PhD, researchers with the Ocular Surface Institute at the University of Houston College of Optometry.

“Vitamin D is being looked at in terms of prevention, to block progression of disease in animal models. New research has focused on its involvement in immune system regulation and as an anti-inflammatory mediator,” Reins explained during a presentation at the American Academy of Optometry meeting in 2014.

“I’m interested in the ocular surface and function of vitamin D,” she continued. “I’ve been looking at how vitamin D can influence gene expression in this tissue and also focusing on the inflammatory component. We want to know if vitamin D can decrease high levels of mediators, such as what would occur in dry eye disease.”

Reins said her research, as part of her PhD program, showed that vitamin D is able to influence gene expression in corneal epithelial cells, in particular, increasing proteins important for innate immunity. She said she also found that vitamin D lowers the production of pro-inflammatory cytokines.

“It’s able to do this even after initiation of inflammation. These results suggest a possible protective role of vitamin D in ocular surface infection and inflammation,” she said at the meeting.

“We definitely feel our results suggest that vitamin D can be important for the ocular surface and the context of inflammation,” Reins, a postdoctoral fellow at the University of Houston, said in an interview with Primary Care Optometry News. “However, clinical studies need to be done to follow up on what we’ve done in animal studies and cell culture. We are moving forward in that direction – so far we’ve taken the gene expression a step further and looked at gene survey analysis, which confirms that vitamin D is regulating various proteins that influence the inflammatory response.”

Recent research published in PLOS ONE by Reins and colleagues involved a mouse model of corneal epithelial wound healing, where acute inflammation is necessary for efficient wound closure. At 18 hours post wounding, vitamin D treatment delayed wound closure by 17% and increased the infiltration of neutrophils into the central cornea, according to the study.

Whole corneas were used in the research, reflecting general corneal expression, with contributions from epithelial, stromal and immune cells, Reins and colleagues wrote.

“Vitamin D is a multifunctional hormone, which not only affects calcium homeostasis, but plays a role in immune system regulation as well as cell growth and survival,” Reins and McDermott wrote in another study from Experimental Eye Research. “Many tissues in the eye are able to both activate and respond to vitamin D, suggesting that vitamin D is a biologically relevant molecule to study throughout the eye.”

Reins and McDermott said in regard to their study with topical vitamin D in a mouse model of wounding “that the data suggest that vitamin D could be active in getting the immune response going in terms of the initial infection and, thus, important in the resolution of inflammatory events.”

Further, “the response to inflammation can change based on the cell types involved, the source of immune stimulus, the tissue microenvironment, timing of vitamin D administration, vitamin D concentration and the relative expression of activating and inactivating hydroxylases,” Reins and colleagues wrote in the PLOS ONE study.

Reins and McDermott said they are excited to move forward to look at clinical studies comparing vitamin D tear levels and the differences between dry eye patients and normal patients.

“Several studies show that vitamin D levels influence dry eye symptoms. So we are interested in looking at clinical signs of dry eye and its association with vitamin D status,” Reins added.

“Currently, all of our findings do not necessitate a change in clinical practice,” McDermott said. “People should be adhering to good diet and good hygiene, general things that are important in eye care.” - by Abigail Sutton

References:
Reins, RY. Vitamin D decreases IL-8 expression after induction of inflammation and influences gene expression in human corneal epithelial cells. Presented at: American Academy of Optometry. November 12-15, 2014; Denver.
Reins RY, McDermott AM. Exp Eye Res. 2015.doi:10.1016/j.exer.2015.02.019.
Reins RY, et al. PLOS ONE. 2016.doi:10.1371/journal.pone.01522889.

For more information:
Alison M. McDermott, PhD, can be reached at: amcdermott@central.uh.edu.
Rose Y. Reins, PhD, can be reached at: rose@reins.org.

Disclosure: McDermott and Reins reported no relevant financial disclosures.