A research paper from Dr Hector Deluca’s lab at the University of Wisconsin has reported a possible role for sunscreens in the treatment of multiple sclerosis (MS). The paper was published in the Proceedings of National Academy of Sciences (PNAS) this month.

MS is an autoimmune disease where the patient’s own immune system wrongly targets and destroys the myelin sheath surrounding neurons in the brain. Myelin sheaths are important for the normal propagation of neural signals, and MS patients often experience physical disabilities as a result.

What causes the immune system to attack the myelin sheath remains unknown. However, scientists have found that MS has a much higher prevalence in regions at high latitudes compared with regions near the equator. One possible explanation for this regional variance in MS prevalence is the amount of sunlight, particularly ultraviolet (UV) light, that people receive. As there is more sunlight available in the tropical regions, it might have protective properties against MS.

Dr DeLuca and colleagues initially designed the study to examine the effects of ultraviolet (UV) light in mice that had been injected with chemicals known to trigger the rodent form of MS. To compare the effects of UV light at preventing MS, the team divided the mice into four groups. The first group received UV light, the second group had sunscreen applied on their back and received UV light, the third group had sunscreen applied but were not subjected to UV light, and the fourth group received neither sunscreen or UV light.

The team expected that MS would progress more slowly in the first group compared with other groups. However, mice groups with sunscreens applied had slower disease progression, even in the group without any UV light. Dr DeLuca went on to further study the ingredients found in the protective sunscreens used in the study and tried these compounds on mice. Homosalate and octisalate, were most effective at slowing disease progression.

The results suggest that sunscreens, particularly the salate derivatives found in their ingredients, might have protective properties against MS. How they work at suppressing MS remains to be studied, though Dr DeLuca suspects their efficacy is as a result of the ability to inhibit the production of cyclooxygenase, which is an enzyme found in the lesion site of MS patients. Further studies on salate derivatives may provide new insight into the mechanisms of the disease and offer additional approaches in the treatment of MS.