Cornell University researchers have developed a chemical tool that is activated by ultraviolet (UV) light to control inflammation. The method will allow scientists to study the immune system and could eventually prove effective as a targeted therapy for inflammatory diseases, while minimizing side effects to healthy tissues.

Inflammation is one of the body’s responses to eliminate infectious pathogens and other foreign or dangerous agents. When inflammation becomes chronic, it can lead to a host of diseases, including asthma, multiple sclerosis, rheumatoid arthritis, colitis and Crohn’s disease.

This image shows how light-activated chemical probes were used to turn off inflammatory activities of immune cells that were irradiated with light, denoted by the dotted line. Irradiated cells are shown in red, and inflammatory molecules are shown in cyan. Image credit: Bibudha Parasar.“Currently, there aren’t a lot of tools that are able to manipulate the immune system in a spatio-temporal fashion,” notes Pamela Chang, assistant professor of microbiology and immunology.

Chang and colleagues created a chemical probe that inhibits a reaction mediated by enzymes called histone deacetylases (HDACs). These enzymes regulate genes that turn on when the immune system is challenged and promote inflammation.

HDACs also have inhibitors that suppress this inflammatory response, and the probe specifically activates these inhibitors—but only in the presence of UV light. This is especially useful, since HDACs are ubiquitous and have other biological effects; most drugs affect the entire system, leading to unintended consequences.

“If you turned off all the HDACs in the body, you would probably be hitting a lot of pathways that you didn’t want to turn off,” says Chang. “We can control when and where we turn off the HDACs using light. The idea is that you can actually target the tissue that has chronic inflammation and regulate it by selectively inhibiting HDACs in the tissue that’s affected.”

Photodynamic therapies are now under development that could potentially use the new tool to inhibit inflammation in patients with certain diseases, Chang says.