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Researchers Shine a Light on UV Light Exposure and Kidney Damage

Exposure to UV light causes damage to everyone’s cellular DNA. Once the cells are damaged, the immune system clears them. However, people with lupus have a much slower clearance of these cells. The dead cells stick around in the body, triggering an immune system attack.

Previous studies have reported that in up to 80% of lupus patients, sun exposure can trigger both local skin inflammation and systemic flares, including kidney disease. However, little is known about the underlying mechanisms that drive this process. Now, researchers at the Geisel School of Medicine at Dartmouth and the University of Washington (UW) demonstrate that neutrophils not only infiltrate the UV-light exposed skin, but they also migrate to the kidney.

Their findings are published in the journal Proceedings of the National Academy of Sciences (PNAS) in a paper titled, “Acute skin exposure to ultraviolet light triggers neutrophil-mediated kidney inflammation.”

“Neutrophils are the most abundant leukocytes in circulation and the first responders to infectious and sterile inflammation, including skin exposure to ultraviolet (UV) light,” the researchers wrote. “We demonstrate that neutrophils not only migrate to the UV light–exposed skin but also disseminate systemically.”

The researchers decided to investigate the role of neutrophils, a type of white blood cell that responds to inflammation, that has been linked to skin and kidney tissue injury in lupus patients. In the study, they looked for markers of inflammation and injury in the skin, the blood, and the kidney at different time points following UV light exposure in mice.

“Interestingly, one subset of these neutrophils, the ones that we think are more damaging, first went to the skin that was exposed to the UV light and then turned around and went to the kidney,” explained Sladjana Skopelja-Gardner, PhD, an assistant professor of medicine at Geisel who worked with Keith Elkon, MD, at UW on the study. “That’s a bit unusual—we normally think of neutrophils as short-lived cells that sort of zoom to where the inflammation is and then die off there.”

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