Neutrophils Mediate Kidney Inflammation Following Acute Skin Exposure to UVB Light

Abstract

Photosensitivity to ultraviolet (UV) light affects up to ~80% of lupus patients and can exacerbate local skin disease as well as systemic disease, including lupus nephritis. While neutrophils have been implicated in local tissue injury in lupus in response to immune complex deposition, whether and how they play a role in photosensitivity induced systemic disease is unknown. Here, we show that following skin exposure to UV light, neutrophils migrate not only to the skin, but also to the kidney, in an IL-17A-dependent manner. Kidney infiltrating neutrophils produced reactive oxygen species and their presence was associated with upregulation of endothelial adhesion molecules and inflammatory cytokines as well as the induction of kidney injury markers, including transient proteinuria. Neutrophils were responsible for inflammation and renal injury as demonstrated by experiments that inhibited neutrophil mobilization. Exploiting a mouse model containing photoactivatable immune cells, we observed that a subset of neutrophils found in the kidney had transited through UV light-exposed skin suggesting reverse transmigration. These findings demonstrate that neutrophils mediate transient kidney injury following skin exposure to UV light and, coupled with observations identifying similar neutrophil phenotypes in human lupus, could provide a mechanistic link to explain sun-induced systemic lupus flares.