Clearance of neutrophil extracellular traps is a promising therapeutic strategy for severe cutaneous drug reactions

Summary: Abstract Body: We have recently reported that neutrophil extracellular traps (NETs) drive keratinocytes to undergo necroptosis, a programmed cell death, in Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Considering that NETs can potentially trigger extensive epidermal death, their prompt degradation is critical for maintaining homeostasis. PMA-induced NETs were effectively degraded in the presence of sera from healthy individuals or patients with maculopapular exanthema (MPE). However, sera from SJS/TEN exhibited minimal impacts on NET clearance, suggesting impaired intrinsic NETs-degrading mechanisms in SJS/TEN. To explore the regulatory mechanism of NETs, sera were collected from acute SJS/TEN patients (n=29), MPE (n=32), DRESS/DIHS (n=19), systemic lupus erythematosus (SLE, n=5), and psoriasis (n=6) across seven institutions in Japan. The level and activity of DNase1 and DNase1-like 3 (DNase1L3), essential enzymes for NETs degradation, were significantly lower in SJS/TEN sera compared to healthy controls and other diseases. To investigate the dysregulated clearance of NETs in vivo, LPS was administered to wild-type mice to induce systemic NET formation. While the production and activity of DNases from their major sources (e.g., kidney, thymus, pancreas, spleen, liver, skin) remained unaffected, circulating DNase levels and activity were decreased following NET formation, which was restored by neutrophil depletion. These results imply that DNases were consumed and metabolized by NETs from the circulation. Collectively, intrinsic DNase1 and DNase1L3 physiologically regulated NETs under steady-state conditions, but they were consumed by NETs in SJS/TEN, promoting further NET formation. Current therapeutic strategies for SJS/TEN, including corticosteroids, immunosuppressants, and anti TNF-α antibodies, had less impacts on NETs. In contrast, exogenous DNase1 effectively degrades SJS/TEN sera-induced NETs, implying DNases is a promising and feasible treatment strategy for SJS/TEN. Manao Kinoshita¹, Youichi Ogawa¹, Shinji Shimada¹, Tatsuyoshi Kawamura¹ 1. Dermatology, University of Yamanashi, Chuo, Yamanashi, Japan. Translational Studies: Cell and Molecular Biology