Increased serum levels of C-C motif chemokine ligand 2 and M2 macrophages in the skin lesions are associated with the keratinocyte death of Stevens-Johnson syndrome and toxic epidermal necrolysis

Summary: Abstract Body: Background: Stevens-Johnson syndrome (SJS) and Toxic epidermal necrolysis (TEN) are life-threatening disorders characterized by widespread epidermal necrosis of the skin. We have previously reported that increased level of C-C motif chemokine ligand 2 (CCL2) in SJS/TEN. However, the clinical significance of CCL2 and its contribution to keratinocyte necroptosis in the pathogenesis of SJS/TEN are unknown. In this study, we focused on CCL2 and macrophages in association with keratinocyte death. Methods: CCL2 levels in pre-treatment serums were measured using ELISA. Skin infiltrating macrophages were identified by immunohistochemistry (IHC). In vitro experiments, normal human epidermal keratinocytes (HEKs) were used for necroptosis and CCL2 stimulation. Results: Serum levels of CCL2 were significantly higher in SJS/TEN than those in healthy controls and patients with another type of drug eruption. A positive correlation was found between the CCL2 and prognostic score. IHC analysis revealed a significant infiltration of CD68 positive macrophages in SJS/TEN skin lesions, with a predominance of M2 macrophages (CD163 positive) over M1 macrophages (CD80 positive). In vitro, CCL2 stimulation did not directly induce an inflammatory response in HEKs while necroptosis in HEKs increased CCL2 expression. CCL2 expression in HEKs was upregulated by co-culture with macrophages. Furthermore, stimulation with conditioned media from M2 macrophages significantly enhanced necroptosis in HEKs. Conclusion: These findings suggest elevated CCL2 levels in SJS/TEN contribute to increased macrophage infiltration, particularly M2 macrophages. These macrophages, in turn, likely promote keratinocyte necroptosis through the release of soluble factors, highlighting a crucial role for the CCL2-macrophage axis in the pathogenesis of SJS/TEN. Tomoya Watanabe¹, Kotaro Yamagata², Yasushi Ototake¹, Yuko Watanabe¹, Miwa Kanaoka², Yukie Yamaguchi¹ 1. Environmental Immuno-Dermatology, Yokohama Shiritsu Daigaku Igakubu Daigakuin Igaku Kenkyuka, Yokohama, Kanagawa Prefecture, Japan. 2. Dermatology, Yokohama Shiritsu Daigaku Fuzoku Shimin Sogo Iryo Center, Yokohama, Kanagawa Prefecture, Japan. Adaptive and Auto-Immunity