Spatial characterization of interface dermatitis in cutaneous lupus reveals novel chemokine axis-mediated recruitment of leukocytes that drive disease

Chemokines play critical roles in the recruitment and activation of immune cells in both homeostatic and pathologic conditions. Here, we examined chemokine ligand-receptor pairs to better understand the immunopathogenesis of cutaneous lupus erythematosus (CLE), a complex autoimmune connective tissue disorder. Our objectives were to investigate the immunopathogenesis and therapeutic targets of interface dermatitis in patients with cutaneous lupus erythematosus. Four subacute cutaneous lupus erythematosus (SCLE), 4 discoid lupus erythematosus (DLE) and 3 healthy margin controls were enrolled for archival tissue sampling for spatial transcriptomics and proteomics. Seven CLE (4 SCLE, 3 DLE) patients and 3 healthy controls were enrolled for fresh tissue blister biopsy sampling of 184 protein analytes in interstitial skin fluid and serum using targeted proteomics, as well as spectral flow cytometry analysis for interface dermatitis cells. An additional 6 CLE and 6 healthy blood donors were enrolled for functional chemotaxis assays. Spatial and targeted proteomics data confirmed elevation of interferon (IFN) and IFN-inducible CXCR3 chemokine ligands. Comparing involved to uninvolved epidermal keratinocytes in CLE samples revealed upregulation of essential inflammatory response genes in areas near interface dermatitis, including AIM2 . Targeted proteomics data confirmed upregulation of Caspase 8, IL-18 which is the final product of AIM2 activation, and induced chemokines including CCL8 and CXCL6 in CLE lesional samples. Chemotaxis assays using peripheral blood mononuclear cells (PBMCs) from healthy and lupus donors revealed that T cells respond to CXCL9 and CXCL11, whereas CD14+CD16+ monocyte populations are more sensitive to CXCL6 via CXCR1 and CD14+ monocytes are more sensitive to CCL8 via CCR2. Furthermore, in vitro blocking assays revealed that hydroxychloroquine blocks CCL8 driven CD14+ monocyte migration, whereas reparixin blocks CXCL6 driven CD14+CD16+ monocyte migration. Taken together, our data map a pathway from keratinocyte injury to lymphocyte recruitment in CLE via AIM2-Casp8-IL-18-CXCL6-CXCR1 CD14+CD16+ monocyte recruitment, CCL8-CCR2 CD14+ monocyte recruitment, and IFNG/IFNL1-CXCL9/CXCL11-CXCR3 T cell recruitment, and suggest a mechanism by which hydroxychloroquine blocks CCR2+ CD14+ monocyte migration. We also identify reparixin and its derivatives as potential novel inhibitors of CXCR1+ CD14+CD16+ monocyte migration.