STAT3 regulates tissue inflammation by repressing interferon responsiveness of vascular endothelial cells

Summary: Abstract Body: Signal transducer and activator of transcription (STAT) 3 is a transcription factor crucial for immunity and tissue homeostasis. Loss-of-function mutations of STAT3 affect multiple cell types and cause autosomal-dominant hyper IgE syndrome (AD-HIES), which features Th17 deficiency, impaired antimicrobial response and wound healing, accompanied by eczematous dermatitis and occasional complication of systemic lupus erythematosus (SLE). To explore the roles of STAT3 in vivo, we performed single-cell RNA-sequencing (scRNAseq) on non-lesional (n=7) and eczematous (n=3) skin from 6 AD-HIES patients. Compared to healthy control skin (n=8), keratinocytes, fibroblasts, and vascular endothelial cells (VECs) in eczematous skin commonly upregulated type I and II interferon (IFN) pathways, which were solely enriched in VECs in non-lesional AD-HIES skin. We then generated mice in which ablation of STAT3 was induced in keratinocytes (Stat3ΔKrt14ERT2), fibroblasts (Stat3ΔCol1a2ERT2), or VECs (Stat3ΔCdh5ERT2). scRNAseq analysis revealed that most differentially expressed genes in targeted cell types were downregulated, consistent with the role of STAT3 in transcriptional activation. Interestingly, type I and II IFN pathways were upregulated in in Stat3ΔCdh5 VECs, which was in line with AD-HIES skin. Stat3ΔCdh5 VECs upregulated MHC II and CD74 proteins at baseline, which were further elevated by i.p. injection of poly I:C, a TLR3 agonist. We then applied the TLR7 agonist imiquimod, which is utilized in psoriasis and SLE models. Strikingly, whereas psoriasiform dermatitis was attenuated in Stat3ΔKrt14ERT2mice, it was exacerbated in Stat3ΔCdh5ERT2 mice. Thus, VECs are central to tissue IFN responses, and STAT3 regulates tissue inflammation by controlling VEC’s IFN responsiveness. Keiko Sakamoto¹, Hiroyuki Nagashima¹, Paul Kim¹, Shubham Goel¹, Yuriko Yamazaki¹, Seon-Pil Jin¹, Doyoung Kim¹, Alexandra Freeman¹, Heidi H. Kong¹, Keisuke Nagao¹ 1. NIH, Bethesda, MD, United States. Innate Immunity, Microbiology, and Microbiome