Dissecting the Stromal-Immune Interactions that Lead to Photosensitivity (Project 2)

University Of Michigan At Ann Arbor, Ann Arbor MI

Investigators

Abstract

ABSTRACT/PROJECT SUMMARY (Project 2) Ultraviolet (UV) light exposures are a frequent trigger for skin inflammation in patients with systemic lupus erythematosus (SLE) or cutaneous lupus erythematosus (CLE) without systemic disease. Sufficient exposure can also lead to increased systemic disease activity. The mechanisms driving photosensitive responses in lupus patients are not well-understood yet are essential for developing strategies to prevent UV light from triggering flares. This project of the University of Michigan Integrated Program for Cutaneous Immune-Stromal interactions in SLE (IPCISS) will build upon an accomplished collaborative working group seeking to understand the etiologies of CLE and SLE. Our ongoing work has identified a critical role for both epidermal/stromal and immune cells in creating a pro-inflammatory milieu in SLE skin after UV exposure. Thus, this project will address our overall hypothesis that dysregulation of stromal-immune interactions in the skin of SLE patients contributes to inflammatory rather than tolerogenic responses to UV light leading to cutaneous and systemic inflammation. This project will synergize with the Program's BIOPSII Core to harness the power of integrative omics work on patient samples in conjunction with careful mechanistic study to identify therapeutic targets for photosensitivity in SLE/CLE. Our specific aims are Aim 1: Map the infiltrate and expression changes within SLE and HC skin after UV exposure. We will identify cellular sources of interferon in the skin after UV exposure and use paired single-cell RNA sequencing and single-cell resolution spatial profiling and functional follow-up to map signal crosstalk from keratinocyte, fibroblast, and endothelial cell networks. We hypothesize that this spread of IFN signal begins in the KC and is transmitted to surrounding cell populations which then transmit signals to induce cellular recruitment. Aim 2: Identify the role of UV-induced extracellular vesicles (EVs) in driving KC-immune crosstalk. Our data support a role for type I IFNs in increasing EV numbers and size after UV exposure. We hypothesize that KC-derived EVs are a critical mediator of immune activation in SLE skin. Thus, we will explore the role of UV-induced EVs as a critical component of paracrine and systemic signal delivery. Aim 3: Determine how UV exposure modulates inflammatory memory within keratinocytes. Our data support unique dysregulation of histone methyltransferase pathways in SLE KCs after UV exposure. We hypothesize that UV exposure in an IFN-rich environment, such as SLE skin, results in histone methylation changes that open inflammatory gene transcriptional programs and could potentially serve as an initiating factor in CLE predisposition. We will thus examine the impact of IFNs and UV exposure on chromatin accessibility in SLE and healthy control KCs and utilize single nuclear/ATAC-seq (multiome) to link inflammatory and epigenetic modifications after UV exposure in SLE, ANA+ without disease, and healthy control subjects in vivo.