AhR Activation Leads to Attenuation of Murine Autoimmune Hepatitis: Single-Cell RNA-Seq Analysis Reveals Unique Immune Cell Phenotypes and Gene Expression Changes in the Liver

Abstract

The aryl hydrocarbon receptor (AhR) is a ubiquitously expressed ligand-activated transcription factor. While initially identified as an environmental sensor, this receptor has been shown more recently to regulate a variety of immune functions. AhR ligands vary in structure and source from environmental chemicals such as 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) and indoles found in cruciferous vegetables to endogenous ligands derived from tryptophan metabolism. In the current study, we used TCDD, a high affinity AhR ligand to study the impact of AhR activation in the murine model of autoimmune hepatitis (AIH). Primarily, we used single-cell RNA-sequencing (scRNA-seq) technology to study the nature of changes occurring in the immune cells in the liver at the cellular and molecular level. We found that AhR activation attenuated concanavalin A (ConA)-induced AIH by limiting chemotaxis of pro-inflammatory immune cell subsets, promoting anti-inflammatory cytokine production, and suppressing pro-inflammatory cytokine production. scRNA-seq analysis showed some unusual events upon ConA injection such as increased presence of mature B cells, natural killer (NK) T cells, CD4+ or CD8+ T cells, Kupffer cells, memory CD8+ T cells, and activated T cells while TCDD treatment led to the reversal of most of these events. Additionally, the immune cells showed significant alterations in the gene expression profiles. Specifically, we observed downregulation of inflammation-associated genes including Ptma, Hspe1, and CD52 in TCDD-treated AIH mice as well as alterations in the expression of migratory markers such as CXCR2. Together, the current study characterizes the nature of inflammatory changes occurring in the liver during AIH, and sheds light on how AhR activation during AIH attenuates liver inflammation by inducing phenotypic and genotypic changes in immune cells found in the liver.

CD4+ T-cell subsets in autoimmune hepatitis: A review

“…A single-cell RNA-sequencing analysis revealed that IL-22 expression was elevated in Con A-induced AIH and was further increased after treatment with the AhR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin. 182 However, ALT levels decreased after 2,3,7,8-tetrachlorodibenzo-p-dioxin treatment. Elevated AhR expression also led to decreases in the Th17/Treg ratio and the activation of CD4 + T cells, CD8 + T cells, B cells, and NK cells.…”

“…Elevated AhR expression also led to decreases in the Th17/Treg ratio and the activation of CD4 + T cells, CD8 + T cells, B cells, and NK cells. 182 Th22 cells may be a potential therapeutic target in AIH, but more studies are needed to clarify the exact mechanism by which Th22 cells are involved in the pathogenesis and progression of AIH.…”

Bioluminescence imaging of Cyp1a1-luciferase reporter mice demonstrates prolonged activation of the aryl hydrocarbon receptor in the lung

“…Our appreciation of the importance of AHR signalling in sensing environmental and pathogen exposures, regulating tissue physiology, immune responses, and disease ontogeny, has increased substantially over the last decade. In particular, advances in the metabolic profiling of dietary response 37 , 38 , single-cell transcriptomic analysis of complex tissues 30 , 39 , 40 , and assessing both canonical and alternative AHR ligands 41 have bolstered knowledge of the pleiotropic roles AHR signalling can play in vivo. Despite this, reagents that enable AHR activity to be reliably monitored in living tissues remain surprisingly limited.…”

The Genetic Selection of HSPD1 and HSPE1 Reduce Inflammation of Liver and Spleen While Restraining the Growth and Development of Skeletal Muscle in Wuzhishan Pigs

“…HSPE1, also named HSP10, may cooperate with HSPD1 to ensure protein folding and maintain proteostasis [ 18 ]. Moreover, HSPE1 is an inflammation-related gene because of its increasing expression during inflammatory activation [ 19 ]. The JAK-STAT signaling pathway is known to induce inflammation by interacting with several pro-inflammatory cytokines, and many genes are involved in this pathway, including JAK2 , JAK3 , STAT1 , STAT2 , STAT3 , and STAT4 , to regulate multiple functions, namely cellular proliferation, senescence, autophagy, and inflammation activation [ 20 , 21 ].…”