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Scholarly Works (4 results)

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Thesis
Peer Reviewed

Aryl Hydrocarbon Receptor Modulation of Intestinal Macrophages and CD4+ T cells in NOD Mice

Malany, Keegan
Advisor(s): Ehrlich, Allison K

UC Davis Electronic Theses and Dissertations (2024)

The intestinal interface allows the host to incorporate and respond to signals from the environment. One way the intestinal contents communicate with the host is through the aryl hydrocarbon receptor (AHR). Highly expressed in the intestinal epithelium and the underlying lamina propria immune cells, the AHR is a cytosolic transcription factor that alters cellular function in a location and cell-dependent manner. Given the evidence that the intestinal environment is dysregulated in type 1 diabetes (T1D), an autoimmunity disorder in which the pancreatic beta cells are attacked, this dissertation examines how modulating AHR signaling in intestinal immune cells may alter diabetes development using the nonobese diabetic (NOD) mouse model of T1D. Chapter 1 is a literature review of AHR signaling in macrophages. The chapter covers what is currently understood about AHR signaling in different contexts, including macrophage differentiation, polarization, function, and immune-mediated diseases. Chapter 2 examines how AHR modulates the gut microbiome during type 1 diabetes development and the role of intestinal CD4+ T cells. Flow cytometric analysis of intestinal CD4+ T cells and 16s microbial data were analyzed from of AHR WT and KO NOD mice at three different time points. Additionally, we utilized specific pathogen-free (SPF) and germ-free (GF) mice to understand the impact of the microbiome on the intestinal CD4+ T cells and diabetes incidence. To investigate how the intestinal T cells interact with the microbiome, we utilized Transkingdom network analysis.

Chapter 3 focuses on the mechanisms occurring upstream of CD4+ T cells in AHR KO NOD mice. Specifically, this chapter identifies intestinal macrophages as a critical target of AhR signaling in the small intestine, utilizing flow cytometry and single-cell RNA sequencing. We then performed experiments using an AHR ligand-enriched diet to demonstrate that macrophages are regulated in an AHR-dependent manner. We provide bioinformatic and functional evidence that suggests these cells interact with intestinal CD4+ T cells in AHR KO NOD mice. Lastly, we used bulk RNA sequencing of intestinal and pancreatic CD45+ cells to perform causal inference analysis to predict how AHR signaling impacts inter-organ communication. Chapter 4 examines the role of AHR signaling in vitro using bone marrow-derived macrophages. Additionally, immunotoxicity of per-and-poly-fluoroalkyl substances (PFAS), ubiquitous environmental pollutants which have been associated with autoimmunity development, is assessed in vitro. By exposing macrophages derived from NOD and B6 mice to PFAS, we model the impact of PFAS exposure in individuals genetically susceptible to T1D. Collectively, the chapters demonstrate that intestinal immune cells are altered by AHR signaling and modulation through AHR signaling may represent a novel mechanism in which the environment influences diabetes development. Additionally, the PFAS study demonstrates that cytokine production is affected by exposure and therefore may alter the host immune response.

Article
Peer Reviewed

Perinatal exposure to environmental tobacco smoke is associated with changes in DNA methylation that precede the adult onset of lung disease in a mouse model

UC Davis Previously Published Works (2017)

Prenatal and early-life environmental tobacco smoke (ETS) exposure can induce epigenetic alterations associated with inflammation and respiratory disease. The objective of this study was to address the long-term epigenetic consequences of perinatal ETS exposure on latent respiratory disease risk, which are still largely unknown. C57BL/6 mice were exposed to prenatal and early-life ETS; offspring lung pathology, global DNA, and gene-specific methylation were measured at two adult ages. Significant alterations in global DNA methylation and promoter methylation of IFN-γ and Thy-1 were found in ETS-exposed offspring at 10-12 and 20 weeks of age. These sustained epigenetic alterations preceded the onset of significant pulmonary pathologies observed at 20 weeks of age. This study suggests that perinatal ETS exposure induces persistent epigenetic alterations in global DNA, as well as IFN-γ and Thy-1 promoter methylation that precede the adult onset of fibrotic lung pathology. These epigenetic findings could represent potential biomarkers of latent respiratory disease risk.

Cover page: Perinatal exposure to environmental tobacco smoke is associated with changes in DNA methylation that precede the adult onset of lung disease in a mouse model

Article
Peer Reviewed

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2-responding CD4+ T cells

UC Davis Previously Published Works (2023)

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4⁺ T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4⁺ T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4⁺ T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4⁺ T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4⁺ T cells increases over the course of activation and proliferation in vivo. The actively dividing Nrp1⁺Foxp3^- cells express the classic effector phenotype of CD44^hiCD45RB^lo, and the increase in Nrp1⁺Foxp3^- cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4⁺ T cells. The downregulation of Nrp1 on CD4⁺ T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4⁺Foxp3^- cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo. Collectively, the data demonstrate that Nrp1 is a CD4⁺ T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4⁺ T cell responses.

Article

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2 responding CD4+ T cells

UC Davis Previously Published Works (2023)

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4 + T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4 + T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4 + T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4 + T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4 + T cells increases over the course of activation and proliferation in vivo . The actively dividing Nrp1 + Foxp3 - cells express the classic effector phenotype of CD44 hi CD45RB lo , and the increase in Nrp1 + Foxp3 - cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4 + T cells. The downregulation of Nrp1 on CD4 + T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4 + Foxp3 - cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo . Collectively, the data demonstrate that Nrp1 is a CD4 + T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4 + T cell responses.

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