Date on Master's Thesis/Doctoral Dissertation

12-2013

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Microbiology and Immunology

Committee Chair

Suttles, Jill

Author's Keywords

Macrophage; T cell; Antigen presentation; Dendritic cell; CD40

Subject

Protein kinases; T cells

Abstract

Inflammatory and metabolic processes are critical to the survival of multicellular organisms. Inflammation and metabolism are closely linked, and many pathologies are associated with dysregulation of both of these processes, including obesity, cancer, diabetes, and atherosclerosis. Understanding the mechanistic links of inflammation and metabolism are critical for the development of treatments of metabolic and inflammatory diseases. AMP-activated protein kinase, AMPK, is a serine/threonine kinase that regulates energy homeostasis and metabolic stress in eukaryotes. When cellular ATP is low, AMPK is activated and turns off ATP-consuming anabolic pathways and turns on ATP-generating catabolic pathways. Previous work from our laboratory, as well as by others, has provided evidence that AMPKa1 acts as a negative regulator of TLR-induced inflammatory function. The goal of this dissertation was to investigate the role of AMPKa1 in myeloid antigen presenting cell activity. Herein we demonstrate that AMPKa1-deficient macrophages and dendritic cells (DCs) exhibit heightened inflammatory function and an enhanced capacity for antigen presentation favoring the promotion of Th1 and Th17 responses. Macrophages and DCs generated from AMPKa1-deficient mice produced higher levels of proinflammatory cytokines and decreased production of the anti-inflammatory cytokine IL-10 in response to both TLR and CD40 stimulation as compared to AMPKa1+/+ cells. In assays of antigen presentation, AMPKa1 deficiency in both the myeloid APC and T cell populations contributed to enhanced IL-17 and IFN? production. Focusing on the CD154-CD40 interaction, we found that CD40 stimulation resulted in increased phosphorylation of ERK1/2, p38, and NF-?B p65 and decreased activation of the antiinflammatory Akt - GSK3ß - CREB pathway in DCs deficient for AMPKa1. AMPKa1 serves to attenuate LPS and CD40-mediated proinflammatory activity of myeloid APC and AMPKa1 activity in both APC and T cells antagonizes the development of proinflammatory T cell responses during antigen presentation. Additionally, we sought to investigate the influence of macrophage-expressed AMPKa1 on tumor-macrophage interactions and macrophage polarization in the tumor microenvironment. Our studies show that macrophage-expressed AMPKa1 polarizes tumor-infiltrating macrophages (TIMs) to an anti-inflammatory phenotype and contributes to tumor growth. To evaluate the role of myeloid cell-expressed AMPKa1 in tumor growth and metastasis, we used an AMPKa1 Cre-lox transgenic mouse model. AMPKa1flox/flox LysM-Cre+ (described subsequently as MacAMPKa1 KO) mice had reduced Lewis lung carcinoma (LLC) tumor growth and metastasis compared to AMPKa1flox/- LysM-Cre- (WT) mice. Additionally, TIMs isolated from MacAMPKa1 KO mice exhibited higher production of proinflammatory cytokines and matrix metalloproteinases (MMPs). Furthermore, TIMs isolated from MacAMPKa1 KO mice had higher phosphorylation of p65 NF-?B and reduced phosphorylation of Akt and CREB. Overall, deficiency of myeloid AMPKa1 results in higher proinflammatory activity of TIMs and decreased tumor growth. Our studies herein demonstrate that AMPKa1 counter-regulates myeloid cell TLR- and CD154-induced inflammatory activity and antagonizes the development of proinflammatory effector T cell responses. Furthermore, myeloid-expressed AMPKa1 contributes to the polarization of TIMs to an anti-inflammatory phenotype and leads to increased tumor growth and metastasis. These studies demonstrate that AMPKa1 is an important link to inflammation and metabolism and is a valuable potential target for the treatment of inflammatory and metabolic diseases. Additionally, these studies provide evidence that activation of AMPKa1 in cancer therapy may contribute to increased tumor growth through polarization of TIMs to an anti-inflammatory phenotype, a valuable observation given that many AMPK activators are being studied as cancer therapeutics.

Download

Share

COinS