Phytoestrogens and the Innate Immunity in ER-Deficient Mice

Abstract
Key Personnel
Specific Objectives

Abstract
Dietary supplementation with plant-derived biologically active compounds is proposed to impact immunity. The goal of this proposal is to determine the range and mechanism(s) of action of phytoestrogens (genistein, daidzein and soy extracts) on innate immune function via estrogen receptor-dependent and independent pathways. This will be accomplished using ERKO (estrogen receptor-deficient), SCID (severe combined immunodeficient) mouse models of bacterial inflammation in the gut, liver and spleen. Alterations in the innate response to infection may predispose premenopausal women to autoimmunity. Given that there are distinct sex biases in autoimmune diseases such as lupus, our hypothesis is that estrogen and therefore, phytoestrogen signaling, via the ER-alpha (ERα) and/or ER-beta (ERβ) receptors, is an important positive regulator of macrophage and NK cell function. Exciting preliminary data indicate that ERα signaling is necessary for a normal immune response in an ERαKO/SCID mouse model of infection. The long-term objectives of the project are to resolve the role of dietary phytoestrogens in the immune reactivity of females using models of acute and chronic inflammation in SCID mice. In this series of studies, we will investigate the role abrogation of signaling via ERα and ERβ plays on mediators of acute and chronic inflammation, namely macrophages and natural killer or NK cells.

Key Personel
D. Mark Estes — Principal Investigator
Craig Franklin — Co-principal Investigator
Dennis Lubahn — Consultant

Specific Objectives
Dietary supplementation with plant-derived biologically active compounds is proposed to impact immunity. The goal of this proposal is to determine the range and mechanism(s) of action of selected botanical compounds on immune function via estrogen receptor-dependent and independent pathways. This will be accomplished using two murine models of bacterial inflammation. The first model proposes to utilize a general model of mycobacterial (intracellular pathogen; a Type 1 response is protective) induced inflammation in the spleen and liver while a second model of Helicobacter hepaticus (extracellular pathogen; a type 1 response exacerbates disease) infection will examine the host response in the gut associated tissues. The project will focus on innate immune function in severe combined immunodeficient (SCID) mice deficient in estrogen receptor alpha (ERα) and/or estrogen receptor beta (ERβ). The function of the innate immune system is to detect molecules that are unique to pathogens as compared to the host. The interconnectivity of the innate immune components with the acquired immune response is a result of pattern recognition by cells of the innate immune system and the subsequent secretion of cytokines and antigen selection of lymphocytes that result in the host response. The innate response has been proposed to "instruct" if not "dictate" the subsequent acquired immune response and thus is an important control point in regulation. As alterations in the innate response to infection may predispose premenopausal women to immune dysfunction, we propose to investigate the effects of estrogen receptor deficiencies and phytoestrogen compounds in inflammation. Investigation of the complex interactions among inflammatory cells during the course of inflammation as a result of bacterial infection is most readily conducted in vivo. A SCID mouse model system provides the ability to measure acute and chronic inflammatory reactions in the absence of lymphocyte functions that may overlap with nonlymphoid cells. Phagocyte recruitment, cytokine/chemokine production, bacterial growth and histopathology will be utilized to monitor alterations in host immune function and inflammation. Our hypothesis is that phytoestrogen signaling via the ER-alpha (ERα) and/or ER-beta (ERβ) receptors is an important positive regulator of innate macrophage and NK cell function.

We will specifically investigate alterations in cytokine and chemokine protein and gene expression in ERα and ERβ knockout and wild-type SCID mice administered a challenge infection to induce inflammation. Bacterial products or infection in experimental animal models have been linked to the onset of arthritis and inflammatory bowel disease and as strong inducers of inflammation as demonstrated by their potent adjuvant activities. The long-term objectives of the project are to resolve the role of phytoestrogens and the innate response in the predisposition of females to immune hypereactivity using a model of acute and chronic inflammation.

Objective 1
Determine the effects of loss of ERα signaling on bacterial-induced inflammation.

Objective 2
Determine the effects of loss of ERβ signaling on bacterial induced inflammation.

Objective 3
Determine the effects of loss of ERα and ERβ signaling on bacterial induced inflammation.