Date of Award

2018

Document Type

Open Access Dissertation

Department

Biomedical Science

Sub-Department

School of Medicine

First Advisor

Gregorio Gomez

Abstract

Mast cells are classically recognized as the effector cells of Immunoglobulin E (IgE)-mediated hypersensitivity reactions (i.e. allergic reactions). Mast cells also play an important role in the innate immune response to parasitic helminth infection. Allergic disease including allergic rhinitis, asthma, atopic dermatitis, and anaphylaxis, is a major health concern in the United States with greater than 60 million Americans suffering from allergy and asthma. In addition, mast cells have more recently been implicated in non-allergic disease including various human cancers, which will affect approximately 39.6% of U.S. men and women. Therefore, understanding the immunological and molecular mechanisms that regulate mast cells is vital to our understanding of their role in both allergic and non-allergic disease in humans. In this study, we identified novel mechanisms that regulate FcεRI-induced biosynthesis of inflammatory Prostaglandin D2 (PGD2) from in situ-matured mast cells from human skin. Specifically, we demonstrated that interleukin-6 (IL-6), a classical pro-inflammatory cytokine, is a positive regulator, whereas Resveratrol, a natural polyphenol found in the skin of red grapes, is a negative regulator of PGD2 biosynthesis. We demonstrate that Resveratrol at relatively low concentrations specifically inhibited the production of PGD2 without affecting degranulation. Mechanistically, Resveratrol inhibited the expression of cyclooxygenase-2 (COX-2), an enzyme in the arachidonic acid pathway that is directly involved in PGD2 biosynthesis, but had no effect on phosphorylation of Syk kinase, which is a critical protein in mast cell degranulation. In contrast, IL-6 enhanced FcεRI-induced COX-2 expression leading to increased PGD2 biosynthesis. In support of this, we showed that FcεRI and gp130 (the signaling portion of the IL-6 receptor) signals cooperate to enhance STAT-3 phosphorylation, a key event in the IL-6 receptor signal pathway. Moreover, inhibition of IL-6-induced phosphorylation of STAT-3 with the specific inhibitor C188-9 also attenuated the increased production of PGD2. Thus, IL-6 potentiates PGD2 production by a STAT-3-dependent mechanism. Jointly, these data demonstrate that Resveratrol is a negative regulator, and IL-6 a positive regulator of FcεRI-induced PGD2 biosynthesis from human skin mast cells. We further demonstrate that IL-6 induced the expression of vascular endothelial growth factor (VEGF), a major regulator of angiogenesis, from human skin mast cells also by a STAT-3-dependent mechanism. Lastly, we demonstrated by proteome profiling analysis that human skin mast cells spontaneously secrete several angiogenesis-related proteins – CXCL16, DPPIV, Endothelin-1, GM-CSF, IL-8, MCP-1, Pentraxin 3, Serpin E1, Serpin F1, TIMP-1, Thrombospondin-1, uPA, and VEGF – at relatively high concentrations. The array data was verified by specific enzyme linked immunoassay (ELISA). This novel data suggests an innate role for mast cells in both human tumorigenesis and normal development of human vasculature. Together, these novel findings enhance our understanding of the mechanisms that regulate the release of allergic mediators from mast cells, and suggest a possible role for mast cells in oncogenesis and normal vascular development.

Available for download on Sunday, May 12, 2019

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