Regulation of human mast cell Activation

Research output: Types of ThesisDoctoral ThesisInternal

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Abstract

Mast cell-mediated diseases, such as allergies and asthma, affect a growing percentage of the population, with significant unmet medical needs. As we slowly untangle the regulatory mechanisms that modulate these complex genetic and environment-influenced diseases, new opportunities in an area of potentially highly specific and effective therapeutic interventions are emerging. In this thesis, we aimed to a) investigate how the activation of a prime effector cell in allergy - the mast cell - can be regulated by dietary compounds such as short-chain fatty acids (SCFAs), b) study the transcriptional response in human mast cells in response to various stimuli to better understand endogenous feedback loops and c) develop a new technology platform to identify and validate novel regulators of human mast cell degranulation.
We summarized the known effects of dietary fiber and its metabolites on immune and non-immune cells (Chapter 2.1), and more specifically, in the context of mast cell-mediated disease (Chapter 2.2). Given the plausible correlation between dietary fiber intake and mast cell–mediated pathology, we investigated the effects of the SCFAs (acetate, propionate, and butyrate) on human mast cell activation, including the molecular mechanisms involved. We showed that butyrate and propionate, but not acetate, potently inhibited human mast cell activation via inhibition of histone deacetylase (HDAC) activity (Chapter 3). Interestingly, butyrate downregulated expression of key signaling molecules involved in IgE-mediated mast cell activation (e.g., BTK, SYK, and LAT), which coincided with deacetylation near promoter regions of such genes. To investigate potential mechanisms underlying gene expression changes in response to butyrate-induced HDAC inhibition, we integrated RNA-Seq and time-course ChIP-Seq data from butyrate-treated primary human mast cells (Chapter 4). Although butyrate evoked broad histone acetylation, our data indicated that butyrate selectively regulated gene transcription in primary human mast cells and had stronger modulatory effects on only a small subset of chromatin regions. Next, we sought to map the transcriptional landscape of activated mast cells using a variety of stimuli that target either the high-affinity IgE receptor (FcεRI)- or Mas-Related G Protein-Coupled Receptor-X2 (MRGPRX2) receptor, and found that mast cells tightly control their own activity by regulating the expression of both positive and negative regulators of (mast) cell activation (Chapter 5). Our understanding of the molecules that regulate mast cell activation and degranulation is primarily based on evidence obtained in (mast cell deficient) mouse models. Unfortunately, the follow-up validation of the exact roles of these regulators in mediating degranulation in human mast cells has been hampered by (i) the limited availability of primary human mast cells and (ii) the lack of suitable methodology to functionally interrogate the putative roles of such regulators of degranulation using small numbers of primary cells. To this end, we developed a novel technology platform that allows for rapid identification of regulators of human mast cell degranulation using functional genomics coupled to high-resolution confocal microscopy (Chapter 6). In Chapter 7 we discuss the interpretations and implications of our main findings, as well as possible limitations of the study. Furthermore, suggestions for future research directions are proposed, in addition to novel therapeutic strategies for targeting mast functions.
In this thesis, we uncovered molecular mechanisms that have evolved to control human mast cell activation. Future studies are bound to discover additional (deficiencies in the) regulatory mechanisms that control mast cell function.
Original languageEnglish
Awarding Institution
  • Erasmus University Rotterdam
Supervisors/Advisors
  • Hendriks, Rudi, Supervisor
  • Maurer, M, Supervisor
  • Stadhouders, Ralph, Co-supervisor
  • Redegeld, F, Co-supervisor
Award date1 Jun 2022
Place of PublicationRotterdam
Print ISBNs978-94-6458-240-6
Publication statusPublished - 1 Jun 2022

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