Cluster of differentiation 1 (CD1) d ist ein antigenpräsentierendes Glykoprotein, das verschiedene Lipidklassen (z.B. Glycerophospholipide und Sphingolipide) bindet. CD1d zeigt intrazellulär eine Verteilung sowohl im sekretorischen als auch im endolysosomalen Kompartiment und bindet dort endogene (körpereigene) und exogene (körperfremde, z.B. mikrobiellen) Lipide, die an natürliche Killer T-Zellen, eine Gruppe lipidreaktiver T-Zellen, präsentiert werden. Nach Antigenerkennung zeigen NKT-Zellen eine schnelle Zytokinsekretion, was wiederum zu einer breiten Aktivierung anderer angeborener und adaptiver Immunzellpopulationen wie dendritischer Zellen, natürlicher Killerzellen, B-Zellen und konventioneller T-Zellen führt. In meiner Dissertation untersuchte ich die Rolle von CD1d und NKT-Zellen im Kontext der intestinalen Tumorentstehung (Kapitel 1). Darüber hinaus untersuchte ich CD1d-abhängige Effekte auf den hepatischen Lipidmetabolismus, verbunden mit der Frage ob diese Effekte zumindest partiell in NKT-Zell-unabhängiger Weise vermittelt werden (Kapitel 2). CD1d und NKT-Zellen in der intestinalen Tumorentwicklung NKT-Zellen beeinflussen CD1d-abhängig entzündliche Prozesse im Darm sowie die intestinale Tumorentwicklung. Verschiedene Modelle und Strategien, die sich mit der Klärung der Rolle der NKT-Zelluntergruppen in diesen Erkrankungen beschäftigten, zeigten, dass hierbei eine komplexe Regulierung durch spezifische NKT-Zelluntergruppen, nämlich invariante (i)NKT-Zellen und diverse (d)NKT-Zellen, mit teils gegensätzlichen Effekten zu beobachten ist. CD1d zeigt eine ubiquitäre Expression und kann in zellspezifischer Weise in die NKT-Zell-Aktivierung eingreifen. So vermittelt CD1d im Kontext der intestinalen Entzündung regulatorische NKT-Zell-Signale wenn die Antigenpräsentation von intestinalen Epithelzellen (IECs) ausgeht, während CD1d-Signale von professionellen Immunzellen intestinale Entzündung in NKT-Zell-abhängiger Weise fördern. Das Ziel des ersten Teils meiner Arbeit (Kapitel 1) war die Analyse zelltypspezifischer Effekte von CD1d in der Aktivierung von NKT-Zellen im Rahmen der intestinalen Tumorentstehung. Unter Verwendung des Cre-lox-Systems zur Erzeugung von IEC- und myeloidspezifischen CD1d-defizienten Mäusen und der ApcMin/+ und Apcfl/wt-Mausemodelle intestinaler Tumorentwicklung untersuchte ich die Wirkung der zelltypspezifischen CD1d-Deletion auf die NKT-Zell-Immunantwort im Rahmen der intestinalen Tumorentwicklung. Ich konnte dabei zeigen, dass CD1d in NKT-Zell-abhängiger Weise das intestinale Tumorwachstum fördert. Während die intestinal-epitheliale Deletion von CD1d keine Effekte auf die Tumorentwicklung hatte, führte die myeloide Deletion von CD1d zumindest zu einem partiell reduzierten Tumorwachstum. Diese Daten zeigen, dass myeloide Zellen zum CD1d- und NKT-abhängigen Tumorwachstum beitragen. Darüber hinaus ist anzunehmen, dass weitere, bislang uncharakterisierte Zellen zur CD1d-abhängigen Regulation der Tumorentwicklung beitragen. NKT-Zell-unabhängige Effekte von CD1d im hepatischen Lipidmetabolismus. Der zweite Teil meiner Dissertation (Kapitel 2) befasste sich mit der Rolle von CD1d in der Regulierung des hepatischen Fettstoffwechsels unter konstitutiven Bedingungen sowie im Kontext der nichtalkoholischen Fettleberkrankheit (NAFLD). Mausmodelle mit konstitutiver Deletion von CD1d zeigten dabei, dass diese Prozesse in CD1d-abhängiger Weise vermittelt werden. Da die Deletion von CD1d mit einem Verlust von NKT-Zellen verbunden ist, wurde daraus geschlossen, dass NKT-Zellen zur Pathogenese metabolischer und inflammatorischer Veränderungen bei NAFLD beitragen. Ob CD1d auch in NKT-Zell-unabhängiger Weise zur Regulation des hepatischen Metabolismus beitragen kann, wurde bislang nicht untersucht. CD1d wird ubiquitär und abundant von verschiedenen Zelltypen einschließlich Enterozyten, Adipozyten und Hepatozyten exprimiert und interagiert mit verschiedenen Lipidtransferproteinen. Ich untersuchte daher, ob CD1d auch in direkter, NKT-Zell-unabhängiger Weise Einfluss auf den hepatischen Lipidmetabolismus nimmt. Hierzu wurden CD1d-exprimierende und CD1d-defiziente Mäuse auf einem genetischen Hintergrund mit Defizienz des recombination activating gene 1 (Rag1) untersucht, in dem aufgrund der fehlenden VDJ-Rekombination reife T- und B-Zellen einschließlich NKT-Zellen fehlen. Meine Ergebnisse zeigen, dass CD1d den hepatischen Lipidstoffwechsel unter konstitutiven Bedingungen wie auch im Kontext der nicht-alkoholischen Fettleber in einer NKT-Zell-unabhängigen Weise regulieren kann. Die Mechanismen über die diese Regulation vermittelt wird, werden derzeit experimentell untersucht. Zusammenfassend habe ich in dieser Arbeit die Rolle von epithelialem und myeloiden CD1d in der intestinalen Tumorentstehung charakterisiert. Darüber hinaus konnte ich zeigen, dass CD1d in NKT-Zell-unabhängiger Weise den hepatischen Lipidmetabolismus reguliert.:Zusammenfassung
Summary
General introduction
1 The CD1 family of antigen presenting proteins
1.1 Structure of CD1 proteins
1.2 Trafficking of CD1 proteins
1.3 Lipid transfer proteins
1.4 CD1 associated lipid repertoire
2 CD1d-restricted T cells
2.1 Lipid antigens presented to CD1 restricted T cells
2.2 NKT cell subsets
2.3 NKT cells in homeostasis and disease
Chapter I: CD1d in intestinal tumor development
Introduction
1 The role of CD1d and NKT cells in intestinal homeostasis
1.1 The intestine: structure and function
1.2 Immune cell populations in the intestine
1.3 Interplay between iNKT cells and intestinal microbiota
1.3.1 The intestinal microbiota shapes mucosal iNKT cells
1.3.2 Effect of the microbiota on systemic iNKT cells
1.3.3 Bacterial lipid antigens influence iNKT cell-dependent mucosal immunity
1.3.4 Effect of CD1d deficiency on commensals
2 CD1d & NKT cells in cancer
2.1 Enhancing anti-tumor immunity
2.2 Suppressing anti-tumor immunity
3 CD1d & NKT cells in colorectal cancer
3.1 Spontaneous tumorigenesis
3.2 Intestinal inflammation and inflammation-induced cancer
Aim of the study
Materials and Methods
Results
1.1. Validation of the conditional CD1d knockout mouse lines
1.2. Analysis of tumorigenesis in the ApcMin/+ and Apcfl/wt models
1.3. The impact of myeloid cell-specific deletion of CD1d on spontaneous tumor development
1.4. The impact of intestinal epithelial cell specific deletion of CD1d on spontaneous tumorigenesis
1.5. Analysis of constitutive deletion of CD1d in spontaneous tumorigenesis model
Discussion
Chapter II: CD1d and hepatic lipid metabolism in non-alcoholic fatty liver disease (NAFLD)
Introduction
1 Metabolic diseases as a multi-organ pathology
2 Lipid metabolism and inflammation in metabolic diseases
3 Non alcoholic fatty liver disease (NAFLD)
3.1 Mouse models of NAFLD
4 NKT cells in metabolic diseases
4.1 NKT cells in obesity
4.2 NKT cells in NAFLD
5 Potential NKT cell-independent roles of CD1d
Materials and methods
Results
2.1 Absence of CD1d on the Rag1-deficient background under constitutive conditions reduces neutral lipid accumulation in the liver
2.2 Deletion of CD1d on a Rag1-deficient background reduces hepatic neutral lipid accumulation in response to a HFD and protects from liver injury
2.3 Choline-deficient HFD as a model of NASH shows no difference between CD1d-deficient Rag1-deficient mice and CD1d-proficient littermates
Discussion
References
Appendix 132
List of abbreviations 132
List of tables 137
List of figures 138
Acknowledgments
Anlage 1
Anlage 2 / Cluster of differentiation 1 (CD1) d is an atypical antigen-presenting glycoprotein which binds diverse lipid classes including glycerophospholipids and sphingolipids. Trafficking through secretory and endolysosomal compartments, CD1d broadly surveys the cell for endogenous (self) and exogenous (e.g. microbial) lipids and presents those lipids to a subset of T cells, named natural killer T (NKT) cells. NKT cells exhibit rapid and abundant cytokine secretion upon antigen recognition, leading to a broad activation of other innate and adaptive immune cell populations such as dendritic cells, natural killer cells, B cells, and conventional T cells. My thesis studied CD1d and NKT cells in the context of intestinal tumorigenesis (chapter I) and investigated a novel NKT cell-independent role of CD1d in the regulation of hepatic lipid metabolism (chapter II). CD1d and NKT cells in intestinal tumor development NKT cells modulate intestinal inflammation and tumor development in a CD1d-dependent manner. Different models and strategies have been used to elucidate the role of NKT cell subsets in these processes, highlighting a complexity of regulation by specific NKT cells subsets, namely invariant (i)NKT cells and diverse (d)NKT cells, and other immune cells and mediators in the tumor microenvironment. In addition, CD1d, which is ubiquitously expressed, can elicit cell-type specific effects on NKT cell subsets as shown in intestinal inflammation, where intestinal epithelial cell (IEC) CD1d provide regulatory cues, while CD1d signal from bone marrow-derived cells promote intestinal inflammation. The first part of my thesis (chapter I) aimed at further dissecting potential cell type-specific effects of CD1d in the activation of NKT cells in the context of intestinal tumorigenesis. Using the Cre-lox system to generate IEC- and myeloid-specific CD1d-deficient mice and the ApcMin/+ and Apcfl/wt mouse models of intestinal tumorigenesis, I investigated the effects of cell type-specific CD1d deficiency on iNKT cell immune responses and tumor development. My findings show that CD1d, presumably through iNKT cells, promotes tumor growth as shown in a model of constitutive CD1d deletion. While epithelial CD1d did not contribute to NKT cell-dependent tumor growth, myeloid deletion of CD1d was associated with a trend towards reduced tumor growth. These results suggest that myeloid CD1d promotes NKT cell-dependent tumor growth and that other, yet uncharacterized cells, have additional contributions to this process. NKT cell-independent roles of CD1d in the regulation of liver metabolism The second part of my thesis (chapter II) tackled the role of CD1d in the regulation of hepatic lipid metabolism under constitutive conditions and in the context of non-alcoholic fatty liver disease (NAFLD), a prevalent metabolic liver disease which is associated, in a subset of individuals, with immune-mediated progression to liver fibrosis and cirrhosis. Inflammation has an important role in the progression of NAFLD and metabolic diseases, and iNKT cells have been linked to these processes. Specifically, constitutive deletion of CD1d, which is associated with loss of NKT cells, has been demonstrated to influence hepatic lipid metabolism and the progression of NAFLD. In this thesis, I investigated whether the effects of CD1d are indeed dependent on NKT cells or whether CD1d has direct, NKT cell-independent effects on liver metabolism. CD1d is expressed ubiquitously and abundantly by various cell types including enterocytes, adipocytes and hepatocytes, and it binds to a plethora of endogenous cellular lipids through the interaction with lipid transfer proteins, which are important regulators of lipid metabolism. To investigate CD1d-mediated effects that are independent from NKT cells, CD1d-proficient and CD1d-deficient mice were analyzed on a recombination activating 1 (Rag1)-deficient background, which lacks mature T and B cells including NKT cells due to the lack of VDJ recombination. My results demonstrate that CD1d can regulate hepatic lipid metabolism in an NKT cell-independent manner under constitutive conditions and in the context of models of NAFDL. The mechanisms by which CD1d can directly regulate hepatic lipid metabolism are currently being addressed. In conclusion, in this thesis I have characterized the cellular contributions to CD1d- and NKT cell-dependent regulation of intestinal tumor development. In addition, I have identified a novel, NKT cell-independent effect of CD1d on hepatic lipid metabolism.:Zusammenfassung
Summary
General introduction
1 The CD1 family of antigen presenting proteins
1.1 Structure of CD1 proteins
1.2 Trafficking of CD1 proteins
1.3 Lipid transfer proteins
1.4 CD1 associated lipid repertoire
2 CD1d-restricted T cells
2.1 Lipid antigens presented to CD1 restricted T cells
2.2 NKT cell subsets
2.3 NKT cells in homeostasis and disease
Chapter I: CD1d in intestinal tumor development
Introduction
1 The role of CD1d and NKT cells in intestinal homeostasis
1.1 The intestine: structure and function
1.2 Immune cell populations in the intestine
1.3 Interplay between iNKT cells and intestinal microbiota
1.3.1 The intestinal microbiota shapes mucosal iNKT cells
1.3.2 Effect of the microbiota on systemic iNKT cells
1.3.3 Bacterial lipid antigens influence iNKT cell-dependent mucosal immunity
1.3.4 Effect of CD1d deficiency on commensals
2 CD1d & NKT cells in cancer
2.1 Enhancing anti-tumor immunity
2.2 Suppressing anti-tumor immunity
3 CD1d & NKT cells in colorectal cancer
3.1 Spontaneous tumorigenesis
3.2 Intestinal inflammation and inflammation-induced cancer
Aim of the study
Materials and Methods
Results
1.1. Validation of the conditional CD1d knockout mouse lines
1.2. Analysis of tumorigenesis in the ApcMin/+ and Apcfl/wt models
1.3. The impact of myeloid cell-specific deletion of CD1d on spontaneous tumor development
1.4. The impact of intestinal epithelial cell specific deletion of CD1d on spontaneous tumorigenesis
1.5. Analysis of constitutive deletion of CD1d in spontaneous tumorigenesis model
Discussion
Chapter II: CD1d and hepatic lipid metabolism in non-alcoholic fatty liver disease (NAFLD)
Introduction
1 Metabolic diseases as a multi-organ pathology
2 Lipid metabolism and inflammation in metabolic diseases
3 Non alcoholic fatty liver disease (NAFLD)
3.1 Mouse models of NAFLD
4 NKT cells in metabolic diseases
4.1 NKT cells in obesity
4.2 NKT cells in NAFLD
5 Potential NKT cell-independent roles of CD1d
Materials and methods
Results
2.1 Absence of CD1d on the Rag1-deficient background under constitutive conditions reduces neutral lipid accumulation in the liver
2.2 Deletion of CD1d on a Rag1-deficient background reduces hepatic neutral lipid accumulation in response to a HFD and protects from liver injury
2.3 Choline-deficient HFD as a model of NASH shows no difference between CD1d-deficient Rag1-deficient mice and CD1d-proficient littermates
Discussion
References
Appendix 132
List of abbreviations 132
List of tables 137
List of figures 138
Acknowledgments
Anlage 1
Anlage 2
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:89088 |
| Date | 17 January 2024 |
| Creators | Ceriotti, Chiara |
| Contributors | Zeissig, Sebastian, Jessberger, Rolf, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | German |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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