Actions of Cannabinoids on Amoebae By Israa Al-hammadi This thesis is submitted for the degree of Doctor of Philosophy April 2020 Department of Biomedical and Life Sciences 2nd April 2020 To Whom It May Concern: Declaration Actions of cannabinoids on amoebae. This thesis has not been submitted in support of an application for another degree at this or any other university. It is the result of my own work and includes nothing that is the outcome of work done in collaboration except where specifically indicated. Many of the ideas in this thesis were the product of discussion with my supervisor Dr. Jackie Parry and Dr. Karen Wright. Israa Al-hammadi MSc. BSc. Table of contents Abstract 1 Chapter 1: General Introduction 3 1.1 Introduction 3 1.2 The Endocannabinoid System (ECS) in humans 3 1.2.1 General overview 3 1.2.2 Main ligands of the endocannabinoid system 3 1.2.2.1 Endocannabinoids 4 1.2.2.2 Phytocannabinoids 7 1.2.3 Main cannabinoid receptors 10 1.2.3.1. CB1 and CB2 receptors 10 1.2.3.2 The transient receptor potential vanilloid type 1 (TRPV1) 11 1.2.3.3 G-protein coupled receptor 55 (GPR55) 11 1.2.4 Other receptors 12 1.2.4.1 Peroxisome Proliferator-activated Receptors (PPARs) 12 1.2.4.2 Dopamine Receptors 14 1.2.4.3 Serotonin receptors (5-HT) 16 1.3. Existence of an endocannabinoid system in single-celled eukaryotes 17 1.3.1. Endocannabinoids in Tetrahymena 18 1.3.2. Enzymes in Tetrahymena 19 1.3.3. Receptors in Tetrahymena 19 1.3.4. Response of Tetrahymena to cannabinoids 20 1.4. Cannabinoids and amoebae 21 1.4.1. Overview of amoebae 21 1.4.2. Amoebic response to cannabinoids 21 1.4.3. Amoebic feeding 23 1.4.3.1. General overview 23 1.4.3.2. Receptor-mediated ingestion of prey (Fig. 1.9, stages 1-2) 24 1.4.3.3. Phagosome formation and trafficking (Fig. 1.9, stages 3-6) 27 1.4.3.4. Defecation and membrane recycling (Fig. 1.9, stages 7-9) 28 1.5. Aims of the study 28 Chapter 2: Methods and Materials 30 2.1 Organisms and maintenance 30 2.1.1. Escherichia coli 30 2.1.2. Synechococcus sp. (‘Pico’) 30 2.1.3. Amoebae 30 2.2. Experimental compounds 31 2.2.1 Fluorescent microspheres (‘beads’) 31 2.2.2. Agonists 32 2.2.3. Antagonists 32 2.2.4. Sugars 32 2.3. Counting cells and beads 32 2.3.1 Counting E. coli cells 32 2.3.2 Counting Synechococcus cells and beads 33 2.3.3. Counting amoeba cells in suspension 33 2.3.4. Counting amoeba cells on agar plates 33 2.3.5. Counting fluorescent prey inside Vermamoeba vermiformis cells 33 2.4. Amoeba population growth experiments 34 2.4.1. Basic experimental protocol 34 2.4.2. Initial screening of amoebae for sensitivity to the agonists 34 2.4.3. Determining MIC, IC50 and lethal dose of agonists against sensitive amoebae 35 2.4.4. Effect of antagonists on population growth 34 2.5. Feeding experiments involving Vermamoeba vermiformis 34 2.5.1. Basic experimental protocol 34 2.5.2. Effect of AEA and CBD on V. vermiformis feeding 36 2.5.3. Effect of CBD concentration of V. vermiformis feeding 36 2.5.4. Effect of PPAR agonists and antagonists of the feeding of V. vermiformis 36 2.5.5. Effect of blocking amoeba prey recognition receptors, prior to adding CBD on V. vermiformis feeding 37 2.6. Effect of CBD on phagosome processing and defecation in V. vermiformis 37 2.7. Bioinformatic analysis 38 Chapter 3: Sensitivity of amoebae to CBD and AEA 39 3.1. Introduction 39 3.2. Results 39 3.2.1 Initial screening of amoebae for sensitivity to AEA and CBD 39 3.2.2. MIC, IC50 and lethal dose values for AEA and CBD against sensitive amoebae 41 3.3. Discussion 43 3.3.1. Differences in sensitivity of amoebae to AEA and CBD 44 3.3.2 Dose-dependent effect of AEA and CBD on amoebic growth 46 3.4. Conclusions 49 Chapter 4: Effect of CBD and AEA on feeding in Vermamoeba vermiformis 50 4.1. Introduction 50 4.2. Results 51 4.2.1. Effect of AEA and CBD (2µM) on V. vermiformis feeding on indigestible bead and Synechococcus (‘Pico’) 53 4.2.2. Effect of CBD concentration on the feeding lag and ingestion rate of V. vermiformis 55 4.2.3. Effect of CBD on phagosome trafficking within V. vermiformis 55 4.2.4. Interaction between CBD and the feeding receptors of V. vermiformis 56 4.3. Discussion 59 4.3.1. Effect of particle type on V. vermiformis ingestion rates 59 4.3.2. Effect of AEA on the feeding of V. vermiformis 60 4.3.3. Overall effect of CBD on the feeding of V. vermiformis 61 4.3.4. Effect of CBD on phagosome trafficking and defecation (Fig. 4.8, stages 6-7) 62 4.3.5. Effect of CBD on phagosome formation (Fig. 4.8, stages 3-5) 63 4.3.6. Effect of CBD on phagosome membrane recycling (Fig. 4.8, stages 8-9) 64 4.3.7. Pre-phagosome membrane availability at the site of phagocytosis (Fig. 4.8, stage 1) 65 4.3.8. Effect of CBD on receptor-mediated prey uptake (Fig. 4.8, stages 1-2) 66 4.3.8.1. Prey uptake in the absence of CBD 66 4.3.8.2. Prey uptake in the presence of CBD 68 4.3.9. Working hypothesis on how CBD affects feeding in V. vermiformis 69 4.4. Conclusions 72 Chapter 5: Involvement of Peroxisome Proliferator-Activated Receptors (PPARs) in the mode of action of CBD against Vermamoeba vermiformis 73 5.1. Introduction 73 5.2. Results 74 5.2.1. Growth experiments 74 5.2.1.1. Response of all amoebae to four PPAR agonists 74 5.2.1.2. Response of all V. vermiformis strains to PPAR agonists in the presence and absence of specific PPAR antagonists 77 5.2.1.3. Response of all V. vermiformis strains to AEA and CBD in the presence and absence of specific PPAR antagonists 78 5.2.1.4. Response of all V. vermiformis strains to CBD in the presence of varying concentrations of specific PPAR antagonists 80 5.2.2. Feeding experiments with V. vermiformis CCAP 1534/14 81 5.3. Discussion 84 5.3.1. Sensitivity of amoebae to PPAR agonists 84 5.3.2. Response of V. vermiformis to PPAR antagonists 86 5.3.2.1. Growth experiments 86 5.3.2.2. Feeding experiments 88 5.3.3. PPAR-induced non-genomic response 89 5.3.4. Signalling cascades responsible for phagosome cup formation (Fig. 4.8, stage 2-3) 91 5.3.4.1. Opsonized phagocytosis in macrophages 91 5.3.4.2. Non-opsonized phagocytosis in macrophages 93 5.3.4.3. Phagocytosis of Mycobacterium spp. and the involvement of PPAR 95 5.4. Conclusion 98 Chapter 6: Involvement of the dopamine and serotonin receptors in the mode of action of CBD against amoebae 100 6.1. Introduction 100 6.2. Results 101 6.2.1. Growth experiments with Haloperidol 101 6.2.2. Feeding experiment with Haloperidol 102 6.2.3. Growth experiments with separate dopamine and serotonin receptor blockers 103 6.3. Discussion 105 6.3.1. Effect of CBD on N. gruberi feeding 105 6.3.2. Blocking experiments 106 6.3.2.1. Suitability of the chosen receptor blockers 106 6.3.2.2. Population growth of amoebae in the presence of AEA and CBD with/without Haloperidol 106 6.3.2.3. Population growth of N. gruberi in the presence of CBD with/without S-WAY 107 6.4. Conclusions 108 Chapter 7: General Discussion 109 7.1. Amoebic sensitivity to AEA and CBD 109 7.2. Amoebic response to AEA 110 7.3. Effect of CBD on amoebic feeding 112 7.3.1. Amoebic feeding in the absence of CBD 112 7.3.2. Amoebic feeding response in the presence of CBD 113 7.4. Mode of action of CBD on V. vermiformis 115 7.5. Comparison of V.vermiformis response to cells of higher animals 117 7.6. Involvement of serotonin receptors in the mode of action of CBD against amoebae 118 7.7. Conclusion 119 References 120 Appendix 1: Media formulations 146 Appendix 2: IC50 graphs of all sensitive amoeba strains with AEA and CBD (Section 3.2.2) 147 Appendix 3: IC50 graphs of all sensitive amoeba strains with OEA, PEA, GW0742 and Rosiglitazone (Section 5.2.1.1) 151 Appendix 4: Response of Vermamoeba vermiformis strains to PPAR agonists in the presence and absence of specific PPAR antagonists (Section 5.2.1.2) 158 Appendix 5: Response of Vermamoeba vermiformis strains to CBD in the presence and absence of three PPAR antagonists (Section 5.2.1.3) 164 Appendix 6: Response of Vermamoeba vermiformis strains to CBD in the presence and absence of three PPAR antagonists at different concentrations (Section 5.2.1.4) 166 Appendix 7: Response of sensitive amoeba strains to CBD and AEA in the presence and absence of Haloperidol (Section 6.2.1.) 173 Abbreviations ECS endocannabinoid system CBD Cannabidiol AEA Arachidonoylethanolamide OEA Oleoylethanolamide PEA Palmitoylethanolamide PPAR Peroxisome proliferator-activated receptor AcEs Acylethanolamines AcGs Acylglycerols CBRs Cannabinoid receptors CB1 Cannabinoid receptor type 1 CB2 Cannabinoid receptor type 2 COX2 Cyclooygenase subtype 2 DAGL Diacylglycerol lipase subtype α DAPI 4',6-diamidino-2-phenylindole FAAH Fatty acid amide hydrolase GPCR G protein–coupled receptor GPR55 G-protein-coupled receptor 55 IC50 half maximal inhibitory concentration MAGL Monoacylglyceride lipase MIC Minimum inhibitory concentration NAPE-PLD N-acyl phosphatidylethanolamide selective phospholipase D THC Delta-9-Tetrahydrocannabinol CBGA cannabigerolic acid CBDAS oxidocyclase cannabindiolic acid synthase TRVP1 Transient receptor potential channel subfamily V member 1 2-AG 2-arachidonoylglycerol GlcNAc N-Acetyl-D-glucosamine GalNAc N-Acetyl-D-galactosamine Syk Tyrosine-protein kinase LAT Linker for activation of T cells PKC Protein Kinase C Acknowledgement First, and most of all, I would like to thank Dr.