Innate human cell activation by bacterial lipopolysaccharide core heptose metabolites and Helicobacter pylori

Faaß, Larissa (2023): Innate human cell activation by bacterial lipopolysaccharide core heptose metabolites and Helicobacter pylori. Dissertation, LMU München: Medizinische Fakultät

Abstract

Lipopolysaccharide (LPS) inner core heptose metabolites, including ADP-heptose, play an essential role in the activation of cell-autonomous innate immune responses in eukaryotic cells via the ALPK1-TIFA-NF-B signaling pathway, as demonstrated for several pathogenic bacteria. The important role of LPS heptose metabolites in the pro-inflammatory activation of gastric epithelial cells during an infection with the pathogenic bacterium Helicobacter pylori (H. pylori) was demonstrated before, in studies by our group and other scientists. The human pathogen H. pylori colonizes more than half of the world’s population, causing chronically active gastritis and ulcers, and long-term infection can lead to gastric cancer. Disease progression and severity depend on virulence factors of the pathogen, such as the Cag type 4 secretion system (T4SS) that enables active transport of proteins and metabolites into host cells. The impact of heptose metabolites and pure ADP-heptose on human myeloid cells was not yet investigated. Therefore, in my project, we aimed to gain a better understanding of the activation and modulation potential of bacterial heptose metabolites on human macrophages and neutrophils. For this purpose, we used pure heptose metabolites and, as a bacterial model, H. pylori, which appears to transport heptose metabolites into the human host cell, most probably via its T4SS. Main questions of my thesis were how bacterial heptose metabolites affect the pro-inflammatory activation and maturation, alone and in the bacterial context, of human macrophages and neutrophils. In addition, we wanted to characterize the effect of heptose metabolites on macrophage functions including phagocytosis and antigen presentation. The main findings of my project were that human macrophages and neutrophils respond with high sensitivity to pure heptose metabolites in cell culture and primary cell models (manuscript I and III). In addition, we discovered that activation of these cells with pure ADP-heptose was dependent on active cellular uptake. Our results are based on pro-inflammatory cytokine production and transcriptional upregulation of pro-inflammatory genes (IL-8) and the transcription factor NF-B after exposure to ADP-heptose. When comparing different cell types, we found that transcriptional changes after co-incubation with pure ADP-heptose were very similar in human gastric epithelial cells, monocyte/macrophage-like cells, and neutrophil-like cells (manuscript III). Using knock-down experiments, I demonstrated that ADP-heptose signaling in monocyte/macrophage-like cells is dependent on TIFA (manuscript I). Moreover, we discovered that stimulation with pure ADP-heptose polarized monocytes into macrophages of predominantly pro-inflammatory type M1 and pre-mature neutrophil-like cells rather into the pro-inflammatory type N1 (manuscript I and III). Furthermore, I found that activation of human macrophages and neutrophils by live H. pylori is strongly influenced by the presence of LPS heptose metabolites and the functionality of its T4SS. In addition, we showed the ability of macrophages to phagocytose does not appear to be affected by heptose metabolites, but ADP-heptose is the decisive factor to reduce antigen presentation by macrophages upon heptose- or bacteria-exposure, due to upregulation of miRNA146b (manuscript I and II). In summary, my work contributed significantly to our new findings that specific heptose metabolites or bacteria producing heptose metabolites elicit a strong activity and modulation of cell-autonomous innate immune responses and cellular functions of human macrophages and neutrophils.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Keywords: Helicobacter pylori, Bacterial heptose metabolites, Chronic infection Inflammation, Innate immune activation, Macrophages, Neutrophils, Type four secretion system
• Themengebiete: 600 Technik, Medizin, angewandte Wissenschaften ; 600 Technik, Medizin, angewandte Wissenschaften > 610 Medizin und Gesundheit
• Fakultäten: Medizinische Fakultät
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 6. November 2023
• 1. Bericht­erstatter:in: Josenhans, Christine