Die Wirkung der sauren Sphingomyelinase im allergischen T$_{H}$2-gerichteten Asthma bronchiale

Böll, Svenja; Pradel, Gabriele (Thesis advisor); Elling, Lothar (Thesis advisor); Martin, Christian (Thesis advisor)

Aachen : RWTH Aachen University (2021)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2021


Acid sphingomyelinase (ASM), an important regulator of the sphingolipid metabolism, catalyzes the hydrolysis of sphingomyelin into ceramide, which regulates various cellular processes as a secondary mediator. Previous studies on the role of ASM in T-lymphocytes show that ASM is considered to play a central role in the adaptive T-cell immune response and represents a potential, new therapeutic target for autoimmune and chronic inflammatory diseases such as bronchial asthma. The aim of this study was to investigate the immunological effects of Asm in allergic TH2-directed bronchial asthma. Therefore, the role of Asm-deficiency and Asm-inhibition via amitriptyline were characterized in vivo in the murine model of ovalbumin-induced bronchial asthma. Lung function analysis on the flexiVent-system showed that Asm-deficiency/inhibition led to an improved lung function due to reduced bronchial hyperreactivity. Using flow cytometry and immunoassays to detect the immune cell influx and T-cell immune response in BALF, we found a protective effect of an Asm-deficiency/inhibition in ovalbumin-induced bronchial asthma, caused by a decreased influx of immune cells, especially eosinophilic granulocytes. This resulted in a reduced secretion of the TH2-cytokines IL-4 and IL-5 into BALF. First results on molecular mechanisms of action of Asm-deficiency or Asm-inhibition via amitriptyline could be obtained in vitro after T-cell stimulation and TH2-differentiation. For a more detailed examination of TH2-signaling pathways, analyses of apoptosis/necrosis, cell viability, respiratory chain inhibition, cell proliferation and calcium influx were performed. In addition, TH2-typical cell surface proteins, transcription factors and cytokines were investigated on protein and gene levels by ELISA, flow cytometry and qPCR. We observed that Asm-deficiency downregulated important regulators of the IL-4-STAT6-signaling pathway such as IL-4R/CD124 and GATA3. This caused a decreased IL-4 production and therefore a deceased IL-4-secretion. Asm-inhibition via amitriptyline also influenced the IL-4-STAT6-signaling pathway and additionally the NFAT2- and IL-2-STAT5-signaling pathway. While IL-4R, GATA3 and NFAT2 were downregulated, amitriptyline increased IL-4- and IL-2-gene expression. Despite reduced calcium influx, this led to normal T-cell proliferation, but inhibited TH2-differentiation. Thus, it could be confirmed that Asm is an important modulator of the adaptive immune system. TH2-cells could be identified as an important immunological cell type affected by Asm. Therefore, Asm-deficiency or Asm-inhibition via amitriptyline represent a new, promising, cost-effective therapy option in allergic TH2-mediated bronchial asthma.