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

Abstract

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.

Institutions

• Department of Biology [160000]
• Department of Cellular and Applied Infection Biology [164020]