Die Untersuchung zellulärer inflammatorischer Prozesse bei Pseudoxanthoma elasticum

The autosomal-recessive disorder Pseudoxanthoma elasticum (PXE) is characterized by progressive calcification and fragmentation of elastic fibers. The cause of PXE are mutations in the gene ATP-binding cassette subfamily C member 6 (ABCC6), encoding ABCC6, an ATP-binding transport protein. Further studies indicate an association between PXE and accelerated aging. In vitro an enhanced activity of senescence-associated ß-galactosidase and the formation of a senescence-associated-secretory phenotype (SASP), was detected. The SASP is associated with high production of inflammatory factors, such as interleukin 6. The molecular mechanism leading to inflammatory processes in PXE are not fully understood. Thus, this study was designed to analyze different molecular aspects and inflammatory signaling pathways in ABCC6 deficient cells to uncover their role in PXE-pathogenesis. <br /><br /> In the first part of this study the complement system and inflammatory pathways were analyzed in human dermal fibroblasts from PXE-patients (PXEF). An upregulation of different complement factors was detected in the PXEF. Especially complement factors of the classical and alternative complement cascade were upregulated in PXEF. Further increased protein expression of the C3 and C3a were identified in the supernatants of PXEF indicating an increased activity of C3-convertase beside initiation of the complement system. Moreover, high activity of the JAK/STAT3 and the NF-κB signaling pathway was identified in PXEF. However, only the inhibition of the JAK/STAT3 pathway resulted in a moderate reduction of the expression of SASP factors and the complement system, while blocking NF-κB-signaling had no effect on inflammation in PXEF. Interestingly, prednisolone, an anti-inflammatory glucocorticoid reduced the inflammatory phenotype of PXEF and could be an interesting therapeutic option in dealing with the disorder.<br /><br /> In the second part of this study, the effect of a knockdown of ABCC6 using small interfering RNA on polarization of human macrophages was analyzed. The loss of ABCC6 expression resulted in upregulation of inflammatory M1-marker in macrophages of the M0- and M1- phenotype. Beside this, M2-markers of anti-inflammatory M2-macrophages were downregulated. This indicates a low-grade shift in the M1/M2 balance which could be involved in the extent of inflammatory processes in PXE-pathogenesis. A co-cultivation of human macrophages and PXEF enhanced gene and protein expression of M1-marker in macrophages. Also, co-cultivation with PXEF reduced expression of M2-markers. Thus, interaction between macrophages and dermal fibroblasts may modulate inflammatory processes in the pathobiochemistry of PXE. <br /><br /> In the last project of this study immune cells and their subpopulations were analyzed in the blood from PXE-patients. A downregulation of lymphocytes especially B-lymphocytes as well as an upregulation of natural killer cells was observed while the plasma concentration of immunoglobulins and C-reactive protein was not altered. This role of other immune cells beside macrophages in PXE pathogenesis should be analyzed in future studies.<br /><br /> In conclusion, the results of this study indicate that inflammatory processes in PXE-pathogenesis seemed to be diverse. Beside different signaling pathways, the communication between immune cells, fibroblasts and maybe also other cells might be involved in inflammatory processes in PXE and could be a target for future therapeutic options.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Universität Bielefeld

Year

2024

Author dc:creator

• Lindenkamp, Christopher

Repository record source_url

https://pub.uni-bielefeld.de/record/2990695

OAI identifier oai:identifier

oai:pub.uni-bielefeld.de:2990695