Impact of the sphingosine-1-phosphate receptor modulator siponimod on functional phenotypes of microglia
by Marlene Carmen Julie Steinleitner
Date of Examination:2024-12-19
Date of issue:2024-11-26
Advisor:Prof. Dr. Martin Weber
Referee:Prof. Dr. Martin Weber
Referee:Prof. Dr. Dr. Hannelore Ehrenreich
Persistent Address:
http://dx.doi.org/10.53846/goediss-10841
Files in this item
Name:Dissertation Marlene Steinleitner_final ohne...pdf
Size:5.16Mb
Format:PDF
This file will be freely accessible after 2025-01-16.
Abstract
English
Over the last decades the number of drugs for the therapy of relapsing remitting multiple sclerosis (RRMS) increased significantly, whereas various approaches to develop an efficient therapy for secondary progressive multiple sclerosis (SPMS) remained disappointing. Moreover, the exact pathomechanisms of progressive multiple sclerosis (MS) forms are still poorly understood. In 2020, a new sphingosine-1-phosphate receptor (S1PR) modulator, siponimod, was approved for therapy of SPMS. In clinical studies, therapy with siponimod revealed a reduction in relapse rate and a slowdown of disability progression in patients with active SPMS, but it remains unclear whether siponimod has an effect within the central nervous system (CNS) in the absence of MS activity. In particular, microglia were assumed to play an important role on driving MS progression, based on their ability to differentiate into different phenotypes, including a proinflammatory M1 and an antiinflammatory M2 phenotype. That is why, in this study the impact of siponimod on functional phenotypes of primary microglia was investigated. Therefore, primary microglia were treated with siponimod followed by activation with different pro- or antiinflammtory agents and analysed by fluorescence-activated cell sorting (FACS) analysis. In addition, the production of proinflammatory cytokines was assessed via enzyme-linked immunosorbent assay (ELISA). Here, analysis of the expression of various cell surface markers involved in activation, antigen presentation, differentiation, and microglia-neuron-interactions, as well as intracellular enzymes involved in microglial differentiation, revealed no changes between siponimod-treated microglia compared to untreated cells, although microglia were demonstrated as adequately stimulated. Siponimod is a selective receptor modulator of the sphingosine-1-phosphate receptor subtype 1 (S1P1R) and the sphingosine-1-phosphate receptor subtype 5 (S1P5R). To investigate whether different stimuli may influence the S1P1R expression on a transcriptional level, diversely stimulated microglia were analysed using quantitative real-time polymerase chain reaction (qPCR) analysis. Thereby, S1P1R gene expression was downregulated, both with pro- and antiinflammatory stimulation, compared to unstimulated microglia. These results suggest that it might be more difficult for siponimod to interact with activated microglia since the S1P1R is less expressed on their cell surface. Although in this study siponimod treatment revealed no impact on microglia directly, it remains unclear if siponimod may exert an effect on microglia indirectly via infiltrating immune cells or via other CNS resident cells such as astrocytes or oligodendrocytes.
Keywords: Secondary progressive Multiple Sclerosis; Sphingosine-1-phosphate receptor; siponimod; microglia
