Ryanodine receptors in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis

by Manuel von Osten
Doctoral thesis
Date of Examination:2015-06-26
Date of issue:2015-10-19
Advisor:Prof. Dr. Alexander Flügel
Referee:Prof. Dr. Dr. Hannelore Ehrenreich
Referee:Prof. Dr. Wolfgang Brück
Persistent Address: http://dx.doi.org/10.53846/goediss-5314

 

 

Files in this item

Name:Dissertation MvO 2015.pdf
Size:21.2Mb
Format:PDF

The following license files are associated with this item:

Abstract

English

The activation of auto-aggressive T cells is crucial for the development of autoimmune diseases, such as multiple sclerosis (MS) or its animal model experimental autoimmune encephalomyelitis (EAE). T cell activation relies on stimulation of the T cell receptor by antigen and results in rapid release of calcium (Ca2+) from the endoplasmic reticulum (ER) into the cytosol. This process is mediated by IP3 receptors and, possibly by ryanodine receptors (RyRs). The release of Ca2+ from the ER into the cytosol follows a second influx of Ca2+ across the plasma membrane through Ca2+ release activated Ca2+ channels (CRAC). This store-operated calcium entry (SOCE) mediates further signal transduction by the activation of Ca2+ sensitive enzymes, such as calcineurin, which then leads to transcription and production of T cell characteristic cytokines. Even though EAE in mice is in many aspects a well studied model, the role of RyRs has not yet been addressed in context of the disease. Previous studies using loss-of-function techniques unveiled the importance of RyR1 and RyR3 for NAADP mediated Ca2+ signaling in Jurkat cells, and in rat adoptive transfer EAE by pharmacological antagonism of NAADP, a putative ligand for RyR1. In the present study we found that the gene encoding for the RyR1 isoform is expressed in antigen-experienced effector, but not in naïve mouse T cells. Genetic deletion of Ryr1 studied in fetal liver chimeric mice did not result in overt immune phenotype, however Ryr1 deficient T lymphocytes show diminished Ca2+ signaling and reduced proliferation in response to TCR stimulation. This supported the observation that these animals developed less severe active EAE than control mice. Although our data indicate that Ryr3 does not play a major role in T cells, yet we observed attenuated clinical EAE and CNS histopathology in mice with a whole-body knockout for the Ryr3 gene. There however, we have excluded that Ryr3 deficiency in T cells is responsible for mitigated neuroinflammation using chimeric mice and T cell transfer experiments. Instead we observed that Ryr3 deficient astrocytes display alteration in stimulated Ca2+ signaling in vitro, produce less chemokines in response to inflammatory stimuli in vitro but also in the inflamed CNS tissue, that limits infiltration of immune cells and associated tissue damage. We also demonstrate that pharmacological inhibition of RyR function has beneficial effects on the EAE disease. Thus, ryanodine receptors seem to play critical roles during autoimmune disease of the CNS (RyR1 in T cells whereas RyR3 in astrocytes) and can be considered as therapeutic targets.
Keywords: Multiple Sclerosis
 
Statistik