Abstract Details

Title Bruton’s Tyrosine Kinase (BTK) Inhibition Promotes Myelin Repair in Two Different Models of Demyelination

Topic Multiple Sclerosis

Presentation(s) S49 - Multiple Sclerosis: Basic Science (2:00 PM-2:12 PM)

Poster/Presentation
Number 006

Objective To investigate the effect of BTK inhibition on remyelination in ex vivo and in vivo experimental models of demyelination.

Background Microglia, the resident macrophages of the CNS, are the Janus of the innate immune response in multiple sclerosis, exerting either a pro-inflammatory or a pro-regenerative function. Inhibition of BTK, a member of the Tec kinase family, blocks B-cell activation via the B-cell receptor, myeloid activation via Fc receptors, and differentiation of pro-inflammatory macrophages in response to GM-CSF in vitro. However, the role of BTK in the CNS, especially CNS glia, is unknown.

Design/Methods

Expression of BTK and its activated form (BTK-phospho-Y223) was determined by immunohistochemistry in normal adult mouse brain tissue sections and organotypic cerebellar slice cultures before and after lysophosphatidylcholine (LPC)-induced demyelination. The effect of a BTK inhibitor (1µM, 3 days) on remyelination was then examined in LPC-induced demyelinated cerebellar organotypic slices and metronidazole-induced demyelinated Xenopus MBP-GFP-NTR transgenic tadpoles.

Results A low BTK signal under normal conditions in brain and cerebellar slices was in sharp contrast with an 8.5-fold increase in the number of BTK-positive cells observed in LPC demyelinated slice cultures. BTK-positive cells were observed largely in Iba1⁺microglia (73.1%) and in a small fraction of S100⁺ astrocytes (25.6%), with minimal labelling in CC1⁺ oligodendrocytes (<1%). BTK was not detected in NeuN⁺ neurons or in Olig2⁺/CC1^- oligodendrocyte precursor cells. Similarly, there was a substantial increase of BTK-phospho-Y223 after LPC-induced demyelination compared with control conditions in cerebellar organotypic slice cultures. BTK-phospho-Y223 was expressed in microglia (75.6%) and astrocytes (20.6%), but not in Olig2⁺, CC1⁺, or NeuN⁺ cells. Of note, 74.9% of BTK⁺ microglia were also BTK-phospho-Y223-positive. BTK inhibition in demyelinated slice cultures and tadpoles improved remyelination by 1.5-fold and 1.7-fold, respectively, compared with spontaneous recovery.

Conclusions Our data demonstrates that inhibition of BTK on microglia is a promising therapeutic target for myelin repair.

Authors/Disclosures
PRESENTER	No disclosure on file
	No disclosure on file
	No disclosure on file
Roland Grenningloh	Roland Grenningloh has received personal compensation for serving as an employee of EMD Serono.
Bruno Stankoff, MD, PhD (Hopital De La Pitie Salpetriere)	The institution of Bruno Stankoff, MD, PhD has received research support from Roche, Sanofi, Serono . The institution of Bruno Stankoff, MD, PhD has received research support from Novartis.
Catherine Lubetzki (Hopital De La Salpetriere)	Catherine Lubetzki has received personal compensation in the range of $500-$4,999 for serving as a Consultant for ROCHE. Catherine Lubetzki has received personal compensation in the range of $500-$4,999 for serving as a Consultant for MERCK SERONO. Catherine Lubetzki has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for REWIND.
	No disclosure on file

��ɫ��

��ɫ��