Browsing by Author "Li, Cenxiao"

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    Fenebrutinib, a Bruton’s tyrosine kinase inhibitor, blocks distinct human microglial signaling pathways
    (2024-10-27) Langlois, Julie; Lange, Simona; Ebeling, Martin; Macnair, Will; Schmucki, Roland; Li, Cenxiao; DeGeer, Jonathan; Sudharshan, Tania J. J.; Yong, V. W.; Shen, Yun-An; Harp, Christopher; Collin, Ludovic; Keaney, James
    Abstract Background Bruton’s tyrosine kinase (BTK) is an intracellular signaling enzyme that regulates B-lymphocyte and myeloid cell functions. Due to its involvement in both innate and adaptive immune compartments, BTK inhibitors have emerged as a therapeutic option in autoimmune disorders such as multiple sclerosis (MS). Brain-penetrant, small-molecule BTK inhibitors may also address compartmentalized neuroinflammation, which is proposed to underlie MS disease progression. BTK is expressed by microglia, which are the resident innate immune cells of the brain; however, the precise roles of microglial BTK and impact of BTK inhibitors on microglial functions are still being elucidated. Research on the effects of BTK inhibitors has been limited to rodent disease models. This is the first study reporting effects in human microglia. Methods Here we characterize the pharmacological and functional properties of fenebrutinib, a potent, highly selective, noncovalent, reversible, brain-penetrant BTK inhibitor, in human microglia and complex human brain cell systems, including brain organoids. Results We find that fenebrutinib blocks the deleterious effects of microglial Fc gamma receptor (FcγR) activation, including cytokine and chemokine release, microglial clustering and neurite damage in diverse human brain cell systems. Gene expression analyses identified pathways linked to inflammation, matrix metalloproteinase production and cholesterol metabolism that were modulated by fenebrutinib treatment. In contrast, fenebrutinib had no significant impact on human microglial pathways linked to Toll-like receptor 4 (TLR4) and NACHT, LRR and PYD domains-containing protein 3 (NLRP3) signaling or myelin phagocytosis. Conclusions Our study enhances the understanding of BTK functions in human microglial signaling that are relevant to MS pathogenesis and suggests that fenebrutinib could attenuate detrimental microglial activity associated with FcγR activation in people with MS.
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    Investigating the Role of BTK in Microglia in Multiple Sclerosis and its Animal Models
    (2023-09-07) Li, Cenxiao; Yong, Voon Wee; Ousman, Shalina; Lohman, Alex; Jirik, Frank
    Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) characterized by demyelination, immune cell infiltration and neurodegeneration. A class of drugs, Bruton’s tyrosine kinase (BTK) inhibitors are currently undergoing phase III clinical trials for the treatment of MS. BTK inhibitors primarily target the activity of B cells, but BTK activation is also downstream of pro-inflammatory signalling pathways in CNS myeloid cells, microglia, and macrophages. Existing research into the role of BTK signalling in microglia and macrophages is cursory, and the connection between BTK expression and pro-inflammatory activities remains to be elucidated. In this thesis, the expression of BTK was evaluated in the CNS tissue of MS and its rodent models, and the effect of BTK inhibition in the experimental autoimmune encephalomyelitis (EAE) model and on microglia in a co-culture system was investigated. In MS brain samples, we observed the expression of BTK and (the active form) pBTK in areas with a high immunoreactivity of Iba1+ microglia/macrophages. In three animal models of MS, BTK and pBTK were observed to be upregulated in the spinal cord lesions, but only pBTK expression was downregulated at later time points. Lineage tracing of CNS macrophages revealed that both microglia and macrophages express BTK and pBTK without a preference by either cell type. Treatment of MOG¬35-55 EAE mice with the BTK inhibitor GDC-0853 initiated from EAE induction day showed significant reduction in the clinical and histological pathologies. However, drug administration from clinical onset only showed marginal reductions in overall clinical signs, and immunofluorescent analyses of the spinal cord lesions did not show detectable differences in the expression of myeloid, myelin and axonal markers. In vitro, stimulation of neuron-microglia co-culture with IFN-γ and LPS resulted in robust neuronal death and elevated secretion of TNF-α, which were not attenuated with the addition of GDC-0853. Drug treatment of microglia activated with iLPS did not show reduced expression of pBTK. These results suggest that BTK inhibition may effectively reduce disease pathophysiology if treatment is initiated early, but its capacity to directly modulate microglial activities remains to be established.