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reported to cause hypomyelination 21, 22, which matches the pathogenic changes that are seen in TSC tubers. This can be explained by, for example, the inhibitory effects of high mTORC1 activity on differentiation of myelinating cells even before myelination onset in these cells 19, and by the toxic effects that accompanies mTOR overactivation in oli- godendrocytes 23. Overall, comparison between the GM and WM in TSC tubers shows a trend where the GM seems more affected compared to the WM, which probably under- lies pathological changes like hypomyelination that are observed in cortical tubers.
Restoring altered gene expression in TSC
To further analyze the TSC tuber transcriptomics data from Chapter 3, and hereby potentially increase the therapeutic and clinical value, we used Library of Integrated Network-Based Cellular Signatures analysis (LINCS analysis, NIH-LINCS Program), a tool that integrates transcriptomics data for detailed information about cell signaling path- ways in order to develop therapies that might restore disturbed networks into normal state. This revealed that the IκB kinase-2 (IKK-2) inhibitor TPCA-1 would be a promis- ing candidate to reverse the changes that are found in cell signaling networks in TSC tubers. Therefore, we performed experiments in which primary astrocyte cultures were treated with different concentrations of TPCA-1 (for details about the cultures and treat- ment see Chapter 6). Indeed, TPCA-1 was able to strongly reduce IL-1β-induced upreg- ulation of several inflammatory components like the pro-inflammatory cytokine IL-6, COX-2, chemokines CCL2 and CCL3, and C3, a component of the complement system, which was highly upregulated in TSC tubers (see Chapter 3). Additionally, TPCA-1 could partly stabilize expression of C1qa, a polypeptide component of C1q, and C4b, which are important factors in the complement system and are believed to serve a protective role through their critical role in opsonization 24, 25. TPCA-1 was previously reported to inhibit both the NF-κB pathway via inhibition of the IκB kinase-2 (IKK-2), which plays a crucial role NF-κB-regulated production of pro-inflammatory molecules 26, and STAT3, which is also implicated in regulation of IL-6 and COX-2 production 27. Therefore, studying the therapeutic value of this compound in relation to brain inflammation and epilepsy in TSC may provide interesting insights. Using the data gathered in this multi-platform analysis of a large cohort of TSC tubers, we now indicated specific deregulated biological signal- ing pathways. With this, we identified novel candidates that are interesting for further research into their potential therapeutic value in treating drug-resistant epilepsy.
Targeting inflammation in epilepsy treatment
Accumulating evidence indicates that inflammation plays a major role in the pathogen- esis of epilepsy, and that targeting inflammatory pathways is beneficial in the treatment of epilepsy 28, 29. For example, inflammatory pathways that were found deregulated in resected brain tissue from patients with epilepsy, also seem to play a role in disease development in experimental models of epilepsy and pharmacological inhibition of these pathways (e.g. IL-1R1/TLR4 signaling, the mTOR pathway, the TGFβ signaling pathway) was shown to reduce epileptogenesis 28. However, the gap between target identification in proof-of-concept preclinical studies and clinical trials yet needs to be filled, and since a limited number of targets has been investigated, more targets need to be identified. One potential target is the (immuno)proteasome. This multicatalytic proteinase complex is