Astrocyte-derived complement C3 is activated in patients with tuberous sclerosis complex and mediates immune injury: an integrated bioinformatics analysis

BACKGROUND: Tuberous sclerosis complex (TSC) is a genetic disorder associated with multiple neurological manifestations. Cortical tubers (CT) are recognized as the hallmark brain lesions of TSC and contribute to neurological and psychiatric symptoms. To understand the molecular mechanism of neuropsychiatric features of TSC, the differentially expressed genes (DEGs) in CT from patients with TSC and those in normal cortex (NC) from participants acting as healthy controls were investigated. METHODS: The dataset of GSE16969, which had already been published and described (https://onlinelibrary.wiley.com/doi/10.1111/j.1750-3639.2009.00341.x), was downloaded from the Gene Expression Omnibus (GEO), including samples of 4 CT and 4 NC. The R package “limma” was used to screen DEGs in CT and NC. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways enrichment analyses of the DEGs were conducted using the R package “clusterProfiler”. The online software Ingenuity Pathway Analysis (IPA) was used to explore activation/inaction of canonical pathways. The hub gene was selected based on the protein-protein interaction (PPI) network constructed using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database and Cytoscape software. Subsequently, the hub genes at messenger (mRNA) and transcriptional levels were tested. We also explored immune cell-type enrichment using the online database xCell, and assessed the correlation between cell types and C3 expression. Then, we verified the source of C3 by constructing TSC2 knockout cells in the U87 astrocyte cell line. The human neuronal cell line SH-SY5Y was used to examine the effects of excessive complement C3 levels. RESULTS: A total of 455 DEGs were identified. A large number of pathways were involved in the immune response process based on the results of GO, KEGG, and IPA. C3 was identified as a hub gene. Complement C3 was also upregulated in the human CT and peripheral blood. Furthermore, based on the enrichment of functions and signaling pathways, complement C3 played a critical role in immune injury in CT of TSC. In the in vitro experiments, we found that excessive complement C3 was derived from TSC2 knockout U87 cells, and there was an increased intracellular reactive oxygen species (ROS) level in SH-SY5Y cells. CONCLUSIONS: Complement C3 is activated in patients with TSC and can mediate immune injury.