Alzheimer’s disease risk genes are differentially expressed upon Lipopolysaccharide stimulation in a myelogenic cell model

Abstract

AbstractBackgroundLipopolysaccharides (LPS) is a molecule present in the outer membrane of Gram‐negative bacteria. Previous studies have shown that LPS treatment can lead to upregulated pro‐inflammatory and chemotactic cytokines, or elevate the expression of anti‐inflammatory factors in mouse or cell models. Inflammation is seen around amyloid plaques and around small cerebral vessels with Ab1‐40 deposits in AD brains. Increased levels of LPS have been found in the hippocampus of patients with Alzheimer’s disease, compared to age‐matched controls. Other studies demonstrated that LPS is also present and associated with white matter injury in AD and aging brains. Continued inflammation activates microglia and macrophages, which are ialso localized in perivascular tissue. However, to what extent the increased inflammation influences the expression of AD risk genes in myelogenic cells is not well known. Here we utilized RNA sequencing on THP‐1 derived macrophages using Aβ and LPS as stressors to further elucidate this.MethodWe performed RNA sequencing on THP1‐derived macrophages, with or without Aβ and LPS stimulation. 50 known AD risk genes were cross‐checked against the differentially expressed genes discovered. Furthermore, KEGG pathway analysis was performed on the Aβ versus the LPS and Aβ group.ResultOut of 50 AD risk genes, we identified a total of 24 genes in the various comparison groups (Figure 1). 14 AD risk genes were discovered in all the groups: TREM2, LILRB2, BIN1, TNIP1, CD2AP, CD33, CASS4, MS4A4A, NCK2, ADAMTS1, SPI1, RIN3, ECHDC3, AGRN (Figure 1 and2). KEGG pathway analysis pointed out TNF signaling pathway, lysosome, endocytosis and ubiquitin mediated proteolysis as enriched for cells stimulated by LPS with Aβ present (Figure 3).ConclusionOur study demonstrates that LPS activates inflammatory responses in myelogenic cells that further affects AD risk gene expression. Enriched pathways not only relate to Aβ uptake and clearance, but also reflect AD pathology. LPS and/or LPS induced inflammation may be a significant initiator or progressive contributor to inflammatory degeneration in AD.