36,37. MS also showed considerable downregulation of Computer (phosphocholine and N-nervonoyl-derythro-sphingosylphosphorylcholine) in

36,37. MS also showed considerable downregulation of Pc (phosphocholine and N-nervonoyl-derythro-sphingosylphosphorylcholine) in ApoE4 mouse brains (Fig. 1f). Varma et al. demonstrated that AD individuals showed lower levels of Pc in both plasma and brain samples than regular individuals38. Downregulation of Pc in ApoE4 mouse brains suggested disruption of intracellular lipid homeostasis39. Unsupervised cluster analysis segregated ApoE3 from ApoE4 mice and revealed prominent differences among their transcriptomes; 76 significantly differentially expressed genes had been detected (Fig. 1g, h). Enrichment evaluation showed pathways involved in the inflammatory response (CXCL1, GBX2, HSPB1, LBP, NFKBIA, and A2M). Moreover, various energy metabolic processes, such as the PI3K-Akt pathway (EPHA2, FLT4, ITGA5, and LPAR6), cholesterol metabolism (APOE and CD36), and insulin resistance (FOLR1, CALM14, and PPP1R3A), have been enriched in ApoE4 mice (Fig. 1i). These enriched pathways indicated dysregulated energetic metabolism in ApoE4 mouse brains. Previous studies showed that fatty acid translocase (CD36), a crucial FA transport protein, was upregulated in ApoE4 mouse brains compared with ApoE3 mice, indicating that upregulation of FA transport most likely explained the larger FA levels in ApoE4 mouse brains39. Additionally, MS final results indicated considerable upregulation of arginine expression in ApoE4 mouse brains compared with ApoE3 mouse brains (Fig. 1j). Enhanced arginine levels indicate much more nitric oxide production, constant with “nitric oxide-mediated signal transduction” pathway enrichment within the ApoE4 mouse brain (Fig. 1i). Immunoblotting showed reduce protein levels of Akt/mTOR and phosphorylated insulin receptor substrate 1 (p-IRS1) in ApoE4 mice than in ApoE3 mice (Fig. 1k, l), suggesting that ApoE4 led to power metabolism dysfunction and insulin resistance. To investigate the effect in the ApoE4 allele on the lipid metabolism on the mouse brain, 3-month-old humanized ApoE3or ApoE4-knockin mice have been subjected to a common diet regime or HFD for three months. Immunofluorescence costaining of NeuN+ neurons, Iba-1+ microglia, or GFAP+ astrocytes with BODIPY was applied to figure out the localization of lipid droplets. Micrographs and three-dimensional (3D) reconstruction pictures revealed that lipid droplets significantly accumulated in each neurons and microglia in ApoE4 HFD mice compared with ApoE3 HFD mice (Fig. 1m, n). TRPV1 activation reversed ApoE4-induced microglial lipid droplet accumulation and immune dysfunction To investigate the effects of ApoE4 on immune cells within the mouse brain, flow cytometry was utilised to quantify immune cells in ApoE3 and ApoE4 mouse brains (Fig.Fmoc-OSu MedChemExpress 2a , Supplementary Fig.Palmitic acid custom synthesis 1).PMID:24059181 Flow cytometry showed that CD45lowCD11b+ microglia were considerably enhanced in ApoE4 mouse brains in comparison to those in ApoE3 mouse brains (Fig. 2a). MHC-IIhighCD45lowCD11b+ microglia had been drastically increased in ApoE4 mouse brains in comparison with these in ApoE3 mouse brains (Fig. 2c). Peripheral immune cells, CD45highCD11b+ monocytes, CD4+ T cells, and CD8+ T cells had been upregulated in ApoE4 mice compared to these in ApoE3 mice (Fig. 2b, d, e). Upregulation of MHC-IIhigh microglia expression indicated neuroinflammation-induced peripheral adaptive immune cell infiltration into the brain40.Experimental Molecular Medicine (2023) 55:347 C. Wang et al.Fig. 1 APOE4 allele led to lipid metabolism dysfunction in neurons and microglia. a Representative immunofluorescent imag.