Alzheimer′s disease (AD) is a growing global health concern with huge implications for individuals and society. In this review, current understanding of the pathogenesis of complement system in Alzheimer′s disease is outlined and current clinical laboratory diagnostic methods are discussed. Some theoretical basis and new ideas for seeking the biomarkers of AD and its treatment are also provided.

Objective:To screen the potential biomarkers for the diagnosis and differential diagnosis of immune-mediated demyelinating diseases by tandem mass tags (TMT) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) technology.Methods:Twenty patients with demyelinating diseases (demyelinating group) and 10 patients with noninflammatory neurological diseases (NND group) from Beijing Tiantan Hospital affiliated to Capital Medical University from January 2020 to January 2021 were enrolled in this study. The demyelinating group included 10 patients with Guillain-Barre syndrome (GBS subgroup) and 10 patients with multiple sclerosis (MS subgroup). TMT proteomics was used to screen out the different protein expression patterns between the demyelinating group and the NND group and between the GBS subgroup and the MS subgroup (difference>2 or<0.5 and with statistical significance), and String database was used to perform gene ontology (GO) analysis and Kyoto encyclopedia of gene and genomes (KEGG) analysis on the pathways involved in the differently expressed proteins between the groups. In addition, 80 demyelinating patients (demyelinating diseases validation group) and 40 healthy subjects (healthy control group) were selected for retrospective analysis of general lipid indexes. The demyelinating diseases validation group included 40 GBS patients (GBS validation group) and 40 MS patients (MS validation group). Receiver operating characteristic (ROC) curve was obtained to evaluate the value of general lipid indexes for the diagnosis of demyelinating diseases and the differential diagnosis between GBS and MS groups.Results:A total of 362 proteins were detected by TMT proteomics. There were 101 differentially expressed proteins between the demyelinating group and the NND group, and 45 differentially expressed proteins between the GBS group and the MS group. Compared with the NND group, GO enrichment analysis showed that the top five enrichment pathways in the demyelinating group were macrophage colony stimulating factor and receptor complex, negative regulation of cholesterol input, negative regulation of very low density lipoprotein particle clearance, triglyceride-rich lipoprotein particle remodeling, and cholesterol reverse transport. Compared with MS group, the top five enriched pathways in GBS group were high-density lipoprotein particle receptor binding, negative regulation of very low density lipoprotein particle remodeling, negative regulation of cholesterol input, negative regulation of very low density lipoprotein particle clearance, and medium density lipoprotein particle. KEGG enrichment analysis results showed that differentially expressed proteins in the demyelinating group and the NND group were enriched in 8 pathways, including phosphatidylinositide 3-kinases-protein kinase B signaling pathway, complement and coagulation cascade reaction, extracellular matrix and its receptor interaction, Staphylococcus aureus infection, cholesterol metabolism, RAS signaling pathway, phagosome, and mitogen-activated protein kinase signaling pathway. Differentially expressed proteins in GBS group and MS group were enriched in 9 pathways: cholesterol metabolism, complement and coagulation cascade, platelet activation, peroxisome proliferators-activated receptors signaling pathway, vitamin digestion and absorption, novel coronavirus infection, fat digestion and absorption, axon guidance, and neutrophil extracellular trap formation pathway. The levels of triglyceride (TG), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C) and apolipoprotein B (apoB) were significantly higher, while high density lipoprotein cholesterol (HDL-C) and apolipoprotein A1 (apoA1) levels were significantly lower in the demyelinating disease validation group than in the healthy control group (all P<0.05 or 0.01). Area under the curve (AUC) of TG, TC, HDL-C, LDL-C, apoA1 and apoB alone or in combination for the diagnosis of immune-mediated demyelinating diseases was 0.746, 0.643, 0.798, 0.703, 0.806, 0.708 and 0.868, respectively. The AUC of HDL-C, apoA1, LDL-C and apoB for differential diagnosis between GBS and MS was 0.692, 0.653, 0.632, 0.695 and 0.718, respectively. Conclusions:There are differences in cerebrospinal fluid proteomics between patients with immune-mediated demyelinating disease and patients with NND, GBS and MS, and the differentially expressed protein patterns mainly exist in the pathways related to lipid metabolism. Lipid related indicators may be used as biomarkers for the diagnosis and differential diagnosis of immune-mediated demyelinating disease.

OBJECTIVE: To investigate the effect of circulating exosomes (EXO) on T cell function in patients with sepsis. METHODS: Plasma EXO were obtained by ultracentrifugation from 10 patients with sepsis admitted to the emergency intensive care unit of Guangdong Provincial People's Hospital Affiliated to Southern Medical University. Transmission electron microscopy observation, nanoparticle tracking analysis (NTA), and Western blotting were used to detect EXO markers to identify their characteristics. Furthermore, peripheral blood mononuclear cells (PBMC) were isolated from the peripheral blood of 5 healthy volunteers, primary T cells were sorted by magnetic beads and expanded in vitro. After 24 hours of intervention with different doses (0, 1, 2.5, 5, 10 mg/L) of circulating EXO in patients with sepsis, T-cell activity was assessed using a cell counting kit-8 (CCK-8). The expression of T cell activation indicators CD69 and CD25 were observed using flow cytometry. Additional evaluations were performed on immunosuppressive indicators including the expression of programmed cell death 1 (PD-1) in CD4⁺ T cells and the proportion of regulatory T cell (Treg). RESULTS: The identification results confirmed that the successful isolation of EXO from the plasma of sepsis patients. The expression level of circulating EXO in sepsis patients was higher than that in healthy control group (mg/L: 48.78±5.14 vs. 22.18±2.25, P < 0.01). After 24 hours of intervention with 5 mg/L of plasma EXO from sepsis patients, T cells activity began to show suppression [(85.84±0.56)% vs. (100.00±0.00)%, P < 0.05]. As the dosage increased, after 24 hours of intervention with 10 mg/L of EXO, T cells activity was significantly suppressed [(72.44±2.36)% vs. (100.00±0.00)%, P < 0.01]. Compared with the healthy control group, after T cells intervention with plasma EXO from sepsis patients, the expression of early activation marker CD69 was significantly reduced [(52.87±1.29)% vs. (67.13±3.56)%, P < 0.05]. Meanwhile, there was an upregulation of PD-1 expression in T cells [(57.73±3.06)% vs. (32.07±0.22)%, P < 0.01] and an increase in the proportion of Treg [(54.67±1.19)% vs. (24.60±3.51)%, P < 0.01]. However, the expression of the late activation marker CD25 remained stable [(84.77±3.44)% vs. (85.93±2.32)%, P > 0.05]. CONCLUSIONS Circulating EXO in sepsis patients induce T cell dysfunction, which may be a novel mechanism lead to immunosuppression in sepsis.
Humans ; Leukocytes, Mononuclear ; Exosomes/metabolism* ; Programmed Cell Death 1 Receptor/metabolism* ; T-Lymphocytes, Regulatory/metabolism* ; Sepsis/metabolism*