Figure 2.

Triggering receptor expressed on myeloid cells 2 (TREM2) upregulation in microglia is a direct response to the increase of amyloid-β (Aβ)_1–42 levels. The levels of soluble and insoluble forms of Aβ_1–42 and Aβ_1–40 were detected by enzyme-linked immunoassay (ELISA), and Pearson's correlation analysis showed that TREM2 expression is positively correlated with soluble and insoluble forms of Aβ_1–42 (a and b) rather than soluble and insoluble forms of Aβ_1–40 (c and d). (e–g) Cultured primary microglia was incubated with vehicle, Aβ_42-1, or different doses of Aβ_1–42 for 24 h. Later, the TREM2 and DAP12 mRNA levels and the protein levels of TREM2 within cells were measured by quantitative reverse transcription-PCR (qRT-PCR) and western blot, respectively. (h–j) Vehicle, Aβ_42-1, or different doses of Aβ_1–42 was injected into the cerebral cortex of the right hemisphere of 7-month-old WT mice. At 24 h after injection, the TREM2 and DAP12 mRNA levels and the protein levels of TREM2 in the cerebral cortex of the right hemisphere were measured by qRT-PCR and western blot analysis, respectively (n=8 per group). (k–m) Vehicle, Aβ_42-1, or different doses of Aβ_1–42 was injected into the hippocampus of the right hemisphere of 7-month-old WT mice. Twenty-four hours later, the TREM2 and DAP12 mRNA levels and the protein levels of TREM2 in the hippocampus of the right hemisphere were measured by qRT-PCR and western blot analysis, respectively (n=8 per group). The data of qRT-PCR were normalized to the levels of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNA, and the data of western blot analysis were normalized to β-actin. Data were analyzed by Pearson's correlation analysis (a–d) or one-way analysis of variance (ANOVA) followed by Tukey's post hoc test (e–m). Columns represent mean±SEM. *P<0.05 vs vehicle-treated cells or animals. It should be noted that cropped gels are used in this figure, and the full-length gels are shown in Supplementary Figure S6.