Fig. 6

Tau protein-induced formation of lipid droplets and changes in membrane fluidity. A BV2 mouse-derived microglia were treated with Tau (151–391/3R) protein (500 nM for 24 h). Representative images of DAPI (blue) and BODIPY+ (green) staining in BV2 cells. B Quantification of BODIPY⁺ relative fluorescence intensity (CN: 23.91 ± 5.62; Tau: 34.41 ± 8.60; p = 0.0013; n = 7; mean ± SD, student’s t-test with p-value). Scale bar 20 μm. C Representative flow cytometry histograms. D Quantification of BODIPY⁺ mean fluorescence intensity in BV2 cells (CN: 1707 ± 227; Tau: 2325 ± 409; p = 0.0234; n = 4; mean ± SD, student’s t-test with p-value). E Effect of Tau (151–391/3R) protein treatment on BV2 cells membrane fluidity. After incubation, BV2 cells were incubated with lipophilic pyrene probe PDA/Pluronic F127 solution (25 °C, 1 h) which undergoes dimerization after the interaction and exhibits changes in its fluorescent properties. Changes in cell membrane lipid order, between the monomer gel/liquid-ordered phase (fluorescent at 430 ∼ 470 nm) and the excimer liquid phase (fluorescent at 480 ∼ 550 nm) were measured by confocal microscopy. F Representative images of changed membrane fluidity. G Quantification of relative fluorescence intensity of monomer vs. excimer ratio (n = 4, mean ± SD; student’s t-test with p-value). H Representative images of DAPI (blue) and BODIPY+ (green), and MitoTracker (red) staining in BV2. Scale bar 20 μm. I ATP levels were decreased in LDs accumulating BV2 cells (CN: 60,346 ± 1310; Tau: 52,267 ± 1032; p = 0.0029, n = 5, mean ± SD; student’s t-test with p-value)