Fig. 4: Hyperphosphorylated tau aggregates elicited calcium transient and stimulated ROS production in human macrophages in a TLR4-dependent manner.

a A pictorial representation of the macrophage assay workflow. The cytosolic calcium and ROS level were simultaneously monitored as different tau aggregates were applied. b Representative image of dual-labeled macrophage (i) and calcium and ROS traces (ii) after the treatment of s-tau aggregates. Scale bar: 25.0 μm. c, d Summary plots of calcium transients (c) and ROX production (d) induced by LPS (n = 123). When treating the cells with RsLA (n = 70, F_(1,4) = 40.78) or TAK-242 (n = 47, F_(1,4) = 84.62), the LPS-induced calcium transients and ROS level elevation were significantly moderated. e, f Summary plots of calcium transients (e) and ROX production (f) induced by different tau species and treatment conditions. Compared to WT tau aggregates (n = 63), s-tau aggregates induced strong calcium transients and ROS production (n = 83, F_(1,4) = 174.88). Since s-tau monomer control did not elicit significant response (n = 89, F_(1,4) = 110.14), ATP and LPS contamination were controlled. The involvement of TLR4 was tested: by pre-treating the cells with RsLA (n = 65, F_(1,4) = 184.60) or TAK-242 (n = 62, F_(1,4) = 170.11), s-tau can no longer elicit significant response. For c and e, data are presented as mean values ± s.d. of three independent experiments. The P-values are based on two-way mixed ANOVA: all p < 0.001 except the one between LPS and RsLA which is p < 0.01. For d and f, boxplots represent median value and interquartile range (25–75% percentiles) excluding outliers. The P-values are based on unpaired two-sided Student’s t-test: ***p < 0.001. Source data are provided as a Source Data file.