Fig. 3. Histone-mediated cytotoxicity for cells does not require cell surface heparan sulfate, histones directly disrupting lipid bilayers and inducing a cellular Ca²⁺ flux that can be blocked by SPAs.

a Effect of removal of cell surface heparan sulfate by bacterial heparinases 1, 2, and 3 or human platelet heparanase on the sensitivity of HMEC-1 to histone cytotoxicity. b Sensitivity of wild-type CHO-K1 and GAG-deficient pgsA-745 CHO-K1 cells to histone cytotoxicity. Data are presented as mean ± s.e.m. (n = 3) and analyzed by two-way ANOVA with Sidak’s multiple comparisons test. c Lifetime of artificial lipid bilayers exposed to histones (HIS) (1 μΜ) alone (n = 47) or in the presence of the SPAs CBS (n = 52) or MTS (n = 40) (10 μM). Control bilayers (n = 125) contained the RγR1 ion channel protein. Data are presented as mean ± s.e.m. and analyzed by non-parametric Kruskal–Wallis test. d Upper panel: Representative flow cytometry plots, using Ca²⁺-sensitive dye Indo-1, showing Ca²⁺ fluxing HMEC-1 1 min following histone addition (100 μg ml⁻¹). Lower panel: Time course of effect of CBS and MTS (100 μg ml⁻¹) on histone-induced Ca²⁺ flux by HMEC-1. Data are presented as mean ± s.e.m. (n = 2) from one of two experiments. Source data are provided as a Source Data File.