Heparin can inhibit histone-mediated cell death in vitro. (A) PI staining of cell death via flow cytometry indicated that preincubation of exogenous histones or histone H4 with antihistone antibody or heparin could significantly decrease cell death in vitro. (B) Administration of histone mixture or recombinant histone H4 increased the levels of TNF-α, IL-1β, IL-6, and IL-10 in the supernatant of culture medium, whereas antihistone antibody or heparin preincubation remarkably decreased these cytokines (^*P < 0.01). IL-1β = interleukin-1β; IL-6 = interleukin-6; IL-10 = interleukin-10; PI = propidium iodide; TNF-α = tumor necrosis factor-α.