PolyP-70-mediated proinflammatory signaling by nuclear cytokines is mediated by a Ca²⁺signal through interaction with P2Y₁. (A) Cell permeability in response to HMGB1 (40 nM), H4 (1.78 μM), and polyP-70 (50 μM) was evaluated in the absence (gray bar) and presence of thapsigargin (black bar) as described in Materials and methods. (B) The same as (A), except that the cell permeability in response to HMGB1 (40 nM), H4 (3.5 μM), polyP-70 (50 μM), polyP-70 (2.5 μM) + HMGB1 (10 nM), and polyP-70 (2.5 μM) + H4 (0.44 μM) was evaluated in the absence (gray bar) and presence (black bar) of the P2Y₁ antagonist MRS-2279. (C) The same as (A), except that the competitive effect of sP2Y₁ (25-50 μM) on cell permeability in response to HMGB1 (40 nM) and polyP-70 (50 μM) was evaluated. (D) The same as (C), except that the competitive effect of sP2Y₁ (1.25-3 μM) on a low concentration of polyP-70 (2.5 μM)-mediated cell permeability by a low concentration of either HMGB1 (10 nM) or H4 (0.44 μM) was evaluated. (E) The same as (C), except that the competitive effect of sP2Y₁ on the expression of either VCAM-1 (gray bar) or E-selectin (black bar) in response to HMGB1 (40 nM) and polyP-70 (50 μM) was evaluated. (F) The same as (D), except that the competitive effect of sP2Y₁ (1.25-3 μM) on the polyP-70 (2.5 μM)-mediated expression of either VCAM-1 (gray bar) or E-selectin (black bar) by a low concentration of either HMGB1 (10 nM) or H4 (0.44 μM) was evaluated. All results are shown as mean ± standard deviation of 3 different experiments. *P < .05; **P < .01; ***P < .001.