Cell death in an ischemic infarct rim model

Using an in vitro model that simulates the microenvironment in the ischemic infarct rim, we have examined the temporal profile and possible mechanisms of cell death in the neuropil (an astrocyte-rich area or ARA) of organotypic hippocampal slice cultures. Two-photon confocal microscopy, propidium iodide, and GFAP-GFP transgenic mice were used to confirm cell death in astrocytes. An 'ischemic solution' (IS) induced major cell death throughout the hippocampus over 24 h, with the earliest injury starting in ARA. Our studies using IS or ion replacements in IS revealed that cell death in ARA was modest when K⁺ was increased or pH lowered. High K⁺ is most effective in reducing cell death when HCO₃⁻ is normal or high. When Cl⁻ or HCO₃⁻ was reduced, cell injury was worsened. 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) protected cells from IS-induced death in a dose-dependent manner (1–4000 μmol/L). We conclude that (i) various areas of the hippocampal formation respond differently to ionic replacements; (ii) K⁺ interacts with other ions to protect cells in ARA; and (iii) DIDS has a substantial protective effect in ARA by blocking DIDS-sensitive membrane exchangers or by interfering with intracellular signaling pathways.