Fig. 7.

Pretreatment with conditioned medium from microglia cultured for 24 h with Aβ_25–35 (CM-Aβ) followed by hypoxia-reoxygenation causes dendritic beading and death of neurons in co-culture with astrocytes. Representative confocal micrographs of immunofluorescence of MAP-2 staining (green) and Etd⁺ uptake (red) by neurons (N) cultured without and with astrocytes (Ast). A – C. Neurons under control conditions or after 3 h hypoxia followed by 1 or 24 h reoxygenation. B. After 3 h hypoxia and 1 h reoxygenation neurons appear normal. C. After 24 h reoxygenation many neurons show beading of neurites, but there is no Etd⁺ uptake indicating that neuronal membranes are intact. D – F. Neurons incubated for 24 h with CM-Aβ prior to 3 h hypoxia and reoxygenation show beading comparable to that in control medium. G – I. Neuron-astrocyte cocultures show no beading or Etd⁺ uptake when subject to hypoxia-reoxygenation as in B – C; astrocytes are protective. J – L. After 24 h pretreatment with CM-Aβ followed by 3 h hypoxia, cocultures of astrocytes and neurons show marked Etd⁺ uptake by astrocytes and by dying neurons at 1 h and 24 h reoxygenation. M – O. Neuronal death and astrocyte Etd⁺ uptake in cocultures caused by CM-Aβ pretreatment and hypoxia/reoxygenation is prevented by the connexin hemichannel blocker, Gap26, applied during reoxygenation. From Orellana et al., 2011.