Apoptotic cells inhibit whereas necrotic cells activate p90Rsk, a downstream substrate of ERK1/2, in BM macrophages
Serum-starved BM macrophages were stimulated with increasing numbers of apoptotic cells, necrotic cells, or latex beads alone for 15 min (A) or stimulated with M-CSF for 15 min following a 30-min pre-exposure to apoptotic cells, necrotic cells, or latex beads (B). Apoptotic or necrotic BUMPT cells were added to macrophages at a cell to macrophage ratio ranging from 1:64 to 1:1 in 2-fold increments, as indicated by the schematic diagram of increasing cell ratio. Non-adherent cells were removed by rinsing, and macrophage lysates were probed with anti-active phospho-p90Rsk antibody. Equal loading was confirmed by Ponceau S staining of blotted proteins as well as probing for total p90Rsk (supplemental Fig. S2). Apo-ptotic and necrotic cells alone contributed no active p90Rsk in these experiments.