For control purposes, cell swelling or cell shrinkage see more of untreated BMDCs (mean FSC 473.6 ± 18.4) was induced by addition of 20% aqua bidest (mean FSC 523.3 ± 12.9) and staurosporin (4 µM) (mean FSC 366.7 ± 13.2), respectively, for 30 min (data not shown). Results were depicted as differences of the means between LPS-treated and untreated cells. As shown in Figure 1a, addition of LPS caused a rapid increase in the cell size in WT DCs after 30 min. Thereafter, the cells size of WT DCs remained on a high level up to 240 min.

In contrast, volume changes in TLR4-deficient DCs were significantly abolished indicating that the increase in the cell volume upon LPS treatment was dependent on TLR4 signaling. Due to the rapid kinetics, these data suggest that cell swelling is an early step in LPS-induced DC migration. Accordingly, it has been reported that LPS induces the dissolution of podosomes, adhesion structures selleckchem of immature DCs, in a TLR4-dependent manner [6]. To analyze the role of LPS/TLR4 signaling in migration of DCs, transwell migration assays were performed. DCs were seeded in the upper wells of a transwell system and migration to the lower wells was analyzed after

4 hr by flow cytometry. To analyze the spontaneous migration rates, the bottom wells were filled with medium alone. By addition of CCL21 to the medium in the bottom wells, the CCL21-directed migration rates were determined. The activity of DCs to migrate towards a CCL21 Urease gradient was depicted as the migration rate to CCL21 divided by the migration rate to medium alone (chemotactic index). As shown in Figure 1b, neither DCs derived from WT nor TLR4−/− mice substantially migrated in a CCL21-directed manner to the bottom wells (chemotactic index: 1.0 and 1.1, respectively). However, stimulation of WT DC by addition of LPS to the upper wells caused an increase in CCL21-directed migration (chemotactic index: 1.9). This effect was nearly abolished in TLR4-deficient DC (chemotactic index: 1.2)

demonstrating that the directed movement of immature BMDC towards CCL21 is dependent on LPS/TLR4-signaling. It is widely accepted that KCa3.1 channels are required for migration of different cell types including cells of the immune system [11, 16-18]. In non-excitable migrating cells, these calcium-activated potassium channels are usually present at the rear end of the cell and are activated by increase in free cytosolic Ca2+ [19]. Activation of KCa3.1 channels may cause an efflux of intracellular K+ and subsequently an osmotic water efflux thereby promoting localized shrinkage and retraction of the rear cell pole which may facilitate migration [19]. In order to analyze the role of KCa3.1 channels in LPS-induced migration, DCs were generated from KCa3.1−/− and WT controls. To analyze LPS-dependent cell volume changes in KCa3.