Figure 6.

TLR4 interaction with Hsp70 promotes efferocytosis by macrophages. A: changes of heat shock protein 70 (Hsp70) in the lung during ventilator-induced lung injury. Mice were mechanically ventilated with a high tidal volume (20 mL/kg) (MV) for the indicated time. The concentration of Hsp70 in the bronchoalveolar lavage (BAL) fluid was measured on days 1, 2, 4, and 7 after ventilation. n = 6 lungs (from 3 male and 3 female mice) each time point. *P < 0.05 and **P < 0.01 vs. control unventilated group (0 h), one-way ANOVA with Bonferroni post hoc test. Data represent means ± SD. B: TLR4 is required for Hsp70-mediated efferocytosis by bone marrow-derived macrophages (BMDMs). BMDMs were treated with Hsp70 (40 μg/mL) or vehicle. Macrophages were labeled with CellTracker Green and incubated with CellTracker Red-labeled apoptotic polymorphonuclear neutrophils (PMN) at a 1:10 ratio for 2 h. The cells were then mounted on a slide and analyzed by fluorescence microscopy. Top: representative fluorescent images showing macrophages engulfing apoptotic PMNs. Scale bars, 10 μm. Bottom: phagocytic index based on the fluorescent images. n = 6 mice (from 3 male and 3 female mice). **P < 0.01, one-way ANOVA with Bonferroni post hoc test. Data represent means ± SD. All images for control and treatment groups were collected at the same time under the same conditions. TLR4, Toll-like receptor 4.