Figure 2

Pathogen recognition receptor expression in cells submitted to cyclic stretch or kept in static condition. (a) mRNA fold induction in A549 cells stretched for 8 hours or kept in static condition. All values are shown as the fold increase compared with control static cells normalized to 1. IL-8 mRNA levels induced by stretch served as a positive control. Both toll-like receptor (TLR)2 and TLR4 mRNA levels were markedly increased by cyclic stretch. MD-2 and CD14 mRNA levels were not significantly modified by stretch. Results are expressed as mean ± standard deviation of three distinct experiments. (b) Surface expression of TLR2, TLR4, MD-2 and CD14 by fluorescence-activated cell sorting (FACS) in A549 cells submitted to a 24-hour cyclic stretch or in cells kept in static condition. Except for CD14, none of these receptors showed significant surface expression. (c) Intracellular expression of TLR2, TLR4, MD-2 and CD14 by FACS in permeabilized A549 cells submitted to a 24-hour cyclic stretch or in cells kept in static condition. TLR2 was detected in permeabilized A549 cells after 24 hours of cyclic stretch. CD14 was detected, but not increased, by cyclic stretch. Neither TLR4 nor MD-2 proteins were detected by FACS in permeabilized cells, regardless of the experimental condition. Results are expressed as the mean fluorescence index (MFI) ± standard deviation of three distinct experiments. *P < 0.05 between static and stretched cells.