Figure 2.

LPS stimulates calpain activity, and calpain inhibition attenuates pulmonary EC barrier disruption in vitro. Human lung microvascular ECs (HLMVECs) were incubated with LPS (0.1–0.5 μg/ml) for 4–24 hours, and then calpain activities were measured by detecting the calpain-mediated cleavage of the fluorogenic peptide Suc-Leu-Leu-Val-Tyr-AMC. (A) LPS treatment for 24 hours. (B) LPS 0.2 μg/ml treatment for 4–24 hours. (C–E) HLMVEC monolayers were incubated with MDL28170 (20 μM) for 30 minutes before LPS (0.2 μg/ml) was added, and then the transendothelial electrical resistance (TER) value was monitored in real time as a measurement of barrier integrity of the HLMVEC monolayer (C and D). The HLMVEC monolayer permeability to FITC-dextran 70 was measured by using a Transwell system (E). Results are expressed as mean ± SE (n = 4); *P < 0.05 versus control; ^#P < 0.05 versus LPS.