Ventilation‐induced leukocyte adhesion is P‐selectin and L‐type calcium channel‐dependent in murine tracheal venules

Abstract

We have previously shown that excessive distention of the tracheal airways results in enhanced leukocyte recruitment to the microvasculature. The objective of this study was to determine 1) whether leukocyte recruitment is dependent on products of Weibel Palade bodies (P-selectin, endothelin, vWF) and 2) whether this process is calcium channel-dependent. Positive-end expiratory pressure (PEEP) was applied 5 times, for a 1 min duration of 8cm H2O, at 10 min intervals, followed by a 60 min superfusion period with buffer. Intravital microscopy was used to quantify leukocyte adhesion in murine tracheal venules. PEEP induced a time-dependent increase in leukocyte adhesion to post-capillary venules, which was significant between 0–60min (P<0.05). PEEP-induced leukocyte adhesion at 60 min (80% increase) was ablated in P-selectin deficient mice. However, adhesion in vWF-deficient mice, and endothelin antagonist (BQ123 and BQ788)-treated mice was comparable to the PEEP counterparts. Whereas leukocyte adhesion was significantly attenuated in mibifredil-treated mice (1.0 ± 0.0 vs. 8.0 ± 1.0 leukocytes, P<0.05), adhesion in verapamil-treated mice was comparable to untreated PEEP mice. These findings indicate that P-selectin contributes to the pro-inflammatory phenotype exhibited by venules after PEEP administration, via a mechanism whereby distention may selectively activate Weibel Palade bodies through T, but not L-type calcium channels (Supported by HL10342).