SOLUBLE ICAM-1 (SICAM-1) PROVOKES PMN ELASTASE RELEASE

Elevated levels of soluble intercellular adhesion molecule-1 have been shown predictive of post-injury multiple organ failure, We hypothesiz ed that sICAM-1 augments distant organ injury via its affect on the PM N and; thus, have examined neutrophil elastase and superoxide producti on in response to sICAM-1. To obtain soluble ICAM-1, Chinese Hamster O varian (CHO) cells were transfected with human ICAM-1 (cDNA vector CD1 .8), lysed and centrifuged at 150,000g for 1 hr; supernatant was passe d over an ICAM-1 affinity gradient, eluted with 0.1 mM glycine . HCl, and concentrated using an Amicon Spin-X filter, PMNs were incubated fo r I hr with sICAM-1 at 37 degrees C. Quiescent and PMA-activated PMNs served as negative and positive controls respectively, Elastase activi ty was measured by the cleavage of succinyl-alalyl-alalyl-prolylvalyl- p-nitroanilide. Superoxide production was determined by superoxide dis mutase inhibitive ferricytochrome C reduction over a 5-60 min incubati on, PMN incubation with sICAM-1 provoked marked increase in elastase r elease 10.43 +/- 2.90 (10(-6) U/hr) compared to control 1.64 +/- 0.57, and was equivalent to PMA-activated PMN elastase release 11.60 +/- 1. 50 (10(-6) U/hr), In contrast, sICAM-1 alone did not promote spontaneo us PMN superoxide production beyond buffer treated PMNs (0.25 +/- 0.09 nmole/2.5 x 10(5) PMN/min). In sum, sICAM-1 stimulates PMN elastase r elease in vitro, Clinically, this may represent a mechanism by which s ICAM-1 participates in the genesis of postinjury multiple organ failur e. (C) 1996 Academic Press, Inc.