Soluble ICAM-1 (sICAM-1) Provokes PMN Elastase Release

Abstract

Elevated levels of soluble intercellular adhesion molecule-1 have been shown predictive of post-injury multiple organ failure. We hypothesized that sICAM-1 augments distant organ injury via its affect on the PMN and; thus, have examined neutrophil elastase and superoxide production in response to sICAM-1. To obtain soluble ICAM-1, Chinese Hamster Ovarian (CHO) cells were transfected with human ICAM-1 (cDNA vectorCD1.8), lysed and centrifuged at 150,000gfor 1 hr; supernatant was passed over an ICAM-1 affinity gradient, eluted with 0.1 mMglycine·HCl, and concentrated using an Amicon Spin-X filter. PMNs were incubated for 1 hr with sICAM-1 at 37°C. Quiescent and PMA-activated PMNs served as negative and positive controls respectively. Elastase activity was measured by the cleavage of methoxy-succinyl-alalyl-alalyl-prolyl-valyl-p-nitroanilide. Superoxide production was determined by superoxide dismutase inhibitive ferricytochrome C reduction over a 5–60 min incubation. PMN incubation with sICAM-1 provoked marked increase in elastase release 10.43 ± 2.90 (10−6U/hr) compared to control 1.64 ± 0.57, and was equivalent to PMA-activated PMN elastase release 11.60 ± 1.50 (10−6U/hr). In contrast, sICAM-1 alone did not promote spontaneous PMN superoxide production beyond buffer treated PMNs (0.25 ± 0.09 nmole/2.5 × 105PMN/min). In sum, sICAM-1 stimulates PMN elastase releasein vitro.Clinically, this may represent a mechanism by which sICAM-1 participates in the genesis of post-injury multiple organ failure.