Effects of heparin and related drugs on neutrophil function

We have previously demonstrated that heparin inhibits neutrophil activation, but the precise mechanism of action remains to be elucidated. The current aim was to further investigate the effects of heparin at inducing apoptosis of neutrophils and whether this was related to antagonism at IP(3) receptors. Furthermore, we investigated the ability of heparin and related molecules to inhibit acute neutrophil-induced injury to human bronchial epithelial cells (HBECs) in vitro. Neutrophils were isolated from human peripheral venous blood. Expression of annexin-V was determined in neutrophils following incubation with LMWH. The effects of LMWH and related molecules upon thapsigargin or m-3M3FBS (phospholipase C activator) induced neutrophil elastase (NE) release were also investigated. The cytotoxic effects of fMLP-activated neutrophils following co-incubation with HBECs were quantified through counting adherent cells before and after incubation. There was no detectable increase in annexin-V positive neutrophils following pre-incubation with LMWH at 30 min, 60 min or 16 h, but an increase was observed with Fas-activating antibody at 16 h. LMWH significantly inhibited NE release induced by either m-3M3FBS (73.4 ± 6.1%, 100 IU ml(-1), P < 0.01) or thapsigargin (62.4 ± 6.9%, 100 IU ml(-1), P < 0.01) in a sulphate-dependent manner. LMWH and related sulphated molecules all abrogated the cytotoxic effects of fMLP-activated neutrophils upon HBECs. In conclusion we were not able to demonstrate that heparin induces apoptosis and we did not find any evidence for heparin acting as an IP(3) receptor antagonist in neutrophils. Nonetheless, the potent inhibitory effects of heparin and related molecules upon neutrophil-induced injury to HBECs provide further evidence of the therapeutic potential of heparin and related molecules in the treatment of chronic inflammatory diseases.