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The effect of thrombin inhibition and platelet depletion on lps-induced airway inflammation in mice
The coagulation system is activated in sepsis and inhibition of coagulation proteinases is an attractive target for the prevention of acute lung injury (ALI) and organ failure that frequently result from the inflammatory response in this disease (Hoffman & Faist, 2000). Inhibition of thrombin has also been shown to inhibit the inflammatory response and subsequent tissue damage in an animal model of arthritis (Marty et al., 2001). In addition to coagulation proteinases, platelets are another component of the coagulation system that may be involved in inflammation since platelet depletion inhibits inflammatory cell (eosinophil) influx in a murine model (Pitchford et al., 2003). In the present study, we have examined whether either inhibition of thrombin or platelet depletion can inhibit neutrophil influx into the airways of mice after inhalation of bacterial lipopolysaccharide (LPS).# Female BALB/c mice (6-8 weeks old) were administered LPS (250µg.kg-1 E.coli 0127:B8) intranasally (under 5% isoflurane) and subsequently killed after 3 or 24 hours. Bronchoalveolar lavage (BAL) was performed and total and differential cell counts were performed to quantify the number of neutrophils in each sample, as an indication of the inflammatory response. One group of animals received an anti-CD41 antibody 24 hours before LPS administration; we have previously found that this treatment lowers circulating platelet numbers by more than 90% for 48 hours. Control animals received an isotype-matched irrelevant antibody. Another group was administered the short-acting thrombin inhibitor lepirudin (3 mg.kg-1;Lepirudin 1) 30 minutes before LPS administration. A final group (Lepirudin 2) received lepirudin at the same dose 30 minutes before LPS and were then boosted with the same dose 30 and 180 minutes later. Because lepirudin has a short half life, animals receiving lepirudin were killed at 3 hours only. In both lepirudin groups, control mice received saline only. At all time points neither inhibition of thrombin nor prior platelet depletion significantly modified the number of neutrophils found in BAL fluid after LPS administration (two-tailed t-test; Table 1). Table 1: Numbers of neutrophils in BAL from each group (cells x10000.mL-1)
These somewhat negative results support previous studies of highly specific anti-coagulants in sepsis (Hoffman & Faist, 2000) and suggest that neutrophils, unlike eosinophils, do not require the presence of platelets for migration into the airways.
Hoffman, JN & Faist, E (2000) Crit. Care Med., 28S, S74-S76. |
