Neutrophil elastase (NE) deficient mice exhibit reduced leukocyte transmigration in response to ischaemia/reperfusion (I/R) injury

Abstract

NE is a serine protease implicated in a variety of inflammatory disease states though details of its precise role remains contentious. We have previously shown that whilst neutrophil transmigration through mouse cremasteric venules (as observed by intravital microscopy) in response to LTB4, IL-1β or TNFα is normal in NE deficient (KO) mice; zymosan-induced neutrophil transmigration is suppressed in these animals. Using the same model, we have now investigated leukocyte responses in NE KO mice as induced by I/R injury. In wild-type (WT) mice, induction of ischaemia (30 min.) followed by reperfusion (120 min.) in the mouse cremaster muscle led to a significant increase in both leukocyte firm adhesion and transmigration, as compared to sham-operated mice. In NE KO animals, whilst adhesion was not significantly effected, leukocyte transmigration was almost totally blocked (91.4% inhibition, p<0.01). I/R-induced transmigration was also suppressed in WT mice treated with a specific NE inhibitor, Sivelestat (72.9% inhibition, p<0.05). Analysis of WT tissue homogenates indicated significant levels of KC, MCP-1 and LTB4, but not IL-1β or TNFα, post induction of I/R injury. Whilst there appeared to be a trend towards suppression of mediator generation in tissues from NE KO mice, no significant differences were noted between KOs and WT animals. Collectively, the results demonstrate a non-redundant role for NE in leukocyte transmigration as elicited by I/R injury though the mechanism by which this occurs is presently unknown. Funded by the BHF, UK