The effect of midazolam on neutrophil mitogen-activated protein kinase

Neutrophil p38 mitogen-activated protein kinase (MAPK) is a key enzyme in the intracellular signalling pathway that is responsible for many neutrophil functions, which are important in neutrophil-endothelial interaction. The imidazole compounds are inhibitors of this enzyme system. The objectives of this in-vitro investigation were to examine the effect of midazolam on neutrophil p38 MAPK activation (phosphorylation) following in-vitro ischaemia-reperfusion injury, and the expression of adhesion molecule CD11b/CD18.

In-vitro injury was produced by incubating the neutrophils with N-formyl-methionyl-leucyl-phenylalanine. Neutrophils were treated with either 10 or 50 times the therapeutic plasma concentrations of midazolam and SB203580 (known inhibitor of p38 MAPK). The concentrations of phosphorylated p38 MAPK and expression of neutrophil adhesion molecules CD11b/CD18 were measured. Flow cytometry was used to estimate adhesion molecule expression.

The concentration of phosphorylated p38 MAPK was less in neutrophils subjected to ischaemia-reperfusion and treated with midazolam either 10 microg ml [13.6 (3.2) ng ml] or 50 microg ml [12.4 (3.6) ng ml], or SB203580 [13 (2.6) ng ml] than those subjected to ischaemia-reperfusion alone [18 (3.18) ng ml] at a P value of less than 0.05.Following ischaemia-reperfusion injury, CD11b/CD18 expression (expression mean channel fluorescence) on neutrophils was greater when compared with controls. The magnitudes of CD11b and CD18 expression on ischaemia-reperfusion-injured neutrophils were decreased by midazolam (10 microg ml) as compared with control of 10.3 (2.6) vs. 14 (3.1) microg ml and 28.3 (12.9) vs. 44 (12.1) microg ml, respectively, at a P value of less than 0.05. Similarly, the expression of CD11b and CD18 was less in ischaemia-reperfusion-injured neutrophils treated with inhibitor of 10.3 (2.8) vs. 14 (3.18) microg ml and 29.5 (12.5) vs. 44.3 (12.3) microg ml when compared with controls at a P value of less than 0.05.

Midazolam diminishes in-vitro ischaemia-reperfusion-induced phosphorylation of p38 MAPK in neutrophils. This decrease in p38 MAPK activation results in decreased neutrophil CD11b/CD18 molecule expression.