Effects of phospholipase D on cardiopulmonary bypass-induced neutrophil priming

To investigate the relationship between phospholipase D (PLD) activation and neutrophil priming induced by cardiopulmonary bypass (CPB), and try to clarify whether CPB-induced systemic inflammatory response can be attenuated by inhibiting neutrophilic PLD activation.

Neutrophils were isolated from arterial blood of 8 patients undergoing valve replacement before operation and 30 min after initiation of CPB respectively. Both the preoperative and CPB-stirred neutrophils were subdivided into 5 groups by receiving different experimental interventions: (1) bacterial lipopolysaccharide (LPS, 10 ng x ml(-1)), (2) N-formylmethionylphenylalanine (fMLP, 1 micromol x L(-1)), (3) LPS+fMLP, (4) 1-butanol (0.5%)+LPS+fMLP, (5) vehicle. Elastase and myeloperoxidase (MPO) release was measured for the parameters of neutrophil activation, neutrophil PLD activity was determined by quantitation of choline produced from the stable product of phosphatidylcholine catalyzed by PLD.

(1) Preoperative neutrophils treated with LPS+fMLP presented significantly higher PLD activity (13.48+/-2.61 nmol choline x h(-1) x mg(-1)) and released more elastase and MPO than cells treated with vehicle (PLD activity 3.70+/-0.49 nmol choline x h(-1) x mg(-1)), P<0.01), LPS (P<0.01) and fMLP respectively. In 1-butanol+LPS+fMLP group, PLD activity of preoperative neutrophils was lower than that in LPS+fMLP group (P<0.01), besides the release of elastase and MPO decreased sharply below both LPS+fMLP and fMLP groups (P<0.01). In LPS group, PLD activity was higher (P<0.01), while elastase and MPO release did not differ from control. fMLP group presented PLD activity, elastase and MPO release higher than control (P<0.01); nevertheless, lower than LPS+fMLP group (P<0.01). (2) CPB-stirred neutrophils presented prominent PLD activity increment, and even the control level was 3.59-fold of the pre-operative control (P<0.01). PLD activity in LPS+fMLP group was higher than that in other groups. Notably, PLD activity was even nonstatistically lower in 1-butanol+LPS+fMLP group than that in LPS or fMLP group. CPB-stirred neutrophils in LPS+fMLP group released more elastase and MPO than control, LPS, and 1-butanol+LPS+fMLP groups did (P<0.01); however, neither of the release was statistically different from that of fMLP group.

Cardiopulmonary bypass enables neutrophil priming accompanied with significant increase in PLD activity. Inhibition of neutrophil PLD activation attenuates its priming and may alleviate CPB-induced systemic inflammatory reaction.