Effects of phospholipase D on cardiopulmonary bypass-induced neutrophil priming

Objective:To investigate the relationship betwe en phospholipase D (PLD) activation and neutrophil priming induced by cardiopulm onary bypass (CPB), and try to clarify whether CPB-induced systemic inflammator y response can be attenuated by inhibiting neutrophilic PLD activation. Methods:Neutrophils were isolated from arterial blood of 8 pat ients undergoing valve replacement before operation and 30 min after initiation of CPB respectively. Both the preoperative and CPB-stirred neutrophils were sub divided into 5 groups by receiving different experimental interventions: (1) bac terial lipopolysaccharide (LPS, 10 ng·ml -1 ), (2) N-formylmethionylph enylalanine (fMLP, 1 μmol·L -1 ), (3) LPS+fMLP, (4) 1-butanol ( 0.5 %)+ LPS+fMLP, (5) vehicle. Elastase and myeloperoxidase (MPO) release was measured f or the parameters of neutrophil activation, neutrophil PLD activity was determin ed by quantitation of choline produced from the stable product of phosphatidylch oline catalyzed by PLD. Results:(1) Preoperative neutrophils treated with LPS+fMLP pre sented significantly higher PLD activity ( 13.48 ± 2.61 nmol choline·h -1 ·mg -1 ) and released more elastase and MPO than cells treated with v ehicle (PLD activity 3.70 ± 0.49 nmol choline·h -1 ·mg -1 , P< 0.01 ), LPS (P< 0.01 ) and fMLP respectively. In 1-butanol+LPS+fMLP group, PLD activity of preoperative neutrop hils was lower than that in LPS+fMLP group (P< 0.01 ), b esides the release of elastase and MPO decreased sharply below both LPS + fMLP a nd fMLP groups (P< 0.01 ). In LPS group, PLD activity wa s higher (P< 0.01 ), while elastase and MPO release did not differ from control. fMLP group presented PLD activity, elastase and MPO rel ease higher than control (P< 0.01 ); nevertheless, lower than LPS+fMLP group (P< 0.01 ). (2) CPB-stirred neutro phils 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 t hat in LPS or fMLP group. CPB-stirred neutrophils in LPS+fMLP group released mo re 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. Conclusions: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 in flammatory reaction.