Effect Of Human Leukocyte Phospholipase D On The Systemic Inflammatory Response Induced By Cardiopulmonary Bypass

Leukocytes activation had been proven to be the central role in tbe initiationand development of cardiopulmonary bypass(CPB) induced systemic inflammatory response, it also had intimate relationship to the CPB induced systemic inflammatory response syndrome and multipule organ dysfunction or even failure, especially respiratory failure. Phospholipase D(PLD) exists widely in mammalian cells. Being activated by various inflammatory mediators, PLD catalyzes its main substrate phosphatidycholine (PC) into direct product phosphatidic acid(PA) and indirect products diacyglycerol (DAG) and lysophosphatidic acid (LPA), this procedure is one of the key signal transduction pathways. PC hydrolyzed by actived PLD involves in many important cell events such as cell proliferation, cell division, calcium mobilization, protein kinase activation, etc. The biological effect of activated PLD is performed through thetwo ways below: 1) Direct or indirect products of PLD (PA, DAG and LPA) act as key second messengers. 2) PLD may cause characteristic alterations in plasma membrane, such as membrane fusibility and synthesis or release of the membrane-related proteins, by hydrolyzing PC which is the main phospholipid of cell membrane. PLD activation is the key step of many biological behaviors of polymorphonuclear leukocyte(PMN), e.g respiratory burst, degranulation and PLA2 activation. Priming is the cell status of hyperesponsibility to agonists. The PLD activity in priming or activated PMN is obviously higher in comparison with that of intact PMN. CPB may lead to leukocyte priming in early phase or late leukocyte dysfunction after activation, and leukocyte mediated tissue injury in early stage or late inflammatory complications correspondingly.However, what alterations will take place in PMN of human systemic inflammatory response (e.g CPB induced inflammatory response) cases and what role will PLD play in such inflammatory response are still puzzle. There has no reports on the relationships between PLD and CPB induced leukocytes priming or activation yet. In this study, leukocytes of CPB induced systemic inflammatory response cases are chose as objects. The questions we intend to solve hi this project are as follow, 1) What alterations will take place in PMN of human systemic inflammatory response (e,g CPB induced inflammatory response) cases and what role will PLD play in such inflammatory response? 2) Will Methylprednisolone and aprotinin effect on leukocytes PLD activity hi CPB induced systemic inflammatory response? 3) What role will PLD play in the CPB induced leukocytes priming and activation?Our study demonstrated that 1) The arterial leukocyte PLD activity rise significantly in the CPB induced systemic inflammatory reaction and its elevation is earlier and more persistent than other inflammation-related indicators being tested; 2) the longer CPB duration (longer than 90 minutes) lead to the higher leukocyte PLD activity than which induced by short CPB duration (less than 60 minutes); 3)blunting post-CPB inflammation by methylprednisolone was related to inhibiting the activation of PLD; 4) PLD activity increased significantly when neutrophils primed by cardiopnlmonary bypass, and PLD inhibitor(butanol) could attenuate this priming of neutrophils.These results suggested that inhibiting PLD activation in leukocytes in early phase of CPB could be an approach to deal with CPB induced systemic inflammatory response syndrome.This study comprised of 3 sections.