Sharma Janhavi, McHowat Jane
Department of Pathology, Saint Louis University School of Medicine, 1402 S. Grand Blvd., St Louis, MO 63104, USA.
Lipids. 2011 May;46(5):391-7. doi: 10.1007/s11745-011-3554-0. Epub 2011 Apr 2.
Inflammation is associated with cardiovascular disease, including myocardial infarction, atherosclerosis, myocarditis and congestive heart failure. Mast cells have been implicated in inflammation, but their precise role in cardiac inflammation remains unclear. Mast cells contain a variety of pre-formed granule-associated mediators, including tryptase. We have previously demonstrated that the majority of the phospholipase A(2) (PLA(2)) activity in isolated rabbit ventricular myocytes is membrane-associated, calcium-independent and selective for plasmalogen phospholipids. We hypothesized that tryptase stimulation of rabbit ventricular myocytes would increase iPLA(2) activity, leading to increased arachidonic acid and prostaglandin E(2) (PGE(2)) release. Isolated rabbit ventricular myocytes were stimulated with tryptase and iPLA(2) activity, arachidonic acid and PGE(2) release were measured. Tryptase stimulation increased iPLA(2) activity after 5 min. Activation of iPLA(2) was accompanied by increased arachidonic acid and PGE(2) release in tryptase-stimulated myocytes. However no increase in platelet activating factor was observed with tryptase stimulation. To distinguish between different iPLA(2) isoforms in the myocardium, we pretreated ventricular myocytes with the (R)- and (S)-enantiomers of bromoenol lactone (BEL) to selectively inhibit iPLA(2)γ and β respectively. Pretreatment with (R)-BEL resulted in complete inhibition of tryptase-stimulated iPLA(2) activity, arachidonic acid and PGE(2) release, suggesting the iPLA(2)γ is the predominant myocardial isoform activated by tryptase. These studies demonstrate that PGE(2) release from tryptase stimulated rabbit ventricular myocytes is mediated primarily by iPLA(2)γ.
炎症与心血管疾病相关，包括心肌梗死、动脉粥样硬化、心肌炎和充血性心力衰竭。肥大细胞与炎症有关，但其在心脏炎症中的具体作用仍不清楚。肥大细胞含有多种预先形成的颗粒相关介质，包括类胰蛋白酶。我们之前已经证明，分离的兔心室肌细胞中大部分磷脂酶A2（PLA2）活性与膜相关，不依赖钙，且对缩醛磷脂具有选择性。我们假设类胰蛋白酶刺激兔心室肌细胞会增加iPLA2活性，导致花生四烯酸和前列腺素E2（PGE2）释放增加。用类胰蛋白酶刺激分离的兔心室肌细胞，并测量iPLA2活性、花生四烯酸和PGE2释放。类胰蛋白酶刺激5分钟后iPLA2活性增加。iPLA2的激活伴随着类胰蛋白酶刺激的肌细胞中花生四烯酸和PGE2释放增加。然而，类胰蛋白酶刺激未观察到血小板活化因子增加。为了区分心肌中不同的iPLA2同工型，我们用溴烯醇内酯（BEL）的（R）-和（S）-对映体预处理心室肌细胞，以分别选择性抑制iPLA2γ和β。用（R）-BEL预处理导致类胰蛋白酶刺激的iPLA2活性、花生四烯酸和PGE2释放完全受到抑制，表明iPLA2γ是类胰蛋白酶激活的主要心肌同工型。这些研究表明，类胰蛋白酶刺激的兔心室肌细胞中PGE2的释放主要由iPLA2γ介导。
