Mazerik Jessica N, Hagele Thomas, Sherwani Shariq, Ciapala Valorie, Butler Susan, Kuppusamy M Lakshmi, Hunter Melissa, Kuppusamy Periannan, Marsh Clay B, Parinandi Narasimham L
Lipid Signaling and Lipidomics Laboratory, Division of Pulmonary, Allergy, Critical Care, The Ohio State University College of Medicine, Columbus, Ohio, USA.
Int J Toxicol. 2007 Nov-Dec;26(6):553-69. doi: 10.1080/10915810701707759.
Mercury has been identified as a risk factor for cardiovascular disease among humans. Through diet, mainly fish consumption, humans are exposed to methylmercury, the biomethylated organic form of environmental mercury. As the endothelium is an important player in homeostasis of the cardiovascular system, here, the authors tested their hypothesis that methylmercury activates the lipid signaling enzyme phospholipase A(2) (PLA(2)) in vascular endothelial cells (ECs), causing upstream regulation of cytotoxicity. To test this hypothesis, the authors used bovine pulmonary artery ECs (BPAECs) cultured in monolayers, following labeling of their membrane phospholipids with [(3)H]arachidonic acid (AA). The cells were exposed to methylmercury chloride (MMC) and then the release of free AA (index of PLA(2) activity) and lactate dehydrogenase (LDH; index of cytotoxicity) were determined by liquid scintillation counting and spectrophotometry, respectively. MMC significantly activated PLA(2) in a dose-dependent (5 to 15 microM) and time-dependent (0 to 60 min) fashion. Sulfhydryl (thiol-protective) agents, calcium chelators, antioxidants, and PLA(2)-specific inhibitors attenuated the MMC-induced PLA(2) activation, suggesting the role of thiols, reactive oxygen species (ROS), and calcium in the activation of PLA(2) in BPAECs. MMC also induced the loss of thiols and increase of lipid peroxidation in BPAECs. MMC induced cytotoxicity in BPAECs as observed by the altered cell morphology and LDH leak, which was significantly attenuated by PLA(2) inhibitors. This study established that PLA(2) activation through thiols, calcium, and oxidative stress was associated with the cytotoxicity of MMC in BPAECs, drawing attention to the involvement of PLA(2) signaling in the methylmercury-induced vascular endothelial dysfunctions.
汞已被确认为人类心血管疾病的一个风险因素。通过饮食，主要是食用鱼类，人类会接触到甲基汞，这是环境汞的生物甲基化有机形式。由于内皮细胞在心血管系统的内环境稳定中起着重要作用，因此，作者在此测试了他们的假设，即甲基汞会激活血管内皮细胞（ECs）中的脂质信号酶磷脂酶A2（PLA2），从而导致细胞毒性的上游调节。为了验证这一假设，作者使用单层培养的牛肺动脉内皮细胞（BPAECs），并用[3H]花生四烯酸（AA）标记其膜磷脂。将细胞暴露于氯化甲基汞（MMC），然后分别通过液体闪烁计数法和分光光度法测定游离AA（PLA2活性指标）和乳酸脱氢酶（LDH；细胞毒性指标）的释放量。MMC以剂量依赖性（5至15微摩尔）和时间依赖性（0至60分钟）的方式显著激活PLA2。巯基（硫醇保护）剂、钙螯合剂、抗氧化剂和PLA2特异性抑制剂减弱了MMC诱导的PLA2激活，表明硫醇、活性氧（ROS）和钙在BPAECs中PLA2激活中的作用。MMC还导致BPAECs中硫醇的损失和脂质过氧化增加。如细胞形态改变和LDH泄漏所示，MMC诱导了BPAECs的细胞毒性，而PLA2抑制剂可显著减弱这种毒性。这项研究表明通过硫醇、钙和氧化应激激活PLA2与MMC在BPAECs中的细胞毒性有关，并提醒人们注意PLA2信号传导参与甲基汞诱导的血管内皮功能障碍。
