Phospholipase A2 activation regulates cytotoxicity of methylmercury in vascular endothelial cells.
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.
Mazerik
Jessica N
JN
Lipid Signaling and Lipidomics Laboratory, Division of Pulmonary, Allergy, Critical Care, The Ohio State University College of Medicine, Columbus, Ohio, USA.
Hagele
Thomas
T
Sherwani
Shariq
S
Ciapala
Valorie
V
Butler
Susan
S
Kuppusamy
M Lakshmi
ML
Hunter
Melissa
M
Kuppusamy
Periannan
P
Marsh
Clay B
CB
Parinandi
Narasimham L
NL
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D016718:Arachidonic Acid / Q000378:metabolism; D001095:Arachidonic Acids / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002614:Chelating Agents / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology; D015227:Lipid Peroxidation / Q000187:drug effects; D008767:Methylmercury Compounds / Q000633:toxicity*; D009281:Naphthalenes / Q000494:pharmacology; D064801:Phospholipase A2 Inhibitors; D054467:Phospholipases A2 / Q000378:metabolism*; D011753:Pyrones / Q000494:pharmacology; D011796:Quinacrine / Q000494:pharmacology; D013438:Sulfhydryl Compounds / Q000378:metabolism
D000975:Antioxidants; D001095:Arachidonic Acids; D002614:Chelating Agents; D008767:Methylmercury Compounds; D009281:Naphthalenes; D064801:Phospholipase A2 Inhibitors; D011753:Pyrones; D013438:Sulfhydryl Compounds; C081565:arachidonyltrifluoromethane; D016718:Arachidonic Acid; C068314:6-(bromomethylene)tetrahydro-3-(1-naphthaleneyl)-2H-pyran-2-one; D054467:Phospholipases A2; D011796:Quinacrine; C004925:methylmercuric chloride; D002118:Calcium; D000111:Acetylcysteine