ATP-induced apoptosis involves a Ca²⁺-independent phospholipase A₂ and 5-lipoxygenase in macrophages

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• 作者：Helio Mir ; a Costa-Junior ; Anderson Nogueira Mendes ; Gustavo Henrique Nolasco Grimmer Davis ; Cristiane Monteiro da Cruz ; Ana Lú ; cia Marques Ventura ; Carlos Henrique Serezani ; Lucia Helena Faccioli ; Auro Nomizo ; Cé ; lio G. Freire-de-Lima ; Rodrigo da Cunha Bisaggio ; Pedro Muanis Persechini
• 关键词：ATP ; P2X₇ ; Phospholipase A₂ ; Macrophage ; Apoptosis ; Necrosis ; 5-Lipoxygenase ; iPLA₂
• 刊名：Prostaglandins and Other Lipid Mediators
• 出版年：2009
• 出版时间：January 2009
• 年：2009
• 卷：88
• 期：1-2
• 页码：51-61
• 全文大小：1021 K

文摘

Macrophages express P2X₇ and other nucleotide (P2) receptors, and display the phenomena of extracellular ATP (ATP_e)-induced P2X₇-dependent membrane permeabilization and cell death by apoptosis and necrosis. P2X₇ receptors also cooperate with toll-like receptors (TLRs) to induce inflammasome activation and IL-1β secretion. We investigated signaling pathways involved in the induction of cell death by ATP_e in intraperitoneal murine macrophages. Apoptosis (hypodiploid nuclei) and necrosis (LDH release) were detected 6 h after an induction period of 20 min in the presence of ATP. Apoptosis was blocked by caspase 3 and caspase 9 inhibitors and by cyclosporin A. The MAPK inhibitors PD-98059, SB-203580 and SB-202190 provoked no significant effect on apoptosis, but SB-203580 blocked LDH release. Neither apoptosis nor necrosis was inhibited when both intra- and extracellular Ca²⁺ were chelated during the induction period. Mepacrine, a generic PLA₂ inhibitor and BEL, an inhibitor of Ca²⁺-independent PLA₂ (iPLA₂) blocked apoptosis, while pBPB and AACOOPF₃, inhibitors of secretory and Ca²⁺-dependent PLA₂ respectively, had no significant effect. Cycloxygenase inhibitors had no effect on apoptosis, while the inhibitors of lipoxygenase (LOX) and leukotriene biosynthesis nordihydroguaiaretic acid (NDGA), zileuton, AA-861, and MK-886 significantly decreased apoptosis. Neither NDGA nor MK-886 blocked apoptosis of 5-LOX^−/− macrophages. CP-105696 and MK-571, antagonists of leukotriene receptors, had no significant effect on apoptosis. None of the inhibitors of PLA₂ and LOX/leukotriene pathway had a significant inhibitory effect on LDH release. Our results indicate that a Ca²⁺-independent step involving an iPLA₂ and 5-LOX are involved in the triggering of apoptosis but not necrosis by P2X₇ in macrophages.