Abstract 9743: Significance of Lipoprotein-Associated Phospholipase A2-Mediated Regulation of Akt and Caspase-7 Activity in Macrophage Apoptosis
Introduction: Lipoprotein-associated phospholipase A2 (Lp-PLA2) is a member of the PLA2 superfamily and is reported to be related to atherosclerosis. However, molecular mechanism by which Lp-PLA2 regulates atherosclerosis is not fully investigated. To explore it, this study was conducted by focusing on macrophage apoptosis, which plays a role in the initiation and progression of atherosclerosis.
Methods: Monocytes were isolated from randomly selected healthy male volunteers in each Lp-PLA2 genotype (wild-type Lp-PLA2 [Lp-PLA2 (V/V)], the heterozygous V279F mutation [Lp-PLA2 (V/F)], the homozygous V279F mutation [Lp-PLA2 (F/F)]), and were differentiated into macrophages. The induction of apoptosis in macrophages after incubation without serum was measured by the annexin V/propidium iodide double staining method. Involvement of caspases and Akt in the Lp-PLA2-mediated apoptosis was further examined using a culture cell line.
Results: The average plasma Lp-PLA2 concentration and activity were significantly low in the Lp-PLA2 (F/F) genotype compared with the Lp-PLA2 (V/V) genotype, but basic clinical characteristics were similar among each genotype. The percentage of apoptotic cells was significantly higher in the Lp-PLA2 (F/F) macrophages compared with those of Lp-PLA2 (V/V). Transfection of the expression plasmid of V279F mutant Lp-PLA2 into monocyte/macrophage-like U937 cells promoted the apoptosis. Knockdown of Lp-PLA2 also increased the number of apoptotic cells. In the cells expressing mutant Lp-PLA2, caspase-7 activity was increased and activated Akt was decreased. In addition, inhibition of caspase-7 activity reduced apoptosis in V279F mutant Lp-PLA2-expressing U937 cells, and on the other hand, an Akt inhibitor facilitated apoptosis in wild-type Lp-PLA2-expressing U937 cells.
Conclusions: V279F mutation of Lp-PLA2 promotes the induction of apoptosis in macrophages, and the increase in caspase-7 activity and the reduction of activated Akt are considered to be crucial for this phenomenon.
Author Disclosures: H. Ogita: None. X. Pang: None. D.P. Zankov: None.
- © 2014 by American Heart Association, Inc.