sPLA2-IIA Augments Oxidized LDL-Induced MCP-1 Expression in Vitro Through Activation of Akt

Group IIA secretory phospholipase A2 (sPLA2-IIA) has an important role in atherosclerosis. In this study, we explored whether sPLA2-IIA overexpression could promote atherosclerosis in normal environment alone or with other inflammatory factors.

Human aortic smooth muscle cells (HASMCs) were transduced with Lv-GFP-sPLA2-IIA, a plasmid containing sPLA2-IIA coupled with green fluorescent protein (GFP). Cells were incubated in the presence or absence of oxidized low-density lipoprotein (LDL), sPLA2 inhibitor LY315920 or PI3K/Akt inhibitor LY294002. The mRNA expression and protein secretion of monocyte chemoattractant protein-1 (MCP-1) were assessed by quantitative real-time polymerase chain reaction (QRT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Phosphorylation of Akt was examined by western blotting.

Lv-GFP-sPLA2-IIA-transduced HASMCs remained fluorescent during 72 h of the study period with infection ratio of around 80%. The mRNA expression and protein secretion of MCP-1 was not altered in groups of HASMCs, Lv-GFP transduced and Lv-GFP-sPLA2-IIA-transduced HASMCs (p>0.05), but was significantly increased in the presence of oxidized LDL especially in Lv-GFP-sPLA2-IIA transduction group (p<0.01). However, with the addition of LY315920, this enhancement was notably decreased (p<0.05). This enhancement was also markedly abolished by co-incubation with LY294002, paralleled with suppressed Akt phosphorylation.

Overexpression of sPLA2-IIA does not alter MCP-1 level at baseline, but could enhance the atherogenic effect of oxidized LDL in HASMCs, at least partly due to activation of Akt. These findings may provide a strategy for treatment of inflammatory cardiovascular diseases.