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Published on: October 12, 2017
Serum amyloid A stimulates lipoprotein-associated phospholipase A2 expression in vitro and in vivo
1Key Laboratory of Cardiovascular Remodeling and Function Research, Chinese Ministry of Education, Chinese Ministry of Public Health, Department of Cardiology, Qilu Hospital of Shandong University, Ji'nan 250012, PR China.
Objectives:
Although lipoprotein-associated phospholipase A2 (Lp-PLA2) has been regarded as a biomarker and a causative agent for acute coronary events recently, the mechanism of the regulation of Lp-PLA2 has not been fully elucidated yet. This study was aimed to investigate the influence of serum amyloid A (SAA) on the expression of Lp-PLA2 in THP-1 cells and ApoE-deficient (ApoE(-/-)) mice.
Methods:
THP-1 cells were stimulated by SAA and the mRNA and protein expression of Lp-PLA2 was detected. ApoE(-/-) mice were intravenously injected with murine SAA1 lentivirus. Formyl peptide receptor like-1 (FPRL1) agonist (WKYMVm) and inhibitor (WRW(4)), mitogen-activated protein kinases (MAPKs) inhibitors, and peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist and inhibitor were used to investigate the mechanism of regulation of Lp-PLA2.
Results:
Recombinant SAA up-regulated Lp-PLA2 expression in a dose and time-dependent manner in THP-1 cells. Immunohistochemical analysis of aortic root of ApoE(-/-) mice also demonstrated that the expression of Lp-PLA2 was up-regulated significantly with SAA treatment. WRW(4) decreased SAA-induced Lp-PLA2 production; while WKYMVm could induce Lp-PLA2 expression. ERK1/2, JNK1/2, and p38 inhibition reduced SAA-induced Lp-PLA2 production. Furthermore, the results suggested the activation of PPAR-γ played a crucial role in this process.
Conclusion:
These results demonstrate that SAA up-regulates Lp-PLA2 production significantly via a FPRL1/MAPKs./PPAR-γ signaling pathway.
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