Mechano-Sensitive PPAP2B Regulates Endothelial Responses to Athero-Relevant Hemodynamic Forces
Rationale: PhosPhatidic-Acid-Phosphatase-type-2B (PPAP2B), an integral membrane protein that inactivates lysophosphatidic acid, was implicated in coronary artery disease (CAD) by genome-wide-association-studies (GWAS). However, it is unclear whether GWAS-identified CAD genes including PPAP2B participate in mechanotransduction mechanisms by which vascular endothelia respond to local athero-relevant hemodynamics that contribute to the regional nature of atherosclerosis.
Objective: To establish the critical role of PPAP2B in endothelial responses to hemodynamics.
Methods and Results: Reduced PPAP2B was detected in vivo in mouse and swine aortic arch endothelia exposed to chronic disturbed flow, and in mouse carotid artery endothelia subjected to surgically-induced acute disturbed flow. In humans, PPAP2B was reduced in the downstream part of carotid plaques where low shear stress prevails. In culture, reduced PPAP2B was measured in human aortic endothelial cells (HAEC) under athero-susceptible waveform mimicking flow in human carotid sinus. Flow-sensitive microRNA-92a and transcription factor KLF2 were identified as upstream inhibitor and activator of endothelial PPAP2B, respectively. PPAP2B suppression abrogated athero-protection of unidirectional flow; Inhibition of lysophosphatidic acid receptor 1 (LPAR1) restored the flow-dependent, anti-inflammatory phenotype in PPAP2B-deficient cells. PPAP2B inhibition resulted in myosin-light-chain phosphorylation and intercellular gaps, which were abolished by LPAR1/2 inhibition. Expression-quantitative-trait-locus-mapping demonstrated PPAP2B CAD risk allele is not linked to PPAP2B expression in various human tissues but significantly associated with reduced PPAP2B in HAEC.
Conclusions: Athero-relevant flows dynamically modulate endothelial PPAP2B expression through miR-92a and KLF2. Mechano-sensitive PPAP2B plays a critical role in promoting anti-inflammatory phenotype and maintaining vascular integrity of endothelial monolayer under athero-protective flow.
- vascular permeability
- Genome Wide Association Study
- endothelial cell
- Received March 23, 2015.
- Revision received May 27, 2015.
- Accepted June 1, 2015.