12/15-lipoxygenase deficiency attenuates disturbed flow-induced LDL oxidation in endothelial cells

Atherosclerosis preferentially develops in regions exposed to disturbed flow, where is more susceptible to trans-endothelial retention of oxidized low-density lipoprotein (ox-LDL) and subsequent vascular inflammation. While 12/15-lipoxygenase (12/15-LOX) is implicated in lipid oxidation, its role in accumulation of oxLDL in disturbed flow areas remains unknown.

Human coronary artery endarterectomy specimens and cultured endothelial cells were analyzed for 12/15-LOX expression and localization under disturbed flow. Oxidized phospholipids were quantified via E06 antibody by ELISA, while ROS generation was measured using DCFH-DA. ApoE^-/- mice with partial carotid ligation and 12/15-LOX knockout (Alox15^-/-) were used to assess oxidized lipid deposition.

Disturbed flow upregulated 12/15-LOX expression in endothelial cells. In vitro, disturbed flow increased LDL oxidation and ROS production, both attenuated by 12/15-LOX siRNA or the specific inhibitor baicalein and ML351. Genetic deletion or pharmacological inhibition of 12/15-LOX reduced oxidized lipid deposition in disturbed flow regions. Mechanistically, 12/15-LOX increased ROS production in disturbed flow conditions in a pathway upstream of NAPDH oxidase 2. However, the 12/15-LOX-mediated LDL oxidation was independent of NOX.

We identify 12/15-LOX as a hemodynamic-sensitive enzyme that is upregulated under disturbed flow to promote LDL oxidation, which proposes a promising target to mitigate atherosclerosis especially in disturbed flow areas.