Abstract
Purpose :
In cardiovascular diseace CVD, ischemia increases the lipid load in macrophages, driving an inflammatory phenotype and promoting vascular damage. This process is poorly understood in ischemic retinopathy. Our studies in a model of oxygen-induced retinopathy have shown that macrophage activation during retinal neovascularization (RNV) is characterized by increased expression of the inflammation amplifiers TREM-1 (triggering receptor expressed on myeloid cells 1) and M-CSF (macrophage colony stimulator factor). Inhibition of TREM-1 reduces vascular injury and limits RNV. Here we examined upstream activators of the TREM1/MCSF pathway. In macrophages, ACAT1 esterifies LDL cholesterol (LDLc) with fatty acids to form cholesterol esters (CEs).
Methods :
Wild-type and LDL receptor knockout mice were maintained in 75% oxygen from postnatal day 7 (P7) to P12 followed by normoxia until P17. Wild-type pups were treated with an ACAT inhibitor (N-[3-(4-hydroxyphenyl)-1-oxo-2-propenyl]-L-phenylalanine, methyl ester 10 mg/Kg, i.p) or vehicle (PBS) on alternate days from P7 to P16. The retinas were collected on P17 and prepared for immunofluorescence or western blot. Human macrophages were maintained in hypoxia (1% O2) or normoxia (21% O2) for 16 hrs, treated with the ACAT inhibitor (10μg/ml) or PBS, and prepared for western blot.
Results :
Wild type mice showed significant increases in LDL receptor expression, lipid accumulation, and CE formation in areas of RNV along with increased expression of ACAT1, TREM-1, M-CSF, and VEGF (p<0.05). ACAT inhibitor treatment significantly abrogated those changes and reduced the areas of RNV and vaso-obliteration (p<0.05). LDL receptor knockout blocked RNV underscoring the role of LDLc metabolism in the pathology. In vitro, hypoxia-induced increases in expression of ACAT1, TREM-1, M-CSF and VEGF were prevented by ACAT inhibitor (p<0.05).
Conclusions :
Hypoxia-induced increases in ACAT1 activity and CE formation are associated with upregulation of TREM-1, M-CSF, VEGF, LDLR and pathological RNV. Liminting the ACAT1 pathway offers a new therapeutic strategy for the treatment and prevention of vascular pathologies during ischemic retinopathy.
This is a 2021 ARVO Annual Meeting abstract.