Overexpression of ABCA1 in Carotid Endothelium of Hyperlipidemic Rabbits Modulates Vascular Inflammation
Bradley K Wacker1, Lianxiang Bi1, Goren Saenz-Pipaon1
1Division of Cardiology, Department of Medicine, University of Washington, Seattle, Washington, USA.
Abstract:
Endothelial activation and dysfunction are key early steps in atherogenesis. Vascular gene therapy targeting endothelial inflammation and cholesterol accumulation could decrease atherosclerosis progression. ATP-binding cassette subfamily A member 1 (ABCA1) exhibits anti-inflammatory properties and promotes cholesterol efflux. A mouse model showed that systemic endothelial overexpression of ABCA1 decreased diet-induced atherosclerosis. To test if local ABCA1 endothelial overexpression protects against atherosclerosis, we used helper-dependent adenoviral vectors (HDAd) to express ABCA1 or a "Null" control in the carotid endothelium of hyperlipidemic rabbits. Both ABCA1 mRNA and endothelial protein were increased 3 days after vector infusion. After 24 weeks on a high-fat diet, laser-microdissected endothelium showed increased ABCA1 mRNA expression, but whole-vessel ABCA1 mRNA was decreased with HDAdABCA1. Endothelial ABCA1 protein could not be measured at 24 weeks, so its overexpression may be transient. CD68 expression was decreased (-23%, p < 0.001), but ITGAM (-15%, p = 0.3) was unchanged. Macrophage markers for both M1-like macrophages (IL1B: -44% [p = 0.02]; IL6: -40% [p = 0.02]; CCL2: -25% [p = 0.02]) and M2-like macrophages (ARG1: -27% [p = 0.03]; IL10: -23% [p = 0.09]; TGFB1: -13% [p < 0.001]) were also decreased. The inflammatory cytokines IL6 (-100%; p < 0.001) and TNF (p < 0.05) were significantly decreased in the laser-microdissected endothelium, but VCAM1 (+5%, p = 1.0) was unchanged and ICAM1 (+101%; p = 0.03) increased. Lesion size, intimal lipid, and intimal macrophage content were all unchanged (p > 0.5 for all), and vascular cholesterol measured by mass spectrometry (-11%; p = 0.9) also showed no difference. There was a small decrease in the intimal/medial ratio. scRNAseq revealed that vector transcripts were not restricted to endothelial cells after 24+ weeks but were detected in most cell types. The exception was modulated smooth muscle cells, which were found in substantial numbers in larger lesions. Overall, transient overexpression of ABCA1 in the vascular endothelium subtly alters the expression of inflammatory markers, providing only a modest atheroprotection.
Insights
Vascular gene therapy using ATP-binding cassette subfamily A member 1 (ABCA1) in rabbits showed transient endothelial overexpression, leading to subtle anti-inflammatory effects but no significant reduction in atherosclerosis.
Area of Science:
- Cardiovascular Biology
- Gene Therapy
- Atherosclerosis Research
Background:
- Endothelial dysfunction is a critical early event in atherosclerosis.
- Vascular gene therapy offers a potential strategy to target endothelial inflammation and cholesterol accumulation.
- ATP-binding cassette subfamily A member 1 (ABCA1) has anti-inflammatory properties and facilitates cholesterol efflux.
Purpose of the Study:
- To investigate the protective effects of local endothelial overexpression of ABCA1 against atherosclerosis.
- To assess the impact of ABCA1 gene delivery on inflammatory markers and lesion development in a rabbit model.
Main Methods:
- Helper-dependent adenoviral vectors (HDAd) were used to deliver ABCA1 to the carotid endothelium of hyperlipidemic rabbits.
- Gene and protein expression were analyzed post-transduction.
- Atherosclerosis progression, inflammatory markers, and cellular content were evaluated after 24 weeks on a high-fat diet.
- Single-cell RNA sequencing (scRNAseq) was employed to analyze cellular distribution of vector transcripts.
Main Results:
- Transient endothelial ABCA1 overexpression was achieved, with decreased expression of macrophage markers (CD68, IL1B, IL6, CCL2, ARG1, IL10, TGFB1) and inflammatory cytokines (IL6, TNF).
- However, lesion size, intimal lipid, and macrophage content remained unchanged, with no significant reduction in vascular cholesterol.
- ICAM1 expression increased, while VCAM1 was unchanged, and vector transcripts were detected in multiple cell types beyond endothelium after 24 weeks.
Conclusions:
- Transient endothelial ABCA1 overexpression exerts subtle anti-inflammatory effects in the vasculature.
- This approach provided only modest atheroprotection, with no significant impact on established atherosclerotic burden in this model.
- Further research is needed to optimize gene delivery and duration for sustained therapeutic benefits.
