Background and purpose: Transgenesis of human paraoxonase 1 (PON1), a HDL-associated enzyme that destroys lipid peroxides, has been reported to reduce early atherogenesis in mice. The present study explored the therapeutic potential of human PON1 gene transfer in old apolipoprotein E-deficient (apoE(-/-)) mice with advanced atherosclerosis.
Experimental approach: ApoE(-/-) mice (18 months, regular chow) were transfected with PON1 adenovirus (AdPON1, n=10) or control adenovirus (AdRR5, n=10). Non-transfected apoE(-/-) (n=9) and C57Bl/6J (WT, n=6) mice served as controls. Three weeks later, plaque size and composition, and endothelial cell (EC) and smooth muscle cell (SMC) function were assessed in the aorta.
Key results: PON1 gene transfer raised total PON1 serum activity 13-15 fold during the 3-week study period, without affecting hypercholesterolaemia or lesion size. However, PON1 decreased the oxLDL content of the plaque. Plaque-free thoracic aorta rings from apoE(-/-) mice displayed, like rings from WT mice, complete relaxation to acetylcholine (ACh, 86+/-2%), ATP (90+/-2%) or UTP (83+/-3%). In contrast, in plaque-bearing segments amplitude (55+/-7%, 68+/-8%, 52+/-8% respectively) and sensitivity were decreased. EC function was completely (ATP, UTP) or largely (ACh) restored by AdPON1. Furthermore, apoE(-/-) SMCs released less intracellular calcium than WT upon sarco-endoplasmic reticulum calcium ATPase (SERCA) inhibition by cyclopiazonic acid. This defect was also restored by AdPON1 transfection.
Conclusions and implications: These data indicate that AdPON1 gene transfer improved vascular wall oxidative stress, EC function, and SMC Ca(2+) homeostasis in segments with pre-existing atherosclerosis, independently of an effect on plaque size.