Paraoxonase 1 gene transfer lowers vascular oxidative stress and improves vasomotor function in apolipoprotein E-deficient mice with pre-existing atherosclerosis

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 C57BI/ 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 Ca2+ homeostasis in segments with pre-existing atherosclerosis, independently of an effect on plaque size.