Treatment of severe hypercholesterolemia in apolipoprotein E-deficient mice by intramuscular injection of plasmid DNA

We report on systemic delivery and long-term biological effects of apolipop rotein E (apoE) obtained by intramuscular (i.m.) plasmid DNA injection. Apo E plays an important role in lipoprotein catabolism and apoE knock-out mice develop severe hypercholesterolemia and diffuse atherosclerosis. We have i njected apoE-deficient mice with 80 mug of a,plasmid vector (pCMV-E3) encod ing the human apoE3 cDNA under the central of the CMV promoter-enhancer in both posterior legs. Local expression of the transgene was demonstrated thr oughout 16 weeks. Human apoE3 recombinant protein reached 0.6 ng/ml serum l evel. After i.m. injection of pCMV-E3 expression vector the mean serum chol esterol concentrations decreased from 439 +/- 57 mg/dl to 253 +/- 99 mg/dl (P < 0.05) 2 weeks after injection and persisted at a significantly reduced level throughout the 16 weeks observation period (P < 0.005). Serum choles terol was unaffected and reached an absolute level of 636+/-67 mg/dl in con trol groups. Finally, injection of pCMV-E3 into apoE-deficient mice resulte d in a redistribution of cholesterol content between lipoprotein fractions, with a marked decrease in VLDL, IDL and LDL cholesterol content and an inc rease in HDL cholesterol. These results demonstrate that severe hypercholes terolemia in apoE-deficient mice can be effectively reversed by i.m. DNA in jection, and indicate that this approach could represent a useful tool to c orrect several hyperlipidemic conditions resulting in atherosclerosis.