EXPRESSION OF HUMAN CHOLESTEROL 7-ALPHA-HYDROXYLASE IN ATHEROSCLEROSIS-SUSCEPTIBLE MICE VIA ADENOVIRUS INFECTION

Adenovirus is a vector for the delivery of genes mainly to the liver. Short-term (similar to 3 days) studies using adenovirus transfection h ave provided valuable insights into how genes can complement normal an d pathological phenotypes. When atherosclerosis-susceptible C57BL/6 mi ce were infected with an adenovirus vector containing the human 7 alph a-hydroxylase cDNA (AV17hl) and fed on a chow diet, human 7 alpha-hydr oxylase mRNA and enzyme activity doubled compared with that in mice in fected with an adenovirus vector (AVINull) alone. In AV17hl-infected m ice fed on a high fat cholic acid (HFCA) diet, mRNA expression and act ivity of both the endogenous and adenovirus (human) 7 alpha-hydroxylas e were repressed. AV17hl-infected mice fed on a HFCA diet and killed a t mid-light had increased 7 alpha-hydroxylase activity and mRNA compar ed with mice killed at mid-dark. Since expression of AV17hl is driven by a constitutive Rous sarcoma virus promoter, the repression of human 7 alpha-hydroxylase by the HFCA diet was unexpected. In spite of this posttranscriptional repression by the HFCA diet, AVl7hl-infected mice expressed the human 7 alpha-hydroxylase mRNA, causing its enzyme acti vity to be 3-fold greater than in AV1Null-infected mice. In AV17hl-inf ected mice, the 7 alpha-hydroxylase enzyme activity varied as a linear function of human mRNA abundance. In conclusion, the accumulation of apolipoprotein B-containing lipoproteins in plasma of C57BL/6 mice fed on the HFCA diet was not reduced by longer-term (2 weeks) 7 alpha-hyd roxylase expression, probably because of its diminished expression cau sed by the diet and hepatic inflammation from the adenovirus infection . These results may suggest that adenovirus is effective in promoting longer-term (2 weeks) expression of 7 alpha-hydroxylase.