NOVEL THERAPEUTIC STRATEGY FOR ATHEROSCLEROSIS - RIBOZYME OLIGONUCLEOTIDES AGAINST APOLIPOPROTEIN(A) SELECTIVELY INHIBIT APOLIPOPROTEIN(A) BUT NOT PLASMINOGEN GENE-EXPRESSION

Background-Because mechanisms of atherosclerosis by lipoprotein(a) [Lp (a)] have been postulated in the decrease in active transforming growt h factor-p conversion by decreased plasmin, selective decrease in apol ipoprotein(a) [apo(a)] independent of plasminogen may have therapeutic values. Although antisense can decrease apo(a), its application may b e difficult because of very high homology of apo(a) gene to plasminoge n. Thus we used ribozyme strategy that actively cleaves targeted genes to selectively inhibit apo(a) expression. Methods and Results-We cons tructed ribozyme oligonucleotides containing phosphorothioate DNA- and RNA-targeted kringle 4 of the apo(a) gene that showed 80% homology to plasminogen, Transfection of human apo(a) gene produced Lp(a) in medi um of HepG2 cells, whereas Lp(a) could not be detected in control cell s. Cotransfection of ribozyme and apo(a) gene resulted in the decrease in mRNA of apo(a) but not plasminogen, Moreover, marked decrease in L p(a) was also observed in the medium transfected with ribozyme and apo (a) gene compared with apo(a) gene alone (P<0.01), whereas there was n o significant change in plasminogen level between ribozyme-transfected and control cells. incubation of human vascular smooth muscle cells ( VSMC) with conditioned medium from apo(a)-transfected HepG2 cells resu lted in a significant increase in VSMC number, whereas addition of con ditioned medium from cells cotransfected with ribozyme oligonucleotide s and apo(a) gene resulted in no VSMC growth (P<0.01). DNA-based contr ol oligonucleotides and mismatched ribozyme oligonucleotides did not h ave an inhibitory effect on Lp(a) production. Conclusions-Overall, our data revealed that transfection of ribozyme against the apo(a) gene r esulted in the selective inhibition of the apo(a) but not the plasmino gen gene, providing novel therapeutic strategy for treatment of high L p(a), a risk factor for atherosclerosis.