Ribozyme-mediated inhibition of rat leukocyte-type 12-lipoxygenase prevents intimal hyperplasia in balloon-injured rat carotid arteries

Background-12-Lipoxygenase (12-LO) products of arachidonate metabolism have growth and chemotactic effects in vascular smooth muscle cells. We have al so recently demonstrated increased 12-LO mRNA and protein expression in the neointima of balloon-injured rat carotid arteries, In this study, we evalu ated whether 12-LO activation plays a role in neointimal thickening in this rat model by using a specific ribozyme (Rz) directed to rat 12-LO. Methods and Results-We designed a chimeric DNA-RNA hammerhead Rz to cleave rat leukocyte-type 12-LO mRNA. This Rz dose-dependently cleaved a 166-nucle otide target 12-LO mRNA substrate in vitro and reduced 12-LO mRNA and prote in expression in rat vascular smooth muscle cells. A control mutant Rz (MRz ) with a point mutation in the catalytic site was inactive. To test the in vivo efficacy of the 12-LO Rz, the left common carotid arteries of rats wer e injured with a balloon catheter. The distal half of the injured arteries was treated with Rz or MRz mixed with lipofectin, The proximal half receive d only lipofectin. Twelve days after injury, intima-to-media ratios were si gnificantly lower in the Rz-treated sections than in untreated sections fro m the same rat (0.742 +/-0.16 versus 1.749 +/-0.12, P<0.001). In contrast, the MRz had no significant effect. Conclusions-These results indicate the important role of the leukocyte-type 12-LO pathway in restenosis in response to injury.