Intimal hyperplasia following vascular injury is not inhibited by an antisense thrombin receptor oligodeoxynucleotide

Abstract

Thrombin is a multifunctional serine protease with central functions in hemostasis, but demonstration of its role in the initiation and maintenance of cell proliferation which occurs following vascular injury is still lacking. To determine the role played by thrombin and its receptor in neointimal accumulation of smooth muscle cells in a rabbit carotid artery model, we have used an 18 mer antisense phosphorothioate oligonucleotide (ODN) directed against the translation initiation region of the human thrombin receptor gene. The antisense ODN inhibited in a dose-dependent manner thrombin- or thrombin receptor activating peptide-induced human aortic smooth muscle cell proliferation. The growth-inhibitory effect of thrombin receptor antisense ODN was preventable by an excess of sense oligomer and specific for thrombin. The suppression of growth was accompanied by a marked decrease of the level of thrombin receptor expression as evidenced by [125I]-thrombin binding to smooth muscle cells. Under the same experimental conditions, the corresponding sense ODN was inactive. The effect of the antisense ODN on intimal smooth muscle hyperplasia in rabbit carotid arteries subjected to endothelial injury was then investigated. The topical application of the antisense (500 microg/artery) but not the sense ODN dissolved in F127 pluronic gel around the injured artery resulted, 2 weeks after the application, in a dramatic reduction of the expression of the thrombin receptor mRNA and protein levels as determined by in situ hybridization and immunohistochemistry. However, intimal smooth muscle cell accumulation as estimated by an intimal to medial cross-sectional area ratio was reduced only by 2.7% (vs. 10.3% for the sense ODN), whereas r-hirudin (200 microg/kg/day, s.c.), a potent direct thrombin inhibitor significantly reduced the formation of neointima in denuded carotid arteries (35.4% inhibition, P = 0.03).

Effector protease receptor 1 mediates the mitogenic activity of factor Xa for vascular smooth muscle cells in vitro and in vivo.

“…These data suggest that EPR-1/factor Xa plays a direct role in restenosis in this animal species. This study complements our previous work in the same animal model using the specific thrombin inhibitor recombinant desulphatohirudin (35), and lends support to the hypothesis that elements of the coagulation system, either through thrombus formation or because of other mitogenic effects, are important in restenosis after vascular injury in this animal model. Therefore, our results demonstrate the existence of functional factor Xa receptors on SMCs, related to EPR-1, represent the first evidence for the possible importance of EPR-1 in the mitogenic effect of factor Xa for these cells, and raise the interesting possibility of an active role of this factor Xa receptor in several processes where abnormal SMC proliferation has been acknowledged, such as atherogenesis.…”

Recombinant thrombomodulin inhibits arterial smooth muscle cell proliferation induced by thrombin

“…[35][36][37] The antisense thrombin receptor oligodeoxynucleotide did not inhibit intimal hyperplasia after vascular injury. 38 This study showed that rTM significantly inhibited SMC DNA synthesis and proliferative effect induced by thrombin. Thrombomodulin is constitutively produced on the endothelium and functions as a key factor in maintaining the nonthrombogenic vessel surface.…”

“…Thrombin inhibitors [34][35][36][37] and antisense thrombin receptor oligodeoxynucleotide 38 have been studied for the prevention of SMC proliferation. This study demonstrated that hirudin, a direct thrombin inhibitor, inhibited SMC proliferation induced by thrombin.…”

Recombinant human thrombomodulin inhibits arterial neointimal hyperplasia after balloon injury

“…Although heparin is a potent inhibitor of SMC growth and intimal hyperplasia in some animal models, it has been ineffective in inhibiting restenosis in studies both animal 44 and human. Other studies have demonstrated varying results with use of hirudin [45][46][47][48][49][50] and argatroban [51][52][53] with respect to their effects on SMC physiology and inflammation in vitro or in the setting of arterial injury. Most show some promise, but are limited solely to the effects resulting from thrombin inhibition.…”