Mechanisms involved in the inhibition of neointimal hyperplasia by abciximab in a rat model of balloon angioplasty

Monoclonal antibodies raised against β₃ integrin are able to inhibit the binding of ligands to certain β₃ integrins such as α_IIbβ₃ (glycoprotein IIb/IIIa complex) and α_vβ₃ (vitronectin receptor) and as such are inhibitors of platelet aggregation and smooth muscle cell (SMC) migration, both of which are involved in neointimal hyperplasia. The present study was designed to explore the detailed mechanisms of abciximab (Reopro), a monoclonal antibody (mAb) raised against α_IIbβ₃ integrin in neointimal hyperplasia. In this study, carotid arteries of Wistar rats were damaged, and neointimal hyperplasia and lumen occlusion was determined at different time points. Abciximab was administered intravenously by an implanted osmotic pump. Abciximab (0.25 mg/kg/day) time-dependently inhibited both neointimal hyperplasia and lumen occlusion after angioplasty in carotid arteries of rats. Furthermore, the electromicrographs highlighted that SMCs were phenotypically different from the typical contractile, spindle-shaped SMCs normally seen in uninjured vessel walls. Platelet-derived growth factor (PDGF)-BB was strongly produced in thrombus formation and neointimal SMCs after angioplasty, while abciximab significantly reduced PDGF-BB expression in vessel lumens and neointimal SMCs after angioplasty. Balloon angioplasty caused a significant increase of nitrate and cyclic GMP as compared with sham-operated rats. Infusion of abciximab (0.25 mg/kg/day) did not significantly change. Furthermore, the plasma level of thromboxane B₂ (TxB₂) obviously increased after angioplasty, while abciximab markedly suppressed the elevation of plasma TxB₂ concentration. The results indicate that abciximab effectively prevents neointimal hyperplasia, possibly through the following 2 mechanisms: (1) Abciximab binds to α_IIbβ₃ integrin on platelet membranes resulting in inhibition of platelet adhesion, secretion, and aggregation in injured arteries, followed by inhibition of thromboxane A₂ formation and PDGF-BB release from platelets. (2) Abciximab may also bind to α_vβ₃ integrin on SMCs, thus, subsequently inhibiting cell migration and proliferation.