Effects of abciximab on key pattern of human coronary restenosis in vitro: impact of the SI/MPL-ratio

Abstract

Background: The significant reduction of angiographic restenosis rates in the ISAR-SWEET study (intracoronary stenting and antithrombotic regimen: is abciximab a superior way to eliminate elevated thrombotic risk in diabetes) raises the question of whether abciximab acts on clopidogrel-independent mechanisms in suppressing neointimal hyperplasia. The current study investigates the direct effect of abciximab on ICAM-1 expression, migration and proliferation.

Methods: ICAM-1: Part I of the study investigates in cytoflow studies the effect of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 microg/ml) on TNF-alpha induced expression of intercellular adhesion molecule 1 (ICAM-1). Migration: Part II of the study explored the effect of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 microg/ml) on migration of HCMSMC over a period of 24 h. Proliferation: Part III of the study investigated the effect of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 microg/ml) on proliferation of HUVEC, HCAEC, and HCMSMC after an incubation period of 5 days.

Results: ICAM-1: In human venous endothelial cells (HUVEC), human coronary endothelial cells (HCAEC) and human coronary medial smooth muscle cells (HCMSMC) no inhibitory or stimulatory effect on expression of ICAM-1 was detected. Migration: After incubation of HCMSMC with abciximab in concentrations of 0.0002-2 microg/ml a stimulatory effect on cell migration was detected, statistical significance was achieved after incubation with 0.002 microg/ml (p < 0.05), 0.002 microg/ml (p < 0.001), and 0.2 microg/ml (p < 0.05). Proliferation: Small but statistically significant antiproliferative effects of abciximab were detected after incubation of HUVEC (0.02 and 2.0 microg/ml; p = 0.01 and p < 0.01), HCAEC (2.0 and 20.0 microg/ml; p < 0.05 and p < 0,01), and HCMSMC (2.0 and 20.0 microg/ml; p < 0.05 and p < 0.05). The significant inhibition (SI) of cell proliferation found in HCAEC and HCMSMC was achieved with drug concentrations more than 10 times beyond the maximal plasma level (MPL), resulting in a SI/MPL-ratio > 1.

Conclusion: Thus, the anti-restenotic effects of systemically administered abciximab reported in the ISAR-SWEET-study were not caused by a direct inhibitory effect on ICAM-1 expression, migration or proliferation.

Figure 1

Expression of ICAM-1. The effects of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 μg/ml) on TNF-α induced expression of intercellular adhesion molecule 1 (ICAM-1) in HUVEC, HCAEC and HCMSMC after 18 h (cytoflow data): Controls (thin grey line), non stimulated basic expression of ICAM-1 (grey line), expression of ICAM-1 after stimulation with TNF-α (thick grey line), expression of ICAM-1 after stimulation with TNF-α plus abciximab (black line).

Figure 2

Migration. Effects of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 μg/ml) on migration of HCMSMC (48 h) in comparison to untreated controls. C = controls, bar 100 μm. (p < 0.05 = *; p < 0.01 = **; p < 0.001 = ***; paired Student's t-test).

Figure 3

Proliferation. Effects of abciximab (0.0002, 0.002, 0.02, 0.2, 2.0, and 20.0 μg/ml) on proliferation of HUVEC (A), HCAEC (B), and HCMSMC (C) in comparison to untreated controls at day six after seeding, C = control, (p < 0.05 = *; p < 0.01 = **; p < 0.001 = ***; paired Student's t-test).