Platelet monocyte aggregates and monocyte chemoattractant protein-1 are not inhibited by aspirin in critical limb ischaemia

Objectives. Platelet monocyte aggregates (PMA) and monocyte chemoattractant protein-1 (MCP-1) play a significant role in atherosclerotic disease but the effect of aspirin and their role in peripheral arterial disease (PAD) requires further investigation. We have compared p-selectin, PMA and MCP-1 in patients with PAD treated with aspirin (75mgs daily), with age matched controls not treated with aspirin. Materials and methods. Using flow cytometry and ELISA, P-selectin, PMA and MCPA were compared in 3 populations; healthy controls (n = 12), intermittent claudication (n = 19) and critical limb ischaemia (CLI), (n = 10). Results. P-selectin was significantly higher in CLI patients (3.48% positive) compared to the claudicants (1. 36% positive) and the controls (1.76% positive). PMA levels were significantly higher for CLI population (44.5% positive) compared to the claudicants (20.48% positive) and the controls (28.33% positive). MCP-1 levels expression was significantly higher for the CLI patients (175.4 pg/mL) compared to the claudicants (76.1 pg/mL) and the controls (117.0 pg/mL). Conclusion. Despite aspirin treatment CLI patients have higher platelet activation and MCPA expression than controls and claudicants. With increasing severity of disease aspirin is unable to suppress markers of platelet activation and pro-atherosclerotic chemokine expression which may represent another form of aspirin resistance.