Author + information
- Received February 10, 2011
- Revision received March 18, 2011
- Accepted March 22, 2011
- Published online August 9, 2011.
- Teresa Mattiello, DPharm⁎,
- Raffaella Guerriero, PhD†,
- Lavinia Vittoria Lotti, PhD⁎,
- Elisabetta Trifirò, PhD⁎,
- Maria Pia Felli, PhD⁎,
- Alessandro Barbarulo, PhD⁎,
- Bruna Pucci, PhD⁎,
- Paola Gazzaniga, MD⁎,
- Carlo Gaudio, MD‡,
- Luigi Frati, MD⁎ and
- Fabio M. Pulcinelli, MD⁎,⁎ ()
- ↵⁎Reprint requests and correspondence:
Dr. Fabio M. Pulcinelli, Department of Experimental Medicine, “Sapienza” University of Rome, Viale Regina Elena 324, 00161 Rome, Italy
Objectives In this study we investigate: 1) the role of multidrug resistance protein-4 (MRP4), an organic anion unidirectional transporter, in modulating aspirin action on human platelet cyclooxygenase (COX)-1; and 2) whether the impairment of aspirin–COX-1 interaction, found in coronary artery bypass grafting (CABG) patients, could be dependent on MRP4-mediated transport.
Background Platelets of CABG patients present a reduced sensitivity to aspirin despite in vivo and in vitro drug treatment. Aspirin is an organic anion and could be a substrate for MRP4.
Methods Intracellular aspirin concentration and drug COX-1 activity, measured by thrombin-induced thromboxane B2 (TxB2) production, were evaluated in platelets obtained from healthy volunteers (HV) and hematopoietic-progenitor cell cultures reducing or not reducing MRP4-mediated transport. Platelet MRP4 expression was evaluated, in platelets from HV and CABG patients, by dot-blot or by immunogold-electromicrographs or immunofluorescence-microscopy analysis.
Results Inhibition of MRP4-mediated transport by dipyridamole or Mk-571 increases aspirin entrapment and its in vitro effect on COX-1 activity (142.7 ± 34.6 pg/108 cells vs. 343.7 ± 169.3 pg/108 cells TxB2-production). Platelets derived from megakaryocytes transfected with MRP4 small interfering ribonucleic acid have a higher aspirin entrapment and drug COX-1 activity. Platelets from CABG patients showed a high expression of MRP4 whose in vitro inhibition enhanced aspirin effect on COX-1 (349 ± 141 pg/108 cells vs. 1,670 ± 646 pg/108 cells TxB2-production).
Conclusions Aspirin is a substrate for MRP4 and can be extruded from platelet through its transportation. Aspirin effect on COX-1 is little-related to MRP4-mediated aspirin transport in HV, but in CABG patients with MRP4 over-expression, its pharmacological inhibition enhances aspirin action in an efficient way.
This work was supported by a grant from Italian Ministry of Education, University and Scientific Research (MIUR), PRIN project 2004 to FMP, and approximately 60% from Ateneo 2006 to 2007 to FMP. All authors have reported that they have no relationships to disclose. Drs. Mattiello and Guerriero contributed equally to this work.
- Received February 10, 2011.
- Revision received March 18, 2011.
- Accepted March 22, 2011.
- American College of Cardiology Foundation