Vascular smooth muscle cell (VSMC) proliferation seems to be an important factor in the development of artherosclerosis, and acetylsalicylic acid (ASA) has been demonstrated to stop this proliferation (Kodama et al. 2000). On the other hand the pleiotropic cytokine transforming growth factor β (TGF-β) shows similar properties (Blobe et al. 2000). Nevertheless its transcription is increased in high-proliferating cells (Satoh et al. 2001).

In order to assess how ASA affects TGF-β function we performed a primary cell culture of VSMC extracted from the thoracic aorta of a rat which was killed humanely with an overdose of pentobarbitone and decapitation. We studied cell proliferation in serum-free medium (PDGF-BB was added as a mitogenic stimulator). Statistical analysis was performed using Student’s unpaired t test. Data are expressed as means ± S.E.M. and P < 0.05 was considered significant. ASA inhibited cell proliferation in a dose-dependant manner at 0.5, 1 and 2 mM (78.87 ± 0.0215, 41.7 ± 0.0103 and 36.3 ± 0.0041 %, respectively). No cytoxicity was observed at these concentrations (LDH increases were not significant). Addition of 50 µg ml^-1 of monoclonal anti-TGF-β1 to 2 mM of ASA reversed this inhibition by 33.25 %, which proves ASA-mediated antiproliferative effect involves the molecule TGF-β.

In Northern blot experiments we found a decrease of TGF-β1 transcription at a dose of 2 mM ASA. In our ELISA measurements of TGF-β1 in conditioned medium we did not find a significant increase in the treated group (48 h of incubation with 2 mM ASA in a serum-free medium) compared with the control group.

Our data suggest an important role of TGF-β in ASA-mediated antiproliferative effect on VSMC.