Low dose of eicosapentaenoic acid inhibits the exaggerated growth of vascular smooth muscle cells from spontaneously hypertensive rats through suppression of transforming growth factor-beta

Objective To evaluate effects of eicosapentaenoic acid (EPA), an n-3 polyun saturated fatty acid, on the exaggerated growth of vascular smooth muscle c ells (VSMC) from spontaneously hypertensive rats (SHR). Design Cultured VSMC were prepared by an explant method from thoracic aorta s in 8-week-old male Wistar-Kyoto (WKY)/lzumo rats and SHR/lzumo. Effects o f EPA on basal DNA synthesis, expression of growth factors and cyclin-depen dent kinase 2 (cdk2) activity were examined in VSMC from WKY rats and SHR. Methods The cell cycles were synchronized with serum deprivation, then DNA synthesis in VSMC was measured by [H-3]-thymidine incorporation. Fatty acid composition of the phospholipid fraction in VSMC was measured by gas chrom atography. Expression of platelet-derived growth factor (PDGF) A-chain, tra nsforming growth factor (TGF)-beta 1and basic fibroblast growth factor (bFG F) mRNAs was evaluated by reverse-transcription and polymerase chain reacti on analysis. Cdk2 activity was determined by autoradiography after polyacry lamide gel electrophoresis of VSMC extracts that had been immunoprecipitate d with anti-cdk2 antibody and protein A sepharose, and then incubated with P-32-ATP and histone H1. Results High concentrations (40 and 80 mu mol/l) o f EPA significantly inhibited basal DNA synthesis in VSMC from both rat str ains. Low dose (20 mu mol/l) of EPA significantly inhibited basal DNA synth esis in VSMC from SHR, whereas the same dose of EPA stimulated DNA synthesi s in VSMC from WKY rats. In analysis of fatty acid composition, low dose of EPA was considerably incorporated in VSMC. Low dose of EPA significantly i nhibited angiotensin II- and phorbol ester milisterol-stimulated DNA synthe sis in VSMC from both rat strains, whereas EPA did not affect PDGF-AA-stimm ulated DNA synthesis in VSMC from either rat strain. Low dose of other poly unsaturated fatty acids such as docosahexaenoic acid, arachidonic acid and linoleic acid did not significantly affect basal DNA synthesis in VSMC from either strain. Low dose of EPA significantly inhibited expression of TGF-b eta 1 mRNA in VSMC from SHR, whereas EPA did not affect expression of PDGF A-chain and bFGF mRNAs in VSMC from SHR. Cdk2 activity in VSMC from SHR was higher than that from WKY rats. Low dose of EPA inhibited cdk2 activity in VSMC from SHR, whereas it stimulated the activity in VSMC from WKY rats. Conclusion Low dose of EPA exerted specific inhibition of the exaggerated g rowth of VSMC from SHR through the suppression of TGF-beta. J Hypertens 199 9, 17:1421 -1430 (C) Lippincott Williams & Wilkins.