20-HETE inhibits the proliferation of vascular smooth muscle cells via transforming growth factor-β

Abstract

20-Hydroxyeicosatetraenoic acid (20-HETE), a cytochrome P450 arachidonic acid metabolite, has been shown to modulate the growth of vascular smooth muscle cells (VSMCs). We asked whether 20-HETE modulates the proliferation of R22D cells, a clonal VSMC from neonatal rats, by releasing transforming growth factor-β (TGF-β). Incubation of R22D cells with 20-HETE for 24 h attenuated [3H]thymidine incorporation in a concentration-dependent manner without causing the release of lactate dehydrogenase. 20-HETE also inhibited platelet-derived growth factor (PDGF)-induced [3H]thymidine incorporation in R22D cells and human VSMCs. At 5 μM, 20-HETE reduced [3H]thymidine incorporation by 34 ± 6%; anti-TGF-β neutralizing antibody, but not nonspecific IgG, completely reversed the attenuated [3H]thymidine incorporation induced by 20-HETE. In addition, 20-HETE attenuated fetal bovine serum- and PDGF-induced expression of cyclin D1, a downstream effector of TGF-β1, which was reversed by anti-TGF-β antibody. Further studies demonstrated that 20-HETE may increase TGF-β release to a level high enough to inhibit [3H]thymidine incorporation without altering the steady-state mRNA level of TGF-β. Nevertheless, pretreatment of indomethacin (a cyclooxygenase inhibitor) or paxilline (a potassium channel inhibitor) did not affect the inhibitory effect on DNA synthesis induced by 20-HETE. These results demonstrate for the first time a growth-inhibitory effect induced by 20-HETE, which may be mediated by TGF-β.

Keywords

• 20-hydroxyeicosatetraenoic acid
• cytochrome P450
• platelet-derived growth factor
• DNA synthesis