| Summary: | 博士 === 長庚大學 === 基礎醫學研究所 === 96 === 20-hydroxyeicosatetraenoic acid (20-HETE), a P450 arachidonic acid metabolite, is an important regulator in vascular smooth muscle cells (VSMC). In present study, we aimed to determine the mechanisms of 20-HETE-induced inhibition of cell proliferation and cyclooxygenase-2 expression in VSMC. Incubation of R22D cells, a clonal VSMC, with 20-HETE for 24 hr attenuated [3H]-thymidine incorporation without causing release of lactate dehydrogenase. 20-HETE also inhibited platelet-derived growth factor (PDGF)-induced [3H]-thymidine incorporation in R22D cells and human VSMC. Since polyunsaturated may cause release of TGF-, we asked whether 20-HETE inhibited cell proliferation by releasing of TGF- Anti-TGF-β neutralizing antibody, but not nonspecific IgG, effectively 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 enough to inhibit [3H]-thymidine incorporation without altering steady state mRNA level of TGF-β. The neointima formation induced by balloon-injured was enhanced by ABT, a P450 inhibitor which may inhibit 20-HETE production.
In addition to the effects on cell proliferation, pretreatment of 20-HETE (10 μM) significantly inhibited ATPγS-induced COX-2 mRNA and protein expression. Since 20-HETE may be a dual activator of PPAR, we asked whether 20-HETE induced inhibitory effect on COX-2 expression by activating PPAR. WY14643, a PPAR- ligand, mimicked the inhibitory effect of 20-HETE on COX-2 expression. Incubation with 20-HETE significantly increased the PPRE promoter activity suggesting that 20-HETE may be a PPAR activator. The inhibitory effect of 20-HETE on ATPγS-induced COX-2 expression was reversed by MK-886, a PPAR-α inhibitor, and by transfection of shPPAR-. In addition, ATPγS-induced COX-2 promoter activity, containing AP-1 site, was also inhibited by pretreatment of 20-HETE and was reversed by MK-886, a PPAR-α inhibitor, and by transfection of shPPAR-. Our results suggesting that 20-HETE may inhibit ATPγS-induced COX-2 expression via activation of PPAR-α. Taken together, 20-HETE may modulate the cell proliferation and inflammation of VSMC to regulate the development of cardiovascular diseases.
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