title: Inhibition of plasminogen activator inhibitor-1 expression in vascular smooth muscle cells by protoporphyrins through a heme oxygenase-independent mechanism.
abstract: Heme oxygenase-1 (HO-1), a rate-limiting enzyme in heme catabolism, has been shown to play a regulatory role in the expression of plasminogen activator inhibitor-1 (PAI-1), a risk factor for vascular disease. Accordingly, we examined the effect of protoporphyrins, both HO inhibitors and activators, on PAI-1 expression in human vascular smooth muscle cells (VSMCs). Tin-protoporphyrin (SnPP) markedly inhibited the transforming growth factor beta1 (TGFbeta1)-induced expression of PAI-1 protein. Protoporphyrins, whether they are inhibitors or activators of HO, produced a similar inhibitory effect. However, SnPP had no effect on the level of PAI-1 mRNA transcripts. Knockdown of human HO-1 with a specific siRNA did not reduce the PAI-1 protein level in TGFbeta1-treated cells. In addition, the proteasome inhibitor lactacystin reversed the inhibitory effect of SnPP on PAI-1 protein expression. Both cobalt-protoporphyrin (CoPP) and CoCl2 markedly induced HO-1 expression. However, CoPP did not affect PAI-1 gene expression, whereas CoCl2 upregulated PAI-1 mRNA in a dose-dependent manner. Our results demonstrate that protoporphyrins can block the TGFbeta1-mediated induction of PAI-1 protein in VSMCs and that this inhibitory effect is independent of HO activity.
authors.affiliation: Biomolecular Science Center, University of Central Florida, 4000 Central Florida Blvd., BMSC, Bldg. 20, Room 133, Orlando, FL 32816-2364, USA. xlong@mail.ucf.edu
authors.forename: Xilin
authors.initials: X
authors.lastname: Long
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Schafer
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics* / Q000378:metabolism; D061988:Proteasome Inhibitors; D011524:Protoporphyrins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D017395:Plasminogen Activator Inhibitor 1; D061988:Proteasome Inhibitors; D011524:Protoporphyrins; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; C067713:lactacystin; C007095:cobaltiprotoporphyrin; D051547:Heme Oxygenase-1; D000111:Acetylcysteine