Rapamycin induces heme oxygenase-1 in human pulmonary vascular cells: implications in the antiproliferative response to rapamycin.
BACKGROUND
Rapamycin is an immunosuppressive agent with antiproliferative properties against not only lymphocytes but also vascular endothelial and smooth muscle cells, and it reduces the fibroproliferative response to vascular injury. Heme oxygenase-1 (HO-1) has also been shown to have graft protective effects and to inhibit vascular remodeling. In this study, we evaluated whether there is an interaction between rapamycin and HO-1.


RESULTS
In human pulmonary artery endothelial or smooth muscle cells, HO-1 expression was evaluated in response to rapamycin or wortmannin, an inhibitor of the upstream modulator of mammalian target of rapamycin (mTOR) PI-3K. We also evaluated whether the inhibitory actions of rapamycin on platelet-derived growth factor-dependent proliferation was mediated by HO using the chemical inhibitor tin protoporphyrin. Rapamycin induced HO-1 expression in both pulmonary endothelial and smooth muscle cells, whereas no to little increase was seen in response to another immunosuppressive agent, cyclosporin A. HO-1 expression was also increased in response to wortmannin, suggesting that the PI-3K-mTOR pathway is required for this induction. Inhibition of HO activity resulted in a loss of the antiproliferative activity of rapamycin in growth factor-stimulated smooth muscle cells.


CONCLUSIONS
The induction of HO-1 expression by rapamycin and, more importantly, the effects of tin protoporphyrin, an inhibitor of HO activity, on the antiproliferative actions of rapamycin suggest that the effects of rapamycin may be, at least in part, modulated by its actions on HO-1.
Visner
Gary A
GA
Department of Pediatrics, College of Medicine, University of Florida, Gainesville 32610, USA. visnega@peds.ufl.edu
Lu
Fuhua
F
Zhou
Hailan
H
Liu
Jun
J
Kazemfar
Kristy
K
Agarwal
Anupam
A
D000730:Androstadienes / Q000494:pharmacology; D015152:Blotting, Northern; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008565:Membrane Proteins; D008665:Metalloporphyrins / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000378:metabolism; D011524:Protoporphyrins / Q000494:pharmacology; D011651:Pulmonary Artery / Q000166:cytology / Q000201:enzymology*; D012333:RNA, Messenger / Q000378:metabolism; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases; D000077191:Wortmannin
D000730:Androstadienes; D004791:Enzyme Inhibitors; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D007166:Immunosuppressive Agents; D008565:Membrane Proteins; D008665:Metalloporphyrins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases; D011524:Protoporphyrins; D012333:RNA, Messenger; D020123:Sirolimus; D058570:TOR Serine-Threonine Kinases; D000077191:Wortmannin; C032628:tin protoporphyrin IX; C496541:HMOX1 protein, human; C546842:MTOR protein, human