Ritonavir exhibits anti-atherogenic properties on vascular smooth muscle cells.
OBJECTIVE
HIV protease inhibitors (PI) such as ritonavir have dramatically decreased HIV-related morbidity and mortality. However they exhibit significant side-effects such as hyperlipidemia, hyperglycemia with or without lipodystrophy, which may increase patients' risk for atherosclerosis. Direct effects of PI on the vascular wall have not been investigated. Platelet-derived growth factor (PDGF) is a major contributor to atherogenesis.


METHODS
In the present study the effects of ritonavir on PDGF-BB-induced responses of vascular smooth muscle cells (VSMCs) were evaluated.


METHODS
PDGF-induced proliferation of VSMCs was measured by BrdU-incorporation, and chemotaxis was assessed by utilizing modified Boyden chambers. Cytotoxicity and apoptosis were quantified using LDH-release- and apoptosis-kits. Immunoprecipitation and Western blot analyses were performed to evaluate betaPDGF receptor (betaPDGFR) expression and phosphorylation, and to monitor intracellular signaling.


RESULTS
Pretreatment of VSMCs with ritonavir resulted in a significant concentration-dependent inhibition of PDGF-BB-induced cellular responses. At a therapeutic concentration (10 microg/ml), ritonavir significantly reduced PDGF-induced DNA synthesis and chemotaxis by 46.8 +/- 5.5% and 37.2 +/- 3.3%, respectively (P < 0.05 each). In addition it significantly inhibited PDGF-dependent downstream signaling, such as Erk activation. These inhibitory effects were not due to cytotoxicity or apoptosis. Instead, ritonavir inhibited the ligand-induced tyrosine phosphorylation of the betaPDGFR, whereas it did not alter betaPDGFR expression.


CONCLUSIONS
Ritonavir has direct effects on VSMCs at clinically relevant concentrations in vitro, as it inhibits betaPDGFR activation and PDGF-dependent proliferation and migration of VSMCs. Although ritonavir may increase the risk of vascular disease by its metabolic side effects, it may exhibit anti-atherogenic properties on the cellular level.
Kappert
Kai
K
Klinik III für Innere Medizin, the Abteilung für Herzchirurgie der Universität zu Köln, Joseph-Stelzmann-Str. 9, 50924 Köln, Klinik I für Innere Medizin, Germany.
Caglayan
Evren
E
Bäumer
Anselm T
AT
Südkamp
Michael
M
Fätkenheuer
Gerd
G
Rosenkranz
Stephan
S
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D000077214:Becaplermin; D002455:Cell Division / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D017320:HIV Protease Inhibitors / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects*; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D011921:Rats, Inbred WKY; D017479:Receptors, Platelet-Derived Growth Factor / Q000187:drug effects / Q000378:metabolism; D019438:Ritonavir / Q000494:pharmacology*
D017320:HIV Protease Inhibitors; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D000077214:Becaplermin; D017479:Receptors, Platelet-Derived Growth Factor; D019438:Ritonavir