Activation of intrinsic apoptotic pathway by Re-188 irradiation and paclitaxel in coronary artery smooth muscle cells.
OBJECTIVE
Intravascular brachytherapy efficiently reduces vascular smooth muscle cell (SMC) proliferation, interstitial matrix production, vascular remodeling and restenosis rate after revascularization injury of coronary arteries. In this study we examined the molecular mechanisms of the cytotoxic effect of Re-188-mediated beta-irradiation on a SMC culture model compared to that of paclitaxel.


METHODS
SMC were irradiated with 1, 3, 10 and 30 Gy with Re-188 or treated with 1, 5, 10 microg/mL paclitaxel. After 24, 48 and 72 h, cell death, apoptosis pathways and cell cycle were examined.


RESULTS
Irradiation and paclitaxel induced cell cycle arrest in G1. Dose-dependent cell death ranged from 40% at 1 Gy to 80% at 30 Gy irradiation, and induced in 45% of SMC treated with paclitaxel. Irradiation induced increasing rates of necrotic cell death up to 40% at 30 Gy. Activation of caspase-3 was detected, and poly(ADP-ribose)polymerase (PARP), the prototype substrate of caspases, was cleaved upon beta-irradiation. In addition, beta-irradiation-mediated apoptosis activated caspase-9, indicating that mitochondria were involved. Further-more, Bax was upregulated. However, upregulation of death-inducing ligands (DIL) or receptors (DIL-R) was not involved in beta-irradiation-induced apoptosis in SMC. Similar to beta-irradiation, the intrinsic mitochondrial apoptosis pathway was activated by paclitaxel.


CONCLUSIONS
These findings demonstrate that beta-irradiation and paclitaxel induced apoptosis and activated apoptosis signaling pathways in SMC at several levels by triggering intrinsic mitochondrial but not external death receptor mediated pathways.
Friesen
C
C
Department of Nuclear Medicine, University of Ulm, Ulm, Germany. claudia.friesen@uni-ulm.de
Lubatschofski
A
A
Glatting
G
G
Debatin
K M
KM
Reske
S N
SN
D017209:Apoptosis; D016923:Cell Death; D049109:Cell Proliferation; D003331:Coronary Vessels / Q000187:drug effects* / Q000473:pathology* / Q000528:radiation effects*; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D008024:Ligands; D008928:Mitochondria / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000473:pathology* / Q000528:radiation effects*; D009336:Necrosis; D017239:Paclitaxel / Q000494:pharmacology; D011868:Radioisotopes / Q000737:chemistry*; D011874:Radiometry; D012211:Rhenium / Q000737:chemistry*; D013997:Time Factors
D008024:Ligands; D011868:Radioisotopes; D012211:Rhenium; D017239:Paclitaxel