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Early molecular changes in irradiated aortic endothelium
C Gajdusek1, K Onoda, S London
1Department of Neurological Surgery, University of Washington, Seattle, WA, USA.
Journal of Cellular Physiology
|May 31, 2001
Summary
Ionizing radiation (IR) triggers DNA damage and apoptosis in aortic endothelial cells (EC). This study details the molecular pathways, including p53 and caspase activation, involved in radiation-induced EC responses.
Area of Science:
- Cell Biology
- Radiation Biology
- Molecular Biology
Background:
- Ionizing radiation (IR) induces significant cellular responses in aortic endothelial cells (EC).
- The precise molecular mechanisms underlying these radiation-induced effects remain incompletely understood.
- Characterizing these pathways is crucial for understanding radiation damage and developing protective strategies.
Purpose of the Study:
- To elucidate the molecular basis of endothelial cell (EC) responses to ionizing radiation (IR).
- To investigate the dose- and time-dependent molecular events following gamma radiation exposure in aortic EC.
- To identify key proteins and pathways involved in radiation-induced EC growth inhibition, apoptosis, and senescence.
Main Methods:
- Exposure of cultured bovine and rat aortic endothelial cells (EC) to varying doses of gamma radiation (0-30 Gy).
- Analysis of DNA strand breaks, cell growth inhibition, and morphological changes post-irradiation.
- Western blot analysis for protein expression (p53, gadd45, p21, bax, PARP, lamin B) and Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) for mRNA levels.
- Assessment of caspase activation, DNA fragmentation (TUNEL), and protease inhibitor effects (zVAD).
Main Results:
- IR induced dose-dependent DNA strand breaks, repaired within 30 minutes.
- Cell growth inhibition occurred at doses >1 Gy, with apoptosis and cell detachment observed at doses >2.5 Gy.
- Expression of p53, gadd45, p21, and bax proteins increased dose- and time-dependently; p53 peaked at 3h, others at 6h.
- gadd45 mRNA increased post-IR, unlike p53 mRNA.
- Caspase activation, evidenced by PARP and lamin B cleavage, peaked at 15h, correlating with apoptosis markers.
- The protease inhibitor zVAD attenuated radiation-induced EC damage and apoptosis.
Conclusions:
- Gamma radiation initiates a dose- and time-dependent cascade of events in aortic endothelial cells (EC).
- These events include growth arrest, apoptosis, and potentially premature senescence in surviving cells.
- The study highlights the roles of p53, gadd45, p21, bax, and caspase activation in mediating radiation responses in EC.