Korean Circ J.  2001 Jan;31(1):63-73. 10.4070/kcj.2001.31.1.63.

The effects of gamma-radiation on cyclin-dependent kinases and their inhibitors in cultured vascular smooth muscle cells

• Zo JH

• KMID: 2029537
• DOI: http://doi.org/10.4070/kcj.2001.31.1.63

Abstract

BACKGROUND: In spite of the clinical introduction of brachytherapy to reduce restenosis, the biologic responses of vascular smooth muscle cells(VSMCs) to radiation have not been well studied. We investigated the effects and mechanisms of gamma-irradiation on the cell cycle of VSMCs using primary cultures of rat aortic VSMCs and 137Cs as a radiation source.
METHODS
& RESULTS: The cell counts after irradiation with 0, 2, 8, 16 Gray (Gy) (n=, each) were 3.28, 2.34, 1.94 and 1.30 x 105/ml at 24h, and 5.10, 2.00, 1.80 and 1.20 x 105/ml at 48h, respectively. The proportions of cells in the G0/G1, S and G2/M phases, as measured by Fluorescence Activated Cell Sorter, were 61, 9 and 30% at 12 hours after 16Gy radiation (control 61, 34 and 5%), 65, 9 and 26% at 24 hours (control 70, 16 and 14%); and 67, 7 and 26% (control 78, 12 and 10%) at 48 hours, which demonstrated G1 and G2 arrest. By immunoblot analysis and kinase assay, gamma-irradiation with 8 or 16 Gy increased the expression of p21, universal cell cycle inhibitor, and decreased the expression and activity of CDK2, an important kinase during the later stages of G1/S progression, as well as the expression and activity of CDK1, which is important in the G2/M phase transition. In contrast, radiation did not affect the expression or activity of either CDK4 or CDK6. The cell-cycle inhibitors, p27 and p16 were not involved in the radiation-induced cell cycle arrest of VSMCs.
CONCLUSION
Gamma-irradiation can effectively inhibit VSMC proliferation because it causes cell cycle arrest at both the G1 phase by enhancing P21 expression and suppressing CDK2, and at the G2/M phase by suppressing CDK1.

MeSH Terms

Animals
Brachytherapy
Cell Count
Cell Cycle
Cell Cycle Checkpoints
Cyclin-Dependent Kinases*
Fluorescence
G1 Phase
Muscle, Smooth, Vascular*
Phase Transition
Phosphotransferases
Rats
Cyclin-Dependent Kinases
Phosphotransferases