Effect of ionizing radiation on the expression of p16, cyclinD1 and CDK4 in mouse thymocytes and splenocytes.
OBJECTIVE
To investigate the effect of ionizing radiation on the expression of p16, CyclinD1, and CDK4 in mouse thymocytes and splenocytes.


METHODS
Fluorescent staining and flow cytometry analysis were employed for the measurement of protein expression.


RESULTS
In time course experiments, it was found that the expression of p16 protein was significantly increased at 8, 24, and 48 h for thymocytes (P < 0.05, P < 0.01, and P < 0.05, respectively) and at 24 h for splenocytes (P < 0.05) after whole body irradiation (WBI) with 2.0 Gy X-rays. However, the expression of CDK4 protein was significantly decreased from 8 h to 24 h for thymocytes (P < 0.05-P < 0.01) and from 8 h to 72 h for splenocytes (P < 0.05-P < 0.01). In dose effect experiments, it was found that the expression of p16 protein in thymocytes and splenocytes was significantly increased at 24 h after WBI with 1.0, 2.0, and 4.0 Gy (P < 0.05-P < 0.01), whereas the expression of CDK4 protein was significantly decreased with 2.0 Gy for thymocytes (P < 0.05) and 0.5-6.0 Gy for splenocytes (P < 0.05-P < 0.01). Results also showed that the expression of CyclinD1 protein decreased markedly in both thymocytes and splenocytes after exposure.


CONCLUSIONS
The results indicate that the expression of p16 protein in thymocytes and splenocytes can be induced by ionizing radiation, and the p16-CyclinD1/CDK4 pathway may play an important role for G1 arrest of thymocytes induced by X-rays.
Department of Radiation Biology, Medical Center in Memorial of Norman Bethune, Jilin University, Changchun 130021, China.
Gui-Zhi
GZ
Ju
Xiao-Mei
XM
Wang
Shi-Bo
SB
Fu
Shu-Zheng
SZ
Liu
D000818:Animals; D019938:Cyclin D1 / Q000096:biosynthesis*; D051358:Cyclin-Dependent Kinase 4; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000096:biosynthesis*; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis*; D004307:Dose-Response Relationship, Radiation; D005434:Flow Cytometry; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D011518:Proto-Oncogene Proteins; D011829:Radiation Dosage; D013154:Spleen / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D013950:Thymus Gland / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D014965:X-Rays
D019941:Cyclin-Dependent Kinase Inhibitor p16; D011518:Proto-Oncogene Proteins; D019938:Cyclin D1; C495902:Cdk4 protein, mouse; D051358:Cyclin-Dependent Kinase 4; D018844:Cyclin-Dependent Kinases