Abstract
It is known that p53 protein expression patterns due to some stresses show different dynamics in some cultured cells over time (1). In addition, p53 protein expression patterns after whole body irradiation might also show different dynamics in some organs over time. It is important to determine p53 protein expression patterns for each organ to decide upon the end point when we estimate radiation sensitivity.
Mice (C57BL female, 7 weeks old) received whole body exposures to 8 Gy gamma rays and the expression of p53 and p21 proteins was monitored in the spleen and skin. We also monitored apoptosis to investigate its relationship to p53 protein expression.
There were biphasic peaks of p53 protein expression in the spleen. The first peak appeared 4 hours after irradiation and the second peak appeared 44 hours later. The two p53 protein expression peaks nearly corresponded to that of p21 protein expression for the same period. However, a clear peak was not shown for p53 or p21 protein in the skin. Because numerous high radiation sensitive cells are included in the spleen, these cells may respond to irradiation at the same time, and our results suggested such a response pattern. In contrast, there are few cells that respond to radiation in the skin, which precluded detecting a clear peak. Spleen cells' apoptosis was attuned to the first p53 peak and the p21 protein, but did not correspond with the second p53 peak. We considered that the first peak corresponded to the cascades of the so-called apoptosis system induced by the p53 protein, but the second peak was not associated with the apoptosis cascade.
These results suggest that the dynamics of the p53 and p21 protein expression patterns over time after whole body irradiation differ within organs.
(1) E. Batchelor, A. Loewer & G. Lahav. The ups and downs of p53: understanding protein dynamics in single cells. Nature Rev. Cancer, 9, 371-377, 2009.
