Characterization of the impact of kidney-centered radiotherapy in mice

Objective:
Kidney irradiation has been associated with renal ischemic preconditioning in mice, with a potential role of cell proliferation. Here, we investigate the impact of kidney-centered irradiation on the regulatory proteins involved in the p53 pathway in mice.

Methods:
Adult male C57bl/6 mice were bilaterally irradiated on both kidneys at a total dose of 8 Gy. One-month post-irradiation, the renal expression of proliferating cell nuclear antigen (PCNA) and Ki67 was quantified by immunostaining. The abundance of phospho-p53 (Ser15) (p53-pS15) and murine double minute2 (MDM2), chromatin licensing and DNA replication factor 1 (CDT-1) (particularly expressed in G1 phase) and Serine 10-phosphorylated histone H3 (p-H3) (particularly expressed in G2/M phase), was assessed by immunoblotting or immunostaining.

Results:
Irradiated kidneys were characterized by statistically increased expression of PCNA- (p<0.001) and Ki67- (p<0.05) positive cells, as well as by an activated p53 signaling evidenced by the downregulation of MDM2 (p<0.05) and the upregulation of p53-pS15 (p<0.05)). Quantification of G2/M-phase cells by p-H3 (p<0.001) revealed a significant increase following irradiation. CDT-1 expression was unchanged in irradiated versus control kidneys.

Conclusion:
Kidney-centered ionizing irradiation activates the p53 pathway. The p53-mediated G2/M cell cycle arrest may participate to cell endocycling hypertrophy in conjunction with cell proliferation.