Role of prokaryotic pprI gene in protecting BALB/c mice from acute radiation injury

Abstract

Objective To investigate the radioresistant effects of pprI gene of Deinococcus radiodurans on BALB/c mice. Methods Male BALB/c mice in SPF level were applied for this work. The pEGFP-c1 plasmid and pEGFP-c1-pprI gene recombinant plasmid were transferred into anterolateral muscle of mice with in vivo electroporation technology. The mice were irradiated by 6 Gy 60Co γ-rays in whole body and the mortality of mice was observed within 30 days after irradiation. In addition, the mouse were irradiated with 4 Gy γ-rays and then the peripheral blood cell number, apoptosis rates of thymocyte cells, spleen cells and bone marrow cells were observed in the days of 1, 7, 14, 28 and 35 after irradiation while the histopathological changes of lung and testis were observed in the days 7 and 28 after γ-ray irradiation. Results The highest gene transfection efficiency of muscle cells was obtained in a Plasmid injection amount of 50 μg/50 μl and electric field strength of 200 V/cm. The acute radiation mortality of pEGFP-c1-pprI gene recombinant plasmid transfer group was 30%, lower than that of irradiation group (60.0%) and pEGFP-c1 plasmid transfer group (63.3%) after 6 Gy γ-ray irradiation(χ2=4.90, 6.24, P<0.05). Compared with the irradiation group and pEGFP-c1 plasmid transfer group, the WBC count of pEGFP-c1-pprI gene recombinant plasmid group in peripheral blood of mice was significantly higher in the days of 1, 7, 14 and 28 (F=16.26, 8.10, 6.37, 10.74, P<0.05), PLT count was significantly higher in days of 7 and 14 (F=7.36, 5.71, P<0.05), meanwhile the lymphocyte percentage was increased significantly on the 7th day (F=18.43, P<0.05) after irradiation. On the other hand, the apoptosis rates of thymocyte cells and bone marrow cells were significantly decreased in the days of 1, 7, 14, 28 and 35 (F=3.88, 14.91, 14.14, 39.86, 5.65, P<0.05 and F=53.70, 11.75, 21.78, 41.40, 4.54, P<0.05) while the apoptosis rate of spleen cells was significantly decreased in the days of 1, 7, 14 and 28 (F=97.95, 56.61, 33.55, 14.71, P<0.05) after irradiation. Finally, the radiation histopathological changes of lung and testis of the pEGFP-c1-pprI gene recombinant plasmid group were slight and easy to recover. Conclusions Transfection of pprI gene of Deinococcus radiodurans by in vivo electroporation has significant protective effect on the acute radiation injury in BALB/c mice, which may have important clinical applications. Key words: Deinococcus radiodurans; pprI gene; BABL/c mice; In vivo electroporation; Acute radiation injury