The Study Of Radiation-Induced Changes Of Mitochondrial Genes In Mice And Biological Behaviours Of NPC Cells

Part one:Valsartan inhibiting NPC cell line CNE-2 proliferation and invasion and promoting its sensitivity to radiationObjectives:To investigate the effects of Angiotensin II and valsartan, an Angiotensinâ…¡type 1 receptor (AT1R) blocker, combined with y-radiation on VEGF expression, radiosensitivity, invasive potential, and proliferation activity of nasopharyngeal carcinoma (CNE-2) in vitro.Methods:RT-PCR and ELISA assayed VEGF expression and secretion in CNE-2 in vitro. Radiosensitization of valsartan on CNE-2 cell in vitro was investigated by a colony forming assay. Effect of AT1R blocker combined with radiation on invasive potential of CNE-2 cell was evaluated using 24 well Matrigel invasion chambers (Transwell). Apoptosis-inducing effect of valsartan combined with irradiation on apoptosis of CNE-2 was identified by flowcytometry (FCM)Results:AT1R was expressed in nasopharyngeal carcinoma cell lines CNE-1 and CNE-2. The expression and secretion of VEGF in CNE-2 could be induced either by Angiotensin II or y-radiation. Furthermore, the suppression of AT1R activation reduced cellular proliferation, invasive potential and resistance to y-radiation in nasopharyngeal carcinoma cells.Conclusion:AT1R plays a significant role not only in proliferation and invasion, but also in radiation resistance in nasopharyngeal carcinoma cells, the mechanism of which may be involved in the regulation of VEGF expression and secretion. Part two:Radiation-Induced Mitochondrial Genes Changes in MiceObjectives:To investigate the effects of radiation on the mice mitochondrial genome in vivo.Methods:Paraffin tissues were selected from mice that whole body exposed to gamma or neutron radiation, similar total dose (550 cGy) and 3 levels of dose rates and fractions were set up. Fresh mice tissues were got from normal mice at 24 hours after 5Gy gamma radiation. Absolute quantification of Realtime-PCR was used to assay the mitochondrial-encoded mitochondrial genes COX1, ND1, MTATP6 and ATPCYB while corresponding nucleus-encoded mitochondrial genes COX6B, NDUFV1, ATP5A1 and CYB5B also were tested. The ratios of each pairgenes were calculated finally.Results:Different tissues have different response to radiation in paraffin tissues from mice. Neutron radiation can bring worse effect than gamma radiation and mtDNA gene copy number decreased other than increased that showed in gamma radiation group. Just one fraction gamma radiation can significantly increase the mtDNA gene copy number in spleen, heart and kidney. Similar results were observed in fresh mice experiment. Besides radiation, kinds of disease and age of death of mice can also influence the mtDNA gene copy number in all tested tissues.Conclusion:mitochondrial DNA gene copy number was varied under radiation, different age of death and disease with tissue specificity. Just acute gamma radiation showed significant effects which may be involved in the mtDNA genome replication and repair mechanism.