A Preliminary Study On The Molecular Mechanism Of Acute Radiation Induced Liver Damage By Cyberknife In Rabbits

Part I A rabbit radiation induced liver damage model for stereotactic body radiation therapyObjective: To evaluate the feasibility of a rabbit acute radiation induced liver damage model via Cyberknife with one single dose and the safety of fiducial implantation via ultrasound.Methods: Real-time guided with high-frequency ultrasound(ALOKA prosound F75),fiducials were implanted into the exterior portion of the right lobe of the liver of twenty rabbits having received skin preparation before operation.The virtual target volumes were irradiated with 20Gy/f if no fiducial displacement occurred.Rabbits were executed at three days and fourteen days after irradiation.Irradiated and non-irradiated tissues were harvested and stained by HE for sections.Also those sectioned tissues were observed via electron microscope.Safety of ultrasound guided fiducial implantation was evaluated by the grade of adverse effects,physical conditions including weight,vitality and food consumption.Successful implanation was defined as no fiducial displacement confirmed by CT scan.Radiation induced liver damage was clarified with pathological changes of irradiated tissues observed under microscope.Results: Fiducials were successfully implanted in 18 rabbits while implantation was failed in 2.During CT scan,fiducial displacement was found in 2 rabbits.Therefore,only16 rabbits were irradiated and the success rate of fiducial implantation was 80%.No rabbits died and no adverse effects occurred from fiducial implantation to execution.There were no significant changes regarding weight,vitality,food consumption and no radiation induced dermatitis was seen.There was no apparent pathological changes in sections stained by HE,while pathological changes of submicroscopic structures were identified via electron microscope,including nuclear condensation and chromatin margination.Typical pathological changes of radiation induced liver damage were found both under microscope and electron microscope.Conclusion: Ultrasound guided fiducial implantation was safe and feasible with high success rates.A rabbit radiation induced liver damage model could be successfully established with 20Gy/f via Cyberknife.Part II Screening of proteins with differential expressions in the rabbit radiation induced liver damage model by proteomicsObjective: To identify proteins closely related with radiation induced liver damage by comparison of the expressions of proteins in irradiated and non-irradiated tissues via proteomic.To preliminary identify the pathogenesis of radiation induced liver disease.Methods: Irradiated and non-irradiated liver tissues of rabbits executed 3 days after radiation were harvested.Six specimen were randomly collected from 3 rabbits.All proteins were collected,determined by Bradford method,enzyme-hydrolyzed and desalinated.Peptides were analyzed via 2D-Nano-LC-ESI-MS/MS.Tandem mass spectrometry was assessed in Swiss-Prot database of rabbits by SEQUEST.Proteins with2-fold changes of expressions were analyzed with database and KEGG.RNAs were collected to verified proteins screened by proteomic via RT-PCR.All proteins with differential expressions were analyzed by GO,COG and KEGG.Besides,predictions of protein-protein interactions were also performed for further identification of those proteins functions.Results: Three hundred and thirty eight proteins were identified with differential expression.Among them,217 were up-regulated and 121 were down-regulated.Significant up-regulations were found in USP47,POLR2 A,CSTB and etc.Marked down-regulations were seen in MCFD2,CAP1,CSNK2A1 and etc.Changes of expressions of m RNA encoding mentioned proteins were consistent with those of the proteins.Analysis via GO,COG and KEGG showed that 17.84% and 17.83% proteins were located in cells and cytoskeletal proteins,respectively.47.66% and 29.58%participated in conjunctions of proteins and cellular metabolism,respectively.11.98%and 10.88% were involved in cellular process and metabolic process,respectively.These proteins functions included general function prediction,posttranslational modifications and chaperones,energy production and conversion,lipid transport and metabolism.Up-regulated proteins were involved in complement and coagulation cascades,VEGF signaling pathway,MAPK signaling pathway,m TOR signaling pathway,nucleotide excision repair and etc.Down-regulated proteins were involved in adipocytokine signaling pathway,tryptophan metabolism,amino sugar and nucleotide sugar metabolism,chemokine signaling pathway,PPAR signaling pathway and etc.Prediction of protein-protein interactions revealed that the gene encoding POLR2 A ranked first among the proteins with differential expressions.Conclusion: There was a close correlation between USP47,POLR2 A and DEPTOR and pathogenesis of radiation induced liver damage,which may provide evidence for further study on radiation induced liver damage.