Granulocyte-macrophage Colony Stimulating Factor Protects Against Radiation-induced Lung Injury

BackgroudRadiation-induced lung injury(RILI),which is a common complication of thoracic cancer radiation therapy,has great impact on long term quality of life and could result in a lethal disorder.However,the exact molecular mechanism remains unknown,and there is no effective treatment method clinically.The growth factor granulocyte and macrophage colonystimulating factor(GM-CSF)is widely recognized to promote proliferation,differentiation,and activation of monocytes,granulocytes,macrophages,and DCs in vivo and plays an important role in immunity.Here,this present study was aimed to determine whether the application of Granulocyte-macrophage colony stimulating factor(GM-CSF)would protect from the development of RILI.ObjectiveThe objective of the study is to establish mice model of radiation-induced lung injury efficiently and explore for the field of radiation-induced lung injury.The purpose is to investigate the roles of GM-CSF in the process of radiation induced lung injury.The treatment of GM-CSF could significantly improve outcomes variety of inflammatory diseases.This study is to investigate the protection of GM-SCF on radiation-induced lung injuries in mice.MethodsA total of 210 mice(C57BL/6 and GM-CSF deficient mice)were randomly divided into six groups:(1)Control group of C57BL/6,(2)Radiation group of C57BL/6,(3)Radiation + GM-CSF group of C57BL/6,(4)Control group of GM-CSF deficient,(5)Radiation group of GM-CSF deficient.(6)Radiation+GM-CSF group of GM-CSF deficient(n=35).RILI was induced by a single fractions of 16-Gy photons of radiation targeted to the whole thorax in both wild-type C57BL/6 mice and GM-CSF-deficient mice.Lung tissues were taken out from mice which were sacrificed after 1,3,6,10,20 weeks postirradiation by linear accelerator in different groups.The results of HE and Masson showed that the collagen deposition were observed in lung tissues under the microscope.Hydroxyproline content was measured by alkaline hydrolysis to evaluate collagen deposition.Mice were sacrificed for molecular biology or histological examination at observed time.The expression of inflammatory cytokines,EMT-related and fibrosis-related markers m RNA were quantitatively detected by real-time PCR.In addition,EMT-related and fibrosis-related markers protein levels in lung tissues were detected by Western blot and Immunohistochemistry staining.A total of 41 patients(28 men and 13 women),who were received definitive thoracic radiation with lung and esophagus primary malignant tumors in Qianfoshan Hospital Affiliated to Shandong University,Shandong University,between May 2015 to January 2018,including 21(51.22%)in the LC(Lung cancer)group and 20(48.78%)in the EC(Esophagus cancer)group.Clinical symptom of cough,fever,dyspnea,chest pain,the changes of lung injury degree grading and CT imaging changes before and after treatment,the data were compared and analyzed by SPSS.Resluts1.After the mice were irradiated,a series of pathological changes including exudative,proliferative and fibrosis stage were occurred in lung tissue.The HE stained of lung tissues showed mainly alveolitis performance: alveolar congestion,alveolar wall thickening,interstitial pulmonary edema and inflammatory cell infiltration,telangiectasia at 10 weeks.The Masson stained results showed that fibrotic lessions is more obvious at 20 weeks in WT mice after radiation.2.the degree of radiation-induced initial pulmonary inflammation and pulmonary fibrosis was much more severe in GM-CSF-deficient mice than in wild-type mice.The results showed that late RILI was alleviated by GM-CSF treatment in both wild-type C57BL/6 mice and GM-CSF-deficient mice,possibly through the role of anti-inflammatory the suppression of epithelial‐to‐mesenchymal transition(EMT)marker expression.3.The analysis of clinicopathologic characteristics from patients was also provided to support the anti-inflammatory role of GM-CSF treatment(P<0.05).ConclusionThe whole chest of C57BL/6 mice and GM-CSF deficient mice were irradiated by16 Gy dose of linear accelerator.A model of radiation-induced lung injury was successfully constructed to further study to provide the basis for research on the mechanisms.Based on histological examination,intraperitoneally administered GM-CSF during the phase of radiation injury not only significantly inhibited pro-fibrotic mediators,the mesenchymal markers and fibrosis markers,but also preserved epithelial markers expression after irradiation‐induced injury of the lungs.Our data also showed that GM-CSF attenuated radiation-induced lung injury through inhibiting epithelial-mesenchymal transition,suggesting GM-CSF as a novel potential radioprotector for RILI.