ABSTRACT
Liver tissue interstitial fluid (TIF) a special microenvironment around liver cells, which may play a vital role in cell communication during liver injury. Moreover, toll-like receptor 4 (TLR4) is an important trigger of the immune response that may also play a role in liver injuries, including radiation-induced liver disease (RILD). Therefore, the purpose of this study was to identify the roles of the TLR4-dependent immune response and TIFs in RILD after radiation therapy (RT) for liver cancer. This study consisted of two phases, and in the primary phase, the livers of TLR4 mutant (TLR4(-)) and normal (TLR4(+)) mice were irradiated with 30 Gy. TIF was then obtained from mouse livers and assessed by cytokine array analysis 20 days after irradiation, and cytokines in the TIFs, TLR4 and RILD were analyzed. In the second or validation phase, hepatocytes were isolated from TLR4(+) or TLR4(-) mice irradiated with 8 Gy and were co-cultured with TIFs from mouse livers, apoptosis of the hepatocytes was then measured using flow cytometry. We found that severe RILD was accompanied by higher expression of granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and vascular endothelial growth factor receptor 2(VEGFR-2) in liver TIFs, from in TLR4(+) mice compared with TLR4(-) mice (P < 0.05). In both TLR4(+) and TLR4(-) hepatocytes, apoptosis after irradiaton was increased significantly after co-culture in TIFs from TLR4(+) mice that had their livers irradiated, compared with TIFs from TLR4(-) mice that had their livers irradiated or TIFs from unirradiated mice (P < 0.05). In summary, these findings indicate that the TLR4-dependent immune response may promote RILD by enhancing the expression of GM-CSF, VEGFR-2 and TRAIL in liver TIFs.
Subject(s)
Liver Neoplasms/radiotherapy , Liver/pathology , Liver/radiation effects , Radiation Injuries, Experimental/immunology , Radiation Injuries, Experimental/pathology , Toll-Like Receptor 4/metabolism , Tumor Microenvironment/radiation effects , Animals , Cytokines/metabolism , Gene Expression Regulation/immunology , Gene Expression Regulation/radiation effects , Hepatocytes/metabolism , Hepatocytes/pathology , Hepatocytes/radiation effects , Liver/metabolism , Male , Mice , Mutation , Radiation Injuries, Experimental/genetics , Radiation Injuries, Experimental/metabolism , Radiation Tolerance/immunology , Radiation Tolerance/radiation effects , Toll-Like Receptor 4/geneticsABSTRACT
Objective: To investigate the changes of radiosensitivity and the expression of cyclooxygenase 2 (COX-2) in the surviving progeny from the irradiated human glioma SHG-44 cells and to provide a theoretical basis for application of COX-2 inhibitors in clinic. Methods: Radiosensitivity of mother SHG-44 cells and that of surviving progeny from the irradiated human glioma SHG-44 cells were studied by measuring the colony-forming rate. The mRNA transcription and protein expression of COX-2 were detected by RT-PCR and immunohistochemical staining, respectively. Results: The radiosensitivity was decreased and the mRNA and protein expressions of COX-2 increased in the surviving progeny of the irradiated SHG-44 cells compared with mother SHG-44 cells. The expression levels of COX-2 were negatively correlated with the radiosensitivity in the irradiated SHG-44 cells. Conclusion: Radiation induced upregulation of COX-2 expression and downregulation of the radiosensitivity in the the surviving progeny from the irradiated human glioma SHG-44 cells. The elevated expression of COX-2 may be one of the reasons for the radioresistance of irradiated SHG-44 cells.
