Study On The Changes Of Macrophage Colony Stimulating Factor And Its Receptor In Prion Infection

Prion diseases are a variety of fatal neurodegenerative disorders,which has the ability to infect humans and numerous mammals.Typical pathological features of prion disease include neuronal loss and gliosis.Microglial activation usually induces increased secretion of a variety of cytokines during infection.Studies have shown that the expression of M-CSF is increased in the middle and late stages of prion infection.Meanwhile,M-CSF associated with various neurodegenerative diseases,but the relationship of Pr P with such specific changes of M-CSF are still unclear.To further confirm the expression levels of M-CSF in prion diseases,brain homogenates of scrapie-infected rodents were subjected to M-CSF specific Western blots.Compared with controls,the signals of M-CSF in brains of prion infected mice were markedly stronger.Prion-infected SMB cells were assessed with M-CSF specific Western blot.The results showed that the expression levels of M-CSF was elevated in SMB-S15 cells,and M-CSF interacted with Pr P were observed in the SMB cell lines.Subcellular components of cultured prion infected cells were subjected to M-CSF specific Western blot,results shown majority amounts of M-CSF presented in the factions of cytosolic and membrane,while the levels of M-CSF in SMB-S15 cells were slightly higher in fractions of cytosolic and membrane compared with controls.The potential changes of CSF1R in prion infected mice and cells were analyzed by CSF1R specific commercial ELISA and Immunofluorescent and RT-PCR.Results indicated that the levels of M-CSF in SMB-S15 cells were higher than that of SMB-PS cells,both in transcriptional and translational levels.Brain homogenates of scrapie-infected hamsters were carried out by immunoprecipitation tests.M-CSF interacted with Pr P in brain homogenates of prion infected hamsters.The signals of M-CSF and Pr P were colocalized closely by Immunofluorescent assay.The serial brain sections of scrapie infected mice were evaluated by IHC assays.Large amounts of M-CSF and Pr P^Sc specific signals at the same positions were observed in various brain regions.Morphoiogical assays revealed that M-CSF signals mainly colocalized with neurons and microglials,but not colocalize with the astrocytes.CSF1R signals mainly colocalized with neurons,but not colocalize with the astrocytes and microglias by Immunofluorescent and Immunohistochemical assay.Further,brain slides of scrapie-infected mices were subjected to IL-34 specific Immunofluorescent and Immunohistochemical assay.Results revealed that IL-34 signals mainly colocalized with neurons in normal mice,while mainly colocalized with the astrocytes and microglias after prion infection.In this study,prion infected rodent model and cells were used to explore the changes,distribution and localization of M-CSF and its receptor CSF1R after prion infection,as well as the correlation with prion,and explain the distribution of IL-34 in brain tissue after prion infected by various experimental methods.It is proved that M-CSF interacts with Pr P and may have stronger binding ability with Pr P^Sc and speculates that M-CSF might be secreted by microglia and act on neurons expressed with its receptor CSF1R.Pr P^Sc may affect the binding of M-CSF to CSF1R and thus affect its downstream functions.Prion infection reduces CSF1R expression in neurons and may acts on other receptors,such as IL-34,in astrocytes and microglias.These results may help to explain the specific molecular mechanism of M-CSF/CSF1R in prion diseases,and provide a theoretical basis for understanding the mechanism of prion diseases.