New Therapies And Mechanisms For The Prevention Of Radiation-induced Oral Mucositis

Purpose:Radiation-induced oral mucositis(ROM),marked by severe oral ulcerations,is a common adverse effect of large-dose radiation used before bone-marrow transplantation or craniofacial radiotherapy for cancer1,2.At present,the pathogenesis of ROM is still unknown.Currently,the treatment and prevention options is very limited.This paper focuses on the protective effect of FTY720 and DMSO on ROM,and the potential new measures and mechanisms was to be proposed.Methods:In the first part,The protective effect of FTY720 on ROM,and its mechanism and target research:I).mice model of rom were established by local X-ray irradiation on mice head and neck.The Protective effect of FTY720 was measured via survival rate assay,1%toluidine blue staining and HE staining,and detection of its dosage regimes and optimal effectiveness;2).the effect of FTY720 on that pathological changes of oral mucosa induced by radiation was observed at different time points after irradiation.Immunohistochemistry assay was employed to explore the protective mechanism of FTY720 on radiation-induced lesions of keratinized epithelial cells and keratinized stem cells;3).the radiosensitity of oral cancer cell lines Ca127 was measured by cloning formation assay;4).protective targets and target cells of FTY720 were verified by making use of systemic conditional knockout of S1 P1 receptor model mice(UBC-cre/ERT2;Slpr1flox/flox)and endothelial cell conditional knockout S1P1 receptor model mice(VE-cre/ERT2;S1pr1flox/flox)furtherIn the second part,the protective effect and mechanism of DMSO on ROM:1).with the first part,the Protective effect of DMSO was determined by pathological methods,and detection of its dosage regimes and Optimal effectiveness;2).the efficiency of FTY720 on DNA double-strand breaks(DSBs)of keratinized stem cells by immunohistochermstry and immunofluorescence assay.The effective groups of DMSO were determined by comparing the effects of similar structure groups.3).The impact of DMSO on the head-and-neck cancer was detected by inoculation of tumor mice.Results:In the first part:1).the mice model of ROM was successfully established.FTY720 was administered to prevent the occurrence of ROM,and the survival rate of 16.5Gy local irradiatied mice was increased to 100%by FTY720 on the day 30 post-irradiation.The protective effect of FTY720 is clear;2).the optimal dosage of FTY720 is 10mg/kg for the effective time window.However,there is no obvious protective effect on ROM when FTY720 was administrated post-irradiation;3).FTY720 could significantly promote the proliferation of keratinized epithelial cells and keratinized stem cells by the observation of ki-67 and p63 markers,which was better than the irradiated group;4).FTY720 had no radioprotective effect on tumor cells.The colony formation rate of FTY720 was significantly lower than the control group after the irradiation of OGy 3Gy,6Gy and 8Gy;5).the preventive target of FTY720 on ROM is Slprl,and the target cells may be endothelial cells.The knockout mice of UBC-cre/ERT2.S1pr1flox/flox and VE-cre/ERT2;The S1pr1flox/flox model mice were able to prevent ROM occurrence which were knocked out S1prl in the systemic cells and endothelial cells,respectively.In the second part:1).the protective effect of DMSO on ROM is clear.The optimal prophylactic administration time of FTY720 is 1h before irradiation.However,DMSO has no therapeutic effect on ROM,when it was administrated post-irradiation;2).DMSO reduced the yiled of DSBs on the keratinized stem cells.In comparion with control group,DMSO treatment demonstrated a significant protective effect on keratinized epithelial cells and keratinized stem cells at the early time points,and the expression of DSBs marker foci on the keratinized stem cells of DMSO was significantly reduced at 6h after exposure;3).the group that protects the ROM from the DMSO is the sulfoxide group.Compared DMSO with dimethyl sulfone,dimethyl sulfide,and tetramethylene sulfoxide,and only the effects of tetramethylene sulfoxide and DMSO were consistent,indicating that the effective group was the sulfone group;4).DMSO had no effect on the growth of head and neck tumors,and there was no difference on tumor growth between the DMSO and the control group with or without irradiation.Conclusion:This study illustrates the protective effect of FTY720 and DMSO on ROM.It proved that S1prl is the target of FTY720,and confirmed that endothelial cells is the effector cells initially;and the underlying mechanism of DMSO may be associated with involved the reduction of DSBs damage on the keratinized stem cells.The efficetive group for DMSO is sulfoxide.