Irradiation Induced DNA Double Strands Break And Long-term Defects In Human Nasal Epithelial Cells

Background:Nasopharyngeal carcinoma(NPC)is a common malignant head and neck cancer with high incidence in Southern China and Southeast Asia.Radiotherapy(RT)is the mainstay of NPC treatment,and intensity-modulated radiotherapy(IMRT)serves as the first choice of NPC management.Despite the advanced effectiveness,many patients who received RT as treatment of NPC suffered from bothersome RT-related nasal symptoms,such as mucositis,xerostomia,and sinusitis.Radiation-induced sinusitis is one of the inevitable complications in patients post-RT,and the mechanism remains poorly understood.Irradiation not only kills tumor cells but also impair normal tissue.The nasal turbinate would be exposed to about 2Gy radiation during treatment,which may result in DNA double-strand break(DSB).DSB is a lethal cellular lesion,failure to restore the chromosome structure can initiate genomic instability and negatively affect cell survival.After DSB happened,H2AX,one of the histone H2A family,phosphorylated into y-H2AX and was recruited at the DSB sites,and the nuclear yH2AX foci represent the initiation of the DNA damage response(DDR).Figure out the mechanism of DSB induced long-term defects in nasal epithelial would shed new light on the prevention or treatment of RT-induced sinusitis.Method:We cultured human nasal epithelial cells(hNECs)on the air-liquid interface(ALI)and exposed them to single or repeated low dose γ-irradiation(1Gy).Immunofluorescence and Western blotting were performed to observe the DNA double strand break(DSB)and its repair progress.Then we evaluated the cellular function of fully differentiated hNECs to investigate the long-term effect of irradiation.Result:Low-dose γ-irradiation can induce DSB in hNECs and can be repaired over time.In the repeated irradiated group,we observed a lower percentage of Ki67+and p63+/Krt5+ cells,loss of cilia and goblet cells,significantly decreased transepithelial electrical resistance(TEER),as well as excessive cytokine secretion under antiviral or antimicrobial circumstances.There was little difference between the single irradiated and control groups.Conclusion:Repeated exposure to low dose irradiation induced DSB in hNECs and resulted in poor proliferation,ciliated cells and goblet cells reduction,epithelial barrier impairment,and hyperreaction towards pathogens invasion.