N. SU; department of radiation oncology, Xijing hospital, Xian, Shaanxi, China
Purpose/Objective(s): Radiation brain injury (RBI) is a major adverse event in the treatment of head and neck tumors, affecting the quality of life for more than 50% of patients to develop radiation-induced brain injury, including cognitive impairment. Although short-term treatments have shown efficacy, no long-term treatments are available for these patients, and preventative drugs and effective drug-delivery methods must be developed. It is reported that ulinastatin exhibit the function of neuroprotective, anti-inflammatory and anti-apoptotic effects. However, it is still not clear how ulinastatin can alleviate neuroinflammation. Recently, it has been shown that brain injury can activate Notch 1 signaling. Inhibition of Notch activation contributes to reduce neuroinflammation and improves the functional outcome after brain damage. According to the above points, we hypothesize that ulinastatin-induced neuroprotection may be mediated by reducing Notch signaling activation. The aim of this study was to explore the neuroprotective effect of pretreatment with ulinastatin and the role of Notch signaling activation in this effect after RBI.Materials/
Methods: Experiment 1, the male C57BL/6 mice were randomly assigned to saline and ulinastatin groups, intravenously administered with 0.2 ml 0.9% saline or ulinastatin (300,000 U/kg) dissolved in saline 20 min before RBI. Experiment 2, an inhibitor of Notch activation, N-[N-(3,5-Difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) was used. Besides the two groups in Experiment 1, additional two group were included: DAPT group (0.03 mg/kg, right cerebral ventricle injection, 20 min before TBI, n= 6); DAPT + ulinastatin group (DAPT combine with ulinastatin, 20 min before RBI, n= 6). Experiment 3,RBP-J-/- and wild type (WT) mice were used to further elucidate the role of Notch signaling pathway in the neuroprotection of ulinastatin against RBI. RBP-J-/- and WT mice were divided into two groups (n = 6 per group) respectively: 0.9% saline, and UTI group. Results: Pretreatment with ulinastatin (300,000 U/kg) has neuroprotection against RBI, alleviating brain edema, decreasing neuronal damage and microglial activation, reducing pro-inflammatory cytokines, and improving neurological severity score (NSS). Besides, ulinastatin treatment inhibited Notch signal activation after RBI, similar to DAPT. In further study, we used DAPT and conditional RBP-J-knockout (RBP-J-/-) mice to elucidate the role of Notch signaling pathway in the neuroprotection of ulinastatin after RBI. The results showed that inhibition of Notch signaling could reduce brain damage and improve functional outcome. However, ulinastatin combined with DAPT or RBP-J-/- mice did not provide more beneficial effects than ulinastatin, DAPT or RBP-J-/- group either after RBI. Conclusion: These results suggest that ulinastatin has neuroprotective effect against RBI in mice, and inhibition of Notch activation may contribute to this neuroprotection of ulinastatin.
