Prevention Study Of Radiation-induced Lung Injury

ObjectiveRadiation-induced pulmonary injury, a frequent complication of pulmonary radiation therapy for lung cancer, is usually unavoidable and is associated with a very poor prognosis. Since lesion progression is often irreversible and can lead to fatal respiratory failure Therefore, strategies to prevent and/or ameliorate radiation-induced lung injury could be beneficial both in the clinical setting and in the event of accidental radiation exposure. In this study, we will observed the effect of ulinastatin on radiation-induced lung injury caused by the linear accelerator in SD rats in order to find a novel way to prevent radiation-induced pulmonary interstitial pneumonia and interstitial fibrosis. This study divided into two parts: 1. Establish the model of radiation-induced lung injury on SD rats by Linear accelerator; 2. Effect of pretreatment with high-dose ulinastatin in preventing radiation-induced pulmonary injury in rats; 3. Effect of Recombinant Human Tumor NecrosisFactor-O Receptor (rhTNFR:Fc) on tumor necrosis factor in rats with radiation-induced lung injury. This research is clinical foundation research, which will have great value to benefit both military medicine and civilian medicine.Methods1. Rats were restrained in custom-built apparatuses and were anesthetized by i.p. injection of pentobarbital (40mg/kg, Sigma, USA). Their heads and abdomens were protected from irradiation by lead, and the indicated dose distribution was achieved by placing a 23-mm thick wax block above their chests. Irradiation was performed with a linear accelerator producing 6 MV photons (Siemens, Germany) at a focus-to-surface distance of 100 cm. Radiation was delivered at a single dose of 20 Gy (2.5 Gy/min) with a field size of 4.5 cm×4.5 cm.2. In ulinastatin treatment exprement, rats were randomized into five groups. Group R (negative control; 60 rats) received i.v. intraperitoneal saline injections, in lieu of ulinastatin, pre- and post-irradiation. Groups P1 and P2 (45 rats each) were treated with ulinastatin (Miraclid, Mochida Pharmaceutical, Japan) for 3 d pre- and 4 d post-irradiation at the pre-determined high (400,000 U/kg body weight/d) or low (200,000 U/kg body weight/d) dose, respectively. Groups A1 and A2 (45 rats each) were treated post-irradiation for 7 days with high or low dose ulinastatin, respectively.3. In rhTNFR:Fc treatment erprement, rats were randomized into three groups: group R (negative control) received radiation and i.v. intraperitoneal saline injections, group C (normal control) only received i.v. intraperitoneal saline injections, group Y (treatment control) received radiation and rhTNFR:Fc at a dose of 5mg?kg-1 twice in first week while rats in control group and irradiation group were injected with the same volume of saline. 4. Observed rats and record the mortality of each group rats after radiation; bronchoalveolar lavage fluid was centrifuged at 360×g for 10 min, and the supernatant used for the measurement of TGF-β1 was stored at ?70°C. Two milliliters of blood were obtained by cardiac puncture, collected on ice using EDTA, and centrifuged to test IL-6,TGF-β,LN,Hyp; A piece of lung tissue was and stored at ?70°C until further processing stained with hematoxylin-eosin or Masson's trichrome to observe the general pathological changes of the lung tissue and collagen fibrils; Immunohistochemical analysis of TGF-βand TNF-α.; Western blot analysis of TGF-βand TNF-α.Results1. Rats in each group suffered different degrees of radiation injury after irradiation. The levels of TGF-β, IL-6 and TNF-αin serum,BLAF and lung tissue were gradually increased which is related to the severity of lung injury, especially the simple radiation group, which suggested that IL-6 and TNF-αand TGF-βplay an important role in radiation-induced pulmonary injury.2. The levels of TGF-β,IL-6 and TNF-αand the severity of radiation-induced lung injury and radiation-induced pulmonary fibrosis in treatment groups were significantly lower than in irradiation group, which means that ulinastatin could prevent radiation-induced lung injury effectively by inhibiting TGF-β, IL-6 and TNF-α.3. After irradiation,pretreatment of high-dose ulinastatin could inhibit TGF-β, IL-6 and TNF-αlevel more effectively than other groups while the lighter severity of radiation-induced lung injury, which was according to the reports that the TGF-β, IL-6 and TNF -αlevel could reflect the degree of radiation-induced pulmonary injury; levels of LN and Hyp in rats of pretreatment of high-dose ulinastatin decreased significantly compared with other treatment groups at 24 weeks after irradiation.4. Expression of TNF-αand IL-6 in rats treated with rhTNFR:Fc decreased significantly compared with rats only accepted radiation.ConclusionsUlinastatin especially pretreatment of high-dose ulinastatin and rhTNFR:Fc can prevent radiation-induced pulmonary injury and fibrosis effectively which provides a novle way to treat radiation-induced pulmonary injury.