Ghobadi Alireza, Shirazi Alireza, Najafi Masoud, Kahkesh Masoud Heidari, Rezapoor Saeed
Department of Radiology, School of Paramedical, Tehran University of Medical Sciences, Tehran.
Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran.
J Med Phys. 2017 Oct-Dec;42(4):241-244. doi: 10.4103/jmp.JMP_60_17.
Radiation causes damage to irradiated tissues and also tissues that do not receive direct irradiation through a phenomenon called out-of-field effects. This damage through signals such as inflammatory responses can be transmitted to unirradiated cells/tissues and causes many effects such as oxidative damage. The radioprotective and anti-inflammatory effects of melatonin have been demonstrated in various studies. The aim of this study was to evaluate the effect of pretreatment with melatonin on oxidative damage caused by direct irradiation and out-of-field effects on the lung tissue after pelvic irradiation in rats.
In this experimental study, 42 adult male Wistar albino rats were divided into seven groups (six rats per group) including control, melatonin treatment, localized irradiation to the pelvis (out-of-field group), whole-body scatter group (which gave radiation dose equal to the amount of radiation that the lung had received from the localized pelvic irradiation), direct irradiation to lung, melatonin administration before localized radiation to the pelvis, and melatonin administration before localized radiation to the lung. A 100 mg/kg of melatonin 30 min before irradiation with 5 Gy γ-rays in a local (3.75 cm × 3.75 cm) field to the lower abdomen was administered to the rats, and after 24 h, all rats were sacrificed and their lungs were excised to measure the biochemical parameters including malondialdehyde (MDA), glutathione peroxidase (GPx), and superoxide dismutase (SOD).
The results showed that localized irradiation to the lung or pelvis caused an increase in the MDA level. Moreover, pelvis and lung irradiation increased the GPx and SOD activity in the lungs. Pretreatment with melatonin before irradiation reduced the GPx and MDA levels in both targeted and nontargeted lung tissues and reduced the SOD activity after lung irradiation.
Although pretreatment with melatonin did not increase the activity of SOD and GPx in comparison to the radiation groups, this study showed that preadministration of melatonin can ameliorate the oxidative damage induced by ionizing radiation.
辐射会对受照射组织造成损伤，同时也会通过一种称为野外效应的现象对未接受直接照射的组织造成损伤。这种通过炎症反应等信号产生的损伤可传递至未受照射的细胞/组织，并引发氧化损伤等多种效应。褪黑素的辐射防护和抗炎作用已在多项研究中得到证实。本研究的目的是评估褪黑素预处理对大鼠盆腔照射后肺组织直接照射及野外效应所致氧化损伤的影响。
在本实验研究中，42只成年雄性Wistar白化大鼠被分为七组（每组6只），包括对照组、褪黑素治疗组、盆腔局部照射组（野外组）、全身散射组（给予的辐射剂量等于肺部从盆腔局部照射所接受的辐射量）、肺部直接照射组、盆腔局部照射前给予褪黑素组以及肺部局部照射前给予褪黑素组。在对大鼠下腹部局部（3.75 cm×3.75 cm）区域进行5 Gyγ射线照射前30分钟，给大鼠注射100 mg/kg褪黑素，24小时后，处死所有大鼠并切除其肺脏，以测量包括丙二醛（MDA）、谷胱甘肽过氧化物酶（GPx）和超氧化物歧化酶（SOD）在内的生化参数。
结果表明，肺部或盆腔局部照射导致MDA水平升高。此外，盆腔和肺部照射增加了肺组织中GPx和SOD的活性。照射前用褪黑素预处理可降低目标和非目标肺组织中的GPx和MDA水平，并降低肺部照射后的SOD活性。
虽然与辐射组相比，褪黑素预处理并未增加SOD和GPx的活性，但本研究表明，预先给予褪黑素可减轻电离辐射所致的氧化损伤。
