Siegal T, Pfeffer M R, Meltzer A, Shezen E, Nimrod A, Ezov N, Ovadia H
Department of Neurology, Hadassah Hebrew University Hospital, Jerusalem, Israel.
Int J Radiat Oncol Biol Phys. 1996 Oct 1;36(3):649-59. doi: 10.1016/s0360-3016(96)00357-4.
This study aimed to investigate long-term, radiation-induced changes in microvessel permeability, the profile of the vasoactive mediators endothelin and nitric oxide, and the response of specific cell systems in the irradiated spinal cord of rats.
The thoracolumbar spinal cords of Fischer rats were irradiated to a dose of 15 Gy, and the rats were sacrificed at various times afterward. Endothelin levels and nitric oxide-synthase (NOS) activity were assayed in extracts of spinal cords. Microvascular permeability and the effect of treatment with recombinant human manganese superoxide dismutase (r-hMnSOD) were assessed quantitatively. Immunohistochemistry evaluated astrocytes, microglia, vascular basal membrane, and neurofilaments.
None of the rats developed neurologic dysfunction. Endothelin levels were significantly reduced at 18 h after irradiation and markedly attenuated after 10 days (p < 0.007). Thereafter, endothelin levels returned to normal values at 56 days after radiation and escalated to markedly high levels after 120 and 180 days (p < 0.002). NOS activity remained very low throughout the period of follow-up and failed to counterbalance the shifts in endothelin levels. Treatment with r-hMnSOD had no effect on normal vascular permeability but it abolished the abnormally increased permeability measured at 18 h after radiation and again after 120 and 180 days. Standard microscopic evaluation failed to reveal abnormalities in the irradiated spinal cord, but immunohistochemical staining showed a progressive increase in the number of microglial cells per field after 120 and 180 days (p < 0003). A similar increase in the number of astrocytic cells per field was noted after more than 180 days, but an earlier short lasting peak was also noted at 14 days after radiation. No abnormalities were found in blood vessel configuration, density, diameter, and basal membrane staining, or in the neurofilaments.
Marked imbalance in the regulatory function of endothelium-derived mediators of the vascular tone is present after radiation therapy probably inducing chronic vasoconstriction. This imbalance favors localized procoagulation that may enhance the consequent loss of function measured as increased permeability. Microglial proliferation may account for continuous release of superoxide that may enhance disruption of normal permeability. The latter is corrected by SOD treatment. Astrocytic proliferation may present a response to the mitogenic effect of endothelin and to microglial-derived paracrine effect of cytokines.
本研究旨在调查大鼠脊髓受辐射后微血管通透性的长期变化、血管活性介质内皮素和一氧化氮的变化情况，以及特定细胞系统的反应。
对Fischer大鼠的胸腰段脊髓进行15 Gy的辐射，然后在不同时间点处死大鼠。检测脊髓提取物中的内皮素水平和一氧化氮合酶（NOS）活性。定量评估微血管通透性以及重组人锰超氧化物歧化酶（r-hMnSOD）治疗的效果。免疫组织化学评估星形胶质细胞、小胶质细胞、血管基底膜和神经丝。
所有大鼠均未出现神经功能障碍。辐射后18小时内皮素水平显著降低，10天后明显减弱（p < 0.007）。此后，辐射后56天内皮素水平恢复正常，120天和180天后升至明显高水平（p < 0.002）。在整个随访期间，NOS活性一直很低，无法抵消内皮素水平的变化。r-hMnSOD治疗对正常血管通透性无影响，但可消除辐射后18小时以及120天和180天后测量到的异常增加的通透性。标准显微镜评估未发现受辐射脊髓有异常，但免疫组织化学染色显示120天和180天后每视野小胶质细胞数量逐渐增加（p < 0.003）。180天以上每视野星形胶质细胞数量也有类似增加，但辐射后14天也出现了一个较早的短暂峰值。在血管结构、密度、直径、基底膜染色或神经丝方面未发现异常。
放疗后血管张力的内皮源性介质调节功能存在明显失衡，可能导致慢性血管收缩。这种失衡有利于局部促凝，可能会增强随后以通透性增加衡量的功能丧失。小胶质细胞增殖可能导致超氧化物的持续释放，这可能会加剧正常通透性的破坏。后者可通过SOD治疗得到纠正。星形胶质细胞增殖可能是对内皮素的促有丝分裂作用以及细胞因子的小胶质细胞衍生旁分泌作用的反应。
