Changes Of IL-1β,TNF-α And IL-6 In Serum And Brain Following Whole-brain Irradiation In Rats

Objective: To investigate the changes of IL-1, TNF-a and IL-6 in brain and serum at various times after different radiation doses in rats and to explore the role of them in the pathogenesis of brain radiation injury.Methods: Eighty female SD rats weighing (200 20)g were randomly divided into four groups, group Irsham irradiation and anaesthesia as control group; group 2: sham irradiation; group 3:10Gy radiation group; group 4:30Gy radiation group. Group 3 and group 4 were further divided into 4 subgroups: 8-hour, 24-hour, 7-day and 1-month postirradiation groups respectively. Group 2 animals were injected with chloral hydrate and sham irradiation. The rat brain radiation injury model was established by irradiation of the rat's whole brain by the single dose of 10 and 30Gy of 4Mev electron beam generated by Philips SL-18 accelerator. To faciliate restraint, 360mg/kg chloral hydrate was administered to each rat intraperitoneally prior to irradiation. Groups of five to eight animals irradiated with lOGy and 30Gy were killed at 8h, 24h, 7d and 1 m postirradiation. Arterial blood and part of cortex samples were taken at the same time. Serum was obtained by centrifugation of blood at 3000r/min for 5minutes.The brain tissue homogenate was then centifugated at 15000r/min for 20 minutes. The supernatant were collected and stored, along with serum, at -70C until test. IL-13, TNF-a and IL-6 levels with consecutive changes in serum and brain tissue supernatant were measured by means of enzyme-linked immunosorbent assay.Results: There is no difference in serum and brain tissue supernatantlevels of IL-1 TNF-a and IL-6 between group2 and control group. Animals irradiated with 10Gy displayed mild increase in levels of IL-1 and TNF-a in serum and brain tissue supernatant at 8h postirradiation, compared with that of control group. The serum and brain tissue supernatant levels of IL-lp and TNF-a at 8h postirradiation in 30Gy group were significantly higher than those of other three groups and the other times of 30Gy group (P < 0.01).While the level of IL-6 in serum of 30Gy group was significantly decreased at 1m than that of control group (P < 0.05).There was positive relationship between serum and brain tissue supernatant IL-1 and TNF-a level.Conclusions: The initial response of the brain to irradiation involves the expression of inflammatory cytokines(IL-lp, TNF-a and IL-6), which may play an important role in brain injury after irradiation. Further studies are needed, however, for clarifying whether the altered expressions of cytokines found in the serum and brain in such a condition reflect a primary pathogenetic process, or are a secondary consequence of the radiation-induced brain injury.