Serum sSelectin-L is an early specific indicator of radiation injury

Abstract

Objective: It's crucial to identify an easily detectable biomarker that is specific to radiation injury in order to effectively classify injured individuals in the early stage in large-scale nuclear accidents.

Methods: C57BL/6J mice were subjected to whole-body and partial-body γ irradiation, as well as whole-body X-ray irradiation to explore the response of serum sSelectin-L to radiation injury. Then, it was compared with its response to lipopolysaccharide-induced acute infection and doxorubicin-induced DNA damage to study the specificity of sSelectin-L response to radiation. Furthermore, it was further evaluated in serum samples from nasopharyngeal carcinoma patients before and after radiotherapy. Simulated rescue experiments using Amifostine or bone marrow transplantation were conducted in mice with acute radiation syndrome to determine the potential for establishing sSelectin-L as a prognostic marker. The levels of sSelectin-L were dynamically measured using the ELISA method.

Results: Selectin-L is mainly expressed in hematopoietic tissues and lymphatic tissues. Mouse sSelectin-L showed a dose-dependent decrease from 1 day after irradiation and exhibited a positive correlation with lymphocyte counts. Furthermore, the level of sSelectin-L reflected the degree of radiation injury in partial-body irradiation mice and in nasopharyngeal carcinoma patients. sSelectin-L was closely related to the total dose of γ or X ray. There was no significant change in the sSelectin-L levels in mice intraperitoneal injected with lipopolysaccharide or doxorubicin. The sSelectin-L was decreased slower and recovered faster than lymphocyte count in acute radiation syndrome mice treated with Amifostine or bone marrow transplantation.

Conclusions: Our study shows that sSelectin-L has the potential to be an early biomarker to classify injured individuals after radiation accidents, and to be a prognostic indicator of successful rescue of radiation victims.

Keywords: Acute radiation syndrome; Biomarker; Irradiation; sSelectin-L.

Fig. 1

Expression of Selectin-L in mouse organs before and after radiation. a. Relative expression of selectin-L mRNA in normal mouse organs. b. Concentration of Selectin-L in normal mouse organs. c. Relative expression of selectin-L mRNA in radiation sensitive organs of mice at 3 days after 2 Gy, 6.5 Gy radiated. (2 Gy Blue, 6.5 Gy Green) d. Level of selectin-L protein in radiation sensitive organs of mice at 3 days after 2 Gy, 6.5 Gy radiated. The density of Western blots was measured by gray value analysis, and all band densities were normalized to beta actin. All data is shown as mean ± SD, n = 4, *P < 0.05, **P < 0.001, ***P < 0.0001.

Fig. 2

Analysis of dose effect of serum sSelectin-L and evaluation of exposure dose in radiated mice. a. Dynamics of sSelectin-L, b. lymphocyte counts, c. the correlationship between Selectin-L and lymphocyte in radiated mice. (0 Gy black, 0.5 Gy Gy, 1 Gy orange, 2 Gy blue, 4 Gy cyan, 6.5 Gy green, 10 Gy red) d. Equation fitting was performed using the levels of serum sSelectin-L in mice after different doses of irradiation. (0 Gy cyan, 2Gy orange, 4 Gy Gy, 6.5Gy light orange, 10Gy blue) e. the formula of sSelectin-L dynamic change fitting curves. f. The dose estimation equation was fitted by sSelectin-L concentration and radiation dose at 1 day, 3 days, 7 days, 11 days and 14 days after irradiation. g. Verification of the dose estimation equation. h. The ROC curve showed that sSelectin-L was an appropriate biomarker to predict exposure dose at 1 day, 3 days, 7 days, 11 days and 14 days after irradiation. All data is shown as mean ± SD, n ≥ 6, *P < 0.05, **P < 0.001, ***P < 0.0001; ns, not significant. (1d black, 3d orange, 7d blue, 11d green, 14d red).

Fig. 3

Changes of sSelectin-L concentration after PBI. a. Schematic of PBI of mice. Mice were shielded lower or upper body in PBI-I or PBI-II group. (TBI green, PBI-I orange. PBI-II cyan) b. Lymphocyte counts of PBI mice. c. sSelectin-L of PBI mice. d. Correlation analysis of sSelectin-L and lymphocyte count. e. Changes in serum sSelectin-L in patients with NPC after radiotherapy. f. The ROC curve shows that sSelectin-L was used as a biomarker to predict radiation exposure in patients with NPC. All data is shown as mean ± SD, n = 6, *P < 0.05, **P < 0.001, ***P < 0.0001; ns, not significant. PBI, partial body irradiation.

Fig. 4

The response of sSelectin-L to different dose rates and radiation sources. Dynamics of lymphocyte count (a) and sSelectin-L concentration (b) of mice after 4 Gy γ ray radiation at different dose rates. (high red, medium blue, low green). Changes in lymphocyte counts (c) and sSelectin-L concentration (d) of mice after 6.5 Gy γ or X ray irradiation at same dose rate. (γ ray red, X ray blue) All data are shown as mean ± SD, n = 4, *P < 0.05, **P < 0.001, ***P < 0.0001; ns, not significant.

Fig. 5

Changes in sSelectin-L concentration after LPS and DOX injection. (a) lymphocyte count and (b) sSelectin-L concentration of mice after LPS intraperitoneal injection. (c) lymphocyte count and (d) sSelectin-L concentration of mice after DOX intraperitoneal injection. (Saline green, LPS red, DOX blue) All data is shown as mean ± SD, n = 5, *P < 0.05, **P < 0.001, ***P < 0.0001; ns, not significant. LPS Lipopolysaccharide, DOX doxorubicin.

Fig. 6

sSelectin-L levels in irradiated mice with Amifostine pre-treatment or BMT. a. Schematic to describe intraperitoneal injection of Amifostine into mice 0.5 h before radiated. b. Lymphocyte count and c. sSelectin-L concentration was detected for 2 weeks after irradiation. (0 Gy + A blue, 6.5 Gy red, 6.5 Gy + A green) d. Schematic to describe transplantation of whole bone marrow into lethally irradiated mice. e. Lymphocyte count and f. sSelectin-L concentration was detected for 20 days after irradiation. (0Gy + T gray, 10Gy red, 10Gy + T blue) All data are shown as mean ± SD, n = 6, *P < 0.05,**P < 0.001,***P < 0.0001; ns, not significant. A, Amifostine, T, transplantation.

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