Radioprotective effect of helium-neon laser radiation for fibroblast cells]

Effects of combined exposure to 633-nm laser waves and gamma-radiation, and laser waves and protons with the energy of 150 MeV on survivablilty of mice fibroblast cells C3H10T1/2 were compared. Cell suspension (1 - 5 x 10(5) cells/ml) was distributed in 2-ml plastic vials with 1 cm in diameter time interval between two exposures in a combination was no more than 60 s. immediately after exposure a required quantity of cells was inoculated in special vials for survivability assessment. Based on results of the experiment, preliminary and repeated laser treatment was favorable to survivability of fibroblast cells subjected to gamma- or proton irradiation (dose variation factor was within 1.3 to 2.2). Simultaneous exposure of C3H10T1/2 cells to the laser and proton beams also increased their survivability. The radioprotective effect of the helium-neon laser on fibroblasts earlier exposed to ionizing radiation is of chief interest, as most of the present-day radioprotectors are effective only if introduced into organism prior to exposure.     

Measurement of biological effects of high-energy carbon ions at low doses using a semi-automated cell detection system

PURPOSE: To study the effects of low-dose, high-LET irradiation in order to detect possible deviations from a linear-quadratic dose dependence. MATERIALS AND METHODS: Experiments using charged particle irradiation were performed, in particular in the low-dose range from 0 to 2 Gy, and compared with experiments using photon radiation. The survival of V79 cells was studied by means of a semi-automated system, which allowed the detection and relocation of positions of individual cells at regular intervals. It consists of an inverted microscope equipped with a computerized stage control and image processing system. With such a technique, the precision of the survival assay is increased by avoiding the stochastic uncertainties of the conventional dilution assay. Furthermore, by means of daily observations, the system allows a detailed study of the growth kinetics of individual cells up to approximately 1 week after irradiation. RESULTS AND CONCLUSION: Up to now, high-LET experiments have been performed using mainly 100 MeV/u carbon ions (LET: 28 keV/microm). A significant hypersensitivity at low doses (0.1 Gy) has been detected for these ions. It is the first report of such a pronounced effect for charged particle irradiation. Although hypersensitivity after carbon ion irradiation apparently is in contrast to other data reported for peak pion irradiation at similar LET values, the difference might possibly be due to differences in the track structure of the particles.     

Measurement of biological effects of high-energy carbon ions at low doses using a semi-automated cell detection system

Purpose : To study the effects of low-dose, high-LET irradiation in order to detect possible deviations from a linear-quadratic dose dependence. Materials and methods : Experiments using charged particle irradiation were performed, in particular in the low-dose range from 0 to 2 Gy, and compared with experiments using photon radiation. The survival of V79 cells was studied by means of a semi-automated system, which allowed the detection and relocation of positions of individual cells at regular intervals. It consists of an inverted microscope equipped with a computerized stage control and image processing system. With such a technique, the precision of the survival assay is increased by avoiding the stochastic uncertainties of the conventional dilution assay. Furthermore, by means of daily observations, the system allows a detailed study of the growth kinetics of individual cells up to approximately 1 week after irradiation. Results and conclusion : Up to now, high-LET experiments have been performed using mainly 100 MeV/u carbon ions (LET: 28 keV/ μ m). A significant hypersensitivity at low doses (0.1 Gy) has been detected for these ions. It is the first report of such a pronounced effect for charged particle irradiation. Although hypersensitivity after carbon ion irradiation apparently is in contrast to other data reported for peak pion irradiation at similar LET values, the difference might possibly be due to differences in the track structure of the particles.     

Neoplastic transformation of mouse fibroblasts under the influence of high-energy protons and gamma-rays]

Oncoginic transformations of mouse fibroblasts C3H10T1/2 after exposure to proton energies 150 and 584 MeV were compared with fibroblast effects of gamma-radiation. Prior to exposure, cell populations (2.7 x 10(3) cells/cm2) were inoculated in plastic vials with the surface area of 75 cm2 and cultivated 11 days. Survivability was determined by comparing the number of cell colonies in irradiated and non-irradiated (control) vials. Transformation rate was calculated by dividing the total transformation focus number by the number of survived cells in a vial. Rate of oncogenic transformations after gamma- and proton (584 MeV) irradiation was essentially identical, i.e. the parameter grew rapidly at the doses < 1 Gy and slowed down at the doses > 1 Gy. In the dose interval between 1 and 5 Gy, transformation rate for proton energy 150 MeV was found low compared with gamma-radiation and proton energy 584 MeV. It is hypothesized that the different transformation rate after exposure to proton energy 150 MeV is linked with the high linear energy transfer as compared with the proton energy of 584 MeV and gamma-radiation.     

Effect of EGFR-inhibition on the radiation response of oral mucosa: experimental studies in mouse tongue epithelium

The aim was to quantify the effect of selective inhibition of the epidermal growth factor receptor (EGFR) on the radiation response of mouse oral mucosa to daily fractionated irradiation. Irradiation comprised graded single doses of 25 kV X-rays to the lower tongue surface or fractionated doses of 5 x 3 Gy week(-1) (200 kV X-rays) over 1 or 2 weeks, followed by graded local doses, to generate full dose-effect curves. For selective inhibition of EGFR, BIBX1382BS, a tyrosine kinase inhibitor, was administered orally at a dose of 50 mg kg(-1), for the entire overall treatment time. The ED50 (the dose expected to induce ulcer in 50% of the mice) for untreated mucosa was 11.9 +/- 1.2 Gy. Fractionated irradiation administered over 1 or 2 weeks yielded ED50 values for the concluding test irradiation of 6.7 +/- 2.1 and 6.5 +/- 1.9 Gy, respectively. Administration of BIBX1382BS resulted in a non-significant increase of the top-up ED50 to 8.3 +/- 1.6 Gy (p = 0.1197) after 1 week and to 7.6 +/- 1.6 Gy (p = 0.2263) after 2 weeks. EGFR inhibition does not alter the radiation response of oral mucosa to fractionated irradiation or interfere with mucosal repopulation processes. This indicates that the regulation of mucosal repopulation is largely independent of EGFR activation.     

Exacerbation of autoimmune thyroiditis by a single low dose of whole-body irradiation in non-obese diabetic-H2h4 mice

PURPOSE: To evaluate how irradiation affects thyroid autoimmunity in mouse models of Hashimoto's thyroiditis and Graves' hyperthyroidism. MATERIALS AND METHODS: Non-obese diabetic (NOD)-H2(h4) mice spontaneously develop anti-thyroglobulin (Tg) antibodies and thyroiditis when supplied with sodium iodine (NaI) in the drinking water. BALB/c mice develop anti-thyrotropin receptor (TSHR) antibodies and hyperthyroidism following immunization with adenovirus expressing TSHR (Ad-TSHR). Mice were irradiated as follows: A single whole-body irradiation with 0.05, 0.5 or 3 Gy one week before or after the beginning of NaI or immunization with Ad-TSHR, fractionated whole-body irradiations with 0.05 Gy twice a week or 0.5 Gy once a week from one week before NaI or Ad-TSHR immunization, or a single regional irradiation to the thyroid gland with 0.5 Gy one week before NaI. The effect of a single irradiation with 0.05, 0.5 or 3 Gy on splenocytes was also evaluated. RESULTS: A single whole-body irradiation with 0.5 Gy one week before NaI exacerbated thyroiditis and increased anti-Tg antibody titers in NOD-H2(h4) mice. In contrast, any irradiation protocols employed did not affect incidence of hyperthyroidism or anti-TSHR antibody titers in BALB/c mice. High-dose irradiation increased the relative ratios of effector T cells to regulatory T cells (an indication of enhanced immune status) but kills most of T cells. CONCLUSIONS: These results indicate that a single whole-body low-dose irradiation with 0.5 Gy exacerbates thyroiditis in NOD-H2(h4) mice, data consistent with some clinical evidence for increased incidence of thyroid autoimmunity by environmental irradiation.     

MIRD continuing education: Bystander and low dose-rate effects: are these relevant to radionuclide therapy?

Bystander and low-dose-rate effects influence the dose-response relationship in a manner not predicted by current dosimetric methodologies. Radiation-induced bystander effects refer to biologic responses in cells that are not traversed by an ionizing radiation track and, thus, not subject to direct energy deposition; that is, the responses occur in nonirradiated cells. Low-dose-rate hypersensitivity effects have been documented as a reduction in the survival of cells irradiated at dose rates of 0.1-1.0 Gy/h, with total doses ranging from 1.5 to 5 Gy. For humans undergoing external radiotherapy, evidence of bystander events has been observed in the form of abscopal effects, wherein irradiation of one portion of the anatomy affects a portion outside the radiation field, whereas low-dose-rate hypersensitivity has not been described. In this report, the historical literature is briefly reviewed, key experiments are summarized, and current understanding of the factors thought to be involved in the bystander and low-dose-rate effects is conveyed. The mechanisms associated with these events are still being investigated, and questions remain on their impact in radionuclide therapy. Although current findings do not yet sufficiently justify changing traditional dose estimates used to predict the outcomes of radionuclide therapy, it is important to appreciate the potential importance of these effects and to begin revising methods to reflect the emerging empiric and mechanistic knowledge.     

γ射线致旁效应细胞脆性组氨酸三联体的表达

目的 研究⁶⁰Coγ射线照射后人淋巴母细胞(AHH-1)及其旁效应细胞中脆性组氨酸三联体(FHIT)基因的表达情况,探讨FHIT基因在电离辐射旁效应中的作用。方法 旁效应细胞模型的制备:分别用不同剂量(0、2和5 Gy) ⁶⁰Coγ射线照射AHH-1细胞后,立即离心,将直接受照细胞与未受照细胞共同培养于Transwell中,此未受照细胞为旁效应1组;另将直接受照细胞培养液转移至未受照细胞培养瓶中形成旁效应2组。于照后0、6、12和24 h收集细胞,抽提细胞总RNA及总蛋白,分别应用RT-PCR和Western blot方法检测 FHIT mRNA及蛋白表达水平;并在照后即刻和24 h收集细胞,应用流式细胞仪检测细胞周期,并应用细胞计数法观察细胞增殖变化。结果 对照细胞、直接受照细胞、旁效应细胞中FHIT基因 mRNA水平变化不明显,而FHIT蛋白表达在直接受照细胞及旁效应细胞中显著下调(F=102.45.P<0.001)。细胞周期分析结果显示直接受照细胞及旁效应细胞G₂期阻滞明显,且增殖能力明显下降。结论 2、5 Gy⁶⁰Coγ射线照射能导致直接照射AHH-1细胞及其旁效应细胞FHIT蛋白表达明显下调,提示FHIT基因在电离辐射旁效应中发挥一定作用。     

Chronic low-dose radiation inhibits the cells death by cytotoxic high-dose radiation increasing the level of AKT and acinus proteins via NF-κB activation

Abstract

Purpose: This study explored the effects of low-dose and low-dose-rate irradiation in human lung fibroblast CCD-18Lu cells and examined the role of AKT (protein kinase B, PKB) in cellular responses.

Materials and methods: We examined cell survival after chronic low-dose irradiation (0.01 Gy or 0.05 Gy) with challenging high-dose (2 or 10 Gy) irradiation. We examined the effect of AKT activation on cell survival after chronic low-dose radiation using transduced cells with retroviral vector expressing constitutively active AKT (CA-AKT).

Results: Chronic low-dose priming irradiation increased cells viability against the challenging high-dose irradiation. Irradiation at 0.05 Gy increased cellular levels of AKT and acinus long form (L) and short form (S). The chronic low-dose radiation promoted cells proliferation in the exogenously expressed CA-AKT cells. It also increased nuclear factor-kappa B (NF-κB) activity in a biphasic induction pattern. Suppression of NF-κB activation by mutant form of inhibitor of kappa B alpha (IκBαM) antagonized the radiation-induced expression of AKT and acinus L and S.

Conclusions: Chronic low-dose radiation increases the levels of AKT and acinus proteins via NF-κB activation, and the NF-κB/AKT pathway responding to chronic low-dose irradiation plays an important role in the radiation adaptive response.     

Effects of Systemic or Topical Administration of Sodium Selenite on Early Radiation Effects in Mouse Oral Mucosa

PURPOSE: To quantify the effect of sodium selenite (selenium) on radiation-induced oral mucositis (mouse) after subcutaneous or topical administration. MATERIAL AND METHODS: Mucosal ulceration of the lower epithelium of mouse tongue was analyzed. Selenium (5 mug) was applied subcutaneously (s.c.) or locally, 60 min or 30 min prior to irradiation, respectively. In combination with single-dose irradiation, a single selenium application was given. With daily fractionated irradiation (3 Gy/fraction) for 1 week (days 0-4), selenium was administered at all 5 days of irradiation. With ten fractions over 2 weeks, selenium was applied in week 1, week 2, or both. All fractionation protocols were terminated by graded test doses to generate full dose-effect curves. RESULTS: In a single-dose control experiment, the ED(50) (dose after which ulcer induction is expected in 50% of the mice) was 12.9 +/- 1.6 Gy. Selenium increased the ED(50) to 17.7 +/- 2.6 Gy (s.c.; p = 0.0003) and 16.3 +/- 3.0 Gy (local; p = 0.0104). The ED(50) for test irradiation after 5 x 3 Gy was 7.4 +/- 2.2 Gy. Subcutaneous administration of selenium resulted in an ED(50) of 11.5 +/- 2.0 Gy (p = 0.0015), local application yielded an ED(50) of 10.0 +/- 2.1 Gy (p = 0.0284). The ED(50) for test irradiation after 10 x 3 Gy/2 weeks was 8.0 +/- 1.7 Gy. Subcutaneous or local administration of selenium in week 1 yielded a significant increase in ED(50) to 10.5 +/- 1.0 Gy (p = 0.0069) and 10.7 +/- 1.0 Gy (p = 0.0039), respectively. By clear contrast, selenium administration in week 2 had no significant effect. Administration in both weeks resulted in an ED(50) of 9.1 +/- 2.0 Gy (s.c.; p = 0.2747) and 9.7 +/- 1.4 Gy (local; p = 0.0541). CONCLUSION: Administration of sodium selenite during clinically relevant fractionated irradiation protocols has a significant effect during the initial treatment phase, i.e., week 1 in the mouse. Therefore, in clinical radiotherapy, the latent time to manifestation of confluent mucositis may be significantly prolonged, and hence the burden for the patient clearly reduced by selenium.     

Exacerbation of autoimmune thyroiditis by a single low dose of whole-body irradiation in non-obese diabetic-H2h4 mice

Purpose: To evaluate how irradiation affects thyroid autoimmunity in mouse models of Hashimoto's thyroiditis and Graves' hyperthyroidism.

Materials and methods: Non-obese diabetic (NOD)-H2^h4 mice spontaneously develop anti-thyroglobulin (Tg) antibodies and thyroiditis when supplied with sodium iodine (NaI) in the drinking water. BALB/c mice develop anti-thyrotropin receptor (TSHR) antibodies and hyperthyroidism following immunization with adenovirus expressing TSHR (Ad-TSHR). Mice were irradiated as follows: A single whole-body irradiation with 0.05, 0.5 or 3 Gy one week before or after the beginning of NaI or immunization with Ad-TSHR, fractionated whole-body irradiations with 0.05 Gy twice a week or 0.5 Gy once a week from one week before NaI or Ad-TSHR immunization, or a single regional irradiation to the thyroid gland with 0.5 Gy one week before NaI. The effect of a single irradiation with 0.05, 0.5 or 3 Gy on splenocytes was also evaluated.

Results: A single whole-body irradiation with 0.5 Gy one week before NaI exacerbated thyroiditis and increased anti-Tg antibody titers in NOD-H2^h4 mice. In contrast, any irradiation protocols employed did not affect incidence of hyperthyroidism or anti-TSHR antibody titers in BALB/c mice. High-dose irradiation increased the relative ratios of effector T cells to regulatory T cells (an indication of enhanced immune status) but kills most of T cells.

Conclusions: These results indicate that a single whole-body low-dose irradiation with 0.5 Gy exacerbates thyroiditis in NOD-H2^h4 mice, data consistent with some clinical evidence for increased incidence of thyroid autoimmunity by environmental irradiation.     

低剂量照射在肿瘤治疗中的应用研究进展

电离辐射生物效应与辐射剂量和剂量率有关,大、中剂量照射以损伤效应为主,低剂量照射可诱导机体的兴奋效应、适应性反应、超敏感性、旁效应等。低剂量全身照射通过诱导免疫增强效应、超敏感性、激活抗氧化酶系统及肿瘤细胞凋亡等机制具有抗肿瘤作用,降低随后较大剂量辐射诱发的肿瘤发生率。目前。低剂量照射在肿瘤防治中的应用正成为研究的热点。     

分割剂量电离辐射对卵巢癌细胞多药耐药的影响

目的 研究不同分割剂量电离辐射方案对卵巢癌细胞多药耐药性的影响.方法 采用卵巢癌亲本细胞SKOV3及其耐药细胞株SKVCR,分别进行假照射、单次照射(10 Gy)、常规分割照射(2 Gy ×5)和超分割照射(1 Gy×2 ×5).MTT方法检测细胞对4种化疗药物硫酸长春新碱( vincristine,VCR)、依托泊苷(etoposide,VP-16)、盐酸吡柔比星(pirarubicin,THP)和顺铂(cisplatin,DDP)敏感性的变化.Western blot检测P-gp蛋白表达量.结果 与SKOV3相比,SKVCR倍增时间增加为1.8倍,P-gp糖蛋白表达增高,4种药物对SKVCR的IC50浓度明显增加(P＜0.05).在SKOV3中,与假照组相比,单次照射后细胞对THP、DDP药敏性降低,常规分割照射后细胞对VCR、THP、VP-16药敏性降低,超分割照射使VP-16药敏性降低;在SKVCR中,与假照组相比,3个照射组对VCR、VP-16的药敏性增高,对DDP的药敏性无明显改变,单次和分割照射均可降低P-gp表达.结论 单次、分割和超分割照射在SKOV3亲本细胞中诱导多药耐药,在耐药株SKVCR中逆转对VCR、VP-16的耐药性.     

Effects of low and high LET radiations on bystander human lung fibroblast cell survival

PURPOSE: This investigation is aimed to determine the role of low LET (linear energy transfer, gamma-rays) and high LET (alpha-particles) radiations on bystander effect of using the same type of cells and its implications on colony-forming efficiency from a single cell. MATERIALS AND METHODS: Normal human fetal lung (MRC-5), immortalized repair deficient ataxia telangiectasia mutated (ATM) (GM5,849C) and normal (GM637H) fibroblast cells were used. Colony-forming efficiency in bystander cells (GM637H) was studied using the medium transfer technique from the two donor (MRC-5 and GM5,849C) cells and the procedure followed for bystander treatment is presented schematically in Figure 1. Evidence of change in colony formation in bystander cells, was assessed by scavenging nitric oxide (NO). RESULTS: Enhancement of 10 - 30% in colony-forming efficiency was observed in bystander GM637H cells treated with irradiated conditioned medium (ICM) from MRC-5 cells collected 1 h after different doses of either gamma-rays (1, 2.5, 5 and 10 Gy) or alpha particles (0.25, 0.5, 1 and 2.5 Gy) irradiation. Similar results were obtained when ICM derived from the ATM (GM5,849C) cells. However, the stimulation was not dose dependent. Furthermore, we also show that the increase in dilutions of ICM (1:1, 1:5 and 1:10) showed an inverse correlation with cloning efficiency. Treatment of MRC-5 cells with PTIO (2-phenyl-4, 4, 5, 5-tetramethylimidazoline-1-oxyl-3-oxide) a NO scavenger, 1 h prior to irradiation reduced the enhancement of ICM mediated cell survival. CONCLUSIONS: In the present study, though both the low and high LET radiations enhanced the clonogenic potential of the bystander recipient cells, medium from the ATM defective (GM5,849C) cells after gamma-irradiation showed less stimulating effect than the medium from the normal (MRC-5) cells. However, after alpha-irradiation an inverse effect was seen. NO may play an important role in enhancing the growth potential in these bystander cells.     

Effectiveness of the biological action of protons and gamma-radiation on cells C3H10T1/2]

Relative biological effectiveness (RBE) of the therapeutic proton beam with an energy of 150 MeV was measured during fractional irradiation of mice fibroblasts C3H101 T1/2 by 4.0 Gy per day, 5 d/w with the total dose of 40 Gy. Lethal effectiveness of the beam at different points of modified Bragg's peak (width of the flat apex = 3.7 cm) was evaluated and effects of acute single gamma-radiation (6CO) of cells were investigated. Results were compared with the data of fractional irradiation to assess reparation processes. It was shown that survivability of the cells in three points of Bragg's peak was essentially the same but a bit higher at the point of entry. Proton RBE in the experiment was equal to zero relative to gamma-radiation. Difference between fractional and acute irradiation leveled off with rising doses; however, the reparative processes still had a place even at 20 Gy.     

Amelioration of Early Radiation Effects in Oral Mucosa (Mouse) by Intravenous or Subcutaneous Administration of Amifostine

PURPOSE: To quantify the reduction of radiation-induced oral mucositis by amifostine as a function of administration route. MATERIAL AND METHODS: Mucosal ulceration of lower mouse tongue epithelium was analyzed. Amifostine was injected at 1.8 mg/injection subcutaneously (s.c.) or intravenously (i.v.), 45 min or 10 min prior to irradiation. With single-dose irradiation, a single amifostine injection was given. During daily fractionated irradiation (5 x 3 Gy) for 1 week, amifostine was administered s.c. or i.v. twice (days 0, 3), or s.c. on all irradiation days (days 0-4). With ten fractions over 2 weeks, five s.c. injections were given in week 1 (days 0-4) or week 2 (days 7-11), or both. Two i.v. injections were given either in week 1 (days 0, 3) or week 2 (days 7, 10). All fractionation protocols were terminated by graded test doses to generate full dose-effect curves. RESULTS: In a single-dose control experiment, the ED(50) (dose after which ulcer induction is expected in 50% of the mice) was 11.7 +/- 1.4 Gy. Intravenous application of amifostine increased the ED(50) to 14.0 +/- 1.4 Gy (p = 0.024), while s.c. administration had no significant effect. The ED(50) for test irradiation after 5 x 3 Gy was 5.8 +/- 1.4 Gy. Two s.c. or i.v. amifostine injections yielded ED(50) values of 7.2 +/- 1.1 Gy (p = 0.0984) or 7.6 +/- 1.2 Gy (p = 0.0334); five s.c. injections increased the ED(50) to 8.2 +/- 0.9 Gy (p = 0.0039). The ED(50) after 10 x 3 Gy/2 weeks was 6.6 +/- 1.8 Gy. Subcutaneous or intravenous administration of amifostine in week 1 yielded a significant increase in ED(50) to 9.4 +/- 2.5 Gy (p = 0.0099) and 10.0 +/- 2.2 Gy (p = 0.0014). By contrast, amifostine administration in week 2 had no significant effect. Administration in weeks 1 and 2 resulted in an ED(50) of 10.8 +/- 3.6 Gy (p = 0.0053). CONCLUSION: Amifostine during daily fractionated irradiation is effective only if administered in the initial treatment phase, i.e., week 1 in the mouse. The differences in the effect in weeks 1 and 2 suggest mechanisms of action other than radical scavenging.     

Biodosimetry using radiation-induced micronuclei in skin fibroblasts

Purpose:?We assessed micronuclei in dermal fibroblasts as a local biodosimeter for estimating accidental in vivo radiation exposure.

Materials and methods:?Male and female C3H/HeJ and C57Bl6 mice of four age groups (～11, 36, 60 and 99 weeks) received a single whole body dose of gamma radiation (0–10 Gy) and radiation-induced micronuclei per 1,000 binucleated cells were assessed in skin fibroblasts in their first division after isolation from biopsies taken on days 1 and 7 post irradiation. The method of generalized estimating equations was used for statistical analyses.

Results:?Total micronuclei were increased on day 1 in a dose-dependent manner in the range of 1–10 Gy, with no significant attenuation of response between day 1 and day 7 and no significant effect of gender. Between-strain differences were observed with C3H/HeJ mice showing lower background micronuclei and a slightly steeper dose response. Age affected only the background micronuclei (moderate increase with age). The model demonstrated that the assay yields ‘unbiased’ prediction of the dose between 0 and 7 Gy. Within this dose range, the predicted dose was found to be accurate within ±1.5–2 Gy. When the specificity is set to 95%, the assay can distinguish between unexposed and 2 Gy exposed mice with a sensitivity of around 60%. The sensitivity approached 100% when discriminating between unexposed mice and mice receiving doses equal to or greater than 4 Gy. The percentage of binucleated cells with micronuclei was shown to be useful as a simpler and slightly faster substitute for the total micronuclei count.

Conclusion:?Micronuclei in dermal fibroblasts isolated up to 1 week after irradiation can be a useful biodosimeter for local dose after accidental radiation exposure.     

Differences in ICAM-1 and TNF-alpha expression between large single fraction and fractionated irradiation in mouse brain

PURPOSE: To elucidate the brain molecular response to irradiation. The expression of the intercellular adhesion molecule (ICAM-1) and tumour necrosis factor-alpha (TNF-alpha) in the mouse brain was compared after single-dose and fractionated whole-brain irradiation. MATERIALS AND METHODS: Mice received a single dose of 2, 10 or 20 Gy or a fractionated dose (2 Gy day(-1)) of 10, 20 or 40 Gy. ICAM-1, and TNF-alpha mRNA expression were quantified by the highly sensitive real-time polymerase chain reaction technique. Expression of ICAM-1 protein was quantified by dual-labelled monoclonal antibody assay. RESULTS: After a 20-Gy single dose, there was an increase in ICAM-1 and TNF-alpha mRNA levels (14- and 11-fold, respectively) as well as a significant increase in the level of ICAM-1 protein (p=0.0243). The expression of ICAM-1 and TNF-alpha mRNA increased at the end of the 40-Gy fractionated regimen (3.55- and 2.30-fold, respectively). CONCLUSIONS: The molecular response of the brain to single-dose irradiation was rapid, while its response to fractionated irradiation was slow. This finding is consistent with clinical observations and could be of use when designing strategies to mitigate radiation sequelae.     

Reduction of oral mucositis by palifermin (rHuKGF): dose-effect of rHuKGF

PURPOSE: The aim of the present study was to determine the dose effect of palifermin (recombinant human keratinocyte growth factor, rHuKGF) for reduction of the response of oral mucosa to fractionated radiotherapy in a mouse model. MATERIAL AND METHODS: Ulceration (confluent mucositis) of mouse tongue epithelium was analysed as the clinically relevant endpoint. Palifermin at doses from 1 - 30 mg/kg was administered before the onset (day -3), at the end of the first (day +4) or the second week of irradiation (day +11) with 5 x 3 Gy/week. Each protocol was terminated by graded radiation test (top-up) doses. In a further experiment, optimally effective doses were given on days -3 and +4, or -3, +4 and +11. RESULTS: Single dose irradiation of mouse mucosa yielded an ED50 (dose inducing ulcer in 50% of the mice) of 10.7 +/- 1.0 Gy. With fractionated irradiation for 1 week an ED50 for test irradiation (day +7) of 5.1 +/- 1.9 Gy was observed. After 2 weeks (day +14), the ED50 was 7.3 +/- 1.9 Gy. Palifermin significantly increased the ED50 values in all protocols tested. Maximally effective doses for single injections were 15.0 mg/kg (day -3, +11) or 22.5 mg/kg (day +4), which yielded ED50 values of 12.1 +/- 1.3 Gy, 13.7 +/- 1.5 Gy and 14.4 +/- 1.3 Gy, respectively. Higher palifermin doses did not further increase the ED50. Repeated injections on days -3 and +4 did not increase the ED50 beyond the value obtained with injections on day +4 alone. An additional injection on day +11 increased the ED50 further to 15.1 +/- 0.1 Gy. CONCLUSIONS: A significant palifermin dose-effect was seen at doses below 15 mg/kg. However, a significant increase in oral mucosal radiation tolerance by palifermin over untreated control tissue was observed already with low doses of 1 mg/kg. This indicates that in clinical studies with palifermin, the dose of the growth factor may be of minor relevance over a wide dose range.