Occupational exposure to ionizing radiation has no effect on T‐ and B‐cell total counts or percentages of helper,cytotoxic and activated T‐cell subsets in the peripheral circulation of male radiation workers

Purpose: To investigate changes in immune cell subsets in the peripheral circulation of a male population occupationally exposed to ionizing radiation.

Materials and methods: Peripheral blood samples were taken from 194 male workers with cumulative exposures of >200?mSv (mean exposure 331.5?mSv, mean age 51 years) and from a reference population of 131 male workers with cumulative exposures of <27.5?mSv (mean exposure 13.9?mSv, mean age 47 years). Samples were analysed by flow cytometry for T‐ and B‐cell total counts and for the T‐cell subset percentages of CD4⁺ (helper T‐cells), CD8⁺ (cytotoxic T‐cells) and CD3⁺/HLA‐DR⁺ (activated T‐cells).

Results: Comparison of the >200 and <27.5?mSv exposure groups using linear regression analysis showed no statistically significant differences between the two groups for T‐cell total count, B‐cell total count or for percentages of the T‐cell subsets CD4⁺, CD8⁺ or CD3⁺/HLA‐DR⁺ and CD4⁺:CD8⁺. However, statistically significant increases in both T‐ and B‐cell total counts were observed within the two exposure groups and data pooled from both groups when non‐smokers (never and ex‐smokers) were compared with current smokers. For pooled data T‐cell total count increased in smokers by 35% (p=0.0001) and B‐cell total count increased by 37% (p=0.0004).

Conclusions: No significant immunological effects were observed in male radiation workers with cumulative exposures of >200?mSv when compared with a reference population with cumulative exposures of <27.5?mSv, although highly significant increases in both T‐ and B‐cell total counts were observed in smokers compared with non‐smokers.     

Analysis of immune cell populations and cytokine profiles in murine splenocytes exposed to whole-body low-dose irradiation

Purpose: In contrast to high-dose therapeutic irradiation, definitive research detailing the physiological effects of low-dose irradiation is limited. Notably, the immunological response elicited after low-dose irradiation remains controversial.

Materials and methods: Female C57BL/6 mice were whole- body-irradiated with a single or three daily fractions up to a total dose of 0.1, 1, or 10 cGy. Blood and spleen were harvested 2, 7 and 14 days after irradiation.

Results: The splenic CD4⁺ T cell subpopulations were temporarily increased at 2 days after single or fractionated irradiation, whereas the percentage of dendritic cells (DC) and macrophages was decreased. Whereas CD8⁺ T cell populations were decreased in single-dose irradiated mice at day 7, early and sustained reduction of CD8⁺ T cell numbers was observed in fractionated- dose-irradiated mice from day 2 until day 14. In addition, single-dose irradiation resulted in a Th1 cytokine expression profile, whereas fractionated-dose irradiation drove a Th2 shift. Additionally, increased expression of immune-related factors was observed at early time-points with single-dose irradiation, in contrast to the dose-independent induction following fractionated-dose irradiation.

Conclusions: Our results demonstrate that low-dose irradiation modulates the immune response in mice, where the sensitivity and kinetics of the induced response vary according to the dosing method.     

Repeated 0.5-Gy γ-ray irradiation attenuates autoimmune manifestations in MRL-lpr/lpr mice

Purpose: MRL-lpr/lpr mice, a model for various autoimmune diseases, were repeatedly irradiated with 0.5 Gy of γ-rays, and changes in their autoimmune manifestations were investigated.

Materials and methods: MRL-lpr/lpr mice at 13 weeks of age were maintained in plastic cages and exposed whole-body to 0.5 Gy γ-ray irradiation from a ¹³⁷Cs source 5 times per week for 4 weeks, from the time they were 13 weeks old until they reached 17 weeks old. Changes of autoimmune manifestations were examined 3 weeks later at the 20th week.

Results: Splenomegaly, lymphadenopathy, and proteinuria in MRL-lpr/lpr mice were clearly ameliorated by a total dose of 10 Gy (0.5 Gy/day×5 days/week for 4 weeks). Histologically severe disease-specific damage to the kidney and the salivary gland, i.e., glomerulonephritis and sialoadenitis, was also improved after irradiation. CD3⁺ CD4^? CD8^? CD45R/B220⁺ T cell numbers, which proliferate abnormally in MRL-lpr/lpr mice, were significantly decreased by the irradiation, possibly through induction of apoptosis. The elevated NO₂^? and NO₃^? (NO_x^?) production by macrophages of MRL-lpr/lpr mice was lowered by the irradiation. The irradiation also prolonged the life span of MRL-lpr/lpr mice. These phenomena may contribute to the amelioration of autoimmune manifestations in MRL-lpr/lpr mice exposed to repeated small-doses of γ-rays.

Conclusions: Repeated small-dose γ-ray exposure ameliorates the autoimmune manifestations in MRL-lpr/lpr model mice.     

Genistein induces radioprotection by hematopoietic stem cell quiescence

Purpose: In this study we addressed whether genistein-induced radioprotection in mice is associated with alterations of the cell cycle of hematopoietic stem and progenitor cells.

Materials and methods: C57BL/6J female mice received a single subcutaneous injection of genistein (200 mg/kg) 24 h prior to a lethal dose (7.75 Gy, ⁶⁰Co) of total body irradiation. Proliferation-associated Ki-67 protein/7-aminoactinomycin-D (Ki67/7AAD) cell cycle staining was used to differentiate between G₀, G₁, and S/G₂/M in bone marrow cell populations negative for expression of mature hematopoietic lineage marker cells but positive for expression of stem cell antigen-1 and tyrosine kinase receptor for stem cell factor (Lin^?Sca-1⁺cKit⁺, LSK⁺). Quantitative real-time polymerase chain reaction (qRT-PCR) microarrays were utilized to examine cell cycle specific genes.

Results: At 24 h following radiation exposure, a greater percentage of LSK⁺ in genistein-treated mice accumulated in the G₀ phase of the cell cycle, whereas a large percentage of LSK⁺ bone marrow cells from untreated and vehicle (PEG-400)-treated mice progressed into the G₁ and S/G₂/M phases. Moreover, the absolute number of marrow total LSK⁺, long-term LSK⁺, and short-term LSK⁺ increased 2.8, 12.1, and 4.2-fold, respectively, at 7 days post-irradiation in genistein-treated vs. untreated irradiated mice. Lin^? cells from genistein-treated mice expressed fewer DNA damage responsive and cell cycle checkpoint genes than LSK⁺ from untreated or vehicle-treated mice.

Conclusion: Pretreatment with genistein provides in vivo protection from acute myelotoxicity through extended quiescence followed by reduced senescence of marrow repopulating LSK⁺.     

Investigating chromosome damage using fluorescent in situ hybridization to identify biomarkers of radiosensitivity in prostate cancer patients

Abstract

Purpose: In order to evaluate fluorescent in situ hybridization (FISH) as a method for predicting radiosensitivity, this study examined the incidence of translocations, after exposure to in vitro radiation, in both normally responding patients and those exhibiting severe late effects after radiotherapy treatment.

Materials and methods: Patients were selected from a randomized trial for intermediate-risk prostate cancer. Of the patients entered on trial with mature follow-up, 3% developed grade 3 late proctitis. Blood samples were taken from this radiosensitive cohort along with matched control patients with no late proctitis. Whole blood samples were exposed to 0 or 4 Gy and cultured according to the recommended methods. Colour junctions were evaluated in the resulting metaphases and scored according to the Protocol for Aberration Identification and Nomenclature Terminology (PAINT) system.

Results: Both groups were statistically similar at 0 Gy. After 4 Gy in vitro radiation, the radiosensitive group had significantly higher rates of chromosome damage in the number of colour junctions per cell (p = 0.002), the number of deletions per cell (p = 0.01) and the number of dicentrics per cell (p = 0.005).

Conclusions: These results indicate that the analysis of translocations using FISH after in vitro irradiation correlates with clinical response to radiation. This cytogenetic assay should be considered as a potential predictor of radiosensitivity.     

Human bone marrow mesenchymal stem cells expressing SDF-1 promote hematopoietic stem cell function of human mobilised peripheral blood CD34+ cells in vivo and in vitro

Purpose:?There is mounting evidence demonstrating that stromal cell derived factor-1 (SDF-1) plays an important role in homing of hematopoietic progenitor cells to bone marrow. This study was aimed to assess whether bone marrow mesenchymal stem cells overexpressing exogenous SDF-1 could synergistically promote the homing of CD34⁺ (Cluster of Differentiation [CD]) cells to bone marrow of lethally irradiated severe combined immunodeficiency (SCID) mice.

Methods:?Human SDF-1 complementary Deoxyribonucleic acid (cDNA) was transfected into bone marrow-derived mesenchymal stem cells with recombinant lentiviral vector. The expression of SDF-1 was detected by real-time Polymerase Chain Reaction (PCR) and Enzyme-Linked Immunosorbent Assay (ELISA), and the ex vivo chemotaxis function on CD34⁺ cells was measured by coculture system and Transwell system. SDF-1 gene-modified mesenchymal stem cell (MSC) and CD34⁺ cells were infused into lethally irradiated SCID mice and the hematopoietic reconstitution in the recipient mice was examined.

Results:?Messenger ribonucleic acid (mRNA) and protein of SDF-1 in infected MSC were significantly higher than that of the non-infected control MSC (p?<?0.05). The infected MSC have significant chemotaxis effect on CD34⁺ cells in?vitro and promote hematopoietic reconstitution after CD34⁺ cell transplantation in?vivo.

Conclusion:?MSC with high-level expression of SDF-1 can synergistically promote hematopoietic reconstitution after CD34⁺ cell transplantation in lethally irradiated SCID mice.     

Post-irradiation viability and cytotoxicity of natural killer cells isolated from human peripheral blood using different methods

Purpose We compared the pre- and post-irradiation viability and cytotoxicity of human peripheral natural killer cell (NK) populations obtained using different isolation methods.

Material and methods Three methods were used to enrich total NK cells from buffy coats: (I) a Ficoll-Paque gradient, plastic adherence and a nylon wool column; (II) a discontinuous Percoll gradient; or (III) the Dynal NK cell isolation kit. Subsequently, CD16⁺ and CD56⁺ NK cell subsets were collected using (IV) flow cytometry or (V) magnetic-activated cell sorting (MACS) NK cell isolation kits. The yield, viability, purity and cytotoxicity of the NK cell populations were measured using trypan blue exclusion, flow cytometry using propidium iodide and ⁵¹Cr release assays after enrichments as well as viability and cytotoxicity after a single radiation dose.

Results The purity of the preparations, as measured by the CD16⁺ and CD56⁺ cell content, was equally good between methods I–III (p?=?0.323), but the content of CD16⁺ and CD56⁺ cells using these methods was significantly lower than that using methods IV and V (p?=?0.005). The viability of the cell population enriched via flow cytometry (85.5%) was significantly lower than that enriched via other methods (99.4–98.0%, p?=?0.003). The cytotoxicity of NK cells enriched using methods I–III was significantly higher than that of NK cells enriched using methods IV and V (p?=?0.000). In vitro the NK cells did not recover cytotoxic activity following irradiation. In addition, we detected considerable inter-individual variation in yield, cytotoxicity and radiation sensitivity between the NK cells collected from different human donors.

Conclusions The selection of the appropriate NK cell enrichment method is very important for NK cell irradiation studies. According to our results, the Dynal and MACS NK isolation kits best retained the killing capacity and the viability of irradiated NK cells.     

Low dose radiation induced immunomodulation: Effect on macrophages and CD8+ T cells

Purpose: The aim of the present investigation was to study the effect of fractionated whole body low dose ionizing radiation (LDR) on the functional responses of T lymphocytes, their subpopulations and macrophages.

Materials and methods: C57BL/6 mice were exposed to 4 cGy from a ⁶⁰Co source, at 0.31 cGy/min, at 24 h intervals for 5 days (total dose 20 cGy). Phagocytic activity was measured by flow cytometry using Bioparticles® and nitric oxide generation was estimated by spectrophotometry. Proliferation of lymphocytes in response to concanavalin A (con A) and alloantigens was measured by ³H thymidine incorporation. Expression of cell surface markers was assessed by flow cytometric analysis of antibody labeled cells. Target cell killing by cytotoxic T cells (CTL) generated against allogenic cells was assessed by flow cytometry using PKH26 labeled target cells. Cytokines were estimated by enzyme linked immunosorbent assay.

Results: Exposure to LDR enhanced nitric oxide secretion and phagocytosis. The expression of early activation antigen, CD69, was enhanced in CD8⁺ T lymphocytes concomitant with enhanced proliferation in response to con A. In addition, mixed lymphocyte reaction (MLR) and CTL response were augmented and secretion of interferon gamma (IFN-γ) was suppressed following LDR exposure.

Conclusions: LDR exposure enhanced the function of macrophages and responses of CD8⁺ T cells in C57BL/6 mice.     

Effect of 211At α-particle irradiation on expression of selected radiation responsive genes in human lymphocytes

Purpose: Analysis of the relative expression of radiation responsive genes (previously shown to respond to γ-radiations) after exposure of human lymphocytes to ²¹¹At α-particles and the suitability of these genes as potential markers for α-biodosimetry.

Materials and methods: Lymphocytes isolated from the peripheral blood of two healthy human donors were exposed in triplicate for 30 min to different concentrations of Na²¹¹At at 37°C (absorbed doses: 0.05–1.6 Gy). Following an incubation period (2 h), the total RNA was isolated from the irradiated lymphocytes and the relative expression of the following 18 genes was tested for change using TaqMan? probes based upon the real-time quantitative polymerase chain reaction.

Method: BBC3 (B-cell lymphoma 2 binding component 3), CD69 (cluster of differentiation 69), CDKN1A (cyclin-dependent kinase inhibitor 1A), DUSP8 (dual specificity phosphatase 8) EGR1 (early growth response 1), EGR4 (early growth response 4), GADD45A (growth arrest and DNA-damage-inducible, alpha), GRAP (growth factor receptor-bound protein 2-related adaptor protein), LAP1B (TOR1AIP1; torsin A interacting protein 1), IFNG (interferon gamma), ISG20L1 (interferon-stimulated exonuclease gene 20kDa – like 1), c-JUN (jun oncogene), MDM2 (mouse double minute 2), PCNA (proliferating cell nuclear antigen), PLK2 (polo-like kinase 2), RND1 (rho family GTPase 1), TNFSF9 (tumour necrosis factor superfamily member 9) and TRAF4 (tumour necrosis factor receptor-associated factor 4).

Results: The expressions of the 18 genes, except GRAP, were up-regulated following exposure to α-radiation. A comparison of the results of two individuals tested here showed great variability. Dependence of gene expression upon α-dose was observed in certain dose intervals for BBC3 (R² = 0.61 [individual 1] / 0.81 [individual 2], significance 0.2–1.6 Gy [1] / 0.05–0.1 Gy [2]) and MDM2 (R² = 0.78/0.54; 0.8–1.6 Gy [1], 0.05–0.1 Gy [2]) genes in both individuals. Additionally, for individual 1 the dose dependence was found for the following genes: ISG20L1 (R² = 0.69, 0.05–0.1 Gy), PCNA (R² = 0.59, 0.8–1.6 Gy) and IFNG (R² = 0.74 up to 0.4 Gy, 0.05–0.1 Gy).

Conclusion: Candidate genes for a possible role in future early-phase (2 h) α-biodosimetry are BBC3, ISG20L1, MDM2, PCNA and IFNG.     

Long-term changes in rat hematopoietic and other physiological systems after high-energy iron ion irradiation

Purpose: To assess the long-term consequences of high-linear energy transfer (LET) iron ion radiation on immune and other critical body systems in the context of assessing potential effects astronauts may experience during exploratory missions.

Materials and methods: Sprague-Dawley rats were nearly whole-body irradiated with 56-Fe (5 GeV/n) to total doses of 0, 1, 2, and 4 Gray (Gy) and euthanized 9 months post-exposure for analyses.

Results: Irradiated groups consistently had low body mass. Numbers of circulating white blood cells (WBC), lymphocytes and monocytes were lower in the 2 Gy group compared to 0 Gy (p < 0.05); a trend for low granulocytes was also noted. Red blood cell counts, hemoglobin, and hematocrit were decreased in irradiated animals (p < 0.05), whereas platelet counts and volume were unaffected. In the spleen, WBC counts and DNA synthesis by T cells were similar among groups and there were no differences in secreted interferon-γ and interleukin-6. However, trends were noted for increased splenocyte capacity to secrete tumor necrosis factor-α and increased level of vascular endothelial cell growth factor in plasma. One or more of the irradiated groups had significant (p < 0.05) aberrations in several blood chemistry parameters associated with liver and kidney function.

Conclusion: The data show that exposure to 56-Fe radiation induced pathological changes in important body systems long after exposure.     

Enhancement of biological effectiveness of carbon-ion beams by applying a longitudinal magnetic field

Abstract

Purpose: A magnetic field longitudinal to an ion beam will potentially affect the biological effectiveness of the radiation. The purpose of this study is to experimentally verify the significance of such effects.

Methods and materials: Human cancer and normal cell lines were exposed to low (12?keV/μm) and high (50?keV/μm) linear energy transfer (LET) carbon-ion beams under the longitudinal magnetic fields of B_// = 0, 0.1, 0.2, 0.3, or 0.6 T generated by a solenoid magnet. The effects of the magnetic fields on the biological effectiveness were evaluated by clonogenic cell survival. Doses that would result in a survival fraction of 10% (D₁₀s) were determined for each cell line and magnetic field.

Results: For cancer cells exposed to the low (high)-LET beams, D₁₀ decreased from 5.2 (3.1) Gy at 0 T to 4.3 (2.4) Gy at 0.1 T, while no further decrease in D₁₀ was observed for higher magnetic fields. For normal cells, decreases in D₁₀ of comparable magnitudes were observed by applying the magnetic fields.

Conclusions: Significant decreases in D₁₀, i.e. significant enhancements of the biological effectiveness, were observed in both cancer and normal cells by applying longitudinal magnetic fields of B_// ≥?0.1 T. These effects were enhanced with LET. Further studies are required to figure out the mechanism underlying the observed results.     

Lymphocyte subsets and their H2AX phosphorylation in response to in vivo irradiation in rats

Abstract

Purpose: The objective of the study was to investigate differences in the radiosensitivity of rat peripheral blood lymphocyte subsets identified by expression of surface clusters of differentiation markers (CD3, CD4, CD8, CD45RA, CD161) after whole-body in vivo gamma-ray irradiation and to assess their individual histone H2AX phosphorylation as an early cell response to irradiation.

Materials and methods: The relative representations of CD45RA B-lymphocytes, CD161 natural killer cells (NK cells), CD3CD4 T-lymphocyte subset and CD3CD8 T-lymphocyte subset in the rat peripheral blood were studied 24–72 hours after irradiation in a dose range of 0–5 Gy. Their intracellular H2AX phosphorylation (γ-H2AX) after 4 Gy and 9 Gy whole-body in vivo irradiation was assessed by multicolour flow cytometry.

Results: We determined the linear dose response of radioresistant CD161 NK cells (24 h), both radiosensitive T-lymphocyte subsets (24 h) and CD45RA B-lymphocytes (72 h) after in vivo irradiation. CD45RA B-lymphocytes showed the highest radiosensitivity and we observed pronounced H2AX phosphorylation which remained expressed in these cells for over 4 h after irradiation.

Conclusion: The combination of the surface immunophenotyping together with intracellular detection of γ-H2AX offers the possibility to assess the absorbed dose of ionizing irradiation with high sensitivity post irradiation and could be successfully applied to biodosimetry.     

Kinetics of B-type natriuretic peptide plasma levels in patients with left-sided breast cancer treated with radiation therapy: Results after one-year follow-up

Purpose: To analyze temporal changes of B-type natriuretic peptide (BNP) used as index of heart remodeling in left-sided breast cancer patients after radiotherapy (RT) and its relationship with dosimetric parameters.

Methods and materials: BNP and dose-volume parameters for heart and ventricle were collected in 59 patients (median age 58.0 years) during a 1-year follow-up. Biochemical measurements were performed before the RT treatment (T0), at 15 days during RT (T_15day), at the end of RT (T_endRT), and then at 1, 3, 6, 9, 12 months (T1, T3, T6, T9 and T12). A logistical regression analysis was performed to identify demographic characteristics, dosimetric variables and risk factors associated with increased values of BNP.

Results: The ratio between the BNP value at T12 and the BNP value at T0 (BNP_T12/BNP_T0) increased significantly (p < 0.01). A significant association was found between the variation of BNP values after 1 year and the isodose received by 50% of the volume (D50% [Gy]) both to the heart (p = 0.03) and ventricle (p = 0.04).

Conclusions: BNP plasma levels could provide additional information about subclinical RT-induced cardiotoxicity earlier than traditional ecocardiographic data.     

Influence of DNA double‐strand break rejoining on clonogenic survival and micronucleus yield in human cell lines

Purpose: To examine the role of DNA double‐strand break (DSB) rejoining in cell survival and micronucleus yield after ⁶⁰Co γ‐irradiation.

Materials and methods: Thirteen human cell lines (six glioblastoma, five prostate, one melanoma, one squamous cell carcinoma) were irradiated with ⁶⁰Co γ‐rays to doses of 0–10?Gy for cell survival and micronucleus measurements and 0–100?Gy for DSB rejoining. Measurements were performed using standard clonogenic, micronucleus and constant‐field gel electrophoresis assays.

Results: Radioresistance and micronucleus yield were positively correlated (r=0.74, p=0.004). A significant cell type‐dependent correlation was demonstrated between total (0–20?h) DSB rejoining and cell survival (r=0.86, p=0.03 for glioblastomas; r=0.79, p=0.04 for other cell lines), with more resistant cell lines showing higher levels of DSB rejoining. No relationship was apparent between fast (0–2?h) or slow (2–20?h) DSB rejoining and clonogenic survival. While there was no relationship between total or slow DSB rejoining and micronucleus yield, a significant and cell type‐specific correlation emerged between fast rejoining and micronucleus yield for the glioblastomas (r=0.89, p=0.04) and other cell lines (r=0.76, p=0.04). Cell lines with higher levels of DSB rejoining within 2?h of irradiation showed higher yields of micronuclei.

Conclusion: Fast DSB rejoining, possibly through interaction with slow DSB rejoining, appears to play an important role in the formation of micronuclei. However, total DSB rejoining reflects intrinsic radiosensitivity. Consideration of differences in DSB rejoining kinetics might contribute to a better understanding of the significance of cell survival and micronucleus data in the clinical and radiation protection setting.     

Role of CD4 and CD8 T-lymphocytes,B-lymphocytes and Natural Killer cells in the prediction of radiation-induced late toxicity in cervical cancer patients

Purpose:?To analyse the role of in vitro radio-induced apoptosis of lymphocyte subpopulations as predictive test for late effects in cervical cancer patients treated with radiotherapy.

Methods and materials:?Ninety-four consecutive patients and four healthy controls were included in the study. Toxicity was evaluated using the Late Effects Normal Tissue-Subjective, Objective, Management, and Analytic (LENT-SOMA) scale. Peripheral blood lymphocyte subpopulations were isolated and irradiated at 0, 1, 2 and 8 Gy, and then collected 24, 48 and 72 h after irradiation. Apoptosis was measured by flow cytometry.

Results:?Radiation-induced apoptosis increased with radiation dose and time of incubation, and data fitted to a semi-logarithmic model defined by two constants: α (percentage of spontaneous cell death) and β (percentage of cell death induced at a determined radiation dose). Higher β values in cytotoxic T-lymphocytes (CD8) and bone cells (B-lymphocytes) were observed in patients with low bowel toxicity (hazard ratio (HR)?=?0.96, p?=?0.002 for B-cells); low rectal toxicity (HR?=?0.96, p?=?0.020; HR?=?0.93, p?=?0.05 for B and CD8 subpopulations respectively); low urinary toxicity (HR?=?0.93, p?=?0.003 for B-cells) and low sexual toxicity (HR?=?0.93, p?=?0.010 for CD8-cells).

Conclusions:?Radiation-induced CD8 T-lymphocytes and, for the first time, B-lymphocytes apoptosis can predict differences in late toxicity in cervical cancer patients.     

Enhanced survival from radiation pneumonitis by combined irradiation to the skin

Abstract

Purpose: To develop mitigators for combined irradiation to the lung and skin.

Methods: Rats were treated with X-rays as follows: (1) 12.5 or 13 Gy whole thorax irradiation (WTI); (2) 30 Gy soft X-rays to 10% area of the skin only; (3) 12.5 or 13 Gy WTI + 30 Gy skin irradiation after 3 hours; (4) 12.5 Gy WTI + skin irradiation and treated with captopril (160 mg/m²/day) started after 7 days. Our end points were survival (primary) based on IACUC euthanization criteria and secondary measurements of breathing intervals and skin injury. Lung collagen at 210 days was measured in rats surviving 13 Gy WTI.

Results: After 12.5 Gy WTI with or without skin irradiation, one rat (12.5 Gy WTI) was euthanized. Survival was less than 10% in rats receiving 13 Gy WTI, but was enhanced when combined with skin irradiation (p < 0.0001). Collagen content was increased at 210 days after 13 Gy WTI vs. 13 Gy WTI + 30 Gy skin irradiation (p < 0.05). Captopril improved radiation-dermatitis after 12.5 Gy WTI + 30 Gy skin irradiation (p = 0.008).

Conclusions: Radiation to the skin given 3 h after WTI mitigated morbidity during pneumonitis in rats. Captopril enhanced the rate of healing of radiation-dermatitis after combined irradiations to the thorax and skin.     

Parallel comparison of pre-conditioning and post-conditioning effects in human cancers and keratinocytes upon acute gamma irradiation

Abstract

Purpose: To determine and compare the effects of pre-conditioning and post-conditioning towards gamma radiation responses in human cancer cells and keratinocytes.

Material and methods: The clonogenic survival of glioblastoma cells (T98G), keratinocytes (HaCaT), and colorectal carcinoma cells (HCT116 p53^+/+ and p53^?/?) was assessed following gamma ray exposure from a Cs-137 source. The priming dose preceded the challenge dose in pre-conditioning whereas the priming dose followed the challenge dose in post-conditioning. The priming dose was either 5 mGy or 0.1?Gy. The challenge dose was 0.5–5?Gy.

Results: In both pre- and post-conditioning where the priming dose was 0.1?Gy and the challenge dose was 4?Gy, RAR developed in T98G but not in HaCaT cells. In HCT116 p53^+/+, pre-conditioning had either no effect or a radiosensitizing effect and whereas post-conditioning induced either radiosensitizing or radioadaptive effect. The different observed outcomes were dependent on dose, the time interval between the priming and challenge dose, and the time before the first irradiation. Post-conditioning effects could occur with a priming dose as low as 5 mGy in HCT116 p53^+/+ cells. When HCT116 cells had no p53 protein expression, the radiosensitizing or radioadaptive response by the conditioning effect was abolished.

Conclusions: The results suggest that radiation conditioning responses are complex and depend on at least the following factors: the magnitude of priming/challenge dose, the time interval between priming and challenge dose, p53 status, cell seeding time prior to the first radiation treatment. This work is the first parallel comparison demonstrating the potential outcomes of pre- and post-conditioning in different human cell types using environmentally and medically relevant radiation doses.     

Cellular response of the rat brain to single doses of 137Cs γ rays does not predict its response to prolonged ‘biologically equivalent’ fractionated doses

Abstract

Purpose: To determine if the brain's response to single doses predicts its response to ‘biologically equivalent’ fractionated doses.

Methods: Young adult male Fischer 344 rats were whole-brain irradiated with either single 11, 14, or 16.5 Gy doses of ¹³⁷Cs γ rays or their ‘biologically equivalent’ 20, 30, or 40 Gy fractionated doses (fWBI) delivered in 5 Gy fractions, twice/week for 2, 3, or 4 weeks, respectively. At 2 months post-irradiation, cellular markers of inflammation (total, activated, and newborn microglia) and neurogenesis (newborn neurons) were measured in 40 μm sections of the dentate gyrus (DG).

Results: Although the total number of microglia in the DG/hilus was not significantly different (p > 0.7) in unirradiated, single dose, and fWBI rats, single doses produced a significant (p < 0.003) increase in the percent-activated microglia; fWBI did not (p > 0.1). Additionally, single doses produced a significant (p < 0.002) dose-dependent increase in surviving newborn microglia; fWBI did not (p < 0.8). Although total proliferation in the DG was reduced equally by single and fWBI doses, single doses produced a significant dose-dependent (p < 0.02) decrease in surviving newborn neurons; fWBI did not (p > 0.6).

Conclusions: These data demonstrate that the rat brain's cellular response to single doses often does not predict its cellular response to ‘biologically equivalent’ fWBI doses.     

Radiation protocols determine acute graft-versus-host disease incidence after allogeneic bone marrow transplantation in murine models

Purpose:?Effects of radiation sources used for total body irradiation (TBI) on Graft-versus-Host Disease (GvHD) induction were examined.

Materials and methods:?In a T cell receptor (TCR) transgenic mouse model, single fraction TBI was performed with different radiation devices (⁶⁰Cobalt; ¹³⁷Cesium; 6 MV linear accelerator), dose rates (0.85; 1.5; 2.9; 5 Gy/min) and total doses before allogeneic bone marrow transplantation (BMT). Recipients were observed for 120 days. Different tissues were examined histologically.

Results:?Acute GvHD was induced by a dose rate of 0.85 Gy/min (⁶⁰Cobalt) and a total dose of 9 Gy and injection of 5×10⁵ lymph node cells plus 5×10⁶ bone marrow cells. Similar results were obtained using 6 MV linear accelerator- (linac-) photons with a dose rate of 1.5 Gy/min and 0.85 Gy/min, a total dose of 9.5 Gy and injection of same cell numbers. TBI with ¹³⁷Cesium (dose rate: 2.5 Gy/min) did not lead reproducibly to lethal acute GvHD.

Conclusions:?Experimental TBI in murine models may induce different immunological responses, depending on total energy, total single dose and dose rate. GvHD might also be induced by TBI with low dose rates.