The oxygen effect in radiation inactivation of DNA and enzymes

Effect of Anesthetic Carrier Gas on In Vivo Circulation Times of Intravenously Administered Phospholipid Oxygen Microbubbles in Rats

OBJECTIVE

For the treatment of tumor hypoxia, microbubbles comprising oxygen as a majority component of the gas core with a stabilizing shell may be used to deliver and release oxygen locally at the tumor site through ultrasound destruction. Previous work has revealed differences in circulation half-life in vivo for perfluorocarbon-filled microbubbles, typically used as ultrasound imaging contrast agents, as a function of anesthetic carrier gas. These differences in circulation time in vivo were likely due to gas diffusion as a function of anesthetic carrier gas, among other variables. This work has motivated studies to evaluate the effect of anesthetic carrier gas on oxygen microbubble circulation dynamics.

METHODS

Circulation time for oxygen microbubbles was derived from ultrasound image intensity obtained during longitudinal kidney imaging. Studies were constructed for rats anesthetized on inhaled isoflurane with either pure oxygen or medical air as the anesthetic carrier gas.

RESULTS

Results indicated that oxygen microbubbles were highly visible via contrast-specific imaging. Marked signal enhancement and duration differences were observed between animals breathing air and oxygen. Perhaps counterintuitively, oxygen microbubbles disappeared from circulation significantly faster when the animals were breathing pure oxygen compared with medical air. This may be explained by nitrogen counterdiffusion from blood into the bubble, effectively changing the gas composition of the core, as has been observed in perfluorocarbon core microbubbles.

CONCLUSION

Our findings suggest that the apparent longevity and persistence of oxygen microbubbles in circulation may not be reflective of oxygen delivery when the animal is anesthetized breathing air.

Dodecafluoropentane Emulsion as a Radiosensitizer in Glioblastoma Multiforme

Purpose

Glioblastoma multiforme (GBM) is a hypoxic tumor resistant to radiotherapy. The purpose of this study was to assess the safety and efficacy of a novel oxygen therapeutic, dodecafluoropentane emulsion (DDFPe), in chemoradiation treatment of GBM.

Experimental Design

In this multicenter phase Ib/II dose-escalation study, patients were administered DDFPe via intravenous infusion (0.05, 0.10, or 0.17 mL/kg) while breathing supplemental oxygen prior to each 2 Gy fraction of radiotherapy (30 fractions over 6 weeks). Patients also received standard-of-care chemotherapy [temozolomide (TMZ)]. Serial MRI scans were taken to monitor disease response. Adverse events were recorded and graded. TOLD (tissue oxygenation level-dependent) contrast MRI was obtained to validate modulation of tumor hypoxia.

Results

Eleven patients were enrolled. DDFPe combined with radiotherapy and TMZ was well tolerated in most patients. Two patients developed delayed grade 3 radiation necrosis during dose escalation, one each at 0.1 and 0.17 mL/kg of DDFPe. Subsequent patients were treated at the 0.1 mL/kg dose level. Kaplan-Meier analysis showed a median overall survival of 19.4 months and a median progression-free survival of 9.6 months, which compares favorably to historical controls. Among 6 patients evaluable for TOLD MRI, a statistically significant reduction in tumor T1 was observed after DDFPe treatment.

Conclusions

This trial, although small, showed that the use of DDFPe as a radiosensitizer in patients with GBM was generally safe and may provide a survival benefit. This is also the first time than TOLD MRI has shown reversal of tumor hypoxia in a clinical trial in patients. The recommended dose for phase II evaluation is 0.1 mL/kg DDFPe.Trial Registration: NCT02189109.

Significance

This study shows that DDFPe can be safely administered to patients, and it is the first-in-human study to show reversal of hypoxia in GBM as measured by TOLD MRI. This strategy is being used in a larger phase II/III trial which will hopefully show a survival benefit by adding DDFPe during the course of fractionated radiation and concurrent chemotherapy.

Optimizing the Safety and Efficacy of Bio-Radiopharmaceuticals for Cancer Therapy

The precise delivery of cytotoxic radiation to cancer cells through the combination of a specific targeting vector with a radionuclide for targeted radionuclide therapy (TRT) has proven valuable for cancer care. TRT is increasingly being considered a relevant treatment method in fighting micro-metastases in the case of relapsed and disseminated disease. While antibodies were the first vectors applied in TRT, increasing research data has cited antibody fragments and peptides with superior properties and thus a growing interest in application. As further studies are completed and the need for novel radiopharmaceuticals nurtures, rigorous considerations in the design, laboratory analysis, pre-clinical evaluation, and clinical translation must be considered to ensure improved safety and effectiveness. Here, we assess the status and recent development of biological-based radiopharmaceuticals, with a focus on peptides and antibody fragments. Challenges in radiopharmaceutical design range from target selection, vector design, choice of radionuclides and associated radiochemistry. Dosimetry estimation, and the assessment of mechanisms to increase tumor uptake while reducing off-target exposure are discussed.

Targeted Radionuclide Therapy with Low and High-Dose Lutetium-177-Labeled Single Domain Antibodies Induces Distinct Immune Signatures in a Mouse Melanoma Model

Targeted radionuclide therapy (TRT) using probes labeled with Lutetium-177 (177Lu) represents a new and growing type of cancer therapy. We studied immunologic changes in response to TRT with 177Lu labeled anti-human CD20 camelid single domain antibodies (sdAb) in a B16-melanoma model transfected to express human CD20, the target antigen, and ovalbumin, a surrogate tumor antigen. High-dose TRT induced melanoma cell death, calreticulin exposure, and ATP-release in vitro. Melanoma-bearing mice received fractionated low and high-dose TRT via tumor targeting anti-human CD20 sdAbs, as opposed to control sdAbs. Tumor growth was delayed with both doses. Low- and high-dose TRT increased IL10 serum levels. Low-dose TRT also decreased CCL5 serum levels. At the tumor, high-dose TRT induced a type I IFN gene signature, while low-dose TRT induced a proinflammatory gene signature. Low- and high-dose TRT increased the percentage of PD-L1pos and PD-L2pos myeloid cells in tumors with a marked increase in alternatively activated macrophages after high-dose TRT. The percentage of tumor-infiltrating T cells was not changed, yet a modest increase in ovalbumin-specific CD8pos T-cells was observed after low-dose TRT. Contradictory, low and high-dose TRT decreased CD4pos Th1 cells in addition to double negative T cells. In conclusion, these data suggest that low and high-dose TRT induce distinct immunologic changes, which might serve as an anchoring point for combination therapy.

Hyperthermia Enhances Efficacy of Chemotherapeutic Agents in Pancreatic Cancer Cell Lines

Chemotherapy (CT) is the standard care for advanced pancreatic ductal adenocarcinoma (PDAC); however, with limited efficacy. Hyperthermia (HT) treatment has been suggested as a sensitizer to improve outcomes. However, the direct effect of the HT and CT combination is not fully understood. Therefore, we aim to assess the direct cytotoxic effect of HT in PDAC cells as monotherapy or in combination with chemotherapeutics. Different temperatures (37-, 40.5-, 41-, and 41.5 °C) and durations (6-, 12-, and 24 h) were tested in PDAC cell lines (BxPC-3, Capan-1, Capan-2, PANC-1, and MIA-PaCa-2). Different concentrations of gemcitabine, 5-fluorouracil, and cisplatin were also tested in these conditions. The impact on cell metabolic activity was determined by an MTS assay. Enhancement of chemosensitivity was assessed by a reduction in half-maximal inhibitory concentration (IC50). HT and chemotherapeutics interactions were classified as antagonistic, additive, or synergistic using the combination index. HT inhibited cell proliferation in a cell type, temperature, and duration-dependent manner. The induction of apoptosis was seen after 6 h of HT treatment, eventually followed by secondary necrosis. The HT and CT combination led to an IC50 reduction of the tested CT. At 12 h of HT, this effect was between 25 to 90% and reached a 95% reduction at 24 h. The additive or synergistic effect was demonstrated in all cell lines and chemotherapeutics, although, again, this depended on cell type, duration, and temperature. HT is cytotoxic and enhances the therapeutic effectiveness of gemcitabine, 5-fluorouracil, and cisplatin on PDAC cells. This result was further confirmed by the decrease in the expression of RRM2, TS, and ERCC1 in BxPC-3 and Capan-2 cells. These observations warrant further study in specific subsets of PDAC patients to improve their clinical outcomes.

Noninvasive evaluation of hypoxia in rabbit VX2 lung transplant tumors using spectral CT parameters and texture analysis

AIM

Noninvasive evaluation of hypoxia in rabbit VX2 lung transplant tumors using spectral CT parameters and texture analysis.

MATERIALS AND METHODS

Twenty-five VX2 lung transplant tumors of twenty-two rabbits were included in the study. Contrast-enhanced spectral CT scanning in the arterial phase (AP) and venous phase (VP) was performed. Tumors were divided into strong and weak hypoxic groups by hypoxic probe staining results. Spectral CT image-related parameters [70 keV CT value, normalized iodine concentration (NIC), slope of spectral HU curve (λ_HU)] were measured and the texture analysis on the monochromatic images was performed. Imaging parameters and texture features between tumors with different hypoxic degrees were compared and their diagnostic efficacies for predicting hypoxia in lung cancers were analyzed using receiver operating characteristic (ROC) curve.

RESULTS

NIC in VP and λ_HU in VP of the strong hypoxic group were significantly higher than those in the weak hypoxic group (p < 0.05). For the texture features, entropy in VP and kurtosis in AP were significantly different between the two hypoxic groups. According to ROC analysis, λ_HU in VP had a better diagnostic ability for predicting hypoxia in tumors [Area Under Curve (AUC): 0.883, sensitivity: 85.7%, specificity: 100%]. The combination of four features improved AUC to 0.955.

CONCLUSION

NIC in VP, λ_HU in VP, entropy in VP and kurtosis in AP have certain values in predicting tumor hypoxia and a combination of image parameters and texture features improves diagnostic efficiency.

The Many Facets of Therapy Resistance and Tumor Recurrence in Glioblastoma

Glioblastoma (GBM) is the most lethal type of primary brain cancer. Standard care using chemo- and radio-therapy modestly increases the overall survival of patients; however, recurrence is inevitable, due to treatment resistance and lack of response to targeted therapies. GBM therapy resistance has been attributed to several extrinsic and intrinsic factors which affect the dynamics of tumor evolution and physiology thus creating clinical challenges. Tumor-intrinsic factors such as tumor heterogeneity, hypermutation, altered metabolomics and oncologically activated alternative splicing pathways change the tumor landscape to facilitate therapy failure and tumor progression. Moreover, tumor-extrinsic factors such as hypoxia and an immune-suppressive tumor microenvironment (TME) are the chief causes of immunotherapy failure in GBM. Amid the success of immunotherapy in other cancers, GBM has occurred as a model of resistance, thus focusing current efforts on not only alleviating the immunotolerance but also evading the escape mechanisms of tumor cells to therapy, caused by inter- and intra-tumoral heterogeneity. Here we review the various mechanisms of therapy resistance in GBM, caused by the continuously evolving tumor dynamics as well as the complex TME, which cumulatively contribute to GBM malignancy and therapy failure; in an attempt to understand and identify effective therapies for recurrent GBM.

Algae-Derived Polysaccharides Promote Growth Performance by Improving Antioxidant Capacity and Intestinal Barrier Function in Broiler Chickens

This study aimed to determine the efficacy of dietary algae-derived polysaccharides (ADPs) from Enteromorpha on growth performance, intestinal morphology, intestinal permeability, and antioxidant capacity in serum, liver, and intestinal mucosa of broilers. Three hundred and ninety six day-old male chicks were randomly assigned to six dietary treatments containing 0 (Control), 1,000, 2,500, 4,000, 5,500, and 7,000 mg ADP/kg basal diet in a 35 day feeding trial. During day 1-21, compared with the control group, dietary 1,000-7,000 mg/kg ADP supplementation improved the average daily gain (ADG) and feed conversion ratio (p < 0.05). Overall (day 1-35), dietary inclusion of 1,000 mg/kg ADP increased the final body weight and ADG (p < 0.05). Besides, on day 21, dietary 2,500 mg/kg ADP supplementation increased the serum catalase (CAT) and liver total superoxide dismutase (T-SOD) activities (p < 0.05), whereas dietary 1,000-5,500 mg/kg ADP supplementation decreased malondialdehyde (MDA) contents in serum and liver (p < 0.05). On day 35, supplementation of 1,000 mg/kg ADP increased the serum glutathione peroxidase and CAT activities and liver T-SOD activities (p < 0.05). It decreased the MDA level of serum and liver (p < 0.05). Also, dietary 2,500 mg/kg ADP increased the villus height of jejunum and ileum on day 21 (p < 0.05), and dietary 4,000 mg/kg ADP increased the villus height of duodenum and ileum on day 35 (p < 0.05). On day 21, dietary 4,000 mg/kg ADP increased the CAT activities of the duodenum and T-SOD activities of jejunum and ileum and decreased the MDA contents in the duodenum, jejunum, and ileum (p < 0.05). On day 35, dietary inclusion of 1,000-7,000 mg/kg ADP reduced MDA contents of duodenum and jejunum (p < 0.05). Furthermore, dietary inclusion of ADP at 1,000-7,000 mg/kg decreased serum DAO activities at day 21 and day 35 (p < 0.05), and the serum D-lactic acid concentration was reduced by dietary supplementation of 1,000, 2,500, and 7,000 mg/kg ADP on day 21. In conclusion, dietary ADP exerted beneficial effects on growth performance, antioxidant capacity, and gut health in broilers; based on the studied parameters, the appropriate recommended dose is 1,000-4,000 mg/kg. These findings provided new insights into the potential application of ADP as natural growth promoters in broilers.

Prognostic potential of mid-treatment nodal response in oropharyngeal squamous cell carcinoma

BACKGROUND

We examine the prognostic implications of mid-course nodal response in oropharyngeal cancer (OPX) to radiation therapy.

METHODS

In 44 patients with node-positive OPX undergoing concurrent chemoradiation, nodal volumes were measured on cone beam CTs from days 1, 10, 20, and 35. Nodal decrease (ND) was based on percent shrinkage from day 1.

RESULTS

At a median follow-up of 17 months, the 2-year disease-free survival (DFS), locoregional control (LRC), distant metastasis-free survival (DMFS), and overall survival (OS) were 87%, 92%, 89%, and 92%, respectively. Patients with ND ≥43% at D20 had improved LRC (100% vs 78.4%, P = .03) compared to D20 ND <43%. On multivariate analysis, D20 ≥43% was independently prognostic for LRC (HR 1.17, P = .05).

CONCLUSION

Patients with low-risk oropharynx cancer with ND of ≥43% by treatment day 20 had significantly improved LRC. The prognostic benefit of ND may assist in identifying candidates for treatment de-escalation.

Mitigative efficacy of the clinical dosage administration of granulocyte colony-stimulating factor and romiplostim in mice with severe acute radiation syndrome

BACKGROUND

It has been reported that the high-dosage administration of domestically approved pharmaceutical drugs, especially granulocyte colony-stimulating factor (G-CSF) and romiplostim (RP), is a rapid and appropriate medical treatment for preventing severe acute radiation syndrome (ARS) of victims exposed to lethal total-body irradiation (TBI). However, it remains unclear whether or not the clinical dosage administration of these drugs can ameliorate TBI-induced ARS and related high mortality in order to find various drug treatment options and less toxic optimum protocol depending on the situation surrounding the radiological accidents.

METHODS

We assessed the clinical dosage administration in combination with G-CSF and RP as intraperitoneal injection in C57BL/6 J mice exposed to more than 7-Gy lethal dose of X-ray TBI for the survival study evaluated by the log-rank test. Bone marrow and splenic cells were collected on the 21st day, when 1 week has passed from last administration, to detect the level of cell apoptosis, intracellular reactive oxygen species (ROS), and nuclear factor erythroid 2-related factor 2 (Nrf2)-related anti-oxidative gene expressions, and enzyme-linked immune sorbent assay using sera was performed for cell senescence and inflammation status analyzed with one-way ANOVA and Tukey-Kramer or Bonferroni/Dunn multiple comparison tests.

RESULTS

The combined once-daily administration of 10 μg/kg G-CSF for 4 times and 10 μg/kg RP once a week for 3 times improve the 30-day survival rate of lethal TBI mice compared with untreated TBI mice, accompanied by a gradual increase in the body weight and hematopoietic cell numbers. The radio-mitigative effect is probably attributed to the scavenging of ROS and the reduction in cell apoptosis. These changes were associated with the upregulation of Nrf2 and its downstream anti-oxidative targets in TBI mice. Furthermore, this combination modulated TBI-induced cell senescence an d inflammation markers.

CONCLUSIONS

This study suggested that the clinical dosage administration in combination with G-CSF and RP may also have radio-mitigative effects on mice exposed to lethal TBI and may be a potent therapeutic agent for mitigating radiation-induced severe ARS.

Hypoxia, metabolism, and the circadian clock: new links to overcome radiation resistance in high-grade gliomas

Radiotherapy is the cornerstone of treatment of high-grade gliomas (HGGs). It eradicates tumor cells by inducing oxidative stress and subsequent DNA damage. Unfortunately, almost all HGGs recur locally within several months secondary to radioresistance with intricate molecular mechanisms. Therefore, unravelling specific underlying mechanisms of radioresistance is critical to elucidating novel strategies to improve the radiosensitivity of tumor cells, and enhance the efficacy of radiotherapy. This review addresses our current understanding of how hypoxia and the hypoxia-inducible factor 1 (HIF-1) signaling pathway have a profound impact on the response of HGGs to radiotherapy. In addition, intriguing links between hypoxic signaling, circadian rhythms and cell metabolism have been recently discovered, which may provide insights into our fundamental understanding of radioresistance. Cellular pathways involved in the hypoxic response, DNA repair and metabolism can fluctuate over 24-h periods due to circadian regulation. These oscillatory patterns may have consequences for tumor radioresistance. Timing radiotherapy for specific times of the day (chronoradiotherapy) could be beneficial in patients with HGGs and will be discussed.

2-Deoxy-d-Glucose and Its Analogs: From Diagnostic to Therapeutic Agents

The ability of 2-deoxy-d-glucose (2-DG) to interfere with d-glucose metabolism demonstrates that nutrient and energy deprivation is an efficient tool to suppress cancer cell growth and survival. Acting as a d-glucose mimic, 2-DG inhibits glycolysis due to formation and intracellular accumulation of 2-deoxy-d-glucose-6-phosphate (2-DG6P), inhibiting the function of hexokinase and glucose-6-phosphate isomerase, and inducing cell death. In addition to glycolysis inhibition, other molecular processes are also affected by 2-DG. Attempts to improve 2-DG’s drug-like properties, its role as a potential adjuvant for other chemotherapeutics, and novel 2-DG analogs as promising new anticancer agents are discussed in this review.

Chemical Composition and Antioxidant Activities of Polysaccharides from Yingshan Cloud Mist Tea

The study was designed to investigate the chemical composition and antioxidant activities of polysaccharides from Yingshan Cloud Mist Tea. The chemical composition of green tea polysaccharides (GTPS) was analyzed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermogravimetric (TGA), gas chromatograph (GC), and high-performance gel-permeation chromatography (HPGPC). Then, the antioxidant activities in vitro of GTPS, effects of GTPS on body weight, and the antioxidant activities in chickens were studied. The results showed that GTPS were composed of rhamnose (Rha), arabinose (Ara), xylose (Xyl), mannose (Man), glucose (Glu), and galactose (Gal) in a molar ratio of 11.4 : 26.1 : 1.9 : 3.0 : 30.7 : 26.8 and the average molecular weight was 9.69×104 Da. Furthermore, GTPS exhibited obvious capacity of scavenging DPPH radical, hydroxyl radical, and superoxide radical and enhanced the ferric-reducing power in vitro. Last, GTPS significantly increased the body weight of chickens, enhanced the T-AOC, SOD, and GSH-Px level, and decreased the content of MDA in chickens. The results indicated that GTPS might be a kind of natural antioxidant, which had the potential application in feed industry.

Chemical Composition and Antioxidant Activities of Polysaccharides from Yingshan Cloud Mist Tea

The study was designed to investigate the chemical composition and antioxidant activities of polysaccharides from Yingshan Cloud Mist Tea. The chemical composition of green tea polysaccharides (GTPS) was analyzed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermogravimetric (TGA), gas chromatograph (GC), and high-performance gel-permeation chromatography (HPGPC). Then, the antioxidant activities in vitro of GTPS, effects of GTPS on body weight, and the antioxidant activities in chickens were studied. The results showed that GTPS were composed of rhamnose (Rha), arabinose (Ara), xylose (Xyl), mannose (Man), glucose (Glu), and galactose (Gal) in a molar ratio of 11.4 : 26.1 : 1.9 : 3.0 : 30.7 : 26.8 and the average molecular weight was 9.69×104 Da. Furthermore, GTPS exhibited obvious capacity of scavenging DPPH radical, hydroxyl radical, and superoxide radical and enhanced the ferric-reducing power in vitro. Last, GTPS significantly increased the body weight of chickens, enhanced the T-AOC, SOD, and GSH-Px level, and decreased the content of MDA in chickens. The results indicated that GTPS might be a kind of natural antioxidant, which had the potential application in feed industry.

Functionalized Superparamagnetic Iron Oxide Nanoparticles (SPIONs) as Platform for the Targeted Multimodal Tumor Therapy

Standard cancer treatments involve surgery, radiotherapy, chemotherapy, and immunotherapy. In clinical practice, the respective drugs are applied orally or intravenously leading to their systemic circulation in the whole organism. For chemotherapeutics or immune modulatory agents, severe side effects such as immune depression or autoimmunity can occur. At the same time the intratumoral drug doses are often too low for effective cancer therapy. Since monotherapies frequently cannot cure cancer, due to their synergistic effects multimodal therapy concepts are applied to enhance treatment efficacy. The targeted delivery of drugs to the tumor by employment of functionalized nanoparticles might be a promising solution to overcome these challenges. For multimodal therapy concepts and individualized patient care nanoparticle platforms can be functionalized with compounds from various therapeutic classes (e.g. radiosensitizers, phototoxic drugs, chemotherapeutics, immune modulators). Superparamagnetic iron oxide nanoparticles (SPIONs) as drug transporters can add further functionalities, such as guidance or heating by external magnetic fields (Magnetic Drug Targeting or Magnetic Hyperthermia), and imaging-controlled therapy (Magnetic Resonance Imaging).

The LNT model for cancer induction is not supported by radiobiological data

The hallmarks of cancer have been the focus of much research and have influenced the development of risk models for radiation-induced cancer. However, natural defenses against cancer, which constitute the hallmarks of cancer prevention, have largely been neglected in developing cancer risk models. These natural defenses are enhanced by low doses and dose rates of ionizing radiation, which has aided in the continuation of human life over many generations. Our natural defenses operate at the molecular, cellular, tissue, and whole-body levels and include epigenetically regulated (epiregulated) DNA damage repair and antioxidant production, selective p53-independent apoptosis of aberrant cells (e.g. neoplastically transformed and tumor cells), suppression of cancer-promoting inflammation, and anticancer immunity (both innate and adaptive components). This publication reviews the scientific bases for the indicated cancer-preventing natural defenses and evaluates their implication for assessing cancer risk after exposure to low radiation doses and dose rates. Based on the extensive radiobiological evidence reviewed, it is concluded that the linear-no-threshold (LNT) model (which ignores natural defenses against cancer), as it relates to cancer risk from ionizing radiation, is highly implausible. Plausible models include dose-threshold and hormetic models. More research is needed to establish when a given model (threshold, hormetic, or other) applies to a given low-dose-radiation exposure scenario.

Hypoxia-targeted drug delivery

Hypoxia is a state of low oxygen tension found in numerous solid tumours. It is typically associated with abnormal vasculature, which results in a reduced supply of oxygen and nutrients, as well as impaired delivery of drugs. The hypoxic nature of tumours often leads to the development of localized heterogeneous environments characterized by variable oxygen concentrations, relatively low pH, and increased levels of reactive oxygen species (ROS). The hypoxic heterogeneity promotes tumour invasiveness, metastasis, angiogenesis, and an increase in multidrug-resistant proteins. These factors decrease the therapeutic efficacy of anticancer drugs and can provide a barrier to advancing drug leads beyond the early stages of preclinical development. This review highlights various hypoxia-targeted and activated design strategies for the formulation of drugs or prodrugs and their mechanism of action for tumour diagnosis and treatment.

Chemical Composition and Antioxidant Activities of Polysaccharides from Yingshan Cloud Mist Tea

The study was designed to investigate the chemical composition and antioxidant activities of polysaccharides from Yingshan Cloud Mist Tea. The chemical composition of green tea polysaccharides (GTPS) was analyzed by Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), thermogravimetric (TGA), gas chromatograph (GC), and high-performance gel-permeation chromatography (HPGPC). Then, the antioxidant activities in vitro of GTPS, effects of GTPS on body weight, and the antioxidant activities in chickens were studied. The results showed that GTPS were composed of rhamnose (Rha), arabinose (Ara), xylose (Xyl), mannose (Man), glucose (Glu), and galactose (Gal) in a molar ratio of 11.4 : 26.1 : 1.9 : 3.0 : 30.7 : 26.8 and the average molecular weight was 9.69 × 10⁴ Da. Furthermore, GTPS exhibited obvious capacity of scavenging DPPH radical, hydroxyl radical, and superoxide radical and enhanced the ferric-reducing power in vitro. Last, GTPS significantly increased the body weight of chickens, enhanced the T-AOC, SOD, and GSH-Px level, and decreased the content of MDA in chickens. The results indicated that GTPS might be a kind of natural antioxidant, which had the potential application in feed industry.

Dose-Dependent Increase of Nrf2 Target Gene Expression in Mice Exposed to Ionizing Radiation

Nuclear factor-erythroid-2-related factor 2 transcription factor (Nrf2) is activated by reactive oxygen species (ROS) and binds to antioxidant response elements in the promoter regions of its target genes involved in redox regulation and antioxidative functions. In this study, we elucidated the relationship between radiation dose and the expression response of Nrf2 target genes involved in oxidative stress, such as heme oxygenase 1, ferritin heavy polypeptide 1 ( Fth1), NADPH dehydrogenase quinone 1, glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione reductase ( Gsr) and thioredoxin reductase 1 genes, in peripheral blood from X-ray irradiated mice. Whole-body radiation doses ranged from 0.5 to 3 Gy, and gene expressions were analyzed using reverse transcription quantitative polymerase chain reaction. A significant relationship was observed only for one gene: a statistically significant positive correlation between radiation dose and Fth1 mRNA expression was detected. However, Fth1 did not show any correlations with the biological damages induced by radiation tested in this study. Furthermore, while Gsr expression was significantly associated with spleen weight loss, splenic cell number reduction and bone marrow cell death apoptosis, no significant correlation was observed between Gsr expression and radiation dose. Together these results indicate that Nrf2 target gene expression is closely related to radiation dose and its level may reflect biological damages induced by ionizing radiation. These findings suggest the possibility for application of these target genes as a bio-dosimeter and/or damage marker in individuals exposed to ionizing radiation.

Stereotactic radiosurgery for brain metastases from malignant melanoma and the impact of hemorrhagic metastases

INTRODUCTION

Stereotactic radiosurgery (SRS) is a common treatment modality among patients with brain metastases, particularly from malignant melanoma. Our objective was to investigate the difference in local control, toxicity, and survival among patients with hemorrhagic and solid melanoma brain metastases.

METHODS

We collected demographic, treatment, local control, toxicity, and survival for 134 patients with a total of 936 intracranial melanoma metastases who underwent SRS between 1998 and 2015. Pre-radiosurgical diagnostic imaging was reviewed for evidence of hemorrhage (melanin-containing or clearly hemorrhagic).

RESULTS

The cohort consisted of 92 men and 42 women with a mea age of 61.7 years (range 21.2-84.9) at the time of radiosurgery. Overall survival of patients with brain metastases from malignant melanoma was 42, 31, 12% at 12, 24, and 72 months from date of first SRS. At 6 months, 43% of the patients with hemorrhagic metastases had local tumor control compared to 83% of solid melanoma metastases (p < 0.001). No significant difference in toxicity was noted between the two groups. Factors that were significantly associated with time to local tumor progression on multivariate analysis include prior WBRT (HR 1.62, p = 0.003), prior chemotherapy (HR 0.69, p = 0.011), margin dose (HR 0.88, p < 0.001) and radiographic features of melanin deposition (HR 3.73, p < 0.001), or clear hemorrhage (HR 2.20, p < 0.001).

CONCLUSIONS

Our findings demonstrate that hemorrhagic intracranial melanoma metastases are associated with inferior local tumor control when treated with SRS, as compared to solid tumors. These results highlight the importance of early radiosurgery among patients with melanoma brain metastases before hemorrhage occurs.

Image-guided adaptive radiotherapy in patients with locally advanced non-small cell lung cancer: the art of PET

With a worldwide annual incidence of 1.8 million cases, lung cancer is the most diagnosed form of cancer in men and the third most diagnosed form of cancer in women. Histologically, 80-85% of all lung cancers can be categorized as non-small cell lung cancer (NSCLC). For patients with locally advanced NSCLC, standard of care is fractionated radiotherapy combined with chemotherapy. With the aim of improving clinical outcome of patients with locally advanced NSCLC, combined and intensified treatment approaches are increasingly being used. However, given the heterogeneity of this patient group with respect to tumor biology and subsequent treatment response, a personalized treatment approach is required to optimize therapeutic effect and minimize treatment induced toxicity. Medical imaging, in particular positron emission tomography (PET), before and during the course radiotherapy is increasingly being used to personalize radiotherapy. In this setting, PET imaging can be used to improve delineation of target volumes, employ molecularly-guided dose painting strategies, early response monitoring, prediction and monitoring of treatment-related toxicity. The concept of PET image-guided adaptive radiotherapy (IGART) is an interesting approach to personalize radiotherapy for patients with locally advanced NSCLC, which might ultimately contribute to improved clinical outcomes and reductions in frequency of treatment-related adverse events in this patient group. In this review, we provide a comprehensive overview of available clinical data supporting the use of PET imaging for IGART in patients with locally advanced NSCLC.

Overcoming hypoxia-induced tumor radioresistance in non-small cell lung cancer by targeting DNA-dependent protein kinase in combination with carbon ion irradiation

Background

Hypoxia-induced radioresistance constitutes a major obstacle for a curative treatment of cancer. The aim of this study was to investigate effects of photon and carbon ion irradiation in combination with inhibitors of DNA-Damage Response (DDR) on tumor cell radiosensitivity under hypoxic conditions.

Methods

Human non-small cell lung cancer (NSCLC) models, A549 and H1437, were irradiated with dose series of photon and carbon ions under hypoxia (1% O₂) vs. normoxic conditions (21% O₂). Clonogenic survival was studied after dual combinations of radiotherapy with inhibitors of DNA-dependent Protein Kinase (DNAPKi, M3814) and ATM serine/threonine kinase (ATMi).

Results

The OER at 30% survival for photon irradiation of A549 cells was 1.4. The maximal oxygen effect measured as survival ratio was 2.34 at 8 Gy photon irradiation of A549 cells. In contrast, no significant oxygen effect was found after carbon ion irradiation. Accordingly, the relative effect of 6 Gy carbon ions was determined as 3.8 under normoxia and. 4.11 under hypoxia. ATM and DNA-PK inhibitors dose dependently sensitized tumor cells for both radiation qualities. For 100 nM DNAPKi the survival ratio at 4 Gy more than doubled from 1.59 under normoxia to 3.3 under hypoxia revealing a strong radiosensitizing effect under hypoxic conditions. In contrast, this ratio only moderately increased after photon irradiation and ATMi under hypoxia. The most effective treatment was combined carbon ion irradiation and DNA damage repair inhibition.

Conclusions

Carbon ions efficiently eradicate hypoxic tumor cells. Both, ATMi and DNAPKi elicit radiosensitizing effects. DNAPKi preferentially sensitizes hypoxic cells to radiotherapy.

Electronic supplementary material

The online version of this article (10.1186/s13014-017-0939-0) contains supplementary material, which is available to authorized users.

Involvement of reactive oxygen species in ionizing radiation-induced upregulation of cell surface Toll-like receptor 2 and 4 expression in human monocytic cells

Toll-like receptors (TLRs) are pattern recognition receptors that recognize pathogen-associated molecular patterns and are indispensable for antibacterial and antiviral immunity. Our previous report showed that ionizing radiation increases the cell surface expressions of TLR2 and TLR4 and enhances their responses to agonists in human monocytic THP1 cells. The present study investigated how ionizing radiation increases the cell surface expressions of TLR2 and TLR4 in THP1 cells. The THP1 cells treated or not treated with pharmaceutical agents such as cycloheximide and N-acetyl-L-cysteine (NAC) were exposed to X-ray irradiation, following which the expressions of TLRs and mitogen-activated protein kinase were analyzed. X-ray irradiation increased the mRNA expressions of TLR2 and TLR4, and treatment with a protein synthesis inhibitor cycloheximide abolished the radiation-induced upregulation of their cell surface expressions. These results indicate that radiation increased those receptors through de novo protein synthesis. Furthermore, treatment with an antioxidant NAC suppressed not only the radiation-induced upregulation of cell surface expressions of TLR2 and TLR4, but also the radiation-induced activation of the c-Jun N-terminal kinase (JNK) pathway. Since it has been shown that the inhibitor for JNK can suppress the radiation-induced upregulation of TLR expression, the present results suggest that ionizing radiation increased the cell surface expressions of TLR2 and TLR4 through reactive oxygen species-mediated JNK activation.

Strategy of Using Intratreatment Hypoxia Imaging to Selectively and Safely Guide Radiation Dose De-escalation Concurrent With Chemotherapy for Locoregionally Advanced Human Papillomavirus-Related Oropharyngeal Carcinoma

PURPOSE

To report a small substudy of an ongoing large, multi-arm study using functional imaging to assess pre-/intratreatment hypoxia for all head and neck cancer, in which we hypothesized that pre- and early-treatment hypoxia assessment using functional positron emission tomography (PET) imaging may help select which human papillomavirus (HPV)-positive (HPV(+)) oropharyngeal cancer (OPC) patients can safely receive radiation de-escalation without jeopardizing treatment outcomes.

METHODS AND MATERIALS

Patients with HPV(+) oropharyngeal carcinoma were enrolled on an institutional review board-approved prospective study of which de-escalation based on imaging response was done for node(s) only. Pretreatment (18)F-fluorodeoxyglucose and dynamic (18)F-FMISO (fluoromisonidazole) positron emission tomography (PET) scans were performed. For patients with pretreatment hypoxia on(18)F-FMISO PET (defined as a >1.2 tumor to muscle standard uptake value ratio), a repeat scan was done 1 week after chemoradiation. Patients without pretreatment hypoxia or with resolution of hypoxia on repeat scan received a 10-Gy dose reduction to metastatic lymph node(s). The 2-year local, regional, distant metastasis-free, and overall survival rates were estimated using the Kaplan-Meier product-limit method. A subset of patients had biopsy of a hypoxic node done under image guidance.

RESULTS

Thirty-three HPV(+) OPC patients were enrolled in this pilot study. One hundred percent showed pretreatment hypoxia (at primary site and/or node[s]), and among these, 48% resolved (at primary site and/or node[s]); 30% met criteria and received 10-Gy reduction to the lymph node(s). At the median follow-up of 32 months (range, 21-61 months), the 2-year locoregional control rate was 100%. One patient failed distantly with persistence of hypoxia on (18)F-FMISO PET. The 2-year distant metastasis-free rate was 97%. The 2-year OS rate was 100%. Hypoxia on imaging was confirmed pathologically.

CONCLUSIONS

Hypoxia is present in HPV(+) tumors but resolves within 1 week of treatment in 48% of cases either at the primary site and/or lymph node(s). Our 100% locoregional control rate suggests that intratreatment functional imaging used to selectively de-escalate node(s) to 60 Gy was confirmed safe using our stringent imaging criteria. Intratreatment functional imaging warrants further study to determine its ultimate role in de-escalation treatment strategies.

Curcumin Stimulates the Antioxidant Mechanisms in Mouse Skin Exposed to Fractionated γ-Irradiation

Fractionated irradiation is one of the important radiotherapy regimens to treat different types of neoplasia. Despite of the immense therapeutic gains accrued by delivering fractionated irradiation to tumors, the radiation burden on skin increases significantly. Low doses of irradiation to skin adversely affect its molecular and metabolic status. The use of antioxidant/s may help to alleviate the radiation-induced changes in the skin and allow delivering a higher dose of radiation to attain better therapeutic gains. Curcumin is an antioxidant and a free radical scavenging dietary supplement, commonly used as a flavoring agent in curries. Therefore, the effect of 100 mg/kg body weight curcumin was studied on the antioxidant status of mice skin exposed to a total dose of 10, 20 and 40 Gy γ-radiation below the rib cage delivered as a single fraction of 2 Gy per day for 5, 10 or 20 days. Skin biopsies from both the curcumin treated or untreated irradiated groups were collected for the biochemical estimations at various post-irradiation times. The irradiation of animals caused a dose dependent decline in the glutathione concentration, glutathione peroxidase, and superoxide dismutase activities and increased the lipid peroxidation in the irradiated skin. Curcumin treatment before irradiation resulted in a significant rise in the glutathione concentration and activities of both the glutathione peroxidase and superoxide dismutase enzymes in mouse skin, whereas lipid peroxidation declined significantly. The present study indicates that curcumin treatment increased the antioxidant status of mouse exposed to different doses of fractionated γ-radiation.

Repeated Nrf2 stimulation using sulforaphane protects fibroblasts from ionizing radiation

Most of the cytotoxicity induced by ionizing radiation is mediated by radical-induced DNA double-strand breaks. Cellular protection from free radicals can be stimulated several fold by sulforaphane-mediated activation of the transcription factor Nrf2 that regulates more than 50 genes involved in the detoxification of reactive substances and radicals. Here, we report that repeated sulforaphane treatment increases radioresistance in primary human skin fibroblasts. Cells were either treated with sulforaphane for four hours once or with four-hour treatments repeatedly for three consecutive days prior to radiation exposure. Fibroblasts exposed to repeated-sulforaphane treatment showed a more pronounced dose-dependent induction of Nrf2-regulated mRNA and reduced amount of radiation-induced free radicals compared with cells treated once with sulforaphane. In addition, radiation- induced DNA double-strand breaks measured by gamma-H2AX foci were attenuated following repeated sulforaphane treatment. As a result, cellular protection from ionizing radiation measured by the 5-ethynyl-2'-deoxyuridine (EdU) assay was increased, specifically in cells exposed to repeated sulforaphane treatment. Sulforaphane treatment was unable to protect Nrf2 knockout mouse embryonic fibroblasts, indicating that the sulforaphane-induced radioprotection was Nrf2-dependent. Moreover, radioprotection by repeated sulforaphane treatment was dose-dependent with an optimal effect at 10 uM, whereas both lower and higher concentrations resulted in lower levels of radioprotection. Our data indicate that the Nrf2 system can be trained to provide further protection from radical damage.

Megakaryocytic differentiation in human chronic myelogenous leukemia K562 cells induced by ionizing radiation in combination with phorbol 12-myristate 13-acetate

Differentiation-induction therapy is an attractive approach in leukemia treatment. It has been suggested that the accumulation of intracellular reactive oxygen species (ROS) is involved in megakaryocytic differentiation induced by phorbol 12-myristate 13-acetate (PMA) in the K562 leukemia cell line. Therefore, a ROS-inducible technique could be a powerful method of differentiation induction. Accordingly, we hypothesized that ionizing radiation contributes to the acceleration of megakaryocytic differentiation through the accumulation of intracellular ROS in leukemia cells. In the present study, ionizing radiation was shown to promote PMA-induced megakaryocytic differentiation. Cells with high CD41 expression sustained intracellular ROS levels effectively. The enhancement of differentiation by ionizing radiation was found to be regulated through the mitogen-activated protein kinase (MAPK) pathway, involving both extracellular signal-regulated protein kinase 1/2 (ERK1/2) and p38 MAPK. Ionizing radiation also controlled mRNA expression of the oxidative stress response gene heme oxygenase-1 (HO1). Consequently, we concluded that intracellular ROS, increased by ionizing radiation, modulate megakaryocytic differentiation downstream of the MAPK pathway.

Response of the Nrf2 protection system in human monocytic cells after ionising irradiation

In response to reactive oxygen species (ROS) or electrophiles, the transcription factor nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) rapidly translocates into the nucleus and induces the expression of various antioxidant genes, such as heme oxygenase-1 (HO-1). Low linear energy transfer (LET) ionising radiations such as X-rays generate ROS, which cause biological damage. However, little is known about whether the Nrf2 system in human monocytic cells is activated by low LET ionising irradiation. Therefore, in this study, the response of the Nrf2 system to X-irradiation in human monocytic THP1 cells was investigated. Following exposure of THP1 cells to X-rays (1-5 Gy), intracellular ROS levels were measured using 2',7'-dichlorodihydrofluorescein diacetate, Nrf2 localisation was determined using immunofluorescence staining and HO-1 mRNA and protein expression were examined. Although ROS were generated by irradiation in a dose-dependent manner, they disappeared immediately after irradiation. Nrf2 translocation into the nucleus was observed 6 h after 5 Gy X-irradiation but was not detected following 1-2 Gy irradiation or in non-irradiated controls. HO-1 expression was significantly higher in 5 Gy-irradiated cells after 24 h than in non-irradiated controls. These results indicate that high-dose irradiation (5 Gy) activates Nrf2 and that the Nrf2 protection system may function from 24 h after irradiation in human monocytic cells.

Animal model for oxidative stress research-Catalase mutant mice

Catalase-deficient mouse strains was initially established by Feinstein et al. through a large scale screening of the progeny of irradiated C3H mice in 1966. Later, Feinstein provided the mice of catalase mutant strain C3H/AnICs(a)Cs(a) (wild-type), C3H/AnICs(b)Cs(b) and C3H/AnlCs(c)Cs(c) to Okayama University Medical School in Japan. It is known that a point mutation at amino acid 11 (from glutamine to histidine) of acatalasemic mouse catalase and a point mutation at amino acid 439 (from as paragine to serine) of hypocatalasemic mouse catalase are responsible for the catalase deficiency of acatalasemic and hypocatalasemic mice, respectively. Recently, a liver cell line from an acatalasemic mouse andEscherichia coli (E. coli) strains with murine normal, hypocatalasemic, or acatalasemic catalase have been established. The construction of these new systems would be useful for studying the effects of oxidative stress at the cellular level. In this review, we give a brief overview of recent findings of studies in utilizing the catalase-deficient mice and evaluate the possibility of these mouse strains as a candidate animal model for oxidative stress research.

Low energy electron stimulated desorption from DNA films dosed with oxygen

Desorption of anions stimulated by 1-18 eV electron impact on self-assembled monolayer (SAM) films of single DNA strands is measured as a function of film temperature (50-250 K). The SAMs, composed of 10 nucleotides, are dosed with O(2). The OH(-) desorption yields increase markedly with exposure to O(2) at 50 K and are further enhanced upon heating. In contrast, the desorption yields of O(-), attributable to dissociative electron attachment to trapped O(2) molecules decrease with heating. Irradiation of the DNA films prior to the deposition of O(2) shows that this surprising increase in OH(-) desorption, at elevated temperatures, arises from the reaction of O(2) with damaged DNA sites. These results thus appear to be a manifestation of the so-called "oxygen fixation" effect, well known in radiobiology.

Induction of Strand Breaks in DNA films by Low Energy Electrons and Soft X-ray under Nitrous Oxide Atmosphere

Five-monolayer (5ML) plasmid DNA films deposited on glass and tantalum substrates were exposed to Al K_α X-rays of 1.5 keV under gaseous nitrous oxide (N₂O) at atmospheric pressure and temperature. Whereas the damage yields for DNA deposited on glass are due to soft X-rays, those arising from DNA on tantalum are due to both the interaction of low energy photoelectrons from the metal and X-rays. Then, the differences in the yields of damage on glass and tantalum substrates, essentially arises from interaction of essentially low-energy electrons (LEEs) with DNA molecules and the surrounding atmosphere. The G-values (i.e., the number of moles of product per Joule of energy absorbed) for DNA strand breaks induced by LEEs (G_LEE) and the lower limit of G-values for soft X-ray photons (G_XL) were calculated and the results compared to those from previous studies under atmospheric conditions and other ambient gases, such as N₂ and O₂. Under N₂O, the G-values for loss of supercoiled DNA are 103±15 nmol/J for X-rays, and 737±110 nmol/J for LEEs. Compared to corresponding values in an O₂ atmosphere, the effectiveness of X-rays to damage DNA in N₂O is less, but the G value for LEEs in N₂O is more than twice the corresponding value for an oxygenated environment. This result indicates a higher effectiveness for LEEs relative to N₂ and O₂ environments in causing SSB and DSB in an N₂O environment. Thus, the previously observed radiosensitization of cells by N₂O may not be only due to OH^• radicals but also to the reaction of LEE with N₂O molecules near DNA. The previous experiments with N₂ and O₂ and the present one demonstrate the possibility to investigate damage induced by LEEs to biomolecules under various type of surrounding atmospheres.

Soft X-ray and low energy electron-induced damage to DNA under N2 and O2 atmospheres

DNA damage induced by low energy electrons (LEEs) and soft X-rays is measured under dry nitrogen and oxygen at atmospheric pressure and temperature. Five-monolayer plasmid DNA films deposited on tantalum and glass substrates are exposed to Al K(α) X-rays of 1.5 keV in the two different environments. From the damage yields for DNA, G values are extracted for X-rays and LEEs. The G values for LEEs are 3.5 and 3.4 higher than those for X-ray photons under N(2) and O(2) atmospheres, respectively. Because most of the measured damage is in the form of single strand breaks (SSB), this result indicates a much higher effectiveness for LEEs relative to X-rays in causing SSB in both environments. The results indicate that the oxygen fixation mechanism, which is highly effective in increasing radiobiological effectiveness, under aerobic conditions, is operative on the type of damage created at the early stage of DNA radiolysis by LEEs.

The genomic, biochemical, and cellular responses of the retina in inherited photoreceptor degenerations and prospects for the treatment of these disorders

The association of more than 140 genes with human photoreceptor degenerations, together with studies of animal models of these monogenic diseases, has provided great insight into their pathogenesis. Here we review the responses of the retina to photoreceptor mutations, including mechanisms of photoreceptor death. We discuss the roles of oxidative metabolism, mitochondrial reactive oxygen species, metabolic stress, protein misfolding, and defects in ciliary proteins, as well as the responses of Müller glia, microglia, and the retinal vasculature. Finally, we report on potential pharmacologic and biologic therapies, the critical role of histopathology as a prerequisite to treatment, and the exciting promise of gene therapy in animal models and in phase 1 trials in humans.

Anti-oxidation activity of the crude polysaccharides isolated from Polygonum cillinerve (Nakai) Ohwi in immunosuppressed mice

AIM OF THE STUDY

Polygonum cillinerve (Nakai) Ohwi is commonly used in China for over 2000 years. Previous research has shown that the crude polysaccharides extracted from Polygonum cillinerve (Nakai) Ohwi (PCCP) have the scavenging free radicals and anti-tumor activities in vitro. In present study, PCCP were further approached the perspective of their anti-oxidation in immunosuppressed mice.

METHODS AND MATERIALS

ICR mice were treated firstly with cyclophosphamide (CY, 150 mg/kg), 1 day later, treated with different dosages of PCCP or saline solution once daily for 21 days. Twenty-four hours later for the last drug administration, the animals were weighed, and then killed by decapitation. The liver, spleen, and thymus indices were investigated, and the biochemical parameters were evaluated for various tissues (liver, heart, and kidney).

RESULTS

The administration of PCCP with gavage was able to overcome the cyclophosphamide-induced immunosuppression, and significantly to raise the TOC, CAT, SOD, and GSH-Px level. It also raised the liver, spleen, and thymus indices, and decreased the MDA level in mice.

CONCLUSIONS

PCCP possess the pronounced free radical-scavenging and antioxidant activities, and could play an important role in the prevention of oxidative damage in immunological system.

Relationship between radiosensitivity and Nrf2 target gene expression in human hematopoietic stem cells

NFE2-related factor 2 (Nrf2), which belongs to the cap "n" collar family of basic region leucine zipper transcription factors, is a key protein in the coordinated transcriptional induction of expression of various antioxidant genes. The purpose of this study was to analyze the expression of Nrf2 target genes, such as heme oxygenase 1 (HO-1), ferritin heavy polypeptide 1 (FTH1), NAD(P)H dehydrogenase, quinone 1 (NQO1), glutamate-cysteine ligase catalytic subunit, glutamate-cysteine ligase modifier subunit, glutathione reductase (GSR) and thioredoxin reductase 1 (TXNRD1), after X irradiation of CD34(+) cells that were prepared from human placental/umbilical cord blood hematopoietic stem cells (HSCs). We evaluated the relationship between radiosensitivity and expression of Nrf2 target genes in HSCs. The number of colony-forming cells derived from 2-Gy-irradiated HSCs decreased to approximately 20% of the nonirradiated control. At the same time, the mRNA expression of HO-1, FTH1, NQO1, GSR and TXNRD1 was significantly increased after X irradiation. A statistically significant negative correlation was observed between the surviving fraction of HSCs and the intrinsic NQO1 mRNA expression, indicating that HSCs in which NQO1 mRNA levels are low may also be radioresistant. The present results suggest that the antioxidant system associated with Nrf2 is involved in the radiosensitivity of HSCs.

Phloroglucinol (1,3,5-trihydroxybenzene) protects against ionizing radiation-induced cell damage through inhibition of oxidative stress in vitro and in vivo

Exposure of cells to gamma-rays induces the production of reactive oxygen species (ROS) that play a main role in ionizing radiation damage. We have investigated the radioprotective effect of phloroglucinol (1,3,5-trihydroxybenzene), phlorotannin compound isolated from Ecklonia cava, against gamma-ray radiation-induced oxidative damage in vitro and in vivo. Phloroglucinol significantly decreased the level of radiation-induced intracellular ROS and damage to cellular components such as the lipid, DNA and protein. Phloroglucinol enhanced cell viability that decreased after exposure to gamma-rays and reduced radiation-induced apoptosis via inhibition of mitochondria mediated caspases pathway. Phloroglucinol reduced radiation-induced loss of the mitochondrial membrane action potential, reduced the levels of the active forms of caspase 9 and 3 and elevated the expression of bcl-2. Furthermore, the anti-apoptotic effect of phloroglucinol was exerted via inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1), c-Jun NH(2)-terminal kinase (JNK) and activator protein-1 (AP-1) cascades induced by radiation exposure. Phloroglucinol restored the level of reduced glutathione (GSH) and protein expression of a catalytically active subunit of glutamate-cysteine ligase (GCL), which is a rate-limiting enzyme in GSH biosynthesis. In in vivo study, phloroglucinol administration in mice provided substantial protection against death and oxidative damage following whole-body irradiation. We examined survival with exposure to various radiation doses using the intestinal crypt assay and determined a dose reduction factor (DRF) of 1.24. Based on our findings, phloroglucinol may be possibly useful as a radioprotective compound.

Ion beam radiobiology and cancer: time to update ourselves

High-energy protons and carbon ions exhibit an inverse dose profile allowing for increased energy deposition with penetration depth. Additionally, heavier ions like carbon beams have the advantage of a markedly increased biological effectiveness characterized by enhanced ionization density in the individual tracks of the heavy particles, where DNA damage becomes clustered and therefore more difficult to repair, but is restricted to the end of their range. These superior biophysical and biological profiles of particle beams over conventional radiotherapy permit more precise dose localization and make them highly attractive for treating anatomically complex and radioresistant malignant tumors but without increasing the severe side effects in the normal tissue. More than half a century since Wilson proposed their use in cancer therapy, the effects of particle beams have been extensively investigated and the biological complexity of particle beam irradiation begins to unfold itself. The goal of this review is to provide an as comprehensive and up-to-date summary as possible of the different radiobiological aspects of particle beams for effective application in cancer treatment.

N-acetyl cysteine protects against ionizing radiation-induced DNA damage but not against cell killing in yeast and mammals

Ionizing radiation (IR) induces DNA strand breaks leading to cell death or deleterious genome rearrangements. In the present study, we examined the role of N-acetyl-L-cysteine (NAC), a clinically proven safe agent, for it's ability to protect against gamma-ray-induced DNA strand breaks and/or DNA deletions in yeast and mammals. In the yeast Saccharomyces cerevisiae, DNA deletions were scored by reversion to histidine prototrophy. Human lymphoblastoid cells were examined for the frequency of gamma-H2AX foci formation, indicative of DNA double strand break formation. DNA strand breaks were also measured in mouse peripheral blood by the alkaline comet assay. In yeast, NAC reduced the frequency of IR-induced DNA deletions. However, NAC did not protect against cell death. NAC also reduced gamma-H2AX foci formation in human lymphoblastoid cells but had no protective effect in the colony survival assay. NAC administration via drinking water fully protected against DNA strand breaks in mice whole-body irradiated with 1Gy but not with 4Gy. NAC treatment in the absence of irradiation was not genotoxic. These data suggest that, given the safety and efficacy of NAC in humans, NAC may be useful in radiation therapy to prevent radiation-mediated genotoxicity, but does not interfere with efficient cancer cell killing.

Radioprotective effect of a metalloporphyrin compound in rat eye model

PURPOSE

The purpose of this study was to evaluate the efficacy of the antioxidant Mn (III) tetrakis (N-ethylpyridinium-2-yl) porphyrin (MnTE-2-PyP) in protecting ocular tissue and retinal microvasculature from radiation damage.

MATERIALS AND METHODS

75 rats were treated with Mn TE-2-PyP at 2.5 micro g/injection into one eye an hour before proton irradiation. The radiation was delivered in a single fraction to total doses of 8 Gray (Gy) or 28 Gy; Rats were sacrificed 3 days and 3, 6, 9, and 12 months thereafter for histology and quantification of photoreceptor cell populations and retinal capillary changes.

RESULTS

By 6 months following radiation, there was significant loss of retinal outer and inner nuclear layers in eyes receiving radiation only (8 and 28 Gy) (p < 0.05) compared to their controls and to the eyes of rats treated with radiation plus metalloporphyrin. Retinal microvessel length density decreased significantly 6 months following 28 Gy (p < 0.05) compared to their controls and to MnTE-2-PyP treated rats. By 12 months following irradiation, irradiated eyes showed extensive damage to the photoreceptor layer, whereas the eyes of animals receiving radiation plus MnTE-2-PyP showed almost no morphological damage. MnTE-2-PyP treatment also suppressed radiation-induced apoptosis in our study.

CONCLUSIONS

These results demonstrated that MnTE-2-PyP protected both photoreceptors and retinal capillaries from radiation damage, suggesting that this metalloporphyrin antioxidant is effective in regulating the damage induced by proton radiation.

The interactions of polarographic measurements of oxygen tension and histological grade in human glioma

PURPOSE

The purpose of this study is to investigate the implications of hypoxia and histological grade for survival in patients with gliomas.

MATERIALS AND METHODS

Tissue oxygen tension was measured intraoperatively using an Eppendorf pO2 Histograph. Survival was calculated from the date of the Eppendorf study to the date of last follow-up. Univariate analysis was performed stratifying patients by patient gender, type of anesthesia used, histological grade, extent of surgery, and patient age. Lastly univariate analysis was performed on the cohort after dichotomizing the median pO2 at 2.0 mmHg, 5.1 mmHg, and 10.0 mmHg.

RESULTS

From March of 1996 to June of 1999, 25 patients were entered into this prospective trial. Two patients were excluded from analysis because polarographic measurements included normal brain tissue as well as tumor. Thus for analysis we included 13 patients with high grade gliomas (HGG) and 10 with low grade gliomas (LGG). The median tumor oxygen pressure for the entire cohort was 5.1 mmHg. Higher grade (P=0.0012) was prognostic for poorer survival. Patients were then stratified into groups with a median tumor oxygen tensions either above or below 2.0 mmHg, 5.1 mmHg, and 10.0 mmHg; there was no significant difference found in overall survival.

CONCLUSIONS

Although histological grade was prognostic for survival, hypoxia, represented as the median tumor oxygen tension, was not a significant independent prognostic indicator of survival in this small and heterogeneous series of patients.

[Induction of glutathione and activation of immune functions by low-dose, whole-body irradiation with gamma-rays]

We first examined the relation between the induction of glutathione and immune functions in mice after low-dose gamma-ray irradiation. Thereafter, inhibition of tumor growth by radiation was confirmed in Ehrlich solid tumor (EST)-bearing mice. The total glutathione level of the splenocytes transiently increased soon after irradiation and reached a maximum at around 4 h postirradiation. Thereafter, the level reverted to the 0 h value by 24 h postirradiation. A significantly high splenocyte proliferative response was also recognized 4 h postirradiation. Natural killer (NK) activity was also increased significantly in a similar manner. The time at which the response reached the maximum coincided well with that of maximum total glutathione levels of the splenocytes in the gamma-ray-irradiated mice. Reduced glutathione exogenously added to splenocytes obtained from normal mice enhanced the proliferative response and NK activity in a dose-dependent manner. The inhibitory effects of radiation on tumor growth was then examined in EST-bearing mice. Repeated low-dose irradiation (0.5 Gy, four times, before and within an early time after inoculation) significantly delayed the tumor growth. Finally, the effect of single low-dose (0.5 Gy), whole-body gamma-ray irradiation on immune balance was examined to elucidate the mechanism underlying the antitumor immunity. The percentage of B cells in blood lymphocytes was selectively decreased after radiation, concomitant with an increase in that of the helper T cell population. The IFN-gamma level in splenocyte culture prepared from EST-bearing mice was significantly increased 48 h after radiation, although the level of IL-4 was unchanged. IL-12 secretion from macrophages was also enhanced by radiation. These results suggest that low-dose gamma-rays induce Th1 polarization and enhance the activities of tumoricidal effector cells, leading to an inhibition of tumor growth.

Effects of gamma irradiation on morphological changes and biological responses in plants

This review discusses the morphological changes and biological responses of plants irradiated with gamma rays. Seedlings exposed to relatively low doses of gamma rays (1-5 Gy) developed normally, while the growth of plants irradiated with a high dose gamma ray (50 Gy) was significantly inhibited. Based on TEM observations, chloroplasts were extremely sensitive to gamma irradiation compared to other cell organelles, particularly thylakoids being heavily swollen. In addition, some portions of the mitochondria and endoplasmic reticulum were structurally altered, for example, distortion and swelling. The cerium perhydroxide deposition, as a maker for H(2)O(2) deposition, was typically manifest on the plasma membranes and cell walls of the tissues from both the control and irradiated plants. However, the intensities of cerium perhydroxide deposits (CPDs) were remarkably increased in the plasma membranes and cell walls of pumpkin tissues such as petiole, cotyledon, hypocotyl and especially leaf after gamma irradiation. These observations are in good agreement with the results of H(2)O(2) content in all tissues. The immuno-localization analysis for peroxidase (POD) on the tissues from pumpkin plant showed the same pattern between the control and irradiated plants, but the density of gold particles as indication of POD localization was significantly increased on the cell corner middle lamellae of parenchyma cells, especially in the petiole after gamma irradiation. However, accumulation and localization of H(2)O(2) and POD in vessels were not significantly different between both plants. The accumulation and localization of both H(2)O(2) and POD were differentially affected by gamma irradiation depending on the different tissue types. The deposition of both H(2)O(2) and POD in parenchyma cells appeared much higher than in vessels, suggesting that the former is more sensitive than the latter against gamma rays.

Oxygen enhances lethal effect of high-intensity, ultrashort electrical pulses

The study explored the effect of ambient oxygen on mammalian cell survival after exposure to 10 ns duration, high voltage electrical pulses (nsEP, 80-90 or 120-130 kV/cm; 200-400 pulses per exposure). Cell samples were equilibrated with pure nitrogen, atmospheric air, or pure oxygen prior to the nsEP treatment and were returned to the incubator (air + 5% CO2) shortly after the exposure. The experiments established that survival of hypoxic Jurkat and U937 cells exceeded that of air-equilibrated controls about twofold (P < .01). Conversely, saturation of the medium with oxygen prior to exposure decreased Jurkat cell survival about 1.5 times, P < .01. Attenuation of the cytotoxic effect under hypoxic conditions resembled a well-known effect of oxygen on cell killing by sparsely ionizing radiations and may be indicative of the similarity of underlying cell damage mechanisms.

Resistance of hypoxic cells to ionizing radiation is influenced by homologous recombination status

PURPOSE

To determine the role of DNA repair in hypoxic radioresistance.

METHODS AND MATERIALS

Chinese hamster cell lines with mutations in homologous recombination (XRCC2, XRCC3, BRAC2, RAD51C) or nonhomologous end-joining (DNA-PKcs) genes were irradiated under normoxic (20% oxygen) and hypoxic (<0.1% oxygen) conditions, and the oxygen enhancement ratio (OER) was calculated. In addition, Fanconi anemia fibroblasts (complementation groups C and G) were compared with fibroblasts from nonsyndrome patients. RAD51 foci were studied using immunofluorescence.

RESULTS

All hamster cell lines deficient in homologous recombination showed a decrease in OER (1.5-2.0 vs. 2.6-3.0 for wild-types). In contrast, the OER for the DNA-PKcs-deficient line was comparable to wild-type controls. The two Fanconi anemia cell strains also showed a significant reduction in OER. The OER for RAD51 foci formation at late times after irradiation was considerably lower than that for survival in wild-type cells.

CONCLUSION

Homologous recombination plays an important role in determining hypoxic cell radiosensitivity. Lower OERs have also been reported in cells deficient in XPF and ERCC1, which, similar to homologous recombination genes, are known to play a role in cross-link repair. Because Fanconi anemia cells are also sensitive to cross-linking agents, this strengthens the notion that the capacity to repair cross-links determines hypoxic radiosensitivity.

Identification of mammalian proteins cross-linked to DNA by ionizing radiation

Ionizing radiation (IR) is an important environmental risk factor for various cancers and also a major therapeutic agent for cancer treatment. Exposure of mammalian cells to IR induces several types of damage to DNA, including double- and single-strand breaks, base and sugar damage, as well as DNA-DNA and DNA-protein cross-links (DPCs). Little is known regarding the biological consequences of DPCs. Identifying the proteins that become cross-linked to DNA by IR would be an important first step in this regard. We have therefore undertaken a proteomics study to isolate and identify proteins involved in IR-induced DPCs. DPCs were induced in AA8 Chinese hamster ovary or GM00637 human fibroblast cells using 0-4 gray of gamma-rays under either aerated or hypoxic conditions. DPCs were isolated using a recently developed method, and proteins were identified by mass spectrometry. We identified 29 proteins as being cross-linked to DNA by IR under aerated and/or hypoxic conditions. The identified proteins include structural proteins, actin-associated proteins, transcription regulators, RNA-splicing components, stress-response proteins, cell cycle regulatory proteins, and GDP/GTP-binding proteins. The involvement of several proteins (actin, histone H2B, and others) in DPCs was confirmed by using Western blot analysis. The dose responsiveness of DPC induction was examined by staining one-dimensional SDS-polyacrylamide gels with SYPRO Tangerine followed by analysis using fluorescence imaging. Quantitation of the fluorescence signal indicated no significant difference in total yields of IR-induced DPCs generated under aerated or hypoxic conditions, although differences were observed for several individual protein bands.