Human-mouse comparison of the multistage nature of radiation carcinogenesis in a mathematical model

Mouse models are vital for assessing risk from environmental carcinogens, including ionizing radiation, yet the interspecies difference in the dose response precludes direct application of experimental evidence to humans. Herein, we take a mathematical approach to delineate the mechanism underlying the human-mouse difference in radiation-related cancer risk. We used a multistage carcinogenesis model assuming a mutational action of radiation to analyze previous data on cancer mortality in the Japanese atomic bomb survivors and in lifespan mouse experiments. Theoretically, the model predicted that exposure will chronologically shift the age-related increase in cancer risk forward by a period corresponding to the time in which the spontaneous mutational process generates the same mutational burden as that the exposure generates. This model appropriately fitted both human and mouse data and suggested a linear dose response for the time shift. The effect per dose decreased with increasing age at exposure similarly between humans and mice on a per-lifespan basis (0.72- and 0.71-fold, respectively, for every tenth lifetime). The time shift per dose was larger by two orders of magnitude in humans (7.8 and 0.046 years per Gy for humans and mice, respectively, when exposed at ~35% of their lifetime). The difference was mostly explained by the two orders of magnitude difference in spontaneous somatic mutation rates between the species plus the species-independent radiation-induced mutation rate. Thus, the findings delineate the mechanism underlying the interspecies difference in radiation-associated cancer mortality and may lead to the use of experimental evidence for risk prediction in humans.

A mathematical model for cancer risk and accumulation of mutations caused by replication errors and external factors

Replication errors influence mutations, and thus, lifetime cancer risk can be explained by the number of stem-cell divisions. Additionally, mutagens also affect cancer risk, for instance, high-dose radiation exposure increases lifetime cancer risk. However, the influence of low-dose radiation exposure is still unclear because this influence, if any, is very slight. We can assess the minimal influence of the mutagen by virtually comparing the states with and without mutagen using a mathematical model. Here, we constructed a mathematical model to assess the influence of replication errors and mutagens on cancer risk. In our model, replication errors occur with a certain probability during cell division. Mutagens cause mutations at a constant rate. Cell division is arrested when the number of cells reaches the capacity of the cell pool. When the number of cells decreases because of cell death or other reasons, cells resume division. It was assumed that the mutations of cancer driver genes occur stochastically with each mutation and that cancer occurs when the number of cancer driver gene mutations exceeds a certain threshold. We approximated the number of mutations caused by errors and mutagens. Then, we examined whether cancer registry data on cancer risk can be explained only through replication errors. Although the risk of leukemia was not fitted to the model, the risks of esophageal, liver, thyroid, pancreatic, colon, breast, and prostate cancers were explained only by replication errors. Even if the risk was explained by replication errors, the estimated parameters did not always agree with previously reported values. For example, the estimated number of cancer driver genes in lung cancer was larger than the previously reported values. This discrepancy can be partly resolved by assuming the influence of mutagen. First, the influence of mutagens was analyzed using various parameters. The model predicted that the influence of mutagens will appear earlier, when the turnover rate of the tissue is higher and fewer mutations of cancer driver genes were necessary for carcinogenesis. Next, the parameters of lung cancer were re-estimated assuming the influence of mutagens. The estimated parameters were closer to the previously reported values. than when considering only replication errors. Although it may be useful to explain cancer risk by replication errors, it would be biologically more plausible to consider mutagens in cancers in which the effects of mutagens are apparent.

Observation of Histone H2AX Phosphorylation by Radiation-Induced Bystander Response Using Titanium Characteristic X-ray Microbeam

Radiation-induced bystander response (RIBR) is a response induced in non-irradiated cells that receive bystander signals from directly irradiated cells. X-ray microbeams are useful tools for elucidating the mechanisms underlying RIBR. However, previous X-ray microbeams used low-energy soft X-rays with higher biological effects, such as aluminum characteristic X-rays, and the difference from conventional X-rays and γ-rays has often been discussed. The microbeam X-ray cell irradiation system at the Central Research Institute of Electric Power Industry has been upgraded to generate higher energy titanium characteristic X-rays (Ti_K X-rays), which have a longer penetration distance sufficient to irradiate 3D cultured tissues. Using this system, we irradiated the nuclei of HeLa cells with high precision and found that the pan-nuclear induction of phosphorylated histone H2AX on serine 139 (γ-H2AX) in the non-irradiated cells increased 180 and 360 min after irradiation. We established a new method to quantitatively evaluate bystander cells, using the fluorescence intensity of γ-H2AX as an indicator. The percentage of bystander cells increased significantly to 23.2% ± 3.2% and 29.3% ± 3.5% at 180 and 360 min after irradiation, respectively. Our irradiation system and the obtained results may be useful for studies of cell competition as well as non-targeted effects.

Molecular and cellular basis of the dose-rate-dependent adverse effects of radiation exposure in animal models. Part I: Mammary gland and digestive tract

While epidemiological data are available for the dose and dose-rate effectiveness factor (DDREF) for human populations, animal models have contributed significantly to providing quantitative data with mechanistic insights. The aim of the current review is to compile both the in vitro experiments with reference to the dose-rate effects of DNA damage and repair, and the animal studies, specific to rodents, with reference to the dose-rate effects of cancer development. In particular, the review focuses especially on the results pertaining to underlying biological mechanisms and discusses their possible involvement in the process of radiation-induced carcinogenesis. Because the concept of adverse outcome pathway (AOP) together with the key events has been considered as a clue to estimate radiation risks at low doses and low dose-rates, the review scrutinized the dose-rate dependency of the key events related to carcinogenesis, which enables us to unify the underlying critical mechanisms to establish a connection between animal experimental studies with human epidemiological studies.

Molecular and cellular basis of the dose-rate-dependent adverse effects of radiation exposure in animal models. Part II: Hematopoietic system, lung and liver

While epidemiological data have greatly contributed to the estimation of the dose and dose-rate effectiveness factor (DDREF) for human populations, studies using animal models have made significant contributions to provide quantitative data with mechanistic insights. The current article aims at compiling the animal studies, specific to rodents, with reference to the dose-rate effects of cancer development. This review focuses specifically on the results that explain the biological mechanisms underlying dose-rate effects and their potential involvement in radiation-induced carcinogenic processes. Since the adverse outcome pathway (AOP) concept together with the key events holds promise for improving the estimation of radiation risk at low doses and low dose-rates, the review intends to scrutinize dose-rate dependency of the key events in animal models and to consider novel key events involved in the dose-rate effects, which enables identification of important underlying mechanisms for linking animal experimental and human epidemiological studies in a unified manner.

INTESTINAL ORGANOIDS FOR STUDYING THE EFFECTS OF LOW-DOSE/LOW-DOSE-RATE RADIATION

Radiation response differs depending on the dose and dose rate in intestinal stem cells; however, the underlying mechanisms are not clear. To understand the effects of low-dose and low-dose-rate radiation, the authors established an organoid system that mimics the in vivo environment and sporadic low-dose-rate irradiation conditions in vitro. Organoid-forming potential and the number of stem cells in the organoids derived from 1 Gy-irradiated cells were lower than those from non-irradiated cells; however, the difference was not significant, although 1 Gy-irradiated stem cells exhibited significant growth disadvantage in the mixed-organoid with non-irradiated and irradiated stem cells. Furthermore, the authors irradiated a cell with X-ray microbeams and performed time-lapse observations and found that irradiated cells did not remain in the organoid. These results suggest that radiation-induced stem cell competition can occur in intestinal organoids and contribute to a low risk of cancers at low-dose-rate exposures.

Ionizing radiation alters organoid forming potential and replenishment rate in a dose/dose-rate dependent manner

Intestinal organoids are an in vitro cultured tissue model generated from intestinal stem cells, and they contain a mixture of epithelial cell types. We previously established an efficient 'one cell/well' sorting method, and defined organoid-forming potential (OFP) as a useful index to evaluate the stemness of individual cells. In this study, we assessed the response to radiation dose and dose-rate by measuring both OFP and the percentage of stem cells in the crypts. After high-dose-rate (HDR, 0.5 Gy/min) irradiation in vivo, the percentage of stem cells in the harvested crypt cells decreased, and the replenishment of cycling stem cells originating from dormant cells was enhanced, but OFP increased in cells irradiated with a total dose of >1 Gy. In contrast, at a total dose of 0.1 Gy the percentage of stem cells reduced slightly, but neither replenishment rate nor OFP changed. Furthermore, the response to 1 Gy of low-dose-rate (LDR) irradiation was similar to the response to 0.1 Gy HDR irradiation. These results suggest that 0.1 Gy HDR irradiation or 1 Gy LDR irradiation does not alter stemness. Additionally, the OFP increase in the colon in response to irradiation was smaller than that in the duodenum, similar to the percentage of stem cells. Understanding the differences in the response of stem cells between the colon and the duodenum to radiation is important to clarify the mechanisms underlying the development of radiation-associated intestinal cancers.

Exposure of the cytoplasm to low-dose X-rays modifies ataxia telangiectasia mutated-mediated DNA damage responses

We recently showed that when a low X-ray dose is used, cell death is enhanced in nucleus-irradiated compared with whole-cell-irradiated cells; however, the role of the cytoplasm remains unclear. Here, we show changes in the DNA damage responses with or without X-ray microbeam irradiation of the cytoplasm. Phosphorylated histone H2AX foci, a surrogate marker for DNA double-strand breaks, in V79 and WI-38 cells are not observed in nucleus irradiations at ≤ 2 Gy, whereas they are observed in whole-cell irradiations. Addition of an ataxia telangiectasia mutated (ATM) kinase inhibitor to whole-cell irradiations suppresses foci formation at ≤ 2 Gy. ABL1 and p73 expression is upregulated following nucleus irradiation, suggesting the induction of p73-dependent cell death. Furthermore, CDKN1A (p21) is upregulated following whole-cell irradiation, indicating the induction of cell cycle arrest. These data reveal that cytoplasmic radioresponses modify ATM-mediated DNA damage responses and determine the fate of cells irradiated at low doses.

A Mathematical Model for Stem Cell Competition to Maintain a Cell Pool Injured by Radiation

The effect of low-dose-rate exposure to ionizing radiation on cancer risk is a major issue associated with radiation protection. Tissue stem cells are regarded as one of the targets of radiation-induced carcinogenesis. However, it is hypothesized that the effect of radiation may be reduced if damaged stem cells are eliminated via stem cell competition between damaged and intact stem cells. This would be particularly effective under very low-dose-rate conditions, in which only a few stem cells in a stem cell pool may be affected by radiation. Following this hypothesis, we constructed a simple mathematical model to discuss the influence of stem cell competition attenuating the accumulation of damaged cells under very low-dose-rate conditions. In this model, a constant number of cells were introduced into a cell pool, and the numbers of intact and damaged cells were calculated via transition and turnover events. A transition event emulates radiation dose, whereby an intact cell is changed into a damaged cell with a given probability. On the other hand, a turnover event expresses cell competition, where reproduction and elimination of cells occur depending on the properties of cells. Under very low-dose-rate conditions, this model showed that radiation damage to the stem cell pool was strongly suppressed when the damaged cells were less reproductive and tended to be eliminated compared to the intact cells. Furthermore, the size of the stem cell pool was positively correlated with reduction in radiation damage.

Mapping QTLs underpin nutrition components in aromatic rice germplasm

As rice is an important staple food globally, research for development and enhancement of its nutritional value it is an imperative task. Identification of nutrient enriched rice germplasm and exploiting them for breeding programme is the easiest way to develop better quality rice. In this study, we analyzed 113 aromatic rice germplasm in order to identify quantitative trait loci (QTL) underpinning nutrition components and determined by measuring the normal frequency distribution for Fe, Zn, amylose, and protein content in those rice germplasm. Comparatively, the germplasm Radhuni pagal, Kalobakri, Thakurbhog (26.6 ppm) and Hatisail exhibited the highest mean values for Fe (16.9 ppm), Zn (34.1 ppm), amylose (26.6 ppm) and protein content (11.0 ppm), respectively. Moreover, a significant linear relationship (R2 = 0.693) was observed between Fe and Zn contents. Cluster analysis based on Mahalanobis D2 distances revealed four major clusters of 113 rice germplasm, with cluster III containing a maximum 37 germplasm and a maximum inter-cluster distance between clusters III and IV. The 45 polymorphic SSRs and four trait associations exhibited eight significant quantitative trait loci (QTL) located on eight different chromosomes using composite interval mapping (CIM). The highly significant QTL (variance 7.89%, LOD 2.02) for protein content (QTL.pro.1) was observed on chromosome 1 at 94.9cM position. Also, four QTLs for amylose content were observed with the highly significant QTL.amy.8 located on chromosome 8 exhibiting 7.2% variance with LOD 1.83. Only one QTL (QTL.Fe.9) for Fe content was located on chromosome 9 (LOD 1.24), and two (QTL.Zn.4 and QTL.Zn.5) for Zn on chromosome 4 (LOD 1.71) and 5 (LOD 1.18), respectively. Overall, germplasm from clusters III and IV might offer higher heterotic response with the identified QTLs playing a significant role in any rice biofortification breeding program and released with development of new varieties.

An Efficient Intestinal Organoid System of Direct Sorting to Evaluate Stem Cell Competition in Vitro

Stem cell competition could shed light on the tissue-based quality control mechanism that prevents carcinogenesis. To quantitatively evaluate stem cell competition in vitro, we developed a two-color intestinal organoid forming system. First, we improved a protocol of culturing organoids from intestinal leucine-rich-repeat containing G-protein-coupled receptor 5 (Lgr5)- enhanced green fluorescent protein (EGFP)^high stem cells directly sorted on Matrigel without embedding. The organoid-forming potential (OFP) was 25% of Lgr5-EGFP^high cells sorted at one cell per well. Using this culture protocol with lineage tracing, we established a two-color organoid culture system by mixing stem cells expressing different fluorescent colors. To analyze stem cell competition, two-color organoids were formed by mixing X-ray-irradiated and non-irradiated intestinal stem cells. In the two-color organoids, irradiated stem cells exhibited a growth disadvantage, although the OFP of irradiated cells alone did not decrease significantly from that of non-irradiated cells. These results suggest that stem cell competition can be evaluated quantitively in vitro using our new system.

Concurrent live imaging of DNA double-strand break repair and cell-cycle progression by CRISPR/Cas9-mediated knock-in of a tricistronic vector

Cell-cycle progression can be arrested by ionizing radiation-induced DNA double-strand breaks (DSBs). Although DSBs are patched by DSB repair systems, which comprise proteins such as p53-binding protein 1 (53BP1), the relationship between DSB repair progression and cell-cycle status in living cells is unclear. The probe FUCCI (fluorescent ubiquitination-based cell-cycle indicator) was previously developed for visualizing cell-cycle status. Here, we established novel live-imaging probes based on custom-designed plasmids designated “Focicles” harboring a tricistronic compartment encoding distinct fluorescent proteins ligated to the murine 53BP1 foci-forming region (FFR) and two cell-cycle indicators that are known components of FUCCI (hCdt1 and hGmnn). We used CRISPR/Cas9-mediated genome editing to obtain Focicle knock-in cell lines in NIH3T3 cells, which were subject to X-ray irradiation that induced comparable numbers of Focicle and endogenous-53BP1 foci. In addition, the Focicle probes enabled the kinetic analysis of both DSB repair and cell-cycle arrest/progression after irradiation, demonstrating that the Focicle knock-in cells progressed to cell division after DNA damage elimination. These newly developed probes can help to gain a better understanding of the dynamics of DSB repair and cell-cycle control to in turn guide cancer treatment development and cancer-risk assessments.

Antithrombotic Mechanisms of Urokinase lmmobilized Polyurethane

Urokinase immobilized polymer is highly antithrombotic, which cannot be explained only by fibrinolysis. We immobllized 10 IU/cm2 of urokinase to polyurethane by using maleic anhydride methylvinyl ether copolymer as a carrier. Then we incubated blood in circular tubes made of this material, measured the clotting factors and observed the surface of the tubes after incubation by scanning electronmicroscopy and immunofluorescence microscopy. After 5 min incubation, the relative activities of factors V, VIII, IX, X and XII, fibrinogeil, plasminogen and α2 plasmin inhibitor decreased, but the activity of factor VII increased. No platelet adhesion to the surface of the urokinase immobilized polyurethane was observed and there was no significant adsorption of serum proteins, including fibrinogen, fibronectin and vWF antigen, or the surface. Urokinase-immobilized polyurethane catalyzed the digestion of clotting factors as well as fibrinolysis and also inhibited platelet adhesion on its surface probably by inhibiting protein adsorption and its clinical application including vessel prosthesis should be developed further.

Sex-specific relevance of diabetes to occlusive vascular and other mortality: a collaborative meta-analysis of individual data from 980 793 adults from 68 prospective studies

BACKGROUND

Several studies have shown that diabetes confers a higher relative risk of vascular mortality among women than among men, but whether this increased relative risk in women exists across age groups and within defined levels of other risk factors is uncertain. We aimed to determine whether differences in established risk factors, such as blood pressure, BMI, smoking, and cholesterol, explain the higher relative risks of vascular mortality among women than among men.

METHODS

In our meta-analysis, we obtained individual participant-level data from studies included in the Prospective Studies Collaboration and the Asia Pacific Cohort Studies Collaboration that had obtained baseline information on age, sex, diabetes, total cholesterol, blood pressure, tobacco use, height, and weight. Data on causes of death were obtained from medical death certificates. We used Cox regression models to assess the relevance of diabetes (any type) to occlusive vascular mortality (ischaemic heart disease, ischaemic stroke, or other atherosclerotic deaths) by age, sex, and other major vascular risk factors, and to assess whether the associations of blood pressure, total cholesterol, and body-mass index (BMI) to occlusive vascular mortality are modified by diabetes.

RESULTS

Individual participant-level data were analysed from 980 793 adults. During 9·8 million person-years of follow-up, among participants aged between 35 and 89 years, 19 686 (25·6%) of 76 965 deaths were attributed to occlusive vascular disease. After controlling for major vascular risk factors, diabetes roughly doubled occlusive vascular mortality risk among men (death rate ratio [RR] 2·10, 95% CI 1·97-2·24) and tripled risk among women (3·00, 2·71-3·33; χ2 test for heterogeneity p<0·0001). For both sexes combined, the occlusive vascular death RRs were higher in younger individuals (aged 35-59 years: 2·60, 2·30-2·94) than in older individuals (aged 70-89 years: 2·01, 1·85-2·19; p=0·0001 for trend across age groups), and, across age groups, the death RRs were higher among women than among men. Therefore, women aged 35-59 years had the highest death RR across all age and sex groups (5·55, 4·15-7·44). However, since underlying confounder-adjusted occlusive vascular mortality rates at any age were higher in men than in women, the adjusted absolute excess occlusive vascular mortality associated with diabetes was similar for men and women. At ages 35-59 years, the excess absolute risk was 0·05% (95% CI 0·03-0·07) per year in women compared with 0·08% (0·05-0·10) per year in men; the corresponding excess at ages 70-89 years was 1·08% (0·84-1·32) per year in women and 0·91% (0·77-1·05) per year in men. Total cholesterol, blood pressure, and BMI each showed continuous log-linear associations with occlusive vascular mortality that were similar among individuals with and without diabetes across both sexes.

INTERPRETATION

Independent of other major vascular risk factors, diabetes substantially increased vascular risk in both men and women. Lifestyle changes to reduce smoking and obesity and use of cost-effective drugs that target major vascular risks (eg, statins and antihypertensive drugs) are important in both men and women with diabetes, but might not reduce the relative excess risk of occlusive vascular disease in women with diabetes, which remains unexplained.

FUNDING

UK Medical Research Council, British Heart Foundation, Cancer Research UK, European Union BIOMED programme, and National Institute on Aging (US National Institutes of Health).

RBC Aggregometer head as a Warning Monitor of Flow Disturbance in Extracorporeal Systems

A simple photoelectric apparatus is described, to monitor the flow condition of whole blood in an extracorporeal system. It can raise an immediate alarm on disturbance of flow. The apparatus comprises an RBC aggregometer head, described previously, for measuring the rate of RBC aggregation in whole blood. Its construction was modified for easy attach-ability and detachability without causing tube damage. In practice, the apparatus was applied by hooking it to the tube of the extracorporeal system in animals and in a clinical case of blood dialysis in a patient with renal failure, in which stoppage of blood flow elicited a dramatic change in the baseline record of light transmission of the mobile blood. The signal of the apparatus was fed to an alarm system via a voltage comparator switch. The apparatus is inexpensive, solid and durable, easy to operate by untrained personnel, and has excellent stability and reproducibility.

Cellular responses and gene expression profiles of colonic Lgr5+ stem cells after low-dose/low-dose-rate radiation exposure

We previously found that high-dose-rate radiation induced a replenishment of the colonic Lgr5+ stem cell pool, whereas low-dose-rate radiation did not. To identify key molecules that determine the dose-rate effects on this stem cell pool, we harvested colonic Lgr5+ stem cells by cell sorting at 2 weeks after exposure to 1 Gy of high-dose-rate (30 Gy/h) or low-dose-rate (0.003 Gy/h) radiation and analyzed their gene expression profiles using RNA-Seq. We found that pathways related to DNA damage response, cell growth, cell differentiation and cell death were upregulated in Lgr5+ stem cells irradiated with high dose rates, whereas pathways related to apical junctions and extracellular signaling were upregulated in low-dose-rate-irradiated colonic Lgr5+ stem cells. Interestingly, biological events involving apical junctions are known to play an important role in the exclusion of transformed cells that are surrounded by normal epithelial cells through 'cell competition'. We speculated that cell competition, through apical junctions and extracellular ligands, might contribute to the dose-rate effect on Lgr5+ cell replenishment. To understand this mechanism, we focused on 69 genes that were significantly upregulated in low-dose-rate-irradiated cells, which we named DREDGE (Dose-Rate Effect Determining GEnes). Based on these findings, we propose a possible mechanism underlying the dose-rate effect observed in the colonic stem cell pool.

Novel function of HATs and HDACs in homologous recombination through acetylation of human RAD52 at double-strand break sites

The p300 and CBP histone acetyltransferases are recruited to DNA double-strand break (DSB) sites where they induce histone acetylation, thereby influencing the chromatin structure and DNA repair process. Whether p300/CBP at DSB sites also acetylate non-histone proteins, and how their acetylation affects DSB repair, remain unknown. Here we show that p300/CBP acetylate RAD52, a human homologous recombination (HR) DNA repair protein, at DSB sites. Using in vitro acetylated RAD52, we identified 13 potential acetylation sites in RAD52 by a mass spectrometry analysis. An immunofluorescence microscopy analysis revealed that RAD52 acetylation at DSBs sites is counteracted by SIRT2- and SIRT3-mediated deacetylation, and that non-acetylated RAD52 initially accumulates at DSB sites, but dissociates prematurely from them. In the absence of RAD52 acetylation, RAD51, which plays a central role in HR, also dissociates prematurely from DSB sites, and hence HR is impaired. Furthermore, inhibition of ataxia telangiectasia mutated (ATM) protein by siRNA or inhibitor treatment demonstrated that the acetylation of RAD52 at DSB sites is dependent on the ATM protein kinase activity, through the formation of RAD52, p300/CBP, SIRT2, and SIRT3 foci at DSB sites. Our findings clarify the importance of RAD52 acetylation in HR and its underlying mechanism.

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016

[This corrects the article DOI: 10.1186/s13054-016-1208-6.].

Enhancement of DNA double-strand break induction and cell killing by K-shell absorption of phosphorus in human cell lines

PURPOSE

To investigate an enhancement of DNA double-strand break (DSB) induction and cell killing effect by K-shell ionization of phosphorus atoms and Auger electrons on human cell lines.

MATERIALS AND METHODS

Induction of DSB, DNA damage responses, cell cycle distributions, and cell killing effects were investigated after exposures of the cells with monochromatic synchrotron radiation soft X-rays of 2153 and 2147 eV, which were the resonance peak and off peak, respectively, of the K-shell photoabsorption of phosphorus.

RESULTS

Higher biological effects in the cells irradiated with soft X-rays at 2153 eV than at 2147 eV were observed in (i) the efficiency of 53BP1/γ-H2AX co-localized foci formation per dose and residual number of foci, (ii) prolonged phosphorylation levels of DSB repair and/or cell cycle checkpoint related proteins and G2 arrest, (iii) the cell killing effects at the 10% survival level of normal human fibroblasts, HeLa cells, and human glioblastoma M059K cells (1.2-1.5 times higher) and that of human ataxia telangiectasia mutated (ATM)-defective cells and glioblastoma DNA-dependent protein kinase catalytic subunit (DNA-PKcs)-defective cells (1.2 times).

CONCLUSION

The yield of DSB and partly less-reparable complex DNA damage induction in human cells was enhanced by K-shell photoabsorption of phosphorus and low-energy Auger electrons.

In cellulo phosphorylation of XRCC4 Ser320 by DNA-PK induced by DNA damage

XRCC4 is a protein associated with DNA Ligase IV, which is thought to join two DNA ends at the final step of DNA double-strand break repair through non-homologous end joining. In response to treatment with ionizing radiation or DNA damaging agents, XRCC4 undergoes DNA-PK-dependent phosphorylation. Furthermore, Ser260 and Ser320 (or Ser318 in alternatively spliced form) of XRCC4 were identified as the major phosphorylation sites by purified DNA-PK in vitro through mass spectrometry. However, it has not been clear whether these sites are phosphorylated in vivo in response to DNA damage. In the present study, we generated an antibody that reacts with XRCC4 phosphorylated at Ser320 and examined in cellulo phosphorylation status of XRCC4 Ser320. The phosphorylation of XRCC4 Ser320 was induced by γ-ray irradiation and treatment with Zeocin. The phosphorylation of XRCC4 Ser320 was detected even after 1 Gy irradiation and increased in a manner dependent on radiation dose. The phosphorylation was observed immediately after irradiation and remained mostly unchanged for up to 4 h. The phosphorylation was inhibited by DNA-PK inhibitor NU7441 and was undetectable in DNA-PKcs-deficient cells, indicating that the phosphorylation was mainly mediated by DNA-PK. These results suggested potential usefulness of the phosphorylation status of XRCC4 Ser320 as an indicator of DNA-PK functionality in living cells.

The application of omics technologies in the functional evaluation of inulin and inulin-containing prebiotics dietary supplementation

Inulin, a natural renewable polysaccharide resource produced by various plants in nature, has been reported to possess a significant number of diverse pharmaceutical and food applications. Recently, there has been rapid progress in high-throughput technologies and platforms to assay global mRNA, proteins, metabolites and gut microbiota. In this review, we will describe the current status of utilizing omics technologies of elucidating the impact of inulin and inulin-containing prebiotics at the transcriptome, proteome, metabolome and gut microbiome levels. Although many studies in this review have addressed the impact of inulin comprehensively, these omics technologies only enable us to understand physiological information at each different stage of mRNA, protein, metabolite and gut microbe. We believe that a synergistic approach is vital in order to fully illustrate the intricate beauty behind the relatively modest influence of food factors like inulin on host health.

Significance of Development and Reversion of Collaterals on MRI in Early Neurologic Improvement and Long-Term Functional Outcome after Intravenous Thrombolysis for Ischemic Stroke

BACKGROUND AND PURPOSE

Predicting response to rtPA is essential in the era of endovascular therapy for stroke. The purpose of this study was to elucidate prognostic factors of early neurologic improvement and long-term outcome with respect to the development and reversion of leptomeningeal collaterals in recanalization therapy after acute ischemic stroke.

MATERIALS AND METHODS

We analyzed consecutive patients with proximal MCA occlusion treated with rtPA from 2007 to 2012 at 2 hospital stroke centers. All patients routinely underwent brain MR imaging before rtPA. To assess the reversion of collateral signs, we included patients who underwent follow-up MR imaging. We assessed the development and reversion of collaterals by using a combination of 2 MR imaging collateral markers, the hyperintense vessel sign and the posterior cerebral artery laterality sign. Early neurologic improvement was defined as a decrease in the NIHSS score of ≥10 or a score of ≤2 at 24 hours of treatment.

RESULTS

Early neurologic improvement was observed in 22 of 48 eligible patients. The development of collaterals at arrival (15/22 versus 9/26, P = .042) was significantly associated with early neurologic improvement. Multivariate analysis adjusting for other variables showed that the development of collaterals at arrival (OR, 4.82; 95% CI, 1.34-19.98; P = .015) was independently associated with early neurologic improvement. Reversion of collaterals was significantly associated with successful recanalization (P < .001), and multivariate analysis showed that the reversion of collaterals was an independent prognostic factor of long-term functional outcome (OR, 5.07; 95% CI, 1.38-22.09; P = .013).

CONCLUSIONS

Our results indicate that the development of leptomeningeal collaterals plays a crucial role in achieving early neurologic improvement, and reversion of collaterals predicts a favorable outcome via arterial recanalization after rtPA treatment for acute stroke.

Nitric oxide-mediated bystander signal transduction induced by heavy-ion microbeam irradiation

In general, a radiation-induced bystander response is known to be a cellular response induced in non-irradiated cells after receiving bystander signaling factors released from directly irradiated cells within a cell population. Bystander responses induced by high-linear energy transfer (LET) heavy ions at low fluence are an important health problem for astronauts in space. Bystander responses are mediated via physical cell-cell contact, such as gap-junction intercellular communication (GJIC) and/or diffusive factors released into the medium in cell culture conditions. Nitric oxide (NO) is a well-known major initiator/mediator of intercellular signaling within culture medium during bystander responses. In this study, we investigated the NO-mediated bystander signal transduction induced by high-LET argon (Ar)-ion microbeam irradiation of normal human fibroblasts. Foci formation by DNA double-strand break repair proteins was induced in non-irradiated cells, which were co-cultured with those irradiated by high-LET Ar-ion microbeams in the same culture plate. Foci formation was suppressed significantly by pretreatment with an NO scavenger. Furthermore, NO-mediated reproductive cell death was also induced in bystander cells. Phosphorylation of NF-κB and Akt were induced during NO-mediated bystander signaling in the irradiated and bystander cells. However, the activation of these proteins depended on the incubation time after irradiation. The accumulation of cyclooxygenase-2 (COX-2), a downstream target of NO and NF-κB, was observed in the bystander cells 6 h after irradiation but not in the directly irradiated cells. Our findings suggest that Akt- and NF-κB-dependent signaling pathways involving COX-2 play important roles in NO-mediated high-LET heavy-ion-induced bystander responses. In addition, COX-2 may be used as a molecular marker of high-LET heavy-ion-induced bystander cells to distinguish them from directly irradiated cells, although this may depend on the time after irradiation.

Bcl11b SWI/SNF-complex subunit modulates intestinal adenoma and regeneration after γ-irradiation through Wnt/β-catenin pathway

SWI/SNF chromatin remodeling complexes constitute a highly related family of multi-subunit complexes to modulate transcription, and SWI/SNF subunit genes are collectively mutated in 20% of all human cancers. Bcl11b is a SWI/SNF subunit and acts as a haploinsufficient tumor suppressor in leukemia/lymphomas. Here, we show expression of Bcl11b in intestinal crypt cells and promotion of intestinal tumorigenesis by Bcl11b attenuation in Apc (min/+) mice. Of importance, mutations or allelic loss of BCL11B was detected in one-third of human colon cancers. We also show that attenuated Bcl11b activity in the crypt base columnar (CBC) cells expressing the Lgr5 stem cell marker enhanced regeneration of intestinal epithelial cells after the radiation-induced injury. Interestingly, BCL11B introduction in human cell lines downregulated transcription of β-catenin target genes, whereas Bcl11b attenuation in Lgr5(+) CBCs increased expression of β-catenin targets including c-Myc and cyclin D1. Together, our results argue that Bcl11b impairment promotes tumor development in mouse and human intestine at least in part through deregulation of β-catenin pathway.

Mechanisms and biological importance of photon-induced bystander responses: do they have an impact on low-dose radiation responses

Elucidating the biological effect of low linear energy transfer (LET), low-dose and/or low-dose-rate ionizing radiation is essential in ensuring radiation safety. Over the past two decades, non-targeted effects, which are not only a direct consequence of radiation-induced initial lesions produced in cellular DNA but also of intra- and inter-cellular communications involving both targeted and non-targeted cells, have been reported and are currently defining a new paradigm in radiation biology. These effects include radiation-induced adaptive response, low-dose hypersensitivity, genomic instability, and radiation-induced bystander response (RIBR). RIBR is generally defined as a cellular response that is induced in non-irradiated cells that receive bystander signals from directly irradiated cells. RIBR could thus play an important biological role in low-dose irradiation conditions. However, this suggestion was mainly based on findings obtained using high-LET charged-particle radiations. The human population (especially the Japanese, who are exposed to lower doses of radon than the world average) is more frequently exposed to low-LET photons (X-rays or γ-rays) than to high-LET charged-particle radiation on a daily basis. There are currently a growing number of reports describing a distinguishing feature between photon-induced bystander response and high-LET RIBR. In particular, photon-induced bystander response is strongly influenced by irradiation dose, the irradiated region of the targeted cells, and p53 status. The present review focuses on the photon-induced bystander response, and discusses its impact on the low-dose radiation effect.

Mycobacterium marinum infection in Japanese forest green tree frogs (Rhacophorus arboreus)

Four Japanese forest green tree frogs (Rhacophorus arboreus) were presented with emaciation, abdominal distention and ulcerative and nodular cutaneous lesions affecting the brisket, limbs, digits and ventral abdomen. Another three frogs had been found dead in the same tank 1 year previously. Necropsy examination of these seven frogs revealed splenomegaly and hepatomegaly, with multiple tan-yellow nodular foci present in the liver, spleen, heart, lungs, ovaries and kidneys. Microscopically, five frogs had necrosis and surrounding granulomatous inflammation in the liver, spleen, kidneys, lungs, intestine and ovaries, with numerous acid-fast bacilli in the areas of necrosis. Two frogs had granulomatous lesions in the lungs, liver, spleen, heart, coelomic membrane, stomach and intestinal wall. These lesions had no or minimal necrosis and few acid-fast bacilli. Mycobacterium spp. was cultured from three frogs and identified as Mycobacterium marinum by colony growth rate and photochromogenicity and DNA sequencing. This is the first report of M. marinum infection in Japanese forest green tree frogs.

A novel in vitro survival assay of small intestinal stem cells after exposure to ionizing radiation

The microcolony assay developed by Withers and Elkind has been a gold standard to assess the surviving fraction of small intestinal stem cells after exposure to high (≥8 Gy) doses of ionizing radiation (IR), but is not applicable in cases of exposure to lower doses. Here, we developed a novel in vitro assay that enables assessment of the surviving fraction of small intestinal stem cells after exposure to lower IR doses. The assay includes in vitro culture of small intestinal stem cells, which allows the stem cells to develop into epithelial organoids containing all four differentiated cell types of the small intestine. We used Lgr5-EGFP-IRES-CreERT2/ROSA26-tdTomato mice to identify Lgr5(+) stem cells and their progeny. Enzymatically dissociated single crypt cells from the duodenum and jejunum of mice were irradiated with 7.25, 29, 101, 304, 1000, 2000 and 4000 mGy of X-rays immediately after plating, and the number of organoids was counted on Day 12. Organoid-forming efficiency of irradiated cells relative to that of unirradiated controls was defined as the surviving fraction of stem cells. We observed a significant decrease in the surviving fraction of stem cells at ≥1000 mGy. Moreover, fluorescence-activated cell sorting analyses and passage of the organoids revealed that proliferation of stem cells surviving IR is significantly potentiated. Together, the present study demonstrates that the in vitro assay is useful for quantitatively assessing the surviving fraction of small intestinal stem cells after exposure to lower doses of IR as compared with previous examinations using the microcolony assay.

X-ray-induced bystander responses reduce spontaneous mutations in V79 cells

The potential for carcinogenic risks is increased by radiation-induced bystander responses; these responses are the biological effects in unirradiated cells that receive signals from the neighboring irradiated cells. Bystander responses have attracted attention in modern radiobiology because they are characterized by non-linear responses to low-dose radiation. We used a synchrotron X-ray microbeam irradiation system developed at the Photon Factory, High Energy Accelerator Research Organization, KEK, and showed that nitric oxide (NO)-mediated bystander cell death increased biphasically in a dose-dependent manner. Here, we irradiated five cell nuclei using 10 × 10 µm(2) 5.35 keV X-ray beams and then measured the mutation frequency at the hypoxanthine-guanosine phosphoribosyl transferase (HPRT) locus in bystander cells. The mutation frequency with the null radiation dose was 2.6 × 10(-)(5) (background level), and the frequency decreased to 5.3 × 10(-)(6) with a dose of approximately 1 Gy (absorbed dose in the nucleus of irradiated cells). At high doses, the mutation frequency returned to the background level. A similar biphasic dose-response effect was observed for bystander cell death. Furthermore, we found that incubation with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), a specific scavenger of NO, suppressed not only the biphasic increase in bystander cell death but also the biphasic reduction in mutation frequency of bystander cells. These results indicate that the increase in bystander cell death involves mechanisms that suppress mutagenesis. This study has thus shown that radiation-induced bystander responses could affect processes that protect the cell against naturally occurring alterations such as mutations.

Associations of vertebral deformities and osteoarthritis with back pain among Japanese women: the Hizen-Oshima study

We examined the spinal distribution of the types of vertebral deformities and the associations of vertebral deformities and osteoarthritis with back pain in Japanese women. Midthoracic and upper lumbar vertebrae were more susceptible to deformity. Vertebral deformity and osteoarthritis were frequent and were associated with back pain.

INTRODUCTION

Vertebral fractures due to osteoporosis and osteoarthritis are both common and significant health problems in aged people. However, little is known about the descriptive epidemiology of the individual deformity types and the relative clinical impact in women in Japan.

METHODS

Lateral radiographs were obtained from 584 Japanese women ages 40 to 89 years old. Deformities were defined as vertebral heights of more than 3 standard deviations (SDs) below the normal mean. Osteoarthritis was defined as Kellgren-Lawrence (KL) grade 2 or higher. Information on upper or low back pain during the previous month was collected by questionnaire. We compared the spinal distribution of the three types of vertebral deformities (wedge, endplate, and crush) typical of fractures and examined the associations of number and type of vertebral deformities and osteoarthritis with back pain.

RESULTS

Fifteen percent of women had at least one vertebral deformity and 74% had vertebral osteoarthritis. The prevalence of upper or low back pain was 30.1%. Deformities were most common in the midthoracic and upper lumbar regions and wedge was the frequent type, followed by endplate and crush. Multiple logistic regression analysis showed that the odds of back pain was 3.0 (95% CI 1.5-6.3) times higher for women with a single wedge deformity and 3.2 (95% CI 1.0--0.6) times higher for women with two or more wedge deformities, compared to women with no wedge deformity. Vertebral osteoarthritis was associated with back pain (OR 1.8, 95% CI 1.1-2.9), independent of other covariates including age and deformities.

CONCLUSION

Our results in this group of Japanese women are similar to and consistent with results reported previously in other populations of Japanese and Caucasians.

Dose response of soft X-ray-induced bystander cell killing affected by p53 status

A radiation-induced bystander response, which is generally defined as a cellular response that is induced in nonirradiated cells that received bystander signals from directly irradiated cells within an irradiated cell population. In our earlier X-ray microbeam studies, bystander cell killing in normal human fibroblasts had a parabolic relationship to the irradiation dose. To elucidate the role of p53 in the bystander cell killing, the effects were assessed using human non-small cell lung cancer cells expressing wild-type or temperature-sensitive mutated p53. The surviving fraction of bystander wild-type p53 cells showed a parabolic relationship to the irradiation dose; survival was steeply reduced up to 0.45 Gy, recovered toward to 2 Gy, and remained at control levels up to 5 Gy. In contrast, in the mutated p53 cells at a nonpermissive temperature, the surviving fraction was steeply reduced up to 1 Gy and remained at the reduced level up to 5 Gy. When the mutated p53 cells were incubated at a permissive temperature, the decrease in the surviving fraction at 2 Gy was suppressed. The wild-type p53 cells were not only restrained in releasing bystander signals at 2 Gy, but were also resistant to the signals released by the mutated p53 cells. These results suggest that the X-ray-induced bystander cell killing depends on both the irradiation dose and the p53 status of the targeted cells and the bystander cells.

Thinopyrum 7Ai-1-derived small chromatin with Barley Yellow Dwarf Virus (BYDV) resistance gene integrated into the wheat genome with retrotransposon

Thinopyrum intermedium is a useful source of resistance genes for Barley Yellow Dwarf Virus (BYDV), one of the most damaging wheat diseases. In this study, wheat/Th. intermedium translocation lines with a BYDV resistance gene were developed using the Th. intermedium 7Ai- 1 chromosome. Genomic in situ hybridization (GISH), using a Th. intermedium total genomic DNA probe, enabled detection of 7Ai-1-derived small chromatins containing a BYDV resistance gene, which were translocated onto the end of wheat chromosomes in the lines Y95011 and Y960843. Random amplified polymorphic DNA (RAPD) analyses using 120 random 10-mer primers were conducted to compare the BYDV-resistant translocation lines with susceptible lines. Two primers amplified the DNA fragments specific to the resistant line that would be useful as molecular markers to identify 7Ai-1-derived BYDV resistance chromatin in the wheat genome. Additionally, the isolated Th. intermedium-specific retrotransposon-like sequence pTi28 can be used to identify Th. intermedium chromatin transferred to the wheat genome.

Insulinoma may mask the existence of Type 1 diabetes

BACKGROUND

Insulinoma is a tumour of insulin-producing cells of the pancreas and is known to be one of the causes of hypoglycaemia. Usually, appropriate removal of the insulinoma results in normalization of blood glucose levels. However, we found novel cases of insulinoma, in which hyperglycaemia developed soon after resection of the insulinoma.

CASE REPORT

We encountered two patients with repeated hypoglycaemia caused by insulinoma. Following removal of the insulinoma, unanticipated hyperglycaemia was observed in both patients. Thereafter, their blood tests revealed low levels of serum C-peptide and high titres of anti-glutamic acid decarboxylase antibody, indicating concomitant Type 1 diabetes. Indeed, histological examination of the resected specimen revealed that one patient showed insulitis in non-tumorous pancreatic tissue in which β-cells had already disappeared. Moreover, inflammatory cells infiltrated the insulinoma, as if it were insulitis of Type 1 diabetes, suggesting the existence of anti-islet autoimmunity.

CONCLUSION

These are first cases of insulinoma associated with underlying Type 1 diabetes. Physicians should be aware of the possibility that insulinoma may mask Type 1 diabetes, and measurement of anti-islet autoantibodies may be helpful to find underlying Type 1 diabetes, such as in these cases. It is pathologically interesting that the immune cell infiltration into insulinoma may be suggestive of anti-islet autoimmunity.

Predictions of the pathological response to neoadjuvant chemotherapy in patients with primary breast cancer using a data mining technique

Nomogram, a standard technique that utilizes multiple characteristics to predict efficacy of treatment and likelihood of a specific status of an individual patient, has been used for prediction of response to neoadjuvant chemotherapy (NAC) in breast cancer patients. The aim of this study was to develop a novel computational technique to predict the pathological complete response (pCR) to NAC in primary breast cancer patients. A mathematical model using alternating decision trees, an epigone of decision tree, was developed using 28 clinicopathological variables that were retrospectively collected from patients treated with NAC (n = 150), and validated using an independent dataset from a randomized controlled trial (n = 173). The model selected 15 variables to predict the pCR with yielding area under the receiver operating characteristics curve (AUC) values of 0.766 [95 % confidence interval (CI)], 0.671-0.861, P value < 0.0001) in cross-validation using training dataset and 0.787 (95 % CI 0.716-0.858, P value < 0.0001) in the validation dataset. Among three subtypes of breast cancer, the luminal subgroup showed the best discrimination (AUC = 0.779, 95 % CI 0.641-0.917, P value = 0.0059). The developed model (AUC = 0.805, 95 % CI 0.716-0.894, P value < 0.0001) outperformed multivariate logistic regression (AUC = 0.754, 95 % CI 0.651-0.858, P value = 0.00019) of validation datasets without missing values (n = 127). Several analyses, e.g. bootstrap analysis, revealed that the developed model was insensitive to missing values and also tolerant to distribution bias among the datasets. Our model based on clinicopathological variables showed high predictive ability for pCR. This model might improve the prediction of the response to NAC in primary breast cancer patients.

The role of Staphylococcal enterotoxin in atopic keratoconjunctivitis and corneal ulceration

BACKGROUND

Patients with atopic eczema frequently experience colonization with Staphylococcus aureus that is directly correlated with the eczema severity. We hypothesized that S. aureus-secreted enterotoxins (SE) are involved in the pathophysiology of atopic keratoconjunctivitis (AKC).

METHODS

A total of 45 subjects (18 with AKC, nine vernal keratoconjunctivitis (VKC), eight seasonal allergic conjunctivitis (SAC), and ten healthy volunteers) were enrolled. Slit lamp examinations, including fluorescein staining, were performed. Scraped samples were collected from the upper tarsal conjunctiva, lower conjunctival sacs, and the skin around the eyelid margins. Superantigen (SAg) genes were detected using polymerase chain reaction (PCR).

RESULTS

Among 45 cases, S. aureus was detected significantly more in AKC patients than VKC patients (P = 0.026), SAC patients (P = 0.0003), and healthy volunteers (P = 0.0001). SAg genes were detected in 11 patients. SEB (2/11), SEG (8/11), and SEI (8/11) were detected, but no other SE. There was a significant difference in SE detection between AKC and SAC patients (P = 0.03). In severe types of ocular allergic disease such as AKC and VKC (N = 27), SE was detected in six of ten patients with corneal ulcers and two of 17 patients without corneal ulcers. SE was detected in significantly more patients with corneal ulcers (P = 0.025).

CONCLUSIONS

In patients with AKC, S. aureus and SE were detected more frequently compared with other patients and healthy volunteers, especially in association with corneal ulceration suggesting a role of SE. So far, it is unknown whether SE leads to tissue damage of the cornea by initiating an immune response or has direct toxic effects.