Variable Dose Rates in Realistic Radiation Exposures: Effects on Small Molecule Markers of Ionizing Radiation in the Murine Model.

Novel biodosimetry assays for use in preparedness and response to potential malicious attacks or nuclear accidents would ideally provide accurate dose reconstruction independent of the idiosyncrasies of a complex exposure to ionizing radiation. Complex exposures will consist of dose rates spanning the low dose rates (LDR) to very high-dose rates (VHDR) that need to be tested for assay validation. Here, we investigate how a range of relevant dose rates affect metabolomic dose reconstruction at potentially lethal radiation exposures (8 Gy in mice) from an initial blast or subsequent fallout exposures compared to zero or sublethal exposures (0 or 3 Gy in mice) in the first 2 days, which corresponds to an integral time individuals will reach medical facilities after a radiological emergency. Biofluids (urine and serum) were collected from both male and female 9-10-week-old C57BL/6 mice at 1 and 2 days postirradiation (total doses of 0, 3 or 8 Gy) after a VHDR of 7 Gy/s. Additionally, samples were collected after a 2-day exposure consisting of a declining dose rate (1 to 0.004 Gy/min) recapitulating the 7:10 rule-of-thumb time dependency of nuclear fallout. Overall similar perturbations were observed in both urine and serum metabolite concentrations irrespective of sex or dose rate, with the exception of xanthurenic acid in urine (female specific) and taurine in serum (VHDR specific). In urine, we developed identical multiplex metabolite panels (N6, N6,N6-trimethyllysine, carnitine, propionylcarnitine, hexosamine-valine-isoleucine, and taurine) that could identify individuals receiving potentially lethal levels of radiation from the zero or sublethal cohorts with excellent sensitivity and specificity, with creatine increasing model performance at day 1. In serum, individuals receiving a 3 or 8 Gy exposure could be identified from their pre-irradiation samples with excellent sensitivity and specificity, however, due to a lower dose response the 3 vs. 8 Gy groups could not be distinguished from each other. Together with previous results, these data indicate that dose-rate-independent small molecule fingerprints have potential in novel biodosimetry assays.

Traditional Chinese Medicine Fuzheng Huayu Prevents Development of Liver Fibrosis in Mice.

AIM: To investigate the therapeutic effect of FZHY on hepatic fibrosis in mice and to determine the mechanism of its action. METHODS: Wild type mice were subjected to toxic (carbon tetrachloride, CCl4) or cholestatic (bile duct ligation, BDL). Upon induction of liver fibrosis, mice were treated with FZHY (4.0g/kg, 2w, oral gavage) or vehicle (PBS). Livers were analyzed by Sirius Red staining, immunostaining and RT-PCR for profibrogenic and pro-inflammatory genes. The effect of FZHY on hepatocytes, inflammatory responses, activation of fibrogenic myofibroblasts, and ROS production was assessed. RESULTS: FZHY strongly inhibited the development of CCl4- and BDL-induced liver fibrosis in mice. Liver fibrosis was significantly improved in FZHY-treated mice, as demonstrated by reduced content of hepatic hydroxyproline and Sirius Red positive area. Moreover, the number of SMA +and Desmin+ myofibroblasts was significantly reduced in the livers of FZHY-treated mice, and correlated with downregulation of the mRNA levels of α-SMA, collagen-α1(I), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1), TGF-ß1 and its receptor TGF-ßRI, and platelet-derived growth factor-ß (PDGF-ß), suggesting that FZHY inhibits activation of fibrogenic myofibroblasts. Furthermore, administration of FZHY markedly decreased recruitment of F4/80+ inflammatory macrophages to the livers of CCl4- and BDL-injured mice, and this effect was associated with downregulation of monocyte chemoattractant protein-1(MCP-1) and macrophage inflammatory protein-1 (MIP-1) mRNA. In addition, the lipid peroxidation products 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA) were reduced, demonstrating that treatment with FZHY can effectively block ROS production in livers of CCl4- and BDL-injured mice. CONCLUSIONS: Traditional Chinese Medicine FZHY has a variety of anti-fibrotic effects, including strong anti-oxidant, anti-inflammatory and anti-fibrotic effects on myeloid cells and hepatocytes. Although FZHY compound does not seem to directly affect HSCs, it regulates HSC activation via inhibition of macrophage recruitment to fibrotic liver.

MECHANISTIC MODELING PREDICTS NO SIGNIFICANT DOSE RATE EFFECT ON HEAVY-ION CARCINOGENESIS AT DOSE RATES RELEVANT FOR SPACE EXPLORATION.

Heavy ion-induced carcinogenesis is a challenge for human space exploration, and mechanistically-motivated mathematical models are needed to predict space-relevant low dose-rate risks, which are difficult to measure experimentally, based on data at higher dose rates. We present such a model, which quantifies targeted and non-targeted radiation effects. We fitted it to lung carcinogenesis data in radon-exposed miners and rats, which provide valuable information on carcinogenesis from protracted exposure to densely-ionizing radiation. We generated model-based estimates for the dose-rate-effect, relative to acute exposures, on heavy ion-induced carcinogenesis at doses/dose rates expected during a Mars mission. A small and not statistically-significant dose-rate effect was predicted: 1.00 (95% CI: 0.54, 1.40) for human data and for combined human and rat data 0.93 (0.06, 1.49). Consequently, heavy ion carcinogenesis estimates from moderate/high dose-rate experimental data may be applicable to doses/dose rates relevant for space exploration.

Radiation exposure from depleted uranium: The radiation bystander effect.

Depleted uranium (DU) is a radioactive heavy metal used primarily in military applications. Published data from our laboratory have demonstrated that DU exposure in vitro to immortalized human osteoblast cells (HOS) is both neoplastically transforming and genotoxic. In vivo studies have also demonstrated that DU is leukemogenic and genotoxic. DU possesses both a radiological (alpha particle) and chemical (metal) component but is generally considered a chemical biohazard. Studies have shown that alpha particle radiation does play a role in DU's toxic effects. Evidence has accumulated that non-irradiated cells in the vicinity of irradiated cells can have a response to ionization events. The purpose of this study was to determine if these "bystander effects" play a role in DU's toxic and neoplastic effects using HOS cells. We investigated the bystander responses between DU-exposed cells and non-exposed cells by co-culturing the two equal populations. Decreased cell survival and increased neoplastic transformation were observed in the non-DU exposed cells following 4 or 24h co-culture. In contrast Ni (II)- or Cr(VI)- exposed cells were unable to alter those biological effects in non-Ni(II) or non-Cr(VI) exposed co-cultured cells. Transfer experiments using medium from the DU-exposed and non-exposed co-cultured cells was able to cause adverse biological responses in cells; these results demonstrated that a factor (s) is secreted into the co-culture medium which is involved in this DU-associated bystander effect. This novel effect of DU exposure could have implications for radiation risk and for health risk assessment associated with DU exposure.

Measurement of UV Emission from a Diffusing Optical Fiber Using Radiochromic Film.

Analysis of the emission pattern from optical diffuser tips is vital to their usage in biomedical applications, especially as they find growing functionality beyond established phototherapy techniques. The use of ultraviolet radiation with diffuser tips increases the need to accurately characterize these devices, both for effective application and to avoid potentially dangerous exposure conditions. This study presents a new method to capture the diffusion pattern at a high resolution through the use of radiochromic film. The film is positioned in a cylinder around the diffuser, light is emitted from the diffuser onto the film and the film expresses a color change relative to the exposure amount. The resulting emission map shows the distribution of power from the diffuser in all direction. This method, which is both quick and inexpensive, generates high-resolution data much simpler than previously published works which required precise goniometric positioning.

Quantitative Metabolomic Analysis of Urinary Citrulline and Calcitroic Acid in Mice after Exposure to Various Types of Ionizing Radiation.

With the safety of existing nuclear power plants being brought into question after the Fukushima disaster and the increased level of concern over terrorism-sponsored use of improvised nuclear devices, it is more crucial to develop well-defined radiation injury markers in easily accessible biofluids to help emergency-responders with injury assessment during patient triage. Here, we focused on utilizing ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) to identify and quantitate the unique changes in the urinary excretion of two metabolite markers, calcitroic acid and citrulline, in mice induced by different forms of irradiation; external γ irradiation at a low dose rate (LDR) of 3.0 mGy/min and a high dose rate (HDR) of 1.1 Gy/min, and internal exposure to Cesium-137 ((137)Cs) and Strontium-90 ((90)Sr). The multiple reaction monitoring analysis showed that, while exposure to (137)Cs and (90)Sr induced a statistically significant and persistent decrease, similar doses of external γ beam at the HDR had the opposite effect, and the LDR had no effect on the urinary levels of these two metabolites. This suggests that the source of exposure and the dose rate strongly modulate the in vivo metabolomic injury responses, which may have utility in clinical biodosimetry assays for the assessment of exposure in an affected population. This study complements our previous investigations into the metabolomic profile of urine from mice internally exposed to (90)Sr and (137)Cs and to external γ beam radiation.

Placebo-controlled trial of high-dose atorvastatin in patients with severe cerebral small vessel disease.

BACKGROUND AND PURPOSE: Uncontrolled studies have shown that statins can improve cerebral vasoreactivity (CVR) in patients with mild small vessel disease. We sought to determine whether high-dose atorvastatin increases CVR compared with placebo in patients with severe small vessel disease. METHODS: Ninety-four adults with recent lacunar stroke were randomly allocated in a double-blind manner to 80 mg of atorvastatin daily or matching placebo after stratification for hypertensive and diabetic status. The primary end point was change in CVR after 3 months of treatment. Secondary outcomes were changes in brachial and carotid artery endothelial-dependent vasodilations. RESULTS: At baseline, all patients had a severely impaired CVR (mean, 12.1%; 95% CI, 9.5-14.7) and carotid (mean, -0.25%; 95% CI, -1.17-0.67) and brachial artery (mean, 2.72%; 95% CI, 1.39-4.05) endothelial function. Despite reductions of 55% in low-density lipoprotein cholesterol and of 30% in high-sensitivity C-reactive protein in the active arm compared to placebo, atorvastatin 80 mg per day did not improve CVR or endothelial dysfunction of carotid and brachial arteries. CONCLUSIONS: We found no positive effect of 3-month treatment with atorvastatin on severe cerebral microvasculature endothelial dysfunction in patients with lacunar stroke.

The enteropathy of prostaglandin deficiency.

BACKGROUND: Small intestinal ulcers are frequent complications of therapy with nonsteroidal anti-inflammatory drugs (NSAIDs). We present here a genetic deficiency of eicosanoid biosynthesis that illuminates the mechanism of NSAID-induced ulcers of the small intestine. METHODS: Eicosanoids and metabolites were measured by isotope dilution with mass spectrometry. cDNA was obtained by reverse transcription and sequenced following amplification with RT-PCR. RESULTS: We investigated the cause of chronic recurrent small intestinal ulcers, small bowel perforations, and gastrointestinal blood loss in a 45-year-old man who was not taking any cyclooxygenase inhibitor. Prostaglandin metabolites in urine were significantly depressed. Serum thromboxane B2 (TxB2) production was 4.6% of normal controls (P<0.006), and serum 12-HETE was 1.3% of controls (P<0.005). Optical platelet aggregation with simultaneous monitoring of ATP release demonstrated absent granule secretion in response to ADP and a blunted aggregation response to ADP and collagen, but normal response to arachidonic acid (AA). LTB4 biosynthesis by ionophore-activated leukocytes was only 3% of controls, and urinary LTE4 was undetectable. These findings suggested deficient AA release from membrane phospholipids by cytosolic phospholipase A2-alpha (cPLA2-alpha), which regulates cyclooxygenase- and lipoxygenase-mediated eicosanoid production by catalyzing the release of their substrate, AA. Sequencing of cPLA2-alpha cDNA demonstrated two heterozygous nonsynonymous single-base-pair mutations: Ser111Pro (S111P) and Arg485His (R485H), as well as a known single nucleotide polymorphism (SNP), Lys651Arg (K651R). CONCLUSIONS: Characterization of this cPLA2-alpha deficiency provides support for the importance of prostaglandins in protecting small intestinal integrity and indicates that loss of prostaglandin biosynthesis is sufficient to produce small intestinal ulcers.

Alcohol, intestinal bacterial growth, intestinal permeability to endotoxin, and medical consequences: summary of a symposium.

This report is a summary of the symposium on Alcohol, Intestinal Bacterial Growth, Intestinal Permeability to Endotoxin, and Medical Consequences, organized by National Institute on Alcohol Abuse and Alcoholism, Office of Dietary Supplements, and National Institute of Diabetes and Digestive and Kidney Diseases of National Institutes of Health in Rockville, Maryland, October 11, 2006. Alcohol exposure can promote the growth of Gram-negative bacteria in the intestine, which may result in accumulation of endotoxin. In addition, alcohol metabolism by Gram-negative bacteria and intestinal epithelial cells can result in accumulation of acetaldehyde, which in turn can increase intestinal permeability to endotoxin by increasing tyrosine phosphorylation of tight junction and adherens junction proteins. Alcohol-induced generation of nitric oxide may also contribute to increased permeability to endotoxin by reacting with tubulin, which may cause damage to microtubule cytoskeleton and subsequent disruption of intestinal barrier function. Increased intestinal permeability can lead to increased transfer of endotoxin from the intestine to the liver and general circulation where endotoxin may trigger inflammatory changes in the liver and other organs. Alcohol may also increase intestinal permeability to peptidoglycan, which can initiate inflammatory response in liver and other organs. In addition, acute alcohol exposure may potentiate the effect of burn injury on intestinal bacterial growth and permeability. Decreasing the number of Gram-negative bacteria in the intestine can result in decreased production of endotoxin as well as acetaldehyde which is expected to decrease intestinal permeability to endotoxin. In addition, intestinal permeability may be preserved by administering epidermal growth factor, l-glutamine, oats supplementation, or zinc, thereby preventing the transfer of endotoxin to the general circulation. Thus reducing the number of intestinal Gram-negative bacteria and preserving intestinal permeability to endotoxin may attenuate alcoholic liver and other organ injuries.