Ferroptosis,a key to unravel the enigma of the FLASH effect?

Ferroptosis is a non-apoptotic form of cell death dependent on iron and lipid peroxides. It has been recently described to have a role on cell death after radiation (RT) through a DNA damage independent mechanism. While the modification of ferroptosis pathways is suggested to enhance radiosensitisation, normal tissue toxicity may limit the combined treatment of RT and ferroptosis inducers. FLASH RT is given at ultra-high dose rates to reduce normal tissue toxicities, which contributes to the RT effect on the tumour. Although several hypotheses including oxygen depletion, reduced ROS, and immune responses are suggested to explain the FLASH effect, the underlying mechanisms of normal tissue sparing effects are still not well understood. Previous studies highlighting the inverse effect of RT dose rates and lipid peroxidation, along with the hypothesis by Spitz et al, suggest that oxygen depletion from the chain reaction of lipid peroxidation and differences in labile pool between normal and tumour tissues may be related to the normal tissue sparing effect of FLASH. Therefore, the role of ferroptosis in ultra-high dose rate FLASH RT needs to be investigated further as it might be the key to increase the therapeutic window of FLASH RT.     

Anti-inflammatory effect of low-dose X-irradiation and the involvement of a TGF-β 1 -induced down-regulation of leukocyte/endothelial cell adhesion

Purpose : Low-dose radiotherapy (LD-RT) is known to exert an anti-inflammatory effect, but the underlying radiobiological and immunological mechanisms remain elusive. In recent studies, we observed a reduced adhesion of peripheral blood mononuclear cells (PBMC) to endothelial cells (EC) after LD-RT (0.3-0.7 Gy). This shows that this treatment affects the initial steps of the inflammatory response. To explore the role of inflammatory mediators in this process, we investigated the expression of Transforming growth factor β 1 (TGF- β 1) and Interleukin 6 (IL-6) after LD-RT. Materials and Methods : EC were grown to subconfluence and irradiated with single-dose LD-RT. Twenty-hours after irradiation, EC were treated with IL-1 β for 4 h and then incubated with peripheral blood mononuclear cells (PBMC). Adherent PBMC were counted when using light microscopy. Expression of the cytokines TGF- β 1 and IL-6 was measured by ELISA, and mRNA levels were analysed by the RNAse-protection assay (RPA). Surface expression of E-selectin was quantified by flow cytometry. Results : A relative minimum of adhesion was observed after LD-RT between 0.3 and 0.7 Gy. This was paralleled by an expression maximum of TGF- β 1 and IL-6, as shown by protein and mRNA levels, respectively. Neutralization of TGF- β 1 by monoclonal antibodies, but not of IL-6, increased PBMC adhesion to EC nearly to control levels. In addition, fluorescence activated cell sorter (FACS) analysis of irradiated EC demonstrated a down-regulation of E-selectin in the same dose range. Conclusion : Low-dose X-irradiation between 0.3 and 0.7 Gy induced a relative maximum of TGF- β 1 production by stimulated EC. This results in a down-regulation of leukocyte/PBMC adhesion and may contribute to the anti-inflammatory effect of LD-RT.     

Value of the radiolabelled GLP-1 receptor antagonist exendin(9–39) for targeting of GLP-1 receptor-expressing pancreatic tissues in mice and humans

Purpose  

Radiolabelled glucagon-like peptide 1 (GLP-1) receptor agonists have recently been shown to successfully image benign insulinomas in patients. Moreover, it was recently reported that antagonist tracers were superior to agonist tracers for somatostatin and gastrin-releasing peptide receptor targeting of tumours. The present preclinical study determines therefore the value of an established GLP-1 receptor antagonist for the in vitro visualization of GLP-1 receptor-expressing tissues in mice and humans.     

Multiplex analysis of genetic polymorphisms within UGT1A9, a gene involved in phase II of Δ9-THC metabolism

We present a novel multiplex assay for the simultaneous detection of 12 polymorphisms within the UGT1A9 sequence, which codes for enzymes involved in phase II biotransformation. The assay combines a multiplexed amplification step with single-base extension sequencing. The method described here is fast, cost-effective, and easy-to-use, combining the relevant features of screening methods for research and diagnostics in pharmacogenetics. To validate the assay, we tested reproducibility and sensitivity and analysed allele frequencies of 110 Caucasian individuals. Furthermore, we describe combining genetic information of individuals consuming Cannabis sativa products with respective plasma concentrations of a metabolite.

     

One component? Two components? Three? The effect of including a nonexchanging “free” water component in multicomponent driven equilibrium single pulse observation of T1 and T2

Quantitative myelin content imaging provides novel and pertinent information related to underlying pathogenetic mechanisms of myelin‐related disease or disorders arising from aberrant connectivity. Multicomponent driven equilibrium single pulse observation of T₁ and T₂ is a time‐efficient multicomponent relaxation analysis technique that provides estimates of the myelin water fraction, a surrogate measure of myelin volume. Unfortunately, multicomponent driven equilibrium single pulse observation of T₁ and T₂ relies on a two water‐pool model (myelin‐associated water and intra/extracellular water), which is inadequate within partial volume voxels, i.e., containing brain tissue and ventricle or meninges, resulting in myelin water fraction underestimation. To address this, a third, nonexchanging “free‐water” component was introduced to the multicomponent driven equilibrium single pulse observation of T₁ and T₂ model. Numerical simulations and experimental in vivo data show that the model to perform advantageously within partial volume regions while providing robust and reproducible results. It is concluded that this model is preferable for future studies and analysis. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Magnetic resonance imaging in the evaluation of iron overload: a comparison of MRI, echocardiography and serum ferritin level in patients with β-thalassemia major

PurposeThis study aimed to evaluate iron levels in cardiac and hepatic tissues using magnetic resonance imaging (MRI) T2?.MethodsCardiac and hepatic MRI was performed for 93 patients with β-thalassemia major.ResultsCardiac T2? was in the range of 2.9–56.6 ms. Myocardial siderosis was detected in 44% of patients; 25 patients had moderate and severe siderosis with serum ferritin level (SFL) of 576–10,284 ng/ml. There was a significant correlation between SFL and cardiac T2? (p<.001).ConclusionsThe effective role of MRI as a noninvasive producible method in measurement of iron concentration in tissues is not accessible with conventional techniques.     

Serum concentrations of C reactive protein, alpha1 antitrypsin, and complement (C3, C4, C1 esterase inhibitor) before and during the Vuelta a Espańa

Objectives

To determine serum concentrations of proinflammatory (C reactive protein, complement C3 and C4) and anti‐inflammatory (α₁ antitrypsin, C1 esterase inhibitor (C1‐INH)) acute phase proteins in elite cyclists before and during a three week cycle tour.

Methods

Seventeen professional cyclists participating in the Vuelta a Espańa volunteered for the study. Their mean (SD) physical characteristics were: age 28 (1) years; height 1.7 (0.06) m; weight 65 (7) kg; body fat 7.6 (0.8)%; Vo₂max 75.3 (2.3) ml/kg/min. Venepuncture was performed on each subject 24 hours before the tour began (T0), on day 11 (the first rest day; T1) and day 21 (the second to last stage of the tour; T2). Samples at T1 and T2 were taken about 17 hours after the previous stage. Analysis of variance was used to determine changes over time. Where significance was found, a Tukey post hoc test was performed.

Results

C reactive protein concentrations were consistently within the normal range, although there was a 228%, non‐significant increase at T1. C3 concentrations fell within the normal range at all times assessed. C4 concentrations before the race were within the normal range and were significantly increased 10 days (T1) into the race. C1‐INH concentrations did not change significantly throughout the race. α₁ Antitrypsin concentration before the race was at the lower end of the normal range and was only significantly raised at T2.

Conclusions

Although not as pronounced as those reported in marathon/ultramarathon runners, elite cyclists participating in a three week cycle tour experienced increases in selected proinflammatory and anti‐inflammatory acute phase proteins, indicating an acute phase/inflammatory response. It is tenable that the increase in α₁ antitrypsin and C1‐INH (anti‐inflammatory mediators) at T2 served to attenuate the acute phase/inflammatory response. The lower than normal resting concentrations of the acute phase proteins supports the notion that chronic aerobic exercise induces an anti‐inflammatory state.     

Femoral morphology and epiphyseal growth plate changes of the hip during maturation: MR assessments in a 1-year follow-up on a cross-sectional asymptomatic cohort in the age range of 9–17?years

Objectives

The goal of this prospective study was to characterize the morphology and physeal changes of the femoral head during maturation using MRI in a population-based group of asymptomatic volunteers.

Materials and methods

Sixty-four pupils (127 hips) of 331 pupils from a primary and high school were asked to take part in this study and were willing to participate. 3T MRI of the hip was obtained at baseline and 1-year follow-up. With these images, we analyzed the femoral morphology and epiphyseal changes related to age, status of the physis, and location on the femur.

Results

The radius of the femoral head and neck increased with age, as expected, (p?p?p?>?0.05). Building groups by using the epiphyseal status, we found that the epiphyseal extension had the highest changes in the "open" group and almost stopped in the "closed" group. The tilt angle did not change significantly (p?>?0.05). Significant smaller alpha-angles were found in the "closed" group, however, these were in a normal range in all of them. Correlated to the position, the highest alpha-angle values were located in anterior-superior and superior-anterior position.

Conclusions

Our data can be used as normative values, which can be compared to patients or cohorts with certain risk factors (e.g., professional athletes), this will offer the chance to detect and understand pathological changes.     

PET imaging of brain with the β-amyloid probe, [11C]6-OH-BTA-1, in a transgenic mouse model of Alzheimer’s disease

Purpose The purpose of this study was to evaluate the capacity of [¹¹C]6-OH-BTA-1 and positron emission tomography (PET) to quantify -amyloid (A) plaques in the Tg2576 mouse model of Alzheimers disease (AD).Methods PET imaging was performed with the NIH ATLAS small animal scanner in six elderly transgenic mice (Tg2576; age 22.0±1.8 months; 23.6±2.6 g) overexpressing a mutated form of human -amyloid precursor protein (APP) known to result in the production of A plaques, and in six elderly wild-type litter mates (age 21.8±1.6 months; 29.5±4.7 g). Dynamic PET scans were performed for 30 min in each mouse under 1% isoflurane inhalation anesthesia after a bolus injection of 13–46 MBq of [¹¹C]6-OH-BTA-1. PET data were reconstructed with 3D OSEM. On the coronal PET image, irregular regions of interest (ROIs) were placed on frontal cortex (FR), parietal cortex (PA), striatum (ST), thalamus (TH), pons (PO), and cerebellum (CE), guided by a mouse stereotaxic atlas. Time–activity curves (TACs) (expressed as percent injected dose per gram normalized to body weight: % ID-kg/g) were obtained for FR, PA, ST, TH, PO, and CE. ROI-to-CE radioactivity ratios were also calculated. Following PET scans, sections of mouse brain prepared from anesthetized and fixative-perfused mice were stained with thioflavin-S.Results TACs for [¹¹C]6-OH-BTA-1 in all ROIs peaked early (at 30–55 s), with radioactivity washing out quickly thereafter in both transgenic and wild-type mice. Peak uptake in all regions was significantly lower in transgenic mice than in wild-type mice. During the later part of the washout phase (12–30 min), the mean FR/CE and PA/CE ratios were higher in transgenic than in wild-type mice (1.06±0.04 vs 0.98±0.07, p=0.04; 1.06±0.09 vs 0.93±0.08 p=0.02) while ST/CE, TH/CE, and PO/CE ratios were not. Ex vivo staining revealed widespread A plaques in cortex, but not in cerebellum of transgenic mice or in any brain regions of wild-type mice.Conclusion Marked reductions in brain uptake of this radioligand in transgenic mice may be due to reduced cerebral blood flow relative to that in wild-type mice. Specific [¹¹C]6-OH-BTA-1 binding to A plaques, if any, is probably very low, as reflected in the small FR/CE and PA/CE ratio differences. FR/CE and PA/CE ratios are considerably higher in AD patients while A plaque densities in 22-month-old transgenic mice may be expected to show essentially the same density as is observed in the AD brain. This implies that the absence of tracer retention in 22-month-old transgenic mice may be due to the smaller number of A plaque binding sites and/or to lower affinity of the binding sites for [¹¹C]6-OH-BTA-1 as compared with AD patients. [¹¹C]6-OH-BTA-1 shows excellent brain uptake in mice.This work was presented at the 51st Annual Meeting of the Society of Nuclear Medicine in Philadelphia, PA, June 19–23, 2004.     

Do CSF levels of t-Tau,p-Tau and β1-42 amyloid correlate with dopaminergic system impairment in patients with a clinical diagnosis of Parkinson disease? A 123I-FP-CIT study in the early stages of the disease

Purpose

To investigate the relationships among cerebrospinal fluid (CSF) levels of t-Tau, p-Tau and Aβ_1-42 amyloid peptide and ¹²³I-FP-CIT uptake.

Methods

The study included 58 subjects (31 men and 27 women, age 67 ± 9 years) with a clinical diagnosis of Parkinson disease diagnosed according to the United Kingdom Parkinson Disease Society Brain Bank criteria. All subjects underwent a CSF assay 28 ± 3 days before ¹²³I-FP-CIT SPECT scanning. The relationships were evaluated by means of linear regression analysis and Pearson correlation.

Results

Striatal ¹²³I-FP-CIT was positively related to both t-Tau and p-Tau CSF values with low levels of t-Tau and p-Tau being related to a low uptake of ¹²³I-FP-CIT. In particular, differences with higher statistical significance were found for the striatum between the contralateral side and the side mainly affected on clinical examination (P?1-42 amyloid peptide and ¹²³I-FP-CIT binding.

Conclusion

The results of our study suggest that the presynaptic dopaminergic system is more involved in Parkinson disease patients with lower t-Tau and p-Tau CSF values while values of Aβ_1-42 amyloid peptide seems not to be related to nigrostriatal degeneration in our series.     

Automation of the radiosynthesis and purification procedures for [18F]Fluspidine preparation,a new radiotracer for clinical investigations in PET imaging of σ1 receptors in brain

The radiosynthesis of [¹⁸F]Fluspidine, a potent σ₁ receptor imaging probe for pre-clinical/clinical studies, was implemented on a TRACERlab^TM FX F-N synthesizer. [¹⁸F]2 was synthesized in 15 min at 85 °C starting from its tosylate precursor. Purification via semi-preparative RP-HPLC was investigated using different columns and eluent compositions and was most successful on a polar RP phase with acetonitrile/water buffered with NH₄OAc. After solid phase extraction, [¹⁸F]Fluspidine was formulated and produced within 59±4 min with an overall radiochemical yield of 37±8%, a radiochemical purity of 99.3±0.5% and high specific activity (176.6±52.0 GBq/µmol).     

Water and tissue equivalence properties of biological materials for photons,electrons, protons and alpha particles in the energy region 10 keV–1 GeV: a comparative study

Purpose: To compare some biological materials in respect to the water and tissue equivalence properties for photon, electron, proton and alpha particle interactions as means of the effective atomic number (Z_eff) and electron density (N_e).

Methods: A Z-wise interpolation procedure has been adopted for calculation of Z_eff using the mass attenuation coefficients for photons and the mass stopping powers for charged particles.

Results: At relatively low energies (100?keV–3?MeV), Z_eff and N_e for photons and electrons were found to be constant while they vary much more for protons and alpha particles. In contrast, Z_eff and N_e for protons and alpha particles were found to be constant after 3?MeV whereas for photons and electrons they were found to increase with the increasing energy. Also, muscle eq. liquid (with sucrose) have Z_eff and N_e values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) within low relative differences below 9%. Muscle eq. liquid (without sucrose) have Z_eff and N_e values close to the Muscle Skeletal (ICRP) and Muscle Striated (ICRU) with difference below 10%.

Conclusions: The reported data should be useful in determining best water as well as tissue equivalent materials for photon, electron, proton and alpha particle interactions.