Membrane signaling induced by high doses of ionizing radiation in the endothelial compartment. Relevance in radiation toxicity

The Protein Kinase A Inhibitor KT5720 Prevents Endothelial Dysfunctions Induced by High-Dose Irradiation

High-dose irradiation can trigger numerous endothelial dysfunctions, including apoptosis, the overexpression of adhesion molecules, and alteration of adherens junctions. Altogether, these endothelial dysfunctions contribute to the development of tissue inflammation and organ damage. The development of endothelial dysfunctions may depend on protein phosphorylation by various protein kinases, but the possible role of protein kinase A (PKA) has not been investigated so far, and efficient compounds able to protect the endothelium from irradiation effects are needed. Here we report the beneficial effects of the PKA inhibitor KT5720 on a panel of irradiation-induced endothelial dysfunctions in human pulmonary microvascular endothelial cells (HPMECs). High-dose X-irradiation (15 Gy) triggered the late apoptosis of HPMECs independent of the ceramide/P38 MAP kinase pathway or p53. In contrast, the treatment of HPMECs with KT5720 completely prevented irradiation-induced apoptosis, whether applied before or after cell irradiation. Immunostainings of irradiated monolayers revealed that KT5720 treatment preserved the overall integrity of endothelial monolayers and adherens junctions linking endothelial cells. Real-time impedance measurements performed in HPMEC monolayers confirmed the overall protective role of KT5720 against irradiation. Treatment with KT5720 before or after irradiation also reduced irradiation-induced ICAM-1 overexpression. Finally, the possible role for PKA in the development of endothelial dysfunctions is discussed, but the potency of KT5720 to inhibit the development of a panel of irradiation-induced endothelial dysfunctions, whether applied before or after irradiation, suggests that this compound could be of great interest for both the prevention and treatment of vascular damages in the event of exposure to a high dose of radiation.

Outcomes in dogs undergoing surgical stabilization and non-stereotactic radiation therapy for axial and appendicular bone tumors

Background

Information on dogs that undergo radiation therapy (RT) with non-stereotactic protocols in addition to surgical stabilization with implant placement for treatment of bone tumors is limited.

Objective

Our primary objectives were to describe the clinical characteristics as well as short- and long-term outcomes, including complications, function, and disease progression, in dogs that underwent both surgical stabilization with implant placement and non-stereotactic RT for local treatment of a bone tumor.

Methods

A bi-institutional retrospective case series was performed.

Animals

Eight client-owned dogs that underwent both surgical stabilization with implant placement and non-stereotactic RT for local treatment of a bone tumor were included.

Results

Tumor types included osteosarcoma or suspected osteosarcoma (5), plasma cell tumor (2), and grade 3 fibrosarcoma (1). Radiation protocols were hypofractionated (palliative intent) in 5 dogs and fractionated (definitive intent) in 3 dogs. Five dogs experienced complications following both RT and surgery, including grade 1 complications in two dogs, a grade 2 complication in one dog, both grade 1 and 2 complications in one dog, and both grade 2 and 3 complications in one dog. Clinical signs subjectively improved in all dogs that had outcomes relative to function documented post-surgery/RT (7). Of these 7 dogs, 4 maintained long-term improvement in function and clinical signs, whereas 3 experienced subsequent recurrence/progression of clinical signs at a median of 133 days (range 91-186) postoperatively in association with biomechanical complications (screw loosening), surgical site infection, and local disease progression in 1 dog each; subsequent treatment resulted in improved clinical signs for each of these 3 dogs, such that overall good long-term functional outcomes were experienced. No dogs required amputation or additional vertebral surgery as salvage for local disease control or palliation. The median progression free interval was 206 days (range 25-1078), and the median survival time was 253 days (range 122-1078) with 1 additional dog lost to follow-up at 575 days. Two dogs experienced local disease progression, and 6 dogs experienced systemic disease progression; both dogs that developed local disease progression received palliative intent RT protocols.

Clinical relevance

In this cohort, dogs with primary bone tumors that underwent surgical stabilization with implant placement and hypofractionated or fractionated non-stereotactic RT for local treatment had a low incidence of major complications, good limb function and ambulation post-treatment, and relatively prolonged survival times despite disease progression.

Crosstalk between Oxidative Stress and Inflammation Induced by Ionizing Radiation in Healthy and Cancerous Cells

Radiotherapy (RT) is a unique modality in cancer treatment with no replacement in many cases and uses a tumoricidal dose of various ionizing radiation (IR) types to kill cancer cells. It causes oxidative stress through reactive oxygen species (ROS) production or the destruction of antioxidant systems. On the other hand, RT stimulates the immune system both directly and indirectly by releasing danger signals from stress-exposed and dying cells. Oxidative stress and inflammation are two reciprocal and closely related mechanisms, one induced and involved by the other. ROS regulates the intracellular signal transduction pathways, which participate in the activation and expression of pro-inflammatory genes. Reciprocally, inflammatory cells release ROS and immune system mediators during the inflammation process, which drive the induction of oxidative stress. Oxidative stress or inflammation-induced damages can result in cell death (CD) or survival mechanisms that may be destructive for normal cells or beneficial for cancerous cells. The present study has focused on the radioprotection of those agents with binary effects of antioxidant and anti-inflammatory mechanisms IR-induced CD.

Gene networks for use in metabolomic data analysis of blood plasma from patients with postoperative delirium

Postoperative delirium (POD) is considered one of the most severe complications, resulting in impaired cognitive function, extended hospitalization, and higher treatment costs. The challenge of early POD diagnosis becomes particularly significant in cardiac surgery cases, as the incidence of this complication exceeds 50 % in certain patient categories. While it is known that neuroinflammation, neurotransmitter imbalances, disruptions in neuroendocrine regulation, and interneuronal connections contribute significantly to the development of POD, the molecular, genetic mechanisms of POD in cardiac surgery patients, along with potential metabolomic diagnostic markers, remain inadequately understood. In this study, blood plasma was collected from a group of patients over 65 years old after cardiac surgery involving artificial circulation. The collected samples were analyzed for sphingomyelin content and quantity using high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS/MS) methods. The analysis revealed four significantly different sphingomyelin contents in patients with POD compared to those who did not develop POD (control group). Employing gene network reconstruction, we perceived a set of 82 regulatory enzymes affiliated with the genetic coordination of the sphingolipid metabolism pathway. Within this set, 47 are assumed to be regulators of gene expression, governing the transcription of enzymes pivotal to the metabolic cascade. Complementing this, an additional assembly of 35 regulators are considered to be regulators of activity, degradation, and translocation dynamics of enzymes integral to the aforementioned pathway. Analysis of the overrepresentation of diseases with which these regulatory proteins are associated showed that the regulators can be categorized into two groups, associated with cardiovascular pathologies (CVP) and neuropsychiatric diseases (NPD), respectively. The regulators associated with CVP are expectedly related to the effects on myocardial tissue during surgery. It is hypothesized that dysfunction of NPD-associated regulators may specifically account for the development of POD after cardiac surgery. Thus, the identified regulatory genes may provide a basis for planning further experiments, in order to study disorders at the level of expression of these genes, as well as impaired function of proteins encoded by them in patients with POD. The identified significant sphingolipids can be considered as potential markers of POD.

Molecular-genetic pathways of hepatitis C virus regulation of the expression of cellular factors PREB and PLA2G4C, which play an important role in virus replication

The participants of Hepatitis C virus (HCV) replication are both viral and host proteins. Therapeutic approaches based on activity inhibition of viral non-structural proteins NS3, NS5A, and NS5B are undergoing clinical trials. However, rapid mutation processes in the viral genome and acquisition of drug resistance to the existing drugs remain the main obstacles to fighting HCV. Identifying the host factors, exploring their role in HCV RNA replication, and studying viral effects on their expression is essential for understanding the mechanisms of viral replication and developing novel, effective curative approaches. It is known that the host factors PREB (prolactin regulatory element binding) and PLA2G4C (cytosolic phospholipase A2 gamma) are important for the functioning of the viral replicase complex and the formation of the platforms of HCV genome replication. The expression of PREB and PLA2G4C was significantly elevated in the presence of the HCV genome. However, the mechanisms of its regulation by HCV remain unknown. In this paper, using a text-mining technology provided by ANDSystem, we reconstructed and analyzed gene networks describing regulatory effects on the expression of PREB and PLA2G4C by HCV proteins. On the basis of the gene network analysis performed, we put forward hypotheses about the modulation of the host factors functions resulting from protein-protein interaction with HCV proteins. Among the viral proteins, NS3 showed the greatest number of regulatory linkages. We assumed that NS3 could inhibit the function of host transcription factor (TF) NOTCH1 by protein-protein interaction, leading to upregulation of PREB and PLA2G4C. Analysis of the gene networks and data on differential gene expression in HCV-infected cells allowed us to hypothesize further how HCV could regulate the expression of TFs, the binding sites of which are localized within PREB and PLA2G4C gene regions. The results obtained can be used for planning studies of the molecular-genetic mechanisms of viral-host interaction and searching for potential targets for anti-HCV therapy.

Study on the protective effect and mechanism of Liriodendrin on radiation enteritis in mice

Patients receiving pelvic or abdominal radiotherapy may experience acute and/or chronic side effects due to gastrointestinal changes. However, effective medicine for treating radiation enteritis has not been found yet. Sargentodoxa cuneata is a famous Chinese medicine used to treat intestinal inflammation, and our research team has found the main biologically active compound through its extraction, which is Liriodendrin. In this study, we found that Liriodendrin can reduce the expression of Cer, Cer1P and S1P in the sphingolipid pathway, thereby reducing the histological damage to the intestinal tract of mice and inhibiting the apoptosis of intestinal tissue cells. In addition, Liriodendrin can reduce the levels of pro-inflammatory cytokines (IL-6 and TNF-α), and it is suggested through flow cytometry that the proportion of neutrophils in the intestinal tissue can decrease due to the existence of Liriodendrin. At the same time, the western blot evaluation revealed that Liriodendrin significantly inhibited the activation of Bcl-2/Bax/Caspase-3 and NF-κB signaling pathways. The results show that Liriodendrin can inhibit intestinal inflammation and intestinal cell apoptosis through the sphingolipid pathway. Therefore, the aforementioned results demonstrated that Liriodendrin may be a promising drug for the treatment of radiation enteritis.

Model studies of the role of oxygen in the FLASH effect

Current radiotherapy facilities are standardized to deliver dose rates around 0.1-0.4 Gy/s in 2 Gy daily fractions, designed to deliver total accumulated doses to reach the tolerance limit of normal tissues undergoing irradiation. FLASH radiotherapy (FLASH-RT), on the other hand, relies on facilities capable of delivering ultrahigh dose rates in large doses in a single microsecond pulse, or in a few pulses given over a very short time sequence. For example, most studies to date have implemented 4-6 MeV electrons with intra-pulse dose rates in the range 10⁶ -10⁷  Gy/s. The proposed dependence of the FLASH effect on oxygen tension has stimulated several theoretical models based on three different hypotheses: (i) Radiation-induced transient oxygen depletion; (ii) cell-specific differences in the ability to detoxify and/or recover from injury caused by reactive oxygen species; (iii) self-annihilation of radicals by bimolecular recombination. This article focuses on the observations supporting or refuting these models in the frame of the chemical-biological bases of the impact of oxygen on the radiation response of cell free, in vitro and in vivo model systems.

Adhesion Molecules ICAM-1 and PECAM-1 as Potential Biomarkers of Central Nervous System Damage in Women Breast Cancer Survivors

Breast cancer (BC) is the most common tumor in women worldwide with high mortality rates. Surgical methods followed by radio–chemotherapy are used to treat these tumors. Such treatment can lead to various side effects, including neurological complications. The development of a reliable biomarker to predict the onset of CNS complications could improve clinical outcomes. In the current study, ICAM-1 and PECAM-1 serum levels were measured as potential biomarkers in 45 female patients in a long-term follow-up period after breast cancer treatment, and compared to 25 age-matched female healthy volunteers. Serum levels of both biomarkers, ICAM-1 and PECAM-1 were significantly higher in patients after breast cancer treatment and could be associated with cognitive dysfunction, depression, and vestibulocerebellar ataxia. In conclusion, our results provide a first hint that elevated serum levels of ICAM-1 and PECAM-1 could serve as early predictive biomarkers in breast cancer survivors that might help to improve the management of these patients.

Activation of Sphingomyelinase-Ceramide-Pathway in COVID-19 Purposes Its Inhibition for Therapeutic Strategies

Effective treatment strategies for severe coronavirus disease (COVID-19) remain scarce. Hydrolysis of membrane-embedded, inert sphingomyelin by stress responsive sphingomyelinases is a hallmark of adaptive responses and cellular repair. As demonstrated in experimental and observational clinical studies, the transient and stress-triggered release of a sphingomyelinase, SMPD1, into circulation and subsequent ceramide generation provides a promising target for FDA-approved drugs. Here, we report the activation of sphingomyelinase-ceramide pathway in 23 intensive care patients with severe COVID-19. We observed an increase of circulating activity of sphingomyelinase with subsequent derangement of sphingolipids in serum lipoproteins and from red blood cells (RBC). Consistent with increased ceramide levels derived from the inert membrane constituent sphingomyelin, increased activity of acid sphingomyelinase (ASM) accurately distinguished the patient cohort undergoing intensive care from healthy controls. Positive correlational analyses with biomarkers of severe clinical phenotype support the concept of an essential pathophysiological role of ASM in the course of SARS-CoV-2 infection as well as of a promising role for functional inhibition with anti-inflammatory agents in SARS-CoV-2 infection as also proposed in independent observational studies. We conclude that large-sized multicenter, interventional trials are now needed to evaluate the potential benefit of functional inhibition of this sphingomyelinase in critically ill patients with COVID-19.

The p38 MAPK Components and Modulators as Biomarkers and Molecular Targets in Cancer

The mitogen-activated protein kinase (MAPK) family is an important bridge in the transduction of extracellular and intracellular signals in different responses at the cellular level. Within this MAPK family, the p38 kinases can be found altered in various diseases, including cancer, where these kinases play a fundamental role, sometimes with antagonistic mechanisms of action, depending on several factors. In fact, this family has an immense number of functionalities, many of them yet to be discovered in terms of regulation and action in different types of cancer, being directly involved in the response to cancer therapies. To date, three main groups of MAPKs have been identified in mammals: the extracellular signal-regulated kinases (ERK), Jun N-terminal kinase (JNK), and the different isoforms of p38 (α, β, γ, δ). In this review, we highlight the mechanism of action of these kinases, taking into account their extensive regulation at the cellular level through various modifications and modulations, including a wide variety of microRNAs. We also analyze the importance of the different isoforms expressed in the different tissues and their possible role as biomarkers and molecular targets. In addition, we include the latest preclinical and clinical trials with different p38-related drugs that are ongoing with hopeful expectations in the present/future of developing precision medicine in cancer.

From the target cell theory to a more integrated view of radiobiology in Targeted radionuclide therapy: The Montpellier group's experience

Targeted radionuclide therapy (TRT) is used to treat disseminated or metastatic tumours in which conventional external beam radiotherapy (EBRT) would have unacceptable side effects. Unlike EBRT, TRT delivers low doses at a continuous low dose rate. In EBRT, the effect increases progressively with the dose rate, and biological effects (tumour control and normal tissue damage) are related to the dose according to a sigmoid curve model. This model is part of the so-called quantitative radiobiology that is mostly based on the target cell theory, according to which cell death is due to (lethal) radiation hits to vital cellular targets. This model was developed for EBRT, but was adapted to low dose-rate situations by including a parameter that reflects the time needed to repair tissue damage. However, a growing body of evidence indicates that the model should take into account also the biological effects, which are due to intercellular communications (bystander effects) and amplify the effects of radiation, as well as the immune system. Moreover, extranuclear targets must be considered, although induced intracellular and intercellular signalling pathways may ultimately result in DNA damage. It is likely that bystander effects and immune response always contribute to the overall response to TRT at different levels, and that dose and dose rate are key parameters in controlling their real contribution. We hypothesize that the dose rate is the key determinant in the balance between the physical and DNA-centred response on one side, and the biological response that integrates all subcellular compartments and intercellular signalling pathways on the other side.

Biological Adaptations of Tumor Cells to Radiation Therapy

Radiation therapy has been used worldwide for many decades as a therapeutic regimen for the treatment of different types of cancer. Just over 50% of cancer patients are treated with radiotherapy alone or with other types of antitumor therapy. Radiation can induce different types of cell damage: directly, it can induce DNA single- and double-strand breaks; indirectly, it can induce the formation of free radicals, which can interact with different components of cells, including the genome, promoting structural alterations. During treatment, radiosensitive tumor cells decrease their rate of cell proliferation through cell cycle arrest stimulated by DNA damage. Then, DNA repair mechanisms are turned on to alleviate the damage, but cell death mechanisms are activated if damage persists and cannot be repaired. Interestingly, some cells can evade apoptosis because genome damage triggers the cellular overactivation of some DNA repair pathways. Additionally, some surviving cells exposed to radiation may have alterations in the expression of tumor suppressor genes and oncogenes, enhancing different hallmarks of cancer, such as migration, invasion, and metastasis. The activation of these genetic pathways and other epigenetic and structural cellular changes in the irradiated cells and extracellular factors, such as the tumor microenvironment, is crucial in developing tumor radioresistance. The tumor microenvironment is largely responsible for the poor efficacy of antitumor therapy, tumor relapse, and poor prognosis observed in some patients. In this review, we describe strategies that tumor cells use to respond to radiation stress, adapt, and proliferate after radiotherapy, promoting the appearance of tumor radioresistance. Also, we discuss the clinical impact of radioresistance in patient outcomes. Knowledge of such cellular strategies could help the development of new clinical interventions, increasing the radiosensitization of tumor cells, improving the effectiveness of these therapies, and increasing the survival of patients.

Revisiting the Radiobiology of Targeted Alpha Therapy

Targeted alpha therapy (TAT) using alpha particle-emitting radionuclides is in the spotlight after the approval of ²²³RaCl₂ for patients with metastatic castration-resistant prostate cancer and the development of several alpha emitter-based radiopharmaceuticals. It is acknowledged that alpha particles are highly cytotoxic because they produce complex DNA lesions. Hence, the nucleus is considered their critical target, and many studies did not report any effect in other subcellular compartments. Moreover, their physical features, including their range in tissues (<100 μm) and their linear energy transfer (50–230 keV/μm), are well-characterized. Theoretically, TAT is indicated for very small-volume, disseminated tumors (e.g., micrometastases, circulating tumor cells). Moreover, due to their high cytotoxicity, alpha particles should be preferred to beta particles and X-rays to overcome radiation resistance. However, clinical studies showed that TAT might be efficient also in quite large tumors, and biological effects have been observed also away from irradiated cells. These distant effects are called bystander effects when occurring at short distance (<1 mm), and systemic effects when occurring at much longer distance. Systemic effects implicate the immune system. These findings showed that cells can die without receiving any radiation dose, and that a more complex and integrated view of radiobiology is required. This includes the notion that the direct, bystander and systemic responses cannot be dissociated because DNA damage is intimately linked to bystander effects and immune response. Here, we provide a brief overview of the paradigms that need to be revisited.

Metabolomics-based predictive biomarkers of radiation injury and countermeasure efficacy: current status and future perspectives

INTRODUCTION

There is an urgent need for specific and sensitive bioassays to augment biodosimetric assessments of unwanted and excessive radiation exposures that originate from unexpected nuclear/radiological events, including nuclear accidents, acts of terrorism, or the use of a radiological dispersal device. If sufficiently intense, such ionizing radiation exposures are likely to impact normal metabolic processes within the cells and organs of the body, thus inducing multifaceted biological responses.

AREAS COVERED

This review covers the application of metabolomics, an emerging and promising technology based on quantitative and qualitative determinations of small molecules in biological samples for the rapid assessment of an individual's exposure to ionizing radiation. Recent advancements in the analytics of high-resolution chromatography, mass spectrometry, and bioinformatics have led to untargeted (global) and targeted (quantitative phase) approaches to identify biomarkers of radiation injury and countermeasure efficacy. Biomarkers are deemed essential for both assessing the radiation exposure levels and for extrapolative processes involved in determining scaling factors of a given radiation countering medicinal between experimental animals and humans.

EXPERT OPINION

The discipline of metabolomics appears to be highly informative in assessing radiation exposure levels and for identifying biomarkers of radiation injury and countermeasure efficacy.

Blood-Derived Biomarkers of Diagnosis, Prognosis and Therapy Response in Prostate Cancer Patients

Prostate cancer is among the most frequent cancers in men worldwide. Despite the fact that multiple therapeutic alternatives are available for its treatment, it is often discovered in an advanced stage as a metastatic disease. Prostate cancer screening is based on physical examination of prostate size and prostate-specific antigen (PSA) level in the blood as well as biopsy in suspect cases. However, these markers often fail to correctly identify the presence of cancer, or their positivity might lead to overdiagnosis and consequent overtreatment of an otherwise silent non-progressing disease. Moreover, these markers have very limited if any predictive value regarding therapy response or individual risk for therapy-related toxicities. Therefore, novel, optimally liquid biopsy-based (blood-derived) markers or marker panels are needed, which have better prognostic and predictive value than the ones currently used in the everyday routine. In this review the role of circulating tumour cells, extracellular vesicles and their microRNA content, as well as cellular and soluble immunological and inflammation- related blood markers for prostate cancer diagnosis, prognosis and prediction of therapy response is discussed. A special emphasis is placed on markers predicting response to radiotherapy and radiotherapy-related late side effects.

Mechanisms of radiation-induced endothelium damage: Emerging models and technologies

Radiation-induced endothelial/vascular injury is a major complicating factor in radiotherapy and a leading cause of morbidity and mortality in nuclear or radiological catastrophes. Exposure of tissue to ionizing radiation (IR) leads to the release of oxygen radicals and proteases that result in loss of endothelial barrier function and leukocyte dysfunction leading to tissue injury and organ damage. Microvascular endothelial cells are particularly sensitive to IR and radiation-induced alterations in endothelial cell function are thought to be a critical factor in organ damage through endothelial cell activation, enhanced leukocyte-endothelial cell interactions, increased barrier permeability and initiation of apoptotic pathways. These radiation-induced inflammatory responses are important in early and late radiation pathologies in various organs. A better understanding of mechanisms of radiation-induced endothelium dysfunction is therefore vital, as radiobiological response of endothelium is of major importance for medical management and therapeutic development for radiation injuries. In this review, we summarize the current knowledge of cellular and molecular mechanisms of radiation-induced endothelium damage and their impact on early and late radiation injury. Furthermore, we review established and emerging in vivo and in vitro models that have been developed to study the mechanisms of radiation-induced endothelium damage and to design, develop and rapidly screen therapeutics for treatment of radiation-induced vascular damage. Currently there are no specific therapeutics available to protect against radiation-induced loss of endothelial barrier function, leukocyte dysfunction and resulting organ damage. Developing therapeutics to prevent endothelium dysfunction and normal tissue damage during radiotherapy can serve as the urgently needed medical countermeasures.

Secretion of Acid Sphingomyelinase and Ceramide by Endothelial Cells Contributes to Radiation-Induced Intestinal Toxicity

Ceramide-induced endothelial cell apoptosis boosts intestinal stem cell radiosensitivity. However, the molecular connection between these two cellular compartments has not been clearly elucidated. Here we report that ceramide and its related enzyme acid sphingomyelinase (ASM) are secreted by irradiated endothelial cells and act as bystander factors to enhance the radiotoxicity of intestinal epithelium. Ceramide and the two isoforms of ASM were acutely secreted in the blood serum of wild-type mice after 15 Gy radiation dose, inducing a gastrointestinal syndrome. Interestingly, serum ceramide was not enhanced in irradiated ASMKO mice, which are unable to develop intestinal failure injury. Because ASM/ceramide were secreted by primary endothelial cells, their contribution was studied in intestinal epithelium dysfunction using coculture of primary endothelial cells and intestinal T84 cells. Adding exogenous ASM or ceramide enhanced epithelial cell growth arrest and death. Conversely, blocking their secretion by endothelial cells using genetic, pharmacologic, or immunologic approaches abolished intestinal T84 cell radiosensitivity. Use of enteroid models revealed ASM and ceramide-mediated deleterious mode-of-action: when ceramide reduced the number of intestinal crypt-forming enteroids without affecting their structure, ASM induced a significant decrease of enteroid growth without affecting their number. Identification of specific and different roles for ceramide and ASM secreted by irradiated endothelial cells opens new perspectives in the understanding of intestinal epithelial dysfunction after radiation and defines a new class of potential therapeutic radiomitigators. SIGNIFICANCE: This study identifies secreted ASM and ceramide as paracrine factors enhancing intestinal epithelial dysfunction, revealing a previously unknown class of mediators of radiosensitivity.

Caveolin-1 regulates the ASMase/ceramide-mediated radiation response of endothelial cells in the context of tumor-stroma interactions

The integral membrane protein caveolin-1 (CAV1) plays a central role in radioresistance-mediating tumor–stroma interactions of advanced prostate cancer (PCa). Among the tumor–stroma, endothelial cells (EC) evolved as critical determinants of the radiation response. CAV1 deficiency in angiogenic EC was already shown to account for increased apoptosis rates of irradiated EC. This study explores the potential impact of differential CAV1 levels in EC on the acid sphingomyelinase (ASMase)/ceramide pathway as a key player in the regulation of EC apoptosis upon irradiation and cancer cell radioresistance. Enhanced apoptosis sensitivity of CAV1-deficient EC was associated with increased ASMase activity, ceramide generation, formation of large lipid platforms, and finally an altered p38 mitogen-activated protein kinase (MAPK)/heat-shock protein 27 (HSP27)/AKT (protein kinase B, PKB) signaling. CAV1-deficient EC increased the growth delay of LNCaP and PC3 PCa cells upon radiation treatment in direct 3D spheroid co-cultures. Exogenous C6 and C16 ceramide treatment in parallel increased the growth delay of PCa spheroids and induced PCa cell apoptosis. Analysis of the respective ceramide species in PCa cells with increased CAV1 levels like those typically found in radio-resistant advanced prostate tumors further revealed an upregulation of unsaturated C24:1 ceramide that might scavenge the effects of EC-derived apoptosis-inducing C16 ceramide. Higher ASMase as well as ceramide levels could be confirmed by immunohistochemistry in human advanced prostate cancer specimen bearing characteristic CAV1 tumor–stroma alterations. Conclusively, CAV1 critically regulates the generation of ceramide-dependent (re-)organization of the plasma membrane that in turn affects the radiation response of EC and adjacent PCa cells. Understanding the CAV1-dependent crosstalk between tumor cells and the host-derived tumor microvasculature and its impact on radiosensitivity may allow to define a rational strategy for overcoming tumor radiation resistance improving clinical outcomes by targeting CAV1.

Cx43 channels and signaling via IP3/Ca2+, ATP, and ROS/NO propagate radiation-induced DNA damage to non-irradiated brain microvascular endothelial cells

Radiotherapeutic treatment consists of targeted application of radiation beams to a tumor but exposure of surrounding healthy tissue is inevitable. In the brain, ionizing radiation induces breakdown of the blood-brain barrier by effects on brain microvascular endothelial cells. Damage from directly irradiated cells can be transferred to surrounding non-exposed bystander cells, known as the radiation-induced bystander effect. We investigated involvement of connexin channels and paracrine signaling in radiation-induced bystander DNA damage in brain microvascular endothelial cells exposed to focused X-rays. Irradiation caused DNA damage in the directly exposed area, which propagated over several millimeters in the bystander area. DNA damage was significantly reduced by the connexin channel-targeting peptide Gap26 and the Cx43 hemichannel blocker TAT-Gap19. ATP release, dye uptake, and patch clamp experiments showed that hemichannels opened within 5 min post irradiation in both irradiated and bystander areas. Bystander signaling involved cellular Ca²⁺ dynamics and IP₃, ATP, ROS, and NO signaling, with Ca²⁺, IP₃, and ROS as crucial propagators of DNA damage. We conclude that bystander effects are communicated by a concerted cascade involving connexin channels, and IP₃/Ca²⁺, ATP, ROS, and NO as major contributors of regenerative signal expansion.

Establishing mechanisms affecting the individual response to ionizing radiation

Purpose: Humans are increasingly exposed to ionizing radiation (IR). Both low (<100 mGy) and high doses can cause stochastic effects, including cancer; whereas doses above 100 mGy are needed to promote tissue or cell damage. 10-15% of radiotherapy (RT) patients suffer adverse reactions, described as displaying radiosensitivity (RS). Sensitivity to IR's stochastic effects is termed radiosusceptibility (RSu). To optimize radiation protection we need to understand the range of individual variability and underlying mechanisms. We review the potential mechanisms contributing to RS/RSu focusing on RS following RT, the most tractable RS group.Conclusions: The IR-induced DNA damage response (DDR) has been well characterized. Patients with mutations in the DDR have been identified and display marked RS but they represent only a small percentage of the RT patients with adverse reactions. We review the impacting mechanisms and additional factors influencing RS/RSu. We discuss whether RS/RSu might be genetically determined. As a recommendation, we propose that a prospective study be established to assess RS following RT. The study should detail tumor site and encompass a well-defined grading system. Predictive assays should be independently validated. Detailed analysis of the inflammatory, stress and immune responses, mitochondrial function and life style factors should be included. Existing cohorts should also be optimally exploited.

KATP Channel Blocker Glibenclamide Prevents Radiation-Induced Lung Injury and Inhibits Radiation-Induced Apoptosis of Vascular Endothelial Cells by Increased Ca2+ Influx and Subsequent PKC Activation

Radiation-induced lung injury (RILI) is a common and severe side effect of thoracic radiotherapy, which compromises patients' quality of life. Recent studies revealed that early vascular injury, especially microvascular damage, played a central role in the development of RILI. For this reason, early vascular protection is essential for RILI therapy. The ATP-sensitive K⁺ (K_ATP) channel is an ATP-dependent K⁺ channel with multiple subunits. The protective role of the K_ATP channel in vascular injury has been demonstrated in some published studies. In this work, we investigated the effect of K_ATP channel on RILI. Our findings confirmed that the K_ATP channel blocker glibenclamide, rather than the K_ATP channel opener pinacidil, remitted RILI, and in particular, provided protection against radiation-induced vascular injury. Cytology experiments verified that glibenclamide enhanced cell viability, increased the potential of proliferation after irradiation and attenuated radiation-induced apoptosis. Involved mechanisms included increased Ca²⁺ influx and PKC activation, which were induced by glibenclamide pretreatment. In conclusion, the K_ATP channel blocker glibenclamide remitted RILI and inhibited the radiation-induced apoptosis of vascular endothelial cells by increased Ca²⁺ influx and subsequent PKC activation.

High-Dose Radiation Increases Notch1 in Tumor Vasculature

PURPOSE

The aim of this study is to characterize the effects of high-dose radiation therapy (HDRT) on Notch signaling components of the tumor vasculature.

METHODS AND MATERIALS

Human umbilical vein endothelial cells monolayers were exposed to different single fraction doses of irradiation; ribonucleic acid RNA was isolated and polymerase chain reaction was performed for Notch signaling components. The vascular response to radiation therapy was examined in a xenograft model of neuroblastoma. Tumors were treated with 0 Gy, 2 Gy, and 12 Gy single fraction doses and analyzed by double immunofluorescence staining for Notch1, Notch ligands Jagged1 and Dll4, and the endothelial cell (EC) marker endomucin. To assess the role of Notch in vivo, NGP xenograft tumors expressing Fc or Notch1-_1-24-decoy (a novel Notch inhibitor) were treated with 0 Gy and 12 Gy. Immunofluorescence staining for endomucin and endomucin/αSMA was performed to analyze the effect of combination treatment on tumor EC and endothelial-to-mesenchymal-transition (EndMT), respectively.

RESULTS

In human umbilical vein endothelial cells monolayers doses ≥8 Gy increased expression of NOTCH1, JAG1, and Notch target genes HEY1 and HEY2 as early as 6 hours after irradiation. In vivo, 12 Gy significantly increased Notch1 and Jagged1 in tumor ECs compared with 0 Gy or 2 Gy after 72 hours. Combining HDRT with Notch inhibition using the Notch1-_1-24-decoy resulted in a greater loss of EC coverage of tumor vessels than HDRT alone at 6 hours and 72 hours post treatment. Notch inhibition reduced EndMT induced by HDRT, as indicated by diminished αSMA staining in ECs.

CONCLUSIONS

HDRT induced Notch1 expression and increased Notch1 signaling in the endothelial component of tumor vasculature, which was not observed with lower doses. This increase in Notch1 activation might protect tumor vessels from HDRT induced damage and regulate EndMT process.

Rationale for hypofractionation

Fractionation was established more than fifty years ago as the best way to obtain a differential effect between tumors and normal tissues. However, new technologies allowed today to spare critical organs from the radiation fields. And so protracted courses of irradiation are no longer required. Hypofractionation have clear practical advantages over classical fractionation: it saves the patient time; it saves money for public health system; it reduces pressure on radiotherapy units. In several localization, it has proved to be as efficient as classical fractionation without increasing late effects. In prostate cancer, some radiobiological considerations argue in favor of a better efficiency, but clinical trials did not demonstrated differences in biological control. In conclusion, for all diseases where hypofractionation was demonstrated efficient, it must be fully implemented. Invoice procedures must be adapted to maintain a sufficient level of reimbursement of radiotherapy centers.

Drugs That Modify Cholesterol Metabolism Alter the p38/JNK-Mediated Targeted and Nontargeted Response to Alpha and Auger Radioimmunotherapy

PURPOSE

For the development of new anticancer therapeutic radiopharmaceuticals, including alpha particle emitters, it is important to determine the contribution of targeted effects in irradiated cells, and also of nontargeted effects in nonirradiated neighboring cells, because they may affect the therapeutic efficacy and contribute to side effects.

EXPERIMENTAL DESIGN

Here, we investigated the contribution of nontargeted cytotoxic and genotoxic effects in vitro and in vivo (in xenografted mice) during alpha (²¹²Pb/²¹²Bi, ²¹³Bi) and Auger (¹²⁵I) radioimmunotherapy (RIT).

RESULTS

Between 67% and 94% (alpha RIT) and 8% and 15% (Auger RIT) of cancer cells were killed by targeted effects, whereas 7% to 36% (alpha RIT) and 27% to 29% (Auger RIT) of cells were killed by nontargeted effects. We then demonstrated that the nontargeted cell response to alpha and Auger RIT was partly driven by lipid raft-mediated activation of p38 kinase and JNK. Reactive oxygen species also played a significant role in these nontargeted effects, as demonstrated by NF-κB activation and the inhibitory effects of antioxidant enzymes and radical scavengers. Compared with RIT alone, the use of RIT with ASMase inhibitor (imipramine) or with a lipid raft disruptor (e.g., methyl-beta-cyclodextrin or filipin) led to an increase in clonogenic cell survival in vitro and to larger tumors and less tissue DNA damage in vivo. These results were supported by an inhibitory effect of pravastatin on Auger RIT.

CONCLUSIONS

Cell membrane-mediated nontargeted effects play a significant role during Auger and alpha RIT, and drugs that modulate cholesterol level, such as statins, could interfere with RIT efficacy.

Effect of Sex on Biomarker Response in a Mouse Model of the Hematopoietic Acute Radiation Syndrome

Sex is an important confounding variable in biomarker development that must be incorporated into biomarker discovery and validation. Additionally, understanding of sex as a biological variable is essential for effective translation of biomarkers in animal models to human populations. Toward these ends, we conducted high-throughput targeted metabolomics using liquid chromatography tandem mass spectrometry and multiplexed immunoassay analyses using a Luminex-based system in both male and female mice in a model of total-body irradiation at a radiation dose consistent with the hematopoietic acute radiation syndrome. Metabolomic and immunoassay analyses identified metabolites and cytokines that were significantly different in plasma from naive and irradiated C57BL/6 mice consisting of equal numbers of female and male mice at 3 d after 8.0 or 8.72 Gy, an approximate LD60-70/30 dose of total-body irradiation. An additional number of metabolites and cytokines had sex-specific responses after radiation. Analyses of sham-irradiated mice illustrate the presence of stress-related changes in several cytokines due simply to undergoing the irradiation procedure, absent actual radiation exposure. Basal differences in metabolite levels between female and male were also identified as well as time-dependent changes in cytokines up to 9 d postexposure. These studies provide data toward defining the influence of sex on plasma-based biomarker candidates in a well-defined mouse model of acute radiation syndrome.

Importance of dosimetry protocol for cell irradiation on a low X-rays facility and consequences for the biological response

PURPOSE

The main objective of radiobiology is to establish links between doses and radiation-induced biological effects. In this context, well-defined dosimetry protocols are crucial to the determination of experimental protocols. This work proposes a new dosimetry protocol for cell irradiation in a SARRP and shows the importance of the modification of some parameters defined in dosimetry protocol for physical dose and biological outcomes.

MATERIALS AND METHODS

Once all parameters of the configuration were defined, dosimetry measurements with ionization chambers and EBT3 films were performed to evaluate the dose rate and the attenuation due to the cell culture medium. To evaluate the influence of changes in cell culture volume and/or additional filtration, 6-well plates containing EBT3 films with water were used to determine the impact on the physical dose at 80 kV. Then, experiments with the same irradiation conditions were performed by replacing EBT3 films by HUVECs. The biological response was assessed using clonogenic assay.

RESULTS

Using a 0.15 mm copper filter lead to a variation of +1% using medium thickness of 0.104 cm to -8% using a medium thickness of 0.936 cm on the physical dose compare to the reference condition (0.313 cm). For the 1 mm aluminum filter, a variation of +8 to -40% for the same medium thickness conditions has been observed. Cells irradiated in the same conditions showed significant differences in survival fraction, corroborating the effects of dosimetric changes on physical dose.

CONCLUSIONS

This work shows the importance of dosimetry in radiobiology studies and the need of an accurate description of the dosimetry protocol used for irradiation.

Emerging Functional Imaging Biomarkers of Tumour Responses to Radiotherapy

Tumour responses to radiotherapy are currently primarily assessed by changes in size. Imaging permits non-invasive, whole-body assessment of tumour burden and guides treatment options for most tumours. However, in most tumours, changes in size are slow to manifest and can sometimes be difficult to interpret or misleading, potentially leading to prolonged durations of ineffective treatment and delays in changing therapy. Functional imaging techniques that monitor biological processes have the potential to detect tumour responses to treatment earlier and refine treatment options based on tumour biology rather than solely on size and staging. By considering the biological effects of radiotherapy, this review focusses on emerging functional imaging techniques with the potential to augment morphological imaging and serve as biomarkers of early response to radiotherapy.

Inhibition of Radiation-Induced Ccl2 Signaling Protects Lungs from Vascular Dysfunction and Endothelial Cell Loss

Aims: Radiation-induced normal tissue toxicity often precludes the application of curative radiation doses. Here we investigated the therapeutic potential of chemokine C-C motif ligand 2 (Ccl2) signaling inhibition to protect normal lung tissue from radiotherapy (RT)-induced injury. Results: RT-induced vascular dysfunction and associated adverse effects can be efficiently antagonized by inhibition of Ccl2 signaling using either the selective Ccl2 inhibitor bindarit (BIN) or mice deficient for the main Ccl2 receptor CCR2 (KO). BIN-treatment efficiently counteracted the RT-induced expression of Ccl2, normalized endothelial cell (EC) morphology and vascular function, and limited lung inflammation and metastasis early after irradiation (acute effects). A similar protection of the vascular compartment was detected by loss of Ccl2 signaling in lungs of CCR2-KO mice. Long-term Ccl2 signaling inhibition also significantly limited EC loss and accompanied fibrosis progression as adverse late effect. With respect to the human situation, we further confirmed that Ccl2 secreted by RT-induced senescent epithelial cells resulted in the activation of normally quiescent but DNA-damaged EC finally leading to EC loss in ex vivo cultured human normal lung tissue. Innovation: Abrogation of certain aspects of the secretome of irradiated resident lung cells, in particular signaling inhibition of the senescence-associated secretory phenotype-factor Ccl2 secreted predominantly by RT-induced senescent epithelial cells, resulted in protection of the endothelial compartment. Conclusions: Radioprotection of the normal tissue via Ccl2 signaling inhibition without simultaneous protection or preferable radiosensitization of tumor tissue might improve local tumor control and survival, because higher doses of radiation could be used.

Mechanisms of vascular dysfunction evoked by ionizing radiation and possible targets for its pharmacological correction

Ionizing radiation (IR) leads to a variety of the cardiovascular diseases, including the arterial hypertension. A number of studies have demonstrated that blood vessels represent important target for IR, and the endothelium is one of the most vulnerable components of the vascular wall. IR causes an inhibition of nitric oxide (NO)-mediated endothelium-dependent vasodilatation and generation of reactive oxygen (ROS) and nitrogen (RNS) species trigger this process. Inhibition of NO-mediated vasodilatation could be due to endothelial NO synthase (eNOS) down-regulation, inactivation of endothelium-derived NO, and abnormalities in diffusion of NO from the endothelial cells (ECs) leading to a decrease in NO bioavailability. Beside this, IR suppresses endothelial large conductance Ca²⁺-activated K⁺ channels (BK_Ca) activity, which control NO synthesis. IR also leads to inhibition of the BK_Ca current in vascular smooth muscle cells (SMCs) which is mediated by protein kinase C (PKC). On the other hand, IR-evoked enhanced vascular contractility may result from PKC-mediated increase in SMCs myofilament Ca²⁺ sensitivity. Also, IR evokes vascular wall inflammation and atherosclerosis development. Vascular function damaged by IR can be effectively restored by quercetin-filled phosphatidylcholine liposomes and mesenchymal stem cells injection. Using RNA-interference technique targeted to different PKC isoforms can also be a perspective approach for pharmacological treatment of IR-induced vascular dysfunction.

Targeted and Off-Target (Bystander and Abscopal) Effects of Radiation Therapy: Redox Mechanisms and Risk/Benefit Analysis

SIGNIFICANCE

Radiation therapy (from external beams to unsealed and sealed radionuclide sources) takes advantage of the detrimental effects of the clustered production of radicals and reactive oxygen species (ROS). Research has mainly focused on the interaction of radiation with water, which is the major constituent of living beings, and with nuclear DNA, which contains the genetic information. This led to the so-called target theory according to which cells have to be hit by ionizing particles to elicit an important biological response, including cell death. In cancer therapy, the Poisson law and linear quadratic mathematical models have been used to describe the probability of hits per cell as a function of the radiation dose. Recent Advances: However, in the last 20 years, many studies have shown that radiation generates "danger" signals that propagate from irradiated to nonirradiated cells, leading to bystander and other off-target effects.

CRITICAL ISSUES

Like for targeted effects, redox mechanisms play a key role also in off-target effects through transmission of ROS and reactive nitrogen species (RNS), and also of cytokines, ATP, and extracellular DNA. Particularly, nuclear factor kappa B is essential for triggering self-sustained production of ROS and RNS, thus making the bystander response similar to inflammation. In some therapeutic cases, this phenomenon is associated with recruitment of immune cells that are involved in distant irradiation effects (called "away-from-target" i.e., abscopal effects).

FUTURE DIRECTIONS

Determining the contribution of targeted and off-target effects in the clinic is still challenging. This has important consequences not only in radiotherapy but also possibly in diagnostic procedures and in radiation protection.

Temporal clustering analysis of endothelial cell gene expression following exposure to a conventional radiotherapy dose fraction using Gaussian process clustering

The vascular endothelium is considered as a key cell compartment for the response to ionizing radiation of normal tissues and tumors, and as a promising target to improve the differential effect of radiotherapy in the future. Following radiation exposure, the global endothelial cell response covers a wide range of gene, miRNA, protein and metabolite expression modifications. Changes occur at the transcriptional, translational and post-translational levels and impact cell phenotype as well as the microenvironment by the production and secretion of soluble factors such as reactive oxygen species, chemokines, cytokines and growth factors. These radiation-induced dynamic modifications of molecular networks may control the endothelial cell phenotype and govern recruitment of immune cells, stressing the importance of clearly understanding the mechanisms which underlie these temporal processes. A wide variety of time series data is commonly used in bioinformatics studies, including gene expression, protein concentrations and metabolomics data. The use of clustering of these data is still an unclear problem. Here, we introduce kernels between Gaussian processes modeling time series, and subsequently introduce a spectral clustering algorithm. We apply the methods to the study of human primary endothelial cells (HUVECs) exposed to a radiotherapy dose fraction (2 Gy). Time windows of differential expressions of 301 genes involved in key cellular processes such as angiogenesis, inflammation, apoptosis, immune response and protein kinase were determined from 12 hours to 3 weeks post-irradiation. Then, 43 temporal clusters corresponding to profiles of similar expressions, including 49 genes out of 301 initially measured, were generated according to the proposed method. Forty-seven transcription factors (TFs) responsible for the expression of clusters of genes were predicted from sequence regulatory elements using the MotifMap system. Their temporal profiles of occurrences were established and clustered. Dynamic network interactions and molecular pathways of TFs and differential genes were finally explored, revealing key node genes and putative important cellular processes involved in tissue infiltration by immune cells following exposure to a radiotherapy dose fraction.

Kaempferol protects against gamma radiation-induced mortality and damage via inhibiting oxidative stress and modulating apoptotic molecules in vivo and vitro

To investigate the potential protective effect of kaempferol, a representative flavonoid, against radiation induced mortality and injury in vivo and vitro.C57BL/6 male mice and human umbilical venous endothelial cells (HUVECs) were pretreated with kaempferol before radiation. We found that kaempferol can effectively increase 30-day survival rate after 8.5 Gy lethal total body irradiation (TBI). Mice were sacrificed at 7th day after 7 Gy TBI, we found kaempferol against radiation-induced tissues damage, by inhibiting the oxidative stress, and attenuating morphological changes and cell apoptosis. In vitro, kaempferol increased HUVECs cell viability and decrease apoptosis. It also mitigated oxidative stress and restored the abnormal expression of prx-5, Cyt-c, Caspase9 and Caspase3 in mRNA and protein level in HUVECs after radiation. Taken together, it suggests kaempferol can protect against gamma-radiation induced tissue damage and mortality. The present study is the first report of the radioprotective role of kaempferol in vivo and vitro.

Effect of captopril on radiation-induced TGF-β1 secretion in EA.Hy926 human umbilical vein endothelial cells

The pathophysiological mechanism involved in the sustained endothelial secretion of cytokines that leads to fibrosis 6–16 months after radiotherapy remains unclear. Angiotensin II (Ang II) is produced by the endothelium in response to stressing stimuli, like radiation, and may induce the synthesis of TGF-β, a profibrotic cytokine. In this study we tested the hypothesis that captopril, an angiotensin-converting enzyme (ACE) inhibitor, inhibits or attenuates radiation-induced endothelial TGF-β1 secretion. The human endothelial hybrid cell line EA.HY926 was irradiated with split doses of x-rays (28 Gy delivered in 14 fractions of 2 Gy). TGF-β1 mRNA, TNF-α mRNA and TGF-β1 protein levels were evaluated by RT-PCR and western blotting each month until the fifth month post radiation. Ang II was detected using radioimmunoassays, NF-κB activity was examined using EMSA, and western blotting was used to detect the expression of Iκ-Bα. To explore the role of Ang II on radiation-induced TGF-β1 release and Iκ-Bα expression, captopril was added to cultured cells before, during, or after irradiation. Sustained strong expression of TGF-β1 was observed after conventional fractionated irradiation. TNF-α, Ang II, and NF-κB activity were also increased in EA.Hy926 cells after radiation. Captopril decreased Ang II expression, inhibited the NF-κB pathway and reduced TGF-β1 expression. These data suggest that captopril might protect the endothelium from radiation-induced injury.

Targeted Metabolomics Identifies Pharmacodynamic Biomarkers for BIO 300 Mitigation of Radiation-Induced Lung Injury

PURPOSE

Biomarkers serve a number of purposes during drug development including defining the natural history of injury/disease, serving as a secondary endpoint or trigger for intervention, and/or aiding in the selection of an effective dose in humans. BIO 300 is a patent-protected pharmaceutical formulation of nanoparticles of synthetic genistein being developed by Humanetics Corporation. The primary goal of this metabolomic discovery experiment was to identify biomarkers that correlate with radiation-induced lung injury and BIO 300 efficacy for mitigating tissue damage based upon the primary endpoint of survival.

METHODS

High-throughput targeted metabolomics of lung tissue from male C57L/J mice exposed to 12.5 Gy whole thorax lung irradiation, treated daily with 400 mg/kg BIO 300 for either 2 weeks or 6 weeks starting 24 h post radiation exposure, were assayed at 180 d post-radiation to identify potential biomarkers.

RESULTS

A panel of lung metabolites that are responsive to radiation and able to distinguish an efficacious treatment schedule of BIO 300 from a non-efficacious treatment schedule in terms of 180 d survival were identified.

CONCLUSIONS

These metabolites represent potential biomarkers that could be further validated for use in drug development of BIO 300 and in the translation of dose from animal to human.

Differential Impact of Single-Dose Fe Ion and X-Ray Irradiation on Endothelial Cell Transcriptomic and Proteomic Responses

Background and Purpose: Radiotherapy is an essential tool for cancer treatment. In order to spare normal tissues and to reduce the risk of normal tissue complications, particle therapy is a method of choice. Although a large part of healthy tissues can be spared due to improved depth dose characteristics, little is known about the biological and molecular mechanisms altered after particle irradiation in healthy tissues. Elucidation of these effects is also required in the context of long term space flights, as particle radiation is the main contributor to the radiation effects observed in space. Endothelial cells (EC), forming the inner layer of all vascular structures, are especially sensitive to irradiation and, if damaged, contribute to radiation-induced cardiovascular disease. Materials and Methods: Transcriptomics, proteomics and cytokine analyses were used to compare the response of ECs irradiated or not with a single 2 Gy dose of X-rays or Fe ions measured one and 7 days post-irradiation. To support the observed inflammatory effects, monocyte adhesion on ECs was also assessed. Results: Experimental data indicate time- and radiation quality-dependent changes of the EC response to irradiation. The irradiation impact was more pronounced and longer lasting for Fe ions than for X-rays. Both radiation qualities decreased the expression of genes involved in cell-cell adhesion and enhanced the expression of proteins involved in caveolar mediated endocytosis signaling. Endothelial inflammation and adhesiveness were increased with X-rays, but decreased after Fe ion exposure. Conclusions: Fe ions induce pro-atherosclerotic processes in ECs that are different in nature and kinetics than those induced by X-rays, highlighting radiation quality-dependent differences which can be linked to the induction and progression of cardiovascular diseases (CVD). Our findings give a better understanding of the underlying processes triggered by particle irradiation in ECs, a crucial aspect for the development of protective measures for cancer patients undergoing particle therapy and for astronauts in space.

Ionizing radiation induces long-term senescence in endothelial cells through mitochondrial respiratory complex II dysfunction and superoxide generation

Ionizing radiation causes oxidative stress, leading to acute and late cellular responses. We previously demonstrated that irradiation of non-proliferating endothelial cells, as observed in normal tissues, induces early apoptosis, which can be inhibited by pretreatment with Sphingosine-1-Phosphate. We now propose to better characterize the long-term radiation response of endothelial cells by studying the molecular pathways associated with senescence and its link with acute apoptosis. First, senescence was validated in irradiated quiescent microvascular HMVEC-L in a dose- and time-dependent manner by SA β-galactosidase staining, p16^Ink4a and p21^Waf1 expression, pro-inflammatory IL-8 secretion and DNA damage response activation. This premature aging was induced independently of Sphingosine 1-Phosphate treatment, supporting its non-connection with acute IR-induced apoptosis. Then, senescence under these conditions showed persistent activation of p53 pathway and mitochondrial dysfunctions, characterized by O2·- generation, inhibition of respiratory complex II activity and over-expression of SOD2 and GPX1 detoxification enzymes. Senescence was significantly inhibited by treatment with pifithrin-α, a p53 inhibitor, or by MnTBAP, a superoxide dismutase mimetic, validating those molecular actors in IR-induced endothelial cell aging. However, MnTBAP, but not pifithrin-α, was able to limit superoxide generation and to rescue the respiratory complex II activity. Furthermore, MnTBAP was not modulating p53 up-regulation, suggesting that IR-induced senescence in quiescent endothelial cells is provided by at least 2 different pathways dependent of the mitochondrial oxidative stress response and the p53 activation. Further characterization of the actors involved in the respiratory complex II dysfunction will open new pharmacological strategies to modulate late radiation toxicity.

The p38 pathway, a major pleiotropic cascade that transduces stress and metastatic signals in endothelial cells

By gating the traffic of molecules and cells across the vessel wall, endothelial cells play a central role in regulating cardiovascular functions and systemic homeostasis and in modulating pathophysiological processes such as inflammation and immunity. Accordingly, the loss of endothelial cell integrity is associated with pathological disorders that include atherosclerosis and cancer. The p38 mitogen-activated protein kinase (MAPK) cascades are major signaling pathways that regulate several functions of endothelial cells in response to exogenous and endogenous stimuli including growth factors, stress and cytokines. The p38 MAPK family contains four isoforms p38α, p38β, p38γ and p38δ that are encoded by four different genes. They are all widely expressed although to different levels in almost all human tissues. p38α/MAPK14, that is ubiquitously expressed is the prototype member of the family and is referred here as p38. It regulates the production of inflammatory mediators, and controls cell proliferation, differentiation, migration and survival. Its activation in endothelial cells leads to actin remodeling, angiogenesis, DNA damage response and thereby has major impact on cardiovascular homeostasis, and on cancer progression. In this manuscript, we review the biology of p38 in regulating endothelial functions especially in response to oxidative stress and during the metastatic process.

Antioxidant Supplementation: A Linchpin in Radiation-Induced Enteritis

Radiation enteritis is one of the most feared complications of abdominal and pelvic regions. Thus, radiation to abdominal or pelvic malignancies unavoidably injures the intestine. Because of rapid cell turnover, the intestine is highly sensitive to radiation injury, which is the limiting factor in the permissible dosage of irradiation. Bowel injuries such as fistulas, strictures, and chronic malabsorption are potentially life-threatening complications and have an impact on patient quality of life. The incidence of radiation enteritis is increasing because of the current trend of combined chemotherapy and radiation. The consequences of radiation damage to the intestine may result in considerable morbidity and even mortality. The observed effects of ionizing radiation are mediated mainly by oxygen-free radicals that are generated by its action on water and are involved in several steps of signal transduction cascade, leading to apoptosis. The oxyradicals also induce DNA strand breaks and protein oxidation. An important line of defense against free radical damage is the presence of antioxidants. Therefore, administration of antioxidants may ameliorate the radiation-induced damage to the intestine.

Synergistic effect of Ebselen and gamma radiation on breast cancer cells

PURPOSE

To explore the synergistic effect of a seleno-organic compound Ebselen (Ebs) and/or γ-radiation to exert antitumor effects on human breast cancer (MCF-7) cell line in vitro.

MATERIALS AND METHODS

Ebs cytotoxicity at various concentrations (10, 25, 50 and 75 μg), cell proliferation and clonogenic assay of Ebs and/or γ-radiation (at 1, 3 and 6 Gy), expression of p-IκBα and NF-κB, inflammatory cytokines levels (TNF-α, IL-2, INF-γ, IL-10 and TGF-β), apoptotic factors (Caspase-3, Granzyme-B and TRAIL) and angiogenic factor (VEGF) were investigated.

RESULTS

The results showed that the effective dosage of this combination was observed at 25 μg/ml of Ebs with γ-radiation at 6 Gy. Data displayed a significant reduction in NF-κB mRNA along with an elevation in granzyme-B mRNA and TRAIL mRNA expression. Furthermore, protein expression of caspase-3 was elevated, whereas p-IκBα and p-NF-κB(p65) protein expression was reduced significantly. Also, a significant decline in TNF-α, IL-2, INF-γ, TGF-β with a significant increase in IL-10 levels were revealed. Meanwhile, a significant decrease in VEGF level and proliferation capacity were observed.

CONCLUSIONS

We conclude that a combination of Ebs with radiotherapy has a major antitumor efficiency in inducing apoptosis and inhibiting cancer cell progression, due to the synergistic effect in regulating gene and protein expression, and in a modulating response of pro-and anti-inflammatory cytokines.

Mesenchymal Stem Cell Therapy Protects Lungs from Radiation-Induced Endothelial Cell Loss by Restoring Superoxide Dismutase 1 Expression

AIMS

Radiation-induced normal tissue toxicity is closely linked to endothelial cell (EC) damage and dysfunction (acute effects). However, the underlying mechanisms of radiation-induced adverse late effects with respect to the vascular compartment remain elusive, and no causative radioprotective treatment is available to date.

RESULTS

The importance of injury to EC for radiation-induced late toxicity in lungs after whole thorax irradiation (WTI) was investigated using a mouse model of radiation-induced pneumopathy. We show that WTI induces EC loss as long-term complication, which is accompanied by the development of fibrosis. Adoptive transfer of mesenchymal stem cells (MSCs) either derived from bone marrow or aorta (vascular wall-resident MSCs) in the early phase after irradiation limited the radiation-induced EC loss and fibrosis progression. Furthermore, MSC-derived culture supernatants rescued the radiation-induced reduction in viability and long-term survival of cultured lung EC. We further identified the antioxidant enzyme superoxide dismutase 1 (SOD1) as a MSC-secreted factor. Importantly, MSC treatment restored the radiation-induced reduction of SOD1 levels after WTI. A similar protective effect was achieved by using the SOD-mimetic EUK134, suggesting that MSC-derived SOD1 is involved in the protective action of MSC, presumably through paracrine signaling.

INNOVATION

In this study, we explored the therapeutic potential of MSC therapy to prevent radiation-induced EC loss (late effect) and identified the protective mechanisms of MSC action.

CONCLUSIONS

Adoptive transfer of MSCs early after irradiation counteracts radiation-induced vascular damage and EC loss as late adverse effects. The high activity of vascular wall-derived MSCs for radioprotection may be due to their tissue-specific action. Antioxid. Redox Signal. 26, 563-582.

Plasma membrane reorganization links acid sphingomyelinase/ceramide to p38 MAPK pathways in endothelial cells apoptosis

The p38 MAPK signaling pathway is essential in the cellular response to stress stimuli, in particular in the endothelial cells that are major target of external stress. The importance of the bioactive sphingolipid ceramide generated by acid sphingomyelinase is also firmly established in stress-induced endothelial apoptotic cell death. Despite a suggested link between the p38 MAPK and ceramide pathways, the exact molecular events of this connection remain elusive. In the present study, by using two different activators of p38 MAPK, namely anisomycin and ionizing radiation, we depicted how ceramide generated by acid sphingomyelinase was involved in p38 MAPK-dependent apoptosis of endothelial cells. We first proved that both anisomycin and ionizing radiation conducted to apoptosis through activation of p38 MAPK in human microvascular endothelial cells HMEC-1. We then found that both treatments induced activation of acid sphingomyelinase and the generation of ceramide. This step was required for p38 MAPK activation and apoptosis. We finally showed that irradiation, as well as treatment with exogenous C₁₆-ceramide or bacterial sphingomyelinase, induced in endothelial cells a deep reorganization of the plasma membrane with formation of large lipid platforms at the cell surface, leading to p38 MAPK activation and apoptosis in endothelial cells. Altogether, our results proved that the plasma membrane reorganization leading to ceramide production is essential for stress-induced activation of p38 MAPK and apoptosis in endothelial cells and established the link between the acid sphingomyelinase/ceramide and p38 MAPK pathways.

First reported treatment of aggressive hemangioma with intraoperative radiation therapy and kyphoplasty (Kypho-IORT)

Aggressive hemangiomas invade the spinal canal and/or paravertebral space and may cause cord compression and neurological symptoms. Radiation therapy was recognized as an effective strategy for the treatment of aggressive hemangiomas. Here, it is reported the first case of aggressive vertebral hemangioma treated by a combination of intraoperative radiation therapy and kyphoplasty (Kypho-IORT).

Single cell ionization by a laser trap: a preliminary study in measuring radiation dose and charge in BT20 breast carcinoma cells

In this work, a preliminary study in the application of a laser trap for ionization of living carcinoma cells is presented. The study was conducted using BT20 breast carcinoma cells cultured and harvested in our laboratory. Each cell, for a total of 50 cells, was trapped and ionized by a high intensity infrared laser at 1064 nm. The threshold radiation dose and the resultant charge from the ionization for each cell were determined. With the laser trap serving as a radiation source, the cell underwent dielectric breakdown of the membrane. When this process occurs, the cell becomes highly charged and its dielectric susceptibility changes. The charge creates an increasing electrostatic force while the changing dielectric susceptibility diminishes the strength of the trapping force. Consequently, at some instant of time the cell gets ejected from the trap. The time inside the trap while the cell is being ionized, the intensity of the radiation, and the post ionization trajectory of the cell were used to determine the threshold radiation dose and the charge for each cell. The measurement of the charge vs ionization radiation dose at single cell level could be useful in the accuracy of radiotherapy as the individual charges can collectively create a strong enough electrical interaction to cause dielectric breakdown in other cells in a tumor.

Hemodynamic Flow-Induced Mechanotransduction Signaling Influences the Radiation Response of the Vascular Endothelium

Hemodynamic shear stress is defined as the physical force exerted by the continuous flow of blood in the vascular system. Endothelial cells, which line the inner layer of blood vessels, sense this physiological force through mechanotransduction signaling and adapt to maintain structural and functional homeostasis. Hemodynamic flow, shear stress and mechanotransduction signaling are, therefore, an integral part of endothelial pathophysiology. Although this is a well-established concept in the cardiovascular field, it is largely dismissed in studies aimed at understanding radiation injury to the endothelium and subsequent cardiovascular complications. We and others have reported on the differential response of the endothelium when the cells are under hemodynamic flow shear compared with static culture. Further, we have demonstrated significant differences in the gene expression of static versus shear-stressed irradiated cells in four key pathways, reinforcing the importance of shear stress in understanding radiation injury of the endothelium. This article further emphasizes the influence of hemodynamic shear stress and the associated mechanotransduction signaling on physiological functioning of the vascular endothelium and underscores its significance in understanding radiation injury to the vasculature and associated cardiac complications. Studies of radiation effect on endothelial biology and its implication on cardiotoxicity and vascular complications thus far have failed to highlight the significance of these factors. Factoring in these integral parts of the endothelium will enhance our understanding of the contribution of the endothelium to radiation biology. Without such information, the current approaches to studying radiation-induced injury to the endothelium and its consequences in health and disease are limited.

Soluble Vascular Endothelial Cadherin as a New Biomarker of Irradiation in Highly Irradiated Baboons with Bone Marrow Protection

Vascular endothelial cadherin is the main component of adherens junctions enabling cohesion of the endothelial monolayer in vessels. The extracellular part of vascular endothelial cadherin (VE-cadherin) can be cleaved, releasing soluble fragments in blood (sVE-cadherin). In some diseases with endothelial dysfunction, a correlation between increased blood sVE-cadherin levels and disease state has been proposed. Irradiation is known to induce endothelial damage, but new serum biomarkers are needed to evaluate endothelial damage after irradiation. Here, the authors investigated whether sVE-cadherin may be an interesting biomarker of irradiation in highly irradiated baboons with bone marrow protection. sVE-cadherin was detected in the plasma of young as well as old baboons. Plasma sVE-cadherin levels significantly decrease a few days after irradiation but recover in the late time after irradiation. Kinetic analysis of plasma sVE-cadherin levels suggests a correlation with white blood cell counts in both the acute phase of irradiation and during hematopoietic recovery, suggesting that plasma sVE-cadherin levels may be partly linked to the disappearance and recovery of white blood cells. Interestingly, after hematopoietic recovery was completed, sVE-cadherin levels were found to exceed control values, suggesting that plasma sVE-cadherin may represent a new biomarker of endothelial damage or neovascularization in the late time after irradiation.

Oxidative stress disassembles the p38/NPM/PP2A complex, which leads to modulation of nucleophosmin-mediated signaling to DNA damage response

Oxidative stress is a leading cause of endothelial dysfunction. The p38 MAPK pathway plays a determinant role in allowing cells to cope with oxidative stress and is tightly regulated by a balanced interaction between p38 protein and its interacting partners. By using a proteomic approach, we identified nucleophosmin (NPM) as a new partner of p38 in HUVECs. Coimmunoprecipitation and microscopic analyses confirmed the existence of a cytosolic nucleophosmin (NPM)/p38 interaction in basal condition. Oxidative stress, which was generated by exposure to 500 µM H2O2, induces a rapid dephosphorylation of NPM at T199 that depends on phosphatase PP2A, another partner of the NPM/p38 complex. Blocking PP2A activity leads to accumulation of NPM-pT199 and to an increased association of NPM with p38. Concomitantly to its dephosphorylation, oxidative stress promotes translocation of NPM to the nucleus to affect the DNA damage response. Dephosphorylated NPM impairs the signaling of oxidative stress-induced DNA damage via inhibition of the phosphorylation of ataxia-telangiectasia mutated and DNA-dependent protein kinase catalytic subunit. Overall, these results suggest that the p38/NPM/PP2A complex acts as a dynamic sensor, allowing endothelial cells to react rapidly to acute oxidative stress.-Guillonneau, M., Paris, F., Dutoit, S., Estephan, H., Bénéteau, E., Huot, J., Corre, I. Oxidative stress disassembles the p38/NPM/PP2A complex, which leads to modulation of nucleophosmin-mediated signaling to DNA damage response.