Radiation-induced Bystander Effects Research Articles

Pollution of ionising radiation diagnostic dose and its targeted and non-targeted effects on human primary fibroblast cells

One of the key issues of current radiation research is the biological effect of low doses of X-ray, which can instigate to chromosomal damage in direct irradiated and bystander cells. Additionally, the direct irradiated and bystander cells demonstrate delayed damage responses within their progeny, underlying radiation-induced genomic instability (GI). In this study we tried to mimic the effects of diagnostic procedure doses of X-ray (0.5 rad) on human fibroblast cells, which are considered as a one of the environmental polluter. Human fibroblast cells were irradiated with 0.5 rad X-ray, which were considered the direct irradiated cells; whilst radiation-induced bystander effects (BE) were induced by media transfer. Both cell populations were propagated until 24 generations for delayed responses. The direct, bystander and their progeny cells were subjected to chromosomal analysis and comet assay to measure chromosomal and total DNA damage in these cells. Early response of chromosome damage was observed in the direct irradiated cells; however it was statistically insignificant. Bystander cells showed higher chromosomal damage than the irradiated cells; but it was insignificant compare to the corresponding control groups. Conversely, comet data demonstrated a significant DNA damage in both direct irradiated and bystander cells as initial responses. Interestingly, progeny of direct irradiated and bystander cells showed a significant chromosomal instability and DNA damage after 24 population doublings following irradiation. The findings suggested that the diagnostic procedure doses of X-ray could cause a profound chromosomal instability within human primary fibroblast cells; which are considered as a hallmark of carcinogenesis.

Radiation-induced Bystander Effect and Its Possible Countermeasures

Ionizing radiation has been indispensable to medical diagnosis. In cancer, radiation therapy or radiotherapy (RT) offers patients a better chance of survival. It destroys cancer by depositing high-energy radiation on the cancer tissues, though it may directly damage a few normal cells. Therefore, the total radiation dose is administered in fractionated modalities over weeks or months. However, experimental evidence indicates that the irradiated cancer cells subsequently release cytokines in the blood that enter into nearby unirradiated nuclei/cells through several signaling pathways and cause radiation-induced bystander effects (RIBEs) such as DNA damage, chromosomal instability, mutation, and apoptosis in them as side effects of RT. Recently, many combined therapeutic protocols consisting of a few natural and synthetic products have been proposed to minimize RIBEs. This article reviews the present understanding of RIBEs and their possible countermeasures. Besides, a new protocol of combined therapy of nanoparticle-based ion treatment (NIT) and RT to minimize RIBEs has been proposed.

Radiation and Diabetic Retinopathy: A Dark Synergy

Exacerbation of the vascular pathology in radiation retinopathy as a result of pre-existing diabetes has been recognized for many years, as reflected by clinical reports and a few early experimental studies. However, the underlying pathogenetic mechanisms for the synergistic interaction of radiation retinopathy (RR) and diabetic retinopathy (DR) have not been compared and evaluated for insight on this phenomenon. The present work draws attention to the roles of reactive oxygen species (ROS) and reactive nitrogen species (RNS) as common mediators of both conditions and sources of ongoing cellular injury in the radiation-induced bystander effect (RIBE) and the senescence-associated secretory phenotype (SASP). Chronic hyperglycemia-mediated oxidative stress and depleted antioxidant defense in diabetes, together with impaired DNA damage sensing and repair mechanisms, were identified as the primary elements contributing to the increased severity of RR in diabetic patients. We conclude that apart from strategic genetic mutations affecting the DNA damage response (DDR), diabetes represents the most significant common risk factor for vascular injury as a side effect of radiotherapy.

Inflammatory mediator-induced bystander effects and genomic instability: role of tissue-specificity

Much evidence showed that radiation-induced inflammation can cause cellular damage in direct irradiated and bystander cells, which are in vicinity of irradiated cells underlying radiation-induced bystander effects (BE). As well as radiation-induced genomic instability (GI) is observed within the progeny of irradiated and bystander cells as a delayed damage responses. This study tried to mimic the effects of radiation-induced GI and BE by exploring the inflammatory effect of lipopolysaccharide (LPS) on human primary fibroblast (HF 19) and umbilical vein endothelial (HUVEC) cells. To prove the principles of LPS can cause DNA damage in HF 19; cells were treated with 1 μg/ml LPS, and BE was induced by media transfer. Comet assay was used to estimate DNA damage in the direct treated and bystander cells. The early DNA damage result was significantly observed in the direct treated and bystander HF 19 cells. However, these cells did not show a significant delayed DNA damage within their progeny. Comet data showed that LPS frequently induced only initial DNA damage in HF 19 cells. The experiment was repeated utilising HF 19 and HUVEC cells, in order to investigate whether LPS could be involved in the induction of GI in a tissue-specificity manner. Both HF 19 and HUVEC cells were treated with 1 μg/ml LPS. BE was also induced by media transfer. Chromosomal analysis was used for early and late chromosomal damage estimation. Data showed that LPS treatment could significantly cause early chromosomal aberrations in the direct treated and bystander HF 19 and HUVEC cells. However, delayed chromosomal instability was observed only in the direct treated HUVEC cells. Our finding suggested that LPS frequently induced BE in HF 19 and HUVEC cells, which could be mediated by pro-inflammatory cytokines that stimulated by LPS treatment. Moreover, LPS could be involved in the GI induction in a tissue-specificity manner.Keywords:

Intracellular and extracellular ion variation measurement in alpha(α)-particle irradiated cells using t-FROZEN! and laser-induced breakdown spectroscopy

Many radiobiological changes occur in unirradiated cells due to concealed signals transmitted from the irradiated cells through the Radiation-induced bystander effect (RIBE). Calcium ions (Ca2+) remain the only ion–molecule extensively studied so far amongst the ions that control cell function. This is partly due to using fluorescent indicators to investigate the signaling process that suffers limitations in labelling procedure and ion specificity. To understand the ion imbalance in irradiated cells and cell medium serving as donor and carrier of the bystander signals. Here, we investigate ion concentrations in the extracellular and intracellular space of α-particle (Am-241) irradiated Chinese hamster ovary (CHO) cells exposed to two different radiation doses (0.3 nGy, and 0.7 nGy). Laser-induced breakdown spectroscopy (LIBS) with our novel t-FROZEN! method separating the cells from its extracellular matrix was employed as a tool. Also, X-ray fluorescence spectroscopy (XRF), inductively coupled plasma-optical emission spectrometry (ICP-OES), and electrical impedance measurements were employed as complementary techniques. Our results show that influx of K+ and outflux of Na+, Mg2+, Cl- and Ca2+ occur in the irradiated cells, compared with controls, leading to an imbalance in the concentration of crucial signaling ions across the cell membrane. Our study has provided vital insights into comprehensive composition of ion-based radiation-induced bystander signals and guide the development of Na+, Mg2+, Cl- and K+ channel targeting drugs.

Radiosensitization of Breast Cancer Cells with a 2-Methoxyestradiol Analogue Affects DNA Damage and Repair Signaling In Vitro.

Radiation resistance and radiation-related side effects warrant research into alternative strategies in the application of this modality to cancer treatment. Designed in silico to improve the pharmacokinetics and anti-cancer properties of 2-methoxyestradiol, 2-ethyl-3-O-sulfamoyl-estra-1,3,5(10)16-tetraene (ESE-16) disrupts microtubule dynamics and induces apoptosis. Here, we investigated whether pre-exposure of breast cancer cells to low-dose ESE-16 would affect radiation-induced deoxyribonucleic acid (DNA) damage and the consequent repair pathways. MCF-7, MDA-MB-231, and BT-20 cells were exposed to sub-lethal doses of ESE-16 for 24 h before 8 Gy radiation. Flow cytometric quantification of Annexin V, clonogenic studies, micronuclei quantification, assessment of histone H2AX phosphorylation and Ku70 expression were performed to assess cell viability, DNA damage, and repair pathways, in both directly irradiated cells and cells treated with conditioned medium. A small increase in apoptosis was observed as an early consequence, with significant repercussions on long-term cell survival. Overall, a greater degree of DNA damage was detected. Moreover, initiation of the DNA-damage repair response was delayed, with a subsequent sustained elevation. Radiation-induced bystander effects induced similar pathways and were initiated via intercellular signaling. These results justify further investigation of ESE-16 as a radiation-sensitizing agent since pre-exposure appears to augment the response of tumor cells to radiation.

Bystander signals from low- and high-dose irradiated human primary fibroblasts and keratinocytes modulate the inflammatory response of peripheral blood mononuclear cells.

Irradiated cells can propagate signals to neighboring cells. Manifestations of these so-called bystander effects (BEs) are thought to be relatively more important after exposure to low- vs high-dose radiation and can be mediated via the release of secreted molecules, including inflammatory cytokines, from irradiated cells. Thus, BEs can potentially modify the inflammatory environment of irradiated cells. To determine whether these modifications could affect the functionality of bystander immune cells and their inflammatory response, we analyzed and compared the in vitro response of primary human fibroblasts and keratinocytes to low and high doses of radiation and assessed their ability to modulate the inflammatory activation of peripheral blood mononuclear cells (PBMCs). Only high-dose exposure resulted in either up- or down-regulation of selected inflammatory genes. In conditioned culture media transfer experiments, radiation-induced bystander signals elicited from irradiated fibroblasts and keratinocytes were found to modulate the transcription of inflammatory mediator genes in resting PBMCs, and after activation of PBMCs stimulated with lipopolysaccharide (LPS), a strong inflammatory agent. Radiation-induced BEs induced from skin cells can therefore act as a modifier of the inflammatory response of bystander immune cells and affect their functionality.

Boosted Radiation Bystander Effect of PSMA-Targeted Gold Nanoparticles in Prostate Cancer Radiosensitization.

Metal nanoparticles are effective radiosensitizers that locally enhance radiation doses in targeted cancer cells. Compared with other metal nanoparticles, gold nanoparticles (GNPs) exhibit high biocompatibility, low toxicity, and they increase secondary electron scatter. Herein, we investigated the effects of active-targeting GNPs on the radiation-induced bystander effect (RIBE) in prostate cancer cells. The impact of GNPs on the RIBE presents implications for secondary cancers or spatially fractionated radiotherapy treatments. Anti-prostate-specific membrane antigen (PSMA) antibodies were conjugated with PEGylated GNPs through EDC-NHS chemistry. The media transfer technique was performed to induce the RIBE on the non-irradiated bystander cells. This study focused on the LNCaP cell line, because it can model a wide range of stages relating to prostate cancer progression, including the transition from androgen dependence to castration resistance and bone metastasis. First, LNCaP cells were pretreated with phosphate buffered saline (PBS) or PSMA-targeted GNPs (PGNPs) for 24 h and irradiated with 160 kVp X-rays (0-8 Gy). Following that, the collected culture media were filtered (sterile 0.45 µm polyethersulfone) in order to acquire PBS- and PGNP- conditioned media (CM). Then, PBS- and PGNP-CM were transferred to the bystander cells that were loaded with/without PGNPs. MTT, γ-H2AX, clonogenic assays and reactive oxygen species assessments were performed to compare RIBE responses under different treatments. Compared with 2 Gy-PBS-CM, 8 Gy-PBS-CM demonstrated a much higher RIBE response, thus validating the dose dependence of RIBE in LNCaP cells. Compared with PBS-CM, PGNP-CM exhibited lower cell viability, higher DNA damage, and a smaller survival fraction. In the presence of PBS-CM, bystander cells loaded with PGNPs showed increased cell death compared with cells that did not have PGNPs. These results demonstrate the PGNP-boosted expression and sensitivity of RIBE in prostate cancer cells.

Radiation-Induced Bystander Effect on the Genome of Bone Marrow Mesenchymal Stem Cells in Lung Cancer.

Aims: Radiation by-radiation effect (RIBE) can induce the genomic instability of bone marrow mesenchymal stem cells (BMSCs) adjacent to lung cancer, and this effect not only exists in the short-term, but also accompanies it in the long-term, but its specific mechanism is not clear. Our goal is to explore the similarities and differences in the mechanism of genomic damage in tumor-associated BMSCs induced by short-term and long-term RIBE, and to provide a theoretical basis for adjuvant drugs for protection against RIBE at different clinical time periods. Results: We found that both short- and long-term RIBE induced genomic instability. We could show a high expression of TGF-β1, TNF-α, and HIF-1α in tumor-associated BMSCs after short-term RIBE whereas only TNF-α and HIF-1α expression was increased in long-term RIBE. We further confirmed that genomic instability is associated with the activation of the HIF-1α pathway and that this is mediated by TNF-α and TGF-β1. In addition, we found differences in the mechanisms of genomic instability in the considered RIBE windows of analysis. In short-term RIBE, both TNF-α and TGF-β1 play a role, whereas only TNF-α plays a decisive role in long-term RIBE. In addition, there were differences in BMSC recruitment and genomic instability of different tissues with a more pronounced expression in tumor and bone marrow than compared to lung. Innovation and Conclusion: We could show dynamic changes in the expression of the cytokines TGF-β1 and TNF-α during short- and long-term RIBE. The differential expression of the two is the key to causing the genomic damage of tumor-associated BMSCs in the considered windows of analysis. Therefore, these results may serve as a guideline for the administration of radiation protection adjuvant drugs at different clinical stages. Antioxid. Redox Signal. 38, 747-767.

Golgi Phosphoprotein 3 Mediates Radiation-Induced Bystander Effect via ERK/EGR1/TNF-α Signal Axis.

The radiation-induced bystander effect (RIBE), an important non-targeted effect of radiation, has been proposed to be associated with irradiation-caused secondary cancers and reproductive damage beyond the irradiation-treated area after radiotherapy. However, the mechanisms for RIBE signal(s) regulation and transduction are not well understood. In the present work, we found that a Golgi protein, GOLPH3, was involved in RIBE transduction. Knocking down GOLPH3 in irradiated cells blocked the generation of the RIBE, whereas re-expression of GOLPH3 in knockdown cells rescued the RIBE. Furthermore, TNF-α was identified as an important intercellular signal molecule in the GOLPH3-mediated RIBE. A novel signal axis, GOLPH3/ERK/EGR1, was discovered to modulate the transcription of TNF-α and determine the level of released TNF-α. Our findings provide new insights into the molecular mechanism of the RIBE and a potential target for RIBE modulation.

Paradoxical Radiosensitizing Effect of Carnosic Acid on B16F10 Metastatic Melanoma Cells: A New Treatment Strategy.

Carnosic acid (CA) is a phenolic diterpene characterized by its high antioxidant activity; it is used in industrial, cosmetic, and nutritional applications. We evaluated the radioprotective capacity of CA on cells directly exposed to X-rays and non-irradiated cells that received signals from X-ray treated cells (radiation induced bystander effect, RIBE). The genoprotective capacity was studied by in vivo and in vitro micronucleus assays. Radioprotective capacity was evaluated by clonogenic cell survival, MTT, apoptosis and intracellular glutathione assays comparing radiosensitive cells (human prostate epithelium, PNT2) with radioresistant cells (murine metastatic melanoma, B16F10). CA was found to exhibit a genoprotective capacity in cells exposed to radiation (p < 0.001) and in RIBE (p < 0.01). In PNT2 cells, considered as normal cells in our study, CA achieved 97% cell survival after exposure to 20 Gy of X-rays, eliminating 67% of radiation-induced cell death (p < 0.001), decreasing apoptosis (p < 0.001), and increasing the GSH/GSSH ratio (p < 0.01). However, the administration of CA to B16F10 cells decreased cell survival by 32%, increased cell death by 200% (p < 0.001) compared to irradiated cells, and increased cell death by 100% (p < 0.001) in RIBE bystander cells (p < 0.01). Furthermore, it increased apoptosis (p < 0.001) and decreased the GSH/GSSG ratio (p < 0.01), expressing a paradoxical radiosensitizing effect in these cells. Knowing the potential mechanisms of action of substances such as CA could help to create new applications that would protect healthy cells and exclusively damage neoplastic cells, thus presenting a new desirable strategy for cancer patients in need of radiotherapy.

Radiation-Induced Rescue Effect: Insights from Microbeam Experiments.

The present paper reviews a non-targeted effect in radiobiology known as the Radiation-Induced Rescue Effect (RIRE) and insights gained from previous microbeam experiments on RIRE. RIRE describes the mitigation of radiobiological effects in targeted irradiated cells after they receive feedback signals from co-cultured non-irradiated bystander cells, or from the medium previously conditioning those co-cultured non-irradiated bystander cells. RIRE has established or has the potential of establishing relationships with other non-traditional new developments in the fields of radiobiology, including Radiation-Induced Bystander Effect (RIBE), Radiation-Induced Field Size Effect (RIFSE) and ultra-high dose rate (FLASH) effect, which are explained. The paper first introduces RIRE, summarizes previous findings, and surveys the mechanisms proposed for observations. Unique opportunities offered by microbeam irradiations for RIRE research and some previous microbeam studies on RIRE are then described. Some thoughts on future priorities and directions of research on RIRE exploiting unique features of microbeam radiations are presented in the last section.

Label-Free Direct Mass Spectrometry Analysis of the Bystander Effects Induced in Chondrocytes by Chondrosarcoma Cells Irradiated with X-rays and Carbon Ions.

Radiation-induced bystander effects are induced changes in cells that were not themselves directly irradiated but were in the vicinity of a radiation path. Such effects, which occur in the microenvironment of an irradiated tumor, remain poorly understood and depend on the cell type and irradiation quality. This study aimed to evaluate bystander effects in non-irradiated chondrocytes that received conditioned medium from irradiated chondrosarcoma cells. SW1353 chondrosarcoma cells were irradiated with X-rays and carbon ions, each at 0.1 Gy and 2 Gy, and the conditioned media of the irradiated cells were transferred to T/C-28A2 chondrocytes and Human Umbilical Venous Endothelial Cells (HUVECs). The whole proteome of bystander chondrocytes was analyzed by label-free mass spectrometry, and a comparative study was performed by dose and irradiation quality. HUVECs were evaluated for inflammatory cytokine secretion. The bystander response of chondrocytes to X-ray irradiation primarily affected the protein translation pathway (DHX36, EIF3B, EIF3D, EIF3M, EIF5, RPL6, RPLP0, RPS24, SYNCRIP), IL-12 (AIP, BOLA2, MIF, GAS6, MIF, PDGFRB) and the oxidative stress pathway (MGST3, PRDX2, PXDN, SOD2, TXN, TXNL1). Following carbon-ion irradiation, the G1/S pathway (PCBP4, PSMD12, PSME, XIAP) and mitotic G2 DNA damage checkpoint pathway (MRE11, TAOK1, UIMC1) were engaged. Changes in the regulation of chromosome separation (BCL7C, BUB3, CENPF, DYNC1LI1, SMARCA4, SMC4) were associated with only low-dose X-ray and carbon-ion irradiation. Modification of the protein translation pathway represented at least 30% of bystander effects and could play a role, possibly along with stress granules, in reduction in cellular metabolism to protect proteins. Stress granules were significantly enriched according to an interaction map. All these accessions corresponded to a window of the proteins modulated in response to the bystander effect. Our chondrosarcoma model clarified the nature of the bystander response of chondrocytes and may suggest several interesting new mechanisms that are specific to particular irradiation doses and qualities.

Cellular analysis on the radiation induced bystander effects due to bismuth oxide nanoparticles with 6 MV photon beam radiotherapy

BackgroundThe therapeutic strategies in killing the cancerous tissue while keeping the normal healthy tissue uninterrupted can be further improved by introducing nanoparticles as radiosensitizer in radiotherapy. Nevertheless, healthy cells might still be affected by radiation-induced bystander effect (RIBE) response due the presence of nanoparticles. Thus, the potential negative effects in non-irradiated adjacent cells must be investigated. AimThe current study aims to explore the cellular effects of bismuth oxide nanoparticles (Bi2O3 NPs) on human breast cancer (MCF-7) and human foetal osteoblast (hFOB 1.19) cells due to the RIBE after irradiation with 6 MV clinical photon beam. Materials and methodsThe irradiated-cell conditioned medium (ICCM) treated with and without Bi2O3 NPs from the irradiated cells were collected and then transferred into the non-targeted cells. The ability of the bystander cells to proliferate and their ROS generation were analyzed. DNA status of the cells and the possibility of apoptosis were evaluated using FTIR spectroscopy and MUSE Cell Analyzer, respectively. ResultsThe current study revealed that MCF-7 and hFOB 1.19 bystander cells may continue to proliferate and survive following short and long-term incubation with ICCM treatment with Bi2O3 NPs. The survival rate of the treated bystander cells increased approximately 3%–8% compared to the untreated group. Although the bystander cells exhibited an increase in ROS and apoptosis, the addition of Bi2O3 NPs had no significant detrimental influence on the cells. Variation in the DNA vibrational amplitude detected by FTIR in bystander cells was less than 5% compared to the control group. ConclusionThis study discovered that the application of Bi2O3 NPs as a radiosensitizer did not give a negative impact on the bystander cells. This outcome may give an advantage to the application of Bi2O3 NPs as radiosensitizer in radiotherapy to enhance cancer cells death without introducing further detrimental effects to the non-targeted cells.

Radiation-Induced Bystander Effect and Cytoplasmic Irradiation Studies with Microbeams.

Simple SummaryMicrobeams are useful tools in studies on non-target effects, such as the radiation-induced bystander effect, and responses related to cytoplasmic irradiation. A micrometer or even sub-micrometer-level beam size enables the precise delivery of radiation energy to a specific target. Here we summarize the observations of the bystander effect and the cytoplasmic irradiation-related effect using different kinds of microbeam irradiators as well as discuss the cellular and molecular mechanisms that are involved in these responses. Non-target effects may increase the detrimental effect caused by radiation, so a more comprehensive knowledge of the process will enable better evaluation of the damage resulting from irradiation.Although direct damage to nuclear DNA is considered as the major contributing event that leads to radiation-induced effects, accumulating evidence in the past two decades has shown that non-target events, in which cells are not directly irradiated but receive signals from the irradiated cells, or cells irradiated at extranuclear targets, may also contribute to the biological consequences of exposure to ionizing radiation. With a beam diameter at the micrometer or sub-micrometer level, microbeams can precisely deliver radiation, without damaging the surrounding area, or deposit the radiation energy at specific sub-cellular locations within a cell. Such unique features cannot be achieved by other kinds of radiation settings, hence making a microbeam irradiator useful in studies of a radiation-induced bystander effect (RIBE) and cytoplasmic irradiation. Here, studies on RIBE and different responses to cytoplasmic irradiation using microbeams are summarized. Possible mechanisms related to the bystander effect, which include gap-junction intercellular communications and soluble signal molecules as well as factors involved in cytoplasmic irradiation-induced events, are also discussed.

MiR-663a Inhibits Radiation-Induced Epithelium-to-Mesenchymal Transition by Targeting TGF-β1

ObjectivemiR-663a has been reported to be downregulated by X-ray irradiation and participates in radiation-induced bystander effect via TGF-β1. The goal of this study was to explore the role of miR-663a during radiation-induced Epithelium-to-mesenchymal transition (EMT). MethodsTGF-β1 or IR was used to induce EMT. After miR-663a transfection, cell migration and cell morphological changes were detected and the expression levels of miR-663a, TGF-β1, and EMT-related factors were quantified. ResultsEnhancement of cell migration and promotion of mesenchymal changes induced by either TGF-β1 or radiation were suppressed by miR-663a. Furthermore, both X-ray and carbon ion irradiation resulted in the upregulation of TGF-β1 and downregulation of miR-663a, while the silencing of TGF-β1 by miR-663a reversed the EMT process after radiation. ConclusionOur findings demonstrate an EMT-suppressing effect by miR-663a via TGF-β1 in radiation-induced EMT.

Exosome-mediated miR-4655–3p contributes to UV radiation-induced bystander effects

Radiation-induced bystander effects (RIBEs) refer to a series of reactions displaying in nonirradiated cells triggered by signals from irradiated cells. Though bystander effects induced by ionizing radiation have been well studied, there are still limited data on ultraviolet(UV) induced bystander effects(UV-RIBEs). Studies have verified that exosomes, acting as a new tool of intercellular communication, participate in ionizing radiation-induced bystander effect. The purpose of what we studied was to explore the function of exosomes in UV-RIBEs, and seeking the relevant mechanism. Human skin fibroblasts (HSFs) were exposed to a single dose of ultraviolet A (UVA) radiation (20 J/cm2) or ultraviolet B (UVB) radiation (60 mJ/cm2), respectively. Exosomes were isolated from the culture medium of HSFs by differential ultracentrifugation. Three endpoints relevant to potodamage were used in the evaluation of UV-RIBEs, which including the cell proliferation, oxidative damage, and apoptosis. Our results showed that exosomes from UV-irradiated cells contributed to UV-RIBEs. The expression of miR-4655–3p in exosomes increased after UV radiation and exosomes assisted in the transportation of miR-4655–3p between cells. The upregulation of miR-4655–3p enhanced the UV-RIBEs in the bystander cells. MiR-4655–3p restrained the expression of E2F2 through direct binding to its 3′-UTR. In addition, E2F2 contributed to the cell proliferation and decreased oxidative damage of HSFs. To sum up that exosomal miR-4655–3p plays a crucial role in UV-RIBEs and this function mentioned partially related to the inhibition of E2F2.

Copper uptake in adult rainbow trout irradiated during early life stages and in non-irradiated bystander trout which swam with the irradiated fish

Purpose This investigation forms part of a wider study into the legacy effects of exposure of rainbow trout eggs 38 h after fertilization, eyed eggs, yolk sac larvae (YSL) or first feeders to a single 0.5 Gy X-ray dose, including the induction of a bystander effect, by the irradiated fish, to non-irradiated fish. Fish may be exposed to multiple environmental stressors, including waterborne metals, during their lifespan and, while there are data on how the legacy of early life stage irradiation and bystander effect induction is affected by waterborne aluminum and cadmium, there are no studies into the effects radiation or the radiation induced bystander effect on metal uptake. Therefore the aim of this investigation was to determine if the legacy of early life stage irradiation included an effect on copper uptake by adult fish and by non-irradiated bystander adult trout which swam with the irradiated fish. Methods The four early life stages mentioned above were exposed to a single 0.5 Gy X-ray dose and then maintained, for two years with no further irradiation. At two years old the irradiated fish were allowed to swim, for 2 h with non-irradiated bystander trout (also two years old). After this time copper uptake was determined using 64Cu. Results Copper uptake was increased in adult trout irradiated as eggs at 48 h after fertilization and as first feeders but eyed egg or YSL irradiation had no effect. Copper uptake was also increased in the bystander trout which swam with trout irradiated as eggs at 48 h after fertilization and as eyed eggs but there was no effect on non-irradiated adult trout which swam with trout irradiated as YSL or first feeders. Conclusions When put in context with the proteomic changes observed in these fish we propose the increased copper uptake in adult trout irradiated as eggs at 48 h after fertilization could be part of an anti-tumorigenic response and the increase in copper uptake in adult trout irradiated as first feeders could be part of a potentially protective pro-apoptotic response. Similarly we propose the increase in copper uptake in non-irradiated adult trout, induced by trout irradiated as eggs at 48 h after fertilization or as eyed eggs, was part of the universally anti-tumorigenic nature of the X-ray induced bystander effect in fish. However this was exclusive to embryonic irradiation.

The Footprint of Exosomes in the Radiation-Induced Bystander Effects.

Radiation therapy is widely used as the primary treatment option for several cancer types. However, radiation therapy is a nonspecific method and associated with significant challenges such as radioresistance and non-targeted effects. The radiation-induced non-targeted effects on nonirradiated cells nearby are known as bystander effects, while effects far from the ionising radiation-exposed cells are known as abscopal effects. These effects are presented as a consequence of intercellular communications. Therefore, a better understanding of the involved intercellular signals may bring promising new strategies for radiation risk assessment and potential targets for developing novel radiotherapy strategies. Recent studies indicate that radiation-derived extracellular vesicles, particularly exosomes, play a vital role in intercellular communications and may result in radioresistance and non-targeted effects. This review describes exosome biology, intercellular interactions, and response to different environmental stressors and diseases, and focuses on their role as functional mediators in inducing radiation-induced bystander effect (RIBE).

Radiation-Induced Bystander Effect Mediated by Exosomes Involves the Replication Stress in Recipient Cells.

Exosomes released by irradiated cells mediate the radiation-induced bystander effect, which is manifested by DNA breaks detected in recipient cells; yet, the specific mechanism responsible for the generation of chromosome lesions remains unclear. In this study, naive FaDu head and neck cancer cells were stimulated with exosomes released by irradiated (a single 2 Gy dose) or mock-irradiated cells. Maximum accumulation of gamma H2A.X foci, a marker of DNA breaks, was detected after one hour of stimulation with exosomes from irradiated donors, the level of which was comparable to the one observed in directly irradiated cells (a weaker wave of the gamma H2A.X foci accumulation was also noted after 23 h of stimulation). Exosomes from irradiated cells, but not from control ones, activated two stress-induced protein kinases: ATM and ATR. Noteworthy is that while direct irradiation activated only ATM, both ATM and ATR were activated by two factors known to induce the replication stress: hydroxyurea and camptothecin (with subsequent phosphorylation of gamma H2A.X). One hour of stimulation with exosomes from irradiated cells suppressed DNA synthesis in recipient cells and resulted in the subsequent nuclear accumulation of RNA:DNA hybrids, which is an indicator of impaired replication. Interestingly, the abovementioned effects were observed before a substantial internalization of exosomes, which may suggest a receptor-mediated mechanism. It was observed that after one hour of stimulation with exosomes from irradiated donors, phosphorylation of several nuclear proteins, including replication factors and regulators of heterochromatin remodeling as well as components of multiple intracellular signaling pathways increased. Hence, we concluded that the bystander effect mediated by exosomes released from irradiated cells involves the replication stress in recipient cells.