Radiation-induced Endothelial Dysfunction Research Articles

The miR-126-5p and miR-212-3p in the extracellular vesicles activate monocytes in the early stage of radiation-induced vascular inflammation implicated in atherosclerosis.

People exposed to radiation in cancer therapy and nuclear accidents are at increased risk of cardiovascular outcomes in long-term survivors. Extracellular vesicles (EVs) are involved in radiation-induced endothelial dysfunction, but their role in the early stage of vascular inflammation after radiation exposure remains to be fully understood. Herein, we demonstrate that endothelial cell-derived EVs containing miRNAs initiate monocyte activation in radiation-induced vascular inflammation. In vitro co-culture and in vivo experimental data showed that endothelial EVs can be sensitively increased by radiation exposure in a dose-dependent manner, and stimulate monocytes releasing monocytic EVs and adhesion to endothelial cells together with an increase in the expression of genes encoding specific ligands for cell-cell interaction. Small RNA sequencing and transfection using mimics and inhibitors explained that miR-126-5p and miR-212-3p enriched in endothelial EVs initiate vascular inflammation by monocyte activation after radiation exposure. Moreover, miR-126-5p could be detected in the circulating endothelial EVs of radiation-induced atherosclerosis model mice, which was found to be tightly correlated with the atherogenic index of plasma. In summary, our study showed that miR-126-5p and miR-212-3p present in the endothelial EVs mediate the inflammatory signals to activate monocytes in radiation-induced vascular injury. A better understanding of the circulating endothelial EVs content can promote their use as diagnostic and prognostic biomarkers for atherosclerosis after radiation exposure.

Organ-Specific Endothelial Dysfunction Following Total Body Irradiation Exposure.

As the single cell lining of the heart and all blood vessels, the vascular endothelium serves a critical role in maintaining homeostasis via control of vascular tone, immune cell recruitment, and macromolecular transit. For victims of acute high-dose radiation exposure, damage to the vascular endothelium may exacerbate the pathogenesis of acute and delayed multi-organ radiation toxicities. While commonalities exist between radiation-induced endothelial dysfunction in radiosensitive organs, the vascular endothelium is known to be highly heterogeneous as it is required to serve tissue and organ specific roles. In keeping with its organ and tissue specific functionality, the molecular and cellular response of the endothelium to radiation injury varies by organ. Therefore, in the development of medical countermeasures for multi-organ injury, it is necessary to consider organ and tissue-specific endothelial responses to both injury and candidate mitigators. The purpose of this review is to summarize the pathogenesis of endothelial dysfunction following total or near total body irradiation exposure at the level of individual radiosensitive organs.

Centella asiatica-Derived Endothelial Paracrine Restores Epithelial Barrier Dysfunction in Radiation-Induced Enteritis.

Radiation-induced enteritis is frequently observed following radiotherapy for cancer or occurs due to radiation exposure in a nuclear accident. The loss of the epithelial integrity leads to ‘leaky gut’, so recovery of damaged epithelium is an important strategy in therapeutic trials. Centella asiatica (CA), a traditional herbal medicine, is widely used for wound healing by protecting against endothelial damage. In this study, we investigated the radio-mitigating effect of CA, focusing on the crosstalk between endothelial and epithelial cells. CA treatment relieved radiation-induced endothelial dysfunction and mitigated radiation-induced enteritis. In particular, treatment of the conditioned media from CA-treated irradiated endothelial cells recovered radiation-induced epithelial barrier damage. We also determined that epidermal growth factor (EGF) is a critical factor secreted by CA-treated irradiated endothelial cells. Treatment with EGF effectively improved the radiation-induced epithelial barrier dysfunction. We also identified the therapeutic effects of CA-induced endothelial paracrine in a radiation-induced enteritis mouse model with epithelial barrier restoration. Otherwise, CA treatment did not show radioprotective effects on colorectal tumors in vivo. We showed therapeutic effects of CA on radiation-induced enteritis, with the recovery of endothelial and epithelial dysfunction. Thus, our findings suggest that CA is an effective radio-mitigator against radiation-induced enteritis.

Endothelial Shp2 deficiency controls alternative activation of macrophage preventing radiation-induced lung injury through notch signaling

SummaryRadiation-induced lung injury is a common late side effect of thoracic radiotherapy. Endothelial dysfunction following leukocytes infiltration is a prominent feature in this process. Here, we established a clinical-mimicking mouse model of radiation-induced lung injury and found the activity of phosphatase Shp2 was elevated in endothelium after injury. Endothelium-specific Shp2 deletion mice showed relieved collagen deposition along with disrupted radiation-induced Jag1 expression in the endothelium. Furthermore, endothelium-derived Jag1 activated the alternative activation of macrophages in vitro and in vivo by paracrine Notch signaling. Consistently, the Notch pathway was significantly activated by chest irradiation in the peripheral blood leukocytes of patients with cancer. Collectively, our work demonstrates that Shp2 participates in the radiation-induced endothelial dysfunction and subsequently inflammatory microenvironment producing during radiation-induced lung injury. Our findings indicate Shp2 as a potential target for radiation-induced lung injury and provide another way for endothelium to participate in the pathological process of radiation-induced lung injury.

Deep models of integrated multiscale molecular data decipher the endothelial cell response to ionizing radiation

SummaryThe vascular endothelium is a hot spot in the response to radiation therapy for both tumors and normal tissues. To improve patient outcomes, interpretable systemic hypotheses are needed to help radiobiologists and radiation oncologists propose endothelial targets that could protect normal tissues from the adverse effects of radiation therapy and/or enhance its antitumor potential. To this end, we captured the kinetics of multi-omics layers—i.e. miRNome, targeted transcriptome, proteome, and metabolome—in irradiated primary human endothelial cells cultured in vitro. We then designed a strategy of deep learning as in convolutional graph networks that facilitates unsupervised high-level feature extraction of important omics data to learn how ionizing radiation-induced endothelial dysfunction may evolve over time. Last, we present experimental data showing that some of the features identified using our approach are involved in the alteration of angiogenesis by ionizing radiation.

Inhibition of EphA2 by Dasatinib Suppresses Radiation-Induced Intestinal Injury.

Radiation-induced multiorgan dysfunction is thought to result primarily from damage to the endothelial system, leading to a systemic inflammatory response that is mediated by the recruitment of leukocytes. The Eph–ephrin signaling pathway in the vascular system participates in various disease developmental processes, including cancer and inflammation. In this study, we demonstrate that radiation exposure increased intestinal inflammation via endothelial dysfunction, caused by the radiation-induced activation of EphA2, an Eph receptor tyrosine kinase, and its ligand ephrinA1. Barrier dysfunction in endothelial and epithelial cells was aggravated by vascular endothelial–cadherin disruption and leukocyte adhesion in radiation-induced inflammation both in vitro and in vivo. Among all Eph receptors and their ligands, EphA2 and ephrinA1 were required for barrier destabilization and leukocyte adhesion. Knockdown of EphA2 in endothelial cells reduced radiation-induced endothelial dysfunction. Furthermore, pharmacological inhibition of EphA2–ephrinA1 by the tyrosine kinase inhibitor dasatinib attenuated the loss of vascular integrity and leukocyte adhesion in vitro. Mice administered dasatinib exhibited resistance to radiation injury characterized by reduced barrier leakage and decreased leukocyte infiltration into the intestine. Taken together, these data suggest that dasatinib therapy represents a potential approach for the protection of radiation-mediated intestinal damage by targeting the EphA2–ephrinA1 complex.

Effect of radiation on endothelial functions in workers exposed to radiation.

OBJECTIVE Our aim is to determine whether radiation affects the endothelial function of hospital staff working in the radiation unit for diagnostic and therapeutic purposes. We have evaluated endothelial function with vascular imaging parameters such as flow-mediated dilatation (FMD) and aortic stiffness index (ASI). METHODS A total of 75 employees, 35 of whom are exposed to radiation due to their profession and 40 as the control group, were included in our single-centered study. Demographic data, FMD, aortic stiffness, and echocardiographic findings of the two groups were compared. RESULTS There were no significant differences in demographic data. Median FMD values tended to be lower in the radiation exposure group [7.89 (2.17-21.88) vs. 11.69 (5.13-27.27) p=0.09]. The FMD value was significantly lower in the catheter laboratory group than in the radiation-exposed (p=0.034) and control (p=0.012) groups. However, there was no statistically significant difference between the non-catheter lab radiation exposed group and the control group (p=0.804). In addition, there was no statistically significant difference in the ASI value between the groups (p=0.201). CONCLUSION We have found that FMD is decreased among hospital staff working in radiation-associated areas. This may be an early marker for radiation-induced endothelial dysfunction.

Radiation‐induced endothelial dysfunction markers are differentially modulated by simulated microgravity

Exposure to ionizing radiation (IR) and microgravity induce greater risks to human space mission. Ground‐based studies on animals and cells have shown that both IR and microgravity cause numerous adverse effects on endothelial cells, which may lead to endothelial dysfunction. However, no systematic studies have been undertaken to investigate whether microgravity differentially modulates the expression of endothelial cell dysfunction markers when exposed either alone or in combination with irradiation. This study was conducted to gain insight into human endothelial cells when subjected to simulated microgravity followed by exposure to IR.MethodsEndothelial cells were grown on micro‐carrier beads to simulate a low shear microgravity environment and subsequently subjected to a rotary culture systems, called high aspect ratio vessels (HARVs) at 10 rpm. The expression of endothelial dysfunction markers were measured by quantitative real‐time PCR.ResultsExposure to microgravity environment induced morphological changes in endothelial cells and enhanced radiation‐induced endothelial cell killing. In addition, IR plus microgravity caused differential expression of E‐selectin, Pecam1, Vcam1, Vegf, and Icam1 as compared to IR exposure alone.ConclusionsThese results suggest that microgravity modifies the effect of IR on endothelial cells.Support or Funding InformationSupported by NASA sponsored Arkansas Space Grant ConsortiumThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Integrative proteomics and targeted transcriptomics analyses in cardiac endothelial cells unravel mechanisms of long-term radiation-induced vascular dysfunction.

Epidemiological data from radiotherapy patients show the damaging effect of ionizing radiation on heart and vasculature. The endothelium is the main target of radiation damage and contributes essentially to the development of cardiac injury. However, the molecular mechanisms behind the radiation-induced endothelial dysfunction are not fully understood. In the present study, 10-week-old C57Bl/6 mice received local X-ray heart doses of 8 or 16 Gy and were sacrificed after 16 weeks; the controls were sham-irradiated. The cardiac microvascular endothelial cells were isolated from the heart tissue using streptavidin-CD31-coated microbeads. The cells were lysed and proteins were labeled with duplex isotope-coded protein label methodology for quantification. All samples were analyzed by LC-ESI-MS/MS and Proteome Discoverer software. The proteomics data were further studied by bioinformatics tools and validated by targeted transcriptomics, immunoblotting, immunohistochemistry, and serum profiling. Radiation-induced endothelial dysfunction was characterized by impaired energy metabolism and perturbation of the insulin/IGF-PI3K-Akt signaling pathway. The data also strongly suggested premature endothelial senescence, increased oxidative stress, decreased NO availability, and enhanced inflammation as main causes of radiation-induced long-term vascular dysfunction. Detailed data on molecular mechanisms of radiation-induced vascular injury as compiled here are essential in developing radiotherapy strategies that minimize cardiovascular complications.

Basic Fibroblast Growth Factor Ameliorates Endothelial Dysfunction in Radiation-Induced Bladder Injury.

This study was designed to explore the effect of basic fibroblast growth factor (bFGF) on radiation-induced endothelial dysfunction and histological changes in the urinary bladder. bFGF was administrated to human umbilical vein cells (HUVEC) or urinary bladder immediately after radiation. Reduced expression of thrombomodulin (TM) was indicated in the HUVEC and urinary bladder after treatment with radiation. Decreased apoptosis was observed in HUVEC treated with bFGF. Administration of bFGF increased the expression of TM in HUVEC medium, as well as in the urinary bladder at the early and delayed phases of radiation-induced bladder injury (RIBI). At the early phase, injection of bFGF increased the thickness of urothelium and reduced inflammation within the urinary bladder. At the delayed phase, bFGF was effective in reducing fibrosis within the urinary bladder. Our results indicate that endothelial dysfunction is a prominent feature of RIBI. Administration of bFGF can ameliorate radiation-induced endothelial dysfunction in urinary bladder and preserve bladder histology at early and delayed phases of RIBI.

Influence of irradiation on release of endothelial microparticles (EMP) in vitro.

Survivors of Hodgkin's disease as well as of breast and lung cancer are at risk of radiation-associated cardiovascular disease. Recent studies demonstrated a correlation between cardiovascular risk factors and circulating endothelial microparticles (EMP) and thereby suggest increased EMP levels in circulation to be an early biomarker of endothelial dysfunction and cardiovascular risk. This prompted us to analyze the amount of EMP released by human aortic endothelial cells (HAEC) after exposure to different doses of X-ray (0.4, 2, 4, 6, and 20 Gy) using antibodies against the endothelial cell markers CD31, CD144, and CD146 by flow cytometry. In this pilot experiment only CD146 proved appropriate for quantification of HAEC-derived EMP. Exposure of HAEC to different doses of X-ray did not significantly influence formation of CD146-positive EMP. However, low doses (0.4 Gy) tended to decrease EMP formation, whereas higher doses (2 or 4 Gy) slightly increased release of CD146-positive EMP. By contrast, inflammatory activation of HAEC by TPA significantly increased EMP release about 15-fold (P < 0.01). In conclusion, under the present experimental conditions EMP did not prove a suitable biomarker for radiation-induced endothelial dysfunction in vitro.

Novel strategies to ameliorate radiation injury: a possible role for tetrahydrobiopterin.

Novel pharmacological strategies are urgently needed to prevent or reduce radiation-induced tissue injury. Microvascular injury is a prominent feature of both early and delayed radiation injury. Radiation-induced endothelial dysfunction is believed to play a key role in the pathogenesis of post-irradiation tissue injury. Hence, strategies that could prevent or improve endothelial malfunction are expected to ameliorate the severity of radiation injury. This review focuses on the therapeutic potential of the nitric oxide synthase (NOS) cofactor 5,6,7,8-tetrahydrobiopterin (BH4) as an agent to reduce radiation toxicity. BH4 is an essential cofactor for all NOS enzymes and a critical determinant of NOS function. Inadequate availability of BH4 leads to uncoupling of the NOS enzyme. In an uncoupled state, NOS produces the highly oxidative radicals superoxide and peroxynitrite at the cost of NO. Under conditions of oxidative stress, such as after radiation exposure, BH4 availability might be reduced due to the rapid oxidation of BH4 to 7,8-dihydrobiopterin (7,8-BH2). As a result, free radical-induced BH4 insufficiency may increase the oxidative burden and hamper NO-dependent endothelial function. Given the growing evidence that BH4 depletion and subsequent endothelial NOS uncoupling play a major role in the pathogenesis of endothelial dysfunction in various diseases, there is substantial reason to believe that improving post-irradiation BH4 availability, by either supplementation with it or modulation of its metabolism, might be a novel strategy to reduce radiation-induced endothelial dysfunction and subsequent tissue injury.

Dietary inhibition of xanthine oxidase attenuates radiation-induced endothelial dysfunction in rat aorta

Radiation exposure is associated with the development of various cardiovascular diseases. Although irradiation is known to cause elevated oxidant stress and chronic inflammation, both of which are detrimental to vascular function, the molecular mechanisms remain incompletely understood. We previously demonstrated that radiation causes endothelial dysfunction and increased vascular stiffness by xanthine oxidase (XO) activation. In this study, we investigated whether dietary inhibition of XO protects against radiation-induced vascular injury. We exposed 4-mo-old rats to a single dose of 0 or 5 Gy gamma radiation. These rats received normal drinking water or water containing 1 mM oxypurinol, an XO inhibitor. We measured XO activity and superoxide production in rat aorta and demonstrated that both were significantly elevated 2 wk after radiation exposure. However, oxypurinol treatment in irradiated rats prevented aortic XO activation and superoxide elevation. We next investigated endothelial function through fluorescent measurement of nitric oxide (NO) and vascular tension dose responses. Radiation reduced endothelium-dependent NO production in rat aorta. Similarly, endothelium-dependent vasorelaxation in the aorta of irradiated rats was significantly attenuated compared with the control group. Dietary XO inhibition maintained NO production at control levels and prevented the development of endothelial dysfunction. Furthermore, pulse wave velocity, a measure of vascular stiffness, increased by 1 day postirradiation and remained elevated 2 wk after irradiation, despite unchanged blood pressures. In oxypurinol-treated rats, pulse wave velocities remained unchanged from baseline throughout the experiment, signifying preserved vascular health. These findings demonstrate that XO inhibition can offer protection from radiation-induced endothelial dysfunction and cardiovascular complications.

Hirudin ameliorates intestinal radiation toxicity in the rat: support for thrombin inhibition as strategy to minimize side‐effects after radiation therapy and as countermeasure against radiation exposure

The small bowel is a dose-limiting normal tissue in radiation therapy of malignancies in the abdomen and pelvis, as well as an important determinant of survival after non-therapeutic radiation exposure. Irradiation of normal tissues, including intestine, causes loss of vascular thromboresistance and upregulation of thrombin receptors. Radiation-induced endothelial dysfunction is thought to be involved in both early and delayed radiation responses. Hence, thrombin may be a potential target for ameliorating normal tissue radiation toxicity. To assess direct thrombin inhibition as a protective strategy against small bowel radiation toxicity. Rat small intestine was exposed to localized orthovoltage X-radiation. Recombinant hirudin, a direct thrombin inhibitor, or vehicle was infused from 2 days before irradiation to 14 days after irradiation. Structural, cellular, and molecular aspects of intestinal radiation injury were assessed at 2 weeks (early toxicity) and 26 weeks (chronic toxicity) after irradiation. Compared with unirradiated intestine, irradiated intestine showed increased expression of tissue factor, increased immunoreactivity for enzymatically active thrombin, and increased extravascular fibrin(ogen) deposition. Hirudin treatment significantly attenuated radiation-induced mucosal damage (P = 0.04), reactive intestinal wall thickening (P = 0.02), transforming growth factor-beta immunoreactivity levels (P = 0.0002), and collagen III deposition (P = 0.003). The differences between hirudin-treated and control rats were more pronounced at 2 weeks than at 26 weeks after irradiation. Hirudin treatment did not affect postradiation granulocyte infiltration. Short-term thrombin inhibition attenuates important aspects of intestinal radiation toxicity. Thrombin is a promising target for minimizing normal tissue injury after radiation therapy of cancer, as well as for protecting normal tissues from the adverse effects of non-therapeutic radiation exposure.

Radiation choroidal vasculopathy: an indocyanine green angiography study.

An indocyanine green angiography (ICG-A) study of choroidal vasculature in the irradiated peritumoral zone in 16 eyes treated with 106Ru/106Rh brachytherapy for choroidal melanoma was performed between 4 and 72 months following treatment. The earliest changes observed were peritumoral atrophy of the retinal pigment epithelium and choriocapillaries. With time, the larger choroidal vessels progressively became non-perfused. There was only minimal staining of the smaller vessels. However, at 2 years or more after radiotherapy the larger choroidal vessels showed progressive vascular wall staining with ICG ('perivasculitis') associated with continuing closure. Previous histopathological studies of radiation damage to the choroid have demonstrated atrophy and occlusion of the vasculature but have shown no evidence of vasculitis. It is suggested that ICG staining of the choroidal vascular wall in radiation choroidopathy is due to radiation-induced endothelial cell loss or dysfunction rather than a true vasculitis. Subsequent progression results in vascular occlusion, and development of new clusters of abnormal choroidal vessels.

Radiation-Induced Endothelial Dysfunction and Fibrosis in Rat Lung: Modification by the Angiotensin Converting Enzyme Inhibitor CL242817

The purpose of this study was to evaluate the angiotensin converting enzyme (ACE) inhibitor CL242817 as a modifier of radiation-induced pulmonary endothelial dysfunction and pulmonary fibrosis in rats sacrificed 2 months after a single dose of 60Co gamma rays (0-30 Gy) to the right hemithorax. CL242817 was administered in the feed continuously after irradiation at a regimen of 60 mg/kg/day. Pulmonary endothelial function was monitored by lung ACE activity, plasminogen activator (PLA) activity, and prostacyclin (PGI2) and thromboxane (TXA2) production. Pulmonary fibrosis was evaluated by lung hydroxyproline (HP) content. Lung ACE and PLA activities decreased with increasing radiation dose, and cotreatment with CL242817 significantly ameliorated both responses. CL242817 dose-reduction factors (DRF) were 1.3-1.5 for ACE and PLA activity. Lung PGI2 and TXA2 production increased with increasing radiation dose, and CL242817 almost completely prevented both radiation responses. The slope of the radiation dose-response curves in the CL242817-treated rats was essentially zero, precluding calculation of DRF values for PGI2 and TXA2 production. Lung HP content also increased with increasing radiation dose, and CL242817 significantly attenuated this response (DRF = 1.5). These data suggest that the ability of ACE inhibitors to ameliorate radiation-induced pulmonary endothelial dysfunction is not unique to captopril [Ward et al., Int. J. Radiat. Oncol. Biol. Phys. 15, 135-140 (1988)], rather it is a therapeutic action shared by other members of this class of compounds. These data also provide the first evidence that ACE inhibitors exhibit antifibrotic activity in irradiated rat lung.

Split-Dose Sparing of γ-Ray-Induced Pulmonary Endothelial Dysfunction in Rats

The purpose of this study was to determine whether radiation-induced pulmonary endothelial dysfunction exhibits split-dose sparing. Rats were sacrificed 2 months after a range of 60Co gamma-ray doses (0-40 Gy) delivered to the right hemithorax in either a single fraction or in two equal fractions separated by 24 h. Pulmonary angiotensin converting enzyme (ACE) activity, plasminogen activator (PLA) activity, and prostacyclin (PGI2) and thromboxane (TXA2) production served as indices of lung endothelial function. There were dose-dependent decreases in ACE and PLA activity and increases in PGI2 and TXA2 production after both single and split-dose exposures. The D2-D1 values determined from the two-fraction minus single-fraction isoeffective doses were 3.9 Gy for ACE activity, 7.2 Gy for PLA activity, 4.8 Gy for PGI2 production, and 4.7 Gy for TXA2 production. Thus these data demonstrate that over the present range of radiation doses approximately 4-7 Gy is repairable as subeffective endothelial damage during the 24-h interval between fractions. These values agree with previously published estimates of split-dose sparing in mouse lung based on lethality and breathing rate assays.