Involvement of inducible nitric oxide synthase in radiation-induced vascular endothelial damage

Dichotomous effects of in vivo and in vitro ionizing radiation exposure on lymphatic function

On the one hand, lymphatic dysfunction induces interstitial edema and inflammation. On the other hand, the formation of edema and inflammation induce lymphatic dysfunction. However, informed by the earlier reports of undetected apoptosis of irradiated lymphatic endothelial cells (LECs) in vivo, lymphatic vessels are commonly considered inconsequential to ionizing radiation (IR)-induced inflammatory injury to normal tissues. Primarily because of the lack of understanding of the acute effects of IR exposure on lymphatic function, acute edema and inflammation, common sequelae of IR exposure, have been ascribed solely to blood vessel damage. Therefore, in the present study, the lymphatic acute responses to IR exposure were quantified to evaluate the hypothesis that IR exposure impairs lymphatic pumping. Rat mesenteric lymphatic vessels were irradiated in vivo or in vitro, and changes in pumping were quantified in isolated vessels in vitro. Compared with sham-treated vessels, pumping was lowered in lymphatic vessels irradiated in vivo but increased in vessels irradiated in vitro. Furthermore, unlike in blood vessels, the acute effects of IR exposure in lymphatic vessels were not mediated by nitric oxide-dependent pathways in either in vivo or in vitro irradiated vessels. After cyclooxygenase blockade, pumping was partially restored in lymphatic vessels irradiated in vitro but not in vessels irradiated in vivo. Taken together, these findings demonstrated that lymphatic vessels are radiosensitive and LEC apoptosis alone may not account for all the effects of IR exposure on the lymphatic system.NEW & NOTEWORTHY Earlier studies leading to the common belief that lymphatic vessels are radioresistant either did not characterize lymphatic pumping, deemed necessary for the resolution of edema and inflammation, or did it in vivo. By characterizing pumping in vitro, the present study, for the first time, demonstrated that lymphatic pumping was impaired in vessels irradiated in vivo and enhanced in vessels irradiated in vitro. Furthermore, the pathways implicated in ionizing radiation-induced blood vessel damage did not mediate lymphatic responses.

Effects of Peppermint Essential Oil on Learning and Memory Ability in APP/PS1 Transgenic Mice

Objective: To explore the effect and mechanism of peppermint essential oil on learning and memory ability of APP/PS1 transgenic mice. Methods: Morris water maze test and shuttle box test were used to explore the changes in learning and memory ability of APP/PS1 transgenic mice after sniffing essential oil. The cellular status of neurons in the hippocampal CA1 region of the right hemisphere, Aβ deposition, oxidative stress level, and serum metabonomics were detected to explore its mechanism. Results: Sniffing peppermint essential oil can improve the learning and memory ability of APP/PS1 transgenic mice. Compared with the model group, the state of neurons in the hippocampal CA1 region of the peppermint essential oil group returned to normal, and the deposition of Aβ decreased. The MDA of brain tissue decreased significantly, and the activity of SOD and GSH-PX increased significantly to the normal level. According to the results of metabonomics, it is speculated that peppermint essential oil may improve cognitive function in AD by regulating arginine and proline metabolism, inositol phosphate metabolism, and cysteine and methionine metabolism.

Radiation-induced cardiovascular disease: an overlooked role for DNA methylation?

Radiotherapy in cancer treatment involves the use of ionizing radiation for cancer cell killing. Although radiotherapy has shown significant improvements on cancer recurrence and mortality, several radiation-induced adverse effects have been documented. Of these adverse effects, radiation-induced cardiovascular disease (CVD) is particularly prominent among patients receiving mediastinal radiotherapy, such as breast cancer and Hodgkin's lymphoma patients. A number of mechanisms of radiation-induced CVD pathogenesis have been proposed such as endothelial inflammatory activation, premature endothelial senescence, increased ROS and mitochondrial dysfunction. However, current research seems to point to a so-far unexamined and potentially novel involvement of epigenetics in radiation-induced CVD pathogenesis. Firstly, epigenetic mechanisms have been implicated in CVD pathophysiology. In addition, several studies have shown that ionizing radiation can cause epigenetic modifications, especially DNA methylation alterations. As a result, this review aims to provide a summary of the current literature linking DNA methylation to radiation-induced CVD and thereby explore DNA methylation as a possible contributor to radiation-induced CVD pathogenesis.

Radiobiological Studies of Microvascular Damage through In Vitro Models: A Methodological Perspective

Ionizing radiation (IR) is used in radiotherapy as a treatment to destroy cancer. Such treatment also affects other tissues, resulting in the so-called normal tissue complications. Endothelial cells (ECs) composing the microvasculature have essential roles in the microenvironment's homeostasis (ME). Thus, detrimental effects induced by irradiation on ECs can influence both the tumor and healthy tissue. In-vitro models can be advantageous to study these phenomena. In this systematic review, we analyzed in-vitro models of ECs subjected to IR. We highlighted the critical issues involved in the production, irradiation, and analysis of such radiobiological in-vitro models to study microvascular endothelial cells damage. For each step, we analyzed common methodologies and critical points required to obtain a reliable model. We identified the generation of a 3D environment for model production and the inclusion of heterogeneous cell populations for a reliable ME recapitulation. Additionally, we highlighted how essential information on the irradiation scheme, crucial to correlate better observed in vitro effects to the clinical scenario, are often neglected in the analyzed studies, limiting the translation of achieved results.

Medical prevention and treatment of radiation-induced carotid injury

Radiotherapy has significantly improved the survival of cancer patients but is also associated with several adversities, including radiation-induced carotid injury (RICI). The RICI mechanisms are complex, including vessel inflammatory injury, carotid atherosclerosis, intimal proliferation, media necrosis, and peri-adventitial fibrosis. The main manifestation and adverse consequence of RICI is carotid artery stenosis (CAS), which can lead to stroke and transient ischemic attack. Currently, carotid artery injury is primarily diagnosed via color-coded duplex sonography. Early detection of traumatic changes in the carotid artery depends on measurements of carotid intima-media thickness; serum biomarker testing also shows great potential. CAS is mainly treated with carotid endarterectomy or carotid angioplasty and stent implantation. Notably, bone marrow mesenchymal stem cells are advantageous in RICI treatment and reduce carotid inflammation, oxidative stress, and delaying atherosclerosis. This review summarizes the mechanisms, examination methods, and latest treatments for RICI to provide data for its clinical prevention and treatment.

Targeting of cellular redox metabolism for mitigation of radiation injury

Accidental exposure to ionizing radiation is a serious concern to human life. Studies on the mitigation of side effects following exposure to accidental radiation events are ongoing. Recent studies have shown that radiation can activate several signaling pathways, leading to changes in the metabolism of free radicals including reactive oxygen species (ROS) and nitric oxide (NO). Cellular and molecular mechanisms show that radiation can cause disruption of normal reduction/oxidation (redox) system. Mitochondria malfunction following exposure to radiation and mutations in mitochondria DNA (mtDNA) have a key role in chronic oxidative stress. Furthermore, exposure to radiation leads to infiltration of inflammatory cells such as macrophages, lymphocytes and mast cells, which are important sources of ROS and NO. These cells generate free radicals via upregulation of some pro-oxidant enzymes such as NADPH oxidases, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Epigenetic changes also have a key role in a similar way. Other mediators such as mammalian target of rapamycin (mTOR) and peroxisome proliferator-activated receptor (PPAR), which are involved in the normal metabolism of cells have also been shown to regulate cell death following exposure to radiation. These mechanisms are tissue specific. Inhibition or activation of each of these targets can be suggested for mitigation of radiation injury in a specific tissue. In the current paper, we review the cellular and molecular changes in the metabolism of cells and ROS/NO following exposure to radiation. Furthermore, the possible strategies for mitigation of radiation injury through modulation of cellular metabolism in irradiated organs will be discussed.

Promising role of filgrastim and α-tocopherol succinate in amelioration of gastrointestinal acute radiation syndrome (GI-ARS) in mice

The protective role of α-tocopherol succinate (α-TCS) and the therapeutic efficacy of filgrastim were investigated in gastrointestinal acute radiation syndrome (GI-ARS) induced following 10 Gy whole-body γ-irradiation. Mice were randomly allocated into 5 groups: [1] normal-control, [2] irradiated-control, [3] subcutaneous (s.c.) injection of filgrastim (5 μg/kg/day) for 4 consecutive days given 1 h post-irradiation, [4] s.c. injection with α-TCS (400 mg/kg) 1 day prior to irradiation, [5] s.c. injection with α-TCS (400 mg/kg) 1 day prior to irradiation and filgrastim (5 μg/kg/day) for 4 consecutive days 1 h post-irradiation. Histopathological analysis, serum citrulline level, intestinal interleukin-1β (IL-1β), reduced glutathione (GSH), and malondialdehyde (MDA) contents as well as myeloperoxidase (MPO) activity were measured. Intestinal caspase-3, p53, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) immunopositivity were examined. In irradiated-control, MDA increased (249%) and GSH decreased (25%) compared to normal and were unaffected by filgrastim. α-TCS alone significantly reduced MDA (84.5%) and normalized GSH. The combination significantly reduced MDA (59%) and dramatically increased GSH (1573%), pointing to a possible synergistic action. In irradiated-control, MPO and IL-1β significantly increased (111% and 613%, respectively) compared to normal-control and both were significantly decreased in all treated groups. Compared to normal-control, citrulline significantly declined (68%) in irradiated-control; a significant elevation was achieved by treatments with α-TCS alone or combined with filgrastim (88% and 94%, respectively). The combination therapy significantly decreased the degree of irradiation-induced injury of the epithelium and cellular infiltration and showed the lowest histopathological scoring compared to the other groups (p ≤ 0.05). In irradiated-control, immune-reactive expressions of iNOS, COX-2, caspase-3, and p53 were remarkable (18.62%, 34.27%, 31.19%, and 27.44%, respectively) and after combination therapy were reduced (1.04%, 22.39%, 8.76%, and 4.91%, respectively). The current findings represent a first-hand strategy in dealing with GI-ARS with a potential preference to using a combined therapy of filgrastim and α-TCS.

Bone Marrow Endothelial Cells Influence Function and Phenotype of Hematopoietic Stem and Progenitor Cells after Mixed Neutron/Gamma Radiation

The bone marrow (BM) microenvironment plays a crucial role in the maintenance and regeneration of hematopoietic stem (HSC) and progenitor cells (HSPC). In particular, the vascular niche is responsible for regulating HSC maintenance, differentiation, and migration of cells in and out of the BM. Damage to this niche upon exposure to ionizing radiation, whether accidental or as a result of therapy, can contribute to delays in HSC recovery and/or function. The ability of BM derived-endothelial cells (BMEC) to alter and/or protect HSPC after exposure to ionizing radiation was investigated. Our data show that exposure of BMEC to ionizing radiation resulted in alterations in Akt signaling, increased expression of PARP-1, IL6, and MCP-1, and decreased expression of MMP1 and MMP9. In addition, global analysis of gene expression of HSC and BMEC in response to mixed neutron/gamma field (MF) radiation identified 60 genes whose expression was altered after radiation in both cell types, suggesting that a subset of genes is commonly affected by this type of radiation. Focused gene analysis by RT-PCR revealed two categories of BMEC alterations: (a) a subset of genes whose expression was altered in response to radiation, with no additional effect observed during coculture with HSPC, and (b) a subset of genes upregulated in response to radiation, and altered when cocultured with HSPC. Coculture of BMEC with CD34+ HSPC induced HSPC proliferation, and improved BM function after MF radiation. Nonirradiated HSPC exhibited reduced CD34 expression over time, but when irradiated, they maintained higher CD34 expression. Nonirradiated HSPC cocultured with nonirradiated BMEC expressed lower levels of CD34 expression compared to nonirradiated alone. These data characterize the role of each cell type in response to MF radiation and demonstrate the interdependence of each cell’s response to ionizing radiation. The identified genes modulated by radiation and coculture provide guidance for future experiments to test hypotheses concerning specific factors mediating the beneficial effects of BMEC on HSPC. This information will prove useful in the search for medical countermeasures to radiation-induced hematopoietic injury.

Intercellular communications-redox interactions in radiation toxicity; potential targets for radiation mitigation

Nowadays, using ionizing radiation (IR) is necessary for clinical, agricultural, nuclear energy or industrial applications. Accidental exposure to IR after a radiation terror or disaster poses a threat to human. In contrast to the old dogma of radiation toxicity, several experiments during the last two recent decades have revealed that intercellular signaling and communications play a key role in this procedure. Elevated level of cytokines and other intercellular signals increase oxidative damage and inflammatory responses via reduction/oxidation interactions (redox system). Intercellular signals induce production of free radicals and inflammatory mediators by some intermediate enzymes such as cyclooxygenase-2 (COX-2), nitric oxide synthase (NOS), NADPH oxidase, and also via triggering mitochondrial ROS. Furthermore, these signals facilitate cell to cell contact and increasing cell toxicity via cohort effect. Nitric oxide is a free radical with ability to act as an intercellular signal that induce DNA damage and changes in some signaling pathways in irradiated as well as non-irradiated adjacent cells. Targeting of these mediators by some anti-inflammatory agents or via antioxidants such as mitochondrial ROS scavengers opens a window to mitigate radiation toxicity after an accidental exposure. Experiments which have been done so far suggests that some cytokines such as IL-1β, TNF-α, TGF-β, IL-4 and IL-13 are some interesting targets that depend on irradiated organs and may help mitigate radiation toxicity. Moreover, animal experiments in recent years indicated that targeting of toll like receptors (TLRs) may be more useful for radioprotection and mitigation. In this review, we aimed to describe the role of intercellular interactions in oxidative injury, inflammation, cell death and killing effects of IR. Moreover, we described evidence on potential mitigation of radiation injury via targeting of these mediators.

Pathological effects of ionizing radiation: endothelial activation and dysfunction

The endothelium, a tissue that forms a single layer of cells lining various organs and cavities of the body, especially the heart and blood as well as lymphatic vessels, plays a complex role in vascular biology. It contributes to key aspects of vascular homeostasis and is also involved in pathophysiological processes, such as thrombosis, inflammation, and hypertension. Epidemiological data show that high doses of ionizing radiation lead to cardiovascular disease over time. The aim of this review is to summarize the current knowledge on endothelial cell activation and dysfunction after ionizing radiation exposure as a central feature preceding the development of cardiovascular diseases.

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.

Defibrotide in the treatment of hepatic veno-occlusive disease

Hepatic veno-occlusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS), represents the most frequent complication in patients in early phase following hematopoietic stem-cell transplantation (HSCT). In its severe form, VOD/SOS can be associated with multiorgan failure and with a mortality rate >80% by day +100. Defibrotide (DF) (a mixture of 90% single-stranded phosphodiester oligonucleotides and 10% double-stranded phosphodiester oligonucleotides derived from controlled depolarization of porcine intestinal mucosal DNA) has been proposed for the treatment of SOS due to its ability to restore thrombo-fibrinolytic balance and protect endothelial cells. The present review highlights why the mechanisms of action of DF allow its successful use in the prevention and treatment of SOS following HSCT.

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.

Nitric oxide synthase inhibitors: a review of patents from 2011 to the present

INTRODUCTION

Nitric oxide synthases (NOSs) are a family of enzymes that play an essential role in synthesizing nitric oxide (NO) by oxidizing l-arginine. As previously reported, NO is a significant mediator in cellular signaling pathways. It serves as a crucial regulator in insulin secretion, vascular tone, peristalsis, angiogenesis, neural development and inflammation. Due to its important role, the inhibition of these vital enzymes provides, as tools, the opportunity to gain an insight into potential therapeutic applications targeting NOSs.

AREAS COVERED

This paper reviews the patent literature between 2011 and mid-2014 that specified inhibitors of NOS family members as the significant targets. Google and Baidu search engines were used to find relevant patents and clinical information using NOSs or NOS inhibitor as search terms.

EXPERT OPINION

Considerable recent progress has been made in the development of NOS inhibitors with pharmacodynamic and pharmacokinetic properties, and such development is likely to continue. The patented compounds attenuated mostly embodying evidence from in vitro and in vivo trials that demonstrate good potential for future clinical human trials and industrial applications. Furthermore, new techniques such as X-ray ligand crystallographic study and structure-activity relationship were popularly utilized, which give new insights for developing novel, safe, efficient and selective NOS inhibitors.

Anti-peroxynitrite treatment ameliorated vasorelaxation of resistance arteries in aging rats: involvement with NO-sGC-cGKs pathway

Declined vasorelaxation function in aging resistance arteries is responsible for aging-related multiple organ dysfunctions. The aim of the present study is to explore the role of peroxynitrite (ONOO-) in aging resistance arterial vasorelaxation dysfunction and the possible mechanism. In the present study, young (3-4 months olds) and aging (20 months olds) male SD rats were randomized to receive vehicle (Saline) or FeTMPyP (ONOO- scavenger) for 2 weeks. The vasorelaxation of resistance arteries was determined in vitro; NOx level was tested by a colorimetric assay; the expression of nitrotyrosine (NT), soluble Guanylate Cyclase (sGC), vasodilator-stimulated phosphoprotein (VASP), phosphorylated VASP (P-VASP) and cGMP in resistance arteries were detected by immunohistochemical staining. In the present study, endothelium-dependent dilation in aging resistance arteries was lower than in those from young rats (young vs. aging: 68.0% ± 4.5% vs. 50.4% ± 2.9%, P<0.01). And the endothelium-independent dilation remained constant. Compared with young rats, aging increased nitrative stress in resistance arteries, evidenced by elevated NOx production in serum (5.3 ± 1.0 nmol/ml vs. 3.3 ± 1.4 nmol/ml, P<0.05) and increased NT expression (P<0.05). ONOO- was responsible for the vasorelaxation dysfunction, evidenced by normalized vasorelaxation after inhibit ONOO- or its sources (P<0.05) and suppressed NT expression after FeTMPyP treatment (P<0.05). The expression of sGC was not significantly different between young and aging resistance arteries, but the cGMP level and P-VASP/VASP ratio (biochemical marker of NO-sGC-cGKs signaling) decreased, which was reversed by FeTMPyP treatment in vivo (P<0.05). The present study suggested that ONOO- mediated the decline of endothelium-dependent vasorelaxation of aging resistance arteries by induction of the NO-sGC-cGKs pathway dysfunction.