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, p16Ink4a and p21Waf1 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.
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•Ionizing radiation induces long-term senescence in non-proliferating endothelial cells.•Apoptosis inhibition by Sphingosine 1-phosphate does not modulate senescence.•p53 activity, mitochondrial superoxide generation and loss of respiratory complex II activity are observed during senescence.•Superoxide dismutase mimetic or pharmacological inhibition of p53 activation prevents senescence.•SOD mimetic, but not p53 inhibition, blocks superoxide generation and revert respiratory complex II dysfunction.
Abstract
Cancer treatment protocols depend on tumor type, localization, grade, and patient. Despite aggressive treatments, median survival of patients with Glioblastoma (GBM), the most common primary ...brain tumor in adults, does not exceed 18 months, and all patients eventually relapse. Thus, novel therapeutic approaches are urgently needed.
Radiotherapy (RT) induces a multitude of alterations within the tumor ecosystem, ultimately modifying the degree of tumor immunogenicity at GBM relapse. The present manuscript reviews the diverse effects of RT radiotherapy on tumors, with a special focus on its immunomodulatory impact to finally discuss how RT could be exploited in GBM treatment through immunotherapy targeting. Indeed, while further experimental and clinical studies are definitively required to successfully translate preclinical results in clinical trials, current studies highlight the therapeutic potential of immunotherapy to uncover novel avenues to fight GBM.
The levels and composition of sphingolipids and related metabolites are altered in aging and in common disorders such as diabetes and cancers, as well as in neurodegenerative, cardiovascular, and ...respiratory diseases. Changes in sphingolipids have been implicated as being an essential step in mitochondria-driven cell death. However, little is known about the precise sphingolipid composition and modulation in mitochondria or related organelles. Here, we used LC-MS/MS to analyze the presence of key components of the ceramide metabolic pathway in vivo and in vitro in purified ER, mitochondria-associated membranes (MAMs), and mitochondria. Specifically, we analyzed the sphingolipids in the three pathways that generate ceramide: sphinganine in the de novo ceramide pathway, SM in the breakdown pathway, and sphingosine in the salvage pathway. We observed sphingolipid profiles in mouse liver, mouse brain, and a human glioma cell line (U251). We analyzed the quantitative and qualitative changes of these sphingolipids during staurosporine-induced apoptosis in U251 cells. Ceramide (especially C16-ceramide) levels increased during early apoptosis possibly through a conversion from mitochondrial sphinganine and SM, but sphingosine and lactosyl- and glycosyl-ceramide levels were unaffected. We also found that ceramide generation is enhanced in mitochondria when SM levels are decreased in the MAM. This decrease was associated with an increase in acid sphingomyelinase activity in MAM. We conclude that meaningful sphingolipid modifications occur in MAM, the mitochondria, and the ER during the early steps of apoptosis.
Over the years, substantial evidence has definitively confirmed the existence of cancer stem-
cells within tumors such as Glioblastoma (GBM). The importance of Glioblastoma stem-
cells (GSCs) in ...tumor progression and relapse clearly highlights that cancer eradication requires killing of GSCs that are intrinsically resistant to conventional therapies as well as eradication of the non-GSCs cells since GSCs emergence relies on a dynamic process. The past decade of research highlights that metabolism is a significant player in tumor progression and actually might orchestrate it. The growing interest in cancer metabolism reprogrammation can lead to innovative approaches exploiting metabolic vulnerabilities of cancer cells. These approaches are challenging since they require overcoming the compensatory and adaptive responses of GSCs. In this review, we will summarize the current knowledge on GSCs with a particular focus on their metabolic complexity. We will also discuss potential approaches targeting GSCs metabolism to potentially improve clinical care.
Tumor areas can now be very precisely delimited thanks to technical progress in imaging and ballistics. This has also led to the development of novel radiotherapy protocols, delivering higher doses ...of ionizing radiation directly to cancer cells. Despite this, radiation toxicity in healthy tissue remains a major issue, particularly with dose-escalation in these new protocols. Acute and late tissue damage following irradiation have both been linked to the endothelium irrigating normal tissues. The molecular mechanisms involved in the endothelial response to high doses of radiation are associated with signaling from the plasma membrane, mainly via the acid sphingomyelinase/ceramide pathway. This review describes this signaling pathway and discusses the relevance of targeting endothelial signaling to protect healthy tissues from the deleterious effects of high doses of radiation.
Abstract In recent years, there has been a surge in the development of methods for cell segmentation and tracking, with initiatives like the Cell Tracking Challenge driving progress in the field. ...Most studies focus on regular cell population videos in which cells are segmented and followed, and parental relationships annotated. However, DNA damage induced by genotoxic drugs or ionizing radiation produces additional abnormal events since it leads to behaviors like abnormal cell divisions (resulting in a number of daughters different from two) and cell death. With this in mind, we developed an automatic mitosis classifier to categorize small mitosis image sequences centered around one cell as “Normal” or “Abnormal.” These mitosis sequences were extracted from videos of cell populations exposed to varying levels of radiation that affect the cell cycle’s development. We explored several deep-learning architectures and found that a network with a ResNet50 backbone and including a Long Short-Term Memory (LSTM) layer produced the best results (mean F1-score: 0.93 ± 0.06). In the future, we plan to integrate this classifier with cell segmentation and tracking to build phylogenetic trees of the population after genomic stress.
Sea-level rise (SLR) can modify not only total water levels, but also tidal dynamics. Several studies have investigated the effects of SLR on the tides of the western European continental shelf ...(mainly the M2 component). We further investigate this issue using a modelling-based approach, considering uniform SLR scenarios from −0.25m to +10m above present-day sea level. Assuming that coastal defenses are constructed along present-day shorelines, the patterns of change in high tide levels (annual maximum water level) are spatially similar, regardless of the magnitude of sea-level rise (i.e., the sign of the change remains the same, regardless of the SLR scenario) over most of the area (70%). Notable increases in high tide levels occur especially in the northern Irish Sea, the southern part of the North Sea and the German Bight, and decreases occur mainly in the western English Channel. These changes are generally proportional to SLR, as long as SLR remains smaller than 2m. Depending on the location, they can account for +/−15% of regional SLR. High tide levels and the M2 component exhibit slightly different patterns. Analysis of the 12 largest tidal components highlights the need to take into account at least the M2, S2, N2, M4, MS4 and MN4 components when investigating the effects of SLR on tides. Changes in high tide levels are much less proportional to SLR when flooding is allowed, in particular in the German Bight. However, some areas (e.g., the English Channel) are not very sensitive to this option, meaning that the effects of SLR would be predictable in these areas, even if future coastal defense strategies are ignored. Physically, SLR-induced tidal changes result from the competition between reductions in bed friction damping, changes in resonance properties and increased reflection at the coast, i.e., local and non-local processes. A preliminary estimate of tidal changes by 2100 under a plausible non-uniform SLR scenario (using the RCP4.5 scenario) is provided. Though the changes display similar patterns, the high water levels appear to be sensitive to the non-uniformity of SLR.
•Tide levels change proportionally to sea-level rise till +2m over most of the shelf.•Proportionality holds in most locations even for a non-uniform sea-level scenario.•Tidal changes are sensitive to coastal defense choices, especially in German Bight.•Sea-level rise induced tide level changes differ from M2 amplitude changes.•Sea-level rise modifies bed friction, resonance properties and reflection.
We have recently shown that the in vitro differentiation of human mesenchymal stem cells (hMSCs) was accompanied by an increased sensitivity toward apoptosis; however, the mechanism responsible for ...this shift is not known. Here, we show that the repair of DNA double-strand breaks (DSBs) was more rapid in undifferentiated hMSCs than in differentiated osteoblasts by quantification of the disappearance of γ-H2AX foci in the nuclei after γ-irradiation-induced DNA damage. In addition, there was a marked and prolonged increase in the level of nuclear Ku70 and an increased phosphorylation of DNA-PKcs. This was accompanied by an augmentation in the phosphorylation of ATM in hMSCs post-irradiation suggesting the nonhomologous end joining repair mechanism. However, when hMSCs were induced to differentiate along the osteogenic or adipogenic pathways; irradiation of these cells caused an expeditious and robust cell death, which was primarily apoptotic. This was in sharp contrast to undifferentiated hMSCs, which were highly resistant to irradiation and/or temozolomide-induced DSBs. In addition, we observed a 95% recovery from DSB in these cells. Our results suggest that apoptosis and DNA repair are major safeguard mechanisms in the control of hMSCs differentiation after DNA damage.
Gastrointestinal (GI) tract damage by chemotherapy or radiation limits their efficacy in cancer treatment. Radiation has been postulated to target epithelial stem cells within the crypts of ...Lieberkühn to initiate the lethal GI syndrome. Here, we show in mouse models that microvascular endothelial apoptosis is the primary lesion leading to stem cell dysfunction. Radiation-induced crypt damage, organ failure, and death from the GI syndrome were prevented when endothelial apoptosis was inhibited pharmacologically by intravenous basic fibroblast growth factor (bFGF) or genetically by deletion of the acid sphingomyelinase gene. Endothelial, but not crypt, cells express FGF receptor transcripts, suggesting that the endothelial lesion occurs before crypt stem cell damage in the evolution of the GI syndrome. This study provides a basis for new approaches to prevent radiation damage to the bowel.
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.
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•Ionizing radiation and anisomycin induce p38 MAPK-dependent apoptosis in endothelial cells.•p38 MAPK activation induced by ionizing radiation or anisomycin is dependent on ceramide generation.•Sphingomyelinase and ceramide-induced formation of membrane large lipid platforms is necessary for p38 MAPK activation.•Formation of large lipid platforms is necessary for ionizing radiation-induced p38 MAPK activation and apoptosis.
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