Effects Of Reoxygenation Research Articles

H2S-producing enzymes in anoxia-tolerant vertebrates: Effects of cold acclimation, anoxia exposure and reoxygenation on gene and protein expression.

To lend insight into the potential role of the gasotransmitter hydrogen sulfide (H2S) in facilitating anoxia survival of anoxia-tolerant vertebrates, we quantified the gene expression of the primary H2S-synthesizing enzymes, 3-mercaptopyruvate sulfurtransferase (3MST), cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), in ventricle and brain of normoxic, anoxic and reoxygenated 21°C- and 5°C-acclimated freshwater turtles (Trachemys scripta) and 10°C-acclimated crucian carp (Carassius carassius). Semi-quantitative Western blotting analysis was also conducted to assess 3MST and CBS protein abundance in ventricle and brain of 5°C turtles and 10°C crucian carp subjected to normoxia, anoxia and reoxygenation. We hypothesized that if H2S was advantageous for anoxia survival, expression levels would remain unchanged or be upregulated with anoxia and/or reoxygenation. Indeed, for both species, gene and protein expression were largely maintained with anoxia exposure (24h, 21°C; 5 d, 10°C; 14 d, 5°C). With reoxygenation, 3MST expression was increased in turtle and crucian carp brain at the protein and gene level, respectively. Additionally, the effect of cold acclimation on gene expression was assessed in several tissues of the turtle. Expression levels were maintained in most tissues, but decreased in others. The maintenance of gene and protein expression of the H2S-producing enzymes with anoxia exposure and the up-regulation of 3MST with reoxygenation suggests that H2S may facilitate anoxic survival of the two champions of vertebrate anoxia survival. The differential effects of cold acclimation on H2S enzyme expression may influence blood flow to different tissues during winter anoxia.

Mitochondrial manganese superoxide dismutase from the shrimp Litopenaeus vannamei: Molecular characterization and effect of high temperature, hypoxia and reoxygenation on expression and enzyme activity.

Climate warming has been increasing ocean water temperature and decreasing oxygen concentrations, exposing aquatic organisms to environmental stress conditions. The shrimp Litopenaeus vannamei manages to survive these harsh environmental conditions by enhancing their antioxidant defenses, among other strategies. In this study, we report the mitochondrial manganese superoxide dismutase (mMnSOD) nucleotide and deduced amino acid sequences and its gene expression in L. vannamei tissues. The deduced protein has 220 amino acids with a signal peptide of 20 amino acids. Expression of mMnSOD was analyzed in hepatopancreas, gills and muscle, where gills had highest expression in normoxic conditions. In addition, shrimp were subjected to high temperature, hypoxia and reoxygenation to analyze the effect on the expression of mMnSOD and SOD activity in mitochondria. High temperature and hypoxia showed a synergistic effect in the up-regulation on expression of mMnSOD in gills and hepatopancreas. Moreover, induction in SOD activity was found in the mitochondrial fraction from gills of normoxia at high temperature, probably due to an overproduction of reactive oxygen species caused by an elevated metabolic rate due to the stress temperature. These results suggest that the combined stress conditions of hypoxia and high temperature trigger molecularly the antioxidant response in L. vannamei in a higher degree than only one stressor.

Effects of hypoxia and reoxygenation on intermediary metabolite homeostasis of marine bivalves Mytilus edulis and Crassostrea gigas

Marine benthic invertebrates are frequently exposed to fluctuating oxygen levels resulting in hypoxia-reoxygenation (H/R) stress in the intertidal, estuarine and shallow coastal habitats. H/R stress can strongly affect the organisms' physiological performance due to the negative shifts in bioenergetics and redox balance. H/R stress commonly leads to the depletion of energy substrates and accumulation of anaerobic end products, but the effects of H/R stress on the homeostasis of the intermediate nitrogenous compounds are not well understood. We studied the effects of the short-term and long-term hypoxia (1 and 6 days, respectively) and subsequent reoxygenation on the metabolite profiles of free amino acids (FAAs), as well as the intermediates of the urea cycle and purine metabolism in two species of hypoxia-tolerant intertidal bivalves, the blue mussels Mytilus edulis and the Pacific oysters Crassostrea gigas. Accumulation of succinate was assessed to determine the role of anaerobiosis in the metabolic responses to H/R stress. Our study showed that the more hypoxia-tolerant of the two studied species (C. gigas) had lower rate of succinate accumulation during hypoxia (indicating stronger metabolic rate suppression) and was better able to maintain the homeostasis of nitrogenous intermediates during H/R stress compared with the less hypoxia-tolerant M. edulis. Furthermore, analysis of the metabolite profiles indicate that the oysters maintain high levels of cytoprotective compounds (such as taurine and GABA), accumulate lower levels of potential prooxidants (such as succinate and hypoxanthine) and experience less damage to oxidation-prone thiol-containing amino acids such as cysteine, homocysteine and methionine during hypoxia and reoxygenation compared with the blue mussels. This study indicates a potentially important role of intermediate metabolite homeostasis in the tolerance to prolonged hypoxia and H/R stress in marine organisms and opens avenue for further testing of this hypothesis in a broader comparative framework.

Waterlogging tolerance of five soybean genotypes through different physiological and biochemical mechanisms

Waterlogging is a serious environmental threat that limits crop growth and yield in low-lying, rainfed areas in many regions across the globe. Here we investigated the effects of waterlogging and subsequent re-oxygenation on the physiology and biochemistry of three soybean [Glycine max (L.) Merrill] genotypes (PELBR10-6000, PELBR11-6028, and PELBR11-6042) and two cultivars (TEC IRGA 6070 and BMX Potência). Plants were grown under greenhouse conditions until the V4 stage when they were subjected to waterlogging for seven days. The water was then drained and plants were allowed to recover for another seven days. Overall, all genotypes suppressed waterlogging stress with distinct mechanisms. Waterlogged PELBR10-6000 surpassed control plant levels of CO2 assimilation rate and readily responded to the energy lack induced by hypoxia by activating the fermentative enzymes and alanine aminotransferase. Similar mechanisms were observed in BMX Potência, which restored metabolism to control levels at the end of the recovery. PELBR11-6028 and PELBR11-6042 activated the antioxidant defenses, and TEC IRGA 6070 did not delay flowering.

Co-Delivery of Metformin Enhances the Antimultidrug Resistant Tumor Effect of Doxorubicin by Improving Hypoxic Tumor Microenvironment

Doxorubicin (DOX) is a first-line chemo drug for cancer therapy, yet it fails to treat multi-drug-resistant tumors. Hypoxia is a major causative factor leading to chemotherapy failure. Particularly, hypoxia up-regulates its responsive transcription factor-hypoxia-inducible factors (HIF)-to induce the overexpression of drug resistant genes. Metformin (MET) is recently found to cooperate with DOX against multiple tumors. As a mitochondrial inhibitor, MET could suppress tumor oxygen consumption, and thereby modulate the hypoxic tumor microenvironment. In this study, we used cationic liposomes to codeliver both DOX and MET for treating multi-drug-resistant breast cancer cells-MCF7/ADR. Faster release of MET enhanced the cytotoxicity of DOX through attenuating hypoxic stress both in vivo and in vitro. MET diminished the cellular oxygen consumption and inhibited HIF1α and P-glycoprotein (Pgp) expression in vitro. In addition, the dual-drug-loaded liposomes increased tumor targeting and intratumoral blood oxygen saturation, which suggested that the tumor reoxygenation effect of MET facilitated the exertion of its synergistic activity with DOX against MCF7/ADR xenografts. In general, our study represents a feasible strategy to boost the therapeutic effect in treating multi-drug-resistant cancer by improving the hypoxic tumor microenvironment.

Impact of SBRT fractionation in hypoxia dose painting - Accounting for heterogeneous and dynamic tumor oxygenation.

Tumor hypoxia, often found in nonsmall cell lung cancer (NSCLC), implies an increased resistance to radiotherapy. Pretreatment assessment of tumor oxygenation is, therefore, warranted in these patients, as functional imaging of hypoxia could be used as a basis for dose painting. This study aimed at investigating the feasibility of using a method for calculating the dose required in hypoxic subvolumes segmented on 18 F-HX4 positron emission tomography (PET) imaging of NSCLC. Positron emission tomography imaging data based on the hypoxia tracer 18 F-HX4 of 19 NSCLC patients were included in the study. Normalized tracer uptake was converted to oxygen partial pressure (pO2 ) and hypoxic target volumes (HTVs) were segmented using a threshold of 10mmHg. Uniform doses required to overcome the hypoxic resistance in the target volumes were calculated based on a previously proposed method taking into account the effect of interfraction reoxygenation, for fractionation schedules ranging from extremely hypofractionated stereotactic body radiotherapy (SBRT) to conventionally fractionated radiotherapy. Gross target volumes ranged between 6.2 and 859.6cm3 , and the hypoxic fraction<10mmHg between 1.2% and 72.4%. The calculated doses for overcoming the resistance of cells in the HTVs were comparable to those currently prescribed in clinical practice as well as those previously tested in feasibility studies on dose escalation in NSCLC. Depending on the size of the HTV and the distribution of pO2 , HTV doses were calculated as 43.6-48.4Gy for a three-fraction schedule, 51.7-57.6Gy for five fractions, and 59.5-66.4Gy for eight fractions. For patients in whom the HTV pO2 distribution was more favorable, a lower dose was required despite a bigger volume. Tumor control probability was lower for single-fraction schedules, while higher levels of tumor control probability were found for schedules employing several fractions. The method to account for heterogeneous and dynamic hypoxia in target volume segmentation and dose prescription based on 18 F-HX4-PET imaging appears feasible in NSCLC patients. The distribution of oxygen partial pressure within HTV could impact the required prescribed dose more than the size of the volume.

Disrupting the vicious cycle created by NOX activation in sickle erythrocytes exposed to hypoxia/reoxygenation prevents adhesion and vasoocclusion

In sickle cell disease (SCD), recurrent painful vasoocclusive crisis are likely caused by repeated episodes of hypoxia and reoxygenation. The sickle erythrocyte (SSRBC) adhesion plays an active role in vasoocclusion. However, the effect of prolonged reoxygenation after hypoxic stress on the molecular mechanisms in SSRBCs involved in onset of episodic vasoocclusion remain unclear. Exposure of human SSRBCs to hypoxia followed by 2 h reoxygenation, increased reactive oxygen species (ROS) production. Using specific pharmacological inhibitors, we show that excess ROS production in both reticulocytes and mature SSRBCs is regulated by NADPH oxidases (NOXs), the mitogen-activated protein kinase (ERK1/2), and G-protein coupled-receptor kinase 2 (GRK2). Consequently, SSRBC ROS create an intracellular positive feedback loop with ERK1/2 and GRK2 to mediate SSRBC adhesion to endothelium in vitro, and vasoocclusion in a mouse model of vasoocclusion in vivo. Importantly, reducing ROS levels in SSRBCs with redox-active manganese (Mn) porphyrins, commonly known as mimics of superoxide dismutase (SOD), disrupted the cycle created by ROS by affecting NOX and GRK2 activities and ERK1/2 phosphorylation, thus abrogating RBC-endothelial interactions. Inhibition adhesion assays show that LW (ICAM-4, CD242) blood group glycoprotein and CD44 are the RBC adhesion molecules mediating endothelial binding. Conversely, hypoxia/reoxygenation of normal RBCs failed to activate this feedback loop, and adhesion. These findings provide novel insights into the pathophysiological significance of the deleterious cycle created by NOX-dependent ROS, GRK2 and ERK1/2 within SSRBCs activated by hypoxia/reoxygenation, and involved in SSRBC adhesion and vasoocclusion. Thus, this loop in SSRBCs, which can be disrupted by Mn porphyrins, likely drives the profound SCD vasculopathy, and may point to new therapeutic targets to prevent chronic vasoocclusive events.

Perfluorocarbon nanodroplets can reoxygenate hypoxic tumors in vivo without carbogen breathing.

Nanoscale perfluorocarbon (PFC) droplets have enormous potential as clinical theranostic agents. They are biocompatible and are currently used in vivo as contrast agents for a variety of medical imaging modalities, including ultrasound, computed tomography, photoacoustic and 19F-magnetic resonance imaging. PFC nanodroplets can also carry molecular and nanoparticulate drugs and be activated in situ by ultrasound or light for targeted therapy. Recently, there has been renewed interest in using PFC nanodroplets for hypoxic tumor reoxygenation towards radiosensitization based on the high oxygen solubility of PFCs. Previous studies showed that tumor oxygenation using PFC agents only occurs in combination with enhanced oxygen breathing. However, recent studies suggest that PFC agents that accumulate in solid tumors can contribute to radiosensitization, presumably due to tumor reoxygenation without enhanced oxygen breathing. In this study, we quantify the impact of oxygenation due to PFC nanodroplet accumulation in tumors alone in comparison with other reoxygenation methodologies, in particular, carbogen breathing.Methods: Lipid-stabilized, PFC (i.e., perfluorooctyl bromide, CF3(CF2)7Br, PFOB) nanoscale droplets were synthesized and evaluated in xenograft prostate (DU145) tumors in male mice. Biodistribution assessment of the nanodroplets was achieved using a fluorescent lipophilic indocarbocyanine dye label (i.e., DiI dye) on the lipid shell in combination with fluorescence imaging in mice (n≥3 per group). Hypoxia reduction in tumors was measured using PET imaging and a known hypoxia radiotracer, [18F]FAZA (n≥ 3 per group).Results: Lipid-stabilized nanoscale PFOB emulsions (mean diameter of ~250 nm), accumulated in the xenograft prostate tumors in mice 24 hours post-injection. In vivo PET imaging with [18F]FAZA showed that the accumulation of the PFOB nanodroplets in the tumor tissues alone significantly reduced tumor hypoxia, without enhanced oxygen (i.e., carbogen) breathing. This reoxygenation effect was found to be comparable with carbogen breathing alone.Conclusion: Accumulation of nanoscale PFOB agents in solid tumors alone successfully reoxygenated hypoxic tumors to levels comparable with carbogen breathing alone, an established tumor oxygenation method. This study confirms that PFC agents can be used to reoxygenate hypoxic tumors in addition to their current applications as multifunctional theranostic agents.

Hypoxia and reoxygenation on antioxidant enzyme activities and histological structure of Macrobrachium nipponense

PDF HTML阅读 XML下载 导出引用 引用提醒 低氧和复氧对日本沼虾抗氧化酶活力及组织结构的影响 DOI: 作者: 作者单位: 1. 南京农业大学无锡渔业学院, 江苏 无锡 214081;2. 中国水产科学研究院淡水渔业研究中心, 农业农村部淡水渔业与种质资源利用重点实验室, 江苏 无锡 214081 作者简介: 杨明(1990-),男,硕士研究生,研究方向为水产动物抗逆育种.E-mail:18931340665@163.com 通讯作者: 中图分类号: S966 基金项目: 国家自然科学基金项目（31672633）；现代农业产业技术体系建设专项（CARS-48）；江苏省现代农业产业技术体系建设项目（JFRS-02）. Hypoxia and reoxygenation on antioxidant enzyme activities and histological structure of Macrobrachium nipponense Author: Affiliation: 1. Wuxi Fishery College, Nanjing Agricultural University, Wuxi 214081, China;2. Freshwater Fisheries Research Center, Chinese Academg of Fishery Sciences;Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture and Rural Affairs, Wuxi 214081, China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究低氧胁迫及恢复后日本沼虾（）抗氧化酶活力和组织结构的变化，将体重（2.0±0.2） g的日本沼虾暴露于（2.0±0.2） mg/L低氧环境中24 h，设定溶解氧（6.0±0.2） mg/L为对照组，每组设置3个重复，于低氧胁迫0 h、6 h、12 h、24 h及复氧1 h、6 h、12 h、24 h分别采集实验组及对照组鳃、肝胰腺及肌肉组织，测定这些组织的抗氧化酶活力，并进行组织切片观察。实验结果表明，低氧胁迫期间肌肉组织中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和谷胱甘肽过氧化物酶（GPX）活力先升高后下降，3种酶活力在低氧胁迫12 h时显著高于对照组（<0.05）。鳃组织中SOD、CAT和GPX酶活力在低氧胁迫12 h时显著高于对照组（<0.05）。在低氧胁迫期间肝胰腺SOD、CAT和GPX酶活力在低氧6 h均达到最大值并显著高于对照组（<0.05）。低氧胁迫及恢复并未对肌肉组织结构产生明显的影响。鳃组织在低氧胁迫期间鳃小片上皮细胞与支柱细胞排列发生紊乱，次级层片发生肥大的现象且有红细胞流入，泌氯细胞形态发生变化且细胞数目有所增加，但复氧后均得到一定程度的恢复。肝胰腺组织在低氧胁迫期间B细胞数量逐渐降低，胞内运转泡体积减小，复氧阶段B细胞数量及体积恢复明显。结果表明急性低氧胁迫能够导致日本沼虾肝胰腺和鳃组织结构损伤并引起抗氧化酶活力发生显著变化，且24 h恢复期不足以让日本沼虾在低氧胁迫中完全恢复。 Abstract:This study examined the effects of hypoxia and reoxygenation on antioxidant enzyme activities and the change in histological structure in with the body weight of (2.0±0.2) g. Experimental prawns were placed in a normal (control) group or hypoxia group with given dissolved oxygen of (6.0±0.2) mg/L and (2.0±0.2) mg/L, respectively. Each group was sampled in triplicate to measure the activities of antioxidant enzymes in the muscle, gill, and hepatopancreas under hypoxia at 0 h, 6 h, 12 h, and 24 h, and under reoxygenation at 1 h, 6 h, 12 h, and 24 h. The histological structures of gill, muscle, and hepatopancreas were also observed. The results showed that the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) enzymes in the muscle, gill, and hepatopancreas from the experimental group first increased and then declined, and the activities of the three enzymes were significantly higher than those of the control group at 12 h under hypoxia stress ( < 0.05). The activities of SOD and CAT in the muscle tissue of prawns in response to reoxygenation was fluctuated over time, and the activities of GPX under reoxygenation at 24 h was significantly lower than that of the control group ( < 0.05). The activities of SOD, CAT, and GPX in gill under hypoxia at 12 h were both significantly higher than that of the control group ( < 0.05), and there was significantly higher GPX enzyme activity under reoxygenation at 24 h than that of the control group ( < 0.05). Compared with the control group, the significantly higher SOD, CAT, and GPX activities in the hepatopancreas of prawns were observed at 6 h ( < 0.05), and the content of MDA in the hepatopancreas of prawns in response to hypoxia and reoxygenation was significantly higher than that that of the control group ( < 0.05). Observation of tissue by paraffin section revealed that hypoxia and recovery did not affect muscle tissue structure. Through the observation of the tissue section of the gill, it was found that the epithelial cells and the pillar cells were disordered after 12 h of hypoxia stress, and the secondary layer was hypertrophied. After 24 h of hypoxia, the secondary layer of hypertrophy was intensified and red blood cells inflowed. The morphology of the cells changed, and the number of cells increased, but it recovered to some extent after reoxygenation. During hypoxia stress, the number of B cells in the hepatopancreatic tissues significantly decreased, but the number and apparent volume of B cells recovered to the level of the control group after reoxygenation. The results showed that acute hypoxia can cause damage to the hepatopancreas and gill of , and affect the activities of antioxidant enzymes. Furthermore, the results showed that acute hypoxia can cause damage to the hepatopancreas and gill of , and affect the activities of antioxidant enzymes. The 24 h recovery period was not sufficient for to completely recover from hypoxia stress. 参考文献 相似文献 引证文献

Synaptic transmission and excitability during hypoxia with inflammation and reoxygenation in hippocampal CA1 neurons

Although a number of experimental and clinical studies have shown that hypoxia typically accompanies acute inflammatory responses, the combinatorial effect of the two insults on basic neural function has not been thoroughly investigated. Previous studies have predominantly suggested that hypoxia reduces network activity; however, several studies suggest the opposite effect. Of note, inflammation is known to increase neural activity. In the current study, we examined the effects of limited oxygen in combination with an inflammatory stimulus, as well as the effects of reoxygenation, on synaptic transmission and excitability. We observed a significant reduction of both synaptic transmission and excitability when hypoxia and inflammation occurred in combination, whereas reoxygenation caused hyperexcitability of neurons. Further, we found that the observed reduction in synaptic transmission was due to compromised presynaptic release efficiency based on an adenosine-receptor–dependent increase in synaptic facilitation. Excitability changes in both directions were attributable to dynamic regulation of the hyperpolarization-activated cation current (Ih) and to changes in the input resistance and the voltage difference between resting membrane potential and action potential threshold. We found that zatebradine, an Ih current inhibitor, reduced the fluctuation in excitability, suggesting that it may have potential as a drug to ameliorate reperfusion brain injury.

Effect of Hypoxia on Macrophage MMP‐2 expression: Role of O2 availability in Determining Atherosclerotic Plaque Stability

Atherosclerotic plaque accumulation at the carotid artery bifurcation is a leading cause of stroke. Stroke symptoms occur when the atherosclerotic plaque ruptures and forms thrombus, causing material to embolize into the cerebral circulation. For years, there has been speculation that increased expression of matrix metalloproteinases (MMPs) within atherosclerotic plaques may be responsible to plaque rupture, however, which MMPs are responsible for increase plaque instability and the potential mechanism(s) that induces this change remain to be elucidated. One proposed mechanism is changes in [O2] in the plaque environment. In the present study, we examined the relative expression of MMPs (MMPs‐2, ‐15 and‐24) in carotid artery plaques (n=36; 23 symptomatic; a history of TIA/stroke within last 4 months and 13 asymptomatic; a history of TIA/stroke &gt;4 months) and blood (n=25; 17 symptomatic and 8 asymptomatic) from patients undergoing carotid endarterectomy procedures (plaque removal).MethodsRelative changes in MMPs levels were measured in both plaques and peripheral blood mononuclear cell (PBMCs) by real‐time quantitative PCR (QPCR). Western blot analysis was utilized to determine changes in MMP‐2 levels in asymptomatic versus symptomatic plaques and PBMCs. Cellular localisation of MMP‐2 in atherosclerotic carotid plaques were examined by immunohistochemistry (IHC). To further investigate the mechanism of MMP‐2 production within atherosclerotic plaques, in‐vitro differentiated THP‐1 macrophage cells were exposed to either hypoxic or normoxic conditions and both RNA and protein levels of hypoxia induced factor‐1 alpha (HIF‐1α) and MMP‐2 were analyzed at different time points. Finally, effects of reoxygenation (normoxia) in hypoxic THP‐1 cells were determined.ResultsOur main findings were (i) Symptomatic patients had significantly lower expression levels of MMP‐2 mRNA in plaques compared to asymptomatic plaques, however there was a significant increase in MMP2 RNA in circulating monocytes of symptomatic patients (ii) Protein levels of MMP‐2 were found markedly up‐regulated in both plaques and blood of symptomatic patients. iii) IHC showed that MMP‐2 were co‐localized to macrophages iv) in‐vitro studies suggest that the hypoxic conditions markedly increased MMP‐2 production in a concentration dependent manner, and v) The reoxygenation to differentiated THP‐1 cells after 24 hours of hypoxia resulted in a sustained expression of MMP‐2, as determined by Western blot assays. These results suggest that increased level of MMP‐2 within atherosclerotic carotid plaques could contribute to atherosclerosis progression, and plaque rupture.ConclusionIt appears that exposure of macrophages to hypoxia induces MMP2 expression and this, in turn, leads to inflammatory changes and matrix degradation within the atherosclerotic lesions. Thus, MMP‐2 could be a potential therapeutic target not only for plaque stabilization but also as a biomarker for vulnerable atherosclerotic plaques in blood.Support or Funding InformationSHRFThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The Effect of Neoadjuvant Androgen Deprivation Therapy on Tumor Hypoxia in High-Grade Prostate Cancer: An 18F-MISO PET-MRI Study

Tumor hypoxia is associated with radioresistance and poor prognosis after radiation therapy for prostate cancer (PCa). In this prospective pilot study, we assessed the ability of 18F-misonidazole (18F-MISO) positron emission tomography (PET)-magnetic resonance imaging (MRI) to detect hypoxia in high-grade PCa patients who were candidates for curative radiation therapy, and we evaluated 18F-MISO PET-MRI modulation after 3months of neoadjuvant androgen deprivation therapy (nADT). Eleven PCa patients with a Gleason score (GS) ≥ 8 underwent 18F-fluorocholine (18F-FCH) PET-computed tomography at diagnosis and an18F-MISO hybrid PET-MRI examination before nADT; a second 18F-MISO PET-MRI examination was acquired after 3 months of nADT for all patients but one who dropped out because of noncompliance with nADT.Immunohistochemistry for tissue hypoxia- and proliferation-related biomarkers (glucose transporter 1, carbonic anhydrase IX, vascular endothelial growth factor A, Ki-67, hypoxia-inducible factor 1 alpha, and epidermal growth factor receptor) was performed in lesions bearing the highest GS.We used nonparametric tests to assess (1) the presence of 18F-MISO-positive regions (tumor-to-background ratio [TBR]≥1.4) at baseline; (2) the correlation between imaging parameters (PET tracer uptake, Prostate Imaging Reporting and Data System [PIRADS] scores, and dynamic contrast enhancement perfusion markers) at baseline; (3) the difference in immunohistochemistry staining between 18F-MISO-positive and -negative lesions; and (4) the changes in 18F-MISO PET-MRI after nADT. Uptake of 18F-MISO was significant in 7 patients, being coincidental with the highest GS region in 5 of them. A significant correlation was found at baseline between GS and 18F-MISO TBR, between 18F-MISO TBR and MRI perfusion markers, between GS and 18F-FCH maximum standardized uptake value, between GS and PIRADS score, and between 18F-FCH maximum standardized uptake value and PIRADS score.No difference was found between 18F-MISO-positive and -negative biopsy specimens with respect to tissue biomarkers. The TBR of 18F-MISO diminished significantly after nADT only in high-grade lesions and in regions with a significant uptake at baseline. PET imaging with 18F-MISO showed variable uptake in PCa, associated with a higher GS, lowering significantly after 3months of nADT in high-grade lesions. These results suggest the existence of a hypoxic microenvironment in PCa and a reoxygenation effect of nADT.

Single fraction computed tomography-guided high-dose-rate brachytherapy or stereotactic body radiotherapy for primary and metastatic lung tumors?

PurposeTo provide a pilot dosimetric study of computed tomography (CT)-guided high-dose-rate (HDR) brachytherapy (BRT) and stereotactic body radiotherapy (SBRT) for primary and metastatic lung lesions.Material and methodsFor nine lung primary and metastasis patients, 3D image-based BRT plan using a single virtual catheter was planned for 34 Gy in single fraction to the gross tumor volume (GTV) + 3 mm margin to account for tumor deformation. These plans were compared to margin-based (MB-) and robustness optimized (RO-) SBRT, assuming the same tumor deformation under real-time tumor tracking. Consistent dose calculation was ensured for both BRT and SBRT plans using the same class of collapsed cone convolution superposition algorithm. Plan quality metrics were compared by Friedman tests and Wilcoxon t-tests.Results and ConclusionsBrachytherapy plans showed significant higher GTV mean dose compared to MB- and RO-SBRT (122.2 Gy vs. 50.4 and 44.7 Gy, p < 0.05), and better dose gradient index (R50) = 2.9 vs. 4.3 and 8.4 for MB- and RO-SBRT, respectively. Dose constraints per the RTOG 0915 protocol were achieved for all critical organs except chest wall in BRT. All other dose-volume histograms (DVH) metrics are comparable between BRT and SBRT. Treatment delivery time of BRT and SBRT plans significantly increased and decreased with increasing GTV size, respectively. SBRT using advanced MLC tracking technique and non-coplanar VMAT can achieve comparable dosimetric quality to HDR BRT. Whether or not, the significantly higher GTV dose can increase killing of radioresistant tumor cells and offset the effect of tumor reoxygenation in single fraction BRT, requires further clinical investigation.

Reoxygenation with 100% Oxygen Following Hypoxia in Mice Causes Apoptosis.

After hypoxia, reoxygenation with air is the consensus treatment for full-term neonates; however, the effect of hyperoxic reoxygenation of adults is unknown. The present study was designed to investigate the effects of reoxygenation with 100% oxygen after hypoxia on inflammation and apoptosis in mice. Eight-week-old mice were either subjected to hypoxia in 8% oxygen for 30 min or air served as controls. Following hypoxia, mice underwent reoxygenation for 30 min with 21% or 100% oxygen. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), caspase-3 and brain derived neurotrophic factor (BDNF) mRNA study and histopathological study were performed. Reoxygenation with 100% oxygen significantly increased TNF-α (2.5 h after hypoxia), IL-1β (5 h after hypoxia), caspase-3 (8 h after hypoxia) mRNA levels in the whole brain compared with 21% oxygen, and significantly decreased erythropoietin mRNA expression compared with 21% oxygen 9 h after reoxygenation. However, reoxygenation with 100% oxygen and 21% oxygen significantly decreased BDNF mRNA levels compared with control air group. There were no clear abnormal findings showing neuronal death among the three groups. Reoxygenation with 100% oxygen after hypoxia induced inflammation and apoptosis in adult mice. Therefore, these results suggest that the reoxygenation with 100% oxygen after hypoxia has harmful effects on adult brain as well as on neonatal brain.

Reoxygenation-Based Radiation Therapy Improve the Tumor Control

Reoxygenation has a deep impact on tumor control in fractionated radiotherapy. With the improvements in radiotherapy technology including IMRT and SRT, it has become much more important to understand the reoxygenation phenomenon clearly. Pulsed electron paramagnetic resonance imaging (EPRI) is a novel imaging method to directly monitor the pO2 in a tumor on a quantitative basis. The purpose of this work was to assess the reoxygenation-based radiation therapy detected by EPRI improve the tumor control using murine models of human cancer. HT29 solid tumors were formed by injecting 1 × 106 cells s.c. into the right hind legs of nude mice. The all experiments were started when tumors grew to approximately 800 mm3. In EPR imaging, it took 12 min to obtain a data set for a 3D pO2 image. The spatial resolution was 1.8 mm. First, we analyzed how irradiation dose affected the reoxygenation, and EPR imaging was performed before and at 30 minutes, 60 minutes, 2 hours, 18 hours, and 24 hours after 3Gy, 10 Gy, 20Gy irradiation in HT29 tumors (n = 6 per time point). Second, we analyzed the tumor control by additional 3Gy, 10 Gy, 20Gy irradiation at 30 minutes, 60 minutes, 2 hours, 18 hours, and 24 hours after 3Gy, 10 Gy, 20Gy irradiation in HT29 tumors (n = 6 per time point). Median pO2 of HT29 tumors was 15.9 ± 1.0 before irradiation, After 3 Gy, 10 Gy, and 20 Gy irradiation, it was, respectively, 15.4 ± 1.1, 14.1 ± 0.3, and 12.7 ± 1.5 at 30 minutes, 14.0 ± 1.0, 13.6 ± 1.0, and 11.8 ± 1.3 at 60 minutes, 15.3 ± 0.6, 13.7 ± 0.5, and 11.4 ± 0.8 at 2 hours, 15.2 ± 0.7, 13.6 ± 1.0, and 13.7 ± 0.5 at 18 hours, 15.4 ± 0.6, 13.6 ± 0.8, and 13.9 ± 0.6 at 24 hours. We could clearly show the phenomenon of reoxygenation after irradiation in HT29 tumors by using EPR pO2 imaging. The median pO2 decreased the most in about 60 minutes after 3Gy, 10 Gy, 20Gy irradiation and the median pO2 was recovered in 24 hours, but as the irradiation dose increased, it took more time to recover, and the median pO2 in 24 hours decreased as the irradiation dose increased. The tumor control by additional irradiation at 60 minutes was worst in additional irradiation at the other after initial 3Gy, 10 Gy, and 20Gy irradiation, and also the tumor control by additional irradiation at 24 hours was best in additional irradiation at the other after initial 3Gy, 10 Gy, and 20Gy irradiation. The difference in radiation response in 3Gy, 10 Gy, and 20Gy irradiation was consistent with the median pO2 of the HT-29 tumor. We could clearly show the phenomenon and effect of reoxygenation in HT29 tumors by using EPR pO2 imaging, and also indicated the possibility and importance of a new radiation therapy concept such as reoxygenation-based radiation therapy that improved the tumor control.

High-Dose-Rate Brachytherapy As Monotherapy for Prostate Cancer: A Meta-analysis of Biochemical Control Rates and Dose Fractionation

To analyze published biochemical control data for different fractionation schemes obtained using high-dose-rate brachytherapy as monotherapy for prostate cancer and to determine optimal dose per fraction by including the effect of intrafraction DNA repair. A meta-analysis was conducted on 31 studies, published between 2009-2017, which estimated biochemical control using Kaplan-Meier (KM) method for 3692 patients: 1413 low-risk (LR), 1161 intermediate-risk (IR), and 470 high risk (HR) (648 unspecified). In these studies, risk was classified using NCCN standards and biochemical control was defined using the Phoenix definition. We compared reported biochemical control as a function of biologically effective dose (BED) calculated using various methods. To account for intrafraction repair, BED was calculated with and without the Lea-Catcheside dose protraction factor for a range of source activities and dose rates. Clinical data suggests prostate cancer has a fast rate of repair which is on the same order of magnitude of delivery time, especially for single fractions. Biologically optimal dose per fraction for a given number of fractionation schemes was determined based on BED. Reported biochemical control rates were ≥ 85% for LR patients in nearly all studies, with the notable exception of a 1-fraction study with biochemical control rates of 66% at a KM projection of 6 years. Among the 31 studies, fractionations ranged from 1 to 9 fractions with BEDs of 180-299 Gy (α/β=1.5 Gy) and 108-167 Gy (α/β=3 Gy). BED was reduced by up to 31.9% (α/β=1.5 Gy) and 29.5% (α/β=3 Gy) for 1-fraction delivery when including corrections for intrafraction repair. The poor biochemical control seen with single fractions may be attributed to underestimating the effect of intrafraction repair. Table 1 shows calculated prescription doses required to match a BED of 207 Gy (α/β=1.5 Gy) including intrafraction repair for the 6x7 Gy scheme (biochemical control of 94% at 8 years). To achieve this BED, a 1-fraction delivery may require 21 (α/β=1.5 Gy) or 22.3 Gy (α/β=3 Gy). Prescription doses may need to be even higher for single fractions as the effects of tumor hypoxia and reoxygenation are neglected. In general, excellent clinical outcomes are achievable with HDR brachytherapy as monotherapy for prostate cancer patients – this study focused on LR. The relatively poor biochemical control rates observed for single fractions suggests multi-fraction HDR brachytherapy may be more clinically effective. If single fractions are used, cautious dose escalation should be considered to improve biochemical control.Abstract 3482# of FxClinically Used [Gy/Fx]Reported Biochemical Control Rates for Low-Risk (LR) Prostate Cancer PatientsRecommended Rx Doses [Gy/Fx]11966% @ 6 y21212-13.592% @ 5 y13.5310-11.585% @ 5 y10.548.5-9.594% @ 5 y966-7.594% @ 8 y776.5N/A [IR patients only]6.586N/A [IR patients only]69685% @ 5 y5.5 Open table in a new tab

Effects of Acute Hypoxia and Reoxygenation on Physiological and Immune Responses and Redox Balance of Wuchang Bream (Megalobrama amblycephala Yih, 1955).

To study Megalobrama amblycephala adaption to water hypoxia, the changes in physiological levels, innate immune responses, redox balance of M.amblycephala during hypoxia were investigated in the present study. When M. amblycephala were exposed to different dissolved oxygen (DO) including control (DO: 5.5 mg/L) and acute hypoxia (DO: 3.5 and 1.0 mg/L, respectively), hemoglobin (Hb), methemoglobin (MetHb), glucose, Na+, succinatedehydrogenase (SDH), lactate, interferon alpha (IFNα), and lysozyme (LYZ), except hepatic glycogen and albumin gradually increased with the decrease of DO level. When M. amblycephala were exposed to different hypoxia time including 0.5 and 6 h (DO: 3.5 mg/L), and then reoxygenation for 24 h after 6 h hypoxia, Hb, MetHb, glucose, lactate, and IFNα, except Na+, SDH, hepatic glycogen, albumin, and LYZ increased with the extension of hypoxia time, while the above investigated indexes (except albumin, IFNα, and LYZ) decreased after reoxygenation. On the other hand, the liver SOD, CAT, hydrogen peroxide (H2O2), and total ROS were all remained at lower levels under hypoxia stress. Finally, Hif-1α protein in the liver, spleen, and gill were increased with the decrease of oxygen concentration and prolongation of hypoxia time. Interestingly, one Hsp70 isoforms mediated by internal ribozyme entry site (IRES) named junior Hsp70 was only detected in liver, spleen and gill. Taken together, these results suggest that hypoxia affects M. amblycephala physiology and reduces liver oxidative stress. Hypoxia-reoxygenation stimulates M. amblycephala immune parameter expressions, while Hsp70 response to hypoxia is tissue-specific.

A radiobiological model of reoxygenation and fractionation effects.

The purpose of this study was to develop a radiobiological model of reoxygenation that fulfills the following goals: (a) Quantify the reoxygenation effect for different fractionations (b) Model the hypoxic fraction in tumors as a function of the number of radiation treatments. (c) Develop a simple analytical expression for a reoxygenation term in biological effect calculations. The model considers tumor cells in two compartments: an aerobic (or normoxic) population of cells and a hypoxic population including cells under a range of reduced oxygen concentrations. The surviving fraction is predicted using the linear-quadratic (LQ) model. A hypoxia reduction factor (HRF) is used to quantify reductions in radiosensitivity parameters αA and βA as cellular oxygen concentration decreases. The HRF is defined as the ratio of the dose at a specific level of hypoxia to the dose under fully aerobic conditions to achieve equal cell killing. The model assumes that a fraction of the hypoxic cells (Δ) moves from the hypoxic to the aerobic compartment after each daily fraction. As an example, we compare the effect of reoxygenation on biological response for a standard dose fractionation for nonsmall cell lung cancer (NSCLC) (d = 2 Gy, n = 33) to typical fractionations for stereotactic body radiotherapy (SBRT) and other nonstandard fractionations. The reoxygenation effect is parameterized for biological effect calculations and an analytic expression for the surviving fraction after n daily treatments is derived. The hypoxic fraction either increases or decreases with n depending on the reoxygenation parameter Δ. For certain combinations of parameters, the biological effect of reoxygenation goes as -(n-1) · ln(1-Δ) providing a simple expression that can be introduced in biologically effective dose (BED) calculations. The model is used to compare fractionation schedules and quantitatively interpret results from molecular imaging studies of hypoxia. Based on the comparison of conventional fractionation and hypo- and hyper-fractionation for NSCLC, the value of Δ is estimated to be between 0.1 and 0.2 assuming plausible radiobiological parameters from the literature. This value is consistent with the preliminary analysis of the molecular imaging studies. A novel radiobiological model was developed that can be used to evaluate the effect of reoxygenation in fractionated radiotherapy.

Identification of HIF-1 signaling pathway in Pelteobagrus vachelli using RNA-Seq: effects of acute hypoxia and reoxygenation on oxygen sensors, respiratory metabolism, and hematology indices.

Oxygen is a vital element in aquatic environments. The concentration of oxygen to which aquatic organisms are exposed is influenced by salinity, water temperature, weather, and surface water runoff. Hypoxia has a serious effect on fish populations, and can lead to the loss of habitat and die-offs. Therefore, in the present study we used next-generation sequencing technology to characterize the transcriptomes of Pelteobagrus vachelli and identified 70 candidate genes in the HIF-1 signaling pathway that are important for the hypoxic response in all metazoan species. For the first time, the present study reported the effects of acute hypoxia and reoxygenation on oxygen sensors, respiratory metabolism, and hematology indices in P. vachelli. The predicted physiological adjustments show that P. vachelli's blood oxygen-carrying capacity was increased through increased RBC, HB, and SI after hypoxia exposure. Glycolysis-related enzyme activities (PFK, HK, and PK) and LDH in the brain and liver also increased, indicating a rise in anaerobic metabolism. The observed reduction in oxidative enzyme level (CS) in the liver during hypoxia suggests a concomitant depression in aerobic metabolism. There were significant increases in oxygen sensor mRNA expression and HIF-1α protein expression during hypoxia and reoxygenation exposure, suggesting that the HIF-1 signaling pathway was activated in the liver and brain of P. vachelli in response to acute hypoxia and reoxygenation. Our findings suggest that oxygen sensors (e.g., HIF-1α) of P. vachelli are potentially useful biomarkers of environmental hypoxic exposure. These data contribute to a better understanding of the molecular mechanisms of the hypoxia signaling pathway in fish under hypoxia and reoxygenation.

Theoretical effectiveness of cell survival in fractionated radiotherapy with hypoxia-targeted dose escalation.

The goal of this article is to compute the cell survival during fractionated radiotherapy with non-uniform hypoxia-targeted dose distribution relative to cell survival for a uniform dose distribution with equal integral tumor dose. The analysis is performed for different parameters of radiotherapy with conventional and hypofractionated dose regimens. Our analysis is done using a parsimonious tumor response model that describes the major components of tumor response to radiotherapy such as radiosensitivity, cell proliferation, and hypoxia using as few variables as possible. Two levels of oxygenated and hypoxic cells with the survival curves described by the linear quadratic (LQ) model are implemented in the model. The model allows for analytical solutions for relative cell survival in a single fraction simulation which can be used for additional validation of our numerical simulations. The relative cell survival was computed for conventional and hypofractionated dose regimens in a model problem with radiobiological parameters for the non-small-cell lung cancer. Sensitivity of cell survival to different parameters of radiotherapy such as the relative volume of hypoxic fraction, boost dose ratio, re-oxygenation rate, and delivery errors was investigated. Our computational and analytical results show that relative cell survival for non-uniform and uniform dose distributions is larger than 1.0 during the first few fractions of radiotherapy with conventional fractionation. This indicates that the uniform dose distribution produces a higher cell killing effect for the equal integral dose. This may stem from domination of linear contribution to the cell killing effect seen in the dose range of 1-2 Gy and a steeper slope of survival curve in the oxygenated tumor region. This effect can only happen if the distribution of clonogens is nearly uniform; therefore, after the first few fractions, the non-uniform dose distributions outperform the uniform dose distribution and relative cell survival becomes less than 1.0. However, re-oxygenation and delivery errors can also reduce the effectiveness of hypoxia-targeted non-uniform dose distributions toward the end of treatment. For hypofractionated radiotherapy with fractional dose >3 Gy, the relative cell survival was always below 1.0, which means the non-uniform dose distributions produced higher cell killing effect than the uniform dose distribution during the entire treatment. The data obtained in this work suggest that non-uniform hypoxia-targeted dose distributions are less effective at cell killing than uniform dose distributions at the beginning of radiotherapy with conventional fractionation. However; non-uniform dose distributions can outperform uniform dose distribution by the end of the treatment if the effects of re-oxygenation and delivery errors are reduced. In hypofractionated radiotherapy, non-uniform hypoxia-targeted dose distributions are more efficient than uniform dose distributions during the entire treatment.