Normoxic Tissue Research Articles

Heterologous expression of NoxA confers aerotolerance in Clostridium sporogenes.

Clostridium is a genus of gram-positive obligate anaerobic bacteria. Some species of Clostridium, including Clostridium sporogenes, may be of use in bacteria-mediated cancer therapy. Spores of Clostridium are inert in healthy normoxic tissue but germinate when in the hypoxic regions of solid tumors, causing tumor regression. However, such treatments fail to completely eradicate tumors partly because of higher oxygen levels at the tumor's outer rim. In this study, we demonstrate that a degree of aerotolerance can be introduced to C. sporogenes by transfer of the noxA gene from Clostridium aminovalericum. NoxA is a water-forming NADH oxidase enzyme, and so has no detrimental effect on cell viability. In addition to its potential in cancer treatment, the noxA-expressing strain described here could be used to alleviate challenges related to oxygen sensitivity of C. sporogenes in biomanufacturing.

Evaluating Tumor Hypoxia Radiosensitization Via Electron Paramagnetic Resonance Oxygen Imaging (EPROI).

Tumor hypoxia contributes to aggressive phenotypes and diminished therapeutic responses to radiation therapy (RT) with hypoxic tissue being 3-fold less radiosensitive than normoxic tissue. A major challenge in implementing hypoxic radiosensitizers is the lack of a high-resolution imaging modality that directly quantifies tissue-oxygen. The electron paramagnetic resonance oxygen-imager (EPROI) was used to quantify tumor oxygenation in two murine tumor models: E0771 syngeneic transplant breast cancers and primary p53/MCA soft tissue sarcomas, with the latter autochthonous model better recapitulating the tumor microenvironment in human malignancies. We hypothesized that tumor hypoxia differs between these models. We also aimed to quantify the absolute change in tumor hypoxia induced by the mitochondrial inhibitor papaverine (PPV) and its effect on RT response. Tumor oxygenation was characterized in E0771 and primary p53/MCA sarcomas via EPROI, with the former model also being quantified indirectly via diffuse reflectance spectroscopy (DRS). After confirming PPV's effect on hypoxic fraction (via EPROI), we compared the effect of 0 versus 2 mg/kg PPV prior to 20 Gy on tumor growth delay and survival. Hypoxic sarcomas were more radioresistant than normoxic sarcomas (p=0.0057, 2-way ANOVA), and high baseline hypoxic fraction was a significant (p=0.0063, Cox Regression Model) hazard in survivability regardless of treatment. Pre-treatment with PPV before RT did not radiosensitize tumors in the sarcoma or E0771 model. In the sarcoma model, EPROI successfully identified baseline hypoxic tumors. DRS quantification of total hemoglobin, saturated hemoglobin, changes in mitochondrial potential and glucose uptake showed no significant difference in E0771 tumors pre- and post-PPV. EPROI provides 3D high-resolution pO2 quantification; EPR is better suited than DRS to characterize tumor hypoxia. PPV did not radiosensitize E0771 tumors nor p53/MCA sarcomas, which may be related to the complex pattern of vasculature in each tumor. Additionally, understanding model-dependent tumor hypoxia will provide a much-needed foundation for future therapeutic studies with hypoxic radiosensitizers.

The roles of brain lipids and polar metabolites in the hypoxia tolerance of deep-diving pinnipeds.

Lipids make up more than half of the human brain's dry weight, yet the composition and function of the brain lipidome is not well characterized. Lipids not only provide the structural basis of cell membranes, but also take part in a wide variety of biochemical processes. In neurodegenerative diseases, lipids can facilitate neuroprotection and serve as diagnostic biomarkers. The study of organisms adapted to extreme environments may prove particularly valuable in understanding mechanisms that protect against stressful conditions and prevent neurodegeneration. The brain of the hooded seal (Cystophora cristata) exhibits a remarkable tolerance to low tissue oxygen levels (hypoxia). While neurons of most terrestrial mammals suffer irreversible damage after only short periods of hypoxia, in vitro experiments show that neurons of the hooded seal display prolonged functional integrity even in severe hypoxia. How the brain lipidome contributes to the hypoxia tolerance of marine mammals has been poorly studied. We performed an untargeted lipidomics analysis, which revealed that lipid species are significantly modulated in marine mammals compared with non-diving mammals. Increased levels of sphingomyelin species may have important implications for efficient signal transduction in the seal brain. Substrate assays also revealed elevated normoxic tissue levels of glucose and lactate, which suggests an enhanced glycolytic capacity. Additionally, concentrations of the neurotransmitters glutamate and glutamine were decreased, which may indicate reduced excitatory synaptic signaling in marine mammals. Analysis of hypoxia-exposed brain tissue suggests that these represent constitutive mechanisms rather than an induced response towards hypoxic conditions.

A myocardial infarct border-zone-on-a-chip demonstrates distinct regulation of cardiac tissue function by an oxygen gradient

After a myocardial infarction, the boundary between the injured, hypoxic tissue and the adjacent viable, normoxic tissue, known as the border zone, is characterized by an oxygen gradient. Yet, the impact of an oxygen gradient on cardiac tissue function is poorly understood, largely due to limitations of existing experimental models. Here, we engineered a microphysiological system to controllably expose engineered cardiac tissue to an oxygen gradient that mimics the border zone and measured the effects of the gradient on electromechanical function and the transcriptome. The gradient delayed calcium release, reuptake, and propagation; decreased diastolic and peak systolic stress; and increased expression of inflammatory cascades that are hallmarks of myocardial infarction. These changes were distinct from those observed in tissues exposed to uniform normoxia or hypoxia, demonstrating distinct regulation of cardiac tissue phenotypes by an oxygen gradient. Our border-zone-on-a-chip model advances functional and mechanistic insight into oxygen-dependent cardiac tissue pathophysiology.

Spatial specific delivery of combinational chemotherapeutics to combat intratumoral heterogeneity.

Hypoxia-induced intratumoral heterogeneity poses a major challenge in tumor therapy due to the varying susceptibility to chemotherapy. Moreover, the spatial distribution patterns of hypoxic and normoxic tissues makes conventional combination therapy less effective. In this study, a tumor-acidity and bioorthogonal chemistry mediated in situ size transformable nanocarrier (NP@DOXDBCO plus iCPPAN3) was developed to spatially deliver two combinational chemotherapeutic drugs (doxorubicin (DOX) and PR104A) to combat hypoxia-induced intratumoral heterogeneity. DOX is highly toxic to tumor cells in normoxia state but less toxic in hypoxia state due to the hypoxia-induced chemoresistance. Meanwhile, PR104A is a hypoxia-activated prodrug has less toxic in normoxia state. Two nanocarriers, NP@DOXDBCO and iCPPAN3, can cross-link near the blood vessel extravasation sites through tumor acidity responsive bioorthogonal click chemistry to enhance the retention of DOX in tumor normoxia. Moreover, PR104A conjugated to the small-sized dendritic polyamidoamine (PAMAM) released under tumor acidity can penetrate deep tumor tissues for hypoxic tumor cell killing. Our study has demonstrated that this site-specific combination chemotherapy is better than the traditional combination chemotherapy. Therefore, spatial specific delivery of combinational therapeutics via in situ size transformable nanocarrier addresses the challenges of hypoxia induced intratumoral heterogeneity and provides insights into the combination therapy.

Development of a pO2-Guided Fine Needle Tumor Biopsy Device.

Tumor biopsies are an important aspect of oncology providing a guide for medical treatment and evaluation of disease progression. Highly heterogenous tumors have complex regions of active cancer cells interdigitated with necrotic tissue and healthy noncancerous tissue. The reliable access to tumor tissue pathology is therefore challenging and usually requires multiple needle insertions with accompanying patient discomfort and risk of infection. Oxygen levels provide a means of detecting and evaluating tumor tissue with levels reduced by 2-fold to 22-fold, depending on the type of organ. However, if the biopsy needle is placed in an area of normal tissue, there is always a chance that no diagnostic cells will be acquired for meaningful pathology and molecular analysis. While not the case in all tumors, there are cases where the in vivo oxygen levels differ with tumor cells having a value of pO2 lying between the anoxic necrotic tissue and normoxic normal tissue. The level of oxygen in tumor cells can also vary with time as related to complex biochemical pathways. The efficacy of radiation therapy is also sensitive to oxygen levels in tumors. Lower levels of oxygen present greater resistance to treatment. To address these concerns, a pO2-guided biopsy needle (OGBN) was developed to determine oxygen levels and fluctuations in highly resolved regions of tumors, in order to aide in determining the optimal region for cell sampling help in determining medical treatment options.

Exploring hypoxic biology to improve radiotherapy outcomes.

Ionising radiotherapy is a well-established, effective cancer treatment modality, whose efficacy has improved with the application of newer technological modalities. However, patient outcomes are governed and potentially limited by aspects of tumour biology that are associated with radioresistance. Patients also still endure treatment-associated toxicities owed to the action of ionising radiation in normoxic tissue adjacent to the tumour mass. Tumour hypoxia is recognised as a key component of the tumour microenvironment and is well established as leading to therapy resistance and poor prognosis. In this review, we outline the current understanding of hypoxia-mediated radiotherapy resistance, before exploring targeting tumour hypoxia for radiotherapy sensitisation to improve treatment outcomes and increase the therapeutic window. This includes increasing oxygen availability in solid tumours, the use of hypoxia-activated prodrugs, targeting of hypoxia-regulated or associated signalling pathways, as well as the use of high-LET radiotherapy modalities. Ultimately, targeting hypoxic radiobiology combined with precise radiotherapy delivery modalities and modelling should be associated with improvement to patient outcomes.

Conditioned CAR-T cells by hypoxia-inducible transcription amplification (HiTA) system significantly enhances systemic safety and retains antitumor efficacy

BackgroundHypoxia is a striking feature of most solid tumors and could be used to discriminate tumors from normoxic tissues. Therefore, the design of hypoxia-conditioned Chimeric Antigen Receptor (CAR) T cells...

Evaluation of cobalt(III) complexes as potential hypoxia-responsive carriers of esculetin

Differentiation between hypoxic and normoxic tissues have been exploited for the development of selective chemotherapeutic agents. In this context, cobalt(III)-based coordination compounds have been designed and investigated as prospective hypoxia-responsive drug delivery systems. Three cobalt(III) complexes, namely [CoIII(esc)(py2en)]ClO4·(CH3OH)2 (1) [CoIII(esc)(TPA)]ClO4·3H2O (2) and [CoIII(bipy)2(esc)]ClO4·2.5H2O (3) (py2en = N,N′-bis(pyridin-2-ylmethyl)ethylenediamine, TPA = tris(2-pyridylmethyl)amine, bipy = 2,2′-bipyridine and esc = 6,7-dihydroxycoumarin or esculetin), were prepared and investigated as potential carriers of esculetin. The spectroscopic and electrochemical properties of 1–3 were investigated and compared. Reactions of the complexes with biologically relevant reducing agents, viz. ascorbic acid, cysteine and glutathione, were monitored spectroscopically for 24 h, in pH 6.2 and 7.4 PBS phosphate buffer saline (PBS) solutions at 37 °C, under air, argon and dioxygen atmospheres. Dissociation of esculetin was observed upon Co3+/Co2+ reduction preferably under hypoxic conditions, with more effective conversion rates for 3 > 2 > 1. These results illustrate the importance to modulate the Co3+/Co2+ redox potential through the donor-acceptor properties of the ancillary ligands. Complex 3 is cytotoxic against HCT-116 but not against HT-29 and HEK-293 cells. In addition, DNA-binding studies indicate that interactions of 1 and 3 with the biomolecule are electrostatic.

A physicochemical model of reaction kinetics supports peroxyl radical recombination as the main determinant of the FLASH effect

Background and purposeFLASH radiotherapy, a technique based on delivering large doses in a single fraction at the micro/millisecond timescale, spares normal tissues from late radiation-induced toxicity, in an oxygen-dependent process, whilst keeping full anti-tumor efficiency. We present a theoretical model taking into account the kinetics of formation and decay of reactive oxygen species, in particular of organic peroxyl radicals ROO. formed by addition of O2 to primary carbon-centred radicals R. and known to play a major role at the origin radio-induced complications. Materials and methodsThe model focuses on the time-dependent evolution of radiolytic products in living matter exposed to continuous irradiation at dose-rates in the range 10-3-107Gy·s-1. The 9 differential rate equations resulting from the radiolytic and enzymatic reactions network were solved using the published values of these reactions rate constants in a cellular environment. ResultsThe model suggests a correlation between the area-under-the-curve of time-evolving [ROO.] and the probability of normal tissue complications. The model does not lend weight to the hypothesis of transient oxygen depletion as a main determinant of FLASH but rather suggests a major role of radical–radical recombination. ConclusionThe model gives support to the reduction of ROO. lifetime as the main root of FLASH and compares favorably with published experimental results. We conclude that any process - in this case radical recombination - that shortens the lifetime or limits the radiolytic yield of ROO. is likely to protect normoxic tissues against the deleterious effects of radiation.

Hypoxia PET imaging beyond 18F-FMISO in patients with high-grade glioma: 18F-FAZA and other hypoxia radiotracers

High-grade gliomas are aggressive primitive brain tumors presenting aberrant vasculature, regional necrosis, and areas of hypoxia. Tumor hypoxia is associated with resistance to conventional treatment and worse prognosis. [18F]-fluoromisonidazole (18F-FMISO) is the most extensively investigated radiotracer for the evaluation of hypoxia. However, the use of 18F-FMISO in clinical practice has been hampered mainly due to the slow clearance of the unbound tracer from normoxic tissue and its low tumor-to-background ratio (TBR). The research community has therefore investigated other radiotracers to overcome the drawbacks of 18F-FMISO. This mini-review aims to present an update on the most relevant PET studies published in the last 15 years evaluating the utility of radiotracers for hypoxia imaging other than 18F-FMISO in high-grade glioma (HGG) patients. A comprehensive computer literature search of studies was carried out in PubMed/MEDLINE database to identify the most relevant studies published in the last 15 years which investigated the utility of hypoxia PET tracers other than 18F-FMISO in the assessment of tumor hypoxia in patients with HGG. 18F-flouroazomycin arabinoside (18F-FAZA) has been proposed as a valid alternative to 18F-FMISO for the assessment of hypoxia, due to its improved biodistribution and enhanced tumor-to-background ratio. Also 1-(2-[18F]fluoro-1[hydroxymethyl]ethoxy)methyl-2-nitroimidazole(18F-FRP170) seems a valuable hypoxia tracer in patients with brain tumor. The value of copper-diacetyl-bis(N4-methylthiosemicarbazone)(Cu-ATSM) seems controversial. Few evidences still exist regarding the utility of 18F-2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)-acetamide (18F-EF5). Hypoxia PET imaging has the potential to provide useful information for the clinicians and to guide hypoxia tailored treatments. According to the present literature, the most promising hypoxic tracer seems to be 18F-FAZA, but well-designed and wide trials to validate hypoxia radiotracers and evaluate their clinical utility in daily practice are still lacking.

Clinical and Pre-clinical Methods for Quantifying Tumor Hypoxia.

Hypoxia, a prevalent characteristic of most solid malignant tumors, contributes to diminished therapeutic responses and more aggressive phenotypes. The term hypoxia has two definitions. One definition would be a physiologic state where the oxygen partial pressure is below the normal physiologic range. For most normal tissues, the normal physiologic range is between 10 and 20mmHg. Hypoxic regions develop when there is an imbalance between oxygen supply and demand. The impact of hypoxia on cancer therapeutics is significant: hypoxic tissue is 3× less radiosensitive than normoxic tissue, the impaired blood flow found in hypoxic tumor regions influences chemotherapy delivery, and the immune system is dependent on oxygen for functionality. Despite the clinical implications of hypoxia, there is not a universal, ideal method for quantifying hypoxia, particularly cycling hypoxia because of its complexity and heterogeneity across tumor types and individuals. Most standard imaging techniques can be modified and applied to measuring hypoxia and quantifying its effects; however, the benefits and challenges of each imaging modality makes imaging hypoxia case-dependent. In this chapter, a comprehensive overview of the preclinical and clinical methods for quantifying hypoxia is presented along with the advantages and disadvantages of each.

Oxygen microbubbles improve radiotherapy tumor control in a rat fibrosarcoma model - A preliminary study.

Cancer affects 39.6% of Americans at some point during their lifetime. Solid tumor microenvironments are characterized by a disorganized, leaky vasculature that promotes regions of low oxygenation (hypoxia). Tumor hypoxia is a key predictor of poor treatment outcome for all radiotherapy (RT), chemotherapy and surgery procedures, and is a hallmark of metastatic potential. In particular, the radiation therapy dose needed to achieve the same tumor control probability in hypoxic tissue as in normoxic tissue can be up to 3 times higher. Even very small tumors (<2–3 mm3) comprise 10–30% of hypoxic regions in the form of chronic and/or transient hypoxia fluctuating over the course of seconds to days. We investigate the potential of recently developed lipid-stabilized oxygen microbubbles (OMBs) to improve the therapeutic ratio of RT. OMBs, but not nitrogen microbubbles (NMBs), are shown to significantly increase dissolved oxygen content when added to water in vitro and increase tumor oxygen levels in vivo in a rat fibrosarcoma model. Tumor control is significantly improved with OMB but not NMB intra-tumoral injections immediately prior to RT treatment and effect size is shown to depend on initial tumor volume on RT treatment day, as expected.

Fluorine-18 radiolabeling of a nitrophenyl sulfoxide and its evaluation in an SK-RC-52 model of tumor hypoxia.

The significance of imaging hypoxia with the positron emission tomography ligand [(18) F]FMISO has been demonstrated in a variety of cancers. However, the slow kinetics of [(18) F]FMISO require a 2-h delay between tracer administration and patient scanning. Labeled chloroethyl sulfoxides have shown faster kinetics and higher contrast than [(18) F]FMISO in a rat model of ischemic stroke. However, these nitrogen mustard analogues are unsuitable for routine production and use in humans. Here, we report on the synthesis and in vitro and in vivo evaluation of a novel sulfoxide, which contains an ester moiety for hydrolysis and subsequent trapping in hypoxic cells. Non-decay corrected yields of radioactivity were 1.18 ± 0.24% (n = 27, 2.5 ± 0.5% decay corrected radiochemical yield) based on K[(18) F]F. The radiotracer did not show any defluorination and did not undergo metabolism in an in vitro assay using S9 liver fractions. Imaging studies using an SK-RC-52 tumor model in BALB/c nude mice have revealed that [(18) F]1 is retained in hypoxic tumors and has similar hypoxia selectivity to [(18) F]FMISO. Because of a three times faster clearance rate than [(18) F]FMISO from normoxic tissue, [(18) F]1 has emerged as a promising new radiotracer for hypoxia imaging.

Abstract 2790: Sensitizing the hypoxic tumor microenvironment with OMX, a breakthrough oxygen delivery protein: From protein engineering to clinical trial

Abstract Hypoxia, or lack of oxygen, is a key modulator of the tumor microenvironment and is associated with immunosuppression, invasiveness, angiogenesis, radiotherapy resistance and poor patient outcomes. Methods to increase oxygen in the hypoxic tumor niche have failed due to the long distance oxygen must diffuse from dysfunctional vasculature to the hypoxic cells. To address this problem, we engineered OMX oxygen carriers that bind oxygen with high affinity and can specifically deliver oxygen to severely hypoxic tumor regions without afecting normoxic tissues. Here, we show that OMX extravasates through leaky tumor vasculature, penetrates into and delivers oxygen to hypoxic tumor tissue. This reduces hypoxia in the tumor microenvironment and sensitizes tumors to therapy. Specifically, OMX accumulation in tumors leads to an increase in tumor oxygenation in mouse human xenograft and immunocompetent rat orthotopic models, as assessed by direct oxygen measurement (oxygen probe), by18F-FMISO PET in vivo imaging and by IHC and ELISA assessment of hypoxia markers (pimonidazole, CAIX, CCI, HIF-1). Moreover, OMX-mediated tumor oxygenation increases efficacy of radiation therapy as demonstrated by ex-vivo clonogenic assay and tumor growth delay. Importantly, while radiation alone only moderately delays tumor growth, combination of OMX and radiation therapy leads to tumor eradication in &amp;gt;50% of tumors. In addition to the enhancement of radiation therapy with OMX, we are currently exploring the capacity of OMX to ameliorate immunosuppressive microenvironment caused by hypoxia. Results from a Phase 0 clinical trial in canine cancer patients indicate that OMX is well tolerated and safe to use in combination with standard of care radiation therapy even in aged and fragile canine patient populations. Similar to rodent tumor models, OMX penetrates the tumor tissue in spontaneous canine brain and melanoma tumors. Furthermore, OMX accumulation correlates with reduced hypoxia in the tumor microenvironment as assessed by multiple hypoxia markers using quantitative IHC and ELISA. Taken together, these preclinical safety and efficacy data in both rodents and canines strongly support our IND submission to initiate human clinical trials in newly diagnosed glioblastoma patients. Results from completed and ongoing studies support the potential of OMX as modulator of hypoxic tumor microenvironment that may significantly impact the effectiveness of radiotherapy, chemotherapy and immunotherapy in a variety of solid tumors where hypoxia is major contributor to therapeutic resistance. Citation Format: Ana Krtolica, Natacha Le Moan, Philberta Leung, Youngho Seo, Jonathan Winger, Henry Van Brocklin, Michael Kent, Stephen Cary. Sensitizing the hypoxic tumor microenvironment with OMX, a breakthrough oxygen delivery protein: From protein engineering to clinical trial. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2790.

Normobaric hyperoxia retards the evolution of ischemic brain tissue toward infarction in a rat model of transient focal cerebral ischemia

Objectives: Oxygen therapy has been long considered a logical therapy for ischemic stroke. Our previous studies showed that normobaric hyperoxia (normobaric hyperoxia (NBO), 95% O2 with 5% CO2) treatment during ischemia reduced ischemic neuronal death and cerebromicrovascular injury in animal stroke models. In this study, we studied the effects of NBO on the evolution of ischemic brain tissue to infarction in a rat model of transient focal cerebral ischemia.Methods: Male Sprague-Dawley rats were given NBO (95% O2) or normoxia (21% O2) during 90-min filament occlusion of the middle cerebral artery (MCAO), followed by 3 or 22.5 h of reperfusion. 2,3,5-triphenyltetrazolium chloride (TTC) staining was used to evaluate the longitudinal evolution of tissue infarction.Results： In normoxic rats, MCA-supplied cortical and striatal tissue was infarcted after 90-min MCAO with 22.5 h of reperfusion. NBO-treated rats showed a 61.4% reduction in infarct size and tissue infarction mainly occurred in the ischemic striatum. When infarction was assessed at an earlier time point, i.e. at 3 h of reperfusion, normoxic rats showed significantly smaller but mature infarction (no TTC staining, white color), with the infarction mainly occurring in the striatum. Unexpectedly, NBO-treated rats only showed immature lesion (partially stained by TTC, light white color) in the ischemic striatum, indicating that NBO treatment also retarded the process of neuronal death in the ischemic core. Of note, NBO-preserved striatal tissue underwent infarction after prolonged reperfusion.Conclusions： Our results demonstrate that NBO treatment given during cerebral ischemia retards the evolution of ischemic brain tissue toward infarction and NBO-preserved cortical tissue survives better than NBO-preserved striatal tissue during the phase of reperfusion.

Oxygen sensing in intestinal mucosal inflammation.

Hypoxia is a hallmark of chronically inflamed tissue. Hypoxia develops from vascular dysfunction and increased oxygen consumption by infiltrating leukocytes. With respect to inflammatory bowel disease (IBD), hypoxia is likely to be of particular importance: Impairment of the intestinal barrier during IBD allows anoxia from the lumen of the gut to spread to formerly normoxic tissue. In addition, disturbed perfusion of inflamed tissue and a higher oxygen demand of infiltrating immune cells lead to low oxygen levels in inflamed mucosal tissue. Here, cells become hypoxic and must now adapt to this condition. The hypoxia inducible factor (HIF)-1 complex is a key transcription factor for cellular adaption to low oxygen tension. HIF-1 is a heterodimer formed by two subunits: HIF-α (either HIF-1α or HIF-2α) and HIF-1β. Under normoxic conditions, hydroxylation of the HIF-α subunit by specific oxygen-dependent prolyl hydroxylases (PHDs) leads to ubiquitin proteasome-dependent degradation. Under hypoxic conditions, however, PHD activity is inhibited; thus, HIF-α can translocate into the nucleus, dimerize with HIF-1β, and bind to hypoxia-responsive elements of HIF-1 target genes. So far, most studies have addressed the function of HIF-1α in intestinal epithelial cells and the effect of HIF stabilization by PHD inhibitors in murine models of colitis. Furthermore, the role of HIF-1α in immune cells becomes more and more important as T cells or dendritic cells for which HIF-1 is of critical importance are highly involved in the pathogenesis of IBD. This review will summarize the function of HIF-1α and the therapeutic prospects for targeting the HIF pathway in intestinal mucosal inflammation.

18F-Fluoromisonidazole Quantification of Hypoxia in Human Cancer Patients Using Image-Derived Blood Surrogate Tissue Reference Regions.

(18)F-fluoromisonidazole ((18)F-FMISO) is the most widely used PET agent for imaging hypoxia, a condition associated with resistance to tumor therapy. (18)F-FMISO equilibrates in normoxic tissues but is retained under hypoxic conditions because of reduction and binding to macromolecules. A simple tissue-to-blood (TB) ratio is suitable for quantifying hypoxia. A TB ratio threshold of 1.2 or greater is useful in discriminating the hypoxic volume (HV) of tissue; TBmax is the maximum intensity of the hypoxic region and does not invoke a threshold. Because elimination of blood sampling would simplify clinical use, we tested the validity of using imaging regions as a surrogate for blood sampling. Patients underwent 20-min (18)F-FMISO scanning during the 90- to 140-min interval after injection with venous blood sampling. Two hundred twenty-three (18)F-FMISO patient studies had detectable surrogate blood regions in the field of view. Quantitative parameters of hypoxia (TBmax, HV) derived from blood samples were compared with values using surrogate blood regions derived from the heart, aorta, or cerebellum. In a subset of brain cancer patients, parameters from blood samples and from the cerebellum were compared for their ability to independently predict outcome. Vascular regions of heart showed the highest correlation to measured blood activity (R(2) = 0.84). For brain studies, cerebellar activity was similarly correlated to blood samples. In brain cancer patients, Kaplan-Meier analysis showed that image-derived reference regions had predictive power nearly identical to parameters derived from blood, thus obviating the need for venous sampling in these patients. Simple static analysis of (18)F-FMISO PET captures both the intensity (TBmax) and the spatial extent (HV) of tumor hypoxia. An image-derived region to assess blood activity can be used as a surrogate for blood sampling in quantification of hypoxia.

Arundo donax L. response to low oxygen stress

Production of nonfood species is promoted to marginal, degraded lands abandoned by mainstream agricultural, where extremes in water availability (droughts and floods) have increased frequency and intensity and account for severe reductions in yields. A metabolic analysis of anoxic and hypoxic stress response was performed in a time-course experiment on Arundo donax L., a perennial rhizomatous grass identified as a leading candidate crop for lignocellulosic feedstock in the Mediterranean environment, due to its positive energy balance, and low ecological/agro-management demands. Tolerance to oxygen deprivation was determined after reoxygenation. Giant reed displayed time-dependent reduction in absolute growth and alterations in the derived physiological attributes under low oxygen stress. Our results show that although giant reed's responses to anoxic and hypoxic treatments share a common energy crisis related to the anaerobic metabolism, they differ in terms of ADH activity and related gene response. In leaves and roots tissues, the expression of this anaerobic gene was strongly enhanced under anoxia, whereas the ADH expression under submergence condition was relatively low. The activity profiles of ADH were not completely reflected in the expression patterns in either tissue. A high basal activity of the enzyme was recorded in both leaves and roots in normoxic tissues. In leaves, the treatments did not significantly affect ADH activity, remaining relatively stables at low levels during the time-course experiment. A different pattern of ADH was observed in roots, with a stronger, albeit transient, induction in both oxygen deficiency treatments.

NPY ő a regulator of hypoxic cerebrovascular remodeling in fetal lambs (853.4)

Prenatal, intra‐partum or post partum exposure of a fetus to hypoxia results in structural and functional changes in cerebral arteries, known as remodeling. Sympathetic nerves have been suggested to contribute to this process. Whereas NE is suggested as the major mediator of adrenergic effects, our preliminary experiments show that there is a guanethidine‐resistant (norepinephrine‐independent) component. This study explores the hypothesis that NPY contributes to hypoxic cerebrovascular remodeling in the fetal cerebral circulation. Chronic hypoxia (CH) produced a 254% ↑ in K‐induced tone and a 30% ↓ in stretch‐induced myogenic tone in fresh nerve‐intact fetal cerebral arteries. CH also increased the magnitude of nerve stimulation induced guanethidine‐resistant contractile tone. Immunohistochemistry revealed that CH significantly ↑ cerebrovascular NPY whereas sympathectomy (SANX) ablated this effect. Likewise, Western blot quantification of NPY‐Y1 receptors revealed that CH increased Y1 receptors 73%. Whereas SANX in normoxic tissues had no significant effect, SANX produced a 30% ↓ in Y1 receptors in hypoxic arteries. Together these results suggest that NPY released from sympathetic cerebrovascular nerves contributes to hypoxic remodeling through increased NPY content/release and Y1 receptor density.Grant Funding Source: Supported by NIH Grants HD‐31266 and NS‐076945