AICAR confers prophylactic cardioprotection in doxorubicin-induced heart failure in rats.

Doxorubicin (DOX) is a widely used chemotherapeutic agent that can cause serious cardiotoxic side effects, leading to heart failure (HF). Impaired mitochondrial function is thought to be key factor driving progression into HF. We have previously shown in a rat model of DOX-HF that heart failure with reduced ejection fraction correlates with mitochondrial loss and dysfunction. Adenosine monophosphate-dependent kinase (AMPK) is a cellular energy sensor, regulating mitochondrial biogenesis and energy metabolism, including fatty acid oxidation. We hypothesised that AMPK activation could restore mitochondrial function and therefore be a novel cardioprotective strategy for the prevention of DOX-HF. Consequently, we set out to assess whether 5-aminoimidazole-4-carboxamide 1-ß-D-ribofuranoside (AICAR), an activator of AMPK, could prevent cardiac functional decline in this chronic intravenous rat model of DOX-HF. In line with our hypothesis, AICAR improved cardiac systolic function. AICAR furthermore improved cardiac mitochondrial fatty acid oxidation, independent of mitochondrial number, and in the absence of observable AMPK-activation. In addition, we found that AICAR prevented loss of myocardial mass. RNAseq analysis showed that this may be driven by normalisation of pathways associated with ribosome function and protein synthesis, which are impaired in DOX-treated rat hearts. AICAR furthermore prevented dyslipidemia and excessive body-weight loss in DOX-treated rats, which may contribute to preservation of myocardial mass. Though it is unclear whether AICAR exerted its cardioprotective effect through cardiac or extra-cardiac AMPK-activation or via an AMPK-independent effect, these results show promise for the use of AICAR as a cardioprotective agent in DOX-HF to both preserve cardiac function and mass.

The effect of sodium-glucose cotransporter-2 inhibitors on inflammatory biomarkers: A meta-analysis of randomized controlled trials.

AIMS: To conduct a meta-analysis of randomized controlled trials (RCTs) to assess the effect of sodium-glucose cotransporter-2 (SGLT2) inhibitors on inflammatory biomarkers. METHODS: Medline, Embase and the Cochrane Library were searched for RCTs investigating the effect of SGLT2 inhibitors on inflammatory biomarkers, adipokine profiles and insulin sensitivity. RESULTS: Thirty-eight RCTs were included (14 967 participants, 63.3% male, mean age 62 ± 8.6 years) with a median (interquartile range) follow-up of 16 (12-24) weeks. Meta-analysis showed that SGLT2 inhibitors significantly improved adiponectin, interleukin-6, tumour necrosis factor receptor-1 (vs. placebo alone: standardized mean difference [SMD] 0.34 [95% confidence interval {CI} 0.23, 0.45], mean difference [MD] -0.85 pg/mL [95% CI -1.32, -0.38], SMD -0.13 [95% CI -0.20, -0.06], respectively), leptin and homeostatic model assessment of insulin resistance index (vs. CONTROL: SMD -0.20 [95% CI -0.33, -0.07], MD -0.83 [95% CI -1.32, -0.33], respectively). There were no significant changes in C-reactive protein (CRP), tumour necrosis factor-α, plasminogen activator inhibitor-1, fibroblast growth factor-21 or monocyte chemoattractant protein-1. CONCLUSIONS: Our analysis shows that SGLT2 inhibitors likely improve adipokine biomarkers and insulin sensitivity, but there is little evidence that SGLT2 inhibitors improve other inflammatory biomarkers including CRP.

A new method for investigating osteoarthritis using Fast Field-Cycling nuclear magnetic resonance.

Osteoarthritis in synovial joints remains a major cause of long-term disability worldwide, with symptoms produced by the progressive deterioration of the articular cartilage. The earliest cartilage changes are thought to be alteration in its main protein components, namely proteoglycan and collagen. Loss of proteoglycans bound in the collagen matrix which maintain hydration and stiffness of the structure is followed by collagen degradation and loss. The development of new treatments for early osteoarthritis is limited by the lack of accurate biomarkers to assess the loss of proteoglycan. One potential biomarker is magnetic resonance imaging (MRI). We present the results of a novel MRI methodology, Fast Field-Cycling (FFC), to assess changes in critical proteins by demonstrating clear quantifiable differences in signal from normal and osteoarthritic human cartilage for in vitro measurements. We further tested proteoglycan extracted cartilage and the key components individually. Three clear signals were identified, two of which are related predominantly to the collagen component of cartilage and the third, a unique very short-lived signal, is directly related to proteoglycan content; we have not seen this in any other tissue type. In addition, we present the first volunteer human scan from our whole-body FFC scanner where articular cartilage measurements are in keeping with those we have shown in tissue samples. This new clinical imaging modality offers the prospect of non-invasive monitoring of human cartilage in vivo and hence the assessment of potential treatments for osteoarthritis. Keywords: Fast Field-Cycling NMR; human hyaline cartilage; Osteoarthritis; T1 dispersion; quadrupolar peaks; protein interactions.

Assessing Oxidative Stress in Tumors by Measuring the Rate of Hyperpolarized [1-13C]Dehydroascorbic Acid Reduction Using 13C Magnetic Resonance Spectroscopy.

Rapid cancer cell proliferation promotes the production of reducing equivalents, which counteract the effects of relatively high levels of reactive oxygen species. Reactive oxygen species levels increase in response to chemotherapy and cell death, whereas an increase in antioxidant capacity can confer resistance to chemotherapy and is associated with an aggressive tumor phenotype. The pentose phosphate pathway is a major site of NADPH production in the cell, which is used to maintain the main intracellular antioxidant, glutathione, in its reduced state. Previous studies have shown that the rate of hyperpolarized [1-13C]dehydroascorbic acid (DHA) reduction, which can be measured in vivo using non-invasive 13C magnetic resonance spectroscopic imaging, is increased in tumors and that this is correlated with the levels of reduced glutathione. We show here that the rate of hyperpolarized [1-13C]DHA reduction is increased in tumors that have been oxidatively prestressed by depleting the glutathione pool by buthionine sulfoximine treatment. This increase was associated with a corresponding increase in pentose phosphate pathway flux, assessed using 13C-labeled glucose, and an increase in glutaredoxin activity, which catalyzes the glutathione-dependent reduction of DHA. These results show that the rate of DHA reduction depends not only on the level of reduced glutathione, but also on the rate of NADPH production, contradicting the conclusions of some previous studies. Hyperpolarized [1-13C]DHA can be used, therefore, to assess the capacity of tumor cells to resist oxidative stress in vivo However, DHA administration resulted in transient respiratory arrest and cardiac depression, which may prevent translation to the clinic.

Imaging Tumor Metabolism to Assess Disease Progression and Treatment Response.

Changes in tumor metabolism may accompany disease progression and can occur following treatment, often before there are changes in tumor size. We focus here on imaging methods that can be used to image various aspects of tumor metabolism, with an emphasis on methods that can be used for tumor grading, assessing disease progression, and monitoring treatment response. Clin Cancer Res; 22(21); 5196-203. ©2016 AACR.

Effects of fasting on serial measurements of hyperpolarized [1-(13) C]pyruvate metabolism in tumors.

Imaging of the metabolism of hyperpolarized [1-(13) C]pyruvate has shown considerable promise in preclinical studies in oncology, particularly for the assessment of early treatment response. The repeatability of measurements of (13) C label exchange between pyruvate and lactate was determined in a murine lymphoma model in fasted and non-fasted animals. The fasted state showed lower intra-individual variability, although the [1-(13) C]lactate/[1-(13) C]pyruvate signal ratio was significantly greater in fasted than in non-fasted mice, which may be explained by the higher tumor lactate concentrations in fasted animals. These results indicate that the fasted state may be preferable for the measurement of (13) C label exchange between pyruvate and lactate, as it reduces the variability and therefore should make it easier to detect the effects of therapy. © 2016 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.

(13) C magnetic resonance spectroscopy measurements with hyperpolarized [1-(13) C] pyruvate can be used to detect the expression of transgenic pyruvate decarboxylase activity in vivo.

PURPOSE: Dissolution dynamic nuclear polarization can increase the sensitivity of the (13) C magnetic resonance spectroscopy experiment by at least four orders of magnitude and offers a novel approach to the development of MRI gene reporters based on enzymes that metabolize (13) C-labeled tracers. We describe here a gene reporter based on the enzyme pyruvate decarboxylase (EC 4.1.1.1), which catalyzes the decarboxylation of pyruvate to produce acetaldehyde and carbon dioxide. METHODS: Pyruvate decarboxylase from Zymomonas mobilis (zmPDC) and a mutant that lacked enzyme activity were expressed using an inducible promoter in human embryonic kidney (HEK293T) cells. Enzyme activity was measured in the cells and in xenografts derived from the cells using (13) C MRS measurements of the conversion of hyperpolarized [1-(13) C] pyruvate to H(13) CO3-. RESULTS: Induction of zmPDC expression in the cells and in the xenografts derived from them resulted in an approximately two-fold increase in the H(13) CO3-/[1-(13) C] pyruvate signal ratio following intravenous injection of hyperpolarized [1-(13) C] pyruvate. CONCLUSION: We have demonstrated the feasibility of using zmPDC as an in vivo reporter gene for use with hyperpolarized (13) C MRS. Magn Reson Med 76:391-401, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Magnetic resonance imaging of tumor glycolysis using hyperpolarized 13C-labeled glucose.

In this study, we monitored glycolysis in mouse lymphoma and lung tumors by measuring the conversion of hyperpolarized [U-2H, U-13C]glucose to lactate using 13C magnetic resonance spectroscopy and spectroscopic imaging. We observed labeled lactate only in tumors and not in surrounding normal tissue or other tissues in the body and found that it was markedly decreased at 24 h after treatment with a chemotherapeutic drug. We also detected an increase in a resonance assigned to 6-phosphogluconate in the pentose phosphate pathway. This technique could provide a new way of detecting early evidence of tumor treatment response in the clinic and of monitoring tumor pentose phosphate pathway activity.

Spin echo measurements of the extravasation and tumor cell uptake of hyperpolarized [1-(13) C]lactate and [1-(13) C]pyruvate.

PURPOSE: To assess the blood-tissue distribution of hyperpolarized (13) C-labeled molecules in vivo. METHODS: Spin-echo experiments with simultaneous acquisition of the free induction decay (FID) signal following the excitation pulse and the spin-echo signal, were used to monitor hyperpolarized [1-(13) C]lactate, [1-(13) C]pyruvate, and the perfusion marker, [(13) C]HP001, following their intravenous injection into tumor-bearing mice. Apparent T2 relaxation times and diffusion coefficients were also measured. RESULTS: An increasing tumor echo/FID ratio was observed for all three molecules, which could be explained by their extravasation into the tumor interstitial space, where T2 relaxation times were longer and diffusion coefficients smaller. Inhibition of the monocarboxylate transporter, which decreased by 40% the label exchange between pyruvate and lactate, reduced the increase in the echo/FID ratio for pyruvate and lactate, but not for HP001, demonstrating that some of the increase in the echo/FID ratio was due to cell uptake of lactate and pyruvate. The different relaxation and diffusion behavior of the intravascular and extravascular signals affected measurements of the apparent label exchange rate constants. CONCLUSION: Simultaneous collection of both FID and echo signals can provide information on cell uptake thus giving further insight into the kinetics of hyperpolarized (13) C label exchange. Care is needed when comparing exchange rate constants determined in spin-echo-based studies.

Magnetic resonance imaging with hyperpolarized [1,4-(13)C2]fumarate allows detection of early renal acute tubular necrosis.

Acute kidney injury (AKI) is a common and important medical problem, affecting 10% of hospitalized patients, and it is associated with significant morbidity and mortality. The most frequent cause of AKI is acute tubular necrosis (ATN). Current imaging techniques and biomarkers do not allow ATN to be reliably differentiated from important differential diagnoses, such as acute glomerulonephritis (GN). We investigated whether (13)C magnetic resonance spectroscopic imaging (MRSI) might allow the noninvasive diagnosis of ATN. (13)C MRSI of hyperpolarized [1,4-(13)C(2)]fumarate and pyruvate was used in murine models of ATN and acute GN (NZM2410 mice with lupus nephritis). A significant increase in [1,4-(13)C(2)]malate signal was identified in the kidneys of mice with ATN early in the disease course before the onset of severe histological changes. No such increase in renal [1,4-(13)C(2)]malate was observed in mice with acute GN. The kidney [1-(13)C]pyruvate/[1-(13)C]lactate ratio showed substantial variability and was not significantly decreased in animals with ATN or increased in animals with GN. In conclusion, MRSI of hyperpolarized [1,4-(13)C(2)]fumarate allows the detection of early tubular necrosis and its distinction from glomerular inflammation in murine models. This technique may have the potential to identify a window of therapeutic opportunity in which emerging therapies might be applied to patients with ATN, reducing the need for acute dialysis with its attendant morbidity and cost.

Probing lactate dehydrogenase activity in tumors by measuring hydrogen/deuterium exchange in hyperpolarized l-[1-(13)C,U-(2)H]lactate.

(13)C magnetic resonance spectroscopy and spectroscopic imaging measurements of hyperpolarized (13)C label exchange between exogenously administered [1-(13)C]pyruvate and endogenous lactate, catalyzed by lactate dehydrogenase (LDH), has proved to be a powerful approach for probing tissue metabolism in vivo. This experiment has clinical potential, particularly in oncology, where it could be used to assess tumor grade and response to treatment. A limitation of the method is that pyruvate must be administered in vivo at supra-physiological concentrations. This problem can be avoided by using hyperpolarized [1-(13)C]lactate, which can be used at physiological concentrations. However, sensitivity is limited in this case by the relatively small pyruvate pool size, which would result in only low levels of labeled pyruvate being observed even if there was complete label equilibration between the lactate and pyruvate pools. We demonstrate here a more sensitive method in which a doubly labeled lactate species can be used to measure LDH-catalyzed exchange in vivo. In this experiment exchange of the C2 deuterium label between injected hyperpolarized l-[1-(13)C,U-(2)H]lactate and endogenous unlabeled lactate is observed indirectly by monitoring phase modulation of the spin-coupled hyperpolarized (13)C signal in a heteronuclear (1)H/(13)C spin-echo experiment.

Hyperpolarized [1-13C]-ascorbic and dehydroascorbic acid: vitamin C as a probe for imaging redox status in vivo.

Dynamic nuclear polarization (DNP) of (13)C-labeled metabolic substrates in vitro and their subsequent intravenous administration allow both the location of the hyperpolarized substrate and the dynamics of its subsequent conversion into other metabolic products to be detected in vivo. We report here the hyperpolarization of [1-(13)C]-ascorbic acid (AA) and [1-(13)C]-dehydroascorbic acid (DHA), the reduced and oxidized forms of vitamin C, respectively, and evaluate their performance as probes of tumor redox state. Solution-state polarization of 10.5 ± 1.3% was achieved for both forms at pH 3.2, whereas at pH 7.0, [1-(13)C]-AA retained polarization of 5.1 ± 0.6% and [1-(13)C]-DHA retained 8.2 ± 1.1%. The spin-lattice relaxation times (T(1)'s) for these labeled nuclei are long at 9.4 T: 15.9 ± 0.7 s for AA and 20.5 ± 0.9 s for DHA. Extracellular oxidation of [1-(13)C]-AA and intracellular reduction of [1-(13)C]-DHA were observed in suspensions of murine lymphoma cells. The spontaneous reaction of DHA with the cellular antioxidant glutathione was monitored in vitro and was approximately 100-fold lower than the rate observed in cell suspensions, indicating enzymatic involvement in the intracellular reduction. [1-(13)C]-DHA reduction was also detected in lymphoma tumors in vivo. In contrast, no detectable oxidation of [1-(13)C]-AA was measured in the same tumors, consistent with the notion that tumors maintain a reduced microenvironment. This study demonstrates that hyperpolarized (13)C-labeled vitamin C could be used as a noninvasive biomarker of redox status in vivo, which has the potential to translate to the clinic.

Detection of tumor response to a vascular disrupting agent by hyperpolarized 13C magnetic resonance spectroscopy.

Nuclear spin hyperpolarization can dramatically increase the sensitivity of the (13)C magnetic resonance experiment, allowing dynamic measurements of the metabolism of hyperpolarized (13)C-labeled substrates in vivo. Here, we report a preclinical study of the response of lymphoma tumors to the vascular disrupting agent (VDA), combretastatin-A4-phosphate (CA4P), as detected by measuring changes in tumor metabolism of hyperpolarized [1-(13)C]pyruvate and [1,4-(13)C(2)]fumarate. These measurements were compared with dynamic contrast agent-enhanced magnetic resonance imaging (DCE-MRI) measurements of tumor vascular function and diffusion-weighted MRI (DW-MRI) measurements of the tumor cell necrosis that resulted from subsequent loss of tumor perfusion. The rate constant describing flux of hyperpolarized (13)C label between [1-(13)C]pyruvate and lactate was decreased by 34% within 6 hours of CA4P treatment and remained at this lower level at 24 hours. The rate constant describing production of labeled malate from hyperpolarized [1,4-(13)C(2)]fumarate increased 1.6-fold and 2.5-fold at 6 and 24 hours after treatment, respectively, and correlated with the degree of necrosis detected in histologic sections. Although DCE-MRI measurements showed a substantial reduction in perfusion at 6 hours after treatment, which had recovered by 24 hours, DW-MRI showed no change in the apparent diffusion coefficient of tumor water at 6 hours after treatment, although there was a 32% increase at 24 hours (P < 0.02) when regions of extensive necrosis were observed by histology. Measurements of hyperpolarized [1-(13)C]pyruvate and [1,4-(13)C(2)]fumarate metabolism may provide, therefore, a more sustained and sensitive indicator of response to a VDA than DCE-MRI or DW-MRI, respectively.

Fluorescent copper(II) bis(thiosemicarbazonates): synthesis, structures, electron paramagnetic resonance, radiolabeling, in vitro cytotoxicity and confocal fluorescence microscopy studies.

Copper bis(4-ethyl-3-thiosemicarbazonato) acenaphthenequinone (1) and copper bis(4-methyl-3-thiosemicarbazonato) acenaphthenequinone (2) are synthesized and characterized in solution, in the solid state, and radiolabeled. Serum-protein binding radioassays show good stability in solution and about 25 % binding to protein over 1 h, which is comparable with the hypoxia selective tracer [(64)Cu(ATSM)]. Cyclic voltammetry shows fast and reversible reduction at redox potentials similar to the values known for hypoxia-selective copper compounds. However, despite this, complex 1 does not show any hypoxic-selective uptake in HeLa cells over 1-h standard assays. Possible reasons for this are studied by using the intrinsic fluorescence of the Cu(II) complexes to determine the cellular distributions and uptake mechanism by confocal microscopy. The complexes are found to bind to the external cell membrane and disperse evenly in the cytoplasm only after a very slow cell internalization (>1 h). No significant changes in distribution are observed by fluorescence imaging under hypoxic conditions. The rate of localization in the cytoplasm contrasts with their Zn(II) analogues, which are known to have fast cell uptake (up to 20 min) and a clear localization in lysosomes and mitochondria. The cytotoxicity mechanism of 1 over 24 h against a number of adherent cell lines is seen to be by membrane disruption and is of a comparable magnitude to that of [Cu(ATSM)], as demonstrated by methyl tetrazolium (MTT) and lactate dehydrogenase (LDH) assays.