Browsing by Author "Sherry, A. Dean"
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Item A Novel Inhibitor of Pyruvate Dehydrogenase Kinase Stimulates Myocardial Carbohydrate Oxidation in Diet-Induced Obesity(American Society for Biochemistry and Molecular Biology Inc.) Wu, C. -Y; Satapati, S.; Gui, W.; Max Wynn, R.; Sharma, G.; Lou, M.; Qi, X.; Burgess, S. C.; Malloy, C.; Khemtong, C.; Sherry, A. Dean; Chuang, D. T.; Merritt, M. E.; Sherry, A. DeanThe pyruvate dehydrogenase complex (PDC) is a key control point of energy metabolism and is subject to regulation by multiple mechanisms, including posttranslational phosphorylation by pyruvate dehydrogenase kinase (PDK). Pharmacological modulation of PDC activity could provide a new treatment for diabetic cardiomyopathy, as dysregulated substrate selection is concomitant with decreased heart function. Dichloroacetate (DCA), a classic PDK inhibitor, has been used to treat diabetic cardiomyopathy, but the lack of specificity and side effects of DCA indicate a more specific inhibitor of PDK is needed. This study was designed to determine the effects of a novel and highly selective PDK inhibitor, 2((2,4-dihydroxyphenyl)sulfonyl) isoindoline-4,6-diol (designated PS10), on pyruvate oxidation in diet-induced obese (DIO) mouse hearts compared with DCA-treated hearts. Four groups of mice were studied: lean control, DIO, DIO + DCA, and DIO + PS10. Both DCA and PS10 improved glucose tolerance in the intact animal. Pyruvate metabolism was studied in perfused hearts supplied with physiological mixtures of long chain fatty acids, lactate, and pyruvate. Analysis was performed using conventional ¹H and ¹³C isotopomer methods in combination with hyperpolarized [1-¹³C]pyruvate in the same hearts. PS10 and DCA both stimulated flux through PDC as measured by the appearance of hyperpolarized [¹³C]bicarbonate. DCA but not PS10 increased hyperpolarized [1-¹³C]lactate production. Total carbohydrate oxidation was reduced in DIO mouse hearts but increased by DCA and PS10, the latter doing so without increasing lactate production. The present results suggest that PS10 is a more suitable PDK inhibitor for treatment of diabetic cardiomyopathy.Item Development of Non-Invasive Responsive Agents for Magnetic Resonance Imaging(2019-05) Paranawithana, Namini Nirodha; Sherry, A. DeanMolecular imaging involves visualizing bioactive molecules or biological parameters in vivo at the molecular level in a live organism. In Magnetic Resonance Imaging (MRI), inorganic complexes with paramagnetic ions, are commonly used to enhance the intrinsic image contrast of the soft tissues—contrast agents (CAs). Gd-based MR probes paved their way towards medical imaging and clinical application. CAs could change their r1 relaxivity in response to the local environment are known as “smart” probes. This dissertation reports the development and optimization of “smart” Magnetic Resonance Imaging agents to detect in-vivo copper ion levels and extracellular pH–two important extracellular biomarkers. Copper is the third most abundant transition metal in the body and a required dietary nutrient. Although the relationship between copper dynamics and its physiological or pathological roles have been extensively studied, information about its extracellular behavior in biologically relevant conditions remains insufficiently understood due to the lack of real-time non-invasive copper detecting techniques. Chapter 2 presents the design and organic synthesis of novel copperresponsive MR sensors. These sensors included a copper-selective bis(benzoic acid)methylamine recognition motif (GdL). We studied the physicochemical properties of the newly developed agents and devised a comprehensive study to understand the possible coordination of GdL1 with copper and HAS. GdL1 shows high selectivity to copper ions and exhibits an increase in relaxivity by 47% upon binding to 1 equivalent of Cu²⁺.Interestingly, when fully bound to Cu²⁺ sensor presents a 270% increase in relaxivity(r1) in the presence of a physiological concentration of human serum albumin. We performed in vivo imaging with healthy mice and visualized extracellular exchangeable copper in the liver for the first-time by MRI. These results will pave the way for unique opportunities to explore the role of copper in the progression of many neurological disorders, including Wilson’s disease. pH is a fundamental physiological parameter tightly regulated by endogenous buffers at the intracellular and extracellular level. Disruption of regulation of pH is associated with pathological conditions such as cancer, acidosis and kidney disease. GdDOTA-4AmP is a T₁ agent for MRI that has been applied non-invasively to image in-vivo tissue. This approach was limited by the use of a dual-contrast agent strategy and with lower elimination time of the agents in vivo due to possible deposition in the bones. In Chapter 3, we describe a set of novel Gd-based T₁ agents that present optimized pH-responsive MRI properties to GdDOTA-1AmP, GdDOTA-2AmP, and GdDOTA-3AmP. The GdDOTA-1AmP, exhibits a surprisingly large increase in r₁ relaxivity from 3.0 to 6.3 mM⁻¹s⁻¹ as the pH is reduced from 9 to 2.5. The origin of this unique pH sensitivity was traced to protonation of the single phosphonate side-chain, which, upon protonation, catalyzes exchange of protons between a Gd-bound water molecule and bulk water. T₁-weighted images of phantoms showed that MR image intensity increased 12-fold between a physiological pH of 7.4 and pH 6. This demonstrates it is possible to design simple, small molecule MRI contrast agents that respond to pH using simple acid-base principles.Item A Europium(Ⅲ)-Based PARACEST Agent for Sensing Singlet Oxygen by MRI(2013-04-04) Song, Bo; Wu, Yunkou; Yu, Mengxiao; Zhao, Piyu; Zhou, Chen; Kiefer, Garry E.; Sherry, A. Dean; Sherry, A. DeanA europium(Ⅲ) DOTA-tetraamide complex was designed as a MRI sensor of singlet oxygen (¹O₂). The water soluble, thermodynamically stable complex reacts rapidly with ¹O₂ to form an endoperoxide derivative that results in an ~3 ppm shift in the position of the Eu(Ⅲ)-bound water chemical exchange saturation transfer (CEST) peak. The potential of using this probe to detect accumulation of the endoperoxide derivative in biological media by ratiometric CEST imaging was demonstrated.;Item In Vivo Assessment of Increased Oxidation of Branched-Chain Amino Acids in Glioblastoma(Nature Publishing Group, 2019-01-23) Suh, Eul Hyun; Hackett, Edward P.; Wynn, R. Max; Chuang, David T.; Zhang, Bo; Luo, Weibo; Sherry, A. Dean; Park, Jae Mo; 0000-0002-7404-6971 (Park, JM); 0000-0001-7150-8301 (Sherry, AD); Sherry, A. Dean; Park, Jae MoAltered branched-chain amino acids (BCAAs) metabolism is a distinctive feature of various cancers and plays an important role in sustaining tumor proliferation and aggressiveness. Despite the therapeutic and diagnostic potentials, the role of BCAA metabolism in cancer and the activities of associated enzymes remain unclear. Due to its pivotal role in BCAA metabolism and rapid cellular transport, hyperpolarized ¹³C-labeled α-ketoisocaproate (KIC), the α-keto acid corresponding to leucine, can assess both BCAA aminotransferase (BCAT) and branched-chain α-keto acid dehydrogenase complex (BCKDC) activities via production of [1-¹³C]leucine or ¹³CO₂ (and thus (H¹³CO₃-), respectively. Here, we investigated BCAA metabolism of F98 rat glioma model in vivo using hyperpolarized ¹³C-KIC. In tumor regions, we observed a decrease in ¹³C-leucine production from injected hyperpolarized ¹³C-KIC via BCAT compared to the contralateral normal-appearing brain, and an increase in H¹³CO₃-, a catabolic product of KIC through the mitochondrial BCKDC. A parallel ex vivo ¹³C NMR isotopomer analysis following steady-state infusion of [U-¹³C] leucine to glioma-bearing rats verified the increased oxidation of leucine in glioma tissue. Both the in vivo hyperpolarized KIC imaging and the leucine infusion study indicate that KIC catabolism is upregulated through BCAT/BCKDC and further oxidized via the citric acid cycle in F98 glioma.Item Incorporating Novel Functionality on In Vitro Microelectrode Arrays(2018-05) Hammack, Audrey Sue; 0000-0001-5620-1993 (Hammack, AS); Gnade, Bruce E.; Pantano, Paul; Sherry, A. Dean; Zheng, JieThe microelectrode array (MEA) is an inexpensive, high throughput platform for measuring and recording extracellular electrical potentials from a culture of electrogenic tissues. However, this technology is not without drawbacks, which this work seeks to address. On conventional MEAs, stimulation of a culture is achieved via electrical stimulation through the electrodes, which may introduce recording artifacts. Optogenetics is a molecular biology technique that can be used to decouple the recording and stimulation functions of the MEA electrode, but hardware required to utilize optogenetics in combination with an MEA is a barrier that prevents utilization of this technique. One project presented here seeks to integrate an MEA with an array of organic light-emitting diodes (OLEDs) driven by thin film transistors (TFTs), to create a multifunctional MEA with optical stimulating capabilities, in order to streamline the hardware required for an in vitro optogenetics recording experiment. Discreet functional components are demonstrated and a proof of concept integrated substrate is presented. Another project presented in this dissertation seeks to insulate the MEA electrodes with polystyrene. The vast set of organic and inorganic materials used to insulate MEA electrodes present challenges to users who must modify cell culture protocols for cell adhesion to the surface of the MEAs. An MEA that features a patterned film of polystyrene, a material that is far more common to cell culture work, as electrode insulation is presented. Viable cell culture on this MEA and recordings that are comparable to other MEA substrates are demonstrated.Item Influence of Dy³⁺ and Tb³⁺ Doping on ¹³C Dynamic Nuclear Polarization(American Institute of Physics Inc, 2017-01-03) Niedbalski, Peter; Parish, Christopher; Kiswandhi, Andhika; Fidelino, L.; Khemtong, C.; Hayati, Z.; Song, L.; Martins, Andr©; Sherry, A. Dean; Lumata, Lloyd L.; Niedbalski, Peter; Parish, Christopher; Kiswandhi, Andhika; Martins, Andr©; Sherry, A. Dean; Lumata, LloydDynamic nuclear polarization (DNP) is a technique that uses a microwave-driven transfer of high spin alignment from electrons to nuclear spins. This is most effective at low temperature and high magnetic field, and with the invention of the dissolution method, the amplified nuclear magnetic resonance (NMR) signals in the frozen state in DNP can be harnessed in the liquid-state at physiologically acceptable temperature for in vitro and in vivo metabolic studies. A current optimization practice in dissolution DNP is to dope the sample with trace amounts of lanthanides such as Gd3+ or Ho3+, which further improves the polarization. While Gd³⁺ and Ho³⁺ have been optimized for use in dissolution DNP, other lanthanides have not been exhaustively studied for use in ¹³C DNP applications. In this work, two additional lanthanides with relatively high magnetic moments, Dy³⁺ and Tb³⁺, were extensively optimized and tested as doping additives for ¹³C DNP at 3.35 T and 1.2 K. We have found that both of these lanthanides are also beneficial additives, to a varying degree, for ¹³C DNP. The optimal concentrations of Dy³⁺ (1.5 mM) and Tb³⁺ (0.25 mM) for ¹³C DNP were found to be less than that of Gd³⁺ (2 mM). W-band electron paramagnetic resonance shows that these enhancements due to Dy³⁺ and Tb³⁺ doping are accompanied by shortening of electron T₁ of trityl OX063 free radical. Furthermore, when dissolution was employed, Tb³⁺-doped samples were found to have similar liquid-state ¹³C NMR signal enhancements compared to samples doped with Gd³⁺, and both Tb³⁺ and Dy³⁺ had a negligible liquid-state nuclear T₁ shortening effect which contrasts with the significant reduction in T₁ when using Gd³⁺. Our results show that Dy³⁺ doping and Tb³⁺ doping have a beneficial impact on ¹³C DNP both in the solid and liquid states, and that Tb³⁺ in particular could be used as a potential alternative to Gd³⁺ in ¹³C dissolution DNP experiments.Item A Novel Class of Polymeric pH-Responsive MRI CEST Agents(2013-05-26) Zhang, Shanrong; Zhou, K.; Huang, G.; Takahashi, Masaya; Sherry, A. Dean; Gao, Jinming; Sherry, A. DeanIn this communication, we report that ionizable, tertiary amine-based block copolymers can be used as pH-responsive contrast agents for magnetic resonance imaging (MRI) through the chemical exchange saturation transfer (CEST) mechanism. The CEST signal is essentially "off" when the polymers form micelles near physiological pH but is activated to the "on" state when the micelles dissociate in an acidic environment.Item PH-Responsive MRI Agents that can be Activated Beyond the Tissue MT Window(2017-05) Wang, Xiaojing; Sherry, A. Dean; Kiefer, Garry E.; Sibert, John W.; Zheng, JieChemical Exchange Saturation Transfer (CEST) has emerged as a novel Magnetic Resonance Imaging (MRI) contrast mechanism and gained increasing attention in applications. The image contrast is obtained by utilizing slow exchange properties of CEST agents that contain protons in exchange with bulk water protons. And continuous transfer of saturation makes the solutes at low concentration indirectly observable. In CEST, application of a pre-saturation pulse results in an extra signal called the Magnetization Transfer (MT) effect, arising from immobile protons bound in proteins and other large macromolecules. It is worthwhile to note that the MT effects always accompany CEST in tissue; as a result, measuring the pure CEST contribution that is separated from MT effect becomes somewhat difficult. Up to now, for the CEST data processing, the most commonly method used is the MTratio (MTR) asymmetry analysis with respect to the water frequency. Good asymmetry analysis requires that the MT profile is symmetric around water. However, over the past few years, several studies have found that in tissue, the z-spectra associated with semi-solid molecular pool are slightly asymmetric around the water proton resonance frequency, probably due to the chemical shift center mismatch between bulk water and semi-solid macromolecules. Thus, the validity of the MTR asymmetry analysis has been compromised. The goal of the present work is to develop CEST-based pH sensors that can be activated without simultaneous activation of the tissue MT signal. Our research efforts are focused under the theme to develop CEST-based pH sensors with large hyperfine shifts, putting them well outside the range of the MT profile. Thus they can be activated via selective RF irradiation without MT interference. Terbium-based complexes were developed, which displayed a water exchange CEST resonance located in the range of -500 to -600 ppm, well-outside the normal MT frequency range of tissues. By using this type of agents, the macromolecule MT effect has no impact on contrast-to-noise ratios in biological systems and MTratio (MTR) asymmetry analysis is not considered as necessary as other agents, thus opening a new way of circumventing the MT contamination and complication. Deprotonation of the phenolic proton resulted in a frequency shift of about 60 ppm in a bound water molecule exchange peak between pH 5 and 8. This allows direct imaging pH without prior knowledge of the agent concentration. A new model for simultaneous measurement of pH and temperature parameters was also proposed. The chemical shift information extracted from imaging data could be used to obtain the local temperature and pH values by simultaneously solving equations in our established model.Item Responsive Agents Detecting Biomarkers with Magnetic Resonance Imaging(2017-08) Zhang, Lei; Sherry, A. DeanParamagnetic chemical exchange saturation transfer (paraCEST) is a novel technique used in magnetic resonance imaging that offers several advantages over the traditional gadolinium T1 agents. In this dissertation, I aimed to investigate new types of paraCEST contrast agents responsive to biologically relevant parameters, such as lactate and pH. In Chapter 1, a description is given detailing the techniques and basic concepts, such as T₁, T_{2ex}, and CEST agents. In Chapter 2, we describe the study of EuDO3A, a well-known lanthanide macrocyclic complex that can be used as a shift reagent for L-lactate, a biologically relevant metabolite overproduced by tumors. Here, we utilized the CEST technique as a means of detecting extracellular L-lactate. The lactate hydroxyl proton shifts from 0.5ppm to 47ppm in the presence of EuDO3A at room temperature. This unique property allows EuDO3A to serve as a shift reagent (SR) for the in vitro imaging of extracellular L-lactate produced by cancer cells. In Chapter 3, we proposed a way that could optimize the lactate SRs and combine better CEST contrast with structural simplicity. We used a revolutionary approach that uses chirality at δ-position centers of the pendant arms in the heptadentate macrocyclic Yb-complexes. This strategy promotes preferential orientation of the conformers in solution and forms selective complexes with lactate in a single conformation. Furthermore, the SRs presented in this chapter can discriminate L- from D-lactate through ¹H NMR and CEST. The approach used might prove useful in the design of metabolite-specific shift reagents for functional MRI. In Chapter 4, we describe the properties of a series of LnDOTAM-amine complexes. Ln-DOTAM-amine complexes prove useful for detecting pH changes in vitro with a bimodal strategy by CEST and T_{2ex} NMR mechanisms. We also proposed a mathematical model to explain the pH sensitivity based on a base-catalyzed amine process. The proton exchange rates were affected by a hydrogen bond network established between bound water protons and outer-sphere amines. Furthermore, since the longitudinal relaxation rates (R₁) remained unchanged through the entire pH range, a concentration independent ratiometric method (r_{2ex}/r₁) can be used for pH imaging by MRI by DyDOTAM-amine complexes. Concluding this dissertation is a chapter providing future perspectives as they pertain to each project and conclusion.