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In Vitro and In Vivo Evaluation of DTPA-HPMA Copolymers as Potential Decorporating Agents for Prophylactic Therapy of Actinide Contamination. Radiat Res 2022; 198:357-367. [PMID: 35913891 DOI: 10.1667/rade-21-00244.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 06/17/2022] [Indexed: 11/03/2022]
Abstract
The release of actinides into the environment represents a significant potential public health concern. Chelation therapy utilizing diethylenetriamine pentaacetate (DTPA) is a U.S. Food and Drug Administration (FDA)-approved therapy capable of mitigating the deposition of some absorbed actinides in the body. However, the pharmacokinetic profile of DTPA is not ideal for prophylactic applications. In this study, we examine the incorporation of DTPA into a HPMA copolymer (P-DTPA) to investigate if the enhanced blood circulation time can offer superior prophylactic protection and of improving in vivo radiometal decorporation. Utilizing lutetium-177 (177Lu) as an actinide model, the performance of P-DTPA and DTPA (control) were evaluated using selectivity studies in the presence of competing biological metals, chelation and stability assays in human serum and cytotoxicity studies using human umbilical vein endothelial cells (HUVEC). The in vivo decorporation efficiency of P-DTPA relative to DTPA and untreated controls was also evaluated over two weeks in CF-1 mice. In the experimental groups, the mice were prophylactically treated with P-DTPA or DTPA (30 μmol/kg) 6 or 24 h prior to 177LuCl3 administration. The in vitro results reveal that P-DTPA gives efficient complexation yields relative to DTPA with a tolerable cytotoxicity profile and good serum stability. The in vivo decorporation studies demonstrated enhanced total excretion of the 177Lu using P-DTPA compared to DTPA in both the 6 and 24 h prophylactic treatment study arms. This enhanced decorporation effect is certainly attributable to the expected prolonged biological half-life of DTPA when grafted to the HPMA polymer.
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Examination of Charge Modifications of an Endolysosomal Trapping Inhibitor in an Antagonistic NTSR1-Targeted Construct for Colon Cancer. Bioconjug Chem 2022; 33:1363-1376. [PMID: 35793523 PMCID: PMC9941984 DOI: 10.1021/acs.bioconjchem.2c00214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Many low-molecular weight targeted radiotherapeutics (TRTs) are capable of rapidly achieving exceptional tumor to non-target ratios shortly after administration. However, the low tumor residence time of many TRTs limits therapeutic dose delivery and has become the Achilles heel to their clinical translation. To combat the tumor efflux of these otherwise promising agents, we have previously presented a strategy of equipping low-molecular weight TRTs with irreversible cysteine cathepsin inhibitors (e.g., E-64 analogues). These inhibitors are capable of forming irreversible adducts with cysteine proteases within the endolysosomal compartments of cells. Using these endolysosomal trapping agents (ETs), the receptor-targeted constructs are able to increase tumor retention and, thus, deliverable therapeutic doses. In this study, we examine this approach in the development of agents targeting the neurotensin receptor subtype 1 (NTSR1), a receptor overexpressed in numerous cancers. Using an antagonistic NTSR1-targeting vector, we explore the impact of charge modification of the ETs on the in vitro and in vivo biological performance of the constructs using HT-29 colon cancer models. Four ETs (based on the epoxysuccinyl peptide E-64) with various charge states were synthesized and incorporated into the structures of the NTSR1-targeted antagonist. These four 177Lu-labeled, ET-enhanced, NTSR1-targeted agents (177Lu-NA-ET1-4), along with the structurally analogous 177Lu-3BP-227, currently in clinical trials, underwent a battery of in vitro assays using HT-29 xenograft colon cancer cells to examine their NTSR1 binding, internalization and efflux, inhibition, and adduct formation properties. The biodistribution profile of these constructs was studied in an HT-29 mouse model. Charge modification of the terminal carboxylic acid and arginine of the ETs had deleterious effects on inhibition kinetics and in vitro adduct formation. Contrastingly, deletion of the arginine resulted in a modest increase in inhibition kinetics. Incorporation of ETs into the NTSR1-targeted agents was well-tolerated with minimal impact on the in vivo NTSR1 targeting but resulted in increased renal uptake. This study demonstrates that the ETs can be successfully incorporated into antagonistic NTSR1-targeted constructs without compromising their adduct formation capabilities. Based on these results, further exploration of the endolysosomal trapping approach is warranted in NTSR1- and other receptor-targeted antagonistic constructs.
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Examination of the impact molecular charge has on NTSR1-targeted agents incorporated with cysteine protease inhibitors. Eur J Med Chem 2022; 234:114241. [PMID: 35306289 PMCID: PMC9007894 DOI: 10.1016/j.ejmech.2022.114241] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2021] [Revised: 02/21/2022] [Accepted: 02/25/2022] [Indexed: 02/05/2023]
Abstract
Our laboratory has previously reported a strategy of employing cysteine cathepsin (CC) inhibitors as adduct forming, trapping agents to extend the tumor residence time of neurotensin receptor subtype 1 (NTSR1)-targeted radiopharmaceuticals. As a follow-up, we herein report a small library of CC trapping agent (CCTA)-incorporated, NTSR1-targeted conjugates with structural modifications that reduce the number of charged functional groups for both the CCTA and the peptide targeting sequence. These modifications were pursued to reduce the renal uptake and increase the translational potential of the CCTA-incorporated, NTSR1-targeted agents as radiotherapeutics. The biological performance of these constructs was examined using a battery of in vitro and in vivo studies employing the NTSR1-positive HT-29 human colon cancer cell line as our model. In vitro studies confirmed the ability of these constructs to target the NTSR1 and efficiently form intracellular adducts with cysteine proteases. Biodistribution studies using an HT-29 xenograft mouse model revealed that truncation (removal of Lys6-Pro7) of the NTSR1-targeted peptide (177Lu-NE2a) had the greatest (3.7-fold) effect at lowering renal recognition/uptake relative to our previously reported construct. Other charge-reducing modifications to the CCTA resulted in unexpected increases in renal uptake. All of the constructs demonstrated similar levels of in vivo NTSR1-positive tumor targeting with the highest tumor residualization resulting from the construct containing the zwitterionic CCTA (177Lu-NE2a). In vivo adduct formation of the conjugates was confirmed using autoradiographic SDS-PAGE analysis.
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Access to Highly Strained Tricyclic Ketals Derived from Coumarins. J Org Chem 2022; 87:4476-4482. [PMID: 35258961 PMCID: PMC8996706 DOI: 10.1021/acs.joc.2c00018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Synthesis of highly strained fused substituted dihydrobenzopyran cyclopropyl lactones derived from coumarin carboxylates are reported. The substrate scope tolerates a variety of 6- and 8-substituents on the coumarin ring. Substitution at the 5- or 7-position is resistant to tricyclic lactone formation except with 7-methyl substitution. Benzamide-containing coumarins afford the tricyclic ketal. A plausible mechanism is proposed for the formation of the fused lactone: intramolecular rearrangement of trans cyclopropyl methyl ketones with phenolic acetate via the formation of a hemiacetal.
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Polymorphism in Carboxamide Compound with High-Z' Crystal Structure. CrystEngComm 2022. [DOI: 10.1039/d2ce01171a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
In the present study, a carboxamide compound (N-(1, 3-thiazol-2-yl)-2-pyrazine) (L) was designed and synthesized by the reaction of 2-aminothiazol with 2-pyrazine carboxylic acid in a solution-based procedure. L was found...
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Structure activity relationship (SAR) study identifies a quinoxaline urea analog that modulates IKKβ phosphorylation for pancreatic cancer therapy. Eur J Med Chem 2021; 222:113579. [PMID: 34098465 PMCID: PMC8373685 DOI: 10.1016/j.ejmech.2021.113579] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 05/19/2021] [Accepted: 05/22/2021] [Indexed: 02/06/2023]
Abstract
Genetic models validated Inhibitor of nuclear factor (NF) kappa B kinase beta (IKKβ) as a therapeutic target for KRAS mutation associated pancreatic cancer. Phosphorylation of the activation loop serine residues (S177, S181) in IKKβ is a key event that drives tumor necrosis factor (TNF) α induced NF-κB mediated gene expression. Here we conducted structure activity relationship (SAR) study to improve potency and oral bioavailability of a quinoxaline analog 13-197 that was previously reported as a NFκB inhibitor for pancreatic cancer therapy. The SAR led to the identification of a novel quinoxaline urea analog 84 that reduced the levels of p-IKKβ in dose- and time-dependent studies. When compared to 13-197, analog 84 was ∼2.5-fold more potent in TNFα-induced NFκB inhibition and ∼4-fold more potent in inhibiting pancreatic cancer cell growth. Analog 84 exhibited ∼4.3-fold greater exposure (AUC0-∞) resulting in ∼5.7-fold increase in oral bioavailability (%F) when compared to 13-197. Importantly, oral administration of 84 by itself and in combination of gemcitabine reduced p-IKKβ levels and inhibited pancreatic tumor growth in a xenograft model.
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In Vitro Evaluation and Biodistribution Studies of HPMA Copolymers Targeting the Gastrin Releasing Peptide Receptor in Prostate Cancer. Pharm Res 2020; 37:229. [PMID: 33098043 DOI: 10.1007/s11095-020-02952-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 10/07/2020] [Indexed: 12/14/2022]
Abstract
PURPOSE The development of diagnostic and therapeutic agents utilizing small peptides (e.g., bombesin (BBN)) to target the overexpression of the gastrin-releasing peptide receptor (GRPR) in cancers has been widely investigated. Herein, we examine the capabilities of BBN-modified HPMA copolymers to target the GRPR. METHODS Four positive, four negative, and two zwitterionic BBN HPMA copolymer conjugates of varying peptide content and charge were synthesized. In vitro and in vivo studies were conducted in a GRPR-overexpressing prostate cancer cell line (PC-3) and a normal CF-1 mouse model, respectively. RESULTS Cellular uptake of the conjugates were found to be charge and BBN density dependent. The positively-charged conjugates illustrated a direct relationship between the extent of cellular internalization, ranging from 0.7 to 20%, and BBN-incorporation density. The negative and zwitterionic conjugates showed low PC-3 uptake values. Blocking studies confirmed the GRPR-targeting effect of the positively-charged constructs. In vivo studies of the positively-charged copolymers resulted in rapid blood clearance by the mononuclear phagocyte system (MPS)-associated tissues (e.g., liver and spleen). CONCLUSION Positively-charged BBN-HPMA copolymer conjugates demonstrated good GRPR-targeting and internalization in vitro. However, the impact of peptide density and charge on in vivo MPS recognition are parameters that must be optimized in future agent development.
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Abstract
1-Substituted and 1,1-disubstituted tetrahydro-β-carbolines undergo sodium periodate oxidative ring expansion in the presence of formaldehyde and other aldehydes to form 5,6-dihydro-7H-1,4-methanobenzo[e][1,4]diazonine-2,7(3H)-diones in 30-81% yield. In most cases, the reaction to form this new 6/8/5-tricyclic ring system proceeds with high diastereoselectivity. These benzannulated medium-ring keto imidazolidin-4-ones expand the menu of tetrahydro-β-carboline oxidation products.
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Coordination chemistry of mercury(ii) halide complexes: a combined experimental, theoretical and (ICSD & CSD) database study on the relationship between inorganic and organic units. Dalton Trans 2020; 49:11859-11877. [DOI: 10.1039/d0dt01541e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The coordination sphere can be influenced by many factors of inorganic and organic units. Despite the predominant role of inorganic unit in coordination sphere determination, organic unit can change it via one major or cooperativity of minor effects.
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Development of Improved Tumor-Residualizing, GRPR-Targeted Agents: Preclinical Comparison of an Endolysosomal Trapping Approach in Agonistic and Antagonistic Constructs. J Nucl Med 2019; 61:443-450. [PMID: 31601697 DOI: 10.2967/jnumed.119.231282] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 09/09/2019] [Indexed: 02/07/2023] Open
Abstract
Receptor-targeted radiopharmaceuticals based on low-molecular-weight carriers offer many clinically advantageous attributes relative to macromolecules but have generally been hampered by their rapid clearance from tumors, thus diminishing tumor-to-nontarget tissue ratios. Herein, we present a strategy using irreversible inhibitors (E-64 derivative) of cysteine cathepsins (CCs) as trapping agents to increase the tumor retention of receptor-targeted agents. Methods: We incorporated these CC-trapping agents into agonistic and antagonistic pharmacophores targeting the gastrin-releasing peptide receptor (GRPR). The synthesized radioconjugates with either an incorporated CC inhibitor or a matching control were examined using in vitro and in vivo models of the GRPR-positive, PC-3 human prostate cancer cell line. Results: From the in vitro studies, multiple techniques confirmed that the CC-trapping, GRPR-targeted constructs were able to increase cellular retention by forming intracellular macromolecule adducts. In PC-3 tumor-bearing xenograft mice, the CC-trapping, GRPR-targeted agonistic and antagonistic constructs led to an approximately 2-fold increase in tumor retention with a corresponding improvement in most tumor-to-nontarget tissue ratios over 72 h. Conclusion: CC endolysosomal trapping provides a pathway to increase the efficacy and clinical potential of low-molecular-weight, receptor-targeted agents.
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Enhanced tumor retention of NTSR1-targeted agents by employing a hydrophilic cysteine cathepsin inhibitor. Eur J Med Chem 2019; 177:386-400. [PMID: 31158752 DOI: 10.1016/j.ejmech.2019.05.068] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/23/2019] [Accepted: 05/24/2019] [Indexed: 01/09/2023]
Abstract
We explored the approach of using an analog of E-64, a well-known and hydrophilic cysteine cathepsin (CC) inhibitor, as a potent cysteine cathepsin-trapping agent (CCTA) to improve the tumor retention of low-molecular-weight, receptor-targeted radiopharmaceuticals. The synthesized hydrophilic CCTA-incorporated, NTSR1-targeted agents demonstrated a substantial increase in cellular retention upon uptake into the NTRS1-positive HT-29 human colon cancer cell line. Similarly, biodistribution studies using HT-29 xenograft mice revealed a significant and substantial increase in tumor retention for the CCTA-incorporated, NTSR1-targeted agent. The intracellular trapping mechanism of the CCTA-incorporated agents by macromolecular adduct formation was confirmed using multiple in vitro and in vivo techniques. Furthermore, utilization of the more hydrophilic CCTA greatly increased the hydrophilicity of the resulting NTSR1-targeted constructs leading to substantial decreases in most non-target tissues in contrast to our previously reported dipeptidyl acyloxymethyl ketone (AOMK) constructs. This work further confirms that the CCTA trapping approach can make significant improvements in the clinical potential of NTSR1-and other receptor-targeted radiopharmaceuticals.
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Exploration of relative π-electron localization in naphthalene aromatic rings by C–H⋯π interactions: experimental evidence, computational criteria, and database analysis. CrystEngComm 2019. [DOI: 10.1039/c9ce00929a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In C–H⋯π interaction, the relative π-electron localization in aromatic ring led to the change of contact position from centre to edges of the ring (C–H⋯πe) which was confirmed by experimental evidences, computational criteria, and database analysis.
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Bioimaging predictors of rilpivirine biodistribution and antiretroviral activities. Biomaterials 2018; 185:174-193. [PMID: 30245386 PMCID: PMC6556898 DOI: 10.1016/j.biomaterials.2018.09.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2018] [Revised: 09/05/2018] [Accepted: 09/11/2018] [Indexed: 12/22/2022]
Abstract
Antiretroviral therapy (ART) has changed the outcome of human immunodeficiency virus type one (HIV-1) infection from certain death to a life free of disease co-morbidities. However, infected people must remain on life-long daily ART. ART reduces but fails to eliminate the viral reservoir. In order to improve upon current treatment regimens, our laboratory created long acting slow effective release (LASER) ART nanoformulated prodrugs from native medicines. LASER ART enables antiretroviral drugs (ARVs) to better reach target sites of HIV-1 infection while, at the same time, improve ART's half-life and potency. However, novel ARV design has been slowed by prolonged pharmacokinetic testing requirements. To such ends, tri-modal theranostic nanoparticles were created with single-photon emission computed tomography (SPECT/CT), magnetic resonance imaging (MRI) and fluorescence capabilities to predict LASER ART biodistribution. The created theranostic ARV probes were then employed to monitor drug tissue distribution and potency. Intrinsically 111Indium (111In) radiolabeled, europium doped cobalt-ferrite particles and rilpivirine were encased in a polycaprolactone core surrounded by a lipid shell (111InEuCF-RPV). Particle cell and tissue distribution, and antiretroviral activities were sustained in macrophage tissue depots. 111InEuCF-PCL/RPV particles injected into mice demonstrated co-registration of MRI and SPECT/CT tissue signals with RPV and cobalt. Cell and animal particle biodistribution paralleled ARV activities. We posit that particle selection can predict RPV distribution and potency facilitated by multifunctional theranostic nanoparticles.
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Increasing time on target: utilization of inhibitors of cysteine cathepsins to enhance the tumor retention of receptor-targeted agents. Chem Commun (Camb) 2018; 54:11268-11271. [PMID: 30182093 DOI: 10.1039/c8cc05982a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
We report a strategy of utilizing irreversible cysteine cathepsin inhibitor as trapping agent to increase the tumor residence time of receptor-targeted agents. The targeted constructs incorporating these cysteine cathepsin trapping agents were able to form high molecular weight adducts with intracellular cysteine cathepsins, thus achieving superior retention in tumor tissues.
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Formation of 2-Imino Benzo[ e]-1,3-oxazin-4-ones from Reactions of Salicylic Acids and Anilines with HATU: Mechanistic and Synthetic Studies. ACS OMEGA 2018; 3:781-787. [PMID: 29399653 PMCID: PMC5793036 DOI: 10.1021/acsomega.7b01824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 01/05/2018] [Indexed: 06/07/2023]
Abstract
We describe a new 1-[Bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate (HATU)-mediated coupling reaction to produce 2-imino benzo[e]-1,3-oxazin-4-ones from salicylic acids and anilines. Mechanistic studies support a reaction pathway in which HATU mediates carbon transfer to the initially formed salicylanilides to form in succession reactive tetramethylisouronium and N-acyl(dimethyl)isouronium intermediates, which then undergo imine-iminium exchange to generate the desired oxazinones.
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Supramolecular synthon and conformational polymorphism in thiazole carboxamide compound. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s2053273317088003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Can substitution effect control the metal–ligand polymerization?! Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s2053273317091136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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How C—H-based interactions affect the packing of mercury halide complexes. Acta Crystallogr A Found Adv 2017. [DOI: 10.1107/s2053273317088921] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Structure-Activity Relationship Studies with Tetrahydroquinoline Analogs as EPAC Inhibitors. ACS Med Chem Lett 2017; 8:1183-1187. [PMID: 29375750 PMCID: PMC5774307 DOI: 10.1021/acsmedchemlett.7b00358] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Accepted: 10/02/2017] [Indexed: 12/18/2022] Open
Abstract
![]()
EPAC proteins are
therapeutic targets for the potential treatment
of cardiac hypertrophy and cancer metastasis. Several laboratories
use a tetrahydroquinoline analog, CE3F4, to dissect the role of EPAC1
in various disease states. Here, we report SAR studies with tetrahydroquinoline
analogs that explore various functional groups. The most potent EPAC
inhibitor 12a exists as a mixture of inseparable E (major) and Z (minor) rotamers. The rotation
about the N-formyl group indeed impacts the activity
against EPAC.
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Renal iron accumulation occurs in lupus nephritis and iron chelation delays the onset of albuminuria. Sci Rep 2017; 7:12821. [PMID: 28993663 PMCID: PMC5634457 DOI: 10.1038/s41598-017-13029-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 09/19/2017] [Indexed: 12/11/2022] Open
Abstract
Proteins involved in iron homeostasis have been identified as biomarkers for lupus nephritis, a serious complication of systemic lupus erythematosus (SLE). We tested the hypothesis that renal iron accumulation occurs and contributes to renal injury in SLE. Renal non-heme iron levels were increased in the (New Zealand Black x New Zealand White) F1 (NZB/W) mouse model of lupus nephritis compared with healthy New Zealand White (NZW) mice in an age- and strain-dependent manner. Biodistribution studies revealed increased transferrin-bound iron accumulation in the kidneys of albuminuric NZB/W mice, but no difference in the accumulation of non-transferrin bound iron or ferritin. Transferrin excretion was significantly increased in albuminuric NZB/W mice, indicating enhanced tubular exposure and potential for enhanced tubular uptake following filtration. Expression of transferrin receptor and 24p3R were reduced in tubules from NZB/W compared to NZW mice, while ferroportin expression was unchanged and ferritin expression increased, consistent with increased iron accumulation and compensatory downregulation of uptake pathways. Treatment of NZB/W mice with the iron chelator deferiprone significantly delayed the onset of albuminuria and reduced blood urea nitrogen concentrations. Together, these findings suggest that pathological changes in renal iron homeostasis occurs in lupus nephritis, contributing to the development of kidney injury.
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Abstract
N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymers have been studied as an efficient carrier for drug delivery and tumor imaging. However, as with many macromolecular platforms, the substantial accumulation of HPMA copolymer by the mononuclear phagocyte system (MPS)-associated tissues, such as the blood, liver, and spleen, has inhibited its clinical translation. Our laboratory is pursuing approaches to improve the diagnostic and radiotherapeutic effectiveness of HPMA copolymers by reducing the nontarget accumulation. Specifically, we have been investigating the use of a cathepsin S (Cat S)-cleavable peptidic linkers to degrade multiblock HPMA copolymers to increase MPS-associated tissue clearance. In this study, we further our investigation into this area by exploring the impact of copolymer block size on the biological performance of Cat S-degradable HPMA copolymers. Using a variety of in vitro and in vivo techniques, including dual labeling of the copolymer and peptide components, we investigated the constructs using HPAC pancreatic ductal adenocarcinoma models. The smaller copolymer block size (S-CMP) demonstrated significantly faster Cat S cleavage kinetics relative to the larger system (L-CMP). Confocal microscopy demonstrated that both constructs could be much more efficiently internalized by human monocyte-differentiated macrophage (hMDM) compared to HPAC cells. In the biodistribution studies, the multiblock copolymers with a smaller block size exhibited faster clearance and lower nontarget retention while still achieving good tumor targeting and retention. Based on the radioisotopic ratios, fragmentation and clearance of the copolymer constructs were higher in the liver compared to the spleen and tumor. Overall, these results indicate that block size plays an important role in the biological performance of Cat S-degradable polymeric constructs.
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Cathepsin S-cleavable, multi-block HPMA copolymers for improved SPECT/CT imaging of pancreatic cancer. Biomaterials 2016; 103:101-115. [PMID: 27372424 PMCID: PMC5018995 DOI: 10.1016/j.biomaterials.2016.05.036] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2015] [Revised: 05/04/2016] [Accepted: 05/17/2016] [Indexed: 02/08/2023]
Abstract
This work continues our efforts to improve the diagnostic and radiotherapeutic effectiveness of nanomedicine platforms by developing approaches to reduce the non-target accumulation of these agents. Herein, we developed multi-block HPMA copolymers with backbones that are susceptible to cleavage by cathepsin S, a protease that is abundantly expressed in tissues of the mononuclear phagocyte system (MPS). Specifically, a bis-thiol terminated HPMA telechelic copolymer containing 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. Three maleimide modified linkers with different sequences, including cathepsin S degradable oligopeptide, scramble oligopeptide and oligo ethylene glycol, were subsequently synthesized and used for the extension of the HPMA copolymers by thiol-maleimide click chemistry. All multi-block HPMA copolymers could be labeled by (177)Lu with high labeling efficiency and exhibited high serum stability. In vitro cleavage studies demonstrated highly selective and efficient cathepsin S mediated cleavage of the cathepsin S-susceptible multi-block HPMA copolymer. A modified multi-block HPMA copolymer series capable of Förster Resonance Energy Transfer (FRET) was utilized to investigate the rate of cleavage of the multi-block HPMA copolymers in monocyte-derived macrophages. Confocal imaging and flow cytometry studies revealed substantially higher rates of cleavage for the multi-block HPMA copolymers containing the cathepsin S-susceptible linker. The efficacy of the cathepsin S-cleavable multi-block HPMA copolymer was further examined using an in vivo model of pancreatic ductal adenocarcinoma. Based on the biodistribution and SPECT/CT studies, the copolymer extended with the cathepsin S susceptible linker exhibited significantly faster clearance and lower non-target retention without compromising tumor targeting. Overall, these results indicate that exploitation of the cathepsin S activity in MPS tissues can be utilized to substantially lower non-target accumulation, suggesting this is a promising approach for the development of diagnostic and radiotherapeutic nanomedicine platforms.
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Crystal structure and solid state computational (DFT/Hirshfeld surface) study for probing a new efficient and recyclable oxidation reagent, 1,2-ethandiylbis(triphenylphosphonium) peroxodisulfate dihydrate. PHOSPHORUS SULFUR 2016. [DOI: 10.1080/10426507.2016.1206106] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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The synthesis of 1,2-ethanediylbis(triphenylphosphonium) ditribromide as a new brominating agent in the presence of solvents and under solvent-free conditions. JOURNAL OF THE IRANIAN CHEMICAL SOCIETY 2016. [DOI: 10.1007/s13738-016-0919-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Liver-targeted antiviral peptide nanocomplexes as potential anti-HCV therapeutics. Biomaterials 2015; 70:37-47. [PMID: 26298393 PMCID: PMC4562313 DOI: 10.1016/j.biomaterials.2015.08.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Revised: 08/05/2015] [Accepted: 08/07/2015] [Indexed: 02/05/2023]
Abstract
Great success in HCV therapy was achieved by the development of direct-acting antivirals (DAA). However, the unsolved issues such as high cost and genotype dependency drive us to pursue additional therapeutic agents to be used instead or in combination with DAA. The cationic peptide p41 is one of such candidates displaying submicromolar anti-HCV potency. By electrostatic coupling of p41 with anionic poly(amino acid)-based block copolymers, antiviral peptide nanocomplexes (APN) platform was developed to improve peptide stability and to reduce cytotoxicity associated with positive charge. Herein, we developed a facile method to prepare galactosylated Gal-APN and tested their feasibility as liver-specific delivery system. In vitro, Gal-APN displayed specific internalization in hepatoma cell lines. Even though liver-targeted and non-targeted APN displayed comparable antiviral activity, Gal-APN offered prominent advantages to prevent HCV association with lipid droplets and suppress intracellular expression of HCV proteins. Moreover, in vivo preferential liver accumulation of Gal-APN was revealed in the biodistribution study. Altogether, this work illustrates the potential of Gal-APN as a novel liver-targeted therapy against HCV.
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Evaluation of DOTA-chelated neurotensin analogs with spacer-enhanced biological performance for neurotensin-receptor-1-positive tumor targeting. Nucl Med Biol 2015; 42:816-23. [PMID: 26302836 DOI: 10.1016/j.nucmedbio.2015.07.010] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2015] [Revised: 06/25/2015] [Accepted: 07/21/2015] [Indexed: 12/18/2022]
Abstract
INTRODUCTION Neurotensin receptor 1 (NTR1) is overexpressed in many cancer types. Neurotensin (NT), a 13 amino acid peptide, is the native ligand for NTR1 and exhibits high (nM) affinity to the receptor. Many laboratories have been investigating the development of diagnostic and therapeutic radiopharmaceuticals for NTR1-positive cancers based on the NT peptide. To improve the biological performance for targeting NTR1, we proposed NT analogs with a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) chelation system and different lengths of spacers. METHODS We synthesized four NTR1-targeted conjugates with spacer lengths from 0 to 9 atoms (null (N0), β-Ala-OH (N1), 5-Ava-OH (N2), and 8-Aoc-OH (N3)) between the DOTA and the pharmacophore. In vitro competitive binding, internalization and efflux studies were performed on all four NT analogs. Based on these findings, metabolism studies were carried out on our best performing conjugate, (177)Lu-N1. Lastly, in vivo biodistribution and SPECT/CT imaging studies were performed using (177)Lu-N1 in an HT-29 xenograft mouse model. RESULTS As shown in the competitive binding assays, the NT analogs with different spacers (N1, N2 and N3) exhibited lower IC50 values than the NT analog without a spacer (N0). Furthermore, N1 revealed higher retention in HT-29 cells with more rapid internalization and slower efflux than the other NT analogs. In vivo biodistribution and SPECT/CT imaging studies of (177)Lu-N1 demonstrated excellent accumulation (3.1 ± 0.4%ID/g) in the NTR1-positive tumors at 4h post-administration. CONCLUSIONS The DOTA chelation system demonstrated some modest steric inhibition of the pharmacophore. However, the insertion of a 4-atom hydrocarbon spacer group restored optimal binding affinity of the analog. The in vivo assays indicated that (177)Lu-N1 could be used for imaging and radiotherapy of NTR1-positive tumors.
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The influence of linker length on the properties of cathepsin S cleavable (177)Lu-labeled HPMA copolymers for pancreatic cancer imaging. Biomaterials 2014; 35:5760-70. [PMID: 24755528 DOI: 10.1016/j.biomaterials.2014.03.056] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 03/21/2014] [Indexed: 10/25/2022]
Abstract
N-(2-hydroxypropyl)-methacrylamide (HPMA) copolymers have shown promise for application in the detection and staging of cancer. However, non-target accumulation, particularly in the liver and spleen, hinders the detection of resident or nearby metastatic lesions thereby decreasing diagnostic effectiveness. Our laboratory has pursued the development of cathepsin S susceptible linkers (CSLs) to reduce the non-target accumulation of diagnostic/radiotherapeutic HPMA copolymers. In this study, we ascertain if the length of the linking group impacts the cleavage and clearance kinetics, relative to each other and a non-cleavable control, due to a reduction in steric inhibition. Three different CSLs with linking groups of various lengths (0, 6 and 13 atoms) were conjugated to HPMA copolymers. In vitro cleavage studies revealed that the longest linking group (13 atoms) led to more rapid cleavage when challenged with cathepsin S. The CSL incorporated HPMA copolymers demonstrated significantly higher levels of excretion and a significant decrease in long-term hepatic and splenic retention relative to the non-cleavable control. Contrary to in vitro observations, the length of the linking group did not substantially impact the non-target in vivo clearance. In the case of HPAC tumor retention, the CSL with the null (0 atom) linker demonstrated significantly higher levels of retention relative to the other CSLs. Given these results, we find that the length of the linking group of the CSLs did not substantially impact non-target clearance, but did influence tumor retention. Overall, these results demonstrate that the CSLs can substantially improve the non-target clearance of HPMA copolymers thereby enhancing clinical potential.
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Synthesis and in vitro and in vivo evaluation of hypoxia-enhanced 111In-bombesin conjugates for prostate cancer imaging. J Nucl Med 2013; 54:1605-12. [PMID: 23896558 DOI: 10.2967/jnumed.112.117986] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
UNLABELLED Receptor-targeted agents, such as gastrin-releasing peptide receptor (BB2r)-targeted peptides, have been investigated extensively in preclinical and clinical studies. In an attempt to increase the effectiveness of diagnostic or radiotherapeutic agents, we have begun to explore the incorporation of the hypoxia-selective prodrug 2-nitroimidazole into receptor-targeted peptides. Hypoxia is a well-known characteristic of many solid tumors, including breast, prostate, and pancreatic cancers. The aim of this approach is to use the hypoxia-trapping capability of 2-nitroimidazoles to increase the retention of the agent in hypoxic, BB2r-positive tumors. We have demonstrated that incorporation of one or more 2-nitroimidazoles into the BB2r-targeted peptide significantly increases the in vitro retention of the agent in hypoxic prostate cancer cells. The study described herein represents our first investigation of the in vivo properties of these hypoxia-enhanced BB2r-targeted agents in a PC-3 xenograft mouse model. METHODS Four (111)In-labeled BB2r-targeted conjugates--(111) IN-1, (111) IN-2, (111) IN-3, and (111) IN-4, composed of 2-nitroimidazole moieties of 0, 1, 2, and 3, respectively--were synthesized, labeled, and purified. The BB2r binding affinities, externalization, and protein-association properties of these radioconjugates were assessed using the BB2r-positive PC-3 human prostate cancer cell line under hypoxic and normoxic environments. The in vivo biodistribution and micro-SPECT/CT imaging of the (111) IN-1, (111) IN-2, and (111) IN-4 radioconjugates were investigated in PC-3 tumor-bearing severely combined immunodeficient mice. RESULTS All conjugates and (nat)In-conjugates demonstrated nanomolar binding affinities. (111) IN-1, (111) IN-2, (111) IN-3, and (111) IN-4 demonstrated 41.4%, 60.7%, 69.1%, and 69.4% retention, correspondingly, of internalized radioactivity under hypoxic conditions relative to 34.8%, 35.3%, 33.2%, and 29.7% retention, respectively, under normoxic conditions. Protein-association studies showed significantly higher levels of association under hypoxic conditions for 2-nitroimidazole-containing BB2r-targeted radioconjugates than for controls. On the basis of the initial 1-h uptake in the PC-3 tumors, (111) IN-1, (111) IN-2, and (111) IN-4 demonstrated tumor retentions of 1.5%, 6.7%, and 21.0%, respectively, by 72 h after injection. Micro-SPECT/CT imaging studies of (111) IN-1, (111) IN-2, and (111) IN-4 radioconjugates resulted in clear delineation of the tumors. CONCLUSION On the basis of the in vitro and in vivo studies, the BB2r-targeted agents that incorporated 2-nitroimidazole moieties demonstrated improved retention. These results indicate that further exploration into the potential of hypoxia-selective trapping agents for BB2r-targeted agents, as well as other targeted compounds, is warranted.
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177Lu-labeled HPMA copolymers utilizing cathepsin B and S cleavable linkers: synthesis, characterization and preliminary in vivo investigation in a pancreatic cancer model. Nucl Med Biol 2013; 40:606-17. [PMID: 23622691 DOI: 10.1016/j.nucmedbio.2013.01.011] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Revised: 01/21/2013] [Accepted: 01/29/2013] [Indexed: 01/03/2023]
Abstract
INTRODUCTION A major barrier to the advancement of therapeutic nanomedicines has been the non-target toxicity caused by the accumulation of the drug delivery systems in organs associated with the reticuloendothelial system, particularly the liver and spleen. Herein, we report the development of peptide based metabolically active linkers (MALs) that are enzymatically cleaved by cysteine cathepsin B and S, two proteases highly expressed in the liver and spleen. The overall goal of this approach is to utilize the MALs to lower the non-target retention and toxicity of radiolabeled drug delivery systems, thus resulting in higher diagnostic and radiotherapeutic efficacy. METHODS In this study three MALs (MAL0, MAL1 and MAL2) were investigated. MAL1 and MAL2 are composed of known substrates of cathepsin B and S, respectively, while MAL0 is a non-cleavable control. Both MAL1 and MAL2 were shown to undergo enzymatic cleavage with the appropriate cathepsin protease. Subsequent to conjugation to the HPMA copolymer and radiolabeling with (177)Lu, the peptide-polymer conjugates were renamed (177)Lu-metabolically active copolymers ((177)Lu-MACs) with the corresponding designations: (177)Lu-MAC0, (177)Lu-MAC1 and (177)Lu-MAC2. RESULTS In vivo evaluation of the (177)Lu-MACs was performed in an HPAC human pancreatic cancer xenograft mouse model. (177)Lu-MAC1 and (177)Lu-MAC2 demonstrated 3.1 and 2.1 fold lower liver retention, respectively, compared to control ((177)Lu-MAC0) at 72h post-injection. With regard to spleen retention, (177)Lu-MAC1 and (177)Lu-MAC2 each exhibited a nearly fourfold lower retention, relative to control, at the 72h time point. However, the tumor accumulation of the (177)Lu-MAC0 was two to three times greater than (177)Lu-MAC1 and (177)Lu-MAC2 at the same time point. The MAL approach demonstrated the capability of substantially reducing the non-target retention of the (177)Lu-labeled HPMA copolymers. CONCLUSIONS While further studies are needed to optimize the pharmacokinetics of the (177)Lu-MACs design, the ability of the MAL to significantly decrease non-target retention establishes the potential this avenue of research may have for the improvement of diagnostic and radiotherapeutic drug delivery systems.
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Development of hypoxia enhanced 111In-labeled Bombesin conjugates: design, synthesis, and in vitro evaluation in PC-3 human prostate cancer. Bioconjug Chem 2012; 23:527-37. [PMID: 22296619 DOI: 10.1021/bc200600w] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The gastrin-releasing peptide receptor (BB2r) has shown great promise for tumor targeting due to the increase of the receptor expression in a variety of human cancers including prostate, breast, small-cell lung, and pancreatic cancer. From clinical investigations, prostate cancer has been shown to be among the most hypoxic of the cancers investigated. Many solid tumors contain regions of hypoxia due to poor organization and efficiency of the vasculature. However, hypoxia is typically not present in normal tissue. Nitroimidazoles, a thoroughly investigated class of hypoxia selective drugs, have been shown to be highly retained in hypoxic tissues. The purpose of this study is to determine if the incorporation of hypoxia trapping moieties into the structural paradigm of BB2r-targeted peptides will increase the retention time of the agents in prostate cancer tumors. The present work involves the design, syntheses, purification, and in vitro investigation of hypoxia enhanced (111)In-BB2r-targeted radioconjugates. A total of four BB2r-targeted conjugates (1-4) were synthesized and coupled with increasing numbers of 2-nitroimidazoles, a hypoxia trapping moiety. Conjugates were radiolabeled with (111)In and purified by HPLC prior to in vitro studies. Receptor saturation assays under both normoxic and hypoxic conditions showed that the BB2r receptor expression on the PC-3 human prostate cancer cell line was not significantly affected by oxygen levels. Competitive binding assays revealed that incorporation of 2-nitroimidazoles had a detrimental effect to BB2r binding when adequate spacer groups, between the hypoxia trapping agent and the pharmacophore, were not employed. All of the 2-nitroimidazole containing BB2r-targeted agents exhibited significantly higher longitudinal retention in PC-3 cells under hypoxic conditions compared to the analogous normoxic studies. Protein association analysis revealed a 3-fold increase in binding of a 2-nitroimidazole containing BB2r-targeted agent under hypoxic relative to normoxic conditions. The positive nature of these results indicate that further exploration into the potential of hypoxia selective trapping agents for BB2r-targeted agents, as well as other targeted compounds, is warranted.
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Eighth International Nanomedicine and Drug Delivery Symposium (NanoDDS'10). J Control Release 2011. [DOI: 10.1016/j.jconrel.2011.05.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Design, synthesis, and biological evaluation of an antagonist-bombesin analogue as targeting vector. Bioconjug Chem 2008; 19:2040-8. [PMID: 18808168 DOI: 10.1021/bc800290c] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The gastrin releasing peptide receptor (GRP-R) is overexpressed on a number of tumors and cancer cell lines including pancreas, prostate, breast, gastrointestinal, and small cell lung cancer (SCLC). Radiolabeled bombesin (BBN) analogues have exhibited high binding affinity and specificity to the GRP-R. A bombesin analogue with an antagonist targeting vector at the C-terminus, DOTA-aminohexanoyl-[D-Phe(6), Leu-NHCH 2CH 2CH3(13), des Met(14)] BBN[6-14] (1, "Bomproamide"), has been synthesized and displays high binding affinity (IC50 = 1.36 +/- 0.09 nM) against (125)I-Tyr (4)-BBN in in vitro competitive assays using PC-3 cells. Maximum internalization of (111)In-1 reached 14% in PC-3 cells after 45 min of incubation. Rapid (0.25 h PI) and high (12.21 +/- 3.2%ID/g) pancreatic uptake of (111)In-1 was observed in healthy CF-1 mice, and 90% of the activity was blocked by coinjection of 100 mug of BBN. Rapid (0.25 h PI) and high uptake (6.90 +/- 1.06%ID/g) was observed in PC-3 prostate cancer xenografts in SCID mice, as well as visualized clearly in a SPECT/CT study. These results support the use of a bombesin construct with an antagonist C-terminal vector as a candidate of choice for specific in vivo imaging of tumors overexpressing GRP-receptors.
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Evaluation of the pharmacokinetic effects of various linking group using the 111In-DOTA-X-BBN(7-14)NH2 structural paradigm in a prostate cancer model. Bioconjug Chem 2008; 19:1803-12. [PMID: 18712899 DOI: 10.1021/bc8001375] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The high incidence of BB2 receptor (BB2r) expression in various cancers has prompted investigators to pursue the development of BB2r-targeted agents for diagnostic imaging, chemotherapy, and radiotherapy. Development of BB2r-targeted agents, based on the bombesin (BBN) peptide, has largely involved the use of the bifunctional chelate approach in which the linking group serves several key roles including pharmacokinetic modification. Understanding the in vivo properties of the various pharmacokinetic modifying linking groups is crucial for developing BB2r-targeted agents with improved targeting and clearance characteristics. The goal of this study was to systematically evaluate the pharmacokinetic profile of aliphatic hydrocarbon, aromatic, and poly(ethylene glycol) (ether) functional groups in order to obtain a better understanding of the in vivo properties of these pharmacokinetic modifiers. Specifically, we synthesized six radioconjugates with the structure 111In-DOTA- X-BBN(7-14)NH2, where X = 8-aminooctanoic acid (8-AOC), 5-amino-3-oxapentyl-succinamic acid (5-ADS), 8-amino-3,6-dioxaoctyl-succinamic acid (8-AOS), p-aminobenzoic acid (AMBA), Gly-AMBA, and Gly- p-aminomethylbenzoic acid (Gly-AM2BA). All of the (nat)In-conjugates demonstrated nanomolar binding affinities to the BB2r. In CF-1 mice, the BB2r uptake in the pancreas of radioconjugates containing aromatic linking groups was found to be significantly higher at 1 h postinjection than the radioconjugates with ether linker moieties. For PC-3 tumor-bearing SCID mice, the tumor uptake was found to be 6.66 +/- 2.00, 6.21 +/- 1.57, 6.36 +/- 1.60, 4.46 +/- 0.81, and 7.76 +/- 1.19 %ID/g for the 8-AOC, 8-ADS, AMBA, Gly-AMBA, and Gly-AM2BA radioconjugates, respectively, at 15 min postinjection. By 24 h postinjection, the radioconjugates containing aromatic groups exhibited the highest percentage tumor retention with 11.4%, 19.8%, 26.6%, 25.8%, and 25.5% relative to the 15 min values remaining in the tumor tissue for the 8-AOC, 8-ADS, AMBA, Gly-AMBA, and Gly-AM2BA radioconjugates, respectively. Fused Micro-SPECT/CT imaging studies performed at 24 h postinjection revealed substantial accumulation of radioactivity in the tumor tissue for all radioconjugates. In both biodistribution and Micro-SPECT/CT imaging studies, the radioconjugates containing aromatic linking groups typically exhibited significantly higher G.I. tract retention than the hydrocarbon or ether linking moieties. In conclusion, our studies indicate that radioconjugates incorporating aromatic linking groups, of the type investigated, generally demonstrated enhanced retention in BB2r expressing tissues in comparison to either the hydrocarbon or ether linking moieties. Furthermore, this investigation clearly demonstrates the significance of the linking group upon not only the in vivo clearance of the radiopharmaceutical, but also on the in vivo uptake and retention of the BB2r-targeted agent in tumor tissue. Future designs of BB2r-targeted agents should include a careful consideration of the effect linking group functionality has upon tumor targeting and retention.
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In vivo evaluation and small-animal PET/CT of a prostate cancer mouse model using 64Cu bombesin analogs: side-by-side comparison of the CB-TE2A and DOTA chelation systems. J Nucl Med 2007; 48:1327-37. [PMID: 17631556 DOI: 10.2967/jnumed.107.039487] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED The BB2 receptor subtype, of the bombesin family of receptors, has been shown to be highly overexpressed in a variety of human tumors, including prostate cancer. Bombesin (BBN), a 14-amino acid peptide, has been shown to target the BB2 receptor with high affinity. 64Cu (half-life = 12.7 h, beta+: 18%, E(beta+ max) = 653 keV; beta-: 37%, E(beta- max) = 578 keV) is a radioisotope that has clinical potential for application in both diagnostic imaging and radionuclide therapy. Recently, new chelation systems such as 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane-4,11-diacetic acid (CB-TE2A) have been reported to significantly stabilize the 64Cu radiometal in vivo. The increased stability of the 64Cu-CB-TE2A chelate complex has been shown to significantly reduce nontarget retention compared with tetraazamacrocycles such as 1,4,7,10-tetraazacyclodoadecane-N,N',N'',N'''-tetraacetic acid (DOTA). The aim of this study was to determine whether the CB-TE2A chelation system could significantly improve the in vivo stability of 64Cu bombesin analogs. The study directly compares 64Cu bombesin analogs using the CB-TE2A and DOTA chelation systems in a prostate cancer xenograft SCID (severely compromised immunodeficient) mouse model. METHODS The CB-TE2A-8-AOC-BBN(7-14)NH2 and DOTA-8-AOC-BBN(7-14)NH2 conjugates were synthesized and radiolabeled with 64Cu. The receptor-binding affinity and internalization profile of each metallated conjugate was evaluated using PC-3 cells. Pharmacokinetic and small-animal PET/CT studies were performed using female SCID mice bearing PC-3 xenografts. RESULTS In vivo BB2 receptor targeting was confirmed by tumor uptake values of 6.95 +/- 2.27 and 4.95 +/- 0.91 %ID/g (percentage injected dose per gram) at the 15-min time point for the 64Cu-CB-TE2A and 64Cu-DOTA radioconjugates, respectively. At the 24-h time point, liver uptake was substantially reduced for the 64Cu-CB-TE2A radioconjugate (0.21 +/- 0.06 %ID/g) compared with the 64Cu-DOTA radioconjugate (7.80 +/- 1.51 %ID/g). The 64Cu-CB-TE2A-8-AOC-BBN(7-14)NH2 radioconjugate demonstrated significant clearance, 98.60 +/- 0.28 %ID, from the mouse at 24 h after injection. In contrast, only 67.84 +/- 5.43 %ID of the 64Cu activity was excreted using the 64Cu-DOTA-8-AOC-BBN(7-14)NH2 radioconjugate because of nontarget retention. CONCLUSION The pharmacokinetic and small-animal PET/CT studies demonstrate significantly improved nontarget tissue clearance for the 64Cu-CB-TE2A8-AOC-BBN(7-14)NH2. This is attributed to the improved in vivo stability of the 64Cu-CB-TE2A chelate complex as compared with the 64Cu-DOTA chelate complex.
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[64Cu-NOTA-8-Aoc-BBN(7-14)NH2] targeting vector for positron-emission tomography imaging of gastrin-releasing peptide receptor-expressing tissues. Proc Natl Acad Sci U S A 2007; 104:12462-7. [PMID: 17626788 PMCID: PMC1914305 DOI: 10.1073/pnas.0705347104] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Radiolabeled peptides hold promise as diagnostic/therapeutic targeting vectors for specific human cancers. We report the design and development of a targeting vector, [(64)Cu-NOTA-8-Aoc-BBN(7-14)NH(2)] (NOTA = 1,4,7-triazacyclononane-1,4,7-triacetic acid, 8-Aoc = 8-aminooctanoic acid, and BBN = bombesin), having very high selectivity and affinity for the gastrin-releasing peptide receptor (GRPr). GRPrs are expressed on a variety of human cancers, including breast, lung, pancreatic, and prostate, making this a viable approach toward site-directed localization or therapy of these human diseases. In this study, [NOTA-X-BBN(7-14)NH(2)] conjugates were synthesized, where X = a specific pharmacokinetic modifier. The IC(50) of [NOTA-8-Aoc-BBN(7-14)NH(2)] was determined by a competitive displacement cell-binding assay in PC-3 human prostate cancer cells using (125)I-[Tyr(4)]-BBN as the displacement ligand. An IC(50) of 3.1 +/- 0.5 nM was obtained, demonstrating high binding affinity of [NOTA-8-Aoc-BBN] for the GRPr. [(64)Cu-NOTA-X-BBN] conjugates were prepared by the reaction of (64)CuCl(2) with peptides in buffered aqueous solution. In vivo studies of [(64)Cu-NOTA-8-Aoc-BBN(7-14)NH(2)] in tumor-bearing PC-3 mouse models indicated very high affinity of conjugate for the GRPr. Uptake of conjugate in tumor was 3.58 +/- 0.70% injected dose (ID) per g at 1 h postintravenous injection (p.i.). Minimal accumulation of radioactivity in liver tissue (1.58 +/- 0.40% ID per g, 1 h p.i.) is indicative of rapid renal-urinary excretion and suggests very high in vivo kinetic stability of [(64)Cu-NOTA-8-Aoc-BBN(7-14)NH(2)] with little or no in vivo dissociation of (64)Cu(2+) from the NOTA chelator. Kidney accumulation at 1 h p.i. was 3.79 +/- 1.09% ID per g. Molecular imaging studies in GRPr-expressing tumor models produced high-contrast, high-quality micro-positron-emission tomography images.
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Synthesis and characterization of a trigonal bipyramidal supramolecular cage based upon rhodium and platinum metal centers. Chem Commun (Camb) 2006:4644-6. [PMID: 17082870 DOI: 10.1039/b608991g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reaction of 4-ethynyl-pyridine with tert-butyl lithium followed by its addition to (Me3tacn)RhCl3 affords the facial octahedral complex (Me3tacn)Rh(CCPy)3, condensation of which with the square planar complex cis-(DCPE)Pt(NO3)2 results in a self-assembled trigonal bipyramidal cage with Rh(III) and Pt(II) atoms occupying the vertices.
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Synthesis and crystallographic characterization of multi-donor N-heterocyclic carbene chelating ligands and their silver complexes: Potential use in pharmaceuticals. J Organomet Chem 2005. [DOI: 10.1016/j.jorganchem.2005.07.102] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Anion Directed Synthesis of Paddlane and Trisilver Tweezer Complexes Based upon Silver Coordination Chemistry. J Am Chem Soc 2005; 127:5738-9. [PMID: 15839642 DOI: 10.1021/ja050154k] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Addition of AgBF4 or Ag(O3SCF3) to the tripodal ligand, Me3tacnRh(CCPh)3, yields a paddlane complex as well as a novel trinuclear silver "tweezer" complex based upon silver acetylene coordination chemistry. The paddlane is composed of two Me3tacnRh(CCPh)3 moieties held together by silver acetylene interactions. The tweezer complex is composed of one tripodal moiety with three silver atoms coordinated to each acetylene-Rh-acetylene face. The tweezer complex is stabilized by additional interactions, including a triflate anion which serves to cap the complex.
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Propene Polymerization Using ansa-Metallocenium Ions: Excess Activator Effects on Polymerization Activity and Polymer Microstructure. Organometallics 2004. [DOI: 10.1021/om0492092] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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The Potential Use of Rhodium N-Heterocyclic Carbene Complexes as Radiopharmaceuticals: The Transfer of a Carbene from Ag(I) to RhCl3·3H2O. Organometallics 2004. [DOI: 10.1021/om049697d] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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A fluorophenylboron-functionalized zirconium silsesquioxane complex. Acta Crystallogr C 2004; 60:m357-9. [PMID: 15237161 DOI: 10.1107/s0108270104012296] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2004] [Accepted: 05/20/2004] [Indexed: 11/10/2022] Open
Abstract
Bis(eta5-cyclopentadienyl)[rel-(1R,5S,7R,14S)-(1,3,5,7,9,11,14-heptacyclopentyl-7,14-dioxidotricyclo[7.3.3(1,9).1(5,11)]heptasiloxan-3-yloxy)bis(pentafluorophenyl)borane2-]zirconium, [Zr(C5H5)2(C47H63BF10O12Si7)], consists of [ZrCp2] (Cp is cyclopentadienyl) and [(C6F5)2B] moieties bound to a silsesquioxane core. The silsesquioxane binds to the Zr atom through two of its O atoms to form a distorted tetrahedron. The [(C6F5)2B] moiety is bound to the silsesquioxane through an O atom, forming an Si-O-B bond angle of 168.4 (4) degrees. The steric and electronic effects of the Zr atom and the borate moieties force the silsesquioxane core to distort. These distortions can be seen by examination of the Si-O-Si bond angles.
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Synthesis and Structural Characterization ofN-Heterocyclic Carbene Complexes of Silver(I) and Rhodium(I) from Caffeine. Organometallics 2004. [DOI: 10.1021/om030689r] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Bulky aluminum alkyl scavengers in olefin polymerization with group 4 catalysts. J Am Chem Soc 2003; 125:9246-7. [PMID: 12889925 DOI: 10.1021/ja030121+] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The binding of H2O to MeAl(OAr)2 (1: Ar = 2,6-di-tert-butyl-4-methylphenyl) in THF-d8 at -40 degrees C provides aquo complex 2, the structure of which was determined by X-ray crystallography. Complex 2 is unstable above 0 degrees C in THF-d8 and decomposes to form ArOH (major), CH4 (minor), and a methyl aluminoxane of undetermined structure. Decomposition of 2 follows first-order kinetics with k = 3.0 x 10-4 s-1 at 5 degrees C. The hindered phenol ArOH slowly reacts with [Cp2ZrMe][MeB(C6F5)3] (4) in bromobenzene-d5 solution at 25 degrees C to furnish CH4 and [Cp2ZrOAr][MeB(C6F5)3] (5), the structure of which was confirmed by X-ray crystallography. This reaction follows second-order kinetics for [ArOH] = [4] = 0.045 M and with k = 2.8 x 10-3 M-1 s-1 at 25 degrees C. This corresponds to a rate that is >107 x slower than the apparent rate of ethylene insertion for 4 at 25 degrees C at typical concentrations encountered in olefin polymerization. The kinetic data, as well as control experiments involving the addition of ArOH to active catalyst producing poly(ethylene), demonstrate that ArOH has essentially no effect on polymerization kinetics involving 4.
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Synthesis and structural characterization of a [Ag4]4+ cluster stabilized by a mixed-donor N-heterocyclic carbene linked cyclophane and the first reported synthesis of a N-heterocyclic carbene complex in water. J Organomet Chem 2003. [DOI: 10.1016/s0022-328x(03)00151-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Synthesis and structural characterization of two bis-imidazolium-linked cyclophanes: precursors toward ‘carbeneporphyrinoid’ ligands. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(02)00557-9] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Synthesis and structural characterization of a silver complex of a mixed-donor N-heterocyclic carbene linked cyclophane. Chem Commun (Camb) 2001:1780-1. [PMID: 12240312 DOI: 10.1039/b105751k] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The synthesis of a dicationic imidazolium-linked cyclophane and a dimeric silver-N-heterocyclic carbene complex, that is the first silver complex with a N-heterocyclic carbene ligand involved in a pi-bonding interaction, is reported.
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Receptor-G protein gamma specificity: gamma11 shows unique potency for A(1) adenosine and 5-HT(1A) receptors. Biochemistry 2001; 40:10532-41. [PMID: 11523995 DOI: 10.1021/bi010950c] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
G protein coupled receptors activate signal transducing guanine nucleotide-binding proteins (G proteins), which consist of an alpha subunit and a betagamma dimer. Whole cell studies have reported that receptors signal through specific betagamma subtypes. Membrane reconstitution studies with the adenosine A(1) and alpha(2A) adrenergic receptors have reached a similar conclusion. We aimed to test the generality of this finding by comparing the gamma subtype specificity for four G(i)-coupled receptors: alpha(2A) adrenergic; A1 adenosine (A(1)-R); 5-hydroxytryptamine(1A) (5-HT(1A)-R); mu opioid. Membranes were reconstituted with Galpha(i)(1) and five gamma subtypes (dimerized to beta1). Using a sensitive alpha-betagamma binding assay, we show that all recombinant betagamma (except beta1gamma1) had comparable affinity for alpha(i)(1). Using high affinity agonist binding as a measure of receptor-G protein coupling, betagamma-containing gamma11 was the most potent for A(1)-R and 5-HT(1A)-R (p < 0.05, one way ANOVA) while gamma7 was most potent for the other two receptors. gamma11 was 3-8-fold more potent for the A(1)-R than were the other gamma subtypes. Also, gamma11 was 2-8-fold more potent for A(1)-R than at the other receptors, suggesting a unique coupling specificity of the A(1)-R for gamma11. In contrast, the discrimination by receptors for the other betagamma subtypes (beta1 and gamma1, gamma2, gamma7, and gamma10) was limited (2-3-fold). Thus the exquisite betagamma specificity of individual receptors reported in whole cell studies may depend on in vivo mechanisms beyond direct receptor recognition of betagamma subtypes.
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MESH Headings
- Animals
- CHO Cells
- Cell Line
- Cricetinae
- GTP-Binding Protein alpha Subunits, Gi-Go/metabolism
- Heterotrimeric GTP-Binding Proteins/agonists
- Heterotrimeric GTP-Binding Proteins/metabolism
- Receptors, Adrenergic, alpha-2/metabolism
- Receptors, Opioid, mu/metabolism
- Receptors, Purinergic P1/metabolism
- Receptors, Serotonin/metabolism
- Receptors, Serotonin, 5-HT1
- Swine
- Tumor Cells, Cultured
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The G protein beta subunit is a determinant in the coupling of Gs to the beta 1-adrenergic and A2a adenosine receptors. J Biol Chem 2001; 276:15801-9. [PMID: 11278863 DOI: 10.1074/jbc.m011233200] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The signaling specificity of five purified G protein betagamma dimers, beta(1)gamma(2), beta(2)gamma(2), beta(3)gamma(2), beta(4)gamma(2), and beta(5)gamma(2), was explored by reconstituting them with G(s) alpha and receptors or effectors in the adenylyl cyclase cascade. The ability of the five betagamma dimers to support receptor-alpha-betagamma interactions was examined using membranes expressing the beta(1)-adrenergic or A2a adenosine receptors. These receptors discriminated among the defined heterotrimers based solely on the beta isoform. The beta(4)gamma(2) dimer demonstrated the highest coupling efficiency to either receptor. The beta(5)gamma(2) dimer coupled poorly to each receptor, with EC(50) values 40-200-fold higher than those observed with beta(4)gamma(2). Strikingly, whereas the EC(50) of the beta(1)gamma(2) dimer at the beta(1)-adrenergic receptor was similar to beta(4)gamma(2), its EC(50) was 20-fold higher at the A2a adenosine receptor. Inhibition of adenylyl cyclase type I (AC1) and stimulation of type II (AC2) by the betagamma dimers were measured. betagamma dimers containing Gbeta(1-4) were able to stimulate AC2 similarly, and beta(5)gamma(2) was much less potent. beta(1)gamma(2), beta(2)gamma(2), and beta(4)gamma(2) inhibited AC1 equally; beta(3)gamma(2) was 10-fold less effective, and beta(5)gamma(2) had no effect. These data argue that the beta isoform in the betagamma dimer can determine the specificity of signaling at both receptors and effectors.
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Synthesis and Structural Characterization of an Imidazolium-Linked Cyclophane and the Silver Complex of an N-Heterocyclic Carbene-Linked Cyclophane. Organometallics 2001. [DOI: 10.1021/om010085s] [Citation(s) in RCA: 139] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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