1
|
Synthesis and Evaluation of a Monomethyl Auristatin E─Integrin α vβ 6 Binding Peptide-Drug Conjugate for Tumor Targeted Drug Delivery. J Med Chem 2023; 66:9842-9852. [PMID: 37417540 PMCID: PMC10388305 DOI: 10.1021/acs.jmedchem.3c00631] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Indexed: 07/08/2023]
Abstract
Many anticancer drugs exhibit high systemic off-target toxicities causing severe side effects. Peptide-drug conjugates (PDCs) that target tumor-specific receptors such as integrin αvβ6 are emerging as powerful tools to overcome these challenges. The development of an integrin αvβ6-selective PDC was achieved by combining the therapeutic efficacy of the cytotoxic drug monomethyl auristatin E with the selectivity of the αvβ6-binding peptide (αvβ6-BP) and with the ability of positron emission tomography (PET) imaging by copper-64. The [64Cu]PDC-1 was produced efficiently and in high purity. The PDC exhibited high human serum stability, integrin αvβ6-selective internalization, cell binding, and cytotoxicity. Integrin αvβ6-selective tumor accumulation of the [64Cu]PDC-1 was visualized with PET-imaging and corroborated by biodistribution, and [64Cu]PDC-1 showed promising in vivo pharmacokinetics. The [natCu]PDC-1 treatment resulted in prolonged survival of mice bearing αvβ6 (+) tumors (median survival: 77 days, vs αvβ6 (-) tumor group 49 days, and all other control groups 37 days).
Collapse
|
2
|
Preclinical evaluation of 68Ga- and 177Lu-labeled integrin α vβ 6-targeting radiotheranostic peptides. J Nucl Med 2022; 64:639-644. [PMID: 36207137 DOI: 10.2967/jnumed.122.264749] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/28/2022] [Accepted: 09/28/2022] [Indexed: 12/30/2022] Open
Abstract
Rationale: The integrin αvβ6, an epithelial-specific cell surface receptor, is overexpressed on numerous malignancies, including the highly lethal pancreatic ductal adenocarcinomas (PDAC). Here, we developed and tested a novel αvβ6-targeting peptide, DOTA-5G (1) radiolabeled with gallium-68 for positron emission tomography/computed tomography (PET/CT) imaging, and lutetium-177 for treatment. With the goal to develop a radiotheranostic, further modifications were made for increased circulation time, renal recycling, and tumor uptake, yielding DOTA-ABM-5G (2). Methods: Peptides 1 and 2 were synthesized on solid phase and their affinity for αvβ6 assessed by ELISA. The peptides were radiolabeled with gallium-68 and lutetium-177. In vitro cell binding, internalization, and efflux of 68Ga-1 and 177Lu-2 were evaluated in αvβ6 (+) BxPC-3 human pancreatic cancer cells. PET/CT imaging of 68Ga-1 and 68Ga-2 was performed in female nu/nu mice bearing subcutaneous BxPC-3 tumors. Biodistribution was performed for 68Ga-1 (1 and 2 h p.i.), 68Ga-2 (2 and 4 h p.i.), and 177Lu-1 and 177Lu-2 (1, 24, 48, and 72 h p.i.). The 177Lu-2 biodistribution data were extrapolated for human dosimetry data estimates using OLINDA/EXM 1.1. Therapeutic efficacy of 177Lu-2 was evaluated in mice bearing BxPC-3 tumors. Results: Peptides 1 and 2 demonstrated high affinity for αvβ6 by ELISA. 68Ga-1, 68Ga-2, 177Lu-1 and 177Lu-2 were synthesized in high radiochemical purity (RCP). Rapid in vitro binding and internalization of 68Ga-1 and 177Lu-2 were observed in BxPC-3 cells. PET/CT imaging and biodistribution studies demonstrated uptake in BxPC-3 tumors. Introduction of the ABM in 177Lu-2 resulted in a 5-fold increase in tumor uptake and retention over time. Based on the extended dosimetry data the dose-limiting organ for 177Lu-2 are the kidneys. Treatment with 177Lu-2 prolonged survival. Conclusion: 68Ga-1 and 177Lu-2 demonstrated high affinity for the integrin αvβ6 both in vitro and in vivo, were rapidly internalized into BxPC-3 cells, and were stable in mouse and human serum. Both radiotracers showed favorable pharmacokinetics in pre-clinical studies with predominantly renal excretion and good tumor-to-normal tissue ratios. Favorable human dosimetry data suggest the potential of 177Lu-2 as a treatment for PDAC.
Collapse
|
3
|
Primary Hemiarthroplasty for the Treatment of Basicervical Femoral Neck Fractures. Cureus 2022; 14:e25210. [PMID: 35746995 PMCID: PMC9211754 DOI: 10.7759/cureus.25210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2022] [Indexed: 11/05/2022] Open
Abstract
Purpose Basicervical femoral neck fractures are uncommon injuries that occur at the extracapsular base of the femoral neck at its transition with the intertrochanteric line. Controversy remains in the orthopedic literature as to the optimal method of treatment for this fracture type given the inherent instability and greater rate of implant failure with traditional fixation constructs. The purpose of this study is to quantify the incidence and preferred treatment methods of basicervical hip fractures at a single, regional, Level 1 trauma center and to identify differences in postoperative complications between treatment options. Methods The present study is a retrospective case series from a single regional health network, including 316 patients with hip fractures. Basicervical femoral neck fractures were identified. Reoperation rates within 90 days, implant failures or nonunions, postoperative ambulation distances and range of motion, and discharge dispositions were compared across patients grouped by surgical treatment with either cephalomedullary nail, sliding hip screw, or hemiarthroplasty (HA). Results Basicervical femoral neck fractures represented 6.6% of this study population. The cephalomedullary nail group demonstrated rates of implant failure and return to the operating room within 90 days of 40% (4/10) and 20% (2/10), respectively. No patients who underwent hemiarthroplasty experienced a failure of fixation or return to the operating room. Conclusions This study suggests a much lower rate of fixation failure or need for reoperation with hemiarthroplasty treatment compared to cephalomedullary nail construct for basicervical femoral neck fractures and may be an underutilized treatment method for this fracture type. The promising results seen with this case series should encourage further investigation into HA as a primary treatment for these uncommon, yet challenging, fractures.
Collapse
|
4
|
A Comparison of Evans Blue and 4-( p-Iodophenyl)butyryl Albumin Binding Moieties on an Integrin α vβ 6 Binding Peptide. Pharmaceutics 2022; 14:pharmaceutics14040745. [PMID: 35456579 PMCID: PMC9025560 DOI: 10.3390/pharmaceutics14040745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 03/23/2022] [Accepted: 03/25/2022] [Indexed: 01/26/2023] Open
Abstract
Serum albumin binding moieties (ABMs) such as the Evans blue (EB) dye fragment and the 4-(p-iodophenyl)butyryl (IP) have been used to improve the pharmacokinetic profile of many radiopharmaceuticals. The goal of this work was to directly compare these two ABMs when conjugated to an integrin αvβ6 binding peptide (αvβ6-BP); a peptide that is currently being used for positron emission tomography (PET) imaging in patients with metastatic cancer. The ABM-modified αvβ6-BP peptides were synthesized with a 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetracetic acid (DOTA) chelator for radiolabeling with copper-64 to yield [64Cu]Cu DOTA-EB-αvβ6-BP ([64Cu]1) and [64Cu]Cu DOTA-IP-αvβ6-BP ([64Cu]2). Both peptides were evaluated in vitro for serum albumin binding, serum stability, and cell binding and internalization in the paired engineered melanoma cells DX3puroβ6 (αvβ6 +) and DX3puro (αvβ6 −), and pancreatic BxPC-3 (αvβ6 +) cells and in vivo in a BxPC-3 xenograft mouse model. Serum albumin binding for [64Cu]1 and [64Cu]2 was 53−63% and 42−44%, respectively, with good human serum stability (24 h: [64Cu]1 76%, [64Cu]2 90%). Selective αvβ6 cell binding was observed for both [64Cu]1 and [64Cu]2 (αvβ6 (+) cells: 30.3−55.8% and 48.5−60.2%, respectively, vs. αvβ6 (−) cells <3.1% for both). In vivo BxPC-3 tumor uptake for both peptides at 4 h was 5.29 ± 0.59 and 7.60 ± 0.43% ID/g ([64Cu]1 and [64Cu]2, respectively), and remained at 3.32 ± 0.46 and 4.91 ± 1.19% ID/g, respectively, at 72 h, representing a >3-fold improvement over the non-ABM parent peptide and thereby providing improved PET images. Comparing [64Cu]1 and [64Cu]2, the IP-ABM-αvβ6-BP [64Cu]2 displayed higher serum stability, higher tumor accumulation, and lower kidney and liver accumulation, resulting in better tumor-to-organ ratios for high contrast visualization of the αvβ6 (+) tumor by PET imaging.
Collapse
|
5
|
Repurposing an atherosclerosis targeting peptide for tumor imaging. Biomed Pharmacother 2021; 145:112469. [PMID: 34864315 DOI: 10.1016/j.biopha.2021.112469] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Revised: 11/15/2021] [Accepted: 11/19/2021] [Indexed: 12/31/2022] Open
Abstract
Cancer and atherosclerosis are chronic diseases that share common characteristics at both early and advanced stages and can arise from multiple factors. Both diseases are characterized by uncontrolled cell proliferation, inflammation, angiogenesis and apoptosis. Herein we investigated the ability of a peptide (CTHRSSVVC), that was previously reported to bind atherosclerotic lesions to home in the tumor microenvironment. The CTHRSSVVC peptide was synthesized on solid phase and N-terminally labeled with a sulfo-Cy5 dye. The specific binding to macrophage was evaluated in vitro with flow cytometry and immunofluorescence and in vivo for tumor targeting in BALB/c mice bearing a 4T1 tumor using optical imaging. The sulfo-Cy5-CTHRSSVVC peptide was synthesized in greater than 99% purity. No selective binding of the sulfo-Cy5-CTHRSSVVC peptide to macrophages in vitro was observed, however in vivo the sulfo-Cy5-CTHRSSVVC peptide accumulated in the 4T1 tumor, with a tumor-to-normal tissue ratio of 7.21 ± 1.44 at 2 h post injection. Ex vivo analysis of tumor tissue by confocal microscopy suggested that the sulfo-Cy5-CTHRSSVVC peptide had accumulated in the stroma of the tumor specifically, in regions of spindle shaped cells. In conclusion, although the target for the sulfo-Cy5-CTHRSSVVC peptide remains to be identified, the Cy5-CTHRSSVVC peptide warrants further investigation as a tumor imaging agent.
Collapse
|
6
|
Evaluation of Copper-64-Labeled α vβ 6-Targeting Peptides: Addition of an Albumin Binding Moiety to Improve Pharmacokinetics. Mol Pharm 2021; 18:4437-4447. [PMID: 34783573 DOI: 10.1021/acs.molpharmaceut.1c00632] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The incorporation of non-covalent albumin binding moieties (ABMs) into radiotracers results in increased circulation time, leading to a higher uptake in the target tissues such as the tumor, and, in some cases, reduced kidney retention. We previously developed [18F]AlF NOTA-K(ABM)-αvβ6-BP, where αvβ6-BP is a peptide with high affinity for the cell surface receptor integrin αvβ6 that is overexpressed in several cancers, and the ABM is an iodophenyl-based moiety. [18F]AlF NOTA-K(ABM)-αvβ6-BP demonstrated prolonged blood circulation compared to the non-ABM parent peptide, resulting in high, αvβ6-targeted uptake with continuously improving detection of αvβ6(+) tumors using PET/CT. To further extend the imaging window beyond that of fluorine-18 (t1/2 = 110 min) and to investigate the pharmacokinetics at later time points, we radiolabeled the αvβ6-BP with copper-64 (t1/2 = 12.7 h). Two peptides were synthesized without (1) and with (2) the ABM and radiolabeled with copper-64 to yield [64Cu]1 and [64Cu]2, respectively. The affinity of [natCu]1 and [natCu]2 for the integrin αvβ6 was assessed by enzyme-linked immunosorbent assay. [64Cu]1 and [64Cu]2 were evaluated in vitro (cell binding and internalization) using DX3puroβ6 (αvβ6(+)), DX3puro (αvβ6(-)), and pancreatic BxPC-3 (αvβ6(+)) cells, in an albumin binding assay, and for stability in both mouse and human serum. In vivo (PET/CT imaging) and biodistribution studies were done in mouse models bearing either the paired DX3puroβ6/DX3puro or BxPC-3 xenograft tumors. [64Cu]1 and [64Cu]2 were synthesized in ≥97% radiochemical purity. In vitro, [natCu]1 and [natCu]2 maintained low nanomolar affinity for integrin αvβ6 (IC50 = 28 ± 3 and 19 ± 5 nM, respectively); [64Cu]1 and [64Cu]2 showed comparable binding to αvβ6(+) cells (DX3puroβ6: ≥70%, ≥42% internalized; BxPC-3: ≥19%, ≥12% internalized) and ≤3% to the αvβ6(-) DX3puro cells. Both radiotracers were ≥98% stable in human serum at 24 h, and [64Cu]2 showed a 6-fold higher binding to human serum protein than [64Cu]1. In vivo, selective uptake in the αvβ6(+) tumors was observed with tumor visualization up to 72 h for [64Cu]2. A 3-5-fold higher αvβ6(+) tumor uptake of [64Cu]2 vs [64Cu]1 was observed throughout, at least 2.7-fold improved BxPC-3-to-kidney and BxPC-3-to-blood ratios, and 2-fold improved BxPC-3-to-stomach ratios were noted for [64Cu]2 at 48 h. Incorporation of an iodophenyl-based ABM into the αvβ6-BP ([64Cu]2) prolonged circulation time and resulted in improved pharmacokinetics, including increased uptake in αvβ6(+) tumors that enabled visualization of αvβ6(+) tumors up to 72 h by PET/CT imaging.
Collapse
|
7
|
The Effects of an Albumin Binding Moiety on the Targeting and Pharmacokinetics of an Integrin α vβ 6-Selective Peptide Labeled with Aluminum [ 18F]Fluoride. Mol Imaging Biol 2021; 22:1543-1552. [PMID: 32383076 DOI: 10.1007/s11307-020-01500-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
PURPOSE The αvβ6-BP peptide selectively targets the integrin αvβ6, a cell surface receptor recognized as a prognostic indicator for several challenging malignancies. Given that the 4-[18F]fluorobenzoyl (FBA)-labeled peptide is a promising PET imaging agent, radiolabeling via aluminum [18F]fluoride chelation and introduction of an albumin binding moiety (ABM) have the potential to considerably simplify radiochemistry and improve the pharmacokinetics by increasing biological half-life. PROCEDURES The peptides NOTA-αvβ6-BP (1) and NOTA-K(ABM)-αvβ6-BP (2) were synthesized on solid phase, radiolabeled with aluminum [18F]fluoride, and evaluated in vitro (integrin ELISA, albumin binding, cell studies) and in vivo in mouse models bearing paired DX3puroβ6 [αvβ6(+)]/DX3puro [αvβ6(-)], and for [18F]AlF 2, BxPC-3 [αvβ6(+)] cell xenografts (PET imaging, biodistribution). RESULTS The peptides were radiolabeled in 23.0 ± 5.7 % and 22.1 ± 4.4 % decay-corrected radiochemical yield, respectively, for [18F]AlF 1 and [18F]AlF 2. Both demonstrated excellent affinity and selectivity for integrin αvβ6 by ELISA (IC50(αvβ6) = 3-7 nM vs IC50(αvβ3) > 10 μM) and in cell binding studies (51.0 ± 0.7 % and 47.2 ± 0.7 % of total radioactivity bound to DX3puroβ6 cells at 1 h, respectively, vs. ≤ 1.2 % to DX3puro for both compounds). The radiotracer [18F]AlF 1 bound to human serum at 16.3 ± 1.9 %, compared to 67.5 ± 1.0 % for the ABM-containing [18F]AlF 2. In vivo studies confirmed the effect of the ABM on blood circulation (≤ 0.1 % ID/g remaining in blood for [18F]AlF 1 as soon as 1 h p.i. vs. > 2 % ID/g for [18F]AlF 2 at 6 h p.i.) and higher αvβ6(+) tumor uptake (4 h: DX3puroβ6; [18F]AlF 1: 3.0 ± 0.7 % ID/g, [18F]AlF 2: 7.2 ± 0.7 % ID/g; BxPC-3; [18F]AlF 2: 10.2 ± 0.1 % ID/g). CONCLUSION Both compounds were prepared using standard chemistries; affinity and selectivity for integrin αvβ6 in vitro remained unaffected by the albumin binding moiety. In vivo, the albumin binding moiety resulted in prolonged circulation and higher αvβ6-targeted uptake.
Collapse
|
8
|
Asymmetric conjugate addition reactions with chiral oxadiazinones: Unusual conformational properties of the oxadiazinones. Tetrahedron 2021. [DOI: 10.1016/j.tet.2021.132002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
9
|
αvβ6-Targeted Molecular PET/CT Imaging of the Lungs After SARS-CoV-2 Infection. J Nucl Med 2020; 61:1717-1719. [PMID: 32948681 PMCID: PMC8679627 DOI: 10.2967/jnumed.120.255364] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 09/15/2020] [Indexed: 01/23/2023] Open
Abstract
The true impact and long-term damage to organs such as the lungs after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection remain to be determined. Noninvasive molecularly targeted imaging may play a critical role in aiding visualization and understanding of the systemic damage. We have identified αvβ6 as a molecular target; an epithelium-specific cell surface receptor that is low or undetectable in healthy adult epithelium but upregulated in select injured tissues, including fibrotic lung. Herein we report the first human PET/CT images using the integrin αvβ6-binding peptide (18F-αvβ6-BP) in a patient 2 mo after the acute phase of infection. Minimal uptake of 18F-αvβ6-BP was noted in normal lung parenchyma, with uptake being elevated in areas corresponding to opacities on CT. This case suggests that 18F-αvβ6-BP PET/CT is a promising noninvasive approach to identify the presence and potentially monitor the persistence and progression of lung damage.
Collapse
|
10
|
Toxic time bombs: Frequent detection of anticoagulant rodenticides in urban reptiles at multiple trophic levels. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 724:138218. [PMID: 32247128 DOI: 10.1016/j.scitotenv.2020.138218] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 03/24/2020] [Accepted: 03/24/2020] [Indexed: 06/11/2023]
Abstract
Anticoagulant rodenticides (ARs) are regularly used around the world to control pest mammals. Second-generation anticoagulant rodenticides (SGARs) are highly persistent in biological tissue and have a high potential for bioaccumulation and biomagnification. Consequently, exposure and poisoning of non-target organisms has been frequently documented, especially in countries with unregulated AR sales and usage. Most of this research has focussed on rodent-predators, usually raptors and predatory mammals, although exposure has also been documented in invertebrates and insectivorous fauna. Few studies have explored non-target exposure in reptiles, despite species sharing similar trophic positions and dietary preferences to other exposed fauna. We tested three abundant urban reptile species in Perth, Western Australia that differ in diet and trophic tiers for multiple AR exposure, the dugite Pseudonaja affinis (rodent-predator), the bobtail Tiliqua rugosa (omnivore) and the tiger snake Notechis scutatus occidentalis (frog-predator). We found frequent exposure in all three species (91% in dugites, 60% in bobtails and 45% in tiger snakes). Mean combined liver concentrations of ARs of exposed individuals were 0.178 mg/kg in dugites, 0.040 mg/kg in bobtails and 0.009 mg/kg in tiger snakes. High exposure frequency and liver concentration was expected for the dugite. Exposure in the other species is more surprising and implies widespread AR contamination of the food web. We discuss the likelihood of global AR exposure of urban reptiles, highlight the potential for reptiles to be important vectors of ARs in the food web and highlight implications for humans consuming wild reptiles.
Collapse
|
11
|
The plant natural product 2-methoxy-1,4-naphthoquinone stimulates therapeutic neural repair properties of olfactory ensheathing cells. Sci Rep 2020; 10:951. [PMID: 31969642 PMCID: PMC6976649 DOI: 10.1038/s41598-020-57793-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 12/11/2019] [Indexed: 01/04/2023] Open
Abstract
Olfactory ensheathing cells (OECs) are crucial for promoting the regeneration of the primary olfactory nervous system that occurs throughout life. Transplantation of OECs has emerged as a promising therapy for nervous system injuries, in particular for spinal cord injury repair. Functional outcomes in both animals and humans are, however, highly variable, primarily because it is difficult to rapidly obtain enough OECs for transplantation. Compounds which can stimulate OEC proliferation without changing the phenotype of the cells are therefore highly sought after. Additionally, compounds which can stimulate favourable cell behaviours such as migration and phagocytic activity are desirable. We conducted a medium-throughput screen testing the Davis open access natural product-based library (472 compounds) and subsequently identified the known plant natural product 2-methoxy-1,4-naphthoquinone as a stimulant of OEC viability. We showed that 2-methoxy-1,4-naphthoquinone: (i) strongly stimulates proliferation over several weeks in culture whilst maintaining the OEC phenotype; (ii) stimulates the phagocytic activity of OECs, and (iii) modulates the cell cycle. We also identified the transcription factor Nrf2 as the compound’s potential molecular target. From these extensive investigations we conclude that 2-methoxy-1,4-naphthoquinone may enhance the therapeutic potential of OECs by stimulating proliferation prior to transplantation.
Collapse
|
12
|
Fully automated peptide radiolabeling from [ 18F]fluoride. RSC Adv 2019; 9:8638-8649. [PMID: 35518701 PMCID: PMC9061836 DOI: 10.1039/c8ra10541c] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 02/26/2019] [Indexed: 11/21/2022] Open
Abstract
The biological properties of receptor-targeted peptides have made them popular diagnostic imaging and therapeutic agents. Typically, the synthesis of fluorine-18 radiolabeled receptor-targeted peptides for positron emission tomography (PET) imaging is a time consuming, complex, multi-step synthetic process that is highly variable based on the peptide. The complexity associated with the radiolabeling route and lack of robust automated protocols can hinder translation into the clinic. A fully automated batch production to radiolabel three peptides (YGGFL, cRGDyK, and Pyr-QKLGNQWAVGHLM) from fluorine-18 using the ELIXYS FLEX/CHEM® radiosynthesizer in a two-step process is described. First, the prosthetic group, 6-[18F]fluoronicotinyl-2,3,5,6-tetrafluorophenyl ester ([18F]FPy-TFP) was synthesized and subsequently attached to the peptide. The [18F]FPy-peptides were synthesized in 13-26% decay corrected yields from fluorine-18 with high molar activity 1-5 Ci μmol-1 and radiochemical purity of >99% in an overall synthesis time of 97 ± 3 minutes.
Collapse
|
13
|
Preclinical Development and First-in-Human Imaging of the Integrin α vβ 6 with [ 18F]α vβ 6-Binding Peptide in Metastatic Carcinoma. Clin Cancer Res 2019; 25:1206-1215. [PMID: 30401687 PMCID: PMC6377828 DOI: 10.1158/1078-0432.ccr-18-2665] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 09/28/2018] [Accepted: 11/02/2018] [Indexed: 01/08/2023]
Abstract
PURPOSE The study was undertaken to develop and evaluate the potential of an integrin αvβ6-binding peptide (αvβ6-BP) for noninvasive imaging of a diverse range of malignancies with PET. EXPERIMENTAL DESIGN The peptide αvβ6-BP was prepared on solid phase and radiolabeled with 4-[18F]fluorobenzoic acid. In vitro testing included ELISA, serum stability, and cell binding studies using paired αvβ6-expressing and αvβ6-null cell lines. In vivo evaluation (PET/CT, biodistribution, and autoradiography) was performed in a mouse model bearing the same paired αvβ6-expressing and αvβ6-null cell xenografts. A first-in-human PET/CT imaging study was performed in patients with metastatic lung, colon, breast, or pancreatic cancer. RESULTS [18F]αvβ6-BP displayed excellent affinity and selectivity for the integrin αvβ6 in vitro [IC50(αvβ6) = 1.2 nmol/L vs IC50(αvβ3) >10 μmol/L] in addition to rapid target-specific cell binding and internalization (72.5% ± 0.9% binding and 52.5% ± 1.8%, respectively). Favorable tumor affinity and selectivity were retained in the mouse model and excretion of unbound [18F]αvβ6-BP was rapid, primarily via the kidneys. In patients, [18F]αvβ6-BP was well tolerated without noticeable adverse side effects. PET images showed significant uptake of [18F]αvβ6-BP in both the primary lesion and metastases, including metastasis to brain, bone, liver, and lung. CONCLUSIONS The clinical impact of [18F]αvβ6-BP PET imaging demonstrated in this first-in-human study is immediate for a broad spectrum of malignancies.
Collapse
|
14
|
N,N,N-Trimethyl-5-[(2,3,5,6-tetrafluorophenoxy)carbonyl]pyridin-2-aminium trifluoromethanesulfonate a precursor for the synthesis of 2,3,5,6-tetrafluorophenyl 6-[ 18F]-fluoronicotinate. ACTA CRYSTALLOGRAPHICA SECTION C-STRUCTURAL CHEMISTRY 2018; 74:604-607. [PMID: 29726470 DOI: 10.1107/s2053229618005430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 04/07/2018] [Indexed: 11/10/2022]
Abstract
The synthesis, recrystallization, and X-ray deterimination of N,N,N-trimethyl-5-[(2,3,5,6-tetrafluorophenoxy)carbonyl]pyridin-2-aminium trifluoromethanesulfonate (PyTFP-precursor), C15H13F4N2O2+·CF3SO3-, is described. This triflate salt precursor is required for the synthesis of 2,3,5,6-tetrafluorophenyl 6-[18F]-fluoronicotinate ([18F]FPyTFP), a prosthetic group used to radiolabel peptides for positron emission tomography (PET), as peptides are increasingly being used as PET-imaging probes in nuclear medicine. Radiolabeling of peptides is typically done using a `prosthetic group', a small synthon to which the radioisotope is attached in the first step, followed by attachment to the peptide in the second step. During the synthesis of the PyTFP-precursor, displacement of a Cl atom with trimethylamine gas and anion replacement with a triflate counter-ion is critical, as incomplete replacement would hinder radioisotopic incorporation of nucleophilic fluorine-18 and result in diminished radiochemical yields. The structural determination of the PyTFP-precursor by X-ray crystallography helped confirm the anion exchange of chloride with triflate.
Collapse
|
15
|
In Vivo Tracking of Copper-64 Radiolabeled Nanoparticles in Lactuca sativa. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:12537-12546. [PMID: 28954194 DOI: 10.1021/acs.est.7b03333] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Engineered nanoparticles (NPs) are increasingly used in commercial products including automotive lubricants, clothing, deodorants, sunscreens, and cosmetics and can potentially accumulate in our food supply. Given their size it is difficult to detect and visualize the presence of NPs in environmental samples, including crop plants. New analytical tools are needed to fill the void for detection and visualization of NPs in complex biological and environmental matrices. We aimed to determine whether radiolabeled NPs could be used as a noninvasive, highly sensitive analytical tool to quantitatively track and visualize NP transport and accumulation in vivo in lettuce (Lactuca sativa) and to investigate the effect of NP size on transport and distribution over time using a combination of autoradiography, positron emission tomography (PET)/computed tomography (CT), scanning electron microscopy (SEM), and transition electron microscopy (TEM). Azide functionalized NPs were radiolabeled via a "click" reaction with copper-64 (64Cu)-1,4,7-triazacyclononane triacetic acid (NOTA) azadibenzocyclooctyne (ADIBO) conjugate ([64Cu]-ADIBO-NOTA) via copper-free Huisgen-1,3-dipolar cycloaddition reaction. This yielded radiolabeled [64Cu]-NPs of uniform shape and size with a high radiochemical purity (>99%), specific activity of 2.2 mCi/mg of NP, and high stability (i.e., no detectable dissolution) over 24 h across a pH range of 5-9. Both PET/CT and autoradiography showed that [64Cu]-NPs entered the lettuce seedling roots and were rapidly transported to the cotyledons with the majority of the accumulation inside the roots. Uptake and transport of intact NPs was size-dependent, and in combination with the accumulation within the roots suggests a filtering effect of the plant cell walls at various points along the water transport pathway.
Collapse
|
16
|
Dichloro-naphthoquinone as a non-classical inhibitor of the mycobacterial carbonic anhydrase Rv3588c. MEDCHEMCOMM 2017; 8:1318-1321. [PMID: 30108843 PMCID: PMC6072524 DOI: 10.1039/c7md00090a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 05/08/2017] [Indexed: 11/21/2022]
Abstract
The soluble mycobacterial carbonic anhydrases Rv3588c and Rv1284 belong to a different class of carbonic anhydrases than those found in humans, making them attractive drug targets by using the inherent differences in the folds of the different classes. By screening a natural product library, we identified naphthoquinone derivatives as a novel non-classical inhibitor scaffold of mycobacterial carbonic anhydrases that lack the sulfonamide/sulfamate group and thus did not affect human carbonic anhydrase II.
Collapse
|
17
|
Abstract
Solid-phase peptide synthesis, head-to-tail cyclization, and subsequent radiolabeling provided a reproducible, simple, rapid synthetic method to generate the cyclic peptide radiotracer cRGDyK([18F]FBA). Herein is reported the first on-resin cyclization and 18F-radiolabeling of a cyclic peptide (cRGDyK) in an overall peptide synthesis yield of 88% (cRGDyK(NH2)) and subsequent radiolabeling yield of 14 ± 2% (decay corrected, n = 4). This approach is generally applicable to the development of an automated process for the synthesis of cyclic radiolabeled peptides for positron emission tomography (PET).
Collapse
|
18
|
Synthesis of cholesteryl-α-D-lactoside via generation and trapping of a stable β-lactosyl iodide. Tetrahedron Lett 2015; 56:3690-3694. [PMID: 26543257 DOI: 10.1016/j.tetlet.2015.05.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The generation of β-lactosyl iodide was carried out under non-in situ-anomerization, metal free conditions by reacting commercially available β-per-O-acetylated lactose with trimethylsilyl iodide (TMSI). The β-iodide was surprisingly stable as evidenced by NMR spectroscopy. Introduction of octanol or cholesterol under microwave conditions gave high yields of α-linked glycoconjugates. Careful analysis of the reaction products and mechanistic considerations suggest an acid catalyzed rearrangement that provides α-linked glycosylation products with a free C2-hydroxyl. Accessibility to these compounds may further advance glycolipidomic profiling of immune modulating bacterial derived-glycans.
Collapse
|
19
|
Synthesis and structural characterization of three unique Helicobacter pylori α-cholesteryl phosphatidyl glucosides. Angew Chem Int Ed Engl 2014; 53:13400-3. [PMID: 25195783 PMCID: PMC4319363 DOI: 10.1002/anie.201406529] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Indexed: 01/28/2023]
Abstract
Steryl glycosides produced by bacteria play important biological roles in the evasion and modulation of host immunity. Step-economical syntheses of three cholesteryl-6-O-phosphatidyl-α-D-glucopyranosides (αCPG) unique to Helicobacter pylori have been achieved. The approach relies upon regioselective deprotection of per-O-trimethylsilyl-α-D-cholesterylglucoside at C6 followed by phosphoramidite coupling. Global TMS ether deprotection in the presence of oxygen and subsequent deprotection of the cyano ethyl phosphoester afforded the target compounds in 16-21 % overall yield starting from D-glucose. The structures of these natural products were determined using a combination of 2D NMR methods and mass spectrometry. These robust synthesis and characterization protocols provide analogues to facilitate glycolipidomic profiling and biological studies.
Collapse
|
20
|
Synthesis and Structural Characterization of Three UniqueHelicobacter pyloriα-Cholesteryl Phosphatidyl Glucosides. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201406529] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
|
21
|
Two-step functionalization of oligosaccharides using glycosyl iodide and trimethylene oxide and its applications to multivalent glycoconjugates. Chemistry 2014; 20:6444-54. [PMID: 24715520 PMCID: PMC4497529 DOI: 10.1002/chem.201400024] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2014] [Indexed: 11/05/2022]
Abstract
Oligosaccharide conjugates, such as glycoproteins and glycolipids, are potential chemotherapeutics and also serve as useful tools for understanding the biological roles of carbohydrates. With many modern isolation and synthetic technologies providing access to a wide variety of free sugars, there is increasing need for general methodologies for carbohydrate functionalization. Herein, we report a two-step methodology for the conjugation of per-O-acetylated oligosaccharides to functionalized linkers that can be used for various displays. Oligosaccharides obtained from both synthetic and commercial sources were converted to glycosyl iodides and activated with I2 to form reactive donors that were subsequently trapped with trimethylene oxide to form iodopropyl conjugates in a single step. The terminal iodide served as a chemical handle for further modification. Conversion into the corresponding azide followed by copper-catalyzed azide-alkyne cycloaddition afforded multivalent glycoconjugates of Gb3 for further investigation as anti-cancer therapeutics.
Collapse
|
22
|
A fused [3.3.0]-neoglycoside lactone derived from glucuronic acid. Acta Crystallogr C 2013; 69:1062-6. [PMID: 24005522 PMCID: PMC3769141 DOI: 10.1107/s0108270113013723] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 05/17/2013] [Indexed: 11/10/2022] Open
Abstract
The bridged next-generation aminoglycoside (neoglycoside), 1-deoxy-1-[(methoxy)methylamino)]-2,5-di-O-triethylsilyl-β-D-glucofuranurono-γ-lactone {systematic name: (3S,3aS,5R,6R,6aS)-5-[methoxy(methyl)amino]-3,6-bis[(triethylsilyl)oxy]-2,3,3a,5,6,6a-hexahydrofuro[3,2-b]furan-2-one}, C20H41NO6Si2, was synthesized in a one-pot manner from commercially available D-glucuronic acid. This structure supports the properties associated with the anomeric effect for furanosides and can be employed to provide insight into the mechanisms by which alkoxyamine-appended natural products derive their enhanced biological activity. To the best of our knowledge, this is the first published crystal structure of a bicyclic neoglycoside and is the first neoglycoside to be completely and unambiguously characterized.
Collapse
|
23
|
Adapting to suburbia: bird ecology on an urban-bushland interface in Perth, Western Australia. ACTA ACUST UNITED AC 2013. [DOI: 10.1071/pc130110] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Birds in urban landscapes must contend with fragmented and degraded remnants of native vegetation and their
survival may be dependent on factors such as their ability to disperse through and/or utilize the urban matrix. We
examined the frequency of occurrence of birds in native bushland in Kings Park, Perth, Western Australia, and in nine
adjacent suburban gardens. We quantified dispersal capacity by observing bird crossing frequency and height over a
major six-lane road separating the bushland from adjacent gardens. Finally we quantified matrix utilisation by recording
foraging behaviour in urban gardens and bushland. Native bushland had a higher species richness than urban gardens
(30 versus 17 species) and 18 species were associated more strongly with bushland. Of these 18 species, 61% were
never recorded in urban gardens. Gardens were typified by three generalist species, the Singing Honeyeater
Lichenostomus virescens and the introduced Laughing Dove Spilopelia senegalensis and Spotted Dove S. chinensis.
Three generalist species, the Red Wattlebird Anthochaera carunculata, Rainbow Lorikeet Trichoglossus haematodus,
and Brown Honeyeater Lichmera indistincta were equally abundant in all habitats. Four of 18 bird species (Singing
Honeyeater Red Wattlebird, Rainbow Lorikeet, and Australian Ringneck Barnardius zonarius) accounted for the majority
of road crossing events. Urban gardens provided a rich resource for generalists and urban exploiters, all of which spent
significantly more time foraging on nectar in gardens and significantly more time foraging on insects in bushland. We
conclude that urban gardens provide habitat for some species that exploit nectar, but most species in bushland,
particularly insectivores, do not use gardens. Our results indicate the importance of retaining well-managed bushland
for supporting viable urban bird populations.
Collapse
|
24
|
COMMUNITIES ARE NOT ALL CREATED EQUAL: DESIGNING ENVIRONMENTS TO PREVENT VIOLENCE. Inj Prev 2012. [DOI: 10.1136/injuryprev-2012-040580d.22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
|
25
|
Chemoenzymatic synthesis of cholesteryl-6-O-tetradecanoyl-α-D-glucopyranoside: a product of host cholesterol efflux promoted by Helicobacter pylori. Chem Commun (Camb) 2012; 48:9083-5. [PMID: 22854787 DOI: 10.1039/c2cc33948j] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In a three-step protocol involving regioselective enzymatic acylation, per-O-trimethylsilylation, and a one-pot α-glycosidation-deprotection sequence, cholesteryl-6-O-tetradecanoyl-α-D-glucopyranoside (α-CAG) of Helicobacter pylori is afforded starting from glucose in an overall yield of 45%. The production of CAG can be scaled to make purified quantities available to the biological community for the first time.
Collapse
|
26
|
(5S)-4-(2,2-Dimethyl-prop-yl)-5-isopropyl-1,3,4-oxadiazinan-2-one. Acta Crystallogr Sect E Struct Rep Online 2010; 66:o3329-30. [PMID: 21589605 PMCID: PMC3011777 DOI: 10.1107/s1600536810048798] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 11/22/2010] [Indexed: 11/25/2022]
Abstract
The title compound, C11H22N2O2, has one chiral center and packs in the monoclinic space group P21. The asymmetric unit has five crystallographically independent molecules, four of which engage in intermolecular N—H⋯O hydrogen bonding.
Collapse
|
27
|
Synthesis, asymmetric aldol reactions, and x-ray crystallography of some oxadiazinanone derivatives. J Heterocycl Chem 2008. [DOI: 10.1002/jhet.5570450502] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
28
|
Gene expression changes in children with autism. Genomics 2007; 91:22-9. [PMID: 18006270 DOI: 10.1016/j.ygeno.2007.09.003] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2007] [Revised: 09/11/2007] [Accepted: 09/15/2007] [Indexed: 01/30/2023]
Abstract
The objective of this study was to identify gene expression differences in blood differences in children with autism (AU) and autism spectrum disorder (ASD) compared to general population controls. Transcriptional profiles were compared with age- and gender-matched, typically developing children from the general population (GP). The AU group was subdivided based on a history of developmental regression (A-R) or a history of early onset (A-E without regression). Total RNA from blood was processed on human Affymetrix microarrays. Thirty-five children with AU (17 with early onset autism and 18 with autism with regression) and 14 ASD children (who did not meet criteria for AU) were compared to 12 GP children. Unpaired t tests (corrected for multiple comparisons with a false discovery rate of 0.05) detected a number of genes that were regulated more than 1.5-fold for AU versus GP (n=55 genes), for A-E versus GP (n=140 genes), for A-R versus GP (n=20 genes), and for A-R versus A-E (n=494 genes). No genes were significantly regulated for ASD versus GP. There were 11 genes shared between the comparisons of all autism subgroups to GP (AU, A-E, and A-R versus GP) and these genes were all expressed in natural killer cells and many belonged to the KEGG natural killer cytotoxicity pathway (p=0.02). A subset of these genes (n=7) was tested with qRT-PCR and all genes were found to be differentially expressed (p<0.05). We conclude that the gene expression data support emerging evidence for abnormalities in peripheral blood leukocytes in autism that could represent a genetic and/or environmental predisposition to the disorder.
Collapse
|
29
|
Synthesis, reactivity and conformational stability of an l-phenylalanine derived oxadiazinanone. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.tetasy.2006.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
30
|
A rapid LC-MS-MS method for the determination of nicotine and cotinine in serum and saliva samples from smokers: validation and comparison with a radioimmunoassay method. J Chromatogr Sci 2005; 43:133-40. [PMID: 15842752 DOI: 10.1093/chromsci/43.3.133] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The development and validation of a rapid liquid chromatography (LC)-tandem mass spectrometry (MS-MS) method for determination of nicotine and cotinine in smokers' serum is described. The method is based on solid-phase extraction in a 96-well plate format and requires only 100 microL of serum. Using normal-phase chromatography, both analytes elute in less than 1 min, which permits high sample throughput applications. The calibrated range is 2-100 ng/mL nicotine and 20-1,000 ng/mL cotinine. For known samples, recovery is 95-116% for nicotine and 93-94% for cotinine. The method is extended to rat serum and human saliva (cotinine only) using partial validation techniques. When compared with an existing radioimmunoassay method in our laboratory, the LC-MS-MS method gives improved accuracy, precision, and sample throughput.
Collapse
|
31
|
Synthesis, X-ray crystallography and computational studies concerning an oxadiazinone derived from d-camphor: a structural limitation of oxadiazinones as chiral auxiliaries. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/j.tetasy.2005.01.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
32
|
A benzylisoquinoline alkaloid from Doryphora sassafras. JOURNAL OF NATURAL PRODUCTS 2001; 64:1572-1573. [PMID: 11754616 DOI: 10.1021/np010132l] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Chemical investigation of the Australian rainforest plant Doryphora sassafras has resulted in the isolation of a new natural product, 2-methyl-1-(p-methoxybenzyl)-6,7-methylenedioxyisoquinolinium chloride (1). The iodide salt of compound 1 has previously been synthesized but only partially characterized. This paper reports the full spectroscopic characterization of 1 by MS, IR, UV, and NMR data.
Collapse
|
33
|
Structural analysis of cDNA encoding thymidylate synthase in hepatic metastases of human colorectal tumors. Int J Colorectal Dis 2001; 16:318-25. [PMID: 11686531 DOI: 10.1007/s003840100319] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The enzyme thymidylate synthase (TS) is an important target of 5-fluorouracil (FUra) that is utilized for the treatment of disseminated colorectal cancer. One determinant of clinical response to FUra-based therapy is TS expression. with high levels of expression being predictive of poor response. In the present investigation the levels of immunoreactive TS were analyzed in human colon metastases in the liver (n=l1). The levels of TS ranged from 0.30 to 4.60 pmol TS/g tissue. A good correlation was observed between the levels of immunoreactive TS and TS mRNA (n=6, r=0.69). Of the 11 metastases analyzed, 5 exhibited relatively high levels of TS expression. Two metastases with high TS expression were obtained from patients who received adjuvant therapy with FUra. In 4 metastases with relatively high levels of TS expression, TS gene copy number was analyzed. No evidence for amplification of TS gene sequences was observed. The basis for the high levels of TS expression was examined by structural analysis of TS cDNA. No nucleotide sequence differences were detected in the coding regions of the TS genes from the metastases. Mutations were detected at positions 961 and/or 1031 in the 3'-untranslated regions of the TS gene from the metastases; mutations at these sites were also detected in DNA isolated from normal colon mucosa (n=4) and primary colorectal tumors (n=4). No correlation was observed between TS expression and the nucleotide alterations at these positions. Polymorphism was observed in the 5'-untranslated regions of the TS gene in hepatic metastases (n=6). A general trend was observed between the structure of the 5'-untranslated region of the gene and TS expression.
Collapse
|
34
|
Increased production of apolipoprotein B-containing lipoproteins in the absence of hyperlipidemia in transgenic mice expressing cholesterol 7alpha-hydroxylase. J Biol Chem 2001; 276:23304-11. [PMID: 11323427 DOI: 10.1074/jbc.m101853200] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The finding that expression of a cholesterol 7alpha-hydroxylase (CYP7A1) transgene in cultured rat hepatoma cells caused a coordinate increase in lipogenesis and secretion of apoB-containing lipoproteins led to the hypothesis that hepatic production of apoB-containing lipoproteins may be linked to the expression of CYP7A1 (Wang, S.-L., Du, E., Martin, T. D., and Davis, R. A. (1997) J. Biol. Chem. 272, 19351-19358). To examine this hypothesis in vivo, a transgene encoding CYP7A1 driven by the constitutive liver-specific enhancer of the human apoE gene was expressed in C56BL/6 mice. The expression of CYP7A1 mRNA (20-fold), protein ( approximately 10-fold), and enzyme activity (5-fold) was markedly increased in transgenic mice compared with non-transgenic littermates. The bile acid pool of CYP7A1 transgenic mice was doubled mainly due to increased hydrophobic dihydroxy bile acids. In CYP7A1 transgenic mice, livers contained approximately 3-fold more sterol response element-binding protein-2 mRNA. Hepatic expression of mRNAs encoding lipogenic enzymes (i.e. fatty-acid synthase, acetyl-CoA carboxylase, stearoyl-CoA desaturase, squalene synthase, farnesyl-pyrophosphate synthase, 3-hydroxy-3-methylglutaryl-CoA reductase, and low density lipoprotein receptor) as well as microsomal triglyceride transfer protein were elevated approximately 3-5-fold in transgenic mice. CYP7A1 transgenic mice also displayed a >2-fold increase in hepatic production and secretion of triglyceride-rich apoB-containing lipoproteins. Despite the increased hepatic secretion of apoB-containing lipoproteins in CYP7A1 mice, plasma levels of triglycerides and cholesterol were not significantly increased. These data suggest that the 5-fold increased expression of the low density lipoprotein receptor displayed by the livers of CYP7A1 transgenic mice was sufficient to compensate for the 2-fold increase production of apoB-containing lipoproteins. These findings emphasize the important homeostatic role that CYP7A1 plays in balancing the anabolic lipoprotein assembly/secretion pathway with the cholesterol catabolic bile acid synthetic pathway.
Collapse
|
35
|
2000 George Lyman Duff Memorial Lecture: atherosclerosis is a liver disease of the heart. Arterioscler Thromb Vasc Biol 2001; 21:887-98. [PMID: 11397693 DOI: 10.1161/01.atv.21.6.887] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The production of apolipoprotein B (apoB)-containing lipoproteins by the liver is regulated by a complex series of processes involving apoB being cotranslationally translocated across the endoplasmic reticulum and assembled into a lipoprotein particle. The translocation of apoB across the endoplasmic reticulum is facilitated by the intraluminal chaperone, microsomal triglyceride transfer protein (MTP). MTP facilitates the translocation and folding of apoB, as well as the addition of lipid to lipid-binding domains (which consist of amphipathic beta sheets and alpha helices). In the absence of MTP or sufficient lipid, apoB exhibits translocation arrest. Thus, apoB translation, translocation, and assembly with lipids to form a core-containing lipoprotein particle occur as concerted processes. Abrogation of >/=1 of these processes diverts apoB into a degradation pathway that is dependent on conjugation with ubiquitin and proteolysis by the proteasome. The nascent core-containing lipoprotein particle that forms within the lumen of the endoplasmic reticulum can be "enlarged" to form a mature very low density lipoprotein particle. Additional studies show that the assembly and secretion of apoB-containing lipoproteins are linked to the cholesterol/bile acid synthetic pathway controlled by cholesterol 7alpha-hydroxylase. Studies in cultured cells and transgenic mice indicate that the expression of cholesterol 7alpha-hydroxylase indirectly regulates the expression of lipogenic enzymes through changes in the cellular content of mature sterol response element binding proteins. Oxysterols and bile acids may also act via the ligand-activated nuclear receptors LXR and FXR to link the metabolic pathways controlling energy balance and lipid metabolism to nutritional state.
Collapse
|
36
|
Abstract
The assembly and secretion of apo B100 containing lipoproteins (i.e., VLDL) by the liver and cholesterol metabolism are interrelated on several different levels and for several different physiologic reasons. Firstly, hepatic VLDL is the major precursor for LDL, which in the human is the major vehicle responsible for transporting cholesterol to peripheral tissues. Secondly, cholesterol is supplied to many tissues by a specific uptake of LDL via LDL receptor, which is expressed in a regulated manner by most mammalian tissues. Thirdly, the rate of hepatic cholesterol biosynthesis and metabolism to bile acids correlates with production of VLDL. This apparent coordinate expression of cholesterol biosynthetic/catabolic enzymes and hepatic VLDL assembly/secretion are mediated at least in part through the sterol response element binding protein (SREBP) transcription factor family. Their gene targets include a plethora of enzymes that regulate glycolysis, energy production, lipogenesis and cholesterol catabolism. Studies of hepatoma cells overexpressing CYP7A1, the rate-limiting enzyme controlling bile acid synthesis, show that as a result of increased mature SREBP1, there is a coordinate induction of lipogenesis and the assembly and secretion of VLDL. These and additional studies show that the bile acid synthetic pathway and the VLDL assembly/secretion pathway are coordinately linked through SREBP-dependent transcription. Based on studies showing that within the liver acinus, the expression of CYP7A1 is mainly in the pericentral region while HMG-CoA reductase is mainly periportal, we propose that a 'metabolic zonal segregation' plays an important role in coordinate regulation of cholesterol and VLDL metabolism. This putative 'metabolic zonal segregation' may provide segregation of metabolic functions which may be mutually antagonistic. For example, there may be physiologic states in which the bile acid synthetic pathway may compete with the VLDL assembly/secretion pathway for a limited amount of cholesterol. Metabolic antagonism (e.g., competition for cholesterol) may be avoided via inducing SREBP-mediated transcription. Adaptation of catabolic hepatocytes to accommodate the expression of VLDL assembly/secretion may occur in response to activation of SREBP-mediated transcription. Support for these is discussed.
Collapse
|
37
|
Minority recruitment and retention in dietetics: issues and interventions. JOURNAL OF THE AMERICAN DIETETIC ASSOCIATION 2000; 100:961-6. [PMID: 10955059 DOI: 10.1016/s0002-8223(00)00278-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To better understand the reasons why minorities and males are underrepresented among registered dietitians (RDs) and dietetic technicians, registered, (DTRs) and to develop focuses for intervention, the investigators performed a telephone survey of newly credentialed RDs and DTRs and directors of RD and DTR education programs. Using lists of students recruited by the American Dietetic Association for participation in the survey, the investigators interviewed 83 RDs and DTRs and 20 education program directors. RDs and DTRs attributed minority underrepresentation primarily to the field's lack of visibility and underrepresentation of men to the traditional association with women. Education program directors attributed minority underrepresentation to educational disadvantages, particularly in scientific subjects. Findings from this study support program-level interventions such as increasing program flexibility, initiating outreach to K-12 schools and lower-division college students, providing tutoring in a nondemeaning atmosphere, and visibly expressing commitment to minority representation. More fundamental changes in the profession itself appear necessary for large-scale increases in minority representation. These include increasing internship opportunities; raising the profession's level of remuneration, prestige, and independence; increasing scholarship support; and advertising nationally through channels capable of reaching minorities.
Collapse
|
38
|
In nonhepatic cells, cholesterol 7alpha-hydroxylase induces the expression of genes regulating cholesterol biosynthesis, efflux, and homeostasis. J Lipid Res 2000; 41:1347-55. [PMID: 10946023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023] Open
Abstract
CHO cells expressing the liver-specific gene product cholesterol-7alpha-hydroxylase showed a 6-fold increase in the biosynthesis of [(14)C]cholesterol from [(14)C]acetate, as well as increased enzymatic activities of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and squalene synthase. Cells expressing cholesterol-7alpha-hydroxylase contained less sterol response element-binding protein 1 (SREBP1) precursor, whereas the cellular content of mature SREBP1, as well as the mRNAs of cholesterol biosynthetic genes (HMG-CoA reductase and squalene synthase), were all increased approximately 3-fold. Cells expressing cholesterol-7alpha-hydroxylase displayed greater activities of luciferase reporters containing the SREBP-dependent promoter elements derived from HMG-CoA reductase and farnesyl diphosphate synthase, in spite of accumulating significantly more free and esterified cholesterol and 7alpha-hydroxycholesterol. While cells expressing cholesterol-7alpha-hydroxylase displayed increased SREBP-dependent transcription, sterol-mediated repression of SREBP-dependent transcription by LDL-cholesterol and exogenous oxysterols was similar in both cell types. Cells expressing cholesterol-7alpha-hydroxylase displayed greater rates of secretion of cholesterol as well as increased expression of the ABC1 cassette protein mRNA. Adding 25-hydroxycholesterol to the culture medium of both cell types increased the expression of ABC1 cassette protein mRNA. The combined data suggest that in nonhepatic CHO cells multiple regulatory processes sensitive to cellular sterols act independently to coordinately maintain cellular cholesterol homeostasis.
Collapse
|
39
|
Bile acid induction of cytokine expression by macrophages correlates with repression of hepatic cholesterol 7alpha-hydroxylase. J Biol Chem 2000; 275:21805-8. [PMID: 10823815 DOI: 10.1074/jbc.c000275200] [Citation(s) in RCA: 126] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
In the studies reported herein, we show that two complementary experimental models: inbred strains of mice (i.e. C57BL/6 and C3H/HeJ), and a differentiated line of rat hepatoma cells (i.e. L35 cells), require the activation of cytokines by monocyte/macrophages to display bile acid negative feedback repression of cholesterol 7alpha-hydroxylase (CYP7A1). Feeding a bile acid-containing atherogenic diet for 3 weeks to C57BL/6 mice led to a 70% reduction in the expression of hepatic CYP7A1 mRNA, whereas no reduction was observed in C3H/HeJ mice. The strain-specific response to repression of CYP7A1 paralleled the activation of hepatic cytokine expression. Studies using cultured THP-1 monocyte/macrophages showed that the hydrophobic bile acid chenodeoxycholate, a well established potent repressor of CYP7A1, induced the expression of mRNAs encoding interleukin 1 (IL-1) and tumor necrosis factor alpha (TNFalpha). In contrast, the hydrophilic bile acid ursodeoxycholate, which does not repress CYP7A1, did not induce cytokine mRNA expression by THP-1 cells. Chenodeoxycholate activation of cytokines by THP-1 cells was blocked by the peroxisome proliferator-activated receptor gamma agonist rosiglitazone. The expression of cytokines (e.g. IL-1 and TNFalpha) by THP-1 cells paralleled with the ability of these cells to produce conditioned medium that when added to rat L35 hepatoma cells, repressed CYP7A1. Moreover, rosiglitazone, which blocks cytokine activation by macrophages, also blocked the repression of CYP7A1 normally exhibited by C57BL/6 mice fed the bile acid-containing atherogenic diet. The combined data indicate that the activation of cytokines may mediate CYP7A1 repression caused by feeding mice an atherogenic diet containing bile acids.
Collapse
|
40
|
Stability of 5-Fluorouracil in an extemporaneously compounded ophthalmic solution. INTERNATIONAL JOURNAL OF PHARMACEUTICAL COMPOUNDING 2000; 4:320-323. [PMID: 23985397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
5-Fluorouracil (5-FU) is used in the treatment of a variety of ophthalmic conditions, including glaucoma, pterygium, retinal detachment and premalignant eye lesions. Specifically for the treatment of pterygium, intravitreal injections of 5-FU have been extemporaneously compounded by pharmacists and typically stored in syringes. No data exist concerning the chemical and physical stability of these solutions. With this in mind, the stability of 5-FU (1mg/0.1mL) in 0.9% sodium chloride injection prepared in the hospital pharmacy laboratory at the University of South Carolina was studied with respect to time and temperature. Admixtures of 5-FU were aseptically prepared and stored in 1-mL tuberculin syringes. The stability of these solutions was evaluated in a freezer, in a refrigerator, at room temperature and in an oven set at 40 deg C. Immediately after prepareation, samples were collected to determine initial concentration using a stability-indicating high-performance liquid chromatography method and to assess the pH of the solution. The same tests were repeated after one, three, five and seven days of storage. Samples were also visually inspected at these times for signs of physical incompatibility. Tuberculin syringes stored at each of the temperatures showed no signs of physical incompatibility (precipitate) or loss of drug. There was also no appreciable change in pH of the solution over the study period. This study showed that aseptically prepared 5-FU ophthalmic solutions packaged in tuberculin syringes can be stored safely for up to seven days at temperatures ranging form -10 to 40 deg C/
Collapse
|
41
|
One or more labile proteins regulate the stability of chimeric mRNAs containing the 3'-untranslated region of cholesterol-7alpha -hydroxylase mRNA. J Biol Chem 2000; 275:19985-91. [PMID: 10764793 DOI: 10.1074/jbc.m002351200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Multiple AUUUA elements similar to those that regulate the degradation of several different mRNAs are conserved in the 3'-untranslated region (3'-UTR) of cholesterol-7alpha-hydroxylase (CYP7A1) mRNAs from several species. We examined if stabilization of mRNA decay could account for the >20-fold increase in the expression of CYP7A1 mRNA without a detectable change in transcription following dexamethasone treatment of rat hepatoma cells (L35 cells). Following RNA polymerase II-dependent transcription block or protein synthesis block, the decay of CYP7A1 mRNA displayed a short half-life ( approximately 30 min). Control experiments showed that in cells pre-treated with a RNA polymerase II inhibitor, dexamethasone had no detectable effect on CYP7A1 mRNA decay. Stable expression of luciferase reporter mRNAs in L35 cells showed that the CYP7A1 3'-UTR was required to observe a dexamethasone induction. To examine the hypothesis that a labile protein is required for dexamethasone-induced mRNA stabilization, cells were stably transfected with a tetracycline-repressible promoter that drives the expression of a green fluorescent protein analogue (ECFP) with or without the 3'-UTR of CYP7A1. Cells expressing ECFP with the 3'-UTR of CYP7A1 displayed a 3-fold dexamethasone induction of ECFP mRNA, whereas cells expressing ECFP without the 3'-UTR did not. Moreover, specific block of the transcription of ECFP containing the 3'-UTR by adding the tetracycline analogue doxycycline clearly displayed dexamethasone-induced stabilization of mRNA decay. These data provide compelling evidence that a putative labile protein and the 3'-UTR of CYP7A1 act together to decrease the rate of CYP7A1 mRNA degradation.
Collapse
|
42
|
Abstract
The mitogen-activated protein (MAP) kinase family members, which include the extracellular response kinases (ERK), p38, and c-Jun amino terminal kinases (JNK), play a role in mediating signals triggered by cytokines, growth factors, and environmental stress. JNK and p38 MAP kinases have been involved in inflammatory processes induced by a variety of stimuli, such as oxidative stress. Here, we describe the role of the JNK and p38 MAP kinase signaling pathways in the development of T cells in the thymus, and activation and differentiation of T cells in the peripheral immune system.
Collapse
|
43
|
10-Hydroxydarlingine, a new tropane alkaloid from the Australian proteaceous plant triunia erythrocarpa. JOURNAL OF NATURAL PRODUCTS 2000; 63:688-689. [PMID: 10843590 DOI: 10.1021/np9906065] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Triunia erythrocarpa was identified as containing alkaloids during chemical screening of Queensland Proteaceae using Dragendorff's reagent. A new tropane, 10-hydroxydarlingine (1), and the known tropane, darlingine (2), were isolated from the leaves of T. erythrocarpa. The absolute stereochemistry of 10-hydroxydarlingine (1) was assigned using the advanced Mosher method. T. erythrocarpa is only the seventh member of the Proteaceae to have been shown to produce alkaloids.
Collapse
|
44
|
Longithorols C-E. Three new macrocyclic sesquiterpene hydroquinone metabolites from the australian ascidian, aplidium longithorax. JOURNAL OF NATURAL PRODUCTS 1999; 62:1405-9. [PMID: 10543902 DOI: 10.1021/np990217a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Chemical investigation of a Great Barrier Reef ascidian, Aplidium longithorax has resulted in the isolation of two new para-substituted cyclofarnesylated hydroquinone compounds, longithorols C (1) and D (2), and a novel macrocyclic chromenol, longithorol E (3). Longithorol C (1) had its absolute stereochemistry determined by the advanced Mosher method and all compounds had their structures determined by interpretation of spectroscopic data.
Collapse
|
45
|
Cell and molecular biology of the assembly and secretion of apolipoprotein B-containing lipoproteins by the liver. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1440:1-31. [PMID: 10477822 DOI: 10.1016/s1388-1981(99)00083-9] [Citation(s) in RCA: 145] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Triglycerides are one of the most efficient storage forms of free energy. Because of their insolubility in biological fluids, their transport between cells and tissues requires that they be assembled into lipoprotein particles. Genetic disruption of the lipoprotein assembly/secretion pathway leads to several human disorders associated with malnutrition and developmental abnormalities. In contrast, patients displaying inappropriately high rates of lipoprotein production display increased risk for the development of atherosclerotic cardiovascular disease. Insights provided by diverse experimental approaches describe an elegant biological adaptation of basic chemical interactions required to overcome the thermodynamic dilemma of producing a stable emulsion vehicle for the transport and tissue targeting of triglycerides. The mammalian lipoprotein assembly/secretion pathway shows an absolute requirement for: (1) the unique amphipathic protein: apolipoprotein B, in a form that is sufficiently large to assemble a lipoprotein particle containing a neutral lipid core; and, (2) a lipid transfer protein (microsomal triglyceride transfer protein-MTP). In the endoplasmic reticulum apolipoprotein B has two distinct metabolic fates: (1) entrance into the lipoprotein assembly pathway within the lumen of the endoplasmic reticulum; or, (2) degradation in the cytoplasm by the ubiquitin-dependent proteasome. The destiny of apolipoprotein B is determined by the relative availability of individual lipids and level of expression of MTP. The dynamically varied expression of cholesterol-7alpha-hydroxylase indirectly influences the rate of lipid biosynthesis and the assembly and secretion lipoprotein particles by the liver.
Collapse
|
46
|
Chinese hamster ovary cells require the coexpression of microsomal triglyceride transfer protein and cholesterol 7alpha-hydroxylase for the assembly and secretion of apolipoprotein B-containing lipoproteins. J Biol Chem 1999; 274:9509-14. [PMID: 10092635 DOI: 10.1074/jbc.274.14.9509] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Due to the absence of microsomal triglyceride transfer protein (MTP), Chinese hamster ovary (CHO) cells lack the ability to translocate apoB into the lumen of the endoplasmic reticulum, causing apoB to be rapidly degraded by an N-acetyl-leucyl-leucyl-norleucinal-inhibitable process. The goal of this study was to examine if expression of MTP, whose genetic deletion is responsible for the human recessive disorder abetalipoproteinemia, would recapitulate the lipoprotein assembly pathway in CHO cells. Unexpectedly, expression of MTP mRNA and protein in CHO cells did not allow apoB-containing lipoproteins to be assembled and secreted by CHO cells expressing apoB53. Although expression of MTP in cells allowed apoB to completely enter the endoplasmic reticulum, it was degraded by a proteolytic process that was inhibited by dithiothreitol (1 mM) and chloroquine (100 microM), but resistant to N-acetyl-leucyl-leucyl-norleucinal. In marked contrast, coexpression of the liver-specific gene product cholesterol 7alpha-hydroxylase with MTP resulted in levels of MTP lipid transfer activity that were similar to those in mouse liver and allowed intact apoB53 to be secreted as a lipoprotein particle. These data suggest that, although MTP-facilitated lipid transport is not required for apoB translocation, it is required for the secretion of apoB-containing lipoproteins. We propose that, in CHO cells, MTP plays two roles in the assembly and secretion of apoB-containing lipoproteins: 1) it acts as a chaperone that facilitates apoB53 translocation, and 2) its lipid transfer activity allows apoB-containing lipoproteins to be assembled and secreted. Our results suggest that the phenotype of the cell (e.g. expression of cholesterol 7alpha-hydroxylase by the liver) may profoundly influence the metabolic relationships determining how apoB is processed into lipoproteins and/or degraded.
Collapse
|
47
|
New lamellarin alkaloids from the australian ascidian, didemnum chartaceum. JOURNAL OF NATURAL PRODUCTS 1999; 62:419-24. [PMID: 10096849 DOI: 10.1021/np9803530] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Five novel lamellarin-class alkaloids have been isolated from a Great Barrier Reef ascidian, Didemnum chartaceum. The structures of the 20-sulfated derivatives of lamellarins B, C, and L (1-3); the 8-sulfated derivative of lamellarin G (4), plus a nonsulfated compound, lamellarin Z (5), were identified by interpretation of spectroscopic data. Lamellarin G 8-sulfate (4) is the first example of this class of compounds sulfated at the C-8 position, while lamellarin Z (5) is the first example of a dimethoxylated lamellarin. The known lamellarins A, B, C, E, G, and L (6-11), plus the triacetate derivatives of lamellarins D (12) and N (13), were also isolated. An aberration in the integration of signals in the 1H NMR spectra of the 20-sulfated derivatives of lamellarins B, C, and L (1-3) led to NMR relaxation studies. T1 values were calculated for all protons in the sulfated lamellarins (1-4) and their corresponding nonsulfated derivatives (7, 8, 10, 11). Interestingly, the protons ortho to the sulfate group in compounds (1-4) had T1 values up to five times larger than the corresponding protons in their nonsulfated derivatives (7, 8, 10, 11).
Collapse
|
48
|
Translocation-arrested apolipoprotein B evades proteasome degradation via a sterol-sensitive block in ubiquitin conjugation. J Biol Chem 1999; 274:1856-62. [PMID: 9880570 DOI: 10.1074/jbc.274.3.1856] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In this study, we explored how sterol metabolism altered by the expression of cholesterol-7alpha-hydroxylase NADPH:oxygen oxidoreductase (7alpha-hydroxylase) affects the ubiquitin-dependent proteasome degradation of translocation-arrested apoB53 in Chinese hamster ovary cells. Stable expression of two different plasmids that encode either rat or human 7alpha-hydroxylase inhibited the ubiquitin conjugation of apoB and its subsequent degradation by the proteasome. Oxysterols (25-hydroxycholesterol and 7-ketocholesterol) reversed the inhibition of apoB degradation caused by 7alpha-hydroxylase. The combined results suggest that the normally rapid proteasome degradation of translocation-arrested apoB can be regulated by a sterol-sensitive polyubiquitin conjugation step in the endoplasmic reticulum. Blocked ubiquitin-dependent proteasome degradation caused translocation-arrested apoB to become sequestered in segregated membrane domains. Our results described for the first time a novel mechanism through which the "quality control" proteasome endoplasmic reticulum degradative pathway of translocation-arrested apoB is linked to sterol metabolism. Sterol-sensitive blocked ubiquitin conjugation appears to selectively inhibit the proteasome degradation of apoB, but not 7alpha-hydroxylase protein, with no impairment of cell vitality or function. Our findings may help to explain why the hepatic production of lipoproteins is increased when familial hypertriglyceridemic patients are treated with drugs that activate 7alpha-hydroxylase (e.g. bile acid-binding resins).
Collapse
|
49
|
Longithorones J and K, two new cyclofarnesylated quinone derived metabolites from the australian ascidian aplidium longithorax. JOURNAL OF NATURAL PRODUCTS 1999; 62:158-60. [PMID: 9917308 DOI: 10.1021/np980275g] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Chemical investigation of a Great Barrier Reef ascidian, Aplidium longithorax, has resulted in the isolation of two new cyclofarnesylated quinone-derived compounds, longithorones J (1) and K (2). Longithorone J (1) is the first example of a gamma-hydroxy-cyclohexenone in this structure class. Longithorone K (2) is a dihydro analogue of longithorone B.
Collapse
|
50
|
Abstract
The relationship between nicotine yield as determined by the FTC method and nicotine absorption was examined in 72 smokers in a more rigorous repetition of a previous study of 33 smokers. For this study, 113 smokers evenly distributed across four FTC "tar" yield ranges were recruited, only 72 demonstrated reasonable compliance with the study criteria with regard to sample collections and cigarette brand style consistency. Subjects recorded the number of cigarettes smoked daily and collected a 24-h urine sample and a saliva sample on 3 consecutive days. Nicotine absorption was determined by monitoring urinary excretion of nicotine and its metabolites. In addition, saliva samples were monitored for cotinine using radioimmunoassay (RIA). The correlation of the relationship for nicotine absorbed per cigarette was positive and significant (r = 0.31, P = 0.008) but weaker than in the previous study. Only smokers in the highest yield range showed any statistical difference from smokers in the lower ranges. Our results suggest that FTC nicotine yield is weakly related to nicotine absorption and that smoker-controlled factors exert a great influence on the amount of nicotine absorbed by smokers. Compensation is substantial but incomplete for the minority (by market share) of smokers at the low end of the yield scale. It is uncertain how well any alternative set of machine parameters would predict nicotine absorption for the majority of smokers, even if it were more predictive for the small number of smokers at the lower yield part of the range.
Collapse
|