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Lu YJ, Wheeler LW, Chu H, Kleindl PJ, Pugh M, You F, Rao S, Garcia G, Wu HY, da Cunha AP, Johnson R, Westrick E, Cross V, Lloyd A, Dircksen C, Klein PJ, Vlahov IR, Low PS, Leamon CP. Targeting folate receptor beta on monocytes/macrophages renders rapid inflammation resolution independent of root causes. CELL REPORTS MEDICINE 2021; 2:100422. [PMID: 34755134 PMCID: PMC8561236 DOI: 10.1016/j.xcrm.2021.100422] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 05/18/2021] [Accepted: 09/22/2021] [Indexed: 12/18/2022]
Abstract
Provoked by sterile/nonsterile insults, prolonged monocyte mobilization and uncontrolled monocyte/macrophage activation can pose imminent or impending harm to the affected organs. Curiously, folate receptor beta (FRβ), with subnanomolar affinity for the vitamin folic acid (FA), is upregulated during immune activation in hematopoietic cells of the myeloid lineage. This phenomenon has inspired a strong interest in exploring FRβ-directed diagnostics/therapeutics. Previously, we have reported that FA-targeted aminopterin (AMT) therapy can modulate macrophage function and effectively treat animal models of inflammation. Our current investigation of a lead compound (EC2319) leads to discovery of a highly FR-specific mechanism of action independent of the root causes against inflammatory monocytes. We further show that EC2319 suppresses interleukin-6/interleukin-1β release by FRβ+ monocytes in a triple co-culture leukemic model of cytokine release syndrome with anti-CD19 chimeric antigen receptor T cells. Because of its chemical stability and metabolically activated linker, EC2319 demonstrates favorable pharmacokinetic characteristics and cross-species translatability to support future pre-clinical and clinical development. Functional folate receptor beta is transiently expressed on inflammatory monocytes EC2319 is an enhancement of traditional dihydrofolate reductase inhibitors EC2319 anti-monocyte activity correlates with local/systemic therapeutic benefit EC2319 inhibition of cytokine release suggests emergency use for hyperinflammation
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Affiliation(s)
- Yingjuan J Lu
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Leroy W Wheeler
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Haiyan Chu
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Paul J Kleindl
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Michael Pugh
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Fei You
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Satish Rao
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Gabriela Garcia
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA
| | - Henry Y Wu
- Department of Ophthalmology, Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Andre P da Cunha
- Department of Ophthalmology, Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Richard Johnson
- Division of Renal Diseases and Hypertension, Department of Medicine, University of Colorado Denver, Aurora, CO 80045, USA
| | - Elaine Westrick
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Vicky Cross
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Alex Lloyd
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | | | - Patrick J Klein
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Iontcho R Vlahov
- Novartis Institutes for Biomedical Research, Cambridge, MA 02139, USA
| | - Philip S Low
- Department of Chemistry, Purdue Institute for Drug Discovery, and Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
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Garcia GE, Lu YJ, Truong LD, Roncal-Jiménez CA, Miyazaki M, Miyazaki-Anzai S, Cara-Fuentes G, Andres-Hernando A, Lanaspa M, Johnson RJ, Leamon CP. A Novel Treatment for Glomerular Disease: Targeting the Activated Macrophage Folate Receptor with a Trojan Horse Therapy in Rats. Cells 2021; 10:2113. [PMID: 34440885 PMCID: PMC8393837 DOI: 10.3390/cells10082113] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/09/2021] [Accepted: 08/12/2021] [Indexed: 02/07/2023] Open
Abstract
Since activated macrophages express a functional folate receptor β (FRβ), targeting this macrophage population with folate-linked drugs could increase selectivity to treat inflammatory diseases. Using a macrophage-mediated anti-glomerular basement membrane (anti-GBM) glomerulonephritis (GN) in WKY rats, we investigated the effect of a novel folic acid-aminopterin (AMT) conjugate (EC2319) designed to intracellularly deliver AMT via the FR. We found that treatment with EC2319 significantly attenuated kidney injury and preserved renal function. Kidney protection with EC2319 was blocked by a folate competitor, indicating that its mechanism of action was specifically FRβ-mediated. Notably, treatment with methotrexate (MTX), another folic acid antagonist related to AMT, did not protect from kidney damage. EC2319 reduced glomerular and interstitial macrophage infiltration and decreased M1 macrophage recruitment but not M2 macrophages. The expression of CCL2 and the pro-fibrotic cytokine TGF-β were also reduced in nephritic glomeruli with EC2319 treatment. In EC2319-treated rats, there was a significant decrease in the deposition of collagens. In nephritic kidneys, FRβ was expressed on periglomerular macrophages and macrophages present in the crescents, but its expression was not observed in normal kidneys. These data indicate that selectively targeting the activated macrophage population could represent a novel means for treating anti-GBM GN and other acute crescentic glomerulonephritis.
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Affiliation(s)
- Gabriela E. Garcia
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Yingjuan J. Lu
- Endocyte, Inc., Novartis Institutes for Biomedical Research, West Lafayette, IN 47906, USA; (Y.J.L.); (C.P.L.)
| | - Luan D. Truong
- Department of Pathology, The Houston Methodist Hospital, Baylor College of Medicine, Houston, TX 77030, USA;
| | - Carlos A. Roncal-Jiménez
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Makoto Miyazaki
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Shinobu Miyazaki-Anzai
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Gabriel Cara-Fuentes
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Ana Andres-Hernando
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Miguel Lanaspa
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Richard J. Johnson
- Department of Medicine, Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA; (C.A.R.-J.); (M.M.); (S.M.-A.); (G.C.-F.); (A.A.-H.); (M.L.); (R.J.J.)
| | - Christopher P. Leamon
- Endocyte, Inc., Novartis Institutes for Biomedical Research, West Lafayette, IN 47906, USA; (Y.J.L.); (C.P.L.)
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Jurczyk M, Jelonek K, Musiał-Kulik M, Beberok A, Wrześniok D, Kasperczyk J. Single- versus Dual-Targeted Nanoparticles with Folic Acid and Biotin for Anticancer Drug Delivery. Pharmaceutics 2021; 13:326. [PMID: 33802531 PMCID: PMC8001342 DOI: 10.3390/pharmaceutics13030326] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 02/10/2021] [Accepted: 02/25/2021] [Indexed: 12/19/2022] Open
Abstract
Cancer is one of the major causes of death worldwide and its treatment remains very challenging. The effectiveness of cancer therapy significantly depends upon tumour-specific delivery of the drug. Nanoparticle drug delivery systems have been developed to avoid the side effects of the conventional chemotherapy. However, according to the most recent recommendations, future nanomedicine should be focused mainly on active targeting of nanocarriers based on ligand-receptor recognition, which may show better efficacy than passive targeting in human cancer therapy. Nevertheless, the efficacy of single-ligand nanomedicines is still limited due to the complexity of the tumour microenvironment. Thus, the NPs are improved toward an additional functionality, e.g., pH-sensitivity (advanced single-targeted NPs). Moreover, dual-targeted nanoparticles which contain two different types of targeting agents on the same drug delivery system are developed. The advanced single-targeted NPs and dual-targeted nanocarriers present superior properties related to cell selectivity, cellular uptake and cytotoxicity toward cancer cells than conventional drug, non-targeted systems and single-targeted systems without additional functionality. Folic acid and biotin are used as targeting ligands for cancer chemotherapy, since they are available, inexpensive, nontoxic, nonimmunogenic and easy to modify. These ligands are used in both, single- and dual-targeted systems although the latter are still a novel approach. This review presents the recent achievements in the development of single- or dual-targeted nanoparticles for anticancer drug delivery.
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Affiliation(s)
- Magdalena Jurczyk
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 41-819 Zabrze, Poland; (M.J.); (M.M.-K.); (J.K.)
- Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia, 41-200 Sosnowiec, Poland; (A.B.); (D.W.)
| | - Katarzyna Jelonek
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 41-819 Zabrze, Poland; (M.J.); (M.M.-K.); (J.K.)
| | - Monika Musiał-Kulik
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 41-819 Zabrze, Poland; (M.J.); (M.M.-K.); (J.K.)
| | - Artur Beberok
- Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia, 41-200 Sosnowiec, Poland; (A.B.); (D.W.)
| | - Dorota Wrześniok
- Department of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia, 41-200 Sosnowiec, Poland; (A.B.); (D.W.)
| | - Janusz Kasperczyk
- Centre of Polymer and Carbon Materials, Polish Academy of Sciences, 41-819 Zabrze, Poland; (M.J.); (M.M.-K.); (J.K.)
- Department of Biopharmacy, Faculty of Pharmaceutical Sciences in Sosnowiec, Medical University of Silesia, 41-200 Sosnowiec, Poland
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Shinde C, Venkatesh MP, Pramod Kumar T, Pai DR. Nanostructured lipid carrier-based smart gel: a delivery platform for intra-articular therapeutics. Autoimmunity 2020; 54:35-44. [PMID: 33183072 DOI: 10.1080/08916934.2020.1846184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The promising potential of nano-structured lipid carrier (NLC) polymeric gel of CUR as an effective treatment for rheumatoid arthritis by intra-articular route of administration was investigated. NLC composed of cetylpalmitate, Labrafac PG & Captex 200, Tween 80 and Labrasol. The hot homogenization method employed by melt ultrasonication was used. The formulated NLC dispersions were characterized and were suitably dispersed into the matrix of pluronic F-127(PLF-127) and pluronic F-68 (PLF-68). A two-factor three-level full factorial design was employed to deduce the optimal concentrations of PLF-127 and PLF-68. The optimized formulations were sterilized by gamma radiation. The formulated NLC smart gels were characterized and evaluated for various parameters. The efficacy evaluation by antigen-induced monoarthritis model and biocompatibility testing by histopathological studies was performed. Formulated NLCs exhibited an average particle size of 165.12 nm, entrapment efficiency of 72.15%, and zeta potential of -21.67 mV. The optimized CUR-NLC smart gel was demonstrated to have a sol-gel transformation at 33.21 °C and 94.32% drug release at 84 h. NLC's which were sterile and easily syringeable, continued to remain within the colloidal range. CUR-NLC smart gels were found to be biocompatible and showed a significant reduction in rat knee joint inflammation compared to free drug.
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Affiliation(s)
- Chetan Shinde
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Mysuru, India
| | - Madhugiri Prakash Venkatesh
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Mysuru, India
| | - Tegginmat Pramod Kumar
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Mysuru, India
| | - Deeksha Ramananda Pai
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Mysuru, India
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Venkatesh MP, Kumar TP, Pai DR. Targeted drug delivery of Methotrexate in situ gels for the treatment of Rheumatoid Arthritis. Saudi Pharm J 2020; 28:1548-1557. [PMID: 33424248 PMCID: PMC7783075 DOI: 10.1016/j.jsps.2020.10.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Accepted: 10/15/2020] [Indexed: 12/16/2022] Open
Abstract
Rheumatoid arthritis (RA) is considered a debilitating disease that increases the risk of significant morbidity and premature mortality. To circumvent drug-related toxicity and ineffectiveness of anti-inflammatory drugs, there is a significant need for an advanced delivery system that increases bioavailability. The feasibility of in situ gel of methotrexate sodium (MTS) as an effective management for Rheumatoid arthritis was investigated. It was formulated with pluronic F-127 (PLF-127) as primary polymer, hydroxypropyl methylcellulose K4M (HK4M), and polycarbophil (PCL) as a copolymer and characterized by various parameters. The efficacy evaluation by Freund's complete adjuvant (FCA) model, biocompatibility assessment by histopathological studies conducted. The optimized in situ gel (M4) was thermoresponsive, released 93.26 ± 2.39% MTS at 96 hours. In addition, distribution of MTS was even in the optimized sterile and syringeable in situ gel. In vivo studies on wistar rats demonstrated a substantial reduction in paw oedema during the 28-day study period and were biocompatible with the tissues at the injection site. The study was successful in formulating, optimizing MTS in situ gel for effective management of RA.
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Affiliation(s)
- Madhugiri Prakash Venkatesh
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Sri Shivarathreeshwara Nagara, Mysuru 570015, Karnataka, India
| | - Tegginmat Pramod Kumar
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Sri Shivarathreeshwara Nagara, Mysuru 570015, Karnataka, India
| | - Deeksha Ramananda Pai
- Department of Pharmaceutics, JSS College of Pharmacy, JSS Academy of Higher Education and Research, Sri Shivarathreeshwara Nagara, Mysuru 570015, Karnataka, India
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Yang Y, Zhao Z, Xie C, Zhao Y. Dual-targeting liposome modified by glutamic hexapeptide and folic acid for bone metastatic breast cancer. Chem Phys Lipids 2020; 228:104882. [PMID: 32017901 DOI: 10.1016/j.chemphyslip.2020.104882] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 01/05/2020] [Accepted: 01/29/2020] [Indexed: 11/17/2022]
Abstract
Bone is the most common organ affected by metastatic breast cancer. Targeting delivery of drugs to bone may not only enhance the treatment efficacy, but also reduce the quantity of drug administered. In order to increase the distribution of paclitaxel (PTX) in bone, herein, a novel bone metastasis-targeted glutamic hexapeptide-folic acid (Glu6-FA) derivative was designed and synthesized as liposome ligand to deliver PTX to bone metastasis effectively. The liposomes were prepared by thin film hydration method and its particle size, zeta potential, encapsulation efficiency, release profile, stability, hemolysis were also characterized. What's more, the anti-tumor effects of PTX-Glu6-FA-Lip were confirmed by the detection of cell cycle, migration, and further measurement of microtubule stabilization. In addition, the PTX-Glu6-FA-Lip showed superior targeting ability in vitro and in vivo evaluation as compared to naked PTX, non-coated, singly-modified and co-modified by physical blending liposomes. All the results suggested that Glu6-FA-modified liposome showed excellent targeting activity to metastatic bone cancer. These findings suggested that Glu6-FA-Lip was a promising bone metastasis-targeting carrier for the delivery of PTX. This study may therefore be conducive to the field of bone-targeting drugs delivery.
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Affiliation(s)
- Yang Yang
- Department of Translational Medicine Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China
| | - Ze Zhao
- Department of Orthopedics, the First Affiliated Hospital of Henan Polytechnic University (the Second People's Hospital of Jiaozuo City), Jiaozuo 454001, China
| | - Changwei Xie
- Department of Orthopedics, the First Affiliated Hospital of Henan Polytechnic University (the Second People's Hospital of Jiaozuo City), Jiaozuo 454001, China
| | - Yi Zhao
- Department of Translational Medicine Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou 450052, China.
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Chandrupatla DMSH, Molthoff CFM, Lammertsma AA, van der Laken CJ, Jansen G. The folate receptor β as a macrophage-mediated imaging and therapeutic target in rheumatoid arthritis. Drug Deliv Transl Res 2019; 9:366-378. [PMID: 30280318 PMCID: PMC6328514 DOI: 10.1007/s13346-018-0589-2] [Citation(s) in RCA: 72] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Macrophages play a key role in the pathophysiology of rheumatoid arthritis (RA). Notably, positive correlations have been reported between synovial macrophage infiltration and disease activity as well as therapy outcome in RA patients. Hence, macrophages can serve as an important target for both imaging disease activity and drug delivery in RA. Folate receptor β (FRβ) is a glycosylphosphatidyl (GPI)-anchored plasma membrane protein being expressed on myeloid cells and activated macrophages. FRβ harbors a nanomolar binding affinity for folic acid allowing this receptor to be exploited for RA disease imaging (e.g., folate-conjugated PET tracers) and therapeutic targeting (e.g., folate antagonists and folate-conjugated drugs). This review provides an overview of these emerging applications in RA by summarizing and discussing properties of FRβ, expression of FRβ in relation to macrophage polarization, FRβ-targeted in vivo imaging modalities, and FRβ-directed drug targeting.
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Affiliation(s)
- Durga M S H Chandrupatla
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, Vrije Universiteit Amsterdam, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Carla F M Molthoff
- Department of Radiology and Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Adriaan A Lammertsma
- Department of Radiology and Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Conny J van der Laken
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, Vrije Universiteit Amsterdam, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Gerrit Jansen
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, Vrije Universiteit Amsterdam, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands.
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Chandrupatla DMSH, Molthoff CFM, Ritsema WIGR, Vos R, Elshof E, Matsuyama T, Low PS, Musters RJP, Hammond A, Windhorst AD, Lammertsma AA, van der Laken CJ, Brands R, Jansen G. Prophylactic and therapeutic activity of alkaline phosphatase in arthritic rats: single-agent effects of alkaline phosphatase and synergistic effects in combination with methotrexate. Transl Res 2018; 199:24-38. [PMID: 29802817 DOI: 10.1016/j.trsl.2018.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2018] [Revised: 03/09/2018] [Accepted: 04/03/2018] [Indexed: 12/16/2022]
Abstract
Alkaline phosphatase (AP) is a gate-keeper of innate immune system responses by detoxifying inflammation triggering moieties released from endogenous and external sources. We examined whether AP's broad mechanism of action constitutes a safe therapeutic, either as single agent or combined with methotrexate (MTX), for chronic inflammatory disorders, for example, rheumatoid arthritis (RA). A rat model for RA was used with repeated intra-articular methylated bovine serum albumin (mBSA) injections in 1 knee ("arthritic" knee), with the contralateral knee serving as internal control. AP (200 µg, subcut) was administered before mBSA injections (prophylactic setting) or after arthritis induction (therapeutic setting) or combined with MTX (0.3 mg/kg or 1 mg/kg; intraperitoneally). As end point of treatment outcome, macrophage infiltration in knees, liver, and spleen was assessed by immunohistochemistry (ED1 and ED2 expression), immunofluoresence (macrophage marker folate receptor-β [FRβ]), and [18F]fluoro-polyethylene glycol-folate positron emission tomography (PET) (macrophage imaging) and ex vivo tissue distribution. Single-agent AP treatment and combinations with MTX were well tolerated. Both prophylactic and therapeutic AP markedly reduced synovial macrophage infiltration in arthritic knees (ED1: 3.5- to 4-fold; ED2: 3.5- to 6-fold), comparable with MTX treatment. AP-MTX combinations slightly improved on single agent effects. PET monitoring and ex vivo tissue distribution studies corroborated the impact of AP, MTX, and AP-MTX on reducing synovial macrophage infiltration. Beyond localized articular effects, AP also revealed systemic anti-inflammatory effects by a 2-fold reduction of ED1, ED2, and FRβ+ macrophages in liver and spleen of arthritic rats. Collectively, single-agent AP and AP combined with MTX elicited local and systemic anti-arthritic activity in arthritic rats.
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Affiliation(s)
- Durga M S H Chandrupatla
- Amsterdam Rheumatology and immunology Center, VU University Medical Center, Amsterdam, The Netherlands
| | - Carla F M Molthoff
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Wayne I G R Ritsema
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Ricardo Vos
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Eline Elshof
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Takami Matsuyama
- Department of Immunology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Philip S Low
- Department of Chemistry, Purdue University, West Lafayette, Indiana
| | - René J P Musters
- Department of Physiology, VU University Medical Center, Amsterdam, The Netherlands
| | - Anthony Hammond
- Department of Rheumatology, KIMS Hospital, Kent, United Kingdom
| | - Albert D Windhorst
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Adriaan A Lammertsma
- Department of Radiology & Nuclear Medicine, VU University Medical Center, Amsterdam, The Netherlands
| | - Conny J van der Laken
- Amsterdam Rheumatology and immunology Center, VU University Medical Center, Amsterdam, The Netherlands
| | | | - Gerrit Jansen
- Amsterdam Rheumatology and immunology Center, VU University Medical Center, Amsterdam, The Netherlands.
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Otsubo H, Tsuneyoshi Y, Nakamura T, Matsuda T, Komiya S, Matsuyama T. Serum-soluble folate receptor β as a biomarker for the activity of rheumatoid arthritis synovitis and the response to anti-TNF agents. Clin Rheumatol 2018; 37:2939-2945. [DOI: 10.1007/s10067-018-4202-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2018] [Revised: 06/10/2018] [Accepted: 07/05/2018] [Indexed: 12/31/2022]
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Imaging and Methotrexate Response Monitoring of Systemic Inflammation in Arthritic Rats Employing the Macrophage PET Tracer [ 18F]Fluoro-PEG-Folate. CONTRAST MEDIA & MOLECULAR IMAGING 2018; 2018:8092781. [PMID: 29681783 PMCID: PMC5841060 DOI: 10.1155/2018/8092781] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/22/2017] [Revised: 12/22/2017] [Accepted: 01/24/2018] [Indexed: 12/23/2022]
Abstract
Background In rheumatoid arthritis, articular inflammation is a hallmark of disease, while the involvement of extra-articular tissues is less well defined. Here, we examined the feasibility of PET imaging with the macrophage tracer [18F]fluoro-PEG-folate, targeting folate receptor β (FRβ), to monitor systemic inflammatory disease in liver and spleen of arthritic rats before and after methotrexate (MTX) treatment. Methods [18F]Fluoro-PEG-folate PET scans (60 min) were acquired in saline- and MTX-treated (1 mg/kg, 4x) arthritic rats, followed by tissue resection and radiotracer distribution analysis. Liver and spleen tissues were stained for ED1/ED2-macrophage markers and FRβ expression. Results [18F]Fluoro-PEG-folate PET and ex vivo tissue distribution studies revealed a significant (p < 0.01) 2-fold lower tracer uptake in both liver and spleen of MTX-treated arthritic rats. Consistently, ED1- and ED2-positive macrophages were significantly (p < 0.01) decreased in liver (4-fold) and spleen (3-fold) of MTX-treated compared with saline-treated rats. Additionally, FRβ-positive macrophages were also significantly reduced in liver (5-fold, p < 0.005) and spleen (3-fold, p < 0.01) of MTX- versus saline-treated rats. Conclusions MTX treatment reduced activated macrophages in liver and spleen, as markers for systemic inflammation in these organs. Macrophage PET imaging with [18F]fluoro-PEG-folate holds promise for detection of systemic inflammation in RA as well as therapy (MTX) response monitoring.
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Chandrupatla DMSH, Jansen G, Vos R, Verlaan M, Chen Q, Low PS, Windhorst AD, Lammertsma AA, van der Laken CJ, Molthoff CFM. In-vivo monitoring of anti-folate therapy in arthritic rats using [ 18F]fluoro-PEG-folate and positron emission tomography. Arthritis Res Ther 2017; 19:114. [PMID: 28569209 PMCID: PMC5452381 DOI: 10.1186/s13075-017-1325-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 05/09/2017] [Indexed: 01/05/2023] Open
Abstract
Background Folate receptor β (FRβ) is involved in facilitating cellular uptake of folates and anti-folates (such as methotrexate (MTX)). In rheumatoid arthritis, FRβ is expressed on synovial macrophages and recently has been explored as a biomarker for imaging in arthritic rats using the folate-based positron emission tomography (PET) tracer [18F]fluoro-PEG-folate. The purpose of this study was to examine whether this folate tracer can also be used to monitor therapeutic efficacy of MTX in arthritic rats. Methods Arthritic rats received either no treatment or MTX therapy (1 mg/kg, either 2× or 4×). Healthy rats did not receive any arthritic induction or therapy. [18F]fluoro-PEG-folate PET-CT scans (60 min) were performed before and after MTX therapy. Following PET, the ex-vivo tissue distribution of radioactivity was determined in excised knees and multiple tissues. Synovial macrophage infiltration in knee sections was quantified by immunohistochemistry using ED1 and ED2 antibodies. Results PET scans clearly visualized increased uptake of [18F]fluoro-PEG-folate in arthritic knees compared with contralateral knees. Significantly lower standard uptake values (1.5-fold, p < 0.01) were observed in arthritic knees of both MTX-treated groups after therapy, approximating the levels seen in healthy rats. Consistently, ex-vivo tissue distribution demonstrated a 2–4-fold lower tracer uptake in the arthritic knee of 2× and 4× MTX-treated rats, respectively, compared with control rats. These results were corroborated with significantly reduced (2–4-fold, p < 0.01) ED1-positive and ED2-positive synovial macrophages in arthritic knees of the MTX-treated rats compared with those of the control rats. Conclusion This study in arthritic rats underscores the potential and usefulness of [18F]fluoro-PEG-folate PET as a therapeutic monitoring tool of MTX therapy and potentially other anti-folate treatment of arthritis.
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Affiliation(s)
- Durga M S H Chandrupatla
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Gerrit Jansen
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Ricardo Vos
- Department of Radiology & Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Mariska Verlaan
- Department of Radiology & Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Qingshou Chen
- Department of Chemistry, Purdue University, 720 Clinic Drive, West Lafayette, IN, 47907-2084, USA
| | - Philip S Low
- Department of Chemistry, Purdue University, 720 Clinic Drive, West Lafayette, IN, 47907-2084, USA
| | - Albert D Windhorst
- Department of Radiology & Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Adriaan A Lammertsma
- Department of Radiology & Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Conny J van der Laken
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands
| | - Carla F M Molthoff
- Department of Radiology & Nuclear Medicine, VU University Medical Center, De Boelelaan 1117, 1081 HV, Amsterdam, The Netherlands.
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12
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Folate-targeted nanoparticles for rheumatoid arthritis therapy. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2016; 12:1113-1126. [DOI: 10.1016/j.nano.2015.12.365] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Revised: 11/25/2015] [Accepted: 12/10/2015] [Indexed: 11/22/2022]
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Tamura T, Higuchi Y, Kitamura H, Murao N, Saitoh R, Morikawa T, Sato H. Novel hyaluronic acid-methotrexate conjugate suppresses joint inflammation in the rat knee: efficacy and safety evaluation in two rat arthritis models. Arthritis Res Ther 2016; 18:79. [PMID: 27039182 PMCID: PMC4818416 DOI: 10.1186/s13075-016-0971-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 03/10/2016] [Indexed: 01/15/2023] Open
Abstract
Background Methotrexate (MTX) is one of the most widely used medications to treat rheumatoid arthritis (RA), and recent studies have also suggested the potential benefit of the drug for the treatment of osteoarthritis (OA) of the knee. MTX is commonly administered in oral formulations, but is often associated with systemic adverse reactions. In an attempt to address this issue, we have shown previously that a conjugate of hyaluronic acid (HA) and MTX exhibits potential as a drug candidate for intra-articular treatment of inflammatory arthritis. In this study, we compare the efficacy and safety of an optimized HA-MTX conjugate, DK226, with that of MTX in inflammatory arthritis rat models. Methods In vitro activity of DK226 was assessed in human fibroblast-like synoviocytes (HFLS) and a synovial sarcoma cell line, SW982. Release of MTX from DK226 was investigated after incubation with rabbit synovial tissue homogenate or synovial fluid. In vivo efficacy of DK226 was evaluated in antigen-induced arthritis (AIA) and collagen-induced arthritis (CIA) in the rat knee. Pharmacokinetics and hematological toxicity after treatment with oral MTX or an intra-articular injection of DK226 were compared in AIA. Results Proliferation of HFLS and SW982 cells was inhibited by DK226, and the inhibitory activity was reversed by cotreatment with excess HA or anti-CD44 antibody. MTX was released from DK226 by incubation with rabbit synovial tissue homogenate or synovial fluid at pH 4.0, but not at pH 7.4. AIA was ameliorated by intra-articular DK226, but not by HA, as potently as oral MTX. Hematological toxicity was induced by oral MTX, but not by DK226. The maximum plasma concentration of MTX after oral MTX was 40 times higher than the concentration of MTX after an intra-articular injection of DK226. Knee swelling in AIA was inhibited by intra-articular injections of DK226, but not by free MTX or a mixture of HA and MTX. In CIA, an injection of DK226 into the right knee joint significantly reduced swelling and synovial inflammation of the treated knee joint, but had no effect on the untreated contralateral knee joint. Conclusions DK226 exerted anti-arthritic effects in two different models of arthritis. The conjugate had a wider therapeutic window than oral MTX, and could be a future drug for treatment of arthritic disorders, including inflammatory OA.
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Affiliation(s)
- Tatsuya Tamura
- Research Division, Chugai Pharmaceutical Co., Ltd., 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan.
| | - Yoshinobu Higuchi
- Research Division, Chugai Pharmaceutical Co., Ltd., 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan
| | - Hidetomo Kitamura
- Research Division, Chugai Pharmaceutical Co., Ltd., 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan
| | - Naoaki Murao
- Research Division, Chugai Pharmaceutical Co., Ltd., 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan
| | - Ryoichi Saitoh
- Research Division, Chugai Pharmaceutical Co., Ltd., 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan
| | - Tadashi Morikawa
- New Business Planning Department, Denka Co., Ltd., 2-1-1 Nihonbashi-Muromachi, Chuo-ku, Tokyo, 103-8338, Japan
| | - Haruhiko Sato
- Research Division, Chugai Pharmaceutical Co., Ltd., 1-135 Komakado, Gotemba, Shizuoka, 412-8513, Japan
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Jansen G, Peters GJ. Novel insights in folate receptors and transporters: implications for disease and treatment of immune diseases and cancer. Pteridines 2015; 26:41-53. [DOI: 10.1515/pterid-2015-0005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/15/2023] Open
Abstract
Abstract
Folate receptors and transporters as well as folate enzymes play an essential role in human disease and form important targets for the treatment of immune diseases and cancer. To discuss new developments in this area, every 2 years a multidisciplinary meeting is held, which aims to be an informal forum for fundamental scientists and clinicians. During this meeting, the regulation of folate transporters and folate enzymes is discussed at the level of expression, transcription, translation, post-translational modification, and splicing and enzyme regulation. Importantly, this knowledge is applied and translated into exciting clinical applications by clinicians with various backgrounds, such as surgeons, nephrologists, rheumatologists and oncologists. Moreover, the meeting provides an excellent forum for a scientific interaction between academia and industry.
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Affiliation(s)
- Gerrit Jansen
- Amsterdam Rheumatology and Immunology Center, VU University Medical Center, Cancer Center Amsterdam, PO Box 7057, 1007 MB Amsterdam, The Netherlands
| | - Godefridus J. Peters
- Department of Medical Oncology, VU University Medical Center, Cancer Center Amsterdam, PO Box 7057, 1007 MB Amsterdam, The Netherlands
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La Porta C, Bura SA, Negrete R, Maldonado R. Involvement of the endocannabinoid system in osteoarthritis pain. Eur J Neurosci 2014; 39:485-500. [PMID: 24494687 DOI: 10.1111/ejn.12468] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 11/25/2013] [Accepted: 12/02/2013] [Indexed: 12/29/2022]
Abstract
Osteoarthritis is a degenerative joint disease associated with articular cartilage degradation. The major clinical outcome of osteoarthritis is a complex pain state that includes both nociceptive and neuropathic mechanisms. Currently, the therapeutic approaches for osteoarthritis are limited as no drugs are available to control the disease progression and the analgesic treatment has restricted efficacy. Increasing evidence from preclinical studies supports the interest of the endocannabinoid system as an emerging therapeutic target for osteoarthritis pain. Indeed, pharmacological studies have shown the anti-nociceptive effects of cannabinoids in different rodent models of osteoarthritis, and compelling evidence suggests an active participation of the endocannabinoid system in the pathophysiology of this disease. The ubiquitous distribution of cannabinoid receptors, together with the physiological role of the endocannabinoid system in the regulation of pain, inflammation and even joint function further support the therapeutic interest of cannabinoids for osteoarthritis. However, limited clinical evidence has been provided to support this therapeutic use of cannabinoids, despite the promising preclinical data. This review summarizes the promising results that have been recently obtained in support of the therapeutic value of cannabinoids for osteoarthritis management.
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Affiliation(s)
- Carmen La Porta
- Laboratori de Neurofarmacologia, Facultat de Ciències de la Salut i de la Vida, Universitat Pompeu Fabra, C/Dr. Aiguader, 88, Barcelona, 08003, Spain
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Lu Y, Wollak KN, Cross VA, Westrick E, Wheeler LW, Stinnette TW, Vaughn JF, Hahn SJ, Xu LC, Vlahov IR, Leamon CP. Folate receptor-targeted aminopterin therapy is highly effective and specific in experimental models of autoimmune uveitis and autoimmune encephalomyelitis. Clin Immunol 2013; 150:64-77. [PMID: 24333534 DOI: 10.1016/j.clim.2013.10.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Revised: 10/01/2013] [Accepted: 10/16/2013] [Indexed: 01/01/2023]
Abstract
EC0746 is a rationally designed anti-inflammatory drug conjugate consisting of a modified folic acid-based ligand linked to a γ-hydrazide analog of aminopterin. In this report, EC0746's effectiveness was evaluated against experimental retinal S-antigen (PDSAg) induced autoimmune uveitis (EAU) and myelin-basic-protein induced autoimmune encephalomyelitis (EAE). In both models, functional FR-β was detected on activated macrophages in local (retinal or central-nervous-system, respectively) and systemic (peritoneal cavity) sites of inflammation. In myelin-rich regions of EAE rats, an increased uptake of (99m)Tc-EC20 (etarfolatide; a FR-specific radioimaging agent) was also observed. EC0746 treatment at disease onset suppressed the clinical severity of both EAU and EAE, and it strongly attenuated progressive histopathological changes in the affected organs. In all parameters assessed, EC0746 activity was completely blocked by a benign folate competitor, suggesting that these therapeutic outcomes were specifically FR-β mediated. EC0746 may emerge as a useful macrophage-modulating agent for treating inflammatory episodes of organ-specific autoimmunity.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Le-Cun Xu
- Endocyte, Inc., West Lafayette, IN, USA
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Müller C. Folate-based radiotracers for PET imaging--update and perspectives. Molecules 2013; 18:5005-31. [PMID: 23629756 PMCID: PMC6269920 DOI: 10.3390/molecules18055005] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2013] [Revised: 04/13/2013] [Accepted: 04/19/2013] [Indexed: 11/17/2022] Open
Abstract
The folate receptor (FR) is expressed in many tumor types, among those ovarian and lung cancer. Due to the high FR affinity of folic acid, it has been used for targeting of FR-positive tumors, allowing specific delivery of attached probes to the malignant tissue. Therefore, nuclear imaging of FR-positive cancer is of clinical interest for selecting patients who could benefit from innovative therapy concepts based on FR-targeting. Positron emission computed tomography (PET) has become an established technique in clinical routine because it provides an increased spatial resolution and higher sensitivity compared to single photon emission computed tomography (SPECT). Therefore, it is of critical importance to develop folate radiotracers suitable for PET imaging. This review article updates on the design, preparation and pre-clinical investigation of folate derivatives for radiolabeling with radioisotopes for PET. Among those the most relevant radionuclides so far are fluorine-18 (t1/2: 110 min, Eavβ+: 250 keV) and gallium-68 (t1/2: 68 min, Eav β+: 830 keV). Recent results obtained with new PET isotopes such as terbium-152 (t1/2: 17.5 h, Eβ+: 470 keV) or scandium-44 (t1/2: 3.97 h, Eav β+: 632 keV) are also presented and discussed. Current endeavors for clinical implementation of PET agents open new perspectives for identification of FR-positive malignancies in patients.
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Affiliation(s)
- Cristina Müller
- Center for Radiopharmaceutical Sciences ETH-PSI-USZ, Paul Scherrer Institute, Villigen-PSI 5232, Switzerland.
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Evaluation of the novel folate receptor ligand [18F]fluoro-PEG-folate for macrophage targeting in a rat model of arthritis. Arthritis Res Ther 2013; 15:R37. [PMID: 23452511 PMCID: PMC3672671 DOI: 10.1186/ar4191] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 02/20/2013] [Indexed: 12/11/2022] Open
Abstract
INTRODUCTION Detection of (subclinical) synovitis is relevant for both early diagnosis and monitoring of therapy of rheumatoid arthritis (RA). Previously, the potential of imaging (sub)clinical arthritis was demonstrated by targeting the translocator protein in activated macrophages using (R)-[11C]PK11195 and positron emission tomography (PET). Images, however, also showed significant peri-articular background activity. The folate receptor (FR)-β is a potential alternative target for imaging activated macrophages. Therefore, the PET tracer [18F]fluoro-PEG-folate was synthesized and evaluated in both in vitro and ex vivo studies using a methylated BSA induced arthritis model. METHODS [18F]fluoro-PEG-folate was synthesized in a two-step procedure. Relative binding affinities of non-radioactive fluoro-PEG-folate, folic acid and naturally circulating 5-methyltetrahydrofolate (5-Me-THF) to FR were determined using KB cells with high expression of FR. Both in vivo [18F]fluoro-PEG-folate PET and ex vivo tissue distribution studies were performed in arthritic and normal rats and results were compared with those of the established macrophage tracer (R)-[11C]PK11195. RESULTS [18F]fluoro-PEG-folate was synthesized with a purity >97%, a yield of 300 to 1,700 MBq and a specific activity between 40 and 70 GBq/µmol. Relative in vitro binding affinity for FR of F-PEG-folate was 1.8-fold lower than that of folic acid, but 3-fold higher than that of 5-Me-THF. In the rat model, [18F]fluoro-PEG-folate uptake in arthritic knees was increased compared with both contralateral knees and knees of normal rats. Uptake in arthritic knees could be blocked by an excess of glucosamine-folate, consistent with [18F]fluoro-PEG-folate being specifically bound to FR. Arthritic knee-to-bone and arthritic knee-to-blood ratios of [18F]fluoro-PEG-folate were increased compared with those of (R)-[11C]PK11195. Reduction of 5-Me-THF levels in rat plasma to those mimicking human levels increased absolute [18F]fluoro-PEG-folate uptake in arthritic joints, but without improving target-to-background ratios. CONCLUSIONS The novel PET tracer [18F]fluoro-PEG-folate, designed to target FR on activated macrophages provided improved contrast in a rat model of arthritis compared with the accepted macrophage tracer (R)-[11C]PK11195. These results warrant further exploration of [18F]fluoro-PEG-folate as a putative PET tracer for imaging (sub)clinical arthritis in RA patients.
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