-
Alzheimer's & Dementia : the Journal of... Apr 2024Synaptic loss is an early prominent feature of Alzheimer's disease (AD). The recently developed novel synaptic vesicle 2A protein (SV2A) PET-tracer UCB-J has shown great...
INTRODUCTION
Synaptic loss is an early prominent feature of Alzheimer's disease (AD). The recently developed novel synaptic vesicle 2A protein (SV2A) PET-tracer UCB-J has shown great promise in tracking synaptic loss in AD. However, there have been discrepancies between the findings and a lack of mechanistic insight.
METHODS
Here we report the first extensive pre-clinical validation studies for UCB-J in control (CN; n = 11) and AD (n = 11) brains using a multidimensional approach of post-mortem brain imaging techniques, radioligand binding, and biochemical studies.
RESULTS AND DISCUSSION
We demonstrate that UCB-J could target SV2A protein with high specificity and depict synaptic loss at synaptosome levels in AD brain regions compared to CNs. UCB-J showed highest synaptic loss in AD hippocampus followed in descending order by frontal cortex, temporal cortex, parietal cortex, and cerebellum. H-UCB-J large brain-section autoradiography and cellular/subcellular fractions binding studies indicated potential off-target interaction with phosphorylated tau (p-tau) species in AD brains, which could have subsequent clinical implications for imaging studies.
HIGHLIGHTS
Synaptic positron emission tomography (PET)-tracer UCB-J could target synaptic vesicle 2A protein (SV2A) with high specificity in Alzheimer's disease (AD) and control brains. Synaptic PET-tracer UCB-J could depict synaptic loss at synaptosome levels in AD brain regions compared to control. Potential off-target interaction of UCB-J with phosphorylated tau (p-tau) species at cellular/subcellular levels could have subsequent clinical implications for imaging studies, warranting further investigations.
Topics: Humans; Alzheimer Disease; Positron-Emission Tomography; Brain; Synaptic Vesicles; Cerebellum; Membrane Glycoproteins; Nerve Tissue Proteins
PubMed: 38363009
DOI: 10.1002/alz.13720 -
Angiogenesis Aug 2023APJ has been extensively described in the pathophysiology of angiogenesis and cell proliferation. The prognostic value of APJ overexpression in many diseases is now...
APJ has been extensively described in the pathophysiology of angiogenesis and cell proliferation. The prognostic value of APJ overexpression in many diseases is now established. This study aimed to design a PET radiotracer that specifically binds to APJ. Apelin-F13A-NODAGA (AP747) was synthesized and radiolabeled with gallium-68 ([Ga]Ga-AP747). Radiolabeling purity was excellent (> 95%) and stable up to 2 h. Affinity constant of [Ga]Ga-AP747 was measured on APJ-overexpressing colon adenocarcinoma cells and was in nanomolar range. Specificity of [Ga]Ga-AP747 for APJ was evaluated in vitro by autoradiography and in vivo by small animal PET/CT in both colon adenocarcinoma mouse model and Matrigel plug mouse model. Dynamic of [Ga]Ga-AP747 PET/CT biodistributions was realized on healthy mice and pigs for two hours, and quantification of signal in organs showed a suitable pharmacokinetic profile for PET imaging, largely excreted by urinary route. Matrigel mice and hindlimb ischemic mice were submitted to a 21-day longitudinal follow-up with [Ga]Ga-AP747 and [Ga]Ga-RGD small animal PET/CT. [Ga]Ga-AP747 PET signal in Matrigel was significantly more intense than that of [Ga]Ga-RGD. Revascularization of the ischemic hind limb was followed by LASER Doppler. In the hindlimb, [Ga]Ga-AP747 PET signal was more than twice higher than that of [Ga]Ga-RGD on day 7, and significantly superior over the 21-day follow-up. A significant, positive correlation was found between the [Ga]Ga-AP747 PET signal on day 7 and late hindlimb perfusion on day 21. We developed a new PET radiotracer that specifically binds to APJ, [Ga]Ga-AP747 that showed more efficient imaging properties than the most clinically advanced tracer of angiogenesis, [Ga]Ga-RGD.
Topics: Animals; Mice; Swine; Apelin; Apelin Receptors; Gallium Radioisotopes; Positron Emission Tomography Computed Tomography; Adenocarcinoma; Colonic Neoplasms; Positron-Emission Tomography; Molecular Imaging; Oligopeptides
PubMed: 36973482
DOI: 10.1007/s10456-023-09875-8 -
European Journal of Nuclear Medicine... Aug 2023Hepatocellular carcinoma (HCC) is a highly vascularized solid carcinoma and tumor vessel-targeted molecular imaging might be effective for early diagnosis of HCC....
PURPOSE
Hepatocellular carcinoma (HCC) is a highly vascularized solid carcinoma and tumor vessel-targeted molecular imaging might be effective for early diagnosis of HCC. Herein, we developed a novel trimeric affibody (Z) with highly specific binding to the platelet-derived growth factor receptor beta (PDGFRβ). The aim of this study is to evaluate the feasibility of Ga-radiolabeled Z ([Ga]Ga-DOTA-Z) as PET tracer for diagnosis of HCC.
METHODS
The bioinformatics analysis of clinical database and immunoblotting of clinical specimens were performed to validate the potential of PDGFRβ as HCC biomarker. The trimeric affibody Z was conjugated with DOTA-NHS-ester and radiolabeled with Ga to produce [Ga]Ga-DOTA-Z conjugate. Immunoreactivity and specific uptake of [Ga]Ga-DOTA-Z were assessed by dose-dependent cell binding, autoradiography, and biodistribution analysis. [Ga]Ga-DOTA-Z PET/CT scanning of diethylnitrosamine (DEN)-induced primary HCC rats and a rare case of idiopathical HCC rhesus monkey was performed to evaluate the imaging capability and radiation dosimetry of [Ga]Ga-DOTA-Z in vivo.
RESULTS
Excessive PDGFRβ was validated as a representative biomarker of HCC neovascularization. The radiolabeling of [Ga]Ga-DOTA-Z was achieved at more than 95% radiochemical yield. In vitro assays showed specific uptake of [Ga]Ga-DOTA-Z in HCC tumor vessels by autoradiography. Animal PET/CT imaging with [Ga]Ga-DOTA-Z successfully visualized the tumor lesions in primary HCC rats and rhesus monkey, and indicated radiation absorbed dose of 2.03E-02 mSv/MBq for each scanning.
CONCLUSIONS
Our results demonstrated that [Ga]Ga-DOTA-Z conjugate could be applied as a promising PET tracer for early diagnosis of hepatocellular carcinoma.
Topics: Rats; Animals; Positron Emission Tomography Computed Tomography; Carcinoma, Hepatocellular; Gallium Radioisotopes; Tissue Distribution; Macaca mulatta; Cell Line, Tumor; Liver Neoplasms; Positron-Emission Tomography; Biomarkers
PubMed: 37256321
DOI: 10.1007/s00259-023-06260-x -
Journal of Nuclear Cardiology :... Dec 2023Vascular adhesion protein-1 (VAP-1) is an adhesion molecule and primary amine oxidase, and Gallium-68-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetra-acetic...
BACKGROUND
Vascular adhesion protein-1 (VAP-1) is an adhesion molecule and primary amine oxidase, and Gallium-68-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetra-acetic acid conjugated sialic acid-binding immunoglobulin-like lectin 9 motif containing peptide ([Ga]Ga-DOTA-Siglec-9) is a positron emission tomography (PET) tracer targeting VAP-1. We evaluated the feasibility of PET imaging with [Ga]Ga-DOTA-Siglec-9 for the detection of myocardial lesions in rats with autoimmune myocarditis.
METHODS
Rats (n = 9) were immunized twice with porcine cardiac myosin in complete Freund's adjuvant. Control rats (n = 6) were injected with Freund's adjuvant alone. On day 21, in vivo PET/computed tomography (CT) imaging with [Ga]Ga-DOTA-Siglec-9 was performed, followed by ex vivo autoradiography, histology, and immunohistochemistry of tissue sections. In addition, myocardial samples from three patients with cardiac sarcoidosis were studied.
RESULTS
[Ga]Ga-DOTA-Siglec-9 PET/CT images of immunized rats showed higher uptake in myocardial lesions than in myocardium outside lesions (SUV, 0.5 ± 0.1 vs 0.3 ± 0.1; P = .003) or control rats (SUV, 0.2 ± 0.03; P < .0001), which was confirmed by ex vivo autoradiography of tissue sections. Immunohistochemistry showed VAP-1-positive staining in lesions of rats with myocarditis and in patients with cardiac sarcoidosis.
CONCLUSION
VAP-1-targeted [Ga]Ga-DOTA-Siglec-9 PET is a potential novel technique for the detection of myocardial lesions.
Topics: Humans; Rats; Animals; Swine; Positron Emission Tomography Computed Tomography; Gallium Radioisotopes; Myocarditis; Freund's Adjuvant; Tomography, X-Ray Computed; Positron-Emission Tomography; Sialic Acid Binding Immunoglobulin-like Lectins; Sarcoidosis
PubMed: 37758963
DOI: 10.1007/s12350-023-03371-8 -
Clinical Nuclear Medicine Jun 2024Tumor-associated macrophages are targets of interest in triple-negative breast cancer (TNBC). The translocator protein 18 kDa (TSPO) is a sensitive marker for...
ABSTRACT
Tumor-associated macrophages are targets of interest in triple-negative breast cancer (TNBC). The translocator protein 18 kDa (TSPO) is a sensitive marker for macrophages and holds potential relevance in TNBC stratification. This pilot prospective study (EITHICS, NCT04320030) aimed to assess the potential of TSPO PET/CT imaging using 18F-DPA-714 in primary TNBC, compared with immunohistochemistry, autoradiography, and TSPO polymorphism.
PATIENTS AND METHODS
Thirteen TNBC patients were included. They underwent TSPO genotyping (HAB, MAB, LAB), 18F-FDG PET/CT, and breast MRI. Semiquantitative PET parameters were computed. VOIs were defined on the tumor lesion, healthy breast tissue, and pectoral muscle to obtain SUV, tumor-to-background ratio (TBR), and time-activity curves (TACs). Additionally, immunohistochemistry, 3H-DPA-714, and 3H-PK-11195 autoradiography were conducted.
RESULTS
The majority of TNBC tumors (11/13, 84%) had a preponderance of M2-polarized macrophages with a median proportion of 82% (range, 44%-94%). 18F-DPA-714 PET/CT clearly identified TNBC tumors with an excellent TBR. Three distinct patterns of 18F-DPA-714 TACs were identified, categorized as "above muscular," "equal to muscular," and "below muscular" with reference to the muscular background. For the "above muscular" group (2 HAB and 2 MAB), "equal muscular" group (3 HAB, 3 MAB, and 1 LAB), and "below muscular" group (1 LAB and 1 MAB), tumor TACs showed a 18F-DPA-714 accumulation slope of 1.35, 0.62, and 0.22, respectively, and a median SUVmean of 4.02 (2.09-5.31), 1.66 (0.93-3.07), and 0.61 (0.43-1.02).
CONCLUSIONS
This study successfully demonstrated TNBC tumor targeting by 18F-DPA-714 with an excellent TBR, allowing to stratify 3 patterns of uptake potentially influenced by the TSPO polymorphism status. Further studies in larger populations should be performed to evaluate the prognostic value of this new biomarker.
PubMed: 38913962
DOI: 10.1097/RLU.0000000000005338 -
Biomedicines Jan 2024The translocator protein (TSPO) has been proven to have great potential as a target for the positron emission tomography (PET) imaging of glioblastoma. However, there is...
BACKGROUND
The translocator protein (TSPO) has been proven to have great potential as a target for the positron emission tomography (PET) imaging of glioblastoma. However, there is an ongoing debate about the potential various sources of the TSPO PET signal. This work investigates the impact of the inoculation-driven immune response on the PET signal in experimental orthotopic glioblastoma.
METHODS
Serial [F]GE-180 and -(2-[F]fluoroethyl)-L-tyrosine ([F]FET) PET scans were performed at day 7/8 and day 14/15 after the inoculation of GL261 mouse glioblastoma cells (n = 24) or saline (sham, n = 6) into the right striatum of immunocompetent C57BL/6 mice. An additional n = 25 sham mice underwent [F]GE-180 PET and/or autoradiography (ARG) at days 7, 14, 21, 28, 35, 50 and 90 in order to monitor potential reactive processes that were solely related to the inoculation procedure. In vivo imaging results were directly compared to tissue-based analyses including ARG and immunohistochemistry.
RESULTS
We found that the inoculation process represents an immunogenic event, which significantly contributes to TSPO radioligand uptake. [F]GE-180 uptake in GL261-bearing mice surpassed [F]FET uptake both in the extent and the intensity, e.g., mean target-to-background ratio (TBR) in PET at day 7/8: 1.22 for [F]GE-180 vs. 1.04 for [F]FET, < 0.001. Sham mice showed increased [F]GE-180 uptake at the inoculation channel, which, however, continuously decreased over time (e.g., TBR in PET: 1.20 at day 7 vs. 1.09 at day 35, = 0.04). At the inoculation channel, the percentage of TSPO/IBA1 co-staining decreased, whereas TSPO/GFAP (glial fibrillary acidic protein) co-staining increased over time ( < 0.001).
CONCLUSION
We identify the inoculation-driven immune response to be a relevant contributor to the PET signal and add a new aspect to consider for planning PET imaging studies in orthotopic glioblastoma models.
PubMed: 38255293
DOI: 10.3390/biomedicines12010188 -
EJNMMI Radiopharmacy and Chemistry Oct 2023Receptor interacting protein kinase 1 (RIPK1) is a serine/threonine kinase, which regulates programmed cell death and inflammation. Recently, the involvement of RIPK1 in...
BACKGROUND
Receptor interacting protein kinase 1 (RIPK1) is a serine/threonine kinase, which regulates programmed cell death and inflammation. Recently, the involvement of RIPK1 in the pathophysiology of Alzheimer's disease (AD) has been reported; RIPK1 is involved in microglia's phenotypic transition to their dysfunctional states, and it is highly expressed in the neurons and microglia in the postmortem brains in AD patients. They prompt neurodegeneration leading to accumulations of pathological proteins in AD. Therefore, regulation of RIPK1 could be a potential therapeutic target for the treatment of AD, and in vivo imaging of RIPK1 may become a useful modality in studies of drug discovery and pathophysiology of AD. The purpose of this study was to develop a suitable radioligand for positron emission tomography (PET) imaging of RIPK1.
RESULTS
(S)-2,2-dimethyl-1-(5-phenyl-4,5-dihydro-1H-pyrazol-1-yl)propan-1-one (GSK'963) has a high affinity, selectivity for RIPK1, and favorable physiochemical properties based on its chemical structure. In this study, since C-labeling (half-life: 20.4 min) GSK'963 retaining its structure requiring the Grignard reaction of tert-butylmagnesium halides and [C]carbon dioxide was anticipated to give a low yield, we decided instead to C-label a GSK'963 analog ((S)-2,2-dimethyl-1-(5-(m-tolyl)-4,5-dihydro-1H-pyrazol-1-yl)propan-1-one, GG502), which has a high RIPK1 inhibitory activity equivalent to that of the original compound GSK'963. Thus, we successfully C-labeled GG502 using a Pd-mediated cross-coupling reaction in favorable yields (3.6 ± 1.9%) and radiochemical purities (> 96%), and molar activity (47-115 GBq/μmol). On autoradiography, radioactivity accumulation was observed for [C]GG502 and decreased by non-radioactive GG502 in the mouse spleen and human brain, indicating the possibility of specific binding of this ligand to RIPK1. On brain PET imaging in a rhesus monkey, [C]GG502 showed a good brain permeability (peak standardized uptake value (SUV) ~3.0), although there was no clear evidence of specific binding of [C]GG502. On brain PET imaging in acute inflammation model rats, [C]GG502 also showed a good brain permeability, and no significant increased uptake was observed in the lipopolysaccharide-treated side of striatum. On metabolite analysis in rats at 30 min after administration of [C]GG502, ~55% and ~10% of radioactivity was from unmetabolized [C]GG502 in the brain and the plasma, respectively.
CONCLUSIONS
We synthesized and evaluated a C-labeled PET ligand based on the methylated analog of GSK'963 for imaging of RIPK1 in the brain. Although in autoradiography of the resulting [C]GG502 indicated the possibility of specific binding, the actual PET imaging failed to detect any evidence of specific binding to RIPK1 despite its good brain permeability. Further development of radioligands with a higher binding affinity for RIPK1 in vivo and more stable metabolite profiles compared with the current compound may be required.
PubMed: 37853253
DOI: 10.1186/s41181-023-00217-z -
European Journal of Nuclear Medicine... Mar 2024Radiation-induced lung injury (RILI) is a severe side effect of radiotherapy (RT) for thoracic malignancies and we currently lack established methods for the early...
PURPOSE
Radiation-induced lung injury (RILI) is a severe side effect of radiotherapy (RT) for thoracic malignancies and we currently lack established methods for the early detection of RILI. In this study, we synthesized a new tracer, [F]AlF-NOTA-QHY-04, targeting C-X-C-chemokine-receptor-type-4 (CXCR4) and investigated its feasibility to detect RILI.
METHODS
An RILI rat model was constructed and scanned with [F]AlF-NOTA-QHY-04 PET/CT and [F]FDG PET/CT periodically after RT. Dynamic, blocking, autoradiography, and histopathological studies were performed on the day of peak uptake. Fourteen patients with radiation pneumonia, developed during or after thoracic RT, were subjected to PET scan using [F]AlF-NOTA-QHY-04.
RESULTS
The yield of [F]AlF-NOTA-QHY-04 was 28.5-43.2%, and the specific activity was 27-33 GBq/μmol. [F]AlF-NOTA-QHY-04 was mainly excreted through the kidney. Significant increased [F]AlF-NOTA-QHY-04 uptake in the irradiated lung compared with that in the normal lung in the RILI model was observed on day 6 post-RT and peaked on day 14 post-RT, whereas no apparent uptake of [F]FDG was shown on days 7 and 15 post-RT. MicroCT imaging did not show pneumonia until 42 days post-RT. Significant intense [F]AlF-NOTA-QHY-04 uptake was confirmed by autoradiography. Immunofluorescence staining demonstrated expression of CXCR4 was significantly increased in the irradiated lung tissue, which correlated with results obtained from hematoxylin-eosin and Masson's trichrome staining. In 14 patients with radiation pneumonia, maximum standardized uptake values (SUVmax) were significantly higher in the irradiated lung compared with those in the normal lung. SUVmax of patients with grade 2 RILI was significantly higher than that of patients with grade 1 RILI.
CONCLUSION
This study indicated that [F]AlF-NOTA-QHY-04 PET/CT imaging can detect RILI non-invasively and earlier than [F]FDG PET/CT in a rat model. Clinical studies verified its feasibility, suggesting the clinical potential of [F]AlF-NOTA-QHY-04 as a PET/CT tracer for early monitoring of RILI.
Topics: Humans; Rats; Animals; Positron Emission Tomography Computed Tomography; Fluorodeoxyglucose F18; Lung Injury; Radiation Pneumonitis; Positron-Emission Tomography; Radiation Injuries; Lung; Receptors, CXCR4
PubMed: 38030744
DOI: 10.1007/s00259-023-06517-5 -
CNS Neuroscience & Therapeutics Apr 2024Aggravated neuronal loss, caused mainly by neuronal apoptosis, is observed in the brain of patients with Alzheimer's disease (AD) and animal models of AD. A truncated...
AIM
Aggravated neuronal loss, caused mainly by neuronal apoptosis, is observed in the brain of patients with Alzheimer's disease (AD) and animal models of AD. A truncated form of Dual-specific and tyrosine phosphorylation-regulated protein kinase 1A (Dyrk1A) plays a vital role in AD pathogenesis. Downregulation of anti-apoptotic Bcl-xL is tightly correlated with neuronal loss in AD. However, the molecular regulation of neuronal apoptosis and Bcl-x expression by Dyrk1A in AD remains largely elusive. Here, we aimed to explore the role and molecular mechanism of Dyrk1A in apoptosis.
METHODS
Cell Counting Kit-8 (CCK8), flow cytometry, and TdT-mediated dUTP Nick-End Labeling (TUNEL) were used to check apoptosis. The cells, transfected with Dyrk1A or/and ASF with Bcl-x minigene, were used to assay Bcl-x expression by RT-PCR and Western blots. Co-immunoprecipitation, autoradiography, and immunofluorescence were conducted to check the interaction of ASF and Dyrk1A. Gene set enrichment analysis (GSEA) of apoptosis-related genes was performed in mice overexpressing Dyrk1A (TgDyrk1A) and AD model 5xFAD mice.
RESULTS
Dyrk1A promoted Bcl-xS expression and apoptosis. Splicing factor ASF promoted Bcl-x exon 2b inclusion, leading to increased Bcl-xL expression. Dyrk1A suppressed ASF-mediated Bcl-x exon 2b inclusion via phosphorylation. The C-terminus deletion of Dyrk1A facilitated its binding and kinase activity to ASF. Moreover, Dyrk1a further suppressed the ASF-mediated Bcl-x exon 2b inclusion and aggravated apoptosis. The truncated Dyrk1A, increased Bcl-xS, and enrichment of apoptosis-related genes was observed in the brain of 5xFAD mice.
CONCLUSIONS
We speculate that increased Dyrk1A and truncated Dyrk1A may aggravate neuronal apoptosis by decreasing the ratio of Bcl-xL/Bcl-xS via phosphorylating ASF in AD.
Topics: Animals; Mice; Alzheimer Disease; Apoptosis; Exons; Phosphorylation; Protein Serine-Threonine Kinases; Protein-Tyrosine Kinases; Dyrk Kinases; Serine-Arginine Splicing Factors; bcl-X Protein
PubMed: 37864462
DOI: 10.1111/cns.14493 -
Life (Basel, Switzerland) Aug 2023This article relates personal recollections and starts with the origin of electron microscopy in the sixties of the previous century at the University of Amsterdam.... (Review)
Review
This article relates personal recollections and starts with the origin of electron microscopy in the sixties of the previous century at the University of Amsterdam. Novel fixation and embedding techniques marked the discovery of the internal bacterial structures not visible by light microscopy. A special status became reserved for the freeze-fracture technique. By freeze-fracturing chemically fixed cells, it proved possible to examine the morphological effects of fixation. From there on, the focus switched from bacterial structure as such to their cell cycle. This invoked bacterial physiology and steady-state growth combined with electron microscopy. Electron-microscopic autoradiography with pulses of [H] Dap revealed that segregation of replicating DNA cannot proceed according to a model of zonal growth (with envelope-attached DNA). This stimulated us to further investigate the sacculus, the peptidoglycan macromolecule. In particular, we focused on the involvement of penicillin-binding proteins such as PBP2 and PBP3, and their role in division. Adding aztreonam (an inhibitor of PBP3) blocked ongoing divisions but not the initiation of new ones. A PBP3-independent peptidoglycan synthesis (PIPS) appeared to precede a PBP3-dependent step. The possible chemical nature of PIPS is discussed.
PubMed: 37629639
DOI: 10.3390/life13081782