The effects of the ß1-adrenergic receptor antagonist bisoprolol administration on mirabegron-stimulated human brown adipose tissue thermogenesis.

AIM: Pharmacological stimulation of human brown adipose tissue (BAT) has been hindered by ineffective activation or undesirable off-target effects. Oral administration of the maximal allowable dose of mirabegron (200 mg), a ß3-adrenergic receptor (ß3-AR) agonist, has been effective in stimulating BAT thermogenesis and whole-body energy expenditure. However, this has been accompanied by undesirable cardiovascular effects. Therefore, we hypothesized that combining mirabegron with a ß1-AR antagonist could suppress these unwanted effects and increase the stimulation of the ß3-AR and ß2-AR in BAT. METHODS: We performed a randomized crossover trial (NCT04823442) in 8 lean men. Mirabegron (200 mg) was administered orally with or without the ß1-AR antagonist bisoprolol (10 mg). Dynamic [11C]-acetate and 2-deoxy-2-[18F]fluoro-d-glucose PET/CT scans were performed sequentially after oral administration of mirabegron ± bisoprolol. RESULTS: Compared to room temperature, mirabegron alone increased BAT oxidative metabolism (0.84 ± 0.46 vs. 1.79 ± 0.91 min-1, p = 0.0433), but not when combined with bisoprolol. The metabolic rate of glucose in BAT, measured using [18F]FDG PET, was significantly higher with mirabegron than mirabegron with bisoprolol (24 ± 10 vs. 16 ± 8 nmol/g/min, p = 0.0284). Bisoprolol inhibited the mirabegron-induced increase in systolic blood pressure and heart rate. CONCLUSION: The administration of bisoprolol decreases the adverse cardiovascular effects of mirabegron. However, the provided dose also blunted the mirabegron-stimulated increase in BAT lipolysis, thermogenesis, and glucose uptake. The attenuation in BAT blood flow induced by the large dose of bisoprolol may have limited BAT thermogenesis.

Electron-Induced Damage by UV Photolysis of DNA Attached to Gold Nanoparticles.

Photolysis of DNA attached to gold nanoparticles (AuNPs) with ultraviolet (UV) photons induces DNA damage. The release of nucleobases (Cyt, Gua, Ade, and Thy) from DNA was the major reaction (99%) with an approximately equal release of pyrimidines and purines. This reaction contributes to the formation of abasic sites in DNA. In addition, liquid chromatography-mass spectrometry/MS (LC-MS/MS) analysis revealed the formation of reduction products of pyrimidines (5,6-dihydrothymidine and 5,6-dihydro-2'-deoxyuridine) and eight 2',3'- and 2',5'-dideoxynucleosides. In contrast, there was no evidence of the formation of 5-hydroxymethyluracil and 8-oxo-7,8-dihydroguanine, which are common oxidation products of thymine and guanine, respectively. Using appropriate filters, the main photochemical reactions were found to involve photoelectrons ejected from AuNPs by UV photons. The contribution of "hot" conduction band electrons with energies below the photoemission threshold was minor. The mechanism for the release of free nucleobases by photoelectrons is proposed to take place by the initial formation of transient molecular anions of the nucleobases, followed by dissociative electron attachment at the C1'-N glycosidic bond connecting the nucleobase to the sugar-phosphate backbone. This mechanism is consistent with the reactivity of secondary electrons ejected by X-ray irradiation of AuNPs attached to DNA, as well as the reactions of various nucleic acid derivatives irradiated with monoenergetic very-low-energy electrons (∼2 eV). These studies should help us to understand the chemistry of nanoparticles that are exposed to UV light and that are used as scaffolds and catalysts in molecular biology, curative agents in photodynamic therapy, and components of sunscreens and cosmetics.

Theranostic 64Cu-DOTHA2-PSMA allows low toxicity radioligand therapy in mice prostate cancer model.

Introduction: We have previously shown that copper-64 (64Cu)-DOTHA2-PSMA can be used for positron emission tomography (PET) imaging of prostate cancer. Owing to the long-lasting, high tumoral uptake of 64Cu-DOTHA2-PSMA, the objective of the current study was to evaluate the therapeutic potential of 64Cu-DOTHA2-PSMA in vivo. Methods: LNCaP tumor-bearing NOD-Rag1nullIL2rgnull (NRG) mice were treated with an intraveinous single-dose of 64Cu-DOTHA2-PSMA at maximal tolerated injected activity, natCu-DOTHA2-PSMA at equimolar amount (control) or lutetium-177 (177Lu)-PSMA-617 at 120 MBq to assess their impact on survival. Weight, well-being and tumor size were followed until mice reached 62 days post-injection or ethical limits. Toxicity was assessed through weight, red blood cells (RBCs) counts, pathology and dosimetry calculations. Results: Survival was longer with 64Cu-DOTHA2-PSMA than with natCu-DOTHA2-PSMA (p < 0.001). Likewise, survival was also longer when compared to 177Lu-PSMA-617, although it did not reach statistical significance (p = 0.09). RBCs counts remained within normal range for the 64Cu-DOTHA2-PSMA group. 64Cu-DOTHA2-PSMA treated mice showed non-pathological fibrosis and no other signs of radiation injury. Human extrapolation of dosimetry yielded an effective dose of 3.14 × 10-2 mSv/MBq, with highest organs doses to gastrointestinal tract and liver. Discussion: Collectively, our data showed that 64Cu-DOTHA2-PSMA-directed radioligand therapy was effective for the treatment of LNCaP tumor-bearing NRG mice with acceptable toxicity and dosimetry. The main potential challenge is the hepatic and gastrointestinal irradiation.

Aza-Residue Modulation of Cyclic d,l-α-Peptide Nanotube Assembly with Enhanced Anti-Amyloidogenic Activity.

Transient soluble oligomers of amyloid-ß (Aß) are considered among the most toxic species in Alzheimer's disease (AD). Soluble Aß oligomers accumulate early prior to insoluble plaque formation and cognitive impairment. The cyclic d,l-α-peptide CP-2 (1) self-assembles into nanotubes and demonstrates promising anti-amyloidogenic activity likely by a mechanism involving engagement of soluble oligomers. Systematic replacement of the residues in peptide 1 with aza-amino acid counterparts was performed to explore the effects of hydrogen bonding on propensity to mitigate Aß aggregation and toxicity. Certain azapeptides exhibited improved ability to engage, alter the secondary structure, and inhibit aggregation of Aß. Moreover, certain azapeptides disassembled preformed Aß fibrils and protected cells from Aß-mediated toxicity. Substitution of the l-norleucine3 and d-serine6 residues in peptide 1 with aza-norleucine and aza-homoserine provided, respectively, nontoxic [azaNle3]-1 (4) and [azaHse6]-1 (7), that significantly abated symptoms in a transgenic Caenorhabditis elegans AD model by decreasing Aß oligomer levels.

DNA radiosensitization by terpyridine-platinum: damage induced by 5 and 10 eV transient anions.

Chemoradiation therapy (CRT), which combines a chemotherapeutic drug with ionizing radiation (IR), is the most common cancer treatment. At the molecular level, the binding of Pt-drugs to DNA sensitizes cancer cells to IR, mostly by increasing the damage induced by secondary low-energy (0-20 eV) electrons (LEEs). We investigate such enhancements by binding terpyridine-platinum (Tpy-Pt) to supercoiled plasmid DNA. Fifteen nanometer thick films of Tpy-Pt-DNA complexes in a molar ratio of 5 : 1 were irradiated with monoenergetic electrons of 5 and 10 eV, which principally attach to the DNA bases to form transient anions (TAs) decaying into a multitude of bond-breaking channels. At both energies, the effective yields of crosslinks (CLs), base damage (BD) related CLs, single and double strand breaks (SSBs and DSBs), non-DSB-cluster lesions, loss of supercoiled configuration and base lesions are 6.5 ± 1.5, 8.8± 3.0, 88 ± 11, 5.3 ± 1.3, 9.6 ± 2.2, 106 ± 17, 189 ± 31 × 10-15 per electron per molecule, and 11.9 ± 2.6, 19.9 ± 4.4, 128 ± 18, 7.7 ± 3.0, 13.4 ± 3.9, 144 ± 19, 229 ± 42 × 10-15 per electron per molecule, respectively. DNA damage increased 1.2-4.2-fold due to Tpy-Pt, the highest being for BD-related CLs. These enhancements are slightly higher than those obtained by the conventional Pt-drugs cisplatin, carboplatin and oxaliplatin, apart from BD-related CLs, which are about 3 times higher. Enhancements are related to the strong perturbation of the DNA helix by Tpy-Pt, its high dipole moment and its favorable binding to guanine (G), all of which increase bond-breaking via TA formation. In CRT, Tpy-Pt could considerably enhance crosslinking within genomic DNA and between DNA and other components of the nucleus, causing roadblocks to replication and transcription, particularly within telomeres, where it binds preferentially within G-quadruplexes.

68Ga-DOTATATE Prepared from Cyclotron-Produced 68Ga: An Integrated Solution from Cyclotron Vault to Safety Assessment and Diagnostic Efficacy in Neuroendocrine Cancer Patients.

Cyclotron production of 68Ga is a promising approach to supply 68Ga radiopharmaceuticals. To validate this capability, an integrated solution for a robust synthesis of 68Ga-DOTATATE prepared from cyclotron-produced 68Ga was achieved. A retrospective comparison analysis was performed on patients who underwent PET/CT imaging after injection of DOTATATE labeled with 68Ga produced by a cyclotron or eluted from a generator to demonstrate the clinical safety and diagnostic efficacy of the radiopharmaceutical as a routine standard-of-care diagnostic tool in the clinic. Methods: An enriched pressed 68Zn target was irradiated by a cyclotron with a proton beam set at 12.7 MeV for 100 min. The fully automated process uses an in-vault dissolution system in which a liquid distribution system transfers the dissolved target to a dedicated hot cell for the purification of 68GaCl3 and radiolabeling of DOTATATE using a cassette-based automated module. Quality control tests were performed on the resulting tracer solution. The internal radiation dose for 68Ga-DOTATATE was based on extrapolation from rat biodistribution experiments. A retrospective comparison analysis was performed on patients who underwent PET/CT imaging after injection of DOTATATE labeled with cyclotron- or generator-produced 68Ga. Results: The synthesis of 68Ga-DOTATATE (20.7 ± 1.3 GBq) with high apparent molar activity (518 ± 32 GBq/µmol at the end of synthesis) was completed in 65 min, and the radiopharmaceutical met the requirements specified in the European Pharmacopoeia monograph on 68Ga-chloride (accelerator-produced) solution for radiolabeling. 68Ga-DOTATATE was stable for at least 5 h after formulation. The dosimetry calculated with OLINDA for cyclotron- and generator-produced 68Ga-DOTATATE was roughly equivalent. The SUVmean or SUVmax of tumoral lesions with cyclotron-produced 68Ga-DOTATATE was equivalent to that with generator-produced 68Ga. Among physiologic uptake levels, a significant difference was found in kidneys, spleen, and stomach wall, with lower values in cyclotron-produced 68Ga-DOTATATE in all cases. Conclusion: Integrated cyclotron production achieves reliable high yields of clinical-grade 68Ga-DOTATATE. The clinical safety and imaging efficacy of cyclotron-produced 68Ga-DOTATATE in humans provide supporting evidence for its use in routine clinical practice.

Early diagnosis and treatment of Alzheimer's disease by targeting toxic soluble Aß oligomers.

Transient soluble oligomers of amyloid-ß (Aß) are toxic and accumulate early prior to insoluble plaque formation and cognitive impairment in Alzheimer's disease (AD). Synthetic cyclic D,L-α-peptides (e.g., 1) self-assemble into cross ß-sheet nanotubes, react with early Aß species (1-3 mers), and inhibit Aß aggregation and toxicity in stoichiometric concentrations, in vitro. Employing a semicarbazide as an aza-glycine residue with an extra hydrogen-bond donor to tune nanotube assembly and amyloid engagement, [azaGly6]-1 inhibited Aß aggregation and toxicity at substoichiometric concentrations. High-resolution NMR studies revealed dynamic interactions between [azaGly6]-1 and Aß42 residues F19 and F20, which are pivotal for early dimerization and aggregation. In an AD mouse model, brain positron emission tomography (PET) imaging using stable 64Cu-labeled (aza)peptide tracers gave unprecedented early amyloid detection in 44-d presymptomatic animals. No tracer accumulation was detected in the cortex and hippocampus of 44-d-old 5xFAD mice; instead, intense PET signal was observed in the thalamus, from where Aß oligomers may spread to other brain parts with disease progression. Compared with standard 11C-labeled Pittsburgh compound-B (11C-PIB), which binds specifically fibrillar Aß plaques, 64Cu-labeled (aza)peptide gave superior contrast and uptake in young mouse brain correlating with Aß oligomer levels. Effectively crossing the blood-brain barrier (BBB), peptide 1 and [azaGly6]-1 reduced Aß oligomer levels, prolonged lifespan of AD transgenic Caenorhabditis elegans, and abated memory and behavioral deficits in nematode and murine AD models. Cyclic (aza)peptides offer novel promise for early AD diagnosis and therapy.

In vivo behavior of [64Cu]NOTA-terpyridine platinum, a novel chemo-radio-theranostic agent for imaging, and therapy of colorectal cancer.

To overcome resistance to chemotherapy for colorectal cancer, we propose to validate in vivo a novel terpyridine-platinum (TP) compound radiolabeled with the radio-theranostic isotope 64Cu. In vivo stability, biodistribution, PET imaging, tumor growth delay, toxicity and dosimetry of [64Cu]NOTA-C3-TP were determined. The current experimental studies show that [64Cu]NOTA-C3-TP is stable in vivo, rapidly eliminated by the kidneys and has a promising tumor uptake ranging from 1.8 ± 0.4 to 3.0 ± 0.2 %ID/g over 48 h. [64Cu]NOTA-C3-TP retarded tumor growth by up to 6 ± 2.0 days and improved survival relative to vehicle and non-radioactive [NatCu]NOTA-C3-TP over 17 days of tumor growth observation. This effect was obtained with only 0.4 nmol i.v. injection of [64Cu]NOTA-C3-TP, which delivers 3.4 ± 0.3 Gy tumoral absorbed dose. No evidence of toxicity, by weight loss or mortality was revealed. These findings confirm the high potential of [64Cu]NOTA-TP as a novel radio-theranostic agent.

High-fructose feeding suppresses cold-stimulated brown adipose tissue glucose uptake independently of changes in thermogenesis and the gut microbiome.

Diets rich in added sugars are associated with metabolic diseases, and studies have shown a link between these pathologies and changes in the microbiome. Given the reported associations in animal models between the microbiome and brown adipose tissue (BAT) function, and the alterations in the microbiome induced by high-glucose or high-fructose diets, we investigated the potential causal link between high-glucose or -fructose diets and BAT dysfunction in humans. Primary outcomes are changes in BAT cold-induced thermogenesis and the fecal microbiome (clinicaltrials.gov, NCT03188835). We show that BAT glucose uptake, but not thermogenesis, is impaired by a high-fructose but not high-glucose diet, in the absence of changes in the gastrointestinal microbiome. We conclude that decreased BAT glucose metabolism occurs earlier than other pathophysiological abnormalities during fructose overconsumption in humans. This is a potential confounding factor for studies relying on 18F-FDG to assess BAT thermogenesis.

64Cu-DOTHA2-PSMA, a Novel PSMA PET Radiotracer for Prostate Cancer with a Long Imaging Time Window.

Prostate cancer imaging and late-stage management can be improved with prostate-specific membrane antigen (PSMA)-targeting radiotracers. We developed a PSMA positron emission tomography (PET) radiotracer, DOTHA2-PSMA radiolabeled with 64Cu (T1/2: 12.7 h), to leverage its large imaging time window. This preclinical study aimed to evaluate the biological and imaging properties of 64Cu-DOTHA2-PSMA. Its stability was assessed in plasma ex vivo and in mice. Cellular behavior was studied for up to 48 h in LNCaP cells. Biodistribution studies were performed in balb/c mice for up to 48 h. Dynamic (1 h) and static (4 h and 24 h) PET imaging was completed in LNCaP tumor-bearing mice. 64Cu-DOTHA2-PSMA was stable ex vivo in plasma and reached cellular internalization up to 34.1 ± 4.9% injected activity (IA)/106 cells at 48 h post-injection (p.i.). Biodistribution results showed significantly lower uptake in kidneys than 68Ga-PSMA-617, our reference PET tracer (p < 0.001), but higher liver uptake at 2 h p.i. (p < 0.001). PET images showed 64Cu-DOTHA2-PSMA's highest tumoral uptake at 4 h p.i., with a significant difference between blocked and non-blocked groups from the time of injection to 24 h p.i. The high stability and tumor uptake with a long tumor imaging time window of 64Cu-DOTHA2-PSMA potentially contribute to the prostate cancer theranostic approach and its local recurrence detection.

Total Postprandial Hepatic Nonesterified and Dietary Fatty Acid Uptake Is Increased and Insufficiently Curbed by Adipose Tissue Fatty Acid Trapping in Prediabetes With Overweight.

Excessive lean tissue uptake of fatty acids (FAs) is important in the development of insulin resistance and may be caused by impaired dietary FA (DFA) storage and/or increased nonesterified FA (NEFA) flux from adipose tissue intracellular lipolysis. Cardiac and hepatic total postprandial FA uptake of NEFA+DFA has, however, never been reported in prediabetes with overweight. In this study, 20 individuals with impaired glucose tolerance (IGT) and 19 participants with normal glucose tolerance (NGT) and normal fasting glucose underwent postprandial studies with whole-body positron emission tomography/computed tomography (PET/CT) with oral [18F]fluoro-thia-heptadecanoic acid and dynamic PET/CT with intravenous [11C]palmitate. Hepatic (97 [range 36-215] mmol/6 h vs. 68 [23-132] mmol/6 h, P = 0.03) but not cardiac (11 [range 4-24] mmol/6 h vs. 8 [3-20] mmol/6 h, P = 0.09) uptake of most sources of postprandial FA (NEFA + DFA uptake) integrated over 6 h was higher in IGT versus NGT. DFA accounted for lower fractions of total cardiac (21% [5-47] vs. 25% [9-39], P = 0.08) and hepatic (19% [6-52] vs. 28% [14-50], P = 0.04) uptake in IGT versus NGT. Increased adipose tissue DFA trapping predicted lower hepatic DFA uptake and was associated with higher total cardiac FA uptake. Hence, enhanced adipose tissue DFA trapping in the face of increased postprandial NEFA flux is insufficient to fully curb increased postprandial lean organ FA uptake in prediabetes with overweight (ClinicalTrials.gov; NCT02808182).

18F-4FMFES and 18F-FDG PET/CT in Estrogen Receptor-Positive Endometrial Carcinomas: Preliminary Report.

This article reports the preliminary results of a phase II clinical trial investigating the use of the estrogen receptor (ER)-targeting PET tracer 4-fluoro-11ß-methoxy-16α-18F-fluoroestradiol (18F-4FMFES) and 18F-FDG PET in endometrial cancers. In parallel, noninvasive interventions were attempted to slow progression of 18F-4FMFES metabolites in the intestines to reduce abdominal background uptake. Methods: In an ongoing study, 25 patients who received prior pathologic confirmation of an ER-positive endometrial cancer or endometrial intraepithelial neoplasia agreed to participate in the ongoing clinical trial. Patients were scheduled for 18F-FDG and 18F-4FMFES PET/CT imaging in random order and within 2 wk. Patients were administered either 4 mg of loperamide orally before 18F-4FMFES tracer injection or repeated intravenous injection of 20 mg of hyoscine N-butylbromide during 18F-4FMFES PET/CT. Regions of interest covering the whole abdomen and excluding the liver, bladder, and uterus were drawn for the 18F-4FMFES PET images, and an SUV threshold of more than 4 was applied. The volume of the resulting region was compared between the different interventions to estimate the extent of the intestinal background uptake. Results: Repeated injection of hyoscine N-butylbromide substantially reduced the intestinal background volume, whereas loperamide had a significant but moderate effect. 18F-4FMFES tumor SUVmax ranged from 3.0 to 14.4 (9.4 ± 3.2), whereas 18F-FDG SUVmax ranged from 0 to 22.0 (7.5 ± 5.1). Tumor-to-background ratio was significantly higher for 18F-4FMFES (16.4 ± 5.4) than for 18F-FDG (7.4 ± 4.6). Significant differences were observed between grade 1 and higher-grade tumors concerning 18F-4FMFES uptake and contrast, 18F-FDG uptake, and the 18F-FDG/18F-4FMFES uptake ratio. Conclusion: It is possible to improve 18F-4FMFES abdominal background using hyoscine N-butylbromide. Both 18F-FDG and 18F-4FMFES PET are suitable for detection of ER-positive endometrial cancers, although 18F-4FMFES yielded a better tumor contrast than did 18F-FDG.

The Triple-Tracer strategy against Metastatic PrOstate cancer (3TMPO) study protocol.

OBJECTIVE: To determine the prevalence of intra-patient inter-metastatic heterogeneity based on positron emission tomography (PET)/computed tomography (CT) in patients with metastatic castration-resistant prostate cancer (mCRPC) and to determine the prevalence of neuroendocrine disease in these patients and their eligibility for radioligand therapies (RLTs). PATIENTS AND METHODS: This multicentre observational prospective clinical study will include 100 patients with mCRPC from five Canadian academic centres. Patients with radiological or biochemical progression and harbouring at least three metastases by conventional imaging will be accrued. Intra-patient inter-metastatic heterogeneity will be determined with triple-tracer imaging using fluorine-18 fluorodeoxyglucose (18 F-FDG), gallium-68-(68 Ga)-prostate-specific membrane antigen (PSMA)-617 and 68 Ga-DOTATATE, which are a glucose analogue, a PSMA receptor ligand and a somatostatin receptor ligand, respectively. The 68 Ga-PSMA-617 and 18 F-FDG PET/CT scans will be performed first. If at least one PSMA-negative/FDG-positive lesion is observed, an additional PET/CT scan with 68 Ga-DOTATATE will be performed. The tracer uptake of individual lesions will be assessed for each PET tracer and patients with lesions presenting discordant uptake profiles will be considered as having inter-metastatic heterogeneous disease and may be offered a biopsy. EXPECTED RESULTS: The proposed triple-tracer approach will allow whole-body mCRPC characterisation, investigating the inter-metastatic heterogeneity in order to better understand the phenotypic plasticity of prostate cancer, including the neuroendocrine transdifferentiation that occurs during mCRPC progression. Based on 68 Ga-PSMA-617 or 68 Ga-DOTATATE PET positivity, the potential eligibility of patients for PSMA and DOTATATE-based RLT will be assessed. Non-invasive whole-body determination of mCRPC heterogeneity and transdifferentiation is highly innovative and might establish the basis for new therapeutic strategies. Comparison of molecular imaging findings with biopsies will also link metastasis biology to radiomic features. CONCLUSION: This study will add novel, biologically relevant dimensions to molecular imaging: the non-invasive detection of inter-metastatic heterogeneity and transdifferentiation to neuroendocrine prostate cancer by using a multi-tracer PET/CT strategy to further personalise the care of patients with mCRPC.

Chemoattraction of Neoplastic Glial Cells with CXCL10, CCL2 and CCL11 as a Paradigm for a Promising Therapeutic Approach for Primary Brain Tumors.

Chemoattraction is a normal and essential process, but it can also be involved in tumorigenesis. This phenomenon plays a key role in glioblastoma (GBM). The GBM tumor cells are extremely difficult to eradicate, due to their strong capacity to migrate into the brain parenchyma. Consequently, a complete resection of the tumor is rarely a possibility, and recurrence is inevitable. To overcome this problem, we proposed to exploit this behavior by using three chemoattractants: CXCL10, CCL2 and CCL11, released by a biodegradable hydrogel (GlioGel) to produce a migration of tumor cells toward a therapeutic trap. To investigate this hypothesis, the agarose drop assay was used to test the chemoattraction capacity of these three chemokines on murine F98 and human U87MG cell lines. We then studied the potency of this approach in vivo in the well-established syngeneic F98-Fischer glioma-bearing rat model using GlioGel containing different mixtures of the chemoattractants. In vitro assays resulted in an invasive cell rate 2-fold higher when chemokines were present in the environment. In vivo experiments demonstrated the capacity of these specific chemoattractants to strongly attract neoplastic glioblastoma cells. The use of this strong locomotion ability to our end is a promising avenue in the establishment of a new therapeutic approach in the treatment of primary brain tumors.

[68Ga]Ga-4HMSA a promising new PET tracer for imaging inflammation.

BACKGROUND: Imaging diagnosis of inflammation has been challenging for many years. Inflammation imaging agents commonly used in nuclear medicine, such as [67Ga]Ga-citrate and 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG) showed some limitations. The identification of a radiotracer with high specificity and low radiation dose is clinically important. With the commercialization of 68Ge/68Ga generators and the high 68Ga cyclotron production capacity, the study of 68Ga-based tracer for inflammation has increased and shown good potential. In the present work, we report the synthesis of 4HMSA, a new acyclic chelator, and its first investigation for 68Ga complexation and as a new positron emission tomography (PET) imaging agent of inflammation in comparison to [68Ga]Ga-citrate. RESULTS: The present experimental studies have shown that the novel [68Ga]Ga-4HMSA is stable allowing imaging of inflammation in a preclinical model of adjuvant- and pathogen-based inflammation involving intraplantar injection of complete Freund's adjuvant (CFA). We also found that [68Ga]Ga-4HMSA displayed similar uptakes in the inflamed paw than [68Ga]Ga-citrate, which are superior compared to those of contralateral (non-injected) paws at days 1-3 from PET imaging. [68Ga]Ga-citrate accumulated in the upper body of the animal such as the liver, lungs and the heart, whereas the [68Ga]Ga-4HMSA revealed low uptakes in the majority of the organs and was cleared relatively rapidly from blood circulation through the kidneys and bladder. CONCLUSION: The results highlight the potential of [68Ga]Ga-4HMSA as an interesting alternative to [68Ga]Ga-citrate for inflammation imaging by PET. The new PET tracer also offers additional advantages than [68Ga]Ga-citrate in term of dosimetry and lower overall background activity.

Profiling DNA Damage Induced by the Irradiation of DNA with Gold Nanoparticles.

The presence of gold nanoparticles (AuNPs) greatly enhances the formation of DNA damage when exposed to therapeutic X-rays. Three types of DNA damage are assessed in irradiated DNA by enzymatic digestion coupled to liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The major type of damage is release of the four nonmodified nucleobases, with a bias toward the release of cytosine and thymine. The second most important pathway involves the formation of several common reduction and oxidation products of DNA. Lastly, eight unique modifications of the 2-deoxyribose moiety are formed, which includes the 2',3'- and 2',5'-dideoxynucleosides (ddNs) of the four canonical nucleosides. The yield of ddNs decreases in the following order: ddG > ddA > ddC > ddT. From the yield and distribution of products, most of the damage is considered to arise from the generation of Auger/low-energy electrons (LEEs) and their reaction with DNA.

Design, Synthesis, and Cytotoxicity Assessment of [64Cu]Cu-NOTA-Terpyridine Platinum Conjugate: A Novel Chemoradiotherapeutic Agent with Flexible Linker.

Maximum benefits of chemoradiation therapy with platinum-based compounds are expected if the radiation and the drug are localized simultaneously in cancer cells. To optimize this concomitant effect, we developed the novel chemoradiotherapeutic agent [64Cu]Cu-NOTA-C3-TP by conjugating, via a short flexible alkyl chain spacer (C3), a terpyridine platinum (TP) moiety to a NOTA chelator complexed with copper-64 (64Cu). The decay of 64Cu produces numerous low-energy electrons, enabling the 64Cu-conjugate to deliver radiation energy close to TP, which intercalates into G-quadruplex DNA. Accordingly, the in vitro internalization kinetic and the cytotoxic activity of [64Cu]Cu-NOTA-C3-TP and its derivatives were investigated with colorectal cancer (HCT116) and normal human fibroblast (GM05757) cells. Radiolabeling by 64Cu results in a >55,000-fold increase of cytotoxic potential relative to [NatCu]Cu-NOTA-C3-TP at 72 h post administration, indicating a large additive effect between 64Cu and the TP drug. The internalization and nucleus accumulation of [64Cu]Cu-NOTA-C3-TP in the HCT116 cells were, respectively, 3.1 and 6.0 times higher than that for GM05757 normal human fibroblasts, which is supportive of the higher efficiency of the [64Cu]Cu-NOTA-C3-TP for HCT116 cancer cells. This work presents the first proof-of-concept study showing the potential use of the [64Cu]Cu-NOTA-C3-TP conjugate as a targeted chemoradiotherapeutic agent to treat colorectal cancer.

Increased postprandial nonesterified fatty acid efflux from adipose tissue in prediabetes is offset by enhanced dietary fatty acid adipose trapping.

The mechanism of increased postprandial nonesterified fatty acid (NEFA) appearance in the circulation in impaired glucose tolerance (IGT) is due to increased adipose tissue lipolysis but could also be contributed to by reduced adipose tissue (AT) dietary fatty acid (DFA) trapping and increased "spillover" into the circulation. Thirty-one subjects with IGT (14 women, 17 men) and 29 with normal glucose tolerance (NGT, 15 women, 14 men) underwent a meal test with oral and intravenous palmitate tracers and the oral [18F]-fluoro-thia-heptadecanoic acid positron emission tomography method. Postprandial palmitate appearance (Rapalmitate) was higher in IGT versus NGT (P < 0.001), driven exclusively by Rapalmitate from obesity-associated increase in intracellular lipolysis (P = 0.01), as Rapalmitate from DFA spillover was not different between the groups (P = 0.19) and visceral AT DFA trapping was even higher in IGT versus NGT (P = 0.02). Plasma glycerol appearance was lower in IGT (P = 0.01), driven down by insulin resistance and increased insulin secretion. Thus, we found higher AT DFA trapping, limiting spillover to lean organs and in part offsetting the increase in Rapalmitate from intracellular lipolysis. Whether similar findings occur in frank diabetes, a condition also characterized by insulin resistance but relative insulin deficiency, requires further investigation (Clinicaltrials.gov: NCT04088344, NCT02808182).NEW & NOTEWORTHY We found higher adipose tissue dietary fatty acid trapping, limiting spillover to lean organs, that in part offsets the increase in appearance rate of palmitate from intracellular lipolysis in prediabetes. These results point to the adaptive nature of adipose tissue trapping and dietary fatty acid spillover as a protective mechanism against excess obesity-related palmitate appearance rate from intracellular adipose tissue lipolysis.

High Cytotoxic Effect by Combining Copper-64 with a NOTA-Terpyridine Platinum Conjugate.

Terpyridine platinum (TP)-based chemotherapeutic agents target three-dimensional structures on DNA known as G-quadruplexes. We report the rational design and synthesis of a TP conjugate combined with copper-64 (64Cu), the decay characteristics of which include emission of ß- and Auger electrons for radiotherapy and ß+ particles for positron emission tomography (PET) imaging. The present experimental studies show that the novel [64Cu]Cu-1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA)-TP is stable, permitting selective killing of cancer cells. The antitumor activity of [64Cu]Cu-NOTA-TP at high apparent molar activity is in the low nanomolar range and 27,800-fold greater than that of natCu-NOTA-TP at 24 h post treatment. These results suggest that this combination of a cytotoxic TP agent with 64Cu has considerable potential for cancer treatment and PET imaging.

Contribution of perfusion to the 11 C-acetate signal in brown adipose tissue assessed by DCE-MRI and 68 Ga-DOTA PET in a rat model.

PURPOSE: Determine if dynamic contrast enhanced (DCE) -MRI and/or 68 gallium 1,4,7,10-tetraazacyclododecane N, N', N″, N‴-tretraacetic acid (68 Ga-DOTA) positron emission tomography (PET) can assess perfusion in rat brown adipose tissue (BAT). Evaluate changes in perfusion between cold-stimulated and heat-inhibited BAT. Determine if the 11 C-acetate pharmacokinetic model can be constrained with perfusion information to improve assessment of BAT oxidative metabolism. METHODS: Rats were split into three groups. In group 1 (N = 6), DCE-MRI with gadobutrol was compared directly to 68 Ga-DOTA PET following exposure to 10 °C for 48 h. 11 C-Acetate PET was also performed to assess oxidation. In group 2 (N = 4), only 68 Ga-DOTA PET was acquired following exposure to 10 °C for 48 h. Finally, in group 3 (N = 10), perfusion was assessed with DCE-MRI in rats exposed to 10 °C or 30 °C for 48 h, and oxidation was measured with 11 C-acetate. Perfusion was quantified with a two-compartment pharmacokinetic model, while oxidation was assessed by a four-compartment model. RESULTS: DCE-MRI and 68 Ga-DOTA PET provided similar perfusion measures, but a decrease in the perfusion signal was noted with longer imaging sessions. Exposure to 10 °C or 30 °C did not affect the perfusion measures, but the 11 C-acetate signal increased in BAT at 10 °C. Without prior information about blood volume, the 11 C-acetate compartment model overestimated blood volume and underestimated oxidation in 10 °C BAT. CONCLUSION: Precise assessment of oxidation via 11 C-acetate PET requires prior information about blood volume which can be obtained by DCE-MRI or 68 Ga-DOTA PET. Since perfusion can change rapidly, simultaneous PET-MRI would be preferred.