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1.
Pharmaceuticals (Basel) ; 17(4)2024 Apr 17.
Article in English | MEDLINE | ID: mdl-38675474

ABSTRACT

Nanodiamonds (NDs) are emerging as a novel nanoparticle class with growing interest in medical applications. The surface coating of NDs can be modified by attaching binding ligands or imaging probes, turning them into multi-modal targeting agents. In this investigation, we assessed the targeting efficacy of octreotide-functionalized 68Ga-radiolabelled NDs for cancer imaging and compared it with the tumor uptake using [68Ga]Ga-DOTA-TOC. In vivo studies in mice bearing AR42J tumors demonstrated the highest accumulation of the radiolabeled functionalized NDs in the liver and spleen, with relatively low tumor uptake compared to [68Ga]Ga-DOTA-TOC. Our findings suggest that, within the scope of this study, functionalization did not enhance the tumor-targeting capabilities of NDs.

2.
J Thromb Haemost ; 22(1): 188-198, 2024 Jan.
Article in English | MEDLINE | ID: mdl-37748582

ABSTRACT

BACKGROUND: During infection, neutrophil extracellular traps (NETs) are associated with severity of pulmonary diseases such as acute respiratory disease syndrome. NETs induce subsequent immune responses, are directly cytotoxic to pulmonary cells, and are highly procoagulant. Anticoagulation treatment was shown to reduce in-hospital mortality, indicating thromboinflammatory complications. However, data are sparsely available on the involvement of NETs in secondary events after virus clearance, which can lead to persistent lung damage and postacute sequelae with chronic fatigue and dyspnea. OBJECTIVES: This study focuses on late-phase events using a murine model of viral lung infection with postacute sequelae after virus resolution. METHODS: C57BL/6JRj mice were infected intranasally with the betacoronavirus murine coronavirus (MCoV, strain MHV-A95), and tissue samples were collected after 2, 4, and 10 days. For NET modulation, mice were pretreated with OM-85 or GSK484 and DNase I were administered intraperitoneally between days 2 to 5 and days 4 to 7, respectively. RESULTS: Rapid, platelet-attributed thrombus formation was followed by a second, late phase of thromboinflammation. This phase was characterized by negligible virus titers but pronounced tissue damage, apoptosis, oxidative DNA damage, and presence of NETs. Inhibition of NETs during the acute phase did not impact virus burden but decreased lung cell apoptosis by 67% and oxidative stress by 94%. Prevention of neutrophil activation by immune training before virus infection reduced damage by 75%, NETs by 31%, and pulmonary thrombi by 93%. CONCLUSION: NETs are detrimental inducers of tissue damage during respiratory virus infection but do not contribute to virus clearance.


Subject(s)
Coronavirus Infections , Coronavirus , Extracellular Traps , Thrombosis , Animals , Mice , Neutrophils , Thromboinflammation , Disease Models, Animal , Inflammation/complications , Thrombosis/complications , Mice, Inbred C57BL , Lung , Coronavirus Infections/complications
3.
J Cereb Blood Flow Metab ; 44(1): 142-152, 2024 01.
Article in English | MEDLINE | ID: mdl-37728771

ABSTRACT

The efflux transporter P-glycoprotein (P-gp) at the blood-brain barrier limits the cerebral uptake of various xenobiotics. To assess the sensitivity of [11C]metoclopramide to measure decreased cerebral P-gp function, we performed [11C]metoclopramide PET scans without (baseline) and with partial P-gp inhibition by tariquidar in wild-type, heterozygous Abcb1a/b(+/-) and homozygous Abcb1a/b(-/-) mice as models with controlled levels of cerebral P-gp expression. Brains were collected to quantify P-gp expression with immunohistochemistry. Brain uptake of [11C]metoclopramide was expressed as the area under the brain time-activity curve (AUCbrain) and compared with data previously obtained with (R)-[11C]verapamil and [11C]N-desmethyl-loperamide. Abcb1a/b(+/-) mice had intermediate P-gp expression compared to wild-type and Abcb1a/b(-/-) mice. In baseline scans, all three radiotracers were able to discriminate Abcb1a/b(-/-) from wild-type mice (2.5- to 4.6-fold increased AUCbrain, p ≤ 0.0001). However, only [11C]metoclopramide could discriminate Abcb1a/b(+/-) from wild-type mice (1.46-fold increased AUCbrain, p ≤ 0.001). After partial P-gp inhibition, differences in [11C]metoclopramide AUCbrain between Abcb1a/b(+/-) and wild-type mice (1.39-fold, p ≤ 0.001) remained comparable to baseline. There was a negative correlation between baseline [11C]metoclopramide AUCbrain and ex-vivo-measured P-gp immunofluorescence (r = -0.9875, p ≤ 0.0001). Our data suggest that [11C]metoclopramide is a sensitive radiotracer to measure moderate, but (patho-)physiologically relevant decreases in cerebral P-gp function without the need to co-administer a P-gp inhibitor.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1 , Blood-Brain Barrier , Mice , Animals , Blood-Brain Barrier/metabolism , ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Metoclopramide/metabolism , Brain/diagnostic imaging , Brain/metabolism , ATP Binding Cassette Transporter, Subfamily B/metabolism , Positron-Emission Tomography
4.
Eur J Pharm Sci ; 184: 106414, 2023 May 01.
Article in English | MEDLINE | ID: mdl-36858275

ABSTRACT

Multidrug resistance-associated protein 1 (MRP1/ABCC1) is a highly abundant efflux transporter in the lungs, which protects cells from toxins and oxidative stress and has been implicated in the pathophysiology of chronic obstructive pulmonary disease and cystic fibrosis. There is evidence from in vitro studies that the inhaled glucocorticoid budesonide can inhibit MRP1 activity. We used positron emission tomography (PET) imaging with 6-bromo-7-[11C]methylpurine ([11C]BMP), which is transformed in vivo into a radiolabeled MRP1 substrate, to assess whether intratracheally (i.t.) aerosolized budesonide affects pulmonary MRP1 activity in rats. Three groups of rats (n = 5-6 each) underwent dynamic PET scans of the lungs after i.t. aerosolization of either [11C]BMP alone, or [11C]BMP mixed with either budesonide (0.04 mg, corresponding to the maximum soluble dose) or the model MRP1 inhibitor MK571 (2 mg). From PET-measured radioactivity concentration-time curves, the rate constant describing radioactivity elimination from the right lung (kE,lung) and the area under the curve (AUClung) were calculated from 0 to 5 min after start of the PET scan as measures of pulmonary MRP1 activity. Co-administration of MK571 resulted in a pronounced decrease in kE,lung (25-fold, p < 0.0001) and an increase in AUClung (5.3-fold, p < 0.0001) when compared with vehicle-treated animals. In contrast, in budesonide-treated animals kE,lung and AUClung were not significantly different from the vehicle group. Our results show that i.t. aerosolized budesonide at an approximately 5 times higher dose than the maximum clinical dose leads to no change in pulmonary MRP1 activity, suggesting a lack of an effect of inhaled budesonide treatment on the MRP1-mediated cellular detoxifying capacity of the lungs. However, the strong effect observed for MK571 raises the possibility for the occurrence of transporter-mediated drug-drug interactions at the pulmonary epithelium with inhaled medicines.


Subject(s)
Budesonide , Multidrug Resistance-Associated Proteins , Rats , Animals , Budesonide/pharmacology , Multidrug Resistance-Associated Proteins/metabolism , Lung/diagnostic imaging , Lung/metabolism , Positron-Emission Tomography/methods
5.
Eur J Pharm Sci ; 183: 106404, 2023 Apr 01.
Article in English | MEDLINE | ID: mdl-36773747

ABSTRACT

In the lungs, the membrane transporter P-glycoprotein (P-gp) is expressed in the apical (i.e. lumen-facing) membrane of airway epithelial cells and in the luminal (blood-facing) membrane of pulmonary capillary endothelial cells. To better understand the influence of P-gp on the pulmonary disposition of inhaled P-gp substrate drugs, we measured the intrapulmonary pharmacokinetics of the intratracheally (i.t.) aerosolized model P-gp substrate [11C]metoclopramide in presence and absence of P-gp activity by means of positron emission tomography (PET) imaging in rats. Data were compared to data previously acquired with the model P-gp substrates (R)-[11C]verapamil and [11C]N-desmethyl-loperamide, using the same experimental set-up. Groups of wild-type rats, either untreated or treated with the P-gp inhibitor tariquidar, and Abcb1a/b(-/-) rats underwent 90-min dynamic PET scans after i.t. aerosolization of [11C]metoclopramide. Lung exposure to [11C]metoclopramide was expressed as the area under the right lung concentration-time curve (AUClung). AUClung values were significantly higher in Abcb1a/b(-/-) rats (1.8-fold, p ≤ 0.0001) and in tariquidar-treated wild-type rats (1.6-fold, p ≤ 0.01) than in untreated wild-type rats. This differed from previously obtained results with (R)-[11C]verapamil and [11C]N-desmethyl-loperamide, which showed decreased exposure in the rat lung in absence of P-gp activity. Our results suggest that transepithelial transfer of [11C]metoclopramide was not or only to a small extent affected by P-gp activity, presumably due to the compound's high passive permeability. The increased lung retention of [11C]metoclopramide may be due to decreased P-gp-mediated clearance into the blood in absence of P-gp activity in capillary endothelial cells. The overall effect of P-gp on the lung exposure to inhaled P-gp substrate drugs may, thus, be determined by a balance of opposing effects at the pulmonary epithelium and endothelium.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1 , Blood-Brain Barrier , Rats , Animals , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Blood-Brain Barrier/metabolism , Metoclopramide/pharmacokinetics , Endothelial Cells/metabolism , ATP Binding Cassette Transporter, Subfamily B/metabolism , Positron-Emission Tomography/methods , Verapamil/pharmacology , Carbon Radioisotopes , Lung/metabolism
6.
Antimicrob Agents Chemother ; 67(3): e0149322, 2023 03 16.
Article in English | MEDLINE | ID: mdl-36786609

ABSTRACT

Transporter-mediated drug-drug interactions (DDIs) are of concern in antimicrobial drug development, as they can have serious safety consequences. We used positron emission tomography (PET) imaging-based pharmacokinetic (PK) analysis to assess the effect of different drugs, which may cause transporter-mediated DDIs, on the tissue distribution and excretion of [18F]ciprofloxacin as a radiolabeled model antimicrobial drug. Mice underwent PET scans after intravenous injection of [18F]ciprofloxacin, without and with pretreatment with either probenecid (150 mg/kg), cimetidine (50 mg/kg), or pyrimethamine (5 mg/kg). A 3-compartment kidney PK model was used to assess the involvement of renal transporters in the examined DDIs. Pretreatment with probenecid and cimetidine significantly decreased the renal clearance (CLrenal) of [18F]ciprofloxacin. The effect of cimetidine (-86%) was greater than that of probenecid (-63%), which contrasted with previously published clinical data. The kidney PK model revealed that the decrease in CLrenal was caused by inhibition of basal uptake transporters and apical efflux transporters in kidney proximal tubule cells. Changes in the urinary excretion of [18F]ciprofloxacin after pretreatment with probenecid and cimetidine resulted in increased blood and organ exposure to [18F]ciprofloxacin. Our results suggest that multiple membrane transporters mediate the tubular secretion of ciprofloxacin, with possible species differences between mice and humans. Concomitant medication inhibiting renal transporters may precipitate DDIs, leading to decreased urinary excretion and increased blood and organ exposure to ciprofloxacin, potentially exacerbating adverse effects. Our study highlights the strength of PET imaging-based PK analysis to assess transporter-mediated DDIs at a whole-body level.


Subject(s)
Anti-Infective Agents , Probenecid , Humans , Mice , Animals , Probenecid/pharmacology , Cimetidine/pharmacology , Kidney/diagnostic imaging , Membrane Transport Proteins , Drug Interactions , Positron-Emission Tomography , Ciprofloxacin/pharmacokinetics
7.
Nucl Med Biol ; 116-117: 108310, 2023.
Article in English | MEDLINE | ID: mdl-36565646

ABSTRACT

PURPOSE: Nanodiamonds (NDs) represent a new class of nanoparticles and have gained increasing interest in medical applications. Modifying the surface coating by attaching binding ligands or imaging probes can transform NDs into multi-modal targeting probes. This study evaluated the biokinetics and biodistribution of 68Ga-radiolabelled NDs in a xenograft model. PROCEDURES: NDs were coated with an albumin-derived copolymer modified with desferrioxamine to provide a chelator for radiolabeling. In vivo studies were conducted in AR42J tumor-bearing CD1 mice to evaluate biodistribution and tumor accumulation of the NDs. RESULTS: Coated NDs were successfully radiolabeled using 68Ga at room temperature with radiolabeling efficiencies up to 91.8 ± 3.2 % as assessed by radio-TLC. In vivo studies revealed the highest accumulation in the liver and spleen, whereas tumor radioactivity concentration was low. CONCLUSIONS: Radiolabeling of coated NDs could be achieved. However, the obtained results indicate these coated NDs' limitations in their biodistribution within the conducted studies.


Subject(s)
Nanodiamonds , Neoplasms , Humans , Mice , Animals , Gallium Radioisotopes , Tissue Distribution , Polymers
8.
J Control Release ; 349: 109-117, 2022 09.
Article in English | MEDLINE | ID: mdl-35798092

ABSTRACT

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are two efflux transporters which are expressed in the apical (i.e. airway lumen-facing) membranes of lung epithelial cells. To assess the influence of P-gp and BCRP on the pulmonary disposition of inhaled drugs, we performed positron emission tomography (PET) imaging in rats after intratracheal aerosolization of two model P-gp/BCRP substrate radiotracers (i.e. [11C]erlotinib and [11C]tariquidar). We studied rat groups in which both transporters were active (i.e. wild-type rats), either of the two transporters was inactive (Abcb1a/b(-/-) and Abcg2(-/-) rats) or both transporters were inactive (Abcg2(-/-) rats in which pulmonary P-gp activity was inhibited by treatment with unlabeled tariquidar). PET-measured lung distribution data were compared with brain-to-plasma radioactivity concentration ratios measured in a gamma counter at the end of the PET scan. For [11C]erlotinib, lung exposure (AUClungs) was moderately but not significantly increased in Abcb1a/b(-/-) rats (1.6-fold) and Abcg2(-/-) rats (1.5-fold), and markedly (3.6-fold, p < 0.0001) increased in tariquidar-treated Abcg2(-/-) rats, compared to wild-type rats. Similarly, the brain uptake of [11C]erlotinib was substantially (4.5-fold, p < 0.0001) increased when both P-gp and BCRP activities were impaired. For [11C]tariquidar, differences in AUClungs between groups pointed into a similar direction as for [11C]erlotinib, but were less pronounced and lacked statistical significance. Our study demonstrates functional P-gp and BCRP activity in vivo in the lungs and further suggests functional redundancy between P-gp and BCRP in limiting the pulmonary uptake of a model P-gp/BCRP substrate, analogous to the blood-brain barrier. Our results suggest that pulmonary efflux transporters are important for the efficacy and safety of inhaled drugs and that their modulation may be exploited in order to improve the pharmacokinetic and pharmacodynamic performance of pulmonary delivered drugs.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1 , Neoplasm Proteins , ATP Binding Cassette Transporter, Subfamily B/metabolism , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 2/metabolism , ATP-Binding Cassette Transporters/metabolism , Animals , Blood-Brain Barrier/metabolism , Brain/metabolism , Erlotinib Hydrochloride , Lung/diagnostic imaging , Lung/metabolism , Neoplasm Proteins/metabolism , Positron-Emission Tomography/methods , Rats
9.
Int J Mol Sci ; 23(12)2022 Jun 10.
Article in English | MEDLINE | ID: mdl-35742960

ABSTRACT

Multidrug resistance-associated protein 1 (MRP1, encoded by the ABCC1 gene) may contribute to the clearance of amyloid-beta (Aß) peptides from the brain into the blood and stimulation of MRP1 transport activity may be a therapeutic approach to enhance brain Aß clearance. In this study, we assessed the effect of thiethylperazine, an antiemetic drug which was shown to stimulate MRP1 activity in vitro and to decrease Aß load in a rapid ß-amyloidosis mouse model (APP/PS1-21), on MRP1 transport activity by means of positron emission tomography (PET) imaging with the MRP1 tracer 6-bromo-7-[11C]methylpurine. Groups of wild-type, APP/PS1-21 and Abcc1(-/-) mice underwent PET scans before and after a 5-day oral treatment period with thiethylperazine (15 mg/kg, once daily). The elimination rate constant of radioactivity (kelim) was calculated from time-activity curves in the brain and the lungs as a measure of tissue MRP1 activity. Treatment with thiethylperazine had no significant effect on MRP1 activity in the brain and the lungs of wild-type and APP/PS1-21 mice. This may either be related to a lack of an MRP1-stimulating effect of thiethylperazine in vivo or to other factors, such as substrate-dependent MRP1 stimulation, insufficient target tissue exposure to thiethylperazine or limited sensitivity of the PET tracer to measure MRP1 stimulation.


Subject(s)
Alzheimer Disease , Thiethylperazine , Alzheimer Disease/diagnostic imaging , Alzheimer Disease/drug therapy , Alzheimer Disease/genetics , Amyloid beta-Peptides/metabolism , Amyloid beta-Protein Precursor/genetics , Amyloid beta-Protein Precursor/metabolism , Animals , Brain/diagnostic imaging , Brain/metabolism , Disease Models, Animal , Mice , Mice, Transgenic , Multidrug Resistance-Associated Proteins/genetics , Multidrug Resistance-Associated Proteins/metabolism , Positron-Emission Tomography/methods , Presenilin-1/genetics , Thiethylperazine/metabolism
10.
J Innate Immun ; 14(4): 293-305, 2022.
Article in English | MEDLINE | ID: mdl-34775384

ABSTRACT

Training of the innate immune system with orally ingested bacterial extracts was demonstrated to have beneficial effects on infection clearance and disease outcome. The aim of our study was to identify cellular and molecular processes responsible for these immunological benefits. We used a murine coronavirus (MCoV) A59 mouse model treated with the immune activating bacterial extract Broncho-Vaxom (BV) OM-85. Tissue samples were analysed with qPCR, RNA sequencing, histology, and flow cytometry. After BV OM-85 treatment, interstitial macrophages accumulated in lung tissue leading to a faster response of type I interferon (IFN) signalling after MCoV infection resulting in overall lung tissue protection. Moreover, RNA sequencing showed that lung tissue from mice receiving BV OM-85 resembled an intermediate stage between healthy and viral infected lung tissue at day 4, indicating a faster return to normal tissue homoeostasis. The pharmacologic effect was mimicked by adoptively transferring naive lung macrophages into lungs from recipient mice before virus infection. The beneficial effect of BV OM-85 was abolished when inhibiting initial type I IFN signalling. Overall, our data suggest that BV OM-85 enhances lung macrophages allowing for a faster IFN response towards a viral challenge as part of the oral-induced innate immune system training.


Subject(s)
Adjuvants, Immunologic , Betacoronavirus , Animals , Bacteria , Immunity, Innate , Lung , Macrophages , Mice
11.
J Control Release ; 342: 44-52, 2022 02.
Article in English | MEDLINE | ID: mdl-34971693

ABSTRACT

Several drugs approved for inhalation for the treatment of pulmonary diseases are substrates of the adenosine triphosphate-binding cassette (ABC) transporter P-glycoprotein (P-gp). P-gp is expressed in the apical membrane of pulmonary epithelial cells and could play a role in modulating the pulmonary absorption and distribution of inhaled drugs, thereby potentially contributing to variability in therapeutic response and/or systemic side effects. We developed a new in vivo experimental approach to assess the functional impact of P-gp on the pulmonary delivery of inhaled drugs in rats. By using positron emission tomography (PET) imaging, we measured the intrapulmonary pharmacokinetics of the model P-gp substrates (R)-[11C]verapamil ([11C]VPM) and [11C]-N-desmethyl-loperamide ([11C]dLOP) administered by intratracheal aerosolization in three rat groups: wild-type, Abcb1a/b(-/-) and wild-type treated with the P-gp inhibitor tariquidar. Lung exposure (AUClung_right) to [11C]VPM was 64% and 50% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b(-/-) rats, respectively, compared to untreated wild-type rats. For [11C]dLOP, AUClung_right was 59% and 34% lower (p < 0.05) in tariquidar-treated and in Abcb1a/b(-/-) rats, respectively. Our results show that P-gp can affect the pulmonary disposition of inhaled P-gp substrates, whereby a decrease in P-gp activity may lead to lower lung exposure and potentially to a decrease in therapeutic efficacy. Our study highlights the potential of PET imaging with intratracheally aerosolized radiotracers to assess the impact of membrane transporters on pulmonary drug delivery, in rodents and potentially also in humans.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1 , Blood-Brain Barrier , ATP Binding Cassette Transporter, Subfamily B/metabolism , ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , Animals , Blood-Brain Barrier/metabolism , Lung/diagnostic imaging , Lung/metabolism , Positron-Emission Tomography/methods , Rats
12.
Alzheimers Res Ther ; 13(1): 175, 2021 10 16.
Article in English | MEDLINE | ID: mdl-34656177

ABSTRACT

BACKGROUND: To better understand the etiology and pathomechanisms of Alzheimer's disease, several transgenic animal models that overexpress human tau or human amyloid-beta (Aß) have been developed. In the present study, we generated a novel transgenic rat model by cross-breeding amyloid precursor protein (APP) rats with tau rats. We characterized this model by performing positron emission tomography scans combined with immunofluorescent labeling and cerebrospinal fluid analyses. METHODS: APP/Tau rats were generated by cross-breeding male McGill-R-Thy1-APP transgenic rats with female hTau-40/P301L transgenic rats. APP/Tau double transgenic rats and non-transgenic (ntg) littermates aged 7, 13, and 21 months were subjected to dynamic [11C] PiB scan and dynamic [18F]THK-5317 scans. For regional brain analysis, a template was generated from anatomical MR images of selected animals, which was co-registered with the PET images. Regional analysis was performed by application of the simplified reference tissue model ([11C]PiB data), whereas [18F]THK-5317 data were analyzed using a 2-tissue compartment model and Logan graphical analysis. In addition, immunofluorescent labeling (tau, amyloid) and cerebrospinal fluid analyses were performed. RESULTS: [11C]PiB binding potential (BPND) and [18F]THK-5317 volume of distribution (VT) showed an increase with age in several brain regions in the APP/Tau group but not in the ntg control group. Immunohistochemical analysis of brain slices of PET-scanned animals revealed a positive correlation between Aß labeling and [11C]PiB regional BPND. Tau staining yielded a trend towards higher levels in the cortex and hippocampus of APP/Tau rats compared with ntg littermates, but without reaching statistical significance. No correlation was found between tau immunofluorescence labeling results and the respective [18F]THK-5317 VT values. CONCLUSIONS: We thoroughly characterized a novel APP/Tau rat model using combined PET imaging and immunofluorescence analysis. We observed an age-related increase in [11C]PiB and [18F]THK-5317 binding in several brain regions in the APP/Tau group but not in the ntg group. Although we were able to reveal a positive correlation between amyloid labeling and [11C]PiB regional brain uptake, we observed relatively low human tau and amyloid fibril expression levels and a somewhat unstable brain pathology which questions the utility of this animal model for further studies.


Subject(s)
Alzheimer Disease , Alzheimer Disease/diagnostic imaging , Alzheimer Disease/genetics , Amyloid beta-Peptides , Amyloid beta-Protein Precursor/genetics , Animals , Female , Male , Positron-Emission Tomography , Rats , Rats, Transgenic
13.
Pharmaceutics ; 13(8)2021 Aug 18.
Article in English | MEDLINE | ID: mdl-34452247

ABSTRACT

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are co-localized at the blood-brain barrier, where they display functional redundancy to restrict the brain distribution of dual P-gp/BCRP substrate drugs. We used positron emission tomography (PET) with the metabolically stable P-gp/BCRP substrates [11C]tariquidar, [11C]erlotinib, and [11C]elacridar to assess whether a similar functional redundancy as at the BBB exists in the liver, where both transporters mediate the biliary excretion of drugs. Wild-type, Abcb1a/b(-/-), Abcg2(-/-), and Abcb1a/b(-/-)Abcg2(-/-) mice underwent dynamic whole-body PET scans after i.v. injection of either [11C]tariquidar, [11C]erlotinib, or [11C]elacridar. Brain uptake of all three radiotracers was markedly higher in Abcb1a/b(-/-)Abcg2(-/-) mice than in wild-type mice, while only moderately changed in Abcb1a/b(-/-) and Abcg2(-/-) mice. The transfer of radioactivity from liver to excreted bile was significantly lower in Abcb1a/b(-/-)Abcg2(-/-) mice and almost unchanged in Abcb1a/b(-/-) and Abcg2(-/-) mice (with the exception of [11C]erlotinib, for which biliary excretion was also significantly reduced in Abcg2(-/-) mice). Our data provide evidence for redundancy between P-gp and BCRP in controlling both the brain distribution and biliary excretion of dual P-gp/BCRP substrates and highlight the utility of PET as an upcoming tool to assess the effect of transporters on drug disposition at a whole-body level.

14.
Eur J Pharm Sci ; 163: 105854, 2021 Aug 01.
Article in English | MEDLINE | ID: mdl-33865975

ABSTRACT

Ciprofloxacin is a commonly prescribed fluoroquinolone antibiotic which is cleared by active tubular secretion and intestinal excretion. Ciprofloxacin is a known substrate of the ATP-binding cassette (ABC) transporters breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 4 (MRP4). In this work, we used positron emission tomography (PET) imaging to investigate the influence of BCRP, MRP4, MRP2 and P-glycoprotein (P-gp) on the excretion of [18F]ciprofloxacin in mice. Dynamic 90-min PET scans were performed after intravenous injection of [18F]ciprofloxacin in wild-type mice without and with pre-treatment with the broad-spectrum MRP inhibitor MK571. Moreover, [18F]ciprofloxacin PET scans were performed in Abcc4(-/-), Abcc2(-/-), Abcc4(-/-)Abcg2(-/-) and Abcb1a/b(-/-)Abcg2(-/-) mice. In addition to non-compartmental pharmacokinetic (PK) analysis, a novel three-compartment PK model was developed for a detailed assessment of the renal disposition of [18F]ciprofloxacin. In MK571 pre-treated mice, a significant increase in the blood exposure to [18F]ciprofloxacin was observed along with a significant reduction in the renal and intestinal clearances. PK modelling revealed a significant reduction in renal radioactivity uptake (CL1) and in the rate constants for transfer of radioactivity from the corticomedullary renal region into blood (k2) and urine (k3), respectively, after MK571 administration. No changes in the renal clearance or in the estimated kidney PK model parameters were observed in any of the studied knockout models, while a significant reduction in the intestinal clearance was observed in Abcc2(-/-) and Abcc4(-/-)Abcg2(-/-) mice. Our data failed to reveal a role of any of the studied ABC transporters in the tubular secretion of ciprofloxacin. This may indicate that ciprofloxacin is handled in the kidneys by more than one transporter family, most likely with a great degree of mutual functional redundancy. Our study highlights the potential of PET imaging for an assessment of transporter-mediated renal excretion of radiolabelled drugs.


Subject(s)
ATP-Binding Cassette Transporters , Ciprofloxacin , ATP Binding Cassette Transporter, Subfamily G, Member 2/genetics , ATP-Binding Cassette Transporters/genetics , Animals , Mice , Mice, Knockout , Multidrug Resistance-Associated Proteins/genetics , Neoplasm Proteins/metabolism , Positron-Emission Tomography
15.
Pharm Res ; 38(1): 127-140, 2021 Jan.
Article in English | MEDLINE | ID: mdl-33559045

ABSTRACT

PURPOSE: To investigate the role of cation transporters (OCTs, MATEs) in the renal and hepatic disposition of the radiolabeled antiemetic drug [11C]metoclopramide in mice with PET. METHODS: PET was performed in wild-type mice after administration of an intravenous microdose (<1 µg) of [11C]metoclopramide without and with co-administration of either unlabeled metoclopramide (5 or 10 mg/kg) or the prototypical cation transporter inhibitors cimetidine (150 mg/kg) or sulpiride (25 mg/kg). [11C]Metoclopramide PET was also performed in wild-type and Slc22a1/2(-/-) mice. Radiolabeled metabolites were measured at 15 min after radiotracer injection and PET data were corrected for radiolabeled metabolites. RESULTS: [11C]Metoclopramide was highly metabolized and [11C]metoclopramide-derived radioactivity was excreted into the urine. The different investigated treatments decreased (~2.5-fold) the uptake of [11C]metoclopramide from plasma into the kidney and liver, inhibited metabolism and decreased (up to 3.8-fold) urinary excretion, which resulted in increased plasma concentrations of [11C]metoclopramide. Kidney and liver uptake were moderately (~1.3-fold) reduced in Slc22a1/2(-/-) mice. CONCLUSIONS: Our results suggest a contribution of OCT1/2 to the kidney and liver uptake and of MATEs to the urinary excretion of [11C]metoclopramide in mice. Cation transporters may contribute, next to variability in the activity of metabolizing enzymes, to variability in metoclopramide pharmacokinetics and side effects.


Subject(s)
Catecholamine Plasma Membrane Transport Proteins/metabolism , Hepatobiliary Elimination , Metoclopramide/pharmacokinetics , Organic Cation Transporter 2/metabolism , Renal Elimination , Animals , Catecholamine Plasma Membrane Transport Proteins/genetics , Female , HEK293 Cells , Humans , Male , Metoclopramide/administration & dosage , Mice , Mice, Knockout , Models, Animal , Organic Cation Transporter 2/genetics
16.
J Cereb Blood Flow Metab ; 41(7): 1634-1646, 2021 07.
Article in English | MEDLINE | ID: mdl-33081568

ABSTRACT

P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2) restrict at the blood-brain barrier (BBB) the brain distribution of the majority of currently known molecularly targeted anticancer drugs. To improve brain delivery of dual ABCB1/ABCG2 substrates, both ABCB1 and ABCG2 need to be inhibited simultaneously at the BBB. We examined the feasibility of simultaneous ABCB1/ABCG2 inhibition with i.v. co-infusion of erlotinib and tariquidar by studying brain distribution of the model ABCB1/ABCG2 substrate [11C]erlotinib in mice and rhesus macaques with PET. Tolerability of the erlotinib/tariquidar combination was assessed in human embryonic stem cell-derived cerebral organoids. In mice and macaques, baseline brain distribution of [11C]erlotinib was low (brain distribution volume, VT,brain < 0.3 mL/cm3). Co-infusion of erlotinib and tariquidar increased VT,brain in mice by 3.0-fold and in macaques by 3.4- to 5.0-fold, while infusion of erlotinib alone or tariquidar alone led to less pronounced VT,brain increases in both species. Treatment of cerebral organoids with erlotinib/tariquidar led to an induction of Caspase-3-dependent apoptosis. Co-infusion of erlotinib/tariquidar may potentially allow for complete ABCB1/ABCG2 inhibition at the BBB, while simultaneously achieving brain-targeted EGFR inhibition. Our protocol may be applicable to enhance brain delivery of molecularly targeted anticancer drugs for a more effective treatment of brain tumors.


Subject(s)
ATP Binding Cassette Transporter, Subfamily G, Member 2/antagonists & inhibitors , Blood-Brain Barrier/drug effects , Brain/drug effects , Carbon Radioisotopes/metabolism , Erlotinib Hydrochloride/pharmacology , Neoplasm Proteins/antagonists & inhibitors , Quinolines/pharmacology , ATP Binding Cassette Transporter, Subfamily B/antagonists & inhibitors , Animals , Antineoplastic Agents/administration & dosage , Antineoplastic Agents/pharmacology , Blood-Brain Barrier/metabolism , Brain/metabolism , Cell Membrane Permeability , Drug Delivery Systems , Drug Therapy, Combination , Erlotinib Hydrochloride/administration & dosage , Female , Human Embryonic Stem Cells/drug effects , Human Embryonic Stem Cells/metabolism , Humans , Macaca mulatta , Male , Mice
17.
Int J Mol Sci ; 21(21)2020 Nov 03.
Article in English | MEDLINE | ID: mdl-33153231

ABSTRACT

BACKGROUND: ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein) are co-localized at the blood-brain barrier (BBB), where they restrict the brain distribution of many different drugs. Moreover, ABCB1 and possibly ABCG2 play a role in Alzheimer's disease (AD) by mediating the brain clearance of beta-amyloid (Aß) across the BBB. This study aimed to compare the abundance and activity of ABCG2 in a commonly used ß-amyloidosis mouse model (APP/PS1-21) with age-matched wild-type mice. METHODS: The abundance of ABCG2 was assessed by semi-quantitative immunohistochemical analysis of brain slices of APP/PS1-21 and wild-type mice aged 6 months. Moreover, the brain distribution of two dual ABCB1/ABCG2 substrate radiotracers ([11C]tariquidar and [11C]erlotinib) was assessed in APP/PS1-21 and wild-type mice with positron emission tomography (PET). [11C]Tariquidar PET scans were performed without and with partial inhibition of ABCG2 with Ko143, while [11C]erlotinib PET scans were only performed under baseline conditions. RESULTS: Immunohistochemical analysis revealed a significant reduction (by 29-37%) in the number of ABCG2-stained microvessels in the brains of APP/PS1-21 mice. Partial ABCG2 inhibition significantly increased the brain distribution of [11C]tariquidar in APP/PS1-21 and wild-type mice, but the brain distribution of [11C]tariquidar did not differ under both conditions between the two mouse strains. Similar results were obtained with [11C]erlotinib. CONCLUSIONS: Despite a reduction in the abundance of cerebral ABCG2 and ABCB1 in APP/PS1-21 mice, the brain distribution of two dual ABCB1/ABCG2 substrates was unaltered. Our results suggest that the brain distribution of clinically used ABCB1/ABCG2 substrate drugs may not differ between AD patients and healthy people.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/metabolism , ATP Binding Cassette Transporter, Subfamily G, Member 2/metabolism , Amyloidosis/metabolism , Amyloidosis/pathology , Brain/metabolism , ATP Binding Cassette Transporter, Subfamily B, Member 1/genetics , ATP Binding Cassette Transporter, Subfamily G, Member 2/genetics , Amyloid beta-Peptides/metabolism , Amyloid beta-Peptides/toxicity , Amyloidosis/diagnostic imaging , Animals , Blood-Brain Barrier/metabolism , Brain/diagnostic imaging , Disease Models, Animal , Female , Mice , Mice, Inbred C57BL , Mice, Transgenic , Positron-Emission Tomography , Quinolines/pharmacokinetics , Tissue Distribution
18.
J Nucl Med ; 61(11): 1650-1657, 2020 11.
Article in English | MEDLINE | ID: mdl-32284394

ABSTRACT

Multidrug resistance-associated protein 1 (adenosine triphosphate-binding cassette subfamily C member 1 [ABCC1]) is abundantly expressed at the lung epithelial barrier, where it may influence the pulmonary disposition of inhaled drugs and contribute to variability in therapeutic response. The aim of this study was to assess the impact of ABCC1 on the pulmonary disposition of 6-bromo-7-11C-methylpurine (11C-BMP), a prodrug radiotracer that is intracellularly conjugated with glutathione to form the ABCC1 substrate S-(6-(7-11C-methylpurinyl))glutathione (11C-MPG). Methods: Groups of Abcc1(-/-) rats, wild-type rats pretreated with the ABCC1 inhibitor MK571, and wild-type control rats underwent dynamic PET scans after administration of 11C-BMP intravenously or by intratracheal aerosolization. In vitro transport experiments were performed with unlabeled BMP on the human distal lung epithelial cell line NCI-H441. Results: The pulmonary kinetics of radioactivity significantly differed between wild-type and Abcc1(-/-) rats, but differences were more pronounced after intratracheal than after intravenous administration. After intravenous administration, lung exposure (area under the lung time-activity curve from 0 to 80 min after radiotracer administration [AUClung]) was 77% higher and the elimination slope of radioactivity washout from the lungs (kE,lung) was 70% lower in Abcc1(-/-) rats, whereas after intratracheal administration, AUClung was 352% higher and kE,lung was 86% lower in Abcc1(-/-) rats. Pretreatment with MK571 decreased kE,lung by 20% after intratracheal radiotracer administration. Intracellular accumulation of MPG in NCI-H441 cells was significantly higher and extracellular efflux was lower in the presence than in the absence of MK571. Conclusion: PET with pulmonary administered 11C-BMP can measure ABCC1 activity at the lung epithelial barrier and may be applicable in humans to assess the effects of disease, genetic polymorphisms, or concomitant drug intake on pulmonary ABCC1 activity.


Subject(s)
Carbon Radioisotopes/pharmacokinetics , Lung/metabolism , Multidrug Resistance-Associated Proteins/metabolism , Purines/pharmacokinetics , Animals , Cells, Cultured , Female , Humans , Positron-Emission Tomography , Propionates/pharmacology , Quinolines/pharmacology , Rats , Rats, Sprague-Dawley
19.
Nucl Med Biol ; 84-85: 28-32, 2020.
Article in English | MEDLINE | ID: mdl-31981857

ABSTRACT

INTRODUCTION: Tau deposition is one of the hallmarks of Alzheimer's disease (AD) and can be visualized and quantified using [18F]THK-5317 together with kinetic modeling. To determine the feasibility of this approach, we measured blood/plasma pharmacokinetics and radiotracer metabolism in female and male rats. METHODS: Female and male rats (n = 11-12) were cannulated via the femoral artery for continuous blood sampling. Blood sampling was performed at regular intervals after intravenous injection of [18F]THK-5317. After collection of the last blood sample, animals were sacrificed, and organs were excised. Blood from minute 5, 20 and 60 was centrifuged to obtain plasma. Radiolabeled metabolites in plasma, brain, liver and urine were analyzed by radio-thin-layer chromatography (radio-TLC). RESULTS: Plasma pharmacokinetics and metabolism were significantly different between female and male rats. [18F]THK-5317 plasma clearance was faster in female (0.66 ± 0.08 mL/h/kg BW) than in male (0.52 ± 0.11 mL/h/kg BW) rats (p = .005). The percentage of unmetabolized parent was significantly different between both sexes at 20 min and 60 min p.i. In the liver, a 1.6-fold higher radioactivity concentration was found in male versus female animals and in addition also the percentage of unmetabolized parent was different. CONCLUSION: Our results show pronounced sex differences in blood/plasma pharmacokinetics and metabolism of [18F]THK-5317 in rats. Female animals showed a faster plasma clearance compared to males. These results underline the importance of investigating both sexes and also support the notion that individual input functions or sex-specific population-based input functions are needed for kinetic modeling analyses. ADVANCES IN KNOWLEDGE: First preclinical study in rats showing pronounced sex differences in blood/plasma pharmacokinetics and metabolism of [18F]THK-5317. IMPLICATIONS FOR PATIENT CARE: Sex-specific differences might also be present in humans and thus clinical trials should have adequate sample size to account for effects in men and women separately.


Subject(s)
Aniline Compounds/pharmacokinetics , Quinolines/pharmacokinetics , Sex Characteristics , Alzheimer Disease/metabolism , Aniline Compounds/blood , Aniline Compounds/metabolism , Animals , Female , Male , Quinolines/blood , Quinolines/metabolism , Radioactive Tracers , Rats , Tissue Distribution , tau Proteins/metabolism
20.
J Cereb Blood Flow Metab ; 40(1): 150-162, 2020 01.
Article in English | MEDLINE | ID: mdl-30354871

ABSTRACT

P-glycoprotein (P-gp, ABCB1) is an efflux transporter at the blood-brain barrier (BBB), which mediates clearance of beta-amyloid (Aß) from brain into blood. We used (R)-[11C]verapamil PET in combination with partial P-gp inhibition with tariquidar to measure cerebral P-gp function in a beta-amyloidosis mouse model (APPtg) and in control mice at three different ages (50, 200 and 380 days). Following tariquidar pre-treatment (4 mg/kg), whole brain-to-plasma radioactivity concentration ratios (Kp,brain) were significantly higher in APPtg than in wild-type mice aged 50 days, pointing to decreased cerebral P-gp function. Moreover, we found an age-dependent decrease in cerebral P-gp function in both wild-type and APPtg mice of up to -50%. Alterations in P-gp function were more pronounced in Aß-rich brain regions (hippocampus, cortex) than in a control region with negligible Aß load (cerebellum). PET results were confirmed by immunohistochemical staining of P-gp in brain microvessels. Our results confirm previous findings of reduced P-gp function in Alzheimer's disease mouse models and show that our PET protocol possesses adequate sensitivity to measure these functional changes in vivo. Our PET protocol may find use in clinical studies to test the efficacy of drugs to induce P-gp function at the human BBB to enhance Aß clearance.


Subject(s)
ATP Binding Cassette Transporter, Subfamily B, Member 1/physiology , Amyloidosis/metabolism , Brain Chemistry , Positron-Emission Tomography/methods , Age Factors , Alzheimer Disease/metabolism , Animals , Biological Transport , Blood-Brain Barrier/metabolism , Disease Models, Animal , Mice , Quinolines/pharmacology
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