Omanische Heilpflanze im Fokus der Phytochemie IPB-Wissenschaftler und Partner aus Dhofar haben jüngst die omanische Heilpflanze Terminalia dhofarica unter die phytochemische Lupe genommen. Die Pflanze ist reich an…
Geschmack ist vorhersagbar: Mit FlavorMiner. FlavorMiner heißt das Tool, das IPB-Chemiker und Partner aus Kolumbien jüngst entwickelt haben. Das Programm kann, basierend auf maschinellem Lernen (KI), anhand der…
Previous data suggest a possible link between multidrug resistance-associated protein 1 (ABCC1) and brain clearance of beta-amyloid (Aβ). We used PET with 6-bromo-7-[11C]methylpurine ([11C]BMP) to measure cerebral ABCC1 transport activity in a beta-amyloidosis mouse model (APP/PS1-21) and in wild-type mice aged 50 and 170 days, without and with pretreatment with the ABCC1 inhibitor MK571. One hundred seventy days-old-animals additionally underwent [11C]PiB PET scans to measure Aβ load. While baseline [11C]BMP PET scans detected no differences in the elimination slope of radioactivity washout from the brain (kelim) between APP/PS1-21 and wild-type mice of both age groups, PET scans after MK571 pretreatment revealed significantly higher kelim values in APP/PS1-21 mice than in wild-type mice aged 170 days, suggesting increased ABCC1 activity. The observed increase in kelim occurred across all investigated brain regions and was independent of the presence of Aβ plaques measured with [11C]PiB. Western blot analysis revealed a trend towards increased whole brain ABCC1 levels in 170 days-old-APP/PS1-21 mice versus wild-type mice and a significant positive correlation between ABCC1 levels and kelim. Our data point to an upregulation of ABCC1 in APP/PS1-21 mice, which may be related to an induction of ABCC1 in astrocytes as a protective mechanism against oxidative stress.
Publikation
Zoufal, V.; Mairinger, S.; Brackhan, M.; Krohn, M.; Filip, T.; Sauberer, M.; Stanek, J.; Wanek, T.; Tournier, N.; Bauer, M.; Pahnke, J.; Langer, O.;Imaging P-Glycoprotein Induction at the Blood–Brain Barrier of a β-Amyloidosis Mouse Model with 11C-Metoclopramide PETJ. Nucl. Med.611050-1057(2020)DOI: 10.2967/jnumed.119.237198
P-glycoprotein (ABC subfamily B member 1, ABCB1) plays an important role at the blood-brain barrier (BBB) in promoting clearance of neurotoxic β-amyloid (Aβ) peptides from the brain into the blood. ABCB1 expression and activity were found to be decreased in the brains of Alzheimer disease patients. Treatment with drugs that induce cerebral ABCB1 activity may be a promising approach to delay the build-up of Aβ deposits in the brain by enhancing clearance of Aβ peptides from the brain. The aim of this study was to investigate whether PET with the weak ABCB1 substrate radiotracer 11C-metoclopramide can measure ABCB1 induction at the BBB in a β-amyloidosis mouse model (APP/PS1-21 mice) and in wild-type mice. Methods: Groups of wild-type and APP/PS1-21 mice aged 50 or 170 d underwent 11C-metoclopramide baseline PET scans or scans after intraperitoneal treatment with the rodent pregnane X receptor activator 5-pregnen-3β-ol-20-one-16α-carbonitrile (PCN, 25 mg/kg) or its vehicle over 7 d. At the end of the PET scans, brains were harvested for immunohistochemical analysis of ABCB1 and Aβ levels. In separate groups of mice, radiolabeled metabolites of 11C-metoclopramide were determined in plasma and brain at 15 min after radiotracer injection. As an outcome parameter of cerebral ABCB1 activity, the elimination slope of radioactivity washout from the brain (k E,brain) was calculated. Results: PCN treatment resulted in an increased clearance of radioactivity from the brain as reflected by significant increases in k E,brain (from +26% to +54% relative to baseline). Immunohistochemical analysis confirmed ABCB1 induction in the brains of PCN-treated APP/PS1-21 mice with a concomitant decrease in Aβ levels. There was a significant positive correlation between k E,brain and ABCB1 levels in the brain. In wild-type mice, a significant age-related decrease in k E,brain was found. Metabolite analysis showed that most radioactivity in the brain comprised unmetabolized 11C-metoclopramide in all animal groups. Conclusion: 11C-metoclopramide can measure ABCB1 induction in the mouse brain without the need to consider an arterial input function and may find potential application in Alzheimer disease patients to noninvasively evaluate strategies to enhance the clearance properties of the BBB.
Publikation
Zoufal, V.; Wanek, T.; Krohn, M.; Mairinger, S.; Filip, T.; Sauberer, M.; Stanek, J.; Pekar, T.; Bauer, M.; Pahnke, J.; Langer, O.;Age dependency of cerebral P-glycoprotein function in wild-type and APPPS1 mice measured with PETJ. Cereb. Blood Flow Metab.40150-162(2020)DOI: 10.1177/0271678X18806640
P-glycoprotein (P-gp, ABCB1) is an efflux transporter at the blood–brain barrier (BBB), which mediates clearance of beta-amyloid (Aβ) 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 Aβ-rich brain regions (hippocampus, cortex) than in a control region with negligible Aβ 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 Aβ clearance.
Publikation
Zoufal, V.; Mairinger, S.; Krohn, M.; Wanek, T.; Filip, T.; Sauberer, M.; Stanek, J.; Traxl, A.; Schuetz, J. D.; Kuntner, C.; Pahnke, J.; Langer, O.;Influence of Multidrug Resistance-Associated Proteins on the Excretion of the ABCC1 Imaging Probe 6-Bromo-7-[11C]Methylpurine in MiceMol. Imaging Biol.21306-316(2019)DOI: 10.1007/s11307-018-1230-y
PurposeMultidrug resistance-associated proteins (MRPs) mediate the hepatobiliary and renal excretion of many drugs and drug conjugates. The positron emission tomography (PET) tracer 6-bromo-7-[11C]methylpurine is rapidly converted in tissues by glutathione-S-transferases into its glutathione conjugate, and has been used to measure the activity of Abcc1 in the brain and the lungs of mice. Aim of this work was to investigate if the activity of MRPs in excretory organs can be measured with 6-bromo-7-[11C]methylpurine.ProceduresWe performed PET scans with 6-bromo-7-[11C]methylpurine in groups of wild-type, Abcc4(−/−) and Abcc1(−/−) mice, with and without pre-treatment with the prototypical MRP inhibitor MK571.Results6-Bromo-7-[11C]methylpurine-derived radioactivity predominantly underwent renal excretion. In blood, MK571 treatment led to a significant increase in the AUC and a decrease in the elimination rate constant of radioactivity (kelimination,blood). In the kidneys, there were significant decreases in the rate constant for radioactivity uptake from the blood (kuptake,kidney), kelimination,kidney, and the rate constant for tubular secretion of radioactivity (kurine). Experiments in Abcc4(−/−) mice indicated that Abcc4 contributed to renal excretion of 6-bromo-7-[11C]methylpurine-derived radioactivity.ConclusionsOur data suggest that 6-bromo-7-[11C]methylpurine may be useful to assess the activity of MRPs in the kidneys as well as in other organs (brain, lungs), although further work is needed to identify the MRP subtypes involved in the disposition of 6-bromo-7-[11C]methylpurine-derived radioactivity.