|
1
|
Hayes TR, Chao CK, Blecha JE, Huynh TL, VanBrocklin HF, Zinn KR, Gerdes JM, Thompson CM. [ 11C]Paraoxon: Radiosynthesis, Biodistribution and In Vivo Positron Emission Tomography Imaging in Rat. J Pharmacol Exp Ther 2024; 388:333-346. [PMID: 37770203 PMCID: PMC10801775 DOI: 10.1124/jpet.123.001832] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 10/03/2023] Open
Abstract
Synthesis of the acetylcholinesterase inhibitor paraoxon (POX) as a carbon-11 positron emission tomography tracer ([11C]POX) and profiling in live rats is reported. Naïve rats intravenously injected with [11C]POX showed a rapid decrease in parent tracer to ∼1%, with an increase in radiolabeled serum proteins to 87% and red blood cells (RBCs) to 9%. Protein and RBC leveled over 60 minutes, reflecting covalent modification of proteins by [11C]POX. Ex vivo biodistribution and imaging profiles in naïve rats had the highest radioactivity levels in lung followed by heart and kidney, and brain and liver the lowest. Brain radioactivity levels were low but observed immediately after injection and persisted over the 60-minute experiment. This showed for the first time that even low POX exposures (∼200 ng tracer) can rapidly enter brain. Rats given an LD50 dose of nonradioactive paraoxon at the LD50 20 or 60 minutes prior to [11C]POX tracer revealed that protein pools were blocked. Blood radioactivity at 20 minutes was markedly lower than naïve levels due to rapid protein modification by nonradioactive POX; however, by 60 minutes the blood radioactivity returned to near naïve levels. Live rat tissue imaging-derived radioactivity values were 10%-37% of naïve levels in nonradioactive POX pretreated rats at 20 minutes, but by 60 minutes the area under the curve (AUC) values had recovered to 25%-80% of naïve. The live rat imaging supported blockade by nonradioactive POX pretreatment at 20 minutes and recovery of proteins by 60 minutes. SIGNIFICANCE STATEMENT: Paraoxon (POX) is an organophosphorus (OP) compound and a powerful prototype and substitute for OP chemical warfare agents (CWAs) such as sarin, VX, etc. To study the distribution and penetration of POX into the central nervous system (CNS) and other tissues, a positron emission tomography (PET) tracer analog, carbon-11-labeled paraoxon ([11C]POX), was prepared. Blood and tissue radioactivity levels in live rats demonstrated immediate penetration into the CNS and persistent radioactivity levels in tissues indicative of covalent target modification.
Collapse
Affiliation(s)
- Thomas R Hayes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Chih-Kai Chao
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Joseph E Blecha
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Tony L Huynh
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Henry F VanBrocklin
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Kurt R Zinn
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - John M Gerdes
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| | - Charles M Thompson
- Department of Biomedical and Pharmaceutical Sciences, University of Montana, Missoula, Montana (C.-K.C., J.M.G., C.M.T.); Department of Radiology and Biomedical Imaging, University of California, San Francisco, San Francisco, California (T.R.H., J.E.B., T.L.H., H.F.V.); and Departments of Radiology, Small Animal Clinical Sciences, and Biomedical Engineering and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan (K.R.Z.)
| |
Collapse
|