Positron emission tomography （PET） is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes wh...Positron emission tomography （PET） is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide routinely used in the radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109.8 min. The delivery of such radiotracers into the brain provides images of transport, metabolic, and neurotransmission processes on the molecular level. After a short introduction into the principles of PET, this review mainly focuses on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as described here provides molecular probes which not only are useful for imaging of human brain diseases, but also allow molecular neuroreceptor imaging studies in various small-animal models of disease, including genetically- engineered animals. Furthermore, they provide a powerful tool for in vivo pharmacology during the process of pre-clinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the pharmacokinetics and pharmacodynamics of drugs in vivo.展开更多
Racemic[^(18)F]FBFP([^(18)F]1)proved to be a potentσ_(1) receptor radiotracer with superior imaging properties.The pure enantiomers of unlabeled compounds(S)-and(R)-1 and the corresponding iodonium ylide precursors w...Racemic[^(18)F]FBFP([^(18)F]1)proved to be a potentσ_(1) receptor radiotracer with superior imaging properties.The pure enantiomers of unlabeled compounds(S)-and(R)-1 and the corresponding iodonium ylide precursors were synthesized and characterized.The two enantiomers(S)-1 and(R)-1 exhibited comparable high affinity forσ_(1) receptors and selectivity overσ_(2) receptors.The Ca^(2+) fluorescence assay indicated that(R)-1 behaved as an antagonist and(S)-1 as an agonist forσ_(1) receptors.The ^(18)F-labeled enantiomers(S)-and(R)-[^(18)F]1 were obtained in>99%enantiomeric purity from the corresponding enantiopure iodonium ylide precursors with radiochemical yield of 24.4%±2.6%and molar activity of 86–214 GBq/μmol.In ICR mice both(S)-and(R)-[^(18)F]1displayed comparable high brain uptake,brain-to-blood ratio,in vivo stability and binding specificity in the brain and peripheral organs.In micro-positron emission tomography(PET)imaging studies in rats,(S)-[^(18)F]1 exhibited faster clearance from the brain than(R)-[^(18)F]1,indicating different brain kinetics of the two enantiomers.Both(S)-and(R)-[^(18)F]1 warrant further evaluation in primates to translate a single enantiomer with more suitable kinetics for imaging theσ_(1) receptors in humans.展开更多
We have discovered and synthesized a series of indole-based derivatives as novel sigma-2(σ_(2))receptor ligands.Two ligands with high σ_(2) receptor affinity and subtype selectivity were then radiolabeled with F-18 ...We have discovered and synthesized a series of indole-based derivatives as novel sigma-2(σ_(2))receptor ligands.Two ligands with high σ_(2) receptor affinity and subtype selectivity were then radiolabeled with F-18 in good radiochemical yields and purities,and evaluated in rodents.In biodistribution studies in male ICR mice,radioligand[18F]9,or 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-4-(2-[18F]fluoroethoxy)-1H-indole,was found to display high brain uptake and high brain-to-blood ratio.Pretreatment of animals with the selective σ_(2) receptor ligand CM398 led to significant reductions in both brain uptake(29%-54%)and brain-to-blood ratio(60%-88%)of the radioligand in a dose-dependent manner,indicating high and saturable specific binding of[18F]9 to σ_(2) receptors in the brain.Further,ex vivo autoradiography in male ICR mice demonstrated regionally heterogeneous specific binding of[18F]9 in the brain that is consistent with the distribution pattern of σ_(2) receptors.Dynamic positron emission tomography imaging confirmed regionally distinct distribution and high levels of specific binding for[18F]9 in the rat brain,along with appropriate tissue kinetics.Taken together,results from our current study indicated the novel radioligand[18F]9 as the first highly specific and promising imaging agent for σ_(2) receptors in the brain.展开更多
文摘Positron emission tomography （PET） is an in vivo molecular imaging tool which is widely used in nuclear medicine for early diagnosis and treatment follow-up of many brain diseases. PET uses biomolecules as probes which are labeled with radionuclides of short half-lives, synthesized prior to the imaging studies. These probes are called radiotracers. Fluorine-18 is a radionuclide routinely used in the radiolabeling of neuroreceptor ligands for PET because of its favorable half-life of 109.8 min. The delivery of such radiotracers into the brain provides images of transport, metabolic, and neurotransmission processes on the molecular level. After a short introduction into the principles of PET, this review mainly focuses on the strategy of radiotracer development bridging from basic science to biomedical application. Successful radiotracer design as described here provides molecular probes which not only are useful for imaging of human brain diseases, but also allow molecular neuroreceptor imaging studies in various small-animal models of disease, including genetically- engineered animals. Furthermore, they provide a powerful tool for in vivo pharmacology during the process of pre-clinical drug development to identify new drug targets, to investigate pathophysiology, to discover potential drug candidates, and to evaluate the pharmacokinetics and pharmacodynamics of drugs in vivo.
基金the financial support from Beijing Natural Science Foundation(No.7212203)National Natural Science Foundation of China(No.21876013)。
文摘Racemic[^(18)F]FBFP([^(18)F]1)proved to be a potentσ_(1) receptor radiotracer with superior imaging properties.The pure enantiomers of unlabeled compounds(S)-and(R)-1 and the corresponding iodonium ylide precursors were synthesized and characterized.The two enantiomers(S)-1 and(R)-1 exhibited comparable high affinity forσ_(1) receptors and selectivity overσ_(2) receptors.The Ca^(2+) fluorescence assay indicated that(R)-1 behaved as an antagonist and(S)-1 as an agonist forσ_(1) receptors.The ^(18)F-labeled enantiomers(S)-and(R)-[^(18)F]1 were obtained in>99%enantiomeric purity from the corresponding enantiopure iodonium ylide precursors with radiochemical yield of 24.4%±2.6%and molar activity of 86–214 GBq/μmol.In ICR mice both(S)-and(R)-[^(18)F]1displayed comparable high brain uptake,brain-to-blood ratio,in vivo stability and binding specificity in the brain and peripheral organs.In micro-positron emission tomography(PET)imaging studies in rats,(S)-[^(18)F]1 exhibited faster clearance from the brain than(R)-[^(18)F]1,indicating different brain kinetics of the two enantiomers.Both(S)-and(R)-[^(18)F]1 warrant further evaluation in primates to translate a single enantiomer with more suitable kinetics for imaging theσ_(1) receptors in humans.
基金supported by the National Natural Science Foundation of China(No.21876013)Beijing Natural Science Foundation(7212203,China)。
文摘We have discovered and synthesized a series of indole-based derivatives as novel sigma-2(σ_(2))receptor ligands.Two ligands with high σ_(2) receptor affinity and subtype selectivity were then radiolabeled with F-18 in good radiochemical yields and purities,and evaluated in rodents.In biodistribution studies in male ICR mice,radioligand[18F]9,or 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-4-(2-[18F]fluoroethoxy)-1H-indole,was found to display high brain uptake and high brain-to-blood ratio.Pretreatment of animals with the selective σ_(2) receptor ligand CM398 led to significant reductions in both brain uptake(29%-54%)and brain-to-blood ratio(60%-88%)of the radioligand in a dose-dependent manner,indicating high and saturable specific binding of[18F]9 to σ_(2) receptors in the brain.Further,ex vivo autoradiography in male ICR mice demonstrated regionally heterogeneous specific binding of[18F]9 in the brain that is consistent with the distribution pattern of σ_(2) receptors.Dynamic positron emission tomography imaging confirmed regionally distinct distribution and high levels of specific binding for[18F]9 in the rat brain,along with appropriate tissue kinetics.Taken together,results from our current study indicated the novel radioligand[18F]9 as the first highly specific and promising imaging agent for σ_(2) receptors in the brain.
