A High-fat and High-Cholesterol Diet Potentiates Oxidative Damage in Hippocampus of Mice Lacking Apolipoprotein E.

OBJECTIVE: We examined genetic and dietary challenge on hippocampal oxidative damage. Mice expressing (ApoE+/+) or lacking apolipoprotein E (ApoE-/-) were maintained on a standard diet or a high fat /high cholesterol (challenge) diet for 11-31 weeks. Similar levels of oxidative species were observed for ApoE+/+ and -/- mice maintained on the basal diet. METHOD: However, treatment of ApoE-/- homogenates with hydrogen peroxide and iron increased oxidative species by >100%, indicating an equivalent amount of potential oxidative species in latent form. We observed a time- and region-specific induction of oxidative damage in the hippocampi of ApoE-/- but not +/+ mice while maintained on the challenge diet. Notably, however, additional significant latent oxidative products were detected during this time. After 31 weeks of dietary challenge, by which time hippocampal oxidative species had doubled, there was an additional 50% in the latent form. CONCLUSION: This highlights the degree to which ApoE deficiency places hippocampal tissue at risk for oxidative damage. Even a modest dietary deficiency may be sufficient to provoke oxidative damage to hippocampal tissue. These results highlight the combinatorial impact of genetic and dietary deficiencies on oxidative damage to hippocampal tissue.

Robot-Embodied Neuronal Networks as an Interactive Model of Learning.

BACKGROUND AND OBJECTIVE: The reductionist approach of neuronal cell culture has been useful for analyses of synaptic signaling. Murine cortical neurons in culture spontaneously form an ex vivo network capable of transmitting complex signals, and have been useful for analyses of several fundamental aspects of neuronal development hitherto difficult to clarify in situ. However, these networks lack the ability to receive and respond to sensory input from the environment as do neurons in vivo. Establishment of these networks in culture chambers containing multi-electrode arrays allows recording of synaptic activity as well as stimulation. METHOD: This article describes the embodiment of ex vivo neuronal networks neurons in a closed-loop cybernetic system, consisting of digitized video signals as sensory input and a robot arm as motor output. RESULTS: In this system, the neuronal network essentially functions as a simple central nervous system. This embodied network displays the ability to track a target in a naturalistic environment. These findings underscore that ex vivo neuronal networks can respond to sensory input and direct motor output. CONCLUSION: These analyses may contribute to optimization of neuronal-computer interfaces for perceptive and locomotive prosthetic applications. Ex vivo networks display critical alterations in signal patterns following treatment with subcytotoxic concentrations of amyloid-beta. Future studies including comparison of tracking accuracy of embodied networks prepared from mice harboring key mutations with those from normal mice, accompanied with exposure to Abeta and/or other neurotoxins, may provide a useful model system for monitoring subtle impairment of neuronal function as well as normal and abnormal development.

Insufficient developmental excitatory neuronal activity fails to foster establishment of normal levels of inhibitory neuronal activity.

The nervous system is composed of excitatory and inhibitory neurons. One major class of inhibitory neurons release the neurotransmitter γ-Aminobutyric acid (GABA). GABAergic inhibitory activity maintains the balance that is disrupted in conditions such as epilepsy. At least some GABAergic neurons are initially excitatory and undergo a developmental conversion to convert to inhibitory neurons. The mechanism(s) behind this conversion are thought to include a critical developmental increase in excitatory activity. To test this hypothesis, we subjected ex vivo developing neuronal networks on multi-electrode arrays to various stimulation and pharmacological regimens. Synaptic activity of networks initially consists of epileptiform-like high-amplitude individual "spikes", which convert to organized bursts of activity over the course of approximately 1 month. Stimulation of networks with a digitized synaptic signal for 5days hastened the decrease of epileptiform activity. By contrast, stimulation for a single day delayed the appearance of bursts and instead increased epileptiform signaling. GABA treatment reduced total signals in unstimulated networks and networks stimulated for 5days, but instead increased signaling in networks stimulated for 1day. This increase was prevented by co-treatment with (2R)-amino-5-phosphonopentanoate and 6-cyano-7-nitroquinoxaline-2,3-dione, confirming that GABA invoked excitatory activity in networks stimulated for 1day. Glutamate increased signals in networks subjected to all stimulation regimens; the GABA receptor antagonist bicuculline prevented this increase only in networks stimulated for 1day. These latter findings are consistent with the induction of so-called "mixed" synapses (which release a combination of excitatory and inhibitory neurotransmitters) in networks stimulated for 1day, and support the hypothesis that a critical level of excitatory activity fosters the developmental transition of GABAergic neurons from excitatory to inhibitory.

Synaptic signal streams generated by ex vivo neuronal networks contain non-random, complex patterns.

Cultured embryonic neurons develop functional networks that transmit synaptic signals over multiple sequentially connected neurons as revealed by multi-electrode arrays (MEAs) embedded within the culture dish. Signal streams of ex vivo networks contain spikes and bursts of varying amplitude and duration. Despite the random interactions inherent in dissociated cultures, neurons are capable of establishing functional ex vivo networks that transmit signals among synaptically connected neurons, undergo developmental maturation, and respond to exogenous stimulation by alterations in signal patterns. These characteristics indicate that a considerable degree of organization is an inherent property of neurons. We demonstrate herein that (1) certain signal types occur more frequently than others, (2) the predominant signal types change during and following maturation, (3) signal predominance is dependent upon inhibitory activity, and (4) certain signals preferentially follow others in a non-reciprocal manner. These findings indicate that the elaboration of complex signal streams comprised of a non-random distribution of signal patterns is an emergent property of ex vivo neuronal networks.

Critical role for inhibitory neurons in modulation of synaptic signaling in ex vivo neuronal networks.

A number of laboratories have modeled aspects of synaptic plasticity using neuronal networks established on micro-electrode arrays. Such studies demonstrate that external stimulation can increase or hasten maturation of network signaling as evidenced an increase in complex bursts. Herein, we demonstrate that repetitive stimulation with a recorded synaptic signal was capable of increasing overall signaling, including the percentage of bursts, over a 5-day period, but that this increase was completely prevented by the presence of the GABAergic antagonist bicuculline. These findings demonstrate a critical role for inhibitory neurons in signal maturation following stimulation, which supports the purported role for inhibitory neuronal activity in long-term potentiation and learning in situ.

Cardiac retention of PET neuronal imaging agent LMI1195 in different species: impact of norepinephrine uptake-1 and -2 transporters.

INTRODUCTION: Released sympathetic neurotransmitter norepinephrine (NE) in the heart is cleared by neuronal uptake-1 and extraneuronal uptake-2 transporters. Cardiac uptake-1 and -2 expression varies among species, but the uptake-1 is the primary transporter in humans. LMI1195 is an NE analog labeled with (18)F for PET evaluation of cardiac neuronal function. This study investigated the impact of cardiac neuronal uptake-1 associated with different species on LMI1195 heart uptake. METHODS: Cardiac uptake-1 was blocked by desipramine, a selective uptake-1 inhibitor, and sympathetic neuronal denervation was induced by 6-hydroxydopamine, a neurotoxin, in rats, rabbits and nonhuman primates (NHP). Tissue biodistribution and cardiac imaging of LMI1195 and (123)I-metaiodobenzylguanidine (MIBG) were performed. RESULTS: In rats, uptake-1 blockade did not alter LMI1195 heart uptake compared to the control at 60-min post injection [1.41 ± 0.07 vs. 1.47 ± 0.23 % injected dose per gram tissue (%ID/g)]. In contrast, LMI1195 heart uptake was reduced by 80% in uptake-1 blocked rabbits. In sympathetically denervated rats, LMI1195 heart uptake was similar to the control (2.18 ± 0.40 vs. 2.58 ± 0.76 %ID/g). However, the uptake decreased by 79% in denervated rabbits. Similar results were found in MIBG heart uptake in rats and rabbits with uptake-1 blockade. Consistently, LMI1195 cardiac imaging showed comparable myocardial activity in uptake-1 blocked or sympathetically denervated rats to the control, but marked activity reduction in uptake-1 blocked or denervated rabbits and NHPs. CONCLUSIONS: LMI1195 is retained in the heart of rabbits and NHPs primarily via the neuronal uptake-1 with high selectivity and can be used for evaluation of cardiac sympathetic denervation. Similar to the human, the neuronal uptake-1 is the dominant transporter for cardiac retention of NE analogs in rabbits and NHPs, but not in rats.

Transient epileptiform signaling during neuronal network development: regulation by external stimulation and bimodal GABAergic activity.

A predominance of excitatory activity, with protracted appearance of inhibitory activity, accompanies cortical neuronal development. It is unclear whether or not inhibitory neuronal activity is solicited exclusively by excitatory neurons or whether the transient excitatory activity displayed by developing GABAergic neurons contributes to an excitatory threshold that fosters their conversion to inhibitory activity. We addressed this possibility by culturing murine embryonic neurons on multi-electrode arrays. A wave of individual 0.2-0.4 mV signals ("spikes") appeared between approx. 20-30 days in culture, then declined. A transient wave of high amplitude (>0.5 mV) epileptiform activity coincided with the developmental decline in spikes. Bursts (clusters of ≥3 low-amplitude spikes within 0.7s prior to returning to baseline) persisted following this decline. Addition of the GABAergic antagonist bicuculline initially had no effect on signaling, consistent with delayed development of GABAergic synapses. This was followed by a period in which bicuculline inhibited overall signaling, confirming that GABAergic neurons initially display excitatory activity in ex vivo networks. Following the transient developmental wave of epileptiform signaling, bicuculline induced a resurgence of epileptiform signaling, indicating that GABAergic neurons at this point displayed inhibitory activity. The appearance of transition after the developmental and decline of epileptiform activity, rather than immediately after the developmental decline in lower-amplitude spikes, suggests that the initial excitatory activity of GABAergic neurons contributes to their transition into inhibitory neurons, and that inhibitory GABAergic activity is essential for network development. Prior studies indicate that a minority (25%) of neurons in these cultures were GABAergic, suggesting that inhibitory neurons regulate multiple excitatory neurons. A similar robust increase in signaling following cessation of inhibitory activity in an artificial neural network containing 20% inhibitory neurons supported this conclusion. Even a minor perturbation in GABAergic function may therefore foster initiation and/or amplification of seizure activity, as well as perturbations in long-term potentiation.

[18F](R)-5-chloro-1-(1-cyclopropyl-2-methoxyethyl)-3-(4-(2-fluoroethoxy)-2,5-dimethyl phenylamino)pyrazin-2(1H)-one: introduction of N3-phenylpyrazinones as potential CRF-R1 PET imaging agents.

Based on a favorable balance between CRF-R1 affinity, lipophilicity and metabolic stability, compound 10 was evaluated for potential development as PET radioligand. Compound [(18)F]10 was prepared with high radiochemical purity and showed promising binding properties in rat brain imaging experiments.

Accelerated establishment of mature signaling patterns following stimulation of developing neuronal networks: "learning" versus "plasticity".

Neuronal networks established on micro-electrode arrays provide useful models for synaptic plasticity. Whether or not this represents a facet of learning is debated since ex vivo networks are deprived of organismal interaction with the environment. We compared developmental signaling of such networks with and without stimulation with a prerecorded synaptic signal from another mature culture as a model of sensory input. Unstimulated networks displayed a developmental increase in individual signals that eventually declined, yielding a pattern containing organized bursts of signaling. Minimal stimulation, to model the onset of sensory input hastened the onset of developmental signaling. However, the overall developmental pattern of stimulated networks, including the total number and type of signals as well as the length of this developmental period, was identical to that of unstimulated networks. One interpretation of these findings is that ongoing plasticity may be essential to establish an appropriate platform for learning once sensory input ensues.

Stimulation with a low-amplitude, digitized synaptic signal to invoke robust activity within neuronal networks on multielectrode arrays.

Multielectrode arrays (MEAs) are used for analysis of neuronal activity. Here we report two variations on commonly accepted techniques that increase the precision of extracellular electrical stimulation: (i) the use of a low-amplitude recorded spontaneous synaptic signal as a stimulus waveform and (ii) the use of a specific electrode within the array adjacent to the stimulus electrode as a hard-grounded stimulus signal return path. Both modifications remained compatible with manipulation of neuronal networks. In addition, localized stimulation with the low-amplitude synaptic signal allowed selective stimulation or inhibition of otherwise spontaneous signals. These findings indicate that minimizing the area of the culture impacted by external stimulation allows modulation of signaling patterns within subpopulations of neurons in culture. The simple modifications described herein may be useful for precise monitoring and manipulation of neuronal networks.

Evaluation of LMI1195, a novel 18F-labeled cardiac neuronal PET imaging agent, in cells and animal models.

BACKGROUND: Heart failure has been associated with impaired cardiac sympathetic neuronal function. Cardiac imaging with radiolabeled agents that are substrates for the neuronal norepinephrine transporter (NET) has demonstrated the potential to identify individuals at risk of cardiac events. N-[3-Bromo-4-(3-[18F]fluoro-propoxy)-benzyl]-guanidine (LMI1195) is a newly developed 18F-labeled NET substrate designed to allow cardiac neuronal imaging with the high sensitivity, resolution, and quantification afforded by positron emission tomography (PET). METHODS AND RESULTS: LMI1195 was evaluated in comparison with norepinephrine (NE) in vitro and 123I-meta-iodobenzylguanidine (MIBG) in vivo. The affinity (Ki) of LMI1195 for NET was 5.16 ± 2.83 µmol/L, similar to that of NE (3.36 ± 2.77 µmol/L) in a cell membrane-binding assay. Similarly, LMI1195 uptake kinetics examined in a human neuroblastoma cell line had Km and Vmax values of 1.44 ± 0.76 µmol/L and 6.05 ± 3.09 pmol/million cells per minute, comparable to NE (2.01 ± 0.85 µmol/L and 6.23 ± 1.52 pmol/million cells per minute). In rats, LMI1195 heart uptake at 15 and 60 minutes after intravenous administration was 2.36 ± 0.38% and 2.16 ± 0.38% injected dose per gram of tissue (%ID/g), similar to 123I-MIBG (2.14 ± 0.30 and 2.19 ± 0.27%ID/g). However, the heart to liver and lung uptake ratios were significantly higher for LMI1195 than for 123I-MIBG. In rabbits, desipramine (1 mg/kg), a selective NET inhibitor, blocked LMI1195 heart uptake by 82%, which was more effective than 123I-MIBG (53%), at 1 hour after dosing. Sympathetic denervation with 6-hydroxydopamine, a neurotoxin, resulted in a marked (79%) decrease in LMI1195 heart uptake. Cardiac PET imaging with LMI1195 in rats, rabbits, and nonhuman primates revealed clear myocardium with low radioactivity levels in the blood, lung, and liver. Imaging in rabbits pretreated with desipramine showed reduced heart radioactivity levels in a dose-dependent manner. Additionally, imaging in sympathetically denervated rabbits resulted in low cardiac image intensity with LMI1195 but normal perfusion images with flurpiridaz F 18, a PET myocardial perfusion imaging agent. In nonhuman primates pretreated with desipramine (0.5 mg/kg), imaging with LMI1195 showed a 66% decrease in myocardial uptake. In a rat model of heart failure, the LMI1195 cardiac uptake decreased as heart failure progressed. CONCLUSIONS: LMI1195 is a novel (18)F imaging agent retained in the heart through the NET and allowing evaluation of the cardiac sympathetic neuronal function by PET imaging.

Synthesis and Cardiac Imaging of (18)F-Ligands Selective for ß1-Adrenoreceptors.

A series of potent and selective ß1-adrenoreceptor ligands were identified (IC50 range, 0.04-0.25 nM; ß1/ß2 selectivity range, 65-450-fold), labeled with the PET radioisotope fluorine-18 and evaluated in normal Sprague-Dawley rats. Tissue distribution studies demonstrated uptake of each radiotracers from the blood pool into the myocardium (0.48-0.62% ID/g), lung (0.63-0.97% ID/g), and liver (1.03-1.14% ID/g). Dynamic µPET imaging confirmed the in vivo dissection studies.

Inhibitory neurons modulate spontaneous signaling in cultured cortical neurons: density-dependent regulation of excitatory neuronal signaling.

Cortical neuronal activity depends on a balance between excitatory and inhibitory influences. Culturing of neurons on multi-electrode arrays (MEAs) has provided insight into the development and maintenance of neuronal networks. Herein, we seeded MEAs with murine embryonic cortical/hippocampal neurons at different densities (<150 or >1000 cells mm(-2)) and monitored resultant spontaneous signaling. Sparsely seeded cultures displayed a large number of bipolar, rapid, high-amplitude individual signals with no apparent temporal regularity. By contrast, densely seeded cultures instead displayed clusters of signals at regular intervals. These patterns were observed even within thinner and thicker areas of the same culture. GABAergic neurons (25% of total neurons in our cultures) mediated the differential signal patterns observed above, since addition of the inhibitory antagonist bicuculline to dense cultures and hippocampal slice cultures induced the signal pattern characteristic of sparse cultures. Sparsely seeded cultures likely lacked sufficient inhibitory neurons to modulate excitatory activity. Differential seeding of MEAs can provide a unique model for analyses of perturbation in the interaction between excitatory and inhibitory function during aging and neuropathological conditions where dysregulation of GABAergic neurons is a significant component.

Cardiac imaging and safety evaluation of BMS747158, a novel PET myocardial perfusion imaging agent, in chronic myocardial compromised rabbits.

BACKGROUND: BMS747158 labeled with (18)F is being developed for PET myocardial perfusion imaging. Imaging studies showed clear detection of necrotic tissue in acute myocardial infarcted (MI) animals and a good safety profile in normal animals. This study evaluated BMS747158 imaging and cardiovascular safety in a rabbit model of chronic MI with cardiac compromise. METHODS AND RESULTS: Chronic MI rabbits were developed by the left coronary artery ligation followed by 4 weeks recovery. Cardiac PET imaging with BMS747158 (~1.5 mCi, iv) in control rabbits showed clear and uniform myocardial uptake. However, imaging in chronic MI rabbits demonstrated obvious defect area in the left ventricular wall. Before BMS747158 injection, baseline electrocardiogram (ECG) waveforms in lead II configuration were normal with positive QRS complexes in control rabbits. In contrast, MI rabbits exhibited negative QRS complexes with enlarged Q waves and inverted T waves. Baseline values of mean intra-arterial pressure (AP, 61 +/- 6 vs 89 +/- 11 mmHg), systolic AP (79 +/- 11 vs 114 +/- 11 mmHg) and diastolic AP (53 +/- 4 vs 76 +/- 10 mmHg) were lower in MI than in control rabbits. Heart rate (162 +/- 36 vs 159 +/- 8 beat/minute) and QTc interval (corrected by Fridericia method, 288 +/- 17 vs 319 +/- 17 ms) were comparable. BMS747158 administration induced no changes from baseline in any of the measured cardiovascular parameters and ECG waveforms in either control or MI rabbits. CONCLUSIONS: Cardiac imaging with BMS747158 allows clear detection of chronic MI without producing any cardiovascular alterations in cardiac compromised rabbits.

Effects of food intake and anesthetic on cardiac imaging and uptake of BMS747158-02 in comparison with FDG.

BACKGROUND: BMS747158-02 is an (18)F-labeled agent being developed for PET myocardial perfusion imaging. This study examined impacts of feeding state and anesthetic on cardiac imaging and uptake of this agent in rats in comparison with (18)F-fluorodeoxyglucose (FDG). METHODS AND RESULTS: Studies were performed in rats either nonfasted or food deprived for 20 hours and anesthetized with either sodium pentobarbital (Pentob) or ketamine and xylazine (Ket/Xyl). Influences of the feeding state and anesthesia were examined by measurement of blood glucose levels, and tissue biodistribution and cardiac imaging of BMS747158-02 and FDG. The blood glucose levels were lower in fasted than nonfasted rats before anesthesia (91 +/- 11 vs 122 +/- 10 mg/dL) and the levels did not significantly change when anesthetized with Pentob. However, the levels increased markedly by 262 +/- 64 mg/dL in nonfasted rats anesthetized with Ket/Xyl. At 60 minutes post-injection, the heart uptake of FDG was significantly lower in fasted than nonfasted rats (0.2 +/- 0.1 vs 2.8 +/- 1.5%ID/g). However, the heart uptake of BMS747158-02 did not differ under these conditions (3.3 +/- 0.9 vs 3.6 +/- 0.9%ID/g, respectively). In nonfasted rats, the heart uptake of FDG was markedly lower when anesthetized with Ket/Xyl than with Pentobl (0.2 +/- 0.1 vs 2.8 +/- 1.5%ID/g). In contrast, the heart uptake of BMS747158-02 was similar with both anesthetics (3.6 +/- 0.5 vs 3.6 +/- 0.9%ID/g). Consistent with the biodistribution studies, the myocardium was not visible following FDG imaging in fasted rats, but clearly seen with BMS747158-02 in both fasted and nonfasted rats anesthetized with either anesthetic. CONCLUSIONS: Unlike FDG, BMS747158-02 cardiac images are clear and not affected by the feeding state and anesthetics.

Assessment of 18F-labeled mitochondrial complex I inhibitors as PET myocardial perfusion imaging agents in rats, rabbits, and primates.

PURPOSE: Myocardial extractions of mitochondria complex I (MC-I) inhibitors were high and well correlated with flow. This study assessed the potential of MC-I inhibitors to be developed as myocardial perfusion imaging (MPI) agents. METHODS: RP1003, RP1004, and RP1005 representing three classes of MC-I inhibitor were synthesized and radio-labeled with (18)F. These agents were evaluated for IC(50) values, tissue biodistribution, and cardiac PET imaging. (18)F-RP1004 was further examined for first-pass extraction and by imaging in non-human primates (NHP) and rats following coronary ligation. RESULTS: RP1003, RP1004, and RP1005 exhibited high MC-I inhibitory activity with IC(50) of 3.7, 16.7, and 14.4 nM. Heart uptakes in rats (percent injected dose per gram tissue) at 15 and 60 min after injection were 3.52 +/- 0.36 and 2.68 +/- 0.20 for (18)F-RP1003, 2.40 +/- 0.21 and 2.67 +/- 0.27 for (18)F-RP1004, and 2.28 +/- 0.12 and 1.81 +/- 0.17 for (18)F-RP1005. The heart to lung and liver uptake ratios were favorable for cardiac imaging with these agents. In isolated perfused rabbit hearts, the uptake of (18)F-RP1004 increased from 0.74 +/- 0.19 to 1.68 +/- 0.39 mL/min/g at flow rates of 1.66 to 5.06 mL/min/g. These values were higher than or similar to that of (99m)Tc-sestamibi. Cardiac imaging with these agents in rats and rabbits allowed visualization of the heart with minimal lung interference and rapid liver activity clearance. Imaging with (18)F-RP1004 also showed clear myocardium and marked liver activity washout in the NHP and clear detection of the perfusion-deficit area associated with left coronary artery ligation in the rat. CONCLUSION: MC-I inhibitors have the potential to be a new class of MPI agent.

Synthesis and biological evaluation of pyridazinone analogues as potential cardiac positron emission tomography tracers.

A series of fluorinated pyridazinone derivatives with IC50 values ranging from 8 to 4000 nM for the mitochondrial complex 1 (MC1) have been prepared. Structure-activity relationship (SAR) assessment indicated preference of the fluorine label to be incorporated on an alkyl side chain rather than directly on the pyridazinone moiety. Tissue distribution studies of a series of analogues ([18F] 22-28) in Sprague-Dawley (SD) rats identified [18F]27 as the most promising radiotracer with high uptake in cardiac tissue (3.41%ID/g; 30 min post injection) in addition to favorable heart to nontarget organ distribution ratios. MicroPET images of SD rats and nonhuman primates after [18F]27 administration allowed easy assessment of the myocardium through 60 min with minimal lung or liver interference.

BMS-747158-02: a novel PET myocardial perfusion imaging agent.

BACKGROUND: BMS-747158-02 is a fluorine 18-labeled pyridaben derivative designed as a new myocardial perfusion imaging agent for use with positron emission tomography (PET). This study evaluated BMS-747158-02 in animal models of cardiac perfusion and compared it with established single photon emission computed tomography agents. METHODS AND RESULTS: In a rat biodistribution study, BMS-747158-02 (15 microCi) had substantially higher myocardial uptake than technetium 99m sestamibi (100 microCi) at 15 minutes (3.5% +/- 0.3% %ID/g vs 1.9% +/- 0.1% %ID/g) and 120 minutes (3.2% +/- 0.4% of injected dose per gram vs 1.8% +/- 0.0% of injected dose per gram) after intravenous administration. Uptake ratios of heart to lung and liver at 60 minutes were also higher for BMS-747158-02 (12.7 +/- 1.4 and 3.7 +/- 0.2, respectively) than Tc-99m sestamibi (5.9 +/- 0.5 and 2.4 +/- 0.4, respectively). In an isolated rabbit heart model at flow rates of 1.66 to 5.06 mL x min(-1).g(-1) wet left ventricular weight, the net BMS-747158-02 heart uptake increased proportionally (0.93 +/- 0.15 to 2.44 +/- 0.40 mL.min(-1) x g(-1)) and to a greater extent than that of thallium 201 (0.76 +/- 0.02 to 1.11 +/- 0.02 mL x min(-1) x g(-1)) or Tc-99m sestamibi (0.49 +/- 0.03 to 0.77 +/- 0.08 mL x min(-1) x g(-1)). PET imaging with BMS-747158-02 showed a clear and sustained cardiac uptake in rats, rabbits, and nonhuman primates with minimal lung interference and rapid liver clearance. Myocardial perfusion deficit zones created by either permanent left coronary ligation or reperfusion after ligation in rats were both clearly identified on PET cardiac images of BMS-747158-02 and had good agreement with in vitro histology. CONCLUSIONS: BMS-747158-02 exhibited high and sustained cardiac uptake that was proportional to blood flow, and it represents a new class of PET myocardial perfusion imaging agent.

Synthesis and biological evaluation of the mitochondrial complex 1 inhibitor 2-[4-(4-fluorobutyl)benzylsulfanyl]-3-methylchromene-4-one as a potential cardiac positron emission tomography tracer.

A series of fluorinated chromone analogs with IC50 values ranging from 9 to 133 nM for the mitochondrial complex 1 (MC-I) has been prepared. A structure-activity relationship (SAR) study of the most potent fluorinated chromone analog 10 demonstrated the linkage heteroatom preference of the side chain region of the molecule while maintaining potent MC-I inhibitory activity. Tissue distribution studies 30 min after [(18)F]10 administration to Sprague-Dawley (SD) rats demonstrated high uptake of the radiotracer from the blood pool into the myocardium (2.24% ID/g), kidney (1.93% ID/g), and liver (2.00% ID/g). After 2 h about 66% of the activity in the myocardium at 30 min had been retained, whereas approximately 70% had been cleared from the liver and kidney. MicroPET images of SD rats after [(18)F]10 administration allowed easy assessment of the myocardium through 60 min with minimal lung or liver interference.

Quinazoline derivatives as MC-I inhibitors: evaluation of myocardial uptake using Positron Emission Tomography in rat and non-human primate.

Several quinazoline derivatives were made as mitochondrial complex 1 inhibitors. Compound 4 showed an IC(50) of 11.3 nM and was the most potent compound of this series. The (18)F analog of 4, [(18)F] 4, was injected in the rat and showed high and rapid heart uptake, fast liver clearance, and low blood uptake. Images obtained using a microPET showed clear delineation of the myocardium in normal rats and perfusion deficit in ischemic rats. In the non-human primate, [(18)F] 4 showed rapid uptake and clearance from the myocardium and high liver uptake.