Monoamine oxidase B single-photon emission tomography with [123I]Ro 43-0463: imaging in volunteers and patients with temporal lobe epilepsy

Astrocytes in the initiation and progression of epilepsy

Epilepsy affects ~65 million people worldwide. First-line treatment options include >20 antiseizure medications, but seizure control is not achieved in approximately one-third of patients. Antiseizure medications act primarily on neurons and can provide symptomatic control of seizures, but do not alter the onset and progression of epilepsy and can cause serious adverse effects. Therefore, medications with new cellular and molecular targets and mechanisms of action are needed. Accumulating evidence indicates that astrocytes are crucial to the pathophysiological mechanisms of epilepsy, raising the possibility that these cells could be novel therapeutic targets. In this Review, we discuss how dysregulation of key astrocyte functions - gliotransmission, cell metabolism and immune function - contribute to the development and progression of hyperexcitability in epilepsy. We consider strategies to mitigate astrocyte dysfunction in each of these areas, and provide an overview of how astrocyte activation states can be monitored in vivo not only to assess their contribution to disease but also to identify markers of disease processes and treatment effects. Improved understanding of the roles of astrocytes in epilepsy has the potential to lead to novel therapies to prevent the initiation and progression of epilepsy.

Newly Synthesized Fluorinated Cinnamylpiperazines Possessing Low In Vitro MAO-B Binding

Herein, we report on the synthesis and pharmacological evaluation of ten novel fluorinated cinnamylpiperazines as potential monoamine oxidase B (MAO-B) ligands. The designed derivatives consist of either cinnamyl or 2-fluorocinnamyl moieties connected to 2-fluoropyridylpiperazines. The three-step synthesis starting from commercially available piperazine afforded the final products in overall yields between 9% and 29%. An in vitro competitive binding assay using l-[³H]Deprenyl as radioligand was developed and the MAO-B binding affinities of the synthesized derivatives were assessed. Docking studies revealed that the compounds 8–17 were stabilized in both MAO-B entrance and substrate cavities, thus resembling the binding pose of l-Deprenyl. Although our results revealed that the novel fluorinated cinnamylpiperazines 8–17 do not possess sufficient MAO-B binding affinity to be eligible as positron emission tomography (PET) agents, the herein developed binding assay and the insights gained within our docking studies will certainly pave the way for further development of MAO-B ligands.

Neuroinflammation imaging markers for epileptogenesis

Epilepsy can be a devastating disorder. In addition to debilitating seizures, epilepsy can cause cognitive and emotional problems with reduced quality of life. Therefore, the major aim is to prevent the disorder in the first place: identify, detect, and reverse the processes responsible for its onset, and monitor and treat its progression. Epilepsy often occurs following a latent period of months to years (epileptogenesis) as a consequence of a brain insult, such as head trauma, stroke, or status epilepticus. Although this latent period clearly represents a therapeutic window, we are not able to stratify patients at risk for long-term epilepsy, which is prerequisite for preventative clinical trials. Moreover, because of the length of the latent period, an early biomarker for treatment response would be of high value. Finally, mechanistic biomarkers of epileptogenesis may provide more profound insight in the process of disease development.

Radiochemistry devoted to the production of monoamine oxidase (MAO-A and MAO-B) ligands for brain imaging with positron emission tomography

Monoamine oxidase (MAO) belongs to a family of flavin-containing integral enzymes that are present in the outer mitochondrial membrane in neurons and glial cells in the central nervous system. These enzymes catalyze the oxidative deamination of various neurotransmitters, biogenic amines, and xenobiotics, thereby influencing their availability and physiological activity in brain and body. Over the past decades, many potential positron emission tomography tracers have been put forward to visualize MAO in the brain with varying success, and recent publications on the topic illustrate the continuing interest in the field. The present review gives an overview of the compounds that have been put forward as possible MAO tracers in the brain and focuses on the radiochemical procedures that have been developed to produce them up till now. Relevant radioligands are grouped by the main radiochemical strategies that have been employed to synthesize them, and some interesting details and findings that are crucial to the radiosyntheses are provided.

Evidence for astrocytosis in ALS demonstrated by [11C](L)-deprenyl-D2 PET

OBJECTIVE

To use deuterium-substituted [11C](L)-deprenyl PET to depict astrocytosis in vivo in patients with amyotrophic lateral sclerosis (ALS).

BACKGROUND

In human brain, the enzyme MAO-B is primarily located in astrocytes. L-deprenyl binds to MAO-B and autoradiography with 3H-L-deprenyl has been used to map astrocytosis in vitro. Motor neuron loss in ALS is accompanied by astrocytosis and astrocytes may play an active role in the neurodegenerative process. Deuterium-substituted [11C](L)-deprenyl PET provides an opportunity to localize astrocytosis in vivo in the brain of patients with ALS.

METHODS

Deuterium-substituted [11C](L)-deprenyl PET was performed in seven patients with ALS and seven healthy control subjects.

RESULTS

Increased uptake rate of [11C](L)-deprenyl was demonstrated in ALS in pons and white matter.

CONCLUSION

This study provides evidence that astrocytosis may be detected in vivo in ALS by the use of deuterium-substituted [11C](L)-deprenyl PET though further studies are needed to determine whether deuterium-substituted [11C](L)-deprenyl binding tracks disease progression and reflects astrocytosis.

Presurgical evaluation and surgical treatment of medically refractory epilepsy

Thanks to today's modern imaging examination techniques and especially to the common use of intracranial electrodes for localizing seizure foci, more and more patients with partial epilepsy can be treated microsurgically. The results of such neurosurgical therapies are very good, particularly in mesial temporal lobe epilepsy. In recent years, good results (60-70% seizure freedom) have also been achieved in extratemporal epilepsy surgery, so that such procedures can now be recommended for carefully selected patients. In this review, presurgical evaluations and the different surgical approaches are presented.

Recent advances in the diagnosis and treatment of epilepsy

Recent advances in the diagnosis and treatment of epilepsies are discussed with special consideration of epidemiology and classification, progress in neuroimaging, electrophysiological studies using EEG and MEG, initiation of medical and surgical treatment, the role of new antiepileptic drugs and selected aspects of genetics of idiopathic epilepsies. In addition from conclusions obtained by the review of recent developments suggestions for future work in Europe are discussed. A constructive approach from multicenter studies requires homologous definitions, documentations and standardization of procedures of trials for European multicenter studies.

PET with 11C-deuterium-deprenyl and 18F-FDG in focal epilepsy

OBJECTIVES

This study compares positron emission tomography (PET) using 11C-deuterium-deprenyl (DED) with PET using 18F-fluorodeoxyglucose(18F-FDG) for examining epileptogenic regions in patients with focal epilepsy.

MATERIAL AND METHODS

Twenty-three patients undergoing evaluation for epilepsy surgery were subjected to PET with DED. Fourteen patients had mesial temporal lobe epilepsy (TLE) and 9 patients had seizures of neocortical origin. In addition, 6 healthy control subjects were examined. Pixel-by-pixel analysis was used to generate graphical images of tracer distribution volume (intercept) and the accumulation rate (slope). Asymmetries with respect to relative intercept and slope were compared in patients with temporal lobe epilepsy (TLE), in patients with extra-temporal lobe epilepsy (exTLE), and in the control subjects. The results were compared with 18F-FDG-PET.

RESULTS

Among the patients with TLE, significant differences between the epileptogenic and the contralateral lobe were found with DED intercept and FDG-uptake. No significant differences were found with DED slope. The exTLE and the control groups showed no significant differences between sides or lobes.

CONCLUSIONS

This study indicates that PET with 11C-deuterium-deprenyl is a useful method for identifying TLE and is equivalent to PET with 18F-FDG in this sense. The method has little localizing value in seizures originating from neocortical structures.

Evaluation of serotonergic transporters using PET and [11C](+)McN-5652: assessment of methods

[11C](+)McN-5652 is an established positron emission tomography tracer used to assess serotonergic transporter density. Several methods have been used to analyze [11C](+)McN-5652 data; however, no evaluation of candidate methods has been published in detail yet. In this study, compartmental modeling using a one-tissue compartment model (K1, k2"), a two-tissue compartment model (K1 to k4), and a noncompartmental method that relies on a reference region devoid of specific binding sites were assessed. Because of its low density of serotonergic transporters, white matter was chosen as reference. Parameters related to transporter density were the total distribution volume DV" (= K1/k2", one tissue compartment), DVtot, (=K1/k1' (1 + k3/k4), two tissue compartments), and Rv (= k3'/k4, noncompartmental method). The DV", DVtot, and Rv values extended over a similar range and reflected the known pattern of serotonergic transporters. However, all parameters related to transporter density were markedly confounded by nonspecific binding. With regard to K1, the one-tissue compartment model yielded markedly lower values, which were, however, more stable. The minimal study duration needed to determine stable values for the distribution volume was approximately 60 minutes. The choice of the method to analyze [11C](+)McN-5652 data depends on the situation. Parametric maps of Rv are useful if no information on K1 is needed. If compartmental modeling is chosen, both the one- and the two-tissue compartment models have advantages. The one-tissue compartment model underestimates K1 but yields more robust values. The distribution volumes calculated with both models contain a similar amount of information. None of the parameters reflected serotonergic transporter density in a true quantitative manner, as all were confounded by nonspecific binding.