Innovative Molecular Imaging for Clinical Research, Therapeutic Stratification, and Nosography in Neuroscience.

Over the past few decades, several radiotracers have been developed for neuroimaging applications, especially in PET. Because of their low steric hindrance, PET radionuclides can be used to label molecules that are small enough to cross the blood brain barrier, without modifying their biological properties. As the use of 11C is limited by its short physical half-life (20 min), there has been an increasing focus on developing tracers labeled with 18F for clinical use. The first such tracers allowed cerebral blood flow and glucose metabolism to be measured, and the development of molecular imaging has since enabled to focus more closely on specific targets such as receptors, neurotransmitter transporters, and other proteins. Hence, PET and SPECT biomarkers have become indispensable for innovative clinical research. Currently, the treatment options for a number of pathologies, notably neurodegenerative diseases, remain only supportive and symptomatic. Treatments that slow down or reverse disease progression are therefore the subject of numerous studies, in which molecular imaging is proving to be a powerful tool. PET and SPECT biomarkers already make it possible to diagnose several neurological diseases in vivo and at preclinical stages, yielding topographic, and quantitative data about the target. As a result, they can be used for assessing patients' eligibility for new treatments, or for treatment follow-up. The aim of the present review was to map major innovative radiotracers used in neuroscience, and explain their contribution to clinical research. We categorized them according to their target: dopaminergic, cholinergic or serotoninergic systems, β-amyloid plaques, tau protein, neuroinflammation, glutamate or GABA receptors, or α-synuclein. Most neurological disorders, and indeed mental disorders, involve the dysfunction of one or more of these targets. Combinations of molecular imaging biomarkers can afford us a better understanding of the mechanisms underlying disease development over time, and contribute to early detection/screening, diagnosis, therapy delivery/monitoring, and treatment follow-up in both research and clinical settings

The alpha2C-adrenoceptor as a neuropsychiatric drug tar-get - PET studies in human subjects

Positron emission tomography imaging has both academic and applied uses in revealing the distribution and density of different molecular targets in the central nervous system. Following the significant progress made with the dopamine D2 receptor, advances have been made in developing PET tracers to allow analysis of receptor occupancy of many other receptor types as well as evaluating changes in endogenous synaptic transmitter concentrations of transmitters e.g. serotonin and noradrenaline. Noradrenergic receptors are divided into α1-, α2- and β-adrenoceptor subfamilies, in humans each of which is composed of three receptor subtypes. The α2-adrenoceptors have an important presynaptic auto-inhibitory function on noradrenaline release but they also have postsynaptic roles in modulating the release of other neurotransmitters, such as serotonin and dopamine. One of the subtypes, the α2C-adrenoceptor, has been detected at distinct locations in the central nervous system, most notably the dorsal striatum. Several serious neurological conditions causing dementia, Alzheimer’s disease and Parkinson’s disease have been linked to disturbed noradrenergic signaling. Furthermore, altered noradrenergic signaling has also been implicated in conditions like ADHD, depression, anxiety and schizophrenia. In order to benefit future research into these central nervous system disorders as well as being useful in the clinical development of drugs affecting brain noradrenergic neurotransmission, validation work of a novel tracer for positron emission tomography studies in humans was performed. Altogether 85 PET imaging experiments were performed during four separate clinical trials. The repeatability of [11C]ORM-13070 binding was tested in healthy individuals, followed by a study to evaluate the dose-dependent displacement of [11C]ORM-13070 from α2C-adrenoceptors by a competing ligand, and the final two studies examined the sensitivity of [11C]ORM-13070 binding to reflect changes in endogenous noradrenaline levels. The repeatability of [11C]ORM-13070 binding was very high. The binding properties of the tracer allowed for a reliable estimation of α2C-AR occupancy by using the reference tissue ratio method with low test-retest variability. [11C]ORM-13070 was dose-dependently displaced from its specific binding sites by the subtype-nonselective α2-adrenoceptor antagonist atipamezole, and thus it proved suitable for use in clinical drug development of novel α2C-adrenoceptor ligands e.g. to determine the best doses and dosing intervals for clinical trials. Convincing experimental evidence was gained to support the suitability of [11C]ORM-13070 for detecting an increase in endogenous synaptic noradrenaline in the human brain. Tracer binding in the thalamus tended to increase in accordance with reduced activity of noradrenergic projections from the locus coeruleus, although statistical significance was not reached. Thus, the investigation was unable to fully validate [11C]ORM-13070 for the detection of pharmacologically evoked reductions in noradrenaline levels.Siirretty Doriast

Alzheimer's disease as a metabolic pathology: new approaches

Treballs Finals de Grau de Farmàcia, Facultat de Farmàcia i Ciències de l'Alimentació, Universitat de Barcelona, 2018. Tutora: Marta Alegret.[eng] Alzheimer’s disease (AD) is the most common cause of dementia and it has been estimated that the number of people suffering it is going to keep growing. AD is a chronic neurodegenerative disease that drives to a loss of connection between nerve cells and finally to their death. Although people are unlikely to experience the condition in exactly the same way, some symptoms like memory loss, confusion and difficulty with language are very common. The etiology of this disease is heterogeneous and wide since a lot of risk factors have been described, including modifiable lifestyle-related factors like diet. Different pathophysiological mechanisms have been hypothesized to explain AD origin and development. The most known one is the “amyloid hypothesis”, but some data support that the onset of the disease might be related to a brain metabolism abnormality. The decreased metabolic activity may increase amyloid beta (Aβ) deposition as a secondary response, and this would lead to the death of neurons causing dementia. At present, the available AD treatments show only modest symptomatic benefits, so a different approach has been considered: a ketogenic diet (KD). It is a high saturated fat/low carbohydrate diet that increases ketogenic bodies. By doing this, the brain can obtain energy from a different source and not only glucose.[cat] La malaltia d’Alzheimer és la causa més comú de demència i s’estima que la incidència seguirà augmentant. És una malaltia crònica neurodegenerativa que desencadena una pèrdua de connexió entre les cèl·lules nervioses i la mort d’aquestes. Tot i la varietat interindividual en la simptomatologia, s’han descrit símptomes comuns com la pèrdua de memòria, la confusió o la dificultat en el llenguatge. L’etiologia de malaltia d’Alzheimer és heterogènia i àmplia ja que s’han descrit molts factors de risc, entre els quals es troben factors modificables com la dieta. Pel que fa a les bases fisiopatològiques, la hipòtesi més establerta és l’amiloide. Tot i això, diferents estudis conclouen que l’inici de la malaltia és realment una disfunció en el metabolisme cerebral. Aquesta disminució en l’activitat metabòlica del cervell provocaria una acumulació de la proteïna beta amiloide (Aβ) com a resposta secundària i això comportaria la mort de les neurones i la demència. Els tractaments actuals de la malaltia només milloren lleugerament els símptomes i per això s’ha proposat un nou enfocament: la dieta cetogènica. Aquesta dieta és alta en greixos saturats i baixa en carbohidrats i això provoca la formació de cossos cetònics. Aquestes molècules proporcionen al cervell una font d’energia diferent a la glucosa

The Effects of Aniracetam Treatment on Cognitive Performance and AMPA Receptor GluR2 Subunit Expression After Moderate Fluid Percussion Injury in Rats

In addition to the acute pathology produced by traumatic brain injury, there are chronic alterations that occur after the trauma, including a depressed state of neuronal activity (Feeney, 1991). This study included a preclinical testing of a novel treatment strategy focusing on increasing neuronal activity during the chronic hypofunctional posttraumatic stage. The present investigation tested the effects of repeated post-injury aniracetam administration on cognitive performance in the Morris water maze (MWM) and on the GluR2 - immunoreactivity and protein expression by Western blot analysis in the hippocampus. The first study examined the optimal dose of aniracetam in the MWM task. Animals received aniracetam (25 mg/kg, 50 mg/kg) or vehicle once daily for fifteen days and on days 11-15 were tested in the MWM. The results indicated that injured aniracetam-treated rats had a significant improvement in MWM performance compared to injured saline-treated animals. When the drug was delayed for 11 days post-injury in the second experiment, its beneficial effects were still present, as injured aniracetam-treated rats performed significantly better that injured saline treated rats on the MWM task. In the third experiment, chronic daily aniracetam administration was terminated after 15 days immediately before MWM testing on days 16-20. The results indicated that termination of aniracetam did not enhance MWM performance as injured terminated aniracetam-treated rats did not have significant improvement over injured saline-treated rats. In the fourth study we investigated the mechanism of aniracetam\u27s effects by examining the expression of the AMPA receptor GluR2 subunit, the only AMPA receptor subunit that is Ca++ impermeable. Using a monoclonal antibody selective for the GluR2 subunit, immunohistochemical results indicated that injured rats treated with aniracetam (50mg/kg for 15 days post-injury) had a slight reduction in the GluR2- IR. The fifth study investigated a change in the GluR2 protein expression in the hippocampus with a Western blot analysis. The results were consistent with the immunohistochemical study outcome as the injured vehicle and injured aniracetam treated animals showed a reduced protein expression in the hippocampus. The changes were not significantly different from the controls. The results of these experiments suggested that chronic aniracetam treatment significantly attenuated injury induced spatial memory deficits when administered continually during the hypofunctional posttraumatic stage and when the treatment was delayed for 11 days, but not when the treatment was terminated before the MWM testing. These effects suggest that the compound does not induce chronic receptor changes and has to be biologically active in an organism for it to exert its beneficial properties. Results from the present studies suggest that aniracetam may become a potential treatment option for brain injury induced cognitive deficits

Functional brain imaging in the dog : Single Photon Emission Tomography as a research and clinical tool for the investigation of canine brain physiology and pathophysiology

summary of doctoral dissertatio

Blood-Brain Barrier Abnormalities Caused by HIV-1 gp120: Mechanistic and Therapeutic Implications

The blood-brain barrier (BBB) is compromised in many systemic and CNS diseases, including HIV-1 infection of the brain. We studied BBB disruption caused by HIV-1 envelope glycoprotein 120 (gp120) as a model. Exposure to gp120, whether acute [by direct intra-caudate-putamen (CP) injection] or chronic [using SV(gp120), an experimental model of ongoing production of gp120] disrupted the BBB, and led to leakage of vascular contents. Gp120 was directly toxic to brain endothelial cells. Abnormalities of the BBB reflect the activity of matrix metalloproteinases (MMPs). These target laminin and attack the tight junctions between endothelial cells and BBB basal laminae. MMP-2 and MMP-9 were upregulated following gp120-injection. Gp120 reduced laminin and tight junction proteins. Reactive oxygen species (ROS) activate MMPs. Injecting gp120 induced lipid peroxidation. Gene transfer of antioxidant enzymes protected against gp120-induced BBB abnormalities. NMDA upregulates the proform of MMP-9. Using the NMDA receptor (NMDAR-1) inhibitor, memantine, we observed partial protection from gp120-induced BBB injury. Thus, (1) HIV-envelope gp120 disrupts the BBB; (2) this occurs via lesions in brain microvessels, MMP activation and degradation of vascular basement membrane and vascular tight junctions; (3) NMDAR-1 activation plays a role in this BBB injury; and (4) antioxidant gene delivery as well as NMDAR-1 antagonists may protect the BBB

Inhibition of prandial and waterspray-induced rat grooming by 8-OH-DPAT

The effects of 8-OH-DPAT treatment on rat grooming behaviour, elicited either prandially or in response to spraying with water were investigated. Dose (≤0.1 mg/kg s.c.) response studies employed momentary time sampling over 30 or 60 min with behaviour being scored in one of 6 or 7 (depending on food availability) mutually exclusive categories (feeding, active, scratching, face-grooming, body grooming, genital-grooming and resting) at 15 s intervals. In non-deprived rats, tested with wet mash available, feeding and activity frequencies were increased, but resting and total grooming were inhibited by 8-OH-DPAT. Face-, body- and genital-grooming occurred at higher levels than scratching, but all categories were reduced with reductions in scratching occurring at a lower dose (0.01 mg/kg). Misting rats with a fine water spray selectively increased body grooming and decreased activity without altering feeding, while 8-OH-DPAT increased feeding and reduced face-, body- and genital-grooming, without affecting already low levels of scratching. In misted rats, tested without food, 8-OH-DPAT reduced face-, body- and genital-grooming and increased resting. These results confirm i) that the water spray technique is a useful method for increasing grooming and ii) that 8-OH-DPAT has a suppressant effect on grooming independent of response competition from enhanced feeding

Nicotinic Acetylcholine Receptor Signaling in Neuroprotection

Alzheimer’s disease; Neurodegenerative diseases; Nicotine; Transporter; Gli