Daniele Tolomeo

The Continuing Failure of Bexarotene in Alzheimer's Disease Mice.

Alzheimers disease (AD) is the most common form of dementia characterized by synaptic dysfunction, memory loss, neuroinflammation, and neuronal cell death. Amyloid-β (Aβ), recognized as the main culprit of AD, aggregates and accumulates in the extracellular compartment as neuritic plaques, after deregulation of its production or clearance. Apolipoprotein E (ApoE) plays a major role in Aβ clearance and its expression is transcriptionally regulated by the liver X receptor and retinoid X receptors (RXRs) system. Bexarotene (BEXA), an RXR agonist that increases ApoE expression and microglia phagocytosis has been proposed as a promising therapy for AD, resolving both the amyloid pathology and memory loss. Despite the first compelling report, however, multiple failures have been documented, raising concern about whether BEXA could in fact become a novel disease-modifying strategy for AD. To help clarify this, we investigated the effect of BEXA in vivo at multiple levels in TASTPM transgenic mice. Seven-day oral administration of BEXA to these mice did not achieve any significant memory improvement, plaque reduction, or enhancement of microglial cell activation. No differences were found when specifically investigating the microglial phagocytic state in vivo. In addition, a brain structural analysis with magnetic resonance did not detect any BEXA-mediated change in the volume reduction of the main affected brain areas in our mice. These results suggest that BEXA has no beneficial effects on the multi-factorial pathologic phenotype of AD mice.

Striatum and entorhinal cortex atrophy in AD mouse models: MRI comprehensive analysis

Alzheimers disease is experimentally modeled in transgenic (Tg) mice overexpressing mutated forms of the human amyloid precursor protein either alone or combined with mutated presenilins and tau. In the present study, we developed a systematic approach to compare double (TASTPM) and triple (APP/PS2/Tau) Tg mice by serial magnetic resonance imaging and spectroscopy analysis from 4 to 26 months of age to define homologous biomarkers between mice and humans. Hippocampal atrophy was found in Tg mice compared with WT. In APP/PS2/Tau the effect was age-dependent, whereas in TASTPM it was detectable from the first investigated time point. Importantly, both mice displayed an age-related entorhinal cortex thinning and robust striatal atrophy, the latter associated with a significant loss of synaptophysin. Hippocampal magnetic resonance spectroscopy revealed lower glutamate levels in both Tg mice and a selective myo-inositol increase in TASTPM. This noninvasive magnetic resonance imaging analysis, revealed common biomarkers between humans and mice, and could, thus, be promoted as a fully translational tool to be adopted in the preclinical investigation of therapeutic approaches.

Multifunctional liposomes delay phenotype progression and prevent memory impairment in a presymptomatic stage mouse model of Alzheimer disease

ABSTRACT The failure of clinical trials largely focused on mild to moderate stages of Alzheimer disease has suggested to the scientific community that the effectiveness of Amyloid‐&bgr; (A&bgr;)‐centered treatments should be evaluated starting as early as possible, well before irreversible brain damage has occurred. Accordingly, also the preclinical development of new therapies should be carried out taking into account this suggestion. In the present investigation we evaluated the efficacy of a treatment with liposomes multifunctionalized for crossing the blood‐brain barrier and targeting A&bgr;, carried out on young APP/PS1 Tg mice, taken as a model of pre‐symptomatic disease stage. Liposomes were administered once a week to Tg mice for 7 months, starting at the age of 5 months and up to the age of 12 when they display AD‐like cognitive and brain biochemical/anatomical features. The treatment prevented the onset of the long‐term memory impairment and slowed down the deposition of brain A&bgr;; at anatomical level, prevented both ventricle enlargement and entorhinal cortex thickness reduction, otherwise occurring in untreated mice. Strikingly, these effects were maintained 3 months after treatment discontinuation. An increase of A&bgr; levels in the liver was detected at the end of the treatment, then followed also by reduction of brain Amyloid Precursor Protein and increase of A&bgr;‐degrading enzymes. These results suggest that the treatment promotes brain A&bgr; clearance by a peripheral ‘sink’ effect and ultimately affects A&bgr; turnover in the brain. Worth of note, the treatment was apparently not toxic for all the organs analyzed, in particular for brain, as suggested by the lower brain TNF‐&agr; and MDA levels, and by higher level of SOD activity in treated mice. Together, these findings promote a very early treatment with multi‐functional liposomes as a well‐tolerated nanomedicine‐based approach, potentially suitable for a disease‐modifying therapy of AD, able to delay or prevent relevant features of the disease.

Single severe traumatic brain injury produces progressive pathology with ongoing contralateral white matter damage one year after injury

ABSTRACT There is increasing recognition that traumatic brain injury (TBI) may initiate long‐term neurodegenerative processes, particularly chronic traumatic encephalopathy. However, insight into the mechanisms transforming an initial biomechanical injury into a neurodegenerative process remain elusive, partly as a consequence of the paucity of informative pre‐clinical models. This study shows the functional, whole brain imaging and neuropathological consequences at up to one year survival from single severe TBI by controlled cortical impact in mice. TBI mice displayed persistent sensorimotor and cognitive deficits. Longitudinal T2 weighted magnetic resonance imaging (MRI) showed progressive ipsilateral (il) cortical, hippocampal and striatal volume loss, with diffusion tensor imaging demonstrating decreased fractional anisotropy (FA) at up to one year in the il‐corpus callosum (CC: −30%) and external capsule (EC: −21%). Parallel neuropathological studies indicated reduction in neuronal density, with evidence of microgliosis and astrogliosis in the il‐cortex, with further evidence of microgliosis and astrogliosis in the il‐thalamus. One year after TBI there was also a decrease in FA in the contralateral (cl) CC (−17%) and EC (−13%), corresponding to histopathological evidence of white matter loss (cl‐CC: −68%; cl‐EC: −30%) associated with ongoing microgliosis and astrogliosis. These findings indicate that a single severe TBI induces bilateral, long‐term and progressive neuropathology at up to one year after injury. These observations support this model as a suitable platform for exploring the mechanistic link between acute brain injury and late and persistent neurodegeneration. Graphical abstract Figure. No Caption available. HighlightsLongitudinal effects of single severe TBI by controlled cortical impact were examined.TBI triggers an evolving damage that at chronic stages spreads to the contralateral hemisphere.Contralateral pathology at one year post TBI, shows a prominent involvement of white matter with ongoing neuroinflammation.Findings support the model for studies interrogating the link between biomechanical impact and late neurodegeneration.

PERK inhibition delays neurodegeneration and improves motor function in a mouse model of Marinesco-Sjögren syndrome

Marinesco-Sjögren syndrome (MSS) is a rare, early onset, autosomal recessive multisystem disorder characterized by cerebellar ataxia, cataracts and myopathy. Most MSS cases are caused by loss-of-function mutations in the gene encoding SIL1, a nucleotide exchange factor for the molecular chaperone BiP which is essential for correct protein folding in the endoplasmic reticulum. Woozy mice carrying a spontaneous Sil1 mutation recapitulate key pathological features of MSS, including cerebellar atrophy with degeneration of Purkinje cells and progressive myopathy. Because the PERK branch of the unfolded protein response is activated in degenerating neurons of woozy mice, and inhibiting PERK-mediated translational attenuation has shown protective effects in protein-misfolding neurodegenerative disease models, we tested the therapeutic efficacy of GSK2606414, a potent inhibitor of PERK. Mice were chronically treated with GSK2606414 starting from a presymptomatic stage, and the effects were evaluated on biochemical, histopathological and clinical readouts. GSK2606414 delayed Purkinje cell degeneration and the onset of motor deficits, prolonging the asymptomatic phase of the disease; it also reduced the skeletal muscle abnormalities and improved motor performance during the symptomatic phase. The protein but not the mRNA level of ORP150, a nucleotide exchange factor which can substitute for SIL1, was increased in the cerebellum of GSK2606414-treated woozy mice, suggesting that translational recovery promoted the synthesis of this alternative BiP co-factor. Targeting PERK signaling may have beneficial disease-modifying effects in carriers of SIL1 mutations.

Chemical exchange saturation transfer MRI shows low cerebral 2-deoxy-D-glucose uptake in a model of Alzheimer’s Disease

Glucose is the central nervous system’s only energy source. Imaging techniques capable to detect pathological alterations of the brain metabolism are useful in different diagnostic processes. Such techniques are also beneficial for assessing the evaluation efficacy of therapies in pre-clinical and clinical stages of diseases. Chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI) is a possible alternative to positron emission tomography (PET) imaging that has been widely explored in cancer research in humans and animal models. We propose that pathological alterations in brain 2-deoxy-D-glucose (2DG) uptake, typical of neurodegenerative diseases, can be detected with CEST MRI. Transgenic mice overexpressing a mutated form of amyloid precusrsor protein (APP23), a model of Alzheimer’s disease, analyzed with CEST MRI showed a clear reduction of 2DG uptake in different brain regions. This was reminiscent of the cerebral condition observed in Alzheimer’s patients. The results indicate the feasibility of CEST for analyzing the brain metabolic state, with better image resolution than PET in experimental models.

MAGNETIC RESONANCE IMAGING AND ALZHEIMER'S DISEASE: A LONGITUDINAL STUDY OF STRUCTURAL CHANGES IN DIFFERENT TRANSGENIC MODELS

Alessandra Paladini, Edoardo Micotti, Angelisa Frasca, Daniele Tolomeo, Moira Marizzoni, Anna Caroli, Claudia Balducci, Sophie Dix, Michael O’Neill, Ozmen Laurence, Christian Czech, Jill Richardson, Giovanni B. Frisoni, Gianluigi Forloni, Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy; IRCCS Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy; 3 IRCCS Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy; 4 IRCCS San Giovanni di Dio Fatebenefratelli, Brescia, Italy; Eli Lilly, Lilly Research Centre, Surrey, United Kingdom; Eli Lilly, Lilly Research Centre, Windlesham, United Kingdom; 7 CNS Research, Hoffmann-La Roche AG, Basel, Switzerland; 8 GlaxoSmithKline, Stevenage, United Kingdom; 9 IRCCS San Giovanni di Dio Fatebenefratelli, Brescia, Italy. Contact e-mail: forloni@ marionegri.it