ABSTRACT
Down syndrome (DS) is the most frequent genetic cause of intellectual disability including hippocampal-dependent memory deficits. We have previously reported hippocampal mTOR (mammalian target of rapamycin) hyperactivation, and related plasticity as well as memory deficits in Ts1Cje mice, a DS experimental model. Here we characterize the proteome of hippocampal synaptoneurosomes (SNs) from these mice, and found a predicted alteration of synaptic plasticity pathways, including long term depression (LTD). Accordingly, mGluR-LTD (metabotropic Glutamate Receptor-LTD) is enhanced in the hippocampus of Ts1Cje mice and this is correlated with an increased proportion of a particular category of mushroom spines in hippocampal pyramidal neurons. Remarkably, prenatal treatment of these mice with rapamycin has a positive pharmacological effect on both phenotypes, supporting the therapeutic potential of rapamycin/rapalogs for DS intellectual disability.
Subject(s)
Dendritic Spines/metabolism , Dendritic Spines/pathology , Down Syndrome/pathology , Down Syndrome/physiopathology , Long-Term Synaptic Depression , Receptors, Metabotropic Glutamate/metabolism , Sirolimus/pharmacology , Animals , Dendritic Spines/drug effects , Disease Models, Animal , Fragile X Mental Retardation Protein/metabolism , Hippocampus/drug effects , Hippocampus/metabolism , Hippocampus/pathology , Hippocampus/physiopathology , Long-Term Synaptic Depression/drug effects , Mice, Transgenic , Mitochondrial Proteins/metabolism , Neuronal Plasticity/drug effects , Proteomics , Pyramidal Cells/drug effects , Pyramidal Cells/metabolism , Pyramidal Cells/pathology , Synapses/drug effects , Synapses/metabolismABSTRACT
Despite the daily consumption of copper chlorophylls (E-141i), the green food colorants in foods high in fats, there is a general need for knowledge regarding their exact composition. Consequently, we have analyzed by HPLC-ESI(+)/APCI(+)-hrTOF-MS2 the accurate composition of different commercial copper chlorophyll colorants for the first time. Data showed a favored yield of copper pheophytins from a series, while pheophytins from b series are preferentially no complexed with copper. The copper pheophytins present in the food colorants consisted mainly of three structural rearrangements. New fragmentation patterns and structural assignments have been described for several copper pheophytins. During the ingestion of copper chlorophylls, no chlorophyll derivative was present in serum nor urine except a new copper-pyroporphyrin a accumulated in a few livers. In any case, this green additive could represent the ideal food colorant, as most of the copper pheophytins are excreted in the feces showing almost no absorption of copper-chlorophylls compounds.
Subject(s)
Chlorophyllides/pharmacokinetics , Food Coloring Agents/chemistry , Food Coloring Agents/pharmacokinetics , Administration, Oral , Animals , Chlorophyllides/analysis , Chlorophyllides/chemistry , Chromatography, High Pressure Liquid , Copper/chemistry , Food Coloring Agents/analysis , Liver/drug effects , Liver/metabolism , Mass Spectrometry , Mice, Inbred C57BL , Pheophytins/chemistry , Pheophytins/pharmacokinetics , Spectrometry, Mass, Electrospray IonizationABSTRACT
SCOPE: The dietary intake of chlorophylls is estimated to be ≈50 mg d-1 . However, their first pass metabolism and systemic assimilation is not well characterized. METHODS AND RESULTS: A group of 30 mice are fed a diet rich in chlorophylls, while 10 mice received a standard diet without chlorophylls (control group). Liver extracts are analyzed every 15 days by HPLC-ESI(+)/APCI(+)-hrTOF- MS/MS to measure the accretion of specific chlorophyll metabolites. The chlorophyll profile found in the livers of mice fed a chlorophyll-rich diet shows that the formation and/or absorption of pheophorbides, pyro-derivatives, and phytyl-chlorin e6 require the occurrence of a precise first-pass metabolism. In addition, the apical absorption of pheorphorbide a-rich micelles is significantly inhibited in Caucasian colon adenocarcinoma-2 cells pre-incubated with BLT1. CONCLUSION: Pheophorbide a absorption is, at least partly, protein-mediated through SR-BI. This active absorption process could explain the specific accumulation of pheophorbide a in the livers of animals fed a chlorophyll-rich diet. A complementary mechanism could be the de-esterification of pheophytin a in the liver, yielding pheophorbide a and phytol, which can explain the origin of phytol in the liver. Hence, the results suggest two molecular mechanisms responsible for the accumulation of the health-promoting compounds pheophorbide and phytol.
Subject(s)
Chlorophyll/analogs & derivatives , Chlorophyll/pharmacokinetics , Animals , Caco-2 Cells , Chlorophyll/analysis , Chlorophyll/metabolism , Cyclopentanes/pharmacology , Diet , Feces/chemistry , Humans , Liver/drug effects , Liver/metabolism , Male , Mice, Inbred C57BL , Pigments, Biological/analysis , Pigments, Biological/chemistry , Scavenger Receptors, Class B/antagonists & inhibitors , Scavenger Receptors, Class B/metabolism , Spirulina/chemistry , Thiosemicarbazones/pharmacology , Tissue DistributionABSTRACT
Several proteomic analyses have been performed on synaptic fractions isolated from cortex or even total brain, resulting in preparations with a high synaptic heterogeneity and complexity. Synaptoneurosomes (SNs) are subcellular membranous elements that contain sealed pre- and post-synaptic components. They are obtained by subcellular fractionation of brain homogenates and serve as a suitable model to study many aspects of the synapse physiology. Here the proteomic content of SNs isolated from hippocampus of adult mice, a brain region involved in memory that presents lower synaptic heterogeneity than cortex, is reported. Interestingly, in addition to pre- and post-synaptic proteins, proteins involved in RNA binding and translation are overrepresented in this preparation. These results validate the protocol previously reported for SNs isolation, and, as reported by other authors, highlight the relevance of local synaptic translation for hippocampal physiology.
Subject(s)
Dendrites/metabolism , Hippocampus/metabolism , Nerve Tissue Proteins/metabolism , Neurons/metabolism , Protein Biosynthesis , Proteome/analysis , Synaptosomes/metabolism , Animals , MiceABSTRACT
Down's syndrome (DS) is the most prevalent genetic intellectual disability. Memory deficits significantly contribute to the cognitive dysfunction in DS. Previously, we discovered that mTOR-dependent local translation, a pivotal process for some forms of synaptic plasticity, is deregulated in a DS mouse model. Here, we report that these mice exhibit deficits in both synaptic plasticity (i.e., BDNF-long term potentiation) and the persistence of spatial long-term memory. Interestingly, these deficits were fully reversible using rapamycin, a Food and Drug Administration-approved specific mTOR inhibitor; therefore, rapamycin may be a novel pharmacotherapy to improve cognition in DS.
Subject(s)
Brain-Derived Neurotrophic Factor/metabolism , Down Syndrome/drug therapy , Long-Term Potentiation/drug effects , Memory, Long-Term/drug effects , Nootropic Agents/pharmacology , Sirolimus/pharmacology , Animals , CA1 Region, Hippocampal/drug effects , CA1 Region, Hippocampal/physiopathology , Disease Models, Animal , Down Syndrome/physiopathology , Down Syndrome/psychology , Long-Term Potentiation/physiology , Male , Maze Learning/drug effects , Maze Learning/physiology , Memory Disorders/drug therapy , Memory, Long-Term/physiology , Mice, Inbred C3H , Mice, Inbred C57BL , Mice, Transgenic , Spatial Memory/drug effects , Spatial Memory/physiology , Synaptic Transmission/drug effects , Synaptic Transmission/physiology , TOR Serine-Threonine Kinases/antagonists & inhibitors , TOR Serine-Threonine Kinases/metabolism , Tissue Culture TechniquesABSTRACT
An increasing amount of evidence suggests that the dysregulation of the Akt-mTOR (Akt-mammalian Target Of Rapamycin) signaling network is associated with intellectual disabilities, such as fragile X, tuberous sclerosis and Rett's syndrome. The Akt-mTOR pathway is involved in dendrite morphogenesis and synaptic plasticity, and it has been shown to modulate both glutamatergic and GABAergic synaptic transmission. We have recently shown that the AktmTOR pathway is hyperactive in the hippocampus of Ts1Cje mice, a model of Down's syndrome, leading to increased local dendritic translation that could interfere with synaptic plasticity. Rapamycin and rapalogs are specific inhibitors of mTOR, and some of these inhibitors are Food and Drug Administration-approved drugs. In this review, we discuss the molecular basis and consequences of Akt-mTOR hyperactivation in Down's syndrome, paying close attention to alterations in the molecular mechanisms underlying synaptic plasticity. We also analyze the pros and cons of using rapamycin/rapalogs for the treatment of the cognitive impairments associated with this condition.
