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Dopamine D3 receptors (D3Rs) modulate neuronal activity in several brain regions including the hippocampus. Although previous studies reported that blocking D3Rs exerts pro-cognitive effects, their involvement in hippocampal synaptic function and memory in the healthy and aged brain has not been thoroughly investigated. We demonstrated that in adult wild type (WT) mice, D3R pharmacological blockade or genetic deletion as in D3 knock out (KO) mice, converted the weak form of long-term potentiation (LTP1) into the stronger long-lasting LTP (LTP2) via the cAMP/PKA pathway, and allowed the formation of long-term memory. D3R effects were mainly mediated by post-synaptic mechanisms as their blockade enhanced basal synaptic transmission (BST), AMPAR-mediated currents, mEPSC amplitude, and the expression of the post-synaptic proteins PSD-95, phospho(p)GluA1 and p-CREB. Consistently, electron microscopy revealed a prevalent expression of D3Rs in post-synaptic dendrites. Interestingly, with age, D3Rs decreased in axon terminals while maintaining their levels in post-synaptic dendrites. Indeed, in aged WT mice, blocking D3Rs reversed the impairment of LTP, BST, memory, post-synaptic protein expression, and PSD length. Notably, aged D3-KO mice did not exhibit synaptic and memory deficits. In conclusion, we demonstrated the fundamental role of D3Rs in hippocampal synaptic function and memory, and their potential as a therapeutic target to counteract the age-related hippocampal cognitive decline.

Several studies including ours reported the detrimental effects of extracellular tau oligomers (ex-oTau) on glutamatergic synaptic transmission and plasticity. Astrocytes greatly internalize ex-oTau whose intracellular accumulation alters neuro/gliotransmitter handling thereby negatively affecting synaptic function. Both amyloid precursor protein (APP) and heparan sulfate proteoglycans (HSPGs) are required for oTau internalization in astrocytes but the molecular mechanisms underlying this phenomenon have not been clearly identified yet. Here we found that a specific antibody anti-glypican 4 (GPC4), a receptor belonging to the HSPG family, significantly reduced oTau uploading from astrocytes and prevented oTau-induced alterations of Ca2+-dependent gliotransmitter release. As such, anti-GPC4 spared neurons co-cultured with astrocytes from the astrocyte-mediated synaptotoxic action of ex-oTau, thus preserving synaptic vesicular release, synaptic protein expression and hippocampal LTP at CA3-CA1 synapses. Of note, the expression of GPC4 depended on APP and, in particular, on its C-terminal domain, AICD, that we found to bind Gpc4 promoter. Accordingly, GPC4 expression was significantly reduced in mice in which either APP was knocked-out or it contained the non-phosphorylatable amino acid alanine replacing threonine 688, thus becoming unable to produce AICD. Collectively, our data indicate that GPC4 expression is APP/AICD-dependent, it mediates oTau accumulation in astrocytes and the resulting synaptotoxic effects.

Aims Early dysfunction in Alzheimer's disease (AD) is characterised by alterations of synapse structure and function leading to dysmorphic neurites, decreased spine density, impaired synaptic plasticity and cognitive deficits. The class II member HDAC4, which recently emerged as a crucial factor in shaping synaptic plasticity and memory, was found to be altered in AD. We investigated how the modulation of HDAC4 may contribute to counteracting AD pathogenesis. Methods Using a cytoplasmic HDAC4 mutant (HDAC4(SD)), we studied the recovery of synaptic function in hippocampal tissue and primary neurons from the triple-transgenic mouse model of AD (3xTg-AD). Results Here, we report that in wild-type mice, HDAC4 is localised at synapses and interacts with postsynaptic proteins, whereas in the 3xTg-AD, it undergoes nuclear import, reducing its interaction with synaptic proteins. Of note, HDAC4 delocalisation was induced by both amyloid-beta and tau accumulation. Overexpression of the HDAC4(SD) mutant in CA1 pyramidal neurons of organotypic hippocampal slices obtained from 3xTg-AD mice increased dendritic length and promoted the enrichment of N-cadherin, GluA1, PSD95 and CaMKII proteins at the synaptic level compared with AD neurons transfected with the empty vector. Moreover, HDAC4 overexpression recovered the level of SUMO2/3ylation of PSD95 in AD hippocampal tissue, and in AD organotypic hippocampal slices, the HDAC4(SD) rescued spine density and synaptic transmission. Conclusions These results highlight a new role of cytoplasmic HDAC4 in providing a structural and enzymatic regulation of postsynaptic proteins. Our findings suggest that controlling HDAC4 localisation may represent a promising strategy to rescue synaptic function in AD, potentially leading to memory improvement.

Aims In the present study, we aimed to develop a percutaneous approach and a reproducible methodology for the isolation and expansion of Cardiac Progenitor Cells (CPCs) from EndoMyocardial Biopsies (EMB) in vivo. Moreover, in an animal model of non-ischemic heart failure (HF), we would like to test whether CPCs obtained by this methodology may engraft the myocardium and differentiate. Methods and results EMB were obtained using a preformed sheath and a disposable bioptome, advanced via right femoral vein in 12 healthy mini pigs, to the right ventricle. EMB were enzymatically dissociated, cells were expanded and sorted for c-kit. We used 3D-Electro-Anatomic Mapping (3D-EAM) to obtain CPCs from 32 patients affected by non-ischemic cardiomyopathy. The in vivo regenerative potential of CPCs was tested in a rodent model of drug-induced non-ischemic cardiomyopathy. c-kit positive CPCs replicative capacity was assessed in 30 patients. Telomere length averaged 7.4 ± 0.4 kbp and telomerase activity was present in all preparations (1.7 × 105copies). The in situ hybridization experiments showed that injected human CPCs may acquire a neonatal myocyte phenotype given the expression of the alpha-sarcomeric actin together with the presence of the Alu probe, suggesting a beneficial impact on LV performance. Conclusions The success in obtaining CPCs characterized by high regenerative potential, in vitro and in vivo, from EMB indicates that harvesting without thoracotomy in patients affected by either ischemic or non-ischemic cardiomyopathy is feasible. These initial results may potentially expand the future application of CPCs to all patients affected by HF not undergoing surgical procedures.

Tau is a microtubule-associated protein exerting several physiological functions in neurons. In Alzheimer’s disease (AD) misfolded tau accumulates intraneuronally and leads to axonal degeneration. However, tau has also been found in the extracellular medium. Recent studies indicated that extracellular tau uploaded from neurons causes synaptic dysfunction and contributes to tau pathology propagation. Here we report novel evidence that extracellular tau oligomers are abundantly and rapidly accumulated in astrocytes where they disrupt intracellular Ca2+ signaling and Ca2+-dependent release of gliotransmitters, especially ATP. Consequently, synaptic vesicle release, the expression of pre- and post-synaptic proteins, and mEPSC frequency and amplitude were reduced in neighboring neurons. Notably, we found that tau uploading from astrocytes required the amyloid precursor protein, APP. Collectively, our findings suggests that astrocytes play a critical role in the synaptotoxic effects of tau via reduced gliotransmitter availability, and that astrocytes are major determinants of tau pathology in AD.

Circulating Endothelial Progenitor Cells (EPCs) were discovered by Asahara et al in 1997 and defined as bone marrow CD34+/KDR+ cells endowed with angiogenic potentialities in vitro and in vivo. The most likely assumption is that EPCs consist of several cell subpopulations with functions targeted at accomplishing the post-natal neovascularization process in a synergic and complementary fashion. Indeed, the subsequent identification of numerous and differentiated hematic populations, characterized by the capacity to develop an endothelial phenotype, has posed a number of questions as to the real identity of EPCs. This concept does not represent a sterile speculation but rather it suggests important implications for the future practice of stem cell therapy. The aim of this report was to explore through a critical analysis the two main experimental methodologies, in vitro culture and flow cytometry, applied to EPCs, followed by a brief revaluation of the endothelial progenitors employing a globally functional approach.

In recent years, much effort has been devoted to identifying stimuli capable of enhancing adult neurogenesis, a process that generates new neurons throughout life, and that appears to be dysfunctional in the senescent brain and in several neuropsychiatric and neurodegenerative diseases. We previously reported that in vivo exposure to extremely low-frequency electromagnetic fields (ELFEFs) promotes the proliferation and neuronal differentiation of hippocampal neural stem cells (NSCs) that functionally integrate in the dentate gyrus. Here, we extended our studies to specifically assess the influence of ELFEFs on hippocampal newborn cell survival, which is a very critical issue in adult neurogenesis regulation. Mice were injected with 5-bromo-2'-deoxyuridine (BrdU) to label newborn cells, and were exposed to ELFEFs 9 days later, when the most dramatic decrease in the number of newly generated neurons occurs. The results showed that ELFEF exposure (3.5 h/day for 6 days) enhanced newborn neuron survival as documented by double staining for BrdU and doublecortin, to identify immature neurons, or NeuN labeling of mature neurons. The effects of ELFEFs were associated with enhanced spatial learning and memory. In an in vitro model of hippocampal NSCs, ELFEFs exerted their pro-survival action by rescuing differentiating neurons from apoptotic cell death. Western immunoblot assay revealed reduced expression of the pro-apoptotic protein Bax, and increased levels of the anti-apoptotic protein Bcl-2, in the hippocampi of ELFEF-exposed mice as well as in ELFEF-exposed NSC cultures, as compared with their sham-exposed counterparts. Our results may have clinical implications for the treatment of impaired neurogenesis associated with brain aging and neurodegenerative diseases.

Among the multiple factors concurring to Alzheimer's disease (AD) pathogenesis, greater attention should be devoted to the role played by infectious agents. Growing epidemiological and experimental evidence suggests that recurrent herpes simplex virus type-1 (HSV-1) infection is a risk factor for AD although the underlying molecular and functional mechanisms have not been fully elucidated yet. Here, we review literature suggesting the involvement of HSV-1 infection in AD also briefly mentioning possible pharmacological implications of these findings.

In recent years, much effort has been devoted to identifying stimuli capable of enhancing adult neurogenesis, a process that generates new neurons throughout life, and that appears to be dysfunctional in the senescent brain and in several neuropsychiatric and neurodegenerative diseases. We previously reported that in vivo exposure to extremely low-frequency electromagnetic fields (ELFEFs) promotes the proliferation and neuronal differentiation of hippocampal neural stem cells (NSCs) that functionally integrate in the dentate gyrus. Here, we extended our studies to specifically assess the influence of ELFEFs on hippocampal newborn cell survival, which is a very critical issue in adult neurogenesis regulation. Mice were injected with 5-bromo-2'-deoxyuridine (BrdU) to label newborn cells, and were exposed to ELFEFs 9 days later, when the most dramatic decrease in the number of newly generated neurons occurs. The results showed that ELFEF exposure (3.5 h/day for 6 days) enhanced newborn neuron survival as documented by double staining for BrdU and doublecortin, to identify immature neurons, or NeuN labeling of mature neurons. The effects of ELFEFs were associated with enhanced spatial learning and memory. In an in vitro model of hippocampal NSCs, ELFEFs exerted their pro-survival action by rescuing differentiating neurons from apoptotic cell death. Western immunoblot assay revealed reduced expression of the pro-apoptotic protein Bax, and increased levels of the anti-apoptotic protein Bcl-2, in the hippocampi of ELFEF-exposed mice as well as in ELFEF-exposed NSC cultures, as compared with their sham-exposed counterparts. Our results may have clinical implications for the treatment of impaired neurogenesis associated with brain aging and neurodegenerative diseases.