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Background: Growing evidence points to altered metabolic signals as a risk factor for Alzheimer's disease (AD). The high fatty acid levels and brain insulin resistance (BIR) found in AD brains may impinge on protein S‐palmitoylation, which is a post‐translational modification critically involved in the regulation of neuronal protein localization and synaptic function. Our previous findings highlighted the critical role of aberrant palmitoylation in BIR‐dependent memory impairment (Spinelli et al., 2017). Method: We analyzed both the expression of palmitoyl‐transferase enzymes (zDHHCs) in mouse AD brains and S‐palmitoylation levels of key proteins in human AD brains. We also tested the effect of chronic intranasal injection of the palmitoylation inhibitor 2‐bromopalmitate (2BP) on a large cohort of male and female 3xTg‐AD mice, starting from 3 months of age, by performing cognitive (novel object recognition and object displacement tests), electrophysiological (LTP), immunohistochemical (Abeta deposition) and molecular analyses (Abeta measurement by ELISA). Finally, we investigated the effects of lentiviral particles‐mediated zDHHC7 or zDHHC21 silencing in the hippocampus of 3xTg‐AD. Result: We found increased levels of zDHHC7 and zDHHC21 in the hippocampus of 3xTg‐AD mice and aberrant palmitoylation of key enzymes triggering beta amyloid aggregation in human AD brains. 2BP delayed the onset of memory deficits in both male and female 3xTg‐AD mice. More importantly, 2BP significantly enhanced cognitive performances in 6‐, 9‐ and 12‐month‐old animals. Accordingly, electrophysiological analyses on hippocampal brain slices from 2BP‐treated 3xTg‐AD mice revealed greater long‐term potentiation at CA3‐CA1 synapses. In addition, both 2BP‐treated male and female mice showed lower Abeta deposition in hippocampus and a significant extension of lifespan. Finally, genetic inhibition of palmitoyl transferase zDHHC7 reverted the aberrant palmitoylation of proteins involved in synaptic plasticity and APP metabolism, and counteracted the onset of neurodegeneration and cognitive deficits in 3xTg‐AD mice. Conclusion: This is the first preclinical study on the effect of 2BP treatment on AD‐related cognitive decline. Our data indicate that aberrant palmitoylation plays a critical role in the onset and progression of AD and unveil the potential druggable role of zDHHC enzymes in dementia‐related neurodegenerative disorders. [ABSTRACT FROM AUTHOR]

Background: The failure of cholinergic transmission and the increase of amyloid‐β peptide (Aβ) and tau protein are key players in Alzheimer's disease (AD). The interaction between α7 nicotinic acetylcholine receptors (α7‐nAChRs) and Aβ has been previously investigated, but few studies have focused on the crosstalk between α7‐nAChRs and tau. We previously reported that Aβ and tau might act independently or concomitantly to impair synaptic plasticity and memory, converging onto common targets such as amyloid precursor protein (APP). Here we investigated the role of α7‐nAChRs on tau‐mediated impairment of synaptic plasticity and memory, tau neuropathology, and their interplay with APP. Method: We used WT (C57Bl6/J) and α7 KO at different ages. 3XTg models of AD were used as positive controls. We performed electrophysiology to investigate synaptic transmission and plasticity at the CA3‐CA1 synapses from hippocampal slices, and behavioral studies (Novel Object Recognition and Location, Fear Conditioning) to evaluate memory. We used western blot for the expression of APP, tau (Ser199, Ser396, Thr205) and GSK‐3β (Ser9) phosphorylation. Formation of tau paired helical filaments (PHFs) and neurofibrillary tangles (NFTs) were evaluated by immunohistochemistry and Bielschowsky staining. Immunoreactivity for NeuN was measured to assess neuronal loss. Result: We found that α7 KO mice presented an AD phenotype characterized by the impairment of Long‐Term Potentiation and Paired Pulse Facilitation, and the reduction of different types of memory starting at 12 months of age. This age‐dependent phenotype was paralleled by an increase of APP expression, hyperphosphorylation of tau, and a decrease of GSK‐3β (Ser9) phosphorylation. α7 KO hippocampi presented a marked tau neuropathology with an increase of PHF‐1 immunoreactivity, the presence of PHFs and NFTs, and neuronal loss. Conclusion: In summary, the lack of α7‐nAChRs was sufficient to trigger an AD‐like phenotype characterized by a marked tau pathology. Our data also suggest that the concomitant increase of APP expression might contribute to tau neurotoxicity. [ABSTRACT FROM AUTHOR]

Background: Dopamine D3 receptors (D3‐Rs) are involved in several functions such as reward and social behavior and they have been proposed as a therapeutical target for addiction, schizophrenia, and Parkinson's disease. However, the role of D3‐Rs in cognition has been poorly investigated, with few studies demonstrating that the activation of D3‐Rs impairs attention and working memory. Results obtained in our laboratory suggested that D3 inhibition exerts a pro‐cognitive effect on long term potentiation (LTP) and recognition memory on healthy wild‐type (WT) mice. Based on these findings, here, we aimed to investigate whether the positive effect shown by D3 inhibition at the synapse could be exploited to counteract the synaptic plasticity and memory impairment found in aged and AD mice. Method: We used D3 knock out (D3‐KO), WT at 18‐22 months of age as a physiological model of aging, the 3XTg transgenic mouse model of AD and a7 KO mice, recently found to present an AD‐like phenotype. The pharmacological inhibition of D3‐Rs was obtained with the selective antagonist NGB‐2904. To test whether the pharmacological inhibition of D3‐Rs or their genetic deletion could rescue LTP and memory impairment, we performed electrophysiological recordings at CA3‐CA1 synapses in hippocampal slices and behavioral experiments of novel object recognition, novel object location and Morris Water Maze. Result: We found that D3‐Rs antagonism rescued the impairment of LTP, and different forms of memory in aged WT mice. Consistently, aged D3 KO mice showed no alteration of LTP and memory, suggesting that the genetic deletion of D3 receptors prevented the synaptic plasticity and memory decline that occurs with aging. The pharmacological inhibition of D3‐Rs was also able to rescue the memory impairment in both 3XTg and a7 KO mice. Conclusion: In conclusion, our findings suggest that the pro‐cognitive effect exerted by D3‐Rs inhibition or genetic deletion could represent a viable therapeutic strategy to treat the cognitive dysfunction occurring during aging and AD. [ABSTRACT FROM AUTHOR]

Background: Growing evidence points to altered metabolic signals as a risk factor for Alzheimer's disease (AD). The high fatty acid levels and brain insulin resistance (BIR) found in AD brains may impinge on protein palmitoylation (P‐S‐palm), a post‐translational modification critically involved in the regulation of neuronal protein localization and synaptic function. Our previous findings highlighted the critical role of aberrant palmitoylation in BIR‐dependent memory impairment (Spinelli et al., 2017). Method: We tested the effect of chronic intranasal injection of the palmitoylation inhibitor 2‐bromopalmitate (2BP) on a large cohort of male and female 3xTg‐AD mice, starting from 3 months of age, by performing cognitive (novel object recognition and object displacement tests), electrophysiological (LTP), immunohistochemical (Abeta deposition) and molecular analyses (Abeta measurement by ELISA). We also analyzed the palmitoyl‐proteome (by acyl biotin exchange assay and mass‐spectrometry) in the hippocampus of 9‐month‐old wild type, 3xTg‐AD and 2BP‐treated 3xTg‐AD mice. Result: 2BP delayed the onset of memory deficits in both male and female 3xTg‐AD mice. More importantly, 2BP significantly enhanced cognitive performances in 6‐, 9‐ and 12‐month‐old animals. Accordingly, electrophysiological analyses on hippocampal brain slices from 2BP‐treated 3xTg‐AD mice revealed greater long‐term potentiation at CA3‐CA1 synapses. In addition, 2BP mice showed lower Abeta deposition in hippocampus. Finally, palmitoyl‐proteome analysis revealed a large number of proteins involved in APP and tau metabolism, synaptic plasticity and brain metabolism aberrantly palmitoylated in the AD mouse model and reverted by 2BP. Conclusion: Our data indicate that aberrant palmitoylation plays a critical role in the onset and progression of AD and reveal novel targets of protein palmitoylation potentially involved in the development of neurodegeneration and dementia. This is also the first preclinical study on the effect of 2BP on AD‐related cognitive decline. [ABSTRACT FROM AUTHOR]