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ACS Omega May 2024Maternal separation (MS) represents a profound early life stressor with enduring impacts on neuronal development and adult cognitive function in both humans and rodents....
Maternal separation (MS) represents a profound early life stressor with enduring impacts on neuronal development and adult cognitive function in both humans and rodents. MS is associated with persistent dysregulations in neurotransmitter systems, including the serotonin (5-HT) pathway, which is pivotal for mood stabilization and stress-coping mechanisms. Although the novel cannabinoid receptor, GPR55, is recognized for its influence on learning and memory, its implications on the function and synaptic dynamics of 5-HT neurons within the dorsal raphe nucleus (DRN) remain to be elucidated. In this study, we sought to discern the repercussions of GPR55 activation on 5-HT synthesis within the DRN of adult C57BL/6J mice that experienced MS. Concurrently, we analyzed potential alterations in excitatory synaptic transmission, long-term synaptic plasticity, and relevant learning and memory outcomes. Our behavioral assessments indicated a marked amelioration in MS-induced learning and memory deficits following GPR55 activation. In conjunction with this, we noted a substantial decrease in 5-HT levels in the MS model, while GPR55 activation stimulated tryptophan hydroxylase 2 synthesis and fostered the release of 5-HT. Electrophysiological patch-clamp analyses highlighted the ability of GPR55 activation to alleviate MS-induced cognitive deficits by modulating the frequency and magnitude of miniature excitatory postsynaptic currents within the DRN. Notably, this cognitive enhancement was underpinned by the phosphorylation of both NMDA and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors. In summary, our findings underscore the capacity of GPR55 to elevate 5-HT synthesis and modify synaptic transmissions within the DRN of juvenile mice, positing GPR55 as a promising therapeutic avenue for ameliorating MS-induced cognitive impairment.
PubMed: 38799363
DOI: 10.1021/acsomega.3c08934 -
Cortico-amygdala synaptic structural abnormalities produced by templated aggregation of α-synuclein.BioRxiv : the Preprint Server For... May 2024Parkinson's disease (PD) and Dementia with Lewy bodies (DLB) are characterized by neuronal α-synuclein (α-syn) inclusions termed Lewy Pathology, which are abundant in...
Parkinson's disease (PD) and Dementia with Lewy bodies (DLB) are characterized by neuronal α-synuclein (α-syn) inclusions termed Lewy Pathology, which are abundant in the amygdala. The basolateral amygdala (BLA), in particular, receives projections from the thalamus and cortex. These projections play a role in cognition and emotional processing, behaviors which are impaired in α-synucleinopathies. To understand if and how pathologic α-syn impacts the BLA requires animal models of α-syn aggregation. Injection of α-synuclein pre-formed fibrils (PFFs) into the striatum induces robust α-synuclein aggregation in excitatory neurons in the BLA that corresponds with reduced contextual fear conditioning. At early time points after aggregate formation, cortico-amygdala excitatory transmission is abolished. The goal of this project was to determine if α-syn inclusions in the BLA induce synaptic degeneration and/or morphological changes. In this study, we used C57BL/6J mice injected bilaterally with PFFs in the dorsal striatum to induce α-syn aggregate formation in the BLA. A method was developed using immunofluorescence and three-dimensional reconstruction to analyze excitatory cortico-amygdala and thalamo-amygdala presynaptic terminals closely juxtaposed to postsynaptic densities. The abundance and morphology of synapses were analyzed at 6- or 12-weeks post-injection of PFFs. α-Syn aggregate formation in the BLA did not cause a significant loss of synapses, but cortico-amygdala and thalamo-amygdala presynaptic terminals and postsynaptic densities with aggregates of α-synuclein show increased volumes, similar to previous findings in human DLB cortex, and in non-human primate models of PD. Transmission electron microscopy showed that PFF-injected mice showed reduced intervesicular distances similar to a recent study showing phospho-serine-129 α-synuclein increases synaptic vesicle clustering. Thus, pathologic α-synuclein causes major alterations to synaptic architecture in the BLA, potentially contributing to behavioral impairment and amygdala dysfunction observed in synucleinopathies.
PubMed: 38798467
DOI: 10.1101/2024.05.15.594419 -
BioRxiv : the Preprint Server For... May 2024RNA editing is a post-transcriptional source of protein diversity and occurs across the animal kingdom. Given the complete profile of mRNA targets and their editing rate...
RNA editing is a post-transcriptional source of protein diversity and occurs across the animal kingdom. Given the complete profile of mRNA targets and their editing rate in individual cells is unclear, we analyzed single cell RNA transcriptomes from larval tonic and phasic glutamatergic motoneuron subtypes to determine the most highly edited targets and identify cell-type specific editing. From ∼15,000 genes encoded in the genome, 316 high confidence A-to-I canonical RNA edit sites were identified, with 102 causing missense amino acid changes in proteins regulating membrane excitability, synaptic transmission, and cellular function. Some sites showed 100% editing in single neurons as observed with mRNAs encoding mammalian AMPA receptors. However, most sites were edited at lower levels and generated variable expression of edited and unedited mRNAs within individual neurons. Together, these data provide insights into how the RNA editing landscape alters protein function to modulate the properties of two well-characterized neuronal populations in .
PubMed: 38798345
DOI: 10.1101/2024.05.17.594696 -
Biomedicine & Pharmacotherapy =... Jul 2024Anxiety-like conditions can interfere with daily activities as the adaptive mechanism fails to cope with stress. These conditions are often linked with increased...
Geraniol mitigates anxiety-like behaviors in rats by reducing oxidative stress, repairing impaired hippocampal neurotransmission, and normalizing brain cortical-EEG wave patterns after a single electric foot-shock exposure.
Anxiety-like conditions can interfere with daily activities as the adaptive mechanism fails to cope with stress. These conditions are often linked with increased oxidative stress, and abrupt neurotransmission and electroencephalography (EEG) wave pattern. Geraniol, a monoterpenoid, has antioxidant and anti-inflammatory activities, as well as brain-calming effects. Therefore, in this study, geraniol was tested for the potential anxiolytic effects in a rat model of anxiety. The rats were exposed to an electric foot shock (1 mA for 1 s) to develop anxiety-like symptoms. Treatment was carried out using geraniol (10 and 30 mg/kg) and the standard diazepam drug. The behavior of the rats was analyzed using the open field test, light-dark test, and social interaction test. Afterward, the rats were decapitated to collect samples for neurochemical and biochemical analyses. The cortical-EEG wave pattern was also obtained. The study revealed that the electric foot shock induced anxiety-like symptoms, increased oxidative stress, and altered hippocampal neurotransmitter levels. The power of low-beta and high-beta was amplified with the increased coupling of delta-beta waves in anxiety group. However, the treatment with geraniol and diazepam normalized cortical-EEG wave pattern and hippocampal serotonin and catecholamines profile which was also reflected by reduced anxious behavior and normalized antioxidant levels. The study reports an anxiolytic potential of geraniol, which can be further explored in future.
Topics: Animals; Acyclic Monoterpenes; Oxidative Stress; Anxiety; Male; Hippocampus; Rats, Wistar; Anti-Anxiety Agents; Rats; Electroencephalography; Synaptic Transmission; Behavior, Animal; Electroshock; Antioxidants; Terpenes; Diazepam; Disease Models, Animal; Brain Waves
PubMed: 38795639
DOI: 10.1016/j.biopha.2024.116771 -
STAR Protocols Jun 2024Generating stable human embryonic stem cells (hESCs) with targeted genetic mutations allows for the interrogation of protein function in numerous cellular contexts while...
Generating stable human embryonic stem cells (hESCs) with targeted genetic mutations allows for the interrogation of protein function in numerous cellular contexts while maintaining a relatively high degree of isogenicity. We describe a step-by-step protocol for generating knockout hESC lines with mutations in genes involved in synaptic transmission using CRISPR-Cas9. We describe steps for gRNA design, cloning, stem cell transfection, and clone isolation. We then detail procedures for gene knockout validation and differentiation of stem cells into functional induced neurons.
Topics: Humans; CRISPR-Cas Systems; Human Embryonic Stem Cells; Neurons; Gene Editing; Cell Differentiation; Gene Knockout Techniques; RNA, Guide, CRISPR-Cas Systems; Synapses
PubMed: 38795356
DOI: 10.1016/j.xpro.2024.103089 -
International Journal of Molecular... May 2024Human evolution is characterized by rapid brain enlargement and the emergence of unique cognitive abilities. Besides its distinctive cytoarchitectural organization and... (Review)
Review
Human evolution is characterized by rapid brain enlargement and the emergence of unique cognitive abilities. Besides its distinctive cytoarchitectural organization and extensive inter-neuronal connectivity, the human brain is also defined by high rates of synaptic, mainly glutamatergic, transmission, and energy utilization. While these adaptations' origins remain elusive, evolutionary changes occurred in synaptic glutamate metabolism in the common ancestor of humans and apes via the emergence of , a gene encoding the human glutamate dehydrogenase 2 (hGDH2) isoenzyme. Driven by positive selection, hGDH2 became adapted to function upon intense excitatory firing, a process central to the long-term strengthening of synaptic connections. It also gained expression in brain astrocytes and cortical pyramidal neurons, including the CA1-CA3 hippocampal cells, neurons crucial to cognition. In mice transgenic for , theta-burst-evoked long-term potentiation (LTP) is markedly enhanced in hippocampal CA3-CA1 synapses, with patch-clamp recordings from CA1 pyramidal neurons revealing increased sNMDA receptor currents. D-lactate blocked LTP enhancement, implying that glutamate metabolism via hGDH2 potentiates L-lactate-dependent glia-neuron interaction, a process essential to memory consolidation. The transgenic (Tg) mice exhibited increased dendritic spine density/synaptogenesis in the hippocampus and improved complex cognitive functions. Hence, enhancement of neuron-glia communication, via evolution, likely contributed to human cognitive advancement by potentiating synaptic plasticity and inter-neuronal connectivity.
Topics: Animals; Humans; Neuronal Plasticity; Glutamic Acid; Cognition; Glutamate Dehydrogenase; Mice; Lactic Acid; Long-Term Potentiation; Mice, Transgenic; Pyramidal Cells; Hippocampus; Evolution, Molecular; Synapses
PubMed: 38791334
DOI: 10.3390/ijms25105297 -
International Journal of Molecular... May 2024Dopamine is a key neurotransmitter involved in physiological processes such as motor control, motivation, reward, cognitive function, and maternal and reproductive... (Review)
Review
Dopamine is a key neurotransmitter involved in physiological processes such as motor control, motivation, reward, cognitive function, and maternal and reproductive behaviors. Therefore, dysfunctions of the dopaminergic system are related to a plethora of human diseases. Dopamine, via different circuitries implicated in compulsive behavior, reward, and habit formation, also represents a key player in substance use disorder and the formation and perpetuation of mechanisms leading to addiction. Here, we propose dopamine as a model not only of neurotransmission but also of neuromodulation capable of modifying neuronal architecture. Abuse of substances like methamphetamine, cocaine, and alcohol and their consumption over time can induce changes in neuronal activities. These modifications lead to synaptic plasticity and finally to morphological and functional changes, starting from maladaptive neuro-modulation and ending in neurodegeneration.
Topics: Humans; Dopamine; Animals; Substance-Related Disorders; Neuronal Plasticity; Synaptic Transmission
PubMed: 38791331
DOI: 10.3390/ijms25105293 -
International Journal of Molecular... May 2024In all cell types, small EVs, very abundant extracellular vesicles, are generated and accumulated within MVB endocytic cisternae. Upon MVB fusion and exocytosis with the... (Review)
Review
In all cell types, small EVs, very abundant extracellular vesicles, are generated and accumulated within MVB endocytic cisternae. Upon MVB fusion and exocytosis with the plasma membrane, the EVs are released to the extracellular space. In the central nervous system, the release of neuronal EVs was believed to occur only from the surface of the body and dendrites. About 15 years ago, MVB cisternae and EVs were shown to exist and function at synaptic boutons, the terminals' pre- and post-synaptic structures essential for canonical neurotransmitter release. Recent studies have revealed that synaptic EVs are peculiar in many respects and heterogeneous with respect to other neuronal EVs. The distribution of synaptic EVs and the effect of their specific molecules are found at critical sites of their distribution. The role of synaptic EVs could consist of the modulation of canonical neurotransmitter release or a distinct, non-canonical form of neurotransmission. Additional roles of synaptic EVs are still not completely known. In the future, additional investigations will clarify the role of synaptic EVs in pathology, concerning, for example, circuits, trans-synaptic transmission, diagnosis and the therapy of diseases.
Topics: Humans; Extracellular Vesicles; Animals; Neurons; Synapses; Signal Transduction; Synaptic Transmission; Exocytosis; Neurotransmitter Agents; Synaptic Vesicles
PubMed: 38791143
DOI: 10.3390/ijms25105103 -
Antioxidants (Basel, Switzerland) May 2024Proteins are essential molecules that play crucial roles in maintaining cellular homeostasis and carrying out biological functions such as catalyzing biochemical... (Review)
Review
Proteins are essential molecules that play crucial roles in maintaining cellular homeostasis and carrying out biological functions such as catalyzing biochemical reactions, structural proteins, immune response, etc. However, proteins also are highly susceptible to damage by reactive oxygen species (ROS) and reactive nitrogen species (RNS). In this review, we summarize the role of protein oxidation in normal aging and Alzheimer's disease (AD). The major emphasis of this review article is on the carbonylation and nitration of proteins in AD and mild cognitive impairment (MCI). The oxidatively modified proteins showed a strong correlation with the reported changes in brain structure, carbohydrate metabolism, synaptic transmission, cellular energetics, etc., of both MCI and AD brains compared to the controls. Some proteins were found to be common targets of oxidation and were observed during the early stages of AD, suggesting that those changes might be critical in the onset of symptoms and/or formation of the pathological hallmarks of AD. Further studies are required to fully elucidate the role of protein oxidation and nitration in the progression and pathogenesis of AD.
PubMed: 38790679
DOI: 10.3390/antiox13050574 -
Brain Sciences May 2024Rotenone is a pesticide used in research for its ability to induce changes similar, in vivo and in vitro, to those observed in Parkinson's disease (PD). This includes a...
Rotenone is a pesticide used in research for its ability to induce changes similar, in vivo and in vitro, to those observed in Parkinson's disease (PD). This includes a selective death of dopaminergic neurons in the substantia nigra. Nonetheless, the precise mechanism through which rotenone modifies structure and function of neurons remains unclear. The PC12 cells closely resemble dopamine terminal neurons. This makes it a preferred model for studying the morphology of central dopamine neurons and predicting neurotoxicity. In this paper, we investigated the effects of 0.5 µM rotenone for 24-48 h on PC12 cell viability and ultrastructure (TEM), trying to identify primary and more evident alterations that can be related to neuronal damages similar to that seen in animal PD models. Cell viability decreased after 24 h rotenone treatment, with a further decrease after 48 h. Ultrastructural changes included vacuolar degeneration, mitochondrial mild swelling, decrease in the number of neuropeptide granules, and the loss of cell-to-cell adhesion. These findings are in agreement with previous research suggesting that rotenone, by inhibiting energy production and increasing ROS generation, is responsible for significant alterations of the ultrastructure and cell death of PC12 cells. Our data confirm the link between rotenone exposure, neuronal damage, and changes in dopamine metabolism, suggesting its role in the pathogenesis of PD.
PubMed: 38790454
DOI: 10.3390/brainsci14050476