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Prevention of infection and propagation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a high priority in the Coronavirus Disease 2019 (COVID-19) pandemic. Here we describe S-nitrosylation of multiple proteins involved in SARS-CoV-2 infection, including angiotensin-converting enzyme 2 (ACE2), the receptor for viral entry. This reaction prevents binding of ACE2 to the SARS-CoV-2 spike protein, thereby inhibiting viral entry, infectivity and cytotoxicity. Aminoadamantane compounds also inhibit coronavirus ion channels formed by envelope (E) protein. Accordingly, we developed dual-mechanism aminoadamantane nitrate compounds that inhibit viral entry and, thus, the spread of infection by S-nitrosylating ACE2 via targeted delivery of the drug after E protein channel blockade. These non-toxic compounds are active in vitro and in vivo in the Syrian hamster COVID-19 model and, thus, provide a novel avenue to pursue therapy., (© 2022. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Background: Alzheimer's disease (AD) is a neurodegenerative disorder that manifests sequential Aβ and tau brain pathology with age-dependent onset. Variants in the microglial immune receptor TREM2 are associated with enhanced risk of onset in sporadic Alzheimer's disease (AD). While recent studies suggest TREM2 dysfunction can aggravate tau pathology, mechanisms underlying TREM2-dependent modulation of tau pathology remains elusive., Methods: Here, we characterized differences in progressive tau spreading from the medial entorhinal cortex (MEC) to the hippocampus in wildtype (WT) and Trem2 knockout (KO) mice by injection of AAV-P301L tau into the MEC, and correlated changes in hippocampal tau histopathology with spatial and fear memory. We also compared effects of intraneuronal dispersion between cultured microglia and neurons using a microfluidic dispersion assay, analyzed differences in microglial tau trafficking following uptake, and quantified exosomal tau secretion and pathogenicity from purified WT and Trem2 KO exosomes., Results: Trem2 deletion in mice (Trem2 KO) can enhance tau spreading from the medial entorhinal cortex (MEC) to the hippocampus, which coincides with impaired synaptic function and memory behavior. Trem2 deletion in microglia enhances intraneuronal dispersion of tau in vitro between neuronal layers cultured in a microfluidic chamber, and the presence of exosome inhibitors can significantly reduce tau in exosomes and extracellular media from tau-loaded microglia. Although microglial Trem2 deletion has no effect on tau uptake, Trem2 deletion enhances distribution to endosomal and cellular pre-exosomal compartments following internalization. Trem2 deletion has little effect on exosome size, however, proteomic analysis indicates that Trem2 deletion can modulate changes in the microglial proteomic landscape with tau and LPS/ATP treatment conditions associated with exosome induction. Furthermore, exosomes from Trem2 KO microglia show elevated tau levels, and feature enhanced tau-seeding capacity in a tau FRET reporter line compared to exosomes from WT microglia., Conclusion: Together, our results reveal a role for Trem2 in suppressing exosomal tau pathogenicity, and demonstrates that Trem2 deletion can enhance tau trafficking, distribution and seeding through microglial exosomes., (© 2022. The Author(s).)

Prevention of infection and propagation of SARS-CoV-2 is of high priority in the COVID-19 pandemic. Here, we describe S-nitrosylation of multiple proteins involved in SARS-CoV-2 infection, including angiotensin converting enzyme 2 (ACE2), the receptor for viral entry. This reaction prevents binding of ACE2 to the SARS-CoV-2 Spike protein, thereby inhibiting viral entry, infectivity, and cytotoxicity. Aminoadamantane compounds also inhibit coronavirus ion channels formed by envelope (E) protein. Accordingly, we developed dual-mechanism aminoadamantane nitrate compounds that inhibit viral entry and thus spread of infection by S-nitrosylating ACE2 via targeted delivery of the drug after E-protein channel blockade. These non-toxic compounds are active in vitro and in vivo in the Syrian hamster COVID-19 model, and thus provide a novel avenue for therapy.

Extended-access methamphetamine self-administration results in unregulated intake of the drug; however, the role of dorsal striatal dopamine D 1 -like receptors (D 1 Rs) in the reinforcing properties of methamphetamine under extended-access conditions is unclear. Acute (ex vivo) and chronic (in vivo) methamphetamine exposure induces neuroplastic changes in the dorsal striatum, a critical region implicated in instrumental learning. For example, methamphetamine exposure alters high-frequency stimulation (HFS)-induced long-term depression in the dorsal striatum; however, the effect of methamphetamine on HFS-induced long-term potentiation (LTP) in the dorsal striatum is unknown. In the current study, dorsal striatal infusion of SCH23390, a D 1 R antagonist, prior to extended-access methamphetamine self-administration reduced methamphetamine addiction-like behavior. Reduced behavior was associated with reduced expression of PSD-95 in the dorsal striatum. Electrophysiological findings demonstrate that superfusion of methamphetamine reduced basal synaptic transmission and HFS-induced LTP in dorsal striatal slices, and SCH23390 prevented this effect. These results suggest that alterations in synaptic transmission and synaptic plasticity induced by acute methamphetamine via D 1 Rs could assist with methamphetamine-induced modification of corticostriatal circuits underlying the learning of goal-directed instrumental actions and formation of habits, mediating escalation of methamphetamine self-administration and methamphetamine addiction-like behavior.

Alzheimer's disease (AD) is an aging-related neurological disorder characterized by synaptic loss and dementia. Wnt/β-catenin signaling is an essential signal transduction pathway that regulates numerous cellular processes including cell survival. In brain, Wnt/β-catenin signaling is not only crucial for neuronal survival and neurogenesis, but it plays important roles in regulating synaptic plasticity and blood-brain barrier integrity and function. Moreover, activation of Wnt/β-catenin signaling inhibits amyloid-β production and tau protein hyperphosphorylation in the brain. Critically, Wnt/β-catenin signaling is greatly suppressed in AD brain via multiple pathogenic mechanisms. As such, restoring Wnt/β-catenin signaling represents a unique opportunity for the rational design of novel AD therapies.

Objective: To review recent research advances on tau, a major player in Alzheimer's disease (AD) pathogenesis, a biomarker for AD onset, and potential target for AD therapy., Data Sources: This review was based on a comprehensive search using online literature databases, including PubMed, Web of Science, and Google Scholar., Study Selection: Literature search was based on the following keywords: Alzheimer's disease, tau protein, biomarker, cerebrospinal fluid (CSF), therapeutics, plasma, imaging, propagation, spreading, seeding, prion, conformational templating, and posttranslational modification. Relevant articles were carefully reviewed, with no exclusions applied to study design and publication type., Results: Amyloid plaques enriched with extracellular amyloid beta (Aβ) and intracellular neurofibrillary tangles comprised of hyperphosphorylated tau proteins are the two main pathological hallmarks of AD. Although the Aβ hypothesis has dominated AD research for many years, clinical Aβ-targeting strategies have consistently failed to effectively treat AD or prevent AD onset. The research focus in AD has recently shifted to the role of tau in AD. In addition to phosphorylation, tau is acetylated and proteolytically cleaved, which also contribute to its physiological and pathological functions. Emerging evidence characterizing pathological tau propagation and spreading provides new avenues for research into the molecular and cellular mechanisms underlying AD pathogenesis. Techniques to detect tau at minute levels in CSF and blood have been developed, and improved tracers have facilitated tau imaging in the brain. These advances have potential to accurately determine tau levels at early diagnostic stages in AD. Given that tau is a potential therapeutic target, anti-tau immunotherapy may potentially be a viable treatment strategy in AD intervention., Conclusion: Detecting changes in tau and targeting tau pathology represent a promising lead in the diagnosis and treatment of AD.

Purpose: Photoreceptor degeneration in the retina is a major cause of blindness in humans. Elucidating mechanisms of degenerative and neuroprotective pathways in photoreceptors should afford identification and development of therapeutic strategies., Methods: We used mouse genetic models and improved methods for retinal explant cultures. Retinas were enucleated from Mef2d+/+ and Mef2d-/- mice, stained for MEF2 proteins and outer nuclear layer thickness, and assayed for apoptotic cells. Chromatin immunoprecipitation (ChIP) assays revealed MEF2 binding, and RT-qPCR showed levels of transcription factors. We used AAV2 and electroporation to express genes in retinal explants and electroretinograms to assess photoreceptor functionality., Results: We identify a prosurvival MEF2D-PGC1α pathway that plays a neuroprotective role in photoreceptors. We demonstrate that Mef2d-/- mouse retinas manifest decreased expression of PGC1α and increased photoreceptor cell loss, resulting in the absence of light responses. Molecular repletion of PGC1α protects Mef2d-/- photoreceptors and preserves light responsivity., Conclusions: These results suggest that the MEF2-PGC1α cascade may represent a new therapeutic target for drugs designed to protect photoreceptors from developmental- and age-dependent loss.

Stroke and vascular dementia are leading causes of morbidity and mortality. Neuroprotective therapies have been proposed but none have proven clinically tolerated and effective. While overstimulation of N-methyl-d-aspartate-type glutamate receptors (NMDARs) is thought to contribute to cerebrovascular insults, the importance of NMDARs in physiological function has made this target, at least in the view of many in 'Big Pharma,' 'undruggable' for this indication. Here, we describe novel NitroMemantine drugs, comprising an adamantane moiety that binds in the NMDAR-associated ion channel that is used to target a nitro group to redox-mediated regulatory sites on the receptor. The NitroMemantines are both well tolerated and effective against cerebral infarction in rodent models via a dual allosteric mechanism of open-channel block and NO/redox modulation of the receptor. Targeted S-nitrosylation of NMDARs by NitroMemantine is potentiated by hypoxia and thereby directed at ischemic neurons. Allosteric approaches to tune NMDAR activity may hold therapeutic potential for cerebrovascular disorders.

Methamphetamine (METH) abuse is frequent in individuals infected with human immunodeficiency virus type-1 (HIV-1) and is suspected to aggravate HIV-associated neurocognitive disorders (HAND). METH is a psychostimulant that compromises several neurotransmitter systems and HIV proteins trigger neuronal injury but the combined effects of viral infection and METH abuse are incompletely understood. In this study we treated transgenic mice expressing the HIV envelope protein gp120 in the brain (HIV-1 gp120tg) at 3-4 months of age with an escalating-dose, multiple-binge METH regimen. The long-term effects were analyzed after 6-7 months of drug abstinence employing behavioral tests and analysis of neuropathology, electrophysiology and gene expression. Behavioral testing showed that both HIV-1 gp120tg and WT animals treated with METH displayed impaired learning and memory. Neuropathological analysis revealed that METH similar to HIV-1 gp120 caused a significant loss of neuronal dendrites and pre-synaptic terminals in hippocampus and cerebral cortex of WT animals. Electrophysiological studies in hippocampal slices showed that METH exposed HIV-1 gp120tg animals displayed reduced post-tetanic potentiation, whereas both gp120 expression and METH lead to reduced long-term potentiation. A quantitative reverse transcription-polymerase chain reaction array showed that gp120 expression, METH and their combination each caused a significant dysregulation of specific components of GABAergic and glutamatergic neurotransmission systems, providing a possible mechanism for synaptic dysfunction and behavioral impairment. In conclusion, both HIV-1 gp120 and METH caused lasting behavioral impairment in association with neuropathology and altered gene expression. However, combined METH exposure and HIV-1 gp120 expression resulted in the most pronounced, long lasting pre- and post-synaptic alterations coinciding with impaired learning and memory., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Injection of large doses of ammonia (1.2g/kg, i.p.) was used to induce acute toxicity in mice which was characterized by hyperresponsiveness, taquipnea, clonic and tonic seizures and death. Pretreatment with 20, 40, or 80 mg/Kg, i.p., of ketamine increased 30 to 55% survival rate. This pretreatment significantly retarded the beginning of the first tonic convulsion attenuating its intensity and delayed the time of the animal death; but did not alter the onset of the first clonic seizures. These experiments may be an evidence that support the hypothesis that seizures due to hyperammonemia involve activation of excitatory amino acid receptors.

Spinal seizures evoked by sudden cooling (SSSC) were used to investigate the anticonvulsant activity of ketamine (KET) injected either intralymphatically (i.l., 5-40 mg/kg) or intrathecally (i.t., 0.5-1.0 mumol/20 microliters) using isolated spinal cord-hindleg preparation. KET inhibited the tonic phase and prolonged the clonic phase in a dose-dependent manner. The cionic phase was depressed or totally blocked at KET doses of 80-160 mg/kg, i.l. or 2 mumol/20 microliters, i.t. This depression was not prevented by i.t. administration of concanavalin A. The latency of onset of seizures was also increased by KET. KET abolishes the tonic-extensor phase of SSSC in which activation of N-methyl-D-aspartate-receptors may play a role.

The effect of low doses of urethane on three phases of spinal seizures evoked by sudden cooling (SSSC) of toad isolated spinal cord was studied. In control toads, SSSC began with a latency of 91 +/- 3 sec (mean +/- S.E.M.) exhibiting brief tremors, followed by clonic muscle contractions and finally reaching a tonic contraction (tonic phase). The latency of onset of seizures was significantly enhanced. The tonic phase was markedly abolished in toads pretreated intralymphatically with 0.15 g/kg of urethane. Tremors were the only phase observed in 55% of toads that received doses of 0.2 g/kg, and a total blockade of seizures was seen after doses of 0.25 g/kg of urethane in 50% of the preparations. A possible depressant effect of urethane on transmission mediated by excitatory amino acids is suggested.