Ginsenoside F1 Protects the Brain against Amyloid Beta-Induced Toxicity by Regulating IDE and NEP

Ginsenoside F1, the metabolite of Rg1, is one of the most important constituents of Panax ginseng. Although the effects of ginsenosides on amyloid beta (Aβ) aggregation in the brain are known, the role of ginsenoside F1 remains unclear. Here, we investigated the protective effect of ginsenoside F1 against Aβ aggregation in vivo and in vitro. Treatment with 2.5 μM ginsenoside F1 reduced Aβ-induced cytotoxicity by decreasing Aβ aggregation in mouse neuroblastoma neuro-2a (N2a) and human neuroblastoma SH-SY5Y neuronal cell lines. Western blotting, real-time PCR, and siRNA analysis revealed an increased level of insulin-degrading enzyme (IDE) and neprilysin (NEP). Furthermore, liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis confirmed that ginsenoside F1 could pass the blood–brain barrier within 2 h after administration. Immunostaining results indicate that ginsenoside F1 reduces Aβ plaques in the hippocampus of APPswe/PSEN1dE9 (APP/PS1) double-transgenic Alzheimer’s disease (AD) mice. Consistently, increased levels of IDE and NEP protein and mRNA were observed after the 8-week administration of 10 mg/kg/d ginsenoside F1. These data indicate that ginsenoside F1 is a promising therapeutic candidate for AD.

HEXA-018, a Novel Inducer of Autophagy, Rescues TDP-43 Toxicity in Neuronal Cells

The autophagy-lysosomal pathway is an essential cellular mechanism that degrades aggregated proteins and damaged cellular components to maintain cellular homeostasis. Here, we identified HEXA-018, a novel compound containing a catechol derivative structure, as a novel inducer of autophagy. HEXA-018 increased the LC3-I/II ratio, which indicates activation of autophagy. Consistent with this result, HEXA-018 effectively increased the numbers of autophagosomes and autolysosomes in neuronal cells. We also found that the activation of autophagy by HEXA-018 is mediated by the AMPK-ULK1 pathway in an mTOR-independent manner. We further showed that ubiquitin proteasome system impairment- or oxidative stress-induced neurotoxicity was significantly reduced by HEXA-018 treatment. Moreover, oxidative stress-induced mitochondrial dysfunction was strongly ameliorated by HEXA-018 treatment. In addition, we investigated the efficacy of HEXA-018 in models of TDP-43 proteinopathy. HEXA-018 treatment mitigated TDP-43 toxicity in cultured neuronal cell lines and Drosophila. Our data indicate that HEXA-018 could be a new drug candidate for TDP-43-associated neurodegenerative diseases.

Infectivity of Human Olfactory Neurons to SARS-CoV-2: A Link to Anosmia

Objectives: We sought to determine whether SARS-CoV-2 infections are associated with anosmia and if this virus infects other neuronal cells. We utilized male and female olfactory neuronal cell lines and other olfactory cell lines to determine the viral targets. Methods: We used four undifferentiated and two partially differentiated human developing neuronal cell lines. Infectivity was confirmed by reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR), immunofluorescence assay (IFA) probing with anti-SARS-CoV-2 antibody, evaluation of cytopathic effects, and neurite formation. We induced partial differentiation of all cell lines (since both olfactory cell lines were terminally differentiated) with retinoic acid (RA) to determine whether differentiation was a factor in viral permissiveness. The expression of serine protease, transmembrane serine protease 2 (TMPRSS2), and angiotensin-converting enzyme II (ACE2) receptors were examined by RT-qPCR and IFA to determine the mechanism of viral entry. Results: Four to five days after exposure, both olfactory cell lines exhibited morphological evidence of infection; IFA analyses indicated that ~30% of the neurons were SARS-CoV-2 positive. At two weeks, 70–80% were positive for SARS-CoV-2 antigens. The partially differentiated (CRL-2266 and CRL-2267) and undifferentiated cell lines (CRL-2142, CRL-2149, CRL-127, and CDL-2271) were essentially non-permissive. After RA treatment, only CRL-127 exhibited slight permissiveness (RT-qPCR). The TMPRSS2 receptor showed high expression in olfactory neurons, but low expression in RA treated CRL-127. ACE2 exhibited high expression in olfactory neurons, whereas other cell lines showed low expression, including RA-treated cell lines. ACE2 expression slightly increased in CRL-127 post RA-treatment. Conclusions: Our studies confirm neurotropism of SARS-CoV-2 to olfactory neurons with viral entry likely mediated by TMPRSS2/ACE2. Other neuronal cell lines were non-permissive. Our results established that the nerve cells were infected regardless of male or female origin and strengthened the reported association of COVID-19 with loss of smell in infected individuals.

Human Neuronal Cell Lines as An In Vitro Toxicological Tool for the Evaluation of Novel Psychoactive Substances

Novel psychoactive substances (NPS) are synthetic substances belonging to diverse groups, designed to mimic the effects of scheduled drugs, resulting in altered toxicity and potency. Up to now, information available on the pharmacology and toxicology of these new substances is very limited, posing a considerable challenge for prevention and treatment. The present in vitro study investigated the possible mechanisms of toxicity of two emerging NPS (i) 4′-methyl-alpha-pyrrolidinoexanophenone (3,4-MDPHP), a synthetic cathinone, and (ii) 2-chloro-4,5-methylenedioxymethamphetamine (2-Cl-4,5-MDMA), a phenethylamine. In addition, to apply our model to the class of synthetic opioids, we evaluated the toxicity of fentanyl, as a reference compound for this group of frequently abused substances. To this aim, the in vitro toxic effects of these three compounds were evaluated in dopaminergic-differentiated SH-SY5Y cells. Following 24 h of exposure, all compounds induced a loss of viability, and oxidative stress in a concentration-dependent manner. 2-Cl-4,5-MDMA activates apoptotic processes, while 3,4-MDPHP elicits cell death by necrosis. Fentanyl triggers cell death through both mechanisms. Increased expression levels of pro-apoptotic Bax and caspase 3 activity were observed following 2-Cl-4,5-MDMA and fentanyl, but not 3,4-MDPHP exposure, confirming the different modes of cell death.

MiR-384 Regulates Reelin by Inhibiting ADAMTS4 in Neuronal Cell Lines

MicroRNAs (miRNAs) are important regulators of gene expression at the post-transcriptional level. The present study aims to investigate the role of miR-384 in Reelin by regulating ADAMTS4 in neuronal cell lines. Brain tissues from Aβ1-42 induced mouse model of Alzheimer's disease and the control group were collected. RT-PCR, Western blotting and immunohistochemistry were performed to detect the levels of ADAMTS4 and miR-384 in tissues. Luciferase reporter assay, Western blotting and in vitro assay were used to validate that ADAMTS4 was the target gene of miR-384. Neuronal cell line, Neuro-2a, was selected for transfection assay. ADAMTS4 was significantly down-regulated in hippocampi of Alzheimer's disease mouse model, and negatively correlated with miR-384. Then, ADAMTS4 was identified as a direct target of miR-384. Over-expressing of miR-384 in Neuro-2a showed that ADAMTS4 and the cleaved Reelin fragments were down regulated, and proliferation of neuronal cell lines (Neuro-2a and SH-SY5Y) were inhibited through DAB-1 pathway. In conclusion, these results revealed that miR-384 may play a regulatory role in Reelin via inhibiting ADAMTS4 in neuronal cell lines.

All-Optical Electrophysiology in hiPSC-Derived Neurons With Synthetic Voltage Sensors

Voltage imaging and “all-optical electrophysiology” in human induced pluripotent stem cell (hiPSC)-derived neurons have opened unprecedented opportunities for high-throughput phenotyping of activity in neurons possessing unique genetic backgrounds of individual patients. While prior all-optical electrophysiology studies relied on genetically encoded voltage indicators, here, we demonstrate an alternative protocol using a synthetic voltage sensor and genetically encoded optogenetic actuator that generate robust and reproducible results. We demonstrate the functionality of this method by measuring spontaneous and evoked activity in three independent hiPSC-derived neuronal cell lines with distinct genetic backgrounds.

The Motor Neuron-Like Cell Line NSC-34 and Its Parent Cell Line N18TG2 Have Glycogen that is Degraded Under Cellular Stress

Brain glycogen has a long and versatile history: Primarily regarded as an evolutionary remnant, it was then thought of as an unspecific emergency fuel store. A dynamic role for glycogen in normal brain function has been proposed later but exclusively attributed to astrocytes, its main storage site. Neuronal glycogen had long been neglected, but came into focus when sensitive technical methods allowed quantification of glycogen at low concentration range and the detection of glycogen metabolizing enzymes in cells and cell lysates. Recently, an active role of neuronal glycogen and even its contribution to neuronal survival could be demonstrated. We used the neuronal cell lines NSC-34 and N18TG2 and could demonstrate that they express the key-enzymes of glycogen metabolism, glycogen phosphorylase and glycogen synthase and contain glycogen which is mobilized on glucose deprivation and elevated potassium concentrations, but not by hormones stimulating cAMP formation. Conditions of metabolic stress, namely hypoxia, oxidative stress and pH lowering, induce glycogen degradation. Our studies revealed that glycogen can contribute to the energy supply of neuronal cell lines in situations of metabolic stress. These findings shed new light on the so far neglected role of neuronal glycogen. The key-enzyme in glycogen degradation is glycogen phosphorylase. Neurons express only the brain isoform of the enzyme that is supposed to be activated primarily by the allosteric activator AMP and less by covalent phosphorylation via the cAMP cascade. Our results indicate that neuronal glycogen is not degraded upon hormone action but by factors lowering the energy charge of the cells directly.

An arylthiazyne derivative is a potent inhibitor of lipid peroxidation and ferroptosis providing neuroprotection in vitro and in vivo

Lipid peroxidation-initiated ferroptosis is an iron-dependent mechanism of programmed cell death taking place in neurological diseases. Here we show that a condensed benzo[b]thiazine derivative small molecule with an arylthiazine backbone (ADA-409-052) inhibits tert-Butyl hydroperoxide (TBHP)-induced lipid peroxidation (LP) and protects against ferroptotic cell death triggered by glutathione (GSH) depletion or glutathione peroxidase 4 (GPx4) inhibition in neuronal cell lines. In addition, ADA-409-052 suppresses pro-inflammatory activation of BV2 microglia and protects N2a neuronal cells from cell death induced by pro-inflammatory RAW 264.7 macrophages. Moreover, ADA-409-052 efficiently reduces infarct volume, edema and expression of pro-inflammatory genes in a mouse model of thromboembolic stroke. Targeting ferroptosis may be a promising therapeutic strategy in neurological diseases involving severe neuronal death and neuroinflammation.