Comprehensive Application of Time-of-flight Secondary Ion Mass Spectrometry (TOF-SIMS) for Ionic Imaging and Bio-energetic Analysis of Club Drug-induced Cognitive Deficiency

Leveraging ToF-SIMS imaging to investigate tenofovir disoproxil fumarate degradation at excipient interfaces in oral compressed tablets

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) imaging has been used to study the hydrolysis of tenofovir disoproxil fumarate (TDF) to tenofovir monosoproxil (TM) within an oral compressed tablet. The ToF-SIMS images displayed a heterogenous distribution of the matrix components. Evaluation of the TM distribution revealed that it was primarily co-localized with areas of higher excipient concentration pointing toward excipient driven degradation. To support these observations, a compatibility study of TDF with each tablet component was performed via liquid chromatography. The ToF-SIMS imaging and compatibility study indicated that the excipient, Avicel® PH-102, was the primary driver of TM formation in the tablet. The hydrolysis degradation mechanism within the tablet is further rationalized through discussion of chemical and physical properties of the matrix components. The sum of this work demonstrates a new analytical workflow for probing and understanding matrix driven degradation in oral compressed tablets utilizing ToF-SIMS imaging.

Olfactory Stimulation Successfully Modulates the Neurochemical, Biochemical and Behavioral Phenotypes of the Visceral Pain

Visceral pain (VP) is the organ-derived nociception in which increased inflammatory reaction and exaggerated activation of the central nucleus of the amygdala (CeA) may contribute to this deficiency. Considering the amygdala also serves as the integration center for olfaction, the present study aimed to determine whether olfactory stimulation (OS) would effectively depress over-activation and inflammatory reaction in CeA, and successfully relieve VP-induced abnormalities. Adult rats subjected to intraperitoneal injection of acetic acid inhaled lavender essential oil for 2 or 4 h. The potential benefits of OS were determined by measuring the pro-inflammatory cytokine level, intracellular potassium and the upstream small-conductance calcium-activated potassium (SK) channel expression, together with detecting the stress transmitters that participated in the modulation of CeA activity. Results indicated that in VP rats, strong potassium intensity, reduced SK channel protein level, and increased corticotropin-releasing factor, c-fos, and substance P immuno-reactivities were detected in CeA. Enhanced CeA activation corresponded well with increased inflammatory reaction and decreased locomotion, respectively. However, in rats subjected to VP and received OS, all above parameters were significantly returned to normal levels with higher change detected in treating OS of 4h. As OS successfully depresses inflammation and CeA over-activation, application of OS may serve as an alternative and effective strategy to efficiently relieve VP-induced deficiency.

Learning and memory impairment induced by 1,4-butanediol is regulated by ERK1/2-CREB-BDNF signaling pathways in PC12 cells

1,4-butanediol (1,4-BD) is a known γ-hydroxybutyric acid (GHB) precursor which affects the nervous system after ingestion, leading to uncontrolled behavioral consequences. In the present study, we investigated whether 1,4-BD induces oxidative stress and inflammation in PC12 cells and evaluated the toxic effects of 1,4-BD associates with learning and memory. CCK-8 results revealed a dose-effect relationship between the cell viability of PC12 cells and 1,4-BD when the duration of action was 2 h or 4 h. Assay kits results showed that 1,4-BD decreased the levels of Glutathione (GSH), Glutathione peroxidase (GSH-px), Superoxide dismutase (SOD), Acetylcholine (Ach) and increased the levels of Malondialdehyde (MDA), Nitric oxide (NO) and Acetylcholinesterase (AchE). Elisa kits results indicated that 1,4-BD decreased the levels of synaptophysin I (SYN-1), Postsynaptic density protein-95 (PSD-95), Growth associated protein-43 (GAP-43) and increased the levels of Tumor necrosis factor alpha (TNF-α) and Interleukin- 6 (IL-6). RT-PCR results showed that the mRNA levels of PSD-95, SYN-1 and GAP-43 were significantly decreased. The expression of phosphorylation extracellular signal-regulated protein kinase 1/2 (p-ERK1/2), phosphorylation cAMP response element binding protein (p-CREB) and brain-derived neurotrophic factor (BDNF) proteins were significantly decreased in PC12 cells by protein blotting. Overall, these results suggest that 1,4-BD may affect synaptic plasticity via the ERK1/2-CREB-BDNF pathway, leading to Ach release reduction and ultimately to learning and memory impairment. Furthermore, oxidative stress and inflammation induced by 1,4-BD may also result in learning and memory deficits. These findings will enrich the toxicity data of 1.4-BD associated with learning and memory impairment.

Cell and Tissue Imaging by TOF-SIMS and MALDI-TOF: An Overview for Biological and Pharmaceutical Analysis

The potential of mass spectrometry imaging (MSI) has been demonstrated in cell and tissue research since 1970. MSI can reveal the spatial distribution of a wide range of atomic and molecular ions detected from biological sample surfaces, it is a powerful and valuable technique used to monitor and detect diverse chemical and biological compounds, such as drugs, lipids, proteins, and DNA. MSI techniques, notably matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) and time of flight secondary ion mass spectrometry (TOF-SIMS), witnessed a dramatic upsurge in studying and investigating biological samples especially, cells and tissue sections. This advancement is attributed to the submicron lateral resolution, the high sensitivity, the good precision, and the accurate chemical specificity, which make these techniques suitable for decoding and understanding complex mechanisms of certain diseases, as well as monitoring the spatial distribution of specific elements, and compounds. While the application of both techniques for the analysis of cells and tissues is thoroughly discussed, a briefing of MALDI-TOF and TOF-SIMS basis and the adequate sampling before analysis are briefly covered. The importance of MALDI-TOF and TOF-SIMS as diagnostic tools and robust analytical techniques in the medicinal, pharmaceutical, and toxicology fields is highlighted through representative published studies.

Olfactory Stimulation Successfully Improves Swallowing Function of Aged Rats through Activating Central Neuronal Networks and Downstream DHPR-RyR-mediated Neuromuscular Activities

Presbyphagia is age-related changes in swallowing function, which imposes a high risk of aspiration in older adults. Considering olfactory stimulation (OS) can influence behavioral activities by modulating neuronal excitability, the present study aims to determine whether OS could improve the swallowing function of aged rats through activating the central neuronal networks and downstream muscular activities participated in the control of swallowing. Aged male Wistar rats received OS by inhaling a mixture of plant-based volatile molecules twice a day for 12 days were subjected to functional magnetic resonance imaging (fMRI) and c-fos, choline acetyltransferase (ChAT) immunostaining to detect the neuronal activities of the orbitofrontal cortex (OFC) and medullary nuclei engaged in swallowing control, respectively. The functional effects of OS on downstream pharyngeal muscle activity were examined by evaluating the dihydropyridine receptor-ryanodine receptor (DHPR-RyR) mediated intra-muscular Ca2 + expression, and analyzing the amplitude/frequency of muscle contraction, respectively. In untreated rats, only moderate signal of fMRI and mild c-fos/ChAT expression was detected in the OFC and medullary nuclei, respectively. However, following OS, intense signals of fMRI and immunostaining were clearly expressed in the orbitofronto-medullary networks. Functional data corresponded well with above findings in which OS significantly enhanced DHPR-RyR-mediated intra-muscular Ca2 + expression, effectively facilitated a larger amplitude of pharyngeal muscle contraction, and exhibited better performance in consuming larger amounts of daily dietary. As OS successfully activates the neuromuscular activities participated in the control of swallowing, applying OS may serve as an effective, easy, and safe strategy to greatly improve the swallow function of aging populations.

Label-Free Time-of-Flight Secondary Ion Mass Spectrometry Imaging of Sulfur-Producing Enzymes inside Microglia Cells following Exposure to Silver Nanowires

There are no methods sensitive enough to detect enzymes within cells, without the use of analyte labeling. Here we show that it is possible to detect protein ion signals of three different H₂S-synthesizing enzymes inside microglia after pretreatment with silver nanowires (AgNW) using time-of-flight secondary ion mass spectrometry (TOF-SIMS). Protein fragment ions, including the fragment of amino acid (C₄H₈N⁺ = 70 amu), fragments of the sulfur-producing cystathionine-containing enzymes, and the Ag⁺ ion signal could be detected without the use of any labels; the cells were mapped using the C₄H₈N⁺ amino acid fragment. Scanning electron microscopy imaging and energy-dispersive X-ray chemical analysis showed that the AgNWs were inside the same cells imaged by TOF-SIMS and transformed chemically into crystalline Ag₂S within cells in which the sulfur-producing proteins were detected. The presence of these sulfur-producing cystathionine-containing enzymes within the cells was confirmed by Western blots and confocal microscopy images of fluorescently labeled antibodies against the sulfur-producing enzymes. Label-free TOF-SIMS is very promising for the label-free identification of H₂S-contributing enzymes and their cellular localization in biological systems. The technique could in the future be used to identify which of these enzymes are most contributory.

Deciphering the Rules for Amino Acid Co-Assembly Based on Interlayer Distances

Metabolite materials are extremely useful to obtain functional bioinspired assemblies with unique physical properties for various applications in the fields of material science, engineering, and medicine by self-assembly of the simplest biological building blocks. Supramolecular co-assembly has recently emerged as a promising extended approach to further expand the conformational space of metabolite assemblies in terms of structural and functional complexity. Yet, the design of synergistically co-assembled amino acids to produce tailor-made functional architectures is still challenging. Herein, we propose a design rule to predict the supramolecular co-assembly of naturally occurring amino acids based on their interlayer separation distances observed in single crystals. Using diverse experimental techniques, we demonstrate that amino acids with comparable interlayer separation strongly interact and co-assemble to produce structural composites distinctly different from their individual properties. However, such an interaction is hampered in a mixture of differentially layer-separated amino acids, which self-sort to generate individual characteristic structures. This study provides a different paradigm for the modular design of supramolecular assemblies based on amino acids with predictable properties.

Adolescent brain cognitive development (ABCD) study: Overview of substance use assessment methods

One of the objectives of the Adolescent Brain Cognitive Development (ABCD) Study (https://abcdstudy.org/) is to establish a national longitudinal cohort of 9 and 10 year olds that will be followed for 10 years in order to prospectively study the risk and protective factors influencing substance use and its consequences, examine the impact of substance use on neurocognitive, health and psychosocial outcomes, and to understand the relationship between substance use and psychopathology. This article provides an overview of the ABCD Study Substance Use Workgroup, provides the goals for the workgroup, rationale for the substance use battery, and includes details on the substance use module methods and measurement tools used during baseline, 6-month and 1-year follow-up assessment time-points. Prospective, longitudinal assessment of these substance use domains over a period of ten years in a nationwide sample of youth presents an unprecedented opportunity to further understand the timing and interactive relationships between substance use and neurocognitive, health, and psychopathology outcomes in youth living in the United States.

Melatonin successfully rescues hippocampal bioenergetics and improves cognitive function following drug intoxication by promoting Nrf2-ARE signaling activity

Prolonged exposure to gamma-hydroxybutyric acid (GHB) would cause drug intoxication in which impaired cognitive function results from enhanced hippocampal oxidative stress may serve as a major symptom in this deficiency. Considering melatonin possesses significant anti-oxidative efficacy, this study aimed to determine whether melatonin would successfully promote the nuclear factor erythroid 2-related factor 2 and antioxidant responsive element (Nrf2-ARE) signaling, depress oxidative stress, and rescue hippocampal bioenergetics and cognitive function following drug intoxication injury. Adolescent rats subjected to 10 days of GHB were received melatonin at doses of either 10 or 100 mg/kg. Time-of-flight secondary ion mass spectrometry, biochemical assay, quantitative histochemistry, [¹⁴ C]-2-deoxyglucose analysis, together with Morris water maze were employed to detect the molecular signaling, oxidative status, bioenergetic level, as well as the cognitive performances, respectively. Results indicated that in GHB-intoxicated rats, enhanced oxidative stress, increased cholesterol level, and decreased anti-oxidative enzymes activities were detected in hippocampal regions. Intense oxidative stress paralleled well with reduced bioenergetics and poor performance in behavioral testing. However, in rats treated with melatonin following GHB intoxication, all above parameters and cognitive function were gradually returned to nearly normal levels. Melatonin also remarkably promoted the translocation of Nrf2 from cytoplasm to nucleus in a dose-dependent manner, thereby increased the Nrf2-ARE signaling-related downstream anti-oxidative enzymes activities. As melatonin effectively rescues hippocampal bioenergetics through depressing the oxidative stress by promoting Nrf2-ARE molecular machinery, this study thus highlights for the first time that clinical use of melatonin may serve as a therapeutic strategy to improve the cognitive function in unsuspecting victims suffered from GHB intoxication injury.

High salt diet impairs memory-related synaptic plasticity via increased oxidative stress and suppressed synaptic protein expression

Scope

A high salt (HS) diet is detrimental to cognitive function, in addition to having a role in cardiovascular disorders. However, the method by which an HS diet impairs cognitive functions such as learning and memory remains open.

Methods and results

In this study, we found that mice on a 7 week HS diet demonstrated disturbed short‐term memory in an object‐place recognition task, and both 4 week and 7 week HS treatments impaired long‐term memory, as evidenced in a fear conditioning test. Mechanistically, the HS diet inhibited memory‐related long‐term potentiation (LTP) in the hippocampus, while also increasing the levels of reactive oxygen species (ROS) in hippocampal cells and downregulating the expression of synapsin I, synaptophysin, and brain‐derived neurotrophic factor in specific encephalic region.

Conclusion

This suggests that oxidative stress or synaptic protein/neurotrophin deregulation was involved in the HS diet‐induced memory impairment. Thus, the present study provides novel insights into the mechanisms of memory impairment caused by excessive dietary salt, and underlined the importance of controlling to salt absorb quantity.

Immobilized enzymes: understanding enzyme – surface interactions at the molecular level

Interactions between immobilized enzymes and supporting surfaces are complex and context-dependent and can significantly alter enzyme structure, stability and activity.