An Efficient Method for Isolating and Purifying Nuclei from Mice Brain for Single-Molecule Imaging Using High-Speed Atomic Force Microscopy.

Nuclear pore complexes (NPCs) on the nuclear membrane surface have a crucial function in controlling the movement of small molecules and macromolecules between the cell nucleus and cytoplasm through their intricate core channel resembling a spiderweb with several layers. Currently, there are few methods available to accurately measure the dynamics of nuclear pores on the nuclear membranes at the nanoscale. The limitation of traditional optical imaging is due to diffraction, which prevents achieving the required resolution for observing a diverse array of organelles and proteins within cells. Super-resolution techniques have effectively addressed this constraint by enabling the observation of subcellular components on the nanoscale. Nevertheless, it is crucial to acknowledge that these methods often need the use of fixed samples. This also raises the question of how closely a static image represents the real intracellular dynamic system. High-speed atomic force microscopy (HS-AFM) is a unique technique used in the field of dynamic structural biology, enabling the study of individual molecules in motion close to their native states. Establishing a reliable and repeatable technique for imaging mammalian tissue at the nanoscale using HS-AFM remains challenging due to inadequate sample preparation. This study presents the rapid strainer microfiltration (RSM) protocol for directly preparing high-quality nuclei from the mouse brain. Subsequently, we promptly utilize HS-AFM real-time imaging and cinematography approaches to record the spatiotemporal of nuclear pore nano-dynamics from the mouse brain.

Nanoscopic Assessment of Anti-SARS-CoV-2 Spike Neutralizing Antibody Using High-Speed AFM.

Anti-spike neutralizing antibodies (S NAbs) have been developed for prevention and treatment against COVID-19. The nanoscopic characterization of the dynamic interaction between spike proteins and S NAbs remains difficult. By using high-speed atomic force microscopy (HS-AFM), we elucidate the molecular property of an S NAb and its interaction with spike proteins. The S NAb appeared as monomers with a Y conformation at low density and formed hexameric oligomers at high density. The dynamic S NAb-spike protein interaction at RBD induces neither RBD opening nor S1 subunit shedding. Furthermore, the interaction was stable at endosomal pH. These findings indicated that the S NAb could have a negligible risk of antibody-dependent enhancement. Dynamic movement of spike proteins on small extracellular vesicles (S sEV) resembled that on SARS-CoV-2. The sensitivity of variant S sEVs to S NAb could be evaluated using HS-AFM. Altogether, we demonstrate a nanoscopic assessment platform for evaluating the binding property of S NAbs.

Spatiotemporal tracking of small extracellular vesicle nanotopology in response to physicochemical stresses revealed by HS-AFM.

Small extracellular vesicles (sEVs) play a crucial role in local and distant cell communication. The intrinsic properties of sEVs make them compatible biomaterials for drug delivery, vaccines, and theranostic nanoparticles. Although sEV proteomics have been robustly studied, a direct instantaneous assessment of sEV structure dynamics remains difficult. Here, we use the high-speed atomic force microscopy (HS-AFM) to evaluate nanotopological changes of sEVs with respect to different physicochemical stresses including thermal stress, pH, and osmotic stress. The sEV structure is severely altered at high-temperature, high-pH, or hypertonic conditions. Surprisingly, the spherical shape of the sEVs is maintained in acidic or hypotonic environments. Real-time observation by HS-AFM imaging reveals an irreversible structural change in the sEVs during transition of pH or osmolarity. HS-AFM imaging provides both qualitative and quantitative data at high spatiotemporal resolution (nanoscopic and millisecond levels). In summary, our study demonstrates the feasibility of HS-AFM for structural characterization and assessment of nanoparticles.

How SARS-CoV-2 and Other Viruses Build an Invasion Route to Hijack the Host Nucleocytoplasmic Trafficking System.

The host nucleocytoplasmic trafficking system is often hijacked by viruses to accomplish their replication and to suppress the host immune response. Viruses encode many factors that interact with the host nuclear transport receptors (NTRs) and the nucleoporins of the nuclear pore complex (NPC) to access the host nucleus. In this review, we discuss the viral factors and the host factors involved in the nuclear import and export of viral components. As nucleocytoplasmic shuttling is vital for the replication of many viruses, we also review several drugs that target the host nuclear transport machinery and discuss their feasibility for use in antiviral treatment.

Hepatoprotective activity of okra (Abelmoschus esculentus L.) in sodium nitrite-induced hepatotoxicity.

BACKGROUND AND AIM: For years, people have used sodium nitrite as a food preservative. This study determined the effect of okra (Abelmoschus esculentus L.) pod methanol extract (OPME) on mice with hepatotoxicity induced by sodium nitrite. The flavonoid and total phenolic levels, serum biochemistry, and liver histology were examined. MATERIALS AND METHODS: Green okra pod extraction was performed using ethanol methanol solvent. Thirty adult male BALB/c mice (8-10 weeks, ~30 g) were divided into six groups: Normal control, negative control (sodium nitrite 50 mg/kg BW exposure), and treatment groups (sodium nitrite exposure and OPME at doses of 50, 100, 200, and 400 mg/kg BW). Subsequently, they were exposed to sodium nitrite and administered multiple doses of OPME for 19 days by gavage. After that, serum was used for biochemical evaluation, and liver histological analysis was performed. All data were statistically analyzed (α=0.05). RESULTS: All doses of OPME reduced the levels of nitric oxide (NO), malondialdehyde (MDA), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). In this research, both superoxide dismutase (SOD) and catalase (CAT) levels increased in all OPME-administered treatments. All doses also reduced necrotic cells, proportion of swollen cells, and inflammation in liver histological analysis. The results of this study showed that OPME exerted hepatoprotective effects by lowering MDA, NO, ALT, and AST levels. It also improved SOD and CAT levels and recovered damaged liver tissue to its normal state. The optimal dose of OPME was 50-100 mg/kg BW. CONCLUSION: OPME has potential as a natural hepatoprotective agent against sodium nitrite exposure.

Hepatoprotective effect of crude polysaccharides extracted from Ganoderma lucidum against carbon tetrachloride-induced liver injury in mice.

BACKGROUND AND AIM: Natural products are currently widely used as alternative treatments for liver disease. The study aimed to determine the hepatoprotective effect of crude polysaccharides extracted from Ganoderma lucidum against liver injury induced by carbon tetrachloride (CCl4). MATERIALS AND METHODS: Twenty-four male BALB/C mice were randomly divided into six groups. Serum and liver samples were taken on day 10 after G. lucidum administration. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were measured using enzyme-linked immunosorbent assays, and the histology of the liver was evaluated using light microscopy. RESULTS: G. lucidum extract significantly decreased the levels of ALT, AST, and MDA and significantly increased the levels of SOD and CAT. In the histological evaluation, the liver tissue of CCl4-treated mice exhibited hydropic degeneration, necrosis, and sinusoidal dilatation. G. lucidum extract administration improved this liver tissue histopathology. CONCLUSION: Crude polysaccharides extracted from G. lucidum showed a hepatoprotective effect, regenerating damaged liver tissue.