Evaluation of the cytotoxic effect of Ly2109761 on HeLa cells using the xCELLigence RTCA system

Characterization of an aspartate aminotransferase encoded by YPO0623 with frequent nonsense mutations in Yersinia pestis

Yersinia pestis, the causative agent of plague, is a genetically monomorphic bacterial pathogen that evolved from Yersinia pseudotuberculosis approximately 7,400 years ago. We observed unusually frequent mutations in Y. pestis YPO0623, mostly resulting in protein translation termination, which implies a strong natural selection. These mutations were found in all phylogenetic lineages of Y. pestis, and there was no apparent pattern in the spatial distribution of the mutant strains. Based on these findings, we aimed to investigate the biological function of YPO0623 and the reasons for its frequent mutation in Y. pestis. Our in vitro and in vivo assays revealed that the deletion of YPO0623 enhanced the growth of Y. pestis in nutrient-rich environments and led to increased tolerance to heat and cold shocks. With RNA-seq analysis, we also discovered that the deletion of YPO0623 resulted in the upregulation of genes associated with the type VI secretion system (T6SS) at 26°C, which probably plays a crucial role in the response of Y. pestis to environment fluctuations. Furthermore, bioinformatic analysis showed that YPO0623 has high homology with a PLP-dependent aspartate aminotransferase in Salmonella enterica, and the enzyme activity assays confirmed its aspartate aminotransferase activity. However, the enzyme activity of YPO0623 was significantly lower than that in other bacteria. These observations provide some insights into the underlying reasons for the high-frequency nonsense mutations in YPO0623, and further investigations are needed to determine the exact mechanism.

Attenuation of Yersinia pestis fyuA Mutants Caused by Iron Uptake Inhibition and Decreased Survivability in Macrophages

Yersinia pestis is the etiological agent of plague, a deadly infectious disease that has caused millions of deaths throughout history. Obtaining iron from the host is very important for bacterial pathogenicity. Y. pestis possesses many iron uptake systems. Yersiniabactin (Ybt) plays a major role in iron uptake in vivo and in vitro, and in virulence toward mice as well. FyuA, a β-barrel TonB-dependent outer membrane protein, serves as the receptor for Ybt. In this study, we examined the role of the fyuA gene in Y. pestis virulence using different challenging ways and explored the underlying mechanisms. The BALB/c mouse infection assay showed that the virulence of the mutant strains (ΔfyuA and ΔfyuAGCAdel) was lower when compared with that of the wild-type (WT) strain 201. Furthermore, the attenuation of virulence of the mutant strains via subcutaneous and intraperitoneal challenges was far greater than that via intravenous injection. Iron supplementation restored lethality during subcutaneous challenge with the two mutants. Thus, we speculated that the attenuated virulence of the mutant strains toward the mice may be caused by dysfunctional iron uptake. Moreover, ΔfyuA and ΔfyuAGCAdel strains exhibited lower survival rates in murine RAW264.7 macrophages, which might be another reason for the attenuation. We further explored the transcriptomic differences between the WT and mutant strains at different temperatures and found that the expressions of genes related to Ybt synthesis and its regulation were significantly downregulated in the mutant strains. This finding indicates that fyuA might exert a regulatory effect on Ybt. Additionally, the expressions of the components of the type III secretion system were unexpectedly upregulated in the mutants, which is inconsistent with the conventional view that the upregulation of the virulence genes enhances the virulence of the pathogens.

Treatment of Acute Kidney Injury Using a Dual Enzyme Embedded Zeolitic Imidazolate Frameworks Cascade That Catalyzes In Vivo Reactive Oxygen Species Scavenging

Significant advances have been made in recent years for the utilization of natural enzymes with antioxidant properties to treat acute kidney injury (AKI). However, these enzymes have been of limited clinical utility because of their limited cellular uptake, poor pharmacokinetic properties, and suboptimal stability. We employed a novel biomimetic mineralization approach to encapsulate catalase (CAT) and superoxide dismutase (SOD) in a zeolitic imidazolate framework-8 (ZIF-8). Next, this SOD@CAT@ZIF-8 complex was anchored with MPEG₂₀₀₀-COOH to yield an MPEG₂₀₀₀-SOD@CAT@ZIF-8 (PSCZ) composite. The composite was then used as a stable tool with antioxidant properties for the integrated cascade-based treatment of AKI, remarkably improved intracellular enzyme delivery. This dual-enzyme-embedded metal-organic framework could effectively scavenge reactive oxygen species. In conclusion, the ZIF-8-based "armor plating" represents an effective means of shielding enzymes with improved therapeutic utility to guide the precision medicine-based treatment of AKI.

Bioproduction, structure elucidation and in vitro antiproliferative effect of eumelanin pigment from Streptomyces parvus BSB49

In this study, the structure of the purified extracellular eumelanin pigment isolated from Streptomyces spp. was elucidated by detailed analysis via two different spectroscopic techniques (FT-IR and NMR). In vitro antiproliferative effects of eumelanin were evaluated on HeLa cell line. These experiments were carried out with the evaluation of the parameters including cell viability, cell index, and mitotic index. With the cell viability and cell index, IC50 concentration of eumelanin was determined as 10 μM. This result showed that the IC50 concentration of eumelanin decreased the values of cell viability, cell index and mitotic index. These changes are statistically significant (p < 0.01). The ability of the dissolved eumelanin (250 μg mL^-1) to scavenge free radicals was determined via DPPH and ABTS and was shown to be about 87.73% and 75.2%, respectively, compared with standard antioxidants. It was observed that dry weights of eumelanin yield among the selected strains ranged from 160 to 240 mg L^-1. The strain with the highest production potential was selected for 16S rDNA sequence analysis and, accordingly, the selected strain BSB49 was identified as Streptomyces parvus and the sequence analysis results were deposited in NCBI under accession number MK894155.

A novel method for evaluating the dynamic biocompatibility of degradable biomaterials based on real-time cell analysis

Degradable biomaterials have emerged as a promising type of medical materials because of their unique advantages of biocompatibility, biodegradability and biosafety. Owing to their bioabsorbable and biocompatible properties, magnesium-based biomaterials are considered as ideal degradable medical implants. However, the rapid corrosion of magnesium-based materials not only limits their clinical application but also necessitates a more specific biological evaluation system and biosafety standard. In this study, extracts of pure Mg and its calcium alloy were prepared using different media based on ISO 10993:12; the Mg²⁺ concentration and osmolality of each extract were measured. The biocompatibility was investigated using the MTT assay and xCELLigence real-time cell analysis (RTCA). Cytotoxicity tests were conducted with L929, MG-63 and human umbilical vein endothelial cell lines. The results of the RTCA highly matched with those of the MTT assay and revealed the different dynamic modes of the cytotoxic process, which are related to the differences in the tested cell lines, Mg-based materials and dilution rates of extracts. This study provides an insight on the biocompatibility of biodegradable materials from the perspective of cytotoxic dynamics and suggests the applicability of RTCA for the cytotoxic evaluation of degradable biomaterials.

Isoimperatorin Induces Apoptosis of Nasopharyngeal Carcinoma Cells via the MAPK/ERK1/2 Signaling Pathway

Objective

To investigate the effect of isoimperatorin on nasopharyngeal carcinoma CNE2 cell apoptosis and the role of the MAPK/ERK1/2 signaling pathway in inducing apoptosis.

Methods

Real-time cellular analysis technology (RTCA) and MTT were used to detect cell proliferation; Annexin V-FITC/PI dual-fluorescence flow cytometry analysis, Hoechst 33342 staining, and mitochondrial membrane potential detection kit were used to detect cell apoptosis; western blot was used to detect protein expression.

Results

Different concentrations of isoimperatorin (10 μM, 20 μM, 20 μM, 20 μM, 20 μM, 20 μM, 20 μM, 20 

Conclusion

Isoimperatorin can induce nasopharyngeal carcinoma CNE2 cell apoptosis through the MAPK/ERK1/2 signaling pathway.