Redox‐modulated colorimetric detection of ascorbic acid and alkaline phosphatase activity with gold nanoparticles

Gold nanoparticles (AuNPs) exhibit characteristic absorption peaks in the ultraviolet visible region due to their special surface plasmon resonance effect. This characteristic absorption peak would change with the relative colour varying from wine red to orange‐yellow upon sequential addition of ascorbic acid (AA) into the mixture of AuNPs and Ag(I). Similar observations also could be found when the hydrolysis product of sodium l ‐ascorbyl‐2‐phosphate with alkaline phosphatase (ALP) was used as an alternative to AA. Results of structure characterization confirmed that the phenomena were due to the reduction of Ag(I) to Ag(0) on the surface of AuNPs and the formation of core‐shell AuNPs@Ag. Therefore, a colorimetric assay for rapid visual detection of AA and ALP based on redox‐modulated silver deposition on AuNPs has been proposed. Under the optimal experimental conditions, the absorbance variation ΔA_{522 nm}/A_{370 nm} of AuNPs was proportional to the concentration of AA (5–60 μmol/L) and ALP (3–18 U/L) with the corresponding detection limit of 2.44 μmol/L for AA and 0.52 U/L for ALP. The assay showed excellent selectivity towards AA and ALP. Moreover, the assay has been applied to detect AA and ALP activity in real samples with satisfying results.     

Low METTL3 level in midgut of the Bombyx mori inhibit the proliferation of nucleopolyhedrovirus

N6-methyladeosine (m⁶A) plays an important role in virus infection and replication. Bombyx mori nuclear polyhedrosis is caused by Bombyx mori nucleopolyhedrovirus (BmNPV) infection. Expression levels of m⁶A-modification-related genes after the infection of BmNPV were detected at first. Then, expression levels of BmNPV nucleocapsid protein gene VP39 and envelope fusion protein gene GP64 after knockdown of METTL3in vitro were quantified to identify the effect of m⁶A modification on BmNPV. BmNPV firstly infects the larval midgut in case of oral infection. Subsequently, to clarify the relationship between m⁶A modification and resistance of the silkworm to BmNPV, we detected the expression levels of m⁶A-modification-related genes invivo before and after infection of BmNPV. The results indicated that low METTL3 level hindered the proliferation of BmNPV to some extent, and silkworm strain with low METTL3 level showed stronger resistance against BmNPV. This study will accumulate new experimental data for elucidating the resistance mechanism of silkworm against BmNPV.     

cDNA cloning,expression, and enzymatic activity of a novel endogenous cellulase from the beetle Batocera horsfieldi

In this study, we report a novel cellulase [β-1,4-endoglucanase (EGase), EC 3.2.1.4] cDNA (Bh-EGase II) belonging to the glycoside hydrolase family (GHF) 45 from the beetle Batocera horsfieldi. The Bh-EGase II gene spans 720 bp and consists of a single exon coding for 239 amino acid residues. Bh-EGase II showed 93.72% protein sequence identity to Ag-EGase II from the beetle Apriona germari. The GHF 45 catalytic site is conserved in Bh-EGase II. Bh-EGase II has three putative N-glycosylation sites at 56–58 (N–K–S), 99–101 (N–S–T), and 237–239 (N–Y–S), respectively. The cDNA encoding Bh-EGase II was expressed in baculovirus-infected insect BmN cells and Bombyx mori larvae. Recombinant Bh-EGase II from BmN cells and larval hemolymph had an enzymatic activity of approximately 928 U/mg. The enzymatic catalysis of recombinant Bh-EGase II showed the highest activity at 50 °C and pH 6.0.     

Overexpression of microRNA-99a Attenuates Cardiac Hypertrophy

Pathological cardiomyocyte hypertrophy is associated with significantly increased risk of heart failure, one of the leading medical causes of mortality worldwide. MicroRNAs are known to be involved in pathological cardiac remodeling. However, whether miR-99a participates in the signaling cascade leading to cardiac hypertrophy is unknown. To evaluate the role of miR-99a in cardiac hypertrophy, we assessed the expression of miR-99a in hypertrophic cardiomyocytes induced by isoprenaline (ISO)/angiotensin-II (Ang II) and in mice model of cardiac hypertrophy induced by transverse aortic constriction (TAC). Expression of miR-99a was evaluated in these hypertrophic cells and hearts. We also found that miR-99a expression was highly correlated with cardiac function of mice with heart failure (8 weeks after TAC surgery). Overexpression of miR-99a attenuated cardiac hypertrophy in TAC mice and cellular hypertrophy in stimuli treated cardiomyocytes through down-regulation of expression of mammalian target of rapamycin (mTOR). These results indicate that miR-99a negatively regulates physiological hypertrophy through mTOR signaling pathway, which may provide a new therapeutic approach for pressure-overload heart failure.     

Mesenchymal stem cells protect against ferroptosis via exosome-mediated stabilization of SLC7A11 in acute liver injury

Mesenchymal stem cells (MSCs) have attracted interest for their potential to alleviate liver injury. Here, the protective effect of MSCs on carbon tetrachloride (CCl₄)-induced acute liver injury (ALI) was investigated. In this study, we illustrated a novel mechanism that ferroptosis, a newly recognized form of regulated cell death, contributed to CCl₄-induced ALI. Subsequently, based on the in vitro and in vivo evidence that MSCs and MSC-derived exosomes (MSC-Exo) treatment achieved pathological remission and inhibited the production of lipid peroxidation, we proposed an MSC-based therapy for CCl₄-induced ALI. More intriguingly, treatment with MSCs and MSC-Exo downregulated the mRNA level of prostaglandin-endoperoxide synthase 2 (Ptgs2) and lipoxygenases (LOXs) while it restored the protein level of SLC7A11 in primary hepatocytes and mouse liver, indicating that the inhibition of ferroptosis partly accounted for the protective effect of MSCs and MSC-Exo on ALI. We further revealed that MSC-Exo-induced expression of SLC7A11 protein was accompanied by increasing of CD44 and OTUB1. The aberrant expression of ubiquitinated SLC7A11 triggered by CCl₄ could be rescued with OTUB1-mediated deubiquitination, thus strengthening SLC7A11 stability and thereby leading to the activation of system X_C⁻ to prevent CCl₄-induced hepatocyte ferroptosis. In conclusion, we showed that MSC-Exo had a protective role against ferroptosis by maintaining SLC7A11 function, thus proposing a novel therapeutic strategy for ferroptosis-induced ALI.Subject terms: Hepatotoxicity, Experimental models of disease

Schematic diagram of the protective effect of MSC-derived exosomes on maintaining SLC7A11 function during ferroptosis involved in CCl₄-induced ALI.     

Preparation and structure of chitosan soluble in wide pH range

Two kinds of chitosans, namely N-acetylated and N-deacetylated chitosan were prepared by the modified processes. They can dissolve in both acid and alkali solution. ¹³C NMR was used to study the basic solution of chitosan, and XRD, FT-IR and SEM were used to study the structure of N-acetylated and N-deacetylated chitosan. The result from X-ray diffraction showed that a transformation of crystal structure occurred during the N-acetylation or N-deacetylation process with the decrease of crystallinity and expansion of crystal lattices. FT-IR spectra revealed that the intermolecular and intramolecular hydrogen bonds were destroyed by both treatments and a looser structure was observed by the SEM. The lower crystallinity, the decreased intermolecular interactions, the more disordered and looser structure were easy for the permeation of LiOH/urea aqueous solution and coordinated with the breakage of intermolecular and intramolecular hydrogen bond by LiOH at low temperature, the prepared chitosans dissolved in LiOH/urea/H₂O mixture.     

Molecular Cytogenetic Identification of a New Wheat-Rye 6R Chromosome Disomic Addition Line with Powdery Mildew Resistance

Rye (Secale cereale L.) possesses many valuable genes that can be used for improving disease resistance, yield and environment adaptation of wheat (Triticum aestivum L.). However, the documented resistance stocks derived from rye is faced severe challenge due to the variation of virulent isolates in the pathogen populations. Therefore, it is necessary to develop desirable germplasm and search for novel resistance gene sources against constantly accumulated variation of the virulent isolates. In the present study, a new wheat-rye line designated as WR49-1 was produced through distant hybridization and chromosome engineering protocols between common wheat cultivar Xiaoyan 6 and rye cultivar German White. Using sequential GISH (genomic in situ hybridization), mc-FISH (multicolor fluorescence in situ hybridization), mc-GISH (multicolor GISH) and EST (expressed sequence tag)-based marker analysis, WR49-1 was proved to be a new wheat-rye 6R disomic addition line. As expected, WR49-1 showed high levels of resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt) pathogens prevalent in China at the adult growth stage and 19 of 23 Bgt isolates tested at the seedling stage. According to its reaction pattern to different Bgt isolates, WR49-1 may possess new resistance gene(s) for powdery mildew, which differed from the documented powdery mildew gene, including Pm20 on chromosome arm 6RL of rye. Additionally, WR49-1 was cytologically stable, had improved agronomic characteristics and therefore could serve as an important bridge for wheat breeding and chromosome engineering.