YBX1 Promotes MSC Osteogenic Differentiation by Activating the PI3K/AKT Pathway.

INTRODUCTION: Bone metabolism has an essential role in bone disease, but its specific mechanism remains unclear. Y-Box Binding Protein 1 (YBX1) is a gene with broad nucleic acid binding properties, which encodes a highly conserved cold shock domain protein. Previous studies have shown that YBX1 is closely related to cell differentiation. However, the function of YBX1 in osteoblast differentiation of bone marrow mesenchymal stem cells (MSCs) was unclear. METHODS: To explore the effect and specific mechanism of YBX1 in osteogenic differentiation of MSCs, we used PCR, Western blot, Alizarin red Staining, alkaline phosphatase (ALP) assays, and siRNA knockdown in our research. We found that YBX1 gradually increased during the process of osteogenic differentiation of MSCs. YBX1 siRNA could negatively regulate the MSCs osteogenic differentiation. Mechanistic studies revealed that YBX1 knockdown could inhibit PI3K/AKT pathway. Furthermore, the specific agonist (SC79) of PI3K/AKT pathway could restore the impaired MSCs osteogenic differentiation which was mediated by YBX1 knockdown. Taken together, we concluded that YBX1 could positively regulate the osteogenic differentiation of MSCs by activating the PI3K/AKT pathway. RESULTS AND DISCUSSION: These results helped us further understand the mechanism of osteogenesis and revealed that YBX1 might be a selectable target in the bone repair field. CONCLUSION: Our study provides a new target and theoretical basis for the treatment of bone diseases.

Natural organic matters promoted conjugative transfer of antibiotic resistance genes: Underlying mechanisms and model prediction.

Dissemination of antibiotic resistance gene (ARG) is a huge challenge around the world. Natural organic matter (NOM) is one of the most commonly components in aquatic systems. Information regarding ARG transfer induced by NOM is still lacking. In this study, experimental exploration and model prediction on RP4 plasmid conjugative transfer between bacteria under NOM exposure was conducted. Compared with no exposure, the conjugative transfer frequency of RP4 plasmid increased 7.1-fold and 3.2-fold under exposure to 10 kDa and 100 kDa NOM exposure, respectively. NOM exposure with a lower molecular weight and higher concentration promoted gene expressions related to reactive oxygen species generation, cell membrane permeability, intercellular contact, quorum sensing, and energy driving force. Concurrently, the expressions of conjugation genes in RP4 plasmid were also upregulated. Moreover, model prediction demonstrated that the maintenance of the acquired plasmid was shortened to 133 h under 10 kDa NOM exposure compared with the control (200 h). Long-term NOM exposure enhanced transfer frequency and transfer rate of ARG. This study firstly theoretically and experimentally revealed the underlying mechanisms for promoting ARG transfer by NOM.

Environmental free radicals efficiently inhibit the conjugative transfer of antibiotic resistance by altering cellular metabolism and plasmid transfer.

Spread of antibiotic-resistant genes (ARGs) is a global public safety issue and inhibition their transfer is imperative. In this study, a novel strategy using environmental free radical exposure was developed to inhibit conjugative transfer of ARGs (RP4 plasmid) in aqueous solutions. Long-time free radical (·OH, 1O2, and O2·-) exposure significantly suppressed the conjugative transfer frequency of ARGs between Escherichia coli (E. coli) strains, and ·OH was more likely to attack ARG, thereby inhibiting the conjugate transfer frequency, compared to 1O2 and O2·-. Compared with the control, the conjugative transfer frequency significantly decreased from 4.08 × 10-5 to 1.2 × 10-8 after 10 min free radical exposure, confirming that the transfer and proliferation of ARGs were well inhibited. Correspondingly, the number of transconjugant significantly decreased by 61.7% after 10 min free radical exposure. Significant reductions in reactive oxygen species levels (ROS content and enzyme levels) and DNA damage-induced responses in the donor strains were observed after 10 min free radical exposure. Concurrently, intercellular contact was also weakened via inhibiting the synthesis of polysaccharides in extracellular polymeric substances. Moreover, the expressions of plasmid transfer genes were down-regulated after 10 min exposure due to the shortage of adenosine-triphosphate supply. This study firstly disclosed the underneath mechanisms for depressing ARGs transfer and dissemination via environmental free radical exposure.

Inhibited conjugative transfer of antibiotic resistance genes in antibiotic resistant bacteria by surface plasma.

Antibiotic resistant bacteria (ARB) and resistance genes (ARGs) are emerging environmental pollutants with strong pathogenicity. In this study, surface plasma was developed to inactivate the donor ARB with Escherichia coli (AR E. coli) as a model, eliminate ARGs, and inhibit conjugative transfer of ARGs in water, highlighting the influences of concomitant inorganic ions. Surface plasma oxidation significantly inactivated AR E. coli, eliminated ARGs, and inhibited conjugative transfer of ARGs, and the presence of NO3-, Cu2+, and Fe2+ all promoted these processes, and SO42- did not have distinct effect. Approximately 4.5log AR E. coli was inactivated within 10 min treatment, and it increased to 7.4log AR E. coli after adding Fe2+. Integrons intI1 decreased by 3.10log (without Fe2+) and 4.43log (adding Fe2+); the addition of Fe2+ in the surface plasma induced 99.8% decline in the conjugative transfer frequency. The inhibition effects on the conjugative transfer of ARGs were mainly attributed to the reduced reactive oxygen species levels, decreased DNA damage-induced response, decreased intercellular contact, and down-regulated expression of plasmid transfer genes. This study disclosed underlying mechanisms for inhibiting ARGs transfer, and supplied a prospective technique for ARGs control.

Co-transport of graphene oxide and titanium dioxide nanoparticles in saturated quartz sand: Influences of solution pH and metal ions.

Increasing production and application of nanomaterials lead to their environmental release possible. The nanomaterials with different properties may transport together in porous media, and consequently affect their environmental fates. In this study, column experiments were conducted to investigate the co-transport of two typical nanomaterials, graphene oxide (GO) and nano-titanium dioxide (nTiO2), in saturated quartz sand in NaCl and CaCl2 electrolyte solutions under both favorable and unfavorable conditions. The breakthrough curves as well as the retained profiles of single and binary nanoparticles were examined. The results indicated that nTiO2 significantly enhanced the GO retention under all examined conditions, especially at lower pH, higher ionic strength and the presence of divalent cation Ca2+. This might be attributed to the formation of less negatively charged and larger-sized GO-nTiO2 agglomerates as well as the increased retention sites on sand surface by preferentially deposited nTiO2. However, GO merely slightly enhanced the transport of nTiO2 in NaCl solutions, whereas had negligible effect on nTiO2 transport and retention in CaCl2 solutions. The highly hydrophilic and mobile GO served as a carrier and facilitated the transport of nTiO2 in NaCl solutions. In CaCl2 solutions, the strong attachment affinity between positively charged nTiO2 and negatively charged quartz sand (at pH 4.5), and dramatical accumulation of large nTiO2 agglomerates near the column inlets (at pH 6.5) led to significant deposition of nTiO2 on quartz sand. The co-presence of GO failed to counteract the retention of nTiO2 particles on sand.