Inactivation of polyphenol oxidase by low intensity DC field: Experiment and mechanism analysis via molecular dynamics simulation and molecular docking.

In this study, inactivation of mushroom polyphenol oxidase (PPO) by low intensity direct current (DC) electric field and its molecular mechanism were investigated. In the experiments under 3 V/cm, 5 V/cm, 7 V/cm and 9 V/cm electric fields, PPOs were all completely inactivated after different exposure times. Under 1 V/cm, a residual activity of 11.88 % remained. The inactivation kinetics confirms to Weibull model. Under 1-7 V/cm, n value closes to a constant about 1.3. The structural analysis of PPO under 3 V/cm and 5 V/cm by fluorescence emission spectroscopy and molecular dynamics (MD) simulation showed that the tertiary structure was slightly changed with increased radius of gyration, higher potential energy and rate of C-alpha fluctuation. After exposure to the electric field, most of the hydrophobic tryptophan (TRP) residues turned to the hydrophilic surface, resulting the fluorescence red-shifted and quenched. Molecular docking indicated that the receptor binding domain of catechol in PPO was changed. PPO under electric field was MD simulated the first time, revealing the changing mechanism of the electric field itself on PPO, a binuclear copper enzyme, which has a metallic center. All these suggest that the low intensity DC electric field would be a promising option for enzymatic browning inhibition or even enzyme activity inactivation.

Fe3O4 coated stent prevent artery neointimal hyperplasia by inhibiting vascular smooth muscle cell proliferation.

In-stent restenosis (ISR), caused by aggressive vascular smooth muscle cell (VSMC) proliferation, is a serious complication of stenting. Therefore, developing therapeutic approaches that target VSMC inhibition is imperative. Our previous study showed that VSMC hyperplasia was attenuated after iron stent degradation, and VSMC proliferation around the stented section was arrested. The corrosion products of the iron stents were primarily Fe3O4 particles. Therefore, we hypothesized that Fe3O4 particles generated by iron stents would prevent neointimal hyperplasia by inhibiting VSMC proliferation. To test this hypothesis, culture assays and flow cytometry were performed to investigate the proliferation of VSMC. Global gene sequencing and Kyoto Encyclopedia of Genes and Genomes enrichment analyses were performed to investigate the underlying mechanisms. Fe3O4-coated stents were implanted into rabbit carotid arteries to evaluate the inhibitory effects of Fe3O4 on neointimal hyperplasia. The major findings of the study were as follows: 1) Fe3O4 attenuated neointimal hyperplasia by preventing VSMC proliferation after stenting; 2) Fe3O4 exerted inhibitory effects on VSMCs by downregulating proliferative genes such as SOX9, EGR4, and TGFB1, but upregulated inhibitory genes such as DNMT1, TIMP3, and PCNA; 3) Fe3O4 inhibited VSMCs by preventing phenotypic transformation from the contractile to the synthetic phase; and 4) Fe3O4-coated stents achieved satisfactory hemocompatibility in a rabbit model. Our study highlights the additional benefits of Fe3O4 particles in inhibiting VSMC proliferation, indicating that Fe3O4 coated stent potentially served as an attractive therapeutic approach for ISR prevention.