Rapid, portable and visualizing nitrite detection enabled by a rationally designed meso-aminoindole substituted pyronine-based fluorescent probe.

Nitrite (NO2-) widely exists in our daily diet, and its excessive consumption can lead to detrimental effects on the human central nervous system and an elevated risk of cancer. The fluorescence probe method for the determination of nitrite has developed rapidly due to its simplicity, rapidity and sensitivity. Despite establishing various nitrite sensing platforms to ensure the safety of foods and drinking water, the simultaneous achievement of rapid, specific, affordable, visualizing, and on-site nitrite detection remains challenging. Here, we designed a novel fluorescent probe by using Rhodamine 800 as the fluorescent skeleton and 5-aminoindole as the specific reaction group to solve this problem. The probe shows a maximal fluorescence emission at 602 nm, thereby avoiding background emission interference when applied to food samples. Moreover, this unique probe exhibited excellent sensing capabilities for detecting nitrite. These included: a rapid response time within 3 min, a noticeable color change that the naked eye can observe, a low detection limit of 13.8 nM, and a remarkable selectivity and specificity to nitrite. Besides that, the probe can detect nitrite quantitatively in barreled drinking water, ham sausage, and pickles samples, with good recoveries ranging from 89.0 % to 105.8 %. More importantly, based on the probe fixation and signal processing technology, a portable and smart sensing platform was fabricated and made convenient and rapid analysis the content of NO2- in real samples possible. The results obtained in this work provide a new strategy for the design of high-performance nitrite probes and feasible technology for portable, rapid and visual detection of nitrite, and this probe holds the potential as a practical tool for alleviating concern regarding nitrite levels.

Specific genetic aberrations of parathyroid in Chinese patients with tertiary hyperparathyroidism using whole-exome sequencing.

Background: Tertiary hyperparathyroidism (THPT) is a peculiar subtype of hyperparathyroidism that usually develops from chronic kidney disease (CKD) and persists even after kidney transplantation. Unlike its precursor, secondary hyperparathyroidism (SHPT), THPT is characterized by uncontrolled high levels of calcium in the blood, which suggests the monoclonal or oligoclonal proliferation of parathyroid cells. However, the molecular abnormalities leading to THPT have not yet been fully understood. Methods: In this study, we analyzed DNA samples from hyperplastic parathyroid and corresponding blood cells of 11 patients with THPT using whole-exome sequencing (WES). We identified somatic single nucleotide variants (SNV) and insertions or deletions variants (INDEL) and performed driver mutation analysis, KEGG pathway, and GO functional enrichment analysis. To confirm the impact of selected driver mutated genes, we also tested their expression level in these samples using qRT-PCR. Results: Following quality control and mutation filtering, we identified 17,401 mutations, comprising 6690 missense variants, 3078 frameshift variants, 2005 stop-gained variants, and 1630 synonymous variants. Copy number variants (CNV) analysis showed that chromosome 22 copy number deletion was frequently observed in 6 samples. Driver mutation analysis identified 179 statistically significant mutated genes, including recurrent missense mutations on TBX20, ATAD5, ZNF669, and NOX3 genes in 3 different patients. KEGG pathway analysis revealed two enriched pathways: non-homologous end-joining and cell cycle, with a sole gene, PRKDC, involved. GO analysis demonstrated significant enrichment of various cellular components and cytobiological processes associated with four genes, including GO items of positive regulation of developmental growth, protein ubiquitination, and positive regulation of the apoptotic process. Compared to blood samples, THPT samples exhibited lower expression levels of PRKDC, TBX20, ATAD5, and NOX3 genes. THPT samples with exon mutations had relatively lower expression levels of PRKDC, TBX20, and NOX3 genes compared to those without mutations, although the difference was not statistically significant. Conclusion: This study provides a comprehensive landscape of the genetic characteristics of hyperplastic parathyroids in THPT, highlighting the involvement of multiple genes and pathways in the development and progression of this disease. The dominant mutations identified in our study depicted new insights into the pathogenesis and molecular characteristics of THPT.

Broad-Specificity Screening of Pyrethroids Enabled by the Catalytic Function of Human Serum Albumin on Coumarin Hydrolysis.

Sensing systems based on cholinesterase and carboxylesterase coupled with different transduction technologies have emerged for pesticide screening owing to their simple operation, fast response, and suitability for on-site analysis. However, the broad spectrum and specificity screening of pyrethroids over organophosphates and carbamates remains an unmet challenge for current enzymatic sensors. Human serum albumin (HSA), a multifunctional protein, can promote various chemical transformations and show a high affinity for pyrethroids, which offer a route for specific and broad-spectrum pyrethroid screening. Herein, for the first time, we evaluated the catalytic hydrolysis function of human serum albumin (HSA) on the coumarin lactone bond and revealed that HSA can act as an enzyme to catalyze the hydrolysis of the coumarin lactone bond. Molecular docking and chemical modifications indicate that lysine 199 and tyrosine 411 serve as the catalytic general base and contribute to most of the catalytic activity. Utilizing this enzymatic activity, a broad specific ratiometric fluorescence pyrethroids sensing system was developed. The binding energetics and binding constants of pesticides and HSA show that pyrethroids bind to HSA more easily than organophosphates and carbamates, which is responsible for the specificity of the sensing system. This study provides a general sensor platform and strategy for screening pesticides and reveals the catalytic activity of HSA on the hydrolysis of the coumarin lactone bond, which may open innovative horizons for the chemical sensing and biomedical applications of HSA.

Engineering a functional thyroid as a potential therapeutic substitute for hypothyroidism treatment: A systematic review.

Background: Hypothyroidism is a common hormone deficiency disorder. Although hormone supplemental therapy can be easily performed by daily levothyroxine administration, a proportion of patients suffer from persisting complaints due to unbalanced hormone levels, leaving room for new therapeutic strategies, such as tissue engineering and regenerative medicine. Methods: Electronic searches of databases for studies of thyroid regeneration or thyroid organoids were performed. A systematic review including both in vitro and in vivo models of thyroid regenerative medicine was conducted. Results: Sixty-six independent studies published between 1959 and May 1st, 2022 were included in the current systematic review. Among these 66 studies, the most commonly involved species was human (19 studies), followed by mouse (18 studies), swine (14 studies), rat (13 studies), calf/bovine (4 studies), sheep/lamb (4 studies) and chick (1 study). In addition, in these experiments, the most frequently utilized tissue source was adult thyroid tissue (46 studies), followed by embryonic stem cells (ESCs)/pluripotent stem cells (iPSCs) (10 studies), rat thyroid cell lines (7 studies), embryonic thyroid tissue (2 studies) and newborn or fetal thyroid tissue (2 studies). Sixty-three studies reported relevant thyroid follicular regeneration experiments in vitro, while 21 studies showed an in vivo experiment section that included transplanting engineered thyroid tissue into recipients. Together, 12 studies were carried out using 2D structures, while 50 studies constructed 3D structures. Conclusions: Each aspect of thyroid regenerative medicine was comprehensively described in this review. The recovery of optimal hormonal equilibrium by the transplantation of an engineered functional thyroid holds great therapeutic promise.

Modulation of the lipophilicity and molecular size of thiosemicarbazone inhibitors to regulate tyrosinase activity.

A group of 5-methylsalicylaldehyde thiosemicarbazone derivatives (HMTs) bearing different lipophilic and steric substituents attached at the 3-position of cresol ring were synthesized and investigated as mushroom tyrosinase (TYR) inhibitors. The ability of HMTs to inhibit the diphenolase activity of TYR was evaluated with L-DOPA as substrate by determining IC50 values in relation to their structure modifications. HMTs displayed distinct inhibitory competencies towards TYR activity with IC50 values in the range of 1.02-143.56 µM. A close correlation between their inhibition potency and both lipophilicity and molecular size was observed. The inhibitory effect of the hydroxyethyl-containing derivatives was much higher than the hydroxyethyl-free ones overall. Among them, HMT-NBO exhibited the most potent effect with IC50 of 5.85 µM, which was nearly 25-fold and 3.8-fold lower than its parent HMT-NBE and the control kojic acid, respectively. The hydroxyethyl clearly benefited the improvement of the inhibitory competences and acted as a regulating group of lipophilicity of the inhibitors. The kinetic analyses showed that HMTs were reversible and mixed type inhibitors against mushroom TYR. The inhibition mechanism was studied by means of fluorescence spectroscopy, FT-IR, ESI-MS and molecular docking analysis. The results indicated that the observed inhibitory effect of HMTs was accomplished by acting on the amino acid residues rather than by chelating the centre copper ions of TYR. Each of HMTs can insert the hydrophobic pocket and interact with the residues of TYR through Van der Waals forces and hydrogen bonds, with additional electrostatic interactions for HMT-NEE and HMT-NEO further strengthening the affinity. Meanwhile, the inhibitors were observed to bind with L-DOPA or/and L-DOPAquinone forming 1:1 stoichiometric complexes, probably exerting indirect inhibition against TYR activity.

Modulation of bovine serum albumin aggregation by glutathione functionalized MoS2 quantum dots.

In present study, a novel glutathione functionalized MoS2 quantum dots (GSH-MoS2 QDs) was synthesized from sodium molybdate dehydrate and glutathione by using a one-pot hydrothermal method. After they were characterized, the influence of GSH-MoS2 QDs on amyloid aggregation of bovine serum albumin (BSA) was investigated by various analytical methods including thioflavin T fluorescence assay, circular dichroism and transmission electron microscope. Moreover, the effect of GSH-MoS2 QDs on cytotoxicity induced by BSA amyloid fibrils and cell penetration were evaluated by MTT assay and confocal fluorescence imaging, respectively. The results indicated that the GSH-MoS2 QDs not only had good water solubility, excellent biocompatibility and low cytotoxicity, but also could obviously inhibit the aggregation of BSA and depolymerize the formed BSA aggregates. The data obtained from this work demonstrated that the GSH-MoS2 QDs is expected to become a candidate drug for the treatment of amyloid-related diseases.

Effect of resveratrol on the repair of kidney and brain injuries and its regulation on klotho gene in d-galactose-induced aging mice.

Resveratrol is a natural polyhydroxy trans-stilbene product with many biological activities. One of the most striking biological activities of it is its anti-aging potential. Resveratrol can exhibit anti-aging activity via a variety of signaling pathways, however, the repair effect of it on kidney and brain injury in aging mice induced by d-galactose and its regulation on klotho gene expression have not been reported. Herein, the anti-aging activity of resveratrol and its effect on the repair of kidney and brain injuries in d-galactose-induced aging mice, as well as its regulation of klotho gene expression in these two tissues were investigated. The results indicated that resveratrol could significantly increase the aged cell viability and improve the pathological status of aging mice via inhibiting the formation of malondialdehyde and enhancing the activities of superoxide dismutase and catalase. The histological analysis suggested that resveratrol could remarkably repair the damages of kidney and brain tissues in aging mice. Moreover, PCR and western blot have shown that resveratrol could obviously increase the anti-aging klotho gene expression in the above tissues. The data in this paper further revealed and enriched the anti-aging mechanism of resveratrol, and the methods established in this study can be used as a tool to evaluate the anti-aging activity of drugs to a certain extent.

Investigation on the effect of three isoflavones on the fibrillation of hen egg-white lysozyme.

In this paper, the effects of three isoflavones including daidzein, genistein, and puerarin on fibrillation of hen egg-white lysozyme were investigated by various analytical methods. The results demonstrated that all isoflavones could effectively inhibit the fibrillogenesis of hen egg-white lysozyme and destabilized the preformed fibrils of hen egg-white lysozyme in a dose-dependent manner. To further understand the inhibition mechanism, molecular modeling was carried out. The docking results demonstrated that the isoflavones could bind to two key fibrogenic sites in hen egg-white lysozyme through van der Waals force, electrostatic forces, and hydrogen bonding, as well as σ-π stacking. By these means, isoflavones could not only obviously enhance the hydrophobicity of the binding sites, but also greatly stabilize the native state of HEWL, which was able to postpone the fibrosis process of hen egg-white lysozyme.

A comparative study on the effects of resveratrol and oxyresveratrol against tyrosinase activity and their inhibitory mechanism.

Resveratrol and oxyresveratrol are two natural polyhydroxy trans-stilbene products. Previous studies have shown that both of them can effectively inhibit the activity of tyrosinase. However, little attention has been paid to study the difference of their inhibitory mechanism. To reveal this difference, in this work a comparative study on the inhibitory effects of resveratrol and oxyresveratrol against cellular tyrosinase activity and melanin content were investigated by B16F0 cells, and the inhibitory mechanism of them on tyrosinase was revealed by cell-free tyrosinase inhibition, intrinsic fluorescence spectrum, circular dichroism and molecular docking. The results showed that the inhibitory capacity of oxyresveratrol toward tyrosinase activity and melanin formation was better than that of resveratrol. The difference of their inhibitory mechanism may be closely related to the different types of inhibition, the different strength of their interaction with tyrosinase and the different number of hydrogen bonds between them. The data in this study provide a scientific basis for revealing the inhibitory mechanisms of resveratrol and oxyresveratrol toward tyrosinase, and lay an experimental foundation for further development and utilization of them.

Simultaneous Detection of Human Serum Albumin and Sulfur Dioxide in Living Cells Based on a Catalyzed Michael Addition Reaction.

As vital important bioactive species, human serum albumin (HSA) and sulfur dioxide (SO2) are essential molecules in the organisms and act a pivotal part in many biological events. Although studies have shown that SO2-induced HSA radicals can cause oxidative damage, the underlying mechanism of the synergistic effect of HSA and SO2 in various diseases is obscure, mainly because of the lack of powerful tools that can simultaneously detect HSA and SO2 in living systems. In this work, we report a novel single-site, double-sensing fluorescent probe 1 for the simultaneous detection of HSA and SO2. The probe is based on our finding that HSA can catalyze a Michael addition reaction between the probe and SO2, which induces a change in fluorescence. Probe 1 can effectively entered the endoplasmic reticulum and can be used to image exogenously introduced and de novo synthesis of HSA in endoplasmic reticulum. Furthermore, the simultaneous detection of HSA and SO2 was realized for the first time with probe 1. More important, we observed that HSA still retains its activity to catalyze the Michael addition reaction of 1 and SO2 in living cells, which may provide a significant boost in the study of the role of HSA in medicine and pharmacy.

A novel fluorescence probe based on specific recognition of GABAA receptor for imaging cell membrane.

Long and real time imaging of cell membrane is very important for better understanding of cell performances in physiological and pathological processes. Nowadays, fluorescence probe analysis has become an indispensable tool for monitoring cell membrane. Herein, a novel fluorescent probe based on specific recognition of GABAA receptor was developed for imaging cell membrane. The probe synthesized in this work has been successfully applied to image different kinds of cell membrane with some advantages over the reported probes. Moreover, the probe also showed good superiority in the preliminary screening GABAA drugs.

Inhibitory effects of four anthraquinones on tyrosinase activity: Insight from spectroscopic analysis and molecular docking.

In this study, the inhibitory effects of four anthraquinones including chrysophanol, emodin, physcione and rhein on tyrosinase were investigated by enzyme inhibition assay. The results indicated that all of anthraquinones could significantly inhibit the activity of tyrosinase in a competitive manner. To gain insight into the inhibitory mechanism of anthraquinones on tyrosinase, spectroscopic analysis combined with molecular docking studies were performed. Fluorescence results showed that anthraquinones interacted with tyrosinase by static quenching in a molecular ratio of 1:1. Circular dichroism and molecular docking suggested that anthraquinones could not chelate directly the copper ions but they could bind to amino acid residues in the active site of tyrosinase via electrostatic forces and hydrophobic interactions, as well as hydrogen bonds, and the binding processes resulted in the conformational changes of tyrosinase and prevented the substrate (L-DOPA) from entering the active site, which led to the decrease of tyrosinase activity. Our study in this paper provides a scientific basis for revealing the inhibition of tyrosinase activity by anthraquinone compounds. As a natural inhibitor of tyrosinase, anthraquinones can be used as a potential agent to reduce enzymatic browning reactions, such as food browning and melanization of skin.

Studies on the effect of a Fupenzi glycoprotein on the fibrillation of bovine serum albumin and its antioxidant activity.

In this study, the effect of a glycoprotein obtained from Fupenzi (FPZ) (Rubus chingii Hu.) on the fibrillation of bovine serum album (BSA) was investigated by multi-spectroscopic methods and transmission electron microscopy. Moreover, the cytotoxicity of the glycoprotein and the effect of it on H2O2-induced cell viability were investigated by cell counting kit and ß-galactosidase kit, respectively. The experimental results indicated that the glycoprotein showed very low toxicity to NRK-52E cells and could obviously delay cell senescence and improve cell viability. Moreover, the glycoprotein could effectively inhibit the formation of BSA fibrils and destroy the stability of preformed BSA fibrils in a concentration-dependent manner. Generally, antioxidant capacities are thought to be related to the anti-amyloidogenic activity of inhibitors; therefore, to reveal the inhibitory mechanism, the anti-oxidative property of the glycoprotein was examined by DPPH and ABTS assays. The results demonstrated that FPZ glycoprotein had a remarkable antioxidant activity and the IC50 values of DPPH and ABTS were 0.249 mg mL-1 and 0.092 mg mL-1, respectively. This work suggested that the FPZ glycoprotein had the potential to be designed a new therapeutic agent for attenuating aging and preventing the age-related diseases.

Cysteamine functionalized MoS2 quantum dots inhibit amyloid aggregation.

In this study, cysteamine-functionalized molybdenum disulfide quantum dots (MoS2 QDs) were synthesized by a one-pot hydrothermal method. A range of techniques including of Thioflavin T and 8-Anilino-1-naphthalenesulfonic acid fluorescence assays, circular dichroism, and transmission electron microscope have been employed to determination the efficacy of MoS2 QDs on the inhibition/reversion of fibrillation and hindering cytotoxicity induced by protofibrils and amyloid fibrils of bovine serum albumin (BSA). Results demonstrated that MoS2 QDs could effectively inhibit the fibrillogenesis and destabilize preformed fibrils of BSA in a concentration-dependent manner. Cytotoxicity protection and imagine on Hela cells was investigated using the methyl thiazolyl tetrazolium (MTT) assay. It was found that MoS2 QDs not only has good biocompatibility, low toxicity and good cell penetration, but also could effectively decrease the cytotoxicity caused by the formed fibrils of BSA. The results obtained in this work suggested the potential biological application of MoS2 QDs in therapeutics and provided new insight into the design of multifunctional nanomaterials for amyloid-related diseases.

Investigation on the binding of aloe-emodin with tyrosinase by spectral analysis and molecular docking.

In this paper, the inhibitory kinetics of aloe-emodin on the activity of tyrosinase and the inhibitory mechanism have been investigated by using spectroscopic and molecular docking techniques. The results showed that aloe-emodin inhibited tyrosinase activity in a competitive manner. The binding constants, number of binding sites and thermodynamic parameters obtained at different temperature suggested that aloe-emodin spontaneously binds to tyrosinase at one binding site, mainly via electrostatic forces. Analysis by UV-vis absorption (UV), circular dichroism (CD) and molecular docking indicated that aloe-emodin bound directly into the catalytic cavity and that binding of aloe-emodin to tyrosinase induced conformational changes of the enzyme and blocked the catalytic center of the enzyme preventing binding of the substrate, which caused the inhibition of the tyrosinase activity.

Studies on the anti-aging activity of a glycoprotein isolated from Fupenzi (Rubus chingii Hu.) and its regulation on klotho gene expression in mice kidney.

In this study, a novel glycoprotein with molecular weight of 22.0 kDa was isolated and purified from Fupenzi (a kind of unripe fruits of Rubus chingii Hu.) by means of anion-exchange (DEAE-52) and gel column chromatography (Sephadex G-100). The glycoprotein consists of a carbohydrate component (81.42 ±â€¯0.96%) and protein component (14.56 ±â€¯1.21%). The anti-aging capability was measured in d­galactose induced aging mice model, and the experimental data showed that the glycoprotein could significantly inhibit the formation of malondialdehyde (MDA) and raise the activities of superoxide dismutase (SOD) and catalase (CAT) in mice kidney and serum. The reverse transcription polymerase chain reaction (RT-PCR), quantitative real time polymerase chain reaction (Q-PCR) and western blots showed that the glycoprotein significantly increase the expression of anti-aging gene klotho in mice kidney. The results suggested that the anti-aging mechanism of FPZ might be achieved by improving the klotho gene expression and repairing the renal function. This study will provide a scientific basis for the view of traditional Chinese medicine that tonifying kidney is the basic way of anti-aging. In addition, the glycoprotein could be exploited as a potent dietary supplement to attenuate aging and prevent age-related diseases in humans.

Effect of silybin on the fibrillation of hen egg-white lysozyme.

In this study, the fibrillation of hen egg-white lysozyme (HEWL) in the absence and presence of different concentrations of silybin was studied by thioflavin T spectroscopy, Congo red binding assays, 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescence assay, circular dichroism, and transmission electron microscopy. The experimental results indicated that not only the fibrillation of HEWL at high temperature (65°C) and low pH (pH = 2.0) could be inhibited effectively by silybin but also the inhibition of HEWL by silybin followed a dose-dependent manner. Molecular docking studies indicated that 2 possible binding modes could be found in the interaction between silybin and HEWL via van der Waals forces and electrostatic forces as well as hydrogen bonding. One of these 2 conformations was directly entered into the cavity of HEWL (binding site I); the other was bound to the surface of HEWL (binding site II). In this way, silybin could not only increase the hydrophobicity of the cavity or the surface of HEWL but also influence the microenvironment of the binding site, which was able to stabilize the structure of HEWL and delay the process of HEWL fibrosis.

Effect of nitrogen-doped graphene quantum dots on the fibrillation of hen egg-white lysozyme.

In this study, the fibrillation of hen egg-white lysozyme (HEWL) in the absence and presence of different amount of nitrogen-doped graphene quantum dots (N-GQDs) was studied by Thioflavin T (ThT) spectroscopy, Congo red (CR) binding assays, 8-anilino-1-naphthalenesulfonic acid (ANS) fluorescence assay, circular dichroism (CD) and transmission electron microscopy (TEM). The experimental results indicated that not only the fibrillation of HEWL at high temperature (65°C) and low pH (pH=2.0) could be inhibited effectively by N-GQDs, but the inhibition of HEWL by N-GQDs followed a dose-dependent manner. The results of this work suggested that the N-GQDs had a great potential for designing new therapeutic agents and were promising for future treatment of amyloid-related diseases.

Spectroscopic and Docking Studies on the Binding of Liquiritigenin with Hyaluronidase for Antiallergic Mechanism.

The inhibitory effect of liquiritigenin on hyaluronidase and its binding mechanism were investigated systematically by UV-vis absorption, fluorescence, and molecular modeling approaches. These results indicated that liquiritigenin could interact with hyaluronidase to form a liquiritigenin-hyaluronidase complex. The binding constant, number of binding sites, and thermodynamic parameters were calculated, which indicated that liquiritigenin could spontaneously bind with hyaluronidase mainly through electrostatic and hydrophobic interactions with one binding site. Synchronous fluorescence, three-dimensional fluorescence, and molecular docking results revealed that liquiritigenin bound directly to the enzyme cavity site and this binding influenced the microenvironment of the hyaluronidase activity site, resulting in reduced hyaluronidase activity. The present study provides useful information for clinical applications of liquiritigenin as a hyaluronidase inhibitor.

Studies on the binding of pepsin with three pyrethroid insecticides by multi-spectroscopic approaches and molecular docking.

In this study, the molecular interactions between pepsin and three pyrethroid insecticides, including fenvalerate, cyhalothrin and deltamethrin, were investigated by multi-spectroscopic and molecular docking methods under mimic physiological pH conditions. The results indicated that all of these insecticides could interact with pepsin to form insecticide-pepsin complexes. The binding constants, number of binding sites and thermodynamic parameters measured at different temperatures indicated that these three pyrethroid insecticides could spontaneously bind with pepsin mainly through electrostatic forces and hydrophobic interactions with one binding site. According to the theory of Föster's non-radioactive energy transfer, the distance (r) between pepsin and three pyrethroid insecticides were all found to be less than 7 nm, which implied that the energy transfer occurred between pepsin and these insecticides, leading to the quenching of pepsin fluorescence. Synchronous and three-dimensional fluorescence, CD spectra and molecular docking results indicated that all tested pyrethroid insecticides bound directly into the enzyme cavity site and the binding of insecticides into the cavity influenced the microenvironment of the pepsin activity site which resulted in the extension of peptide strands of pepsin with loss of α-helix structures.Copyright © 2016 John Wiley & Sons, Ltd.