Carbene Footprinting Directs Design of Genetically Encoded Proximity-Reactive Protein Binders.

Genetically encoding proximal-reactive unnatural amino acids (PrUaas), such as fluorosulfate-l-tyrosine (FSY), into natural proteins of interest (POI) confer the POI with the ability to covalently bind to its interacting proteins (IPs). The PrUaa-incorporated POIs hold promise for blocking undesirable POI-IP interactions. Selecting appropriate PrUaa anchor sites is crucial, but it remains challenging with the current methodology, which heavily relies on crystallography to identify the proximal residues between the POIs and the IPs for the PrUaa anchorage. To address the challenge, here, we propose a footprinting-directed genetically encoded covalent binder (footprinting-GECB) approach. This approach employs carbene footprinting, a structural mass spectrometry (MS) technique that quantifies the extent of labeling of the POI following the addition of its IP, and thus identifies the responsive residues. By genetically encoding PrUaa into these responsive sites, POI variants with covalent bonding ability to its IP can be produced without the need for crystallography. Using the POI-IP model, KRAS/RAF1, we showed that engineering FSY at the footprint-assigned KRAS residue resulted in a KRAS variant that can bind irreversibly to RAF1. Additionally, we inserted FSY at the responsive residue in RAF1 upon footprinting the oncogenic KRASG12D/RAF1, which lacks crystal structure, and generated a covalent binder to KRASG12D. Together, we demonstrated that by adopting carbene footprinting to direct PrUaa anchorage, we can greatly expand the opportunities for designing covalent protein binders for PPIs without relying on crystallography. This holds promise for creating effective PPI inhibitors and supports both fundamental research and biotherapeutics development.

Associations between sleep-behavioral traits and healthspan: A one-sample Mendelian randomization study based on 388,909 participants of the UK-Biobank.

BACKGROUND: Although the association between sleep behavior and morbidity and mortality risk has been reported before, there is still uncertainty whether the observed associations are causal or confounding. Therefore, we investigated the causal relationships between sleep-behavioral traits and terminated healthspan risk using Mendelian randomization (MR). METHODS: We conducted a one-sample MR analysis to evaluate causality between six sleep-behavioral traits (sleep duration, chronotype/morningness, napping, sleeplessness/insomnia, and getting up from bed) and risk of healthspan termination among 388, 909 UK Biobank (UKB) participants. Instrumental variables for sleep behaviors (N = 590) were obtained from recent genome-wide association studies (GWAS). We defined healthspan based on eight predominant health-terminating events associated with longevity (congestive heart failure, myocardial infarction, chronic obstructive pulmonary disease, stroke, dementia, diabetes, cancer, and death). We further constructed a sleep score and a weighted genetic risk score to increase the predictive ability of the sleep-behavioral traits. Cox regression models and Inverse Probability Treatment Weighting (IPTW) were implemented, followed by MR to assess causation. We used inverse-variance-weighted MR to estimate causal effects, and weighted-median and MR-egger for sensitivity analysis to test the pleiotropic effects. RESULTS: In IPTW, we observed a decreased risk of terminated healthspan for healthy sleep behaviors such as 'sleep duration 7-8h/d' (Hazard ratio, HR = 0.93; 95 % confidence interval, CI: 0.92-0.96; P < 0.001); 'morningness' (HR = 0.95; 95%CI: 0.93-0.98; P < 0.01); 'napping' (HR = 0.93; 95%CI: 0.91-0.94; P < 0.001); 'easy getting up from bed' (HR = 0.91; 95%CI: 0.88-0.93; P < 0.001); and, 'never/rarely experience sleeplessness/insomnia' (HR = 0.94; 95%CI: 0.92-0.96; P < 0.001). MR results further indicated causal associations between healthy sleep duration (OR = 0.98; 95%CI: 0.97-1.00; P = 0.036) and insomnia (OR = 1.02; 95%CI: 1.01-1.03; P < 0.001) with terminated healthspan. MR-egger did not suggest any potential pleiotropy. CONCLUSION: This study supports abnormal sleep duration and insomnia as potential causal risk factors for terminated healthspan. Thus, healthy sleep behavior is valuable for the extension of healthspan, and well-designed and tailored sleep health interventions are warranted.

Effects of Yinzhihuang on Alleviating Cyclosporine A-Induced Cholestatic Liver Injury via Farnesoid X Receptor-Mediated Regulation of Transporters and Enzymes in Vitro and in Vivo.

Yinzhihuang (YZH), a traditional Chinese medicine prescription, was widely used to treat cholestasis. Cholestatic liver injury limited the use of the immunosuppressive drug cyclosporine A (CsA) in preventing organ rejection after solid organ transplantation. Clinical evidences suggested that YZH could enhance bile acids and bilirubin clearance, providing a potential therapeutic strategy against CsA-induced cholestasis. Nevertheless, it remains unclear whether YZH can effectively alleviate CsA-induced cholestatic liver injury, as well as the molecular mechanisms responsible for its hepatoprotective effects. The purpose of the present study was to investigate the hepatoprotective effects of YZH on CsA-induced cholestatic liver injury and explore its molecular mechanisms in vivo and vitro. The results demonstrated that YZH significantly improved the CsA-induced cholestatic liver injury and reduced the level of liver function markers in serum of Sprague-Dawley (SD) rats. Targeted protein and gene analysis indicated that YZH increased bile acids and bilirubin efflux into bile through the regulation of multidrug resistance-associated protein 2 (Mrp2), bile salt export pump (Bsep), sodium taurocholate cotransporting polypeptide (Ntcp) and organic anion transporting polypeptide 2 (Oatp2) transport systems, as well as upstream nuclear receptors farnesoid X receptor (Fxr). Moreover, YZH modulated enzymes involved in bile acids synthesis and bilirubin metabolism including Cyp family 7 subfamily A member 1 (Cyp7a1) and uridine 5'-diphosphate (UDP) glucuronosyltransferase family 1 member A1 (Ugt1a1). Furthermore, the active components geniposidic acid, baicalin and chlorogenic acid exerted regulated metabolic enzymes and transporters in LO2 cells. In conclusion, YZH may prevent CsA-induced cholestasis by regulating the transport systems, metabolic enzymes, and upstream nuclear receptors Fxr to restore bile acid and bilirubin homeostasis. These findings highlight the potential of YZH as a therapeutic intervention for CsA-induced cholestasis and open avenues for further research into its clinical applications.

Stimulus-responsive biomaterials for Helicobacter pylori eradication.

BACKGROUND: Helicobacter pylori (H. pylori), the only bacterium classified as a type I (definite) carcinogen, is strongly associated with the development of gastric inflammation and adenocarcinoma. It infects the stomach of approximately half of the global population, equivalent to nearly 4.4 billion people. However, due to physiological barriers in the stomach, microbial barriers and increased antibiotic resistance, the therapeutic efficiency of standard antibiotic therapy is limited and cannot meet the clinical needs in some areas. Combining stimulus-responsive biomaterials with certain stimuli is an emerging antibacterial strategy. Stimulus-responsive biomaterials can respond to chemical, biological or physical cues in the environment with corresponding changes in their own properties and functions, highlighting a more intelligent, targeting and efficient aspect for H. pylori therapy. AIM OF REVIEW: This review describes the critical obstacles in the current treatment of H. pylori, summarizes the recent advances in stimulus-responsive biomaterials against H. pylori by elucidating their working mechanisms and antibacterial performances under different types of stimuli (pH, enzymes, light, magnetic and ultrasound irradiations), and attempts to analyze the future prospects of such smart biomaterial for H. pylori eradication. Key Scientific Concepts of Review: Any characteristic property or change in the biomilieu at the H. pylori infected site (endogenous stimuli) or specific iatrogenic conditions in vitro (exogenous stimuli) can act as cues to activate or potentiate the antibacterial activity of responsive biomaterials. The responsiveness of these materials to endogenous stimuli enhances antimicrobial targeting, and makes physiological barriers that would otherwise hinder conventional H. pylori therapies a key factor in facilitating antibacterial effects. The responsiveness to exogenous stimuli greatly prolongs the action time of antimicrobial materials and pinpoints the site of infection, thereby reducing toxic side effects. These findings pave the way for the development of more precise and effective anti-H. pylori treatment.

Polygenic risk for termination of the 'healthspan' and its interactions with lifestyle factors: A prospective cohort study based on 288,359 participants.

OBJECTIVES: To investigate whether a polygenic risk score (PRS) and its interactions with lifestyle factors are associated with termination of the 'healthspan' (the number of years living without serious diseases or degeneration). DESIGN, EXPOSURES AND PARTICIPANTS: Death or the incidence of any of seven independent morbidities (cancer, congestive heart failure, myocardial infarction, chronic obstructive pulmonary disease, stroke, dementia, and diabetes) strongly associated with aging were considered to define the termination of the healthspan. A total of 288,359 healthy participants from the UK Biobank were included in this prospective cohort study to evaluate the associations between PRS, lifestyle, and healthspan. The PRS was generated by weighting 12 healthspan-related genetic loci, which and scores were then categorized into three groups in Cox regression models. A lifestyle index was developed that incorporated body mass index (BMI), alcohol consumption, diet, smoking, and physical activity, and these scores were also categorized into three groups. The risk of termination of the healthspan was calculated across the different PRS and lifestyle index groups using Cox regression models. Interactions were estimated with the marginal effect of lifestyle on the risk of termination of healthspan across values of the moderator PRS using kernel estimation. RESULTS: During an average follow-up of 9.83 years, 68,903 healthspan-termination events occurred. It was calculated that people with high polygenic risk could reduce their risk of healthspan termination by 40 % if they maintain a favorable lifestyle. The marginal effect of lifestyle on the risk of healthspan termination increased with growing genetic risk. Smoking and diet showed monotonic changes in opposite directions, while BMI, physical activity, and alcohol had a U-shaped interaction with genetic risk. CONCLUSIONS: Favorable lifestyle can attenuate the risk of termination of the healthspan, especially for people with high genetic risk. The improvement afforded by ideal lifestyle behaviors varies for each individual.

Genetically encoded chemical crosslinking of carbohydrate.

Protein-carbohydrate interactions play important roles in various biological processes, such as organism development, cancer metastasis, pathogen infection and immune response, but they remain challenging to study and exploit due to their low binding affinity and non-covalent nature. Here we site-specifically engineered covalent linkages between proteins and carbohydrates under biocompatible conditions. We show that sulfonyl fluoride reacts with glycans via a proximity-enabled reactivity, and to harness this a bioreactive unnatural amino acid (SFY) that contains sulfonyl fluoride was genetically encoded into proteins. SFY-incorporated Siglec-7 crosslinked with its sialoglycan ligand specifically in vitro and on the surface of cancer cells. Through irreversible cloaking of sialoglycan at the cancer cell surface, SFY-incorporated Siglec-7 enhanced the killing of cancer cells by natural killer cells. Genetically encoding the chemical crosslinking of proteins to carbohydrates (GECX-sugar) offers a solution to address the low affinity and weak strength of protein-sugar interactions.

Analyses of rare predisposing variants of lung cancer in 6,004 whole genomes in Chinese.

We present the largest whole-genome sequencing (WGS) study of non-small cell lung cancer (NSCLC) to date among 6,004 individuals of Chinese ancestry, coupled with 23,049 individuals genotyped by SNP array. We construct a high-quality haplotype reference panel for imputation and identify 20 common and low-frequency loci (minor allele frequency [MAF] ≥ 0.5%), including five loci that have never been reported before. For rare loss-of-function (LoF) variants (MAF < 0.5%), we identify BRCA2 and 18 other cancer predisposition genes that affect 5.29% of individuals with NSCLC, and 98.91% (181 of 183) of LoF variants have not been linked previously to NSCLC risk. Promoter variants of BRCA2 also have a substantial effect on NSCLC risk, and their prevalence is comparable with BRCA2 LoF variants. The associations are validated in an independent case-control study including 4,410 individuals and a prospective cohort study including 23,826 individuals. Our findings not only provide a high-quality reference panel for future array-based association studies but depict the whole picture of rare pathogenic variants for NSCLC.

The interactions between oral-gut axis microbiota and Helicobacter pylori.

In the human body, each microbial habitat exhibits a different microbial population pattern, and these distinctive microflorae are highly related to the development of diseases. The microbial interactions from host different niches are becoming crucial regulators to shape the microbiota and their physiological or pathological functions. The oral cavity and gut are the most complex and interdependent microbial habitats. Helicobacter pylori is one of the most important pathogens from digestive tract, especially the stomach, due to its direct relationships with many gastric diseases including gastric cancer. H. pylori infections can destroy the normal gastric environment and make the stomach a livable channel to enhance the microbial interactions between oral cavity and gut, thus reshaping the oral and gut microbiomes. H. pylori can be also detected in the oral and gut, while the interaction between the oral-gut axis microbiota and H. pylori plays a major role in H. pylori's colonization, infection, and pathogenicity. Both the infection and eradication of H. pylori and its interaction with oral-gut axis microbiota can alter the balance of the microecology of the oral-gut axis, which can affect the occurrence and progress of related diseases. The shift of oral-gut axis microbiota and their interactions with H. pylori maybe potential targets for H. pylori infectious diagnosis and treatment.

Single-cell profiling of human CD127+ innate lymphoid cells reveals diverse immune phenotypes in hepatocellular carcinoma.

BACKGROUND AND AIMS: Innate lymphoid cells (ILCs) are tissue-resident lymphocytes that play critical roles in cytokine-mediated regulation of homeostasis and inflammation. However, relationships between their immune phenotypic characteristics and HCC remain largely unexplored. APPROACH AND RESULTS: We performed single-cell RNA sequencing analysis on sorted hepatic ILC cells from human patients with HCC and validated using flow cytometry, multiplex immunofluorescence staining, and functional experiments. Moreover, we applied selection strategies to enrich ILC populations in HCC samples to investigate the effects of B cells on the immune reaction of inducible T cell costimulator (ICOS)+ ILC2 cells. Dysregulation of ILCs was manifested by the changes in cell numbers or subset proportions in HCC. Seven subsets of 3433 ILCs were identified with unique properties, of which ICOS+ ILC2a were preferentially enriched in HCC and correlated with poor prognosis. Mechanistically, we report that B cells, particularly resting naïve B cells, have a previously unrecognized function that is involved in inflammatory differentiation of ILC2 cells. B cell-derived ICOSL signaling was responsible for exacerbating inflammation through the increased production of IL-13 in ICOS+ ILC2a cells. Heat shock protein 70 (HSP70) genes Heat Shock Protein Family A Member 1A (HSPA1A) and Heat Shock Protein Family A Member 1B (HSPA1B) were highly expressed in ILC2s in late-stage HCC, and targeting to ICOS and its downstream effector HSP70 in ILC2s suppressed tumor growth and remodeled the immunosuppressive tumor microenvironment. CONCLUSIONS: This in-depth understanding sheds light on B cell-driven innate type 2 inflammation and provides a potential strategy for HCC immunotherapy.

Effect of capsaicin on breast cancer resistance protein (BCRP/Abcg2) and pharmacokinetics of probe substrates in rats.

Breast cancer resistance protein (BCRP/Abcg2 in human, Bcrp/Abcg2 in rat), a member of the ATP-binding cassette (ABC) transporter family, acts as an efflux pump for xenobiotics, with ability to transport various drugs out of cells. Capsaicin may have the potential to modulate the function of Bcrp transport. This study was to evaluate the effects of capsaicin on the pharmacokinetics of sulfasalazine, a Bcrp substrate, in rats and investigate the mechanism of this food-drug interaction.The rats were pre-treated with 5% carboxymethylcellulose sodium (vehicle), capsaicin (3, 8, 25 mg/kg) and cyclosporine A (10 mg/kg) by gastric gavage for 7 days. On day 7, blood, liver and intestine samples were collected after sulfasalazine administered. Liquid chromatography tandem mass spectrometry (LC-MS/MS) was used to study the effects of capsaicin on the pharmacokinetics of sulfasalazine in rats. RT-PCR and western blotting were used to study the mechanism in biomolecules in rats, respectively.Compared with vehicle group, AUC0-∞ of sulfasalazine in rats were increased by 1.5-folds, 1.6-folds and 1.7-folds in 3, 8 and 25 mg/kg/d capsaicin pre-treated groups. At the same time, the CL/F in rats were decreased by 33%, 38% and 42% in the three groups. In addition, we found Bcrp mRNA levels and protein expressions in rat livers and intestines were decreased in 3, 8 and 25 mg/kg/d capsaicin-treated groups.Our study demonstrated that long-term ingestion of capsaicin significantly enhanced the AUC of sulfasalazine involved down-regulate Bcrp gene and protein expression in rat liver and intestine.

Therapeutic peptides: current applications and future directions.

Peptide drug development has made great progress in the last decade thanks to new production, modification, and analytic technologies. Peptides have been produced and modified using both chemical and biological methods, together with novel design and delivery strategies, which have helped to overcome the inherent drawbacks of peptides and have allowed the continued advancement of this field. A wide variety of natural and modified peptides have been obtained and studied, covering multiple therapeutic areas. This review summarizes the efforts and achievements in peptide drug discovery, production, and modification, and their current applications. We also discuss the value and challenges associated with future developments in therapeutic peptides.

Genetically encoding latent bioreactive amino acids and the development of covalent protein drugs.

As natural proteins generally do not bind targets in a covalent mode, the therapeutic potential of covalent protein drugs remains largely unexplored. Recently, latent bioreactive amino acids have been incorporated into proteins through genetic code expansion, which selectively react with nearby natural residues via proximity-enabled reactivity, generating diverse covalent linkages for proteins in vitro and in cells. These new covalent linkages provide novel avenues for protein research and engineering. In addition, a general platform technology, proximity-enabled reactive therapeutics (PERx), has been established for the development of covalent protein drugs. The first covalent protein drug demonstrates advantageous features in cancer immunotherapy in mice. Selective introduction of covalent bonds into proteins will advance biological studies, synthetic biology, and biotherapeutics with the power of biocompatible covalent chemistries.

A Genetically Encoded Fluorosulfonyloxybenzoyl-l-lysine for Expansive Covalent Bonding of Proteins via SuFEx Chemistry.

Genetically introducing novel chemical bonds into proteins provides innovative avenues for biochemical research, protein engineering, and biotherapeutic applications. Recently, latent bioreactive unnatural amino acids (Uaas) have been incorporated into proteins to covalently target natural residues through proximity-enabled reactivity. Aryl fluorosulfate is particularly attractive due to its exceptional biocompatibility and multitargeting capability via sulfur(VI) fluoride exchange (SuFEx) reaction. Thus far, fluorosulfate-l-tyrosine (FSY) is the only aryl fluorosulfate-containing Uaa that has been genetically encoded. FSY has a relatively rigid and short side chain, which restricts the diversity of proteins targetable and the scope of applications. Here we designed and genetically encoded a new latent bioreactive Uaa, fluorosulfonyloxybenzoyl-l-lysine (FSK), in E. coli and mammalian cells. Due to its long and flexible aryl fluorosulfate-containing side chain, FSK was particularly useful in covalently linking protein sites that are unreachable with FSY, both intra- and intermolecularly, in vitro and in live cells. In addition, we created covalent nanobodies that irreversibly bound to epidermal growth factor receptors (EGFR) on cells, with FSK and FSY targeting distinct positions on EGFR to counter potential mutational resistance. Moreover, we established the use of FSK and FSY for genetically encoded chemical cross-linking to capture elusive enzyme-substrate interactions in live cells, allowing us to target residues aside from Cys and to cross-link at the binding periphery. FSK complements FSY to expand target diversity and versatility. Together, they provide a powerful, genetically encoded, latent bioreactive SuFEx system for creating covalent bonds in diverse proteins in vitro and in vivo, which will be widely useful for biological research and applications.

Developing Covalent Protein Drugs via Proximity-Enabled Reactive Therapeutics.

Small molecule covalent drugs provide desirable therapeutic properties over noncovalent ones for treating challenging diseases. The potential of covalent protein drugs, however, remains unexplored due to protein's inability to bind targets covalently. We report a proximity-enabled reactive therapeutics (PERx) approach to generate covalent protein drugs. Through genetic code expansion, a latent bioreactive amino acid fluorosulfate-L-tyrosine (FSY) was incorporated into human programmed cell death protein-1 (PD-1). Only when PD-1 interacts with PD-L1 did the FSY react with a proximal histidine of PD-L1 selectively, enabling irreversible binding of PD-1 to only PD-L1 in vitro and in vivo. When administrated in immune-humanized mice, the covalent PD-1(FSY) exhibited strikingly more potent antitumor effect over the noncovalent wild-type PD-1, attaining therapeutic efficacy equivalent or superior to anti-PD-L1 antibody. PERx should provide a general platform technology for converting various interacting proteins into covalent binders, achieving specific covalent protein targeting for biological studies and therapeutic capability unattainable with conventional noncovalent protein drugs.

Effects of cyclosporin A on the pharmacokinetics and toxicities of irinotecan mediated by UGT1A1 in vitro and in vivo.

Irinotecan (CPT-11) is a broad spectrum agent for the treatment of solid tumor malignancies, despite severe diarrhea is limiting its widespread usage. The local effects of SN-38 in the small intestine were considered to be responsible for the irinotecan-induced delayed diarrhea. It was proposed that cyclosporin A (CsA) inhibiting biliary excretion could attenuate this side effect, but in fact, it could not improve the therapeutic index of irinotecan. At present, most studies focused on the inhibition of bile excretion by cyclosporin A through the transporters MRP2 and MDR1 and its effect the irinotecan treatment in vivo. However, UDP glucuronyltransferase-1 polypeptide A1 (UGT1A1) was related to a significantly altered disposition of irinotecan and its metabolites, and was therefore associated with irinotecan-induced toxicity. This study focused on UGT1A1-mediated conversion of SN-38 to SN-38G, and systematically investigated the CsA-irinotecan interactions in vitro and in vivo. After treatment with 10 mg·kg-1 CsA for 7 days, the bile excretion of irinotecan and its metabolites decreased and AUC0-∞ increased significantly. The AUC0-∞ (SN-38G)/AUC0-∞ (SN-38) was significantly reduced when compared with that in vehicle-treated rats. In the liver microsome incubation system, the IC50 of CsA for UGT1A1 enzyme was 9.4 µM. Furthermore, the UGT1A1 mRNA and protein expression levels were significantly reduced. The present study indicated that CsA treatment could enhance the systemic exposure and toxicity of SN-38 by inhibiting the UGT1A1 enzyme. The inhibition of UGT1A1 enzyme might be a critical factor in the failure of CsA improving irinotecan's treatment index.

IDO and TDO as a potential therapeutic target in different types of depression.

Depression is highly prevalent worldwide and a leading cause of disabilty. However, the medications currently available to treat depression fail to adequately relieve depressive symptoms for a large number of patients. Research into the aberrant overactivation of the kynurenine pathway and the production of various active metabolites has brought new insight into the progression of depression. IDO and TDO are the first and rate-limiting enzymes in the kynurenine pathway and regulate the production of active metabolites. There is substantial evidence that TDO and IDO enzyme are activated during depression, and therefore, IDO and TDO inhibitors have been identified as ideal therapeutic targets for depressive disorder. Hence, this review will focus on the kynurenine branch of tryptophan metabolism and describe the role of IDO and TDO in the pathology of depression. In addition, this review will compare the relative imbalance between KYNA and neurotoxic kynurenine metabolites in different psychiatric disorders. Finally, this review is also directed toward assessing whether IDO and TDO are potential therapeutic target in depression associated with other diseases such as diabetes and/or cancer, as well as the development of potent IDO and TDO inhibitors.

Effects of aprepitant on the pharmacokinetics of imatinib and its main metabolite in rats.

Aprepitant (APT), an antiemetic drug belonging to the class of substance P antagonists is efficiently used in both acute and delayed chemotherapy-induced nausea and vomiting. Nausea and vomiting induced by imatinib (IMA) as a chemotherapeutic drug could be reduced by APT. This study investigated the effect of APT on the pharmacokinetics of IMA and its major metabolite N-desmethyl imatinib (N-D IMA) in rats and the mechanism of this drug-drug interaction. The results indicated that after 3 days of pretreatment with APT (10 mg/kg), the blood concentration of IMA was decreased in both of oral and intravenous routes of IMA administration compared to vehicle treated rats, whereas the blood concentration of N-D IMA was not significantly changed. The total clearance (CL/F) of oral and intravenous given IMA was increased by 1.41 and 1.32-fold, and the bioavailability was greatly decreased about 30.43% and 24.40% respectively. At this time, the P-gp and the hepatic CYP3A1 were increased at both the mRNA and protein levels. These results demonstrated that ingestion of APT will decrease the bioavailability of IMA to a significant extent in rats and the drug-drug interaction between APT and IMA appears to be due to modulation of P-gp and CYP3A1.

Fluorescent Protein-Based Turn-On Probe through a General Protection-Deprotection Design Strategy.

We demonstrated a general protection-deprotection strategy for the design of fluorescent protein biosensors through the construction of a turn-on Hg2+ sensor. A combination of fluorescent protein engineering and unnatural amino acid mutagenesis was used. Unlike previously reported fluorescent protein-based Hg2+ sensors that relied on the binding of Hg2+ to the sulfhydryl group of cysteine residues, a well-established chemical reaction, oxymercuration, was transformed into biological format and incorporated into our sensor design. This novel Hg2+ sensor displayed good sensitivity and selectivity both in vitro and in live bacterial cells. Over 60-fold change in fluorescence signal output was observed in the presence of 10 µM Hg2+, while such a change was undetectable when nine other metal ions were tested. This new design strategy could expand the repertoire of fluorescent protein-based biosensors for the detection of small-molecule analytes.

Capsaicin induces metabolism of simvasatin in rat: involvement of upregulating expression of Ugt1a1.

Capsaicin (CAP, trans-8-methyl-N-vanillyl-6-nonenamide) is a major pungent substance in hot pepper. However, little is known about the interactions between CAP and clinically used drugs. This study investigated the effect of acute and chronic ingestion of CAP on pharmacokinetics of simvastatin (SV) and the mechanism of this CAP--drug intercation. CAP was orally administered at doses of 3 and 8 mg x kg(-1) for seven consecutive days once daily and on the 1st day and the 7th day, SV (8 mg x kg(-1)) was injected intravenously. Plasma concentrations of SV were determined using LC/MS/MS and expression of Ugt1a1 was analyzed by RT-qPCR and Western Blotting. We found that there were 78.0% (P < 0.05) and 81.2% (P < 0.05) reduction in the AUC(0-∞) of SV, respectively, following pretreatment with two doses of CAP. The AUC(0-∞) of SV in the two dose group pretreated with CAP for 7 days were decreased significantly, compared to the group for 1 day. Both the RT-qPCR and Western Blotting data indicated that 7 days pretreatment with CAP increased the expression level of Ugt1a1 in liver. In conclusion, chronic ingestion of CAP enhanced the expression level of Ugt1a1 in liver, causing the food -drug interaction and decrease in SV exposure in rats to a significant extent.

Interactions between m-phenylenediamine and bovine serum albumin measured by spectroscopy.

This study explored interactions between m-phenylenediamine (MPD) and bovine serum albumin (BSA) by spectrophotometry. The Stern-Volmer equation and UV-vis spectra examination at different temperatures and pH were used to explore different quenching mechanisms. Under simulated physiological conditions, the binding distance between MPD and BSA was 5.18 nm with a ratio of 1:1. The quenching effect of MPD on BSA intrinsic fluorescence depended strongly on pH, and maximum quenching was observed at alkaline pH. Moreover, the thermodynamic parameters of the MPD-BSA system showed that the predominant acting force between MPD and BSA was a hydrophobic force. The impact of MPD on the conformation of BSA and the effects of co-ions on binding interactions were also examined.