Effect of tryptophan position and lysine/arginine substitution in antimicrobial peptides on antifungal action

Every year, the overprescription, misuse, and improper disposal of antibiotics have led to the rampant development of drug-resistant pathogens and, in turn, a significant increase in the number of patients who die of drug-resistant fungal infections. Recently, researchers have begun investigating the use of antimicrobial peptides (AMPs) as next-generation antifungal agents to inhibit the growth of drug-resistant fungi. The antifungal activity of alpha-helical peptides designed using the cationic amino acids containing lysine and arginine and the hydrophobic amino acids containing isoleucine and tryptophan were evaluated using 10 yeast and mold fungi. Among these peptides, WIK-14, which is composed of a 14-mer with tryptophan sequences at the amino terminus, showed the best antifungal activity via transient pore formation and ROS generation. In addition, the in vivo antifungal effects of WIK-14 were investigated in a mouse model infected with drug-resistant Candida albicans. The results demonstrate the potential of AMPs as antifungal agents.

Anti-Biofilm Effects of Rationally Designed Peptides against Planktonic Cells and Pre-Formed Biofilm of Pseudomonas aeruginosa

Biofilms are resistant to antibiotics and are a major source of persistent and recurring infections by clinically important pathogens. Drugs used for biofilm-associated infections are limited because biofilm-embedded or biofilm-matrix bacteria are difficult to kill or eradiate. Therefore, many researchers are developing new and effective antibiofilm agents. Among them, antimicrobial peptides have an attractive interest in the development of antibiofilm agents. The present study evaluated the effects of 10 synthetic peptides on growth inhibition, inhibition of biofilm formation, and biofilm elimination in drug-resistant Pseudomonas aeruginosa. The planktonic cell growth and biofilm formation were dose-dependently inhibited by most of the peptides. WIK-14 eliminated preformed biofilm masses by removing carbohydrates, extracellular nucleic acids, proteins, and lipids constituting extracellular polymeric substances. The results demonstrated that WIK-14 and WIKE-14 peptides might provide novel therapeutic drugs to overcome multidrug resistance in biofilm-associated infections.

Potent Anti-Inflammatory Effects of a Helix-to-Helix Peptide against Pseudomonas aeruginosa Endotoxin-Mediated Sepsis

Although considerable scientific research data is available for sepsis and cytokine storm syndrome, there is a need to develop new treatments or drugs for sepsis management. Antimicrobial peptides (AMPs) possess anti-bacterial and anti-inflammatory activity, neutralizing toxins such as lipopolysaccharides (LPS, endotoxin). Most AMPs have been designed as a substitute for conventional antibiotics, which kill drug-resistant pathogens. The present study aimed to determine the anti-inflammatory potential of 10 designed XIW (X: lysine, arginine, or glutamic acid) α-helical peptides in macrophages and a mouse model in the presence of LPS. Among them, WIKE-14, a peptide with a helix-to-helix structure, having the 12th amino acid substituted with glutamic acid, suppressed pro-inflammatory cytokines in RAW 264.7 macrophages. This reaction was mediated by the inhibition of the binding between LPS and macrophages. In addition, the WIKE-14 peptide exhibited a potent anti-inflammatory activity in mice ears and lungs inflamed using LPS. Thus, our results may provide useful insights for the development of anti-sepsis agents via the sequence and structure information of the WIKE-14 peptide.

Design of Antimicrobial Peptides with Cell-Selective Activity and Membrane-Acting Mechanism against Drug-Resistant Bacteria

Antimicrobial peptides (AMPs) can combat drug-resistant bacteria with their unique membrane-disruptive mechanisms. This study aimed to investigate the antibacterial effects of several membrane-acting peptides with amphipathic structures and positional alterations of two tryptophan residues. The synthetic peptides exhibited potent antibacterial activities in a length-dependent manner against various pathogenic drug-resistant and susceptible bacteria. In particular, the location of tryptophan near the N-terminus of AMPs simultaneously increases their antibacterial activity and toxicity. Furthermore, the growth inhibition mechanisms of these newly designed peptides involve cell penetration and destabilization of the cell membrane. These findings provide new insights into the design of peptides as antimicrobial agents and suggest that these peptides can be used as substitutes for conventional antibiotics.

Functional Characterization of an Arabidopsis Profilin Protein as a Molecular Chaperone under Heat Shock Stress

Profilins (PFNs) are actin monomer-binding proteins that function as antimicrobial agents in plant phloem sap. Although the roles of Arabidopsis thaliana profilin protein isoforms (AtPFNs) in regulating actin polymerization have already been described, their biochemical and molecular functions remain to be elucidated. Interestingly, a previous study indicated that AtPFN2 with high molecular weight (HMW) complexes showed lower antifungal activity than AtPFN1 with low molecular weight (LMW). These were bacterially expressed and purified to characterize the unknown functions of AtPFNs with different structures. In this study, we found that AtPFN1 and AtPFN2 proteins have LMW and HMW structures, respectively, but only AtPFN2 has a potential function as a molecular chaperone, which has never been reported elsewhere. AtPFN2 has better protein stability than AtPFN1 due to its higher molecular weight under heat shock conditions. The function of AtPFN2 as a holdase chaperone predominated in the HMW complexes, whereas the chaperone function of AtPFN1 was not observed in the LMW forms. These results suggest that AtPFN2 plays a critical role in plant tolerance by increasing hydrophobicity due to external heat stress.

Candidacidal and Antibiofilm Activity of PS1-3 Peptide against Drug-Resistant Candida albicans on Contact Lenses

The recent emergence of antibiotic-resistant fungi has accelerated research on novel antifungal agents. In particular, Candida albicans infections are related to biofilm formation on medical devices, such as catheters, stents, and contact lenses, resulting in high morbidity and mortality. In this study, we aimed to elucidate the antifungal and antibiofilm effects of a peptide against drug-resistant C. albicans. α-Helical peptides in which the sequence of KWYK was repeated twice and four times, designated peptide series 1 (PS1)-1 and PS1-3, respectively, were generated, and the candidacidal activities of PS1-1, PS1-3, and fluconazole against drug-resistant C. albicans cells were assessed. The PS1-3 peptide showed higher killing activity than PS1-1 or fluconazole and acted via a membranolytic mechanism. In addition, the PS1-3 peptide exhibited more potent activity than PS1-1 and fluconazole in terms of fungal biofilm inhibition and reduction at the minimum fungicidal concentration on the contact lens surface. Overall, these findings established PS1-3 as a potential candidacidal agent for applications on contact lenses.

Polyethylenimine grafted-chitosan based Gambogic acid copolymers for targeting cancer cells overexpressing transferrin receptors

Recent advancements in gene delivery systems that specifically target a variety of cancer types have increased demand for tissue-specific gene therapy. The current study describes the synthesis of a copolymer (GPgWSC) composed of a polyethylenimine (PEI)-grafted water-soluble chitosan (WSC) and gambogic acid (GA). It was validated as a ligand capable of enabling targeted attachment to transferrin receptors in HCT116 cancer cell lines. GPgWSC demonstrated superior antitumor activity in vitro in HCT116 compared to LoVo or MCF-7 cell lines, facilitated by the apoptotic activity of psiRNA-hBCL2. Pre-incubation of transferrin significantly inhibited GFP expression in the GPgWSC polyplex, demonstrating that GA is an extremely effective transferrin receptor targeting molecule. Additionally, in the HCT116-bearing mouse model, the tumor mass of PBS-treated mice increased to 2270 mm² after 22 days, but the injection of GPgWSC polyplex significantly reduced the mass-increasing rate as a mass size of 248 mm².

Antifungal Mechanism of Vip3Aa, a Vegetative Insecticidal Protein, against Pathogenic Fungal Strains

Discovering new antifungal agents is difficult, since, unlike bacteria, mammalian and fungal cells are both eukaryotes. An efficient strategy is to consider new antimicrobial proteins that have variety of action mechanisms. In this study, a cDNA encoding Bacillus thuringiensis Vip3Aa protein, a vegetative insecticidal protein, was obtained at the vegetative growth stage; its antifungal activity and mechanism were evaluated using a bacterially expressed recombinant Vip3Aa protein. The Vip3Aa protein demonstrated various concentration- and time-dependent antifungal activities, with inhibitory concentrations against yeast and filamentous fungi ranging from 62.5 to 125 µg/mL and 250 to 500 µg/mL, respectively. The uptake of propidium iodide and cellular distributions of rhodamine-labeled Vip3Aa into fungal cells indicate that its growth inhibition mechanism involves its penetration within cells and subsequent intracellular damage. Furthermore, we discovered that the death of Candida albicans cells was caused by the induction of apoptosis via the generation of mitochondrial reactive oxygen species and binding to nucleic acids. The presence of significantly enlarged Vip3Aa-treated fungal cells indicates that this protein causes intracellular damage. Our findings suggest that Vip3Aa protein has potential applications in the development of natural antimicrobial agents.

Improved Cell Selectivity of Pseudin-2 via Substitution in the Leucine-Zipper Motif: In Vitro and In Vivo Antifungal Activity

Several antimicrobial peptides (AMPs) have been discovered, developed, and purified from natural sources and peptide engineering; however, the clinical applications of these AMPs are limited owing to their lack of abundance and side effects related to cytotoxicity, immunogenicity, and hemolytic activity. Accordingly, to improve cell selectivity for pseudin-2, an AMP from Pseudis paradoxa skin, in mammalian cells and pathogenic fungi, the sequence of pseudin-2 was modified by alanine or lysine at each position of two amino acids within the leucine-zipper motif. Alanine-substituted variants were highly selective toward fungi over HaCaT and erythrocytes and maintained their antifungal activities and mode of action (membranolysis). However, the antifungal activities of lysine-substituted peptides were reduced, and the compound could penetrate into fungal cells, followed by induction of mitochondrial reactive oxygen species and cell death. In vivo antifungal assays of analogous peptide showed excellent antifungal efficiency in a Candida tropicalis skin infection mouse model. Our results demonstrated the usefulness of selective amino acid substitution in the repeated sequence of the leucine-zipper motif for the design of AMPs with potent antimicrobial activities and low toxicity.

Imaging and Targeted Antibacterial Therapy Using Chimeric Antimicrobial Peptide Micelles

Infectious diseases induced by multidrug-resistant bacteria are a challenging problem in medicine because of global rise in the drug resistance to pathogenic bacteria. Despite great efforts on the development of antibiotics and antimicrobial agents, there is still a great need to develop a strategy to early detect bacterial infections and eradicate bacteria effectively and simultaneously. The innate immune systems of various organisms produce antimicrobial peptides, which kill a broad range of bacteria with minimal cytotoxicity to mammalian cells. Therefore, antimicrobial peptides have recently attracted increasing attention as an alternative to conventional antibiotics in antibacterial medications. Here, we report a new family of antibacterial agents, which is formulated from self-assembly of a chimeric antimicrobial lipopeptide (DSPE-HnMc) and amphiphilic biodegradable polymers. HnMc micelles could effectively bind the bacterial membrane to kill a wide spectrum of bacteria and bacterial biofilms. In the studies of mouse models of drug-resistant bacterial infections, HnMc micelles could target bacterial infections with high specificity and also kill drug-resistant bacteria effectively, demonstrating the great potential of HnMc micelles as imaging and targeted antibacterial agents. These findings also provide new insight into the design of antimicrobial peptide-based nanomedicine for detection and treatment of bacterial infections.

Functional Characterization of a Rice Thioredoxin Protein OsTrxm and Its Cysteine Mutant Variant with Antifungal Activity

Although there are many antimicrobial proteins in plants, they are not well-explored. Understanding the mechanism of action of plant antifungal proteins (AFPs) may help combat fungal infections that impact crop yields. In this study, we aimed to address this gap by screening Oryza sativa leaves to isolate novel AFPs. We identified a thioredoxin protein with antioxidant properties. Being ubiquitous, thioredoxins (Trxs) function in the redox balance of all living organisms. Sequencing by Edman degradation method revealed the AFP to be O. sativa Thioredoxin m-type isoform (OsTrxm). We purified the recombinant OsTrxm and its cysteine mutant proteins (OsTrxm C/S) in Escherichia coli. The recombinant OsTrxm proteins inhibited the growth of various pathogenic fungal cells. Interestingly, OsTrxm C/S mutant showed higher antifungal activity than OsTrxm. A growth inhibitory assay against various fungal pathogens and yeasts confirmed the pertinent role of cysteine residues. The OsTrxm protein variants penetrated the fungal cell wall and membrane, accumulated in the cells and generated reactive oxygen species. Although the role of OsTrxm in chloroplast development is known, its biochemical and molecular functions have not been elucidated. These findings suggest that in addition to redox regulation, OsTrxm also functions as an antimicrobial agent.

Functional Mechanisms Underlying the Antimicrobial Activity of the Oryza sativa Trx-like Protein

Plants are constantly subjected to a variety of environmental stresses and have evolved regulatory responses to overcome unfavorable conditions that might reduce or adversely change a plant’s growth or development. Among these, the regulated production of reactive oxygen species (ROS) as a signaling molecule occurs during plant development and pathogen defense. This study demonstrates the possible antifungal activity of Oryza sativa Tetratricopeptide Domain-containing thioredoxin (OsTDX) protein against various fungal pathogens. The transcription of OsTDX was induced by various environmental stresses known to elicit the generation of ROS in plant cells. OsTDX protein showed potent antifungal activity, with minimum inhibitory concentrations (MICs) against yeast and filamentous fungi ranging between 1.56 and 6.25 and 50 and 100 µg/mL, respectively. The uptake of SYTOX-Green into fungal cells and efflux of calcein from artificial fungus-like liposomes suggest that its killing mechanism involves membrane permeabilization and damage. In addition, irregular blebs and holes apparent on the surfaces of OsTDX-treated fungal cells indicate the membranolytic action of this protein. Our results suggest that the OsTDX protein represents a potentially useful lead for the development of pathogen-resistant plants.

Hydrophilic Linear Peptide with Histidine and Lysine Residues as a Key Factor Affecting Antifungal Activity

Increases in the numbers of immunocompromised patients and the emergence of drug-resistance fungal pathogens have led to the need for new, safe, efficacious antifungal agents. In this study, we designed a histidine-lysine-lysine (HKK) motif and synthesized six HKK peptides with repetitions of the motif. These peptides showed length-dependent antifungal activity against drug-susceptible and drug-resistant fungal pathogens via membranolytic or non-membranolytic action. None of the peptides were cytotoxic to rat erythrocytes or NIH3T3 mouse embryonic fibroblasts. Short-length peptides were directly translocated in fungal cytosol and reacted with mitochondria, resulting in apoptosis. Membrane-permeabilizing activity occurred in the presence of long peptides, and peptides were able to transfer to the cytosol and induce reactive oxygen species. Our results suggest that peptides composed only of cationic amino acids may be good candidates as antifungal agents.

Cell-selectivity of tryptophan and tyrosine in amphiphilic α-helical antimicrobial peptides against drug-resistant bacteria

The increasing emergence of drug-resistant bacteria creates a requirement for new antibiotics and various types of antibiotic materials such as proteins, peptides, polymers, and chemical compounds. Among these, antimicrobial peptides (AMPs) are considered to be promising antibiotic candidates for clinical treatments. In this study, we have designed a novel series of peptides with repeated sequences of minimum membrane-active motif, 'XWZX' basic sequence (X: lysine or arginine, Z: leucine, tyrosine, valine, or glycine), and an α-helical secondary structure. Some peptides displayed a potent antibacterial activity via membranolytic action and high therapeutic index (toxic dose/minimum inhibitory concentration) in vitro. Furthermore, in vivo experiments using bacterial ear-skin infection models verified that these peptides have the potential to be powerful and safe antibiotics. The present study provides a lead sequence for designing peptide antibiotics against bacterial membranes and information for cell-selectivity of hydrophobic amino acids with aromatic side chains such as Trp and Tyr.

Molecular mechanism of Arabidopsis thaliana profilins as antifungal proteins

BACKGROUND

It remains an open question whether plant phloem sap proteins are functionally involved in plant defense mechanisms.

METHODS

The antifungal effects of two profilin proteins from Arabidopsis thaliana, AtPFN1 and AtPFN2, were tested against 11 molds and 4 yeast fungal strains. Fluorescence profiling, biophysical, and biochemical analyses were employed to investigate their antifungal mechanism.

RESULTS

Recombinant AtPFN1 and AtPFN2 proteins, expressed in Escherichia coli, inhibited the cell growth of various pathogenic fungal strains at concentrations ranging from 10 to 160 μg/mL. The proteins showed significant intracellular accumulation and cell-binding affinity for fungal cells. Interestingly, the AtPFN proteins could penetrate the fungal cell wall and membrane and act as inhibitors of fungal growth via generation of cellular reactive oxygen species and mitochondrial superoxide. This triggered the AtPFN variant-induced cell apoptosis, resulting in morphological changes in the cells.

CONCLUSION

PFNs may play a critical role as antifungal proteins in the Arabidopsis defense system against fungal pathogen attacks.

GENERAL SIGNIFICANCE

The present study indicates that two profilin proteins, AtPFN1 and AtPFN2, can act as natural antimicrobial agents in the plant defense system.

One-step synthesis of gene carrier via gamma irradiation and its application in tumor gene therapy

Introduction

Although numerous studies have been conducted with the aim of developing drug-delivery systems, chemically synthesized gene carriers have shown limited applications in the biomedical fields due to several problems, such as low-grafting yields, undesirable reactions, difficulties in controlling the reactions, and high-cost production owing to multi-step manufacturing processes.

Materials and methods

We developed a 1-step synthesis process to produce 2-aminoethyl methacrylate-grafted water-soluble chitosan (AEMA-g-WSC) as a gene carrier, using gamma irradiation for simultaneous synthesis and sterilization, but no catalysts or photoinitiators. We analyzed the AEMA graft site on WSC using 2-dimensional nuclear magnetic resonance spectroscopy (2D NMR; 1H and 13C NMR), and assayed gene transfection effects in vitro and in vivo.

Results

We revealed selective grafting of AEMA onto C6-OH groups of WSC. AEMA-g-WSC effectively condensed plasmid DNA to form polyplexes in the size range of 170 to 282 nm. AEMA-g-WSC polyplexes in combination with psi-hBCL2 (a vector expressing short hairpin RNA against BCL2 mRNA) inhibited tumor cell proliferation and tumor growth in vitro and in vivo, respectively, by inducing apoptosis.

Conclusion

The simple grafting process mediated via gamma irradiation is a promising method for synthesizing gene carriers.

Antifungal Effect of Arabidopsis SGT1 Proteins via Mitochondrial Reactive Oxygen Species

The highly conserved SGT1 (suppressor of the G2 alleles of skp1) proteins from Arabidopsis are known to contribute to plant resistance to pathogens. While SGT1 proteins respond to fungal pathogens, their antifungal activity is not reported and the mechanism for this inhibition is not well understood. Therefore, recombinant Arabidopsis SGT1 proteins were cloned, expressed, and purified to evaluate their antifungal activity, resulting in their potent inhibition of pathogen growth. Dye-labeled proteins are localized to the cytosol of Candida albicans cells without the disruption of the cell membrane. Moreover, we showed that entry of the proteins into C. albicans cells resulted in the accumulation of reactive oxygen species (ROS) and cell death via altered mitochondrial potential. Morphological changes of C. albicans cells in the presence of proteins were visualized by scanning electron microscopy. Our data suggest that AtSGT1 proteins play a critical role in plant resistance to pathogenic fungal infection and they can be classified to a new plant antifungal protein.

Algicidal effect of hybrid peptides as potential inhibitors of harmful algal blooms

OBJECTIVES

To biochemically characterize synthetic peptides to control harmful algal blooms (HABs) that cause red tides in marine water ecosystems.

RESULTS

We present an analysis of several short synthetic peptides and their efficacy as algicidal agents. By altering the amino acid composition of the peptides we addressed the mode of algicidal action and determine the optimal balance of cationic and hydrophobic content for killing. In a controlled setting, these synthetic peptides disrupted both plasma and chloroplast membranes of several species known to result in HABs. This disruption was a direct result of the hydrophobic and cationic content of the peptide. Furthermore, by using an anti-HAB bioassay in scallops, we determined that these peptides were algicidal without being cytotoxic to other marine organisms.

CONCLUSIONS

These synthetic peptides may prove promising for general marine ecosystem remediation where HABs have become widespread and resulted in serious economic loss.

Novel chimeric peptide with enhanced cell specificity and anti-inflammatory activity

An antimicrobial peptide (AMP), Hn-Mc, was designed by combining the N-terminus of HPA3NT3 and the C-terminus of melittin. This chimeric AMP exhibited potent antibacterial activity with low minimal inhibitory concentrations (MICs), ranging from 1 to 2 μM against four drug-susceptible bacteria and ten drug-resistant bacteria. Moreover, the hemolysis and cytotoxicity was reduced significantly compared to those of the parent peptides, highlighting its high cell selectivity. The morphological changes in the giant unilamellar vesicles and bacterial cell surfaces caused by the Hn-Mc peptide suggested that it killed the microbial cells by damaging the membrane envelope. An in vivo study also demonstrated the antibacterial activity of the Hn-Mc peptide in a mouse model infected with drug-resistant bacteria. In addition, the chimeric peptide inhibited the expression of lipopolysaccharide (LPS)-induced cytokines in RAW 264.7 cells by preventing the interaction between LPS and Toll-like receptors. These results suggest that this chimeric peptide is an antimicrobial and anti-inflammatory candidate as a pharmaceutic agent.

Evaluation of polyethylene glycol-conjugated novel polymeric anti-tumor drug for cancer therapy

A novel polymeric prodrug (PXPEG) was prepared to enhance the solubility of an anti-cancer drug, paclitaxel, in aqueous solutions and decrease the cytotoxicity by PEGylation, which means PEG attached to another molecule. In addition, the targeting ligand, transferrin (TF), was modified to PXPEG to enhance the therapeutic efficacy. The targeting ligand-modified PXPEG (TFPXPEG) was examined by (1)H-NMR to confirm the successful synthesis. The synthesized TFPXPEG had better solubility than the free drug against aqueous solution. The particle size of TFPXPEG was approximately 197.2nm and it had a spherical shape. The MTT assay showed that the anti-tumor efficiency of TFPXPEG was better than that of TF-unmodified PXPEG. In the KB tumor-bearing mouse model, the tumor volume of TFPXPEG treated groups was decreased dramatically by more than 2 fold or 3 fold compared to the PBS or PXPEG treated groups. The in vitro and in vivo evaluation showed that TFPXPEG had better efficacy than that of PXPEG due to the targeting effect of targeting ligands, such as TF.

Preparative isolation of sargachromanol E from Sargassum siliquastrum by centrifugal partition chromatography and its anti-inflammatory activity

Centrifugal partition chromatography (CPC) can be used to isolate various bioactive compounds from natural materials by one-step. We confirmed antioxidative compounds existed in chloroform (CHCl3) fraction of Sargassum siliquastrum using online-HPLC. Fractions (A, B, C, D and E) were separated from the CHCl3 fraction by preparative CPC (n-hexane:ethyl acetate:methanol:water, 5:5:7:3, v/v). In this study, we proved that the isolated compounds exhibit anti-inflammatory activities using lipopolysaccharide (LPS) stimulated RAW 264.7 macrophages. The fraction A which exhibited the strongest inhibitory effect on nitric oxide (NO) production level, was confirmed as sargachromanol E by LC-MS-ESI, (1)H NMR and (13)C NMR data. The sargachromanol E significantly reduced the inflammatory response in LPS induced macrophages, decreasing LPS-induced transcription factor of pro-inflammatory cyclooxygenase-2, NO synthase, phosphate P38, phosphate ERK1/2, LPS-stimulated tumor-necrosis factor alpha, interleukin-1 beta and prostaglandin E2 release. In conclusion, it was suggested that sargachromanol E inhibited inflammation in LPS induced RAW 264.7 cells via MAPK pathway.

Protective effect of dieckol isolated from Ecklonia cava against ethanol caused damage in vitro and in zebrafish model

In the present study, the protective effects of phlorotannins isolated from Ecklonia cava against ethanol-induced cell damage and apoptosis were investigated both in vitro and in vivo. Three phlorotannin compounds, namely phloroglucinol, eckol and dieckol, were successively isolated and identified from the extract. Dieckol showed the strongest protective effect against ethanol-induced cell apoptosis in Chang liver cells, with the lowest cytotoxicity. It was observed that dieckol reduced cell apoptosis through activation of Bcl-xL and PARP, and down-regulation of Bax and caspase-3 in Western blot analyses. In the in vivo study, the protective effect of ethanol induced by dieckol was investigated in a zebrafish model. The dieckol treated group scavenged intracellural reactive oxygen species and prevented lipid peroxidation and ethanol induced cell death in the zebrafish embryo. In conclusion, dieckol isolated from E. cava might possess a potential protective effect against ethanol-induced liver diseases.

Branched polyethylenimine-grafted-carboxymethyl chitosan copolymer enhances the delivery of pDNA or siRNA in vitro and in vivo

To generate a good carrier for gene transfection, O-carboxymethyl chitosan-graft-branched polyethylenimine (OCMPEI) copolymers were synthesized by increasing the weight percentage of branched polyethylenimine conjugated to the carboxyl groups of O-carboxymethyl chitosan. These spherical polyplexes with plasmid deoxyribonucleic acid (pDNA) or small interfering ribonucleic acid (siRNA) had diameters of ∼200–300 nm or ∼10–25 nm, respectively, and displayed significant transfection efficiency in normal and tumor cells. In particular, expression of green fluorescent protein (GFP) following pDNA transfection was effectively suppressed by delivery of GFP-specific siRNA with the same copolymer. The optimized copolymer and polyplexes were nontoxic in vitro and in vivo. The use of endocytosis inhibitors to investigate the mechanisms of transfection of the polyplexes suggested the involvement of macropinocytosis. An in vivo study in mice showed excellent GFP expression in the lung, kidney, and liver. The results demonstrated that the OCMPEI copolymer prepared in this study is a promising carrier for in vitro and in vivo gene delivery applications.

Encapsulation of paclitaxel into lauric acid-O-carboxymethyl chitosan-transferrin micelles for hydrophobic drug delivery and site-specific targeted delivery

Transferrin/PEG/O-carboxymethyl chitosan/fatty acid/paclitaxel (TPOCFP) micelles were tested for suitability as a drug carrier characterized by low cytotoxicity, sustained release, high cellular uptake, and site-specific targeted delivery of hydrophobic drugs. Characterization, drug content, encapsulation efficiency, and in vitro drug release were investigated. When the feeding amount of paclitaxel (PTX) was increased, the drug content increased, but loading efficiency decreased. TPOCFP micelles had a spherical shape, with a particle size of approximately 140-649 nm. In vitro cell cytotoxicity and hemolysis assays were conducted to confirm the safety of the micelles. Anticancer activity and confocal laser scanning microscopy (CLSM) were used to confirm the targeting efficiency of target ligand-modified TPOCFP micelles. Anticancer activity and CLSM results clearly demonstrated that transferrin-modified TPOCFP micelles were quickly taken up by the cell. The endocytic pathway of TPOCFP micelles was analyzed by flow cytometry, revealing transfection via receptor-mediated endocytosis. These results suggest that PTX-encapsulated TPOCFP micelles may be used as an effective cancer-targeting drug delivery system for chemotherapy.

Long-term efficacy of entecavir in adefovir-refractory chronic hepatitis B patients with prior lamivudine resistance

This study aimed to evaluate the long-term efficacy of entecavir (ETV) in adefovir (ADV)-refractory chronic hepatitis B (CHB) patients with prior lamivudine (LMV) resistance. A total of 55 ADV-refractory CHB patients with prior LMV resistance, who received rescue therapy with ETV 1 mg daily for at least 12 months, were consecutively enrolled and analysed. Forty-four patients were men, and their median age was 47 (25-69). Ten patients had liver cirrhosis and 46 patients were positive for hepatitis B e antigen (HBeAg). Median hepatitis B virus DNA levels were 6.6 (4.3-8.0) log(10) copies/mL, and the median duration of ETV therapy was 24 (12-47) months. Cumulative virologic response rates at 6, 12, 24 and 36 months were 18%, 29%, 58% and 75%, respectively. HBeAg loss occurred in 10 (21.7%) of 46 HBeAg-positive patients. In multivariate analysis, only initial virologic response at 3 months remained as an independent predictor for virologic response (RR 3.143; 95% CI 1.387-7.120; P = 0.006). The patients with a virological response at 3 months had not only a significantly higher probability of achieving a virologic response (P < 0.001) but also lower probability of experiencing a virologic breakthrough (P = 0.043) than the patients without an early response. Viral breakthrough was observed in 29 patients during the follow-up period. Cumulative breakthrough rates at 6, 12, 24 and 36 months were 0%, 15%, 45% and 73%, respectively. ETV monotherapy may be considerably efficacious in cases with an initial virological response but its efficacy is attenuated by frequent emergence of ETV resistance in ADV-refractory CHB patients with prior LMV resistance.

Chitosan: a novel platform in proton-driven DNA strand rearrangement actuation

Nanometre-scaled DNA machine based on molecular recognition properties of DNA has now become a powerful tool in nanodevices, miniaturized structure, and nanofabrication. The common principle behind designing a DNA nanomachine is DNA strand exchange or rearrangement, which is solely controlled by the stabilization through associative and dissociative forces arising from base pair interaction of DNA molecules. Thus, highly effective DNA reaction actuator will make DNA nanomachine more flexible, controllable, and powerful device. Here, we report the novel polymer-mediated platform in proton-driven DNA strand rearrangement actuation. This cationic low molecular weight water-soluble chitosan (LMWSC) exhibited pH-dependent complexation with oligodeoxynucleotides (ODN). It formed complex with ODN only at low pH and accelerated the DNA strand exchange (or rearrangement) reaction between dsDNA and its complementary ssDNA at pH 5.0. However, no complexation was observed between LMWSC and ODN at neutral pH. We assume that at physiological pH, LMWSC is not protonated enough for formation of complex with ODN. Therefore, it can not diminish the electrostatic repulsion among the negatively charged DNA strands of the three-stranded intermediate formed during the strand exchange reaction. In contrast, LMWSC becomes positively charged at acidic pH, and it stabilizes the three-stranded intermediate by spreading out the accumulated counter-ions and increasing the entropy of the system. This fascinating observation prompted us to believe that this intelligent proton-driven DNA reaction actuator has a potential for the precise control of DNA nanomachine and would be applied for operating and controlling nanoscaled machine.

Methotrexate-incorporated polymeric nanoparticles of methoxy poly(ethylene glycol)-grafted chitosan

We prepared methotrexate (MTX)-encapsulated polymeric nanoparticles using methoxy poly(ethylene glycol) (MPEG)-grafted chitosan (ChitoPEG) copolymer. MTX-encapsulated polymeric nanoparticles of ChitoPEG copolymer has around 50-300nm in particle size and showed spherical shape when observed by transmission electron microscope (TEM). In (1)H nuclear magnetic resonance (NMR) study, the specific peaks of MTX and chitosan as a drug carrying inner-core disappeared at D(2)O and only the specific peak of MPEG was observed, while specific peaks of MPEG, MTX, and chitosan appeared in DCl/D(2)O mixtures. These results indicated that MTX was complexed with chitosan and then core-shell type nanoparticles had formed in aqueous environment, i.e., MTX/chitosan complexes composed of inner-core and MPEG composed of outer-shell of the nanoparticles. Loading efficiency of MTX in the polymeric nanoparticles was 94% (w/w) of ChitoPEG-1, 91.1% (w/w) of ChitoPEG-2, 90.1% (w/w) of ChitoPEG-3 and 65.2% (w/w) of ChitoPEG-4, expectively. The higher the drug feeding ratio, the higher the drug content and the lower the loading efficiency. The higher the MPEG graft ratio in the copolymer, the lower the drug content and loading efficiency. Drug contents evaluated by (1)H NMR were the same as found by UV spectrophotometer.

Investigation of the antifungal activity and mechanism of action of LMWS-chitosan

Chitosan, a cationic polysaccharide, has been widely used as a dietary supplement and in a variety of pharmacological and biomedical applications. The antifungal activity and mechanism of action of low molecular weight water-soluble chitosan (LMWS-chitosan) were studied in fungal cells and vesicles containing various compositions of fungal lipids. LMWS-chitosan showed strong antifungal activity against various pathogenic yeasts and hyphae-forming fungi but no hemolytic activity or cytotoxicity against mammalian cells. The degree of calcein leakage was assessed on the basis of lipid composition (PC/CH; 10:1, w/w). Our result showing that LMWS-chitosan interacts with liposomes demonstrated that chitosan induces leakage from zwitterionic lipid vesicles. Confocal microscopy revealed that LMWS-chitosan was located in the plasma membrane. Finally, scanning electron microscopy revealed that LMWS-chitosan causes significant morphological changes on fungal surfaces. Its potent antibiotic activity suggests that LMWS-chitosan is an excellent candidate as a lead compound for the development of novel anti-infective agents.

Galactosylated poly(ethylene glycol)-chitosan-graft-polyethylenimine as a gene carrier for hepatocyte-targeting

Chitosan and chitosan derivatives have been proposed as alternative and biocompatible cationic polymers for non-viral gene delivery. However, the low transfection efficiency and low specificity of chitosan is an aspect of this approach that must be addressed prior to any clinical applications. In the present study a chitosan derivative, galactosylated poly(ethylene glycol)-chitosan-graft-polyethylenimine (Gal-PEG-CHI-g-PEI), was investigated as a potential hepatocyte-targeting gene carrier. The composition of Gal-PEG-CHI-g-PEI was characterized using (1)H nuclear magnetic resonance ((1)H NMR), and the particle size and zeta potential of Gal-PEG-CHI-g-PEI/DNA complexes were measured using dynamic light scattering (DLS). The Gal-PEG-CHI-g-PEI exhibited lower cytotoxicity compared to PEI 25K as a control. Likewise, Gal-PEG-CHI-g-PEI/DNA complexes showed good hepatocyte specificity. Furthermore, Gal-PEG-CHI-g-PEI/DNA complexes transfected liver cells more effectively than PEI 25K in vivo after intravenous (i.v.) administration. Together, these results suggest that Gal-PEG-CHI-g-PEI, which has improved transfection efficiency and hepatocyte specificity both in vitro and in vivo, may be useful for gene therapy.

Aspartate aminotransferase to platelet ratio index (APRI) can predict liver fibrosis in chronic hepatitis B

BACKGROUND

There have been still few valuable markers that can be used as indirect markers of liver fibrosis in chronic hepatitis B.

AIMS

This study aimed to evaluate efficacy of several indirect markers of liver fibrosis and to identify the most valuable test in chronic hepatitis B.

PATIENTS AND METHODS

A total of 264 patients with chronic hepatitis B were consecutively enrolled. Fibrosis was staged by a single blinded pathologist according to the METAVIR system. Significant fibrosis was defined as stage >or=2. We investigated diagnostic accuracy of four indirect markers including aspartate aminotransferase to platelet ratio index for predicting significant fibrosis.

RESULTS

Mean age was 28 years. 53% (141/264) had significant hepatic fibrosis. Of indirect markers, aspartate aminotransferase to platelet ratio index yielded the best area under the receiver operating characteristic curve (0.86; 95% confidence interval, 0.82-0.91). Positive predictive value/negative predictive value at 0.5, 1.5 and 2.0 of aspartate aminotransferase to platelet ratio index score for predicting significant fibrosis were 63%/91%, 83%/74% and 86%/65%, respectively. The odds ratio for aspartate aminotransferase to platelet ratio index >or=1.4 relative to less than aspartate aminotransferase to platelet ratio index of 1.4 was 17.971 (p<0.0001; 95% confidence interval, 9.677-33.376).

CONCLUSIONS

Of simple markers already developed in chronic hepatitis C, aspartate aminotransferase to platelet ratio index may be the most accurate and simple marker for predicting significant fibrosis in chronic hepatitis B.

Preparation and spectroscopic characterization of methoxy poly(ethylene glycol)-grafted water-soluble chitosan

The object of this study was to test the solubility of a methoxy poly(ethylene glycol) (MPEG)-grafted chitosan copolymer in organic solvents and aqueous solution. Water-soluble chitosan with low molecular weight (LMWSC) was used in a PEG-graft copolymerization. The MPEG was conjugated to chitosan using 4-dicyclohexylcarbodimide (DCC), and N-hydroxysuccimide (NHS). Introduction of PEG was confirmed by (1)H and (13)C NMR spectroscopy and FT-IR spectroscopy. The degree of substitution (DS) of MPEG into chitosan was calculated from (1)H NMR data and also by estimating the molecular weight (MW) using gel permeation chromatography (GPC). The DS values obtained from (1)H NMR spectroscopy and GPC were similar, indicating that MPEG-grafted LMWSC was synthesized and properly characterized. Furthermore, the introduction of PEG into chitosan increases the solubility in aqueous solutions over a range of pH values (4.0-11.0) and organic solvents such as DMF, DMSO, ethanol, and acetone.

Five-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside attenuates poly (I:C)-induced airway inflammation in a murine model of asthma

BACKGROUND

Asthma can frequently be induced or exacerbated by respiratory viral infections. Oxidative stress might also play an essential role in the pathogenesis of allergic airway diseases, indicating that antioxidant therapy may have a potential effect in controlling allergic airway diseases. Recent studies showed that 5-aminoimidazole-4-carboxamide-1-beta-4-ribofuranoside (AICAR) has the potential ability to modulate NADPH oxidase activity, indicating the antioxidant activity of AICAR. This study investigated the inhibitory effects of AICAR as an anti-inflammatory modulator on allergic airway inflammation in murine animal models.

METHODS

The anti-inflammatory effects of AICAR were evaluated in two experimental asthma models: (1) an ovalbumin (OVA)-induced experimental asthma model and (2) an OVA plus polyinosinic-polycytidylic acid [poly (I:C)]-induced experimental asthma model to mimic respiratory viral infections. The inhibitory effects of AICAR in poly (I:C)-mediated signalling for NF-kappaB activation and production of TNF-alpha were analysed in vitro.

RESULTS

AICAR was shown to have a marginal inhibitory effect in an OVA-induced asthma model. Interestingly, AICAR significantly attenuated poly (I:C)-induced airway hyperresponsiveness and airway inflammation, as shown by the attenuation of the influx of total inflammatory cells and soluble products into bronchoalveolar lavage fluid, such as macrophages, eosinophils, IL-5, IL-13, TNF-alpha and IFN-gamma. AICAR also significantly reduced the serum levels of OVA-specific IgE and IgG2a antibodies. Histologic and flow cytometric studies showed that AICAR inhibited poly (I:C)-induced lung inflammation and the infiltration of CD11b+CD11c+ dendritic cells into the lung. Moreover, AICAR effectively inhibited poly (I:C)-mediated activation of NF-kappaB and the production of TNF-alpha.

CONCLUSION

These findings suggest that AICAR may be a novel immunomodulator with promising beneficial effects for the treatment of respiratory viral infection in airway allergic diseases.

Glucocorticoid receptor represses the Dex-mediated induction of human androgen response element-linked Luc activity

A human androgen response element (hARE), identified within intron 8 of the human sterol regulatory element-binding protein cleavage-activating protein, interacts with both glucocorticoid receptor (GR) and androgen receptors (AR). The aim of this study was to test the hypothesis that human GR (hGR) might modulate the expression of a hARE-linked reporter gene by dexamethasone (Dex). The hypothesis was tested by: a) co-transfecting HepG2 cells with a hGR and a luciferase (Luc)-reporter gene for performing in vitro investigations and b) by their co-injection into the tail vein of mice for in vivo investigation. In vitro co-transfected cells and the in vivo co-injected mice were then treated with Dex. Our results have led us to concluded that both transfection and injection of the hGR leads to a repression in the Dex-mediated induction of hARE-linked Luc activity both in vitro and in vivo settings. These findings suggest that this assay system allows screening of drug candidates affecting to a signal transduction pathway of the GR and AR and may help in the future discovery and analysis of novel and selection of GR and AR agonists.

Retinol-encapsulated low molecular water-soluble chitosan nanoparticles

This aim of this study was to encapsulate retinol into chitosan nanoparticles and reconstitute it into aqueous solution. Retinol-encapsulated chitosan nanoparticles were prepared for application of cosmetic and pharmaceutical applications. Retinol-encapsulated chitosan nanoparticle has a spherical shape and its particle sizes were around 50-200 nm according to the drug contents. Particle size was increased according to the increase of drug contents. Solubility of retinol is able to increase by encapsulation into chitosan nanoparticles more than 1600-fold. It was suggested that retinol was encapsulated into chitosan nanoparticles by ion complex as a result of FT-IR spectra. Specific peak of chitosan at 1590 cm(-1) was divided to semi-doublet due to the electrostatic interaction between amine group of chitosan and hydroxyl group of retinol. At (1)H NMR spectra, specific peaks of retinol disappeared when retinol-encapsulated chitosan nanoparticles were reconstituted into D(2)O while specific peaks both of retinol and chitosan appeared at D(2)O/DMSO (1/4, v/v) mixture. XRD patterns also showed that crystal peaks of retinol were disappeared by encapsulation into chitosan nanoparticles. Retinol-encapsulated nanoparticles were completely reconstituted into aqueous solution as same as original aqueous solution and zeta potential of reconstituted chitosan nanoparticles was similar to their original solution. At HPLC study, retinol was stably and efficiently encapsulated into chitosan nanoparticles.