Antimicrobial peptides (AMPs) are a class of peptides widely existing in nature with broad-spectrum antimicrobial activity. It is considered as a new alternative to traditional antibiotics because of its unique mechanism of antimicrobial activity. The development and application of natural AMPs are limited due to their drawbacks such as low antimicrobial activity and unstable metabolism. Therefore, the design and optimization of derived peptides based on natural antimicrobial peptides have become recent research hotspots. In this paper, we focus on ribosomal AMPs and summarize the design and optimization strategies of some related derived peptides, which include reasonable primary structure modification, cyclization strategy and computer-aided strategy. We expect to provide ideas for the design and optimization of antimicrobial peptides and the development of anti-infective drugs through analysis and summary in this paper.
Antimicrobial Cationic Peptides/chemistry* ; Antimicrobial Peptides ; Drug Design ; Anti-Infective Agents/pharmacology* ; Anti-Bacterial Agents

Currently, all the conventional antibiotics have developed corresponding drug-resistant pathogenic strains, which have increasingly become a serious threat to people's health. Development of completely new types of antibiotics is one of effective ways to solve the drug resistance issue. Antimicrobial peptides with broad-spectrum antibacterial and antimicrobial activity and wild variety become the ideal alternative to traditional antibiotics. Antimicrobial peptides are derived from wide range of sources, such as plants, animals, and microorganisms. Mechanism of function of the antimicrobial peptides and the investigation approaches of different antimicrobial peptides also vary dramatically. In this paper, we give an overview of preparation, antibacterial mechanisms, and research methodology of antimicrobial peptides.
Animals ; Anti-Bacterial Agents ; Anti-Infective Agents ; Antimicrobial Cationic Peptides ; pharmacology ; Humans

The hinge structure, also known as hinge region or bend, is a special structure found in some antimicrobial peptides. Most studies on antimicrobial peptides focused on the standard secondary structure of α-helix and β-sheet, while the hinge structure and its functions were rarely studied. The hinge structure confers the antimicrobial peptides an improved structural flexibility, which may promote their disruptive effect on bacterial membrane or their binding efficiency to the intracellular targets, thus resulting in a higher antibacterial activity. Meanwhile, the hinge structure may reduce the structural rigidity, which may eliminate the cytotoxicity of antimicrobial peptides to eukaryotic cells. This article reviews the structural characteristics of the hinge structure, its effects on the biological activity of antimicrobial peptides and application in the molecular design, with the aim to provide a reference for the design and development of new antimicrobial peptides.
Anti-Bacterial Agents/pharmacology* ; Anti-Infective Agents/pharmacology* ; Antimicrobial Cationic Peptides/pharmacology* ; Pore Forming Cytotoxic Proteins ; Protein Structure, Secondary

Due to their lower risk for induction of resistance, membrane-active antimicrobial peptides with anticancer effect are attractive in cancer therapy. Because cell binding contributes to the cytotoxicity of peptide, it is possible to enhance the cytotoxicity of antimicrobial peptide in tumor cells by conjugation to a cell-penetrating peptide (CPP). In this paper, a fusion peptide MPGA by conjugation of antimicrobial peptide MP to CPP Antp at its N-terminus was constructed. After compared the cytotoxicity of unconjugated MP with that of the fusion peptide, it was found that MPGA showed higher cytotoxicity than that of unconjugated MP. And the fusion peptide MPGA induced cell death in tumor cells by membrane disruption. These results demonstrated that the cytotoxicity of antimicrobial peptide can be significantly enhanced by conjugation to CPP, which might be an effective way to develop novel anticancer drugs.
Antimicrobial Cationic Peptides ; pharmacokinetics ; pharmacology ; Antineoplastic Agents ; pharmacokinetics ; pharmacology ; Cell Line, Tumor ; Cell Membrane Permeability ; drug effects ; Humans

This study was aimed to evaluate the cyto-compatibility of PGLA film for periodontal guided tissue regeneration (GTR) and their degradable products. Different extraction temperature, time and ratio were used to assess the cell relative growth rate (RGR) for PGLA. The degradable solution were brought into contact with cultured cells in vitro to observe the effects of cytotoxicity at 2, 4, 6, 8 and 10 weeks. The results showed when the extraction ratio was 0.1 g/ml, the extraction time has no effects on cytotoxicity at 37 degrees C. When the ratio was 0.1 cm2/ml, slight cytotoxic reaction appeared with the increase of extraction temperature (50 degrees C or 70 degrees C). When the extraction ratio was 0.5 cm2/ml in contract with the degradable solution at 37 degrees C for 72 h, the cell growth rate decreased. When the ratio was 6 cm2/ml, the cytotoxicity existed in some degree even if the temperature was at 37 degrees C for 24 h. After 2-4 w, the degradable solution had no obvious toxic effects on cells. However, the RGR gradually decreased as the degradation period increased. In conclusion, the effects of the extraction temperature, time, ratio and the degradation products accumulating in solution on RGR may exist. PGLA film has a good cytocompatibility.
Animals ; Antimicrobial Cationic Peptides ; metabolism ; pharmacology ; Biodegradation, Environmental ; Cell Division ; drug effects ; Cells, Cultured ; Guided Tissue Regeneration ; Materials Testing ; Mice

Animals ; Antimicrobial Cationic Peptides ; chemistry ; pharmacology ; Fluorescence Resonance Energy Transfer ; Humans ; Peptide Chain Elongation, Translational ; drug effects ; Single Molecule Imaging

OBJECTIVEThis study aimed to evaluate the biological characteristics of a human specifically targeted antimi- crobial peptide C16LL-37 against Streptococcus mutans (S. mutans).

METHODSIn this study, an antimicrobial peptide LL-37, a peptide derived from CSP(C16) (S. mutans competence stimulating peptide), and recombinant peptide C16LL-37 were synthesized by Fmoc-chemistry-based strategy. The selectivity and antibacterial activity of C16LL-37 were identified by the colony counting method on microbial culture plates. After treatment of C16LL-37 at 32 µmol · L⁻¹, the morphological changes in S. mutans were observed by using scanning electron microscopy (SEM). In addition, enzyme-linked immunosorbent assay was used to evaluate the hemolytic activity and antibacterial activity of C16LL-37 under different conditions.

RESULTS1) The minimum inhibitory concentration of C16LL-37 was 16 µmol · L⁻¹, and the minimum bactericidal concentration was 64 μmol ·L⁻¹. 2) The survival rate of S. mutans was 3.46% after C16LL-37 treatment at 64 µmo-L⁻¹ for 30 min, whereas it was 0% at 64 µmol · L⁻¹ for 60 min. The survival rates of four other kinds of bacteria were more than 60% at any time (P < 0.05). 3) The morphological change in S. mutans was observed after C16LL-37 treatment at 32 µmol · L⁻¹ by using SEM. S. mutans presented an irregular shape, rough surface, and evident splitting. 4) The hemolysis rate of C16LL-37 (≤ 64 µmol · L⁻¹) was less than 0.33%. 5) This study showed no significant in- fluence on the antibacterial activity of C16LL-37 under different conditions, such as temperature, pH, salinity, and trypsin at low concentration (P > 0.05).

CONCLUSIONC16LL-37 exhibited obvious specificity for S. mutans, strong antibacterial activity, low toxicity, and high stability. Thus, C16LL-37 has good potential in caries research and clinical application.

Anti-Infective Agents ; pharmacology ; Antimicrobial Cationic Peptides ; pharmacology ; Bacterial Proteins ; Dental Caries ; Enzyme-Linked Immunosorbent Assay ; Humans ; Microbial Sensitivity Tests ; Microscopy, Electron, Scanning ; Peptides ; Streptococcus mutans ; drug effects

OBJECTIVETo express antibacterial peptide thanatin in the prokaryotic expression system and test its antibacterial activity.

METHODSThe DNA sequence coding for the 21 peptides of thanatin was synthesized using the preferred genetic codes of E. coli, cloned into pTYB11 plasmid, and transformed into E.coli ER2566. The expression of thanatin fused with intein was induced by IPTG in E.coli, and intein-thanatin specifically bound to the column through intein tag was cleaved overnight at 4 degrees celsius; in DTT/cysteine buffer.

RESULTSThe cleaved thanatin was eluted with a protein concentration of 245 microg/ml in the first 4 ml. The purified thanatin had showed strong antibacterial activities against G- bacteria such as Shigella flexneri, Klebsiella pneumoniae, Shigella snnei, Escherichia coli O157, toxin producing Escherichia coli, Pseudomonas aeruginosa, and fungi such as Candida albicans, with especial potency in killing drug-resistant Klebsiella pneumoniae, Pseudomonas aeruginosa, and extended-spectrum beta-lactamases (ESBL)-producing E.coli. Eighty strains of drug-resistant (ESBL-producing) and 30 strains of sensitive E. coli were used for anti-bacterial assay, and no significant differences in the antibacterial activity of thanatin were found between the sensitive and drug-resistant E. coli (P>0.05).

CONCLUSIONThe recombinant thanatin obtained shows strong antibacterial activity against drug-resistant and sensitive bacteria, and can be a potential substitute for routine antibiotics in the treatment of G- bacterial infections.

Anti-Bacterial Agents ; metabolism ; pharmacology ; Antimicrobial Cationic Peptides ; biosynthesis ; genetics ; pharmacology ; Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; Recombinant Proteins ; biosynthesis ; genetics ; pharmacology

This study was aimed to investigate the effect of rhIL-6 and rhEPO on hepcidin mRNA expression in HepG2 cells and human primary hepatocytes, and mechanism of rhEPO in treatment of anemia of chronic disease (ACD). The HepG2 cells and human primary hepatocytes were cultured with medium containing different concentrations of rhIL-6 and rhEPO for a certain time, then mRNA was isolated and its RT-PCR was performed, the bands were photographed and analyzed by UVI band, the hepcidin and G3PDH mRNA ratio were semi-quantitatively analyzed. The expression levels of hepcidin in GepG2 cells and human primary hepatocytes at different conditions were compared. The results showed that the hepcidin mRNA expression in HepG2 cells and human primary hepatocytes could be enhanced by rhIL-6, the rhEPO could inhibit rhIL6-induced hepcidin mRAN expression. The rhEPO alone basically did not influence hepcidin mRNA expression in HepG2 cells. It is concluded that Hepcidin mRNA expression in HepG2 cells and human primary hepatocytes can be elevated by rhIL-6 with concentration- and time-dependent manner in certain range. rhEPO can inhibit this effect of rhIL-6.
Antimicrobial Cationic Peptides ; genetics ; metabolism ; Erythropoietin ; pharmacology ; Hep G2 Cells ; Hepatocytes ; drug effects ; metabolism ; Hepcidins ; Humans ; Interleukin-6 ; pharmacology ; RNA, Messenger ; genetics ; Recombinant Proteins ; pharmacology

OBJECTIVETo investigate the in vitro effect of erythropoietin (EPO) on hepcidin of monocytes and its molecular mechanisms.

METHODSHepcidin and signaling molecules including C/EBPalpha, Smad1/5/8, p-Smad1/5/8 and p-STAT3 were detected by real time PCR and Western blot. THP-1 monocytes were stimulated by interleukin-6 (IL-6) or lipopolysaccharide (LPS). EPO receptor (EPOR) antibody was added to observe its antagonistic effect on EPO and impact on the signaling proteins.

RESULTSEPO suppressed mRNA expression of THP-1 hepcidin of monocytes induced by 20 ng/ml IL-6 or 1 microg/ml LPS in both dose and time dependent manner. The most decrease of hepcidin expression was observed at 2 IU/ml EPO for 6 hours. EPO also down-regulated hepcidin protein induced by 20 ng/ml IL-6. At 2 IU/ml EPO for 6 hours hepcidin protein was down-regulated, as was C/EBPalpha, p-Smad1/5/8 and p-STAT3. Antibody to EPOR antagonized the down-regulation of EPO on hepcidin and signaling proteins.

CONCLUSIONSMonocytes hepcidin can be reduced by EPO when stimulated by IL-6 or LPS. The mechanism of which may be at least in part, via suppression of C/EBPalpha, p-Smad1/5/8 and p-STAT3 signaling.

Antimicrobial Cationic Peptides ; metabolism ; Cells, Cultured ; Erythropoietin ; pharmacology ; Hepcidins ; Humans ; Interleukin-6 ; pharmacology ; Lipopolysaccharides ; pharmacology ; Monocytes ; drug effects ; metabolism ; Signal Transduction