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

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

Microbial biofilm, a consortium of microbial cells protected by a self-produced polymer matrix, is considered as one main cause of current bacterial drug resistance. As a new type of antimicrobial agents, antimicrobial peptides provide a new strategy for the treatment of antibiotic resistant bacteria biofilm infections. Antimicrobial peptides have shown unique advantages in preventing microbial colonization of surfaces, killing bacteria in biofilms or disrupting the mature biofilm structure. This review systemically analyzes published data in the recent 30 years to summarize the possible anti-biofilm mechanisms of antimicrobial peptides. We hope that this review can provide reference for the treatment of infectious diseases by pathogenic microbial biofilm.
Anti-Bacterial Agents ; pharmacology ; Antimicrobial Cationic Peptides ; pharmacology ; Bacteria ; drug effects ; Biofilms ; drug effects ; Drug Resistance, Bacterial ; drug effects ; Microbial Sensitivity Tests ; Research ; trends

BACKGROUND: Glucocorticoids have been widely used to treat patients with chronic obstructive pulmonary disease (COPD). Nevertheless, corticosteroid insensitivity is a major barrier to the effective treatment of COPD and its mechanism remains unclear. This study aimed to evaluate the effect of cathelicidin LL-37 on corticosteroid insensitivity in COPD rat model, and to explore the involved mechanisms. METHODS: COPD model was established by exposing male Wistar rats to cigarette smoke combined with intratracheal instillation of lipopolysaccharide (LPS). Inhaled budesonide and LL-37 were consequently applied to COPD models separately or collectively to confirm the effects on inflammatory cytokines (tumor necrosis factor [TNF]-α and transforming growth factor [TGF]-β) by enzyme-linked immunosorbent assay (ELISA) and lung tissue histopathological morphology. Expression of histone deacetylase-2 (HDAC2) and phosphorylation of Akt (p-AKT) in lung were also measured. RESULTS: Briefly, COPD model rats showed an increased basal release of inflammatory cytokines (lung TNF-α: 45.7 ± 6.1 vs. 20.1 ± 3.8 pg/mL, P < 0.01; serum TNF-α: 8.9 ± 1.2 vs. 6.7 ± 0.5 pg/mL, P = 0.01; lung TGF-β: 122.4 ± 20.8 vs. 81.9 ± 10.8 pg/mL, P < 0.01; serum TGF-β: 38.9 ± 8.5 vs. 20.6 ± 2.3 pg/mL, P < 0.01) and COPD related lung tissue histopathological changes, as well as corticosteroid resistance molecular profile characterized by an increase in phosphoinositide 3-kinase (PI3K)/Akt (0.5 ± 0.1 fold of control vs. 0.2 ± 0.1 fold of control, P = 0.04) and a decrease in HDAC2 expression and activity (expression: 13.1 ± 0.4 μmol/μg vs. 17.4 ± 1.1 μmol/μg, P < 0.01; activity: 1.1 ± 0.1 unit vs. 1.4 ± 0.1 unit, P < 0.01), compared with control group. In addition, LL-37 enhanced the anti-inflammatory effect of budesonide in an additive manner. Treatment with combination of inhaled corticosteroids (ICS) and LL-37 led to a significant increase of HDAC2 expression and activity (expression: 15.7 ± 0.4 μmol/μg vs. 14.1 ± 0.9 μmol/μg, P < 0.01; activity: 1.3 ± 0.1 unit vs. 1.0 ± 0.1 unit, P < 0.01), along with decrease of p-AKT compared to budesonide monotherapy (0.1 ± 0.0 fold of control vs. 0.3 ± 0.1 fold of control, P < 0.01). CONCLUSIONS This study suggested that LL-37 could improve the anti-inflammatory activity of budesonide in cigarette smoke and LPS-induced COPD rat model by enhancing the expression and activity of HDAC2. The mechanism of this function of LL-37 might involve the inhibition of PI3K/Akt pathway.
Animals ; Antimicrobial Cationic Peptides ; pharmacology ; therapeutic use ; Glucocorticoids ; metabolism ; Histone Deacetylase 2 ; metabolism ; Humans ; Inflammation ; chemically induced ; drug therapy ; Lipopolysaccharides ; pharmacology ; Male ; Phosphatidylinositol 3-Kinases ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Pulmonary Disease, Chronic Obstructive ; drug therapy ; metabolism ; Rats ; Rats, Wistar ; Smoking ; adverse effects ; Tumor Necrosis Factor-alpha ; metabolism

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

Herbal extracts have been extensively used worldwide for their application on memory improvement, especially among aged and memory-deficit populations. In the present study, the memory loss induced by human Abeta protein over-expression in fruitfly Alzheimer's disease (AD) model was rescued by multiple extracts from Gardenia jasminoides. Three extracts that rich with gardenia yellow, geniposide, and gardenoside components showed distinct rescue effect on memory loss. Further investigation on adding gardenoside into a formula of Ganoderma lucidum, Panax notoginseng and Panax ginseng (GPP) also support its therapeutic effects on memory improvement. Interestingly, the application of GPP and gardenoside did not alter the accumulation of Abeta proteins but suppressed the expression of immune-related genes in the brain. These results revealed the importance and relevancy of anti-inflammation process and the underlying mechanisms on rescuing memory deficits, suggesting the potential therapeutic use of the improved GPP formulation in improving cognition in defined population in the future.
Alzheimer Disease ; drug therapy ; Animals ; Antimicrobial Cationic Peptides ; genetics ; Brain ; drug effects ; immunology ; Cognition ; drug effects ; Disease Models, Animal ; Drosophila ; Drosophila Proteins ; genetics ; Gardenia ; chemistry ; Gene Expression Regulation ; drug effects ; Immunity, Innate ; drug effects ; Iridoids ; chemistry ; isolation & purification ; pharmacology ; Plant Extracts ; chemistry ; isolation & purification ; pharmacology ; Polymerase Chain Reaction

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

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

OBJECTIVETo investigate the effect of antibacterial peptide hCAP18/LL-37 on ovarian cancer microenvironment and the regulatory mechanism of its expression.

METHODSWe assessed the effect of macrophage-promoted ovarian cancer cells invasion using BioCoat Matrigel invasion chamber. The expressions of hCAP18/LL-37 and versican V1 were determined by real-time PCR and Western blot analysis. SKOV3 cells were transfected with shRNA plasmid to abrogate the expression of versican V1, and then the expression of hCAP18/LL-37 in macrophages and the invasiveness of SKOV3 cells were assayed.

RESULTSThe Matrigel invasion assay showed that after co-culture with macrophages for 4 days, the number of penetrated SKOV3 cells was 112.8±17.1/per high power field, significantly higher than that in the SKOV3 cells cultured alone (8.2±1.9/per high power field) (P<0.05). Addition of hCAP/LL-37 neutralizing antibody into the co-cultured macrophage-SKOV3 cells markedly inhibited the macrophage-promoted SKOV3 cells invasion. The penetrated SKOV3 cells was 22.2±5.6/per high power field, significantly lower than the 100.6±25.2/per high power field in the control macrophage- SKOV3 co-cultured cells (P<0.05). The expressions of hCAP18/LL-37 mRNA and protein in macrophages were remarkably enhanced upon co-culture with SKOV3 cells, but not changed in SKOV3 cells cultured alone. The expression and secretion of versican V1 in the ovarian cancer cells were also significantly increased after co-cultured with macrophages. Knockdown of versican V1 in SKOV3 cells by small interfering RNA significantly reduced the expression of hCAP18/LL-37 mRNA and protein in the macrophages, as well as decreased the invasiveness of SKOV3 cells (P<0.05).

CONCLUSIONSIn the cancer microenvironment, the macrophage-secreted hCAP18/LL-37 promote the invasiveness of ovarian cancer cells, and the hCAP18/LL-37 expression is regulated by versican V1 protein released by ovarian cancer cells.

Antimicrobial Cationic Peptides ; metabolism ; pharmacology ; Cell Line, Tumor ; Coculture Techniques ; Collagen ; Drug Combinations ; Female ; Humans ; Laminin ; Macrophages ; metabolism ; Neoplasm Invasiveness ; Neoplasm Proteins ; metabolism ; Ovarian Neoplasms ; metabolism ; pathology ; physiopathology ; Plasmids ; Proteoglycans ; RNA, Messenger ; metabolism ; RNA, Small Interfering ; Real-Time Polymerase Chain Reaction ; Transfection ; Tumor Microenvironment ; drug effects ; Versicans ; metabolism

Penaeidin-2 (Pen-2) is an important antimicrobial peptide derived from the Pacific white shrimp, Penaeus vannamei, and possesses both antibacterial and antifungal activities. Recent studies suggest that recombinant penaeidins show similar activities to the native Pen-2 protein. Previous researches have shown that some antimicrobial peptides (AMPs) exhibit cytotoxic activity against cancer cells. To date, there have been no studies on the antitumor effects of Pen-2. This study evaluated the potential of recombinant pen-2 (rPen-2) in the selective killing of kidney cancer cell lines ACHN and A498, and its action mechanism. MTT assays found the maximal growth inhibition of HK-2, ACHN and A498 cells treated with 100 μg/mL rPen-2 at 48 h was 13.2%, 62.4%, and 70.4%, respectively. DNA-specific fluorescent dye staining showed a high percentage of apoptosis on cancer cells. Flow cytometry revealed that the apoptosis rate of HK-2, ACHN and A498 cells was 15.2%, 55.2%, and 61.5% at 48 h respectively, suggesting that rPen-2 induced higher apoptosis rate in cancer cells than in HK-2 cells. Laser confocal scanning microscopy demonstrated that the plasma membrane was the key site where rPen-2 interacted with and destroyed tumor cells. Scanning electron microscopy showed the morphologic changes of the cell membranes of kidney cancer cells treated with rPen-2. These results suggest that rPen-2 is a novel potential therapeutic agent that may be useful in treating kidney cancers.
Animals ; Antimicrobial Cationic Peptides ; genetics ; pharmacology ; Antineoplastic Agents ; pharmacology ; Apoptosis ; drug effects ; Arthropod Proteins ; genetics ; pharmacology ; Drug Screening Assays, Antitumor ; Humans ; Kidney Neoplasms ; drug therapy ; metabolism ; pathology ; Penaeidae ; genetics ; Recombinant Proteins ; genetics ; pharmacology